JP3603586B2 - Fixing device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fixing device for fixing an unfixed toner image with heat and pressure in an image forming apparatus such as a copying machine, a printer, and a facsimile, and more particularly, to a so-called belt nip type fixing using a belt-shaped fixing member. It relates to improvement of the device.
[0002]
[Prior art]
Conventionally, as a fixing device of this type, a roll-shaped or belt-shaped pressing member is pressed against a heating fixing member such as a heating roll, and a pressing portion formed between the heating fixing member and the pressing member is provided. There is a known type in which a sheet carrying an unfixed toner image is passed through a (nip) portion, and the unfixed toner image on the sheet is fixed on the sheet by heating and pressing.
[0003]
In recent years, in an image forming apparatus using this type of fixing device, in particular, a full-color image forming apparatus, from the viewpoint of improving the color developing property and image quality of a toner image, the recording paper is combined on the front side or both sides of the sheet. So-called coated paper, in which a coating layer made of rubber, synthetic resin, or the like is coated to a thickness of several μm to several tens μm, has been used.
[0004]
When the unfixed toner image formed on the coated paper is fixed by the above-described fixing device, a phenomenon called a blister, in which a coat layer on the coated paper is partially pushed up when excessive heat is applied to the coated paper, is called a blister. (Hereinafter simply referred to as blisters) may occur.
This phenomenon occurs when the moisture contained in the coated paper inside the coated paper is heated by the heating / fixing member of the fixing device to evaporate and expand into water vapor, and when the water vapor is radiated to the outside, the water vapor is diffused to the outside of the coated paper surface. This is caused by being hindered by the coat layer and consequently being intensively emitted to the outside from a thin portion of the coat layer or a portion where the coat layer is absent.
Therefore, when such blisters are generated, the smoothness of the surface of the coated paper is lost, and the image quality on the coated paper is impaired.
[0005]
In addition, in addition to the phenomenon called blister, for example, when fixing the coated paper on which a high density unfixed toner image such as a full-color image is formed by the fixing device, bubbles are generated in the toner layer on the coated paper. A phenomenon called a so-called toner blister (hereinafter simply referred to as a toner blister) may occur.
This phenomenon occurs because when the moisture contained in the toner or the moisture contained in the coated paper is heated by the heat-fixing member of the fixing device to evaporate and expand into water vapor, these water vapors diffuse to the back side of the paper. This is caused by being hindered by the coat layer on the surface of the coated paper and consequently being intensively discharged from the portion where the toner layer exists on the coated paper to the outside.
Therefore, even when such a toner blister is generated, the image on the coated paper suffers from image quality failure similarly to the blister.
[0006]
The following two methods are already known as technical means for preventing the above-mentioned blisters and toner blisters.
The first method is a method in which the fixing operation is performed at a high temperature and in a short time. This method heats only the surface of the recording paper and completes the fixing operation before the heat is transmitted to the inside of the recording paper. It suppresses the evaporation of moisture inside and prevents the occurrence of blisters and toner blisters.
The second method is a method of reducing the amount of heat applied to the back side of the recording paper, and suppresses the evaporation of water inside the recording paper and prevents the occurrence of blisters and toner blisters as in the first method. Things.
[0007]
However, when the first method is used, it is necessary to maintain the fixing device at a high temperature, and the power consumption of the fixing device increases accordingly. In particular, when the present invention is applied to a high-speed fixing device, power consumption is further increased, and there is a problem that it is difficult to apply the present invention to a high-speed fixing device having a limited power consumption.
[0008]
Further, in the case of the second method, although a relatively long heating time is required as compared with the first method, the power consumption is suppressed by keeping the temperature on the back side of the paper low. Therefore, application to a high-speed fixing device is also possible.
[0009]
As a fixing device capable of increasing the heating time and increasing the fixing speed as described above, for example, as shown in JP-A-5-150679, an endless belt-shaped fixing belt stretched over a plurality of rolls There is known a so-called belt nip type fixing device in which the fixing device is pressed against a heating roll.
However, this type of belt nip type fixing device has the following problems.
[0010]
That is, in the case where the fixing of the coated paper is performed using the above-described belt nip type fixing device, the fixing device stops during the standby, and the surface temperature of the fixing belt during the standby is different from that of the heating roll. Only the pressed portion is heated to a temperature substantially equal to that of the heating roll and becomes high, while the other portions remain at low temperature.
Therefore, when the fixing operation is started from this state, a high-temperature portion is generated partially along the circumferential direction of the fixing belt, and as a result, the recording paper is nipped at the high-temperature portion of the fixing belt. In such a case, blisters and toner blisters may be generated.
[0011]
Such non-uniformity of the surface temperature of the belt fixing temperature can be eliminated by idling the fixing belt before starting the fixing operation. Since the temperature rises to the same temperature as the surface temperature of the toner, the occurrence of blisters and toner blisters cannot be prevented.
[0012]
In view of the above, the applicant of the present application has disclosed in Japanese Patent Application No. 10-1865 as a fixing device capable of realizing the second method, a fixing belt having a heating source stretched by a plurality of rolls on the surface of a heating roll. In a fixing device that performs a fixing process by heat and pressure by causing a transfer material carrying an unfixed toner image to pass through a pressure contact portion between the heating roll and the fixing belt, the set temperature of the heating roll and the fixing belt Setting the set temperature to different values, and providing a contacting / separating means for contacting and separating the heating roll and the fixing belt, and proposing a driving means for independently driving the belt fixing member to rotate. I have.
[0013]
In the fixing device described above, during standby, the heating roll and the fixing belt are separated by the contacting / separating means, the fixing belt is idled by the driving means, and the fixing end belt is heated to a temperature lower than that of the heating roll to perform fixing. If the surface temperature of the belt is heated to a constant temperature lower than that of the heating roll, and the heating roll and the fixing belt are pressed against each other by the contacting / separating means at the time of fixing, the heat is applied from the front and back of the paper in the fixing nip area at the time of fixing. Since a difference occurs in the temperature, the evaporation of the water inside the recording paper can be suppressed, and blisters and toner blisters can be prevented.
[0014]
[Problems to be solved by the invention]
In the above technical means, the relationship between the timing of starting and ending the movement of the fixing belt and the timing of starting and stopping the driving of the fixing belt by the driving unit is important.
For example, in a case where the driving of the fixing belt by the driving unit is started before the heating roll and the fixing belt are separated from each other, the heating roll and the fixing belt are separately driven while being pressed against each other, In particular, when there is a speed difference between the two, there is a technical problem that unnecessary loads are applied to the respective driving sources of the heating roll and the fixing belt, and the components of the driving source are likely to be damaged. Can be
Further, when the heating roller and the fixing belt are shifted from a separated state to a pressed state, when the driving of the fixing belt by the driving unit is not stopped even after the heating roller and the fixing belt are pressed, Again, the heating roll and the fixing belt are driven separately while being pressed against each other, which may cause the same trouble as described above.
[0015]
Further, in a type in which the fixing belt is connected to the driving unit via a gear mechanism when the fixing belt is separated from the heating roll, if the operation start timing of the driving unit is not accurately controlled, a gear mechanism There is a concern that poor meshing may occur.
[0016]
The present invention has been made to solve such a technical problem, and optimizes the relationship between the timing of starting and ending the movement of the fixing belt and the timing of starting and stopping the driving of the fixing belt by the driving unit. Accordingly, an object of the present invention is to provide a belt nip type fixing device capable of preventing the occurrence of blisters and toner blisters, and at the same time, preventing the occurrence of component damage and the like.
[0017]
[Means for Solving the Problems]
That is, as shown in FIG. 1, the present invention provides a heating and fixing member 1 having a heating source and rotatably disposed, and a plurality of rolls having a heating source for heating the heating and fixing member 1 to a different temperature. A fixing position A, which is rotatably mounted on the group 2 and is in pressure contact with the heat fixing member 1 to heat and pressurize and fix an unfixed image on a recording material, and a standby position B, which is separated and on standby. An endless belt-shaped belt fixing member 3 movably disposed between the belt fixing member 3, a belt moving unit 4 for moving the belt fixing member 3, and a belt driving unit 5 for rotationally driving the belt fixing member 3 at positions other than the fixing position. In the fixing device including: a movement detecting unit 6 that detects the movement of the belt fixing member 3 from the fixing position A and the standby position B, and the movement of the belt fixing member 3 from the fixing position A is detected by the movement detecting unit 6. Detected condition To start driving the belt drive means 5, characterized in that it comprises a belt control unit 7 stops the drive of the belt drive means 5 under conditions motion is detected in the belt fixing member 3 from the standby position B.
[0018]
In such technical means, as the heat fixing member 1, a roll-shaped member having an internal or external heat source, an endless belt-shaped member, or the like may be appropriately selected.
[0019]
Further, the fixing position A, which is one end of the moving range of the belt fixing member 3, may be appropriately selected from a position where an appropriate nip pressure necessary for fixing is formed by the pressure contact between the heating fixing member 1 and the belt fixing member 3. On the other hand, the standby position B at the other end may be appropriately selected from at least a position where the heat fixing member 1 and the belt fixing member 3 are separated from each other.
[0020]
Further, from the viewpoint of reliably performing the control for stopping the movement of the belt fixing member 3 at the fixing position A and the standby position B, the belt control unit 7 uses the movement detecting unit 6 to move to the fixing position A and the standby position B. It is preferable to control the belt moving means to stop the movement of the belt fixing member 3 under the condition that the arrival of the belt fixing member 3 is detected.
[0021]
Next, the operation of the above technical means will be described.
In FIG. 1, when the belt fixing member 3 starts moving from the fixing position A to the standby position B by the belt moving means 4, the movement detecting means 6 detects that the belt fixing member 3 has moved from the fixing position A, and A signal is sent to the control means 7, and based on the detection result, the belt control means 7 starts driving the belt driving means 5.
[0022]
On the other hand, when the belt moving member 4 starts moving the belt fixing member 3 from the standby position B to the fixing position A, the movement detecting means 6 detects that the belt fixing member 3 has moved from the standby position B, and The belt control means 7 stops driving of the belt driving means 5 based on the detection result.
Therefore, at the fixing position A where the heat fixing member 1 and the belt fixing member 3 are pressed against each other, the driving of the belt fixing member 3 is not performed, and the occurrence of damage to components and the like is prevented.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
FIG. 2 shows an embodiment of a fixing device to which the present invention is applied.
In the figure, reference numeral 11 denotes a heating fixing roll having a heating source and driven to rotate at a predetermined speed in a direction indicated by an arrow by a driving source (not shown).
In the present embodiment, the heat-fixing roll 11 includes, for example, an aluminum cylinder having a core outer diameter of 61 mm and a thickness of 1.5 mm covering a heating source formed of a halogen lamp, and a 2 mm-thick silicon film having a hardness of 33 mm coated on the surface thereof. It is composed of a rubber layer and a 2 μm thick Viton rubber (registered trademark of DuPont) layer coated thereon, and its surface temperature is set to, for example, 150 ° C. by a temperature controller (not shown). Is controlled.
[0024]
A belt unit 20 including a fixing belt 24 that forms a nip area with the heat fixing roll 11 is disposed below the heat fixing roll 11.
Here, as shown in FIGS. 2 and 3, the belt unit 20 mainly includes a fixing belt 24 that is stretched around and rotatably disposed on the support rolls 21, 22, and 23. , 22, and 23 are provided with shafts 21a, 22a, and 23a at the centers of the respective rotation axes.
A support plate 27 is provided on each side of the axial end of each of the support rolls 21, 22, and 23. The shafts 21a, 22a, and 23a are rotatably fitted into holes provided in the support plate 27. Has been supported.
[0025]
Here, the support rolls 21, 22, and 23 are made of stainless steel, and the fixing belt 24 is made of a polyimide film having a thickness of 75 μm, a width of 340 mm, and an outer diameter of 68 mm. (Registered trademark) is used.
[0026]
In addition, a heating source such as a halogen lamp is built in the support roll 23, and serves as a heating roll that heats the fixing belt 24 to a temperature different from that of the heating fixing roll 11. The heating temperature is set so as to be heated to a temperature lower by 30 ° C. than that of the heating and fixing roll 11, so that the amount of heat applied to the back side of the sheet P carrying the toner image T is suppressed.
[0027]
Further, a pressure pad 26 made of silicon rubber is fitted into a notch formed on a support plate 27 at both ends on the inner surface side of the fixing belt 24 at a pressure contact portion between the heat fixing roll 11 and the fixing belt 24. It is arranged so that it is.
[0028]
Further, a latch unit 30 that supports and moves the belt unit 20 is attached to the belt unit 20.
In the present embodiment, the latch unit 30 is rotatable in the forward and reverse directions for swinging the lift member 31 via the rotation shaft 32 with the lift member 31 supporting the belt unit 20 from both ends of the belt unit 20. And a stepping motor 33.
[0029]
Here, the support of the belt unit 20 by the lift member 31 is such that the shaft 21 a passes through and is fixed to the through hole 31 a provided on the upper side of the swing free end of the lift member 31, and the upper edge portion of the lift member 31. Both ends of a support shaft 28 disposed below the pressure pad 26 of the belt unit 20 so as to penetrate both end surfaces of the support plate 27 are mounted in a concave portion 31 b having a substantially semicircular shape provided substantially in the center. It is done by doing.
Further, as shown in FIG. 3, the rotating shaft 32 is provided rotatably through both side surfaces of the frame 51, and the stepping motor 33 is provided outside the frame 51.
[0030]
Further, a belt driving mechanism 40 that idles the fixing belt 24 during standby is provided below the support roll 21.
In the present embodiment, the belt driving mechanism 40 engages with a driving motor 41 serving as a driving source, a gear 43 to which driving force of the driving motor 41 is transmitted via a rotating shaft 42, and this gear 43 during standby. And a gear 25 that rotationally drives the support roll 21.
[0031]
Here, as shown in FIG. 3, the rotating shaft 42 is provided so as to be rotatable once through the side surface of the frame 51, and the driving force of the driving motor 41 provided outside the frame 51 is applied to the gear 43. It is designed to communicate.
The gear 25 is attached to the shaft 21 a outside the lift member 31, and engages with the gear 43 when the belt unit 20 is moved downward by the latch unit 30.
[0032]
Further, in the present embodiment, as shown in FIG. 4, a belt control system 100 for controlling the movement of the belt unit 20 is provided.
In the present embodiment, the belt control system 100 includes a sheet detection sensor 101 that detects the entry of the sheet P into the fixing device, and a stepping motor 33 and a driving motor 41 based on the sheet detection signal of the sheet detection sensor 101. And a control device 102 for controlling the operation. Here, the control device 102 also controls the operation of the heat fixing roll 11.
[0033]
Further, the belt control system 100 is provided with a position detection sensor 103 for detecting the position of the belt unit 20.
In the present embodiment, the position detection sensor 103 detects the fixing position at which the fixing belt 24 of the belt unit 20 is pressed against the heat fixing roll 11 at an appropriate nip pressure, and the fixing belt 24 and the heat fixing roll 11 are separated from each other. This is to detect a standby position where the gear 25 provided on the support roll 21 of the unit 20 and the gear 43 of the belt drive mechanism 40 are completely engaged.
Then, based on the detection result of the position detection sensor 103, the control device 102 also serves as the position control means of the belt unit 20.
In the present embodiment, as the sheet detection sensor 101 and the position detection sensor 103, for example, an optical sensor or the like is used.
[0034]
Next, the fixing process in the present embodiment will be described based on the timing chart shown in FIG. 5 and the flowchart shown in FIG.
First, before performing the fixing process, the control device 102 stops the rotation of the heat-fixing roll 11, stops the belt unit 20 at the standby position, and rotates the drive motor 41. Accordingly, at the standby position, the fixing belt 24 is driven to rotate by the engagement of the gear 25 of the belt unit 20 and the gear 43 of the belt driving mechanism 40.
In this state, the heat fixing roller 11 is heated to 150 ° C., and the fixing belt is heated to 120 ° C.
[0035]
Then, at time t1, when the paper detection sensor 101 detects the entry of the paper P carrying the toner image T, the control device 102 starts the rotation of the heat fixing roll 11, and operates the stepping motor 33. To start moving the belt unit 20 from the standby position to the fixing position. At this time, the driving motor 41 rotates until the time t2 at which the engagement between the gear 25 and the gear 43 is released with the movement of the belt unit 20, and drives the fixing belt 24 to rotate. Stop rotation at the time
[0036]
Thereafter, at time t3, when the belt unit 20 reaches the fixing position and this is detected by the position detection sensor 103, the control device 102 stops the operation of the stepping motor 33 and stops and holds the belt unit 20 at the fixing position. .
Then, the fixing of the toner image T on the sheet P is performed between the times t4 and t5. At this time, since the temperature of the fixing belt 24 side is lower than that of the heat fixing roll 11, the occurrence of blisters, toner blisters, and the like is prevented.
[0037]
When the paper P passes through the fixing nip area at time t5, the control device 102 operates the stepping motor 33 in the reverse direction to start moving the belt unit 20 from the fixing position to the standby position, and at the same time, the driving motor 41 Is started to rotate the gear 43 idly.
Then, at time t6, the gear 25 and the gear 43 are engaged, and the fixing belt 24 is again driven to rotate by the belt driving mechanism 40.
[0038]
When the belt unit 20 reaches the standby position at time t7 and is detected by the position detection sensor 103, the control device 102 stops the operation of the stepping motor 33 and stops the belt unit 20 at the standby position. Hold.
[0039]
As described above, when the belt unit 20 moves from the fixing position to the standby position, the gear 43 of the belt driving mechanism 40 is idled in advance, so that even when the gear 25 comes into contact with the gear 43, Engagement is performed without causing poor meshing between them.
[0040]
In this embodiment, although the start of driving of the driving motor 41 were simultaneous with movement starting time t5 of the belt unit 20 is not limited to this, the gear 25 and the belt of the belt unit 20 from the time t5 The timing may be appropriately selected from the timing until the time t6 when the gear 43 of the drive mechanism 40 comes into contact with the gear 43.
[0041]
Further, in this embodiment, the transmission of the driving force between the belt driving mechanism 40 and the belt unit 20 is performed by the gear. However, the present invention is not limited to this, and the roll is pressed against the surface of the fixing belt 24 by pressing. May go.
In such an embodiment, if the roll provided for transmitting the driving force is also used as an oil supply roll for supplying the release agent to the fixing belt 24, the number of parts can be reduced.
[0042]
【The invention's effect】
As described above, according to the present invention, it is possible to optimize the relationship between the timing of starting and ending the movement of the belt fixing member and the timing of starting and stopping the driving of the belt fixing member by the driving unit. While preventing the occurrence of blisters and toner blisters, it is also possible to prevent the occurrence of parts breakage and the like.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an outline of a fixing device according to the present invention.
FIG. 2 is an explanatory diagram showing one embodiment of a belt fixing device to which the present invention is applied.
FIG. 3 is an explanatory diagram of the fixing device according to the exemplary embodiment as viewed from above.
FIG. 4 is an explanatory diagram illustrating a control system of the fixing device according to the exemplary embodiment.
FIG. 5 is a timing chart illustrating an operation of the fixing device according to the exemplary embodiment.
FIG. 6 is a flowchart illustrating an operation of the fixing device according to the exemplary embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Heat fixing member, 2 ... Roll group, 3 ... Belt fixing member, 4 ... Belt moving means, 5 ... Belt driving means, 6 ... Movement detecting means, 7 ... Belt control means, A ... Fixing position, B ... Standby position

Claims (2)

A heating fixing member having a heating source and rotatably disposed,
The heating / fixing member has a heating source for heating to a temperature different from that of the heating / fixing member. The heating / fixing member is rotatably stretched around a plurality of roll groups, and is pressed against the heating / fixing member to heat / press an unfixed image on the recording material. An endless belt-shaped belt fixing member movably disposed between a fixing position for fixing and a standby position separated and on standby,
Belt moving means for moving the belt fixing member,
A belt driving unit that rotationally drives the belt fixing member at a position other than the fixing position.
Movement detection means for detecting movement of the belt fixing member from the fixing position and the standby position;
The driving of the belt driving unit is started under the condition that the movement of the belt fixing member from the fixing position is detected by the movement detecting unit, and the belt driving unit is driven under the condition that the movement of the belt fixing member is detected from the standby position. And a belt control means for stopping the driving of the fixing device. The fixing device according to claim 1,
The belt control unit controls the belt movement control unit so as to stop the movement of the belt fixing member under the condition that the movement detection unit detects the arrival of the belt fixing member at the fixing position and the standby position. Fixing device.

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