Patent Application
20180210380
The present invention relates to an image forming apparatus such as a copying machine or a printer which uses an electrophotographic system or an electrostatic recording system. Moreover, the present invention relates to an image heating apparatus such as a fixing unit mounted in an image forming apparatus or a gloss applying apparatus that improves a gloss level of a toner image by re-heating the toner image fixed to a recording material.
In an image heating apparatus such as a fixing unit or a gloss applying apparatus used in an electrophotographic image forming apparatus (hereinafter an image forming apparatus) such as a copying machine or a printer, a method of selectively heating image portions formed on a recording material has been proposed in order to save power (see Japanese Patent Application Publication No. H06-95540). In this method, a heat generation range of a heater is divided into a plurality of heat generating blocks in a longitudinal direction (a direction orthogonal to a conveying direction of the recording material) and heat generation of respective heat generating blocks is selectively controlled depending on the presence of an image on the recording material. That is, energization of a heat generating block in a portion in which an image is not formed (a non-image portion) on the recording material is stopped to save power.
On the other hand, there is a demand to increase a recording material processing speed per unit time of the image heating apparatus to enhance image productivity. Therefore, it is requested to increase a recording material conveying speed. When a recording material conveying speed in such an image heating apparatus of Embodiment 11 as disclosed in Japanese Patent Application Publication No. H06-95540 increases, when energization control is switched from a non-image portion (an energization stop state) to an image portion, since a heating time is short, there may be a case in which the image portion cannot be sufficiently heated to a control temperature. In order to prevent this, a method of performing energization control so that the temperature reaches a predetermined control temperature at the time of switching to energization of a heat generating block of the non-image portion to thereby allow the temperature to quickly reach the control temperature of the image portion has been considered. In this case, the control temperature of the image portion is set to be lower than the control temperature of the non-image portion so that both a power saving effect and image productivity can be achieved.
However, in an image heating apparatus that performs heat generation control using different control temperatures for respective heat generating blocks, a variation may occur in a heat accumulation state of respective heat generating blocks. As a result, this variation may cause a recording material conveying defect such as a paper wrinkle or a trailing edge pop-up, increase a load applied to a fixing member, and decrease durability of constituent members. That is, in an image heating apparatus having heat generating blocks divided in the longitudinal direction, since the heat generating quantities of respective heat generating blocks is different depending on an image pattern on a recording material that passes through the heat generating block, a heat accumulation state of the fixing member is different in respective heat generating blocks. Since a roller or the like used in the fixing member is thermally expanded according to the heat accumulation amount, a recording material conveying performance or a rotational driving force of the fixing member is different in respective heat generating blocks. Therefore, due to a difference in conveying performance or rotational driving force of heat generating blocks in the image heating apparatus, there is a possibility that a conveying defect such as a paper wrinkle or a trailing edge pop-up may occur in a recording material. Moreover, since the rotational driving force of the fixing member is different in the longitudinal direction of the image heating apparatus, there is a possibility that the force of pulling a fixing film in one direction increases and the durability of the fixing film or a pressure roller decreases.
An object of the present invention is to provide a technology capable of enhancing power saving function while suppressing occurrence of a recording material conveying defect and a decrease in durability of a fixing member.
In order to achieve the object described above, an image heating apparatus according to the present invention includes: a heater having a plurality of heat generating elements arranged in a longitudinal direction orthogonal to a conveying direction of a recording material; and a control portion capable of controlling electric power to be supplied to the plurality of heat generating elements to control individual heat generating quantities of the plurality of heat generating elements, wherein an image formed on the recording material is heated by the heat generated by the heater, wherein the image heating apparatus comprises an acquisition portion that acquires a plurality of count values indicating heat accumulation amounts of a plurality of heating regions heated by the plurality of heat generating elements, and wherein the control portion controls the heat generating quantities of the plurality of heat generating elements so that a difference between a first count value indicating a heat accumulation amount of a heating region heated by a first heat generating element among the plurality of heat generating elements and a second count value indicating a heat accumulation amount of a heating region heated by a second heat generating element among the plurality of heat generating elements is maintained within a predetermined range.
In order to achieve the object described above, an image forming apparatus according to the present invention includes: an image forming portion that forms an image on a recording material; and a fixing portion that fixes the image formed on the recording material, to the recording material, wherein the fixing portion is the image heating apparatus.
Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings).
Hereinafter, a description will be given, with reference to the drawings, of embodiments(examples) of the present invention. However, the sizes, materials, shapes, their relative arrangements, or the like of constituents described in the embodiments may be appropriately changed according to the configurations, various conditions, or the like of apparatuses to which the invention is applied. Therefore, the sizes, materials, shapes, their relative arrangements, or the like of the constituents described in the embodiments do not intend to limit the scope of the invention to the following embodiments.
When a print signal is generated, a scanner unit 21 emits a laser beam modulated according to image information to scan a photosensitive drum 19 which is charged to a predetermined polarity by a charging roller 16. In this way, an electrostatic latent image is formed on the photosensitive drum 19. When toner is supplied from a developing roller 17 to the electrostatic latent image, the electrostatic latent image on the photosensitive drum 19 is developed as a toner image. On the other hand, a recording material (a recording sheet) P stacked on a sheet feed cassette 11 is fed by a pickup roller 12 one by one and is conveyed toward a registration roller pair 14 by a conveying roller pair 13. Furthermore, the recording material P is conveyed from the registration roller pair 14 to a transfer position in synchronization with a timing at which the toner image on the photosensitive drum 19 reaches a transfer position formed by the photosensitive drum 19 and a transfer roller 20. The toner image on the photosensitive drum 19 is transferred to the recording material P in the course in which the recording material P passes through the transfer position. After that, the recording material P is heated by a fixing apparatus 200 as a fixing portion of an image heating apparatus and the toner image is heated and fixed to the recording material P. The recording material P that bears the toner image fixed thereto is discharged to a tray in an upper part of the image forming apparatus 100 by conveying roller pairs 26 and 27.
Reference numeral 18 is a drum cleaner that cleans the photosensitive drum 19, and reference numeral 28 is a sheet feed tray (a manual tray) having a pair of recording material regulating plates, the width of which can be adjusted according to the size of the recording material P. The sheet feed tray 28 is provided so as to support a recording material P having a size other than standard sizes. Reference numeral 29 is a pickup roller that feeds the recording material P from the sheet feed tray 28 and reference numeral 30 is a motor that drives the fixing apparatus 200 and the like. A control circuit 400 as heater driving means connected to a commercial alternating-current power supply 401 supplies electric power to the fixing apparatus 200. The photosensitive drum 19, the charging roller 16, the scanner unit 21, the developing roller 17, and the transfer roller 20 form an image forming portion that forms a non-fixed image on the recording material P. In the present embodiment, the photosensitive drum 19, the charging roller 16, a developing unit including the developing roller 17, and a cleaning unit including the drum cleaner 18 are configured as a process cartridge 15 so as to be detachably attached to a main body of the image forming apparatus 100.
The image forming apparatus 100 of the present embodiment is configured such that a largest sheet passing width in a direction orthogonal to the conveying direction of the recording material P is 216 mm and the apparatus can print 44.3 pages of a standard sheet of a letter (LTR) size (216 mm×279 mm) per minute at a conveying speed of 232.5 mm/sec.
The fixing film 202 is a heat-resistant multilayer film formed in a tubular form, and a heat-resistant resin such as polyimide or a metal such as stainless steel is used as a base layer of the fixing film 202. Moreover, the surface of the fixing film 202 is coated with a heat-resistant resin with excellent releasability such as a tetrafluoroethylene-perfluoro (alkyl vinyl ether) copolymer (PFA) in order to prevent toner adhesion and secure separability from the recording material P to thereby form a releasing layer thereon. Furthermore, in an apparatus which forms color images particularly, in order to improve image quality, heat-resistant rubber such as silicone rubber may be formed between the base layer and the releasing layer as an elastic layer. The pressure roller 208 includes a core metal 209 formed of a material such as iron or aluminum and an elastic layer 210 formed of a material such as silicon rubber. The heater 300 is held by a heater holding member 201 formed of a heat-resistant resin and heats heating regions A1 to A7 (the details will be described later) provided in the fixing nip portion N to thereby heat the fixing film 202. The heater holding member 201 also has a guiding function of guiding rotation of the fixing film 202. An electrode E is provided in the heater 300 on an opposite side of the fixing nip portion N and electric power is fed from an electrical contact C to the electrode E. The metal stay 204 receives pressurizing force (not illustrated) and biases the heater holding member 201 toward the pressure roller 208. Moreover, a safety element 212 which is a thermo-switch, a temperature fuse, or the like and which is actuated in the event of abnormal heat generation of the heater 300 to interrupt electric power supplied to the heater 300 is in direct contact with the heater 300 or in indirect contact with the heater 300 with the heater holding member 201 interposed therebetween.
The pressure roller 208 rotates in a direction indicated by arrow R1 in response to motive power from the motor 30. The fixing film 202 rotates in a direction indicated by arrow R2 following the rotation of the pressure roller 208. The heat of the fixing film 202 is applied to the recording material P while being conveyed in a state of being pinched at the fixing nip portion N whereby the non-fixed toner image on the recording material P is fixed. Moreover, in order to secure slidability of the fixing film 202 and to obtain a stable rotation state, a lubricant (not illustrated) having high heat resistance is interposed between the heater 300 and the fixing film 202.
A configuration of the heater 300 according to the present embodiment will be described with reference to
The heater 300 includes a ceramic substrate 305, a back surface layer 1 provided on the substrate 305, a back surface layer 2 that covers the back surface layer 1, a sliding surface layer 1 provided on a surface on the opposite side of the back surface layer 1 on the substrate 305, and a sliding surface layer 2 that covers the sliding surface layer 1.
The back surface layer 1 has conductors 301 (301a and 301b) provided along the longitudinal direction of the heater 300. The conductor 301 is divided into the conductors 301a and 301b, and the conductor 301b is disposed on a downstream side in the conveying direction of the recording material P in relation to the conductor 301a. Moreover, the back surface layer 1 has conductors 303 (303-1 to 303-7) provided in parallel to the conductors 301a and 301b. The conductors 303 are provided between the conductors 301a and 301b along the longitudinal direction of the heater 300.
Furthermore, the back surface layer 1 has a heat generating element 302a (302a-1 to 302a-7) and a heat generating element 302b (302b-1 to 302b-7) which are heat generating resistors that generate heat upon energization. The heat generating elements 302a are provided between the conductors 301a and 303 so as to generate heat in response to electric power supplied via the conductors 301a and 303. The heat generating elements 302b are provided between the conductors 301b and 303 so as to generate heat in response to electric power supplied via the conductors 301b and 303.
A heat generating portion that includes the conductor 301, the conductor 303, the heat generating element 302a, and the heat generating element 302b is divided into seven heat generating blocks (HB1 to HB7) with respect to the longitudinal direction of the heater 300. That is, the heat generating element 302a is divided into seven regions of heat generating elements 302a-1 to 302a-7 with respect to the longitudinal direction of the heater 300. Moreover, the heat generating element 302b is divided into seven regions of heat generating elements 302b-1 to 302b-7 with respect to the longitudinal direction of the heater 300. Furthermore, the conductor 303 is divided into seven regions of conductors 303-1 to 303-7 in alignment with the dividing positions the heat generating elements 302a and 302b. The seven heat generating blocks (HB1 to HB7) are configured such that the amounts of energization of heat generating resistors in respective blocks are controlled individually whereby the heat generating quantities of the respective heat generating blocks are controlled individually.
In the present embodiment, a heat generating range ranges from the left end in the drawing of the heat generating block HB1 to the right end in the drawing of the heat generating block HB7 and the entire length is 220 mm. Moreover, the longitudinal lengths of respective heat generating blocks are approximately the same as 31 mm but the lengths may be different from each other.
Moreover, the back surface layer 1 has electrodes E (E1 to E7, E8-1, and E8-2). The electrodes E1 to E7 are provided within the regions of the conductors 303-1 to 303-7, respectively, and are electrodes for supplying electric power to the heat generating blocks HB1 to HB7 via the conductors 303-1 to 303-7, respectively. The electrodes E8-1 and E8-2 are provided at the ends in the longitudinal direction of the heater 300 so as to be connected to the conductor 301 and are electrodes for supplying electric power to the heat generating blocks HB1 to HB7 via the conductor 301. In the present embodiment, although the electrodes E8-1 and E8-2 are provided at both ends in the longitudinal direction of the heater 300, the electrode E8-1 only may be provided on one end, for example. Moreover, although electric power is supplied to the conductors 301a and 301b using a common electrode, individual electrodes may be provided to the conductors 301a and 301b and electric power may be supplied via the respective electrodes.
The back surface layer 2 is configured as a surface protection layer 307 having an insulating property (in the present embodiment, formed of glass) and covers the conductor 301, the conductor 303, and the heat generating elements 302a and 302b. Moreover, the surface protection layer 307 is formed in a region outside the portions of the electrodes E so that the electrical contacts C can be connected to the electrodes E from the side of the back surface layer 2 of the heater.
The sliding surface layer 1 is provided on a surface of the substrate 305 on the opposite side of a surface on which the back surface layer 1 is provided and has thermistors TH (TH1-1 to TH1-4 and TH2-5 to TH2-7) as detection means for detecting the temperature of the heat generating blocks HB1 to HB7. The thermistor TH is formed of a material having PTC characteristics or NTC characteristics (in the present embodiment, NTC characteristics) and can detect the temperature of all heat generating blocks by detecting the resistance thereof.
Moreover, the sliding surface layer 1 has conductors ET (ET1-1 to ET1-4 and ET2-5 to ET2-7) and conductors EG (EG1 and EG2) in order to energize the thermistor TH to detect the resistance thereof. The conductors ET1-1 to ET1-4 are connected to the thermistors TH1-1 to TH1-4, respectively. The conductors ET2-5 to ET2-7 are connected to the thermistors TH2-5 to TH2-7. The conductor EG1 is connected to four thermistors TH1-1 to TH1-4 to form a common conduction path. The conductor EG2 is connected to three thermistors TH2-5 to TH2-7 to form a common conduction path. The conductors ET and EG are formed up to the longitudinal ends along the longitudinal direction of the heater 300 and are connected to the control circuit 400 via electrical contacts (not illustrated) at the longitudinal ends of the heater.
The sliding surface layer 2 is formed of a surface protection layer 308 having slidability and an insulating property (in the present embodiment, formed of glass) and is configured to cover the thermistor TH and the conductors ET and EG and secure the ability to slide on the inner surface of the fixing film 202. Moreover, the surface protection layer 308 is formed in a region outside both ends in the longitudinal direction of the heater 300 in order to provide electrical contacts for the conductors ET and EG.
Subsequently, a method of connecting the electrical contacts C to the respective electrodes E will be described.
A method of detecting the temperature of the heater 300 will be described. The temperature of the heater 300 is detected by the thermistors TH (TH1-1 to TH1-4 and TH2-5 to TH2-7). Voltages divided by the thermistors TH1-1 to TH1-4 and resistors 451 to 454 are detected by the CPU 420 as signals TH1-1 to TH1-4, and the CPU 420 converts the signals TH1-1 to TH1-4 to temperatures. Similarly, voltages divided by thermistors TH2-5 to TH2-7 and resistors 465 to 467 are detected by the CPU 420 as signals TH2-5 to TH2-7, and the CPU 420 converts the signals TH2-5 to TH2-7 to temperatures.
Internal processing of the CPU 420 involves calculating electric power to be supplied by PI control (proportional integral control), for example, on the basis of control temperatures (control target temperatures) TGTi of respective heat generating blocks to be described later and the detection temperatures of the thermistors. Furthermore, the CPU 420 converts the electric power to be supplied to a control level of a phase angle (phase control) or a frequency (frequency control) corresponding to the electric power and controls the triacs 411 to 417 according to the control condition. The CPU 420 executes energization control and various operations associated with temperature control of the heater 300 as a control portion and an acquisition portion of the present invention.
Relays 430 and 440 are used as means for interrupting the supply of electric power to the heater 300 when the temperature of the heater 300 increases excessively due to fault or the like. A circuit operation of the relays 430 and 440 will be described. When a signal RLON changes to the High state, a transistor 433 enters into the ON state, a current flows from a supply voltage node Vcc to a secondary-side coil of the relay 430, and a primary-side contact of the relay 430 enters into the ON state. When the signal RLON changes to the Low state, the transistor 433 enters into the OFF state, the current flowing from the supply voltage node Vcc to the secondary-side coil of the relay 430 is interrupted, and the primary-side contact of the relay 430 enters into the OFF state. Similarly, when the signal RLON changes to the High state, a transistor 443 enters into the ON state, a current flows from a supply voltage node Vcc to a secondary-side coil of the relay 440, and a primary-side contact of the relay 440 enters into the ON state. When the signal RLON changes to the Low state, the transistor 443 enters into the OFF state, the current flowing from the supply voltage node Vcc to the secondary-side coil of the relay 440 is interrupted, and the primary-side contact of the relay 440 enters into the OFF state. Resistors 434 and 444 are current limiting resistors.
Next, the operation of a safety circuit which uses the relays 430 and 440 will be described. When any one of the temperatures detected by the thermistors TH1-1 to TH1-4 exceeds a predetermined value set thereto, a comparator 431 operates a latch 432, and the latch 432 latches a signal RLOFF1 to the Low state. When the signal RLOFF1 changes to the Low state, the relay 430 can be maintained in the OFF state (a stable state) since the transistor 433 is maintained in the OFF state even when the CPU 420 puts the signal RLON into the High state. In a non-latched state, the signal RLOFF1 of the latch 432 enters into the open state. When any one of the temperatures detected by the thermistors TH2-5 to TH2-7 exceeds a predetermined value set thereto, a comparator 441 operates a latch 442, and the latch 442 latches a signal RLOFF2 to the Low state. When the signal RLOFF2 changes to the Low state, the relay 440 can be maintained in the OFF state (a stable state) since the transistor 443 is maintained in the OFF state even when the CPU 420 puts the signal RLON into the High state. Similarly, in a non-latched state, the signal RLOFF2 of the latch 442 enters into the open state.
A specific example of a classification of the heating region Ai will be described with reference to
Each of the heating regions Ai (i=1 to 7) is classified into a recording material edge region AE, a recording material central region AM, an image heating region AI, and a non-image heating region AP. When a recording material edge PE passes through the heating region Ai, the heating region Ai is classified as the recording material edge region AE. When a recording material central portion other than the recording material edge PE passes through the heating region Ai, the heating region Ai is classified as the recording material central region AM. The recording material edge determined herein is an extreme edge PE in the direction orthogonal to the conveying direction of the recording material as illustrated in
That is, by the classification based on the recording material size information, since the heating regions A1 and A7 are classified as the recording material edge region AE since the recording material edge PE passes through the heating regions A1 and A7. Moreover, the heating regions A2, A3, A4, A5, and A6 are classified as the recording material central region AM. A heat generating element that forms the heating regions A1 and A7 corresponds to a first heat generating element of the present invention, and a heat generating element that forms the heating regions A2, A3, A4, A5, and A6 corresponds to a second heat generating element of the present invention. Moreover, according to image data (image information), in the segment T1, the heating regions A1, A2, A3, and A4 are classified as the image heating region AI since the image range passes through the heating regions A1, A2, A3, and A4, and the heating regions A5, A6, A7 are classified as the non-image heating region AP since the image range does not pass through the heating regions A5, A6, and A7. In the segments T2 to T5, the heating regions A2, A3, A4, A5, and A6 are classified as the image heating region AI since the image range passes through the heating regions A2, A3, A4, A5, and A6, and the heating regions A1 and A7 are classified as the non-image heating region AP since the image range does not pass through the heating regions A1 and A7.
Next, a heater control method according to the present embodiment (that is, a method of controlling the heat generating quantity of the heat generating block HBi (i=1 to 7)) will be described. The heat generating quantity of the heat generating block HBi is determined by the electric power supplied to the heat generating block HBi. The heat generating quantity of the heat generating block HBi increases when the electric power supplied to the heat generating block HBi is increased, and the heat generating quantity of the heat generating block HBi decreases when the electric power supplied to the heat generating block HBi is decreased. The electric power supplied to the heat generating block HBi is calculated on the basis of the control temperatures TGTi (i=1 to 7) set to respective heat generating blocks and the temperature detected by the thermistor. In the present embodiment, the supplied electric power is calculated by PI control (proportional integral control) so that the temperatures detected by the respective thermistors are equal to the control temperatures TGTi of the respective heat generating blocks. The control temperatures TGTi of the respective heat generating blocks are set according to the classification of the heating regions Ai determined by the flow of
That is, on the basis of the size information of a recording material, it is determined whether the heating region Ai is a region through which the recording material edge PE passes or a region through which a region other than the recording material edge passes (S1002). When the recording material edge PE passes through the heating region Ai, the heating region Ai is classified as the recording material edge region AE (S1003). When the recording material central portion other than the recording material edge PE passes through the heating region Ai, the heating region Ai is classified as the recording material central region AM (S1004). Subsequently, it is determined whether the heating region Ai classified as the recording material central region AM is an image range on the basis of the image data (image information) (S1005). When the heating region Ai is the image range, the heating region Ai is classified as the image heating region AI (S1006). When the heating region Ai is not the image range, the heating region Ai is classified as the non-image heating region AP (S1007). The classification of the heating region Ai is used for controlling the heat generating quantity of the heat generating block HBi as will be described later. When the heating region Ai is classified as the image heating region AI (S1006), the control temperature TGTi is set as TGTi=TAI−KAI (S1008).
Here, TAI is a reference temperature of the image heating region and is set as a temperature appropriate for fixing a non-fixed image to the recording material P. When a standard sheet is passed in the fixing apparatus 200 of the present embodiment, TAI is set to 198° C. The reference temperature TAI of the image heating region is preferably variable according to the type of the recording material P such as a thick paper or a thin paper. Moreover, the reference temperature TAI of the image heating region may be adjusted according to image information such as an image density or a pixel density.
Moreover, KAI is a temperature correction term of the image heating region and is set according to a heat accumulation count value CTi in each heating region Ai as illustrated in
However, a heat amount for fixing a toner image to the recording material P is given by the heat generating quantity of the heat generating block HBi and the heat accumulation amount in the heating region Ai. That is, the larger the heat accumulation amount in the heating region Ai, the more the toner image is likely to be fixed to the recording material P even if the heat generating quantity of the heat generating block HBi is small. Therefore, in the image forming apparatus 100 of the present embodiment, the larger the heat accumulation amount (heat accumulation count value CTi), the larger the set temperature correction term KAI of the image heating region so that the control temperature TGTi is decreased and the heat generating quantity of the heat generating block HBi is decreased. By doing so, an excessive heat amount prevented from being applied to the toner image when the heat accumulation amount in the heating region Ai is large and power saving is realized.
Next, a case in which the heating region Ai is classified as the non-image heating region AP (S1007) will be described. When the heating region Ai is classified as the non-image heating region AP, the control temperature TGTi is set as TGTi=TAP−KAP (S1009).
Here, TAP is a reference temperature of the non-image heating region and is set as a temperature lower than the reference temperature TAI of the image heating region so that the heat generating quantity of the heat generating block HBi in the non-image heating region AP is lower than that of the image heating region AI to realize power saving of the image forming apparatus 100. However, if the reference temperature TAP of the non-image heating region is decreased too much, there may be case in which it is difficult to perform heating sufficiently up to the control temperature of the image portion even if a largest possible electric power is supplied to the heat generating block HBi when the heating region Ai is changed from the non-image heating region AP to the image heating region AI. In this case, since there is a possibility that a phenomenon (a fixing defect) wherein the toner image is not sufficiently fixed to the recording material occurs, it is necessary to set the reference temperature TAP of the non-image heating region to an appropriate value. According to the test performed by present inventors, it has found that, in the image forming apparatus 100 of the present embodiment, when the reference temperature TAP of the non-image heating region is set to 158° C. or higher, and the heating region is changed from the non-image heating region AP to the image heating region AI, a fixing defect did not occur. From the viewpoint of power saving, since it is preferable to decrease the control temperature TGTi as much as possible to decrease the heat generating quantity of the heat generating block HBi, TAP is set to 158° C. in the present embodiment. The reference temperature TAP of the non-image heating region is preferably variable according to the type of the recording material P such as a thick paper or a thin paper. Moreover, the reference temperature TAP of the non-image heating region may be adjusted according to image information such as an image density or a pixel density.
Moreover, KAP is a temperature correction term of the non-image heating region, and as illustrated in
Next, a case in which the heating region Ai is classified as the recording material edge region AE (S1003) will be described. In S1010, it is determined whether a heat accumulation count value CTe (first count value) of the recording material edge region AE satisfies Expression 1 below.
CT
e
<CT
m
−W
e (Expression 1)
CTm is a heat accumulation count value (second count value) of each heating region in the recording material central region AM, and We is a determination value (predetermined value) for determining occurrence of a conveying defect at the recording material edge.
Next, S1010 will be described in detail. In S1010, it is determined whether the image heating apparatus is in a state in which paper wrinkle which is a recording material conveying defect occurs. As described above, the heat accumulation count value CT is a parameter correlated with the heat accumulation amount of the fixing apparatus 200 in each heating region, and the larger the heat accumulation count value, the larger heat accumulation amount. Therefore, the larger the heat accumulation count value CT, the larger the heat accumulation amount of the pressure roller 208 which is a fixing member of the image heating apparatus.
The pressure roller 208 has the silicon rubber layer 210 which is an elastic layer formed on the core metal thereof. When the heat accumulation amount is large, the silicon rubber layer thermally expands and the outer diameter of the pressure roller increases. In the fixing apparatus of the present embodiment, the recording material is conveyed according to rotation of the pressure roller 208. Therefore, the larger the heat accumulation count value CT, the more the pressure roller expands, the larger the outer diameter, and the larger the conveying force of the recording material. In this manner, the heat accumulation count value CT is correlated with the conveying force of the recording material.
On the other hand, as means for suppressing a paper wrinkle of a recording material, the pressure roller of the present embodiment is configured such that the outer diameter at the end thereof is larger by approximately 100 μm than the outer diameter in the central portion thereof. This is to set the conveying force at the end of the pressure roller to be larger than the conveying force in the central portion so as to apply a force of pulling the recording material from the recording material central region toward the recording material edge PE to thereby prevent a paper wrinkle of the recording material. However, for example, when such an image pattern as illustrated in
When the heat accumulation count value CTe becomes smaller than the heat accumulation count value CTm by the determination value We or more which is a value for determining the occurrence of a conveying defect at the recording material edge as illustrated in Expression 1 in S1010 of the control flow, a paper wrinkle of the recording material may occur due to the above-described change. In the present embodiment, the determination value We is set to 150. The determination value We is set such that the paper wrinkle of the recording material is within an allowable range. The determination value We is preferably variable according to the type (paper weight) of the recording material P such as a thick paper or a thin paper. Moreover, the determination value We may be adjusted according to a use environment (temperature or humidity).
When the determination criterion of S1010 is not satisfied (that is, a difference obtained by subtracting the heat accumulation count value CTe as the first count value from the heat accumulation count value CTm as the second count value is larger than the determination value We as the predetermined value, the flow proceeds to S1005). Moreover, the heating region Ai is classified into the image heating region AI and the non-image heating region AP similarly to the recording material central region AM (S1006 and S1007), and the control temperature is determined according to the classification (S1008 and S1009).
When the determination criterion of S1010 is satisfied (that is, the difference obtained by subtracting the heat accumulation count value CTe from the heat accumulation count value CTm is equal to or smaller than the predetermined value (that is, the count value We), the heating region Ai is classified as the recording material edge heating correction region AW (S1011)). When the heating region Ai is classified as the recording material edge heating correction region AW, the control temperature is set so that a paper wrinkle does not occur. In S1012, regardless of whether the image range passes through the heating region Ai, the control temperature TGTi is set as TGTi=TAI−KAI (S1012). TAI is the reference temperature of the image heating region and KAI is the temperature correction term of the image heating region similarly to S1008. In the present embodiment, when a standard sheet is passed, TAI is set to 198° C.
By the above-described setting, even when such an image as the image pattern illustrated in
As for the heat generating quantity control temperature TGTi of the heat generating block HBi in an inter-sheet interval when a plurality of images are printed continuously (a segment between a preceding recording material and a subsequent recording material), the control temperature is set as TGTi=TAP−KAP by applying the same idea as the non-image heating region AP. As for the heat generating quantity control temperature TGTi of the heat generating block HBi at a post-rotation (an idling segment until the printer enters into a print standby state after the recording material P at the end of printing passed through the heating region Ai), the control temperature is set as TGTi=TAP−KAP by applying the same idea as the non-image heating region AP.
A method of controlling the heat generating quantity of the heat generating block HBi at the time of pre-rotation (startup segment) will be described. Here, the pre-rotation is an idling segment before the recording material P at the start of printing reaches the heating region Ai and is a segment in which control is performed so that the temperature of the heating region Ai reaches a predetermined temperature. In the image forming apparatus 100 of the present embodiment, the control temperature TGTi during a startup operation is expressed by Expression 2 below.
TGT
i=(TAI−KAI−T0i)÷3×t+T0i (Expression 2)
In Expression 2, TAI is the reference temperature of the image heating region and KAI is the temperature correction term of the image heating region. Moreover, t represents the time (seconds) elapsed from the start of a startup operation and T0i represents the temperature detected by the thermistor TH corresponding to the heating region Ai at the start of the startup operation. That is, the control temperature TGTi is changed linearly from T0i to TAI−KAI every three seconds.
As described above, in the present embodiment, the control temperature TGTi of the respective heating regions Ai is determined according to the classification and the heat accumulation count value CTi of the heating region Ai. The setting values of the reference temperature (TAI and TAP) of each heating region, the temperature correction term (KAI and KAP) of each heating region, and the determination value We are to be determined appropriately by taking the configuration of the image forming apparatus 100 and the fixing apparatus 200 and the printing conditions into consideration. That is, these values are not limited to the above-described values.
In the present embodiment, the heat accumulation count value CTi is provided for respective heating regions Ai as a parameter correlated with the heat accumulation amount of each heating region Ai. The heat accumulation count value CTi indicates how much the respective heating regions Ai are heated and how much heat the respective heating regions Ai have radiated and is used for predicting the heat accumulation amount by storing and counting the thermal history (heating history and heat radiation history). The heating history can be acquired, for example, on the basis of at least one of a heater temperature and the amount of electric power supplied to the heat generating element. Moreover, the heat radiation history can be acquired, for example, on the basis of at least one of whether the recording material has passed through the heating region, a period in which electric power is not supplied to the heat generating element, and a change over time in the heater temperature. dCTi expressed as Expression 3 below is accumulated and added to the heat accumulation count value CTi of each heating region Ai every predetermined update timings.
dCT
i=(TC−RMC−DC)+WUC (Expression 3)
Here, TC, RMC, DC, and WUC in Expression 3 will be described with reference to
TC in Expression 3 is a value indicating a heating amount of the heating region Ai by the heat generating block HBi and is calculated on the basis of the control temperature of the heater 300 and the amount of electric power supplied to each heat generating element. In Embodiment 1, TC is determined according to the control temperature TGTi of each heating region as illustrated in
RMC in Expression 3 indicates a heat amount deprived from the image heating apparatus by the recording material P and is set according to a passing state (the presence of passing or the like) of the recording material P in each heating region Ai as illustrated in
DC in Expression 3 indicates the amount of heat radiated outside the fixing apparatus 200 by heat transfer or radiation and is determined according to the heat accumulation count value CTi of each heating region. Since the larger the heat accumulation amount, the larger the temperature difference from the outside temperature, and the larger the heat radiation amount, the larger the heat accumulation count value CTi, the larger the DC value as illustrated in
Updating of the heat accumulation count value CTi on the basis of TC, RMC, and DC is performed at the CTi update interval of 0.24 seconds in an inter-sheet interval when a plurality of images are printed continuously. Moreover, the heat accumulation count value CTi is updated at the CTi update interval of 0.24 seconds in a standby segment where a printing operation is not performed at the time of post-rotation at the end of printing. When the inter-sheet interval, the post-rotation, or the standby segment ends in the middle of the period of 0.24 seconds, an addition/subtraction amount of TC, RMC, or DC is adjusted. For example, since an inter-sheet interval time in Embodiment 1 is 0.12 seconds which is half the CTi update interval of 0.24 seconds, the heat accumulation count value CTi is updated using TC, RMC, and DC which are half the values illustrated in
WUC in Expression 3 indicates an addition amount of the heat accumulation count value CTi at the time of pre-rotation (startup segment). At the time of pre-rotation, the heat accumulation count value CTi is not added or subtracted using TC, RMC, and DC. The heat accumulation count value CTi is added using WUC at a time point (a leading edge time point of the recording material P) at which the pre-rotation ends. As illustrated in
The heat accumulation count value CTi determined in the above-described manner shows that the larger the heat accumulation count value CTi, the larger the heat accumulation amount in the heating region Ai. The setting values of TC, RMC, DC, and WUC are to be determined appropriately by taking the configuration of the image forming apparatus 100 and the fixing apparatus 200 and the printing conditions into consideration and are not limited to the values illustrated in
Advantages of the present embodiment will be described using a comparative example.
Next, the advantages of the present invention will be described by way of a specific example of Embodiment 1 to be described later as a specific printing example. In the specific example of Embodiment 1, in a state in which the fixing apparatus 200 is in a room-temperature state (that is, a state in which the heat accumulation count value CTi of each heating region Ai is 0), 100 pages of a recording material (LTR size: a sheet width of 216 mm, a sheet length of 279 mm, and a paper weight of 75 g/m2) illustrated in
Moreover,
In
In the heating regions (A2, A3, A4, A5, and A6) classified as the recording material central region AM in Embodiment 1, the heat accumulation count values CT2 to CT6 increase as the number of printed pages increases. Since the heating regions (A2, A3, A4, A5, and A6) are classified as the image heating region AI, the temperature TAI of the image heating region is set to 198° C., and the heat accumulation count values CT2 to CT6 of the 39th page reach 185.
Moreover, since the heating regions (A1 and A7) classified as the recording material edge region AE is classified as the non-image heating region, the temperature TAP of the image heating region is set to 158° C. Therefore, although the heat accumulation count values CT1 and CT7 increase as the number of printed pages increases, since the heat generating quantity of the heat generating block HBi is decreased, the heat accumulation count values CT1 and CT7 do not increase to be larger than the heat accumulation count values CT2 to CT6 of the recording material central region AM. The heat accumulation count values CT1 and CT7 of the 39th page reach 33. As described above, the determination value We is set to 150. Therefore, the condition of Expression 1 illustrated in S1010 of the control flow of
As illustrated in
Although the pressure roller of the present embodiment is configured such that the outer diameter at the ends is larger by approximately 100 μm than the outer diameter at the central portion, a paper wrinkle can be suppressed when the outer diameter difference is maintained to 70 μm or more. Although the heat accumulation count value is a parameter correlated with the outer diameter of the pressure roller, the heat accumulation count value difference of 150 corresponds to a pressure roller outer diameter difference of 30 μm. Therefore, in such a printing example as the specific example of Embodiment 1, although the pressure roller outer diameter difference decreases, the outer diameter difference can be maintained to 70 μm or more. Therefore, in Embodiment 1, the pressure roller outer diameter difference in the recording material edge region AE and the recording material central region AM can be maintained within a certain range and the occurrence of a paper wrinkle can be suppressed.
In the comparative example, as illustrated in
As described above, in the present embodiment, the difference in the heat accumulation amount of the recording material edge region AE and the recording material central region AM does not increase up to a certain level or more. Therefore, it is possible to maintain the outer diameter difference of the pressure roller to be within a certain range and to suppress the occurrence of a paper wrinkle. Moreover, by changing the control temperature TGTi between the image heating region AI and the non-image heating region AP, it is possible to decrease the heat generating quantity of the non-image heating region and to achieve power saving.
In the present embodiment, a heating region of the heat generating element disposed at the first stage in the longitudinal direction of the plurality of heat generating elements is determined as the recording material edge region AE, and a heating region of the heat generating element other than the heat generating element is determined as the recording material central region AM. However, the present invention is not limited to such a configuration. That is, depending on the correspondence between the number of arranged heat generating elements and the size in the longitudinal direction of the recording material, a heating region of a heat generating element disposed on the inner side than the first stage may be determined as the recording material edge region AE. In this case, a heating region of a heat generating element disposed on the inner side in the longitudinal direction than the heat generating element, the heating region of which is determined as the recording material edge region AE, is determined as the recording material central region AM.
Embodiment 2 of the present invention will be described. In Embodiment 2, the heat accumulation count values CT which are the thermal history between the recording material edge region and the recording material central region are compared, and the control temperature of the image heating region and the control temperature of the non-image heating region in the recording material edge region are changed according to the comparison result using a paper wrinkle correction term. A basic configuration and operations of the image forming apparatus and the image heating apparatus of Embodiment 2 are the same as those of Embodiment 1. Therefore, elements of Embodiment 2 having the same or corresponding function and configuration as those of Embodiment 1 are denoted by the same reference numerals and the description thereof will be omitted. Matters that are not particularly described in Embodiment 2 are similar to those of Embodiment 1.
That is, on the basis of the size information of a recording material, it is determined whether the heating region Ai is a region through which the recording material edge PE passes or a region through which a region other than the recording material edge passes (S1032). When the recording material edge PE passes through the heating region Ai, the heating region Ai is classified as the recording material edge region AE (S1033). When the recording material central portion other than the recording material edge PE passes through the heating region Ai, the heating region Ai is classified as the recording material central region AM (S1034). Subsequently, it is determined whether the heating region Ai classified as the recording material central region AM is an image range on the basis of the image data (image information) (S1035). When the heating region Ai is the image range, the heating region Ai is classified as the image heating region AI (S1036). When the heating region Ai is not the image range, the heating region Ai is classified as the non-image heating region AP (S1037). The classification of the heating region Ai is used for controlling the heat generating quantity of the heat generating block HBi as will be described later.
When the heating region Ai is classified as the image heating region AI (S1036), the control temperature TGTi is set as TGTi=TAI−KAI (S1038). When a standard sheet is passed in the fixing apparatus 200 of the present embodiment, TAI is set to 198° C.
Next, a case in which the heating region Ai is classified as the non-image heating region AP (S1037) will be described. When the heating region Ai is classified as the non-image heating region AP, the control temperature TGTi is set as TGTi=TAP−KAP (S1039).
Here, TAP is a reference temperature of the non-image heating region and is set as a temperature lower than the reference temperature TAI of the image heating region so that the heat generating quantity of the heat generating block HBi in the non-image heating region AP is lower than that of the image heating region AI to realize power saving of the image forming apparatus 100. In the present embodiment, TAP is set as 158° C. The reference temperature TAI of the image heating region and the reference temperature TAP of the non-image heating region are preferably variable according to the type of the recording material P such as a thick paper or a thin paper. Moreover, the reference temperature may be adjusted according to image information such as an image density or a pixel density.
Moreover, the temperature correction term KAI of the image heating region and the temperature correction term KAP of the non-image heating region are set according to the heat accumulation count value CTi in each heating region Ai as illustrated in
Next, a case in which the heating region Ai is classified as the recording material edge region AE (S1033) will be described. In S1040, it is determined whether a heat accumulation count value CTe of the recording material edge region AE satisfies Expression 1 below.
CT
e
<CT
m
−W
e (Expression 1)
CTm is a heat accumulation count value of each heating region in the recording material central region AM, and We is a determination value for determining occurrence of a conveying defect at the recording material edge.
Next, S1040 will be described in detail.
In S1040, it is determined whether the image heating apparatus is in a state in which paper wrinkle which is a recording material conveying defect occurs. As described above, the heat accumulation count value CT is a parameter correlated with the heat accumulation amount of the fixing apparatus 200 in each heating region, and the larger the heat accumulation count value, the larger heat accumulation amount. Therefore, the larger the heat accumulation count value CT, the larger the heat accumulation amount of the pressure roller 208 which is a fixing member of the image heating apparatus. Therefore, the larger the heat accumulation count value CT, the more the outer diameter of the pressure roller is expanded, and the larger the recording material conveying force. As described above, the heat accumulation count value CT is a parameter correlated with the recording material conveying force.
When the heat accumulation count value CTe becomes smaller than the heat accumulation count value CTm by the determination value We or more as illustrated in Expression 1 in S1040 of the control flow, a paper wrinkle of the recording material may occur due to the above-described change. In the present embodiment, the determination value We is set to 150. The determination value We is preferably variable according to the type (paper weight) of the recording material P such as a thick paper or a thin paper. Moreover, the determination value We may be adjusted according to a use environment (temperature or humidity).
First, when the determination criterion of S1040 is not satisfied, it is determined that the difference in the heat accumulation amount of the pressure roller is within a predetermined range and a paper wrinkle of the recording material resulting from a change in the outer diameter of the pressure roller does not occur and the flow proceeds to S1035. Moreover, the heating region Ai is classified into the image heating region AI and the non-image heating region AP similarly to the recording material central region AM (S1036 and S1037), and the control temperature is determined according to the classification (S1038 and S1039).
When the determination criterion of S1040 is satisfied, it is determined that a paper wrinkle of the recording material resulting from a change in the outer diameter of the pressure roller may occur if the difference in the heat accumulation amount of the pressure roller increases further, and the control temperature of the heat generating block is controlled to the control temperature TGTe for paper wrinkle correction. First, it is determined whether the heating region Ai is an image range on the basis of the image data (image information) (S1041). When the heating region Ai is the image range, the heating region Ai is classified as the image heating region AI (S1042). When the heating region Ai is not the image range, the heating region Ai is classified as the non-image heating region AP (S1043). The classification of the heating region Ai is used for controlling the heat generating quantity of the heat generating block HBi as will be described later.
When the heating region Ai is classified as the image heating region AI (S1042), the control temperature is set as TGTe=TAI−KAi+WAI (S1044).
Here, TAI is a reference temperature of the image heating region and is set as a temperature appropriate for fixing a non-fixed image to the recording material P. When a standard sheet is passed in the fixing apparatus 200 of the present embodiment, TAI is set to 198° C.
Moreover, KAI is a temperature correction term of the image heating region and is set according to a heat accumulation count value CTi in each heating region Ai as illustrated in
Moreover, WAI is a paper wrinkle correction term of the image heating region and is set as illustrated in
Next, a case in which the heating region Ai is classified as the non-image heating region AP (S1043) will be described. When the heating region Ai is classified as the non-image heating region AP, the control temperature is set as TGTe=TAP−KAP+WAP (S1045). Here, TAP is a reference temperature of the non-image heating region and is set as a temperature appropriate for fixing a non-fixed image to the recording material P. When a standard sheet is passed in the fixing apparatus 200 of the present embodiment, TAP is set to 158° C.
Moreover, KAP is a temperature correction term of the non-image heating region and is set according to the heat accumulation count value CTi in each heating region Ai as illustrated in
Moreover, WAP is a paper wrinkle correction term of the non-image heating region and is set as illustrated in
For example, in a state in which the heat accumulation count value CTi is 100 or smaller, the control temperature of the non-image heating region AP is set as TGTe=193° C.
By the above-described control flow, even when such an image as the image pattern illustrated in
The setting values of the reference temperature (TAI and TAP) of each heating region, the temperature correction term (KAI and KAP) of each heating region, the paper wrinkle correction term (WAI and WAP), and the determination value We for a conveying defect at the edges of the recording material are determined appropriately by taking the configuration of the image forming apparatus 100 and the fixing apparatus 200 and the printing conditions into consideration. However, these values are not limited to the above-described values.
Next, the advantages of Embodiment 2 will be described by way of a heater control method using a comparative example and a specific example of Embodiment 2 to be described later will be described as a specific printing example. In the specific example of Embodiment 2, in a state in which the fixing apparatus 200 is in a room-temperature state (that is, a state in which the heat accumulation count value CTi of each heating region Ai is 0), 100 pages of a recording material illustrated in
Moreover,
In
In the heating regions (A2, A3, A4, A5, and A6) classified as the recording material central region AM in Embodiment 2, the heat accumulation count values CT2 to CT6 increase as the number of printed pages increases. Since the heating regions (A2, A3, A4, A5, and A6) are classified as the image heating region AI, the temperature TAI of the image heating region is set to 198° C., and the heat accumulation count values CT2 to CT6 of the 39th page reach 185.
Moreover, since the heating regions (A1 and A7) classified as the recording material edge region AE is classified as the non-image heating region, the temperature TAP of the image heating region is set to 158° C. Therefore, although the heat accumulation count values CT1 and CT7 increase as the number of printed pages increases, since the heat generating quantity of the heat generating block HBi is decreased, the heat accumulation count values CT1 and CT7 do not increase to be larger than the heat accumulation count values CT2 to CT6 of the recording material central region AM. The heat accumulation count values CT1 and CT7 of the 39th page reach 33. As described above, the determination value We is set to 150. Therefore, the condition of Expression 1 illustrated in S1040 of the control flow of
For the 39th and subsequent pages, the heat accumulation count values CT1 and CT7 increase as illustrated in
In the comparative example, as illustrated in
As described above, in the present embodiment, the difference in the heat accumulation amount of the recording material edge region AE and the recording material central region AM does not increase up to a certain level or more. Therefore, it is possible to maintain the outer diameter difference of the pressure roller to be within a certain range and to suppress the occurrence of a paper wrinkle. Moreover, regardless of the presence of an image in the recording material edge region AE, it is possible to suppress a difference in the heat accumulation amount and to suppress a paper wrinkle more stably. Moreover, by changing the control temperature TGTi between the image heating region AI and the non-image heating region AP, it is possible to decrease the heat generating quantity of the non-image heating region and to achieve power saving.
Embodiment 3 of the present invention will be described. In Embodiment 3, the heat accumulation count values CT which are the thermal history between the recording material edge region and the recording material central region are compared, and the control temperature of the image heating region and the control temperature of the non-image heating region in the recording material edge region are changed according to the comparison result using a paper conveying defect correction term. A basic configuration and operations of the image forming apparatus and the image heating apparatus of Embodiment 3 are the same as those of Embodiment 1. Therefore, elements of Embodiment 3 having the same or corresponding function and configuration as those of Embodiment 1 are denoted by the same reference numerals and the description thereof will be omitted. Matters that are not particularly described in Embodiment 3 are similar to those of Embodiment 1.
That is, on the basis of the size information of a recording material, it is determined whether the heating region Ai is a region through which the recording material edge PE passes or a region through which a region other than the recording material edge passes (S1052). When the recording material edge PE passes through the heating region Ai, the heating region Ai is classified as the recording material edge region AE (S1053). When the recording material central portion other than the recording material edge PE passes through the heating region Ai, the heating region Ai is classified as the recording material central region AM (S1054). Subsequently, it is determined whether the heating region Ai classified as the recording material edge region AE is an image range on the basis of the image data (image information) (S1055). When the heating region Ai is the image range, the heating region Ai is classified as the image heating region AI (S1056). When the heating region Ai is not the image range, the heating region Ai is classified as the non-image heating region AP (S1057). The classification of the heating region Ai is used for controlling the heat generating quantity of the heat generating block HBi as will be described later.
When the heating region Ai is classified as the image heating region AI (S1056), the control temperature TGTi is set as TGTi=TAI−KAI (S1058). When a standard sheet is passed in the fixing apparatus 200 of the present embodiment, TAI is set to 198° C.
Next, a case in which the heating region Ai is classified as the non-image heating region AP (S1057) will be described. When the heating region Ai is classified as the non-image heating region AP, the control temperature TGTi is set as TGTi=TAP−KAP (S1059).
Here, TAP is a reference temperature of the non-image heating region and is set as a temperature lower than the reference temperature TAI of the image heating region so that the heat generating quantity of the heat generating block HBi in the non-image heating region AP is lower than that of the image heating region AI to realize power saving of the image forming apparatus 100. In the present embodiment, TAP is set as 158° C. The reference temperature TAI of the image heating region and the reference temperature TAP of the non-image heating region are preferably variable according to the type of the recording material P such as a thick paper or a thin paper. Moreover, the reference temperature may be adjusted according to image information such as an image density or a pixel density.
Moreover, the temperature correction term KAI of the image heating region and the temperature correction term KAP of the non-image heating region are set according to the heat accumulation count value CTi in each heating region Ai as illustrated in
Next, a case in which the heating region Ai is classified as the recording material central region AM (S1054) will be described. In S1060, it is determined whether a heat accumulation count value CTm of the recording material central region AM satisfies Expression 4 below.
CT
m
<CT
e
−X
e (Expression 4)
CTe is a heat accumulation count value of each heating region in the recording material edge region AE, and Xe is a determination value for determining a recording material conveying defect.
Next, S1060 will be described in detail.
In S1060, it is determined whether the image heating apparatus is in a state in which a recording material trailing edge pop-up which is a recording material conveying defect occurs. A recording material trailing edge pop-up is a phenomenon in which a trailing edge of a recording material in the conveying direction pops up toward an image surface on an upstream side of the image heating apparatus and is a phenomenon in which the trailing edge makes contact with a constituent member of the image forming apparatus to cause an image defect. As described above, the heat accumulation count value CT is a parameter correlated with the heat accumulation amount of the fixing apparatus 200 in each heating region, and the larger the heat accumulation count value, the larger the heat accumulation amount. Therefore, the larger the heat accumulation count value CT, the larger the heat accumulation amount of the pressure roller 208 which is a fixing member of the image heating apparatus. Therefore, the larger the heat accumulation count value CT, the more the outer diameter of the pressure roller is expanded, and the larger the recording material conveying force. As described above, the heat accumulation count value CT is a parameter correlated with the recording material conveying force.
When the heat accumulation count value CTm illustrated in Expression 4 in S1060 of the control flow becomes smaller than the heat accumulation count value CTe by the determination value Xe or more, an image defect resulting from a trailing edge pop-up may occur due to the above-described change. In the present embodiment, the determination value Xe is set to 150. The determination value Xe is preferably variable according to the type (paper weight) of the recording material P such as a thick paper or a thin paper. Moreover, the determination value Xe may be adjusted according to a use environment (temperature or humidity).
First, when the determination criterion of S1060 is not satisfied, it is determined that the difference in the heat accumulation amount of the pressure roller is within a predetermined range and a trailing edge pop-up of the recording material resulting from a change in the outer diameter of the pressure roller does not occur and the flow proceeds to S1055. Moreover, the heating region Ai is classified into the image heating region AI and the non-image heating region AP similarly to the recording material edge region AE (S1056 and S1057), and the control temperature is determined according to the classification (S1058 and S1059).
When the determination criterion of S1060 is satisfied, it is determined that a trailing edge pop-up of the recording material resulting from a change in the outer diameter of the pressure roller may occur if the difference in the heat accumulation amount of the pressure roller increases further, and the control temperature of the heat generating block is controlled to the control temperature TGTm for paper conveyance correction. First, it is determined whether the heating region Ai is an image range on the basis of the image data (image information) (S1061). When the heating region Ai is the image range, the heating region Ai is classified as the image heating region AI (S1062). When the heating region Ai is not the image range, the heating region Ai is classified as the non-image heating region AP (S1063). The classification of the heating region Ai is used for controlling the heat generating quantity of the heat generating block HBi as will be described later.
When the heating region Ai is classified as the image heating region AI (S1062), the control temperature is set as TGTe=TAI−KAi+XAI (S1064).
Here, TAI is a reference temperature of the image heating region and is set as a temperature appropriate for fixing a non-fixed image to the recording material P. When a standard sheet is passed in the fixing apparatus 200 of the present embodiment, TAI is set to 198° C.
Moreover, KAI is a temperature correction term of the image heating region and is set according to a heat accumulation count value CTi in each heating region Ai as illustrated in
Moreover, XAI is a paper conveyance correction term of the image heating region and is set as illustrated in
Next, a case in which the heating region Ai is classified as the non-image heating region AP (S1063) will be described. When the heating region Ai is classified as the non-image heating region AP, the control temperature is set as TGTm=TAP−KAP+XAP (S1065). Here, TAP is a reference temperature of the non-image heating region and is set as a temperature appropriate for fixing a non-fixed image to the recording material P. When a standard sheet is passed in the fixing apparatus 200 of the present embodiment, TAP is set to 158° C.
Moreover, KAP is a temperature correction term of the non-image heating region and is set according to the heat accumulation count value CTi in each heating region Ai as illustrated in
Moreover, XAP is a paper wrinkle correction term of the non-image heating region and is set as illustrated in
For example, in a state in which the heat accumulation count value CTi is 100 or smaller, the control temperature of the non-image heating region AP is set as TGT=193° C.
By the above-described control flow, even when such an image as the image pattern illustrated in
The setting values of the reference temperature (TAI and TAP) of each heating region, the temperature correction term (KAI and KAP) of each heating region, the conveying defect correction term (XAI and XAP), and the determination value Xe for a conveying defect of the recording material are determined appropriately by taking the configuration of the image forming apparatus 100 and the fixing apparatus 200 and the printing conditions into consideration. However, these values are not limited to the above-described values.
Next, the advantages of Embodiment 3 will be described by way of a heater control method using a comparative example and a specific example of Embodiment 3 to be described later will be described as a specific printing example. In the specific example of Embodiment 3, in a state in which the fixing apparatus 200 is in a room-temperature state (that is, a state in which the heat accumulation count value CTi of each heating region Ai is 0), 100 pages of a recording material illustrated in
Moreover,
In
In the heating regions (A1 and A7) classified as the recording material edge region AE in Embodiment 3, the heat accumulation count values CT1 and CT7 increase as the number of printed pages increases. Since the heating regions (A1 and A7) are classified as the image heating region AI, the temperature TAI of the image heating region is set to 198° C., and the heat accumulation count values CT1 and CT7 of the 39th page reach 185.
Moreover, since the heating regions (A2, A3, A4, A5, and A6) classified as the recording material central region AM is classified as the non-image heating region, the temperature TAP of the image heating region is set to 158° C. Therefore, although the heat accumulation count values CT2 to CT6 increase as the number of printed pages increases, since the heat generating quantity of the heat generating block HBi is decreased, the heat accumulation count values CT2 to CT6 do not increase to be larger than the heat accumulation count values CT1 and CT7 of the recording material edge region AE. The heat accumulation count values CT2 to CT6 of the 39th page reach 33. As described above, the determination value Xe is set to 150. Therefore, the condition of Expression 4 illustrated in S1060 of the control flow of
For the 39th and subsequent pages, the heat accumulation count values CT2 to CT6 increase as illustrated in
In the comparative example, as illustrated in
As described above, in the present embodiment, the difference in the heat accumulation amount of the recording material edge region AE and the recording material central region AM does not increase up to a certain level or more. Therefore, it is possible to maintain the outer diameter difference of the pressure roller to be within a certain range and to suppress the occurrence of a trailing edge pop-up. Moreover, regardless of the presence of an image in the recording material edge region AE, it is possible to suppress a difference in the heat accumulation amount and to suppress a trailing edge pop-up more stably. Moreover, by changing the control temperature TGTi between the image heating region AI and the non-image heating region AP, it is possible to decrease the heat generating quantity of the non-image heating region and to achieve power saving.
Embodiment 4 of the present invention will be described. In Embodiment 4, the heat accumulation count values CT which are the thermal history between the heating regions at symmetric positions in relation to the central position of the image heating apparatus in the direction orthogonal to the conveying direction of the recording material are compared, and the control temperature of the image heating region and the control temperature of the non-image heating region are changed according to the comparison result. A basic configuration and operations of the image forming apparatus and the image heating apparatus of Embodiment 4 are the same as those of Embodiment 1. Therefore, elements of Embodiment 4 having the same or corresponding function and configuration as those of Embodiment 1 are denoted by the same reference numerals and the description thereof will be omitted. Matters that are not particularly described in Embodiment 4 are similar to those of Embodiment 1.
Next, a heater control method according to the present embodiment (that is, a method of controlling the heat generating quantity of the heat generating block HBi (i=1 to 7)) will be described. When the heating region Ai is classified as the image heating region AI (S1073), the control temperature TGTi is set as TGTi=TAI−KAI (S1075). When a standard sheet is passed in the fixing apparatus 200 of the present embodiment, TAI is set to 198° C. Next, a case in which the heating region Ai is classified as the non-image heating region AP (S1074) will be described. When the heating region Ai is classified as the non-image heating region AP, the control temperature TGTi is set as TGTi=TAP−KAP (S1076).
Here, TAP is a reference temperature of the non-image heating region and is set as a temperature lower than the reference temperature TAI of the image heating region so that the heat generating quantity of the heat generating block HBi in the non-image heating region AP is lower than that of the image heating region AI to realize power saving of the image forming apparatus 100. In the present embodiment, TAP is set as 158° C. The reference temperature TAI of the image heating region and the reference temperature TAP of the non-image heating region are preferably variable according to the type of the recording material P such as a thick paper or a thin paper. Moreover, the reference temperature may be adjusted according to image information such as an image density or a pixel density.
Moreover, the temperature correction term KAI of the image heating region and the temperature correction term KAP of the non-image heating region are set according to the heat accumulation count value CTi in each heating region Ai as illustrated in
Next, comparison of heat accumulation count values in the heating region Ai (S1077) will be described. In S1077, it is determined whether the heat accumulation count value CTi in each heating region Ai satisfies a heat accumulation count value comparison expression illustrated in Table 1 below. In the present embodiment, the heat accumulation count values CT which are the thermal history between heating regions A1 and A7, between heating regions A2 and A6, and between heating regions A3 and A5 which are at symmetric positions in relation to the central position of the image heating apparatus are compared. That is, the heat accumulation count values in the heating regions formed by the pair of heat generating elements disposed symmetrically in the longitudinal direction about the heat generating element disposed at the center in the longitudinal direction among the plurality of heat generating elements are compared with each other. Expression 1-7 is a heat accumulation count value comparison expression for comparing heating regions Ai and A7, and Expression 2-6 is a heat accumulation count value comparison expression for comparing heating regions A2 and A6. Table 1 includes six heat accumulation count value comparison expressions for comparing heating regions.
In the present embodiment, S1, S2, and S3 are determination values for determining skew of the fixing film and are set to 200.
Comparison of heat accumulation count values will be described in detail using Expression 1-7 as a representative example.
CT
1
<CT
7
−S
1 (Expression 1-7)
CT1 is the heat accumulation count value in the heating region A1, CT7 is the heat accumulation count value in the heating region A7, and S1 is a skew determination value of the fixing film in the heating region A1. The skew determination value S1 of the fixing film is set to 200.
In S1077, it is determined whether the fixing film receives a predetermined level of pulling force or higher in the longitudinal direction of the image heating apparatus. As described above, the heat accumulation count value CT is a parameter correlated with the heat accumulation amount of the fixing apparatus 200 in each heating region, and the larger the heat accumulation count value, the larger heat accumulation amount. Therefore, the larger the heat accumulation count value CT, the larger the heat accumulation amount of the pressure roller and the larger the outer diameter of the pressure roller. As described above, the heat accumulation count value CT is a parameter correlated with the outer diameter of the pressure roller. Therefore, when the heat accumulation count value CT1 becomes smaller than the heat accumulation count value CT7, the outer diameter of the pressure roller in the heating region A7 becomes larger than the outer diameter of the pressure roller in the heating region A1 and a pulling force of pulling the fixing film from the heating region A1 toward the heating region A7 is generated. Therefore, when the force of pulling the fixing film from the heating region A1 toward the heating region A7 increases, a pressing force applied to a flange member that holds a fixing film end (not illustrated) increases and wearing of the fixing film end is accelerated. The same is true to comparison of heat accumulation count values in the other heating regions.
When the heat accumulation count value comparison expression is satisfied in S1077, the control temperature is corrected (S1078). As for control temperature correction, as illustrated in Table 1, the control temperature TGTi in the image heating region is set as TGTi=TAI−KAI+SAI. The control temperature TGTi in the non-image heating region is set as TGTi=TAP−KAP+SAP. TAI is the reference temperature of the image heating region, KAI is the temperature correction term of the image heating region, SAI is the skew correction term of the image heating region, and SAP is the skew correction term of the non-image heating region. In the present embodiment, the skew correction term SAI of the image heating region is set to 1° C., and the skew correction term SAP of the non-image heating region is set to 35° C. By the above-described setting, even when the image pattern illustrated in
As described above, in the present embodiment, the control temperature TGTi of the respective heating regions Ai is determined according to the classification and the heat accumulation count value CTi of the heating region Ai. The setting values of the reference temperature (TAI and TAP) of each heating region, the temperature correction term (KAI and KAP) of each heating region, and the skew correction term (SAI and SAP) of each heating region are determined appropriately by taking the configuration of the image forming apparatus 100 and the fixing apparatus 200 and the printing conditions into consideration. That is, these values are not limited to the above-described values.
Next, the advantages of Embodiment 4 will be described by way of a heater control method using a comparative example and a specific example of Embodiment 4 to be described later will be described as a specific printing example. In Embodiment 4, in a state in which the fixing apparatus 200 is in a room-temperature state (that is, a state in which the heat accumulation count value CTi of each heating region Ai is 0), 100 pages of a recording material (LTR size: a sheet width of 216 mm, a sheet length of 279 mm, and a paper weight of 75 g/m2) illustrated in
Moreover,
In the comparative example, the control temperatures TGTi of the image heating region AI and the non-image heating region AP are set similarly to those of Embodiment 4 using the control flow of
In
In the heating regions (A5 to A7) classified as the image heating region AI in Embodiment 4, the heat accumulation count values CT5 to CT7 increase as the number of printed pages increases. Since the heating regions (A5 to A7) are classified as the image heating region AI, the temperature TAI of the image heating region is set to 198° C., and the heat accumulation count values CT5 to CT7 of the 55th page reach 242. Moreover, since the heating regions (A1 to A4) classified as the non-image heating region AP is classified as the non-image heating region, the temperature TAP of the image heating region is set to 158° C. Therefore, although the heat accumulation count values CT2 and CT6 increase as the number of printed pages increases, since the heat generating quantity of the heat generating block HBi is decreased, the heat accumulation count values CT2 and CT6 do not increase to be larger than the heat accumulation count values CT5 to CT7 of the recording material central region AM. The heat accumulation count values CT2 and CT6 of the 25th page reach 41. Therefore, Expressions 1-7, 2-6, and 3-5 which are heat accumulation count value comparison expressions in S1077 of the control flow illustrated in
As illustrated in
In the comparative example, as illustrated in
As described above, in the PE, the difference in the heat accumulation amount between the heating regions in the longitudinal direction of the image heating apparatus does not increase up to a certain level or more. Therefore, it is possible to maintain the outer diameter difference of the pressure roller to be within a certain range and to suppress wearing of the fixing film end resulting from an increase in the pulling force. Moreover, by changing the control temperature TGTi between the image heating region AI and the non-image heating region AP, it is possible to decrease the heat generating quantity of the non-image heating region and to achieve power saving.
The respective configurations of the above-described embodiments may be combined as much as possible.
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. 2017-12046, filed on Jan. 26, 2017, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-012046 | Jan 2017 | JP | national |
