JP2021015190A - Image forming apparatus - Google Patents

Abstract

To solve the problem in which in a case where image formation is executed before paper feeding, when failure in paper feeding occurs, a toner image needs to be collected without printing, which increases unnecessary toner consumption.SOLUTION: An image forming apparatus predicts failure in paper feeding from an image transfer time from an image forming unit to a transfer unit and a sheet conveyance time from a sheet loading unit to the transfer unit, and determines which of image formation and paper feeding should be preferentially performed.SELECTED DRAWING: Figure 1

Description

The present invention relates to an image forming apparatus that starts transporting a recording sheet after starting an image forming operation to form an image on the recording sheet.

In a color-compatible electrophotographic image forming apparatus, an image corresponding to each color formed on a plurality of photosensitive drums is once transferred to an intermediate transfer body and superimposed. Then, a method (intermediate transfer method) in which a full-color image on which these images of a plurality of colors are superimposed is transferred to a recording sheet is common.

In this intermediate transfer method, if the image-forming process on each photosensitive drum is started after the recording sheet is fed, the printing efficiency is not improved if the time required from the start of the image-forming operation to the transfer is long. There was a problem. For this reason, if it takes a long time from the start of the image formation operation to the transfer in the intermediate transfer method, the "image image advance method" is used to start the image formation process on the photosensitive drum before starting the feeding of the recording sheet. By adopting it, the printing efficiency is improved.

However, in the image-drawing advance method, the image-drawing process is started before confirming whether or not the recording sheet has been fed normally. Therefore, if a recording sheet feeding failure occurs, it is recorded in the image of the intermediate transfer body. There is a possibility that the seat will not catch up.

In response to such poor paper feeding of the recording sheet, Patent Document 1 states that the same image is imaged again when the feeding process is performed again and the feeding is successful, and the subsequent image and the recording sheet are subjected to the same image. A technique has been proposed that achieves both reduction of jam occurrence and avoidance of reduction of printing efficiency by adopting the image formation precedent method again.

Japanese Unexamined Patent Publication No. 2008-052257

However, in the conventional technique disclosed in Patent Document 1 described above, when the image-forming preceding method is implemented in order to improve the printing efficiency in printing in a low-temperature environment outside the operation guarantee where paper feeding defects are likely to occur, paper feeding is performed. Every time a defect occurs, the previously formed toner image cannot be printed and must be collected, which increases unnecessary toner consumption.

In order to solve the above problems, the image forming apparatus according to the present invention is
An image forming section for forming an image, a paper loading section for loading paper, a feeding section for feeding sheets loaded on the paper loading section, and an image forming section and the feeding section are provided. , A sheet transporting unit that transports sheets fed from the paper feeding unit, a sheet detecting unit that detects the sheets transported by the sheet transporting unit, a transfer unit that transfers the formed image to the sheet, and an apparatus. A first operation mode in which the printing operation is performed before the paper feeding operation and a second operation mode in which the printing operation is performed after the paper feeding operation, which are provided with a temperature sensor for detecting the temperature inside. The printing operation is performed after the paper feeding operation, and the printing operation has a third operation mode in which the sheet detecting unit detects the sheet and then performs the printing operation, from the image forming unit to the transfer unit. Which of the first to third operation modes is to be executed is determined from the image movement time, the paper movement time from the paper loading unit to the transfer unit, and the value of the temperature sensor. It is characterized by.

According to the image forming apparatus according to the present invention, unnecessary toner consumption is increased by determining whether to precede the paper feeding or the image drawing in consideration of the condition that the paper feeding failure is likely to occur. Can be avoided.

Sectional drawing of image forming apparatus which showed embodiment of this invention Control block diagram showing an embodiment of the present invention Explanatory drawing of image formation precedent mode Explanatory drawing of image formation precedent mode Explanatory drawing of paper feed preceding mode Explanatory drawing of paper feed preceding mode Explanatory drawing of image formation mode after paper feed is confirmed Explanatory drawing of image formation mode after paper feed is confirmed Flow chart for determining the operation mode of the embodiment of the present invention Explanatory diagram of the detection method of delayed jam Flow chart for determining the operation mode of the embodiment of the present invention

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

[Rough configuration of image forming apparatus and basic image forming operation]
FIG. 1 is a schematic cross-sectional view of an image forming apparatus.

The image information transmitted from the external connection cable (not shown) is processed by the control device 200 (not shown). Further, a laser beam is emitted from the laser scanner unit 152 by a signal based on the processing result to form an electrostatic latent image on the photoconductor drums (151Y, 151M, 151C, 151K), and the electrostatic latent image on the photoconductor drum is formed. Is developed by a developer (153Y, 153M, 153C, 153K) to form a toner image on the photoconductor drum. After that, a predetermined pressing force and an electrostatic load bias are applied by the primary transfer device (154Y, 154M, 154C, 154K), and the toner image is transferred onto the intermediate transfer belt 155. In the case of FIG. 1, the image forming unit 150 includes four sets of yellow Y, magenta M, cyan C, and black Bk.

Next, the intermediate transfer belt 155 will be described.

The intermediate transfer belt 155 is rotationally driven in the direction of arrow A in FIG. The image forming process of each color is performed at the timing of superimposing on the upstream toner image primaryly transferred on the intermediate transfer belt 155. As a result, a full-color toner image is finally formed on the intermediate transfer belt 155 and transferred to the secondary transfer unit 156.

On the other hand, the sheets S loaded on the cassette 111 are separated one by one by the cassette paper feed roller pair 110 and fed. The fed sheet S is directed toward the skew correction device 130 arranged on the downstream side in the sheet transfer direction (hereinafter, simply referred to as “downstream side”) by the cassette pull-out roller pair 114 and the pre-registration transfer roller pair 121. It is conveyed and the skew of the sheet S is corrected. After that, the sheet S is conveyed by the register roller pair 131 at the timing when the toner image formed on the intermediate transfer belt 155 and the secondary transfer unit 156 overlap each other (hereinafter, this timing is referred to as the registration ON timing).

A full-color toner image is secondarily transferred onto the sheet S in the secondary transfer unit 156 by the transfer process and the image forming process of the sheet S described above. After that, the sheet S is conveyed to the fuser 160. The fuser 160 melts and fixes the toner on the sheet S by applying a predetermined pressing force by an opposing roller or belt and a heating effect generally by a heat source such as a heater. The sheet S having the fixed image thus obtained passes through the transport unit 170 after fixing, and is aligned on the paper ejection tray 180 installed in the body of the image forming apparatus 100 by the paper ejection device 171. However, if it is loaded or if double-sided image formation is required, the front end side of the sheet S is once put out on the output tray 180, and when the rear end of the sheet S passes the branch point 172, it is switched back and the reverse transfer device Route selection is performed so that it is transported to 190.

The sheet S transported to the reversing transfer device 190 is sequentially transported to the drawing roller pair 115 and the pre-registration transfer roller pair 121 by the reversing transfer device 190, and toward the sheet skew correction device 130 arranged on the downstream side. Be transported. After the skew of the sheet S is corrected by the sheet skew correction device 130, it is conveyed to the secondary transfer unit 156, and the toner image on the second surface side is transferred to the sheet S. Regarding the path of the sheet S after the toner image is transferred to the sheet S, as described above, the sheet S passes through the fixing device 160 and the transfer unit 170 after fixing, and is loaded and discharged on the paper ejection tray 180 by the paper ejection device 171. ..

In the feeding of the sheet S, the sheet S loaded on the multi-tray 113 is transported by the multi-conveying roller pair 112, and the sheet skew correction device is transported by the drawing roller pair 115 on the downstream side and the sheet skew compensator pair 121 in front of the cash register. There is also a route to 130.

FIG. 2 is a block diagram of the image forming apparatus of the present invention. The control unit 200 controls the entire image forming apparatus 100. The control unit 200 includes a CPU 201, a ROM 202, a RAM 203, a motor drive circuit 204, a sensor input / output detection circuit 205, and a temperature detection circuit 206.
The ROM 202 stores a control program for controlling each process executed by the image forming apparatus 100. The RAM 203 is a system work memory used by the CPU 201 to execute a control program.

The motor drive circuit 204 controls each connected motor. A control signal is output to each motor according to the rotation speed of the motor determined by the CPU 201 for each motor. In this image forming apparatus, the registration motor 133 is connected to the registration roller pair 131. Further, the pre-registration transfer motor 145 is connected to the pre-registration transfer roller pair 121, the cassette drawing roller pair 114, and the multi-drawing roller pair 115. Further, a multi-conveying motor 146 is connected to the multi-conveying roller pair 112.

Based on the input signal of each connected sensor, the sensor input / output detection circuit 205 is a high-level signal if the received light amount of each sensor is equal to or more than the threshold value, and a low-level signal if the received light amount of each sensor is less than the threshold value. Recognize that. For example, when the sheet reaches the position of the multi-drawing roller pair 115, the CPU 201 recognizes that the light-receiving amount becomes equal to or more than the threshold value and the sensor is turned on.

The temperature detection circuit 206 has a function of converting the temperature based on the input signal of each connected temperature sensor.

The operation unit 301 functions as a display means for notifying the user of the state of the image forming apparatus by a signal from the CPU 201, and as an input means for receiving an operation instruction of the image forming apparatus when the CPU 201 receives a signal from the operation unit 301. ..

Since the image forming unit 150 and the fixing device 160 are described in FIG. 1, the description thereof will be omitted here.

[Explanation of image-preceding mode]
Next, with reference to FIG. 3, a control method for performing image drawing and paper transfer so that the tip of the paper and the tip of the toner image on the intermediate transfer belt 155 coincide with each other at the secondary transfer unit 156 will be described.

FIG. 3A shows a distance A (hereinafter, image movement distance A) from the image forming position to the secondary transfer unit 156 in the schematic cross-sectional view of the image forming apparatus of FIG. 1, and a sheet loaded on the multi-tray 113. The distance B (hereinafter, paper transport distance B) from the paper feed start position of S to the secondary transfer unit 156 is shown. The image formation position in this case indicates a case in which a laser beam is emitted from the laser scanner unit 152 and a latent image is formed on the photoconductor drum (151Y), that is, a color image formation start position. Further, FIG. 3B shows the image formation timing and the paper diagram, and it is assumed that the time has elapsed as the time elapses toward the right in both the image formation timing and the paper diagram. Shows that the higher the line, the more the paper is moving in the transport direction. In this example, two sheets of sheet S loaded on the multi-tray 113 are fed.

Ti shown at the image formation timing in FIG. 3B is the image movement time from the image formation position to the secondary transfer unit 156, and Ti is the speed at which the intermediate transfer belt 155 advances the image movement distance A (hereinafter, process). Calculated from speed), "Ti = image movement distance A / process speed". Further, Tcom is an image formation interval and is a value defined by the productivity of the main body. For example, when the productivity is 60 ppm, the Tcom is 1000 ms. On the other hand, Tp is the time for the paper to move within the paper transport distance B from the paper feed unit to the secondary transfer unit 156, and is a value designed in advance for each paper type and paper feed unit (cassette 111 or multi-tray 113). Is. Even if the same paper type is used, variations may occur due to paper delays and the like for each paper transfer, but these are absorbed by the standby time of the register roller unit.

In the example of FIG. 3, the relationship is Ti> Tp, and the specified productivity can be satisfied by starting the image formation before the start of feeding the paper. However, when paper transport failure occurs, it is necessary to collect the formed toner image without printing. Such a pattern in which an image is formed before the start of paper feeding is hereinafter referred to as an image drawing preceding mode.

[Explanation of paper feed preceding mode]
Next, with reference to FIG. 4, a control method for performing image drawing and paper transfer so that the paper tip and the tip of the toner image on the intermediate transfer belt 155 coincide with each other at the secondary transfer unit 156 will be described.

FIG. 4A shows a distance A'(hereinafter, image movement distance A') from the image forming position to the secondary transfer unit 156 in the schematic cross-sectional view of the image forming apparatus of FIG. 1, and the image is loaded on the multi-tray 113. The distance B (hereinafter, paper transport distance B) from the paper feed start position of the sheet S to the secondary transfer unit 156 is shown. As a difference from FIG. 3A, the image formation position in this case indicates a case in which laser light is emitted from the laser scanner unit 152 and latently imaged on the photoconductor drum (151K), that is, a monochrome image formation start position. ing. Further, FIG. 4B shows the image formation timing and the paper diagram, and it is assumed that the time has elapsed as the time elapses toward the right in both the image formation timing and the paper diagram. Shows that the higher the line, the more the paper is moving in the transport direction. In this example, two sheets of sheet S loaded on the multi-tray 113 are fed.

In the example of FIG. 4, the relationship is Ti <Tp, and the paper feeding is started before the image formation. Since paper feeding is started before image formation, if paper transport failure occurs before image formation, it is not necessary to collect the toner image without printing, and the specified productivity can be satisfied. it can. The pattern in which paper feeding is started before such image formation is hereinafter referred to as a paper feeding preceding mode.

[Explanation of image production mode after paper feed is confirmed]
Next, with reference to FIG. 5, a control method for performing image drawing and paper transfer so that the tip of the paper and the tip of the toner image on the intermediate transfer belt 155 coincide with each other at the secondary transfer unit 156 will be described.

5 (a) shows the distance A (hereinafter, image movement distance A) from the image forming position to the secondary transfer unit 156 and the multi-tray in the schematic cross-sectional view of the image forming apparatus of FIG. 1 as in FIG. 3 (a). The distance B (hereinafter, paper transport distance B) from the paper feed start position of the sheet S loaded on 113 to the secondary transfer unit 156 is shown. Further, FIG. 5B shows an image formation timing and a paper diagram, and it is assumed that the time has elapsed as the time elapses toward the right in both the image formation timing and the paper diagram, and the line is on the paper diagram. The more you go, the more the paper is moving in the transport direction. In this example, two sheets of sheet S loaded on the multi-tray 113 are fed.

In the example of FIG. 5, although the relationship is Ti> Tp, the paper feeding is started before the image formation. Then, image formation is started at the timing when the paper is successfully fed. In this example, the timing at which the tip of the paper arrives at the multi-pull-out detection sensor (131) is defined as the paper feed success timing. In order to start image formation after waiting for successful paper feeding, the paper side waits Tp_wait for the time until the image arrives at a predetermined position by the register roller (131). By doing so, the image and the paper can be matched by the secondary transfer unit 156. However, when the first sheet of paper waits for Tp_wait on the register roller (131), it is necessary to delay the subsequent second sheet of paper. This is because the following paper collides with the stopped preceding paper. Therefore, the paper feed adjustment time Tp_wait2 is awaited.

If the speed after feeding is not changed depending on the presence or absence of the feeding adjustment time, Tp_wait2 = Tp_wait.

For the second sheet of paper, image formation is started at the timing when the paper is successfully fed. Therefore, the image formation interval T'com is Tcom <T'com with respect to the Tcom in the image formation preceding mode, and there is a feature that the specified productivity is not obtained. On the other hand, when a paper transport failure occurs, the toner image is not printed and is not collected because the image is not drawn. The pattern in which the paper feed is preceded when Ti> Tp is satisfied and the image formation is started after the paper feed is successfully completed is hereinafter referred to as the image feed mode after the paper feed is confirmed.

[Explanation of mode selection flow]
FIG. 6 is a mode determination flow of paper feeding and image drawing timing stored in the ROM 202 and the RAM 203, and is executed by the CPU 201 with a print job received by the operation unit 301 as a trigger.

First, Ti (image movement time from the image forming position to the secondary transfer unit 156) is calculated with the start of the mode determination. Ti is calculated by the image movement distance A / process speed (S1001). Next, Tp is calculated (paper transport time from the paper feed unit to the secondary transfer unit 156). The paper transport time is a value designed in advance for each paper type and paper feed unit (cassette 111 or multi-tray 113), and is stored in the ROM 202 (S1002). Next, the values of Ti and Tp are compared (S1003). When the Tp is larger, that is, when it takes longer for the paper to arrive than the image for the secondary transfer unit 156, the operation mode is selected as the paper feed preceding mode (S1004).

On the other hand, when Ti is larger, that is, when the image arrives longer than the paper for the secondary transfer unit 156, the in-flight temperature Tin is further acquired from the temperature detection circuit 206 and set to the temperature threshold Tth. Compare (S1005). The temperature threshold value Tth is a pre-designed value, and is, for example, a temperature obtained in an experiment in which paper feed failure is likely to occur, and is set to 2.5 ° C. here. The value is stored in ROM 202. Although it depends on the material of the roller, the friction coefficient μ of the roller generally decreases at a low temperature and tends to be slippery.

Then, when the in-flight temperature Tin is higher than the temperature threshold value Tth, the operation mode is selected as the image formation preceding mode (S1006). On the other hand, when the in-machine temperature Tin is lower than the temperature threshold value Tth, the operation mode is selected as the image drawing mode after the paper feed is confirmed (S1007).

In this way, with the start of the job, the timing mode of image drawing and paper feeding is determined using the image arrival time to the secondary transfer unit 156, the paper transport time, and the in-machine temperature. By doing so, it is possible to carry out a printing operation that satisfies the specified productivity when the conditions are not prone to paper feed defects, and unnecessary toner consumption is performed under conditions where paper feed defects are likely to occur. Can be avoided.

[Explanation of delay jam detection method and detection jam counter]
Next, the delay jam detection of paper transport will be described with reference to FIG. 7.

FIG. 7 shows the drive speed of the multi-conveyor roller 112 and the logic of the multi-pull-out detection sensor 132 when the paper loaded on the multi-tray 113 is fed. Hereinafter, delay jam detection using the multi-pull-out detection sensor 132 when the loaded paper of the multi-tray 113 is fed will be described.

When the multi-conveying motor 146 is driven to rotate the multi-conveying roller 112 at the paper feeding speed V, the paper tip arrival time t2 of the multi-drawing detection sensor 132 can be calculated from the paper conveying speed (= V). At this time, the transfer efficiency may decrease due to wear of the transfer roller or the configuration of the transfer mechanism itself. Assuming that the time considering this amount is the transport margin m2, it can be predicted that it will take t2 + m2 hours from the start of driving of the multi-conveyor motor 146 to the arrival of the paper tip of the multi-drawing detection sensor 132.

Therefore, if the arrival of the paper tip cannot be detected by the paper transport sensor 171 even though t2 + m2 hours have elapsed, it is determined that the jam is delayed. The jam detection determination is an example, and the present invention is not limited to the jam detection method.

Next, the detection jam counter will be described with reference to Table 1.

Table 1 is a delay jam detection count table. The detection jam counter holds the number of delay jam detections at each paper feed position, and is stored in the RAM 203. However, the number of detected delay jams is not always retained, and the number of delay jams that occur when the in-flight temperature Tin is equal to or less than the temperature threshold Tth is retained. Further, it does not hold the total number of delay jams from the start of use of the device, but holds the number of times in the last 100 times of feeding when the in-flight temperature Tin is equal to or less than the temperature threshold Tth. By referring to this value, it is possible to predict whether or not a paper feed failure occurs when the in-machine temperature is Tin, which is equal to or lower than the temperature threshold value Tth.

[Explanation of mode selection flow 2]
FIG. 8 is a mode determination flow of paper feeding and image drawing timing stored in the ROM 202 and RAM 203, which incorporates the prediction of the occurrence of paper feeding failure shown in Table 1, and shows the print job received by the operation unit 301. It is executed by the CPU 201 as a trigger.

First, Ti (image movement time from the image forming position to the secondary transfer unit 156) is calculated with the start of the mode determination. Ti is calculated by the image movement distance A / process speed (S2001). Next, Tp is calculated (paper transport time from the paper feed unit to the secondary transfer unit 156). The paper transport time is a value designed in advance for each paper type and paper feed unit (cassette 111 or multi-tray 113), and is stored in the ROM 202 (S2002). Next, the values of Ti and Tp are compared (S2003). When the Tp is larger, that is, when the paper arrives longer than the image with respect to the secondary transfer unit 156, the operation mode is selected as the paper feed preceding mode (S2004).

On the other hand, when Ti is larger, that is, when the image arrives longer than the paper for the secondary transfer unit 156, the in-flight temperature Tin is further acquired from the temperature detection circuit 206 and set to the temperature threshold Tth. Compare (S2005). The temperature threshold value Tth is a pre-designed value, and is, for example, a temperature obtained in an experiment in which paper feed failure is likely to occur, and is set to 2.5 ° C. here. The value is stored in ROM 202. Then, when the in-flight temperature Tin is higher than the temperature threshold value Tth, the operation mode is selected as the image formation preceding mode (S2006). On the other hand, when the in-machine temperature Tin is lower than the temperature threshold value Tth, the jam detection number N in the corresponding paper feed unit of the print job is acquired and compared with the jam number threshold Nth (S2008). The jam frequency threshold Nth is a value designed in advance, for example, a value determined based on the amount of toner recovered obtained in an experiment, and is set to once here. The value is stored in RAM 203. When the jam detection count N is larger than the jam count threshold Nth, the operation mode is selected as the image drawing mode after the paper feed is confirmed (S2007). On the other hand, if it is smaller than the jam count threshold value Nth, the operation mode is selected as the image formation preceding mode.

In this way, with the start of the job, the timing mode of image drawing and paper feeding is determined using the time to the secondary transfer unit 156, the temperature inside the machine, and the number of jam detections held for each paper feeding unit. By doing so, it is possible to carry out a printing operation that satisfies the specified productivity when the conditions are not prone to paper feed defects, and unnecessary toner consumption is performed under conditions where paper feed defects are likely to occur. Can be avoided. In addition, by using the actual number of jam detections, the accuracy of predicting the occurrence of paper feed defects is improved, and the frequency with which the image feed mode is selected after the paper feed is confirmed that does not meet the specified productivity is determined from the mode selection flow in FIG. It will be possible to reduce it.

100 image forming device, 105 temperature sensor,
110 cassette paper feed roller pair, 111 paper paper cassette,
112 multi-conveyor roller pair, 113 multi-tray,
114 cassette extraction roller pair, 115 multi extraction roller pair,
132 Multi-pull-out detection sensor, 136 Cassette pull-out detection sensor,
146 multi-conveyor motor, 150 image forming part,
155 Intermediate transfer belt, 156 Secondary transfer unit, 301 Operation unit

Claims (2)

The image forming part that forms the image and
A paper loading section for loading paper and
A paper feeding unit that feeds the sheets loaded on the paper loading unit,
A sheet transport unit provided between the image forming unit and the paper feed unit to convey the sheet fed from the paper feed unit, and a sheet transport unit.
A sheet detection unit that detects the sheet conveyed by the sheet transfer unit, and
A transfer unit that transfers the formed image to a sheet, a temperature sensor that detects the temperature inside the device, and
With
A first operation mode in which the printing operation is performed before the paper feeding operation, a second operation mode in which the printing operation is performed after the paper feeding operation, and a printing operation performed after the paper feeding operation, and further The printing operation has a third operation mode in which the sheet detecting unit detects the sheet and then performs the printing operation, the image transfer time from the image forming unit to the transfer unit, and the transfer operation from the paper loading unit to the transfer unit. An image forming apparatus comprising determining which of the first to third operation modes is to be executed from the paper moving time to the paper and the value of the temperature sensor. It further has a measuring unit that measures the number of paper feed defects that did not reach the sheet detection unit, and a calculation unit that calculates the paper feed failure history from the number of paper feed defects, and the image from the image forming unit to the transfer unit. The image forming apparatus according to claim 1, wherein the operation mode is determined in consideration of the moving time, the paper moving time from the paper loading unit to the transfer unit, the value of the temperature sensor, and the paper feed failure history. ..