Patent Grant
10061254
The present invention relates to an image forming system including an image forming apparatus and a recording material discharging device and particularly relates to feeding stability of a recording material.
As a heating type of a fixing device mounted in the image forming apparatus, there is a film heating type using a fixing film, and in a side opposing the fixing film, a pressing roller which is an elastic member and which is a thermally expandable rotatable member is used. In the case where the film heating type is employed, the pressing roller thermally expands by heating from the fixing film and fluctuates in outer diameter. In the case where rotatable members provided upstream and downstream of the pressing roller of the fixing device in a feeding path only slightly expand thermally, a feeding speed of a recording material by the pressing roller becomes high, and therefore a peripheral speed relationship between each rotatable member and the pressing roller fluctuates, so that a feeding state of the recording material becomes unstable. As a result, there is a liability that paper jam of the recording material and image defect are generated.
Therefore, in the case where a transfer portion upstream of the pressing roller in the feeding path is driven by a driving source, a degree of flection (bending) of the recording material between the transfer portion and the fixing device is detected using a loop sensor. Then, on the basis of a detection result, by changing a driving speed of the driving source for the pressing roller, the feeding speed of the recording material by the pressing roller is made substantially constant irrespective of an outer diameter fluctuation of the pressing roller (hereinafter this control is referred to as loop control). As a result, the feeding state of the recording material is stabilized while avoiding pulling of the recording material between the rotatable members and excessive flection of the recording material. Such a technique is disclosed in Japanese Laid-Open Patent Application (JP-A) 2001-106380, for example.
Further, also as regards a fixing discharging roller provided downstream of the pressing roller in the feeding path, similarly as in the above-described loop control, in the case where the pressing roller and the fixing discharging roller are driven by different driving sources, a loop sensor is provided between the pressing roller and the fixing discharging roller. Then, on the basis of a detection result of the loop sensor, loop control is effected, so that the recording material feeding state is stabilized. Such a constitution is disclosed in JP-A 2013-105125.
However, in the above-described conventional examples, the recording material feeding speed between feeding rollers in the image forming apparatus is controlled. For example, in the case where a discharging device of the recording material is provided downstream of the image forming apparatus in the recording material feeding path, it is difficult to control a feeding speed relationship between a mostdownstream roller in the feeding path in the image forming apparatus side and a mostupstream roller in the feeding path in the discharging device side. For this reason, by a change in recording material feeding speed of the mostdownstream roller in the image forming apparatus side, pushing and pulling of the recording material generate between the mostdownstream roller in the image forming apparatus side and the mostupstream roller in the discharging device, with the result that there is a problem such that paper jam and image defect due to friction of the recording material with the feeding path generate.
The present invention has been accomplished in view of the above-described circumstances. A principal object of the present invention is to provide an image forming system capable of stabilizing a feeding state of a recording material between an image forming apparatus and a discharging device.
According to an aspect of the present invention, there is provided an image forming system comprising: an image forming apparatus for forming an image on a recording material; and a discharging device for discharging the recording material on which the image is formed, wherein the image forming apparatus includes, a first rotatable member for feeding the recording material, a second rotatable member positioned downstream of the first rotatable member along a feeding path with respect to a recording material feeding direction, first driving means for driving the first rotatable member and the second rotatable member, and first control means for controlling the first driving means, wherein the discharging device includes, a third rotatable member for feeding the recording material fed from the image forming apparatus, second driving means for driving the third rotatable member, and second control means for controlling the second driving means, wherein the first control means controls a driving speed of the second rotatable member depending on a driving speed of the first rotatable member and feeds the driving speed of the first rotatable member to the second control means, and wherein the second control means controls a driving speed of the third rotatable member depending on the driving speed fed from the first control means.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
In
In
In
In
In
In
In
In
Embodiments of the present invention will be described specifically with reference to the drawings. First, in advance of description of Embodiments described later, problems of recording material feeding in the case of an image forming system in which a recording material discharging device or the like is provided downstream of an image forming apparatus in a recording material feeding path will be described in detail.
During an image forming operation, a pressing roller of a fixing device thermally expands by heat conducted from a fixing film and its outer diameter fluctuates. On the other hand, a fixing discharging roller provided in a mostdownstream side of the image forming apparatus in the recording material fixing device does not contact the fixing film which is a heat source, and therefore a degree of the outer diameter fluctuation due to thermal expansion is small compared with the pressing roller. Here, the case where the pressing roller and the fixing discharging roller are driven by the same driving source 41 (
For example, in such a situation that the pressing roller is cool, the driving source 41 is rotated at high speed in order to avoid accumulation of flection (loop) of the recording material between the transfer portion and the fixing device. Then, the feeding speed of the fixing discharging roller driven by the same driving source 41 is higher than the feeding speed of the mostupstream feeding roller in the discharging device side in some cases, so that the flection of the recording material excessively accumulates between the fixing discharging roller and the mostupstream feeding roller in the discharging device side in some instances. As a result, in the case of low-rigidity paper such as thin paper, when waving, paper jam due to an insufficient feeding force and deposition of a contaminant on the feeding path are caused, there is a liability that image defect due to the deposition of the contamination or the like on the recording material and the damage of the recording material due to friction are generated. On the other hand, in the case of a high-rigidity recording material such as thick paper, the flection of the recording material accumulates between the fixing discharging roller and the mostupstream feeding roller in the discharging device side and slides with the feeding path, so that a back tension to the mostupstream feeding roller in the discharging device side increases. As a result, there is a liability that the paper jam, the image defect due to the slide (friction) of the recording material with the feeding path, and the damage of the recording material generate.
Further, in a situation that the pressing roller thermally expands by the heat conducted from the fixing film, the driving source 41 is rotated at high speed in order to avoid pulling of the recording material between the transfer portion and the fixing device. Then, the feeding speed of the fixing discharging roller driven by the same driving source 41 is lower than the feeding speed of the mostupstream feeding roller in the discharging device side in some cases, so that the recording material is pulled between the fixing discharging roller and the mostupstream feeding roller in the discharging device side and is excessively extended linearly in some instances. As a result, the recording material slides with a curved feeding path, and an excessive tension is exerted on the fixing discharging roller and the discharging device-side feeding roller, so that there is a liability that the image defect and the recording material damage generate. Further, by the slide of the recording material with the feeding path, the back tension is applied to the mostupstream feeding roller in the discharging device side, so that there is also a liability that the paper jam occurs.
In order to solve these problems, it would be considered that the following countermeasures are taken. For example, the feeding path is made long, and thus a time when the recording material is carried and fed between the fixing discharging roller and the discharging device-side feeding roller is decreased, so that a time when the fixing discharging roller pushes the recording material is shortened. As a result, it is possible to decrease a degree of accumulation of the loop (flection) of the recording material between the fixing discharging roller and the discharging device-side feeding roller. Further, it would be considered that a countermeasure having a constitution in which the feeding path is broadened (increased in width) with respect to a direction perpendicular to a recording material feeding direction and thus the recording material does not readily slide with the feeding path even in the case where the loop accumulates and in the case where the recording material is pulled between the rollers is taken. However, from the market, downsizing of the image forming apparatus and the discharging device is required from the viewpoint of ease of arrangement of the apparatus and the device, so that in the above-described two countermeasures, the apparatus (device) size becomes large, and therefore goes against needs of the market. Further, it would be also considered that a countermeasure that the pulling and the loop of the recording material between the rollers are eliminated by providing a loop detecting portion, e.g., between the fixing discharging roller and the discharging device-side feeding roller is taken. In this case, in order to provide the loop detecting portion, there is a need to use a member such as a sensor flag or a photo-interrupter, so that a cost thereof increases.
(Embodiment 1)
[Image Forming Apparatus]
An image forming apparatus in this embodiment will be described.
The image forming portion A includes an electrophotographic photosensitive member (photosensitive drum) 1 which is an image bearing member. The photosensitive drum 1 is rotatably supported by the main assembly M of the image forming apparatus constituting a casing of the image forming apparatus. At a periphery of the photosensitive drum 1, along a rotational direction (counterclockwise direction) shown by an arrow, a charging roller 3, a laser scanner 4, a developing device 5, a transfer roller 6 and a cleaning device 2 are provided in a named order.
The recording material feeding portion B includes sending rollers 10 and 11, and the sending roller rotates at predetermined timing an unshown driving source and sends the recording material P, stacked and accommodated in a cassette 7, to a recording material feeding path. In the image forming apparatus along the fixing device of the recording material P, a top sensor 8, a feeding roller 9, a loop detecting portion 12, a fixing discharging sensor 13, a fixing discharging roller 14, a switching flapper 15, a discharging roller 16 and a discharge tray 17 are provided in a named order.
Further, the image forming apparatus includes a controller 31 which is a control means for controlling the image forming portion A, the recording material feeding portion B, the fixing device C and the like. The controller 31 includes unshown CPU, ROM and RAM, and a control program for effecting speed control or the like described later is stored in the ROM, and the RAM is used for storing data for the control therein. The controller 31 as a first controller controls a driving speed of a driving source for driving the respective rollers for feeding the recording material P on the basis of a detection result obtained from the loop detecting portion 12 described later, and calculates an average speed of feeding speeds of the recording material P on the basis of the driving speed. Further, in the case where the above-described discharging device 18 is mounted, the controller 31 sends speed information and the like to a controller 32 as a second controller for controlling the discharging device 18.
During image formation, a drum motor for driving the photosensitive drum 1 is rotationally driven by the controller 31, so that the photosensitive drum 1 is rotated at a predetermined peripheral speed (hereinafter referred to as process speed) in an arrow direction in
Further, in synchronism with timing when the toner image formed on the photosensitive drum 1 reaches a transfer nip where the photosensitive drum 1 and the transfer roller 6 contact each other, a driving motor (not shown) provided in the recording material feeding portion B is rotationally driven. Then, the sending roller 10 sends the recording material P from the cassette 7 to the sending roller 11. The sent recording material P is fed by the sending roller 11 and passes through the top sensor 8, and then is fed to a transfer nip formed by contact of the surface of the photosensitive drum 1 with the transfer roller 6. By the above-described application of the transfer voltage to the transfer roller 6, the toner image is transferred from the surface of the photosensitive drum 1 onto the fed recording material P. The recording material P on which the toner image is transferred is fed to the fixing device C while a recording material feeding state is stabilized by the loop detecting portion 12. In the fixing device C, an unfixed toner image on the recording material P is heated and pressed, and thus is fixed on the recording material P. Then, the recording material P on which the toner image is fixed is fed by the fixing discharging roller 14 and the feeding roller 16, and then is discharged onto the discharge tray 17 constituting an upper surface of the main assembly M. The toner remaining on the surface of the photosensitive drum 1 after the toner image is transferred onto the recording material P is removed by a cleaning blade 27 of a cleaning device 2. The image forming apparatus repeats the above-described image forming operation, so that the recording materials P are sequentially subjected to printing. The image forming apparatus in this embodiment in which the fixing device C is mounted is capable of performing the printing at a print speed of 65 sheets/min in the case of A4-sized recording materials P.
The image forming apparatus to which this embodiment is applicable is not limited to the image forming apparatus shown in
[Fixing Device]
The fixing device C which is a fixing portion in this embodiment will be described with reference to
(Heater)
In (a) of
(Pressing Roller)
As shown in (a) of
(Fixing Film)
As shown in (a) of
As a material of the base layer 261, polyimide is used. As another material, in order to enhance a heat-conductive property and durability, it is also possible to use SUS or a heat-resistant resin material with low thermal capacity, such as polyamideimide, PEEK or PES. The base layer 261 is required to satisfy not only start agility such that the thermal capacity is made small and a time when a fixing film temperature reaches a fixable temperature is short but also mechanical strength, and therefore as the base layer 261 in this embodiment, a 70 μm-thick cylindrical polyimide (PI) bare tube was used.
Further, the elastic layer 262 is formed of a silicone rubber as a material thereof. By providing the elastic layer 262, the toner image can be covered with the fixing film 26 and heat can be uniformly supplied to the toner image, with the result that it is possible to obtain a good image which has high glossiness and which is free from unevenness. The elastic layer 262 is low in heat-conductive property when the elastic layer 262 is formed of the silicone rubber alone, and therefore a heat-conductive filler is added to the silicone rubber. As thermal conductivity, about 1.2 W/mK may preferably be ensured. As a candidate for the heat-conductive filler, it is possible to cite alumina, metal silicon, silicon carbide, zinc oxide and the like.
The surface layer 263 shown in (b) of
A primary layer 264 shown in (b) of
(Fixing Discharging Roller)
The fixing (sheet) discharging roller 14 which is a second rotatable member is formed of a heat-resistant silicone, a volume resistivity thereof is adjusted to about 1.0×103-3×104 (Ω.cm) by adding an electroconductive material such as carbon black, so that the (sheet) discharging roller 14 is made electroconductive. The discharging roller 14 is 11 mm in outer diameter, and as a shaft portion thereof, a solid or hollow metal material such as iron or aluminum is used. Further, as a rubber material, EPDM (ethylene-propylene-diene rubber) or TPU (thermoplastic urethane resin elastomer) or the like is used in some cases. Further, as a roller opposing the discharging roller 14, a roller formed of a ROM material is used, and is rotated by rotation of the discharging roller 14.
[Loop Detecting Portion]
The loop detecting portion 12 which is a detecting means for detecting an amount of a loop (loop amount) formed on the recording material P will be described with reference to
In this embodiment, the fed recording material P contacts the loop sensor flag 121 and rotates the loop sensor flag 121, so that the loop sensor flag blocks the light beam or permits transmission of the light beam, and thus a feeding state of the recording material P is detected. Incidentally, the loop detecting portion 21 may also be constituted using an optical sensor for directly detecting the feeding state of the recording material P without using the loop sensor flag 121 as in this embodiment.
Further, a position where the loop sensor 120 is provided is, as shown in
[Loop Control]
Loop control in which a feeding speed of the recording material by the pressing roller 25 is made substantially constant irrespective of an outer diameter fluctuation of the pressing roller 25 by changing a driving speed of the driving source for the pressing roller 25 will be described. The outer diameter of the pressing roller 25 fluctuates by heat conducted from the heater 20 which heats the fixing film 26. For that reason, even when the pressing roller 25 is driven at the same rotational speed (driving speed), the feeding speed at which the pressing roller 25 feeds the recording material P fluctuates. As a result, the loop amount of the recording material P in the feeding path between the transfer nip and the fixing device C fluctuates. That is, when the outer diameter of the pressing roller 25 increases and the feeding speed becomes high, the loop amount decreases, and when the outer diameter of the pressing roller 25 decreases due to a lowering in temperature of the pressing roller 25 and the feeding speed becomes low, the loop amount increases. Therefore, the controller adjusts the feeding speed of the pressing roller 25, i.e., the driving speed of the driving source 41 for driving the pressing roller 25 as described later, and thus effects control so that the loop amount falls within a predetermined range, so that a recording material feeding state is stabilized.
A relationship between a loop detection state of the recording material P by the loop detecting portion 12 and feeding speed control of the recording material P in the fixing device C will be described using (c) of
On the other hand, the case where the loop of the recording material P is detected by the loop sensor 120, i.e., in the case where the output of the loop sensor 120 is in an on state ((b) of
A loop control operation by the controller 31 will be described specifically using
In a section S1 (section to the circled numeral 1 in
[Recording Material Discharging Device]
A structure of the discharging device 18 and a feeding operation of the recording material P will be described using a portion (A) in
As regards the structure of the discharging device 18, as shown at a portion (B) in
(Feeding Roller)
The feeding rollers (conveying rollers) 181, 183, 185 and 186 provided in the discharging device 18 are constituted by a heat-resistant silicone rubber and are adjusted to have a volume resistivity of 1.0×103-3×104 (Ω.cm) by adding therein an electroconductive agent such as carbon black, so that these feeding rollers are made electroconductive. An outer diameter of each of the feeding rollers 181, 183, 185 and 186 is 12 mm, and a shaft portion of each feeding roller is formed of a solid or hollow metal material such as iron or aluminum. Further, as a rubber material, EPDM (ethylene-propylene-diene rubber) or TPU (thermoplastic polyurethane (resin) elastomer) may also be used. Rollers opposing the feeding rollers 181, 183, 185 and 186 are formed of a POM (thermoplastic polyoxymethylene) material, and are rotated by rotation of the feeding rollers 181, 183, 185 and 186, respectively.
[Feeding Control of Recording Material]
First, a constitution relating to control of the feeding speed of the recording material P between the image forming apparatus and the discharging device 18 will be described with reference to the drawings.
The feeding speed control of the recording material P between the image forming apparatus and the discharging device 18 will be described with reference to the drawings. In
Next, a feeding speed relationship among the pressing roller 25 of the fixing device C, the discharging roller 14 and the feeding roller 181 will be described with reference to
A relationship between the feeding speed V1 of the pressing roller 25 of the fixing device C and the feeding speed V2 of the discharging roller 14 will be described. In the abscissa of (a) and (b) of
As described above, the controller 31 repeats setting of the driving speed of the driving source 41 to two values in the high mode and the low mode, so that the feeding speed V1 of the pressing roller 25 is maintained at a certain speed. That is, the pressing roller 25 is heated by heat conducted from the fixing film 26 which is a heat source and is fluctuated in outer diameter, whereby the feeding speed for feeding the recording material P fluctuates even at the same driving speed (rotational speed). For that reason, the controller 31 switches the mode of the driving speed of the driving source 41 for driving the pressing roller 25 to high mode (101.3% of the process speed) or the low mode (95.3% of the process speed) depending on the loop state of the recording material P. As a result, the feeding speed V1 of the recording material P by the pressing roller 25 is kept at a certain speed.
On the other hand, the discharging roller 14 driven by the same driving source as the pressing roller 25 is, different from the pressing roller 25, little influenced by the heat from the fixing film 26, and therefore a degree of the fluctuation in outer diameter is small. As a result, depending on the fluctuation of the driving speed of the driving source 41, the feeding speed V2 of the recording material P by the discharging roller 14 largely changes, so that a peripheral speed difference generates between the feeding speed V1 and the feeding speed V2 in some cases. In the case where the recording material feeding speed V1 of the pressing roller 25 is higher than the recording material feeding speed V2 of the discharging roller 14, a loop of the recording material P generates between the pressing roller 25 and the discharging roller 14, so that a waving phenomenon generates. The waving phenomenon is such a phenomenon that the recording material P waves and loses its smoothness. In order to avoid this phenomenon, the magnitude relationship between the feeding speeds V1 and V2 is set at V2>V1 so that the feeding speed V2 is very higher than the feeding speed V1. Further, by setting the feeding speed relationship at V2>V1, the discharging roller 14 pulls the recording material P fed by the pressing roller 25. For that reason, when the discharging roller 14 excessively pulls the recording material P, there is a liability that abrasion of the fixing film 26 by an edge portion of the recording material P and improper fixing of the toner image due to a decrease in passing time of the recording material P through the fixing device C generate. Therefore, in order to avoid these influences, the magnitude relationship between the recording material feeding force F1 of the pressing roller 25 and the recording material feeding force F2 of the discharging roller 14 are set at F1>F2 in which the feeding force F1 is very larger than the feeding force F2 ((a) of
Next, a relationship between the feeding speed V2 of the discharging roller 14 driven by the driving source 41 and the feeding speed V2 of the feeding rollers 181, 185 and 186 of the discharging device 18 driven by the driving source 42 will be described. In the following, only the mostupstream feeding roller 181 in the feeding path of the recording material P in the discharging device 18 will be described as a representative example, but is also true for other feeding rollers 183, 185 and 186. In (a) and (b) of
Accordingly, the driving speed of the driving source 41 changes depending on the detection result of the loop detecting portion 12, so that even when the feeding speed V2 of the discharging roller 14 fluctuates, the feeding speed V3 of the feeding roller 181 of the discharging device 18 is unchanged.
Here, between the feeding roller 181 of the discharging device 18 and the discharging roller 14, in order that the recording material P is not excessively pulled at all times and that the loop (flection) is not excessively accumulated at all times, it is ideal that the relationship between the feeding speeds V2 and V3 is set at the following relationship. That is, the relationship between the feeding speeds V2 and V3 is set at V2=V3, so that the recording material feeding speeds of the respective rollers are made equal to each other. In
Next, a relationship among the feeding force F3 and the feeding forces F1 and F2 will be described. As described above, the feeding force F2 of the discharging roller 14 is set so as to be weaker than the feeding force F1 of the pressing roller 25 (F1>>F2). In the case where when the discharging device 18 is mounted, the weak feeding force F2 of the discharging roller 14 is dominant over the feeding force F3 of the feeding roller (e.g., the feeding roller 181) of the discharging device 8 (F2>F3), the feeding force F2 is insufficient for feeding a recording material having a large basis weight, such as thick paper or OHT. For that reason, the feeding force F3 of the feeding roller is set at a large value, so that an insufficient feeding force is avoided (F3>F2) ((a) of
The feeding speed V3 of the feeding rollers 181, 183, 185 and 186 of the discharging device 18 when the discharging device 18 is mounted in the image forming apparatus will be described with reference to (b) and (c) of
[Flowchart of feeding control]
A flowchart of the feeding control of the recording material P in this embodiment is shown in
First, the flowchart of (a) of
The controller 31 discriminates whether or not a first predetermined time T1 has elapsed from start of the image formation (S3). The first predetermined time T1 is set correspondingly the process speed corresponding to the feeding speed of the recording material P and is a time required until the leading end of the recording material P enters the fixing nip. When the controller 31 discriminated that the first predetermined time T1 elapsed, the controller 31 starts loop control of the recording material P by the loop detecting portion 12 (S4). That is, in the case where the loop detecting portion 12 is turned on (S5), the controller 31 sets the feeding speed of the recording material P by the pressing roller 25 at a high speed (S6), and in the case where the loop detecting portion 12 is turned off (S5), the controller 31 sets the feeding speed of the recording material P by the pressing roller 25 at a low speed (S7).
The controller 31 discriminates whether or not a second predetermined time T2 has elapsed from the start of the image formation (S8). The second predetermined time T2 is set correspondingly to the process speed for the recording material P and is a time required until the leading end of the recording material P enters the mostupstream feeding roller of the discharging device 18. When the controller 31 discriminated that the second predetermined time T2 elapsed, the controller 31 calculates the average feeding speed V′ in the previous and current sections (S9). The controller 31 sends information on the calculated average feeding speed V′ to the controller 32 of the discharging device 18 (S10).
The controller 31 discriminates whether or not a third predetermined time T3 has elapsed from the starts of the image formation (S11). The third predetermined time T3 is a time required until the trailing end of the recording material P passes through the transfer roller 6. When the controller 31 discriminated that the third predetermined time T3 elapsed, the controller 31 ends the loop control and calculates the average feeding speed V in the previous and current sections (S12). Then, the controller 31 controls the driving speed of the driving source 41, and sets the feeding speed of the recording material P by the pressing roller 25 at the calculated average feeding speed V (S13). The controller 31 discriminates whether or not the recording material P is discharged from the image forming apparatus (S14), and when the controller 31 discriminated that the recording material P was discharged, the controller 31 checks whether or not a subsequent image forming instruction is provided (S15). In the case where the subsequent image forming instruction is provided, the process of the controller 31 returns to S1. In the case where the subsequent image forming instruction is not provided, the control in this flowchart is ended.
The flowchart of (b) of
(Comparison Evaluation of Embodiment 1 and Conventional Examples)
As described above, in this embodiment, the feeding speed V2 of the discharging roller 14 and the feeding speed V3 of the feeding roller of the discharging device 18 are speeds such that there is substantially no speed difference, but in the following, a feeding state in which there is a speed difference between the two feeding speeds V2 and V3 will be described.
First, with reference to (A) of
On the other hand, in the case where the feeding speed V3 of the feeding roller 181 of the discharging device 18 shown in (A-2) of (A) of
Next, with reference to (b) of
On the other hand, in the case where the feeding speed V3 of the feeding roller 183 of the discharging device 18 shown in (B-2) of (B) of
Then, evaluation results as to a generation frequency of the image defect due to the slide of the recording material and a generation frequency of the paper jam in the constitution in this embodiment are shown in Tables 1 and 2 together with evaluation results in conventional examples. Evaluation in this embodiment shown in Tables 1 and 2 was made using the constitution of the portion (B) of
The constitutions in the respective tables are the same. In a leftmost column, a ratio (%) of the feeding speed to the process speed (“FIXING DISCHARGE RATIO” in the table) and is 98%, 100%, 102% and 104% with an increment of 2%. Incidentally, the feeding speed of the discharging roller 14 is controllable in a range from 98.3% to 104.3%, which are the associated calculated values +3% as described above, so as to change in increments of 0.1%. On the other hand, other three columns are those corresponding to the feeding speeds of the feeding roller 181 or the like of the discharging device 18. The second column from the leftmost column shows the evaluation result in the case where the feeding speed control of the feeding roller in this embodiment was effected. The right-hand two columns show the evaluation result in the case where the feeding speed of the feeding roller of the discharging device 18 was the fixed speed (“FIXED SPEED” in the table) described with reference to (d) of
From Table 1, it is understood that the image defect generates due to the slide of the recording material P with the guiding wall in the case where the feeding speed of the feeding roller of the discharging device in the conventional example is a fixed speed, but does not generate by effecting the above-described feeding speed control of the rollers in the case of Embodiment 1. Further, also from Table 2, it is understood that the paper jam generates in the case where the feeding speed of the feeding roller of the discharging device in the conventional example is the fixed speed, but does not generate by effecting the above-described feeding speed control of the rollers in the case of Embodiment 1. That is, from Tables 1 and 2, it is understood that the recording material P is prevented from contacting the guiding wall of the recording material feeding path by the feeding speed control of the rollers and thus degrees of the image defect due to the slide of the recording material P and the paper jam decreases.
As described above, according to this embodiment, the average speed information of the recording material feeding by the loop control between the transfer portion and the fixing device is fed back to the discharging device, so that the loop of the recording material is maintained at a certain amount between the discharging roller and the feeding roller of the discharging device. That is, the information on the feeding speed of the discharging roller of the image forming apparatus is fed from the controller of the image forming apparatus to the controller of the discharging device, and then the controller of the discharging device provides an instruction of the feeding speed of the feeding roller of the discharging device depending on the fed feeding speed. As a result, the loop of the recording material is maintained at a certain amount and a feeding property of the recording material between the fixing discharging roller and the discharging device feeding roller is stabilized, so that it is possible to suppress the generation of the paper jam and reduce degrees of damage on the recording material and the generation of the image defect.
Further, the loop detecting portion is provided downstream of the fixing device, so that there is no need to provide an additional member and extend a width of the feeding path, and thus an increase in cost does not generate. In addition, no sensor is used and the feeding path is shortened and reduced, so that also a space reduction effect in the image forming apparatus can be expected and thus leads to downsizing of the image forming apparatus.
As described above, it is possible to stabilize the feeding state of the recording material between the image forming apparatus and the discharging device.
(Embodiment 2)
In Embodiment 1, the constitution in which the controller 31 calculates the average value of the feeding speed of the pressing roller 25 to be controlled on the basis of the detection result by the loop detecting portion 12 and then feeds the calculated average feeding speed value to the controller 32 provided in the discharging device 18 side, and the controller 32 of the discharging device 18 controls the feeding speed of the feeding roller 181 and the like was described. In Embodiment 2, a constitution in which in the case where the image forming apparatus is not provided with the loop detecting portion 12 in the image forming apparatus, the feeding speed of the discharging device 18 is controlled depending on a degree of heating of the pressing roller 25 by the heat from the heater 20 will be described.
[Degree of Heating of Fixing Device and prediction by Fixing Counter]
First, the degree of heating of the pressing roller 25 will be described. In general, it is known that the heat generated by the heater 20 heats the unfixed toner image on the recording material and fixes the toner image on the recording material and that a part of the heat of the heater 20 is conducted to the pressing roller 25 having a relatively large thermal capacity. For that reason, with repetition of the printing operation, the temperature of the pressing roller 25 gradually increases. This phenomenon continues until heat balance between an amount of flow of the heat from the heater 20 to the pressing roller 25 and an amount of dissipation of heat from the pressing roller 25 is achieved. For that reason, in a state in which the temperature of the pressing roller 25 is relatively low, it can be said that the heat (quantity) generated in the heater 20 easily flows (conducts) into the pressing roller 25. In this embodiment, as an index of ease of the flowing-in of the heat, the temperature of the pressing roller 25 is noted and is defined as the degree of heating of the pressing roller 25.
Next, a fixing counter prediction method for predicting the degree of heating of the pressing roller 25 will be described. In the fixing counter prediction method in this embodiment, every predetermined time during the printing operation, a predetermined coefficient (count value) depending on an operation state is added, and depending on an integrated count value of the fixing counter, a current temperature of the pressing roller 25 is predicted. Specifically, the state of the printing operation is divided into a plurality of stages (states), and a coefficient (count value) is determined every divided time (operation state or operation stage). The divided time is a time of pre-heating (from start of electric power supply to the heater 20 to turning-on of the top sensor 8 by detection of the leading end of the recording material P) or a time of sheet passing (from the turning-on of the top sensor 8 to turning-off of the top sensor 8 by passing of the trailing end of the recording material P through the top sensor 8). Further, the divided time is, for example, a time of a sheet interval (from the turning-off of the top sensor 8 to turning-on of the top sensor 8 by detection of a subsequent recording material P) or a time of a rest of the main assembly (when the printing operation is not performed). The predetermined coefficient (count value) is a value proportional to an amount of heat added to the pressing roller 25 per unit time and is a value calculated on the basis of a difference in a supplied electric power amount to the heater 20, heat dissipation amount from the heater 20 and the like.
In
The controller 31 adds an associated coefficient in Table 3 to the count value of the fixing counter every time when 200 msec has elapsed in an associated operation state, and then predicts the current temperature of the pressing roller 25 depending on an integrated count value. For example, in the case where the count value of the fixing counter is 1000 in the pre-heating state, 7 is added to the fixing counter, and in the case where the count value of the fixing counter is 3000 during the sheet passing, 3 is added to the fixing counter. Further, in the case where the count value of the fixing counter is 4500 in the rest of the main assembly, 18 is subtracted from the count value of the fixing counter. When a power source of the main assembly of the image forming apparatus is turned off, the count value of the fixing counter is reset. When the power source is turned on, an initial value of the fixing counter is determined on the basis of temperature information by a thermistor 24 which is a temperature detecting member for detecting the temperature of the heater 20 when the power source is turned on. Thereafter, every lapse of a predetermined time, to the initial value set to the fixing counter, the coefficient corresponding to the operation state shown in Table 3 is added in real time.
In the case where a constitution employing an environment sensor for measuring a temperature and a humidity of a placement environment is used, the added coefficient may also be corrected on the basis of the temperature and/or the humidity. In that case, accuracy of current temperature prediction of the pressing roller 25 is improved in view of a difference, in temperature of the recording material P, heat dissipation amount of the pressing roller 25, supplied electric power amount which vary depending on the environment, as a factor having the influence on the temperature of the pressing roller 25. The method for predicting the degree of heating of the pressing roller 25 is not limited to the above-described method, but may also be, e.g., a method for discriminating the degree of heating from a print number.
[Feeding Speed of Recording Material by Image Forming Apparatus]
In this embodiment, in order to stabilize the feeding state of the recording material P from the transfer nip to the fixing device C in the feeding path, the change in feeding speed due to outer diameter expansion of the pressing roller 25 generated by the heat of the heater 20 is calculated and predicted. Then, depending on the predicted change in feeding speed, the driving speed of the driving source 41 is changed, so that the feeding speed of the recording material P is maintained at a certain value to the possible extent. Such speed control is effected. In
[Feeding Speed of Discharging Device]
The feeding speed of the feeding rollers (e.g., the feeding roller 181 and the like) of the discharging device 18 is, similarly as in Embodiment 1, determined by the controller 32 on the basis of the process speed of the pressing roller 25 in each of the regions (A), (B) and (C), fed from the controller 31. Table 4 is a table showing a relationship among the fixing counter region, the driving speed of the pressing roller and the feeding speed of the discharging device.
The four columns of Table 4 are constituted by the fixing counter, the region, a predicted value of the driving speed of the pressing roller, and the feeding speed of the discharging device from a leftmost column. In the column of the fixing counter, count value ranges of the fixing counter corresponding to the regions (A), (B) and (C), respectively are shown. In the column of the predicted value of the driving speed of the pressing roller 25, predicted values of the driving speeds of the pressing roller 25 corresponding to the regions (A), (B) and (C), respectively are shown, i.e., 101.3%, 98.3% and 96.2% which are the center values in the respective regions shown in (a) of
[Flowchart of Feeding Control]
A flowchart of the feeding control of the recording material P in this embodiment is shown in
First, the flowchart of (a) of
The controller 31 discriminates whether or not a first predetermined time T1 has elapsed from start of the image formation (S23). The first predetermined time T1 is set correspondingly the process speed corresponding to the feeding speed of the recording material P and is a time required until the leading end of the recording material P enters the fixing nip. When the controller 31 discriminated that the first predetermined time T1 elapsed, the controller 31 starts the above-described speed renewal control (S24). That is, in the case where the controller 31 checks that a warm-air counter belongs to any one of the regions (A), (B) and (C) (S25) at that time, and sets the feeding speed of the recording material P by the pressing roller 25 at a feeding speed Vi in an associated region (S26).
The controller 31 discriminates whether or not a second predetermined time T2 has elapsed from the start of the image formation (S27). The second predetermined time T2 is set correspondingly to the process speed for the recording material P and is a time required until the leading end of the recording material P enters the mostupstream feeding roller of the discharging device 18. When the controller 31 discriminated that the second predetermined time T2 elapsed, the controller 31 sends information on the feeding speed Vi of the recording material P at that time to the controller 32 of the discharging device 18 (S28).
The controller 31 discriminates whether or not a third predetermined time T3 has elapsed from the starts of the image formation (S29). The third predetermined time T3 is a time required until the trailing end of the recording material P passes through the transfer roller 6. When the controller 31 discriminated that the third predetermined time T3 elapsed, the controller 31 ends the speed renewal control (S30). Then, the controller 31 controls the driving speed of the driving source 41, and maintains the feeding speed of the recording material P by the pressing roller 25 at the feeding speed Vi (S31). The controller 31 discriminates whether or not the recording material P is discharged from the image forming apparatus (S32), and when the controller 31 discriminated that the recording material P was discharged, the controller 31 checks whether or not a subsequent image forming instruction is provided (S33). In the case where the subsequent image forming instruction is provided, the process of the controller 31 returns to S1. In the case where the subsequent image forming instruction is not provided, the control in this flowchart is ended.
The flowchart of (b) of
Then, evaluation results as to a generation frequency of the image defect due to the slide of the recording material and a generation frequency of the paper jam in the constitution in this embodiment shown at the portion (B) of
The constitutions in the respective tables are the same. In a leftmost column, a ratio (%) of the feeding speed to the process speed (“FIXING DISCHARGE RATIO” in the table) and is 99.2%, 101.3% and 104.3% with an increment of 2%. On the other hand, other three columns are those corresponding to the feeding speeds of the feeding roller 183 or the like of the discharging device 18. The second column from the leftmost column shows the evaluation result in the case where the feeding speed control of the feeding roller in this embodiment was effected. The right-hand two columns show the evaluation result in the case where the feeding speed of the feeding roller of the discharging device 18 was the fixed speed (“FIXED SPEED” in the table) described with reference to (d) of
From Table 5, it is understood that the image defect generates due to the slide of the recording material P with the guiding wall in the case where the feeding speed of the feeding roller of the discharging device in the conventional example is a fixed speed, but does not generate by effecting the above-described feeding speed control of the rollers in the case of Embodiment 1. Further, also from Table 6, it is understood that the paper jam generates in the case where the feeding speed of the feeding roller of the discharging device in the conventional example is the fixed speed, but does not generate by effecting the above-described feeding speed control of the rollers in the case of Embodiment 1. That is, from Tables 5 and 6, it is understood that the recording material P is prevented from contacting the guiding wall of the recording material feeding path by the feeding speed control of the rollers on the basis of the prediction of the temperature of the pressing roller 25 and thus degrees of the image defect due to the slide of the recording material P and the paper jam decreases.
As described above, according to this embodiment, it is possible to stabilize the feeding state of the recording material between the image forming apparatus and the discharging device.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Applications Nos. 2015-202125 filed on Oct. 13, 2015, and 2016-158956 filed on Aug. 12, 2016, which are hereby incorporated by reference herein in their entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-202125 | Oct 2015 | JP | national |
| 2016-158956 | Aug 2016 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5819149 | Watanabe | Oct 1998 | A |
| 8068778 | Kaino et al. | Nov 2011 | B2 |
| 8430392 | Nada et al. | Apr 2013 | B2 |
| 8646776 | Agata et al. | Feb 2014 | B2 |
| 20040037600 | Eda | Feb 2004 | A1 |
| 20060051116 | Koshida | Mar 2006 | A1 |
| 20070009271 | Tanonaka | Jan 2007 | A1 |
| Number | Date | Country |
|---|---|---|
| 2001-106380 | Apr 2001 | JP |
| 2002-311659 | Oct 2002 | JP |
| 2006-124125 | May 2006 | JP |
| 2013-105125 | May 2013 | JP |
| 2013-130741 | Jul 2013 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20170102654 A1 | Apr 2017 | US |
