JPH1010921A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of preventing the generation of fixing failure and shortening the time required by the starting of image forming operation after paper clogging is treated. SOLUTION: When paper clogging is generated, the control of a heater is stopped S1, and time elapsed from a copy impossible state is measured with a timer S2. When paper clogging is treated and a device becomes a copy operation ready state, measurement with the timer is finished, the lighting of a heater is started S3 to raise the temperature of a fixing roller whose temperature is lowered. In this time, time tB is judged, S5, and if to is within the constant time to, forward rotation operation is not conducted S6 when a device main body is moved from the copy ready state to a copy possible state, and if tB exceeds tC, forward rotation operation is conducted S7), and after that, the fixing temperature is controlled so as to keep T1 .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus provided with a fixing device for performing predetermined temperature control.

[0002]

2. Description of the Related Art FIG. 5 shows a conventional image forming apparatus. FIG.
In the image forming apparatus shown in FIG.
A document 102 placed on the top is illuminated by a light source 103, and its light image is formed by an image forming unit 1 by an optical system including a plurality of reflection mirrors 104 and a zoom lens 105.
06.

Here, the cassette 107 or the cassette 1
After the sheet stacked on the sheet 08 is separated by the separation unit 109, the sheet is fed to the sheet feeding unit 110, and is conveyed to the image forming unit 106 by the sheet feeding unit 110.

At this time, the sheet is conveyed by a feed roller pair 110a of a sheet feed unit 110 so as to coincide with a visible image on a photosensitive drum 106a of an image forming unit 106, and the visible image on the photosensitive drum 106a is charged by a charger. The sheet is transferred to the sheet by 106b. After the image transfer, the sheet is transferred to the transport unit 111.
After the image on the sheet is fixed, the sheet is sent to a discharge unit 113 and discharged out of the apparatus.

Here, it is necessary that the light source 103, the reflection mirror 104, and the zoom lens 105 be placed at predetermined positions in order to turn on the power of the image forming apparatus main body and to enable the copying operation. However, what determines the wait-up time before the copying operation is enabled is the time required for adjusting the temperature of the fixing device 112, particularly the temperature of the fixing roller therein.

That is, as shown in FIG. 6, the fixing device 112 is provided with a fixing roller 10 having a heater 17 therein, and is provided below the fixing roller 10 so as to fix a toner image on the sheet. A pressure roller 11 made of a heat-resistant elastic material such as silicone rubber for pressing
A cleaning web 1 disposed above the fixing roller 10 for removing residual toner adhered to the fixing roller 10
3, a sponge roller 14 for pressing the sheet, an entrance guide 15 for guiding the sheet to the nip portion A of the fixing roller 10 and the pressure roller 11, and a sheet for fixing the sheet to the fixing roller 1.
0, separation claw 18a for separating from the pressure roller 11,
18b, and usually the fixing roller 1
The temperature of 0 needs to be about 200 ° C. in order to melt and fix the toner image transferred onto the sheet.

[0007] Although this temperature varies depending differentially copy speed of the toner differences and the apparatus main body, generally becomes a 10 ° C. temperature lower by about T ₀ than the set temperature in this position, so causing defective fixing.

For this reason, the fixing roller 10 needs to be sufficiently warmed up over a long period of time, and although it is not so preferable, it takes some time to increase the weight.

For example, when an image forming apparatus is used in an office or the like, the power is turned on when the user comes to work in the morning, and it takes time only for the first startup, but once the fixing device is warmed up, the main power is turned on. If this is done, there is no need to wait for a long time again, so that it takes some time for the copying machine to wait for a certain amount of time.

Whether the fixing roller 10 has reached a sufficient temperature or not is determined by a thermistor 1 as a temperature measuring means pressed against the fixing roller 10 as shown in FIG.
2 is determined based on the measured temperature. That is, the temperature of the thermistor 12 is transmitted to the controller 16 of the image forming apparatus main body, when the temperature of the fixing roller 10 does not reach the copy operable temperatures T _1, as shown in FIG. 7, the controller 16 The heater 17 inside the fixing roller 10 is turned on to heat the fixing roller 10.

[0011] For example, if you turn on the image forming apparatus main body, by turning on the heater 17, the fixing roller 10 is as temperature rises shown in FIG. 7, and reaches the copying operation allow temperatures T ₁ Heater 17 Is the controller 16
Is controlled to become so becomes constant at a temperature T _1.

However, when the copy start key is pressed, the fixing roller 10 starts rotating in the direction of arrow B in FIG. Accordingly, the pressure roller 11 starts to rotate in the direction indicated by the arrow C. However, in the pressure roller 11 having no heater inside, the portion except for the nip portion A in contact with the fixing roller 10 is completely warmed. Because there was no
When the pressure roller 11 rotates and the unheated portion touches the fixing roller 10, the fixing roller 10
A large amount of heat from the surface of the fixing roller 10, the surface temperature of the fixing roller 10 is lowered, and the toner cannot be sufficiently fixed on the conveyed sheet.

In order to prevent this, when the temperature of the fixing roller 10 reaches a temperature shortly before reaching T ₁ (approximately 5 ° C. to 10 ° C.), the controller 16 detects the temperature and changes the surface of the pressure roller 11. In order to heat the entire circumference, a pre-rotation operation of rotating the fixing roller 10 is performed.

When this pre-rotation operation is performed, the temperature of the fixing roller 10 temporarily decreases at t ₁ when the rotation is started as shown in FIG. 8, the heat is taken by the pressure roller 11, and the heat is applied at t ₂ . When pressure roller 11 is warmed up roughly, the temperature of the fixing roller 10 also begin to return, reach copy operable temperatures T ₁ at time t ₃ later.

As described above, when the pre-rotation operation is performed, the time required for waiting up becomes longer by Δt.
This is indispensable for producing a good copy image.

[0016]

However, according to the above-mentioned conventional example, the surface temperature of the pressure roller 11 changes as shown in FIG. 8 when the pre-rotation operation is performed. FIG. 8 shows a change in the surface temperature of the pressure roller 11 other than the nip portion. The surface temperature suddenly rises from the time t _{1 at} which the pre-rotation operation is started, and after a short time t ₂ , the surface temperature rises. less reached temperature T ₂ is not deprived of heat, converge at a lower temperature T ₃ than the T ₁ and the temperature gradually rises from there. In other words, if the temperature of the surface of the pressure roller 11 is T ₂ ,
When rotating from the fixing roller 10, heat is taken away to fix the fixing roller 1.
It means that the surface temperature of 0 is hardly reduced. Further, as described above, the pressure roller 11 is made of a heat-resistant elastic member, and has a much larger heat capacity than the fixing roller 10 which is usually made of metal. Therefore, after the surface is warmed by the pre-rotation operation, the copying operation is repeated, and the heat is transferred to the inside by being gradually heated in the nip portion, and in a state where the pressure roller 11 having a large heat capacity is sufficiently warmed, for some reason. Even if the power is turned off and the heater 17 of the fixing roller 10 is turned off, the temperature of the pressure roller 11 does not drop sharply.
The temperature is T ₂ or less, takes a certain amount of time.

On the other hand, when the power is turned off and the heater 17 is turned off, the temperature of the fixing roller 10 made of metal is lower as shown in FIG. I do.

In spite of such a difference in temperature transition, in the image forming apparatus of the above-described conventional example, in which a pre-rotation operation is performed, only the surface temperature of the fixing roller 10 is monitored, and the controller 16 controls the apparatus. If the surface temperature of the fixing roller 10 is not at the temperature T ₁ at which the copying operation can be performed, the heater 17 is turned on, and the surface temperature T of the fixing roller 10 becomes T ₀ or T ₀ <T <
If turned to T _1, it will begin with a pre-rotation operation.

Therefore, as described above, for some reason, for example, due to a paper jam, the power of the apparatus is turned off, the heater 17 is turned off, the surface temperature of the fixing roller 10 is lowered, and the paper jam processing is completed. After the power is turned on and the heater 17 is turned on, the fixing roller 10 can be turned on even if it does not take much time to recover from the paper jam.
There If it is set to T ₁ below, follow the sequence described above.

However, in this case, the surface temperature of the pressure roller 11 may not be reduced so much, and although the pre-rotation operation is not required, the pre-rotation operation is performed as described above. .

If the temperature of the pressure roller 11 is equal to or higher than T ₂ , there is no practical problem in the copying operation. However, the convergence temperature is T ₃ to the last. Take away. Therefore, after the power loss due to troubles such as after a paper jam, even if the temperature of the pressure roller 11 was T _2, requires pre-rotation operation a predetermined time to perform, usually conducted a pre-rotation operation In a conventional apparatus that adopts a sequence, there is a case where the next copying operation cannot be immediately performed, such as after a paper jam.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of shortening the time until the start of an image forming operation after a paper jam or the like without causing a fixing failure.

[0023]

According to a first aspect of the present invention, an object of the present invention is to provide a roller pair of a fixing roller and a pressure roller, a heater for heating the fixing roller, and a heating roller. A driving unit for rotating the pressure roller, a temperature measuring unit for measuring the temperature of the fixing roller, and controlling the driving of the heater based on the temperature measured by the temperature measuring unit to adjust the temperature of the fixing roller to a predetermined temperature. And control means for controlling the rotational drive of the roller pair by the drive means, wherein the control means determines that the temperature measured by the temperature measuring means is a predetermined reference value before the fixing operation is performed by the roller pair. When the temperature is equal to or lower than the temperature, the heater is driven to raise the temperature of the fixing roller to a predetermined temperature, and the driving unit rotates the roller pair a predetermined number of times before rotation. In the image forming apparatus set as described above, the heater is provided with a timer operable even during a control suspension period when the heater is not under the control state of the control unit, and the control unit performs the control suspension period measured by the timer. However, when the temperature is within a predetermined time, even if the temperature measured by the temperature measuring means is equal to or lower than a predetermined reference temperature, the above-described setting is made so that the pre-rotation is not performed. You.

According to the second aspect of the present invention,
The object is, in the first aspect, having at least one or more exterior covers, and means for detecting that the exterior covers have been opened, and the predetermined means in the exterior covers by the means. This is achieved because the control stop period of the heater is set to start when it is detected that the outer cover is opened.

Further, according to a third aspect of the present invention, the above object is provided in the first or second aspect, further comprising means for detecting a paper jam in the image forming apparatus. This is achieved by setting so that the control stop period of the heater is started when a paper jam is detected.

According to the fourth invention of the present application,
An object of the present invention is to provide the control device according to any one of the first to third inventions, further comprising a second timer capable of measuring a temperature control period in which the temperature of the fixing roller is controlled to a predetermined temperature. When the control stop period of the heater is started, the temperature control period of the fixing roller until immediately before the start of the control stop period is detected by the second timer, and according to the length of the detected period. This is achieved by setting so as to change a predetermined time that is a reference for determining whether or not to perform the pre-rotation.

Further, according to the fifth aspect of the present invention, the above object is to provide a roller pair of a fixing roller and a pressure roller, a heater for heating the fixing roller, and rotating the fixing roller and the pressure roller. A driving unit for driving, a temperature measuring unit for measuring the temperature of the fixing roller, and controlling the driving of the heater based on the temperature measured by the temperature measuring unit to adjust the temperature of the fixing roller to a predetermined temperature; Control means for controlling the rotational drive of the roller pair by a drive means, wherein the control means is configured to execute a fixing operation by the roller pair and perform a fixing operation when the temperature measured by the temperature measuring means is equal to or lower than a predetermined reference temperature. In the method, the heater is driven to raise the temperature of the fixing roller to a predetermined temperature, and the driving unit rotates the roller pair a predetermined number of times. The set image forming apparatus further includes a pressure roller temperature measurement unit that measures the temperature of the pressure roller, and the control unit controls the temperature of the pressure roller measured by the pressure roller temperature measurement unit. But,
When the temperature is equal to or higher than a predetermined temperature, the pre-rotation is not performed even when the fixing roller temperature measured by the fixing roller temperature measuring unit is equal to or lower than a predetermined reference temperature. This is achieved by:

According to the sixth aspect of the present invention,
The object is, in the fifth invention, at least one or more exterior covers, and means for detecting that the exterior covers have been opened, and the predetermined means in the exterior covers by the means is provided. This is achieved by setting the temperature of the pressure roller to be measured by the pressure roller temperature measuring means when the opening of the outer cover is detected to determine whether or not the pre-rotation is possible.

Further, according to a seventh aspect of the present invention, the above object is achieved in the fifth or the sixth aspect, further comprising means for detecting a paper jam in the image forming apparatus, and This is achieved by setting so that when a paper jam is detected, the temperature of the pressure roller is measured by the pressure roller temperature measuring means to determine whether or not the pre-rotation is possible.

According to an eighth aspect of the present invention,
An object of the present invention is to provide the control device according to any one of the fifth to seventh aspects, further comprising a second timer capable of measuring a temperature control period in which the temperature of the fixing roller is controlled to a predetermined temperature. When the temperature of the pressure roller is measured by the pressure roller temperature measuring means to determine whether or not the pre-rotation is possible,
The temperature control period of the fixing roller immediately before the start of the temperature measurement of the pressure roller is detected by the second timer, and a predetermined reference serving as a criterion for determining whether or not the pre-rotation is possible is determined according to the length of the detected period. This is achieved by setting the predetermined temperature to be changed.

That is, in the first invention according to the present application, when the heater of the fixing roller shifts to the control stop period in which the heater of the fixing roller is not under the control state of the control means for some reason, the timer stops the control stop period. If the measured period is within a predetermined period of time, it is determined that the temperature of the pressure roller has not fallen to such a degree that the pre-rotation is necessary. Even if the measured temperature is lower than the predetermined reference temperature, the pre-rotation is not performed.

Further, in the second invention according to the present application, the first invention comprises at least one or more exterior covers, and means for detecting that the exterior covers have been opened, Since the control stop period of the heater is set to start when it is detected that the predetermined outer cover in the outer cover is opened by the means, the period until the outer cover is closed again is short. In this case, the pre-rotation is not performed, and the image forming operation is started immediately.

Further, according to a third aspect of the present invention, there is provided a means for detecting a paper jam in the image forming apparatus according to the first or second aspect of the present invention. Since the control stop period of the heater is set to be started, if the period required for the paper jam process is short, the pre-rotation is not performed and the image forming operation is started immediately.

In the fourth invention according to the present application, the temperature control period in which the temperature of the fixing roller according to any one of the first invention to the third invention is controlled to a predetermined temperature can be measured. A second timer, and the control means comprises:
When the control stop period of the heater is started, the second timer detects the temperature control period of the fixing roller immediately before the start of the control stop period, and determines whether or not the pre-rotation is possible according to the detected time. Since the predetermined predetermined time serving as the reference is changed, appropriate control according to the temperature transition during the control suspension period is performed on the pressure roller that has been receiving heat supply from the fixing roller during the temperature control period. Therefore, a fixing failure does not occur.

Further, in the fifth invention according to the present application, when the heater of the fixing roller shifts to a control stop period in which the heater of the fixing roller is not under the control state of the control means for some reason, the temperature measurement means for the pressure roller. And if the measured temperature is equal to or higher than a predetermined temperature, it is determined that the pre-rotation is not necessary. Does not perform pre-rotation even if is less than or equal to a predetermined reference temperature.

According to a sixth aspect of the present invention, in the fifth aspect, there is provided at least one or more exterior covers, and means for detecting that the exterior covers have been opened, When detecting that the predetermined exterior cover in the exterior cover is opened by the means, the temperature measurement of the pressure roller by the pressure roller temperature measuring means and the determination of whether or not the pre-rotation is possible are performed. If the period until the outer cover is closed again is short, the temperature of the pressure roller does not decrease to the extent that the pre-rotation is necessary, and the pre-rotation is not performed, so that the image forming operation is started immediately.

Further, according to a seventh aspect of the present invention, there is provided a means for detecting a paper jam in the image forming apparatus according to the fifth or sixth aspect of the present invention. The temperature of the pressure roller is measured by the pressure roller temperature measuring means, and whether or not the pre-rotation is possible is determined. Therefore, if the period required for paper jam processing is short, the temperature of the pressure roller requires the pre-rotation. Since the pre-rotation is not performed so much and the pre-rotation is not performed, the image forming operation is started immediately.

In the eighth invention according to the present application, the temperature control period in which the temperature of the fixing roller according to any one of the fifth invention to the seventh invention is controlled to a predetermined temperature can be measured. A second timer, and the control means comprises:
When measuring the temperature of the pressure roller by the pressure roller temperature measuring means and determining whether or not the pre-rotation is possible, the second timer detects the temperature control period of the fixing roller immediately before, and detects the temperature. Since a predetermined temperature that is a reference for determining whether or not to perform the pre-rotation is changed in accordance with the performed time,
Appropriate control is performed on the pressure roller that has been receiving heat supply from the fixing roller during the temperature control period in accordance with the temperature transition during the measurement period, so that a fixing defect does not occur.

[0039]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram illustrating a schematic configuration of an image forming apparatus according to the present embodiment. In FIG.
The fixing roller 10 is heated by the driving means (not shown), and the sheet is pressed against the fixing roller 10 in order to fix the toner image transferred to the sheet, and is rotated by the rotation of the fixing roller 10. A pressure roller 11 is provided. Further, on the outer peripheral surface of the fixing roller 10,
A thermistor 12 as a temperature measuring means for measuring the surface temperature of the fixing roller 10 is provided, and the surface temperature is transmitted to a controller 16 as a control means of the apparatus main body.

When the main switch 22 is turned on to start the image forming apparatus, the main body of the apparatus is turned on,
The heater 17 for heating the fixing roller 10 is turned on. After a while, the surface temperature of the fixing roller 10 reaches a pre-rotation start temperature, which is several degrees lower than the copy operable temperature, and a driving unit (not shown) for rotationally driving the fixing roller 10 starts driving to fix. The roller 10 starts rotating, and accordingly, the pressure roller 11 starts driven rotation.
The state of the temperature change at this time is as described in the conventional example, and the surface temperature of the fixing roller 10 is reduced.
When the temperature reaches a certain temperature, the surface temperature of the fixing roller 10 starts to rise again. Thereafter, when the temperature reaches the copy operable temperature T ₁ , the heater 17 is controlled by the controller 16 so as to control the temperature at the temperature T _1. At the beginning, the pre-rotation operation is stopped.

Although the above control is the same as that of the conventional example, the present embodiment is different from the conventional example in the subsequent processing when a paper jam is caused due to an unexpected situation. Hereinafter, the control of this embodiment will be described based on the flowchart of FIG.

First, when a paper jam is caused,
The drive power of the apparatus main body is turned off, the copying is disabled, and the control of the heater 17 is stopped as shown in FIG. 2 (step S1). At that time, the power of the main body by the main switch is kept turned on, and the controller 16 is in a state where the apparatus main body can be monitored, and is set in a copy disabled state by a timer (not shown) provided on the controller 16. The time from when it has been reached is measured (step S2). At this time, even if the interlock switch of the AC power supply of the apparatus main body is turned off, the timer can be operated and the measurement can be performed.

After that, the paper jam process is completed, the apparatus main body is in a copy operation ready state, the measurement by the timer is completed, and the heater 17 is turned on again to raise the temperature of the fixing roller 10 whose temperature has dropped again ( Step S3).

At this time, the time t _B from the start to the end of the measurement, which was measured earlier, is determined (steps S4 to S5). If t _B is within a certain time t _C , the apparatus body is copied from the copy ready state. The pre-rotation operation is not performed when heading to the possible state (step S6). However, if it exceeds t _C ,
A pre-rotation operation is performed (step S7). And, thereafter performs control so as to maintain the fixing temperature T ₁ (step S
8).

According to an experiment, for example, in a device for 50 sheets / A4 per minute, when the pressure roller 11 is sufficiently warmed before a paper jam, the maximum time t _C at which no pre-rotation is required is performed. It has been found that the value t _Cmax is t _Cmax = about 40 sec.

For example, in the above-described apparatus, t _C = 4
Recovery time of the device when the 0 sec, the time until the so-called fixing roller 10 reaches the temperatures T ₁ again, turned out by also experiments that there is a difference of about 11sec in the case of not performing the case of performing the pre-rotation operation ing. This corresponds to Δt in FIG. 8 described in the conventional example. Below, t _C = 10,2
The time difference Δt at 0, 30, and 40 seconds is shown.

[0048]

[Table 1]

Since the above example is an example in which a certain case is taken, this numerical value t _Cmax should be obtained by each device, and can be calculated to some extent by the heat capacities of the fixing roller 10 and the pressure roller 11. However, it should be determined by experiment.

The specific example described above relates to the relationship between t _C and Δt when the pressure roller 11 is sufficiently warmed. If the pressure roller 11 is not sufficiently heated, for example, When the power is turned on, the copying operation is immediately performed, and the first sheet is jammed, the above-mentioned numerical value is not obtained. That is, since only the surface of the pressure roller 11 is warmed and the inside is not sufficiently heated, the heater 1 is _{turned off} at time t _{OFF as} shown in FIG.
When the control of step 7 is stopped, the temperature of the pressure roller 11 thereafter decreases much faster than when the pressure roller 11 shown in D is sufficiently warmed. That is, t _CF , which is the time to reach the temperature T ₂ of the pressure roller 11 that does not require the pre-rotation operation after the paper jam processing, is earlier than t _{CD in} the case of D. The difference in the degree of warming of the pressure roller 11 is as follows.

That is, as shown in FIG. 3, at time t ₀ , the main switch 22 is turned on, and the heater 17 is turned on.
After heating the fixing roller 10, the copy work after reaching copying operable temperatures T ₁ at time t ₃ is continued, a paper jam at a certain time t _OFF, the control of the heater 17 is turned off, then the temperature The degree of reduction generally depends on the length of time Δt during which the fixing roller 10 is controlled at a constant temperature. As described above, the limit time t _C can be calculated as a function of Δt by calculating from the heat capacities of the fixing roller 10 and the pressure roller 11 as described above. However, in this case as well, since there are various factors as well, it is better to actually obtain numerical values by experiments.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 4, the pressure roller 11 of this embodiment is provided with a thermistor 20 as a pressure roller temperature measuring means for measuring the surface temperature of the pressure roller 11. The temperature is monitored by the controller 16 similarly to the thermistor 12 for measuring the surface temperature of the fixing roller 10. As in the first embodiment, when the driving power is turned off due to a paper jam or the like and the heater 17 for heating the fixing roller 10 is turned off, the surface temperatures of both the fixing roller 10 and the pressure roller 11 start to decrease. . However, as described in the section of the conventional example, the state of the decrease is as shown in FIG.
The reduction rate of the pressure roller 11 is smaller than that of the fixing roller 10. The controller 16 stores a preset limit temperature T ₂ of the pressure roller 11, and continues to monitor the temperature T ′ of the pressure roller 11 even while the heater 17 is turned off, so that the paper jam may occur. When the process is completed and the heater 17 is turned on again, the pressure roller 11
If the surface temperature T ′ does not become lower than T ₂ , the same effect as in the first embodiment can be obtained by taking a sequence in which the pre-rotation operation is not performed at the time of restart.

In each of the above-described embodiments, when a paper jam is detected, measurement of the predetermined time t _C is started.
Alternatively, the monitoring of the temperature T 'of the pressure roller 11 is started, but these processes may be started by detecting that one of the outer covers of the image forming apparatus has been opened.

Further, a period during which the temperature of the fixing roller is controlled to a predetermined temperature immediately before the heater 17 is turned off is measured by a timer, and the predetermined time t _C and the limit temperature T ₂ are determined based on the measured values. It may be changed.

[0056]

As described above, the first embodiment according to the present application is described.
According to the invention, when the heater of the fixing roller shifts to the control stop period in which the heater of the fixing roller is not under the control state of the control unit for any reason, the control stop period is measured by the timer, and the measured period is determined in advance. If it is within the predetermined time, even if the temperature measured by the temperature measuring means is lower than the predetermined reference temperature, the pre-rotation is not performed, so that the time until the start of the image forming operation can be greatly reduced. it can.

According to the second invention of the present application,
The first invention includes at least one or more exterior covers, and means for detecting that the exterior covers are opened, and the predetermined exterior cover in the exterior covers is opened by the means. Is set to start the control stop period of the heater when it is detected that
If the period until the outer cover is closed again is short, the pre-rotation is not performed, and the image forming operation can be started immediately.

Further, according to the third invention of the present application, there is provided a means for detecting a paper jam in the image forming apparatus of the first invention or the second invention, and the paper jam is detected by the means. Sometimes, the control stop period of the heater is set to start, so that if the period required for the paper jam processing is short, the pre-rotation is not performed and the image forming operation can be started immediately.

According to the fourth invention of the present application,
A second timer capable of freely measuring a temperature control period in which the temperature of the fixing roller according to any one of the first invention to the third invention is controlled to a predetermined temperature, wherein the control means controls the heater. When the stop period is started, the second timer detects the temperature control period of the fixing roller immediately before the start of the control stop period, and determines whether or not the pre-rotation is possible based on the length of the detected period. Since the predetermined predetermined time serving as the reference is changed, appropriate control according to the temperature transition during the control suspension period is performed on the pressure roller that has been receiving heat supply from the fixing roller during the temperature control period. Therefore, fixing failure can be prevented.

Further, according to the fifth aspect of the present invention, when the heater of the fixing roller shifts to a control stop period in which the heater of the fixing roller is not under the control of the control means for any reason, the temperature measurement for the pressure roller is performed. The temperature of the pressure roller is measured by the means, and when the measured temperature is equal to or higher than a predetermined temperature, even if the measured temperature of the fixing roller by the temperature measuring means is equal to or lower than a predetermined reference temperature, Since the pre-rotation is not performed, the time until the start of the image forming operation can be greatly reduced.

According to the sixth aspect of the present invention,
The fifth invention includes at least one or more exterior covers, and means for detecting that the exterior covers have been opened, and the predetermined exterior cover in the exterior covers is opened by the means. When it is detected that the temperature of the pressure roller is measured by the pressure roller temperature measuring means and whether or not the pre-rotation can be performed, if the period until the outer cover is closed again is short, the pressure Because the roller temperature does not drop to the extent that pre-rotation is necessary and pre-rotation does not take place,
The image forming operation can be started immediately.

Further, according to the seventh aspect of the present invention, there is provided means for detecting a paper jam in the image forming apparatus according to the fifth or sixth aspect, and the paper jam is detected by the means. In some cases, the temperature of the pressure roller is measured by the pressure roller temperature measuring means, and the determination of whether or not the pre-rotation is possible is performed. Since the pre-rotation is not performed without being lowered as much as necessary, the image forming operation can be started immediately.

According to the eighth aspect of the present invention,
A second timer capable of measuring a temperature control period in which the temperature of the fixing roller according to any one of the fifth to seventh inventions is controlled to a predetermined temperature; Temperature measurement of the pressure roller by the temperature measuring means for
When determining whether or not the pre-rotation is possible, the second timer detects the temperature control period of the fixing roller immediately before the second timer and determines a reference for determining whether or not the pre-rotation is possible according to the length of the detected period. Since the predetermined predetermined temperature is changed, the pressure roller receiving the heat supply from the fixing roller during the temperature control period is appropriately controlled according to the temperature transition during the measurement period. Poor fixing can be prevented.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic configuration of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a flowchart of control according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating temperature transitions of a fixing roller and a pressure roller according to the first embodiment of the present invention.

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

FIG. 5 is a diagram illustrating a schematic configuration of an image forming apparatus in a conventional example.

FIG. 6 is a diagram illustrating a fixing device in a conventional example.

FIG. 7 is a diagram showing a temperature transition of a fixing roller at the time of startup in a conventional example.

FIG. 8 is a diagram showing a difference in temperature transition between a fixing roller and a pressure roller from the time of startup in a conventional example.

FIG. 9 is a diagram illustrating a difference in temperature transition between a fixing roller and a pressure roller after heater driving is stopped in a conventional example.

[Explanation of symbols]

 Reference Signs List 10 fixing roller 11 pressure roller 12 thermistor (temperature measuring means) 16 controller (control means) 17 heater 20 thermistor (temperature measuring means for pressure roller)

Claims (8)

[Claims] 1. A roller pair of a fixing roller and a pressure roller, a heater for heating the fixing roller, a driving unit for driving the fixing roller and the pressure roller to rotate, and a temperature measurement for measuring a temperature of the fixing roller. Means for controlling the driving of the heater based on the temperature measured by the temperature measuring means to adjust the temperature of the fixing roller to a predetermined temperature, and controlling means for controlling the rotational driving of the roller pair by the driving means. The control means controls the temperature of the fixing roller by driving the heater when the temperature measured by the temperature measuring means is equal to or lower than a predetermined reference temperature before performing the fixing operation by the roller pair. In the image forming apparatus set to raise the temperature and perform the pre-rotation of rotating the roller pair by a predetermined number of times by the driving unit, The control means is provided with a timer which can be operated also during a control suspension period not under the control state of the control means, and the control means is adapted to control when the control suspension period measured by the timer is within a predetermined time. In
An image forming apparatus, wherein the pre-rotation is not performed even if the temperature measured by the temperature measuring means is equal to or lower than a predetermined reference temperature. 2. The apparatus according to claim 1, further comprising at least one or more exterior covers, and means for detecting that the exterior covers have been opened, wherein the predetermined exterior covers in the exterior covers have been opened by the means. 2. The image forming apparatus according to claim 1, wherein a setting is made such that a control stop period of the heater is started when the detection is made. 3. The apparatus according to claim 1, further comprising means for detecting a paper jam in the image forming apparatus, wherein the control stop period of the heater is started when the paper jam is detected by the means. An image forming apparatus according to claim 1. And a second timer capable of measuring a temperature control period in which the temperature of the fixing roller is controlled to a predetermined temperature. A second timer detects a temperature control period of the fixing roller immediately before the start of the control suspension period, and a predetermined time period serving as a reference for determining whether or not the pre-rotation is possible according to the detected length of the period. The image forming apparatus according to claim 1, wherein the image forming apparatus is set so as to change the image forming apparatus. 5. A roller pair of a fixing roller and a pressure roller, a heater for heating the fixing roller, a driving unit for driving the fixing roller and the pressure roller to rotate, and a temperature measurement for measuring a temperature of the fixing roller. Means for controlling the driving of the heater based on the temperature measured by the temperature measuring means to adjust the temperature of the fixing roller to a predetermined temperature, and controlling means for controlling the rotational driving of the roller pair by the driving means. The control means controls the temperature of the fixing roller by driving the heater when the temperature measured by the temperature measuring means is equal to or lower than a predetermined reference temperature before performing the fixing operation by the roller pair. In the image forming apparatus which is set to perform a pre-rotation in which the roller pair is rotated a predetermined number of times by the driving unit while raising the temperature, Pressure roller temperature measurement means for measuring the temperature of the roller, wherein the control means is such that the pressure roller temperature measured by the pressure roller temperature measurement means is equal to or higher than a predetermined temperature In this case, the image forming apparatus is set so that the pre-rotation is not performed even if the fixing roller temperature measured by the fixing roller temperature measuring unit is equal to or lower than a predetermined reference temperature. 6. At least one or more exterior covers, and means for detecting that the exterior covers have been opened, wherein a predetermined exterior cover in the exterior covers has been opened by the means. The image forming apparatus according to claim 5, wherein when the detection is made, the temperature of the pressure roller is measured by the pressure roller temperature measuring means to determine whether or not the pre-rotation is possible. 7. A means for detecting a paper jam in the image forming apparatus, wherein when the paper jam is detected by the means, the temperature of the pressure roller is measured by a temperature measurement means for the pressure roller to determine whether the pre-rotation is possible. The image forming apparatus according to claim 5, wherein the image forming apparatus is set so as to make a determination. 8. A second timer capable of measuring a temperature control period during which the temperature of the fixing roller is controlled to a predetermined temperature, wherein the control means controls the temperature of the pressure roller by the temperature measurement means for the pressure roller. When measuring to determine whether pre-rotation is possible,
The temperature control period of the fixing roller immediately before the start of the temperature measurement of the pressure roller is detected by the second timer, and a predetermined reference serving as a criterion for determining whether or not the pre-rotation is possible is determined according to the length of the detected period. The image forming apparatus according to claim 5, wherein the predetermined temperature is set to be changed.