JP3279422B2 - Image forming device - Google Patents

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 for conveying a sheet-like recording medium to form an image on the recording medium, and more particularly to a recording medium detecting means.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a digital printer, a copying machine, a facsimile machine, etc., a detecting means for detecting the conveyance of a sheet-shaped recording medium is generally supplied from any of a plurality of paper feeding ports. And monitoring the electric signal in time series to determine the presence / absence information of the recording medium.

With reference to FIGS. 1 and 2, an example of such a conventional recording medium conveyance detecting means will be described. FIG. 1 shows the operation of the photo sensor 41 and the sensor lever 42 constituting the paper feed sensor 3a. FIG. 2 shows the timing of an electric signal obtained from the photo sensor.

As shown in FIG. 1, the leading end of a sheet-shaped recording medium (cut sheet) P is detected as follows.
When the recording medium P is conveyed in the direction of the missing mark shown in the figure, the sensor lever 42 is pushed by the leading end of the recording medium and rotates clockwise about the rotation shaft 43. According to this rotation,
An initial state in which a light receiving portion of a photo sensor 41 called a photo coupler is shielded from light by a part of a sensor lever 42 (FIG. 1)
(A)), the light is passed through the photosensor 41 to cause a change in the signal of A at the sensor output (FIG. 1 (b)). This change in the signal indicates that the leading end of the recording medium has been conveyed to the position (position A) of the paper feed sensor 3a. The rotated sensor lever 42 continues to rotate as the paper is conveyed, interrupts the light from the photo sensor 41 (FIG. 1C), and the output of the photo sensor becomes the B signal level. The signal level of B indicates that the leading end of the recording medium has been conveyed to the position of B in the loading. Similarly, the change of the signal level at the passing points C and E ((d) and (e) in FIG. 1) causes the recording medium to move to the predetermined positions C and E on the transport path.
Can be obtained. The change in the output signal of the photo sensor 41 at this time is shown in FIG.
S (Hi) → A (Lo ↓) → B (Hi)
↑) → C (Lo ↓) → B (Lo), and by detecting the falling state of A (Lo), information that a recording medium is present is obtained. Note that Hi is at a high level and Lo is at a low level.

In FIG. 1, the rear end of the recording medium is detected as follows. After the recording medium has passed, the sensor lever 42 rotates in the opposite direction, ie, counterclockwise, due to its own weight or a return spring, and returns to the original position ((a) in FIG. 1). The output signal of the photo sensor 41 at this time is, as shown in FIG. 2A, E (Lo) → C (Hi ↑) → B (Lo ↓) → A (Hi).
↑) → S (Hi). By detecting the rising state of C (Hi), it is determined that the conveyed recording medium has passed through the paper feed sensor 3a and has passed through the sensor lever 42, and that there is no recording medium at the paper feed sensor position. Was.

Further, in the case of manual sheet feeding, the above C (H
At the timing when the signal change of i) is detected, the driving of the sheet feeding roller 3 described later (see FIG. 3) is stopped.

Further, in an image forming apparatus in which the accurate length information of the sheet-shaped recording medium cannot be recognized in advance and the transport distance from the start of feeding to printing is relatively long,
Conventionally, in general, a video controller corresponding to an image processing unit, a paper size setting unit, and a print processing unit receives paper size code data and image code data from an external device, and sends the paper size code data to a printer engine. After analyzing the code data, the image data is stored in the internal memory, and after the code data analysis is completed, a print start signal for instructing the printer engine to start a print operation is transmitted. When the printer engine receives the print start signal, it starts feeding the recording paper in accordance with the transport sequence of the previously received paper size code data, and performs transport / process control. In addition, the video controller does not receive the paper size code data from the external device, and when the appropriate paper size information is not set, there is a problem such as missing of an image on all recording media of a specified length that can be transported by the image forming apparatus. In order to prevent such a situation from occurring, a transport timing is set as an initial setting assuming a recording medium having a maximum paper size within the above-mentioned specification.

[0008]

However, in the above-described conventional image forming apparatus based on the recording medium detection system in which the signal level is detected in chronological order by one detecting means, the sensor lever 42 shown in FIG. Depending on the movement, the detection level of the detection signal transmitted to the controller does not always match the information on the presence or absence of paper. At this time, there has been a problem that the transport information of the recording medium is completely opposite to the current transport status.
This point will be described below with reference to FIGS. 1F and 2B using a laser beam printer as an example.

As shown in FIG. 1F, the user manually feeds the paper P 'at a position C (Hi) where the recording medium P passes through the paper feed sensor 3a and the sensor lever 42 is returning.
Is arbitrarily inserted, the driving of the paper feed roller 3 is stopped at the timing of C (Hi) as a normal transport sequence as described above.
It stays at the position (Hi). Therefore, while the sensor lever 42 is in contact with the leading edge of the paper ((g) in FIG. 1), the output signal of the photo sensor 41 indicates (Hi) information of the recording medium “absent”, and the actual recording medium “presence”. The fact that it is different from the fact occurred. That is, since the signal level of the paper feed sensor is inverted from the paper presence / absence information as shown in FIG. 2B, paper is fed even though paper is present, causing a jam in the apparatus, or image output failure. And the printer cannot satisfy the printing request. This has generally occurred frequently due to arbitrary insertion of a recording medium by a user.

Further, as described above, in the conventional image forming apparatus in which the transport distance from the start of feeding to printing is relatively long, the longest recording medium (for example, A3
In the paper conveyance control at the conveyance timing assuming the size of the paper, even when actually printing on a recording medium shorter than the set recording medium, it is necessary to start printing one page and finish the printing operation. This will take a long time. That is, when printing a frequently used recording medium (for example, A4 size paper) shorter than the longest recording medium, the number of printable sheets per unit time is extremely small. Since such a problem has occurred in the conventional apparatus, it is necessary to set an arbitrary recording medium length for paper size setting from an external device such as a personal computer or a user's operation panel.

An object of the present invention is to provide an image forming apparatus capable of appropriately determining the presence or absence of a recording medium irrespective of the timing at which a recording medium is inserted by a user in order to solve the conventional problems as described above. To provide.

[0012]

[0013]

[0014]

In order to achieve the above object, an image forming apparatus according to the present invention comprises a conveying means for conveying a recording medium, and a recording medium conveyed by the conveying means passing through a leading end or a trailing end of the recording medium. Detecting means for outputting an output signal capable of changing a level a plurality of times between a first level and a second level in response thereto; and determining presence or absence of a recording medium based on the output signal output from the detecting means. Determining means for determining that the output signal from the detecting means has changed from the first level to the second level with respect to the passage of the rear end of the recording medium, Whether the level changes to the first level is monitored for a predetermined time, and based on the monitoring result, when it is determined that the next recording medium is not inserted, the determination of the presence or absence of the recording medium is changed from presence to absence. It is characterized by That.

[0015]

[0016]

[0017]

[0018]

According to the present invention, there is provided an image forming apparatus having a detecting means for outputting an output signal capable of changing a level a plurality of times between a first level and a second level according to the passage of the leading end or the trailing end of a recording medium. In the apparatus, regarding the passage of the rear end of the recording medium,
After the output signal from the detection means changes from the first level to the second level, it is monitored for a predetermined time whether the level changes from the second level to the first level, and based on the monitoring result, If it is determined that the next recording medium has not been inserted, the presence / absence of the recording medium is appropriately determined regardless of the timing at which the user inserts the recording medium by changing the presence / absence of the recording medium from presence to absence. Can be determined.

[0019]

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(Embodiment 1) FIG. 3 shows a sectional structure of an image forming apparatus according to an embodiment (referred to as Embodiment 1) of the present invention. In FIG. 3, reference numeral 1 denotes a laser beam printer main body, 2a denotes a manual paper feed port, and 2b denotes a cassette paper feed port. By driving the paper feed roller 3, the fed recording medium P is fed to the position where the registration roller 4 is provided, and the paper feed sensor 3a as shown in FIG. 1 detects the paper feed timing. Reference numeral 5 denotes a known image transfer unit including a laser unit, a photosensitive drum, a developing device, and the like, and forms an image up to the transfer of a toner image on a recording sheet of a conveyed recording medium. Note that the image forming process in the image transfer unit 5 is not directly related to the present invention, and thus the description is omitted. Reference numeral 6 denotes a fixing unit that applies heat and pressure to the recording medium on which the transfer process has been completed to fix an image. Reference numeral 7 denotes a paper discharge roller, which discharges the recording medium that has passed through the fixing unit 6 to a paper discharge tray 8. Reference numeral 100 denotes a controller (control unit) that controls each device in a comprehensive manner based on a control procedure (program) stored in an internal memory in advance.

FIG. 4 shows the controller 100 shown in FIG.
3 shows a detailed circuit configuration. In FIG. 4, 9 is an MPU.
(Microprocessor unit), 28 is a RAM (random access memory) in the MPU 9;
8 stores control data such as a flag for control and a determination time t for measuring the passage detection time of the recording medium.
0 is set. 21a and 21b are counters, and M
The count value is reset by a reset signal 22 output from the PU 9, and the counting is performed at a count pulse signal 23, for example, 1 pulse / msec. 24 is counter 2
Count data output from 1a and 21b, for example, an 8-bit data signal. This count data 2
4 is cleared to “0” by the input of the reset signal 22 and is incremented by “1” every time the count pulse signal 23 is input. The count output value 24 of the first counter 21a is stored in the predetermined area EE1, EE2 of the RAM 28 in the MPU 9 in the MPU 9 as the transport time t0, and the second counter 21b is stored as the count value C0 'of the counter buffer.

In the image forming apparatus constructed as described above, when the recording medium is fed by the paper feed roller 3 in FIG. 3 and the trailing end of the recording medium is detected by the paper feed sensor 3a, a counter serving as a timing means is provided. The MPU 9 measures a certain time from the detection of the trailing end of the fed recording medium, and the MPU 9 monitors the measuring time of the counter and the electric signal of the paper feed sensor 3a during that period to determine whether or not the recording medium is present. Know exactly.

FIG. 5 shows a control procedure according to the present invention stored in advance in a ROM (read only memory) 31 in the MPU 9 in FIG. Hereinafter, the M of the image forming apparatus according to the first embodiment of the present invention will be described with reference to a flowchart shown in FIG.
The procedure of the paper feed recording medium presence / absence detection processing executed by the PU 100 will be described. S1 to S13 in FIG. 5 indicate each step. However, in the procedure shown in FIG. 5, when the print request is received and printing is started, the conveyance of the last sheet is finished, and then another sheet is not fed (the sheet is conveyed by the signal timing of FIG. 2A). Case), and the operation of detecting the presence or absence of recording paper when another sheet is fed next (when transported at the signal timing in FIG. 6).

First, a printing operation is started by a printing operation start signal (S1). Sensor lever 42 of paper feed sensor 3a
The sensor return detection counter C1 (21b) for monitoring that (see FIG. 1) has reliably returned to the initial position is cleared in advance (S2). When the timing at which the recording medium passes through the paper feed sensor 3a, that is, the timing of C at the rear end of the recording medium is detected by the paper feed sensor signal in FIG. 2A (S3), the rear end detection timer TM1 inside the MPU is reset. Start (S4).

Next, the rear end detection timer TM1 is set to 500 ms.
ec is monitored (S5). The normal case where the operation for the print request is completed and the paper is not fed next (the case where the paper is conveyed at the signal timing of FIG. 2A) will be described first.
First, it is monitored whether or not a Lo (low level) signal is input (S6). When the Lo signal is input from the paper feed sensor 3a, the sensor return detection counter C1 (21b)
Is incremented by 1 (S7). It is checked whether or not the count value of the sensor return detection counter C1 (21b) has become equal to 5 (S9). If the count value does not exceed 5, the process returns to step S5 again to continue monitoring the timer TM1. If a Hi (high level) signal is input even once during this time from the paper feed sensor 3a (S6), the sensor return detection counter C1 (21b) is cleared (S8), and the process returns to step S5. Lo signal from the paper feed sensor 3a is continuously 5
When the number of times is input, it is determined that there is no paper in the manual paper feed port 2a.
Clear the manual feed flag in the RAM 28 (S1
0). Accordingly, it is determined that the normal paper conveyance has been completed, and the sensor return detection counter C1 (21b) is cleared (S1).
1) Stop and clear the rear end detection timer TM1 (S
12).

Next, when the recording medium is fed manually by another sheet after the end of the operation for the print request, which is a processing operation unique to the present invention (the case where the recording medium is conveyed at the signal timing in FIG. 6). The paper presence detection operation will be described. In this case, as described in the section “Problems to be Solved by the Invention”, as shown in FIG. 6, the paper remains at the same position from the paper trailing edge detection position C. Remain in the Hi level state of C. Therefore, if the output signal of the paper feed sensor 3a is not determined to be Lo and remains Hi while the above-mentioned paper trailing edge detection timer TM1 is 500 msec (S5), Hi of this signal is not used as the paper absence information. Then, it is determined that there is paper, and the manual paper presence flag remains set (S13). Then, it is determined that the paper conveyance in response to the print request has ended, and the sensor return detection counter C1 (2
1b) is cleared (S11), and the rear end detection timer TM1 is stopped and cleared (S12).

It should be noted that, based on the paper presence / absence information of FIG. 6, it is possible to recognize the paper that has been fed even though there is no print request, and notify the user as a jam.

(Embodiment 2) FIG. 7 shows a circuit configuration of a data processing system in a laser beam printer according to another embodiment (referred to as Embodiment 2) of the present invention. In FIG. 7, reference numeral 30 denotes a CPU (Central Processor Unit), which has a ROM 31 storing a control program and a RAM 32 described later used as a register and the like, and is coded from a host computer or the like via an external interface 39. It receives image information (code data) and paper size information (code data), and sends the code data to the image processing unit 34. The image processing unit 34 stores the code data in the RAM 35, analyzes the code data, reads out the data from the character font stored in the ROM 36 as necessary, and converts the code data into dot image video data. , In the frame memory 37. As a result, when one page of video data is stored in the frame memory 37, the CPU 30 sends a print command to the printer engine control unit 38 via the video interface 33, and the main / sub scanning from the printer engine control unit 38 is performed. The video data stored in the frame memory 37 is sequentially transmitted to the printer engine control unit 38 in synchronization with the synchronization signal.

FIG. 8 shows a sectional structure of a laser beam printer according to a second embodiment of the present invention. In FIG. 8, reference numeral 2 denotes a cassette paper feed port, and 2A denotes a paper presence sensor for detecting the presence of paper in the cassette. The controller 110 is composed of circuits such as 30 to 38 in FIG. Controller 1
The configuration is such that it takes a long distance and takes a long time for the recording medium to be conveyed to the position of the registration roller 4 after the driving of the paper feed roller 3 is started by a print start command from 10. Other configurations are the same as those of the first embodiment of the present invention shown in FIG.

FIG. 9 shows a detailed circuit configuration of the controller 110 according to the second embodiment of the present invention shown in FIG. FIG.
, A RAM 32 for storing control data such as control flags and the like, and for storing respective transport timing setting times t1, t2, t3... For each set paper size data in a corresponding area, After the front end of the fed recording medium is detected by the paper feed sensor 3a, the conveyance time of the recording medium from which time measurement is started is stored in the register t0.
Other configurations are the same as those of the first embodiment of the present invention shown in FIG.

In the image forming apparatus constructed as described above, when the recording medium is fed by the paper feed roller 3 shown in FIG. 8 and the front end of the recording medium is detected by the paper feed sensor 3a, a counter 21a serving as a timer is provided. Starts measuring time and measures the transport time from the detection of the front end of the recording medium. The MPU 9 monitors the transport timing time for the designated paper size based on the measured time of the counter, and also detects the paper feed sensor 3a at that time. By detecting whether or not the recording medium is being conveyed, the length information of the recording medium is grasped.

FIGS. 10 to 13 are flowcharts showing a recording medium transport control procedure executed by the MPU 110 of the image forming apparatus according to the second embodiment of the present invention and its modification.
Note that S100 to S113, S200 to S203, S3
00 to S302 indicate each step. These procedures are stored in the ROM 31 in advance.

The flowcharts of FIGS. 10 and 11 are as follows.
When the printing operation is started without setting the paper size code data after the power of the laser beam printer 1 is turned on or after the paper is detected from the absence of the paper by the paper feed sensor 3a for detecting the presence or absence of the paper, the initial setting is performed. Second Embodiment Performing Printing Operation at Second Transport Timing Time DATA2
1 shows an example of a transfer control processing procedure in the first embodiment. In the image recording apparatus of this embodiment, the transport timing time data at the longest paper size that can be printed and transported (in this description, a legal size is set as an example) is DATA1, which is generally shorter than the longest size. The transfer timing time data for a large paper size (for example, A4 size is set in this description) is DATA2.

First, when it is determined in step S100 in FIG. 10 that the laser beam printer 1 has just been powered on,
Alternatively, the transport timing time data is set to DATA2 in a state where the paper presence is detected after the paper absence is detected by the paper presence sensor 2A in step S101 (S10).
2). Before inputting the print start signal, the controller 11
When the paper size setting is received from 0 (S103), the transfer timing is changed to the transport timing setting time DATAx according to the paper size (S104). However, if the paper size is not set, the process returns to step S100, and steps S100 to S10.
The process waits for the input of a print start signal while repeating steps up to 4.
Thereafter, when a print start signal is received without setting the paper size (S105), printing is performed by the print start signal using the transport timing time data DATA2 set in step S102.

That is, when a print start signal is received in step S105, paper feed is started by the paper feed roller 3 in step S106 in FIG. 11, and the front end of the fed recording medium is detected by the paper feed sensor 3a (S107). At the same time, the print transport control timer TMR is started (S108). In step S109, the printing operation is started, and after the printing mechanisms 5 to 7 shown in FIG. 8 have passed, the print transport control timer TMR is monitored in step S110.
Monitor the transfer control time t2 msec of DATA2 set in step (2). In step S111, the end of the printing operation is monitored,
Upon completion of the printing operation, the timer TM is set in step S112.
Clear R. Step S113 When the conveyance of the recording medium is completed, the entire printing operation is completed.

Until the next print request is input, the transport timing time data remains DATA2 at step S in FIG.
At 103, the paper size setting is monitored.

(Modification 1 of Embodiment 2) FIG. 12 is a flowchart showing a modification of Embodiment 2 of the present invention. In the example of FIG. 12, after the power of the laser beam printer 1 is turned on, or after the paper presence sensor 2A detects the presence of paper from the absence of paper, the paper size setting means starts the printing operation without setting the paper size code data, The transport time is monitored for the first sheet that has started feeding, and the transport timing time data is changed when it is determined that the monitored actual transport time is longer than the transport timing time (DATA2) of the initially set paper size. (DATA1).

In FIG. 12, steps S106 to S1
Up to 10 is the same as in the second embodiment of FIG. Step S
At 110, the transport timing timer DATA2 (t2 msec), which is the initial setting, is monitored by the print transport control timer TMR, and at the time t2 msec, whether or not the recording paper is still being transported is determined by the output signal of the paper feed sensor 3a. Detect. If it is detected that the paper is being conveyed (S200), it is determined that the paper being conveyed is longer than the data length of DATA2,
In step S201, the transfer timing time is set to R in advance.
Change to DATA1 (t1 msec) stored in AM32. If the paper is not being conveyed, it is determined that it is within the paper length of DATA2, and the printing operation is continued with the conveyance control timing data DATA2. When the printing operation is completed (S11
1), Steps S112 to S112 as in the second embodiment in FIG.
113, and if the paper-out state is detected in step S202, the transfer timing time data is set to DATA.
2 (S203).

(Modification 2 of Embodiment 2) FIG. 13 is a flowchart showing a further modification of the control procedure of FIG. As shown in FIG. 13, after the power of the laser beam printer 1 is turned on, or after the paper presence sensor 2A detects the presence of paper from the absence of paper, the paper size setting unit starts the printing operation without setting the paper size code data. The transport time is monitored for the first sheet that has started feeding, and when it is determined that the monitored actual transport time is longer than the transport time (DATA2) of the initially set paper size, the transport timing time data is output. Change (DAT
A1) Then, during the continuous printing operation, if the paper-out state is detected without any change, the transport timing data is changed to DATA.
By returning to 2, the continuous paper can be conveyed.

That is, after the timer clear processing in step S112 in FIG. 13, the presence or absence of a print start request signal is monitored in step S300, and the feeding timing time data is changed to DATA1 and the next page and subsequent pages are fed ( (S301) and the printing operation (S302) are continued. And step S
When the paper-out state is detected in step S202, the transfer timing
Return to TA2 (S203).

[0042]

As described above, according to the present invention,
In an image forming apparatus having a detection unit that outputs an output signal that can change a level between a first level and a second level a plurality of times in response to passage of a leading end or a trailing end of a recording medium, With respect to the passage of the end, after the output signal from the detection means changes from the first level to the second level, it is monitored for a predetermined time whether or not the level changes from the second level to the first level. If it is determined based on the monitoring result that the next recording medium has not been inserted,
By changing the determination of the presence or absence of a recording medium from yes to no,
It is possible to appropriately determine the presence or absence of a recording medium regardless of the timing at which the user inserts the recording medium.

[0043]

[Brief description of the drawings]

FIG. 1 is a state diagram showing a paper feed sensor according to the present invention and a series of movements thereof.

FIG. 2 is a timing chart showing a relationship between a signal of a paper feed sensor and paper presence / absence information in a conventional example.

FIG. 3 is a schematic cross-sectional view illustrating a configuration of the image forming apparatus according to the first exemplary embodiment of the present invention.

4 is a block diagram showing a detailed circuit configuration of the controller shown in FIG.

FIG. 5 is a flowchart illustrating a paper presence / absence detection processing procedure according to the first embodiment of the present invention.

FIG. 6 is a timing chart showing a relationship between a signal of a paper feed sensor and paper presence / absence information according to the first embodiment of the present invention.

FIG. 7 is a block diagram illustrating a circuit configuration of a data processing system of the laser beam printer according to the second embodiment of the present invention.

FIG. 8 is a schematic sectional view illustrating a configuration of an image forming apparatus according to a second embodiment of the present invention.

FIG. 9 is a block diagram showing a detailed circuit configuration of the controller shown in FIG. 7;

FIG. 10 is a flowchart illustrating a transfer control timing initial setting processing procedure according to the second embodiment of the present invention.

FIG. 11 is a flowchart illustrating a printing operation processing procedure according to the initially set transport control timing in the second embodiment of the present invention.

FIG. 12 is a flowchart illustrating a transport control timing change processing procedure according to a modification of the second embodiment of the present invention.

FIG. 13 is a flowchart illustrating a transfer control timing changing procedure in still another modification of the second embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 2 cassette feed port 2a manual feed port 2A paper presence sensor 3 paper feed roller 3a paper feed sensor 5 image transfer unit 6 fixing unit 7 discharge roller 8 discharge tray 41 paper feed sensor (photo interrupter) 42 paper feed sensor lever 9 MPU 21a counter 21b counter 31 ROM 28, 32 RAM 34 image processing unit 41 photo sensor 42 sensor lever 43 rotation axis 100, 110 controller (control unit)

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-267169 (JP, A) JP-A-5-155472 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B65H 7/00

Claims (1)

(57) [Claims] A transport unit configured to transport a recording medium; and a plurality of levels between a first level and a second level according to a passage of a leading end or a trailing end of the recording medium transported by the transporting unit. Detecting means for outputting a changeable output signal; and determining means for determining the presence or absence of a recording medium based on the output signal output from the detecting means. With respect to the passage, after the output signal from the detecting means changes from the first level to the second level, it is monitored for a predetermined time whether or not the level changes from the second level to the first level. An image forming apparatus characterized in that, when it is determined that the next recording medium is not inserted, the determination of the presence or absence of the recording medium is changed from presence to absence.