JP2009058802A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of preventing paper from curling or wrinkling, capable of saving energy even when the image forming apparatus is cold and, at the same time, preventing the degradation in the fixability of an image when the first paper is subjected to printing. <P>SOLUTION: If a press roller 72 (image forming apparatus 10) is cold and a printing environment temperature is lower than a specific temperature, the timing of driving a paper feed roller 84 or clutch 88 is delayed by a predetermined time (ts in FIG. 2: three sec). Accordingly, the timing of feeding the first paper to a fixing section 64 is delayed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus including a fixing unit that fixes an image on a sheet.

A fixing unit of a conventional image forming apparatus includes a heat roller incorporating a heater lamp, a press roller pressed against the heat roller, and a thermistor that measures the surface temperature of the heat roller. In this fixing unit, the surface temperature of the heat roller is measured by a thermistor, and the heater lamp is driven based on the measured temperature so that the surface temperature of the heat roller becomes an appropriate temperature. As a result, the fixing accuracy of the image is kept constant.
JP 2006-201636 A

  By the way, the printing of the first sheet when the image forming apparatus is cold is because the heat amount of the heat roller is deprived not only by the sheet but also by the press roller and the surrounding environment. In comparison, the fixability tends to deteriorate.

  Conversely, if the fixing conditions are set so as to ensure sufficient image fixability of the first sheet when the image forming apparatus is cold, an excessive amount of heat is applied to the second and subsequent sheets. As a result, the paper is curled and the paper is wrinkled. Furthermore, it is not preferable to provide an excessive amount of heat from the viewpoint of energy saving.

  Accordingly, the present invention prevents the occurrence of curling and wrinkling on the paper and also fixes the image when the first paper is printed while realizing energy saving even when the image forming apparatus is cold. An object of the present invention is to provide an image forming apparatus capable of preventing the deterioration of the property.

  The present invention includes a fixing unit that fixes an image on paper, a paper storage unit that stores paper, a paper feeding unit that sends the paper stored in the paper storage unit to the fixing unit at a predetermined paper feeding timing, and printing And a control unit that delays the paper feeding timing of the paper by the paper feeding unit by a predetermined time when the environmental temperature is equal to or lower than a predetermined temperature.

  According to this configuration, the paper stored in the paper storage unit is sent to the fixing unit by the paper supply unit at a predetermined paper supply timing, and the image of the paper is fixed by the heat of the fixing unit. Here, when the printing environment temperature is equal to or lower than the predetermined temperature, the paper feeding timing by the paper feeding unit is delayed by a predetermined time by the control unit. As a result, since the fixing unit is continuously heated for the delayed time, the image on the sheet is fixed when the fixing unit reaches a predetermined fixing temperature. As a result, even when the printing environment temperature is equal to or lower than the predetermined temperature, it is possible to prevent the fixability of the image on the paper from being lowered.

  Further, since it is not necessary to set the fixing temperature high in accordance with the case where the printing environment temperature is equal to or lower than the predetermined temperature, it is possible to prevent an excessive amount of heat from being given to the sheet. Thereby, it is possible to prevent the paper from curling or wrinkling and to realize energy saving.

  In the present specification, the “printing environment temperature” is a temperature indicating how the image forming apparatus is cooled, and means, for example, the surface temperature of the press roller.

  Further, the invention is characterized in that the sheet whose paper feeding timing is delayed by the control unit is a sheet printed on the first sheet.

  According to this configuration, the sheet whose feeding timing is delayed by the control unit is only the sheet printed on the first sheet, and the sheet feeding timing of all printed sheets is not delayed. It is possible to prevent the printing end time from significantly extending.

  Further, according to the present invention, the fixing unit includes a first roller unit, a second roller unit that is pressed from the first roller unit and fixes an image by sandwiching a sheet between the first roller unit, A heating unit that heats the second roller unit, and the control unit determines the printing environment temperature based on a time until the temperature of the second roller unit reaches a predetermined temperature. And

  According to this configuration, in the fixing unit, the second roller unit is heated by the heating unit, and the sheet is sandwiched between the first roller unit and the second roller unit to fix the image. Here, the printing environment temperature is determined by the control unit based on the time until the temperature of the second roller unit reaches a predetermined temperature. That is, if the time until the temperature of the second roller portion reaches a predetermined temperature is longer than the predetermined time, the control unit determines that the printing environment temperature is lower than the predetermined temperature. Conversely, if the time until the temperature of the second roller portion reaches a predetermined temperature is shorter than the predetermined time, the control unit determines that the printing environment temperature is higher than the predetermined temperature. As described above, since the printing environment temperature can be appropriately determined by a simple method, the fixability of the image on the sheet can be maintained at a high level.

  According to the present invention, curling and wrinkling are prevented from occurring on a sheet, and even when the image forming apparatus is cold, the image is fixed when the first sheet is printed while realizing energy saving. It can prevent that property falls.

  Next, an image forming apparatus according to a first embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the image forming apparatus 10 is configured as a so-called multi-function machine having a facsimile function and a copy function, and includes an MPU 12, an NCU (Network Control Unit) 14, a MODEM 16, a ROM 18, a RAM 20, A printer I / F 32 to which an image memory (DRAM) 22, a CODEC (encoder / decoder) 24, an operation unit 26, a scanner 28, and a personal computer (PC) 30 are connected, and a paper feed cassette (sheet storage) Part) 33.

  The MPU 12 controls each unit constituting this apparatus. The NCU 14 controls the connection with the telephone line network (PSTN), receives the data of the received manuscript, and detects the function of sending a dial signal corresponding to the telephone number (including the FAX number) of the other party and the incoming call. It has a function for. MODEM 16 is an ITU (International Telecommunication Union) -T recommendation T.30. 30 based on the facsimile transmission control procedure according to 17, V.R. 27ter, V.I. The transmission data is modulated and the received data is demodulated in accordance with 29. Alternatively, in addition to these, V.P. 34, modulation of transmission data and demodulation of reception data are performed.

  The ROM 18 stores a program for controlling this apparatus. The RAM 20 temporarily stores data and the like. The image memory 22 temporarily stores received data or image data read by the scanner 28. In order to transmit the read image data, the CODEC 24 encodes (encodes) the MH, MR, MMR method, etc., and decodes (decodes) the received image data. The operation unit 26 is used by the user to give instructions such as FAX transmission / reception and printing (paper printing). The scanner 28 reads image data of a document when performing FAX transmission.

  The printer of this apparatus includes a printer controller 34 that controls each part of the printer. The printer controller 34 includes a CPU (control unit) 36, a RAM 38, and a timer 40.

  The CPU 36 controls the entire system related to image forming processing for paper. In particular, when the printing environment temperature is lower than a predetermined temperature, the CPU 36 controls the drive of the paper feed roller (paper feed unit) 84 or the clutch (paper feed unit) 88 to print the first sheet to be printed. The paper feed timing to the fixing unit 64 is delayed by a predetermined time (ts in FIG. 2). As a result, when the printing environment temperature is lower than the predetermined temperature, the paper stored in the paper feed cassette 33 has the paper feed timing for the time delayed from the conventional feed timing (ts in FIG. 2). The paper feed roller 84 feeds it out to the paper transport path so as to be delayed.

  The RAM 38 stores a program for controlling each unit in order to appropriately execute an image forming process for forming an image on a sheet. The timer 40 mainly measures the time until a heat roller (second roller portion) 68 described later reaches a predetermined temperature. In particular, the timer 40 is turned on after the heater 66 of the heat roller 68 is turned on. The time until the drive start temperature (for example, 140 ° C.) is measured.

  Here, in the RAM 38, the time from when the heater 66 of the heat roller 68 is turned on until the drive start temperature of the drive motor 78 and the temperature of the surface of the press roller (first roller portion) 72 described later (of the image forming apparatus 10). A table indicating a relationship with (temperature) is stored. That is, in this table, when the time from when the heater 66 of the heat roller 68 is turned on until the drive start temperature of the drive motor 78 is longer than a predetermined time as a threshold, the press roller 72 (image forming apparatus 10) It cools, indicating that the printing environment temperature is lower than the predetermined temperature. On the other hand, when the time from when the heater 66 of the heat roller 68 is turned on until the drive start temperature of the drive motor 78 is shorter than a predetermined time, which is a threshold, this table shows the press roller 72 (image forming apparatus 10). Indicates that the printing environment temperature is higher than a predetermined temperature. Here, since the temperature of the surface of the press roller 72 can be regarded as the temperature of the entire image forming apparatus 10, the temperature of the entire image forming apparatus 10 (that is, the printing environment temperature) is estimated by estimating the temperature of the surface of the press roller 72. ) As described above, the CPU 36 determines how the press roller 72 (the image forming apparatus 10) is cooled, that is, whether the printing environment temperature is high or low, based on the measurement result of the timer 40 and the table stored in the ROM 38. In addition, instead of the time from when the heater 66 of the heat roller 68 is turned on until the drive start temperature of the drive motor 78, the feed start temperature of the drive motor 78 (eg, 140 ° C.) to the feed start temperature of the feed roller 84 is changed. You may use the time to (for example, 160 degreeC).

  As shown in FIG. 2, when the image forming apparatus 10 is not cooled and the temperature of the surface of the press roller 72 is not low, when the heater 66 is driven, the press roller 72 that contacts the heat roller 62 is deprived. Since the amount of heat decreases, the temperature of the surface of the heat roller 68 rises rapidly, and the temperature gradient is as shown by the broken line in FIG. Thus, since the temperature gradient of the surface temperature of the heat roller 68 suddenly rises, the time (tn in FIG. 2) from when the heater 66 is driven until the fixing temperature (TN in FIG. 2 is 180 ° C.) is reached. Shorter. On the other hand, when the image forming apparatus 10 is cooled and the surface temperature of the press roller 72 is low, the amount of heat taken by the press roller 72 that contacts the heat roller 62 when the heater 66 is driven increases. The temperature increase rate of the surface 68 decreases, and the temperature gradient is as shown by the solid line in FIG. In this case, since the temperature gradient of the surface temperature of the heat roller 68 becomes gentle, the time (th in FIG. 2) from when the heater 66 is driven to the fixing temperature (TN in FIG. 2 is 180 ° C.) is long. Become. Using this property, when the time from when the heater 66 of the heat roller 68 is turned on until the drive start temperature of the drive motor 78 is longer than a predetermined time as a threshold, the amount of heat taken away by the press roller 72 is large. Therefore, it is determined that the press roller 72 (image forming apparatus 10) is cold and the printing environment temperature is lower than a predetermined temperature. Conversely, if the time from when the heater 66 of the heat roller 68 is turned on until the drive start temperature of the drive motor 78 is shorter than a predetermined time, which is a threshold value, the amount of heat taken away by the press roller 72 is reduced. It is determined that the roller 72 (image forming apparatus 10) is not cooled and the printing environment temperature is higher than a predetermined temperature.

  Further, the RAM 38 has the press roller 72 (the image forming apparatus 10) cooled, and the drive timing of the paper feed roller 84 or the connection timing of the clutch 88 when it is determined that the printing environment temperature is lower than a predetermined temperature. A program for delaying by a predetermined time (ts in FIG. 2) is stored. Here, after the predetermined delay time (ts in FIG. 2) exceeds the lowest point of the ripple of the heat roller 68 (point P in FIG. 2), the first sheet is printed on the fixing unit 64. It is set to a time to reach (elapsed time at the lowest ripple point). Specifically, the predetermined time (ts in FIG. 2) for delaying the drive timing of the paper feed roller 84 or the connection timing of the clutch 88 is set to 3 seconds.

  As shown in FIG. 1, a photosensitive drum 42 having a photoconductive film on its outer peripheral surface as a photosensitive member is disposed inside the image forming apparatus 10, and the photosensitive drum 42 is rotated by a drive source (not shown). Is done. A charging brush 44 is disposed around the photosensitive drum 42 as a brush roller type charger, and a predetermined bias voltage is applied to the charging brush 44 by a charging bias application circuit 46. The charging brush 44 applied with the bias voltage uniformly charges the outer peripheral surface of the photosensitive drum 42 to about −750 V while rotating.

  An LED print head 48 serving as an exposure unit disposed around the photosensitive drum 42 includes a large number of LEDs arranged in parallel. The LED print head 48 irradiates light to the outer peripheral surface of the photosensitive drum 42 based on input image information. An electrostatic latent image corresponding to the image information is formed. Note that the output of the LED print head 48 is controlled by the CPU 36 of the printer controller 34.

  The developing device disposed around the photosensitive drum 42 includes a supply roller 50, a developing roller 52, a blade 54, a developing device bias application circuit 56, and the like. The supply roller 50 supplies toner to the developing roller 52 while charging the toner from a toner case (not shown) containing toner. The supply roller 50 is supplied with a predetermined bias voltage (−300 V) by a developing device bias application circuit 56. ~ -700V, preferably about -500V). A predetermined bias voltage (−300 V to −400 V, preferably −350 V) is applied to the developing roller 52 disposed in contact with the supply roller 50 and the photosensitive drum 42 by the developing device bias applying circuit 56. The developing device bias application circuit 56 is controlled by the CPU 36 of the printer controller 34.

  The blade 54 elastically contacts the outer peripheral surface of the developing roller 52 and uniformizes the layer thickness of the toner adhering to the outer peripheral surface of the developing roller 52. The blade 54 is predetermined by a developer bias application circuit 56. The bias voltage (−300 V to −700 V, preferably about −400 V) is applied.

  Further, a transfer roller 58 serving as a transfer unit disposed around the photosensitive drum 42 is disposed so as to contact the outer peripheral surface of the photosensitive drum 42 with the sheet conveyance path interposed therebetween, and is rotated by a drive source (not shown). The A predetermined bias voltage (transfer bias) is applied to the transfer roller 58 by a transfer bias application circuit 60. When a bias voltage is applied to the transfer roller 58, an inflow current flows through the transfer roller 58, but the inflow current of the transfer roller 58 is detected by the current detection unit 62. The detected current value is stored in the RAM 38 of the printer controller 34. The transfer bias application circuit 60 is controlled by the CPU 36 of the printer controller 34.

  The fixing unit 64 disposed on the sheet delivery side of the sheet conveyance path includes a heat roller 68 including a heater 66 such as a halogen lamp, a heater driving circuit 70, a press roller 72, and the like. The heat roller 68 is rotationally driven by a drive motor 78. The heater 66 of the heat roller 68 is heated to a predetermined temperature by a heater drive circuit 70 controlled by the CPU 36 of the printer controller 34.

  As shown in FIG. 1, in the image forming apparatus 10, a memory removal brush 74 is disposed around the photosensitive drum 42. The memory removal brush 74 is for removing a toner image (memory image) remaining on the outer peripheral surface of the photosensitive drum 42 along the contour of the image after transfer. The memory removal brush 74 includes a memory removal brush voltage application circuit. A predetermined bias voltage is applied by 76.

  The image forming apparatus 10 is provided with a temperature sensor 80 that measures the surface temperature of the heat roller 68. The measurement result obtained by the temperature sensor 80 can be output to the printer controller 34. The temperature sensor 80 is preferably a thermistor that is in contact with the outer peripheral surface of the heat roller 68.

  Further, a PSS 82 for detecting paper is disposed on the upstream side of the photosensitive drum 42 in the paper conveyance direction. The detection result of the PSS 82 is output to the printer controller 34. The transported paper is detected by the PSS 82, and using this detection result as a trigger, image formation on the paper is realized downstream in the paper transport direction.

  Further, a paper feed roller 84 is provided in the vicinity of the paper feed cassette 33 of the image forming apparatus 10. The paper feed roller 84 is for sequentially supplying the paper stored in the paper feed cassette 33 to a paper transport path (not shown). A motor 86 as a drive source is connected to the paper feed roller 84 via a clutch 88. In a state where the paper feed roller 84 is connected to the motor 86 via the clutch 88, the driving force of the motor 86 is transmitted to the paper feed roller 84, and the paper feed roller 84 rotates.

  In the image forming apparatus 10 configured as described above, the printing operation is well known. However, in general, the photosensitive drum 42 is uniformly charged to about −750 V by the charging brush 44, and the LED print head is applied to the photosensitive drum 42. An electrostatic latent image corresponding to the image information is formed by 48, toner is adsorbed to the electrostatic latent image on the photosensitive drum 42 by the developing roller 52, and a toner image is formed on the photosensitive drum 42. Then, the toner image on the photosensitive drum 42 is transferred onto the paper by the transfer roller 58. After the transfer, the paper is heated and pressurized by the heat roller 68 and the press roller 72, and the toner image is fixed on the paper as a permanent image.

  Next, the operation of the image forming apparatus 10 according to the first embodiment will be described.

  As shown in FIG. 3, when a print job is started based on an input from the operation unit 26 or a print signal from the PC 30, the CPU 36 drives the heater 66 via the heater drive circuit 70 (heater ON). , S100). In S100, the timer 40 starts counting at the same time.

  Next, it is determined whether the count value by the timer 40 is larger than a predetermined value (S120). Here, in the determination step of S120, when the count value is larger than the predetermined value, it means that the time until the heat roller 68 reaches the predetermined temperature is long. This means that even when the heat roller 68 is heated by the heater 66 as described above, most of the heat is taken away by the press roller 72 or the like, so that the heat roller 68 is difficult to increase in temperature. As a result, it is estimated that the press roller 72 (image forming apparatus 10) is cold and the printing environment temperature is lower than a predetermined temperature. On the contrary, when the count value is smaller than the predetermined value, it means that the time until the heat roller 68 reaches the predetermined temperature is short. As described above, this means that even if the heat roller 68 is heated by the heater 66, the amount of heat taken away by the press roller 72 or the like is reduced, and the heat roller 68 is likely to rise in temperature. As a result, it is estimated that the press roller 72 (image forming apparatus 10) is not cooled and the printing environment temperature is higher than a predetermined temperature.

  If it is determined that the count value by the timer 40 is larger than the predetermined value (S120: YES), a new count is started by the timer 40 (S140). Then, it is determined whether or not the new count value by the timer 40 is a predetermined value (S160). The predetermined value in S160 is the delay time (ts in FIG. 2) stored in the RAM 38, and is printed on the first sheet after exceeding the lowest point of ripple of the heat roller 68 (point P in FIG. 2). The time required for the paper to reach the fixing unit 64 (elapsed time at the lowest ripple point) is a reference. That is, in S160, if the count value by the timer 40 is less than the elapsed time of the ripple bottom point, the process does not proceed to the next step S180, and the count value by the timer 40 is greater than or equal to the elapsed time of the ripple lowest point. If so, the process proceeds to the next step S180.

  When it is determined that the new count value by the timer 40 is equal to or greater than the predetermined value (S160: YES), the clutch 88 is connected by the CPU 36 and the paper feed roller 84 is driven by the CPU 36 (S180). As a result, the first sheet to be printed is fed out from the sheet feeding cassette 33 to the sheet conveyance path, and compared with a case where the printing environment temperature is higher than the specified temperature (ts in FIG. 2: 3 seconds). ) And is sent to the fixing unit 64 with a delay.

  On the other hand, when it is determined that the count value by the timer 40 is smaller than the predetermined value (S120: NO), the paper feed start temperature is set to 175 ° C. (S200). When the paper feed start temperature reaches 175 ° C. (S220: YES), the clutch 88 is connected by the CPU 36 and the paper feed roller 84 is driven by the CPU 36 (S240). As a result, the first sheet to be printed is fed from the sheet feeding cassette 33 to the sheet conveyance path, and is sent to the fixing unit 64 without delay.

  In addition, after the process of S180 or the process of S240 is complete | finished, the new count by the timer 40 is started (S260). When the count value by the timer 40 reaches a predetermined value (S280: YES), print control after the next process is executed (S300).

  As described above, according to the present embodiment, the timer 40 measures the time from when the heater 66 of the heat roller 68 is turned on to when the drive motor 78 starts driving. Then, the CPU 36 determines the degree of cooling of the press roller 72 and thus the image forming apparatus 10 based on the measurement result and the table stored in the RAM 38. That is, when the heat roller 68 is rotationally driven by the drive motor 78, the press roller 72 is also in contact with the heat roller 68 while rotating. When the press roller 72 is cold, as shown in FIG. 2, even if the heat roller 68 is heated by the heater 66, the amount of heat taken away by the press roller 72 increases, so that the temperature gradient of the heat roller 68 is increased. Becomes smaller. As a result, when the press roller 72 is cold, the time (tn in FIG. 2) until the heat roller 68 reaches the fixing temperature (TN: 180 ° C. in FIG. 2) becomes longer. If the press roller 72 is not cooled, the amount of heat taken away by the press roller 72 when the heat roller 68 is heated by the heater 66 is reduced as shown in FIG. Becomes larger. As a result, when the press roller 72 is not cooled, the time (tn in FIG. 2) until the heat roller 68 reaches the fixing temperature (180 ° C.) is shortened.

  By utilizing this fact, it is possible to easily and accurately estimate the cooling condition of the press roller 72 (image forming apparatus 10) without separately providing a thermistor or a temperature sensor for measuring the surface temperature of the press roller 72. . When the press roller 72 (image forming apparatus 10) is cooled and the printing environment temperature is lower than the predetermined temperature, the drive timing of the paper feed roller 84 or the clutch 88 is set for a predetermined time (ts in FIG. 2). Delaying the timing of feeding the first sheet to the fixing unit 64 is delayed. Thus, after the heat roller 68 reaches a predetermined temperature, in other words, the first sheet can be sent to the fixing unit 64 after the lowest point of ripple (point P in FIG. 2) has elapsed. As a result, it is possible to prevent the image fixability on the first sheet from being deteriorated.

  In particular, since it is not necessary to set a high fixing temperature in the fixing unit 64, it is possible to prevent an excessive amount of heat from being applied to the sheet. As a result, it is possible to prevent the paper from curling due to heat and to prevent wrinkles from occurring on the paper. At the same time, since the heat roller 68 can be prevented from being heated excessively, an energy saving effect can be obtained.

  Further, only the feeding timing of the first sheet to be printed is delayed by a predetermined time (ts in FIG. 2), and the feeding timings of all the sheets to be printed are not delayed, respectively. It can be prevented that the time required is significantly increased.

  Further, since it is not necessary to separately provide a thermistor or a temperature sensor for measuring the surface temperature of the press roller 72, it is possible to prevent the manufacturing cost of the image forming apparatus 10 from increasing.

  Next, an image forming apparatus according to a second embodiment of the present invention will be described with reference to the drawings. The same reference numerals are given to the same components as those of the image forming apparatus according to the first embodiment of the present invention, and description thereof will be omitted as appropriate.

  As shown in FIG. 4, the image forming apparatus of the second embodiment is provided with a temperature sensor 90 that measures the surface temperature of the press roller 72. The temperature sensor 90 is preferably a thermistor in contact with the outer peripheral surface of the press roller 72. The temperature of the press roller 72 measured by the temperature sensor 90 is output to the printer controller 34 as data.

  The CPU 36 controls the driving of the paper feed roller 84 or the clutch 88 based on the temperature data of the press roller 72 output to the printer controller 34. That is, the RAM 38 stores a table showing the relationship between the surface temperature of the press roller 72 and the drive of the paper feed roller 84 or the clutch 88, and the drive of the paper feed roller 84 or the clutch 88 is driven based on this table. Be controlled. Specifically, when the surface temperature of the press roller 72 is lower than a predetermined temperature, the driving of the paper feed roller 84 or the clutch 88 is delayed by a predetermined time (ts: 3 seconds in FIG. 2), and the surface temperature of the press roller 72 is reduced. When the temperature is higher than the predetermined temperature, the driving of the paper feed roller 84 or the clutch 88 is controlled so as not to be delayed.

  According to the image forming apparatus of the second embodiment, the drive of the heater 66 is controlled based on the surface temperature of the press roller 72. When the surface temperature of the press roller 72 is lower than the predetermined temperature, the driving of the paper feed roller 84 or the clutch 88 is delayed by a predetermined time (ts: 3 seconds in FIG. 2) and supplied to the fixing unit 64. Paper timing is delayed. On the other hand, when the surface temperature of the press roller 72 is higher than a predetermined temperature, the drive of the paper feed roller 84 or the clutch 88 is not delayed, and the timing of paper feed to the fixing unit 64 is not delayed.

  As described above, according to the second embodiment, by directly measuring the surface temperature of the press roller 72, it is possible to accurately specify the temperature of the press roller 72 and thus the image forming apparatus 10. In this respect, in the first embodiment, the surface temperature of the press roller 72 (the temperature of the image forming apparatus 10) is estimated using the temperature gradient of the heat roller 68, but according to the second embodiment, the temperature sensor 90 is provided. Since it is provided separately, the number of parts and cost increase, but the surface temperature of the press roller 72 can be directly measured, and the drive of the paper feed roller 84 or the clutch 88 can be controlled appropriately. As a result, the timing of feeding the printed paper to the fixing unit 64 is appropriate, and it is possible to prevent the image fixability of the first printed paper from being deteriorated.

1 is a system diagram illustrating a schematic configuration of an image forming apparatus according to a first embodiment of the present invention. 6 is a graph showing a temperature gradient of a second roller unit (heat roller) of the image forming apparatus according to the first embodiment of the present invention and a paper feed timing. 3 is a flowchart illustrating an operation (print job) of the image forming apparatus according to the first embodiment of the present invention. It is a block diagram which shows the principal part of the image forming apparatus which concerns on 2nd Embodiment of this invention.

Explanation of symbols

10 Image forming apparatus 33 Paper feed cassette (paper storage unit)
36 CPU (control unit)
64 Fixing part 66 Heater (heating part)
68 Heat roller (second roller part)
72 Press roller (first roller part)
84 Paper feed roller (paper feed unit)
88 Clutch (paper feed unit)

Claims (3)

A fixing unit for fixing an image on paper;
A paper storage section for storing paper;
A paper feed unit that sends the paper stored in the paper storage unit to the fixing unit at a predetermined paper feed timing;
A control unit that delays the paper feeding timing of the paper by the paper feeding unit by a predetermined time when the printing environment temperature is equal to or lower than a predetermined temperature;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the sheet whose paper feeding timing is delayed by the control unit is a sheet printed on a first sheet. The fixing unit is
A first roller portion;
A second roller part that is pressed from the first roller part and sandwiches a sheet between the first roller part and fixes an image;
A heating unit for heating the second roller unit;
Have
The image forming apparatus according to claim 1, wherein the control unit determines the printing environment temperature based on a time until the temperature of the second roller unit reaches a predetermined temperature.

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