JP2001188435A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device by which a stabilized image is always fixed by preventing excessive oil application to a heat roller during idling. SOLUTION: The supporting member 76 of the fixing device 56 is turned by having a hinge 77 as a supporting point, and is energized to the side of the heat roller 58 by a pressing spring 78, and rotatably supports an oil coating roller 62 at a lower end. A felt supporting member 82 is turned by having a hinge 83 as the supporting point, and is energized to the side of the heat roller 58 by a press spring 84, and supports a cleaning member 79 made of felt by sticking at the lower end. A changeover cam 85 is rotated so as to be in the state of 'the separation of the oil coating roller 62 and the press- contact of the cleaning member 79' during the idling of a main body device, and is rotated so as to be switched in the state of 'the press-contact of the oil coating roller 62 and the separation of the cleaning member 79' when paper enters the fixing device 56.

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 toner image transferred to a sheet such as plain paper or OHP paper by heat and pressure.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, a fixing device for fixing an unfixed toner image transferred on a sheet (hereinafter referred to as a sheet) to a sheet surface by heat and pressure is provided in a main body device. It has been incorporated.

FIG. 11 is a side sectional view showing such a conventional fixing device and a configuration in the vicinity thereof. As shown in FIG. 1, the fixing device 1 includes a heat fixing roller pair 2 including a heat roller 2a having a heat source and a pressure roller 2b provided to press the heat roller 2a. Heat fixing roller pair 2
While holding the paper such as plain paper or OHP paper which is guided into the fixing device 1 from the right by being guided by the guide plate 3 and transports the paper backward (to the left in the figure), The unfixed toner formed by the image forming unit and transferred onto the sheet is fixed based on heat and pressure. Around the heat roller 2a, an oil application roller 4, a thermistor 5, a thermostat 6, a peeling claw 7, a cleaning member 8, and the like are disposed in contact with or in proximity to the surface of the heat roller 2a.

The oil application roller 4 improves the releasability between the surface of the heat roller 2a and the toner on the paper in order to prevent a so-called offset phenomenon in which the toner on the paper is reversely transferred to the surface of the heat roller 2a. In order to apply a releasable oil by pressing against the surface of the heat roller 2a. Generally, silicone oil is used as the releasable oil, and the oil application roller 4 is usually impregnated with silicon oil enough to be applied to tens of thousands of sheets. The oil application roller 4 is unitized, and is replaced with a new one when it becomes old.

[0005] Although not particularly shown, there is an oil applying member of a type having a separate oil tank and applying oil supplied from the oil tank. In any case, in the fixing device having the above configuration, the conventional general oil applying mechanism is a rubbing type in which oil is supplied from a free-rotating roller member or an oil tank impregnated with oil as described above. The oil applying member is always in pressure contact with the heat roller and constantly supplies oil to the surface of the heat roller.

Generally, when printing on OHP paper, that is, when passing OHP paper through a fixing device, about three times the amount of oil must be applied to the heat roller as compared with the case where plain paper is passed. . This difference is caused by the difference between the fixing temperature (175 ° C.) when passing plain paper and the fixing temperature (185 ° C.) when passing OHP paper.

Normally, the viscosity of oil is adjusted to the specifications of OHP paper in view of the frequency of occurrence of offset.
If the viscosity of the oil is high, the surface of the OHP paper will not be glossy and the formed image will be in a cloudy state. Therefore, for OHP paper, a low viscosity of about 1000 cSt (cm
Stokes (the smaller the number, the more viscous it becomes) is often used.

The thermistor 5 is provided with a heat roller 2
a is provided for detecting the temperature of the surface. As such a thermistor, a contact-type thermistor is often used as shown in FIG. The thermostat 6 is provided to prevent the heating of the heat roller 2a. Further, the peeling claw 7 is disposed in contact with or close to the surface of the heat roller 2a, abuts against the leading edge of the sheet that is conveyed backward while being fixed, and peels the leading edge of the sheet from the surface of the heat roller 2a. It is provided in.

The cleaning member 8 is provided for removing toner remaining on the surface of the heat roller 2a and paper dust adhering thereto. Although it depends on the design method,
There is also a configuration in which a cleaning member is not provided and an oil application member also serves as a cleaning member. This configuration can simplify the configuration of the fixing device, and contributes to promotion of downsizing of the main body device.

An unloading roller 9 for unloading the fixed sheet out of the apparatus is provided downstream of the fixing device 1 in the sheet conveying direction.
and a switching flap 11 for guiding the paper to be carried out upward or to the side, a paper discharge path 12 when the paper is guided upward, and a discharge flap 12 at the end of the paper discharge path 12. A discharge roller pair 13 including a discharge roller 13a and a roller 13b for discharging a sheet which is conveyed while being inverted from above by the discharge path 12, and formed on the upper surface of the main body device. A paper discharge tray 14 is provided.

In a main unit (printer) having such a fixing device inside, when a user first turns on the power switch of the main unit in the morning or in a normal mode in which printing on plain paper is performed, OHP paper printing is performed. When the printing mode is switched from the monochrome printing mode to the color printing mode in an image forming apparatus capable of performing color printing, or in an image forming apparatus capable of performing color printing, the main unit normally drives each driven portion normally. After idling for a while until an operation standby state or an operation standby state suitable for the set print mode is reached, the operation becomes a full operation state in which printing can be executed.

The paper includes plain paper as described above and OHP.
There are different types of paper according to the type of paper. Generally, a method of detecting such a type of paper is to recognize switching between a plain paper print mode and an OHP paper print mode by key input from an operation panel. Is an automatic recognition method.
Immediately after the paper is fed, plain paper or O is detected by physical detection using a lever-type sensor and transparency detection using an optical sensor.
It is determined whether the sheet is an HP sheet, and when it is recognized that the OHP sheet has been fed, the mode is automatically switched to the OHP sheet print mode.

[0013]

By the way, during the idling, that is, during the temporary operation in which the paper such as the plain paper and the OHP paper is not passed through the fixing device, the oil application to the heat roller is continuously performed. Have been done. For this reason,
An excessive amount of oil adheres to, for example, the first sheet of plain paper or OHP paper printed after idling. Then, there is a problem that plain paper becomes oily and OHP paper becomes poor in transmittance.

[0014] Further, the lower the viscosity of the oil, the easier it is to consume it. Therefore, a printer which is set to use only plain paper (although such specifications are not usually used),
The use of oil having a viscosity of about 5000 cSt results in longer oil consumption. However, a printer having a common specification for plain paper and OHP paper has a problem in that the design is restricted to use 1000 cSt oil.

Further, in the case of OHP paper, as three times as much oil as that of plain paper is applied as described above, if image formation is continuously performed on OHP paper, the applied oil is accumulated and generally If the peeling claw is of a contact type, oil adheres to the peeling claw, and there is also a problem that traces thereof appear as vertical stripes on the OHP paper surface. In addition, since the OHP paper has poor oil absorbency, there has been a problem that excess oil becomes sticky or image transmission is poor.

The above-mentioned cleaning member is usually
It is made of a felt member. Even if there is no problem when the felt is new, when it is used, the toner and paper powder burn and adhere to the cleaning surface of the felt. in this way,
If toner or paper dust burns and adheres to the cleaning surface of the cleaning member, the oil applied to the heat roller is partially scraped off. In particular, in the case of OHP paper, this scraping portion remains as a vertical streak. Therefore, a problem occurs that the projected image is damaged.

Further, even if the peripheral surface of the heat roller is cleaned with a cleaning member or an oil application roller also serving as a cleaning, a small amount of toner remains. This toner adheres to the contact portion (detection portion) of the thermistor and accumulates between the thermistor and the heat roller, thereby causing a temperature detection failure,
As a result, there is also a problem that control of the fixing temperature is disrupted.

Further, the cleaning member is a member to be replaced periodically, and in some cases, the cleaning member is configured to clean the detection surface of the contact type thermistor at the time of the replacement. However, if the user forgets to replace the cleaning member, dirt is deposited on the detection surface and the thermal conductivity deteriorates, so that correct temperature detection cannot be performed. Cannot be maintained, and the fixing temperature cannot be controlled.

In addition, printers that are capable of printing on both sides of a sheet of paper have been put to practical use. In this case, the above-described releasable oil is pressed not only by a heat roller but also by a pressure roller. It must be applied to the roller. However, if the oil applying device constantly applies oil to both the upper and lower rollers of the fixing roller pair, when printing on one side, unnecessary oil is applied to the non-printing side and consumed, In addition to the problem of increasing costs,
Even in the case of single-sided printing, there is a possibility that oil adheres to both sides of the paper and causes oil contamination in the main unit, which is a problem.

Further, even in the case of double-sided printing, if oil adheres to both sides of the sheet during the first single-sided printing (printing on the front side), the oil on the photosensitive drum or the intermediate transfer member is printed in the second printing (printing on the backside). Contamination occurs and becomes a problem. In addition, at the time of the second printing, the paper feed roller for transporting the reversed paper is contaminated with oil, which causes a problem such as a transport slip.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional circumstances,
In addition to ensuring a proper and stable amount of oil applied regardless of whether it is plain paper or OHP paper, it protects the thermistor and periodically cleans the detection unit to actively remove excess oil. An object of the present invention is to provide a fixing device that always applies a stable image by applying only oil.

[0022]

The construction of the fixing device according to the present invention will be described below. First, the fixing device according to the first aspect of the present invention includes a heat roller having a heat source and a pressure roller provided to press the heat roller, and carries the unfixed toner formed and transferred according to image information. A pair of heat fixing rollers for fixing the unfixed toner to the sheet based on heat and pressure while nipping and conveying the sheet with the unfixed toner surface facing the heat roller, and releasing oil on the surface of the heat roller. An application roller for applying, a cleaning member for cleaning the heat roller surface, a detection member for contacting the heat roller surface and outputting a detection signal for controlling the roller surface temperature, And a peeling claw that is disposed in contact with the front end of the sheet and peels the sheet from the surface of the heat roller. The cleaning member is separated from the heat roller at the same time that the cleaning member is pressed and conveyed by the heat fixing roller pair, and the cleaning member is pressed against the heat roller at times other than the timing. It is provided with a moving mechanism for separating the application roller from the heat roller and a control means for controlling the operation of the moving mechanism.

Next, the fixing device according to the second aspect of the present invention
A sheet, comprising a heat roller having a heat source and a pressure roller provided to press the heat roller, is formed in accordance with image information and carries the transferred unfixed toner, with the unfixed toner surface facing the heat roller. A pair of heat fixing rollers for fixing the unfixed toner to the sheet based on heat and pressure while nipping and conveying, a coating roller for applying release oil to the surface of the heat roller, and contacting the surface of the heat roller. A detection member that outputs a detection signal for controlling the roller surface temperature, and a peeling claw that is disposed in contact with or close to the heat roller surface and abuts on the sheet tip to separate the sheet from the heat roller surface. In the fixing device provided with, as the application roller, one of two application rollers having different viscosities of the releasable oil to be impregnated comes into contact with the heat roller and the other is applied. Provided with in order to septum, a detection means for the sheet coming is nipped and conveyed to the heat fixing roller pair detects whether the OHP sheet or plain paper,
Application roller control means for controlling the application roller impregnated with the viscous release oil corresponding to the sheet detected by the detection means to make contact with the heat roller.

According to a third aspect of the present invention, there is provided a fixing device comprising a heat roller having a heat source and a pressure roller provided for pressing the heat roller, the unfixed image formed and transferred according to image information. A pair of heat fixing rollers for fixing the unfixed toner to the sheet based on heat and pressure while nipping and conveying the sheet carrying the toner with the unfixed toner surface facing the heat roller; An application roller for applying mold oil, a detection member that contacts the heat roller surface and outputs a detection signal for controlling the roller surface temperature, and is disposed in contact with or close to the heat roller surface and at the sheet tip. A peeling claw that abuts and peels off the sheet from the heat roller surface, and a detection surface cleaning member provided so as to be interposed in a contact portion between the heat roller and the detection member. Ete constructed.

The application roller is configured as an exchange unit that can be replaced according to a predetermined use time, and the detection surface cleaning member is integrated with the exchange unit. You. Further, for example, as described in claim 5, a moving means for interposing the detection surface cleaning member at the contact portion at a predetermined timing is provided.

Further, the fixing device of the invention according to claim 6 is
A sheet, comprising a heat roller having a heat source and a pressure roller provided to press the heat roller, is formed in accordance with image information and carries the transferred unfixed toner, with the unfixed toner surface facing the heat roller. A pair of heat fixing rollers for fixing the unfixed toner to the sheet based on heat and pressure while nipping and conveying, a coating roller for applying release oil to the surface of the heat roller, and contacting the surface of the heat roller. A detection member that outputs a detection signal for controlling the roller surface temperature, and a peeling claw that is disposed in contact with or close to the heat roller surface and abuts on the sheet tip to separate the sheet from the heat roller surface. In the fixing device provided, the fixing device is provided so as to be able to freely contact and separate from the sheet discharged from the heat fixing roller pair downstream of the heat fixing roller pair, and to contact the sheet. Configured with a wiping means for wiping the said release oil to adhere to the sheet.

According to a seventh aspect of the present invention, there is provided a detecting means for detecting whether the sheet nipped and conveyed by the pair of heat fixing rollers is a plain paper or an OHP sheet. When the detected sheet is an OHP sheet, the wiping unit is operated to contact the sheet, and when the detected sheet is plain paper, the wiping unit is provided with a wiping unit control mechanism for separating the wiping unit from the sheet. .

Further, the fixing device of the invention according to claim 8 is:
A sheet, comprising a heat roller having a heat source and a pressure roller provided to press the heat roller, is formed in accordance with image information and carries the transferred unfixed toner, with the unfixed toner surface facing the heat roller. A pair of heat fixing rollers for fixing the unfixed toner to the sheet based on heat and pressure while nipping and conveying, a coating roller for applying release oil to the surface of the heat roller, and contacting the surface of the heat roller. A detection member that outputs a detection signal for controlling the roller surface temperature, and a peeling claw that is disposed in contact with or close to the heat roller surface and abuts on the sheet tip to separate the sheet from the heat roller surface. An oil application roller for a pressure contact roller, which is capable of coming in contact with and separating from the pressure contact roller so as to apply release oil to the surface of the pressure contact roller; When the sheet conveyed by the pair of rollers has a fixed toner surface on the back side of the unfixed toner surface, the oil application roller for the pressure roller is pressed against the pressure roller, otherwise the pressure roller is pressed. An oil application roller control mechanism for a press roller that is separated from the roller is provided.

[0029]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side sectional view of an electrophotographic color printer according to an embodiment of the present invention. The color printer 20 shown in FIG. 1 is a tandem type full color page printer that performs printing for each cut sheet, and has a resource saving type double-sided printing mechanism. The color printer 20 has an upper lid 22 on the upper surface of a main body 21 and a paper cassette 23 that is detachable from the front (right side in the figure) at the lower part. A large number of sheets can be placed and stored in the sheet cassette 23.

An openable paper feed tray 2 is provided on the front of the main body 21.
4, a power switch (not shown) on the front upper surface 25,
A liquid crystal display device and an operation panel provided with a plurality of input keys are provided, and the upper cover 22 is provided so as to cover substantially the entire rear side thereof. The upper lid 22 has a rear
1 together with the rear upper surface to form an upper discharge tray 26,
It is opened and closed up and down with the hinge 27 as a fulcrum.

At the center of the main body 21, a transport belt 28 formed in a flat loop shape at the front and rear is disposed with the transport surface horizontal. The transport belt 28 is stretched between the driving roller 31 and the driven roller 32, is driven by the driving roller 31, and circulates in the counterclockwise direction in the drawing. Above the transport belt 28, four image forming and transferring sections 33
(33a, 33b, 33c, 33d) correspond to the transport belt 28.
Are arranged in a multistage manner along the paper transport direction (from right to left in the figure).

Each of the image forming / transferring sections 33 (only the image forming / transferring section 33c is indicated by a number) surrounds the photosensitive drum 34 and the peripheral surface of the photosensitive drum 34 in a clockwise direction. , Cleaner 35, initialization charger 3
6. Various devices such as a transfer sheet 41 and the like are arranged with the exposure head 37, the developing device 38, the developing roller 39, and the transport belt 28 interposed therebetween. The four photoconductor drums 34 are arranged in contact with the upper circulation portion (paper transport surface) of the transport belt 28, respectively.

The four developing devices 38 contain magenta (M), cyan (C), yellow (Y) and black (Bk) color toners, respectively. The four exposure heads 37 are supported on the back surface of the upper lid 22 via the support member 42, and move up and down in an arc-shaped trajectory as the upper lid 22 opens and closes. As a result, the photosensitive drum 34 is arranged to face the photosensitive drum 34.

On the upper surface of the end of the conveyor belt 28 on the upstream side (right side in the drawing) in the sheet conveying direction, a suction roller 43 is provided.
And is in pressure contact with the driven roller 32. Suction roller 4
A high-voltage bias power supply (not shown) is connected to 3. Further, a standby roller pair 44 and a paper feed sensor 45 are disposed on the upstream side.

Further, the upstream side is branched laterally and downwardly, and a paper supply roller 46, a separating member 47, and the above-mentioned openable / closable paper supply tray 24 are disposed in the horizontal direction. Further, a feed path 48 composed of two guide plates is formed below, and a conveying roller pair 49 is disposed in the middle of the feed path 48 extending downward.
The lower part branches downward and backward. A paper feed roller pair 51 and a paper guide roller 52 are provided below, and below the paper feed end of the paper cassette 23 described above. Above the paper feed end of the paper feed cassette 23, a paper feed roller 53 having a half-moon cross section is disposed.

On the other hand, on the downstream side (left side in the drawing) of the conveyance belt 28 in the sheet conveyance direction, the sheet separation claw 5
4, a guide plate 55 is provided downstream thereof, and a fixing device 56 is provided downstream thereof. The fixing device 56
The heat generating roller 58 and the pressing roller 5 are housed in the heat insulating housing 57.
9, a fixing / separating claw 61 which comes into contact with the heat roller 58, an oil application roller 62 which can come and go with the heat roller 58, and the like. Further, another oil application roller 60 is disposed below the pressing roller 59 so as to be able to freely contact and separate.

Although not shown in the figure, the oil application roller 62 is unitized with a cleaning member as will be described later in detail, and is mounted on the fixing device 56 in a replaceable manner. ing.

Downstream of the fixing device 56, a pair of paper discharge rollers 63
And a switching flap 64 are provided. The switching flap 64 changes into three modes: an intermediate position indicated by a solid line in the figure, a position pivoting upward and a position pivoting downward. Corresponding to these three modes, the paper path downstream of the switching flap 64 is branched into three directions, that is, upward, lateral, and downward. At the end of the path 65, an upper discharge port 67 in which a pair of discharge rollers 66 is disposed opens above the rear part of the upper discharge tray 26. A rear discharge port 68 is open to the outside in a lateral direction downstream of the switching flap 64.

Further, below the switching flap 64, a return transport path 69 for returning the sheet exclusively to the upstream side includes a first reverse transport roller pair 71 and six reverse transport roller pairs, and a pair of reverse transport roller pairs. It is constituted by a reverse conveyance path 72 disposed therebetween. The end 73 of the return transport path 69
Merges with the sheet supply path 48 from the open / close sheet supply tray 24 via the supply path 48.

The feed-back transport path 69 and the paper cassette 2
3, an electrical component 74 capable of mounting a predetermined number of circuit boards.
Are arranged. A control device including a plurality of electronic components is mounted on a circuit board provided in the electrical component unit 74. The control device includes a controller unit and an engine unit (not shown). The controller unit includes a CPU (central processing unit), a ROM (read only memory), an EEP
It comprises a ROM (rewritable read memory), a frame memory, an image data transfer circuit, and the like, analyzes print data input from a host computer or the like, creates print data, and transfers it to the engine unit.

The engine unit includes a CPU, a ROM, and the like.
On the input side, data and command signals from the controller unit, the output of the paper detection sensor, etc. are input, and on the output side, a motor driver that drives a motor (not shown), and a drive system that transmits the drive of the motor to each rotating member Driver, an electromagnetic driver for driving the switching flap, a cam driver or an electromagnetic driver for switching the contact and separation of an oil application unit described later, a print driver for driving the exposure head 37 based on print data, an initialization charging Vessel 3
6, developing roller 39, transfer sheet 41, suction roller 43
And the like are connected to a bias power supply driver or the like that supplies a predetermined bias current. The engine unit controls the driving of each unit based on data and command signals from the controller unit, the output of the sheet detection sensor, and the like.

Next, the basic operation of the color printer 20 having the above configuration will be described. First, the power is turned on to the main unit 20, and printing (printing) is started when the number of sheets to be used, the print mode, and other designations are input as a key input or a signal from a connected host device. That is, the paper feed roller 53 makes one rotation to take out one sheet of the uppermost sheet stored in the paper cassette 23, and passes through the paper guide roller 52, the paper feed roller pair 51, the transport roller pair 49, and the feed path 48. To the standby roller pair 44. The paper feed sensor 45 detects the leading edge of the fed paper to confirm that the paper has been fed normally, and detects the trailing edge of the paper being transported to check the size of the paper. I do.

The standby roller pair 44 temporarily stops rotating,
The advance of the sheet is stopped by abutting the leading end of the sheet against the holding portion, and the skew of the sheet is corrected, and the conveyance timing is waited. The driving roller 31 rotates counterclockwise,
The circulation movement of the transport belt 28 is started. Each image forming and transferring section 33 is sequentially driven in synchronization with the printing timing, and the photosensitive drum 34 rotates clockwise.

The initialization charger 36 applies a uniform high negative charge while sliding on the peripheral surface of the photosensitive drum 34 to initialize the photosensitive drum 34. The exposure head 37 is arranged facing the photosensitive drum 34 with a predetermined distance therebetween.
Exposure according to the image signal is performed on the peripheral surface of the photosensitive drum 34 to form an electrostatic latent image composed of a high negative potential portion by initialization and a low negative potential portion by the exposure. Developing roller 3
Reference numeral 9 denotes a photosensitive drum which is rotatably supported by an opening at the lower part of the main body of the developing device 38, presses against the photosensitive drum 34, and transfers the toner in the developing device 38 to a low potential portion of the electrostatic latent image. A toner image is formed (reversal development) on the 34 peripheral surface.

The image forming / transferring unit 33 at the uppermost stream in the paper transport direction
At the timing when the leading end of the magenta toner image on the peripheral surface of the photosensitive drum 34 is rotated and conveyed to the portion opposed to the conveyor belt 28, the standby position is set so that the print start position of the paper coincides with the opposed portion. The roller pair 44 starts rotating and feeds the paper toward the transport belt 28.

The suction roller 43 applies a high-voltage bias supplied from a high-voltage bias power supply (not shown) to the sheet while holding the sheet together with the driven roller 32 and the conveyance belt 28 and sending the sheet onto the conveyance belt 28. It is adsorbed on the conveyor belt 28. Thus, the sheet is conveyed while maintaining a stable posture, and is conveyed to the first image transfer unit formed by the photosensitive drum 34 and the transfer sheet 41 of the image forming transfer unit 33a.

The transfer sheet 41 applies a transfer current output from a transfer bias power supply (not shown) to the sheet via the transport belt 28. As a result, the magenta toner image on the photosensitive drum 34 is transferred to the paper. Subsequently, the cyan toner image is transferred by the photosensitive drum 34 of the second image forming and transferring unit 33b and the transfer sheet 41 from the upstream in the sheet transport direction, and further transferred to the photosensitive drum 34 of the third image forming and transferring unit 33c. The yellow toner image is transferred by the sheet 41, and the black toner image is transferred by the transfer sheet 41 and the photosensitive drum 34 of the most downstream image forming and transferring unit 33 d.

The sheet on which the toner images of the four colors are superimposed and transferred is separated from the conveyor belt 28 by the sheet separating claws 54 and is carried into the fixing device 56. The fixing device 56 presses and holds the sheet by the heating roller 58 and the pressing roller 59,
While being conveyed in the downstream direction, heat and pressure are applied to the paper to fix the toner image on the paper, and the paper is discharged backward.

For example, in the case of single-sided printing, if the switching flap 64 is rotated to the solid line position (intermediate position) shown in FIG. At the end, the sheet is further turned forward in the apparatus, nipped by a pair of paper discharge rollers 66, and the transfer is continued, and the upper paper discharge tray 2 with the image forming surface facing downward from the upper paper discharge port 67.
6 is discharged. When the switching flap 64 is rotated to a position higher than the solid line position in the figure, the switching flap 64 is fed substantially horizontally rearward, with the image forming surface facing upward and the rear discharge port 6.
8 to be discharged outside the machine.

When the sheet is double-sided printing, first, the switching flap 64 is located at the solid line position in FIG.
, And is nipped by a pair of paper discharge rollers 66 to be discharged halfway. Then, at the timing when the trailing edge of the sheet has just passed the sheet discharging roller pair 63, the sheet stops. This stop timing is
Based on the detection of the paper size by the paper feed sensor 45, the control unit of the electrical unit 74 determines the number of drive pulses of, for example, a stepping motor for driving the paper discharge roller pair 63 to a predetermined value. Of course, the discharge roller pair 6
A sensor may be provided immediately after 3 to detect the trailing edge of the sheet.

Thereafter, the switching flap 64 is rotated downward (clockwise) from the solid line position in the figure to connect the paper discharge path 65 and the return transport path 69. Next, the paper discharge roller pair 66 starts rotating in the reverse direction and feeds back the paper, and the trailing end of the paper is fed back to the first reverse feed roller pair 71
Is sandwiched between. Then, the sheet is sequentially fed back by the reverse conveying path 72 and the other five pairs of reverse conveying rollers, is again conveyed by the conveying roller pair 49, passes through the feeding path 48, and reverses to reverse the first image forming surface. 2nd face down and no image
The trailing edge of the sheet with the surface facing upward comes into contact with the standby roller pair 44 and temporarily stops.

Thereafter, in the same manner as in the case of the first surface, toner images of four colors are sequentially transferred to the second surface of the sheet, and the toner images are fixed by the fixing device 56. At this time, prior to the fixing, the lower oil application roller 60 is controlled so as to abut against the pressure roller 59 and apply oil to the surface of the pressure roller 59. As a result, the toner image previously formed and fixed on the first surface of the sheet is again transferred to the fixing device 56.
To prevent offset that occurs when heat and pressure are applied and melted. The sheet on which double-sided printing has been completed as described above is discharged out of the apparatus from the upper discharge port 67 or the rear discharge port 68.

FIGS. 2A and 2B show the first example of the fixing device 56.
1A and 1B are diagrams showing a detailed configuration of an oil application roller 62 and a cleaning member not shown in FIG. 1 in the embodiment. FIG. FIG.
FIG. 4 is a diagram showing an example of driving by an electromagnet.

As shown in FIG. 7A, one oil application roller 62 is rotatably supported at the lower end of an application roller support member 76 in an application roller unit 75.
The application roller support member 76 is rotatable around an application roller hinge 77 and is urged by an application roller pressing spring 78 to press against the heat roller 58.

The other cleaning member 79 is made of felt.
It is attached to and supported by the lower end of the felt support member 82. The felt support member 82 includes a felt hinge 83.
, And is urged by a felt pressing spring 84 to press against the heat roller 58.

A switching cam 85 is provided between the application roller supporting member 76 and the felt supporting member 82. When the switching cam 85 rotates, the switching cam 85 rotates.
The state of “separation of oil application roller 62 and cleaning member 79 pressure contact” shown by a solid line in FIG. 7A and the state of “oil application roller 62 pressure contact and cleaning member 79 separation” shown by two-dot chain line in FIG. The switching timing is set in accordance with, for example, detecting the leading edge of the entering paper by the paper entering detection sensor 86. Based on this setting timing, the switching cam 85 is rotated by 180 ° by a drive mechanism (not shown). The state is switched from the state of "" to the state of "". The rear end of the sheet is the fixing device 56
Is controlled to return to the state of "" again after exiting from.

As shown in FIG. 7A, the other oil application roller 60 is rotatably supported on the upper end of an application roller support member 87. The application roller support member 87 is
It is rotatable around the application roller hinge 88 as a fulcrum, and is urged to be separated from the pressure roller 59 by an application roller pulling spring 91 that is locked between the lower right end thereof and the main body frame 89. The end of the electric element 93 of the electromagnet 92 is engaged with the lower left end of the application roller supporting member 87.

When the motor 93 is not driven, the motor 9
3 is in a free state, the oil application roller 60 is at a separated position indicated by a solid line in FIG. 4A by the urging force of the application roller pulling spring 91, and when the motor 93 is driven, the motor 93 is drawn into the electromagnet 92. Oil application roller 60
Is switched to a press-contact position shown by a dashed line in FIG. 7A against the urging force of the application roller pulling spring 91, and is switched to apply oil to the press-contact roller 59. The switching timing is also set by detecting the leading edge of the sheet re-entering the fixing device 56 after image formation and transfer after the above-described feed back conveyance during double-sided printing by the sheet entry detection sensor 86.

FIG. 9B shows the oil application roller 62.
An example in which an electromagnet is used in place of the switching cam 85 in switching between the pressure contact of the cleaning member 79 with the heat roller 58 and the separation is shown. Also in FIG. 13B, one oil application roller 62 is rotatably supported at the lower end of an application roller support member 94, and the application roller support member 94 is rotatable about an application roller hinge 95 as a fulcrum. An application roller pressing spring 96 urges the heat roller 58 to be in pressure contact with the heat roller 58. Application roller hinge 9 of application roller support member 94
The end above 5 is engaged via an engagement pin 101 with the other end of a shaft 99, one end of which is engaged with the electric element 98 of the electromagnet 97.

The other cleaning member 79 is also attached and supported at the lower end of the felt support member 102, and the felt support member 102
03 can be turned around, and the felt pressing spring 1
04 is urged to press against the heat roller 58.
The upper end of the felt support member 102 above the felt hinge 103 is engaged with the other end of the shaft 99 via the engagement pin 105 similarly to the application roller support member 94.

The electric element 98 of the electromagnet 97 is shown in FIG.
(b) moves back and forth to a left position 98a indicated by a solid line and a right position 98b indicated by a two-dot chain line. As the armature 98 moves forward and backward, the state shown in the solid line in FIG.
(b) is shown by a two-dot chain line.
The state of “separation of cleaning member 79” is switched. This switching timing is set in accordance with the detection of the paper entry by the paper entry detection sensor 86 as in the case of FIG.

In the above example, the oil application roller 62 and the cleaning member 79 are independently mounted on the fixing device 56 as separate units regardless of whether the driving device is a cam or an electromagnet. , May be an integrated unit. This will be described below as a second embodiment.

FIGS. 3A and 3B are views showing an example in which the oil application roller 62 and the cleaning member 79 according to the second embodiment are formed as an integral unit.
FIG. 3 shows an example in which the switching of contact and separation with respect to these heat rollers is driven by a switching cam, and FIG. The configuration of the other parts is the same as the configuration shown in FIG. As shown in FIG. 3A, in one oil application / cleaning unit 106, one end of one support member 107 rotatably supports the oil application roller 62, and the other end includes a cleaning member 79. Is attached and supported.

The support member 107 includes the oil application roller 62
Almost the middle between the cleaning member 79 and the cleaning member 79 is rotatably supported by a hinge 108. A portion of the support member 107 above the hinge 108 is formed to be inclined toward the oil application roller 62, and one end of a pull spring 109 is locked at the upper end thereof, and the other end of the pull spring 109 is locked to the unit frame. ing. The pulling spring 109 allows the support member 107
Is urged clockwise with the hinge 108 as a fulcrum. That is, on the one hand, the oil application roller 62 is pressed against the heat roller 58 and, on the other hand, the cleaning member 79 is constantly urged to separate from the heat roller 58.

The cleaning member 7 of the support member 107
The switching cam 110 is in contact with the upper surface on the 9th side. The rotation of the switching cam 110 causes the support member 1 to rotate.
07 rotates about the hinge 108 in the counterclockwise direction to the position indicated by the solid line in FIG. 3A against the urging force of the pulling spring 109, or the two points in FIG. Rotate clockwise to the dashed line position.

When the support member 107 rotates to the position indicated by the solid line, the oil application roller 62 is separated from the heat roller 58 and the cleaning member 79 is pressed against the heat roller 58. Support member 107
Is rotated to the two-dot chain line position, the oil application roller 62 is pressed against the heat roller 58 and the cleaning member 7 is pressed.
9 is switched to be separated. This switching timing is also set by detecting the leading edge of the sheet entering the fixing device 56 by the sheet entry detection sensor 86.

FIG. 11B shows one oil application / cleaning unit 11 as in the case of FIG.
In the configuration of the oil application roller 62 and the cleaning member 79 supported by one support member 112 in 1,
These are connected to the electromagnet 97, the electric element 98,
And an example in which the shaft 99 is driven to rotate.
As shown in FIG. 2B, the support member 112
When the electromagnet 97 is not driven when the electromagnet 97 is not driven, as shown in the solid line position in FIG.
Due to the urging force of 14, the oil application roller 62 is separated from the heat roller 58, and the cleaning member 79 is pressed against the heat roller 58. When the electromagnet 97 is driven, the armature 98 is pulled from the position 98a to the position 98b, and the support member 107
Is rotated clockwise to the position indicated by the two-dot chain line and the heat roller 5 is rotated.
8 is switched so that the oil application roller 62 is pressed against the cleaning member 8 and the cleaning member 79 is separated. This switching timing is also set by detecting the leading edge of the sheet entering the fixing device 56 by the sheet entry detection sensor 86.

By the way, as described above, there is also a configuration in which the oil applying member also serves as the cleaning member without providing the cleaning member as described above. The oil application member of the fixing device described below is an example in which the oil application roller is also configured to also serve as the cleaning member, and the oil application roller corresponds to the type of paper (the difference in the material between plain paper and OHP paper). It is devised to make it different. Hereinafter, this will be described as a third embodiment.

FIGS. 4A and 4B show that the fixing device 56 according to the third embodiment uses plain paper or O
FIG. 9 is a diagram illustrating an example in which an oil application roller is different depending on whether the sheet is HP paper. As shown in FIG. 7A, above the heat roller 58 of the fixing device 56, the large-diameter oil application roller 116 and the small-diameter oil Application roller 11
7 are provided. The support member 115 is rotatably supported by a hinge 118 at an upper part of a forked base. A portion above the hinge 118 of the support member 115 is formed in a T-shape. The right end of the T-shape is engaged with the tip of the electric motor 121 of the electromagnet 119 via the pin 122, and the left end of the T-shape is connected to one end of the extension spring 123. I agree. The other end of the pull spring 123 is locked to a frame (not shown) of the main body device.

When the electromagnet 119 is not driven,
Due to the urging force of the pulling spring 123, the large-diameter oil application roller 116 is separated from the heat roller 58 and the small-diameter oil application roller 117 is pressed against the heat roller 58, as shown by the solid line in FIG. When the electromagnet 119 is driven, the motor 1
21 is retracted to the position of the stopping flange 124, and the support member 115 rotates clockwise to the position shown by the two-dot chain line against the urging force of the pulling spring 123. Diameter oil application roller 11
6 are pressed against each other, and the small-diameter oil application roller 117 is separated.

The one small-diameter oil application roller 117
Is an oil application roller for plain paper, which is impregnated with a somewhat high viscosity oil of about 5000 cSt. The other large-diameter oil application roller 116 is an oil application roller for OHP paper, and is impregnated with a slightly low viscosity oil of about 1000 cSt.

In general, when the same oil is used, for example, an oil application unit which can use up to about 10,000 sheets of plain paper is used.
When printing is performed up to about 000 sheets, the oil runs out and the oil application unit must be replaced.

In this example, as described above, plain paper and OHP
In addition to changing the viscosity of the oil between the paper and the paper, the large-diameter oil application roller 116 for OHP paper has a larger diameter than the small-diameter oil application roller 117 for plain paper. Even a large amount of oil is impregnated. Further, the pressure contact of the small-diameter oil application roller 117 for plain paper to the heat roller 58 is based on the urging force of the pulling spring 123 and is relatively weak.
The press-contact of the large-diameter oil application roller 116 for the paper to the heat roller 58 is based on the attraction force of the electromagnet 119 and is extremely powerful, that is, it can extrude and apply more oil.

Since the amount of applied oil can be changed depending on the strength of the pressing force as described above, instead of using oils having different viscosities for plain paper and OHP paper as described above, an oil having the same viscosity is used. Alternatively, only the application amount may be changed by rollers having different pressing forces.

Next, FIG. 2B shows a cross-shaped support member 12.
5, two oil application rollers 1 for plain paper
26 and two OHP paper oil application rollers 127 are rotatably supported, and the rotation supporting shafts of these four oil application rollers are provided with pressing springs 128 and 12 having different urging forces.
9 are engaged. The urging force of the press spring 128 of the plain paper oil application roller 126 is slightly weak, and the urging force of the press spring 129 of the OHP paper oil application roller 127 is set slightly higher.

The cross-shaped support member 125 has the center of the cross formed on the oil application roller clutch 1 via a support shaft 131.
32 and fixedly supported. Plain paper print mode and O
Each time the mode is switched to the HP paper print mode, the oil application roller clutch 132 makes a quarter turn, whereby the support member 125 rotates 90 degrees in the clockwise direction indicated by the arrow A in the figure. As a result, the plain paper oil application roller 126 and the OHP paper oil application roller 127 are sequentially and alternately pressed against the heat roller 58.

In this case, the oil application roller 126 for plain paper and the oil application roller 127 for OHP paper also
The oils to be impregnated may have different viscosities or may have the same viscosity. Further, the diameters of the plain paper oil application roller 126 and the OHP paper oil application roller 127 may be made different as shown in FIG.

When the diameters of the rollers are different, the length of the cross-shaped arm of the support member 125 may be changed according to the diameter. By doing so, even if the diameters of the rollers are different, the contact portions of the respective rollers with the heat roller 58 can be maintained within the same rotation peripheral surface.

As described above, in the third embodiment,
The viscosity of the oil is changed between plain paper and OHP paper, the total amount of oil that can be applied is changed, and the amount of oil applied to the heat roller surface at one time is changed. This makes it possible to use the oil application roller for plain paper and OHP paper, and to always apply the appropriate oil to the paper, thereby maintaining the optimum offset prevention function. Also,
Since the oil application roller is selectively used for plain paper and OHP paper, the life of the oil application unit can be extended, the frequency of replacement of the oil application unit can be reduced, and the trouble of replacement can be reduced.

By the way, it has been repeatedly stated that a user who frequently uses OHP paper has a higher fixing temperature when using OHP paper than when plain paper is used, so that a larger amount of oil is applied. , Fixing separation claw 6
1 (see FIG. 1 and numbering is omitted in FIGS. 2 (a) to 4 (b)). For this reason,
When printing using OHP paper, there is no problem as long as the number of papers is small, but when the number of papers is large, oil stays in the fixing separation claw 61, and the oil eventually adheres excessively to the OHP paper. Easy to occur.

FIGS. 5 (a) and 5 (b) show a fixing device according to the fourth embodiment, in which a cleaning member for cleaning oil retained in the fixing separation claw 61 at the time of idling is provided in order to solve the above problem. FIG.
(a) is a diagram showing the configuration, and (b) is a diagram showing the operation state.

As shown in FIG. 11A, a support member 133 having a T-shaped upper portion and a bifurcated lower portion is rotatably supported by a hinge 134 above the heat roller 58 of the fixing device 56. . The T-shaped left end of the support member 133 is engaged with the tip of the electric element 136 of the electromagnet 135 via a pin 137, and the T-shaped right end is engaged with one end of a pull spring 138. The other end of the extension spring 138 is connected to the frame 13 of the main unit.
9.

An oil application roller 141 is rotatably supported at a forked lower end of the support member 133, and an elastic thin plate 1 is provided on a forked left lower end thereof.
A heat roller cleaning member 143 made of a slightly thick felt member or the like is provided on the inner side of the elastic thin plate 142 facing the heat roller 58.
The fixing and separating claw cleaning member 1 made of a slightly thin felt member or the like is provided on the outer surface opposite to the fixing member.
44 are provided.

In the normal reference state, the electromagnet 135 is not driven, and the motor 136 is in a free state.
By the urging force of the pull 138, as shown in FIG.
The oil application roller 141 is always in pressure contact with the heat roller 58. Further, in this state, the other elastic thin plate 142 is in the retracted position in a state where it is slightly pulled up, whereby the heat roller cleaning member 143 is
And the fixing / separating claw cleaning member 144
Are also separated from the fixing separation claw 61.

Then, at the time of warming-up or idling at the time of turning on the power, or at the time of switching the OHP paper printing mode, the electromagnet 135 is driven and the motor 136 is moved to the stopping flange as shown in FIG. The support member 133 is rotated counterclockwise about the hinge 134 against the urging force of the tension spring 138. By this rotation, the oil application roller 141 is separated from the heat roller 58 and the elastic thin plate 142 is lowered, whereby the heat roller cleaning member 143 slides on the heat roller 58 and the lower end of the elastic thin plate 142 is fixed. The fixing / separating claw cleaning member 144, which is inserted between the separating claw 61 and the heat roller 58 and disposed outside thereof, slidably contacts the tip of the fixing / separating claw 61 to remove the oil pool at the tip of the fixing / separating claw 61. to clean up.

As described above, the heat roller cleaning member 143 is separated from the heat roller 58 and alternately slidably comes into contact with the heat roller 58 at the time of warming up or idling at the time of turning on the power, or at the time of switching the OHP paper print mode. Since the fixing / separating claw cleaning member 144 is provided integrally with the cleaning member 143, the fixing / separating claw cleaning member 144 is provided at the time of warm-up at power-on, at the time of idling, or
The oil pool at the tip of the fixing / separating claw 61 can be automatically cleaned at the time of switching of the HP paper printing mode, and the like, whereby excessive oil adhesion to the paper can be prevented.

Incidentally, in the fixing device 56 as described above, although not shown in FIG.
A member such as the thermistor 5 or the thermostat 6 shown in FIG. 1 that contacts the heat roller and detects the temperature of the heat roller is provided. In this case, since the heat roller is constantly rotating, not only the contact part of the thermistor or thermostat is easily worn, but also oil contamination and paper dust accumulate on the contact surface, which lowers the detection accuracy and reduces the appropriateness of the heat roller. It may not be possible to set a proper temperature. The structure of a fixing device that solves this problem will be described below as a fifth embodiment.

FIG. 6A is a side sectional view of a fixing device according to the fifth embodiment, and FIG. 6B is a perspective view showing the oil application unit. It should be noted that FIG.
Similarly to the above, only the oil application roller 62 is typically shown above the heat roller 58 of the fixing device 56, but actually, as shown in FIG. 2, FIG. 3, FIG. 4 or FIG. Various oil application members, cleaning members, and the like are provided in the oil cleaning unit 146.

As shown in FIG. 6A, on the right side of the heat roller 58 of the fixing device 56, a thermistor 147 and a thermostat 148 are respectively divided into right and left sides (in FIG. (Split). oil·
The cleaning unit 146 is provided with handles 149 on both ends thereof as shown in FIGS. 7A and 7B, and is configured to be detachable from the fixing device 56 by gripping the handles 149 and manually. I have. A thermistor protection cover 151 and a thermostat protection cover 152 are provided at positions corresponding to the contact portions of the oil cleaning unit 146 with the thermistor 147 and the thermostat 148 with the heat roller 58, respectively.

This oil cleaning unit 146
Has expired, and the new oil cleaning unit 146 is moved to the fixing device 56 as shown in FIG.
Is attached to the thermistor protection cover 151 and the thermostat protection cover 152, respectively.
47 and the contact portion between the heat roller 58 and the thermostat 14
8 and the heat roller 58 are inserted through the contact portion.
8 is a protective cover for the thermistor 147 and a protective cover for the thermostat 148.

As described above, the contact portion of the thermistor 147 with the heat roller 58 and the heat roller 5 of the thermostat 148
8 are in contact with the thermistor protection cover 151, respectively.
In addition, since the thermostat protection cover 152 protects the thermostat 58 from sliding contact with the heat roller 58 at all times, the thermostat does not wear, the durability is improved, and the life of the thermistor 147 and the thermostat 148 can be greatly extended.

Also, every time the oil cleaning unit 146, which is a regular replacement part, is replaced with oil dirt or paper dust that should accumulate on the contact surface with the heat roller 58, the thermistor protection cover of the old oil cleaning unit 146 is replaced. 151 and the thermostat protection cover 152 are removed by attaching to the new thermistor protection cover 15.
1 and the thermostat protective cover 152 are replaced, so that no stain is generated on the detection member, and therefore, a detection error due to the stain on the detection member can be always kept low.

In the above example, a protective cover is always attached to the thermistor 147 and the thermostat 148. However, the protective cover is not used, and the contact portions of the thermistor 147 and the thermostat 148 with the heat roller are periodically arranged. Cleaning may be performed. A fixing device having such a configuration will be described below as a sixth embodiment, taking up the case of periodic cleaning of the thermistor.

FIG. 7A is a side sectional view of a fixing device according to the sixth embodiment, and FIG. 7B is a diagram showing an operation state of the thermistor cleaning device. Figure (a)
As shown in (1), the fixing device 56 in this example includes a moving member 153 that can move up and down. Moving member 153
Is equipped with a brace 153-1 that extends sideways,
A thin plate-shaped cleaning member 153-2 is vertically disposed at the extending end of the cleaning member 153 downward. When the moving member 153 is at the upper position shown in FIG. 11A, the tip of the cleaning member 153-2 is separated from the contact portion of the detection plate 147-1 of the thermistor 147 with the heat roller 58 in close proximity. are doing.

When the moving member 153 moves downward as shown by the arrow B in FIG. 7B in conjunction with the movement of the other members, the cleaning member is accordingly moved via the arm 153-1. 153-2 moves downward as shown by the arrow C in FIG.
47-1 is inserted between the heat roller 58 and the detection plate 147.
-1 is brought into sliding contact with the heat roller 58. Thus, the contact portion of the detection plate 147-1 with the heat roller 58 is cleaned.

FIG. 8 is a diagram showing an example in which the moving member 153 is interlocked with the opening of the upper lid 22 as an example interlocked with the movement of another member. As shown in the figure, after the rear part 21-1 of the main unit is opened rearward and retracted, the upper lid 22 is rotated rearward to be opened, and the pusher disposed near the hinge 27 of the upper lid 22 is opened. The member 154 is the moving member 15 described above.
3 is configured to be pushed downward. As a result, the detection plate 147 of the thermistor 147 shown in FIG.
The cleaning of the contact portion with the heat roller 58 at -1 is performed.

Since the opening and closing of the upper cover 22 for maintenance work such as replacement of the image forming / transferring section 33 (33d) is a work that is performed periodically, the detection plate 147- of the thermistor 147 is used.
1 is also periodically performed, whereby the detection plate 14 serving as a detection member of the thermistor 147 is removed.
7-1 is always kept clean.

In the OHP paper print mode,
As described above, excessive oil easily adheres to OHP paper. The configuration of a fixing device that removes this excess oil from OHP paper will be described below as a seventh embodiment.

FIGS. 9 (a) and 9 (b) are side sectional views of a fixing device according to the seventh embodiment, showing the structure and operation of removing excess oil from OHP paper. .
Generally, when printing on OHP paper, OHP
In order not to lose the transparency of the toner image that has just been fixed on the surface by applying unnecessary bending to the paper,
In order to discharge the paper outside the machine in a horizontal state without bending the paper,
As shown in FIG. 9A, the switching flap 64 is rotated to the upper position to guide the OHP sheet discharged from the fixing device 56 to the rear discharge port 68 shown in FIG.
In this example, a cleaning member is provided which operates in such a manner as to wipe off the oil on the OHP sheet surface in conjunction with the rotation to the upper position of the switching flap 64.

That is, when the switching flap 64 is rotated counterclockwise from the lower position shown in FIG. 11B to the upper position shown in FIG. Lever 1 integrally formed with switching flap 64
56 rotates counterclockwise from the right position shown in FIG. 4B to the left position shown in FIG. The rotating end of the lever 156 is engaged with the left end of a bar 158 via a pin 157, and the right end of the bar 158 is engaged with the upper end of a “reverse-shaped” rotating member 161 via a pin 159. are doing. The turning member 161 has a corner portion of the inverted shape supported by the hinge 162, and has a lower end rotatably supporting the upper felt roller 163.

When the lever 156 is turned from the right position to the left position as described above, the turning member 1 is moved through the bar 158.
The upper end of the rotating member 161 is pulled from the right position shown in FIG. 6B to the left position shown in FIG.
2 rotates in a counterclockwise direction with the fulcrum as a fulcrum, and the upper felt roller 163 supported at the lower end thereof moves down, and is rotatably supported by the upper left end of the bracket 164 that swingably supports the pressing roller 59. To the lower felt roller 165. By a cleaning roller pair including the upper felt roller 163 and the lower felt roller 165,
The OHP sheet on which the image is fixed by the fixing device 56 and carried out is sandwiched from above and below, whereby the oil on the sheet is wiped off.

In the case of plain paper, control is performed so that the fixed paper is discharged to the upper discharge tray 26, which is generally easy to handle even from the front of the main unit. That is, the switching flap 64 pivots to the lower position shown in FIG. 9B, whereby the upper felt roller 163 moves in the opposite direction.
Rises and is separated from the lower felt roller 165 to release the oil wiping state by the cleaning roller pair.

By the way, OHP in a color printer
In the paper print mode, it is necessary to perform sufficient fixing, particularly to improve the transparency of a color image. As a method for fixing the toner image to the toner image on the paper surface, either by lowering the paper conveyance degree or increasing the fixing temperature. Give enough heat. In this case, switching of the OHP paper print mode is usually set by key input from the operation panel. However, in this case, a key input operation is required every time OHP paper is used. There is also a possibility that a setting error may occur at the time of key input.

The automatic setting of the print mode by detecting the paper with the sensor is performed by setting the OHP
During the idling period when switching to the paper print mode, it is necessary to mount a complicated configuration such as a clutch mechanism that shuts off the drive of the transport roller in order to place the paper in the standby state in the transport path inside the main unit. come.

In addition, there has been a problem that a defect occurs in a formed image due to static electricity and other state changes that occur between the time when the OHP sheet is stopped in the standby state and the time when the OHP sheet is fed again. Further, it is necessary to perform a process for switching the sheet conveyance speed after re-feeding, and it is necessary to perform these processes for each sheet. Therefore, extremely complicated control is required.

However, there is a simple solution to this problem. Generally, OHP paper has a distinction between front and back, and predetermined corners are cut out so that the front and back can be easily distinguished. By utilizing the front / back discrimination portion, the main apparatus can recognize the distinction between the plain paper and the OHP paper when the paper is placed on the paper cassette 23 or the openable / closable paper feed tray 24. By doing so, the setting of the operation corresponding to each print mode can be started before the start of paper feeding, and the various problems described above are solved.

FIG. 10 is a view for explaining a sheet sorting method using notches for distinguishing front and back of OHP sheets. The figure shows A4 size paper 166, letter size paper 167, and O
An HP sheet 168 is shown. OHP paper 1 shown in FIG.
A portion d where the A4 size paper 166 and the letter size paper 167 overlap in the cutout portion 68 is detected by the sensor. As the sensor, a lever type sensor or a transmission type optical sensor is used. This enables the main unit to recognize the type of the paper when the paper is placed on the paper cassette 23 or the openable / closable paper feed tray 24, and to set the operation corresponding to the print mode before starting the paper feeding. Can be launched.

In this embodiment, since the smoothness of the receiving layer of the OHP paper is set to 2000 seconds or less in the Bec system, the reflected light on the paper surface is detected using a reflection type photo sensor. Plain paper and no reflected light may be recognized as OHP paper. Also in this manner, the type of paper can be recognized on the main unit side when the paper is placed on the paper cassette 23 or the openable / closable paper tray 24, as described above.

[0109]

As described above in detail, according to the first and second embodiments of the present invention, at the time of idling, the oil application roller is separated from the oil application target roller, and the paper passes through the fixing device. Pressurized only when idling, preventing excessive oil application to the first sheet immediately after idling without excessive oil application even after idling, so that it is always stable under any printing condition settings By applying the applied oil, it is possible to fix an image without any trouble.

Further, when the sheet passes through the fixing device, the cleaning member is separated from the roller to be cleaned and retracted, so that no scraping marks are generated on the oil-applied surface by the cleaning member.
The generation of vertical stripes of oil marks on the paper is prevented, and a good image can always be fixed regardless of the type of paper.

Further, since the time during which the oil application roller is in pressure contact with the heat roller is shorter than that of the conventional product, unnecessary pressure contact of the oil application roller with the heat roller is eliminated, and the influence of temporal deformation due to heat and pressure is eliminated. Which reduces
The life of the oil application roller and the cleaning member is prolonged.

According to the third embodiment of the present invention,
By using different oil application rollers for plain paper and OHP paper, the viscosity of oil can be changed appropriately for plain paper and OHP paper, the total amount of oil that can be applied is changed, and oil is applied to the heat roller surface at once. The amount can be changed, so that the proper oil is always applied to the paper regardless of plain paper or OHP paper to maintain the optimal offset prevention function and the life of the oil application unit is extended, The frequency of replacement can be reduced, and the trouble of replacement can be reduced.

According to the fourth embodiment of the present invention,
When warming up or idling at power on,
Alternatively, a fixing / separating claw cleaning member is provided integrally with the heat roller cleaning member that slides on the heat roller alternately with the separation of the heat roller cleaning member from the heat roller when switching the OHP paper print mode, so that power is turned on. When warming up, idling, or O
The oil pool at the tip of the fixing / separating claw can be automatically cleaned at the time of switching of the HP paper print mode, and the like, whereby excessive oil adhesion to the paper can be prevented.

Further, according to the fifth embodiment of the present invention,
The contact part of the thermistor with the heat roller and the contact part of the thermostat with the heat roller are always protected from sliding contact with the heat roller by a protective cover that is integrated with the regular replacement parts, thus preventing wear of the thermistor and the thermostat And the durability is improved, and oil stains and paper dust accumulated on the contact surface with the heat roller are
Since a new protective cover is attached to and removed from the protective cover of the old regular replacement part and replaced with a new protective cover, no stain is generated on the detection member, and therefore, a detection error due to the contamination of the detection member can always be reduced.

Further, according to the sixth embodiment of the present invention,
The contact portion of the thermistor with the heat roller is cleaned by a cleaning member that is linked to another member that moves during regular maintenance, so that oil stains and paper dust adhering to the thermistor are periodically cleaned. The detector is always kept clean.

According to the seventh embodiment of the present invention,
A pair of cleaning rollers that come and go in conjunction with the operation of the switching flap that switches the discharge guide direction of plain paper and OHP paper is provided, and this pair of cleaning rollers is separated for plain paper and abuts for OHP paper. As a result, the oil remaining on the surface of the fixed OHP paper is wiped off, thereby eliminating the problem that the image printed on the OHP paper is stained with excessive oil.

[Brief description of the drawings]

FIG. 1 is a side sectional view of an electrophotographic color printer according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a detailed configuration of an oil application roller and a cleaning member of the fixing device according to the first embodiment. FIG. 2A illustrates an example in which switching of contact and separation with respect to these heat rollers is driven by a switching cam. (B) is a diagram showing an example of driving by an electromagnet.

FIG. 3 is a diagram showing an example in which an oil application roller and a cleaning member according to a second embodiment are formed as an integrated unit, and FIG. 3 (a) shows switching of contact and separation with respect to these heat rollers by a switching cam. FIG. 7B is a diagram illustrating an example, and FIG. 8B is a diagram illustrating an example of driving by an electromagnet.

FIGS. 4A and 4B are diagrams illustrating an example in which an oil application roller is changed depending on whether a sheet passed in a fixing device according to a third embodiment is plain paper or OHP sheet.

FIGS. 5A and 5B are diagrams illustrating an example in which a cleaning member that cleans oil retained in a fixing / separating claw at the time of idling is provided in a fixing device according to a fourth embodiment; FIG. ) Is a diagram showing the operation state.

FIG. 6A is a sectional side view of a fixing device according to a fifth embodiment, and FIG. 6B is a perspective view showing an oil application unit thereof.

FIG. 7A is a sectional side view of a fixing device according to a sixth embodiment, and FIG. 7B is a diagram illustrating an operation state of the thermistor cleaning device.

FIG. 8 is a diagram illustrating an example in which a moving member of a fixing device according to a sixth embodiment is interlocked with opening of an upper cover as an example of interlocking with the movement of another member.

FIGS. 9A and 9B are side sectional views of a fixing device according to a seventh embodiment, showing a configuration and an operation state when excess oil is removed from OHP paper.

FIG. 10 is a diagram illustrating a paper sorting method using a notch for distinguishing front and back of OHP paper.

FIG. 11 is a side sectional view showing a configuration of a conventional fixing device and a configuration in the vicinity thereof.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Fixing apparatus 2 Thermal fixing roller pair 2a Heat roller 2b Pressure contact roller 3 Guide plate 4 Oil application roller 5 Thermistor 6 Thermostat 7 Peeling claw 8 Cleaning member 9 Discharge roller pair 9a Discharge roller 9b Roller 11 Switching flap 12 Discharge path 13 Discharge Roller pair 13a Paper discharge roller 13b Roller 14 Paper discharge tray 21 Main body 21-1 Main unit rear part 22 Top lid 23 Paper cassette 24 Openable paper feed tray 25 Front upper surface 26 Upper paper discharge tray 27 Hinge 28 Transport belt 31 Drive roller 32 Follower roller 33 (33a, 33b, 33c, 33d) Image forming and transferring unit 34 Photoconductor drum 35 Cleaner 36 Initializing charger 37 Exposure head 38 Developing device 39 Developing roller 41 Transfer sheet 42 Support member 43 Suction roller 44 Standby roller pair 45 Feed sensor 4 Paper feed roller 47 Separation member 48 Feed path 49 Feed roller pair 51 Paper feed roller pair 52 Paper guide roller 53 Paper feed roller 54 Paper separation claw 55 Guide plate 56 Fixing device 57 Housing 58 Heating roller 59 Pressure contact roller 60, 62 Oil Coating roller 61 Fixing / separating claw 63 Discharge roller pair 64 Switching flap 65 Discharge path 66 Discharge roller pair 67 Upper discharge port 68 Rear discharge port 69 Send-back transport path 71 Reverse transport roller pair 72 Reverse transport path 73 Send-back End of conveyance path 74 Electrical unit 75 Application roller unit 76 Application roller support member 77 Application roller hinge 78 Application roller pressing spring 79 Cleaning member 81 Cleaning unit 82 Felt support member 83 Felt hinge 84 Felt pressing spring 85 Switching cam 86 Paper entry detection sensor 87 Application Roller support 88 Coating roller hinge 89 Main unit frame 91 Coating roller pulling spring 92 Electromagnet 93 Electric element 94 Coating roller support member 95 Coating roller hinge 96 Coating roller pressing spring 97 Electromagnet 98 Motor 99 Shaft 101 Engagement pin 102 Felt support member 103 Felt hinge 104 Felt Push spring 105 Engagement pin 106 Oil application / cleaning unit 107 Support member 108 Hinge 109 Pull spring 110 Switching cam 111 Oil application / cleaning unit 112 Support member 113 Hinge 114 Press spring 115 Support member 116 Large diameter oil application roller 117 Small diameter oil application Roller 118 Hinge 119 Electromagnet 121 Motor 122 Pin 123 Pulling spring 124 Stopping flange 125 Cross support member 126 Oil application roller for plain paper 127 Oil application roller for OHP paper 128, 129 Press spring 131 Support shaft 132 Oil application roller clutch 133 Support member 134 Hinge 135 Electromagnet 136 Electric element 137 Pin 138 Pull spring 139 Body device frame 141 Oil application roller 142 Elastic thin plate 143 Heat roller cleaning member 144 Fixing separation claw cleaning member 145 Stopping flange 146 Oil cleaning unit 147 Thermistor 147-1 Detection plate 148 Thermostat 149 Handle 151 Thermistor protection cover 152 Thermostat protection cover 153 Moving member 153-1 Arm member -2 cleaning member 154 pressing member 155 support shaft 156 lever 157 pin 158 bar 159 pin 1 1 rotating member 162 hinge 163 upper felt roller 164 bracket 165 lower felt roller 166 A4-size paper 167 letter size paper 168 OHP sheet

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akiyoshi Furusawa 2-229 Sakuragaoka, Higashiyamato-shi, Tokyo Inside Casio Computer Co., Ltd. Tokyo Office (72) Inventor Tetsushi Kurokawa 2-229 Sakuragaoka, Higashiyamato-shi, Tokyo Casio Inside the computer office of Tokyo Co., Ltd. (72) Inventor Yusuke Tokuda 2-229 Sakuragaoka, Higashiyamato-shi, Tokyo Casio Computer Co., Ltd. Tokyo office (72) Kenichiro Asako 2-229 Sakuragaoka, Higashiyamato-shi, Tokyo Casio Computer Co., Ltd. (72) Inventor Zenji Abe 2-229 Sakuragaoka, Higashiyamato-shi, Tokyo Casio Computer Co., Ltd.Tokyo Office (72) Inventor Toshihiko Numazu 2-229 Sakuragaoka, Higashiyamato-shi, Tokyo Casio Computer Co., Ltd. Tokyo In-house F-term (reference) 2H033 BA30 BA43 BA46 BA52 BA59 CA16 CA22 CA39

Claims (8)

[Claims] An unfixed toner sheet, which is formed by a heat roller having a heat source and a pressure roller provided to press against the heat roller, is formed according to image information and carries the transferred unfixed toner. A pair of heat fixing rollers for fixing the unfixed toner to the sheet based on heat and pressure while nipping and transporting the heat roller side; a coating roller for applying release oil to the surface of the heat roller; A cleaning member that cleans the roller surface; a detection member that contacts the heat roller surface and outputs a detection signal for controlling the roller surface temperature; and a detection member that is disposed in contact with or close to the heat roller surface and contacts the sheet front end. And a peeling claw that peels off the sheet from the heat roller surface in contact with the heat roller. The cleaning member is separated from the heat roller while being pressed against the heat roller in accordance with the timing of nipping and conveying, and at other times than the timing, the cleaning member is pressed against the heat roller and the coating roller is separated from the heat roller. A fixing device comprising: a moving mechanism for causing the moving mechanism; and control means for controlling the operation of the moving mechanism. 2. A sheet, comprising a heat roller having a heat source and a pressure roller provided to press against the heat roller, carrying the unfixed toner formed and transferred in accordance with image information, and fixing the unfixed toner surface to the sheet. A pair of heat fixing rollers for fixing the unfixed toner to the sheet based on heat and pressure while nipping and transporting the heat roller side; a coating roller for applying release oil to the surface of the heat roller; A detection member that contacts the roller surface and outputs a detection signal for controlling the roller surface temperature, and peels off the sheet from the heat roller surface by contacting or closely disposed with the heat roller surface and abutting on the sheet front end A peeling claw, wherein one of two coating rollers having different viscosities of the releasable oil to be impregnated is used as the coating roller. Detecting means for detecting whether the sheet conveyed by being nipped and conveyed by the heat fixing roller pair is a plain paper or an OHP sheet, and a sheet detected by the detecting means. And a coating roller control means for controlling the application roller impregnated with the viscous release oil corresponding to the application roller to come into contact with the heat roller. 3. A sheet, comprising a heat roller having a heat source and a pressure roller provided to press against the heat roller, carrying the unfixed toner formed and transferred in accordance with image information, and fixing the unfixed toner surface to the sheet. A pair of heat fixing rollers for fixing the unfixed toner to the sheet based on heat and pressure while nipping and transporting the heat roller side; a coating roller for applying release oil to the surface of the heat roller; A detection member that contacts the roller surface and outputs a detection signal for controlling the roller surface temperature, and peels off the sheet from the heat roller surface by contacting or closely disposed with the heat roller surface and abutting on the sheet front end A fixing surface cleaning member provided so as to be interposed in a contact portion between the heat roller and the detection member. The fixing device to be. 4. The fixing device according to claim 3, wherein the application roller is configured as an exchange unit that can be exchanged according to a predetermined use time, and the detection surface cleaning member is integrated with the exchange unit. apparatus. 5. The fixing device according to claim 3, further comprising moving means for interposing the detection surface cleaning member at the contact portion at a predetermined timing. 6. A sheet, comprising a heat roller having a heat source and a pressure roller provided to press against the heat roller, carrying a sheet carrying untransferred toner formed and transferred in accordance with image information, and fixing the unfixed toner surface to the sheet. A pair of heat fixing rollers for fixing the unfixed toner to the sheet based on heat and pressure while nipping and transporting the heat roller side; a coating roller for applying a release oil to the surface of the heat roller; A detection member that contacts the roller surface and outputs a detection signal for controlling the roller surface temperature, and peels off the sheet from the heat roller surface by contacting or closely disposed with the heat roller surface and abutting on the sheet front end A fixing claw, which is provided downstream of the thermal fixing roller pair and is detachably provided to the sheet discharged from the thermal fixing roller pair. A fixing device, characterized in that it comprises a wiping means for wiping the releasability oil adhering to the sheet in contact with and. 7. A detecting means for detecting whether the sheet nipped and conveyed by the heat fixing roller pair is a plain paper or an OHP sheet, and the sheet detected by the detecting means is an OHP sheet. 7. The fixing device according to claim 6, further comprising a wiping unit control mechanism that operates the wiping unit to contact the sheet at a certain time, and separates the wiping unit from the sheet when the paper is plain paper. 8. A sheet, comprising a heat roller having a heat source and a pressure roller provided to press against the heat roller, carrying a sheet carrying untransferred toner formed and transferred in accordance with image information, and fixing the unfixed toner surface to the sheet. A pair of heat fixing rollers for fixing the unfixed toner to the sheet based on heat and pressure while nipping and transporting the heat roller side; a coating roller for applying release oil to the surface of the heat roller; A detection member that contacts the roller surface and outputs a detection signal for controlling the roller surface temperature, and peels off the sheet from the heat roller surface by contacting or closely disposed with the heat roller surface and abutting on the sheet front end A fixing roller comprising: an oil application roller for a pressure roller that is freely contactable to and detachable from the pressure roller so as to apply release oil to the surface of the pressure roller; When the sheet conveyed by being pinched and conveyed by the heat fixing roller pair has an already fixed toner surface on the back surface of the unfixed toner surface, the oil application roller for the pressure roller is pressed against the pressure roller. A fixing device for controlling an oil application roller for the pressing roller that is separated from the pressing roller.