JP2002082568A - Fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that it is uneconomical in terms of power consumption because rise time is long. SOLUTION: At the rising time, only a 1st heating element 2 for heating a spot corresponding to a heating range for a specified small size recording sheet in a fixing member 1 is driven. After rising, the 1st heating element 2 is selectively driven continuously if the size of the recording sheet to be used is not over the specified small size, and at least a heating element 3 other than the 1st heating element 2 is driven if the size of the recording sheet to be used is larger than the specified small size.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used in an image forming apparatus and an image forming apparatus such as a copying machine, a printer, a facsimile, and the like.

[0002]

2. Description of the Related Art Generally, in an image forming apparatus such as a copying machine, a printer, and a facsimile, a pressing member such as a fixing roller and a fixing belt is pressed against a pressing member such as a pressing roller, a pressing belt and a pressing pad. 2. Description of the Related Art A fixing device that fixes toner on a recording sheet to the recording sheet by heating and pressing when a recording sheet such as a transfer sheet passes between a fixing member and a pressing member is used.

Japanese Patent Application Laid-Open No. 8-220930 discloses that a fixing roller is heated by a first heater during standby and during warm-up when a small size is designated as a paper passing size, and a large paper passing size. A fixing device in which a fixing roller is heated by a first heater and a second heater during warm-up when a size is designated is described.

Japanese Patent Application Laid-Open No. 6-236128 discloses that all heaters are used in a process of starting from a low temperature state to a predetermined temperature, and after reaching the predetermined temperature, the heaters are used in order of small numbers. A fixing device for maintaining a temperature is described.

[0005]

Problems to be Solved by the Invention
In the fixing device described in Japanese Patent Laid-Open Publication No. 0-206, when a large size is specified as the paper passing size, the fixing roller is heated by a heater having a paper passing area width for passing a large size recording sheet, and the small paper passing size is set. When the size is specified, the fixing roller is heated by a heater having a paper passage area width for passing a large-sized recording sheet and a heater having a paper passage area width for passing a small-sized recording sheet. At the time of startup, the fixing roller must be heated over the entire area to wait for the temperature to reach a constant temperature over the entire area of the fixing roller, and a long time is required for startup. For this reason, the customer is made to wait and it is made to show. In addition, the frequency at which the large size is specified as the paper passing size is low, and the customer who specifies only the small size as the paper passing size wastes power consumption.

In the fixing device described in JP-A-6-236128, all the heaters are used in the process of starting from a low temperature state to a predetermined temperature, and after reaching the predetermined temperature, the heaters are sequentially turned in a small number. Since the heater is used to maintain the temperature, all heaters are driven at a stage where it is not known which recording sheet is to be passed, which is uneconomical in terms of power consumption. In addition, waiting for the temperature to reach a certain temperature over the entire area of the fixing roller requires a long time, which may cause annoyance to the customer.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing device and an image forming apparatus which are efficient in power consumption, can be started up early, and can be expected to save energy.

[0008]

To achieve the above object, according to the first aspect of the present invention, there is provided a fixing member for heating a toner image on a recording sheet to fix the toner image on the recording sheet;
In a fixing device having a plurality of heating elements for heating portions corresponding to a plurality of heating ranges for a plurality of sizes of recording sheets in the fixing member, at the time of startup, the plurality of sizes of the plurality of heating elements in the fixing member out of the plurality of heating elements. Only the first heating element that heats a portion corresponding to the heating range for the predetermined small-sized recording sheet is driven, and if the size of the recording sheet to be used is smaller than or equal to the predetermined small size after startup, it is optional. The first heating element is continuously driven, and if the size of the recording sheet to be used is larger than the predetermined small size, at least one of the plurality of heating elements other than the first heating element is driven. is there.

According to a second aspect of the present invention, in the fixing device according to the first aspect, the plurality of heating elements respectively heat different portions of the fixing member corresponding to a plurality of heating ranges for recording sheets of a plurality of sizes. A plurality of heating elements.

According to a third aspect of the present invention, in the fixing device according to the first aspect, the predetermined small size is a commonly used size.

According to a fourth aspect of the present invention, in the fixing device of the third aspect, the thickness of the fixing member is such that a portion heated by the first heating element is thinner than other portions.

According to a fifth aspect of the present invention, there is provided a fixing device according to any one of the first to fourth aspects.

[0013]

FIG. 1 shows a circuit configuration of a fixing device according to a first embodiment of the present invention, and FIG. 2 shows a temperature control flow of the fixing device according to the first embodiment. This first
The embodiment is an embodiment of an image forming apparatus having the fixing device according to the first, third, and fourth aspects of the invention, and is an embodiment of the fifth aspect of the invention.

In the fixing device, recently, a member having a thin core has been often used as a fixing member in order to quickly start up. Therefore, as the fixing member, a material having high rigidity such as iron or stainless steel is selected. This material has poor thermal conductivity and poor heat transfer in the axial direction compared to aluminum. The first embodiment solves the above-mentioned problem by utilizing this characteristic in reverse.The core metal material of the fixing member is made of a material having poor heat conductivity, and is selectively formed at the time of startup. Since only the heating element having a small heat distribution is driven, there is no need to heat an extra area of the fixing member, which is efficient in terms of power consumption, and can be started up early to irritate customers. Disappears.

In the fixing device according to the first embodiment, FIG.
As shown in (1), a pressing roller (which may be a pressing belt or a pressing pad) as a pressing member is pressed against a fixing roller (or a fixing belt or the like) 1 as a fixing member by pressing means. 1 and the pressure roller are rotationally driven by a drive mechanism (not shown). In the first embodiment, a recording sheet such as a transfer sheet is fixed to the recording sheet by heating and pressing the toner on the recording sheet when the sheet passes through a nip portion between the fixing roller 1 and the pressure roller. , For example, recording sheets of two sizes. Heaters 2 and 3 as two heating elements are arranged inside or outside the fixing roller 1. The heater 2 is provided within the fixing roller 1 to pass a small-size (smaller one of the two sizes) recording sheet in a sheet passing width area (hereinafter, referred to as a small size sheet passing width area), that is, a small size. Is provided at a location facing a heating range for heating the recording sheet. . The heater 3 is provided within the fixing roller 1 for passing a recording sheet of a large size (the larger one of the two sizes) through which a recording sheet is passed (hereinafter, referred to as a large-size sheet passing width area). Is provided at a location facing a heating range for heating the recording sheet.

The heaters 2 and 3 are independently driven by drivers 4 and 5 as power supply control means, and a thermistor 6 as a temperature detecting device uses a small size recording sheet and a large size recording sheet in the fixing roller 1 in common. To detect the surface temperature of the place where the paper is passed. The detection signal of the thermistor 6 is supplied to a CPU 8 as a control means through an input circuit 7.
The CPU 8 controls the drivers 4 and 5 based on the detection signal from the thermistor 6.

In the first embodiment, at the time of installation, either the quick start mode or the normal mode is selected by a known selecting means such as an operation monitor (not shown). As shown in FIG. 2, when the power is turned on, the CPU 8 checks in step S1 whether the quick start mode or the normal mode is selected by the selection means.
If the quick start mode is selected, the heater 2 as the first heating element is energized via the driver 4 in step S2 based on the output value of the thermistor 6 so that the surface of the fixing roller 1 in the small-size sheet passing width area is controlled. Control is performed so that the temperature becomes the first set temperature.

In the first embodiment, the core metal of the fixing roller 1 is thin (0.1 to
0.5 mm) of iron, and the fixing roller 1 has a heater 2
As a result, only the small-size paper passing width area is heated, and the surface temperature of the small-size paper passing width area reaches the first set temperature early.

The CPU 8 checks in step S3 whether a print (image forming) request signal has been input from the operation unit. If the print request signal has not been input, the output value of the first thermistor 6 is determined in step S4. Set value (1st
(A value corresponding to the set temperature) is determined. C
If the output value of the first thermistor 6 has not reached the set value, the PU 8 returns to step S2, and returns if the output value of the first thermistor 6 reaches the set value.

If the print request signal has been input in step S3, the CPU 8 determines in step S5 the paper passing size of the print request (the size selected by the operation unit or automatically).
(The size of the recording sheet to be used) is checked to determine whether or not the size is larger than the sheet passing width area of the small-size recording sheet. If the paper passing size of the print request is equal to or smaller than the paper passing width area of the small-sized recording sheet, the CPU 8 determines in step S6
The heater 2 is controlled via the driver 4 so that the output value of the first thermistor 6 becomes the set value corresponding to the second set temperature higher than the first set temperature (the surface temperature of the small-size sheet passing width region of the fixing roller 1 is changed). The first thermistor 6 is driven at step S7 to determine whether or not the output value of the first thermistor 6 has reached a set value (a value corresponding to the second set temperature). CPU
8 returns to step S6 if the output value of the first thermistor 6 has not reached the set value corresponding to the second set temperature,
When the output value of the thermistor 6 reaches a set value corresponding to the second set temperature, the image forming apparatus controls the respective units such as an image forming unit to perform an image forming operation.

The CPU 8 can vertically feed the recording sheet in step S8 if the printing request sheet passing size in step S5 is larger than the sheet passing width area of the small-size recording sheet (the recording sheet to be used is vertically fed in step S8). In this case, it is determined whether or not the sheet passing width area of the recording sheet is equal to or smaller than the sheet passing width area of the small-sized recording sheet. If the recording sheet can be fed vertically, the CPU 8 causes the sheet to be used to be fed vertically from a sheet feeding device, which will be described later, at the time of image formation.
Move to

If the recording sheet cannot be fed vertically, the CPU 8 determines in step S9 whether it is possible to reduce the size of the print request image (hereinafter referred to as reduced image formation). I do. If a reduced image can be formed, the CPU 8 controls each unit such as an image forming unit of the image forming apparatus described below to form a reduced image. The heater 2 is turned off, and the heater 3 is turned on via the driver 5 so that the output value of the first thermistor 6 becomes a set value corresponding to the second set temperature (the surface temperature of the large-size paper passing width region of the fixing roller 1 is reduced). (To reach the second set temperature).

Next, the CPU 8 determines whether or not the output value of the thermistor 6 has reached the set value corresponding to the second set temperature in step S11. If the output value of the thermistor 6 has not reached the set value, the process proceeds to step S10. When the output value of the thermistor 6 reaches the set value, the image forming apparatus controls the respective units such as the image forming unit to perform the image forming operation.

As described above, since the core of the fixing roller 1 is made of a thin iron core, the rise time can be shortened, and at the same time, the minimum heat transfer of the fixing roller 1 can be achieved by utilizing the difficulty of heat transfer in the axial direction of the iron core. Since only the limited range is heated and the range in which the fixing roller 1 is not used is not heated, the energy efficiency is good and the rise time can be further shortened.

Further, a user who uses many large-sized recording sheets or dislikes forming a reduced image selects the normal mode by the selecting means. CPU8
If the normal mode is selected by the selection means in step S1, the driver 5 is controlled via the driver 5 in step S12 such that the surface temperature of the large-size paper passing width region becomes the second set temperature based on the output value of the thermistor 6. To drive the heater 3. Next, the CPU 8 determines whether or not the output value of the thermistor 6 has reached the set value corresponding to the second set temperature in step S13, and returns to step S12 if the output value of the thermistor 6 has not reached the set value. When the output value of the thermistor 6 reaches the set value, each unit such as an image forming unit of the image forming apparatus is controlled to perform an image forming operation.

FIG. 6 shows a core metal shape of the fixing roller 1. The fixing roller 1 is configured such that the thickness t1 of the portion 1a corresponding to the small-size sheet passing width region of the cored bar is smaller than the thickness t2 of the portion 1b corresponding to a region other than the small-sized sheet passing width region of the cored bar. . That is, the heater 2 heats only the portion 1a corresponding to the small-size sheet passing width region of the core of the fixing roller 1, and changes the thickness t1 of the portion 1a corresponding to the small-size sheet passing width region other than the small-size sheet passing width region. Thickness t2 of location 1b corresponding to the region of
The reason for this is that the portion 1a corresponding to the small-size sheet passing width region reaches the predetermined temperature more quickly by making it thinner.

In the first embodiment, the small-size sheet passing width area is A4 vertical size, which is commonly used in the world,
Accordingly, it is considered that most customers are satisfied with the small-size paper width area (use the small-size paper width area). For this reason, the machine can be started up without waiting for the customer, and the customer who frequently uses the A4 vertical size can benefit from power consumption.

FIG. 3 shows the whole of the first embodiment. A charging unit 10 is provided around a drum-shaped photosensitive member 101 as an image carrier which is rotated in a direction indicated by an arrow by a driving unit (not shown).
2. A cleaning unit 103, a developing unit 107 including a developing sleeve 105 as a developing unit for developing an electrostatic latent image on the photoconductor 101, and a transfer unit 106 are arranged.

After the photosensitive member 101 is uniformly charged by the charging means 102, it is exposed to laser light L from a laser optical system 140 as a writing means (exposure means) to form an electrostatic latent image. The electrostatic latent image is developed by 107 to become a toner image. The toner image on the photoreceptor 101 is transferred to a sheet P as a recording sheet as described later.
Cleaning. Therefore, the charging means 10
2. the laser optical system 140 and the developing unit 107
An image forming means for forming a toner image thereon is constituted.

At the lower part of the apparatus, there is provided a paper feeder having a paper feed cassette 110 which is detachable in the direction of arrow a. The sheet P accommodated in the sheet cassette 110 has a middle plate 111.
And is pressed against the paper feed roller 113 via the arm 112 by the force of a spring (not shown). The uppermost sheet in the sheet feed cassette 110 is fed by a rotation of the sheet feed roller 113 in response to a command from a control unit (not shown), and while the double feed is prevented by the separation pad 114, the registration roller pair 115 on the downstream side Transported to

An operation surface is disposed on the right side of the apparatus, and an operation panel 130 protrudes from the upper front surface of the exterior part 131 (the right side on the apparatus in FIG. 3). Further, a paper feed tray 132 constituting the paper feed device is rotatably mounted by a pin 133, and the uppermost sheet in the paper feed tray 132 is fed by a paper feed roller and double feed is prevented by a separation pad. While being transported to the registration roller pair 115 on the downstream side. The sheets in the sheet cassettes 110 and 132 are sheets having different sizes from each other, and one of the sheets is selectively fed.

The registration roller pair 115 sends the conveyed sheet P to the transfer means 106 at a timing synchronized with the image (toner image) on the photosensitive member 101. The transfer unit 106 transfers the image on the photoconductor 101 to the paper P sent from the pair of registration rollers 115,
The sheet P on which the image has been transferred is conveyed to the fixing device 116. As the fixing device 116, the above-described fixing device is used, and the toner on the sheet P is fixed to the sheet P by heating and pressing.

The sheet P on which the image has been fixed from the fixing device 116
Are discharged onto a paper discharge tray 122 from a paper discharge port 121 by a paper discharge roller pair 120 and stacked. The ejection stopper 125 is slidable in the direction of arrow b to correspond to the size of the ejected paper. In a case 134 arranged on the left side in the drawing, electric equipment and control devices such as a power supply circuit 135 and a printed board 136 (engine driver board) are housed, and a controller board 137 is also housed. The cover 138 constituting the paper discharge tray 122 can be opened around the pivot 139. Note that the first embodiment has a well-known scaling function, and can form a reduced image and an enlarged image.

According to the fixing device of the first embodiment,
A fixing roller 1 serving as a fixing member for heating a toner image on a recording sheet to fix the toner image on the recording sheet, and portions of the fixing member 1 corresponding to a plurality of heating ranges for a plurality of sizes of recording sheets are heated. In the fixing device having the heaters 2 and 3 as a plurality of heating elements, at the time of startup (at the time of warm-up), a predetermined small one of the plurality of sizes of the fixing member 1 of the plurality of heating elements 2 and 3 is used. Only the first heating element 2 that heats a portion corresponding to the heating range for the recording sheet of the size is driven, and if the size of the recording sheet to be used is equal to or smaller than the predetermined small size after startup (after warm-up), Selectively driving the first heating element 2 continuously, and if the size of the recording sheet to be used is larger than the predetermined small size, Since driving at least the first heating element 2 heating elements 3 other than the one of the number of heating elements 2 and 3, the power consumption to improve efficiency, can be started up quickly.

Further, according to the first embodiment, since the predetermined small size is a commonly used size, it is possible to enhance the effect that power consumption is efficient and the system can be started up early. it can. Further, according to the first embodiment, the thickness of the fixing member 1 is thinner at a portion heated by the first heating element 2 than at other portions. On the other hand, an energy saving effect can be expected when fixing is performed, and an image can be formed with a shorter rise time. Also,
According to the first embodiment, since the fixing device 116 is provided, the entire image forming apparatus has high power consumption efficiency,
Can be launched early.

FIG. 4 shows a circuit configuration of the fixing device according to the second embodiment of the present invention, and FIG. 5 shows a temperature control flow of the fixing device according to the second embodiment. The second embodiment is an embodiment of an image forming apparatus having a fixing device according to the first to fourth aspects of the invention, and is an embodiment of the fifth aspect of the invention.

In the second embodiment, a heater 9 is provided in place of the heater 3 in the first embodiment. The heater 9 is provided so as to heat only a region other than the small-size paper passage width region (a region that does not overlap with the small-size paper passage width region) in the large-size paper passage width region of the fixing roller 1. Driven by 10. The thermistor 11 as a temperature detecting device detects the surface temperature of a portion of the large-size paper passing width area of the fixing roller 1 heated by the heater 9, and the thermistor 6 detects the surface temperature of the small-size paper passing width area of the fixing roller 1. I do. The detection signal of the thermistor 11 is read into the CPU 8 via the input circuit 12.

In the first embodiment, only one of the heaters 2 and 3 is driven, and both of the heaters 2 and 3 are not driven at the same time.
In the case where heating of the large-size sheet passing width area is required, the heaters 2 and 9 are simultaneously driven. An advantage of the second embodiment is that the CPU 8 controls the heater 2 via the driver 4 based on the output value of the thermistor 6 and the heater 9 via the driver 10 based on the output value of the thermistor 11.
Is controlled, the large-size sheet passing width region of the fixing roller 1 can be maintained at a uniform temperature in the axial direction, and energy efficiency is good.

As shown in FIG. 5, if a reduced image cannot be formed in step S9, the CPU 8 controls the heater 2 as the first heating element via the driver 4 in step S14.
The driving of the thermistor 6 is performed so that the output value of the thermistor 6 becomes a set value corresponding to the second set temperature.
Driving is performed so that the output value of 1 becomes a set value corresponding to the second set temperature.

Next, the CPU 8 determines whether or not the output value of the thermistor 6 has reached the set value corresponding to the second set temperature in step S16. If the output value of the thermistor 6 has not reached the set value, the process proceeds to step S14. Return to Next, the CPU 8
When the output value of the thermistor 6 reaches the set value, it is determined in step S17 whether the output value of the thermistor 11 has reached the set value corresponding to the second set temperature, and the output value of the thermistor 11 is set to the set value. If not reached, return to step S15,
When the output value of the thermistor 11 reaches the set value, the image forming apparatus controls each unit such as an image forming unit to perform an image forming operation.

If the normal mode is selected by the selection means in step S1, the CPU 8 controls the heater 2 via the driver 4 in step S18, and the output value of the first thermistor 6 corresponds to the second set temperature. The heater 9 is driven to the set value, and the heater 9 is driven via the driver 10 in step S19 so that the output value of the second thermistor 11 becomes the set value corresponding to the second set temperature.

Next, the CPU 8 determines whether or not the output value of the thermistor 6 has reached the set value corresponding to the second set temperature in step S20. If the output value of the thermistor 6 has not reached the set value, the process proceeds to step S18. Return to When the output value of the thermistor 6 reaches the set value, the CPU 8 proceeds to step S21.
It is determined whether or not the output value of the thermistor 11 has reached the set value corresponding to the second set temperature. If the output value of the thermistor 11 has not reached the set value, the process returns to step S19, and the output value of the thermistor 11 is set. When the value reaches the value, each unit such as an image forming unit of the image forming apparatus is controlled to perform an image forming operation.

According to the second embodiment, the same effects as those of the first embodiment can be obtained. further,
The plurality of heating elements 2 and 9 correspond to a plurality of heating ranges for the recording sheets of a plurality of sizes in the fixing member 1 and are a plurality of heating elements for heating different portions 1a and 1b, respectively. When the size is larger than the predetermined small size, the heating range for heating the recording sheet of the fixing member 1 can be maintained at a uniform temperature in the axial direction, and energy efficiency is good.

[0044]

As described above, according to the first aspect of the present invention, power can be efficiently consumed and the apparatus can be started up early. According to the second aspect of the invention, when the size of the recording sheet to be used is larger than the predetermined small size, the heating range for heating the recording sheet of the fixing member can be maintained at a uniform temperature in the axial direction, and energy efficiency can be improved. Is good.

According to the third aspect of the present invention, it is possible to enhance the effect that power can be efficiently started and power can be started early. According to the fourth aspect of the present invention, an energy saving effect can be expected when fixing a recording sheet generally used in the market, and an image can be formed with a shorter rise time. Claim 5
According to the present invention, the image forming apparatus as a whole is efficient in power consumption and can be started up early.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a circuit configuration of a fixing device according to a first embodiment of the present invention.

FIG. 2 is a flowchart illustrating a temperature control flow of the fixing device according to the first embodiment.

FIG. 3 is a sectional view showing the whole of the first embodiment.

FIG. 4 is a block diagram illustrating a circuit configuration of a fixing device according to a second embodiment of the present invention.

FIG. 5 is a flowchart illustrating a temperature control flow of a fixing device according to the second embodiment.

FIG. 6 is a cross-sectional view illustrating a core metal shape of the fixing roller of the embodiment.

[Explanation of symbols]

 1 Fixing roller 2, 3, 9 Heater 4, 5, 10 Driver 6, 11 Thermistor 7, 12 Input circuit 8 CPU 1a Location corresponding to small-size paper width region 1b Location corresponding to other than small-size paper width region

Claims (5)

[Claims] A fixing member for heating a toner image on a recording sheet and fixing the toner image on the recording sheet, and a plurality of portions for heating portions of the fixing member corresponding to a plurality of heating ranges for recording sheets of a plurality of sizes. A first heat generating unit that heats, at the time of startup, a portion of the plurality of heating elements corresponding to a heating range for a predetermined small-sized recording sheet of the plurality of sizes in the fixing member. Only the body is driven, and after the rising, if the size of the recording sheet to be used is equal to or smaller than the predetermined small size, the first heating element is selectively driven continuously, and the size of the recording sheet to be used is the predetermined small size. If the size is larger than at least one of the plurality of heating elements, a heating element other than the first heating element is driven. Apparatus. 2. The fixing device according to claim 1, wherein the plurality of heating elements correspond to a plurality of heating ranges for recording sheets of a plurality of sizes in the fixing member, and each of the plurality of heating elements heats different portions. A fixing device. 3. The fixing device according to claim 1, wherein the predetermined small size is a commonly used size. 4. The fixing device according to claim 3, wherein a thickness of the fixing member is smaller at a portion heated by the first heating element than at other portions. 5. An image forming apparatus comprising the fixing device according to claim 1.