Patent Grant
10921737
The present invention relates to a fixing apparatus and an image forming apparatus including the fixing apparatus.
An electrophotographic copying machine and an electrophotographic printer is equipped with a fixing apparatus that heats and fixes a toner image formed on a recording material. In such a fixing apparatus, when print is performed continuously on recording materials with a width narrower than that of a recording material having a maximum size for print in the image forming apparatus (hereinafter, referred to as small size sheet), the following phenomenon occurs. That is, in regions of the fixing nip portion in the longitudinal direction where a small size sheet does not pass (hereinafter, referred to as non-sheet-feeding portions), a phenomenon in which the non-sheet-feeding portions gradually rise in temperature (hereinafter, referred to as non-sheet-feeding portion temperature rise) occurs. If the temperature of the non-sheet-feeding portions becomes excessively high, the temperature has various influences on components in the apparatus. If print is performed on a large size sheet having a width larger than that of a small size sheet in a state where the non-sheet-feeding portion temperature rise occurs, a phenomenon called high-temperature offset may occur in regions corresponding to the non-sheet-feeding portions in the small size sheet.
As a configuration to prevent such non-sheet-feeding portion temperature rise, for example, Japanese Patent Application Laid-Open No. 2001-100558 discloses the following configuration. That is, a configuration that includes a plurality of heat generation members having different lengths and exclusively switches by a switch relay a heat generation member that supplies electric power, so as to selectively use a heat generation member having a length corresponding to a size of a recording material.
However, the size of the recording material does not necessarily match one of the lengths of the heat generation members, and there is a case where a recording material of an intermediate size of the heat generation members having the different length (hereinafter, referred to as an intermediate size sheet) is caused to pass a fixing nip portion. In such a case, a measure in which, for example, a sheet number of recording materials to pass (hereinafter, referred to as feeding sheet number) per unit time (hereinafter, referred to as throughput) is decreased to restrain occurrence of the non-sheet-feeding portion temperature rise. For that reason, there is a demand for restraining the occurrence of the non-sheet-feeding portion temperature rise without decreasing the throughput even for intermediate size sheets.
An aspect of the present invention is a fixing apparatus for performing fixing processing on an unfixed toner image on a recording material, including a heater including at least a first heat generation member and a second heat generation member having a length in a longitudinal direction shorter than a length of the first heat generation member in the longitudinal direction, a switching unit configured to switch a heat generation member to which electric power is supplied, to one of the first heat generation member and the second heat generation member, and a control unit configured to control the switching unit, wherein in a case where the fixing processing is performed continuously on recording materials having a width in the longitudinal direction shorter than a length of the first heat generation member in the longitudinal direction and longer than a length of the second heat generation member in the longitudinal direction, and wherein the control unit sets a timing to switch between the first heat generation member and the second heat generation member by the switching unit, based on information relating to a size of the recording materials.
Another aspect of the present invention is an image forming apparatus including an image forming unit configured to form an unfixed toner image on a recording material, and a fixing apparatus for performing fixing processing on an unfixed toner image on a recording material, including a heater including at least a first heat generation member and a second heat generation member having a length in a longitudinal direction shorter than a length of the first heat generation member in the longitudinal direction, a switching unit configured to switch a heat generation member to which electric power is supplied, to one of the first heat generation member and the second heat generation member, and a control unit configured to control the switching unit, wherein in a case where the fixing processing is performed continuously on recording materials having a width in the longitudinal direction shorter than a length of the first heat generation member in the longitudinal direction and longer than a length of the second heat generation member in the longitudinal direction, and wherein the control unit sets a timing to switch between the first heat generation member and the second heat generation member by the switching unit, based on information relating to a size of the recording materials, wherein the fixing apparatus fixes the unfixed toner image formed on the recording material by the image forming unit on the recording material.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Embodiments of the present invention will be described below with reference to the drawings. “Passing a recording paper through a fixing nip portion” is referred to also as feeding paper in the following Embodiments. In addition, regions of the fixing nip portion in the longitudinal direction where a small size sheet does not pass is referred to as non-sheet-feeding portions, and a phenomenon in which the non-sheet-feeding portions gradually rises in temperature is referred to as non-sheet-feeding portion temperature rise.
[Overall Structure]
In the first station, a photosensitive drum 1a being an image bearing member is an organic photoconductor (OPC) photosensitive drum. The photosensitive drum 1a is made by stacking a plurality of layers of functional organic materials including a carrier generation layer that generates electrical charge when exposed to light, a charge transport layer that transports the generated electrical charge, and the like, on a metallic cylinder, where an outermost layer has such a low electric conductivity that the photosensitive drum 1a is substantially insulative. A charging roller 2a being a charging unit abuts against the photosensitive drum 1a, and as the photosensitive drum 1a rotates, the charging roller 2a follows the rotation to rotate, charging a surface of the photosensitive drum 1a uniformly. To the charging roller 2a, a DC voltage or a voltage superimposed on an AC voltage is applied, and the photosensitive drum 1a is charged by discharge occurring in a minute air gap upstream or downstream of a nip portion formed by the charging roller 2a and the surface of the photosensitive drum 1a in a rotating direction. A cleaning unit 3a is a unit that removes toner left on the photosensitive drum 1a after transfer described below. A developing unit 8a being a development unit is formed of a developing roller 4a, a nonmagnetic one-component toner 5a, and a developer application blade 7a. The photosensitive drum 1a, the charging roller 2a, the cleaning unit 3a, and the developing unit 8a form an integral process cartridge 9a that is attachable and detachable with respect to the image forming apparatus.
An exposure device 11a being an exposure unit is formed of a scanning unit that scans laser light with a polygon mirror or a light emitting diode (LED) array, and irradiates the photosensitive drum 1a with a scanning beam 12a modulated based on an image signal. The charging roller 2a is connected to a high voltage power supply for charge 20a, which is a voltage supply unit for the charging roller 2a. The developing roller 4a is connected to a high voltage power supply for development 21a, which is a voltage supply unit for the developing roller 4a. A primary transfer roller 10a is connected to a high voltage power supply for primary transfer 22a, which is a voltage supply unit for the primary transfer roller 10a. The first station has the configuration described above, and the second, third and fourth stations each have the same configuration. In the other stations, components having the same functions as those of the first station will be denoted by the same reference numerals, which are followed by b, c and d as indices for respective stations. In the following description, the indices a, b, c and d will be omitted except for cases where a specific station is described.
An intermediate transfer belt 13 is supported by three rollers, as its tensioning members, including a secondary transfer opposing roller 15, a tension roller 14, and an auxiliary roller 19. The tension roller 14 alone applies a force in a direction of stretching the intermediate transfer belt 13 using a spring, by which the intermediate transfer belt 13 keeps an appropriate force of tension. The secondary transfer opposing roller 15 receives rotary drive from a main motor (not illustrated) to rotate, causing the intermediate transfer belt 13 wound around an outer circumference of the secondary transfer opposing roller 15 to rotate. The intermediate transfer belt 13 moves in a forward direction (e.g., clockwise direction in
Next, image forming operation of the image forming apparatus in Embodiment 1 will be described. Upon receiving print instructions in a standby state, the image forming apparatus starts the image forming operation. The photosensitive drum 1, the intermediate transfer belt 13, and the like start rotating by their main motors (not illustrated) in the arrow directions at a predetermined process speed. In Embodiment 1, the process speed is, for example, 100 mm/s (millimeter per second). The photosensitive drum 1a is uniformly charged by the charging roller 2a to which voltage is applied by the high voltage power supply for charge 20a, and is subsequently irradiated with the scanning beam 12a from the exposure device 11a, by which an electrostatic latent image according to image information is formed on the photosensitive drum 1a. Toner 5a in the developing unit 8a is negatively charged by the developer application blade 7a and is applied to the developing roller 4a. Then, to the developing roller 4a, a predetermined development voltage is supplied from the high voltage power supply for development 21a. When the electrostatic latent image formed on the photosensitive drum 1a reaches the developing roller 4a as the photosensitive drum 1a rotates, the electrostatic latent image becomes visible by the negatively charged toner adhered to the electrostatic latent image, and thus a toner image of a first color (e.g., Y (yellow)) is formed on the photosensitive drum 1a. The stations of the other colors, M (magenta), C (cyan) and K (black), (process cartridges 9b to 9d) operate similarly. Electrostatic latent image made by exposure are formed on the photosensitive drums 1a to 1d, with drawing signals from a controller (not illustrated) being delayed with constant timings based on distances between primary transfer positions of the respective colors. To the respective primary transfer rollers 10a to 10d, high direct current voltages with a polarity opposite to that of toner are applied. Through the above-described process, toner images are transferred on the intermediate transfer belt 13 one by one (hereinafter, referred to as primary transfer), and a multiplexed toner image is formed on the intermediate transfer belt 13.
Thereafter, in synchronization with the formation of the toner image, a sheet P being one of recording materials loaded in a cassette 16 is fed (picked up) by a feeding roller 17 that is driven to rotate by a sheet feeding solenoid (not illustrated). The fed sheet P is conveyed to registration rollers 18 by a conveyance roller. The sheet P is conveyed to a transfer nip portion by the registration rollers 18 in synchronization with the toner image on the intermediate transfer belt 13, the transfer nip portion being an abutting portion of the intermediate transfer belt 13 and a secondary transfer roller 25. The registration rollers 18 are provided with a registration sensor (not illustrated) for sensing presence/absence of the sheet P. To the secondary transfer roller 25, a voltage with a reversed polarity to that of the toner is applied by the high voltage power supply for secondary transfer 26, which causes the multiplexed toner image of the four colors beard on the intermediate transfer belt 13 is collectively transferred to the sheet P (recording material) (hereinafter, referred to as secondary transfer). The members contribute to the formation of an unfixed toner image on the sheet P (e.g., the photosensitive drum 1) function as an image forming unit. After completion of the secondary transfer, toner left on the intermediate transfer belt 13 is removed by the cleaning unit 27. The sheet P after the completion of the secondary transfer is conveyed to a fixing apparatus 50 being a fixing unit, and with the toner image fixed thereto, the sheet P is discharged to a discharge tray 30 as an image formed matter (print, copy). The fixing apparatus 50 includes a film 51, a nip forming member 52, a pressing roller 53, and a heater 54, which will be described below. A sensor S is a sensor that is provided downstream of the fixing apparatus 50 in a conveyance direction of the sheet P and senses a passage of the sheet P.
In a print mode in which a plurality of sheets P are printed continuously (continuous job), the print is performed such that a toner image T on the intermediate transfer belt 13 and a sheet P are conveyed in synchronization with each other so that a distance between a trailing edge of a leading sheet P and a leading edge of a subsequent sheet P is equal to a setting value in each embodiment.
[Block Diagram of Image Forming Apparatus]
The video controller 91 converts the image data from the PC 110 into exposure data and transmits the exposure data to an exposure control device 93 in an engine controller 92. The exposure control device 93 is controlled by a CPU 94 to control the exposure device 11 according to on/off in the exposure data. Upon receiving the print instructions, the CPU 94 being a control unit starts an image forming sequence.
The engine controller 92 is equipped with the CPU 94, a memory 95, and the like and performs operations that are programmed in advance. The CPU 94 is assumed to have a timer 94a. The memory 95 stores information relating to switch timings for a heat generation member described below (Table 1 described below, etc.). A high voltage power supply 96 includes the high voltage power supply for charge 20, the high voltage power supply for development 21, the high voltage power supply for primary transfer 22, and the high voltage power supply for secondary transfer 26, which are previously described. A power control unit 97 includes a bidirectional thyristor (hereinafter, referred to as triac) 56, a heat generation member switching device 57 as a switching unit that exclusively selects a heat generation member to which electric power is to be supplied. The power control unit 97 selects a heat generation member that is to generate heat in the fixing apparatus 50 and determines an electric energy to supply. In Embodiment 1, the heat generation member switching device 57 is, for example, a C contact relay.
A driving device 98 includes a main motor 99, a fixing motor 100, and the like. A sensor 101 includes a fixing temperature sensor 59 that senses a temperature of the fixing apparatus 50, sheet presence sensors 102 each of which has a flag and senses presence/absence of a sheet P, and the like, and sensing results from the sensor 101 are sent to the CPU 94. The sensor S previously described is one of the sheet presence sensors 102. The CPU 94 acquires the sensing results from the sensor 101 in the image forming apparatus and controls the exposure device 11, the high voltage power supply 96, the power control unit 97, and the driving device 98. By forming an electrostatic latent image, transferring a developed toner image, fixing the toner image to a sheet P, and the like with these components, the CPU 94 controls an image forming process in which exposure data is printed on the sheet P in a form of the toner image. The image forming apparatus to which the present invention is applied is not limited to the image forming apparatus having the configuration described with reference to
[Fixing Apparatus]
Next, a configuration of the fixing apparatus 50 in Embodiment 1 will be described with reference to
A sheet P bearing an unfixed toner image Tn is conveyed from the left of
The film 51 being a first rotary member is a fixing film as a heating rotary member. In Embodiment 1, the film 51 is formed of three layers including a base layer, an elastic layer, and a release layer. For the base layer, polyimide is used, for example. On the base layer, the elastic layer made of silicone rubber and the release layer made of PFA are used. A thickness of the base layer is, for example, 50 μm, a thickness of the elastic layer is, for example, 200 μm, and a thickness of the release layer is, for example, 20 μm. An outer diameter of the film 51 is, for example, 18 mm. To an inner surface of the film 51, grease is applied to reduce frictional force that occurs between the film 51, and the nip forming member 52 and the heater 54 due to rotation of the film 51.
The nip forming member 52 takes a role of guiding the film 51 on an inner side of the film 51, as well as forming the fixing nip portion N with the pressing roller 53 across the film 51. The nip forming member 52 is a member having rigidity, heat-resistant properties, and heat-insulation properties, and is formed of liquid crystal polymer, or the like. The film 51 is fitted over this nip forming member 52. The pressing roller 53 being a second rotary member is a roller as a pressing rotary member. The pressing roller 53 is a core 53a made of copper, an elastic layer 53b made of silicone rubber, and a release layer 53c made of PFA material. A diameter of the core 53a is, for example, 12 mm, a thickness of the elastic layer 53b is, for example, 3 mm, and a thickness of the release layer 53c is, for example, 50 μm. A diameter of the pressing roller 53 is, for example, 20 mm. The pressing roller 53 is held rotatably at its both ends and is driven to rotate by the fixing motor 100 (see
(Heater)
The heater 54 will be described in detail with reference to
The heat generation member 54b1 being a first heat generation member has a length in the longitudinal direction (hereinafter, referred to also as size) different from that of the heat generation member 54b2 being a second heat generation member. The heater 54 in Embodiment 1 includes at least the heat generation members 54b1 and 54b2. Specifically, the length in the longitudinal direction of the heat generation member 54b1 is L1, the length in the longitudinal direction of the heat generation member 54b2 is L2, and the length L1 and the length L2 satisfy a relation of L1>L2. The length L1 of the heat generation member 54b1 in the longitudinal direction is, for example, L1=222 mm. The length L2 of the heat generation member 54b2 in the longitudinal direction is, for example, L2=185 mm. Resistance values of the heat generation members 54b1 and 54b2 are set at, for example, 20Ω and 24Ω, respectively. The length L1 of the heat generation member 54b1 is set at a length that enables a sheet P having a largest width of sheets P that can be printed (or conveyed) by this image forming apparatus (hereinafter, referred to as maximum-sheet-feeding width) to be subjected to fixing. The heat generation member 54b1 is electrically connected to the contacts 54d1 and 54d3 via the conductors 54c, and the heat generation member 54b2 is electrically connected to the contacts 54d2 and 54d3 via the conductors 54c. That is, the contact 54d3 is a contact that is connected to the heat generation members 54b1 and 54b2 in common.
The fixing temperature sensor 59 is positioned on an opposite surface of the substrate 54a to the protection glass layer 54e, disposed at a center position a of the heat generation members 54b1 and 54b2 in the longitudinal direction, and pressed against the substrate 54a at 200 grams-force (gf). The fixing temperature sensor 59 is, for example, a thermistor, senses a temperature of the heater 54, and outputs a sensing result to the CPU 94. Based on the sensing result from the fixing temperature sensor 59, the CPU 94 controls the temperature in fixing processing. In Embodiment 1, the power control unit 97 performs the temperature control of the fixing apparatus 50 at, for example, 180° C.
(Power Control Unit)
The heat generation member switching device 57 is, for example, a C contact relay in Embodiment 1. Specifically, the heat generation member switching device 57 includes a contact 57a connected to the AC power supply 55, a contact 57b1 connected to the contact 54d1, and a contact 57b2 connected to the contact 54d2. The heat generation member switching device 57 assumes one of a state where the contact 57a is connected to the contact 57b1 and a state where the contact 57a is connected to the contact 57b2, under control by the CPU 94. Switching of the heat generation member switching device 57 causes exclusive selection of whether to supply electric power to the heat generation member 54b1 or the 54b2. That is, the heat generation member switching device 57 switches the heater 54 to one of the heat generation member 54b1 and the heat generation member 54b2. The heat generation member switching device 57 performs the switching upon receiving a signal from the CPU 94. To prevent the contacts from fusing in the heat generation member switching device 57 being a C contact relay, the switching of the heat generation member switching device 57 is performed in a state where the triac 56 is out of conduction (state where power supply to the heat generation member 54b1 or the heat generation member 54b2 is cut off).
[Switch Operation of Heat Generation Member]
In Embodiment 1, switching between the heat generation members 54b is performed during a sheet interval time period. Here, the sheet interval time period refers to as a time period from a time point at which a trailing edge of a leading sheet P (first recording material) passes the fixing nip portion N until a time point at which a leading edge of a sheet P continuously passing the fixing nip portion N subsequently to the sheet P (second recording material) enters the fixing nip portion N. In addition, a sheet interval refers to as a distance between the trailing edge of the leading sheet P and the leading edge of the subsequent sheet P. Operation to switch from the heat generation member 54b1 to the heat generation member 54b2 during the sheet interval time period will be described below.
The CPU 94 acquires a time at which the leading edge of the leading sheet P passes the sensor S provided downstream of the fixing nip portion N, based on a sensing result from the sensor S. Based on the time at which the leading edge of the leading sheet P passes the sensor S, a length of the sheet P in the conveyance direction, and the process speed, the CPU 94 calculates a timing t1 at which the trailing edge of this sheet P passes the fixing nip portion. The CPU 94 refers to the timer 94a, and at the timing t1 at which the trailing edge of the leading sheet P passes the fixing nip portion N, in other words, at a time when the sheet interval time period comes, the CPU 94 turns off the triac 56 using the power control unit 97 to cut off the supply of electric power to the heat generation member 54b1.
At a timing t2 at which 20 ms elapses from the timing t1, the CPU 94 uses the power control unit 97 to send a signal for switching between the heat generation members 54b to the heat generation member switching device 57. Then, at a timing t3 at which another 200 ms elapses from the timing t2, switching from the heat generation member 54b1 to the heat generation member 54b2 by the heat generation member switching device 57 is completed. At a timing t4 at which 100 ms elapses from the timing t3, the CPU 94 uses the triac 56 to start the supply of electric power to the heat generation member 54b2. Here, 100 ms is provided between the timing t3 and the timing t4 to avoid fusion of the contacts in the heat generation member switching device 57 reliably even when an error occurs in an operating time of the heat generation member switching device 57. A total time from the timing t1 to the timing t4 is 320 ms (=20 ms+200 ms+100 ms), and this time is set to fall within the sheet interval time period. This is because the time from the timing t1 to the timing t4 being longer than the sheet interval time period causes the following phenomenon. That is, this disables the heat generation member 54b2 to heat the leading end of the subsequent sheet P and its vicinity until the timing t4, which may bring about a poor fixing in the subsequent sheet P.
Here, sheets P having widths (hereinafter, referred to as paper width) equal to or shorter than a length of the heat generation member 54b1 in the longitudinal direction (hereinafter, referred to as width) and equal to or longer than a width of the heat generation member 54b2 are referred to as intermediate size sheets. Of the intermediate size sheets, sheets P having paper widths equal to or longer than a paper width of A4 size, 210 mm (A4 size, letter (LTR) size, legal (LGL) size, etc.) are referred to as large size sheets. Sheets P having widths shorter than the width of the heat generation member 54b2 will be referred to as small size sheets.
[Printing Operation]
Upon receiving the print command, the CPU 94 executes a process including step (hereinafter, abbreviated to S) 701 and its subsequent steps. In S701, the CPU 94 acquires sheet size information on a sheet P, that is, the standard size information in Embodiment 1, from the PC 110. In S702, the CPU 94 acquires a count value described below. In S703, according to the sheet size information acquired in S701 (the standard size information in Embodiment 1) and the count value acquired in S702, the CPU 94 refers to Table 1 described below showing switch timings of the heat generation member 54b and acquires the switch timing of the heat generation member 54b. In S704, the CPU 94 performs print on the sheet P while controlling the heater 54 according to the switch timing of the heat generation member 54b acquired in S703. Note that the print here means print performed continuously on a plurality of sheets P.
(Switch Timing of Heat Generation Member 54b)
In S703, the CPU 94 acquires the following information when causing large size sheets, intermediate size sheets, and small size sheets selected through the sequence of
Table 1 is a table showing a list that includes typical standard size sheets including the large size sheet, the intermediate size sheet, and the small size sheet, and includes ratios of sheet numbers for which electric power is supplied to the heat generation member 54b1 or the heat generation member 54b2. In Table 1, its first column shows size classification of sheets P (large size sheet, etc.), its second column shows names of the standard size sheets (A4, etc.), and its third column shows sizes of the sheets P (e.g., for A4, width W=210 mm and length Z=297 mm). A fourth column of Table 1 shows a predetermined sheet number (e.g., three for A4) for which the heat generation member 54b1 is forcibly used to perform the print in a case where the print is started from a cold state. The cold state refers to a case where the count value described below is less than a first target count value (predetermined value) (being less than the predetermined value) at a time of starting the print. A state where the count value is equal to or greater than the first target count value (being equal to or greater than the predetermined value) is referred to as a hot state. A fifth column of Table 1 shows ratios of sheet numbers for which electric power is supplied, and these ratios are categorized into a zone 1 and a zone 2. For each zone, the fifth column shows a ratio between sheet numbers for which the heat generation member 54b1 and the heat generation member 54b2 are used. For example, in a case of the intermediate size sheet and the zone 1, a ratio between the heat generation member 54b1 and the heat generation member 54b2 is 5 to 1. This shows a process including fixing processing on five sheets P using the heat generation member 54b1 and subsequent fixing processing on one sheet P using the heat generation member 54b2 is repeated. Information shown in Table 1, that is, information on switch control of the heat generation members 54b based on the sheet size information and the count value, in other words, information on patterns of which of the heat generation members 54b is used to how many sheets P will be referred to as heat generation member patterns. In Table 1, a sheet number of the sheets P on which the fixing processing is performed using the heat generation member 54b1 in a case where the count value is equal to or greater than the first target count value is set to be less than that in a case where the count value is less than the first target count value.
As shown in the row regarding the large size sheet in Table 1, a column of ratio showing “1” for the heat generation member 54b1 and “-” for the heat generation member 54b2 indicates that print is performed using only the heat generation member 54b1 and print using the heat generation member 54b2 is not performed. Regarding the intermediate size sheet, a column of ratio showing “5” for the heat generation member 54b1 and “1” for the heat generation member 54b2 (Zone 1) indicates that print is performed on five sheets using only the heat generation member 54b1 and print is performed on one sheet using only the heat generation member 54b2.
For the small size sheet, the column of ratio shows “-” for the heat generation member 54b1 and “1” for the heat generation member 54b2. Here, regarding the small size sheet, “-” is set for the heat generation member 54b1, which means that, in a case where print is started from the cold state, the heat generation member 54b1 is forcibly used to perform the print on first three sheets and then the print is performed using only the heat generation member 54b2. A reason for performing the print on the first three sheets forcibly using the heat generation member 54b1 is as follows. That is, in this manner, the heat generation member 54b1 transmits heat to an entire region of the fixing nip portion N in the longitudinal direction uniformly, so as to uniformly soften the grease on the inner surface of the film 51. This prevents the film 51 from deforming due to unevenness in sliding load between the film 51 and the heater 54. A reason for using the heat generation member 54b2 for a fourth small size sheet onward is to suppress occurrences of the non-sheet-feeding portion temperature rise as much as possible and to increase a production speed for small size sheets by using the heat generation member 54b2 having a smaller non-sheet-feeding portion than the heat generation member 54b1 having a larger non-sheet-feeding portion.
Thereafter, a case where the CPU 94 determines that a sheet P is of the intermediate size sheet will be described. The intermediate size sheet used in Embodiment 1 is a sheet P of 16K size (195 mm wide, 267 mm long). From a viewpoint of preventing the deformation of the film 51 previously described, the heat generation member 54b1 is forcibly used to perform print on three sheets for all of the standard size sheets in a case where the print is performed from the cold state. To perform print on intermediate size sheets, a switch timing of heat generation members 54b are set for each of the zone 1 and the zone 2. For example, in the zone 1, the heat generation member 54b1 is used to perform the fixing processing on five intermediate size sheets, and then the heat generation member 54b2 is used to perform the fixing processing on one intermediate size sheet. For example, in the zone 2, the heat generation member 54b1 is used to perform the fixing processing on four intermediate size sheets, and then the heat generation member 54b2 is used to perform the fixing processing on one intermediate size sheet.
[Continuous Print Using Switch Timing in Table 1]
Next, a count prediction system and zones will be described. In Embodiment 1, a count prediction system to predict temperatures of members of the fixing apparatus 50 (the film 51, the pressing roller 53, the nip forming member 52, etc.) is adopted. The count value is incremented by +1 every time the fixing processing is performed on one sheet P, and the count value increases with an increase in sheet number of sheet P subjected to the fixing processing. In contrast, in a standby state after fixing processing of the continuous print is ended, the count value is also decremented with time as the members of the fixing apparatus 50 are cooled down naturally. Specifically, the members of the fixing apparatus 50 are investigated in advance regarding their cooling properties, and the count value is decremented using an arithmetic expression that is a function of elapsed time. While the fixing processing is performed continuously on sheets P, the count value increases according to a sheet number of the sheets P, and after the fixing processing fixing processing continuously performed is ended, the count value is counted such that the count value decreases according to a drop in temperature of the heater 54. As seen from the above, management of the count value enables the temperatures of the members of the fixing apparatus 50 to be predicted. The management of the count value is performed by the CPU 94. As previously described, the count value is used for determining between the cold state and the hot state as well as for determination between the zone 1 and the zone 2 described below.
In Embodiment 1, the zone 1 refers to a zone from a count value of zero to the first target count value, the zone 2 refers to a zone from the first target count value to the second target count value, and a switch frequency of the heat generation members 54b (a ratio in Table 1) is changed for each zone. Note that a number of the zones is not necessarily limited to two and a plurality of zones may be provided. In Embodiment 1, the first target count value is set at, for example, 30, and a second target count value is set at, for example, 100. In a case where print is started from the cold state (the count value is zero), the count value reaches 30, which is the first target count value, at a time when 30 sheets are subjected to the print. Therefore, the zone 1 ends at the 30th sheet and is switched to the zone 2 from a 31st sheet onward. That is, when the count value reaches the first target count value, the CPU 94 determines that the non-sheet-feeding portion temperature rise has reached a high temperature, and switches from the heat generation member 54b1 to the heat generation member 54b2.
In
In contrast, there are different switch timings for a case where the count value before print on the intermediate size sheets is started is less than 30, that is, a case of the cold state, and for a case where the count value is equal to or greater than 30, that is, a case of the hot state. A reason for this is that a surface temperature of the non-sheet-feeding portions of the film 51 in the hot state tends to be high as compared with the cold state, and thus it is necessary to suppress the non-sheet-feeding portion temperature rise by making switching the heat generation members 54b more frequency in the hot state than the cold state. In the case of (iii) of
(Printing 50 Sheets of Intermediate Size)
In Embodiment 1, a case of printing 50 sheets from the cold state will be described. As illustrated in (ii) of
In addition, in regions K at both end portions of the sheet P illustrated in
As described above, performing the control in Embodiment 1 can suppress the non-sheet-feeding portion temperature rise while ensuring good fixing properties, which enables 50 16K-size sheets being the intermediate size sheets to be printed continuously at a production speed as high as 19 sheets per minute. Therefore, a time taken to continuously print the 50 intermediate size sheets was about 156 seconds.
A configuration of an image forming apparatus applied in Comparison Example 1 will be described with the same components in Embodiment 1 denoted by the same reference characters.
In Comparison Example 1, a case where only the heat generation members 54b3 are used to continuously print 50 16K-size sheets as in Embodiment 1 will be described. In Comparison Example 1, the length of the heat generation members 54b3 is set as L1=222 mm as in Embodiment 1. Therefore, the non-sheet-feeding portion temperature rise occurs in the regions of the widths H=13.5 mm as in Embodiment 1 since the width W of the 16K-size sheet is set as width W=195 mm. In Comparison Example 1, note that there are no non-heat widths M because there is no heat generation member having a width smaller than that of the heat generation members 54b3, such as the heat generation member 54b2.
In Embodiment 1, to print the intermediate size sheets, the control to switch between the heat generation member 54b1 and the heat generation member 54b2 according to the sheet size information on the sheets P and the count value is performed as described above. Specifically, the fixing processing is performed on a first sheet number of sheets P by the heat generation member 54b1 in a state where electric power is supplied to the heat generation member 54b. When a state where the electric power is supplied to the heat generation member 54b1 is switched by the heat generation member switching device 57 to a state where the electric power is supplied to the heat generation member 54b2, the fixing processing is performed by the heat generation member 54b2 on a second sheet number of sheets P that is less than the first sheet number. This can suppress the non-sheet-feeding portion temperature rise, preventing a decrease in throughput, and thus the time to print 50 sheets can be shortened by 42 seconds as compared with the configuration in Comparison Example 1.
As described above, according to Embodiment 1, the non-sheet-feeding portion temperature rise can be suppressed without decreasing throughput also in a case where the intermediate size sheets are caused to pass the fixing nip portion.
In a configuration of an image forming apparatus applied in Embodiment 2, the same components in Embodiment 1 will be denoted by the same reference characters and will not be described.
In Table 2, its first column shows size classification of sheets P (large size sheet, etc.), and its second column shows sheet widths W (mm) of the sheets P (e.g., 210>W≥208). A third column of Table 2 shows a sheet number (e.g., three) for which the heat generation member 54b1 is forcibly used to perform the print in a case where the print is started from the cold state. As in Embodiment 1, from a viewpoint of preventing the deformation of the film 51, the heat generation member 54b1 is forcibly used to print, for example, three sheets, for all of the sheet widths W in a case where the print is performed from the cold state. A fourth column of Table 2 shows ratios of sheet numbers for which electric power is supplied, and these ratios are categorized into the zone 1 and the zone 2 as in Table 1 in Embodiment 1. For each zone, the fourth column shows a ratio between sheet numbers for which the heat generation member 54b1 and the heat generation member 54b2 are used.
A feature of Embodiment 2 is that a switch timing of the heat generation members 54b according to the acquired sheet width information is applied even in a case an intermediate size sheet other than the standard size sheets is specified. Note that there may be a method in which a plurality of areas of the sheet size are provided by including the sheet width information as well as information on the length of the sheet P in the conveyance direction, and a switch timing of the heat generation member 54b optimum for each area is set.
[Continuous Print Using Switch Control in Table 2]
Sheets P used in Embodiment 2 are sheets P having a sheet width W being the same as that of a 16K-size sheet, 195 mm, and a length Z being the same as that of a LGL-size sheet, 355.6 mm A case where these 50 sheets P are continuously printed from the cold state will be described (see
The CPU 94 acquires the sheet width W as W=195 mm based on the sheet width information, and from Table 2, performs such control that the heat generation member 54b1 is used to perform the fixing processing on four intermediate size sheets in the zone 1, and then the heat generation member 54b2 is used to perform the fixing processing on one intermediate size sheet. In addition, from Table 2, the CPU 94 performs such control that the heat generation member 54b1 is used to perform the fixing processing on three intermediate size sheets in the zone 2, and then the heat generation member 54b2 is used to perform the fixing processing on one intermediate size sheet. Other Respects (black dots and the like, count value, first target count value, etc.) are the same as those in Embodiment 1.
As described above, performing the control in Embodiment 2 can suppress the non-sheet-feeding portion temperature rise while ensuring good fixing properties even for the intermediate size sheets that are long as with the LGL size and are influenced significantly by the non-sheet-feeding portion temperature rise. In addition, even for such intermediate size sheets, the continuous print can be performed on 50 intermediate size sheets while keeping a production speed as high as 14 sheets per minute. As seen from the above, according to Embodiment 2, by using the sheet width information to apply a switch timing of the heat generation members 54b according to the sheet width information, a high production speed can be obtained irrespective of the sheet width W.
As described above, according to Embodiment 2, the non-sheet-feeding portion temperature rise can be suppressed without decreasing throughput also in a case where the intermediate size sheets are caused to pass the fixing nip portion.
In a configuration of an image forming apparatus applied in Embodiment 3, the same components in Embodiment 1 will be denoted by the same reference characters and will not be described.
The sheet size information in Embodiment 3 contains a product (H×Z) of the non-sheet-feeding portion width H and the sheet P length Z, and a produce (M×Z) of the non-heat width M and the sheet P length Z, that is, an area of the non-heat region K, illustrated in
With these pieces of information acquired, the CPU 94 can predict a degree E1 of the non-sheet-feeding portion temperature rise occurring in the fixing nip portion N every time one sheet P is printed, and a degree E2 that is a degree of heat necessary for fixing the non-heat regions K and a degree of cooling the non-heat widths H. In Embodiment 3, the degree E1 is predicted as E1=Non-sheet-feeding portion width H×Sheet P length Z, and the degree E2 is predicted as E2=Non-heat width M×Sheet P length Z. The degree E1 being a first degree is a degree of a temperature rise occurring in portions where the heat generation member 54b1 is out of contact with a sheet P (non-sheet-feeding portions) in a case where the heat generation member 54b1 is used to perform the fixing processing based on a width of the sheet P. The degree E2 being a second degree is a degree of heat necessary for portions where the heat generation member 54b2 does not heat a sheet P (non-heat regions K) in a case where the heat generation member 54b2 is used to perform the fixing processing based on a width of the sheet P, and a degree of cooling the non-sheet-feeding portions. As seen from the above, with the configuration in Embodiment 3, the calculation of the degree E1 and the degree E2 enables the setting of a switch timing for the heat generation members 54b so as to obtain an optimum performance for any size of intermediate size sheets other than the standard size sheets.
[Continuous Print Using Switch Control in Table 3]
Hereinafter, control in Embodiment 3 will be described specifically with a case where intermediate size sheets in Embodiment 3 are continuously printed, by way of example. Sheets P used in Embodiment 3 are sheets P having a sheet width W being the same as that of a 16K-size sheet, 195 mm, and a length Z being half that of a LGL-size sheet, 178 mm Fifty of these sheets P are continuously printed from the cold state. Before starting the print, the CPU 94 calculates the non-sheet-feeding portion width H=13.5 mm and the non-heat width M=5 mm, from the sheet size information input into the PC 110. In addition, using these values, the CPU 94 calculates the degree E1=Non-sheet-feeding portion width H×Sheet P length Z=2403 mm2 and the degree E2=Non-heat width M×Sheet P length Z=890 mm2.
Table 3 is a table that is set from a viewpoint of suppressing the non-sheet-feeding portion temperature rise and a viewpoint of obtaining good fixing properties in the non-heat regions K, in the zone 1 and the zone 2. That is, Table 3 is a table showing E1 target integrated values with which the heat generation member 54b1 has to be switched to the heat generation member 54b2 and E2 target integrated values with which the heat generation member 54b2 has to be switched to the heat generation member 54b1. Here, the E1 target integrated values refer to integrated values of the degree E1 with which the heat generation member 54b1 has to be switched to the heat generation member 54b2 (hereinafter, referred to as E1 integrated values). The E2 target integrated values refer to integrated values of the degree E2 with which the heat generation member 54b2 has to be switched to the heat generation member 54b1. In Table 3, its first column shows the integrated values, its second column shows target integrated values of the integrated values in the zone 1, and its third column shows the target integrated values in the zone 2. For example, in the zone 1, the E1 target integrated value of the E1 integrated value is 20000 mm2, and the E2 target integrated value of the E2 integrated value is 2000 mm2. With respect to these target integrated values, the CPU 94 calculates that the target integrated value is reached at an n-th sheet of the continuous print and the target integrated value is exceeded at an n+l-th sheet to set a switch timing of the heat generation members 54b.
Specifically, with the degree E1=2403 mm2 as previously described and n=8 sheets, the calculation is as E1 integrated value=19224 mm2 (=2403 mm2×8 sheets) in a case where the heat generation member 54b1 is used to perform the fixing processing in the zone 1 in Embodiment 3. In addition, with n+1=9 sheets, the calculation is as E1 integrated value=21627 mm2 (=2403 mm2×9 sheets). From the above, the CPU 94 sets the switch timing of the heat generation members 54b such that the heat generation member 54b1 is switched to the heat generation member 54b2 when the printed sheet number reaches n=8 sheets that produces not more than 20000, which is the E1 target integrated value of the E1 integrated value in the zone 1 in Table 3.
Similarly, with the degree E2=890 mm2 as previously described and n=2 sheets, the calculation is as E2 integrated value=1780 mm2 (=890 mm2×2 sheets) in a case where the heat generation member 54b2 is used to perform the fixing processing in the zone 1 in Embodiment 3. In addition, with n+1=3 sheets, the calculation is as E2 integrated value=2670 mm2 (=890 mm2×3 sheets). From the above, the CPU 94 sets the switch timing of the heat generation members 54b such that the heat generation member 54b2 is switched to the heat generation member 54b1 when the printed sheet number reaches n=2 sheets that produces not more than 2000, which is the E2 target integrated value of the E2 integrated value in the zone 1 in Table 3.
Moreover, in the zone 2, with the degree E 1=2403 mm2 as previously described and n=7 sheets, the calculation is as E1 integrated value=16821 mm2 (=2403 mm2×7 sheets) in a case where the heat generation member 54b1 is used to perform the fixing processing. In addition, with n+1=8 sheets, the calculation is as E1 integrated value=19224 mm2 (=2403 mm2×8 sheets). From the above, the CPU 94 sets the switch timing of the heat generation members 54b such that the heat generation member 54b1 is switched to the heat generation member 54b2 when the printed sheet number reaches n=7 sheets that produces not more than 18000, which is the E1 target integrated value of the E1 integrated value in Table 3. In addition, in a case where the heat generation member 54b2 is used to perform the continuous print in the zone 2, the E2 target integrated value is 2000, which is the same as the E2 target integrated value in the zone 1. From this, the CPU 94 sets the switch timing of the heat generation members 54b such that the heat generation member 54b2 is switched to the heat generation member 54b1 at n=2 sheets, as in the zone 1.
As seen from the above, before starting the print, the CPU 94 calculates the degree E1 and the degree E2 and compares them with the target integrated values in Table 3 to calculate the sheet number n at which the heat generation members 54b have to be switched. As a result, switch timings of the heat generation members 54b as illustrated in
In the zone 2, the heat generation member 54b1 is used to perform the fixing processing on seven intermediate size sheets, and then the heat generation member 54b2 is used to perform the fixing processing on two intermediate size sheets. As illustrated in (ii) of
In addition, in Embodiment 3, the sheet interval time period is calculated based on the degree E1, such that, for example, sheet interval time period=0.0834×E1+149.4 (in ms). In the case of the intermediate size sheets in Embodiment 3, the sheet interval time period is calculated as 350 ms since the degree E1=2403 mm2. This calculation formula calculates an optimum sheet interval time period from the degree E1 of the non-sheet-feeding portion temperature rise. As a result, by performing the control in Embodiment 3, the continuous print of the intermediate size sheets is performed at a production speed of 28 sheets per minute.
Here, a case where the control in Embodiment 2 is used to print intermediate size sheets having a length half that of the LGL size in Embodiment 3 will be described. Since the control in Embodiment 2 is based on the sheet width information, the same switch frequency of the heat generation members 54b and the same sheet interval time period (550 ms) as those in Embodiment 2 are set also for the intermediate size sheets in Embodiment 3, and based on the sheet interval time period, the print is performed at a production speed of 25 sheets per minute. In Table 2 in Embodiment 2, the zone 1 (four for the heat generation member 54b1, one for the heat generation member 54b2) and the zone 2 (three for the heat generation member 54b1, one for the heat generation member 54b2) of “200>W≥194” for the intermediate size sheet having the sheet width W (=195 mm) are used.
However, from a viewpoint of a durability of the heat generation member switching device 57, an increase in number of switches is not desirable, and it is desirable to keep the number of switches at a minimum. In addition, from a viewpoint of improving a production speed of print per minute, it is desirable to set a bare minimum of the sheet interval time period. Considering the above viewpoints, it is possible that the configuration in Embodiment 3 is more desirable.
As described above, the configuration in Embodiment 3 enables the setting of an optimum switch frequency of the heat generation members 54b and an optimum sheet interval time period for the sheet width W and the length Z of the intermediate size sheet, which can suppress the non-sheet-feeding portion temperature rise while ensuring good fixing properties in the non-heat regions K. As previously described, in a case of the control performed based on the sheet width information in Embodiment 2, the intermediate size sheets in Embodiment 3 can be printed at a production speed of 25 sheets per minute. In contrast, in a case of the control in Embodiment 3, the intermediate size sheets in Embodiment 3 can be printed at a production speed of 28 sheets per minute, which enables a further improvement in production speed. In addition, the switch frequency of the heat generation member 54b1 and the heat generation member 54b2 during printing the 50 intermediate size sheets can be reduced to 10 in Embodiment 3 in contrast to 21 by the control in Embodiment 2.
As described above, according to Embodiment 3, the non-sheet-feeding portion temperature rise can be suppressed without decreasing throughput also in a case where the intermediate size sheets are caused to pass the fixing nip portion.
In a configuration of an image forming apparatus applied in Embodiment 4, the same components in Embodiment 1 will be denoted by the same reference characters and will not be described.
In Embodiment 4, a case where 50 intermediate size sheets of 16K size are printed continuously as in Embodiment 1 will be described. In addition, based on information on printing the sheets of the 16K size as in Embodiment 1, a standard size, the same switch timing of the heat generation members 54b as that in Embodiment 1 is used to print the 50 sheets from the cold state. Note that, considering the effect of settling down the non-sheet-feeding portion temperature rise brought by the heatsinks 120, the sheet interval time period is set at 330 ms in Embodiment 4 while the sheet interval time period in Embodiment 1 is 450 ms. As a result, the production speed per minute is improved to 20 sheets in Embodiment 4 in contrast to 19 sheets in Embodiment 1.
Note that the method for switch control of the heat generation members 54b described in Embodiment 4 is merely an example, and any control that is set optimally for the standard sizes of various kinds of intermediate size sheets, the sheet width W, or both of the sheet width W and the sheet length Z may be used. That is, the controls described in Embodiment 1 to Embodiment 3 may be applied to the configuration including the heatsinks 120. In addition, the length and the number of the heat generation members 54b, the thickness and the length of the heatsinks 120, and the like are merely an example and are not limited to the described numeric values. In addition, the material of the heatsinks 120 may be a metal other than aluminum described in Embodiment 4 or a high heat conducting sheet such as a graphite sheet.
As described above, according to Embodiment 4, the non-sheet-feeding portion temperature rise can be suppressed without decreasing throughput also in a case where the intermediate size sheets are caused to pass the fixing nip portion.
[Modification]
Moreover, the length and the number of the heat generation members 54b are not limited to the numeric values described in the embodiments previously described. For example, as illustrated in
The heater used in a heating apparatus in the modification and a power control unit 97 being a heater control circuit are illustrated in
For example, lengths of the heat generation members 54b1, the heat generation member 54b2, and the heat generation member 54b3 set at to be longer by about several millimeters than a width 215.9 mm of letter size, a width 182 mm of B5 size, and a width 148 mm of A5 size, respectively. By providing a plurality of kinds of the heat generation members 54b in this manner, the intermediate size sheets having more kinds of the sizes can be supported. That is, in a case where an intermediate size sheet having a size between the letter size and the B5 size is fed, the heat generation members 54b1 and the heat generation member 54b2 may be switched alternately. In a case where an intermediate size sheet having a size between the B5 size and the A5 size is fed, the heat generation members 54b1 and the heat generation member 54b3 may be switched alternately.
The contact 54d1 is connected to a first electrode of the AC power supply 55 via a triac 56a being a first switch unit. The contact 54d2 is connected to the first electrode of the AC power supply 55 via a triac 56b being a second switch unit. The contact 54d3 is connected to the first electrode of the AC power supply 55 via a triac 56c being a third switch unit. The contact 54d4 is connected to a second electrode of the AC power supply 55 via no triac or the like. The contact 54d2 and the contact 54d4 are connected to an electromagnetic relay 57a of the contact configuration of “a” being a first switching unit. The electromagnetic relay 57a brings an electric path between the contact 54d2 and the contact 54d4 (electric power supply path) into a connected state (hereinafter, referred to as short-circuit state) or an open state.
Next, a method for a case where electric power is supplied while the heat generation members 54b1 and the heat generation member 54b2, and the heat generation members 54b1 and the heat generation member 54b3 are switched respectively from one to another, will be described.
(Supply of Electric Power to Heat Generation Members 54b1)
Current in a case where electric power is supplied from the AC power supply 55 to the heat generation members 54b1 flows along a route illustrated by bold lines in
(Supply of Electric Power to Heat Generation Member 54b2)
Current in a case where electric power is supplied from the AC power supply 55 to the heat generation member 54b2 flows along a route illustrated by bold lines in
(Supply of Electric Power to Heat Generation Member 54b3)
Current in a case where electric power is supplied from the AC power supply 55 to the heat generation member 54b3 flows along a route illustrated by bold lines in
[Switch Between Power Supply Paths]
In switching between the electric power supply path to the heat generation members 54b1 (
This holds true for switching between the electric power supply path to the heat generation member 54b1 (
In contrast, in switching between the electric power supply path to the heat generation member 54b2 (
However, in a case where transition between the electric power supply path (
The electromagnetic relay 57a is not limited to an electromagnetic relay having a contact configuration of “a”, and a contact switch such as an electromagnetic relay having a b contact configuration and an electromagnetic relay having a c contact configuration may be used. In addition, as the electromagnetic relay 57a, a contactless switch such as a solid state relay (SSR), a photo MOS relay, and a triac may be used.
As described above, according to the present invention, the non-sheet-feeding portion temperature rise can be suppressed without decreasing throughput also in a case where the intermediate size sheets are caused to pass the fixing nip portion.
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 Application No. 2019-006466, filed Jan. 18, 2019, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-006466 | Jan 2019 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 6580883 | Suzumi | Jun 2003 | B2 |
| 20100080590 | Takahashi | Apr 2010 | A1 |
| Number | Date | Country |
|---|---|---|
| 10-301443 | Nov 1998 | JP |
| 2001-100558 | Apr 2001 | JP |
| 2013-235181 | Nov 2013 | JP |
| Entry |
|---|
| Co-pending U.S. Appl. No. 16/744,669, filed Jan. 16, 2020. |
| Co-pending U.S. Appl. No. 16/781,109, filed Feb. 4, 2020. |
| Co-pending U.S. Appl. No. 16/822,426, filed Mar. 18, 2020. |
| Number | Date | Country | |
|---|---|---|---|
| 20200233346 A1 | Jul 2020 | US |
