JP2644320B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an image forming apparatus such as a laser beam printer, and more particularly, to an image forming apparatus capable of smoothly conveying a transfer sheet on a supply path. Related to the device.

(Prior art)

In a general image forming apparatus, a transfer sheet such as a paper or a film supplied by a feed roller is transported one by one while being prevented from being double-fed by a separating roller, and the leading edge of the transferred transfer sheet is aligned by a registration roller. And sent out to the transfer section.

In this case, there is an image forming apparatus in which a feed roller for supplying a transfer sheet and the separating roller are simultaneously driven.

In such an image forming apparatus, in order to increase the processing speed as much as possible, it is necessary to reduce the gap of the transfer sheet downstream of the registration roller. In this case, since the supplied transfer sheet is temporarily stopped by the registration roller, the sheet interval at the upstream of the registration roller needs to be shortened by the stop time at the registration roller. Is a restriction condition. Therefore, in order to compensate for the loss time of the temporary stop at the registration roller, and to secure a necessary amount of sheet interval, the transport speed of the transfer sheet to the registration roller is adjusted by the subsequent registration roller. Speed, that is, higher than the speed at which image processing is performed by the transfer unit.

[Problems to be solved by the invention]

FIG. 3 shows a state of an example of the transfer sheet transfer near the separating roller in the above-described supply path.

As shown in (a) of this figure, the transfer sheet 51 is the same as the driven roller 52 in the driven state indicated by the dashed arrow X.
It is gripped by a friction roller 53 provided opposite to 52 and is conveyed by a resist roller 54 in a positively rotating state indicated by an arrow Y.

However, in the conventional image forming apparatus, in the above state,
When it is time to supply the next transfer sheet to be supplied,
At the same time as the rotation of the feed roller (not shown) starts, as shown in FIG. 3 (b), the separating roller 52, which rotates simultaneously with the feed roller, is switched from the driven state to the positively rotated state shown by arrow Z. At this time, as described above, the speed at which the separation roller 52 conveys the transfer sheet 51 is faster than the speed at which the registration roller 54 conveys, so that a large `` bending '' 55 occurs in the transfer sheet 51, and This causes the transfer sheet 51 to be jammed in this supply path.

In addition, as shown in FIG.
When the transfer sheet 51 is not gripped between the transfer roller 52 and the friction roller 53, the supply of the next transfer sheet is performed in exactly the same manner as described above, and the separation roller 52 is positively actuated as indicated by an arrow Z '. When the state was switched to the rotation state, the separating roller 52 was unnecessarily worn due to frictional resistance with the friction roller 53.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an image forming apparatus in which a transfer sheet is supplied without being clogged in a supply path, and wear of a separating roller can be prevented.

[Means for solving the problem]

In order to achieve the above object, the present invention relates to an image forming method in which a transfer sheet reaches a registration roller via a separation roller, and is fed toward the transfer section at a lower speed than the conveyance speed before reaching the registration roller by the registration roller. A switching means provided upstream of the separating roller for detecting the leading end of the transfer sheet supplied to the separating roller; and the separating roller being driven when the leading end of the transfer sheet is detected by the switch means. A first separating roller switching means for switching from the positive rotation state to a positive rotating state, and the transfer sheet is conveyed to the registration roller via the separation roller, and the separation roller is moved after the leading end of the transfer sheet is gripped by the registration roller. A second separating roller switching means for returning from the positive rotation state to the original driven state. It is configured as an image forming apparatus according to claim.

In the above configuration, since the driven state indicates a driven state by the transfer sheet, the stopped state is set when the transfer sheet is not sandwiched.

[Action]

Therefore, if this image forming apparatus is used, for example, based on a predetermined start operation such as pressing an image processing start switch,
A transfer sheet is sent via a separation roller and the like to the registration roller, and is provided upstream of the separation roller in a path where the transfer sheet is sent out toward the transfer unit by the registration roller at a lower speed than the conveyance speed before reaching the registration roller. The leading end of the transfer sheet supplied to the separating roller is detected by the provided switch means. Based on this detection signal, the separating roller is switched from the driven state to the positively rotating state by the first separating roller switching means, and the transfer sheet is conveyed to the registration roller through the separating roller.

Therefore, the separating roller is driven only when the transfer sheet is fed, so that the roller is not wasted.

Then, after the leading end of the transfer sheet is gripped by the registration roller, the second separation roller switching unit is driven, and the separation roller is returned from the positive rotation state to the original driven state.

Therefore, "bending" of the transfer sheet due to the difference in the transport speed between the registration roller and the separating roller is prevented.

Therefore, the transfer sheet is fed smoothly, and the transfer sheet is not jammed.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.

FIG. 1 is a schematic vertical sectional view of an image forming apparatus according to one embodiment of the present invention, and FIG. 2 is a flowchart showing an example of a transfer sheet conveying process in the image forming apparatus.

After a transfer sheet (not shown) is set in the cassette (upper stage) 2 or the cassette (lower stage) 3 of the image forming apparatus 1 according to the embodiment of the present invention shown in FIG. 4 or 5 is positively driven to rotate as shown by the arrow _4x or _5x, and the supply of the transfer sheet is performed by the arrow.
Starts like _4y or _5y .

The cassettes 2 and 3 are usually arbitrarily selected depending on the size of the transfer sheet to be subjected to image processing.

The leading end of the transfer sheet supplied as described above is detected by a microswitch SW1, which is an example of a switch provided upstream of the separation roller 6, and the transfer sheet is separated by the separation roller based on a conveyance processing procedure described later. 6
And the photosensitive drum 8
Image processing is performed by the image forming unit 9 including

This figure shows an image forming portion 9 of the laser beam printer as an example, the laser beam path for image processing is schematically shown as arrows 9 _a.

Transfer sheet on which an image is processed as described above is discharged to the discharge unit 11 as indicated by an arrow 10 _x via the discharge roller 10 and the like.

The microswitch SW2 provided on the upstream side in the vicinity of the registration roller 7 is for determining the start of the timing for obtaining a slightly bent state in which the leading end of the transfer sheet being transported hits the registration roller 7.

Further, a micro switch SW3 provided in a transport path between the registration roller 7 and the photosensitive drum 8 is for giving a timing of starting image processing.

Next, an example of a transfer sheet transport processing procedure in the image forming apparatus 1 according to one embodiment of the present invention will be described in the order of steps S1, S2,... With reference to FIG.

An operator sets a transfer sheet for image processing in the cassette 2 or 3 and selects and specifies the size of the transfer sheet, and then turns on a predetermined start operation, for example, a print start switch (S1).

Then the feed roller 5 provided in the vicinity of, for example, the cassette 3 corresponding to the size of the transfer sheet that is the selected specified is driven positively rotated as indicated by arrow 5 _x, transfer sheet is indicated by the arrow 5 _y (S2).

The leading end of the supplied transfer sheet is detected by the aforementioned microswitch SW1 (S3).

The separating roller 6 based on the detection signal of the microswitch SW1 is switched from the driven state to actively rotating state indicated by arrow 6 _x, the tip of the transfer sheet is gripped between the separation roller 6 and the friction roller 6 _a , Conveyed (S
Four).

At this time, the separating roller 6 is connected to the friction roller _6a.
At the same time, the double feed generated when the transfer sheet is supplied by the feed roller 5 is damped, and the transfer sheet is separated into one sheet.

Therefore, since the separating roller 6 is driven only when the transfer sheet is fed, the roller is not wasted.

Means for realizing the function of switching the separation roller 6 from the driven state to the positive rotation state when the leading edge of the transfer sheet is detected by the microswitch SW1 is an example of the first separation roller switching means. Such switching of the rotation state is achieved by turning on / off a clutch interposed in the drive system of the separating roller 6 and the like.

As described above, when the leading end of the transfer sheet conveyed through the separation roller 6 is detected by the microswitch SW2 (S5), the timers 1 and 2 (not shown) are turned on (S6). Then, it notifies that the timer 1 has reached the predetermined time (S7).

The predetermined time is set to, for example, a time until the transfer sheet is conveyed to the registration roller 7 via the separation roller 6 and the leading end of the transfer sheet hits the registration roller 7 and is aligned and gripped. Then, after this predetermined time, the feed roller 5 and the separating roller 6 are returned from the positive rotation state to the original driven state (S8, S9).

Then, the timer 2 has reached the predetermined time (S10), the registration roller 7 is driven positively rotated as shown by arrow 7 _x,
The gripped transfer sheet is transported (S11).

Note that the transfer speed of the transfer sheet of the registration roller 7 at this time is lower than the transfer speed of the separating roller 6 and the feed roller 5 described above, but the separating roller 6 and the feed roller 5 are driven as described above. Since the state is switched to the state, no “bending” occurs between the registration roller 7 and the separation roller 6.

Therefore, the transfer sheet can be smoothly conveyed, and "clogging" of the transfer sheet in the supply path can be prevented.

The above-described transfer sheet is conveyed to the registration roller 7 via the separation roller 6, and after the leading end of the transfer sheet is gripped by the registration roller 7, the separation roller 6 is returned from the positive rotation state to the original driven state. Is an example of a second separating roller switching unit.

When the leading end of the transfer sheet conveyed by the registration roller 7 is detected by the micro switch SW3 (S12), the timer 3 is turned on and the time limit is started (S1).
3).

Then, the photosensitive drum 8 and the like are operated to perform predetermined image processing (S14), and the image-processed transfer sheet is discharged to the discharge unit 11. At this time, the registration roller 7 also stops.

The above is the processing relating to the first (or preceding) transfer sheet.

Next, when the timer 3 notifies the end of the above-described image processing (S15), unless a continuous print instruction is given by the operator (S16), a predetermined print end routine is performed (S17), and the image processing is performed. To end.

In step S16, if an instruction for continuous printing has been given, the process proceeds to step S18, and processing relating to the subsequent transfer sheet is executed. For example, when the lower paper feed mode is selected, the process proceeds to the next step S19.

In step S19, the presence or absence of the transfer sheet is detected by the microswitch SW4 provided in the transport path downstream of the feed roller 5. At this time, if the transfer sheet is not detected by SW4 (SW4 off), step S2
And the following steps S3,... Are executed.

If double transfer of the transfer sheet by the feed roller 5 has occurred and the transfer sheet in the transport path is detected by SW4 (SW4 ON), the next step S20
Move on to

In this step S20, the preceding transfer sheet is transferred to the microswitch SW2 provided upstream of the registration roller 7.
When the preceding transfer sheet passes the microswitch SW2 and there is no danger of double feeding, the feed roller 5 is turned on (S2).
1). Returning to step S3, the following steps S4,.

If the upper sheet feeding mode is selected in step S18, the process proceeds to step S22, and the presence or absence of the transfer sheet in the transport path is detected by the micro switch SW1.

At this time, if the transfer sheet in the transport path is detected by the switch SW1 due to the double feeding of the transfer sheet by the feed roller 4, the process proceeds to step S20, and the same processing is performed thereafter. You.

However, in this case, since the upper paper feed mode is selected, the transfer sheet of the cassette (upper) 2 is supplied by the feed roller 4 in step S21.

Further, since the distance between the microswitch SW1 for detecting the double feed and the outlet of the upper cassette 2 is considerably large, the following special processing is performed. On the other hand, even if the leading edge of the multi-fed transfer sheet protrudes from the outlet of the upper cassette 2 by a considerable amount, the transfer may not be detected by the microswitch SW1. Therefore, if the transfer sheet is not detected by SW1 in step S22, the transfer sheet of the cassette 2 is supplied by the feed roller 4 (S23), and at the same time, the timer 4 (not shown) starts the time limit (S24). ). If the length of the transfer sheet protruding from the outlet of the cassette is long, the transfer sheet supplied by the feed roller 4 within the predetermined time set by the timer 4 is detected by the microswitch SW1 (S25), (S26). ). The feeding of the transfer sheet is temporarily stopped (S27) to prevent the transfer sheet from overlapping with the preceding transfer sheet (S20, S21).

If the microswitch SW1 is turned on after the set time of the timer 4 in S25 and S26, that is, if the amount of protrusion of the multi-feed transfer sheet from the upper cassette is small (in the case of YES in step S26), it is left as it is. Since the transfer sheets do not overlap even if the sheet feeding is continued, the process proceeds to S4 with the feed roller 4 being rotated.

However, the micro switch SW1
Is set to be equal to or less than the maximum amount of protrusion of the transfer sheet from the cassette 2 that does not overlap with the preceding transfer sheet, the process proceeds to step S23, S24,. You may return to S2.

〔The invention's effect〕

According to the present invention, in the image forming apparatus in which the transfer sheet reaches the registration roller via the separation roller and is sent out by the registration roller toward the transfer unit at a lower speed than the conveyance speed before reaching the registration roller, the transfer sheet upstream of the separation roller A switch means for detecting a leading end of the transfer sheet supplied to the separating roller, and a first means for switching the separating roller from a driven state to a positive rotation state when the leading end of the transfer sheet is detected by the switch means. The transfer sheet is conveyed to the registration roller via the separation roller switching unit and the separation roller, and after the leading end of the transfer sheet is gripped by the registration roller, the separation roller is driven from the positive rotation state to the original rotation state. Image forming apparatus comprising: a second separating roller switching unit for returning to a state. Location is provided.

Therefore, the transfer sheet is supplied without being clogged in the supply path.

 Also, wear of the separating roller is prevented.

[Brief description of the drawings]

FIG. 1 is a schematic vertical sectional view of an image forming apparatus according to an embodiment of the present invention, FIG. 2 is a flowchart showing an example of a transfer sheet conveying process in the image forming apparatus, and FIGS. FIGS. 4B and 4C are schematic cross-sectional views illustrating an example of the vicinity of a separating roller in a transfer path of a transfer sheet. [Explanation of Reference Symbols] 1... Image forming apparatus 6... Separation roller 7... Registration roller SW1...

Claims (1)

(57) [Claims] 1. An image forming apparatus in which a transfer sheet reaches a registration roller via a separation roller, and is fed by the registration roller toward a transfer section at a lower speed than a conveyance speed before reaching the registration roller. A switch means for detecting a leading end of the transfer sheet supplied to the separating roller; and a switch means for switching the separating roller from a driven state to a positive rotation state when the leading end of the transfer sheet is detected by the switch means. (1) the separation roller switching means, the transfer sheet is conveyed to the registration roller via the separation roller, and after the leading end of the transfer sheet is gripped by the registration roller, the separation roller is moved from the positive rotation state to the original state. An image forming apparatus comprising: a second separating roller switching unit for returning to a driven state. Location.