Patent Application
20190212679
This application claims the benefit of Japanese Patent Application No. 2018-000873, filed on Jan. 5, 2018, which is hereby incorporated by reference herein in its entirety.
The present invention relates to an image heating apparatus, such as a fixing unit, that is mounted on an image forming apparatus utilizing an electrophotographic system or an electrostatic recording system, such as a copying machine or a printer, or a gloss-imparting device for reheating a toner image fixed on a recording material, thereby increasing the gloss level of the toner image. The present invention also relates to an image forming apparatus including the image heating apparatus.
As an image heating apparatus, there is an apparatus including a tubular film, a heater in contact with the inner surface of the film, and a roller forming a nip portion together with the heater through the film. When an image forming apparatus, in which the image heating apparatus is mounted, performs printing successively with small-sized sheets, there occurs a phenomenon in which the temperature of a region (non-sheet passing portion) through which the sheets do not pass, in the longitudinal direction of the nip portion, gradually increases (non-sheet passing portion temperature rise). In the image heating apparatus, it is necessary to prevent the non-shR:eet passing portion from reaching a temperature exceeding the heat-resistant temperature of each member in the apparatus. As an approach to preventing the non-sheet passing portion temperature rise, there is proposed an apparatus in which a heat generating resistor on a heater is divided in the longitudinal direction of the heater into a plurality of groups (heat generating blocks), and heat generation distribution (heating region) is changed on the basis of the size of recording materials (Japanese Patent Application Laid-open No. 2014-59508). In the above-mentioned apparatus, the temperature of a sheet passing portion through which a recording material passes is controlled to a temperature necessary for fixing a toner image, and the temperature of a non-sheet passing portion is controlled to a lower-limit temperature necessary for a film to rotate by lowering a control temperature or interrupting heat generation, in order to save energy, among other benefits. The plurality of heat generating blocks, which are obtained through division, each include a detection member for detecting the temperature of a heat generating element, and the amount of heat generation is controlled on the basis of the result of detection. With regard to a heat generating block corresponding to the end position of a recording material, one heat generating block has the sheet passing portion and the non-sheet passing portion, and thus, the one heat generating block has a temperature difference in the longitudinal direction. In view of this, there is also proposed an apparatus in which a plurality of temperature detecting units different in longitudinal position are arranged for each heat generating block, and the temperature of each portion is detected to be used for control (Japanese Patent Application No. 2017-41743). There is also proposed a method for controlling, in this case, the heat generating block on the basis of a temperature detected by a temperature detecting unit, which is close to a conveyance reference position of a recording material in the longitudinal direction, among the plurality of temperature detecting units.
When a heat generating block, of the heat generating blocks, which are obtained through division, corresponding to the non-sheet passing portion is controlled with the detection member, which is close to the conveyance reference position, among the plurality of temperature detecting units, however, the temperature of a portion far from the conveyance reference position falls below the lower-limit temperature necessary for the film to rotate in some cases. The temperature detecting unit close to the conveyance reference position detects a temperature greater than the control temperature due to the effect of the temperature of the sheet passing region, which has a high temperature, or the non-sheet passing portion temperature rise. Thus, when the heat generating block is controlled with the temperature detecting unit close to the conveyance reference position, electrical power is reduced so that the temperature converges to the control temperature, and the temperature of the portion that is far from the conveyance reference position, and that is thus not affected by the non-sheet passing portion temperature rise, falls below the control temperature. The control temperature for the heat generating block corresponding to the non-sheet passing portion is set to the lower-limit temperature necessary for the film to rotate, and hence, the viscosity of grease for helping the film rotation, increases to increase the torque in the portion having a temperature falling below the control temperature, which hinders the film rotation. As a result, the occurrence of a conveyance failure of recording materials is possible.
It is an object of the present invention to provide a technology for appropriately controlling the temperature of each of entire longitudinal regions of a plurality of heat generating blocks, thereby enabling stable conveyance of recording materials.
In order to achieve the above-mentioned object, according to one aspect, the present invention provides an image heating apparatus including an image heating portion that includes a heater including a substrate and a plurality of heat generating elements provided on the substrate and aligned in a longitudinal direction of the substrate, and heats an image formed on a recording material using heat of the heater, a plurality of temperature detecting elements for detecting temperatures of the plurality of heat generating elements, and an energization controlling portion for selectively controlling, based on the temperature detected by each of the plurality of temperature detecting elements, electrical power to be supplied to the plurality of heat generating elements, in order to selectively heat a plurality of heating regions that are heated by the plurality of heat generating elements, wherein the plurality of temperature detecting elements are arranged in each of the plurality of heat generating elements, and wherein the energization controlling portion controls electrical power supply to the plurality of heat generating elements for the purpose of heating a non-sheet-passing heating region, through which the recording material does not pass, among the plurality of heating regions, based on a temperature detected by a temperature detecting element, which is farthest from a conveyance reference position of the recording material, among the plurality of temperature detecting elements arranged in the non-sheet-passing heating region.
In order to achieve the above-mentioned object, according to another aspect, the present invention provides an image heating apparatus including an image heating portion that includes a heater including a substrate and a plurality of heat generating elements provided on the substrate and aligned in a longitudinal direction of the substrate, and heats an image formed on a recording material using heat of the heater, a plurality of temperature detecting elements for detecting temperatures of the plurality of heat generating elements, and an energization controlling portion for selectively controlling, based on the temperature detected by each of the plurality of temperature detecting elements, electrical power to be supplied to the plurality of heat generating elements, in order to selectively heat a plurality of heating regions that are heated by the plurality of heat generating elements, wherein the plurality of temperature detecting elements are arranged in each of the plurality of heat generating elements, and wherein, when images formed on a plurality of recording materials are successively heated, the energization controlling portion controls a conveyance interval of the recording materials based on a temperature detected by a temperature detecting element, which is farthest from a conveyance reference position of the recording materials, among the plurality of temperature detecting elements arranged in a non-sheet-passing heating region, through which the recording materials do not pass, among the plurality of heating regions.
In order to achieve the above-mentioned object, according to still another aspect, the present invention provides an image heating apparatus including an image heating portion that includes a heater including a substrate and a plurality of heat generating elements provided on the substrate and aligned in a longitudinal direction of the substrate, and heats an image formed on a recording material using heat of the heater, a plurality of temperature detecting elements for detecting temperatures of the plurality of heat generating elements, and an energization controlling portion for selectively controlling, based on the temperature detected by each of the plurality of temperature detecting elements, electrical power to be supplied to the plurality of heat generating elements, in order to selectively heat a plurality of heating regions that are heated by the plurality of heat generating elements, wherein the plurality of temperature detecting elements are arranged in each of the plurality of heat generating elements, and wherein the energization controlling portion controls electrical power supply to the plurality of heat generating elements for the purpose of heating an adjacent heating region, which is adjacent to a sheet-passing heating region through which the recording material passes, among non-sheet-passing heating regions, through which the recording material does not pass, among the plurality of heating regions, based on a temperature detected by a temperature detecting element, which is farthest from a conveyance reference position of the recording material, among the plurality of temperature detecting elements arranged in the adjacent heating region, with a target temperature being a temperature that is greater than a target temperature for heating a non-adjacent heating region, which is not adjacent to the sheet-passing heating region, among the non-sheet-passing heating regions, and is less than a target temperature for heating the sheet-passing heating region.
In order to achieve the above-mentioned object, according to yet another aspect, the present invention provides an image heating apparatus including an image heating portion that includes a heater including a substrate and a plurality of heat generating elements provided on the substrate and aligned in a longitudinal direction of the substrate, and heats an image formed on a recording material using heat of the heater, a plurality of temperature detecting elements for detecting temperatures of the plurality of heat generating elements, and an energization controlling portion for selectively controlling, based on the temperature detected by each of the plurality of temperature detecting elements, electrical power to be supplied to the plurality of heat generating elements, in order to selectively heat a plurality of heating regions that are heated by the plurality of heat generating elements, wherein the plurality of temperature detecting elements are arranged in each of the plurality of heat generating elements, and wherein the energization controlling portion controls electrical power supply to the plurality of heat generating elements for the purpose of heating a non-adjacent heating region, which is not adjacent to a sheet-passing heating region through which the recording material passes, among non-sheet-passing heating regions, through which the recording material does not pass, among the plurality of heating regions, based on a temperature detected by a temperature detecting element, which is farthest from a conveyance reference position of the recording material, among the plurality of temperature detecting elements arranged in an adjacent heating region, which is adjacent to the sheet-passing heating region, among the non-sheet-passing heating regions, with a target temperature being a temperature that is greater than a target temperature for heating the adjacent heating region and is less than a target temperature for heating the sheet-passing heating region.
In order to achieve the above-mentioned object, according to yet another aspect, the present invention provides an image heating apparatus including an image heating portion that includes a heater including a substrate and a plurality of heat generating elements provided on the substrate and aligned in a longitudinal direction of the substrate, and heats an image formed on a recording material using heat of the heater, a plurality of temperature detecting elements for detecting temperatures of the plurality of heat generating elements, and an energization controlling portion for selectively controlling, based on the temperature detected by each of the plurality of temperature detecting elements, electrical power to be supplied to the plurality of heat generating elements, in order to selectively heat a plurality of heating regions that are heated by the plurality of heat generating elements, wherein the plurality of temperature detecting elements are arranged in each of the plurality of heat generating elements, and wherein the energization controlling portion controls electrical power supply to the plurality of heat generating elements for the purpose of heating a non-image heating region, through which the image formed on the recording material does not pass, among the plurality of heating regions, based on a temperature detected by a temperature detecting element, which is farthest from a conveyance reference position of the recording material, among the plurality of temperature detecting elements arranged in the non-image heating region.
In order to achieve the above-mentioned object, according to yet another aspect, the present invention provides an image heating apparatus including an image heating portion that includes a heater including a substrate and a plurality of heat generating elements provided on the substrate and aligned in a longitudinal direction of the substrate, and heats an image formed on a recording material using heat of the heater, a plurality of temperature detecting elements for detecting temperatures of the plurality of heat generating elements, and an energization controlling portion for selectively controlling, based on the temperature detected by each of the plurality of temperature detecting elements, electrical power to be supplied to the plurality of heat generating elements, in order to selectively heat a plurality of heating regions that are heated by the plurality of heat generating elements, wherein the plurality of temperature detecting elements are arranged in each of the plurality of heat generating elements, and wherein when images formed on a plurality of recording materials are successively heated, the energization controlling portion controls a conveyance interval of the recording materials based on a temperature detected by a temperature detecting element, which is farthest from a conveyance reference position of the recording materials, among the plurality of temperature detecting elements arranged in a non-image heating region, through which the images formed on the recording materials do not pass, among the plurality of heating regions.
In order to achieve the above-mentioned object, according to yet another aspect, the present invention provides an image heating apparatus including an image heating portion that includes a heater including a substrate and a plurality of heat generating elements provided on the substrate and aligned in a longitudinal direction of the substrate, and heats an image formed on a recording material using heat of the heater, a plurality of temperature detecting elements for detecting temperatures of the plurality of heat generating elements, and an energization controlling portion for selectively controlling, based on the temperature detected by each of the plurality of temperature detecting elements, electrical power to be supplied to the plurality of heat generating elements, in order to selectively heat a plurality of heating regions that are heated by the plurality of heat generating elements, wherein the plurality of temperature detecting elements are arranged in each of the plurality of heat generating elements, and wherein the energization controlling portion controls electrical power supply to the plurality of heat generating elements for the purpose of heating a non-image heating region, through which the image formed on the recording material does not pass, among the plurality of heating regions, as follows: (i) when heating regions adjacent to the non-image heating region are both image heating regions through which the image formed on the recording material passes, the energization controlling portion performs the control based on a temperature detected by a temperature detecting element, among the plurality of temperature detecting elements arranged in the non-image heating region, the temperature detecting element being closest to an image heating region through which a greater amount of toner passes, among the image heating regions adjacent to the non-image heating region, and (ii) when one or none of the heating regions adjacent to the non-image heating region is the image heating region, the energization controlling portion performs the control based on a temperature detected by a temperature detecting element, which is farthest from the image, among the plurality of temperature detecting elements arranged in the non-image heating region.
In order to achieve the above-mentioned object, according to yet another aspect, the present invention provides an image forming apparatus including an image forming portion for forming an image on a recording material, and a fixing portion for fixing, to the recording material, the image formed on the recording material, wherein the fixing portion is the image heating apparatus.
According to the present inventions, it is possible to appropriately control the temperature of each of the entire longitudinal regions of the plurality of heat generating blocks, thereby enabling stable conveyance of recording materials.
Further features of the present inventions will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Hereafter, a description will be given, with reference to the drawings, of embodiments of the present inventions. The sizes, materials, shapes, their relative arrangements, or the like, of constituents described in the embodiments may, however, 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.
The laser printer 100 of the present embodiment supports a plurality of recording material sizes. In the sheet-feeding cassette 11, letter size sheets (about 216 mm×279 mm), A4 sheets (210 mm×297 mm), executive size sheets (about 184 mm×267 mm), and A5 sheets (148 mm×210 mm) can be set, for example.
Basically, the printer 100 of the present embodiment is a laser printer for feeding sheets by short edge feeding (conveying a sheet with the long side of the sheet being in parallel with the conveyance direction). The configuration according to the present embodiment can also be applied to a printer for feeding sheets by long edge feeding. Further, a recording material having the largest size (largest width), out of recording materials having standard widths (recording material widths on the brochure) supported by the apparatus, is a letter size sheet having a width of about 216 mm. Further, the above-mentioned image forming apparatus is described by taking a monochrome laser printer using monochrome toner with a single color as a representative example, but the present invention is not limited thereto. The present invention can also be applied to, for example, a tandem type color printer for transferring toners of two or more colors onto a recording material through an intermediate transfer belt, thereby forming an image.
To sliding portions between the film 202, and the heater 1100 and the holding member 201, viscous grease, which is not shown, is applied. This grease is a mixture of a fluorine resin and a fluorine oil, and has a role of lowering sliding resistance between the film 202, and the heater 1100 and the holding member 201. The viscosity of the grease is correlated with temperature. As temperature becomes higher, the viscosity becomes lower to improve the slidability.
The pressure roller 208 rotates in a direction indicated by the arrow when receiving power from a motor 30, which serves as a power source. When the pressure roller 208 rotates, the film 202 follows the rotation to rotate. The recording material P bearing an unfixed toner image is subjected to fixing treatment at the fixing nip portion N by being heated while being nipped and conveyed. As described above, the fixing apparatus 200 includes the tubular film 202 and the heater 1100 in contact with the inner surface of the film 202, and heats an image formed on a recording material with the heat from the heater 1100 through the film 202.
The heater 1100 includes a substrate 1105 made of ceramic and a heat generating resistor (heat generating element) (see
A protective element 212 is, for example, a thermal switch or a thermal fuse configured to operate to cut off the supply of electrical power to the heater 1100 when there is abnormal heat generation of the heater 1100. The protective element 212 is placed in abutment against the heater 1100 or is placed with a slight gap between the heater 1100 and the protective element 212. A metal stay 204 applies the pressure of a spring, which is not shown, to the holding member 201. The stay 204 also has a role of reinforcing the holding member 201 and the heater 1100.
The printer of the present embodiment is a center-reference printer configured to convey a recording material with the center of the recording material in the width direction (a direction orthogonal to the conveyance direction) being matched with the conveyance reference position X.
Next, the configuration of the heater 1100 is described in detail. The heater 1100 includes a back-surface layer 1 that is a heater surface opposite to a heater surface in contact with the film 202. On the back-surface layer 1, a plurality of heat generating blocks, each of which is a combination of a first conductor 1101, a second conductor 1103, and a heat generating resistor (heat generating element) 1102, are provided in the longitudinal direction of the heater 1100. The heater 1100 of the present embodiment has a total of seven heat generating blocks HB11 to HB17, and forms various heat generation ranges based on the size of recording materials by selectively combining the seven heating regions, which are obtained through division in the longitudinal direction. Individual control for the heat generating blocks is described later.
The heat generating blocks each include the first conductor 1101 provided along the longitudinal direction of the substrate, and the second conductor 1103 provided along the longitudinal direction of the substrate. The first conductor 1101 and the second conductor 1103 are provided at positions different in the lateral direction (a direction orthogonal to the longitudinal direction) of the substrate. The heat generating block further includes the heat generating resistor 1102 that is provided between the first conductor 1101 and the second conductor 1103 and generates heat when being supplied with electrical power through the first conductor 1101 and the second conductor 1103.
The heat generating resistor 1102 of each heat generating block is divided into a heat generating resistor 1102a and a heat generating resistor 1102b that are formed at positions symmetric to each other with respect to a substrate center in the lateral direction of the heater 1100. Further, the first conductor 1101 is divided into a conductor 1101a connected to the heat generating resistor 1102a, and a conductor 1101b connected to the heat generating resistor 1102b. The heat generating resistor 1102a and the heat generating resistor 1102b are formed at the positions symmetric to each other with respect to the substrate center.
The heater 1100 has the seven heat generating blocks HB11 to HB17, and hence, the heat generating resistor 1102a is divided into seven heat generating resistors 1102a-1 to 1102a-7. In a similar manner, the heat generating resistor 1102b is divided into seven heat generating resistors 1102b-1 to 1102b-7. In addition, the second conductor 1103 is divided into seven second conductors 1103-1 to 1103-7. The heat generating resistors 1102a-1 to 1102a-7 are arranged in the substrate 1105 upstream of the conveyance direction of the recording material P, and the heat generating resistors 1102b-1 to 1102b-7 are arranged in the substrate 1105 downstream of the conveyance direction of the recording material P.
On a back-surface layer 2 of the heater 1100, the insulting surface protective layer 1107 (glass in the present embodiment) for covering the heat generating resistor 1102, the first conductor 1101, and the second conductor 1103 is provided. The surface protective layer 1107 does not, however, cover electrode portions E11 to E17, E18-1, and E18-2 with which electrical contacts for power supply C11 to C17, C18-1, and C18-2 are in contact. The electrodes E11 to E17 are electrodes configured to supply electrical power to the heat generating blocks HB11 to HB17 through the respective second conductors 1103-1 to 1103-7. The electrodes E18-1 and E18-2 are electrodes configured to supply electrical power to the heat generating blocks HB11 to HB17 through the first conductors 1101a and 1101b.
Incidentally, the conductors have resistance values which are not zero, and thus affect heat generation distribution in the longitudinal direction of the heater 1100. In view of this, the electrodes E18-1 and E18-2 are provided at the end portions of the heater 1100 in the longitudinal direction so that uniform heat generation distribution is maintained even with the effect of electrical resistance of the first conductors 1101a and 1101b and the second conductors 1103-1 to 1103-7.
As illustrated in
The electrodes are provided on the back surface of the heater 1100. It is thus not necessary to secure, on the substrate 1105, a region for wires to be electrically connected to the respective second conductors 1103-1 to 1103-7, and hence, the width of the substrate 1105 in the lateral direction can be shortened. Consequently, an increase in size of the heater can be prevented. As illustrated in
As described later, the heater 1100 of the present example independently controls the plurality of heat generating blocks, thereby being capable of forming various heat generation distribution patterns (heating regions). For example, the heater 1100 can set heat generation distribution based on the size of recording materials. In addition, the heat generating resistor 1102 is made of a material having a positive temperature coefficient (PTC). When the material having a PTC is used, temperature rise in a non-sheet passing portion can be prevented even in a case in which the end portion of a recording material and the boundary between the heat generating blocks are not matched with each other.
On a sliding-surface layer 1 on the sliding surface side of the heater 1100, a plurality of thermistors T1-C to T7-C, T1-E to T3-E, T4-E1, T4-E2, and T5-E to T7-E for detecting temperatures of the heat generating blocks HB11 to HB17 are formed. The sliding surface is a surface of the heater 1100 that is in contact with the film 202. The thermistor (temperature detecting element) may be made of a material having a large positive or negative temperature coefficient of resistance (TCR). In the present example, a material having a negative temperature coefficient (NTC) is thinly printed on the substrate to form the thermistor, which serves as temperature detecting means. With the use of the thermistors, the film is controlled to have a target temperature.
An arrangement of the thermistors for each heat generating block is described.
As illustrated in
In the configuration of the present embodiment, the thermistor T5-C is placed in an end portion region adjacent to the heat generating block HB14, and the thermistor T5-E is placed in an end portion region adjacent to the heat generating block HB16. Depending on sheet sizes, the edge of a sheet passes through the heat generating block HB15 in some cases. The thermistor T5-C is placed in the end portion close to the sheet passing reference so that the thermistor T5-C is mostly included in the sheet passing region regardless of a change in sheet width. The thermistor T5-E is, on the other hand, placed in the end portion far from the sheet passing reference so that the thermistor T5-E is mostly included in the non-sheet passing region.
In a similar manner, for the heat generating blocks HB11 to HB17, the thermistors T1-C to T7-C close to the sheet passing reference, and the thermistors T1-E to T3-E, T4-E1, T4-E2, and T5-E to T7-E are arranged far from the sheet passing reference.
The longitudinal positions of the thermistors are not limited to the ones in the present embodiment. For example, the thermistors T1-C to T7-C may be arranged at the longitudinal centers of the respective heat generating blocks.
On a surface (sliding-surface layer 2) on the fixing nip portion N side of the substrate 1105, in order to ensure the slidability of the film 202, the insulating surface protective layer 1108 (made of glass in the present embodiment) is formed through coating. The surface protective layer 1108 covers the thermistors, the conductive patterns, and the common conductive pattern. The surface protective layer 1108, however, partly exposes the conductive patterns and the common conductive pattern at the end portions of the heater 1100, as illustrated in
Of the heat generating blocks, which are obtained through division, a heat generating block through which a recording material passes is set to the target temperature of a “sheet passing portion”, and is controlled so that the film temperature reaches a target temperature necessary for fixing a toner image on the recording material. Meanwhile, a heat generating block through which the recording material does not pass is set to the target temperature of the “non-sheet passing portion”, and is set to a temperature as low as possible (a heat generating element corresponding to the heat generating block is supplied with the small amount of electrical power) in the light of energy saving.
When the target temperature of the “non-sheet passing portion” is set to a significantly low value, however, the slidability of the grease applied to the sliding surfaces of the film 202 and the heater 1100 is lost to increase the torque, which hinders the rotation of the film 202. It is concerned as a result that recording materials may not be stably conveyed. When the temperature of the film 202 falls below 110° C., the rotation of the film 202 is adversely affected, and hence, in the configuration of the present embodiment, the target temperature of the “non-sheet passing portion” is set to 120° C., which has a margin to 110° C. by 10° C.
As a comparative example of the present embodiment, there is described a case in which, as in the related art, the temperature of each heat generating block is controlled with the thermistor close to the sheet passing reference regardless of the width of a recording material (the width of a feeding sheet in the longitudinal direction of the fixing apparatus). The thermistor that is used for controlling the temperature of each heat generating block is as in Table 2 below.
In this example, a case in which A5 size sheets (a width of 148 mm) are successively fed is considered. The printer 100 used in the present embodiment is a printer capable of feeding 70 A5 size sheets per minute (=70 ppm: paper per minute).
The heat generating blocks HB16 and HB17 corresponding to the non-sheet passing portion are controlled to a low temperature (120° C. in the present embodiment) in the light of energy saving. The non-sheet passing portion temperature rise in the heat generating block HB15 propagates, however, to the heat generating block HB16. The thermistor T6-C, which is adjacent to the heat generating block HB15, is, therefore affected by the non-sheet passing portion temperature rise, and thus, detects a temperature greater than the non-sheet passing portion target temperature. Because the heat generating block HB16 is controlled so that the temperature of the thermistor T6-C reaches the non-sheet passing portion target temperature, the amount of heat generation is reduced. Thus, when the sheet feeding continues, the film temperature shows the distribution indicated by the dashed line in
In order to solve this problem, in the present embodiment, as illustrated in the flowchart of
Table 3 shows the following.
When the recording material width W satisfies W>210 mm, all the heat generating blocks correspond to the sheet passing portion, and hence, in each of the heat generating blocks HB11 to HB17, the control is performed with the thermistor close to the sheet passing reference in each heat generating block.
When the recording material width W satisfies 185 mm<W≤210 mm, in the heat generating blocks HB12 to HB16 that are heat generating blocks through which the recording material passes, the control is performed with the thermistors T2-C to T6-C close to the sheet passing reference in the respective heat generating blocks. Further, in the heat generating blocks HB11 and HB17 corresponding to the non-sheet passing portion, the control is performed with the thermistors T1-E and T7-E far from the sheet passing reference.
When the recording material width W satisfies 105 mm<W≤185 mm, in the heat generating blocks HB13 to HB15 that are heat generating blocks through which the recording material passes, the control is performed with the thermistors T3-C to T5-C close to the sheet passing reference in the respective heat generating blocks. Further, in the heat generating blocks HB11, HB12, HB16, and HB17 corresponding to the non-sheet passing portion, the control is performed with the thermistors T1-E, T2-E, T6-E, and T7-E far from the sheet passing reference.
When the recording material width satisfies W≤105 mm, in the heat generating block HB14 that is a heat generating block through which the recording material passes, the energization control is performed with the thermistor T4-C close to the sheet passing reference. In the remaining heat generating blocks HB11 to HB13 and HB15 to HB17, which correspond to the non-sheet passing portion, the control is performed with the thermistors T1-E to T3-E and T5-E to T7-E far from the sheet passing reference.
A case in which A5 size sheets (a width of 148 mm) are successively fed while the control of the present embodiment is performed is considered.
In the present embodiment, the heat generating block HB16 is controlled with the thermistor T6-E. Thus, even when the sheet feeding continues, the amount of heat generation in the heat generating block HB16 is not changed, and the entire region of the heat generating block HB16 can always be maintained at the target temperature or greater, as illustrated in
A similar effect can be obtained in the heat generating block HB12 that is opposite to the heat generating block HB16 with respect to the conveyance reference line X in the longitudinal direction. Consequently, a conveyance failure of recording materials that occurs when the film temperature falls below the non-sheet passing portion target temperature can be prevented.
The printer of the present embodiment obtains, before starting sheet feeding, sheet width information that is set by a user. The method for obtaining sheet width information can be selected from, for example, a method for determining a width with sheet-width sensors provided to the sheet-feeding cassette and the sheet-feeding tray, and a method for determining a width with the use of a sensor, such as a flag, provided on the sheet conveyance path.
When width information is obtained on the conveyance path, first, as of print start, the temperature control is performed with the thermistors close to the sheet passing reference in all the heat generating blocks. Then, when a sheet arrives at the position of the sensor and sheet width information is determined, the control in a heat generating block corresponding to the non-sheet passing portion is switched to the one with the thermistor far from the sheet passing reference. In this way, a similar effect can be obtained.
Further, in the example described in the present embodiment, control is performed in which the thermistor that is used for controlling the temperature of the non-sheet passing portion is switched to the thermistor far from the sheet passing reference when sheet width information is determined, but the switching timing may not be a timing at which sheet width information is determined. The following method may be employed, for example: first, the temperature control is performed with the thermistor close to the sheet passing reference, and the control is switched when the thermistor far from the sheet passing reference falls below a predetermined temperature.
In the present embodiment, the image heating apparatus in which the conveyance reference position of recording materials is at the longitudinal center of the image forming apparatus is described, but in an apparatus in which the reference position is not at the center and a recording material is conveyed at a position closer to one side than other side, a similar effect can be obtained through the same control as that in the present embodiment. Further, in the present embodiment, the target temperature of the sheet passing portion is set to 170° C., and the target temperature of the non-sheet passing portion is set to 120° C., but target temperatures are not limited to the temperatures in the present embodiment either.
As described above, the temperature of a heat generating block corresponding to the non-sheet passing portion is controlled with the thermistor far from the sheet passing reference, with the result that the entire longitudinal region of the heat generating block can be maintained at the lower-limit temperature, which is necessary for the film rotation, or greater, and recording materials can thus be stably conveyed.
As Embodiment 1, there is described the method in which, in a heat generating block that corresponds to the non-sheet passing portion, and thus has a low film temperature in a region far from the sheet passing reference, the thermistor that is used for the control is switched to the thermistor far from the sheet passing reference so that a predetermined temperature is maintained. In Embodiment 2, there is described an example in which the thermistor that is used for the temperature control is not switched from the thermistor close to the sheet passing reference as in the example shown in Table 2, and each heat generating block is maintained at a predetermined temperature or higher by another method. Description of the same matters as those in Embodiment 1, such as the apparatus configuration, is omitted.
As in Embodiment 1, a case in which A5 size sheets (a width of 148 mm) are successively fed is considered. When sheet feeding of the A5 sheets continues, as illustrated in
Also in the present embodiment, the heat generating blocks HB14 to HB17, which are symmetric to each other, are used for description. When the A5 sheet is fed, the temperature of the thermistor T6-E, which is a thermistor included in the heat generating block HB16 corresponding to the non-sheet passing portion and is far from the sheet passing reference, is monitored. Then, when a temperature detected by the thermistor T6-E falls below 120° C., which is the non-sheet passing portion target temperature, a measure is taken to increase the sheet-feeding intervals (conveyance intervals between recording materials when images are formed successively on a plurality of recording materials). Specifically, when the temperature of the thermistor T6-E falls below 120° C., control for reducing the throughput of the A5 sheets from 70 ppm to 35 ppm is performed.
When the target temperature of the sheet passing portion is set to 140° C. and the target temperature of the non-sheet passing portion is set to 120° C., a target temperature difference between the sheet passing portion and the non-sheet passing portion is small, and hence, the amount of heat that propagates from the heat generating block HB15 to the heat generating block HB16 is reduced. Further, when an interval between sheets is increased through the throughput down control, the non-sheet passing portion temperature rise in the heat generating block HB15 is reduced. With the two effects described above, the amount of heat that propagates from the heat generating block HB15 to the heat generating block HB16 is remarkably small as compared to a case in which sheets are fed at 70 ppm. As a result, as illustrated in
The advantage of selecting the method of Embodiment 2 is that the choice of components that can be used in the image heating apparatus is widened. When the method of Embodiment 1 is employed, the temperature of the entire region of the heat generating block HB16 can be maintained at a predetermined temperature or greater, but the non-sheet passing portion of the heat generating block HB15 tends to have a high temperature. Thus, it is necessary that components that are affected by the non-sheet passing portion temperature rise have sufficiently high heat-resistant temperatures. When the method of Embodiment 2 is employed, on the other hand, the non-sheet passing portion temperature rise in the heat generating block HB15 can be reduced, and hence, components having low heat-resistant temperatures can be selected.
A method other than the throughput down control can be employed as the measure that is taken when the thermistor far from the sheet passing reference falls below a predetermined temperature in the case in which the thermistor that is used for controlling the temperature of a heat generating block corresponding to the non-sheet passing portion is not switched from the thermistor close to the sheet passing reference. Description of matters in Embodiment 3 that are common to those in Embodiments 1 and 2 is omitted.
In the present embodiment, as illustrated in the flowchart of
When the A5 sheets are fed and the temperature distribution as illustrated in
In Embodiment 4, there is proposed still another method that may be employed as the measure that is taken when the thermistor far from the sheet passing reference falls below a predetermined temperature in the case in which the thermistor that is used for controlling the temperature of a heat generating block corresponding to the non-sheet passing portion is not switched from the thermistor close to the sheet passing reference. Description of matters in Embodiment 4 that are common to those in Embodiments 1 to 3 is omitted. In the present embodiment, as illustrated in the flowchart of
When the A5 sheets are fed and the temperature distribution as illustrated in
As described so far, the temperature of a thermistor that is included in a heat generating block corresponding to the non-sheet passing portion and is far from the sheet passing reference is monitored, and, when the temperature falls below a predetermined temperature, the measure is taken. Consequently, the entire region of the heat generating block can be maintained at a predetermined temperature or greater, and a conveyance failure of recording materials can, therefore, be prevented.
In the present embodiment, there is described an example in which the temperature control is switched on the basis of the width of a toner image to be formed on a recording material, instead of the width of a recording material. Description of the same matters as those in Embodiment 1, such as the apparatus configuration, is omitted.
In the fixing apparatus having the heat generating blocks, which are obtained through division in the longitudinal direction, control for achieving energy saving is performed by performing the temperature control depending on the presence or absence of a toner image in the sheet passing region. Specifically, the temperature of a portion of the sheet passing region in which a toner image is present is raised to a temperature necessary for fixing the toner image, and the temperature of a portion of the sheet passing region in which the toner image is not present is lowered to the lower-limit temperature necessary for the film rotation.
For example, when an image having a width of 148 mm is printed on a letter size sheet having a width of 216 mm as illustrated in
In the related art, in the heat generating block HB14, which is a heat generating block whose entire region corresponds to an image portion, the temperature control is performed with the thermistor T4-C close to the sheet passing reference position X. Further, in the heat generating blocks HB13 and HB15, which are heat generating blocks partly corresponding to the image portion, the temperature control is performed with the thermistors T3-C and T5-C included in a printing region in order to ensure the fixing performance in the printing region. In addition, in the heat generating blocks HB11, HB12, HB16, and HB17, which are heat generating blocks whose entire regions correspond to a non-image portion, the temperature control is performed with the thermistors T1-C, T2-C, T6-C, and T7-C close to the sheet passing reference X. When a heat generating block corresponding to the non-image portion is controlled with the thermistor close to the sheet passing reference X as in the related art, however, a problem similar to the one in the related art, which is described in Embodiment 1, arises.
Of the heat generating blocks, the heat generating blocks HB14 and HB15 through which the image passes are controlled to a temperature (image portion target temperature: 170° C.) for fixing a toner image. Here, the temperature of the heat generating block HB15, through which the end position of the image passes, is controlled so that the thermistor T5-C in the image reaches 170° C.
The sheet and the toner both take the heat from the film in the region in which the toner image is present, but in the region in which the toner image is not present, only the sheet takes the heat, which means that the heat is consumed a little. Thus, as illustrated in
The heat generating blocks HB16 and HB17 corresponding to the non-sheet passing portion are controlled to the lower-limit temperature (non-image portion target temperature: 120° C.) necessary for the film rotation in the light of energy saving. The heat of the heat generating block HB15, which has a greater temperature than the heat generating block HB16 and causes temperature rise in the non-image portion, propagates, however, to the heat generating block HB16, and hence, the thermistor T6-C adjacent to the heat generating block HB15 detects a temperature greater than the target temperature. Because the heat generating block HB16 is controlled so that the temperature of the thermistor T6-C reaches the non-image portion target temperature, the amount of heat generation is reduced. Thus, when the sheet feeding continues, the temperature distribution as illustrated in
In order to solve this problem, in the present embodiment, as illustrated in the flowchart of
As illustrated in
In the present embodiment, the case in which a sheet having formed thereon a symmetrical image is fed is described, but a similar control can be used even when an image is not symmetrical. A similar measure can be used for a case in which an image is only printed on one of the left and right sides of a letter size sheet as in
In the present embodiment, the thermistor that is used for the temperature control is switched when image information is determined, but the switching timing may not be a timing at which image information is determined. A similar effect can be obtained by the following method, for example: first, the temperature control is performed with the thermistor close to the sheet passing reference, and the control is switched when the thermistor far from the image portion falls below a predetermined temperature.
As described above, when the temperature of a heat generating block corresponding to the non-image portion is controlled with the thermistor far from the image portion, the entire longitudinal region of the heat generating block can be maintained at the film target temperature or greater, and a conveyance failure of recording materials can, therefore, be prevented.
In the present embodiment, there is described an example in which the temperature control is switched on the basis of the width and the amount of toner of a toner image to be formed on a recording material. Description of the same matters as those in the above-mentioned embodiments, such as the apparatus configuration, is omitted.
In the fixing apparatus having the heat generating blocks, which are obtained through division in the longitudinal direction, control for achieving energy saving is performed by performing the temperature control depending on the presence or absence of a toner image in the sheet passing region. Specifically, the temperature of a portion of the sheet passing region in which a toner image is present is raised to a temperature necessary for fixing the toner image, and the temperature of a portion of the sheet passing region in which the toner image is not present is lowered to the lower-limit temperature necessary for the film rotation. Further, the region in which the toner image is present has a region in which the amount of toner is small, and, in such a region, the image can be fixed with a low target temperature. Thus, optimal temperature control based on the amount of toner is performed, to thereby achieve energy saving.
In the image forming apparatus of the present embodiment, at the start of printing, toner amount information and position information on an image to be printed on a recording material is obtained, and appropriate temperature control is performed on each of the heat generating elements, which are obtained through division in the longitudinal direction. In this way, electrical power usage is minimized.
Specifically, an image on a feeding sheet is divided per unit area (for example, 10 mm×10 mm), and what percentage of each division does the area of a toner printing region account for is calculated as a coverage rate X. A position in the heat generating block to which the calculated coverage rate corresponds is calculated, and the highest coverage rate in the unit areas in each heat generating block is used as a coverage rate (heat generating block HB-X) that is used for the temperature control of the heat generating block in question. Each heat generating block is controlled on the basis of the value of the heat generating block HB-X with target temperatures in Table 4 below.
Also in such an example, it is necessary that a thermistor that is used for the temperature control be determined so that the film temperature always exceeds a predetermined temperature.
As an example, a case in which an image having a coverage rate of 100% and letters having a coverage rate of 15% are mixed on a letter size sheet as in
The heat generating blocks HB11, HB14, and HB15 are heat generating blocks through which the image having the coverage rate of 100% passes, and hence, are controlled to 170° C., which is a temperature corresponding to the coverage rate of 100%. The heat generating block HB14 is a heat generating block through which the letters having the coverage rate of 15% and the image having the coverage rate of 100% both pass, and is controlled to a temperature for fixing the image that has the coverage rate of 100% and requires a large amount of heat for fixation. The heat generating block HB13 is controlled to 150° C. to fix the letters having the coverage rate of 15%. The heat generating blocks HB12, HB16, and HB17 are heat generating blocks through which no toner image passes, and hence, are set to 120° C., which is close to the lowest temperature necessary for the film rotation.
Next, the thermistors that are used for the temperature control are described. In the heat generating block through which the toner image passes, of the thermistors in the heat generating block, a thermistor corresponding to a region having a high coverage rate is used. This is because toner takes more heat in the region having the high coverage rate to less the film temperature, with the result that the thermistor detects a lower temperature. Through control in the portion at a low film temperature, the temperature of the entire region of the heat generating block can be maintained.
For example, the heat generating block HB11 includes two thermistors of the thermistor T1-E corresponding to the image portion having the coverage rate of 100% and the thermistor T1-C corresponding to the non-image portion having a coverage rate of 0%. Of the thermistors, the thermistor T1-E detects a lower temperature. Thus, the temperature control is performed with the thermistor T1-E so that a predetermined temperature or greater can be maintained. In a similar manner, also in the heat generating blocks HB13 and HB15, the thermistors T3-C and T5-C that correspond to high coverage rate regions are used.
In the heat generating block through which the toner image does not pass, the thermistor far from the image is basically used like Embodiment 5. In the heat generating blocks HB16 and HB17, the thermistors T6-E and T7-E far from the image are used. In a heat generating block through which a toner image does not pass, but which is sandwiched between heat generating blocks through which the toner image passes, such as the heat generating block HB12 in
The above-mentioned contents are summarized in the flowchart of
Although no description is given in the example of
As described above, in the configuration in which the temperature control of each heat generating block is switched on the basis of the image position and the toner amount information, the thermistor that is used for the temperature control is switched so that the target temperature of each heat generating block can be maintained, and a conveyance failure of recording materials can, therefore, be prevented.
The method for maintaining each heat generating block at the target temperature or greater with the use of the position information or the toner amount information on an image is not limited to the above-mentioned method. The method as described in Embodiment 2 may be employed. Specifically, the temperature of the thermistor is monitored, and, when the temperature falls below a predetermined temperature, the measurement is taken.
The configurations of the above-mentioned embodiments can be combined with each other as far 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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-000873 | Jan 2018 | JP | national |
