JPH0675218B2 - Laser printer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser printer, and more particularly to a laser printer in which a paper size error and a paper jam error are detected separately by the same paper sensor.

[Prior Art] Generally, in a laser printer, as shown in FIG. 10, the photosensitive drum 1 is charged along the circumference of the photosensitive drum 1 which is rotating at a constant speed by a main motor in a case, for example. Charging unit 2, exposure unit for scanning a laser beam corresponding to character data input from the outside in the axial direction of the photosensitive drum 1.
3, a developing unit 4 for developing an image formed on the photosensitive drum 1, a transfer unit 7 for transferring the developed image to a sheet 6 fed from a sheet feeding cassette 5 as a sheet feeding mechanism, and an image having been transferred A charge eliminating unit 8 for erasing is removed. Further, at the bottom of the case, the paper feed cassette 5, a paper feed roller 9 for pulling out the paper 6 from the paper feed cassette 5, a paper feed sensor 10 for detecting the paper 6 fed from the paper feed cassette 5, a transfer unit 7, a paper A fixing unit 11 for thermally fixing the image transferred onto the sheet 6, and a sheet discharge sensor 13 arranged near the sheet discharge port 12 of the case to detect that the sheet 6 is discharged from the sheet discharge port 12 are provided. There is. The path from the paper feed cassette 5 to the paper discharge port 12 serves as a paper transport path 14.

In the thus configured laser printer, the occurrence of paper jam in the paper transport path 14 is detected by the two paper sensors, the paper feed sensor 10 and the paper discharge sensor 11. That is, since the conveyance speed V of the paper 6 in the paper conveyance path 14 is constant, if the distance between the paper feed sensor 10 and the paper discharge sensor 13 is L, the paper feed sensor 10 detects the leading edge of the paper 6. The required time Tc between the sensors until the discharge sensor 13 detects the leading edge of the paper 6 after that becomes a constant value (Tc = L / V). If the leading edge of the paper does not reach the paper discharge sensor 13 even after the time Tc, it is determined that there is a paper jam, the printing operation is stopped, and the paper jam indicator lamp that urges the removal work of the paper jam is turned on. At the same time, it sends a paper jam error signal to the host computer.

Further, generally, a plurality of types of paper feed cassettes 5 are prepared for each paper size, and the paper feed cassette 5 corresponding to the paper size is prepared.
I am trying to wear. Then, make sure that the paper size specified by the host computer is correct in the paper transport path.
The paper feed sensor 10 detects whether or not paper is fed to the paper 14.
That is, since the paper width of the designated paper size in the carrying direction is constant depending on the paper size, the paper detection time Tx in the paper feed sensor 10 is calculated from the length obtained by adding the minute distance ΔL including the error to the paper width and the carrying speed V. Is decided. Therefore, the paper detection time of the paper feed sensor 10 is the designated paper detection time Tx.
When it exceeds the value, it is determined that a paper jam has occurred near the paper feed sensor 10, and the paper jam error processing similar to that described above is executed.

[Problems to be Solved by the Invention] However, the laser printer configured to detect a paper jam according to the above-described procedure still has the following problems to be solved.

That is, if the paper detection time from the detection of the leading edge of the paper 6 to the detection of the trailing edge of the paper 6 exceeds the paper detection time Tx corresponding to the specified paper size, a paper jam error will occur unconditionally. Judgment was made and paper jam error processing was executed.
However, as described above, since the laser printer is configured so that the paper cassettes 5 having a plurality of paper sizes can be mounted, the paper cassette 5 having a paper size different from the paper size designated by the host computer is mounted. Or, when a plurality of types of paper feed cassettes 5 can be installed at the same time, an incorrect paper size may be selected by the operation button.

In such a case, if the actual paper size is larger than the designated paper size, the paper feed sensor 10 determines that there is a paper jam error, and the above-described predetermined paper jam error process accompanied by the stop of the printing operation is executed. Therefore, the operator opens the side cover of the laser printer and opens the paper feed path 14 near the paper feed sensor 10.
It is necessary to remove the inside paper 6. However, in this case, since the paper is not actually jammed, the printing operation is continued as it is, the characters are printed on the papers of different paper sizes, and the paper 6 is ejected from the paper ejection port 12 to make the paper size correct. It is more efficient to print the same data again after setting.

That is, it is necessary to separately detect a paper jam error due to a true paper jam condition and a paper jam error caused by a paper size error.

The present invention can distinguish and detect a paper size error and a paper jam error by determining a paper jam error only when the paper detection time of the paper feed sensor exceeds the maximum paper detection time corresponding to the maximum paper size. An object of the present invention is to provide a laser printer which can reduce the number of jamming operations and improve operability.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a charging unit, an exposure unit, a developing unit, and a transfer unit along the circumference of a photosensitive drum,
The image formed by the exposure unit on the photosensitive surface of the photosensitive drum charged by the charging unit and developed by the developing unit is transferred to the paper fed from the paper feeding mechanism by the transfer unit, and this transfer unit In a laser printer that discharges the paper on which the image has been transferred to the outside through a fixing unit, the laser printer is installed in the paper transport path from the paper feed mechanism to the paper exit, and is transported at a constant speed through the paper transport path. Paper detection sensor that detects the amount of paper that is loaded, the paper detection time memory that stores the paper detection time for each paper detection sensor that can be set in the paper feed mechanism, and the specified paper size that is specified externally. And a paper size error determination means for determining a paper size error when the paper detection time of the paper feed sensor during printing operation is different from the detection time corresponding to the specified paper size. The paper size error output means that responds to the paper size error output, and the paper jam error that is judged only when the paper detection time of the paper feed sensor during printing exceeds the maximum paper detection time of the paper detection time memory. The determination means and the paper jam error processing means for executing a predetermined paper jam error processing including the stop of the printing operation in response to the paper jam error judgment are provided.

In addition, in another invention, in addition to the above means, if the paper detection time of the paper feed sensor during the printing operation is longer than the detection time corresponding to the specified paper size, the printing operation is continued as it is. .

In still another invention, in addition to the above-mentioned means,
When the paper detection time of the paper feed sensor during the printing operation is shorter than the detection time corresponding to the specified paper size, the predetermined paper size error processing including the exposure operation stop in the exposure unit is executed.

[Operation] With the laser printer configured as described above, a paper jam error is determined only when the actual paper detection time of the paper feed sensor exceeds the maximum paper detection time stored in the paper detection time memory. Executes paper jam error processing, including printing operation stop. If the actual paper detection time is different from the paper detection time corresponding to the specified designated paper size, it is determined as a paper size error, and the paper size error is output.

Then, the work of removing the jammed paper may be carried out only in the case of a jammed error.

According to another invention, in addition to the above operation, when a paper size larger than the designated paper size is set due to a paper size error, the printing operation is continued and the operator ejects the paper from the paper ejection port. Only one sheet of paper may be discarded and reprinted, or the periphery of the large printed paper may be cut off to fit the specified paper size.

In addition to the above-described operation, when the actual paper size is smaller than the specified paper size, when printing is performed on the small paper, the print data overflows the paper, and unnecessary toner has already been transferred. Since the photosensitive drum remains on the photosensitive drum and the deterioration of the photosensitive drum progresses, when the paper size error is detected, the paper size error process including the stop of the exposure operation in the exposure unit is executed.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a laser printer of the embodiment. The schematic sectional view of the laser printer is the same as that shown in FIG. In FIG. 1, via the bus line 16 to the CPU 15 that executes various information processing,
A ROM 17 for storing a control program, a RAM 18 for storing various variable data, an interface 20 for inputting print data from a host computer 19, and a paper feed sensor 10 for paper 6
2 that measures the elapsed time T after detecting the tip of the
1. The I / O port 22 and the like to which various components are connected are connected.

The I / O port 22 includes a main motor 23 that rotates the photosensitive drum 1, a charging unit 2, an exposure unit 3, a developing unit 4, a transfer unit 7, a charge eliminating unit 8, a paper feed roller 9, a fixing unit 11, and a feeding unit. Paper sensor 1
In addition to 0 and the paper discharge sensor 13, a paper jam indicator lamp 24 and a paper size error lamp 25 are connected.

FIG. 2 is a schematic diagram showing the exposure unit 3, in which the laser beam output from the laser diode 3a is a polygon mirror 3b.
And is scanned in the axial direction of the outer peripheral surface of the photosensitive drum 1 via the reflection mirror 3c. Then, the scanning start timing of the laser beam is detected by the scanning start sensor 3d. The output timing of the laser beam in the exposure unit 3 is executed by the optical system interrupt process shown in FIG. 3 by the scanning start sensor 3d. That is, when the scanning start sensor 3d detects a laser beam, the laser data (image data) obtained from the print data of the reception buffer 18f is output for one scan, and the scanning number S for one page is subtracted by one. When the number of scans S is reduced to 0, interruption is prohibited and laser data output is prohibited.

As shown in FIG. 4, in the RAM 18, a memory 18a for storing an exposure start time T1 from the time when the leading edge of the paper 6 reaches the paper feed sensor 10 to the exposure start time by the exposure unit 3, each paper feed A paper detection time memory 18b that stores each paper detection time Tx1 to Tx6 in the paper feed sensor 10 corresponding to each paper size set in the cassette 5, and a memory 18c that stores the inter-senna required time Tc shown in FIG. 5 described above. , A memory 18d that stores a paper ejection required time T2 from the paper leading edge detection time of the paper feeding sensor 10 to the paper end time of the paper ejection sensor 13, a paper size that stores a designated paper size input together with print data from the host computer 19 A memory 18e, a reception buffer 18f for storing print data input from the host computer 19, and the like are formed.

Exposure start time T1 of the memory 18a, as shown in FIG. 5, the distance L ₁ between the transfer position of the transfer portion 7 and the exposure position on the photosensitive drum 1, the transfer position and the sheet feeding sensor 10 Distance between
It is calculated from L ₂ and the moving speed V.

T1 = (L ₁ −L ₂ ) / V Furthermore, each paper detection time Tx1 to the paper detection time memory 18b
As shown in FIG. 6 and FIG. 7, Tx6 is each paper width L _{B5 to} L _{LG in} the transport direction of four kinds of paper sizes [B5] [LT] [A4] [LG] that can be used with this laser printer. The sheet detection times Tx2, Tx3, Tx4, Tx6 obtained by dividing the distance obtained by adding the minute distance ΔL for avoiding the error by the transport speed V are set. Further, the paper detection time corresponding to the distance obtained by subtracting the minute distance ΔL from the paper width L _{B5 of} the minimum paper size [B5].
Paper detection time Tx corresponding to the distance obtained by subtracting the minute distance ΔL from Tx1 and the paper width L _{LG of the} maximum paper size [LG]
5 is set. FIG. 7 shows each sheet [B5] -in the state where the elapsed time (timer value) T after the sheet feed sensor 10 detects the leading edge of the sheet reaches the sheet detection time Tx1 to Tx6.
It is a figure which shows the front-end | tip position of [LG].

Then, when the laser printer is turned on and the print data is input from the host computer 19, the CPU 15
Executes print processing according to the flowchart of FIG.

When the flow chart starts, the designated paper size sent from the host computer 19 is detected and stored in the paper size memory 18e of the RAM 18. Then, the main motor 23 of the photosensitive drum 1 and the motor of the paper feed roller 9 are activated. next,
When one sheet of paper 6 is pulled out from the paper feed cassette 5 and the leading edge of the paper 6 reaches the paper feed sensor 10, the paper feed sensor 10 is turned on. When the paper feed sensor 10 detects the leading edge of the paper, the timer 21 is started. When the timer value T of the timer 21 reaches the exposure disclosure time T1 of the memory 18a, the laser data scanning number S is set and the optical system interrupt is permitted. Then, the third
According to the procedure shown in the figure, the exposure unit 3 starts laser exposure of the print data.

Next, in P1 and P2, the designated paper size stored in the paper size memory 18e is checked, and the paper detection processing corresponding to the designated paper size is executed in P3 and P4. If the specified paper size is not [LT] in P2, the process unconditionally advances to P4 and the LG paper detection process is executed.

Now, if the specified paper size is [B5], the 9th at P3
The B5 sheet detection process shown in the figure is executed.

When the B5 paper detection processing of FIG. 9 is started, the timer value T of the timer 21 reaches the paper detection time Tx1 corresponding to a distance (L _B5 −ΔL) shorter than the paper width L _B of [B5] by a minute distance. After waiting for, check the state of the paper feed sensor 10 at P5. If the paper 6 is not detected in this state, [B
When it is judged that a small non-standard paper 6 of less than 5] has been set, the optical system interrupt in the exposure unit 3 is prohibited and the output of the laser data is stopped. Then, the paper size error signal is output to the host computer 19, and the paper size error lamp 25 is turned on. And memory 18
Set the paper ejection required time T2 of d to (Tc + Tx1). After that, the process returns to the print routine of FIG.

If the paper feed sensor 10 still detects the paper 6 at P5, the timer value T of the timer 21 corresponds to the distance (L _B5 + ΔL) obtained by adding the minute distance to the paper width of the specified paper size [B5]. Wait until the paper detection time Tx2 is reached. Then, the state of the paper feed sensor 10 is checked at P6. If the paper feed sensor 10 does not detect the paper 6, the paper 6 set in the paper feed cassette 5 matches the specified size, so the paper discharge required time T2 of the memory 18d is set to (Tc + Tx2). And
Return to FIG.

If the paper feed sensor 10 still detects the paper 6 in P6, the paper size of the paper 6 fed from the paper feed cassette 5 is larger than the specified paper size [B5], and therefore the paper size error signal is output. The paper size error lamp 25 is turned on while the data is sent to the host computer 19. Then, when the timer value T corresponds to the next paper size [LT], the paper detection time Tx3
Wait to reach.

If the paper feed sensor 10 does not detect the paper 6 in P7, the size of the fed paper 6 is [LT].
Set the paper discharge required time T2 of d to (Tc + Tx3). Then, returning to FIG.

If the paper feed sensor 10 still detects the paper 6 in P7,
Wait until the timer value T reaches the paper detection time Tx4 corresponding to the next paper size [A4]. Then, at P8, paper feed sensor 1
If 0 does not detect the paper 6, the paper size of the fed paper 6 is [A4], so the paper discharge required time T2 of the memory 18d is set to (Tc + Tx4). Then, returning to FIG.

If the paper feed sensor 10 still detects the paper 6 in P8,
Wait until the timer value T reaches the paper detection time Tx5 corresponding to a distance (L _LG −ΔL) that is a minute distance shorter than the maximum paper size [LG]. If the paper feed sensor 10 does not detect the paper 6 at P9, the paper discharge required time T2 of the memory 18d is set to (Tc + Tx5). Then, returning to FIG.

If the paper feed sensor 10 still detects paper 6 in P9,
Wait until the timer value T reaches the paper detection time Tx6 corresponding to the maximum paper size [LG]. Then, at P10, the paper feed sensor
If 10 does not detect the paper 6, the paper size of the fed paper 6 is [LG], so the paper discharge required time T2 is set to (Tc + Tx6). Then, returning to FIG.

If the paper feed sensor 10 still detects the paper 6 on P10,
When it is determined that a paper jam has occurred in the paper conveyance path 14 near the paper feed sensor 10, a paper jam error signal is sent to the host computer 19, and the paper jam indicator lamp 24 is turned on. Then, the main motor 3 is stopped and the laser data output in the exposure unit 3 is also stopped. Further, the timer value T of the timer 21 is cleared to end the flow chart, and the operator waits for the work of removing the jammed paper.

In FIG. 8, when the B5 sheet detection process in P3 is completed, the timer value T waits for the sensor-to-sensor required time Tc in P11, and the state of the sheet discharge sensor 13 is checked in P12. If the leading edge of the paper 6 has not reached the discharge sensor 13 yet, a paper jam has occurred in the transport path 14, and as a paper jam error, a paper jam error signal is sent, a paper jam display lamp is turned on, the main motor is stopped, and exposure is performed. Execute predetermined paper jam error processing such as stop.

When the paper ejection sensor 13 is in the paper detection state in P12, the timer value T is waited for reaching the paper ejection required time T2 of the memory 18d, and the status of the paper ejection sensor 13 is checked again in P13. If the paper discharge sensor 13 does not detect the paper 6, the paper 6 is normally discharged from the paper discharge port 12, so the main motor 23 is stopped, the timer value T is cleared, and this one The print output process for the paper 6 is completed.

If the paper discharge sensor 13 still detects the paper 6 at P13, it can be determined that the paper 6 is jammed at a position near the paper discharge sensor 13, so the paper jam error processing described above is performed. To execute.

It should be noted that although the sheet detection processing according to the sheet sizes of [LT], [A4], and [LG] other than [B4] is not shown, it is not shown in FIG.
Follow the paper detection process. That is, when the actual paper detection time in the paper feed sensor 10 is shorter than the paper detection time corresponding to the specified paper size, the paper size error process including the exposure stop of the exposure unit 3 is executed to execute the specified paper. If the size does not match and the size is larger than the specified paper size, the paper size error processing is not executed, and only the paper size error occurrence is displayed on the paper size error lamp 25. Then, the actual printing operation is continued.

With the laser printer configured as above, if the paper detection time of the paper 6 fed from the paper feed cassette 5 by the paper feed sensor 10 does not correspond to the paper size specified by the host computer 19, the paper size is determined. Is it an error,
It can be determined whether there is a paper jam error.

Therefore, only when the paper jam error is detected, the paper jam error process for stopping all the printing operations is executed, and the operator may perform the work for removing the jammed paper. Since the main motor does not stop when a paper size error is detected, the paper 6 is ejected from the paper outlet 12
Emitted from. Therefore, in the case of a paper size error, the operator does not have to remove the paper 6 stopped on the paper transport path 14 in the case.

As compared with the conventional laser printer, the number of operations for removing the paper in the case is reduced, so that the operability as the laser printer can be improved.

Further, when the paper cassette 5 having a paper size different from the paper size specified by the host computer 19 is mounted, the exposure unit 3 sets the paper size only when the paper size of the actually mounted paper cassette 5 is smaller than the specified paper size. The exposure operation for the photosensitive drum 1 is stopped. Therefore, it is possible to prevent a tomer image from being formed on the surface of the photosensitive drum 1 that does not contact the actual paper 6 in the transfer unit 7.
Further, it is possible to prevent a large amount of untransferred toner from adhering to the cleaner and the charge removing unit 8 arranged in the vicinity of the transfer unit 7.

If the actual paper size is larger than the specified paper size, the print data is printed as is on the large paper and discharged from the paper discharge port 12. Therefore, by cutting the periphery of the paper 6, the specified paper size is set. It can be used as it is.

When a paper size error occurs in this way, the corresponding paper is ejected from the paper ejection port 12 in a blank or printed state, and the operator only has to set the paper size correctly from the next one. Therefore, as compared with the conventional laser printer, the operation processing after the paper size error occurs is significantly simplified.

EFFECTS OF THE INVENTION As described above, in the laser printer of the present invention, a paper jam error is determined only when the paper detection time of the paper feed sensor exceeds the maximum paper detection time corresponding to the maximum paper size. Therefore, a paper size error and a paper jam error can be detected separately, the number of paper jam cancellation operations can be reduced, and operability can be improved.

Further, the paper size changing work performed by the operator when a paper size error occurs is greatly simplified.

[Brief description of drawings]

1 to 9 show a laser printer according to an embodiment of the present invention. FIG. 1 is a block diagram, FIG. 2 is a diagram showing an exposure unit, and FIG. 3 is an operation of the exposure unit. FIG. 4 is a diagram showing each memory of the storage unit, FIGS. 5 and 7 are diagrams for explaining the calculation method of each time, and FIG.
FIG. 8 is a diagram showing the paper size, FIGS. 8 and 9 are flow charts showing the operation, and FIG. 10 is a schematic sectional view showing a general laser printer. 1 ... Photosensitive drum, 3 ... Exposure unit, 5 ... Paper feed cassette, 6 ...
Paper, 7 ... Transfer unit, 10 ... Paper feed sensor, 12 ... Paper outlet,
13 ... Paper ejection sensor, 14 ... Paper transport path, 15 ... CPU, 18 ... R
AM, 18b ... Paper detection time memory, 18e ... Paper size memory, 19 ... Host computer, 21 ... Timer, 24 ... Paper jam indicator lamp, 25 ... Paper size error lamp.

Claims (3)

[Claims] 1. A charging unit, an exposing unit, a developing unit, and a transferring unit are provided along the circumference of a photosensitive drum, and an image is formed by the exposing unit on the photosensitive surface of the photosensitive drum charged by the charging unit and developed. A laser printer in which an image developed by a transfer section is transferred to a sheet fed from a sheet feeding mechanism at a transfer section, and the sheet on which the image is transferred at the transfer section is discharged to the outside through a fixing section. Disposed in the paper conveyance path from the paper feed mechanism to the paper discharge port,
A paper feed sensor that detects a paper fed at a constant speed through the paper feed path, and a paper detection time memory that stores the paper detection time of each of the paper feed sensors of a plurality of paper sizes that can be set in the paper feed mechanism. And a paper size memory that stores a specified paper size specified from the outside, and a paper that determines a paper size error if the paper detection time of the paper feed sensor during printing operation is different from the detection time corresponding to the specified paper size. Size error judgment means, paper size error output means for outputting a paper size error in response to this paper size error judgment, paper detection time of the paper feed sensor during printing operation, maximum paper detection time of the paper detection time memory Paper jam error judgment means that judges a paper jam error only when it exceeds the limit, and in response to this paper jam error judgment, it includes the printing operation stop. Laser printer, characterized in that a Kamitsume error processing means for executing a predetermined paper packed error processing. 2. The laser printer according to claim 1, wherein if the paper detection time of the paper feed sensor during the printing operation is longer than the detection time corresponding to the specified paper size, the printing operation is continued. 3. A predetermined paper size error process including stopping an exposure operation in an exposure unit is executed when the paper detection time of a paper feed sensor during a printing operation is shorter than a detection time corresponding to a designated paper size. The laser printer according to claim 1.