JP3398500B2 - Fixing temperature control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to an image forming apparatus such as an electrostatic copying machine and controls a fixing temperature by controlling energization to a heater for heating a heat roller of a fixing device. Regarding the device.

[0002]

2. Description of the Related Art In recent years, an electrostatic copying machine has been provided which is capable of copying a large-sized original such as Japanese Industrial Standard A-row No. 0 (hereinafter referred to as "A0 size"). Has reached. "A0 size" here is one of the finished dimensions of paper according to Japanese Industrial Standards,
It refers to the size of 841 (mm) x 1189 (mm).

Since it is difficult to handle the large copy sheets such as the A0 size one by one, usually, a continuous strip-shaped copy sheet is wound around a core rod to copy the copy sheet. The roll sheet accommodated in the machine body is applied. On the other hand, generally, in an electrostatic copying machine, a copy image of a document is formed on a copy sheet as follows. That is, the original is illuminated and scanned, and the photoconductor is exposed by the reflected light from the original. As a result, an electrostatic latent image is formed on the surface of the photoconductor. This electrostatic latent image is visualized as a toner image, and the toner image is heated and fixed on the copy sheet. As a result, a copy image of the original is formed on the copy sheet.

The above-mentioned fixing device includes a pressure roller made of rubber and a heat roller heated by a heater, and heat-fixes the toner on the copy sheet passing between both rollers. In order to perform heat fixing, the fixing device needs to reach a predetermined temperature. Therefore, conventionally, the temperature of the heat roller is detected, and the heater is turned on / off based on the detected temperature to control the temperature of the heat roller to approach a predetermined control temperature.

[0005]

By the way, in the copying machine capable of copying the AO size as described above, there are cases where a large number of narrow sheets such as the A2 size are continuously copied.
In such a case, the sheet passes through the central portions of the heat roller and the pressure roller in the longitudinal direction, the heat is removed, and the sheet is maintained at a predetermined control temperature. On the other hand, in the portion including both ends of the heat roller and the pressure roller in the longitudinal direction, the sheet is not passed, and thus the temperature becomes considerably higher than the control temperature.

Then, the diameter of both ends of the rubber pressure roller becomes large, and the pressure roller is deformed at both ends of the pressure roller. Therefore, when a wide sheet is passed between the rollers, there is a problem that the sheet is wrinkled. This is a problem that is commonly present not only in the above-described copying machine for copying large-sized originals but also in copying machines for copying multiple-sized originals.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing temperature control device capable of preventing the sheet from wrinkling due to the temperature difference between the central portion and the end portion of the pressure roller.

[0008]

In order to solve the above-mentioned problems, the invention according to claim 1 includes a heat roller heated by a pressure roller and a heater, and heat-fixes toner on a sheet passing between both rollers. In a fixing temperature control device including a fixing device for driving the heat roller and a pressure roller, the central temperature detecting means for detecting the temperature of the central portion in the longitudinal direction of the pressure roller, and the pressure roller. End temperature detecting means for detecting the temperature of the end in the longitudinal direction, cooling means for sending air to the pressure roller to cool it, and temperatures detected by the central temperature detecting means and the end temperature detecting means. when conditions including that the difference is greater than a threshold value predetermined are met, to drive the cooling unit in a state of stopping the drive off and and the drive means the power supply to the heater E Bei and control means for setting a cooling mode, the above sheet is low fed out from the roll
Sheet is included in the above conditions,
It is characterized in that it further comprises inputting a relevant signal .

The invention according to claim 2 is the pressure roller and
And a heat roller heated by a heater, and
A fixing device that heats and fixes the toner on the sheet that passes between
And a driving hand for rotating and driving the heat roller and the pressure roller.
In a fixing temperature control device including a step, the pressure roller
Temperature detecting means for detecting the temperature of the central portion in the longitudinal direction of the
And an end for detecting the temperature of the end of the pressure roller in the longitudinal direction.
Air is sent to the section temperature detection means and the pressure roller to cool it.
Cooling means, central temperature detecting means and end temperature detecting means
The difference between the temperatures detected by the steps is a predetermined threshold
When conditions are met, including greater than
Turn off the power to the heater and stop the driving of the driving means.
Set the cooling mode to drive the above cooling means when stopped
And control means for, in the sheet, includes the roll sheet fed out from the roll, the above conditions, and characterized in that further includes inputting a signal related to the switching of the roll unwinding the roll sheet It is something.

[0010]

According to the structure of the invention described in claim 1, the temperature of the end portion of the pressure roller rises and the temperature of the end portion and the center portion of the pressure roller is increased by fixing a large number of narrow sheets continuously. When the difference becomes large, the cooling mode is entered, and the pressure roller is cooled by the cooling fan in a state in which the power supply to the heater is turned off and the rotation of the heat roller and the pressure roller is stopped. As a result, the temperature at the center of the pressure roller and the temperature at the end can be made uniform.

In particular, the pressure roller can be cooled at a timing that does not interfere with the image formation by entering the cooling mode at the time of setup change for replacing the roll of the roll sheet. According to the configuration of the invention according to claim 2 , when the delivery roll is switched, the cooling mode is entered. The pressure roller can be cooled at a timing that does not interfere with image formation.

[0012]

Embodiments will be described in detail below with reference to the accompanying drawings. FIG. 1 is a schematic sectional view of the internal structure of a copying machine including a fixing temperature control device according to an embodiment of the present invention.
FIG. 2 is a perspective view showing the external configuration, and FIG. 3 is a perspective view showing the external appearance of the copying machine during copying. This copying machine is for obtaining a copied image of a large-sized original such as A0 size. In this copying machine, while the document is being conveyed, the surface of the document is illuminated and scanned by the fixed optical system,
An image is formed based on this illumination scan.

Referring to FIG. 1, the main body 1 of the copying machine is provided with caster wheels 2 on its bottom portion so that it can be moved freely. 1 to 3, the copying machine main body 1
A document transport unit 10 for transporting a document 9 along a document transport path 41 formed on the upper surface of the copying machine body 1 is provided above the document transport unit 10.
Is provided. The front surface 1a of the copying machine main body 1 is provided with a discharge port 54 for discharging the sheet on which the toner image is transferred. The sheet discharged from the discharge port 54 is
As shown in FIG. 3, while being guided by the guide member 91, it is dropped with its front end facing downward and is sequentially accommodated in the pocket 92 formed by the front cover 5 along the front surface 1a of the copying machine body 1 through the introduction opening 93. It is like this.
Further, at the end of the upper surface of the copying machine main body 1, there is provided an operation unit 100 having switches, keys and the like for making various settings related to copying.

Referring to FIG. 1, upper and middle lower three roll sheets 4A, 4B and 4C wound in a roll shape are provided in a lower portion from a central portion in a height direction inside the copying machine main body 1. Is housed. These roll sheets 4A, 4B and 4C
Are wound on supply reels 51, 52 and 53, respectively. Examples of the types of the roll sheets 4A, 4B and 4C include plain paper, film and tracing paper. In addition, a cut sheet of A0 size to A4 size or the like, which is cut in advance to a predetermined length, is supplied to the central portion of the copying machine main body 1 through the manual sheet feeding section 30 on the front surface 1a of the copying machine main body 1. Bypass paper feed path D4
Is provided. Referring to FIG. 9, at least a part of the front surface 1a of the copying machine main body 1 has roll sheets 4A and 4B.
Front door 1b that can be opened when changing the rolls of 4C and 4C
The front door 1b is provided in the main body 1 of the copying machine.
A front door opening / closing sensor 110 for detecting opening / closing of the front door is arranged. Note that, in FIG. 9, the illustration of the front cover 5 for forming the pocket 92 is omitted.

The upper roll sheet 4A includes the supply reel 51, the paper feed roller 61, and the roll sheet 4A to be conveyed.
A leading edge detecting switch 71 for detecting the leading edge of the sheet, a conveying roller 62, a cutter mechanism 80, a conveying roller 63, a second edge detecting switch 72 for detecting the leading edge of each of the conveyed sheets 4A, 4B, 4C, 4D, The first sheet feeding path D1 reaching the photoconductor drum 20 through the conveying roller 33 and the conveying roller 33 in sequence.
Is transported along.

The roll sheet 4B in the middle stage is provided with the supply reel 5
2, a paper feed roller 64, a third leading edge detection switch 73 that detects the leading edge of the conveyed roll sheet 4B, a feeding roller 62, a cutter mechanism 80, a feeding roller 63, a second leading edge detection switch 72, and a feeding roller 33. Through the
The sheet is conveyed along the second sheet feeding path D2 that reaches the photosensitive drum 20. The path after the transport roller 62 is common to the first paper feed path D1.

The lower roll sheet 4C is the supply reel 5
3, the paper feed roller 65, a fourth leading edge detection switch 74 for detecting the leading edge of the conveyed roll sheet 4C, the feeding roller 62, the cutter mechanism 80, the feeding roller 63, the second leading edge detection switch 72, and the feeding roller 33. Through the
The sheet is conveyed along the third sheet feeding path D3 that reaches the photosensitive drum 20. The path after the transport roller 62 is common to the first paper feed path D1.

The bypass sheet feeding path D4 is provided with a fifth leading edge detecting switch 75 for detecting the leading edge of the cut sheet 4D introduced from the manual sheet feeding section 30 and a sliding contact plate (not shown). Separation roller 3 for separating cut sheets (separating them one by one) by sliding them against each other
2. A path leading to the photosensitive drum 20 through the sixth leading edge detection switch 76 for detecting the leading edge of the conveyed cut sheet, the registration roller 39, the second leading edge detection switch 72, and the conveyance roller 33 in this order. is there. The path of the bypass paper feed path D4 after the second leading edge detection switch 72 is common to the first paper feed path D1.

Further, the cutter mechanism 80 has a long fixed blade 81 extending in a direction orthogonal to the conveying direction of the roll sheet 4A, 4B or 4C in the casing 80A, and between the fixed blade 81. , The roll sheets 4A, 4 being conveyed
And a rotary blade 82 for cutting B or 4C. Each roll sheet 4A, 4 when being conveyed through the cutter mechanism 80
The transport direction K of B and 4C is upward.

The original document transport unit 10 switches the transport direction to the forward direction R1 or the reverse direction R2 and transports the original document 9. The image forming operation is performed when the document is conveyed in the forward direction R1. When a plurality of sheets are copied from the same original document, the original document transporting unit 10 transports the original document 9 by alternately switching the transport direction between the forward direction R1 and the reverse direction R2. Further, on the upper surface of the copying machine body 1, the forward direction R1
With respect to the document transport section 10, the above-described document transport path 41 is formed up to a position where it projects from the upper surface of the copying machine body 1.

The above-described document conveying section 10 has a first document edge detecting switch 11, a first conveying roller 12, a second document edge detecting switch 16, a second conveying roller 14 along the forward direction R1. And the third conveying roller 15 are sequentially arranged. The first transport roller 12 is started to be driven when the first document end detection switch 11 is switched from OFF to ON and detects the leading end of the document 9 (the end on the downstream side in the forward direction R1). The second transport roller 14 is provided at a position facing the transparent plate 13 for slit exposure of the document 9, and brings the document 9 into close contact with the transparent plate 13. The third transport roller 15 discharges the exposed original document 9.

The second document edge detection switch 16 is also provided.
Is switched from OFF to ON when the document 9 is conveyed in the forward direction R1, and thus the document 9 in the forward direction R1 is
Detect the tip of. This second document edge detection switch 16
Depending on that the roll sheet is turned on, the roll sheet 4A, 4B or 4C (hereinafter, the roll sheet A, 4B or 4C conveyed for transfer is simply referred to as "roll sheet 4").
Is started, and as a result, the original and the roll sheet 4 are synchronized.

The first document edge detection switch 11 is also provided.
Is switched from ON to OFF when the document 9 is conveyed in the forward direction R1, so that the document 9 in the forward direction R1
Detect the rear edge of. The cutter mechanism 80 is driven and the roll sheet 4 is cut at a predetermined timing after a predetermined time has elapsed from the timing of this detection. In this embodiment, the transfer corona discharger 2 from the cutter mechanism 80 is transferred.
The length of the feed path of the roll sheet 4 to the transfer position 20b of No. 4 is larger than the length of the document feed path from the first document edge detection switch 11 to the document exposure position 44. The length is set longer by the length from 20a to the transfer position 20b. As a result, an image corresponding to the trailing edge of the original 9 can be formed on the trailing edge of the roll sheet 4 obtained by cutting at the above timing.

The second document edge detection switch 16 is also provided.
When the document 9 is conveyed in the reverse direction R2, the document 9 is switched from ON to OFF, so that the document 9 in the reverse direction R2 is
Detect the trailing edge of. This second document edge detection switch 16
Is turned off, the transport rollers 12, 14, 1
The drive of 5 is stopped. At this time, the leading edge of the original 9 is nipped by the conveying roller 12 and is ready for the next copying operation. Reference numeral 8 denotes a reversing member that reverses the direction of the document to prevent the document 9 from falling behind the copying machine body 1.

In relation to the transparent plate 13, a light source 17 as a document scanning means for illuminating the document surface of the document 9 is fixedly arranged. The light from the light source 17 is applied to the document surface through the transparent plate 13. Then, the reflected light from the surface of the original 9 is transmitted by the SELFOC lens 18 to the copying machine main body 1
Is guided to the surface of the photoconductor drum 20 provided in the substantially central portion of. The surface of the photosensitive drum 20 before being exposed by the light from the SELFOC lens 18 is uniformly charged by the charging corona discharger 21. Therefore, an electrostatic latent image corresponding to the original image is formed on the surface of the photosensitive drum 20 after exposure. This electrostatic latent image is visualized as a toner image by the developing device 22. The toner image is guided to the vicinity of the transfer corona discharger 24 as the photosensitive drum 20 rotates in the direction of arrow 23.

On the other hand, the roll sheet 4 guided to the photoconductor drum 20 from each sheet feeding path D1, D2 or D3 is further guided to the vicinity of the transfer corona discharger 24, and the corona discharge of the transfer discharger 24 is performed. Thus, the toner image on the surface of the photoconductor drum 20 is transferred to the roll sheet 4. The roll sheet 4 onto which the toner image is transferred is a corona discharger 2 for peeling.
It is separated from the surface of the photoconductor drum 20 by the corona discharge at 5, and further guided to the fixing device 35 through the conveyance path 34. In the fixing device 35, the toner is fixed on the surface of the roll sheet 4 by heating and pressing the roll sheet 4 between the heat roller 37 and the pressure roller 38. The roll sheet 4 on which the toner is fixed is discharged from the discharge roller 36 to the outside of the copying machine main body 1 via the discharge detection switch 55, and is accommodated in the pocket 92 via the guide member 91 as described above. On the other hand, the toner remaining on the surface of the photoconductor drum 20 after the transfer of the toner image is removed by the cleaning device 26, and preparation for forming the next electrostatic latent image is made. Similarly, the toner image is transferred and fixed on the cut sheet 4D guided from the bypass sheet feeding path D4 to the photoconductor drum 20, and the cut sheet 4D is discharged to the pocket 92.

A guide auxiliary plate 94 is arranged above the guide member 91. This guide auxiliary plate 94
Is a stay 9 attached to the front surface 1a of the copying machine body 1.
The roll sheet 4 is rotatably supported by 5 and is rotated to guide the roll sheet 4 that hangs down in front of the guide member 91 and is discharged to the pocket 92 together with the guide member 91 (indicated by a chain line in FIG. 1). (Shown) and the storage posture held by the stay 95 (shown by the solid line in FIG. 1)
It can be displaced to and.

An image forming means is constituted by the photosensitive drum 20, the developing device 22, the transfer corona discharger 24 and the like. In this embodiment, a main motor MM for driving the image forming unit, a sheet feeding motor DM for driving a roller group for feeding the sheets 4A to 4D, and a heat roller of the fixing device 35. 37 and pressure roller 38
Motor FM for fixing as a driving means for driving
And a document feeding motor OM for driving the document feeding unit 10.

Next, referring to FIG. 4, the heating roller 37 is internally provided with a heater 37H for heating the heating roller 37. Further, with reference to FIG. 5A, a cooling fan 107 that mainly blows air on the pressure roller 38 is arranged close to one end face of the pressure roller 38 in the longitudinal direction. The cooling fan 107 is driven by a fan motor FM. Referring to FIGS. 4 and 5A, a first temperature sensor Th1 that detects the temperature of the peripheral surface of the heat roller 37 and a center that detects the temperature of the peripheral surface of the pressure roller 38 at a substantially central portion in the longitudinal direction. A second temperature sensor Th2 as a temperature detecting means and a third temperature sensor Th3 as an end temperature detecting means for detecting the temperature of the peripheral surface of one end in the longitudinal direction of the pressure roller 38 are arranged. On the other hand, a fourth temperature sensor Th4 for detecting the environmental temperature is arranged in a portion of the copying machine body 1 which is not affected by heat (see FIG. 1). These temperature sensors Th1 and T
h2, Th3 and Th4 are composed of a thermistor or the like.

Referring to FIG. 6, which is a block diagram showing an electrical schematic configuration of a portion mainly relating to fixing of the copying machine, the temperature sensors Th1, Th2, Th3 and Th4, the front door opening / closing sensor 110, In addition, the paper type selection key 111 (the roll sheet 4 of each stage is arranged on the operation unit 100).
Plain paper, tracing paper, film, etc. are selected corresponding to A, 4B, and 4C) are connected to a control unit C including a microcomputer, etc., and temperature sensors Th1, Th2, Th3, and Th4, Front door open / close sensor 1
10 and the signal from the paper type selection key 111 are transmitted to the control unit C.
It is designed to be input to. In addition, the control unit C uses the relay 1 for turning on and off the power supply to the heater 37H.
Is connected to a relay drive circuit 102 for driving 03, a motor drive circuit 104 for driving the fixing motor FM, and a fan motor drive circuit 105 for driving the fan motor 106. , Relay 103, fixing motor FM and fan motor 106
The operation of is controlled.

The control section C, the relay drive circuit 102, and the relay 103 constitute an energization control means. The fixing motor F is controlled by the control unit C and the motor drive circuit 104.
Drive control means for controlling M is configured. Next, the control flow will be described with reference to the flowcharts of FIGS. 7 and 8.

First, when the power key of the copying machine is turned on and the processing is started, first, the second temperature sensor Th2 and the third temperature sensor Th2
The central temperature T _P2 and the end temperature T _{P3 of} the pressure roller 38, which are respectively detected by the temperature sensor Th3, are read (step S1), and the difference (T _P2- T _P3 ) between the temperatures is 15 ° C.
If it is above, the cooling mode is entered (step S
2) When the difference is less than 15 ° C., the cooling mode is released under the condition that the cooling mode is in progress, and then the warm-up is performed to make the temperature of the heat roller 37 start up to a predetermined temperature in a stable manner. After the control, the process shifts to the normal control for turning on / off the energization of the heater 37H with the target of the predetermined control temperature (steps S2, S4 to S7). In step S2 immediately after the start of processing, if the difference is less than 15 ° C, the warm-up control is immediately performed without entering the cooling mode.

In the above cooling mode, the cooling fan 107
Is operated with the maximum air volume, and the fixing motor FM and the heater 3
7H is turned off. Next, during normal control, the roll sheet 4A, 4B, or 4C of the sheet feed stage is switched (that is, the switching signal from the paper type selection key 111 is input), and the sheet feed stage. Of the roll sheet 4A, 4B, or 4C of (1) is exchanged (that is, the front door is opened for exchange, and an opening signal is input from the front door opening / closing sensor 110). On the condition that (step S
9, S10), the central temperature T _P2 and the end temperature T _{P3 of} the pressure roller 38 are read (step S11), and if the difference (T _P2 −T _P3 ) between the temperatures is 7 ° C. or more, cooling is performed. The mode is entered (step S13), and when the difference becomes less than 7 ° C., the cooling mode is released on condition that the cooling mode is in progress (steps S14 and S15).

Next, the central temperature T _P2 and the end temperature T _{P3 of} the pressure roller 38 are read (step S16), and when the difference (T _P2 -T _P3 ) between the two is 26 ° C. or more (step S16). S17), fixing motor FM during copying
The rotation speed V of the
0, the speed is increased (steps S18 and S1).
9). That is, in step S19, the rotation speed V is calculated by the formula V = V when 26 ° C ≦ (T _P2 −T _P3 ) ≦ 39 °.
c × [1 + 0.48 × (T _P2 −T _P3 −26) / 13], and at 39 ° C <(T _P2 −T _P3 ), the formula V =
It is calculated by 1.48 × Vc.

Then, step S8 and step S19 are repeated, and when copying is completed (step S8),
Be stopped. Thus, increasing the rotation speed V is
If the difference between the end temperature T _P3 and the central temperature T _P2 (T _P2 −
T _P3) is, even when it becomes large as shown in FIG. 5 (b), by increasing the rotational speed of the heat roller 37 and the pressure roller 38, due to thermal expansion of the end portion of the pressure roller 38 This is to compensate for the decrease in the carrying force. Due to this compensation, there is no difference in the carrying force between the heat roller 37 and the pressure roller 38 and the carrying roller 33 on the upstream side thereof. As a result, the roll sheet 4 and the cut sheet 4D are not loosened between the heat roller 37, the pressure roller 38, and the transport roller 33 on the upstream side thereof, and therefore, at the transfer position 20b of the photoconductor drum 20. It is possible to prevent the toner from being deviated and transferred to the conveyed roll sheet 4 or the like.

According to this embodiment, the difference between the center temperature T _P2 and the end temperature T _P3 of the pressure roller 38 (immediately after the power is turned on or after a large number of narrow sheets are continuously fixed) ( T _P2 −
When T _P3 ) becomes larger than a predetermined threshold value, the cooling mode is entered to cool the pressure roller 38. In cooling mode,
The energization of the heater 37H is turned off, the rotation of the heat roller 37 and the pressure roller 38 is stopped, and the temperature rise of the pressure roller 38 is suppressed, and the pressure roller 38 is cooled by the cooling fan 107. As a result, the center temperature T _P2 and the end temperature T _P3 of the pressure roller 38 can be made uniform, and as a result, it is possible to prevent the occurrence of wrinkling when the wide sheet 4 or 4D is fixed.

In particular, since the cooling mode is entered when the rolls of the roll sheet 4 in the paper feed stage are exchanged or when the rolls 4 in the supply stage are switched, the image formation is not supported. The pressure roller can be cooled with. Note that the difference (T _P2 −T
The threshold value of _P3 ) is set to 15 ° C immediately after the power is turned on.
The reason why it is set to be larger than the threshold value of 7 ° C. during normal control is as follows. That is, immediately after the power is turned on, the heat roller 37 and the pressure roller 38 are rotationally driven (so-called aging) in order to quickly stabilize the temperature of the heat roller 37 and the pressure roller 38. The difference (T _P2 −T _P3 ) between the central temperature T _P2 and the end temperature T _{P3 of the} pressure roller 38 may be large. In such a case, if the above threshold value is set to a small value, the cooling mode may be entered during aging, and it may not be possible to raise the heat roller or pressure roller to a stable temperature. Is.

Besides, various modifications can be made within the scope of the present invention.

[0039]

According to the structure of the invention of claim 1, the temperature of the end portion of the pressure roller rises due to the continuous fixing of a large number of narrow sheets, and the end portion and the central portion of the pressure roller rise. When the temperature difference between the pressure rollers becomes large, the pressure fan is cooled by the cooling fan in a state where the power supply to the heater is turned off and the rotation of the heat roller and the pressure roller is stopped. As a result, the center temperature and the end temperature of the pressure roller can be made uniform, and as a result, it is possible to prevent the occurrence of wrinkling when a wide sheet is fixed.

In particular , the pressure roller can be cooled at a timing that does not interfere with the image formation, such as when the roll of the roll sheet is exchanged for setup. According to the configuration of the second aspect of the present invention, the pressure roller can be cooled at a timing at which the feeding roll is switched, that is, when the image formation is not supported.

[Brief description of drawings]

FIG. 1 is a simplified sectional view showing an internal configuration of a copying machine as an embodiment of the present invention.

FIG. 2 is a perspective view showing an external configuration of a copying machine.

FIG. 3 is a perspective view of the copying machine in use.

FIG. 4 is a schematic side view schematically showing a main part of a fixing device.

5 (a) is Ri schematic side view showing a main part of a fixing device schematically, (b) is a schematic diagram showing the temperature distribution of the pressure roller
Is.

FIG. 6 is a block diagram showing an electrical configuration mainly relating to fixing of the copying machine.

FIG. 7 is a control flowchart.

8 is a flowchart following the flowchart of FIG.

FIG. 9 is a schematic plan view of a copying machine that schematically shows opening and closing of a front door.

FIG. 10 shows the difference between the center temperature and the end temperature of the pressure roller,
It is a figure which shows the relationship of the rotation speed of a fixing motor.

[Explanation of symbols]

35 Fixing Device 37 Heat Roller 37H Heater 38 Pressure Roller C Control Section Th2 Second Temperature Sensor (Central Temperature Detection Means) Th3 Third Temperature Sensor (End Temperature Detection Means) T _P2 Central Temperature T _P3 Edge Temperature FM Fixing Motor 102 relay drive circuit 103 relay 104 motor drive circuit 105 fan drive circuit 106 fan motor 107 cooling fan 110 front door open / close sensor 111 paper type selection key

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-279278 (JP, A) JP-A-5-197235 (JP, A) JP-A-61-11774 (JP, A) Actual Kaihei 2- 90861 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 13/20 G03G 15/20

Claims (2)

(57) [Claims] 1. A fixing device including a pressure roller and a heat roller heated by a heater, which heats and fixes the toner on a sheet passing between the rollers, and a driving means for rotationally driving the heat roller and the pressure roller. A fixing temperature control device comprising: a central temperature detecting means for detecting a temperature of a central portion in the longitudinal direction of the pressure roller; an end temperature detecting means for detecting a temperature of an end portion in the longitudinal direction of the pressure roller; When a condition including a cooling unit that sends air to the pressure roller to cool it and a difference between the temperatures detected by the central temperature detecting unit and the end temperature detecting unit is larger than a predetermined threshold value is satisfied. in, e Bei and control means for setting a cooling mode for driving the cooling unit in a state of stopping the drive off and and the drive means the power supply to the heater, in the sheet, b Roll sheet fed out from Le
The above conditions include signals related to the roll replacement
A fixing temperature control device characterized by further comprising: 2. A heat roller heated by a pressure roller and a heater.
Toner on the sheet that contains the rollers and passes between the rollers.
A fixing device that heats and fixes the sheet, and a driving unit that rotationally drives the heat roller and the pressure roller.
In a fixing temperature control device provided, a center for detecting the temperature of the central portion in the longitudinal direction of the pressure roller.
The temperature detecting means and the end temperature for detecting the temperature of the end of the pressure roller in the longitudinal direction.
Detection means, cooling means for sending air to the pressure roller to cool, and detection by the central temperature detection means and the end temperature detection means.
The difference between the set temperatures is greater than a predetermined threshold.
When the conditions including the
With the power supply turned off and the drive of the drive means stopped
Control means for setting a cooling mode for driving the cooling means
And a roll sheet fed from a roll is included in the sheet, and the condition further includes inputting a signal related to switching of the roll feeding the roll sheet. Fixing temperature control device.