JPH0524715A - Image forming device - Google Patents

Abstract

PURPOSE:To shorten sheet conveying time in an image forming device with a sheet conveying passage for automatic sheet feed and a sheet conveying passage for manual sheet feed. CONSTITUTION:First sensors 20 and 21 are provided near the junction point of a conveying passage for sheets automatically fed from a cassette 6 and a conveying passage for sheets manually fed from a manual feed tray 22, and second sensors 25 and 26 are provided on the down stream sides of the sensors 20 and 21 to switch automatic sheet feed mode and manual sheet feed mode by the first sensors 20 and 21 and to prefeed sheets by the second sensors 2 and 26. By this constitution, sheets can be on standby near a photosensitive drum 15, and sheet conveying time in printing can be shortened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a laser beam printer.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 21, there is an image forming apparatus capable of automatically feeding paper from a paper feed cassette 6 and manually feeding paper from a manual feed tray 22.

In this apparatus, in the case of automatic sheet feeding, the sheet P sent out from the sheet feeding cassette 6 by the sheet feeding roller 10 is conveyed by the conveying roller 11 along the guide G1, and the lower paper guide G2 and the upper paper guide G2. It is sent to the photosensitive drum 15 through G3.

In the case of manual feeding, the sheet P on the manual feeding tray 22 is guided by the conveying roller 11 to guide G2.
And G3, and is sent to the photosensitive drum 15. In addition,
Reference numerals 13a, 13b and 13c are rollers that are in pressure contact with the conveyance roller 11, and the sheet P is the conveyance roller 11 and the rollers 13a,
It is sandwiched between 3b and 13c and sent.

A sensor 20 is arranged at the confluence of the automatic paper feed transport path and the manual paper feed transport path.

In the case of automatic sheet feeding, the sensor 20 detects the sheet P sent from the sheet feeding cassette 6 and the photosensitive drum 15.
It has the function of adjusting the copy timing of the. Further, in the case of manual sheet feeding, when the sensor 20 detects the manual sheet P while the signal for automatic sheet feeding is not output, there is a function of switching from the automatic sheet feeding mode to the manual sheet feeding mode, and manually feeding the sheet. It also has a function of adjusting the copy timing of the sheet P and the photosensitive drum 15.

[0007]

In the above-mentioned prior art, both in the automatic paper feed mode and the manual paper feed mode,
When the sensor 20 detects the sheet P, the conveyance roller 11 is stopped and the conveyance is stopped. Then, the transfer timing with the photosensitive drum 15 is matched and the conveyance is started. For example, in a laser beam printer, a data signal sent from a host computer is expanded into an image signal by a signal expansion device, and a laser scanner unit outputs a laser beam based on this image signal to form an electrostatic latent image on a photosensitive drum. Then, the electrostatic latent image is developed to form a toner image, and the toner image is transferred to the sheet. Here, the sheet P sent out from the paper feed cassette 6 and the manually fed sheet P are detected by the sensor 20 and the conveyance is stopped, and the signal developing device completes developing the data signal into an image forming signal. I will be kept waiting until that position. for that reason,
If the distance from the standby position where the sheet is conveyed to the transfer position is long, the time is lost and the printing time is long. In particular, in copiers and printers, it is desired to shorten the image forming time, and it is important to shorten the sheet feeding time.

The present invention has been made in view of the above problems, and an object of the present invention is to reduce the conveying time with a simple structure in a sheet feeding apparatus having an automatic sheet feeding mode and a manual feeding mode. It is in.

[0009]

As means for solving the above problems, in an image forming apparatus having a conveyance path for automatic sheet feeding and a conveyance path for manual sheet feeding, a confluence section of the conveyance paths is provided. A first sensor is provided in the vicinity of the first sensor.
A second sensor is provided on the downstream side of the sensor for switching the automatic sheet feeding mode and the manual sheet feeding mode based on the sheet detection by the first sensor, and the sheet pre-processing based on the sheet detection by the second sensor. The control means for feeding is provided.

As another means, a first position and a second position downstream of the first position are provided in the vicinity of the confluence of the automatic paper feed transport path and the manual paper feed transport path. A sensor capable of detecting a sheet at two positions is provided, and switching between the automatic sheet feeding mode and the manual sheet feeding mode is performed based on the sheet detection at the first position, and based on the sheet detection at the second position. A control means for pre-feeding the sheet is provided.

[0011]

According to the former configuration, the first sensor switches the automatic sheet feeding mode and the manual sheet feeding mode, and at the same time, the sheet is conveyed until the second sensor detects it, and the photosensitive drum or the like is conveyed. Since the sheet can be pre-fed to the vicinity of the image forming unit, the sheet conveying time can be shortened.

Further, according to the latter configuration, one sensor can achieve the same operation as the above.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a first embodiment of the present invention will be described with reference to FIGS.

In FIG. 1 and FIG. 2, in the image forming apparatus 1
Is a signal development device 2 for developing a data signal sent from a host computer H outside the image forming device into an image signal, and a controller for controlling a laser beam L described later by the image signal sent from the signal development device 2. 3, a laser scanner unit 4 for irradiating the laser beam L, and a photosensitive drum 15 rotating in the arrow direction.

The data transmitted from the host computer H is converted into an image signal by the signal developing device 2, and the irradiation of the laser light L is controlled by the controller 3 to output the laser light L from the laser scanner 4. This laser light L is passed through the mirror 5 to the photosensitive drum 15
Then, an electrostatic latent image is formed on the photosensitive drum 15. A toner image is formed by developing the electrostatic latent image by the developing device 19, and the toner image is transferred to the conveyed sheet P by the transfer charger 16.

On the downstream side of the photosensitive drum 15, a pair of fixing rollers 17a and 17b for fixing the toner image and a pair of discharging rollers 18a and 18b for discharging the sheet P after fixing to the outside of the apparatus.
Etc. are arranged respectively.

On the upstream side of the photosensitive drum 15, there is a sheet feed cassette 6 including an intermediate plate 7, a compression spring 8 for urging the intermediate plate 7 upward, and a separation claw 9, and the inside of the sheet feed cassette 6 is also provided. A paper feed roller 10 is arranged above and has a role of sending out a sheet on the middle plate 7. Further, a conveyance roller 11 whose rotation is controlled by a clutch 12 is arranged near the downstream side of the intermediate plate 7, and the sheet P fed by the paper feed roller 10 is conveyed by the conveyance roller 11 and a roller 13a.
It is sandwiched between the rollers 13b and 13c and is conveyed to the photosensitive drum 15. Note that G1, G2, and G3 are guides.

Further, in addition to the paper feed from the cassette 6, there is a manual feed tray 22 for feeding one by one on the same plane as the paper lower guide G2, and between the manual feed tray 22 and the upper paper guide G3. When the sheet P is inserted into the sheet P, the sheet P is nipped between the conveyance roller 11 and the rollers 13b and 13c and conveyed to the photosensitive drum 15.

In the path along which the sheet P is conveyed to the photosensitive drum 15, the function of detecting the write start position timing when recording on the sheet P, and the detection of the insertion of the leading end of the sheet P are performed. There is a sensor arm 20 and a photo sensor 21 which also have a function of switching the mode from the automatic paper feed mode to the manual paper feed mode. Further, there are a pre-feed sensor arm 25 and a pre-feed photo sensor 26 for detecting the stop position in the recording preparation state. Detection signals from these sensors 21 and 26 are input to the control means C, and the control means C controls the clutch 12 connected to the conveyance roller 11 to thereby cause the sheet P
Are appropriately conveyed.

The operation of these sensors 21, 26 will be described.

When the sheet P is inserted into the manual paper feed port guided by the manual paper feed tray 22, the sensor arm 20 becomes
By rotating counterclockwise from the position shown in FIG. 7 to the position shown in FIG. 8, and the photo sensor 21 detecting it,
The paper feed mode is switched to the manual feed mode, and at the same time, the carry roller 11 rotates to start carrying the sheet P. The switching from the automatic paper feed mode to the manual paper feed mode is performed when the photo sensor 21 detects the manually fed sheet P while the instruction signal for performing the automatic paper feed mode is not output, and is determined to be the manual paper feed mode. . When the sheet P reaches the position shown in FIG. 9, the clutch 12 receives the signals detected by the pre-feed sensor arm 25 and the pre-feed photo sensor 26, and the clutch 12 temporarily stops the transmission of the drive to the conveying roller 11. In this state, the sheet P is kept on standby until the image signal development is completed. Hereinafter, temporarily stopping the conveyance of the sheet P at the position shown in FIG. 9 and waiting for the completion of the image signal development will be referred to as pre-feed. By performing the pre-feed, the fed sheet is not stored in the cassette 6 but the photosensitive drum 15
In addition, since it is possible to wait at a closer position, it is possible to save the time from the completion of the development of the image signal to the arrival at the photosensitive drum 15.

After the pre-feeding, when the development of the image signal is completed, the transmission of the drive to the conveying roller 11 is restarted again, and when the sensor arm 20 reaches the position shown in FIG. The sub-scanning synchronization signal is detected, and the laser light L is output at an appropriate timing.

Then, the toner image formed on the photosensitive drum 15 as described above is transferred to the sheet P by the transfer charger 16, and as described above, the fixing roller pair 17a,
After being fixed by 17b, it is discharged out of the apparatus by a pair of discharge rollers 18a and 18b.

When the sheet P is fed from the sheet feeding cassette 6, the feeding roller 11 is rotated at the same time as the sheet is fed, and thereafter, the pre-feed is performed at the position shown in FIG. 6, the sub-scanning synchronization signal is detected at the position shown in FIG. 6, the image is transferred by the photosensitive drum 15 and the transfer charger, and then fixed by the pair of fixing rollers 17a and 17b.
It is then discharged. It should be noted that in the case of paper feeding from the paper feeding cassette 6, no action occurs in FIGS.

(Other Embodiments) Next, a second embodiment of the present invention will be described with reference to FIGS. In addition,
The same members as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

In the path along which the sheet P is conveyed to the photosensitive drum 15, a function of detecting a sub-scanning synchronization signal when recording on the sheet P and the insertion of the leading end of the sheet P are detected, and the sheet feeding mode There is a sensor arm 20 which has a function of switching the automatic paper feed mode from the manual paper feed mode to a stop position detection of the recording preparation state of the paper P.

Here, the sensor arm 20 has a light shielding surface for shielding the photosensor 21, and a part thereof is cut out so that the part transmits light.

When the sheet P is fed from the sheet feeding cassette 6, the sensor arm 20 feeds the sheet and then the conveying roller 11
Thus, it is rotated counterclockwise from the position shown in FIG. When the sheet P is conveyed to the position shown in FIG. 14, the cutout portion on the light shielding surface of the sensor arm 20 passes through the photo sensor 21. Then, when the paper P is conveyed to the position shown in FIG. 15, the light shielding surface of the sensor arm 20 again becomes
The photo sensor 21 is blocked. Then, the clutch 12 is activated by the signal detected at this position, and the transport roller 1
Stop transmitting drive to 5. As a result, the sheet P remains stopped at that position until the development into the image signal is completed. Then, when the image signal development is completed, the clutch 12 starts transmitting the drive again, and the conveyance of the sheet P is restarted.

Then, when the sheet P is conveyed to the position shown in FIG. 16, the image writing position is detected. Then, the laser light L is received in response to the timing detected here.
Is irradiated at an appropriate timing. Sheet P is roller 13
After passing through c, since there are no rollers up to the photosensitive drum 15, it is possible to convey to the photosensitive drum 15 in a stable state without a rush shock to the roller.

In the case of manual feeding, the sheet P is inserted between the manual feeding tray 22 and the paper guide G3. When the paper P is fed, the sensor arm 20 rotates counterclockwise from the position shown in FIG. 17, and when reaching the position shown in FIG. 18, the cutout portion of the light shield plate of the sensor arm 20 has the photo sensor 21. Then, it is detected that the sheet P is fed from the manual feed tray 22. At this point, the paper feed mode is switched to the manual feed mode and the transport roller 11 rotates, so that the sheet P is transported to the transport roller 11, the rollers 13b, and the rollers 13.
It is sandwiched between c and conveyed. The sheet P is shown in FIG.
When the position 9 is reached, as in the case where the paper is fed from the paper feeding cassette 6, the paper feeding is stopped once at this position and the pre-feed state is set. At this position, the leading edge of the sheet P is located past the roller 13b, and the leading edge of the sheet P is sandwiched between the transport roller 11 and the roller 13b. It never falls. When the development of the image signal is completed, the transport roller 11
Is transmitted, and the conveyance of the sheet P is restarted. Then, similarly to the case of feeding the cassette, the sub scanning synchronization signal is detected at the position shown in FIG. 20, and the laser beam L is emitted at an appropriate timing.

Further, the sheet P passes through the guide plate G2 and the guide plate G3 as described above, and is conveyed to the photosensitive drum 15. Then, the toner image formed on the photosensitive drum 15 is transferred onto the sheet P by the transfer charger 16 and then conveyed along the paper conveyance guide G4, and as described above, the fixing device roller pair 17a, 17b. After being fixed, the sheet is discharged outside the apparatus by the pair of discharging rollers 18a and 18b.

As described above, according to each embodiment, there are the following unique effects. 1) By stopping the sensor arm at the position shown in FIGS. 9 and 19, the sheet P is pre-fed while the leading edge of the sheet P is nipped by the nip portion between the transport roller 11 and the roller 13b during manual feeding. It is possible, and the paper will not drop even if you take your hand off the paper. 2) By detecting the sub-scanning synchronization signal at a position past the roller 13c, which is the last on the upstream side of the photosensitive drum, after the detection of the sub-scanning synchronization signal, an error occurs due to a rush impact on a roller or the like. This can be avoided, and the adverse effect on the printing accuracy can be avoided. 3) In the second embodiment, the detecting means detects that the leading edge of the sheet has been inserted into the main body of the apparatus through the manual feed port, and switches the paper feed mode to the manual paper feed mode. By having a configuration in which one sensor has a function of detecting the stop position for stopping the sheet at a predetermined position in the ready state and a function of discharging the sub-scanning synchronization signal, space saving and cost reduction are achieved. It will be possible.

[0033]

As described above in detail, according to the present invention, in the sheet having the automatic sheet feeding mode and the manual sheet feeding mode, the sheet is pre-fed so that the conveying time can be shortened. It is possible to provide an image forming apparatus capable of achieving high speed image formation.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a main part on the upstream side of the photosensitive drum in FIG.

FIG. 3 is a diagram showing a state of a sensor in an automatic paper feed mode from a cassette.

FIG. 4 is a diagram showing a state of a sensor in an automatic paper feed mode from a cassette.

FIG. 5 is a diagram showing a state of a sensor in an automatic paper feed mode from a cassette.

FIG. 6 is a diagram showing a state of a sensor in an automatic paper feed mode from a cassette.

FIG. 7 is a diagram showing a state of a sensor in a manual paper feeding mode by manual feeding.

FIG. 8 is a diagram showing a state of a sensor in a manual paper feeding mode by manual feeding.

FIG. 9 is a diagram showing a state of a sensor in a manual paper feeding mode by manual feeding.

FIG. 10 is a diagram showing a state of a sensor in a manual paper feeding mode by manual feeding.

FIG. 11 is a vertical cross-sectional view of the image forming apparatus according to the second embodiment of the present invention.

12 is a perspective view showing a main part on the upstream side of the photosensitive drum in FIG.

FIG. 13 is a diagram showing a state of a sensor in a cassette automatic feed mode.

FIG. 14 is a diagram showing a state of a sensor in an automatic paper feed mode from a cassette.

FIG. 15 is a diagram showing a state of a sensor in a cassette automatic feed mode.

FIG. 16 is a diagram showing a state of a sensor in a cassette automatic feed mode.

FIG. 17 is a diagram showing a state of a sensor in a manual paper feeding mode for manual feeding.

FIG. 18 is a diagram showing a state of a sensor in a manual paper feeding mode by manual feeding.

FIG. 19 is a diagram showing a state of a sensor in a manual paper feed mode by manual feeding.

FIG. 20 is a view showing a state of a sensor in a manual paper feed mode for manual feeding.

FIG. 21 is a vertical sectional view showing an example of a conventional image forming apparatus.

[Explanation of symbols]

6 cassettes 10 Paper feed roller 11 Conveyor roller 20 sensor arms 21 Photo sensor 22 Bypass tray 25 Pre-feed sensor arm 26 Pre-feed photo sensor

Claims (3)

[Claims] 1. A conveyance path for automatic sheet feeding and a conveyance path for manual sheet feeding, wherein a first sensor is provided in the vicinity of a junction of the conveyance path, and a downstream side of the first sensor is provided. Is provided with a second sensor, and the automatic paper feed mode and the manual paper feed mode are switched based on the sheet detection of the first sensor.
Further, the image forming apparatus is provided with a control means for pre-feeding the sheet based on the sheet detection by the second sensor. 2. The control means, in the case of automatic paper feeding,
When the second sensor detects the sheet, the conveyance unit that conveys the sheet is stopped, and in the case of manual sheet feeding, when the first sensor detects the sheet, the conveyance unit conveys the sheet and the sheet is conveyed. The image forming apparatus according to claim 1, wherein when the second sheet is detected by the second sensor, the conveying unit is stopped. 3. A transport path for automatic sheet feeding and a transport path for manual sheet feeding, wherein a first position and a first downstream side of the first position are provided in the vicinity of a joining portion of the transport path. A sensor capable of detecting a sheet is provided at two positions, that is, the second position, and the automatic paper feed mode and the manual paper feed mode are switched based on the detection of the sheet at the first position by the sensor, and The image forming apparatus is provided with a control unit that pre-feeds the sheet based on the sheet detection at the position.