JP2001201976A - Fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device and an image forming device which are prevented from getting complicated and getting large even though they are equipped with a pressurizing force adjusting means and realize excellent fixation even in the case of using a recording medium easily wrinkled and having a large heat capacity such as an envelope. SOLUTION: In this fixing device, an image is fixed by holding and carrying the recording medium on which the image is carried in a press-contact nip between rotating bodies 81 and 82 coming into press-contact with each other by pressurizing means 86 and 88. The device is equipped with the pressuring force adjusting means 89 varying the pressuring force of the pressuring means 86 and 88, and the adjusting means 89 is driven by a driving source 98 driving the rotating bodies.

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 an unfixed image on a recording medium and an image forming apparatus provided with the fixing device. The present invention relates to a copying machine, a printer, a facsimile, and the like for forming.

[0002]

2. Description of the Related Art In a fixing device of an image forming apparatus, the nip width between a fixing rotator and a pressure rotator is generally set to a fixed value. The optimum nip width depends on the type of recording medium and When the recording medium is paper, it differs depending on the thickness.

That is, thick paper requires a large amount of heat for toner fixing when passing through the fixing nip, and the paper itself also takes a large amount of heat. For this reason, in the case of thick paper, if the fixing nip width is not set sufficiently wide, the fixing property may be deteriorated.

On the other hand, in the case of thin paper, if the fixing nip width is wider than necessary, an excessive amount of heat is applied which is larger than the amount of heat required for fixing toner on the paper, which causes distortion of the paper and rigidity of the paper. However, there is a problem that wrinkles are likely to be generated because the wrinkles are low in the first place.

[0005] Further, since the envelope is manufactured by bending and pasting, there is a problem that when the envelope passes through the nip, distortion is apt to occur and wrinkles are easily generated.

In order to solve such a problem, for example, in an electrophotographic apparatus disclosed in Japanese Patent Application Laid-Open No. Hei 5-297763, the type and thickness of a recording medium are detected, and the pressure is adjusted based on the detected output to optimize the recording medium. Nip width.

The pressure adjusting means comprises a pressure spring for pressing the fixing rotary member and the pressure rotary member, a cam for pressing the pressure spring, and an independent motor for rotating the cam.

[0008]

However, in the above conventional example, the following problem may occur.

Since an independent motor is provided, the number of parts is increased and the cost is likely to increase.

Further, the size of the apparatus main body becomes large.

When a recording medium, such as an envelope, which easily generates wrinkles and has a large heat capacity is used, if the pressure is adjusted low to prevent wrinkles, sufficient fixability may not be obtained.

Accordingly, a first object of the present invention is to provide a fixing device and an image forming apparatus which are provided with a pressurizing force adjusting means and which can suppress the complexity and size of the apparatus.

A second object of the present invention is to provide a fixing device and an image forming apparatus which are capable of satisfactorily fixing even when a recording medium having a large heat capacity, such as an envelope, is easily wrinkled.

[0014]

A fixing device and an image forming apparatus according to the present invention have the following features to solve the above-mentioned problems.

[1] In a fixing device for fixing an image by nipping and transporting a recording medium carrying an image by a pressure nip of rotating bodies pressed against each other by a pressure means, the pressing force of the pressure means is reduced. A fixing device, comprising: a pressing force adjusting unit that is variable; wherein the pressing force adjusting unit is driven by a driving source that drives the rotating body.

[2] The fixing device according to [1], wherein the driving source has a driving speed adjusting means for adjusting a rotation speed of the rotating body.

[3]: In a fixing device for fixing an image by nipping and transporting a recording medium carrying an image by a pressure nip of rotating bodies pressed against each other by a pressure means, the pressing force of the pressure means is reduced. It is characterized in that it comprises variable pressing force adjusting means, and driving speed adjusting means for adjusting the rotation speed of the rotating body, wherein the pressing force adjusting means is driven by a drive source for driving the rotating body. Fixing device.

[4] The fixing device according to [2] or [3], wherein the drive speed adjusting means adjusts the speed according to the type of the recording medium.

[5]: There is provided a drive switching means for selectively switching between driving of the rotating body and driving of the pressing force adjusting means, [1], [2], [3] or [ 4] The fixing device according to the above.

[6] The fixing device according to any one of [1] to [5], wherein the pressing force adjusting means is selectively driven.

[7]: [1] to [6], wherein the pressing force adjusting means is driven when the driving source is reversely rotated.
The fixing device according to claim 1.

[8] The fixing device according to any one of [1] to [7], wherein the pressing force adjusting means selects a pressing force according to a type of a recording medium.

[0023]

[9] The fixing device according to any one of [1] to [8], wherein the rotating body has a shape of a roller or an endless belt.

[10]: [1] to [1], wherein the rotating bodies are a fixing rotating body and a pressing rotating body.

[9] The fixing device according to any one of [9].

[11] A heating means is provided inside at least one of the fixing rotating body and the pressing rotating body, and the recording medium is heated by heat from the heating means. The fixing device according to any one of the above items [10] to [10].

[12]: An unfixed toner image is heated to fix the image on a recording medium [1].
The fixing device according to any one of the above items [11] to [11].

[13]: In an image forming apparatus having an image forming means for forming an image on a recording medium and a fixing means for fixing the image on the recording medium, the fixing means [1] to [12] An image forming apparatus comprising the fixing device according to any one of the preceding claims.

<Operation> According to the above configuration, in the fixing device or the image forming apparatus, the pressing force and the fixing speed can be set to optimum conditions in accordance with the type and thickness of the recording medium, so that sufficient fixing property is ensured. , Wrinkles can be prevented.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of an image forming apparatus to which the present invention is applied will be described in detail with reference to the drawings.

<First Embodiment> An image forming apparatus according to a first embodiment will be described in detail with reference to FIGS.

First, a schematic configuration of the image forming apparatus will be described with reference to FIG. FIG. 5 is a longitudinal sectional view showing a schematic configuration of the image forming apparatus according to the present invention. In the present embodiment, a full-color laser beam printer employing an electrophotographic method is exemplified as one mode of the image forming apparatus.

The image forming apparatus A shown in FIG. 4 includes a drum type electrophotographic photosensitive member (hereinafter, referred to as "photosensitive drum") 1 as a first image carrier. The photosensitive drum 1
The motor is rotated counterclockwise in FIG. 4 by a driving unit (not shown). A charging device 2 for uniformly charging the surface of the photosensitive drum 1 is irradiated with a laser beam based on image information around the photosensitive drum 1 in order according to the rotation direction, and an electrostatic latent image is formed on the photosensitive drum 1. , A developing unit 4 for applying toner to an electrostatic latent image to develop it as a toner image, and a transfer unit as a second image carrier on which the toner image on the photosensitive drum 1 is primarily transferred 5, a cleaning device 6 for removing residual toner remaining on the surface of the photosensitive drum 1 after the primary transfer is provided.

Here, the photosensitive drum 1, the charging device 2, and the cleaning device 6 for removing toner are integrally formed as a cartridge to form a process cartridge B, which is detachable from the apparatus main body 14 of the image forming apparatus A. Has become.

In addition, a recording medium (third image carrier) S
Means 7 for feeding the recording medium S toward the transfer unit 5, conveying means 12 for conveying the recording medium S, a fixing device 80 for fixing the toner image on the recording medium after the secondary transfer, and a machine for fixing the recording medium S after the fixing. Discharge transport means 9 for transporting outside and a discharge tray 10 on which discharged recording media are stacked are provided.

Hereinafter, the photosensitive drum 1 will be described in detail.

The photosensitive drum 1 is, for example, about 47 m in diameter.
An organic photoconductor layer (OPC photoreceptor) is applied to the outer peripheral surface of an aluminum cylinder of m. The photosensitive drum 1 is rotatably supported at both ends by a support member, and is driven to rotate in the direction of the arrow by transmitting a driving force from a driving motor (not shown) to one end.

The charging device 2 is described in, for example,
A so-called contact charging type as shown in JP-A-149669 can be used. The charging member is a conductive roller formed in the shape of a roller. The roller is brought into contact with the surface of the photosensitive drum 1 and a charging bias is applied to the roller by a power supply (not shown) to thereby charge the photosensitive drum. This is for uniformly charging one surface.

The exposure means 3 has a polygon mirror 3a, and the polygon mirror 3a is irradiated with image light corresponding to an image signal by a laser diode (not shown). The polygon mirror 3a is rotated at a high speed by a scanner motor (not shown), and selectively exposes the surface of the charged photosensitive drum 1 to the reflected image light via the imaging lens 3b, the reflection mirror 3c, and the like. It is configured to form an electrostatic latent image.

The developing device 4 accommodates a rotating member 4A rotatable around a shaft 4d and four developing devices mounted thereon, ie, toners of yellow, magenta, cyan, and black, respectively. Developing units 4Y, 4M, 4C, 4B
k. When the electrostatic latent image on the photosensitive drum 1 is developed, a predetermined developing device of a color to be attached to the electrostatic latent image is arranged at a developing position. That is, the predetermined developing device is the rotating body 4A.
After being stopped at the developing position opposed to the photosensitive drum 1 by the indexing rotation, the developing sleeve 4b of the developing device is positioned so as to face the photosensitive drum 1 at a small interval (about 300 μm). The electrostatic latent image on the photosensitive drum 1 is developed. This development is performed as follows. The toner in the container of the developing device corresponding to the color to be developed is sent to the application roller 4a by a feed mechanism, and is rotated by the application roller 4a and the toner regulating blade 4c.
A thin layer of toner is applied to the outer periphery of the rotating developing sleeve 4b, and a charge is applied to the toner (frictional charging). The developing sleeve 4b and the photosensitive drum 1 on which the electrostatic latent image is formed
Is applied with a developing bias to cause toner to adhere to the electrostatic latent image and develop as a toner image. The developing sleeve 4b of each of the developing devices 4Y, 4M, 4C, and 4Bk is connected to a high-voltage power supply for developing each color provided in the image forming apparatus main body 14 when each developing device is disposed at the developing position. The voltage is selectively applied for each color development. In addition, each developing unit 4Y, 4M, 4
C and 4Bk are individually provided for the rotating body 4A and
A is configured to be detachable from the apparatus main body 14, respectively.

Transfer unit 5 as second image carrier
Is to collectively transfer a plurality of toner images sequentially primary-transferred and superposed from the photosensitive drum 1 to the recording medium S in a batch. The transfer unit 5 includes an intermediate transfer belt 5a running in the direction of arrow R5. The intermediate transfer belt 5a of the present embodiment is a belt having a circumference of about 440 mm,
It is wrapped around three rollers: a driving roller 5b, a secondary transfer opposing roller 5c, and a driven roller 5d. The intermediate transfer belt 5a is moved close to the driven roller
And the intermediate transfer belt 5a is pressed against the photosensitive drum 1
Roller 5j which retreats to take a position away from
It has. The intermediate transfer belt 5a includes a driving roller 5b.
The vehicle runs in the direction of arrow R5 by the rotation of. Further, at a predetermined position outside the intermediate transfer belt 5a, there is provided a cleaning unit 5e which can be brought into contact with and separated from the surface of the intermediate transfer belt 5a. Remove residual toner. The cleaning unit 5e brings the charging roller 5f into contact with the intermediate transfer belt 5a to give the toner a charge opposite to that at the time of transfer. The toner to which the opposite charge has been applied is electrostatically attached to the photosensitive drum 1 and then collected by a cleaning device 6 for the photosensitive drum 1 described later. The cleaning method of the intermediate transfer belt 5a is not limited to the above-described electrostatic cleaning, but may be a mechanical method such as a blade or a fur brush, or a method using both of them.

After the toner developed on the photosensitive drum 1 by the developing device 4 is primarily transferred to the intermediate transfer belt 5a, the cleaning device 6 removes so-called untransferred toner remaining on the surface of the photosensitive drum 1 without being transferred. It is to be removed.

The feeding unit 7 feeds the recording medium S to the image forming unit, and stores a plurality of recording media S,
The image forming apparatus includes a feeding cassette 7a to be loaded in a lower portion of the image forming apparatus main body 14. Pickup member 7 during image formation
e, the transport roller 7b is driven and rotated in accordance with the image forming operation, and separates and feeds the recording medium S in the feed cassette 7a one by one, while being guided by the guide plate 7c, and passing through the registration roller 7d for intermediate transfer. The sheet is fed to the belt 5a.

A recording medium type detecting means 203 for detecting the type of the recording medium is installed near the registration roller 7d, and is connected to a CPU (not shown).

The conveying means 12 conveys the recording medium S after image formation to the fixing device 80, and includes a plurality of belts and the like.

The fixing device 80 fixes a plurality of toner images secondary-transferred onto the recording medium S. A fixing roller 81 serving as a fixing rotating body that rotates and drives is pressed against the recording medium S by pressing against the fixing roller 81. And a pressure roller 82 as a pressure rotating body for applying heat and pressure. That is, a secondary transfer roller 5n that collectively transfers the toner on the intermediate transfer belt 5a
When the recording medium S passes through the fixing device 80, heat and pressure are applied by the fixing roller 81 and the pressure roller 82. As a result, toner images of a plurality of colors are formed on the recording medium S.
Settled on the surface. The configuration and operation of the fixing device 80 will be described later in more detail.

In the sheet discharging and conveying means 9, a conveying belt 9a is stretched over a driving roller 9b and a pair of conveying rollers 9c and 9d, and the driving roller 9b is driven by a driving motor (not shown) so that the pair of conveying rollers 9c and 9d is driven. The recording medium S that has rotated and passed through the fixing device 80 is conveyed and discharged out of the apparatus.

Next, an image forming operation of the image forming means including the charging means 2, the photosensitive drum 1, the exposing means 3, the developing device 4, the transfer unit 5 and the like of the image forming apparatus having the above-described structure will be described.

The photosensitive drum 1 is rotated in the direction of the arrow (counterclockwise) in FIG. 4 in synchronization with the rotation of the intermediate transfer belt 5a, and the surface of the photosensitive drum 1 is uniformly charged by the charging device 2; The exposure unit 3 irradiates light of a yellow image to form a yellow electrostatic latent image on the photosensitive drum 1. At the same time as the formation of the electrostatic latent image, the developing device 4
To place the yellow developing device 4Y at the developing position,
Applying a voltage of the same polarity and substantially the same potential as the charging polarity of the photoconductor drum 1 so that yellow toner adheres to the electrostatic latent image on the photoconductor drum 1 to cause yellow toner to adhere to the electrostatic latent image. develop. A voltage having a polarity opposite to that of the toner is applied to the primary transfer roller (driven roller) 5d, and the yellow toner image on the photosensitive drum 1 is primarily transferred onto the intermediate transfer belt 5a.

When the primary transfer of the yellow toner image is completed as described above, the next developing unit is rotated and positioned at the developing position facing the photosensitive drum 1, and the magenta and the yellow toner images are moved in the same manner as in the case of yellow. The formation of an electrostatic latent image and the primary transfer of development are sequentially performed for each color of cyan and black, and four color toner images are superimposed on the intermediate transfer belt 5a. These toner images are collectively and secondarily transferred onto the recording medium S supplied from the feeding unit 7.

(Configuration of Fixing Device) Next, the configuration and operation of the fixing device according to the first embodiment will be described in detail with reference to FIGS. FIG. 1 is a perspective view of the fixing device according to the first embodiment, FIG. 2 is a schematic diagram of a side portion of the fixing device according to the first embodiment, and FIG. 3 is a partial cross-sectional view of the fixing device according to the first embodiment.

In FIG. 1 to FIG. 3, reference numeral 81 denotes a fixing roller as a fixing rotating body, which comprises a metal pipe (core bar) 81b and an elastic layer 81a. Reference numeral 82 denotes a pressure roller as a pressure rotating body, which is likewise a metal pipe (core metal) 82.
b and the elastic layer 82a. Both ends of the fixing roller 81 are rotatably supported by a fixing frame 84 via bearings 83. The pressure roller 82 is rotatably supported at both ends by a pressure frame 86 via bearings 85. The pressing frame 86 is swingably supported by a support shaft 87 fixed to the fixing frame 84, and is urged by a pressing spring 88 as pressing means so that the pressing roller 82 is pressed against the fixing roller 81. ing.

A gear 112 is attached to one end of the fixing roller 81 so as to rotate integrally with the fixing roller 81.

The driving force is transmitted to the gear 112 from a motor 98 as a driving source via gears 97, 96, 95, 107, and 106. The gear 107 incorporates a one-way clutch (one-way clutch) 107a.
7 is rotated only in the direction of arrow 107b.
106 rotates together with 1.

Reference numeral 89 denotes a cam as a pressing force adjusting means which is driven to rotate by a motor 98. The cam 89 is fixed to both sides of a cam shaft 90 rotatably supported by the fixing frame 84, and is integral with the cam shaft 90. It is designed to rotate. The cam 89 fixed to the cam shaft 90
1, 92, 93, 94, 108, 109, 95, 96,
The motor 98 rotates through a motor 97.

A one-way clutch (one-way clutch) 109a is incorporated in the gear 109, and the gear 108 rotates integrally with the rotating shaft 110 only when the gear 109 rotates in the direction of the arrow 109b.

The fixing device 80 is configured to adjust the pressing force by adjusting the working length of the pressure spring 88 by the rotation of the cam 89.

H is a halogen heater as a heat generating means provided in the fixing roller 81, and heats the recording medium via the metal core 81b and the elastic layer 81a.

Although the fixing device 80 has other members such as a guide member for guiding the conveyance of the recording medium S, it is not a feature of the present embodiment, so that the detailed description is omitted here.

In the apparatus according to the present embodiment having such a configuration, the temperature of the fixing roller 81 is adjusted to a predetermined fixing temperature by the heat generated by the heater H, and the fixing roller 81 is stably rotated at a predetermined speed. Then, the recording medium S carrying the unfixed toner image T from the above-mentioned image forming means is introduced into the nip N, and the toner image T is transferred to the recording medium by the pressure of the nip N and the heat from the fixing roller 81. Fix to S.

Next, the pressure adjusting means will be described.

The adjustment of the pressing force between the fixing roller 81 and the pressure roller 82 is performed by a CPU 201 as a control means (switching means) as shown in FIG. The adjustment of the pressing force is performed.

The working length of the pressure spring 88 is defined by the cam 89, and is normally in the state shown in FIG.

From this state, adjustment of the pressing force (reduction of the pressing force)
Is determined by the CPU 201, the rotation direction of the motor 98 is switched to rotate in the direction of arrow 97a opposite to the direction of fixing (hereinafter abbreviated as reverse rotation), and the gear 96 moves in the direction of arrow 96a.
The gear 95 rotates in the direction of arrow 95a. Since the gear 109 rotates in the direction of the arrow 109b, the gear 109, the rotating shaft 110, and the gear 108 rotate integrally, and FIG.
The cam 89 is rotated 180 degrees as shown in FIG. As a result, the operating length of the spring 88 becomes longer, and becomes lower than the initial pressing force.

At this time, although the gear 107 rotates in the direction of arrow 107c, a one-way clutch (one-way clutch)
Since idling occurs between the rotation shaft 109a and the rotation shaft 111, the gear 106 and the rotation shaft 111 do not rotate, and the fixing roller 81 does not rotate.

When fixing is started in this state, the rotation direction of the motor 98 is switched by the CPU 201 and the gear 97 fixed to the output shaft is rotated in the direction of arrow 97a (hereinafter abbreviated as forward rotation). Gear 96 rotates in the direction of arrow 96b, and gear 95 rotates in the direction of arrow 95a. As a result, the gear 107 rotates in the direction of the arrow 107 b, so that the gear 107, the rotating shaft 111 and the gear 106 rotate integrally, and the fixing roller 8 via the gear 112.
1 can be rotated.

At this time, the gear 109 has an arrow 109c.
However, since the idle rotation occurs between the one-way clutch (one-way clutch) 109a and the rotating shaft 110, the gear 108 and the rotating shaft 110 do not rotate. Therefore, the gears 94, 93, 92, and 91 do not rotate, and the camshaft 9 does not rotate.
0 and the cam 89 do not rotate either.

Further, when the CPU (not shown) judges the adjustment of the pressing force (increase of the pressing force) from this state, the motor 9 is again activated.
8 is reversed, and the gears 97, 96, 95, 109, 10
The cam shaft 90 rotates via 8, 94, 93, 92, and 91, and as shown in FIG. 2A, the cam 89 is rotated by about 180 degrees from the state of FIG. 2B. As a result, the working length of the pressure spring 88 is reduced to the initial length, and the pressing force returns to the initial value.

In this embodiment, a stepping motor is used as the motor 98. This is the motor 98
This is because it is necessary to rotate forward and reverse, and to rotate and stop by a certain number of rotations, which is easy for a stepping motor.

Next, the determination of the pressing force adjustment by the CPU will be described. The CPU 201 includes a recording medium type detecting unit 20.
3 are connected. The recording medium type detection means 203 is a known technique, which is an optical detection means for detecting the amount of light transmitted through the recording medium, and the capacitance between the conductive rollers when the paper is passed through and sandwiched between the rollers. Any means may be used, such as an electrical detection means for detecting the thickness, a means for mechanically detecting the thickness, and the like. Further, a recording medium type input unit 204 for manually inputting the type of the recording medium may be used.

A motor driver 202 for driving the motor 98 is connected to the CPU 201 so that the rotation of the motor 98 can be controlled.

Table 1 summarizes the relationship between the type of recording medium and the optimum pressing force. The pressing force of thick paper (basis weight 100 g / m ² or more), OHT, glossy paper is high, and thin paper (basis weight 100
g / m ² ), and the pressure of the envelope is low.

[0072]

[Table 1]

The CPU 201 selects an optimum pressing force based on the detected or input type of the recording medium based on the data corresponding to Table 1 stored in the ROM 205, and compares it with the current pressing force (cam position). When it is determined that the pressing force needs to be changed, a control signal is sent to the motor driver 202, the motor 98 is rotated in the reverse direction, the cam 89 is rotated to a target position, and the pressing force is adjusted. When the adjustment of the pressing force is completed, the motor 98 rotates forward and the fixing roller 81 is driven.

According to the above configuration, the pressing force of the nip N can be set to the optimum condition in accordance with the type and thickness of the recording medium, so that sufficient fixability can be ensured and wrinkles can be prevented. The driving force from the motor 98, which is the same driving source as the fixing roller (rotating body) 81, is supplied to the CPU 201.
(Switching means) to switch the cam (pressing force adjusting means) 8
9 and selectively drive the cam 89 to adjust the pressing force, eliminating the need to use a driving source dedicated to the pressing force adjusting means, increasing the size of the apparatus, increasing the number of parts, and Cost was reduced.

In the present embodiment, the form in which the pressing force is adjusted in two steps of high and low is exemplified. However, the present invention is not limited to this. The adjustment is made in three or more steps or steplessly. Is also good.

When the power switch (not shown) of the image forming apparatus A is turned off, the power is turned off after adjusting the pressing force to a low state. By doing so, permanent deformation of the elastic layers of the fixing roller and the pressure roller can be prevented.

<Second Embodiment> A fixing device and an image forming apparatus according to a second embodiment of the present invention will be described in detail. Note that the outlines of the fixing device and the image forming apparatus are the same as those in the above-described embodiment, and thus the description of the same portions will be omitted.

The configuration and operation of the fixing device 80 according to the second embodiment will be described in detail with reference to Table 2. Table 2 shows types of recording media and driving modes of the fixing device according to the second embodiment.

[0079]

[Table 2]

In the first embodiment, the pressing force is adjusted according to the type of the recording medium S. In the present embodiment, the pressing force and the fixing roller 8 are adjusted according to the type of the recording medium S.
1 is a configuration in which the drive speed (conveyance speed of the recording medium) is adjusted.

In Table 2, thick paper 1 (basis weight 135 g / m
² ), the pressure of OHT and glossy paper is high, the driving speed is low, and the thick paper 2 (basis weight 100 g / m ² or more and less than 135 g / m ² ) is high in pressure and driving speed, and the thin paper (basis weight 100 g /
(less than m ² ), the pressure is low, the drive speed is high, and the pressure and drive speed of the envelope are low.

Next, switching of the pressing force and the driving speed will be described.

In FIG. 5, the CPU 201 first selects an optimum pressing force based on data corresponding to Table 2 stored in the ROM 205 according to the type of the recording medium detected or input, and sends a control signal to the motor driver 302. Feeding, the motor 98 is rotated in the reverse direction, the cam 89 is rotated to the target position, and the pressing force is adjusted.

When the adjustment of the pressing force is completed, the CPU 201
Selects an optimal driving speed, sends a control signal to a motor driver 302 as driving speed adjusting means, and
That is, the driving speed is adjusted so that the fixing roller 81 is driven to rotate forward at the optimum driving speed.

According to the above configuration, the pressing force and the fixing speed can be set to optimum conditions according to the type and thickness of the recording medium, so that sufficient fixing property can be ensured and wrinkles can be prevented. Even when using a recording medium such as an envelope which easily generates wrinkles and has a large heat capacity, and even when the pressing force is reduced in order to prevent the generation of wrinkles, the drive speed is reduced and sufficient heat is applied to the recording medium. Therefore, fixing can be performed completely. Further, it is possible to suppress an increase in the size of the apparatus, an increase in the number of parts, and an increase in cost due to the increase in the number of parts.

In this embodiment, the form in which the pressing force and the driving speed are adjusted in two stages of high and low, respectively, has been exemplified. However, the present invention is not limited to this. It may be adjusted in stages.

<Other Embodiments> (1) In the above-described embodiment, the roller fixing system is exemplified as the fixing device. However, the present invention is not limited to this, and it goes without saying that the present invention can be applied to a belt fixing system.

(2) As an image forming apparatus, a laser beam printer adopting an electrophotographic system has been exemplified. However, the present invention is not limited to this. For example, other image forming apparatuses such as a copying machine and a facsimile can be used. good.

(3) Although the multi-color image forming apparatus capable of forming a color image has been exemplified, the present invention is not limited to this.
For example, a monochrome image forming apparatus capable of forming a monochrome image may be used.

(4) The example in which the halogen heater is used as the heat generating means has been described. However, the present invention is not limited to this. For example, a ceramic heater or an electromagnetic induction heat generating means may be used.

(5) In the above-described embodiment, an example in which an unfixed image is permanently fixed has been described. However, the present invention is not limited to this.
May be applied to a device or the like for reforming.

(6) The present invention is not limited to the heat fixing device,
It may be a pressure fixing device.

[0093]

As described above, according to the present invention,
A fixing device and an image forming apparatus can be provided in which the apparatus is provided with a pressurizing force adjusting unit while suppressing the complexity and size of the apparatus.

Further, it is possible to provide a fixing device and an image forming apparatus which can easily form wrinkles, such as envelopes, and can perform satisfactory fixing even when using a recording medium having a large heat capacity.

[Brief description of the drawings]

FIG. 1 is a perspective view of a fixing device according to a first embodiment.

FIG. 2 is a schematic diagram of a fixing device side portion according to the first embodiment.

FIG. 3 is a schematic cross-sectional view of the fixing device according to the first embodiment.

FIG. 4 is an explanatory diagram of drive control according to the first embodiment.

FIG. 5 is a longitudinal sectional view showing a schematic configuration of an image forming apparatus according to the present invention.

FIG. 6 is an explanatory diagram of drive control according to a second embodiment.

[Explanation of symbols]

 Reference Signs List A Image forming apparatus B Process cartridge H Heater (heating means) N nip S Recording medium T Toner image 1 Photoconductor drum 2 Charging device 3 Exposure means 3a Polygon mirror 3b Imaging lens 3c Reflection mirror 4 Developing device 4A Rotating body 4Y, 4M , 4C, 4Bk Developing device 4a Coating roller 4b Developing sleeve 4c Toner regulating blade 4d shaft 5 Transfer unit 5a Intermediate transfer belt 5b Driving roller 5c Secondary transfer facing roller 5d Followed roller 5e Cleaning unit 5f Charging roller 5j Roller 5n Secondary transfer roller Reference Signs List 6 Cleaning device 7 Feeding means 7a Feeding cassette 7b Transport roller 7c Guide plate 7d Registration roller 7e Pickup member 9 Discharge transport means 9a Transport belt 9b Driving roller 9c, 9d Transport roller pair 10 Discharge tray 12 Transport Means 14 Apparatus main body 80 Fixing device 81 Fixing roller 81a Elastic layer 81b Metal pipe 82 Pressure roller 82a Elastic layer 82b Metal pipe 83, 85 Bearing 84 Fixing frame 86 Pressure frame 87 Support shaft 88 Pressure spring 89 Cam 90 Cam Shafts 91 to 97 Gear 98 Motor 106 to 109 Gear 107a, 109a One-way clutch 110, 111 Rotating shaft 112 Gear 201 CPU 202, 302 Motor driver 203 Recording medium type detection means 204 Recording medium type input means 205 ROM

Claims (13)

[Claims] 1. A fixing device for fixing an image by nipping and conveying a recording medium carrying an image by a pressing nip of rotating bodies pressed against each other by a pressing unit, wherein the pressing force of the pressing unit is variable. A fixing device, comprising: a pressing force adjusting unit that drives the rotating body. 2. The fixing device according to claim 1, wherein the driving source includes a driving speed adjusting unit that adjusts a rotation speed of the rotator. 3. A fixing device for fixing an image by nipping and transporting a recording medium carrying an image by a pressing nip of rotating bodies pressed against each other by a pressing unit, wherein the pressing force of the pressing unit is variable. Pressurizing force adjusting means,
And a driving speed adjusting means for adjusting a rotation speed of the rotating body, wherein the pressing force adjusting means is driven by a driving source for driving the rotating body. 4. The fixing device according to claim 2, wherein the driving speed adjusting unit adjusts the speed according to the type of the recording medium. 5. The fixing device according to claim 1, further comprising a drive switching unit that selectively switches between driving of the rotating body and driving of the pressing force adjusting unit. 6. The fixing device according to claim 1, wherein the pressing force adjusting unit is selectively driven. 7. The fixing device according to claim 1, wherein the pressing force adjusting unit is driven when the driving source rotates in the reverse direction. 8. The fixing device according to claim 1, wherein the pressing force adjusting unit selects a pressing force according to a type of a recording medium. 9. The fixing device according to claim 1, wherein the rotating body has a shape of a roller or an endless belt. 10. The fixing device according to claim 1, wherein the rotating body is a fixing rotating body and a pressing rotating body. 11. The image forming apparatus according to claim 1, wherein a heat generating means is provided inside at least one of the fixing rotator and the pressure rotator, and the recording medium is heated by heat from the heat generating means. The fixing device according to claim 1. 12. The fixing device according to claim 1, wherein the unfixed toner image is heated to fix the image on a recording medium. 13. An image forming apparatus comprising: an image forming unit for forming an image on a recording medium; and a fixing unit for fixing the image on the recording medium, wherein the fixing unit is used as the fixing unit. An image forming apparatus comprising the fixing device according to any one of the preceding claims.