JPH04204472A - Fixing device - Google Patents

Abstract

PURPOSE:To prevent the consumption of releasing agent from being increased, to prevent frictional force from being increased, to prevent an abnormal sound from being given and to prevent the surface of an elastic body from being damaged by bringing a releasing agent applying mechanism into contact with a fixing roller in a prescribed time from initial rotation at a warming-up time. CONSTITUTION:The releasing agent applying mechanism 63 is brought into contact with the fixing rollers 41 and 42 in the prescribed time from the initial rotation of the rollers 41 and 42 at the warming-up time. Since the temperature of the rollers 41 and 42 is not raised at the initial time of the warming-up, the rollers 41 and 42 are slid on a thermistor 71a with which the rollers 41 and 42 are brought into contact while the impregnating releasing agent does not bleed out. However, even the fixing roller 41 having the mirror elastic surface which is easily set under a high friction state by being brought into contact with the other can be prevented from being made to adhere to the thermistor 71a or the like by the releasing action of the applied releasing agent and contact friction between both of them is reduced. Thus, it is evaded without wasting oil that the abnormal sound is given caused by the shortage of lubrication or the elastic surface of the fixing roller is damaged.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fixing device that fixes a toner image transferred onto a recording material, and more specifically, a pair of fixing rollers that press each other to perform rotational heat fixing. and a release agent application mechanism that is moved toward and away from the fixing roller, one surface elastic body of the fixing roller has a substantially mirror surface, and the release agent application mechanism is separated from the fixing roller at times other than when fixing. The present invention relates to a fixing device.

(Prior Art) This type of fixing device is mainly used in image forming apparatuses such as electrophotographic copying machines and laser beam printers that form color images. Formation of a color image by this device is performed by combining toner images of different colors, and when these toner images are thermally fixed, the toner is melted to perform color combination and obtain a color image.

In a fixing device that performs such fixing, the fixing roller is required to have high surface smoothness. This is because surface smoothness greatly affects the gloss and image quality of color images and the color reproducibility of transmitted images.

Therefore, the surface of the fixing roller on the side that contacts the toner image bearing surface on the transfer side has a substantially mirror surface. Furthermore, the gloss and image quality of a color image are affected by the viscosity of the toner used for color image formation, and the viscosity of the toner resin used for color image formation is lower than usual.

This is because it is necessary to fix an image with a large amount of toner adhesion compared to a monochrome image. This low viscosity toner easily adheres to the surface of the elastic body. To solve this problem, it is necessary not only to improve the release properties of the roller surface material, but also to apply a release agent to the surface, and a release agent application mechanism is provided.

This release agent application mechanism is designed to be able to come into contact with and separate from the fixing roller so that the release agent can be applied only when necessary, that is, only during fixing, in order to avoid indiscriminate consumption of release agent. .

Furthermore, regarding the color reproducibility of transparent images formed on transparent sheets used for documents for overhead projectors (hereinafter referred to as OHP), the toner image is fixed as a uniform surface, and the light image is It is important to suppress scattering during transmission within the interior. In order to satisfy this requirement, the surface material of the fixing roller whose surface is substantially mirror-finished is made of an elastic material.

(Problem to be Solved by the Invention) A thermistor is in contact with the surface of the fixing roller that performs thermal fixing in order to control the fixing temperature. The elastic surface of the fixing roller, which has a concave mirror surface, is highly smooth and therefore tends to come into close contact with the thermistor and the like that are in contact with it.

For this reason, if the applied mold release agent is insufficient, the frictional force between the thermistors and the like increases, causing abnormal noises and easily damaging the surface of the elastic body.

The inventors have experienced the occurrence of abnormal noises and scratches from time to time when using the conventional apparatus as described above. After repeated experiments on this issue, it has been found that the occurrence of abnormal noises and scratches is concentrated in the early stages of the warming amplifier of the developing device when the power is turned on first thing in the morning. This is because the release agent is not applied to the fixing roller when not fixing, and when the fixing roller is hot, the release agent impregnated bleeds out and exerts a release effect, but at low temperatures, the release agent bleeds out. This seems to be due to the fact that there is no.

Therefore, the present invention is based on such knowledge, and only at extremely limited timing when the image forming apparatus is used.
To provide a fixing device which can solve the above-mentioned problems without unnecessarily increasing the consumption of the releasing agent by applying a releasing agent regardless of whether fixing is not performed. This is the issue.

(Means for Solving the Problems) In order to achieve the above-mentioned problems, the present invention provides a pair of fixing rollers that rotate and perform heat fixing while in pressure contact with each other, and a release agent that is brought into contact with and separated from the fixing rollers. In a fixing device including a coating mechanism, in which one surface elastic body of the fixing roller has a substantially mirror surface, and the release agent coating mechanism is separated from the fixing roller at times other than fixing, the fixing roller rotates during warming up. The present invention is characterized in that the release agent application mechanism is brought into contact with the fixing roller for a predetermined period of time from the beginning.

(Function) Normally, the release agent application mechanism is activated only when fixing is performed and applies release agent to the surface of the fixing roller, so the toner on the transfer material adheres to the surface of the fixing roller and causes offset. This will prevent things like this from happening. In particular, when the power is turned on to an image forming apparatus, if a warming-up is performed that involves rotation so that the fixing roller quickly and uniformly reaches a predetermined temperature, the initial rotation of the fixing roller during this warming amplifier is limited. During the predetermined period of time, the release agent application mechanism is activated to apply the release agent to the surface of the fixing roller. The fixing roller will come into sliding contact with the thermistor, etc. that it is in contact with without bleed-out, but even if the fixing roller has a mirror-like elastic surface that is likely to come into close contact with other objects and cause a high friction state, the applied release agent can be released. The mold action prevents close contact with the thermistor etc. and reduces contact friction between the two.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a color copying machine 1 equipped with a developing device to which the present invention is applied. To give you an overview of this,
The copying machine 1 is equipped with four developing devices. An original placed on an original glass 2 is exposed to light by an exposure lamp 3 and a lens array 4 to a CCD line sensor 5, and is read as a color signal. This color signal is converted by the image processing circuit into a 3- or 4-value signal of Y (yellow), M (magenta), C (cyan), or K (black) added thereto, and the laser optical system 6 is transmitted as an output signal. The copying machine 1 of this embodiment does not have an image memory for three colors, and the image reader unit 7 repeats scanning every time when forming an image for each color, and based on this, the
, M, C or Y, M, C, are transmitted to the laser optical system 6.

The laser optical system 6 includes a scanning polygon mirror 8, an fθ lens 9, a reflection mirror 10, etc., and emits laser light for image formation of each color based on the Y, M, C, or Y, M, C, signals. Exposure is performed by irradiating the photosensitive drum 11 with light. The photosensitive drum 11 is rotationally driven in the direction of the arrow.

The surface of the photosensitive drum 11 is provided with an organic optical semiconductor laminated on a conductive substrate, and is particularly sensitive to the wavelength of laser light used. Further, in this embodiment, the photosensitive drum 11 is negatively charged by the charging charger 12. Photosensitive tram 1
1, there are a drum cleaner 13, a toner collection roller 14, an eraser lamp 15, and a charging charger 12.
are arranged, and four types of developing devices are also arranged. The first developing device 16 is cyan, the second developing device 17 is centered, the third developing device 18 is yellow, and the fourth developing device 1 is
Reference numeral 9 supplies black toner, and these toners are negatively charged.

Toner supply to each developing device 16 to 19 is performed by each developing device 1.
Toner of each color stocked in toner hoppers 20a to 20d corresponding to 6 to 19 is transported to each developing device 16 to 19 as appropriate via a 1 toner conveying pipe (not shown) according to each toner replenishment signal. It is done by being done.

Recording materials 56 such as plain paper and OHP paper are stored in the paper feed cassette 2.
1a, 21b in a stacked state, or are set one by one in the manual paper feed center 80, and the paper feed rollers 22a,
22b or the like, the sheets are fed one by one into the inside of the copying machine. Then, the tip of the recording material 56 is connected to the registration roller 2.
By temporarily stopping the recording material 56 when it comes into contact with the recording material 3, the subsequent timing is measured, and skew correction is performed at the same time. A paper sensor 24 is used for this purpose.

In order to sequentially transfer the C, M, and Y images formed on the photosensitive drum 11 onto the recording material 56, a transfer drum 25 is provided in the transfer section and is driven to rotate in the direction of the arrow. The transfer drum 25 has a chucking claw 31 on its outer periphery for gripping the recording material 56, and has a suction charger 26, a transfer charger 27,
A separation charger 28 is arranged. Further, a separation charger 30 is arranged outside the transfer drum 25 opposite to the separation charger 28 .

L, - Goo optical system 6 The photosensitive tram 1 is exposed to light.
The electrostatic latent image formed on the image forming apparatus 1 is visualized by each of the developing devices 16 to 19 using a so-called reversal development method.

On the other hand, the recording material 56 fed from the registration roller 23 is gripped by the chunking pawl 31 on the transfer tram 25, and is electrostatically wound onto the transfer drum 25 by the suction charger 26 as the transfer tram 25 rotates. . Then, the recording material 56 is transferred to the transfer charger 27.
and the photosensitive drum 11.
The toner image formed thereon is transferred to the recording material 56.

When obtaining a color image, the transfer drum 2 is placed on the recording material 56.
5, four transfer steps are performed one after another. After the transfer process has been completed, the recording material 56 is neutralized by the separation charger 28 , 30 , separated from the transfer drum 25 by the separation claw 32 , and fed to the fixing device 40 by the transport deck 33 .

The fixing device 40 includes an upper fixing roller 41 and a lower fixing roller 42.
, a cleaning roller 43, 44, an oil application unit 60, a separating claw 45, 46, an oil recovery blade 47, etc. The toner image transferred and formed on the recording material 56 is heated by upper and lower fixing rollers 41, 42. It is pressurized, fixed on the recording material 56, and discharged onto the paper discharge tray 35.

Further, as shown in FIGS. 2 and 3, the oil application unit 60 lubricates the nearly mirror-like elastic surface of the upper fixing roller 41 to reduce contact friction with the thermistor 71 and to offset the toner. It is made up of oil supply rollers 61, 62, oil application rollers 63, oil regulation plates 64, etc. Oil tank 365
The silicone oil as a mold release agent stored in
The oil is pumped up to the top and leveled by the oil regulating blade 64 to ensure an appropriate amount of application. Further, the oil application roller 63 is brought into pressure contact with the upper fixing roller 41 by a pressure contact control cam 65 that is driven in accordance with the timing when the recording material 56 is fed to the fixing device 40 and the timing of the initial rotation of the fixing roller when the power is turned on. Alternatively, the separation is controlled and the supply of oil to the upper fixing roller 41 is controlled.

Furthermore, the oil regulating blade 64 also has an oil application roller 6 to prevent foreign matter from adhering to the oil regulating blade 64.
The pressure contact and separation with respect to 3 are controlled by a pressure contact control cam 66. Note that 71a is a thermistor in contact with the lower fixing roller 42.

The mechanism for performing the above control will be described in detail. The oil application roller 63 is supported by a swing frame 73 together with oil supply rollers 61 , 62 that supply oil thereto, and this swing frame 73 is pivotally supported by a shaft 74 on a fixed bracket 75 . The fixed bracket 75 bears a rotary ring 76 of the pressure contact control cam 65,66. Further, the oil regulating blade 64 is pivotally supported by the swing frame 73 at its base frame 376 by a shaft 77.

The swing frame 73 and the base frame 376 are biased clockwise in FIG. 2 by a spring 78 acting between them.
The respective driven pieces 73a and 76a are in pressure contact with the pressure contact control cams 65 and 66. As a result, the swing frame 7
3 and the base frame 376 are their passive pieces 73a.
, 76a, the swing frame 73 moves the oil application roller 63 toward and away from the upper fixing roller 41. Further, the base frame 376 is swung on the oscillating frame 73 to cause the oil regulating blade 64 to approach and separate from the upper fixing roller 41 .

The pressure contact control cams 65 and 66 that perform this contact and separation are on the cam operation side shown in FIGS. 4 and 5. This is done by the al1 mechanism.

Drive from the main motor (not shown) is through gears 81 and 82.
It is transmitted to the spring clutch 83 via .

This spring clutch 83 is of a normally closed type. This clutch 83 has an outer cylinder 86 having pawls 86a at two locations on the circumference, and is connected to one end of a spring 87. In this state, the spring 87 is also tightened by the rotation of the gear 820, and the rotation cannot be transmitted to the cam drive shaft 89.

In other words, it is in an off state.

The clutch control pawl 88 is connected to the spring 92 by the solenoid 91.
When the outer cylinder 86 is rotated against the above-described locking, the spring 87 is immediately tightened and becomes an on state in which the rotation of the gear 82 is transmitted to the cam drive shaft 89.

Since the solenoid 91 is turned off again when the lock is released, the clutch control pawl 88 is biased by the spring 92 so that the pawl 86
It is immediately returned to the alignment position with a.

Therefore, when the cam drive shaft 89 to which the rotational force has been transmitted rotates half a rotation, the pawl 86a engages with the clutch control pawl 88 and locks the outer cylinder 86, so that the spring clutch 83 is automatically turned off. be done.

Therefore, each time the solenoid 91 is turned on, the spring clutch 83 rotates the cam drive shaft 89 by half a rotation due to the rotation of the main motor. At the solid line position in FIG. 2, the oil application roller 63 is separated from the upper fixing roller 41, and the oil regulating blade 64 is separated from the oil application roller 63 and is in a non-operating state. In this state, when the solenoid 91 is turned on, the pressure control cams 65 and 66 are rotated half a turn to the position of the imaginary line, and the pressure control cam 66 is moved to the oil regulating blade 64.
After the oil application roller 63 is brought into pressure contact with the oil application roller 63, the pressure contact control cam 65 brings the oil application roller 63 into pressure contact with the upper fixing roller 41.

As a result, the oil application roller 63 is brought into pressure contact with the upper fixing roller 41 after the amount of oil supplied from the oil supply rollers 61 and 62 is regulated, and oil is applied to the upper fixing roller 41.

Therefore, no excess oil is applied to the upper fixing roller 41 even for a moment.

This oil application is applied during a predetermined period of time at the beginning of the rotation of the fixing rollers 41 and 42 when the copier 1 is powered on first thing in the morning and the fixing rollers 41 and 42 are warmed up. 1 is performed during image formation for a predetermined time t2 when the recording material is passed through the fixing rollers 41 and 42 for fixing (FIG. 12). The oil application roller 63 is pressed against the upper fixing roller 41 by the cam drive shaft 8
This is confirmed by the position detection sensor 96 detecting the position display piece 95 provided at the position indicator 9 .

The oil application during t1 is to lubricate between the upper fixing roller 41 and the thermistor in contact with it at the initial stage when the fixing rollers 41 and 42 are warmed up.
Initially, the temperature is low and the impregnated oil does not bleed out, so the nearly mirror-like elastic surface of the upper fixing roller 41 comes into close contact with the thermistor 71, creating a high friction state, which may cause abnormal noise or It is possible to avoid damage to the body surface.

However, the oil supply roller 61 during warming up.
62. The oil application roller 63 is driven by the drive mechanism 101 along with the drive of the main motor, but since it takes some time to reach the oil application roller 63 via the oil supply rollers 61 and 62, the oil application roller 63 is not used during warming up. 61.62. In order to prevent unnecessary friction, it is preferable to delay the pressing of the oil regulating blade 64 against the oil applying roller 63 from the start of rotation of the oil applying roller 63 until the oil reaches the oil applying roller 63. The - side fixing rollers 41 and 42 start rotating during the warming amplifier, and there is a slight delay in the time when the elastic surface of the upper fixing roller 41 comes into close contact with the thermistor 71 and an abnormality occurs. If the oil application timing is delayed from this point, it is preferable to delay the start of rotation of the fixing rollers 41, 42 during warming up by the amount of the delay.

The oil application during the time t2 during the fixing is to prevent toner on the recording material from adhering to the elastic surface of the upper fixing roller 41 and causing offset.

At this time, the oil application roller 63 is attached to the oil regulating blade 64.
Since the upper fixing roller 41 is pressed against the upper fixing roller 41 with the amount of oil being regulated by the pressure contact, no excess oil is applied to the upper fixing roller 41. Therefore, it is possible to avoid spoiling the transparency of images formed on OHP paper due to excessive oil. Further, the timing is adjusted so that the recording material enters the fixing rollers 41 and 42 at the same time that the starting point of oil application on the upper fixing roller 41 reaches the fixing position opposite to the lower fixing roller 42.

As a result, the oil applied to the upper fixing roller 41 reaches the fixing position almost at the same time that fixing starts.
It is possible to reliably prevent the toner on the recording material to be fixed from adhering to the surface of the upper fixing roller 41, and the oil applied to the upper fixing roller 41 is transferred to the lower fixing roller 42 before the start of fixing. It is possible to avoid a situation in which the fixing roller reaches a position facing the lower fixing roller 42 and is wasted.

When the solenoid 91 is turned on again in the oil application state in the various cases described above, the pressure contact control cam 65.6
6 is rotated half a turn from the state shown by the imaginary line in FIG. 2 to the original solid line position, and the pressure contact control cam 65 separates the oil application roller 63 from the upper fixing roller 41 to immediately stop oil application, and then the pressure contact control cam 65 moves the oil application roller 63 away from the upper fixing roller 41 and immediately stops oil application. A cam 66 separates the oil regulating blade 64 from the oil application roller 63. It is preferable to set the timing for stopping oil application during fixing according to the size of the recording material to be fixed. According to this, the oil finally applied to the upper fixing roller 41 is applied to the fixing roller 41 regardless of the size of the recording material.
When the rear end of the recording material is fixed at 42, it reaches the part facing the lower fixing roller 42, and the supply of oil is completed with just the right amount.

Note that oil supply rollers 61 and 62, oil application roller 6
The drive mechanism 101 of No. 3 has a roller 61 as shown in FIG.
．． 63 at one end thereof, and a passive gear 105 directly connected to the other end of the uppermost oil application roller 63. Among the three connecting gears 102 to 1o4, the oil rotates from the lowest gear 1゜2, which is immersed in oil, so if an external gear for driving is engaged with any of them, this external gear will also be rotated. This will cause the oil to circulate and drip onto the outside. Therefore, a passive gear 105 directly connected to the uppermost roller 63 is provided,
The rotation of the drive gear 106 that meshes with an external gear and receives the drive of the main motor is controlled by the drive shaft 107 and the gear train 1.
The information is transmitted via 08. and drive gear 1
Since the transmission system from 06 to the gear train 108 is floating above the oil, it is possible to prevent the oil circulating around the connecting gears 102 to 104 from leaking out through the drive system.

The cleaning rollers 43, 44, which are in pressure contact with each of the fixing rollers 41, 42,
In particular, toner and paper powder that adhere to the surface of the upper fixing roller 41 little by little are removed without impairing the surface smoothness that is provided to ensure the quality of the transparent image formed on the OHP recording material 56 of the upper fixing roller 41. There is a need. In addition, it is preferable to take measures to prevent the generation of foreign matter such as hair when removing the cleaning material, which causes uneven oil application.

However, as conventional cleaning members, cleaning webs, release agent-filled rollers, release agent-impregnated rollers, and the like have been put into practical use. The materials used for the surface materials in all of these cleaning members are 1, mainly those using fibers. The fibers used here have a large fiber diameter and easily fall off and transfer to the fixation. In particular, when the surface elastic body has a high surface smoothness such as the surface roughness of the upper fixing roller 41, which is in contact with the upper fixing roller 41, for example, R2≦2 μm, conventionally used nonwoven fabrics, flocked cloth, etc. cannot prevent this hair loss. It is impossible to do so, and the roller surface will be damaged by the fibers. Furthermore, if an excessive amount of resin or the like is added between the fibers to prevent shedding, the original cleaning properties will be impaired. Therefore, the leaning characteristic described above cannot be obtained.

In order to satisfy this requirement, in this embodiment, as shown in FIG.
A cleaning surface material 114 and a roller core 11
Good results were obtained when 3 was a cylindrical body made of metal or heat-resistant resin, and the cleaning surface material 114 was wrapped with Miracle or Ecsaine (trade name, manufactured by Toshi Co., Ltd.). In short, as the surface material of the cleaning member, it is preferable to use a nonwoven fabric or a woven fabric whose surface member is mainly composed of polyester fibers having a diameter of 5 μm or less.

In addition, as shown in FIG. 7, cleaning rollers 43 and 44
, the roller core 113 and the cleaning surface material 114
By providing the intermediate elastic body 115 between the fixing rollers 41 and 42, the contact stress with the fixing rollers 41 and 42 was reduced and cleaning performance was improved. The intermediate elastic body 115 is preferably made of silicone rubber, fluorine rubber, silicone sponge, or the like.

Further, it is common practice to operate the fixing speed and the system speed at different speeds. For example, by setting the system speed at the time of warming up and forming a monochrome image, the temperature of the surface of the fixing roller 41, 42 is set early during warming up to achieve a uniform temperature, and at the same time, the formation speed of the monochrome image that does not satisfy a predetermined image quality is reduced. Don't be late. On the other hand, when forming a color image, the speed is reduced to 172 of the system speed when the recording material reaches the position just in front of the fixing device so that toner images of different colors can be sufficiently combined. Further, when forming a color image on OHP paper, the speed is further reduced to 1/4 of the system speed in order to obtain an image with particularly low light dispersion.

In this way, if you try to operate the fusing speed at a speed different from the system speed of the device, the distance from the transfer position of the developed image from the photoreceptor to the recording material to the fusing device is the maximum that the device can use. It becomes necessary to design the paper to be longer than the length of the paper.

For this reason, it is important to perform the speed change from the system speed to the fixing speed in the paper transport section as close to the fixing device as possible in order to downsize the device.

However, during gear shifting, it is unavoidable that the shifting speed will fluctuate due to mechanical or electrical factors in the transmission device.

This variation does not have a large effect on the paper passing stability of ordinary paper, but it has a great effect on the paper passing stability of resin paper such as MI bHP paper. This effect is particularly noticeable in a fixing device where oil is applied because the applied oil prevents the fixing roller from entering.

Therefore, in this embodiment, when the recording material 56 is fed to the fixing device 40, the transport deck 33, the upper and lower fixing rollers 41, 42
The conveying speed is changed to a preset fixing speed.

In that case, the sensor provided on the transport deck 33 = 121
Shifting is performed by time control based on the signal from (Fig. 1) (Fig. 12).

In the case of plain paper, the clutches 131 and 132 perform a speed change operation after a predetermined time t4 from the time when the signal from the sensor 121 is input. Then, when the time required for the paper to be ejected has elapsed, the system speed is restored again.

In the case of OHP paper, after the optical chunking sensor 122 (FIG. 1) arranged on the transfer drum 25 determines that the paper is OHP paper, it is processed only by the clutch 132 after L5 from the time when the signal from the sensor 121 is input. A gear shifting operation is performed (FIG. 12). Then, when the time required for the paper to be ejected has elapsed, the system speed is restored again.

It goes without saying that the time difference t between t4 and t5 is sufficient time for the speed fluctuation during gear shifting to become small.
In the color copying machine 1, it is approximately 1.5 seconds.

Further, detection of OHP paper, etc. may be performed based on a designation signal from the user.

The speed switching of the fixing device as described above is performed together with the transport deck 33 that supplies recording to the fixing device, so as to avoid problems in transferring recording materials between them. FIG. 8 shows a transmission device for changing the speed. I will discuss this. This device consists of two spring clutches 1
31.132, clutch control pawl 133 that controls these
．． 134, and the clutch control pawl 133.134
are operated by solenoids (not shown), respectively.
The spring clutch 131 is a normally open type, and the spring clutch 132 is a normally closed type.

In the normal state where the spring clutches 131 and 132 are not operating, the drive from the main motor is from drive gear 135 to gear 136, 137, and gear 138.1.
39 and is transmitted to the fixing device 40 and the transport deck 33.

When the recording material is ordinary paper, the clutch control pawls 134 and 135 act on the spring clutches 131 and 132 as the recording material enters the fixing device 40, and the spring clutch 1
31 is turned on and spring clutch 132 is turned off.

Therefore, the drive is from gear 135 to gears 141 and 142.
, gears 13L and 139.

When the recording material is OHP paper, the clutch control pawl 134 is activated by the spring clutch 13 as the recording material enters the fixing device 40.
2. Therefore, the drive is transmitted from the gear 135 to the gears 143, 144 and 138, 139.

This allows the above-mentioned high-speed operation to be performed.

9 and 10 show an overall view and a partially enlarged view of the operation panel 201 provided in the color copying machine 1. As shown in FIG.

Referring to FIG. 9, an operation panel 201 includes a print start key 202 for starting a copying operation, an interrupt key 203 for specifying interrupt copying, and a clear/stop key 20.
4. All reset key 205, numeric keypad 206, set key 207, cancel key 208, various function keys 209.212, jog dials 213.214. for setting areas during trimming and masking.
A display unit 21 consisting of a liquid crystal display, etc., which displays the original image and various messages in order to set the 93 area.
5 is provided. Here, function key 20
9 to 212 perform magnification designation, paper designation, density adjustment, and the like. FIG. 1O shows an example of the display on the display section 215. If you press the function key 209 here, magnification specification mode 21
When 0 is pressed, paper designation mode 211 is pressed, and the mode shifts to density adjustment mode. For example, in case of paper specification mode, display section 2
15 displays A3, B4, A4, and B5 in correspondence with function keys 209 to 212, and allows the paper size to be selected using the function keys.

FIG. 11 is a block diagram of a control circuit for controlling the various operations, in which each input/output element is connected to the CPU 301, and control regarding the fixing device is performed according to the time chart shown in FIG. 12.

Note that the use of OHP paper may not be detected by the chucking sensor, but the operation corresponding to the P mode designation key 302 provided on the operating panel 201 may be operated to perform the operation corresponding to the P mode designation key 302 provided on the operating panel 201.

In this embodiment, the oil application mechanism is operated for a predetermined time when the fixing roller is warmed up when the power is turned on, but if the power is turned on again relatively quickly after the last use. , the fixing roller may be in a state where oil lubrication is possible due to bleed-out even though the temperature has not dropped significantly. In such a case, oil application can be omitted based on temperature information from the fixing roller. On the other hand, even if the operation is to be resumed after a problem has been resolved, it is preferable to apply oil when the fixing roller is warmed up at a temperature below a predetermined temperature.

(Effects of the Invention) According to the present invention, the power is not turned on to the image forming apparatus except when the release agent applying mechanism is activated during fixing to apply the release agent to the surface S of the fixing roller. When using
When a warming amplifier with rotation is performed so that the fixing roller quickly and uniformly rises to a predetermined temperature, a release agent application mechanism is activated for a limited predetermined period of time from the initial rotation of the fixing roller during warming up. Since the release agent is applied to the surface of the fixing roller, the temperature of the fixing roller is still raised at the beginning of the warming amplifier, and therefore the roller comes into sliding contact with the thermistor, etc. in contact without bleeding out of the impregnated release agent. However, even if the fixing roller has a mirror-like elastic surface that tends to come into close contact with other objects and cause high friction, the releasing action of the applied release agent prevents it from coming into close contact with the thermistor, etc. Contact friction can be reduced, without wasting oil and preventing abnormal noises caused by insufficient lubrication between the elastic surface of the fixing roller and the thermistor, etc. in contact with it, and scratches on the elastic surface of the fixing roller. It is possible to avoid this.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of a color copying machine equipped with a developing device to which the present invention is applied, Fig. 2 is a cross-sectional view showing the oil application mechanism of the fixing device, and Fig. 3 is a driving force transmission of the oil application mechanism. A perspective view showing the system, FIG. 4 is a sectional view of the driving force connection/disconnection mechanism of the oil application mechanism, FIG. 5 is a side view of the connection/disconnection operation mechanism of the driving force connection/disconnection mechanism, and FIGS. 6 and 7 are respectively 8 is a cross-sectional view of the speed switching mechanism of the fixing device, FIG. 9 is a front view of the operation panel of the copying machine, and FIG. 10 is a part of the operation panel. It is an enlarged view. FIG. 11 is a block diagram of the control circuit, and FIG. 12 is a time chart of operations related to the fixing device.

Claims (1)

[Claims] (1) A pair of fixing rollers that rotate while in pressure contact with each other to perform heat fixing, and a release agent application mechanism that is brought into contact with and separated from the fixing rollers, the elastic surface of one of the fixing rollers having a substantially mirror surface; In a fixing device in which the release agent application mechanism is separated from the fixing roller except during fixing, the release agent application mechanism is brought into contact with the fixing roller for a predetermined period of time from the initial rotation of the fixing roller during warm-up. A fixing device characterized by: