JPH0588583A - Fixing device - Google Patents

Abstract

PURPOSE:To resolve the problem of the rubbing of a fixing roller against a temperature sensor or a releasing agent recovery means, coming into contact with the fixing roller, even if the quantity of releasing agent bleeding out from the surface of the fixing roller is less, at the time of starting warming up the fixing roller. CONSTITUTION:In a fixing device 40 provided with a pair of fixing rollers 41, 42 press-contacted each other and rotated, a releasing agent coating means 63 contacted/uncontacted to the fixing rollers 41, 42, and a temperature sensor 71 coming into contact with the fixing rollers 41, 42 and detecting their temperatures, and executing warming-up control for rotating/driving the fixing rollers 41, 42 until they starts the electrification to heaters UH, LH, and then, obtains a prescribed temperature, the temperature sensor 71 can be contacted/ uncontacted to the fixing rollers 41, 42, and when a warming-up starts, the temperature sensor 71 is separated from the fixing rollers 41, 42, until the releasing agent coating means 63 is brought into contact with the fixing rollers 41, 42 for a fixed time, and the top end positions of the releasing agents with which the surfaces of the fixing rollers 41, 42 are coated reach a position where the temperature sensor 71 faces the fixing rollers 41, 42, as a characteristic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device, and more particularly, to a pair of fixing rollers which rotate in pressure contact with each other, a release agent applying means which separates and contacts the fixing rollers, and a fixing roller which contacts the fixing rollers. The present invention relates to a fixing device that includes a temperature sensor that detects the temperature of a fixing roller, and that performs warming-up control that rotationally drives the fixing roller after the heater starts energizing and reaches a predetermined temperature.

[0002]

2. Description of the Related Art This type of fixing device is mainly used for electrophotographic copying machines or laser beam copying machines for forming color images.
Used in image forming apparatuses such as printers.

An electrophotographic copying machine or printer is equipped with a fixing device for fixing the toner image transferred from the photoconductor to a recording material. As a general fixing device, a device including a pair of fixing rollers is known.

A heater is built in at least one of the fixing rollers. By the heating by the heater, the toner image on the sheet passing through the nip portion of the pair of fixing rollers is heated and melted and fixed on the recording material.

In order to fix the toner image, the fixing roller needs to reach a predetermined surface temperature, and the surface temperature of the fixing roller is required to be uniform.

In order to satisfy this, warming-up control is performed in which the fixing roller is rotationally driven until the heater reaches a predetermined temperature after the energization of the heater.

Conventionally, in such a fixing device, in order to prevent the offset of the toner to the fixing roller, a releasing agent applying mechanism for applying a releasing agent or an offset preventing agent to the fixing roller is provided. ..

This release agent application mechanism is brought into contact with and separated from the fixing roller, and contacts the fixing surface area where the image is fixed, facing the sheet fed into the nip portion of the fixing roller, for example, and releases the release agent. It is applied and the others are separated. This makes it possible to avoid applying extra release agent.

On the other hand, when images of different colors are combined to form a color image, gloss, image quality, and translucent color reproducibility are required, and the fixing roller is required to have high surface smoothness.

The glossiness and image quality of a color image are also affected by the viscosity of the toner used to form the color image, and the viscosity of the toner resin used to form the color image is lower than that of the monochrome image. Is used.

This is because it is necessary to fix a toner image having a large amount of adhesion as compared with a monochromatic image, and thus offset is likely to occur. In order to prevent this, it is indispensable not only to improve the releasing property of the fixing roller surface, but also to apply the releasing agent to the fixing roller surface.

Further, regarding the color reproducibility of the translucent image, it is important to fix the toner image as a uniform surface and suppress the scattering of the transmission of light in the image. Therefore, the surface of the fixing roller becomes elastic. It is also necessary to make it a surface material that you have.

Therefore, in order to obtain an elastic surface having excellent smoothness, the surface material of the fixing roller is made of silicone rubber or the like.

[0014]

However, as described above, the surface of the elastic body having excellent smoothness has a large contact friction with the temperature sensor or the like contacting with the surface of the elastic body, and when the release agent is insufficient, an abnormal noise is generated. Or, the surface of the elastic body is scratched to affect the fixed image.

When the above-mentioned silicone rubber is used on the surface of the elastic body, when the surface of the elastic body is in a high temperature state, the release agent bleeds out from the inside of the elastic body, so that the occurrence of abnormal noise and scratches is reduced. ..

However, when it is left at room temperature,
Bleed-out of the release agent is small, and noise and scratches are likely to occur during warming up.

Therefore, it is possible to apply a release agent at the start of warming up. However, simply doing so requires some time for the applied release agent tip to reach the portion where the temperature sensor of the fixing roller and the release agent collecting member are in contact, so there is a difference during that time. Sound and scratches may occur.

In view of these points, it is an object of the present invention to provide a fixing device which can eliminate the generation of abnormal noise and the damage on the surface of the fixing roller during warming up.

[0019]

In order to solve the above problems, the present invention provides a pair of fixing rollers that rotate in pressure contact with each other, a release agent applying means that separates and contacts the fixing rollers, and a fixing roller. And a temperature sensor for detecting the temperature of the fixing roller, and in the fixing device for performing warming-up control for rotationally driving the fixing roller from the start of energization of the heater to a predetermined temperature, the temperature sensor is used as a fixing roller. When the warm-up is started, the release agent applying means is kept in contact with the fixing roller for a certain period of time, and the tip of the release agent applied to the surface of the fixing roller is located at the position where the temperature sensor and the fixing roller face each other. Until you reach
It is characterized in that the temperature sensor is separated from the fixing roller.

It is possible to stop energizing the heater of the fixing roller while the temperature sensor is separated from the fixing roller, and to stop the detection and display of troubles related to the fixing temperature.

At least one surface elastic body of the fixing roller may be an elastic roller having a surface roughness R _Z ≦ 2 μm and high surface smoothness.

Further, a releasing agent collecting means for contacting the fixing roller and collecting an excessive amount of the releasing agent on the fixing roller is provided so as to be capable of coming into contact with the fixing roller, and when warming up is started,
Alternatively, the release agent collecting unit may be separated from the fixing roller until the tip of the release agent applied to the surface of the fixing roller by the release agent applying unit reaches the position where the release agent collecting unit and the fixing roller face each other. it can.

[0023]

According to the above-mentioned structure of the present invention, at the start of warming up from room temperature, the release agent applying means is in contact with the fixing roller for a certain period of time to apply the release agent thereto.
Even if the surface temperature of the fixing roller is low and the bleed-out of the releasing agent from the surface elastic body of the fixing roller is small, it is possible to supply a sufficient amount of the releasing agent, and the releasing agent applied on the surface of the fixing roller. The temperature sensor is kept away from the fixing roller until the tip position of the agent reaches the position where the fixing roller and the temperature sensor face each other. Therefore, it is possible to prevent the release agent from running out when the temperature sensor comes into contact with the surface of the fixing roller and detects the temperature at the start of warming up.

While the temperature sensor is separated from the fixing roller, if the energization of the heater of the fixing roller is stopped, or the detection and display of troubles related to the fixing temperature are stopped, the temperature of the fixing roller cannot be detected. It is possible to prevent the danger that the heater of the fixing roller is energized in a state where the temperature control is impossible, or avoid wasteful detection and display of troubles.

When the surface roughness of at least one surface elastic body of the fixing roller has a high smoothness of R _Z ≤2 μm, the glossiness of the color image, the image quality and the translucent color reproducibility are well guaranteed, Also, it is possible to prevent the offset when a low-viscosity toner resin is adopted as the developer, and even such a high smoothness fixing roller is caused by the contact friction with the temperature sensor depending on the coating state of the release agent. It is possible to prevent abnormal noise and scratches.

Further, when a release agent collecting means for contacting the fixing roller and collecting the excess release agent on the fixing roller is provided, this can also be brought into contact with the fixing roller and fixed at the start of warming up. The releasing agent collecting means is separated from the fixing roller until the tip of the releasing agent applied to the roller reaches the position where the releasing agent collecting means and the fixing roller face each other, and the releasing agent on the fixing roller is sufficiently applied and supplied. Since the mold release agent collecting means contacts the fixing roller and collects the excess mold release agent at the start of warming up, the mold release agent becomes insufficient and abnormal noise or scratches occur. This can be avoided.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 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 fixing device to which the present invention is applied. The original placed on the original glass 2 is CCD by the exposure lamp 3 and the lens array 4.
The line sensor 5 is exposed and read as a color signal. This color signal is converted into Y (yellow), M (magenta), C (cyan), or K by the image processing circuit.
It is converted to a signal with (black) added.

The copying machine 1 of the present embodiment does not have an image memory for three colors, and the image reader unit 7 repeats scanning each time when forming an image of each color, and based on this, Y,
M, C or Y, M, C, K signals are transmitted to the laser optical system 6.

The laser optical system 6 is a polygon mirror 8, f
A θ lens 9 and a reflection mirror 10 are provided, and a laser beam modulated based on the Y, M, C or Y, M, C, K image signals is irradiated toward the photosensitive drum 11 to perform exposure. ..

Around the photosensitive drum 11, a drum cleaner 13, a toner collecting roller 14, an eraser lamp 15 and a charging charger 12 are arranged, and four kinds of developing devices are arranged. The photosensitive drum 11 is a charging charger.
It is negatively charged by 12.

The first developing device 16 is cyan, and the second developing device 17 is
Is magenta, third developing device 18 is yellow, and fourth developing device
Numeral 19 supplies black translucent toners, respectively, and these toners are negatively charged.

The electrostatic latent image formed on the photosensitive drum 11 by the image exposure by the laser optical system 6 is developed by the developing machines 16-19.
Each is visualized by a so-called reversal development method.

Toner supply to the developing devices 16 to 19 is carried by transporting the toner of each color stocked in the toner hoppers 20a to 20d corresponding to the developing devices 16 to 19 through a toner transport pipe (not shown). It is done by doing.

The recording materials 56 of plain paper and OHP sheets are stored in the paper feed cassettes 21a and 21b in a stacked state or set one by one in the manual feed tray 80 and copied one by one by the paper feed rollers 22a and 22b. It is fed toward the inside of the device of the machine 1.

The leading end of the recording material 56 is the register roller 23.
The recording material 56 is temporarily stopped at the time when it abuts on the sheet, and the subsequent timing is achieved, and at the same time, the skew is corrected. The paper sensor 24 is used for this purpose.

C, M, Y formed on the photosensitive drum 11
In order to sequentially transfer the respective K toner images to the recording material 56, a transfer drum 25 is provided at the transfer portion and is rotationally driven in the direction of the arrow. The transfer drum 25 has a chucking claw 31 on its outer peripheral portion for gripping the recording material 56, and also has a suction charger 26, a transfer charger 27, inside thereof.
Separation charger 28, optical chucking sensor 12
Two are arranged. Further, a separation charger 30 is arranged outside the transfer drum 25 so as to face the separation charger 28.

On the other hand, the recording material 56 fed from the register roller 23 is gripped by the chucking claw 31 on the transfer drum 25, and electrostatically deposited on the transfer drum 25 by the suction charger 26 as the transfer drum 25 rotates. Wrapped around. Then, the toner visible image formed on the photosensitive drum 11 is transferred onto the recording material 56 while the recording material 56 passes between the transfer charger 27 and the photosensitive drum 11.

When a color image is to be obtained, the transfer drum 25 performs three or four transfer steps one after another on the recording material 56. The recording material 56 for which the transfer process has been completed is neutralized by the separation chargers 28 and 30, separated from the transfer drum 25 by the separation claw 32, and fixed by the conveyance belt 33.
Delivered to 40.

The fixing device 40 includes an upper fixing roller 41, a lower fixing roller 42, and a cleaning roller 4, as clearly shown in FIG.
3, 44, an oil application unit 60, separation claws 45, 46, an oil recovery blade 47, etc., the toner image transferred and formed on the recording material 56 is heated and pressed by the upper and lower fixing rollers 41, 42. , Output tray 35 fixed on recording material 56
(Fig. 1) is discharged on top.

The upper fixing roller 41 and the lower fixing roller 42 are
Each has a built-in heater UH and LH for heat fixing operation.

The upper and lower fixing rollers 41, 42 are provided with an elastic layer such as silicone rubber on the surface thereof, and the surface of the upper fixing roller 41 is substantially mirror-finished.

Reference numeral 71 is a thermistor which is in contact with the upper fixing roller 41 and detects the temperature of the fixing roller 41.

The oil applying unit 60 supplies a releasing agent to the mirror-finished surface of the upper fixing roller 41. As shown in FIGS. 2 to 4, the oil supplying rollers 61, 62, the oil applying roller 63, It is composed of an oil regulation blade 64 and the like. Silicone oil as a release agent stored in the oil tank 365 (FIGS. 1 and 2) is pumped up to the oil application roller 63 by the oil supply rollers 61 and 62, and an appropriate application amount is obtained by the oil regulation blade 64. So that it is evened out.

Further, the oil application roller is driven by the oil application pressure contact control cam 65 which is driven in accordance with the timing of feeding the recording material 56 to the fixing device 40 and the initial timing of rotation of the upper and lower fixing rollers 41 and 42 during warming up. The pressure contact with or separation from the upper fixing roller 41 is controlled, and as a result, the supply of oil to the upper fixing roller 41 is controlled.

The oil regulating blade 64 is also driven by the oil regulating blade pressure contact control cam 66 which is driven together with the oil coating pressure contact control cam 65.
The amount of oil on the oil applying roller 63 is regulated while preventing the foreign matter from adhering to the oil applying roller 63 and transferring it to the fixing roller.

A mechanism for performing the above control will be described with reference to FIGS.
Will be described in detail. As shown in FIG. 3, the oil application roller 63 is an oil supply roller 6 that supplies oil to the oil application roller 63.
The swing frame 73 is supported together with the first and the second swing frames 73, and the swing frame 73 is pivotally supported by a fixed bracket 75 by a shaft 74. The fixed bracket 75 bears the rotary shafts 76 of the press control cams 65 and 66.

The oil control blade 64 is pivotally supported by the shaft 77 on the swing frame 73 at the base frame 376 thereof. The oscillating frame 73 and the base frame 376 are urged in the clockwise direction in FIG. 3 by a spring 78 which acts between them, and the respective passive pieces 73a and 76a are in pressure contact with the pressure control cams 65 and 66.

As a result, the swing frame 73 and the base frame 376 are driven by the pressure contact control cams 65 and 66 by their passive pieces 73a and 76a. Therefore, the cam 65 brings the oil applying roller 63 into contact with and separates from the upper fixing roller 41. Further, the oil regulating blade 64 is brought into contact with and separated from the upper fixing roller 41.

Pressure contact control cams 65 and 66 for performing this separation / contact.
Is operated by the cam operation control mechanism shown in FIGS.

The drive from the main motor (not shown) is transmitted to the spring clutch 83 via the gears 81 and 82. The spring clutch 83 is a normally closed type.

In this clutch 83, an outer cylinder 86 having claws 86a at two locations on the circumference is connected to one end of a spring 87, and when the claw 86a is locked by a clutch control claw 88, The rotation of the gear 82 cannot be transmitted to the cam drive shaft 89. That is, it is in the off state.

When the clutch control pawl 88 is turned against the spring 92 when the solenoid 91 is turned on and is released from the engagement when the pawl 86a is turned on, the spring 87 immediately tightens to rotate the gear 82 to rotate the cam drive shaft 89. Will be transmitted to the ON state.

Since the solenoid 91 is turned off immediately after that, the clutch control pawl 88 is immediately returned to the engagement position with the pawl 86a by the bias of the spring 92.

Therefore, each time the solenoid 91 is turned on, the spring clutch 83 rotates the cam drive shaft 89 by half by the rotation of the main motor.

At the solid line position in FIG. 3, the oil applying roller 63 is separated from the upper fixing roller 41, and the oil regulating blade 64 is separated from the oil applying roller 63 in a non-operating state.

In this state, when the solenoid 91 is turned on, the pressure contact control cams 65 and 66 are half-turned to the position of the imaginary line, and the pressure contact control cam 66 presses the oil regulating blade 64 against the oil applying roller 63. The press contact control cam 65 presses the oil applying roller 63 into contact with the upper fixing roller 41.

As a result, the oil application roller 63 regulates the amount of oil supplied from the oil supply rollers 61 and 62 by the oil regulation blade 64, and then the upper fixing roller.
The oil is applied to the upper fixing roller 41 by pressing it against 41. Therefore, it is possible to prevent excess oil from being applied to the upper fixing roller 41.

The pressure contact of the oil applying roller 63 with the upper fixing roller 41 is confirmed by the position detecting sensor 96 detecting the position indicating piece 95 provided on the cam driving shaft 89.

The drive mechanism 101 for the oil supply rollers 61, 62 and the oil applying roller 63 is constituted by a roller 61 as shown in FIG.
Gear 10 gearing each of the ~ 63 at one of their ends
2 to 104 and a passive gear 105 directly connected to the other end of the uppermost oil application roller 63.

In the three connecting gears 102 to 104, since the oil rotates from the lowermost gear 102 which is immersed in the oil in the oil reservoir 365, an external gear for driving is engaged with any one of them. If this happens, the oil will also go around to this external gear and cause it to leak outside.

Therefore, a passive gear 105 directly connected to the uppermost roller 63 is provided, and the rotation of the drive gear 106 which meshes with the external gear and receives the drive of the main motor is controlled by the drive shaft 107,
The transmission is made through the gear train 108.

Since the transmission system from the drive gear 106 to the gear train 108 floats above the oil, the connecting gear 10
The oil around 2 to 104 is prevented from leaking outside through the drive system.

By the way, in the warming-up of the fixing device 40, after the main switch is turned on, the heaters UH and LH are energized while driving the fixing rollers 41 and 42 for a predetermined period of time to rise to a predetermined temperature.

At this time, the thermistor 71 is attached to the upper fixing roller 41.
And the oil recovery blade 47 is pressed against the lower fixing roller 42. If the fixing rollers 41 and 42 are made of silicone rubber and the fixing rollers 41 and 42 are in a high temperature state, the oil bleeds out, so that the contact friction at the pressure contact portion can be reduced.

However, since the temperature is lowered to room temperature during warming up, the oil bleed out is small and sufficient lubrication cannot be expected. Therefore, it may cause abnormal noise and scratches.

Therefore, in this embodiment, both the thermistor 71 and the oil recovery blade 47 are connected to the upper fixing roller 41.
And the lower fixing roller 42 can be contacted with and separated from the lower fixing roller 42. At the start of warming up, the oil application unit 60 is operated to apply the oil to the fixing rollers 41 and 42, and the tip of the applied oil forms the upper fixing roller 41 and the thermistor 71. Of the upper fixing roller 41, the oil applied to the upper fixing roller 41 is transferred to the lower fixing roller 42, and the lower fixing roller 42 and the oil collecting blade 47 face each other. After the leading edge of the lower fixing roller 42 is reached, the oscill recovery blade 47 is pressed against the lower fixing roller 42.

In the concrete control, referring to FIG. 13, the following control is performed with the start of warming up when the main switch is turned on.

Each part of the copying machine 1 is inspected from the time point to the time point, and the idle rotation of the fixing rollers 41 and 42 is started at this time point. This idle rotation causes the fixing rollers 41 and 42 to rise to a predetermined temperature faster.

At this time, the thermistor 71 and the oil collecting blade 47 are separated from the fixing rollers 41 and 42 by the thermistor separating solenoid 406 (FIG. 8) and the oil collecting blade separating solenoid (not shown).

As a result, the temperature is lowered to about room temperature and sufficient bleed-out of the oil can be expected, and the fixing rollers 41, 42 and the thermistor 71 and the oil recovery blade 47, which are apt to run out of oil, are prevented from coming into contact with each other.

When a predetermined time has elapsed from the above point, the oil application pressure contact cam 65 is operated to move the upper fixing roller.
Press it against 41. This pressure contact is performed for a predetermined time until the time point of and oil is applied to the upper fixing roller 41.

The oil applied to the upper fixing roller 41 is removed by the idle rotation of the fixing rollers 41 and 42.
Is carried on the surface of the fixing roller 41, 4
The oil applied and conveyed to the upper fixing roller 41 at the nip portion between the two moves to the lower fixing roller 42, and is also conveyed thereafter by the lower fixing roller 42.

The tip of the oil applied on the upper fixing roller 41 from the time point up to the point reaches the facing portion between the upper fixing roller 41 and the thermistor 71 at the time point, and at this time point, the thermistor separating solenoid 406 is used. The thermistor 71 is brought into pressure contact with the upper fixing roller 41.

The tip of the oil on the lower fixing roller 42 reaches the position where the oil collecting blade 47 and the lower fixing roller 42 face each other at a point of time, and at this point of time, the oil collecting blade 4 is separated by the oil collecting blade separating solenoid.
7 is brought into pressure contact with the lower fixing roller 42.

As described above, at the start of warming up from the room temperature, the oil application roller 63 is pressed against the upper fixing roller 41 for a predetermined time to apply oil thereto, and this oil is also transferred to the lower fixing roller 42 and supplied. Even if the surface temperature of the fixing rollers 41, 42 is low and the bleed-out of the releasing agent from the surface elastic body of the fixing rollers is small, it is possible to supply a sufficient releasing agent and to apply it to the surface of the fixing roller. The temperature sensor is separated from the fixing roller until the leading end position of the release agent reaches the position where the fixing roller and the temperature sensor face each other, so that the part of the fixing roller on which the release agent has been sufficiently applied and supplied comes into contact. , At the start of warming up, the temperature sensor comes into contact with the surface of the fixing roller to detect the temperature, but the release agent is insufficient, resulting in abnormal noise and scratches on the surface of the fixing roller. Such a thing can be prevented.

Since the oil recovery blade 47 is also pressed against the oil-coated portion of the lower fixing roller 42,
The contact friction between the two can be reduced, and even if the oil bleed out is small, it is possible to prevent the generation of abnormal noises and scratches.

Further, when the thermistor 71 is pressed against the upper fixing roller 41, the heater UH of the upper fixing roller 41 is energized, and the temperature control of the fixing rollers 41 and 42 based on the temperature information from the thermistor 71 and its display are performed. Start.

Since the heater LH of the lower fixing roller 42 has a small capacity, it is energized at the same time when the power is turned on, so that the rise of the heater LH is not delayed. This can be controlled to the same energization state as the upper heater UH.

As shown in FIG. 7, for controlling the separation and contact of the thermistor 71 as described above, the thermistor 71 is held by a holder 402 that is rotatably supported by a shaft 401, and the shaft 401 of the holder 402 is used as a center. By this rotation, the thermistor 71 can be brought into and out of contact with the upper fixing roller 41.

Then, the passive lever 402a of the holder 402 is rotated by rotating the cam 404 connected to a drive shaft (not shown) via a spring clutch 403 by half rotation.
The thermistor 71 by pushing or releasing this push.
Is separated from the upper fixing roller 41 or brought into pressure contact therewith.

The spring clutch 403 has a diameter of 2
A cam control claw 403a is provided at a position, and when the stopper lever 405 is engaged with the cam control claw 403a, the cam control claw 403a is turned off to move the cam 4 from the drive shaft.
04, the cam 404 is stopped at the position at the time of the engagement, and when the stopper lever 405 is disengaged by the momentary turning on of the thermistor separation solenoid 406, the spring clutch 403 is turned on. The rotation of the drive shaft is transmitted to the cam 404 to rotate it.

When this rotation makes a half rotation, the returning stopper lever 405 engages with another cam control pawl 403a of the spring clutch 403 to turn off the spring clutch 403 again. Stop at the half-turned position.

As described above, the cam 404 is rotated half a turn each time the thermistor separation solenoid 406 is turned on. For example, in the separated state of FIG. 8A, the half rotation of FIG. 8C, the state of FIG. 8C is changed to the separated state of FIG. 8E through the half rotation state of FIG. 8D.

The oil collecting blade 47 is shown in FIG.
As shown in FIG. 5, the middle part is held at the tip of a lever 502 pivotally supported by a shaft 501 to be able to come in and out of contact with the lower fixing roller 42, and is pressed into contact with the lower fixing roller 42 by a spring 503 acting on the tail end of the lever 502. I am urged to do so.

On the tail end side of the lever 502, a cam disk 504 is operated which rotates 1/4 each time an oil recovery blade press contact solenoid (not shown) is turned on.

The cam disk 504 is provided with large-diameter pins 505 at two locations on the diameter line at the outermost peripheral portion of the end face, and small-diameter pins 5 at two locations on the diameter line intersecting with the diameter line at the outer periphery and the inner portion at right angles.
06 is provided.

These pins 505 and 506 are sequentially brought into contact with the lever 502 at every 1/4 rotation of the cam disk 504, and the lever 5 is moved as shown in FIGS.
02 is pushed and released to make the oil recovery blade 47 supported by the lever 502 separate from and contact the lower fixing roller 42, and when the small pin 506 faces the lever 502, the lever 502 causes the spring 503. Is pressed against the lower fixing roller 42.

With such a separating / contacting mechanism, the oil recovery blade 47 is also separated from the lower fixing roller 42 while the oil has not yet reached at the start of warming up, and is pressed against the oil after the oil has reached. As a result, even if the lower fixing roller 42 is not a mirror surface, it has a relatively smooth elastic body surface and the contact friction with the oil recovery blade 47 is not small. The effect is that there is no out,
Avoid noise and scratches.

The cleaning rollers 43 and 44, which are in pressure contact with the fixing rollers 41 and 42, are
In particular, it is necessary to remove the toner and paper dust that adhere to the surface little by little without impairing the surface smoothness of the upper fixing roller 41.

Further, the fixing speed and the system speed are operated at different speeds. At the time of warming up and during formation of a monochromatic image, the fixing speed is set to a system speed, whereby the surface temperatures of the upper and lower fixing rollers 41 and 42 at the time of warming up are made uniform and quick start up, and a monochromatic image which easily satisfies a predetermined image quality is high. Maintains image forming efficiency.

On the other hand, at the time of forming a color image, the fixing speed is set to the system speed when the recording material 56 reaches the position immediately before the fixing rollers 41 and 42 in order to sufficiently perform the color composition of the toner images of different colors. Set to 1/2. Further, when the toner is fixed on the OHP sheet, the fixing speed is reduced to 1/4 of the system speed in order to prevent the light from being dispersed and form an image having excellent translucency.

The switching of the fixing speed in the fixing device 40 as described above is carried out together with the conveyor belt 33 which conveys the recording material 56 to the fixing device 40 so that there is no problem in exchanging the recording material 56 with each other. ing.

After a lapse of time required for the recording material 56 to pass through the fixing device, the system speed is restored again.

By the way, when the fixing speed is different from the system speed, it is necessary to convey the recording material 56 at the fixing speed after finishing passing the transfer position on which the toner image is transferred from the photosensitive drum. Therefore, the distance from the transfer position to the fixing device must be longer than the maximum length of the recording material 56.

10 and 11 show an overall view and a partially enlarged view of the operation panel 201 provided in the copying machine 1.

Referring to FIG. 10, the operation panel 201 includes a print 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 2
09 to 212, jog dials 213 and 214 for setting an area at the time of trimming and masking, and a display unit 215 made of a liquid crystal or the like for displaying an original image for setting the area and displaying various messages.

Here, the function keys 209 to 212
Performs magnification designation, paper designation, density adjustment, and the like. FIG. 11 shows an example of the display on the display unit 215. If you press the function key 209 here, the magnification specification mode, function key
Press 210 to select paper mode, function key 211
Press to switch to the density adjustment mode.

For example, in the paper designation mode, the display unit 215
Displays A3, B4, A4, and B5 in correspondence with the function keys 209 to 212, and makes it possible to select the paper size with the function keys.

FIG. 12 is a block diagram of a control circuit for controlling the above-mentioned various operations. It relates to a fixing device in which each input / output element is connected to a CPU 301 and which includes separation / contact control of the thermistor 71 and an oil recovery blade 47. Control is shown in FIG.
It is performed according to the time chart of.

[0101]

According to the present invention, at the start of warming up from room temperature, the release agent applying means is in contact with the fixing roller for a certain period of time to apply the release agent to the fixing roller, so that the surface temperature of the fixing roller is low. Even if there is little bleed-out of the release agent from the surface elastic body of the fixing roller, sufficient release agent can be supplied, and the tip position of the release agent applied to the surface of the fixing roller is the same as that of the fixing roller. The temperature sensor is separated from the fixing roller until it reaches a position facing the temperature sensor, and the portion of the fixing roller where the release agent is sufficiently applied and applied is brought into contact with the temperature sensor. It is possible to prevent an abnormal noise and a scratch on the surface of the fixing roller from occurring due to a shortage of the release agent when the temperature is detected by contacting with.

While the temperature sensor is separated from the fixing roller, if the energization of the heater of the fixing roller is stopped or the detection and display of the trouble relating to the fixing temperature are stopped, the temperature of the fixing roller cannot be detected. It is possible to prevent the danger that the heater of the fixing roller is energized in the state where the temperature control is impossible, or to avoid the trouble detection and display in vain. It can be prevented.

Even when the surface roughness of at least one surface elastic body of the fixing roller has a high smoothness of R _Z ≦ 2 μm, generation of abnormal noise or scratches is prevented depending on the coating state of the release agent. It is possible to form a color image or a translucent image successfully without such a problem.

Further, when a releasing agent collecting means for contacting the fixing roller and collecting an excess releasing agent on the fixing roller is provided, this can also be brought into contact with the fixing roller and fixed at the start of warming up. The releasing agent collecting means is separated from the fixing roller until the tip of the releasing agent applied to the roller reaches the position where the releasing agent collecting means and the fixing roller face each other, and the releasing agent on the fixing roller is sufficiently applied and supplied. Since the contact is made from the contacted portion, the release agent collecting means contacts the fixing roller at the start of warming up and collects the excess release agent.
It is possible to avoid the occurrence of abnormal noise and scratches due to lack of release agent.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a color copying machine as an embodiment including a developing device to which the present invention is applied.

FIG. 2 is a schematic side view around a fixing device.

FIG. 3 is a cross-sectional view showing an oil application mechanism of the fixing device.

FIG. 4 is a perspective view showing a driving force transmission system of an oil application mechanism.

FIG. 5 is a cross-sectional view of a drive force connecting / disconnecting mechanism of the oil applying mechanism.

FIG. 6 is a side view of the connecting / disconnecting operation mechanism of the driving force connecting / disconnecting mechanism.

FIG. 7 is a perspective view showing a separating / connecting mechanism of the thermistor.

FIG. 8 is an exploded side view showing a separation / contact control state of the thermistor.

FIG. 9 is a side view showing a separation / contact mechanism of an oil recovery blade and a control state.

FIG. 10 is a front view of an operation panel of the copying machine.

FIG. 11 is a partially enlarged view of the operation panel.

FIG. 12 is a block diagram of a control circuit.

FIG. 13 is a time chart of the main operation of the fixing device.

[Explanation of symbols]

 40 fixing device 41 upper fixing roller 42 lower fixing roller 47 oil collecting blade 63 oil applying roller 65 oil applying pressure contact cam 71 thermistor 301 CPU 402 holder 403 spring clutch 404 cam 405 stopper lever 406 thermistor separating solenoid 502 lever 502 503 spring 504 cam disk UH, LH heater

Claims (5)

[Claims] 1. A pair of fixing rollers, which rotate in pressure contact with each other, and a release agent applying means which is brought into contact with and separated from the fixing rollers.
A fixing device that includes a temperature sensor that is in contact with the fixing roller and detects the temperature of the fixing roller, and that performs warming-up control that rotationally drives the fixing roller after it starts energizing the heater until it reaches a predetermined temperature. The sensor is detachable from the fixing roller, and at the start of warming up, the releasing agent applying means is kept in contact with the fixing roller for a certain period of time, and the tip end position of the releasing agent applied to the surface of the fixing roller is the temperature sensor and the fixing roller. The fixing device is characterized in that the temperature sensor is separated from the fixing roller until it reaches a position opposite to. 2. The fixing device according to claim 1, wherein energization of the heater of the fixing roller is stopped while the temperature sensor is separated from the fixing roller. 3. The fixing device according to claim 1, wherein detection and display of a trouble relating to the fixing temperature are stopped while the temperature sensor is separated from the fixing roller. 4. The fixing device according to claim 1, wherein at least one surface elastic body of the fixing roller is an elastic roller having a surface roughness R _Z ≦ 2 μm and high surface smoothness. 5. A release agent collecting means for contacting the fixing roller to collect an excess release agent on the fixing roller is provided so as to be able to come into contact with and separate from the fixing roller, and by the release agent applying means at the start of warming up. 5. The releasing agent collecting means is separated from the fixing roller until the tip of the releasing agent applied to the surface of the fixing roller reaches a position where the releasing agent collecting means faces the fixing roller. The fixing device described in 1.