JPH11223969A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an image by reducing such a state that front and behind sheets on which the image is formed and which are being carried are superposed and accurately carrying the sheet on which the image is formed in prescribed image forming timing even when a carrying interval between the sheets on which the image is formed is shortened. SOLUTION: A supply roll 51 is fitted to the plunger 53 of a solenoid unit 52 at the upper part of a housing tray 30 housing the plural sheets S so that the roll 51 can be,moved up and down. On the downstream side of the roll 51, a feeding roll 54 and a pre-feeding sensor 56 are disposed. Then, a carrying action is controlled based on time until the leading edge part of the sheet S is detected by the sensor 56 after the carrying action is started. When the leading edge part of the sheet S is detected earlier than expected, the driving timing of the roll 51 and the sensor 56 are delayed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus for forming an image by sending an image forming target sheet stored in a tray to an image forming section.

[0002]

2. Description of the Related Art In an image forming apparatus, when an image is continuously formed on a plurality of sheets, the sheets stored in a storage tray are sequentially sent out to an image forming section.
Then, an image is formed on the paper sequentially conveyed to the image forming unit.

In such an image forming process, there is a possibility that a sheet sent out next from an accommodation tray overlaps a sheet sent out next and a problem such as a paper jam occurs. As an apparatus for solving this problem, Japanese Patent Application Laid-Open No. 9-908 is disclosed.
No. 49 discloses an apparatus for preventing the sheets from being overlapped by feeding the next sheet with a large gap from the previous sheet.

Further, Japanese Patent Application Laid-Open No. 3-95043 discloses that
A method is disclosed in which the trailing end of a conveyed sheet is detected by a sensor, and the timing for feeding the next sheet is determined based on the detection result.

[0005]

However, Japanese Patent Application Laid-Open No. 9-9 / 1990
The apparatus disclosed in Japanese Patent Application Laid-Open No. 0849 has a disadvantage that the time required for image formation becomes longer because the interval between the conveyed sheets becomes wider.

In the method disclosed in Japanese Patent Application Laid-Open No. 3-95043, the paper feed timing of paper conveyed later is affected by the conveyance state of paper conveyed earlier, so that the paper feed timing varies. Sometimes. Therefore, it is unsuitable for color image formation, composite image formation, and the like that require paper to be sent to the image forming unit at a predetermined timing.

The present invention has been made in view of the above circumstances, and reduces the overlap of the image forming target sheets before and after being conveyed even when the conveying interval of the image forming target sheet is shortened. It is another object of the present invention to provide an image forming apparatus capable of forming an image by accurately conveying an image forming target sheet in accordance with a predetermined image forming timing.

[0008]

In order to solve the above-mentioned problems, an image forming apparatus according to the present invention comprises a tray capable of storing an image forming target sheet, and the image forming target sheet stored in the tray. Transport means for transporting the sheet in the transport direction, detecting means for detecting the leading end of the image forming target sheet downstream of the transport means in the transport direction, and detecting when the transport operation of the image forming target sheet is started. Control means for determining whether to delay the transport timing by the transport means based on the time until the leading end of the image forming target sheet is detected by the means, and controlling the transport means according to the determination result; An image forming unit configured to form an image on the image forming target sheet conveyed by the conveying unit.

In the image forming apparatus according to the present invention, the transport operation by the transport unit is delayed based on the time from the start of the transport operation by the transport unit to the detection of the leading end of the image forming target sheet by the detection unit. Can be. Thus, when the leading end of the image forming target sheet is detected earlier than the predetermined time, the conveying timing by the conveying unit can be delayed, and the conveying unit conveys the image forming target sheet earlier than expected. No more. Accordingly, when a plurality of image forming target sheets are sequentially sent to the image forming unit to form an image, even if the conveying interval of the image forming target sheet is shortened for speeding up the image forming process, the image forming target sheet is conveyed before. The problem that the image forming target sheet conveyed later overlaps the image forming target sheet is reduced.

Further, the control means can control the conveying means so that the sheet to be image-formed is conveyed at a predetermined timing by delaying the conveying operation by the conveying means. Therefore, it is also suitable as an apparatus for forming a color image or a composite image.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. A. Image Forming Section First, FIG. 1 is a diagram showing a configuration of an image forming apparatus according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a photosensitive drum as an image carrier. Around the photosensitive drum 1, a transfer belt 4 rotated by a charging corotron 2, a developing unit 3, and a plurality of rolls 4b in a direction indicated by an arrow in FIG. The photoreceptor drum 1 is rotated in the direction indicated by the arrow in FIG.
As a result, the surface of the photosensitive drum 1 is uniformly charged.

Thereafter, light from a mirror (not shown) of the image reading device, a latent image writing device, or the like is irradiated onto the photosensitive drum 1. As a result, a latent image corresponding to an image to be formed on a sheet S such as paper or an OHP sheet conveyed by a conveyance mechanism described later is written on the surface of the photosensitive drum 1. The toner supplied from the developing device 3 is electrostatically attached to the latent image to form a visible toner image, and the toner image is transferred onto the transfer belt 4.

The sheet S is transported between the transfer belt 4 and the transfer roll 4a by a transport mechanism described later. Then, the toner image on the transfer belt 4 is transferred to the sheet S by the electric field generated by the transfer roll 4a. Note that a broken line in FIG. 1 indicates a path along which the sheet S is conveyed.

Thereafter, the sheet S is conveyed to the heat fixing device 22. The heat fixing device 22 includes a heating roll 22a and a pressure roll 22b that are arranged substantially in parallel with each other, and the toner image is heated and pressed by passing the sheet S through a nip between the two. Is fixed on the sheet S. Downstream of the heat fixing device 22, a discharge tray 4 for extending the sheet S to the outside of the cabinet of the image forming apparatus.
Discharge rolls 46 for discharging to 5 are provided.

B. Sheet transport mechanism By the way, reference numerals 30, 31, 32, and 33 denote sheets S first.
1 shows a sheet storage tray for storing a sheet. From any one of the sheet storage trays 30, 31, 32, 33, the main transport path 3 is fed by a sheet feeder (first transport unit) 50.
4, the sheet S is pulled out. The main transport path 34 is provided with a plurality of pairs of transport rolls (second transport means) 35, a pair of pre-registration rolls 36, and a registration roll 37, which are used to transfer the sheet S to the transfer belt. It is transported toward a nip between the transfer roller 4 and the transfer roll 4a.

Reference numeral 38 denotes a manual feed tray extending outside the cabinet of the image forming apparatus. The sheet S is also introduced into the main transport path 34 from the manual feed tray 38 by a roll 38 a or the like, and is transported toward the registration roll 37.

Next, the sheet feeding device 50 will be described with reference to FIG. As shown in FIG.
A feeding roll 51 is disposed above the feeding roll 51. Above the feeding roll 51, a solenoid unit 52 is fixedly arranged. The center axis of the feeding roll 51 is rotatably supported by a plunger 53 of the solenoid unit 52, and the feeding roll 51 is driven by the plunger 53 in the vertical direction. When a sheet is conveyed, current is supplied to the solenoid unit 52 so that
Is moved downward to come into contact with the uppermost sheet S stored in the storage trays 30 to 33.
The sheet S is fed out in the transport direction, which is the left side in the drawing, by rotating the feeding roll 51 in a state of being in contact with the sheet S.

On the downstream side of the delivery roll 51 in the transport direction,
A feed roll 54 and a retard roll 55 are disposed, and the sheet S fed by the feed roll 51 is
Is transported toward a nip between the feed roll 54 and the retard roll 55.

The center axis of the feed roll 54 and the center axis of the feed roll 51 are linked by a gear (not shown) or the like, and the feed roll 54 is rotated by a motor 66 (see FIG. 3) described later. Accordingly, the feeding roll 51 is also rotated accordingly.

C. Control System Next, a control system of the above-described sheet transport mechanism will be described with reference to FIG. As shown in the figure, the control system includes a pre-feed sensor (detection unit) 56, a feed-out sensor (second detection unit) 61, a control unit (control unit) 60, and an operation panel (size detection unit). ) 6
And 5.

As shown in FIG. 2, the pre-feed sensor 5
Reference numeral 6 is provided on the downstream side of the feed roll 54 in the transport direction. The pre-feed sensor 56 detects the presence or absence of the sheet S below the pre-feed sensor 56, and outputs the detection result to the control unit 60 shown in FIG.

The feed-out sensor 61 is disposed near the transport roll 35 shown in FIG. 2, and detects the presence or absence of the sheet S between the paired transport rolls 35, that is, the transport of the sheet S by the transport roll 35. It detects whether or not it can be performed, and outputs the detection result to the control unit 60.

The control unit 60 includes a CPU (central processing unit) 6
2, a ROM (read only memory) 63 in which basic programs and the like necessary for sheet conveyance control are stored, and a RAM (random access memory) 6 for taking in detection results of the pre-feed sensor 56 and the feed-out sensor 61 and the like.
And 4. The control unit 60 controls the solenoid unit 52, the motor 66, and the motor 67 based on the sheet size information input by the user via the operation panel 65 and the detection results of the pre-feed sensor 56 and the feed-out sensor 61. Control. Here, the motor 66
Drives the feeding roll 51 and the feed roll 54,
The motor 67 drives the transport roll 35.

D. Operation and Effect of Sheet Conveying Mechanism FIG. 4 illustrates a case where a plurality of sheets S stored in any of the storage trays 30 to 33 are sequentially conveyed in accordance with the image forming timing in the image forming unit, that is, an ideal sheet. The relationship between the position of the leading edge and the trailing edge of the sheet S when the sheet is conveyed and the time are shown, where A is the leading edge of the previously sent sheet, B is the trailing edge of the sheet, and C is the trailing edge. The leading edge D of the fed sheet indicates the relationship between the position of the trailing edge of the sheet and time.

In order to feed the succeeding sheet to the image forming section without delaying to the timings shown by the solid lines C and D in FIG. 4, the leading end of the succeeding sheet has a stable conveying force by the time point b. It is necessary to reach the position of the transport roll 35. For this reason, in this image forming apparatus, the feeding roll 5
In consideration of the delay due to the transport error 1 and the like, the subsequent sheet transport operation is performed at a time point a ₁ earlier than the transport start timing a ′ when there is no transport loss of the feeding roll 51 and the like indicated by the broken line in the figure. Has started.

In order to start the transport operation at a timing t ₁ earlier as described above, in order to reduce the image forming time,
Since it is necessary to shorten the transport interval (time) of the preceding and following sheets, the time t ₂ from the transport timing of the rear end of the previously fed sheet to the transport start timing of the subsequent sheet.
Becomes shorter. If the t ₂ is shortened, after the sheet there is a high possibility that overlaps the previous sheet.

Therefore, in the image forming apparatus according to the present embodiment, the sheet conveying speed in the vicinity of the feeding roll 51 is set higher than the sheet conveying speed in the image forming section.
The sheet conveyance interval (distance) in the vicinity of the feeding roll 51 is increased to reduce the possibility that the front and rear sheets overlap. Also, in order to shorten the sheet conveyance interval (time) to shorten the image forming time and to reduce the overlap of the preceding and succeeding sheets, the second sheet in the case of performing the subsequent sheet, that is, the continuous image forming is performed. During the subsequent sheet conveyance, the sheet conveyance control according to the conveyance state is performed from the start of the feeding operation by the feeding roll 51 to the time when the sheet reaches the conveying roll 35. Hereinafter, control and operation of the sheet conveyance timing will be described.

As described above, in the image forming apparatus according to the present embodiment, the control unit 60 executes the processing shown in FIG. 5 based on the size of the conveyed sheet and the detection results of the pre-feed sensor 56 and the feed-out sensor 61. The solenoid unit 52 and the motors 66 and 67 are controlled according to the procedure.

As shown in FIG. 5, when the sheet conveying operation is started, first, in step S1, the control unit 60 determines that the sheet size input by the user via the operation panel 65 is equal to or smaller than a predetermined size. It is determined whether or not the sheet is conveyed, and the conveyance control is switched according to the size of the conveyed sheet (length in the conveyance direction). This is because the required sheet conveyance interval is different between the case where the sheet size is large and the case where the sheet size is small, and it is necessary to increase the conveyance interval when the sheet size is large. That is, in this image forming apparatus, it is possible to control the conveyance timing according to the size of the sheet conveyance interval.

If the sheet size confirmed in step S1 is larger than the predetermined size, the detection signal of the pre-feed sensor 56 is confirmed in step S2. here,
When the detection signal of the pre-feed sensor 56 is off, that is, when the sheet S has not reached the downstream side of the feed roll 54, the control of the mode M1 is performed.

FIG. 6 is a timing chart showing the operations of the pre-feed sensor 56, the feed-out sensor 61, the solenoid unit 52, and the motors 66 and 67 when the above-described mode M1 is controlled.
As shown in the figure, in the mode M1, the current supply to the solenoid unit 52 is started at the start of the conveyance, and the feeding roll 51 comes into contact with the sheet S stored in the storage tray.
At the same time, the feeding rolls 51 by the motors 66 and 67,
The feed roll 54 and the transport roll 35 are driven, and the feeding roll 51 performs a sheet feeding operation.

When the ON signal of the pre-feed sensor 56 is detected, that is, when it is confirmed that the leading end of the sheet S has reached the downstream side of the feed roll 54, the control unit 6
A value of 0 stops the supply of current to the solenoid unit 52, whereby the feeding roll 51 moves upward, and the sheet feeding operation by the feeding roll 51 ends.

If the ON signal of the pre-feed sensor 56 is not detected after the sheet feeding operation by the feeding roll 51 is performed, the current supply to the solenoid unit 52 is temporarily stopped as shown in FIG. Then, the current is supplied to the solenoid unit 52 again,
A sheet feeding operation by the feeding roll 51 is performed.
If the ON signal of the pre-feed sensor 56 is not detected within a predetermined time after performing the sheet feeding operation by the feeding roll 51, the control unit 60 causes a paper jam to occur on a display panel (not shown) or the like. Is displayed, and the user is notified to that effect.

After the sheet feeding operation by the feed roller 51 is completed, the sheet S is sent to the main transport path 34 by the feed roller 54. Then, as shown in FIGS. 6 and 7, an ON signal from the feed-out sensor 61 is detected, that is, the sheet S is positioned at the position of the transport roll 35.
When the leading end of the motor 66, 67 reaches the motor 66, 67
Is stopped, and the conveyance operation of the sheet S is stopped.

Thereafter, the motor 67 is driven again to rotate the transport roll 35. As a result, the sheet S is transported in the transport direction. In the present embodiment, the sheet S is conveyed in synchronization with the image forming timing in the image forming section shown in FIG. 4, that is, the conveying roll 35 is driven again at the time point b. Thus, the transport timing can be adjusted by the transport roll 35 having a more stable transport force than the feeding roll 51. Therefore, the sheet S can be accurately sent to the image forming unit at an optimal timing, and is suitable as an apparatus for performing color image formation, composite image formation, and the like.

On the other hand, if the detection signal of the pre-feed sensor 56 is turned on in step S2, that is, if the sheet S has reached the downstream side of the feed roll 54, the control unit 60
Controls the mode M2 shown in FIG.

In the mode M2, the pre-feed sensor 56 is turned on when the carrying operation is started. This is because when the feeding roll 51 feeds out the previous sheet in the conveying direction, a plurality of sheets may be fed out at the same time, and sheets other than the sheet conveyed toward the image forming unit by the conveying roll 35 or the like are pressed. This is a state remaining at the position of the feed sensor 56. In such a state, it is not necessary to newly feed out the sheet S from the storage trays 30, 31, 32, and 33.
No current is supplied to 2. Also, the feed roll 54
In addition, by making the drive start timing of the transport roll 35 later than in the case of the above-described mode M1, the possibility that the sheet S overlaps with the previously transported sheet is reduced.

Then, the sheet S is sent to the main conveyance path 34 in the same manner as in the case of the mode M1, and then conveyed at the image forming timing in the image forming section.

Returning to FIG. 5, if the sheet size confirmed in step S1 is smaller than or equal to the predetermined size, the detection signal of the pre-feed sensor 56 is confirmed in step S3. Here, the pre-feed sensor 56
Is OFF, that is, if the sheet S has not reached the downstream side of the feed roll 54, the process proceeds to step S4.
Then, a current is supplied to the solenoid unit 52, and the transport operation by the feeding roll 51 is started. Thereafter, when the ON signal of the pre-feed sensor 56 is detected within a predetermined time, the control of the mode M3 shown in FIG. 9 is performed.

In the mode M3, the control unit 60 stops the power supply to the solenoid unit 52 after detecting the ON signal of the pre-feed sensor 56. Thus, the sheet feeding operation by the feeding roll 51 ends. At the same time, the feed roll 54 also stops, and the sheet S is temporarily stopped. Thereafter, the feed roll 54 and the transport roll 35 are rotated by the motors 66 and 67, and the sheet S is transported in the transport direction. As described above, when the sheet size is small, that is, when the sheet conveyance interval is short, the sheet S is temporarily stopped after detecting the ON signal of the pre-feed sensor 56,
The possibility of overlapping the previous sheet is reduced.

Thereafter, when an ON signal from the feed-out sensor 61 is detected as in the case of the mode M1, the control unit 60 stops the feed roll 54 and the transport roll 35 to temporarily stop the transport operation of the sheet S. I do. Then, the transport roll 35 is driven again in accordance with the image forming timing in the image forming section, whereby the sheet S is transported again in the transport direction.

On the other hand, if the detection signal of the pre-feed sensor 56 is ON in step S3, that is, if the sheet S has reached the downstream side of the feed roll 54, the control of the mode M4 shown in FIG. 10 is performed.

In the mode M4, since the leading end of the sheet S to be conveyed at the start of the conveying operation has reached the downstream side of the feed roll 54, there is no need to perform the sheet feeding operation by the feeding roll 51, and the solenoid unit 52 No current is supplied. In addition, the drive timing of the feed roll 54 and the transport roll 35 is delayed to reduce the possibility of overlapping the previous sheet.

Thereafter, similarly to the mode M3, after the ON signal of the feed-out sensor 61 is detected, the feed roll 54 and the transport roll 35 are stopped. Then, the transport roll 35 is driven again in accordance with the image forming timing in the image forming section.

If the ON signal of the pre-feed sensor 56 is not detected within a predetermined time after the feeding operation by the feeding roll 51 in step S4, the control of the mode M5 shown in FIG. 11 is performed. . In the mode M5, the current supply to the solenoid unit 52 is temporarily stopped. Then, again, the solenoid unit 52
Current to the feed roll 5
4. The transport roll 35 is driven. As a result, the sheet feeding operation by the feeding roll 51 is performed again.

Thereafter, when the ON signal of the pre-feed sensor 56 is detected, the sheet S
4 and the conveyance roll 35 conveys in the conveyance direction. After detecting the ON signal of the feed-out sensor 61 as in the mode M3, the feed roll 54 and the transport roll 35 are stopped. Then, the transport roll 35 is driven again in accordance with the image forming timing in the image forming section.

On the other hand, the pre-feed sensor 5
When the ON signal of No. 6 is not detected, the control unit 60
The fact that a paper jam has occurred is displayed on a display panel (not shown) or the like, and the user is notified of the fact.

In the image forming apparatus according to this embodiment, like the transport operation shown in the modes M1 to M5,
Pre-feed sensor 5 from sheet size and conveyance start
The drive timing of the feeding roll 51, the feed roll 54, and the transport roll 35 can be delayed according to the time until the ON signal of No. 6 is detected. Therefore, even when the sheet conveyance interval is shortened, it is possible to reduce a possibility that a sheet conveyed later overlaps a sheet conveyed earlier.

E. Modification In the above-described embodiment, the control is performed based on the sheet size information input by the user via the operation panel 65. However, other information, such as a tray selected by the user or an image forming operation, may be performed. The sheet size may be detected from image size information or the like formed by the unit, and conveyance control may be performed based on the detected sheet size.

[0050]

As described above, according to the present invention,
Even when the conveying interval of the image forming target sheet is shortened to speed up the continuous image forming process, it is possible to reduce the overlap of the image forming target sheets before and after being conveyed. Further, an image forming target sheet can be conveyed with high accuracy in accordance with a predetermined image forming timing to form an image, and is also suitable as an apparatus for performing color image formation or composite image formation.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a mechanical configuration of an image forming apparatus according to an embodiment of the present disclosure.

FIG. 2 is a diagram illustrating the vicinity of a sheet supply device of the image forming apparatus.

FIG. 3 is a block diagram illustrating a configuration of a control system of a sheet conveying mechanism in the image forming apparatus.

FIG. 4 is a diagram showing the relationship between the position of the leading end and the trailing end of the sheet and the time when the image forming apparatus conveys the sheet.

FIG. 5 is a flowchart illustrating a processing procedure when the control system conveys a sheet.

FIG. 6 is a timing chart illustrating operations of various elements related to sheet conveyance in the image forming apparatus.

FIG. 7 is a timing chart illustrating operations of various elements related to sheet conveyance in the image forming apparatus.

FIG. 8 is a timing chart illustrating operations of various elements related to sheet conveyance in the image forming apparatus.

FIG. 9 is a timing chart illustrating operations of various elements related to sheet conveyance in the image forming apparatus.

FIG. 10 is a timing chart illustrating operations of various elements related to sheet conveyance in the image forming apparatus.

FIG. 11 is a timing chart illustrating operations of various elements related to sheet conveyance in the image forming apparatus.

[Explanation of symbols]

S: sheet, 1: photosensitive drum, 4: transfer belt, 3
0.31, 32, 33: accommodation tray, 35: transport roll (second transport means), 50: sheet supply device (transport means), 51: feeding roll, 52: solenoid unit,
53: plunger, 54: feed roll, 55: retard roll, 56: pre-feed sensor (detection means),
Reference numeral 60: control unit (control means), 61: feed-out sensor (second detection means), 65: operation panel (size detection means), 66, 67: motor

Claims (7)

[Claims] A tray capable of accommodating the image forming target sheet; a conveying unit configured to convey the image forming target sheet accommodated in the tray in a conveying direction; and a downstream of the conveying unit in the conveying direction. Detecting means for detecting the leading edge of the image forming target sheet on the side, based on the time from when the conveying operation of the image forming target sheet starts to when the detecting means detects the leading edge of the image forming target sheet. A control unit that determines whether to delay the transport timing by the transport unit and controls the transport unit according to the determination result; and an image forming unit that forms an image on the image forming target sheet transported by the transport unit. An image forming apparatus comprising: a unit. 2. The method according to claim 1, wherein the detecting unit detects a leading end of the image forming target sheet before starting a conveying operation of the image forming target sheet stored in the tray.
The image forming apparatus according to claim 1, wherein the control unit delays a time at which the conveyance unit starts conveying the image forming target sheet. 3. The image forming apparatus according to claim 1, wherein a conveying speed of the image forming target sheet by the conveying unit is higher than a conveying speed of the image forming target sheet when the image forming unit forms an image. The image forming apparatus as described in the above. 4. A second conveying unit provided downstream of the conveying unit in the conveying direction and conveying the image forming target sheet conveyed by the conveying unit toward the image forming unit; And a second detecting means for detecting a leading end of the image forming target sheet at a position where the second conveying means is disposed, wherein the leading end of the image forming target sheet is detected by the second detecting means. In the case, the control means is configured to control the second
4. The method according to claim 1, further comprising, after temporarily stopping the conveying unit, conveying the image forming target sheet toward the image forming unit in accordance with a predetermined image forming timing in the image forming unit. An image forming apparatus according to any one of the above. 5. When the leading end of the image forming target sheet is not detected by the detecting means within a predetermined time from the start of conveyance of the image forming target sheet stored in the tray, the control is performed. The image forming apparatus according to claim 1, wherein the unit temporarily stops the conveyance unit and then drives the conveyance unit again. 6. A size detection unit for detecting a size of the image formation target sheet stored in the tray, wherein the control unit is configured to detect a size of the image formation target sheet detected by the size detection unit. The image forming apparatus according to any one of claims 1 to 5, wherein the conveying unit is controlled by a controller. 7. A feeding roll, which is provided above the tray and rotates while contacting the image forming target sheet to feed out the image forming target sheet in a conveying direction, and the feeding roll. A feed roll that is provided further downstream in the transport direction and that transports the image formation target sheet fed out by the feed roll in the transport direction, and the detection unit detects the image formation target sheet. The image forming apparatus according to claim 1, wherein when the leading end is detected, the control unit stops the feeding operation of the image forming target sheet by the feeding roll.