JP2009196341A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent images from being deteriorated by making influence to a conveying system as small as possible and, at the same time, suppress cost through the sure and effective detection of the humidity of the surface of a printed medium to be recorded. <P>SOLUTION: In the image forming apparatus, in which the medium to be recorded is conveyed so as to form an image on the front surface of the medium to be recorded and, after the formation of the image on the front surface, the rear surface conveyance of the medium to be recorded is executed at a perfecting unit 7 so as to form an image on the rear surface of the recording medium, a humidity sensor 53 for detecting the humidity of the printed medium to be recorded, a storage device 54, in which values corresponding to reference humidities according to the kind of the media are set in advance, and a control part 50 for controlling the time until the medium to be recorded is conveyed to the perfecting unit 7 by comparing the humidity of the medium to be recorded detected by the humidity sensor 53 with the set reference humidity, are equipped. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as an ink jet recording apparatus.

  2. Description of the Related Art Conventionally, a printing method called a serial head method has been the mainstream in inkjet image forming apparatuses that have become extremely popular with the spread of personal computers. However, the serial head method in which the print head is reciprocated many times in the direction orthogonal to the paper feed direction tends to increase the printing time. For this reason, in recent years, a line head system has been devised as one of high-speed technologies. The line head is composed of a plurality of short heads arranged over a recording medium width or longer. Alternatively, a single long head can record an image for one line at a time, and can print an image in a shorter time compared to the serial head method.

  However, on the other hand, there is a concern about the dry state of the image-printed surface of the recording medium, on the other hand, while the merit that high-speed printing of the line head is possible. In particular, at the time of double-sided printing, the first printing surface is brought into close contact with the conveying means in order to reverse the recording medium. At this time, if the printing surface is not sufficiently dried, the image quality may be deteriorated due to fading of the printed image, or the ink may adhere to a conveying means such as a roller or a belt. As a countermeasure method, there is a method of detecting the atmospheric humidity inside the apparatus and controlling it so as to become the reference humidity. For example, in Patent Document 1, a dehumidifier is used in order to achieve the reference humidity.

JP 2005-138463 A

  However, in the conventional techniques as described above, the internal structure of the apparatus is complicated, so the surface humidity of the recording medium and the humidity inside the apparatus atmosphere do not always match, so that the apparatus is sufficiently dried. There is a risk that the image will deteriorate even if it is transported. On the other hand, if the heating is excessive, the atmosphere around the nozzle head is too dry, causing ink clogging and image deterioration. Moreover, a space is required to install the dehumidifying function, which is not suitable for downsizing of the apparatus, and causes an increase in cost.

  The present invention has been made in view of the above, and reliably and effectively detects the humidity of the surface of a printed recording medium with as little influence on the transport system as possible and suppresses the cost. The object is to prevent image degradation.

  In order to solve the above-described problems and achieve the object, the invention according to claim 1 is directed to conveying a recording medium, forming an image on the surface of the recording medium, and forming an image on the surface. An image forming apparatus for conveying the back side of the recording medium by a double-sided conveying unit to form an image on the back side of the recording medium, the humidity detecting unit for detecting the humidity of the recording medium after printing, and the recording medium A storage unit that preliminarily sets a value corresponding to a reference humidity according to the type, and a comparison between the humidity of the recording medium detected by the humidity detection unit and the set reference humidity, according to the comparison result, And control means for controlling the time until it is conveyed to the double-sided conveying means.

  The invention according to claim 2 is characterized in that one humidity detecting means is arranged.

  The invention according to claim 3 is characterized in that one humidity detecting means is arranged to detect humidity at a plurality of locations while conveying the recording medium.

  The invention according to claim 4 further includes a dehumidifying means inside the recording medium and the housing.

  Further, the invention according to claim 5 is characterized in that a plurality of the humidity detecting means are arranged, and the control means controls a time until it is conveyed to the double-sided conveying means by using a plurality of humidity detection data. And

  According to a sixth aspect of the present invention, a plurality of the humidity detection means are arranged in the main scanning direction, and the control means performs humidity detection at a plurality of places at the same timing, and adopts the higher humidity as the detection value. It is characterized by that.

  According to a seventh aspect of the present invention, a plurality of the humidity detecting means are arranged in the main scanning direction, and the control means performs the same timing at a plurality of places while conveying the recording medium to detect the higher humidity. It is adopted as a value.

  In the invention according to claim 8, a plurality of the humidity detection means are arranged in the main scanning direction, and the control means performs humidity detection at a plurality of places at the same timing, and adopts an average value thereof as a detection value. It is characterized by that.

  According to a ninth aspect of the present invention, a plurality of the humidity detecting means are arranged in the main scanning direction, and the control means performs the same timing at a plurality of positions while conveying the recording medium, and detects an average value thereof. It is adopted as a value.

  According to a tenth aspect of the present invention, a plurality of the humidity detecting means are arranged in the transport direction of the recording medium, and the control means detects the humidity at the same location of the recording medium a plurality of times with a time interval. It is characterized by that.

  The invention according to claim 11 is characterized in that a plurality of humidity detecting means are arranged in the main scanning direction in addition to the conveyance direction of the recording medium.

  The invention according to claim 12 is further characterized in that a front end detecting means for detecting a front end position of the recording medium to be conveyed is provided.

  The invention according to claim 13 further includes an original reading means, a storage means for reading a test chart by the original reading means and printing it on a recording medium, and reading and storing humidity data of the recording medium; Based on the storage data of the storage means, using the time calculation means for calculating the time required for the test-printed recording medium to be conveyed to the double-side conveyance means, and the calculation time by the time calculation means, It is characterized by comprising adjusting means for adjusting the time until it is conveyed to the double-sided conveying means.

  The invention according to claim 14 further includes a test print pattern generation unit, a storage unit that reads and stores the humidity data of the recording medium subjected to the test print, and a test print based on the storage data of the storage unit The time calculation means for calculating the time required for the recorded recording medium to be conveyed to the double-sided conveyance means, and the time until it is conveyed to the double-sided conveyance means are adjusted using the time calculated by the time calculation means The adjusting means is provided.

  According to the image forming apparatus of the present invention, since the humidity of the surface of the recording medium after printing is detected and the printed surface is dried and then inserted into the double-sided conveying means, high-quality image quality without blurring can be obtained. In addition, since there is no fear of the printed ink adhering to the roller of the double-sided conveying means, secondary image quality deterioration and internal deterioration of the apparatus can be prevented. Since the corresponding humidity is used as a criterion, there is an effect that accurate conveyance control is possible.

  Exemplary embodiments of an image forming apparatus according to the present invention will be explained below in detail with reference to the accompanying drawings.

(Embodiment)
FIG. 1 is an explanatory diagram showing a configuration of an image forming apparatus according to an embodiment of the present invention. The ink jet recording apparatus as an image forming apparatus includes an image forming unit 2 and the like inside the apparatus main body 1, and includes a paper feeding unit 4 on the lower side of the apparatus main body 1. A paper feed tray 14 on which a medium (paper) 15 can be stacked is provided. The paper 15 fed from the paper feed tray 14 is taken in, and a required image is formed by the image forming unit 2 while the paper 15 is conveyed by the paper conveyance unit 5. Then, the paper 15 is discharged to the paper discharge tray 6 mounted on the side of the apparatus main body 1.

  In addition, the double-sided unit 7 that can be attached to and detached from the apparatus main body 1 is provided, and when performing double-sided printing, after the single-sided (surface) printing is completed, the paper-conveying unit 5 conveys the paper 15 in the opposite direction and enters the double-sided unit 7 The other side (back side) is set as a printable side, that is, switched back and sent to the paper transport unit 5 again, and after the other side (back side) is printed, the paper 15 is discharged to the paper discharge tray 6. Make paper.

  Here, the image forming unit 2 is composed of, for example, four full-line liquid ejection heads that eject droplets of each color of black (K), cyan (C), magenta (M), and yellow (Y). Recording heads 11k, 11c, 11m, and 11y (referred to as “recording head 11” when colors are not distinguished), and each recording head 11 is a head holder with the nozzle surface on which nozzles for discharging droplets are directed downward. 13 is attached.

  In addition, maintenance recovery mechanisms 12k, 12c, 12m, and 12y for maintaining and recovering the head performance corresponding to each recording head 11 (referred to as “maintenance recovery mechanism 12” when colors are not distinguished) are provided, purge processing, During the head performance maintenance operation such as the wiping process, the recording head 11 and the maintenance / recovery mechanism 12 are relatively moved so that the capping member constituting the maintenance / recovery mechanism 12 faces the nozzle surface of the recording head 11.

  For example, as shown in FIG. 2, one recording head 11 has a plurality of head chips (liquid ejection heads) 111 a to 111 f placed on a head chip support member 110 in a direction orthogonal to the medium transport direction (paper transport direction). A configuration in which the arrangement direction of the plurality of nozzles 112 is arranged in a staggered manner with the arrangement direction of the head chips as the head chip arrangement direction (this is referred to as “staggered recording head 11”) can be used.

  For example, as shown in FIG. 3, one recording head 10 includes a plurality of head chips (liquid ejection heads) 111 a to 111 g in a head chip support member 110 in the medium transport direction (paper transport direction). It is also possible to use an arrangement in which the nozzles 112 are arranged so as to be inclined so that the arrangement direction of the nozzles 112 is inclined (this is referred to as “the inclined recording head 11”).

  For example, as shown in FIG. 4, one recording head 11 includes a plurality of head chips (liquid ejection heads) 111 a to 111 c on a head chip support member 110 and a recording medium conveyance direction (paper conveyance direction). A configuration in which the divided recording heads 11 arranged in a zigzag manner are arranged along the direction in which the two sets of nozzles 112 are arranged in an orthogonal direction with the arrangement direction of the plurality of nozzles 112 as the head chip arrangement direction. Can also be used.

  As shown in FIG. 5, one head chip 111 in these recording heads 11 has a first nozzle row 112A and a second nozzle row 112B in which nozzles 112 for discharging droplets are arranged in a staggered manner. Configured.

  Here, the recording head 11 that ejects droplets of each color in the order of yellow, magenta, cyan, and black is arranged from the upstream side in the paper conveyance direction, but the arrangement and the number of colors are not limited thereto. Further, the line type head and the recording liquid cartridge for supplying the recording liquid to the head can be integrated or separated.

  Further, as a head chip (liquid ejection head) constituting the recording head 11, the diaphragm is deformed by an electromechanical conversion element such as a piezoelectric element as pressure generation means (actuator means) for generating pressure for ejecting droplets. Piezoelectric actuators, thermal actuators that generate bubbles due to film boiling in liquids using electrothermal transducers, electrostatic actuators that deform diaphragms with electrostatic force generated between diaphragms and electrodes, etc. Any method may be used.

  Returning to FIG. 1, the paper 15 in the paper feed tray 14 of the paper feed unit 4 is separated one by one by a paper feed roller (half-moon roll) 21 and a separation pad (not shown) and fed into the apparatus main body 1, and the conveyance guide It is sent between the registration roller 25 and the transport roller 31 along the guide surface 23a of the member 23, and sent to the image forming area by the recording head 11 via the guide member 26 at a predetermined timing.

  The transport guide member 23 is also formed with a guide surface 23 b for guiding the paper 15 fed from the duplex unit 7. Further, a guide member 27 for guiding the paper 15 returned from the paper transport unit 5 to the duplex unit 7 during duplex printing is also provided.

  The sheet conveying unit 5 includes an endless conveying belt 33 that is stretched between a conveying roller 31 that is a driving roller and a driven roller 32, a charging roller 34 that charges the conveying belt 33, and the image forming unit 2. , A platen member 35 that maintains the flatness of the conveyor belt 33 at a portion facing it, a pressing roller 36 that presses the paper 15 fed from the conveyor belt 33 toward the conveyor roller 31, and other recordings attached to the conveyor belt 33 (not shown). It has a cleaning roller made of a porous body or the like that is a cleaning means for removing liquid (ink).

  A paper discharge roller 38 and a spur 39 for sending the paper 15 on which an image is recorded to the paper discharge tray 6 are provided on the downstream side of the paper transport unit 5.

  In the image forming apparatus configured as described above, the conveying belt 33 moves in the direction indicated by the arrow, and is positively charged by coming into contact with the charging roller 34 to which a high potential applied voltage is applied. In this case, the charging belt 34 is charged at a predetermined charging pitch by switching the polarity of the charging voltage of the charging roller 34 at predetermined time intervals.

  Here, when the paper 15 is fed onto the conveying belt 33 charged to this high potential, the inside of the paper 15 is in a polarized state, and the charge on the conveying belt 33 is opposite in polarity to the conveying belt 33 of the paper 15. The charge on the transport belt 33 and the charge on the transported paper 15 are electrostatically attracted to each other, and the paper 15 is electrostatically attracted to the transport belt 33. Is done. In this way, the sheet 15 strongly adsorbed to the transport belt 33 is calibrated for warpage and unevenness, and a highly flat surface is formed.

  Then, the paper 15 is moved around the conveyor belt 33 and droplets are ejected from the recording head 11, whereby a required color image is formed on the paper 15. The paper is discharged to the paper discharge tray 6 by 38.

  FIG. 6 is a block diagram showing a main system configuration of the ink jet recording apparatus according to the embodiment of the present invention. As shown in FIG. 6, reference numeral 50 is a control unit that is configured by a normal microcomputer system such as a CPU, a ROM, a RAM, and a timer, and controls the apparatus in an integrated manner. The control unit 50 includes an operation panel 51, a scanner 52, a paper feed unit 4, an image forming unit 2, a paper transport unit 5, a duplex unit 7, a humidity sensor 53, a storage device 54, a time calculation unit 55, and a tip detection unit 56. A test pattern generation unit 57, a dehumidifying means 58, a host computer 60, and the like are connected. The time calculation unit 55 and the test pattern generation unit 57 may be configured to be included in software or hardware of the control unit 50.

  The operation panel 51 displays the setting state of the operation unit and the device in which keys for initial setting by the user and keys for setting various modes are arranged, and the state of the device, and can be input by pressing in a predetermined mode. A panel for displaying soft keys is provided. The scanner 52 optically scans and reads a document image or a test pattern image to be formed. The humidity sensor 53 detects the temperature of the recording medium (paper 15) after printing. The storage device 54 is for setting a reference value for humidity according to the type (material, thickness, etc.) of the recording medium (paper 15). The time calculation unit 55 is for calculating the time until it is transported to the duplex unit 7. The leading edge detection unit 56 is provided in the conveyance path of the paper conveyance unit 5 and detects the leading edge of the recording medium (paper 15). For example, the test pattern generation unit 57 inputs an image pattern into the storage device 54 in advance, reads out the image pattern, and generates a predetermined image pattern to check the state of the device. The host computer 60 transmits image data to be printed to the apparatus.

  FIG. 7 is an explanatory diagram illustrating a printing state of the ink jet recording apparatus according to the embodiment of the present invention, in which the lower part represents a front view and the upper part represents a plan view. The left side of the drawing represents the state of paper conveyance during printing, and shows the arrangement of the paper conveyance unit 5, the recording head 11, and the humidity detection sensor 53. The right side of the figure shows a state in which the recording medium (paper 15) is reversed (switched back) by the duplex unit 7.

  The recording medium (paper 15) is transported in accordance with the rotation of the transport roller 31 while being attracted to the transport belt 33 of the paper transport unit 5. By changing the rotation direction of the transport roller 31, transport in the opposite direction can also be performed. As a method for attracting the recording medium to the conveyance belt, methods such as electrostatic adsorption and air adsorption are generally known.

  The duplex unit 7 includes a paper feed roller, a transport belt, and a belt transport roller, and reverses the front and back of the recording medium (paper 15) inserted in the duplex unit 7 and then transports it to the paper transport unit 5 side.

  Next, the operation of the ink jet recording apparatus according to the embodiment of the present invention will be described with reference to a flowchart. FIG. 15 is a flowchart showing an operation example (part 1) of the ink jet recording apparatus according to the embodiment of the present invention. This operation is executed by the control unit 50. First, as shown in FIG. 7, the recording medium (paper 15) is conveyed from the arrow A1 direction to the A2 direction while being attracted to the conveyance belt 33. An image is printed on the surface with ink ejected from the recording head 11 (step S1). After completion of image printing on the front surface (step S2), it is determined whether or not humidity control is to be performed (step S3). When humidity control is to be performed (Yes in step S3), the recording medium (paper 15) Is temporarily stopped at a position where the humidity sensor 53 can detect the surface humidity of the recording medium. Alternatively, a method may be considered in which the recording medium is transported in the reverse direction after passing too much and then stopped (step S4). An example of setting whether or not to execute humidity control will be described later with reference to FIG.

  Subsequently, the reference humidity corresponding to the recording medium (paper 15) is set in the storage device 54 (step S5). The reference humidity can be set at a stage where the recording medium (paper 15) is known (for example, on a predetermined display panel of the operation panel 51 or input from the host computer 60). It can also be performed when the operation is initialized or before printing is started. Thereafter, the humidity of the surface of the recording medium (paper 15) is detected by the humidity sensor 53 (step S6). Subsequently, the detected humidity is compared with the preset reference humidity (step S7). If the humidity detection data is larger than the reference humidity as a result of comparison (No in step S7), the humidity detection operation (step S6) and the humidity comparison operation (step S7) are continued after stopping for a certain period of time. If the humidity detection data is smaller than the reference humidity (Yes in Step S7), the conveyance of the recording medium is resumed in the direction of the arrow A3 (Step S8), and the recording medium (paper 15) is transferred to the duplex unit 7. ). The temporary stop of the sheet conveyance (step S4) is also for ensuring a natural drying time of the sheet and performing more accurate humidity detection.

  The recording medium (sheet 15) inserted into the duplex unit 7 is reversed inside and out along the sheet reversing path in the direction of arrow A4, and is output to the sheet conveying section 5 (step S9). At this time, the conveyance belt 33 moves in the direction opposite to that during front surface printing, and the recording medium is conveyed in the direction of the arrow A1. Further, the image is printed at the timing when the recording medium is conveyed in the direction of arrow A2 and the back surface of the recording medium reaches just below the recording head 11 (step S10).

  If humidity control is not performed (No in step S3), the recording medium (paper 15) is sent to the duplex unit 7 without stopping conveyance and the front and back are reversed (step S9). Then, back side printing is performed (step S10).

  Here, the reading of the humidity detection data (step S6) can be performed at an arbitrary position such as the front end, the center, or the rear end of the recording medium (paper 15). For example, if humidity detection can be performed on a portion where the printed image has a high surplus rate, more accurate humidity detection is possible.

  As described above, according to the operation example shown in FIG. 15, it is possible to wait until the surface of the printed recording medium reaches a dry level that does not cause a problem even if it is transported. Even if they are in close contact with each other, deterioration such as blurring of the image does not occur. In addition, it is possible to prevent image deterioration due to adhesion of ink in the middle of fixing to a roller or belt during conveyance and further secondary transfer to another recording medium. Further, since no dehumidifying device is required, image quality can be ensured at low cost.

  The reason why the reference humidity is set according to the recording medium (paper 15) is that the degree of the humidity of the paper varies depending on the thickness and material. That is, when the recording medium is easily affected by humidity, the reference humidity is set high. When the recording medium is not easily affected by humidity, the reference humidity is set low.

  Although several humidity sensors 58 are conceivable, a heat conduction type semiconductor absolute humidity sensor is more suitable, for example, as in the technology disclosed in Japanese Patent No. 3722453. A sensor that uses two sensors as a set and heats a heater as a heat source can be used as an absolute humidity sensor, and a sensor that does not heat a heater can be used as a temperature sensor. Moreover, relative humidity can be uniquely determined from the relationship between absolute humidity and temperature. Usually, it is considered that a better correlation can be obtained by using relative humidity, but a more appropriate one may be used according to actual measurement results.

  Further, the installation position of the humidity sensor 53 is not limited to the example of FIG. 7, but may be disposed on the opposite side across the recording head 11 as shown in FIG. By arranging the humidity sensor 53 at the position shown in FIG. 8, it is possible to secure a long time from printing to humidity detection, and to shorten the pause time associated with humidity detection. The paper transport direction during printing is not limited to the example shown in FIG. For example, as shown in FIG. 8, a method of starting the front surface conveyance from the direction of the arrow A5, starting the back surface conveyance from the direction of the arrow A8 through the double-sided conveyance function, and in this case, the conveyance distance is shorter than that in FIG. Therefore, high-speed printing is possible.

  In the example of FIGS. 7 and 8, when the reference humidity is not reached, it is paused and naturally dried. However, when it is desired to dry faster, the dehumidifying means 58 is used as an auxiliary device (see FIG. 9). . Specifically, the relative humidity is reduced by heating the recording medium (paper 15) and exhausting the internal atmosphere. In FIG. 9, the dehumidifying means 58 is added to the paper transport unit 5 of FIG. 7, but the installation location is not limited because it differs depending on the configuration of the apparatus.

  Here, if humidity is detected at a plurality of locations while the recording medium (paper 15) is being conveyed, the humidity of the surface after printing can be more accurately observed. For example, in FIG. 10, the humidity in the front end side region (FIG. 10A) of the recording medium is first, then the intermediate region (FIG. 10B), and finally the rear end side region (FIG. 10C). Are sequentially observed, and after confirming that all the parts are within the reference humidity, a state of conveying to the duplex unit 7 is shown.

  The overall control can be realized by replacing steps S6 and S7 in FIG. 15 with the flowchart in FIG. In FIG. 16, a case where N = 3 will be described. N represents the number of humidity detection points of each recording medium, and a predetermined value is set in advance (step S11 in FIG. 16).

  When the humidity control is performed (Yes in step S3), first, the conveyance of the recording medium is stopped in accordance with the printed portion of the leading end portion of the paper 15 (step S4). Thereafter, a reference humidity corresponding to the material and thickness of the recording medium is set in the storage means (step S5), and humidity detection data is read (step S12). If the humidity measured at this position is higher than the reference humidity (No in step S13), the image near the print surface may be deteriorated if it directly touches the transport mechanism. Return and wait because the humidity is lower than the standard. When the humidity is lower than the reference humidity (Yes in step S13), the N value is subtracted (step S14), and the sheet is conveyed by a preset length W. W needs to be determined by the length L in the sheet conveyance direction and the number N of humidity detection points. The following relational expression holds between the three parties. L> N × W (see FIG. 10).

  Until N = 0, the flow of (Step S12) to (Step S16) is repeatedly executed. When N = 0, the humidity detection is finished, and the processing from FIG. 15 (Step S8) is performed. . Note that the number of humidity detection points may be less or more than three. In addition, the intervals between the detection areas may be uniform or non-uniform. As an example of non-uniform detection, there may be a case where control is performed so as to detect an area having a large image print area. In this case, there is an advantage that detection accuracy is improved.

  When the main scanning direction (perpendicular to the transport direction) is wide, there is a possibility that accurate humidity detection cannot be performed with only one humidity sensor 53. As a countermeasure, it is effective to equip a plurality of humidity sensors (53a, 53b, 53c) in the main scanning direction as shown in FIG.

  The overall control in this case can be realized by replacing step S6 in FIG. 15 with the flowchart in FIG. When the humidity detection operation is performed (step S31) and the humidity control is performed (Yes in step S3), the humidity sensor (53a, 53b, 53c) individually reads the detection data Da, Db, Dc (step S32), Is adopted as humidity detection data at the transport position (step S33). By measuring such a wide area and adopting the maximum value, it is possible to perform accurate humidity control.

  Further, if a plurality of locations on the recording medium are measured while shifting the transport position, a wider area can be observed, so that more accurate humidity detection and humidity control can be performed. The flowchart is shown in FIG. The entire control flow can be realized by replacing steps S6 and S7 in FIG. 15 with the flowchart in FIG.

  As a method of processing a plurality of humidity detection data obtained simultaneously with the above configuration, there is a method of adopting the average value. This method has an advantage that stable control can be performed by reducing the influence of noise and the like. The flowchart is shown in FIG. The entire flowchart can be realized by replacing step S6 in FIG. 15 with the flowchart in FIG. Further, FIG. 20 shows a flowchart for measuring a plurality of locations on the recording medium while shifting the transport position. The entire flowchart can be realized by replacing steps S6 and S7 in the flowchart of FIG. 15 with the flowchart of FIG. This has the effect of preventing erroneous detection due to noise.

  As a configuration example in which a plurality of humidity sensors 53 are arranged, there is a method of arranging a plurality of humidity sensors 53 only in the transport direction (see FIG. 12). In this configuration example, the recording head 11 is disposed at two positions near the duplex unit 7 to read the humidity at substantially the same position of the recording medium (paper 15). As a result, humidity data at a timing closer to when the recording surface is actually in close contact with the paper conveyance unit 5 can be obtained, so that accurate conveyance control is possible. Moreover, the approximate drying time can be predicted by taking a record of changes in humidity with time and calculating the degree of change. Furthermore, the detection accuracy can be further improved by providing a plurality of humidity sensors 53 in the main scanning direction (see FIG. 14).

  When the humidity sensor 53 is arranged on a plurality of conveyance routes, it is necessary to detect the same area of the recording medium at each location. Although it is possible to calculate the transport amount from a transport route that is known in advance, there may be a slight positional shift due to slipping of the paper 15 or the like. Therefore, a front end detection unit 56 that detects the front end position of the paper 15 is disposed near the humidity sensor 53 (see FIG. 13) so that the same position can always be detected. Thereby, highly accurate humidity detection becomes possible.

  In the above-described example, the temporary stop time in the transport direction for drying the recording medium is calculated for each printing on the recording medium by reading the humidity with the humidity sensor 53. The humidity detection operation can be simplified or deleted according to the environment and the original to be used. FIG. 21 is a flowchart illustrating an example of an operation for detecting and storing the stop time. First, printing of print data transmitted from the host computer 60 is started, or printing of a document read by the scanner 52 is started (step S71), and after finishing (step S72), paper conveyance is stopped (step S73). Thereafter, the reference humidity corresponding to the recording medium is set in the storage device 54 (step S74), and humidity detection is started (step S75). If the humidity detection data is larger than the reference humidity (No in step S76), the humidity detection is continued. If the humidity detection data becomes smaller than the reference humidity (Yes in step S76), the automatic stop time Ts of the recording medium is set to, for example, the storage device 54. (Step S77), and then the conveyance of the sheet 15 is stopped (step S78), the sheet 15 is discharged, and the operation is terminated.

  Next, FIG. 22 shows a flowchart for printing using the automatic stop time Ts stored in the previous section. When the humidity control is performed after the printing is finished (step S82) (YES in step S83), after the sheet conveyance is stopped (step S84), the control using the Ts time is performed (YES in step S85). Stops for Ts time (step S89) and resumes conveyance (step S90). When the humidity control is not performed (NO in step S83), the reference humidity corresponding to the recording medium is set in the storage device 54 (step S86), and the control after the humidity detection (step S87) is performed.

  Here, with reference to FIG. 23, a setting example of whether or not to execute humidity control will be described. As shown in FIG. 23, a selection button 51b is provided on the operation panel 51, and a humidity control selection screen is displayed on the panel unit 51a by pressing this selection button 51b. Select ON / OFF of the soft key on this humidity control selection screen. After the humidity control is turned on, after selecting the type of recording medium such as plain paper, cardboard / coated paper, thin paper, and film, the OK button is touch-inputted. In addition, this setting example is an example and is not limited to this.

  Therefore, according to the embodiment described above, since the humidity of the surface of the recording medium after printing is detected and inserted into the duplex unit 7 after the printing surface is dry, high-quality image quality without blurring. Is obtained. In addition, since there is no possibility that the printed ink adheres to the roller of the duplex unit 7 or the like, it is possible to prevent secondary image quality deterioration and internal deterioration of the apparatus. In addition, since the humidity according to the recording medium is used as a criterion, accurate conveyance control is possible. Furthermore, since a high-speed, high-sensitivity and small heat conduction microsensor is used as the humidity sensor 53, the accuracy of humidity detection can be increased.

  Further, when the humidity sensor 53 is controlled by a single unit, the humidity sensor 53 and its detection locations are small, so that the apparatus configuration and control operation are simplified, and the apparatus can be realized at low cost. Further, by performing humidity detection at a plurality of locations while conveying the recording medium with a single humidity sensor 53, the humidity detection is performed a plurality of times, so that improvement in detection accuracy can be expected.

  In addition, by disposing the dehumidifying means 58 inside the housing, the waiting time for conveyance can be shortened. By arranging the humidity sensors 53 at a plurality of locations, improvement in detection accuracy can be expected. By increasing the humidity detection area in the main scanning direction, further improvement in detection accuracy can be expected.

  Further, the detection accuracy can be further improved by expanding the humidity detection area in the transport direction in addition to the main scanning direction. In addition, by arranging a plurality of humidity sensors 53 in the conveyance direction of the recording medium, it becomes possible to grasp a change in humidity, and an improvement in detection detection accuracy can be expected.

  Further, by providing a plurality of humidity sensors 53 in the main scanning direction, further improvement in detection detection accuracy can be expected. Further, by providing the leading edge detection unit 56 of the recording medium, it is possible to detect the humidity of the same area humidity of the recording medium with the humidity sensor 53 arranged at different positions of the transport position, and further detection detection Improvement in accuracy can be expected.

  Further, since the humidity of the recording medium can be detected when the read original is printed, the control accuracy can be improved by predicting the control of the transport system when printing a similar image. Further, since the humidity of the recording medium can be detected by printing an arbitrarily generated basic pattern, the control accuracy can be improved by predicting the control of the transport system during actual printing.

  As described above, the image forming apparatus according to the present invention is useful for an inkjet recording apparatus and the like, and is particularly suitable for an inkjet recording apparatus that performs double-sided printing using ink or the like.

It is explanatory drawing which shows the structure of the image forming apparatus concerning embodiment of this invention. FIG. 6 is an explanatory diagram illustrating a configuration example of a staggered recording head. FIG. 6 is an explanatory diagram illustrating a configuration example of an inclined recording head. It is explanatory drawing which shows the structural example (the 1) of another recording head. FIG. 10 is an explanatory diagram illustrating a configuration example (No. 2) of another recording head. 1 is a block diagram showing a main system configuration of an ink jet recording apparatus according to an embodiment of the present invention. It is explanatory drawing which shows the mode of printing of the inkjet recording device concerning embodiment of this invention, the lower part is a front view, and the upper part is a top view. It is explanatory drawing which shows the example which has arrange | positioned the humidity sensor in the position different from FIG. It is explanatory drawing which shows the example which has arrange | positioned the dehumidification means to the structure of FIG. It is explanatory drawing which shows the example which performs humidity detection, conveying a recording medium. It is explanatory drawing which shows the example which has arrange | positioned the humidity sensor in multiple places in the main scanning direction. It is explanatory drawing which shows the example which performs humidity detection of several places, conveying a recording medium. It is explanatory drawing which shows the example which has arrange | positioned the front-end | tip detection part in FIG. It is explanatory drawing which shows the example which has arrange | positioned the front-end | tip detection part in FIG. 4 is a flowchart illustrating a control example (No. 1) of the ink jet recording apparatus according to the embodiment of the present invention. It is a flowchart which shows the control example (the 2nd: detection of the maximum value of a conveyance direction) of the inkjet recording device concerning embodiment of this invention. 6 is a flowchart illustrating a control example (part 3: maximum value in the main scanning direction) of the ink jet recording apparatus according to the embodiment of the present invention. 6 is a flowchart illustrating a control example (No. 4: main scanning direction + maximum value in the transport direction) of the ink jet recording apparatus according to the embodiment of the present invention. It is a flowchart which shows the control example (the 5: average value of the main scanning direction) of the inkjet recording device concerning embodiment of this invention. It is a flowchart which shows the control example (the 6th: average value of the main scanning direction + conveyance direction) of the inkjet recording device concerning embodiment of this invention. It is a flowchart which shows the control example (the 7: detection of temporary stop time) of the inkjet recording device concerning embodiment of this invention. It is a flowchart which shows the control example (the 8: use of memorize | stored temporary stop time) of the inkjet recording device concerning embodiment of this invention. It is explanatory drawing which shows the example of the humidity control setting screen by the operation panel concerning embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Apparatus main body 2 Image formation part 4 Paper feed part 5 Paper conveyance part 7 Duplex unit 50 Control part 51 Operation panel 52 Scanner 53 Humidity sensor 54 Storage device 55 Time calculation part 56 Tip detection part 57 Test pattern generation part 58 Dehumidification means

Claims (14)

After transporting the recording medium, forming an image on the surface of the recording medium, and forming an image on the surface, the back surface of the recording medium is transported by a double-sided transport unit to form an image on the back surface of the recording medium. An image forming apparatus,
Humidity detecting means for detecting the humidity of the recording medium after printing;
Storage means in which a value corresponding to a humidity serving as a reference according to the type of the recording medium is set in advance;
A control means for comparing the humidity of the recording medium detected by the humidity detection means with the set reference humidity, and for controlling the time until it is conveyed to the double-sided conveyance means according to the comparison result;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein one humidity detecting unit is arranged.   The image forming apparatus according to claim 2, wherein one humidity detection unit is arranged to perform humidity detection at a plurality of locations while conveying the recording medium.   The image forming apparatus according to claim 1, further comprising a dehumidifying unit inside the recording medium or the housing. Arranging a plurality of the humidity detecting means,
The image forming apparatus according to claim 1, wherein the control unit controls a time until it is transported to the double-sided transport unit using a plurality of humidity detection data. A plurality of the humidity detection means are arranged in the main scanning direction,
The image forming apparatus according to claim 5, wherein the control unit performs humidity detection at a plurality of locations at the same timing, and employs a higher humidity as a detection value. A plurality of the humidity detection means are arranged in the main scanning direction,
The image forming apparatus according to claim 5, wherein the control unit performs the same operation at a plurality of locations while conveying the recording medium, and adopts the higher humidity as the detection value. A plurality of the humidity detection means are arranged in the main scanning direction,
The image forming apparatus according to claim 5, wherein the control unit performs humidity detection at a plurality of locations at the same timing, and employs an average value thereof as a detection value. A plurality of the humidity detection means are arranged in the main scanning direction,
The image forming apparatus according to claim 5, wherein the control unit performs the same operation at a plurality of locations while conveying the recording medium, and employs an average value thereof as a detection value. A plurality of the humidity detecting means are arranged in the recording medium conveyance direction,
The image forming apparatus according to claim 5, wherein the control unit detects the humidity at the same location of the recording medium a plurality of times at intervals of time.   6. The image forming apparatus according to claim 5, wherein a plurality of humidity detecting units are arranged in the main scanning direction in addition to the recording medium conveyance direction.   The image forming apparatus according to claim 10, further comprising a leading edge detecting unit that detects a leading edge position of the recording medium to be conveyed.   Further, based on the original reading means, the storage means for reading the test chart by the original reading means and printing it on the recording medium, reading and storing the humidity data of the recording medium, and the storage data of the storage means, Time calculating means for calculating the time required for the test-printed recording medium to be conveyed to the double-sided conveying means, and the time until the recording medium is conveyed to the double-sided conveying means using the time calculated by the time calculating means The image forming apparatus according to claim 10, further comprising an adjusting unit that adjusts the angle.   Furthermore, the test print pattern generation means, the storage means for reading and storing the humidity data of the test-printed recording medium, and the recording medium that has been test-printed based on the storage data of the storage means is a double-side conveying means And a time calculating means for calculating a time required until the paper is conveyed to the double-sided conveying means using a time calculated by the time calculating means. The image forming apparatus according to claim 10, 11 or 12.

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