JP2006227374A - Fixing device and recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that when a form with large heat capacity such as a label paper sheet and a card paper sheet is printed, an overshoot of heat roll temperature at the end of the printing is large and a wait time up to the start of next printing becomes long. <P>SOLUTION: A fixing device of an image forming apparatus which has a heat roll having at least a plurality of heaters inside and a pressure roll rotating while pressed against it and passes a transfer paper sheet between the heat roll and pressure roll to fix a toner image formed on the transfer paper sheet is provided with a means of reducing the overshoot of the heat roll temperature after printing. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thermal fixing apparatus and a recording apparatus used in an image forming apparatus such as an electrostatic information recording apparatus and an electrophotographic copying apparatus.

  In the conventional fixing device, a fixing roll having a plurality of heat pipes is provided with a heater having a heat generating area of the entire width of the fixing roll and two heaters having heat generating areas at both ends of the fixing roll to heat the fixing roll. Then, the sheet is fed to the nip portion formed by the pressure contact between the heating roll and the pressure roll and fixed by heat (for example, see Patent Document 1).

JP-A-5-181390

  In the conventional fixing device, when printing is performed by sending paper to the nip portion formed by the pressure contact between the heating roll and the pressure roll of the fixing device and printing by heat fixing, there is a problem in printing ordinary ordinary paper and high-quality paper However, for label paper and card paper that are thicker than this and have a large heat capacity, the amount of heat absorbed by the paper from the heating roll is large. The balance is greatly lost. When the next printing is started without recovering the state in which the balance of the specified temperature is greatly lost, the fixing strength in the initial printing may be lowered.

  Normally, the temperature of the heating roll is controlled by causing the heater lamp inside the heating roll to emit light in order to maintain a specified value, but the emission of the heater lamp is stopped when printing is stopped. However, since there is a time lag before the heat from the heater lamp emission reaches the surface of the heating roll, the heat from the emission immediately before stopping printing is accumulated on the surface of the heating roll after stopping printing, and the absolute value of temperature is the temperature during printing. This causes a phenomenon called overshoot that becomes higher than that. If printing is stopped for a certain time, the temperature of the heating roll is released from the overshoot state and returns to a normal value. This overshoot has the same tendency even with ordinary general paper, but since it does not have a heat capacity enough to break the temperature balance of the heating roll, the temperature is controlled within a specified value and there is no problem. However, the temperature control of the heating roll functions in the case of paper with a large heat capacity, such as composite paper in which the moisture content of the printing paper is very high or thick and a card or the like is bonded to the paper, or plastic paper such as PET. Thus, the steady value is maintained, the heater lamp emits light frequently during printing, and the overshoot after the printing stops is more noticeable.

  In this way, when printing is started during a high overshoot, the heating roll temperature is maintained at a high value exceeding the specified value even though a large amount of heat is required at the beginning of printing. The light emission frequency of the heater lamp is not high.

When printing a sheet with a large heat capacity in this state, the heating roll is quickly deprived of heat by the sheet, but it detects that the temperature of the heating roll has fallen below the specified value and causes the heater lamp to emit light frequently. However, as described above, there is a time lag until the heat reaches the surface of the heating roll, and therefore the temperature of the heating roll at the beginning of printing starts to be the lowest, which may cause fixing failure.
For this reason, printing of a sheet with a large heat capacity has the inconvenience of waiting for a certain period of time until the overshoot is canceled when switching the sheet box or printing up to the next job. This is a great barrier to speeding up the fixing device.

  In addition, the conventional apparatus is provided with a heat pipe inside to prevent uneven temperature on the surface of the fixing roll, but it cannot be denied that the shape of the fixing roll is complicated and expensive. As the thickness of the fixing roll increases, the thermal response deteriorates, and it becomes difficult to secure a necessary amount of heat at the beginning of printing. In a high-speed fixing device, the thermal response is further severe, and it is difficult to ensure the fixing strength.

  The object of the present invention is to provide a fixing device capable of reducing overshoot after stopping printing even on such a large heat capacity paper and capable of fixing at high speed and stably and providing a comfortable printing operation. It is.

  The object is to have a heating roll containing at least a plurality of heaters and a pressure roll rotating in pressure contact with the transfer roll, and passing the transfer paper between the heating roll and the pressure roll, thereby transferring the transfer paper. In a fixing device of an image forming apparatus that fixes a toner image formed on paper, means for reducing overshoot of the heating roll temperature after stopping printing is provided.

  Preferably, the means for reducing the overshoot of the heating roll temperature includes a heat absorption roll that rotates in contact with the heating roll when printing is stopped.

  Preferably, the heat absorbing roll that rotates in contact with the heating roll when the printing is stopped has a specific heat capacity, and rotates in contact with the heating roll until the heating roll enters a specified temperature or temperature range. Features.

  Preferably, the means for reducing the overshoot of the heating roll temperature after stopping printing includes an air blower for forcibly cooling the heating roll to a specified temperature when printing is stopped.

  According to the present invention, even when printing on paper with a large heat capacity such as label paper or card paper, overshoot of the heating roll temperature at the end of printing or at the time of printing is reduced, and the next printing starts while maintaining the fixing performance. This shortens the waiting time until it can provide a printing apparatus capable of performing a flexible printing operation and the like.

  In addition, there is an advantage that the life of the heating roll can be improved.

  An embodiment of the present invention will be described below with reference to FIGS.

  FIG. 1 is a temperature transition diagram during printing of a heating roll in a fixing unit of a continuous paper laser beam printer (hereinafter referred to as continuous paper LBP) according to an embodiment of the present invention.

  FIG. 2 is a configuration diagram of the fixing device 51 in the fixing unit of the continuous paper LBP. In FIG. 2, heater lamps 54 a to 54 d heat the heating roll 52. The specific temperature detector 53 attached to the end of the heating roll 52 detects that the heating roll 52 has reached a certain temperature. In addition, a plurality of thermistors 55a, 55b, and 55c for detecting the surface temperature of the heating roll 52 are provided above the heating roll 52 from the non-driving side to the driving side.

  Reference numeral 56 denotes an abnormal temperature detector which detects when the temperature of the air heated by the heating roll 52 (atmosphere temperature) exceeds a certain temperature. 62 is a heat absorption roll. This is a heat absorbing roll having a specific heat capacity that rotates in contact with the heating roll 52 upon completion of printing, and rotates in contact with the heating roll 52 until the heating roll 52 enters a specified temperature or temperature range. This is to reduce overshoot.

  The toner image 58 transferred to the continuous paper 57 is pressed against the heating roll 52 by the pressure roll 60 and is then melted and fixed to form a fixed toner image 59.

  FIG. 3 shows a schematic configuration diagram of the heater 54. The heater lamps 54a, 54b, and 54c have heating wires that divide the length of the heating roll 52 in the width direction into three parts and heat the respective parts. The heater lamp 54d has a heating wire for heating the entire heating roll 52.

  At the time of printing, the temperature of the heating roll is detected by the thermistors 55a, 55b, and 55c based on the heating roll temperature raised by the heater lamps 54a to 54d. Heater lamps 54a to 54d suitable for fusing and fixing the transferred toner image 58 are ON / OFF controlled, respectively.

  In the above configuration, the toner image 58 formed on the continuous paper 57 by electrostatic transfer is preheated by passing over the preheater 61, passes between the heating roll 52 and the pressure roll 60, and is nipped and conveyed. As a result, it is heated and pressurized and fixed on the continuous paper 57.

  In FIG. 1, the horizontal axis represents time, and the vertical axis represents the surface temperature of the heating roll. The solid line in the figure shows the change in the surface temperature of the heating roll 52 in the prior art. Conventionally, the overshoot of the surface temperature of the heating roll 52 at the end of printing or at the time of stopping printing was large. For this reason, the waiting time 1a until the next printing is long and inconvenient. On the other hand, according to the present invention, the heat absorbing roll 62 having a specific heat capacity that rotates in contact with the heating roll 52 when printing is stopped causes the heating roll 52 to enter the specified temperature or temperature range. Since it rotates in contact, overshoot can be reduced, and the waiting time 2a until the next printing is shortened. This allows for flexible operation.

  In this embodiment, the heat absorption roll 62 is used as a means for reducing the overshoot of the surface temperature of the heating roll 52 at the end of printing, but instead of this, or in combination with this, the surface temperature of the heating roll 52 when printing is stopped. An air blower that forcibly cools to a specific temperature may be provided.

  In the present embodiment, the thermistors 55a, 55b and 55c are used as the means for detecting the surface temperature of the heating roll 52. However, a radiation thermometer may be used, and the heater lamp 54 is divided into three lengths in the width direction of the heating roll 52. However, it is not limited to this. Needless to say, the present invention is applicable not only to continuous paper LBP but also to cut paper LBP.

It is a heating roll temperature transition figure at the time of printing in the fixing part of the continuous paper LBP which is one Example of this invention. FIG. 2 is a configuration diagram of a fixing device 51 in a fixing unit for continuous paper LBP according to an embodiment of the present invention. It is a schematic block diagram of the heater of the continuous paper LBP which is one Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a ... Conventional printing standby time, 2a ... Printing standby time in this invention, 51 ... Fixing device, 52 ... Heating roll, 53 ... Specific temperature detector, 54a-54d ... Heater lamp, 55a-55c ... Thermistor, 56 ... an abnormal temperature detector, 57 ... continuous paper, 58 ... transferred toner image, 59 ... fixed toner image, 60 ... pressure roll, 61 ... preheater, 62 ... heat absorption roll.

Claims (5)

  It has a heating roll containing at least a plurality of heaters, and a pressure roll that rotates in pressure contact therewith, and is formed on the transfer paper by passing the transfer paper between the heating roll and the pressure roll. In the fixing device of the image forming apparatus for fixing the toner image, means for reducing overshoot of the heating roll temperature after stopping printing is provided.   2. The fixing device according to claim 1, wherein the means for reducing the overshoot of the heating roll temperature after stopping printing includes a heat absorption roll that rotates in contact with the heating roll when printing is stopped.   The heat absorption roll that rotates in contact with the heating roll when printing stops has a specific heat capacity, and rotates in contact with the heating roll until the heating roll enters a specified temperature or temperature range. Item 3. The fixing device according to Item 2.   The fixing device according to claim 1, wherein the means for reducing the overshoot of the heating roll temperature after stopping printing includes an air blower that forcibly cools the heating roll to a specific temperature when printing is stopped. A recording apparatus comprising the fixing device according to claim 1.

Images