Patent Grant
8725018
This application claims priority based on 35 USC 119 from prior Japanese Patent Application No. P2010-029364 filed on Feb. 12, 2010, entitled “IMAGE FORMING APPARATUS”, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The invention relates to an image forming apparatus including a fixing section configured to fix a toner image onto a recording medium.
2. Description of the Related Art
An image forming apparatus using an electrophotographic method, for example, an electrophotographic printer includes a fixing section configured to fix toner images, which are transferred onto a sheet as a recording medium, onto the sheet with heat and pressure. For example, Japanese Patent Application Publication No. Hei 7-64436 (Abstract and
However, there is a likelihood that the image quality may deteriorate because the images fail to be fixed satisfactorily.
An object of an aspect of the invention is to improve the image quality.
An aspect of the invention is an image forming apparatus including: a toner image forming section including an image carrier, and configured to form a toner image on the image carrier; a toner image conveying section including an intermediate transfer member and a moving part configured to move the intermediate transfer member in a predetermined movement direction; a primary transfer section configured to transfer the toner image on the image carrier onto the intermediate transfer member; a recording medium conveying section configured to convey a recording medium in a predetermined conveyance direction; a secondary transfer section configured to transfer the toner image on the intermediate transfer member onto the recording medium; a fixing section including a heater, and configured to heat the toner image on the recording medium with the heater; a fixability judging part configured to judge whether or not a temperature of the fixing section reaches a fixable temperature; a condition judging part configured to judge whether or not a condition of the image forming apparatus following input of a first print request into the image forming apparatus is an abnormal temperature rising condition in which an estimated value of a rise time needed for the temperature of the fixing section to reach the fixable temperature exceeds a predetermined reference time; and a print controller. When the fixability judging part judges that the temperature of the fixing section has not reached the fixable temperature yet and the condition judging part judges that the condition of the image forming apparatus is the abnormal temperature rising condition, the print controller causes the toner image conveying section to move the toner image on the intermediate transfer member to a predetermined toner image standby position upstream of the secondary transfer section in the movement direction and to put the toner image on standby at the toner image standby position, and causes the recording medium conveying section to put the recording medium on standby at a predetermined sheet standby position upstream of the secondary transfer section in the conveyance direction. Thereafter, when the fixability judging part judges that the temperature of the fixing section reaches the fixable temperature, the print controller causes the secondary transfer section to transfer the toner image on the intermediate transfer member onto the recording medium.
According to the aspect of the invention, the image quality is improved.
Descriptions are provided herein below for embodiments based on the drawings. In the respective drawings referenced herein, the same constituents are designated by the same reference numerals and duplicate explanation concerning the same constituents is omitted. All of the drawings are provided to illustrate the respective examples only.
As shown in
Toner image forming section 110 includes toner image forming units 111, 112, 113, 114 for the respective colors (for example, black, yellow, magenta and cyan). Image forming units 111, 112, 113, 114 respectively include photosensitive drums 111a, 112a, 113a, 114a as the image carriers for the colors. It should be noted that, although
Exposing section 120 includes LED heads 121, 122, 123, 124 provided with LED arrays, and serving as light source units for the colors, as well as configured to emit rays of light (rays of recording light) for forming the electrostatic latent images on photosensitive drums 111a, 112a, 113a, 114a. It should be noted that, instead of the LED heads, other light sources such as laser light sources may be used.
Toner image conveying section 130 includes: endless intermediate transfer belt 131 having no joint, and serving as the intermediate transfer member; and driving roller 132, belt coupled-driving roller 133 and secondary transfer backup roller 134 around which intermediate transfer belt 131 is wound. Intermediate transfer belt 131 is made of, for example, a semi-conductive plastic film having a high resistance. Driving roller 132 is configured to convey the toner images on intermediate transfer belt 131 in a movement direction Da by: rotating itself with a driving force which is transmitted from an intermediate transfer section driving mechanism including a driving motor (intermediate transfer belt moving motor 135 shown in
Primary transfer section 140 has primary transfer rollers 141, 142, 143, 144 for the colors in positions which are respectively opposed to photosensitive drums 111a, 112a, 113a, 114a with intermediate transfer belt 131 interposed in between. Primary transfer rollers 141, 142, 143, 144 are configured to respectively transfer (perform primary transfer of) the single-color toner images, which are formed on photosensitive drums 111a, 112a, 113a, 114a, onto intermediate transfer belt 131. The single-color toner images transferred onto intermediate transfer belt 131 are made into a multi-color toner image by being superimposed one on another on intermediate transfer belt 131.
Sheet conveying section 150 includes: pickup roller 151 configured to feed sheets P, with which sheet cassette 181 is loaded, on the one-by-one basis; paired sheet conveying rollers 152, 153, and paired sheet conveying rollers 154, 155, configured to convey sheet P, which is picked up by pickup roller 151, in the sheet conveying direction Db; and other conveying rollers, which are not illustrated.
Secondary transfer section 160 includes: secondary transfer backup roller 134 (which is a component of toner image conveying section 130 as well); and secondary transfer roller 161 placed opposite to secondary transfer backup roller 134 with intermediate transfer belt 131 interposed in between. Secondary transfer roller 161 is, for example, a semi-conductive roller having a high resistance, and is in contact with intermediate transfer belt 131 in a position opposed to secondary transfer backup roller 134. Secondary transfer section 160 is configured to transfer the toner images that have been transferred onto intermediate transfer belt 131 (primary transfer) onto sheet P (secondary transfer).
Fixing section 170 includes: fixing roller 171 as a heating/pressing member configured to apply heat and pressure to sheet P and the toner images transferred onto sheet P; press roller 172 opposed to and in contact with fixing roller 171 (or in contact with fixing roller 171 with sheet P interposed in between), and serving as a press member configured to apply pressure to the toner images and sheet P. As a heating device, heater 171a is provided inside fixing roller 171. Fixing section 170 further includes thermistor 173 as a temperature detector configured to detect the temperature of the surface or vicinity of fixing roller 171. Incidentally, the structure of fixing section 170 is not limited to the illustrated structure.
Manipulation panel 190 includes a display device (not illustrated) such as a liquid crystal panel; and a manipulation device (not illustrated) such as manipulation buttons. For example, manipulation panel 190 displays setting items on the display device, and a user inputs various setting items by use of the manipulation device while looking at the displayed contents on the display device.
Print controller 10 includes: transfer voltage controller 11 configured to control voltages to be respectively applied to primary transfer section 140 and secondary transfer section 160; motor controller 12 configured to control the drives of the motors including toner image forming section motor 117, intermediate transfer belt moving motor 135 and sheet conveying motor 156; fixability judging part 13 configured to judge whether or not the temperature of fixing section 170 reaches a fixable temperature (that is, printable temperature) on the basis of a result of detecting the temperature of the surface of fixing roller 171 which is acquired by thermistor 173; and temperature controller 14 configured to control the temperature of the surface of fixing roller 171 to a predetermined temperature. Print controller 10 further includes condition judging part 15 configured to judge whether a condition of the image forming apparatus following the input of the first print request into the image forming apparatus (for example, following the turning on of the power supply of the image forming apparatus) is a “normal temperature rising condition” (shown in
Condition judging part 15 is configured to judge whether the condition following the input of the first print request is the “normal temperature rising condition” or the “abnormal temperature rising condition,” for example, on the basis of the temperature which is detected by thermistor 173. This judging method based on the temperature to be detected by thermistor 173 is hereinafter referred to as a “first condition judging method” for the sake of convenience.
The first condition judging method is now described in detail. Condition judging part 15 calculates amounts of change in the temperature that is detected by thermistor 173 at intervals of a predetermined length of time (for example, at intervals of one second) for the predetermined period of time (for example, 5 seconds) after the input of the first print request into the image forming apparatus. For example, if at least one of the amounts of change in the temperature thus calculated is equal to or larger than an amount-of-change threshold value, condition judging part 15 judges that the condition of image forming apparatus 100 is the “normal temperature rising condition.” If all of the amounts of change in the temperature are smaller than the amount-of-change threshold value, condition judging part 15 judges that the condition of image forming apparatus is the “abnormal temperature rising condition.” These judgments are equivalent to a judgment of whether a rate (pitch) of rise in the temperature of thermistor 173 is not less or less than a predetermined threshold value. Incidentally, the predetermined length of time following the input of the first print request is not limited to 5 seconds, and the intervals of the predetermined length of time are not limited to intervals of the one second.
Alternatively, another judgment scheme may be used in order to make condition judging part 15 judge that the condition of image forming apparatus 100 is the “abnormal temperature rising condition” if the number of calculated amounts of change in the temperature that are less than a predetermined amount-of-change threshold value is equal to or greater than a predetermined number (for example, if half or more of the calculated amounts of change in the temperature are less than the predetermined amount-of-change threshold value).
Otherwise, condition judging part 15 may be configured to: compare a maximum value or an average value of the calculated amounts of change in the temperature with a predetermined threshold value; judge that the condition following the input of the first print request is the “normal temperature rising condition” if the maximum value or the average value is equal to or greater than the predetermined threshold value; and judge that the condition is the “abnormal temperature rising condition” if otherwise.
The “abnormal temperature rising condition” (shown in
Moreover, condition judging part 15 may use a second condition judging method, which is described below, instead of the first condition judging method. In the case where condition judging part 15 uses the second condition judging method, condition judging part 15 judges whether the condition following the input of the first print request is the “normal temperature rising condition” or the “abnormal temperature rising condition” on the basis of the power supply voltage which is detected by power supply voltage detector 16 for the predetermined period of time after the input of the first print request (for example, after the turning on of the power supply of the image forming apparatus). On this occasion, condition judging part 15 detects the power supply voltage at intervals of the predetermined length of time (for example, at intervals of one second) for the predetermined period of time (for example, 5 seconds) after the input of the first print request. Subsequently, condition judging part 15 judges that the condition of image forming apparatus 100 is the “normal temperature rising condition,” for example, if one or more of the thus-detected power supply voltages are equal to or greater than a voltage threshold value, and judges that the condition of image forming apparatus 100 is the “abnormal temperature rising condition” if all of the power supply voltages are less than the voltage threshold value.
Alternatively, another judgment scheme may be used in order to make condition judging part 15 judge that the condition of image forming apparatus 100 is “abnormal temperature rising condition” if the number of calculated amounts of power supply voltages which are less than a predetermined voltage threshold value is equal to or more than a predetermined number (for example, if half or more of the calculated amounts of power supply voltages are less than the predetermined voltage threshold value).
Otherwise, condition judging part 15 may be configured to: compare a maximum value or an average value of the calculated power supply voltages with a predetermined voltage threshold value; judge that the condition following the input of the first print request is the “normal temperature rising condition” if the maximum value or the average value is equal to or greater than the predetermined voltage threshold value; and judge that the condition is the “abnormal temperature rising condition” if otherwise.
In addition, on the basis of the user's input through manipulation panel 190, an operation to be performed when the condition of the image forming apparatus is the “abnormal temperature rising condition” is executed by print controller 10. For example, when the user knows beforehand the drop of the power supply voltage (such as when fixation failure occurs in one of multiple image forming apparatuses of the same type used by the user) the operation to be performed when the condition of the image forming apparatus is the “abnormal temperature rising condition” is executed on the basis of the user's input.
Print controller 10 controls as follows when: fixability judging part 13 judges that the temperature of fixing section 170 does not reach the fixable temperature; and condition judging part 15 judges that the condition of image forming apparatus 100 following the input of the first print request is the “abnormal temperature rising condition.” In this case, print controller 10 causes toner image conveying section 130 to put the toner images on intermediate transfer member 131 on standby at a predetermined toner image standby position upstream of secondary transfer section 160 in the movement direction Da after moving the toner image there. In addition, print controller 10 causes sheet conveying section 150 to put sheet P on standby at a predetermined sheet standby position upstream of secondary transfer section 160 in the conveyance direction Db. Thereafter, when the temperature of fixing section 170 is judged to have reached the fixable temperature, print controller 10 causes toner image conveying section 130 to move intermediate transfer belt 131 in the movement direction Da, sheet conveying section 150 to convey sheet P in the conveyance direction Db, and secondary transfer section 160 to transfer the toner images on intermediate transfer belt 131 onto sheet P. Incidentally, in a case where the conveyance speed of sheet P is sufficiently fast, the standby position of sheet P may be the inside of sheet cassette 181.
Next, operation of image forming apparatus 100 of the first embodiment is described. Upon receipt of a print instruction through the user's input or a print instruction from an external apparatus (not illustrated) such as a host computer, print controller 10 causes LED heads 121, 122, 123, 124 to form electrostatic latent images on photosensitive drums 111a, 112a, 113a, 114a of toner image forming section 110 by emitting rays of recording light onto photosensitive drums 111a, 112a, 113a, 114a in accordance with print data. Subsequently, print controller 10 causes a developing section (not illustrated) of toner image forming section 110 to develop the electrostatic latent images on photosensitive drums 111a, 112a, 113a, 114a to form toner images on photosensitive drums 111a, 112a, 113a, 114a. It should be noted that the control of the drive and stop of toner image forming section motor 117 is implemented by motor power supply 116 on the basis of a control signal from motor controller 12. In addition, the control of the drive and stop of intermediate transfer belt moving motor 135 is implemented by motor power supply 136 on the basis of a control signal from motor controller 12.
Transfer voltage controller 11 in print controller 10 causes primary transfer section power supply 145 to apply a voltage to primary transfer section 140 at an appropriate time, and thus causes primary transfer section 140 to transfer the toner images, which are formed on photosensitive drums 111a, 112a, 113a, 114a, onto intermediate transfer belt 131 with the toner images superimposed one on another (primary transfer). Motor controller 12 in print controller 10 causes sheet conveying section 150 to convey sheet P in accordance with an image forming timing by controlling the supply of electric power to motor power supply 157.
Once the toner images on intermediate transfer belt 131 and sheet P are conveyed to secondary transfer section 160, transfer voltage controller 11 in print controller 10 causes secondary transfer voltage power supply 162 to apply a voltage to secondary transfer section 160 at an appropriate time, and thus causes secondary transfer section 160 to transfer the toner images onto sheet P (secondary transfer).
Thereafter, once sheet P is conveyed to fixing section 170 by sheet conveying section 150, temperature controller 14 in print controller 10 controls the temperature of fixing section 170 by controlling heater power supply 174, and causes the toner images on sheet P to be fixed onto sheet P by applying heat and pressure. Sheet P onto which the toner images are fixed is conveyed and discharged out of the apparatus.
Next, operation of image forming apparatus 100 of the first embodiment is described in detail.
On the basis of a detection signal from thermistor 173 configured to output the detection signal in accordance with the temperature of fixing section 170, fixability judging part 13 in print controller 10 judges whether or not the temperature of fixing section 170 falls within the predetermined fixable (printable) temperature range (in step S102). If fixability judging part 13 judges in step S102 that the temperature of fixing section 170 is equal to or higher than a predetermined printable temperature, print controller 10 carries out a process (print process) for: forming toner images on photosensitive drums 111a, 112a, 113a, 114a; performing the primary transfer of the toner images onto intermediate transfer belt 131; starting the conveyance of sheet P; and performing the secondary transfer of the toner images onto sheet P (in step S112).
If fixability judging part 13 judges in step S102 that the temperature of fixing section 170 is lower than the fixable temperature, condition judging part 15 in print controller 10 judges whether or not the condition of image forming apparatus 100 is the “abnormal temperature rising condition” (for example, the lower voltage condition) (in step S103).
If condition judging part 15 judges that the condition of image forming apparatus 100 is not the “abnormal temperature rising condition,” or that the condition of image forming apparatus 100 is the “normal temperature rising condition,” print controller 10 calculates a time (an estimated value of the rise time) needed for the temperature of fixing section 170 to reach the fixable temperature (in step S106). If the estimated value of the temperature-rise time is shorter than a sheet conveyance time (in step S108), print controller 10 carries out the print process including the conveyance of the sheet and the forming of the toner images. In this respect, the sheet conveyance time is a length of time needed to convey sheet P from sheet cassette 181 to fixing section 170.
If condition judging part 15 judges in step 103 that the condition of image forming apparatus 100 is the “abnormal temperature rising condition,” print controller 10 causes toner image forming section 110 to start to form the toner images on photosensitive drums 111a, 112a, 113a, 114a (in step S104). On this occasion, print controller 10 causes toner image forming units 111, 112, 113, 114 in toner image forming section 110 to form their respective toner images, while transfer voltage controller 11 causes primary transfer power supply 145 to apply the voltage to primary transfer section 140 at the appropriate time.
Print controller 10 causes intermediate transfer belt 131 to move and sheet P to be conveyed in parallel to cause toner image forming section 110 to form the toner images (in step S105).
Subsequently, print controller 10 initiates conveyance of both the toner images on intermediate transfer belt 131 and sheet P to a position immediately before secondary transfer section 160. While sheet P is being conveyed by sheet conveying section 150, motor controller 12 stops the conveyance of sheet P at the time when print controller 10 detects the position of sheet P by use of IN sensor 182 (in step S107). The conveyance of the toner images to the position by the movement of intermediate transfer belt 131 is achieved by a scheme in which: print controller 10 calculates the position of the toner images on the basis of a rotation amount of the photosensitive drums and a rotation amount of intermediate transfer belt roller 132 (or the amount of movement of intermediate transfer belt 131); and print controller 10 causes motor controller 12 to stop the conveyance of the toner images by intermediate transfer belt 131 at the time when the toner images are judged as reaching the position immediately before secondary transfer section 160 (in step S107).
Afterward, fixability judging part 13 judges whether or not the temperature of fixing section 170 reaches the fixable temperature (in step S109). Until the temperature of fixing section 170 is judged to have reached the fixable temperature, print controller 10 puts the print operation on standby by causing motor controller 12 to suspend the conveyance of the toner images by intermediate transfer belt 131 (toner image conveying section 130) and the conveyance of sheet P by sheet conveying section 150 in the position immediately before secondary transfer section 160 (in step S110).
Thereafter, once fixability judging part 13 judges that fixing section 170 becomes ready for fixation after the temperature of fixing section 170 reaches the fixable temperature and falls within the predetermined temperature range, motor controller 12 causes toner image conveying section 130 to resume conveyance of the toner image and causes sheet conveying section 150 to resume conveyance of sheet P, and transfer voltage controller 11 causes secondary transfer section power supply 162 to resume the application of voltage to secondary transfer section 160. Thereby, the toner images are transferred onto sheet P (secondary transfer) (in step S111).
Furthermore, when print controller 10 causes sheet conveying section 150 to convey sheet P, sheet P passes fixing section 170. Fixing section 170 fixes the toner images to sheet P by applying heat and pressure thereto.
Once the print process starts in response to the occurrence of the print request at time t0 (
Time t1 (steps S106, S108 in
Time t2 denotes the time at which sheet P is judged to need to start to be conveyed for the purpose of equalizing the time needed for the leading edges of toner images IM to reach secondary transfer section 160 with the time needed for the leading edge of sheet P to reach secondary transfer section 160. If motor controller 12 causes sheet conveying section 150 to start to convey sheet P (
Time t3 denotes the time at which sheet P reaches secondary transfer section 160. The arrival of sheet P at secondary transfer section 160 is detected when IN sensor 182 (
Time t4 denotes the time at which the leading edge of sheet P reaches OUT sensor 183. At time t4, parts of toner images IM are already transferred onto sheet P. Time t5 denotes the time at which the trailing edge of toner images IM pass OUT sensor 183. The continuing of the conveyance of sheet P discharges sheet P, on which toner images IM are printed, out of image forming apparatus 100. The print process for the first sheet thus ends.
Furthermore, while in the “normal temperature rising condition,” as shown in
Once the print process starts in response to the occurrence of the print request at time t10 (
Time t11 denotes the time at which the conveyance of sheet P to the position immediately before secondary transfer section 160 is completed. Once print controller 10 detects the conveyance of sheet P to the position immediately before secondary transfer section 160 through the detection by IN sensor 182 (
Time t12 denotes the time at which the forming of toner images IM is completed and the positions of the leading edges of toner images IM are located immediately before secondary transfer section 160. At time t12, the process of primary transfer section 140 and the process of toner image forming section 110, which are controlled by transfer voltage controller and motor controller 12, are completed (
Time t13 denotes the time at which the temperature of fixing section 170 reaches the fixable temperature, that is to say, the time at which the process for raising the temperature (a warm-up) is completed. The positions of toner images IM and the position of sheet P at time t13 remain the same as the positions of toner images IM and the position of sheet P at time t12. At time t13, print controller 10 starts the movement of intermediate transfer belt 131 (
Time t14 denotes the time at which the leading edge of sheet P reaches OUT sensor 183 after passing fixing section 170. Toner images IM, which are transferred onto sheet P by secondary transfer section 160, are fixed onto sheet P by fixing section 170 by applying heat and pressure thereto.
Time t15 denotes the time at which the trailing edge of sheet P passes OUT sensor 183. Subsequently, the continuation of the conveyance of sheet P discharges sheet P, on which toner images IM are printed, out of image forming apparatus 100. The print process for the first sheet thus ends.
In the “abnormal temperature rising condition,” as shown in
As described above, when fixability judging part 13 judges that the temperature of fixing section 170 does not reach the fixable temperature and condition judging part 15 judges that the condition of image forming apparatus 100 following the input of the first print request is the “abnormal temperature rising condition,” image forming apparatus 100 of the first embodiment puts toner images IM on intermediate transfer member 131 on standby at the predetermined toner image standby position after moving toner images IM there, and puts sheet P on standby at the predetermined sheet standby position. Thereafter, when the temperature of fixing section 170 is judged to have reached the fixable temperature, image forming apparatus 100 causes intermediate transfer belt 131 to move, and sheet P to be conveyed; and causes secondary transfer section 160 to transfer toner images IM to sheet P. For this reason, once the temperature of fixing section 170 is judged to have reached the fixable temperature, image forming apparatus 100 is capable of causing secondary transfer section 160 to transfer toner images IM on intermediate transfer belt 131 to sheet P, and fixing section 170 to fix toner images IM to sheet P. Accordingly, image forming apparatus 100 of the first embodiment can reduce the time needed from the occurrence of the print request through the completion of the print, particularly, the time needed from the occurrence of the first print request through the completion of the print of the first sheet.
In addition, even in a case where the power supply voltage is unstable, image forming apparatus 100 of the first embodiment can reduce the frequency at which fixation failure occurs. That is because: image forming apparatus 100 completes part of the print process which is to be performed before secondary transfer section 160 undertakes its own part of the print process, and holds the remaining part of the print process in abeyance; and image forming apparatus 100 resumes the print process once fixing section 170 is judged to be ready for the fixation.
It should be noted that, after the power supply of the image forming apparatus is turned on, the temperature of the fixing section may not reach the fixable temperature within a rise time acquired from the table, in some cases such as a case where the voltage (for example, the power supply voltage from the electric outlet) to be applied to the heater in the fixing section fluctuates (for example, a case of a low voltage condition) and a case where the ambient temperature in the location of the image forming apparatus is low (in other words, a case of a low-temperature ambient condition). Under such a condition which makes it difficult to estimate the rise time needed for the temperature of the fixing section to reach the fixable temperature, the sheet is likely to reach the fixing section before the temperature of the fixing section reaches the fixable temperature. This causes a problem that the toner images fail in fixation. However, image forming apparatus 100 of the first embodiment can reduce the frequency at which the fixation failure occurs.
Furthermore, image forming apparatus 100 of the first embodiment makes it possible to reduce the distance between secondary transfer section 160 and fixing section 170. For this reason, image forming apparatus 100 can be easily constructed in a smaller size.
Moreover, image forming apparatus 100 of the first embodiment causes sheet conveying section 150 and toner image conveying section 130 to stop in standby until the temperature of fixing section 170 reaches the fixable temperature. For this reason, it is possible to reduce the power consumption of image forming apparatus 100.
Toner image forming section separating mechanism 211 is, for example, a mechanism configured to move the rotational axes of photosensitive drums 111a, 112a, 113a, 114a of toner image forming section 110 in vertical direction Dc. Toner image forming section separating mechanism 211 is, for example, the mechanism configured to: support the rotational axes of photosensitive drums 111a, 112a, 113a, 114a of toner image forming section 110 by abutting the axes against inclined surfaces of supporting members 231, 232, 233, 234 which are wedge shaped, respectively; and to move the rotational axes of photosensitive drums 111a, 112a, 113a, 114a in the vertical direction Dc by moving supporting members 231, 232, 233, 234 in the horizontal direction (a direction which is orthogonal to the vertical direction Dc, and which is orthogonal to the rotational axes of photosensitive drums 111a, 112a, 113a, 114a). It should be noted that the movement of supporting members 231, 232, 233, 234 in the horizontal direction can be achieved by transmitting a driving force of separation motor 212 to supporting members 231, 232, 233, 234 via a power transmission mechanism such as gears (not illustrated). However, toner image forming section separating mechanism 211 is not limited to the above-described example. Toner image forming section separating mechanism 211 may be realized by another configuration configured to move the rotational axes of photosensitive drums 111a, 112a, 113a, 114a in the vertical direction orthogonal to the rotational axes.
Secondary transfer section separating mechanism 221 is, for example, a mechanism configured to move the rotational axis of secondary transfer roller 161 in vertical direction Dc. Secondary transfer section separating mechanism 221 is, for example, the mechanism configured to: support the rotational axis of secondary transfer roller 161 by abutting the axis against inclined surfaces of supporting member 241 which is wedge shaped; and to move the rotational axis of secondary transfer roller 161 in the vertical direction Dd by moving supporting member 241 in the horizontal direction (a direction which is orthogonal to vertical direction Dd, and which is orthogonal to the rotational axis of secondary transfer roller 161). It should be noted that the movement of supporting member 241 in the horizontal direction can be achieved by transmitting a driving force of separation motor 222 to the supporting member via a power transmission mechanism such as gears (not illustrated). However, secondary transfer section separating mechanism 221 is not limited to the above-described example. Secondary transfer section separating mechanism 221 may be realized by another configuration configured to move the rotational axis of secondary transfer roller 161 in the direction orthogonal to the rotational axis.
Next, operation of toner image forming section separating mechanism 211 and secondary transfer section separating mechanism 221 is described. Approximation/separation controller 21 in print controller 20 causes separation motor 212 to rotate by controlling the supply of electric power to separation motor 212 by motor power supply 213, and moves supporting members 231, 232, 233, 234 of photosensitive drums 111a, 112a, 113a, 114a by transmitting the rotary driving force of separation motor 212 via a power transmission mechanism such as gears, thus moving photosensitive drums 111a, 112a, 113a, 114a in the vertical direction Dc. Photosensitive drums 111a, 112a, 113a, 114a can be separated from or approximated to intermediate transfer belt 131 through this movement of photosensitive drums 111a, 112a, 113a, 114a in the vertical direction Dc. The configuration of secondary transfer section separating mechanism 221 may be similar to that of toner image forming section separating mechanism 211.
When fixability judging part 13 in print controller 20 judges that the temperature of fixing section 170 does not reach the fixable temperature and condition judging part 15 in print controller 20 judges that the condition of image forming apparatus 200 following the input of the first print request is the “abnormal temperature rising condition,” e.g., “low voltage condition” image forming apparatus 200 of the second embodiment operates as follows.
When the length of the sheet in the conveyance direction is not more than the distance L1, print controller 20 causes first approximation/separation unit 210 to reduce the space between intermediate transfer belt 131 and photosensitive drums 111a, 112a, 113a, 114a, and causes second approximation/separation unit 220 to reduce the space between intermediate transfer belt 131 and secondary transfer roller 161 of secondary transfer section 260. Subsequently, while maintaining these reduced spaces, print controller 20 puts the toner images on intermediate transfer belt 131 on standby at a predetermined position upstream of secondary transfer section 260 in the movement direction after moving the toner images there. Thereafter, print controller 20 causes sheet conveying section 150 to convey the sheet; causes the toner images on intermediate transfer belt 131 to move; and causes secondary transfer section 260 to transfer the toner images on intermediate transfer belt 131 to sheet P.
In addition, when the sheet length is more than the distance L1 but not more than the total value (L1+L2) of the distance L1 and the distance L2, print controller 20 causes the space between intermediate transfer belt 131 and photosensitive drums 111a, 112a, 113a, 114a to decrease, and causes the space between intermediate transfer belt 131 and secondary transfer section 260 to decrease. Subsequently, while maintaining these decreased spaces, print controller 20 causes the toner images to be formed on intermediate transfer belt 131. Thereafter, print controller 20 causes photosensitive drums 111a, 112a, 113a, 114a to be separated away from intermediate transfer belt 131, and puts the toner images on intermediate transfer belt 131 on standby at a predetermined position upstream of secondary transfer section 260 in the movement direction after moving the toner images there. Afterward, print controller 20 causes transfer roller 160 of secondary transfer section 260 to come into contact with intermediate transfer belt 131. Thereafter, print controller 20 causes sheet P to be conveyed; causes the toner images on intermediate transfer belt 131 to move; and causes secondary transfer section 260 to transfer the toner images on intermediate transfer belt 131 onto sheet P.
When the sheet length is more than the total value (L1+L2) of distance L1 and the distance L2, print controller 20 causes the toner images to be formed on intermediate transfer belt 131 after the temperature of fixing section 170 reaches the fixable temperature; causes sheet P to be conveyed; causes the toner images on intermediate transfer belt 131 to move; and causes secondary transfer section 260 to transfer the toner images on intermediate transfer belt 131 to sheet P.
Next, operation of image forming apparatus 200 of the second embodiment is described in detail.
Upon reception of the print request from the external apparatus (not illustrated), print controller 20 causes heater power supply 174 to supply electric power to heater 171a of fixing section 170, and thus starts to control the temperature of fixing section 170 (in step S201 in
On the basis of a detection signal from thermistor 173 configured to output the detection signal in accordance with the temperature of fixing section 170, fixability judging part 13 in print controller 20 judges whether or not the temperature of fixing section 170 reaches the predetermined fixable temperature (in step S202 in
If fixability judging part 13 in print controller 20 judges in step S202 that the temperature of fixing section 170 is lower than the fixable temperature, condition judging part 15 in print controller 20 judges whether or not the condition of image forming apparatus 200 is the “abnormal temperature rising condition” (for example, the lower voltage condition) (in step S203 in
If condition judging part 15 in print controller 20 judges in step 203 that the condition of image forming apparatus 200 is the “normal temperature rising condition,” (for example, the normal voltage condition) print controller 20 causes the process to proceed to step S206, where print controller 20 carries out processes which are the same as those in step S101 to S112 (in this case, processes which are the same as those in step S106, S108, S111) in
If condition judging part 15 in print controller 203 judges in step 203 that the condition of image forming apparatus 200 is the “abnormal temperature rising condition,” (for example, the low voltage condition) print controller 20 compares the sheet length of the sheet to be printed with the distance L1 on intermediate transfer belt 131 (in step S204 in
Subsequently, print controller 20 compares the sheet length with the total distance value (L1+L2) (in step S205 in
When judging in step S205 that the sheet length is shorter than the total distance value (L1+L2), print controller 20 causes the process to proceed to step S209 in
In step S209 in
Subsequently, approximation/separation controller 21 in print controller 20 causes secondary transfer section separating mechanism 221 to operate to separate transfer roller 160 of secondary transfer section 260 away from intermediate transfer belt 131 (in step S210 in
Thereafter, transfer voltage controller 11 in print controller 20 causes the toner images on photosensitive drums 111a, 112a, 113a, 114a of toner image forming section 110 to be transferred onto intermediate transfer belt 131 (primary transfer) by controlling the application of the transfer voltage to the primary transfer section 140. In parallel with this operation, motor controller 13 of print controller 20 causes sheet conveying section 150 to start the conveyance of sheet P (in step S211 in
Once print controller 20 detects that sheet P is conveyed to a position immediately before secondary transfer section 260 on the basis of a result of detection by IN sensor 182, motor controller 13 in print controller 20 causes sheet conveying section 150 to suspend the conveyance of sheet P (in step S212 in
Print controller 20 causes toner image forming section 110 and primary transfer section 140 to continue forming toner images IN to intermediate transfer belt 131 until toner images IM corresponding to the sheet length finishes being formed on intermediate transfer belt 131 (in step S213 in
Once toner images IM corresponding to the sheet length finish being formed on intermediate transfer belt 131, print controller 20 completes the toner image forming process (in step S214 in
Subsequently, approximation/separation controller 21 in print controller 20 causes toner image forming section separating mechanism 211 to operate to separate transfer roller 160 of toner image forming section 110 away from intermediate transfer belt 131 (in step S215 in
Subsequently, print controller 20 detects the position of toner images IM on the basis of the amount of movement of intermediate transfer belt 131 by motor controller 12, and thus causes toner images IM to move to the position immediately before secondary transfer section 260 (in step S216 in
Motor controller 12 in print controller 20 causes intermediate transfer belt 131 to stop. Subsequently, approximation/separation controller 21 causes secondary transfer roller 161 of secondary transfer section 260 to come into contact with intermediate transfer belt 131 by controlling secondary transfer section separating mechanism 221 (in step S217 in
Fixability judging part 13 in print controller 20 puts the print process on standby by causing toner image forming section 119 to suspend the toner image formation, and causing the conveyance of sheet P to be suspended, until the temperature of the fixing roller is judged to have reached the fixable temperature (in step S218 in
Once fixability judging part 13 judges that the temperature of fixing roller 171 reaches the fixable temperature, print controller 20 resumes the print process. To put it specifically, motor controller 12 resumes the movement of intermediate transfer belt 131; sheet conveying part 15 resumes the conveyance of sheet P; and transfer voltage controller 11 resumes the application of the voltage to secondary transfer section 260 (in step S219 in
Print controller 20 measures the amount of movement of intermediate transfer belt 131 by motor controller 12. Once print controller 20 detects that the trailing edge of toner images IM moves to toner image forming unit 111 (namely, the most downstream position (position K0 in
In the case where the condition of image forming apparatus 200 is judged as being the “abnormal temperature rising condition,” the implementation of the foregoing process makes it possible to reduce the time needed for the print to be completed while preventing fixation failure even if the sheet length is longer than the distance L1.
Next, an example of the operation of the image forming apparatus in the case where the print request occurs when the condition of the image forming apparatus is the “abnormal temperature rising condition,” for example, the low voltage condition (in step S209 and ensuing steps in
Once the print process starts in response to the occurrence of the first print request at time t20 (
Time t21 denotes the time at which the leading edge of sheet P reaches a position immediately before secondary transfer section 260. Print controller 20 judges the position of sheet P on the basis of a result of detection by IN sensor 182 (
Time t22 denotes the time at which the toner image formation is completed. Once the primary transfer process (
Time t23 denotes the time at which the leading edges of toner images IM move to the position immediately before secondary transfer section 260. The movement of intermediate transfer belt 131 (
Time t24 denotes the time at which the temperature of fixing section 170 reaches the fixable temperature. At time t24, the movement of intermediate transfer belt 131 (
Time t25 denotes the time at which the trailing edges of toner images IM finish passing the most downstream portion (position K0) of primary transfer section 140. At time t25, toner image forming section separating mechanism 211 (
Time t26 denotes the time at which the trailing edge of sheet P passes OUT sensor 183. Thereafter, the conveyance of sheet P continues, and the print is completed.
As described above, even when the temperature of fixing section 260 does not reach the fixable temperature and the condition of image forming apparatus 200 is judged as being the “abnormal temperature rising condition,” image forming apparatus 200 of the second embodiment makes it possible to reduce the time needed for the print, in particular, the time needed for the print of the first sheet to be completed, by using the scheme in which: when the sheet length is less than the distance L1, image forming apparatus 200 carries out the same processes as in the first embodiment; and when the sheet length is not less than the distance L1 but less than the total value (L1+L2), image forming apparatus 200 carries out the processes shown in
In addition, even in a case where the power supply voltage is unstable, image forming apparatus 200 of the second embodiment can reduce the frequency at which fixation failure occurs. That is because: image forming apparatus 200 completes part of the print process which is to be performed before secondary transfer section 260 undertakes its own part of the print process, and holds the remaining part of the print process in abeyance; and image forming apparatus 200 resumes the print process once it is judged as becoming ready for fixation.
Furthermore, image forming apparatus 200 of the second embodiment makes it possible to reduce the length of intermediate transform belt 131. For this reason, image forming apparatus 200 can be easily constructed in a smaller size.
Moreover, image forming apparatus 200 of the second embodiment stops sheet conveying section 150 and toner image conveying section 130 to standby until the temperature of fixing section 170 reaches the fixable temperature. For this reason, it is possible to reduce the power consumption of image forming apparatus 100.
The invention includes other embodiments in addition to the above-described embodiments without departing from the spirit of the invention. The embodiments are to be considered in all respects as illustrative, and not restrictive. The scope of the invention is indicated by the appended claims rather than by the foregoing description. Hence, all configurations including the meaning and range within equivalent arrangements of the claims are intended to be embraced in the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-029364 | Feb 2010 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4897696 | Matsumoto | Jan 1990 | A |
| Number | Date | Country |
|---|---|---|
| 07-064436 | Mar 1995 | JP |
| 2003098935 | Apr 2003 | JP |
| Entry |
|---|
| Hamano (JP 2003-098935 A), Apr. 2003, JPO Machine Translation. |
| Number | Date | Country | |
|---|---|---|---|
| 20110200344 A1 | Aug 2011 | US |
