JP2000305403A - Fixing device and method for detecting nip width, and thickness of recording material adopted therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a fixation process excellently and stably in accordance with setting, regardless of changes on various fixing conditions such as the change of the surface temp. of a heating member. SOLUTION: In order to make a unfixed image 1 heat fixed on recording material 2 that the unfixed image 1 is held thereon, the fixing device provided with the heating member 3 for heating the unfixed image 1, and the pressure member 5 disposed in press contact with this heating member 3, in order to form a nip 4 for holding/transporting a recording material 2 with the heating member 3, is provided with nip width changing means 6 for changing the width B without step in the transporting direction of the recording material 2 of the nip 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for fixing a recording material holding an unfixed image by heating while passing through a nip, and a method for detecting the nip width and the thickness of the recording material.

[0002]

2. Description of the Related Art For example, in an image forming apparatus employing an electrophotographic system, a latent image on a photoreceptor as an image carrier is developed by toner development to form an image, and the developed toner image is directly or intermediately transferred. The recording material holding the unfixed toner image after receiving the electrostatic transfer is sent to a nip formed by a heating member and a pressing member pressed against the recording material. While nipping and transporting between the two members, the unfixed toner image is heated and pressed to perform a fixing process, thereby finishing the image.

The width of the nip when the recording material is nipped and conveyed at a constant speed is proportional to the heating and pressurizing time for the fixing process, and mainly depends on the type of toner and whether the image is a monochrome image or a color image. They are set according to the differences.
The color image is set to have a larger nip width than that of the monochrome image in order to fuse and combine the three or four color toner images and obtain higher gloss than the monochrome image.

The required nip width is obtained by forming at least one surface of a heating member and a pressing member with a rubber-based elastic body and elastically deforming a portion where both are pressed against each other. For this reason, the elastic layer for fixing a color image is often set to be softer than that for fixing a monochrome image.

On the other hand, if the thickness of the recording material is different, the width of the nip deviates from the set value, and the fixing characteristic changes. Further, the fixing characteristics also differ depending on the material of the recording material. Also,
The fixing characteristics differ depending on the type of the toner for a monochrome image or the toner for a color image.

[0006] If the difference is accommodated by adjusting the temperature of the heating member, the response of the thermal control is poor and it is not practical. Therefore, conventionally, there has been provided a fixing device in which the pressing force of the heating member and the pressing member can be switched in a plurality of stages according to a plurality of device use modes set in advance.

[0007]

However, in recent years, as further improvement in image quality is desired, types of recording materials, types of toners, desired image quality, and the like have been diversified, and the above-mentioned conventional fixing device cannot cope with the problems. It's gone. In particular, it responds to continuous or fine changes such as changes in surface temperature due to heat consumption due to heating member fixing processing, changes in fixing temperature due to changes in ambient temperature, and changes in temperature immediately before fixing processing of the recording material itself. It is difficult to further improve the image quality. Moreover, when the fixing condition is switched in the above-described conventional fixing device in accordance with environmental conditions and the like, if the switching is performed in the middle of the fixing process, the switching is stepwise, which may affect the image quality.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing device capable of performing a fixing process satisfactorily and stably as set even if there are changes in various fixing conditions such as a change in the surface temperature of a heating member, and a method for detecting the thickness of a recording material used in the fixing device. It is to provide a method.

[0009]

In order to achieve the above object, a fixing device according to the present invention is a fixing device in which an image is heated and fixed on a recording material holding an unfixed image. A heating member for heating an image, a pressurizing member provided in pressure contact with the heating member to form a nip for nipping and conveying the recording material between the heating member, and a recording material for the nip And a nip width changing means for changing the width in the conveying direction steplessly.

In such a configuration, the nip width for heating and pressurizing and fixing the recording material while nipping and transporting the recording material between the heating member and the pressing member is controlled by the nip width changing means. Since it can be changed steplessly without stepless adjustment of the pressing force between the heating member and the pressing member through the control means, etc., the fixing conditions, for example, the temperature of the heating member,
Desired glossiness of the image, recording material thickness, recording material conveyance speed, ambient temperature, temperature of recording material before entering the nip, fixing mode, white / black ratio of unfixed image on recording material It is possible to freely adjust by adjusting the nip width according to the continuous or fine condition change such as image state, etc., or the difference of various condition settings, to achieve good and stable fixing processing as set it can. In addition, since the adjustment of the nip width during the fixing process is performed in a stepless manner, the image quality is hardly affected, and there is no problem.

The temperature of the heating member is a temperature sensor, and the thickness of the recording material is, for example, a change in a driving current of a motor for driving the nipping conveyance by the heating member and the pressing member when passing through the nip. With the rotation or movement of the encoder linked to the passing speed of the predetermined distance or the conveyance, the ambient temperature or the temperature of the recording material before entering is a temperature sensor, and the information of the unfixed image on the recording material is used in digital image formation. Automatically respond in real time to changes in various fixing conditions by controlling nip width change based on changes in the detection results, which can be automatically detected from image signals etc. corresponding to each page. Can be. Also,
Desired gloss, recording material thickness, transport speed, fixing mode, etc. are set by the user's input means, and these are automatically detected from such setting information and various settings are made in real time. Can respond.

In order to detect the nip width and the thickness of the recording material as described above, when the driving current of the motor performing the nipping and conveying is monitored, the time when the recording material of the monitored driving current passes through the nip is detected. From the change, the width of the nip and the thickness of the recording material can be determined and detected.

[0013] Further objects and features of the present invention will become apparent from the following detailed description and drawings. Each feature of the present invention can be used alone or in combination as variously as possible.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to FIGS.

In this embodiment, an electrostatic latent image on a photoreceptor is developed and visualized mainly by using resin powder toner.
This is an example of a case where the visualized toner image is electrostatically transferred onto a recording material, and the unfixed toner image on the transferred recording material is heated and pressed to perform a fixing process. However, the present invention is not limited to this, and a monochrome image, a composite image, a color image, or the like is formed indirectly or directly as an unfixed image on a recording material using various toners such as powder and liquid. This is effective when applied to various cases.

In this embodiment, as shown in FIG. 1, a heating member for heating the unfixed image 1 is used to heat and fix the image 1 on a recording material 2 holding the unfixed image 1. 3 and a pressing member 5 provided in pressure contact with the heating member 3 in order to form a nip 4 for nipping and conveying the recording material 2 between the heating member 3 and the above object. For this purpose, a nip width changing means 6 for continuously changing the width B of the nip 4 in the conveying direction of the recording material 2 is provided.

It is sufficient that one of the heating member 3 and the pressing member 5 is brought into pressure contact with the other, and in some cases, both may be movable and brought into pressure contact with each other. Both the heating member 3 and the pressing member 5 are simple rotating rollers, and at least one surface thereof has a nip 4.
May be formed of an elastic material for obtaining the required width B of
In this embodiment, the heating member 3 uses the fixing belt 7 for heating for fixing. The pressing member 5 includes a pressing roller 1
One unit is used. The fixing belt 7 is stretched by a heating roller 8 and an upper roller 9 located on the side of the unfixed recording material 2 on the screen 2a, and is heated from the inside by the heating roller 8. The upper roller 9 backs up the fixing belt 7 from the inside and provides a pressure contact with the pressure roller 11 to form a nip 4 therebetween.
The recording material 2 supplied thereto is heated by a heated fixing belt 7 while being nipped and conveyed while being pressed by the nip 4 to perform a fixing process. In the embodiment shown in FIG.
The first side is driven by a motor 51, and the fixing belt 7 and the upper roller 9 are driven by the motor 51, so that the fixing belt 7 and the like are not forced.

In the embodiment shown in FIG. 1 and FIG.
Is a nickel material formed in a belt shape by electroforming and has a thickness of about 40 μm on a surface of 200 to 300 μm.
It is coated with silicon rubber of about μm. Since the heat capacity of each part of the fixing belt 7 is small, the amount of heat heated by the heating roller 8 is almost constant.
Most are consumed by the fixing process. Accordingly, the temperature at the time of the fixing process can be accurately controlled by the temperature at which the fixing belt 7 is heated by the heating roller 8. The surface temperature of the heating roller 8 is controlled by housing the heating source 12 such as a halogen lamp in the heating roller 8 and heating the heating roller 8, and monitoring the surface temperature of the heating roller 8 at that time by a thermistor 13. I am trying to do it.

The heating roller 8 is formed by coating a surface of an aluminum cylindrical base material with PTFE (ethylene tetrafluoride) or PFA (copolymer of perfluoroalkoxy and PTFA). The upper roller 9 is a soft roller having a sponge rubber layer provided on the surface of a metal base material.
To form the nip 4. Correspondingly, the pressure roller 11 is provided on the surface of the metal base material with Teflon (registered trademark).
It is a hard roller having a resin layer or a soft roller in which a metal substrate is coated with a plurality of elastic layers on the surface. When the pressure roller 11 is a soft roller, the surface of the pressure roller 11 is also an elastic layer, so that the upper roller 9 is a soft roller.
The recording material 2 can be stably nipped and conveyed without slippage in cooperation with a fixing belt whose surface is an elastic layer.

The pressure roller 11 also has a built-in heating source 14 for contributing to heating for fixing, and the surface temperature thereof is monitored and controlled by a thermistor 15. The fixing belt 7 is provided with an oil application mechanism 16 for controlling glossiness for fixing a color image and improving releasability of a toner having a large viscosity. The oil application mechanism 16 is shown in FIG.
As shown in FIG. 1, as an example, an oil application roller 17 in which the surface of a material impregnated with oil is covered with paper or the like, and the oil supplied from the oil application roller 17 are transferred to the surface of the fixing belt 7 while smoothing between the two. It comprises a donor roller 18 for application and a cleaning roller 19 for cleaning the surface of the donor roller 18 with a surface such as paper.

As shown in FIG. 2, the heating member 3 and the oil application mechanism 16 are provided on a fixing frame 21 fixed to the main body of the image forming apparatus. The pressure roller 11 is mounted on a pressure lever 23 hinged by a fulcrum shaft 22 for pressure, and is actuated between the fixing frame 21 and the pressure lever 23 by the urging of a pressure contact spring 24 shown in FIG. Is pressed against the upper roller 9. The upper roller 9 is fixed on the fixing frame 21, and the sensor holder 25 holding the thermistor 13 is pressed against the heating roller 8 by a spring 27 on the support block 26 to press the thermistor 13 against the surface of the heating rotor 8. It is like that. The lower roller 9 can be retracted rearward with respect to an abnormally thick passing object so as not to be damaged. The thermistor 15 is supported by a spring plate 28 and pressed against the surface of the pressure roller 11. Recording material 2 is plain paper, thin paper, postcards, envelopes,
There is a resin sheet for OHP. These differ from each other only in the thickness, and the amount of heat consumed at the time of fixing varies, which affects the fixing characteristics.

The nip width changing means 6 of this embodiment adjusts the spring force of the pressure contact spring 24 steplessly so that the width B of the nip 4 can be changed steplessly. For this reason, as shown in FIG. 1, a pressure adjustment lever 31 is supported on the fixing frame 21 so as to be rotatable by a shaft 32, and a spring seat 34 on a shaft 33 connected to one end of the pressure adjustment lever 31 and a pressure lever. 23, the rotation position of the pressure contact adjustment lever 31 is steplessly displaced by a motor 37 via a drive gear 36 meshing with a sector gear 35 at the other end, so that the pressure contact spring 24 11 is adjusted steplessly to adjust the spring force for pressing the upper roller 9 against the upper roller 9.
The width B of the nip 4 formed by the spring force of No. 4 can be changed steplessly. The motor 37 is controlled by the control means 38 for continuously changing the width B of the nip 4. Depending on the type of the motor 37, the motor 37 may be directly connected to the drive gear 36, but may be connected via a speed reduction mechanism 39 to facilitate stepless adjustment.

As shown in FIG. 3, the reference pressing positions of the heating member 3 and the pressing member 5 are determined by setting a signal portion 31a on the pressing adjustment lever 31 side and a photo interrupter 4 on the fixing frame 21 side.
The combination of the sensors 1 and the
The control means 38 first drives the motor 37 so as to be in a normal reference pressure contact state, and determines whether or not the motor is in a rotation position corresponding to the reference pressure contact position. By driving the motor 37 to the side, various pressure contact states are obtained in a stepless manner.

In response to the large pressing load of the heating member 3 and the pressing member 5, pressure contact adjusting levers 31 are provided on both left and right sides of the fixing frame 21 by being supported by shafts 32. Drive shaft 43 in which the drive gear 36 of FIG.
, The pressure roller 11 is stably evenly left and right with respect to the upper roller 9 by the pair of left and right pressure contact adjustment levers 31 and the pair of left and right pressure contact springs 24 operated between the pair of pressure contact adjustment levers 31 and the left and right of the pressure lever 23. So that they can be pressed against each other. Correspondingly, the driving force from the motor 37 can be obtained by connecting a reduction mechanism 39 or the like to one of the driving gears 36 as shown in FIG.

Reference width B0 of nip 4 based on reference pressure contact position
The width B of the nip 4 can be controlled, for example, from the relationship between the driving time of the motor 37, the driving direction of the press-contact adjusting lever 31 at that time, and the width B of the nip 4, as shown in FIG. The driving direction is easily determined by selecting the forward / reverse driving of the motor 37, but may be performed using a driving direction switching mechanism. Further, it can be controlled by the relationship as shown in FIG. 5 between the rotation angle and the rotation amount of the motor 37 and the pressure adjusting lever 31 driven by the motor 37 and the width B of the nip 4. This method is effective when the control is not stable depending on the driving time of the motor 37, and specifically, the motor 37 and the driving gear 3
6. A pulse disk or the like interlocked with the pressure adjustment lever 31, the pressure lever 23, etc., can be used as the rotation detecting means. Further, the control means 38 controls the motor 3
In the case of a stepping motor or the like for controlling the drive of the motor 7, the control can also be performed by the relationship between the number of input pulses and the width B of the nip 4 as shown in FIG. Further, the pressure roller 11
The driving torque of a member for driving the nip 4 is detected, and control can be performed from the relationship between the driving torque and the width B of the nip 4 as shown in FIG.

As described above, in the present embodiment, the width B of the nip 4 for heating and pressing while fixing the recording material 2 between the heating member 3 and the pressing member 5 to carry the fixing process is changed by the nip width changing means. 6, the pressing force between the heating member 3 and the pressing member 5 through the control means 38 for controlling the changing operation is steplessly changed by the stepless adjustment or the like.
For example, the temperature of the heating member 3, the desired glossiness of the image, the thickness and material of the recording material 2, the conveying speed of the recording material 2, the ambient temperature, the temperature of the recording material 2 before entering the nip 4, the fixing mode At least one of continuous or minute condition changes such as an image state such as a white / black ratio of the unfixed image 1 on the recording material 2 or a difference in various condition settings.
In addition, the nip width B can be adjusted to suit the entire nip width B as needed, and a satisfactory and stable fixing process can be achieved as set. In addition, since the adjustment of the nip width B during the fixing process is performed in a stepless manner, the image quality is hardly affected and there is no problem.

The temperatures of the heating member 3 and the pressing member 5 can be detected by the thermistors 13 and 15 as temperature sensors, and the thickness of the recording material 2 is determined by the heating member 3 and the pressing member 5 when passing through the nip 4, for example. The change in the driving current of the motor for nipping and conveying can be detected by using the internal function of the control means 38, and the conveying speed is controlled by the passing speed of the recording material 2 over a predetermined distance or the rotation or movement of the encoder linked to the conveyance. The ambient temperature and the temperature of the recording material 2 before the entry can be detected by temperature sensors such as thermistors 52 and 53 shown in FIG. The information is obtained from an image signal IM or the like corresponding to each page in digital image formation by the control means 3.
8 can be automatically detected using the internal functions of the control unit 38. The stepless change control of the nip width B by the control means 38 based on such a change in the detection result makes it possible to detect various changes in the fixing conditions. It can respond automatically and in real time. Also, desired glossiness, thickness of the recording material 2,
The transport speed, the fixing mode, and the like are set by the user's input means from the operation panel 54 or the like, and these are automatically detected from such setting information using the internal function of the control means 38. It can respond to various settings in real time. FIG. 1 shows a control system for performing such control, centering on the control means 38.

In the image formation for fixing as described above, various print modes such as continuous printing, double-sided printing, monochrome printing, and color printing are set, and these also affect the fixing characteristics together with the fixing mode. It is preferable that these are detected by the internal function of 38 and reflected in the control of the width B of the nip 4.

In this embodiment, the rotation angle and the rotation amount relating to the driving of the nip width changing means 6 set in advance are set.
The case where the drive for changing the nip width B is performed by the input frequency in the case of applying the pulse current, the pressing force against the driving torque or the nip width B, etc., is described.
By detecting the width B of the fixing device and correcting the data based on the detection result, individual variations in the fixing characteristics of the fixing device can be significantly reduced, and the fixing accuracy is further improved. As a method for sequentially detecting the width B of the nip 4, specifically, a means for detecting the driving torque or the number of rotations of the driving member of the pressure roller 11 is provided, and when the recording material 2 enters the nip 4, Alternatively, there is a method of calculating the width B of the nip 4 based on a change in torque or rotation speed at the time of discharge or both.

Referring now to FIG. 8, the heating member 3 and the pressing member 5 monitor the drive current of the motor that is nipping and conveying the recording material 2, and the monitored recording material 2 of the driving current is nipped. 4, the width B of the nip 4
Alternatively, a specific method for determining the thickness and length of the recording material 2 will be described.

FIG. 8A shows the result of monitoring the driving current of the motor when the recording material 2 passes through the nip 4. The driving current is oscillated by low-pass filtering or averaging. Is removed, the current changes as shown in FIG. Needless to say, the low-pass filter processing and the averaging processing are performed in a very short time unit that does not eliminate the change in the drive current before and after the recording material 2 passes through the nip 4.

From the changing point of the drive current in FIG. 8B, the recording material 2 in FIG.
This corresponds to a state immediately before passing the nip 4 between the pressure member 5 and the pressure member 5 to a state immediately after passing through the nip 4. Therefore, the change in the current to the current change in FIG. 8B corresponds to the time when the leading end and the rear end of the recording material 2 pass through the width B of the nip 4. Since the magnitude of the change Ih is proportional to the thickness of the recording material 2, the thickness of the recording material 2 is determined from the magnitude of the current change Ih at the rise or fall of the monitor current. And can be automatically determined and detected. 8B corresponds to a period from when the leading end of the recording material 2 enters the nip 4 to when the trailing end of the recording material 2 passes through the nip 4. The size in the transport direction of the recording material 2 that has passed through can be automatically detected using the internal function of the control means 38 or the like.

[0033]

According to the present invention, as apparent from the above description, the width of the nip for fixing by heating and pressing while holding and conveying the recording material between the heating member and the pressing member is as follows.
Since the nip width changing means is steplessly changed by stepless adjustment of the pressing force between the heating member and the pressing member through the control means for controlling the changing operation, the fixing conditions are continuously or finely adjusted. The nip width can be freely adjusted by adjusting the nip width in response to various condition changes or differences in various condition settings, and a good and stable fixing process can be achieved as set. In addition, since the adjustment of the nip width during the fixing process is performed in a stepless manner, the image quality is hardly affected, and there is no problem.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a fixing device showing one example according to a representative embodiment of the present invention.

FIG. 2 is a sectional view showing the internal structure of the device of FIG.

FIG. 3 is a configuration diagram of a nip width changing unit of FIG. 2;

FIG. 4 is a graph showing a relationship between a driving time of a motor for driving nipping conveyance and a nip width.

FIG. 5 is a graph showing a relationship between a rotation angle and a rotation amount of a motor for driving nipping conveyance and a nip width.

FIG. 6 is a graph showing a relationship between an input pulse and a nip width when a motor for driving nipping conveyance is energized by a pulse.

FIG. 7 is a graph showing a relationship between a driving torque of a driving unit for driving the nipping conveyance and a nip width.

FIG. 8 is an explanatory diagram for detecting a nip width, a thickness of a recording material, and the like from a change in a driving current when a recording material of a motor driving the nipping conveyance passes through the nip, and FIG. (B) is a graph showing a current change when the current change of (a) is subjected to the low-pass filter processing or the averaging processing, and (c) is a graph showing the time from immediately before the recording material passes through the nip to immediately after it passes. It is a state diagram which shows the state of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Unfixed image 2 Recording material 3 Heating member 4 Nip 5 Pressing member 6 Nip width changing means 13, 15, 52, 53 Thermistor 21 Fixing frame 22 Support shaft 23 Pressure lever 24 Pressure spring 37, 51 Motor 31 Pressure adjustment Lever 36 Drive gear 38 Control means B Width Ih Current change magnitude

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hayashi English 3-2-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka Inside Osaka International Building Minolta Co., Ltd. (72) Inventor Tetsu Yoneda Azuchi-cho, Chuo-ku, Osaka-shi, Osaka 2-3-13, Osaka International Building Minolta Co., Ltd. (72) Inventor Takashi Yamada 2-3-13, Azuchicho, Chuo-ku, Osaka City, Osaka Prefecture Osaka International Building Minolta Co., Ltd. (72) Inventor Masanori Murakami Osaka 2-13-13 Azuchicho, Chuo-ku, Osaka F-term (reference) in Osaka International Building Minolta Co., Ltd. DA12 DA19 LA02 LB03

Claims (13)

[Claims] 1. A fixing device for heating and fixing an unfixed image on a recording material holding the unfixed image, comprising: a heating member for heating the unfixed image; A pressurizing member provided in pressure contact with the heating member to form a nip for nipping and conveying; and a nip width changing unit for continuously changing a width of the nip in the conveying direction of the recording material. A fixing device. 2. The fixing device according to claim 1, wherein the nip width changing unit changes the nip width by continuously adjusting a pressing force between the pressing member and the heating member. 3. The fixing device according to claim 1, further comprising control means for controlling a changing operation of the nip width changing means. 4. The fixing device according to claim 3, further comprising detecting means for detecting a temperature of the heating member, and controlling a changing operation of the nip width changing means based on a detection result of the detecting means. 5. The image processing apparatus according to claim 3, further comprising an input unit for inputting a desired glossiness of the fixed image, wherein the changing operation of the nip width changing unit is controlled based on the input by the input unit. Fixing device. 6. The change operation of the nip width changing unit based on information of a type including a thickness of the recording material input by an input unit or detected by a detecting unit. 3. The fixing device according to claim 1. 7. The fixing device according to claim 3, wherein a change operation of the nip width changing unit is controlled based on information on a conveying speed of the recording material set in advance or detected by the detecting unit. . 8. A nip width changing means for controlling a change operation of a nip width changing means based on a detection result of the detecting means for detecting an ambient temperature of the recording material conveyance path.
The fixing device according to claim 1. 9. A recording apparatus according to claim 3, further comprising detecting means for detecting a temperature of the recording material before entering the nip, and controlling a changing operation of the nip width changing means based on a detection result of the detecting means.
9. The fixing device according to claim 8, wherein 10. The fixing device according to claim 3, further comprising a detecting unit that detects a fixing mode, and controlling a change operation of the nip width changing unit based on a detection result of the detecting unit. 11. A detecting means for detecting data of an unfixed image on the recording material, wherein a changing operation of a nip width changing means is controlled based on a detection result of the detecting means.
The fixing device according to any one of claims 10 to 10. 12. A heating member for heating the unfixed image and a heating member provided in pressure contact with the heating member to form a nip for nipping and conveying the recording material between the heating member and the heating member. A nip width detection method for a fixing device including a pressure member, wherein a driving current of a motor driving the nipping conveyance is monitored,
A nip width detection method for a recording material, wherein the nip width is determined and detected based on a change in a monitored drive current when the recording material passes through the nip. 13. A heating member for heating the unfixed image and a heating member provided in pressure contact with the heating member to form a nip for nipping and conveying the recording material between the heating member and the heating member. A pressure member and a recording material thickness detection method of a fixing device, comprising: monitoring a drive current of a motor that drives the nipping conveyance;
A method of detecting a thickness of a recording material, comprising determining and detecting the thickness of the recording material based on a change in the monitored drive current when the recording material passes through a nip.