JPH11153925A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the surface temperature of a fixing roller from being lowered in the early stage of consecutive paper passing operation and to consistently fix a color image with high glossiness by shortening a toner image fixing cycle in accordance with the increase of the number of toner image fixing times. SOLUTION: A fixing cycle control means controls so that the toner image forming cycle may be shortened in accordance with the increase of the number of toner image forming times. Namely, a control substrate performs paper passing operation at a time interval being a1 when the passing of recording paper S is started, and performs the paper passing operation at the time interval which gets shorter according to the number of paper passing times such as a2, a3, a4, a5 and a6 thereafter. When the paper passing interval gets to a6, the paper passing operation is performed at the paper passing interval in which a6 is set as a fixed cycle thereafter. Thus, when fixing is consecutively performed, the quantity of heat supplied by a heater till performing next fixing gets large just after starting the fixing, and the sufficient quantity of heat is stored in a thermal fixing means. Therefore, the temperature of the thermal fixing means is not lowered at the time of starting the fixing, and the thermal fixing means is always kept at a temperature high enough to perform fixing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device provided in an apparatus for forming an image by electrophotography.

[0002]

2. Description of the Related Art An electrophotographic image forming apparatus such as a copying machine is provided with a fixing device for fixing an unfixed toner image formed on a recording sheet as a recording medium to the recording sheet. The fixing device includes, for example, a fixing roller having a surface having a releasing property to toner, a pressing roller for fixing a toner image on recording paper in cooperation with the fixing roller, and at least a fixing roller or a pressing roller. It has a heater built in and heated by the toner to heat and melt the toner, and a recording paper transport unit capable of continuously transporting the recording paper holding the unfixed toner between the fixing roller and the pressure roller (nip). doing.

An electrophotographic image forming apparatus forms a toner image on recording paper on the surface of a photosensitive drum, and conveys the recording paper to a nip portion via a recording paper conveyance unit. At this time, the toner image on the recording paper is unfixed, but is pressed at the nip portion and melted by heat generated by the heater to be fixed on the recording paper.

When an image forming apparatus exclusively prints a monochrome image, a hard roller having a rigid surface is generally used as a fixing roller. As the rigid body, for example, aluminum or the like having excellent heat conductivity is used. In some cases, a Teflon layer (Teflon: registered trademark of DuPont) is provided on the aluminum surface to extend the life of the fixing roller.

The hard rollers include a thick hard roller having a relatively thick aluminum (about 8 mm) and a thin hard roller having a relatively thin (about 1 mm) aluminum. Thick hard rollers have the advantage that the pressure applied to the recording paper at the nip is greater than thin hard rollers, while thin hard rollers require less heat in the heater in a shorter time than thick hard rollers. It has the advantage of being transmitted to the roller surface.

FIGS. 12 to 14 show a surface temperature of a hard roller when a recording paper is continuously supplied (passed) to a nip portion and a toner image is continuously fixed, and a heater built in the hard roller. (For example, a halogen lamp) is an ON timing, and the interval at which paper passing is performed (paper passing interval). In each case, the horizontal axis indicates time. 12 to 14 use a hard roller as a fixing roller, FIGS. 12 and 13 show characteristics when a thick hard roller is used, and FIG. 14 shows a case when a thin hard roller is used. Represents the characteristics.

In FIG. 12, the heater is heated by warming up, and the surface temperature of the hard roller is raised to T1 before the start of sheet feeding. At this time, the recording paper is continuously passed at regular intervals (continuous paper passing).

[0008] When paper feeding starts (ie, fixing starts),
Heat is taken from the surface of the fixing roller due to heating and melting of the toner image. For this reason, the temperature of the fixing roller surface decreases,
As shown in the figure, the temperature may drop below the minimum temperature T2 required for fixing. Such a decrease in the roller surface temperature is approximately 50 CPM (CPM is Copy Per Minut
This is an abbreviation of e, which means the number of copies that can be made per minute), which is particularly remarkable in a high-speed machine having a processing capacity of about (1).

[0009] Such energy shortage related to fixing can be avoided if the image forming apparatus is configured to supply more electric power to the heater. However, the power supplied to the heater is limited by the life of the halogen lamp and the power supply of the image forming apparatus, and it is often difficult to supply a larger power.

For this reason, in the conventional image forming apparatus, for example, the temperature of the fixing roller is detected, and the sheet is passed until the surface temperature of the fixing roller reaches T2 (9 sheets in the example of FIG. 12). Temporarily, and wait for the temperature of the fixing roller surface to rise again, or determine the fixing cycle according to the number of recording sheets that are continuously passed, or change the fixing cycle according to the number of times of fixing. And so on.

FIG. 13 is a diagram specifically illustrating a method of changing the fixing cycle in accordance with the number of times of fixing. In the method of FIG. 13, the setting is made so that the paper passing interval becomes wider as the number of times of fixing is increased, that is, the fixing cycle becomes longer.
With this setting, the amount of heat stored on the surface of the fixing roller between fixing and fixing increases as the number of times of fixing increases.

For this reason, the temperature of the fixing roller surface gradually decreases, and the amount of heat taken away by fixing and the amount of heat supplied from the heater are in an equilibrium state, and the surface of the fixing roller is kept from falling below the temperature T2. be able to.

FIG. 14 uses a thin hard roller as the fixing roller as described above. Accordingly, the amount of heat generated by the heater is efficiently transmitted to the surface of the fixing roller, and the fixing roller can obtain sufficient energy for fixing from the heater. In the example of FIG. 14, the heater is turned on intermittently to prevent the temperature of the surface of the fixing roller from unnecessarily increasing.

[0014]

By the way, there are many recent electrophotographic image forming apparatuses capable of printing a color image. To fix a color image, the toner surface is melted uniformly and finished with high gloss.
A fixing roller having a mirror surface and an elastic body is used. As the fixing roller, a thin rubber roller is generally used in which a thin silicon rubber having high releasability is provided on a surface of a roller using thin aluminum.

FIG. 15 shows the surface temperature of the fixing roller when such a thin rubber roller is used as a fixing roller.
FIG. 4 is a diagram illustrating ON timing of a heater built in the fixing roller and intervals at which paper is passed, and the horizontal axis indicates time.

Silicon rubber provided on the surface of the thin rubber roller is a member having a lower thermal conductivity than metal. Therefore, the temperature of the heater is transmitted to the surface of the fixing roller later than that of the hard roller, and the surface of the fixing roller is not sufficiently stored at the start of fixing. For this reason, at the start of sheet passing, the heater ON time is set longer than the subsequent ON time. However, this setting is also not enough to compensate for the shortage of heat storage on the roller surface. If continuous paper passing is performed at regular intervals, the temperature of the fixing roller surface starts to decrease immediately after the start of fixing. The lowered temperature then rises again after reaching a peak, and is maintained at a constant temperature determined by the amount of heat taken away by the fixing and the power intermittently supplied from the heater.

However, the temperature of the roller at the time of fixing is
This is an element that affects the gloss of a printed image, and particularly has a significant effect on image quality when fixing a color image. For this reason, if the temperature of the surface of the thin rubber roller temporarily decreases, there is a possibility that the image quality of the color image formed by continuous paper passing may be deteriorated or uneven.

The present invention has been made in view of the above points, and prevents the temperature of the surface of the fixing roller from being lowered in the early stage of continuous paper feeding, so that a color image can be consistently formed with high gloss. It is an object to provide a fixing device for fixing.

[0019]

According to a first aspect of the present invention, there is provided a fixing device comprising:
A fixing device for fixing a toner image to a recording medium, provided in an image forming apparatus having a recording medium conveying unit capable of continuously conveying a recording medium on which a toner image is formed, wherein the toner on the recording medium is A heating and fixing unit for fixing the recording medium while heating and melting, and when the toner images are continuously fixed on the plurality of recording media continuously conveyed from the recording medium conveying unit, the number of toner image fixing increases. Therefore, a fixing cycle control means for shortening the cycle of fixing the toner image is provided.

With this arrangement, when fixing is performed continuously, the fixing cycle at the start of fixing is longer than the cycle of fixing performed thereafter. Therefore, immediately after the start of fixing, the amount of heat supplied by the heater is increased until the next fixing is performed, and a sufficient amount of heat is stored in the heat fixing unit. Therefore, the temperature of the heat fixing unit does not decrease even at the start of fixing, and the temperature of the heat fixing unit can always be maintained at a temperature sufficient for fixing. Further, by shortening the period of the subsequent fixing, it is possible to prevent the processing time of the fixing from being lengthened.

Further, by using a thin rubber roller for such a heat fixing means, it is possible to provide a fixing device suitable for fixing a color image without a temperature decrease of the heat fixing means at the beginning of the fixing process.

According to a second aspect of the present invention, there is provided a fixing device provided in an image forming apparatus having a recording medium conveying means capable of continuously conveying a recording medium on which a toner image is formed, and fixing the toner image on the recording medium. A heating and fixing unit for fixing toner on the recording medium while heating and melting the toner on the recording medium; and a toner image continuously on the plurality of recording media continuously conveyed from the recording medium conveying unit. Fixing the toner image on a predetermined number of the recording media among the plurality of recording media, and then shortening the cycle of fixing the toner image as the number of times of fixing the toner image increases. It is characterized by the following.

With this configuration, the fixing can be performed in a normal relatively short fixing cycle while the temperature of the heat fixing unit does not decrease. For this reason, it is possible to prevent the time required for fixing from becoming long.

Further, by using a thin rubber roller for the heat fixing means of such a fixing device, the temperature of the heat fixing means does not decrease even after several sheets have passed from the start of the fixing process, so that a color image can be fixed. It is possible to provide a fixing device suitable for the above.

According to a third aspect of the present invention, in the fixing device, the fixing cycle control means shortens a cycle of fixing the toner image by increasing a conveying speed of the recording medium in the recording medium conveying means. is there.

With this configuration, the period of fixing the toner image can be easily shortened.

According to a fourth aspect of the present invention, in the fixing device, the fixing cycle control means shortens a cycle of fixing the toner image by shortening an interval of the recording medium conveyed by the recording medium conveying means. Things.

With this configuration, the period of fixing the toner image can be easily reduced.

According to a fifth aspect of the present invention, in the fixing device, the heat fixing unit fixes the toner image on the recording medium in cooperation with a fixing unit having a surface having a releasing property to the toner and the fixing unit. And a heating unit incorporated in at least one of the fixing unit and the pressing unit, and heating and melting the toner.
The fixing cycle control unit causes the heating unit to generate heat for a longer time than the heat generation time after the start of the process related to the formation of the toner image.

With this configuration, the amount of heat applied to the heater at the start of the toner image forming process can be increased. Therefore, immediately after the start of fixing, the amount of heat supplied to the heating and fixing unit by the heater becomes large, and a sufficient amount of heat is stored in the heating and fixing unit in a short time. For this reason, the temperature of the heat fixing unit does not decrease immediately after the start of fixing, and the temperature of the heat fixing unit can always be maintained at a temperature sufficient for fixing.

According to a sixth aspect of the present invention, in the fixing device, the fixing cycle control means controls a cycle for fixing the toner image in accordance with the size of the recording medium.

With this configuration, the recording medium size can be considered in the fixing cycle of the toner image. In other words, when the size of the recording medium is large, the amount of heat lost by the heating and fixing means due to the fixing performed at one time is larger than when the recording medium is small. For example, by setting the fixing cycle longer, or by delaying the start of the process for shortening the fixing cycle, it is possible to perform control in accordance with the state in which further fixing is performed.

According to a seventh aspect of the present invention, in the fixing device, the fixing cycle control means controls a cycle for fixing the toner image in accordance with a length of the recording medium in the conveying direction.

With this configuration, the length of the recording medium in the transport direction can be considered in the fixing cycle of the toner image. For example, when the length of the recording medium in the transport direction is long, the amount of heat lost by the heating and fixing unit due to fixing performed at one time is larger than when the length is short. Therefore, when the length of the recording medium in the transport direction is long, the fixing cycle immediately after the start of fixing is set longer than that in the case where the length is short. Can be determined.

The fixing device according to the present invention is characterized in that the fixing cycle control means controls a cycle for fixing the toner image in accordance with a basis weight of the recording medium.

With this configuration, the basis weight of the recording medium can be considered in the fixing cycle of the toner image. For example, when the basis weight of the recording medium is large, the heat capacity of the recording medium increases, so that the amount of heat lost to the fixing unit increases. Therefore, when the basis weight of the recording medium is large,
The temperature of the heating and fixing unit can be adjusted by, for example, making the fixing cycle longer than in the case of a small size.

According to a ninth aspect of the present invention, in the fixing apparatus, the fixing cycle control means controls a cycle for fixing the toner image in accordance with all of the size, length in the conveying direction, and basis weight of the recording medium. It is assumed that.

With this configuration, finer control can be performed according to the characteristics of the recording medium.

[0039]

Embodiments of the present invention will be described below. The fixing device of the present invention is provided in an image forming apparatus such as a printer or a copying machine. The fixing device according to the embodiment described below is assumed to be built in a copying apparatus in any of the embodiments. This fixing device is operated in accordance with the operation timing of the copying apparatus in order to facilitate the operation of the entire copying apparatus. Hereinafter, in the present specification, it is assumed that the fixing timing of the fixing device is equal to the copying (image formation) timing of the copying device.

<Embodiment 1> FIG. 1 is a diagram showing a schematic configuration of a fixing device common to each embodiment described below. The present fixing device is provided in a copying apparatus having a transport system 200 (FIG. 2) as a recording medium transport means capable of continuously transporting a recording sheet S, which is a recording medium on which a toner image is formed, and records the toner image. Fixes on paper S. The fixing device includes a heat fixing unit that fixes the toner T on the recording paper S to the recording paper S while heating and melting the toner T, and continuously forms a toner image on a plurality of the recording media conveyed continuously from a conveyance system. A control board 10 (FIG. 2) which is a fixing cycle control means for shortening the cycle of fixing the toner image as the number of times of fixing the toner image increases when fixing is performed. The control board 1
0 (fixing cycle control means) may be incorporated in an image forming apparatus main body such as a copying apparatus.

The heat fixing means is a fixing roller 2 which is a fixing unit having a surface having a releasability from the toner T, and a pressing unit which fixes a toner image on recording paper in cooperation with the fixing roller 2. It has a pressure roller 1 and a heater 3 which is built in at least one of the fixing roller 2 and the pressure roller 1 and is a heating means for heating and melting the toner. In this embodiment, a halogen lamp is used as the heater 3.

The fixing roller 2 is a thin rubber roller having a silicon rubber layer 2a of about 0.3 mm provided on a surface of aluminum 2b of about 1 mm. In the illustrated configuration, the pressing roller 1 is also an elastic roller having an elastic surface.
A nip portion N is formed at a contact portion between the fixing roller 2 and the pressure roller 1. In the nip portion N, the unfixed toner T
Is transported from the transport system 200 (FIG. 2).

When the recording paper S is continuously conveyed from the conveyance system 200, the fixing at the nip N is also performed continuously. For this reason, in the first embodiment, the fixing cycle of the fixing device is changed by changing the paper interval. The contents will be described later.

FIG. 2 is a block diagram for explaining a configuration for controlling the fixing device having the above configuration.

The configuration shown in the figure includes a transport system 200 including a drive motor 20 and a paper feed clutch 21 and an operation panel 4.
0, heater 3, and control board 10 for controlling the above configuration.
And a commercial power supply 5 for supplying electric power to the heater 3. Further, a thermostat 7 for detecting abnormal heating and a solid state relay 9 for supplying power to the heater are provided between the heater 3 and the commercial power supply 5. The control board 10 inputs the detected temperature of the thermistor 30 for detecting the temperature of the surface of the fixing roller 2, controls the solid state relay 9 according to this temperature, and turns the heater 3 on and off.

The drive motor 20 is a common motor for driving a plurality of rollers (transport rollers) for transporting the recording paper S in the copying apparatus, the fixing roller 2 and the pressure roller 1. The paper feed clutch 21 is a clutch that connects or disconnects the drive motor 20 and a transport roller driven by the drive motor 20. The operation panel 40
Is a panel on which a user sets conditions such as an image forming mode and the number of sheets.

The control board 10 is a member formed by electrically connecting a plurality of electronic components. The plurality of electronic components constitute a memory, a timer, a switch, and the like according to the purpose. The memory incorporated in the control board 10 stores the fixing cycle, the ON time of the heater 3, and the like. The timer is for measuring a fixing cycle and the like.

The configuration described above operates as follows.

When an instruction to start image formation is input to the operation panel 40, the control board 10 drives the drive motor 20 and turns on the paper feed clutch 21 to feed the recording paper S to the nip N by the transport rollers. And convey. Then, the toner T on the recording paper S is pressurized while being heated and melted in the nip portion N, and is fixed on the recording paper S.

FIG. 3 is a diagram for explaining a fixing cycle and a heater ON timing performed in the first embodiment.
The vertical axis in FIG. 3 indicates the surface temperature of the fixing roller 2 and the ON timing of the heater 3, and the horizontal axis indicates time. Also,
Below the horizontal axis, the paper passing interval of the recording paper S passed through the fixing device is shown. In the first embodiment, the fixing cycle of the fixing device is determined based on the sheet passing interval.

As shown, in the first embodiment, the fixing roller 2 is heated by turning on the heater 3 intermittently.
The ON time h1 immediately after the start of fixing is set longer than the subsequent ON time h2 immediately after the start of fixing. An example of the process for setting the ON timing of the heater 3 in this manner will be described later in a fifth embodiment.

The fixing cycle of this embodiment is controlled so that the cycle of fixing the toner image is shortened as the number of times of fixing the toner image increases.

That is, as shown in FIG.
When the recording paper S is started, the paper is passed at the time interval a1 (paper passing interval), and thereafter, the paper is passed at the paper passing intervals a2, a3, a4, a5, and a6. As is clear from the figure, a1
The paper passing interval of a to a6 becomes shorter as the number of times of paper passing increases. And the paper passing interval is a6 in the figure.
After that, the sheet is passed at a sheet passing interval with this a6 being a constant cycle.

In the first embodiment, the sheet passing intervals a1 to a6 are made shorter by a fixed time.
The fixing cycle corresponding to the sheet passing interval a1 immediately after the start of the fixing corresponds to the initial fixing cycle L1, the fixing cycle corresponding to the fixed sheet passing interval a6 corresponds to the normal fixing cycle L0, and the fixed shortening of the sheet passing interval. The time ΔL is stored in the control board 10 in advance.

By controlling the paper passing interval as described above, the temperature of the surface of the fixing roller is kept constant as shown in the figure.

FIG. 4 is a flowchart for explaining processing by the control board 10 for shortening the fixing cycle according to the first embodiment.

First, when a copy start is input to the operation panel 40 (S1), the rotation of the drive motor 20 is started to convey the recording paper S to the fixing device (S2). Then, the fixing cycle L is set to the initial fixing cycle L1 (corresponding to a1 in FIG. 3) stored in the control board 10 in advance (S
3) At this time, it is determined whether or not copying has been completed (S4). If the result of this determination is that copying has not been completed, the current fixing cycle L is changed to the normal fixing cycle L0 (FIG. 3).
(Corresponding to a6 of the above) (S5). As a result of this decision,
If the fixing cycle L is longer than the normal fixing cycle LO, a new fixing cycle L is obtained by subtracting a predetermined time ΔL from the cycle L after a predetermined time t has elapsed (S6). And
Returning to step 4, the processing of steps S4 to S6 is repeated.

By the above processing, the fixing cycle L is set to the time t.
Each time, it becomes shorter by ΔL and becomes equal to or lower than the normal fixing cycle Lo (S5: NO). At this time, it is determined whether the copying is completed (S7). If the copying is continued, the copying is continued in the fixing cycle Lo (S7: N).
O). On the other hand, when the copy is completed (S7: YE
S), the drive motor 20 is stopped, and the processing of this flowchart ends (S8).

In the first embodiment described above, the fixing cycle is set relatively long at the beginning of fixing, so that the temperature of the fixing roller 2 is prevented from lowering immediately after the start of fixing, and the surface of the fixing roller 2 is always fixed. Can be maintained at a sufficient temperature. Further, by shortening the period of the subsequent fixing, it is possible to prevent the entire processing time of the fixing from being lengthened.

The present invention is not limited to the embodiment described above. For example, in the first embodiment,
Although an elastic roller is used as the pressure roller 1, it may be a rigid roller.

In the first embodiment, the heater 3 is turned on intermittently, and this on time is set to be long especially immediately after the start of fixing. However, for example, the heater 3
It may be set so that it is always on for a fixed time.

<Embodiment 2> It is also apparent from FIG. 15 that the decrease in the surface temperature of the fixing roller 2 reaches a peak after several sheets of recording paper S have passed through and fixed. In the second embodiment, attention has been paid to this point. After a predetermined number of recording papers S out of a plurality of recording papers S have been subjected to toner image fixing, the toner The control is performed so as to shorten the image fixing cycle.

Therefore, in the second embodiment, the value of the predetermined number m is stored in the control board 10 in advance.

FIG. 5 is a flowchart illustrating a process for shortening the fixing cycle according to the second embodiment.

When a copy start is input to the operation panel 40 (S21), the rotation of the drive motor 20 for conveying the recording paper S to the fixing device is started (S22). Then, the fixing cycle L is set to the initial fixing cycle L1 preset on the control board 10 (S23).

Next, it is determined whether or not the number of sheets passed so far has reached a predetermined number m set in advance on the control board 10 (S24). If it is determined in step S24 that the number of passed sheets is less than m (S24: YES), the fixing cycle L is maintained at the initial fixing cycle L1, and when the number of passed sheets reaches m, copying ends at this time. It is determined whether or not it has been performed (S25). If the result of this determination is that copying has not been completed, the current fixing cycle L is compared with the normal fixing cycle L0 (S26). If the result of this determination is that the fixing cycle L is longer than the normal fixing cycle Lo, a predetermined time ΔL is subtracted from the cycle L after a lapse of a predetermined time t to obtain a new fixing cycle L (S27). Then, the process returns to step S25, and the processing of steps S25 to S27 is repeated.

By the above processing, the fixing cycle L is changed to the time t.
Each time, it becomes shorter by ΔL and becomes equal to or lower than the normal fixing cycle Lo (S26: NO). At this time, it is determined whether the copying is completed (S28). If the copying is continued, the copying is continued at the fixing cycle LO (S2).
8: NO). On the other hand, when the copy is completed (S2
8: YES), the drive motor 20 is stopped, and the processing of this flowchart ends (S29). Note that the time required from the start of fixing to the time when m sheets are passed is shorter than the time t.

According to the second embodiment described above, the fixing cycle can be extended only when the temperature of the fixing roller surface decreases. Therefore, it is possible to further enhance the effect of preventing the processing time required for fixing from being lengthened while preventing the fixing roller surface temperature from lowering.

<Embodiment 3> Embodiment 3 is to shorten the cycle of fixing a toner image by increasing the rotation speed of the drive motor 20. Therefore, in the third embodiment, the initial rotation speed R1 which is the rotation speed of the drive motor 20 at the start of fixing, the rotation speed ΔR which is an increase in the rotation speed,
The normal motor rotation speed R0, which is the rotation speed after the process of increasing the rotation speed of the drive motor 20, is stored in the control board 10 in advance.

FIG. 6 is a flowchart illustrating a process for shortening the fixing cycle according to the third embodiment.

When the copy start is input to the operation panel 40 (S31), the drive motor 20 starts rotating (S31).
32). Here, the motor rotation speed R of the drive motor 20 is
The initial rotational speed R1 stored in the control board 10 is set in advance (S33).

Next, it is determined whether or not copying has been completed (S34). If the result of this determination is that copying has not been completed (S34: NO), the motor speed R is compared with the normal motor speed RO. (S35). If the result of determination in step S35 is that the motor rotation speed R is smaller than the normal motor rotation speed RO, a predetermined rotation speed ΔR is added to the motor rotation speed R after a predetermined time t has elapsed, and this value is added to a new motor rotation speed. The rotation speed is set to R (S36). Then, the process returns to step S34, and the processes of steps S34 to S36 are repeated.

With the above processing, the motor rotation speed R increases by the rotation speed ΔR at each time t. Motor speed R
Is equal to or greater than the normal motor rotational speed RO (S35: NO), it is determined whether the copy is completed (S37). If the result of this determination is that copying is continuing, copying is continued at the motor rotation speed RO (S37:
NO). On the other hand, when the copy is completed (S37: Y
ES), the drive motor 20 is stopped, and the processing of this flowchart ends (S38).

Next, a description will be given of a modification of the third embodiment in which the process of shortening the fixing cycle by increasing the number of rotations of the motor is performed after the toner image is fixed on a predetermined number of recording sheets S. For this reason, in this example, in addition to the initial rotation speed R1, the normal rotation speed R1, and the rotation speed ΔR, the recording paper S
Is stored in the control board 10.

FIG. 7 is a flowchart illustrating a process for shortening the fixing cycle according to a modification of the third embodiment.

The flowchart of FIG. 7 performs substantially the same processing as the flowchart of FIG. That is, the copy start input to the operation panel 40 (S32
1) The rotation of the drive motor 20 is started (S322).
Here, the motor speed R of the drive motor 20 is set to the initial speed R1 stored in the control board 10 in advance (S323).

Next, in this modified example, it is determined whether or not the number of passed sheets has reached a predetermined number m (S324). If the result of this determination is that the number of passed sheets has reached the predetermined number m (S324: NO), it is determined whether or not copying has been completed (S325). If the result of this determination is that copying has not been completed (S325: NO), the motor speed R is compared with the normal motor speed RO (S326). If the result of determination in step S326 is that the motor rotation speed R is smaller than the normal motor rotation speed RO, a predetermined rotation speed ΔR is added to the motor rotation speed R after a predetermined time t has elapsed, and this value is added to a new motor rotation speed. The rotation speed is set to R (S327). Then, the process returns to step S325, and returns to step S325 to step S325.
327 is repeated.

By the above processing, the motor rotation speed R becomes m
After the fixing of the recording paper S, the number of rotations ΔR increases every time t. And the motor speed R
Is equal to or greater than the normal motor rotation speed RO (S326: NO), it is determined whether the copying has been completed (S328). If the result of this determination is that copying is continuing, copying is continued at the motor rotation speed RO (S32).
8: NO). On the other hand, when the copy is completed (S32
8: YES), the drive motor 20 is stopped, and the processing of this flowchart ends. Note that the time required from the start of fixing to the time when m sheets are passed is shorter than the time t.

According to the third embodiment described above, the transport speed of the recording paper S can be increased without changing the mechanical configuration of the image forming apparatus and the fixing device. Therefore, the fixing cycle can be shortened only by changing the data stored in the control board 10, and the shortening of the fixing cycle can be easily performed.

<Fourth Embodiment> In a fourth embodiment, the interval at which the toner image is fixed is shortened by decreasing the paper feed interval of the recording paper S. For this reason, in the fourth embodiment, the initial paper feed interval T1 which is the paper feed interval immediately after the start of fixing, the time ΔT which is a decrease in the paper feed interval, and the paper feed interval after the process of reducing the paper feed interval is completed Is stored in the control board 10 in advance.

FIG. 8 is a flowchart illustrating a process for shortening the fixing cycle according to the fourth embodiment.

When a copy start is input to the operation panel 40 (S41), the drive motor 20 starts rotating (S41).
42).

Next, in the fourth embodiment, the paper feed interval T of the recording paper S is set to the initial paper feed interval T1 set in advance on the control board 10 (S43). Then, it is determined whether or not copying has been completed (S44). If the result of this determination is that copying has not been completed (S44: NO), the paper feed interval T is compared with the normal paper feed interval TO (S45). . As a result of this determination, if the paper feed interval T is larger than the normal paper feed interval To (S45: YES), after a predetermined time t has elapsed, the time ΔT is subtracted from the paper feed interval T to obtain a new paper feed interval T. (S46). Then, the process returns to step S44, and the processing of steps S44 to S46 is repeated.

By the above processing, the paper feeding interval is reduced by ΔT at every time t, and the paper feeding interval T becomes the normal paper feeding interval T
If it is equal to or less than O (S45:
NO) It is determined whether the copy has been completed (S47). If the result of this determination is that copying is continuing, copying is continued at the paper feed interval TO (S47: NO). On the other hand, if the copy has been completed (S47: YES), the drive motor 20 is stopped, and the processing of this flowchart ends (S48).

The paper feed interval can be changed, for example, by adjusting the timing of connecting and disconnecting the paper feed clutch 21 shown in FIG.

Next, a description will be given of a modification of the fourth embodiment in which the process of shortening the fixing cycle by shortening the paper feed interval is performed after the toner image is fixed on a predetermined number of recording sheets S. Therefore, in this example, the initial paper feed interval T
1. In addition to the normal paper feed interval T0 and the time ΔT, a predetermined number m of recording paper S is stored in the control board 10.

FIG. 9 is a flowchart illustrating a process for shortening the fixing cycle according to a modification of the fourth embodiment.

The flowchart of FIG. 9 performs substantially the same processing as the flowchart of FIG. That is, when a copy start is input to the operation panel 40 (S42)
1) The rotation of the drive motor 20 is started (S422).
Here, the paper feed interval T of the recording paper S is set to the initial paper feed interval T1 previously stored in the control board 10 (S42).
3).

Next, in this modification, it is determined whether or not the number of passed sheets has reached a predetermined number m (S424). If the result of this determination is that the number of passed sheets has reached the predetermined number m (S424: NO), it is determined whether or not copying has been completed (S425). If the result of this determination is that copying has not been completed (S425: NO), the paper feed interval T is compared with the normal paper feed interval To (S426). Step S426
As a result of the determination, when the number T of the paper feed intervals is larger than the normal paper feed interval To, a predetermined time ΔT is subtracted from the paper feed interval T after a predetermined time t has elapsed, and this value is added to the new paper feed interval. T (S427). Then, the process returns to step S425, and the processing of steps S425 to S427 is repeated.

By the above-described processing, the sheet feeding interval T is reduced by the time ΔT at every time t after the fixing is performed on the m recording sheets S. If the paper feed interval T is equal to or less than the normal paper feed interval To (S42).
6: NO), it is determined whether the copying has been completed (S42).
8). If the result of this determination is that copying is continuing, copying is continued at the paper feed interval TO (S428: NO). on the other hand,
When the copying is completed (S428: YES), the drive motor 20 is stopped, and the processing of this flowchart ends (S429). Note that the time required from the start of fixing to the time when m sheets are passed is shorter than the time t.

According to the fourth embodiment described above, the fixing cycle can be shortened by shortening the sheet feeding interval. For this reason,
The fixing cycle can be shortened only by changing the data stored in the control substrate 10, and the shortening of the toner image fixing cycle can be easily performed without changing the mechanical configuration of the image forming apparatus and the fixing apparatus. .

<Fifth Embodiment> In a fifth embodiment, a fixing device is provided in which a fixing roller 2 having a releasability from toner on its surface is used.
A pressure roller 1 for fixing the toner image on the recording medium in cooperation with the fixing roller 2; and a heater 3 built in at least one of the fixing roller 2 and the pressure roller 1 for heating and melting the toner. In addition, the control board 10 is characterized in that the heater 3 generates heat for a longer time than the heat generation time after the start of the process related to the formation of the toner image.

The heater 3 according to the fifth embodiment is similar to the heater 3 according to the first embodiment.
As shown in FIG. 3 at the beginning, the fixing roller 2 is turned on for a time h1 at the start of fixing to compensate for a shortage of heat stored in the fixing roller 2 at the beginning of fixing. When the heat storage amount of the fixing roller 2 is stabilized, the fixing roller 2 is turned on intermittently for a fixed time h2 shorter than h1, and the temperature of the surface of the fixing roller 2 is kept constant (FIG. 3).

The fifth embodiment exemplifies a specific method for turning on the heater 3 as described above. In the fifth embodiment, the ON time h of the heater 3
1 and h2 are stored in the control board 10 in advance, and a timer for measuring the ON times h1 and h2 is provided.

FIG. 10 is a flowchart illustrating a process for shortening the fixing cycle according to the fifth embodiment.

In the illustrated flowchart, first, when a copy start is input to the operation panel 40 (S51),
Immediately after this, the heater 3 is forcibly turned on for h1 seconds (S
52). Then, in order to transport the recording paper S to the fixing device,
The rotation of the drive motor 20 is started (S53). Further, the fixing cycle L is set to the initial fixing cycle L1 stored in the control board 10 in advance (S54), and it is determined whether or not copying has been completed at this time (S55). If the result of this determination is that copying has not been completed, the current fixing cycle L is compared with the normal fixing cycle L0 (S56). If the result of this determination is that the fixing cycle L is longer than the normal fixing cycle Lo, a predetermined time ΔL is subtracted from the cycle L after a predetermined time t has elapsed to obtain a new fixing cycle L (S5).
7). Then, returning to step S55, step S55
Step S57 is repeated.

As a result, the fixing cycle L becomes the normal fixing cycle L
If it is equal to or less than O (S56:
NO) It is determined whether the copy is completed (S58). If the copy is continued, the copy is continued in the normal fixing cycle L0 (S58: NO). On the other hand, if the copy has been completed (S58: YES), the drive motor 20 is stopped, and the processing of this flowchart ends (S59).

Next, a modified example in which the process of shortening the fixing cycle in the fifth embodiment is performed after the toner image is fixed on a predetermined number of recording sheets S will be described. Therefore, in this example, the initial fixing cycle L1, the normal fixing cycle L1, the time Δ
L, the heater on time h1, h2, and a predetermined number m of the recording paper S are stored in the control board 10.

FIG. 11 is a flowchart illustrating a process for shortening the fixing cycle according to a modification of the fifth embodiment.

The flowchart in FIG. 11 performs substantially the same processing as the flowchart in FIG. That is,
When a copy start is input to the operation panel 40 (S52)
1) Immediately after this, the heater 3 is forcibly turned on for h1 seconds (S522). Then, the rotation of the drive motor 20 is started (S523), and the fixing cycle L is set to the initial fixing cycle L1 preset on the control board 10 (S52).
4).

Next, it is determined whether or not the number of sheets passed so far has reached a predetermined number m set in the control board 10 (S525). In the judgment of step S525,
While the number of passed sheets is less than m (S525: YES),
The fixing cycle L is maintained at the initial fixing cycle L1, and the number of sheets passed is m
Is reached, it is determined whether or not the copying is completed at this time (S526). If the result of this determination is that copying has not been completed, the current fixing cycle L is compared with the normal fixing cycle L0 (S527). If the result of this determination is that the fixing cycle L is longer than the normal fixing cycle LO, a new fixing cycle L is obtained by subtracting a predetermined time ΔL from the cycle L at every predetermined time t (S528). Then, the process returns to step S526, and returns to steps S526 to S52.
Step 8 is repeated.

By the above processing, the fixing cycle L is set to the time t.
Each time, it becomes shorter by ΔL and becomes equal to or lower than the normal fixing cycle Lo (S527: NO). At this time, it is determined whether the copying is completed (S529). If the copying is continued, the copying is continued in the fixing cycle L0 (S529: NO). On the other hand, if the copy has been completed (S529: YES), the drive motor 20 is stopped, and the processing of this flowchart ends (S530). Note that the time required from the start of fixing to the time when m sheets are passed is shorter than the time t.

According to the fifth embodiment described above, the temperature of the heat fixing means does not decrease immediately after the start of fixing, and the fixing roller can always be kept at a temperature sufficient for fixing.

The fixing cycle L and the lighting time of the heater 3 described above are the amount of heat taken by the fixing roller, the amount of heat supplied to the fixing roller 2 by the heater 3, and the heat conduction of the members on the surface of the fixing roller 2. Roller 2
Are set so that the temperature of the surface becomes constant. In setting these conditions, calculations or experiments are performed in advance.

Further, the amount of heat taken by the fixing roller 2 is:
It also depends on various conditions of the recording paper S. Therefore,
If it is necessary to more strictly set a paper passing interval or a condition for turning on the heater 3 for keeping the surface temperature of the fixing roller 2 constant, it is necessary to consider the characteristics of the recording paper S. The characteristics of the recording paper S that have a relatively large effect on the fixing conditions include the size of the recording paper S and the basis weight. In addition, the grammage is
The weight per unit area (1 m ² ) of the paper is expressed in g, and is a value that can be an index of the heat capacity of the recording paper S.

That is, when the size of the recording paper S is large, the paper is sufficiently heated and the toner is sufficiently heated and melted, so that a larger amount of heat is required. In such a case, it is necessary to make the paper passing interval longer than for recording paper S of a smaller size.

The amount of heat taken by the roller 2 depends more on the direction (conveying direction) of the recording sheet S conveyed by the fixing device than on the width direction thereof. May be detected, and the cycle of fixing the toner image may be shortened according to the length.

The recording paper S having a large basis weight has a larger heat capacity than the recording paper S having a smaller basis weight, and more heat is taken from the fixing roller 2 than the recording paper S having a small basis weight in the process of performing the thermal transfer. Become. Such a change in the temperature of the surface of the fixing roller 2 depending on the grammage of the recording paper S is such that when the grammage is large, the fixing cycle is set to be longer, or the predetermined number m of passed sheets is set to be smaller. Alternatively, the adjustment can be performed by setting the forced lighting time of the heater 3 to be long.

As described above, the surface temperature of the fixing roller 2 and the ON timing of the heater 3 can be more strictly controlled by considering the characteristics of the recording paper S.

The present invention is not limited to each of the above-described embodiments. For example, the control substrate 10 may be configured to control the toner in accordance with all of the size of the recording paper S, the length in the transport direction, and the basis weight. It goes without saying that the fixing device can be controlled so as to shorten the image fixing cycle.

[0111]

According to the first aspect of the present invention, the temperature of the heat fixing unit does not decrease immediately after the start of fixing, and the temperature of the heat fixing unit can always be maintained at a temperature sufficient for fixing. Also,
By shortening the period of the subsequent fixing, it is possible to prevent the fixing processing time from becoming longer.

Further, by using a thin rubber roller for the heat fixing means of such a fixing device, it is possible to provide a fixing device for consistently fixing a color image with high gloss.

According to the second aspect of the invention, the fixing cycle can be extended only when necessary, and the effect of preventing the processing time required for fixing the toner image from being lengthened can be further enhanced.

Further, by using a thin rubber roller for the heat fixing means of such a fixing device, a fixing device for fixing a color image with high gloss consistently even when the temperature of the heat fixing means is lowered is provided. be able to.

According to the third aspect of the present invention, the period of fixing the toner image can be easily shortened by increasing the conveying speed of the recording medium.

According to the fourth aspect of the invention, the period of fixing the toner image can be easily reduced by shortening the interval between the recording media.

According to a fifth aspect of the present invention, a sufficient amount of heat is stored in the heating / fixing means in a short time, and the temperature of the heating / fixing means does not decrease immediately after the start of fixing. Can be kept.

According to the sixth aspect of the present invention, it is possible to determine the fixing cycle in consideration of the size of the recording medium, and to perform control in accordance with a state in which further fixing is performed.

According to the fixing device of the present invention, it is possible to determine the fixing cycle in consideration of the length of the recording medium in the conveying direction, and to control the fixing cycle in accordance with the state of further fixing.

According to the fixing device of the present invention, it is possible to determine the fixing cycle in consideration of the basis weight of the recording medium, and to control the fixing cycle in accordance with the state of performing further fixing.

In the fixing device according to the ninth aspect, the fixing device can be more finely controlled according to the characteristics of the recording medium.

[Brief description of the drawings]

FIG. 1 is a diagram showing a mechanical schematic configuration of a fixing device common to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration for controlling a fixing device common to the embodiment of the present invention.

FIG. 3 is a diagram illustrating a fixing roller surface temperature, a heater-on timing, and a sheet passing interval according to the first embodiment of the present invention.

FIG. 4 is a flowchart illustrating a process according to the first embodiment of the present invention.

FIG. 5 is a flowchart illustrating a process according to a second embodiment of the present invention.

FIG. 6 is a flowchart illustrating a process according to a third embodiment of the present invention.

FIG. 7 is a flowchart illustrating a process according to a modification of the third embodiment of the present invention.

FIG. 8 is a flowchart illustrating a process according to a fourth embodiment of the present invention.

FIG. 9 is a flowchart illustrating a process according to a modification of the fourth embodiment of the present invention.

FIG. 10 is a flowchart illustrating a process according to a fifth embodiment of the present invention.

FIG. 11 is a flowchart illustrating a process according to a modification of the fifth embodiment of the present invention.

FIG. 12 is a diagram illustrating the surface temperature of a thick hard roller, the ON timing of a heater incorporated in the thick hard roller, and a paper passing interval when recording paper is continuously passed.

FIG. 13 is a diagram illustrating that when the recording paper is continuously passed, the decrease in the surface temperature of the thick hard roller is suppressed by the paper interval.

FIG. 14 is another diagram showing the surface temperature of the thin hard roller, the ON timing of a heater built in the thin hard roller, and the paper passing interval when recording paper is continuously passed.

FIG. 15 is another diagram showing the surface temperature of the thin rubber roller, the ON timing of the heater incorporated in the thin rubber roller, and the paper passing interval when recording paper is continuously passed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Pressure roller (pressure part), 2 ... Fixing roller (fixing part), 2a ... Aluminum, 2b ... Silicon rubber, 3 ... Heater (heating means), 5 ... Commercial power supply, 7 ... Thermostat, 9 ... Solid state Relay: 10: control board (fixing cycle control means), 20: drive motor (transport means), 21: paper feed clutch, 30: thermistor, 40: operation panel 200: transport system (recording medium transport means), N: nip Parts: S: recording paper (recording medium), T: toner.

Claims (9)

[Claims] 1. A fixing device provided in an image forming apparatus having a recording medium conveying means capable of continuously conveying a recording medium on which a toner image is formed, wherein the fixing device fixes the toner image on the recording medium. A heating and fixing unit for fixing the toner to the recording medium while heating and melting the toner, and a toner image fixing frequency when continuously fixing the toner images to the plurality of recording media continuously conveyed from the recording medium conveying unit. A fixing cycle control unit for shortening the cycle of fixing the toner image as the number of toner images increases. 2. A fixing device provided in an image forming apparatus having a recording medium conveying means capable of continuously conveying a recording medium on which a toner image has been formed, wherein the fixing device fixes the toner image on the recording medium. Heating and fixing means for fixing the toner on the recording medium while heating and melting the toner, and fixing the toner images to the plurality of recording media continuously conveyed from the recording medium conveying means. A fixing device comprising: a fixing cycle control unit configured to fix a toner image on a predetermined number of recording media among the media and then shorten a cycle of fixing the toner image as the number of times of fixing the toner image increases. 3. The fixing device according to claim 1, wherein the fixing cycle control unit shortens a cycle of fixing the toner image by increasing a conveying speed of the recording medium in the recording medium conveying unit. apparatus. 4. The image forming apparatus according to claim 1, wherein the fixing cycle control unit shortens a cycle in which the toner image is fixed by shortening an interval of the recording medium conveyed by the recording medium conveying unit. Fixing device. 5. The fixing device according to claim 1, wherein the heat fixing unit includes a fixing unit having a releasable surface from the toner, a pressing unit configured to fix the toner image on the recording medium in cooperation with the fixing unit, and the fixing unit. Or a heating unit which is built in at least one of the pressurizing units and heats and melts the toner. The fixing device according to claim 1, wherein heat is generated for a long time. 6. The fixing device according to claim 1, wherein the fixing cycle control unit controls a cycle of fixing the toner image according to a size of the recording medium. 7. The fixing device according to claim 1, wherein the fixing cycle control unit controls a cycle in which the toner image is fixed according to a length of the recording medium in a conveying direction. 8. The fixing device according to claim 1, wherein the fixing cycle control unit controls a cycle of fixing the toner image according to a basis weight of the recording medium. 9. The fixing cycle controller according to claim 1, wherein the fixing cycle controller controls a cycle of fixing the toner image in accordance with all of a size, a length in a conveying direction, and a basis weight of the recording medium. 3. The fixing device according to claim 1.