JPH07114285A - Image forming method - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent an increase in drive load and damage to the fixing device due to toner sticking during toner replenishment operation at the toner end. [Structure] When the toner replenishing mode is entered, first the temperature control of the fixing device is started (S1), and when the temperature exceeds the set temperature, it is determined that the toner fixation has been released, and the drive system and the maximum waiting time timer are started ( S4, S5). Thereafter, it is determined whether the toner end state is no longer present (S6), and when the end state is no longer present, the toner end display is canceled (S6).
7) The temperature control of the fixing device, the drive system, and the cooling fan are stopped to exit the replenishment mode. When the maximum waiting time timer elapses in the end state (S11), the toner end display is not canceled and the replenishment mode is exited.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention forms an image composed of a heat-fusible toner on a support such as paper or an OHP sheet by an electrophotographic process, and melts and fixes it by heat from a heat roller or a heat belt. The present invention relates to an image forming method for a copying machine, a printer, a facsimile or the like having a fixing device, and more particularly to a method for controlling the fixing device in the apparatus when toner is supplied.

[0002]

2. Description of the Related Art Conventionally, image forming apparatuses such as copying machines, printers, and facsimiles have replenished toner directly to a developing device when the toner runs out. However, in order to directly supply the toner to the developing device, a space for bringing the toner bottle to the vicinity of the developing device is required, which is an obstacle to downsizing the apparatus. Therefore, in a small device, by exchanging an integrated cartridge including a toner storage portion, a photoconductor, a charger, a developing device, a cleaner, and the like,
The toner was being replenished.

In recent years, however, resource saving and reduction of dust have become a social issue, and a consumable supply method, which replaces the cartridge method in which parts other than the consumable toner, are also discarded, has been studied. At that time, the toner hopper method, in which only the toner tank containing the toner can be replaced and the toner can be replenished without increasing the size of the apparatus, is disclosed in Japanese Patent Publication No. 3-60433 and the toner circulation method is disclosed in Japanese Patent Application No. 4-2.
46771.

Regarding the operation at the time of replenishment by such a toner replenishing method, it is described in Japanese Patent Publication No. 3-60433 that toner is conveyed from the toner hopper to the developing unit by the hopper motor when the amount of toner in the developing unit decreases. There is.

On the other hand, in such a small apparatus, in order to save the space of the driving system, it is preferable to use one driving motor and simultaneously drive the toner circulation system, the image forming system and the fixing system. Since there is only one drive motor, not only the control system for driving the apparatus is simplified, but also it becomes easy to adjust the image support carrying speed between a plurality of processes such as transfer and fixing. This is because the motor generally generates heat when it is driven, but by using one motor, the heat source is located in one place, and it is easy to take measures against exhaust heat, which is particularly important in a small device. Further, since the fixing device and the drive motor generate heat during image formation, the temperature inside the apparatus including the toner circulation path rises. However, by using only one drive motor, the toner conveying operation is always performed during image formation. This is convenient because the toner does not stay in the circulation path whose temperature has risen, and problems such as toner melting and aggregation are prevented.

[0006]

As described above, there are various advantages in synchronizing the driving of the entire apparatus by using one motor, but the one motor is used, and the toner described in the above patent publication is used. When the replenishing operation is performed, there is no problem in replenishing the toner immediately after the image is formed, but if the toner is replenished after a short time has elapsed after the image is formed, the fixing device does not rotate and the drive motor is locked. occured.
This is because when the temperature of the fixing roller decreases after forming an image, it accumulates between the fixing member and a contact member such as a sensor pad, a cleaning pad, a pressure roller, or a separating claw that is in contact with the fixing roller. This is because the toner solidifies and the fixing roller and the contact member are fixed. Therefore, when the drive motor was changed to a large-sized one to break the sticking so that it could rotate, the sticking sensor pad or cleaning pad could be damaged.

The present invention solves the above-mentioned problems in the case of using only one drive motor without adding any constituent elements. This is to prevent the fixing device from being damaged due to sticking, and to reduce the starting torque when replenishing the toner so that a small motor can be used.

[0008]

An image forming method according to the present invention comprises a process section for forming a toner image by an electrophotographic process, a toner reservoir, and a replenishing means for replenishing toner from the toner reservoir to the process section. A fixing device for fixing unfixed toner on the support mainly by heat is provided, and the toner replenishing operation by the replenishing means is started when the fixing device is heated. In addition, a process unit that forms a toner image by an electrophotographic process, a toner storage unit, a replenishment unit that replenishes toner from the toner storage unit to the process unit, and unfixed toner is fixed onto a support mainly by heat. When the fixing device is at a temperature equal to or higher than a predetermined temperature, the toner replenishing operation by the replenishing means is started. Further, after the toner replenishing operation is started, the temperature of the fixing device is controlled to be lower than the temperature at the start of the toner replenishing operation. Also,
The heating of the fixing device is stopped after the toner supply operation is started. Further, it is characterized in that the toner replenishing operation is started when the temperature of the fixing device is higher than a predetermined temperature higher than room temperature.

[0009]

In the heated state of the fixing device, the fixing between the fixing roller and the member in contact with it is eliminated or weakened. Since the toner replenishing operation is started in this state, the force for breaking the fixing becomes small, the toner in the fixing portion is always broken, and the peripheral members are not broken.

[0010]

EXAMPLES The present invention will be described below with reference to examples.

(Embodiment 1) FIG. 1 is an embodiment in which the present invention is applied to a printer. This device includes a paper feed roller 11
And a separation pad 12, a sheet feeding section, a laser light source and a polarizing device 21 (not shown), an exposing section 20 including a folding mirror 22, a photosensitive drum 31, a charging roller 32, a developing unit 33,
Transfer roller 34, toner circulation path 35, toner tank 36
An electrophotographic process unit 30 including: a fixing roller 41 that contacts the toner surface, a fixing roller 40 including a pressure roller 42, communication with an external host computer, fixing unit heater control, motor drive control, electrophotographic process A control circuit unit 50 for controlling the power supply for the power source and the like is contained in a frame 60.

When this printer receives print data from the host computer, it is latently placed on the photosensitive drum 31 which is uniformly charged in advance by the charging roller 32 by the laser light from the exposure section 20 controlled according to the data. An image is formed. The latent image on the photosensitive drum 31 is transferred to the developing device 33.
To form a toner image. The transfer sheet S, which is a support on the paper feed tray 13, is sent to the nip portion between the photosensitive drum 31 and the transfer roller 34 by the paper feed roller 11 in synchronization with the image formation on the photosensitive drum 31, and the toner image is transferred there. To be done. The transfer sheet on which the unfixed toner image after the transfer is placed is sent to the transfer roller 34 and advances to the fixing unit 40. At the nip portion between the fixing roller 41 and the pressure roller 42, the heat of the fixing roller and the pressure of the pressure roller cause the transfer sheet to move. , The toner image is fixed. The transfer sheet that has passed through the fixing unit is discharged to the outside of the apparatus by the discharge roller 80.

A drive system 70 (not shown) is a drive motor 71.
The gear train 72 transmits power to the toner circulation system, the photosensitive drum 31, the fixing roller 41, and the like.
The drive motor 71 is a step motor and is controlled by the control system 51 to slow up, slow down, rotate at a constant speed, or the like.

The cover 61 constituting the frame 60 can be opened by the user, and is opened when the toner tank 36 is replaced. The interlock switch 62 is released when the cover 61 is opened, and is set when the cover is closed. For the safety of the user, all the actuators are inoperative when the cover 61 is open, that is, when the interlock is released. LE on the surface of the frame 60
There is a display section 63 mainly composed of D, and a toner end display lamp 64 is also provided here. Further, the air inside the frame 60 is discharged outside the apparatus by a cooling fan 81 (not shown).

FIG. 2 is a main sectional view of the fixing device 40. Reference numeral 41 denotes a fixing roller having a heater 43 provided therein, which is driven by a drive system 70 via a gear provided at an end portion. The fixing roller 41 was formed by grinding an aluminum pipe into a desired shape such as an inverted crown and having a central portion having a diameter of 18 mm and a wall thickness of 0.6 mm, and the surface thereof was coated with PTFE as a release layer at a thickness of 30 ± 5 μm. It is a thing. The heater 43 is a halogen heater, and AC power is applied through the SSR 52 that is turned on / off by a signal from the control system 51, and its blinking is controlled. A pressure roller 42 is pressed against the fixing roller 41 with a total load of 6 kgf by a pressure mechanism (not shown). The pressure roller 42 is LT on the metal core 421 such as free-cutting steel.
An elastic material layer 422 such as V silicone rubber is provided to reduce the outer diameter to 1
It is 8 mm, and the metal core 421 is electrically grounded. When the temperature of the pressure roller 42 is near room temperature, the electric resistance of the elastic material layer 422 is large, but the electric resistance becomes smaller as the temperature rises. Therefore, electric charges exist on the surface of the pressure roller 42 in the temperature range normally used for fixing. Even then, the core that has been gradually grounded escapes through the elastic material layer 422 to the core 421, and excessive charges do not accumulate on the surface. A temperature detection element 44 such as a thermistor is pressed against the fixing roller 41 via a polyimide sheet 441 by an elastic pad 442 and a leaf spring 443, and the surface temperature is detected with a delay of a certain time constant. The heat-resistant nylon cleaning pad 45 rubs the roller surface by the rotation of the fixing roller 41 to wipe off dirt such as toner. The separation claw 46 is made of PPS resin coated with fluororesin, and is pressed against the fixing roller 41 by a spring 461 to prevent the transfer sheet after fixing from winding around the fixing roller 41. During the fixing operation, the fixing roller 41 is rotationally driven by the drive system 70 at a peripheral speed of 24 mm / sec, and based on the signal from the temperature detecting element 44,
The blinking of the heater 43 is controlled, and the surface temperature of the fixing roller 41 is controlled within a predetermined range.

FIG. 3 is a partially cutaway perspective view showing the structure of the toner circulation system and the toner tank 36. Stirrer 363 inside
When the toner tank 36 having a and 363b is set in the apparatus, the toner circulation path 35 is opened from the opening 362 of the lid 361.
Send toner to. The toner circulation path 35 has an endless shape in which the developing device 33 and the cleaner portion 37 are connected and closed. A toner transport spring belt 351 is provided in the toner circulation path.
Are endlessly stretched, and the toner conveying spring belt 351 is driven by a gear 352 to convey the toner in the circulation path 35. The gear 352 is driven by the drive system 70. The toner end sensor 353 is a reflective optical sensor including a light emitting portion and a light receiving portion, and is attached to the bottom of the circulation path 35. A reflection plate 354 is provided on the ceiling portion of the circulation path, which is opposed to that of the circulation path, and reflects the light emitted from the light emitting portion of the sensor 353 to the light receiving portion. The amount of light received by the sensor changes depending on the amount of toner in the circulation path, and the output of the sensor also changes according to the amount of light received. During normal use, the amount of toner near the sensor is within the predetermined range, so the output of the sensor is also within the predetermined range. When the toner is consumed by printing and the amount of toner in the apparatus decreases, the amount of light received increases and the sensor output becomes a level higher than the predetermined range. After that, when the toner is further consumed, the amount of received light is further increased, and the sensor output is further increased, it is determined that the toner is out. The received light amount level for these determinations can be set arbitrarily.

FIG. 4 is a diagram showing the connection relationship between the control system 51 and the fixing unit and other units related to the toner replenishing operation. The control system is connected to various other elements of the electrophotographic process. It is omitted here. The thin lines in the figure indicate electrical connections,
The thin double line indicates the transmission of the driving force. Control system 51
The output signal of the toner end sensor 353, the output signal of the temperature detecting element 44 in contact with the fixing roller, the signal of the interlock switch 62, and the like are input to the input terminal, and the information is processed by an internal program to transfer the fixing roller and toner. The drive signal of the system is output to the drive system 70, the energization signal of the fixing device heater 43 is output to the SSR 52, the toner end display signal is output to the toner end display 64, and the fan drive signal is output to the cooling fan 11. The memory 53 retains its contents even when the power of the apparatus such as NV-RAM is turned off, and records information such as whether the toner is in the end state or the like. Drive system 70
Rotates the motor 71 according to the drive signal from the control system 51, and the driving force is transmitted to the fixing roller 43 and the toner conveying gear 352 via the gear train 72. The SSR 52 receives the energization signal from the control system 51, and the AC power supply 54 and the heater 43.
Connect or disconnect. When no energization signal is given, the power supply 54 and the heater 43 are shut off. The outputs of the toner end sensor 353 and the temperature detection element 44 are A / D converted and input to the control system 51 and processed by the digital value thereof. However, a predetermined value is set by a circuit including a comparator between the sensor and the control system. The determination result of whether or not the above may be input.

The control system 51 controls the operation of the device while it is operating.
The output of the toner end sensor 353 is monitored at predetermined time intervals to monitor whether the output level is out of the predetermined range and the toner amount is small. It is determined that the toner amount is small when the toner tank 36 is empty and can be replaced. The amount of toner in the circulation path does not change until the toner in the toner tank is exhausted. Therefore, if the sensor 353 is provided in the toner circulation path as described above, the output level of the sensor will be changed after the toner tank 36 is emptied. Since it changes, false detection is prevented. If the toner end sensor 353 is located upstream of the developing device 33 and downstream of the toner tank 36 in the toner circulation path, the developing device 33
Therefore, even if a large amount of toner is temporarily consumed, false detection is not made, which is convenient. At this time, if a sensor output level fluctuation due to noise in the electric circuit or a temporary sensor output level fluctuation due to local density of toner in the toner circulation path is expected, even if the sensor output once deviates from the predetermined range,
The toner low state may not be determined immediately, but the toner low state may be determined after a plurality of detections.

When it is judged that the toner amount is low, the control device blinks the toner end display on the display panel to notify the user that the toner amount is low (toner low display). You can change the blinking interval depending on the remaining amount of toner,
You may change the display color. Alternatively, a toner remaining amount meter may be provided, and the toner end display and the toner low display may be displayed by independent display devices. Printing is enabled while the toner low is displayed.

After the toner low is displayed, the user sets the toner tank 3
When 6 is replaced, the toner is re-supplied to the toner conveyance path 35, and the toner amount in the toner end sensor section also increases due to the toner conveyance accompanying the printing operation, the output level of the toner end sensor returns to the predetermined range, and the toner low display is canceled. To be done.

After the toner low is displayed, if the toner tank is not replaced and printing is continued, the amount of toner in the toner conveying path is further reduced. When the output level of the toner end sensor further changes, the toner end state is determined by the same determination criteria as in the case of toner low. When the toner end state is determined, the toner end state is recorded in the memory 53 that is retained even when the power of the apparatus is turned off. By doing so, it is possible to omit operating the device to monitor the toner amount when the power is turned on next time.

When the toner end state is detected during printing, even if a print request for the next page is made, only the sheet SH1 currently being printed is printed, and printing for the next page and thereafter is not performed. After the SH1 fixing is completed, the print data memory holds the data for the next and subsequent pages.
The temperature control of 0 is stopped and the heater 43 is not energized. After the discharge of SH1, the toner end display 64 is turned on to inform the user of the toner end. The user who knows the toner end opens the cover 61 of the apparatus and replaces the empty toner tank 36 with a new toner tank 36 '. Since the toner end is displayed after SH1 is discharged, it is possible to prevent the user from opening the cover 61 and stopping the apparatus without waiting for SH1 to be discharged, and as a result, the SH1 remains in the apparatus. In addition, the temperature of the fixing device 40 may not immediately drop even when the power supply to the heater 43 is stopped, such as when printing is continuously performed for a long time. In this state, when the cover 61 is opened, the interlock switch 62 is released, and for the safety of the user, the cooling fan 81
Since the operation of all actuators including is stopped, the heat near the fixing device, which has been discharged by the cooling fan 81, is not discharged. Therefore, until the temperature of the fixing device decreases, the toner end display may be set to "blinking" instead of "lighting" in a state where printing is stopped, and the user may wait until the cover is opened. At this time, it is determined that the temperature of the fixing device has decreased by detecting that the temperature detected by the temperature detecting element 44 is equal to or lower than a predetermined temperature, or that the temperature of the fixing device has decreased for a predetermined time determined based on the experimentally obtained fixing device temperature lowering characteristic. Can be done over time.

When the toner end state is detected other than during printing, the start of new printing is prohibited, the toner end is displayed immediately when the fixing device temperature is low, and as described above when the fixing device temperature is high. Wait for the temperature of the fixing device to drop and display the toner end.

Further, the heat capacity of the fixing device is reduced, and the heat accumulated in the vicinity of the fixing device is reduced to a negligible amount by exhaust heat due to natural convection or the like, so that the temperature of the fixing device is not lowered as described above. Alternatively, the toner tank may be replaced. Furthermore, even if the cover of the device is not opened, the toner tank can be replaced by opening only the cover for toner tank replacement so that the cooling fan does not stop and the temperature of the fixing device does not drop. Alternatively, the toner end display and the toner tank replacement may be performed. At this time, there is also an advantage that the temperature rise of the fixing roller for releasing the toner fixation, which will be described later, is shortened because the temperature drop of the fixing roller is small.

Now, after recognizing the toner end indication and the user replacing the toner tank 36, the user again covers the cover 6
When 1 is closed, toner supply is started. In this embodiment,
When it is detected that the cover 61 is closed by setting the interlock switch 62 from the released state when the toner end state is held in the memory 53, the toner replenishment mode is entered. Other conditions for entering the toner replenishment mode are when the toner end state is detected immediately after the cover is closed, when the power is turned on in the toner end state and the cover is closed, or by a switch operated by the user. It can be set in various ways.

FIG. 5 is a flow chart showing the control flow of the toner replenishment mode. When you enter the toner supply mode,
In step S1, the heater control is started when the surface temperature of the fixing roller is 90 ° C. Further, the cooling fan 81 is also operated to discharge the heat of the fixing device (S2). Next, it is determined whether the temperature detected by the thermistor is 90 ° C. or higher (S3),
If the temperature is lower than 90 ° C, the process does not proceed to the next step until the temperature becomes 90 ° C or higher. When the temperature detected by the thermistor exceeds 90 ° C., it is determined that the toner fixation is released, the drive system 70 is started (S4), and the toner replenishment maximum waiting time timer is started (S5). At this time, since the temperature of the pressure roller is also higher than room temperature, the electric resistance from the surface of the pressure roller to the core is reduced, and the electric charge on the roller surface gradually escapes through the core. After the drive system is started, the operation of the toner end sensor is restarted, and it is determined whether the toner end state is lost (S6). The determination that the toner is not in the end state is made based on whether the output level of the toner end sensor has returned to within the predetermined range described above. The judgment may be delayed. If it is determined that the toner end state is not reached, the toner end display is canceled (S7),
The temperature control of the fixing device is stopped (S8). After that, the drive system is stopped (S9), the cooling fan is stopped (S10), and the toner replenishing mode is ended. If it is determined that the toner end state is still maintained, it is determined whether the maximum waiting time timer has elapsed (S11). If not, the toner replenishing operation is continued. When the maximum waiting time timer has elapsed, the drive system is stopped without canceling the toner end display, the toner replenishment mode is exited, and the same state as at the toner end determination is returned. The maximum waiting time timer is a timer to stop the operation when the cover is opened and closed without replacing the toner tank in the toner end state, and it is necessary to select a time longer than the time required for normal toner supply operation. In the example, it was set to 2 minutes.

In this embodiment, the fixing device is set to a predetermined temperature (90
The toner fixation is released by raising the temperature to (° C.). The toner release temperature can be calculated from the phase change temperature and thermal conductivity of the toner, but the type of toner, the amount of toner accumulated and how it accumulates (whether it accumulates thickly or widely) is fixed. It changes depending on the other party. Therefore, in order to obtain the toner fixation release temperature, the following experiment was performed.

(Experiment) The fixing device, which has fixed a life of 100,000 sheets of the fixing device, is heated from room temperature while monitoring the surface temperature with a radiation thermometer having a short time delay, and the surface temperature is 100 ° C. At that time, rotation of the fixing roller was started and the starting torque was measured. The measurement was performed also when the surface temperature was 90 ° C. and 80 ° C., and the following results were obtained.

[0029]

[Table 1]

From these results, it was found that fixing can be released by raising the temperature from room temperature to bring the surface temperature to 90 ° C.

To release the toner fixation, not only the temperature but also the time is required. However, since the temperature detection element including the thermistor used in this embodiment has a time delay, at the time of detection of the fixation release temperature by the temperature detection element. Since the time corresponding to the time delay has elapsed, the sticking has been released.

When the melting point of toner is low and the number of parts contacting the fixing roller is small, the toner fixation releasing temperature is
Although the temperature is slightly higher than room temperature, which depends on the configuration of the apparatus including the toner, the above experiment can be repeated to obtain the value. However, in order to obtain this predetermined temperature more easily, for example, if the predetermined temperature is set as the fixing temperature, it takes a little longer for the temperature of the fixing device to rise, but the fixing temperature is sufficiently higher than the temperature at which the fixing strength weakens, and the fixing is released. In addition, since the control temperature is the same as that during normal fixing, the structure of the control system can be simplified. Further, the release of the toner fixation may be predicted not only by the temperature detected by the temperature detecting element, but also by the heater off time, the rate of change in the temperature detected by the temperature detecting element, and the like.

In this embodiment, the fixing device is controlled at 90 ° C., which is lower than the fixing temperature, during the toner replenishing mode. However, if the toner replenishing mode is entered during printing, printing can be performed immediately after the replenishment is completed. The fixing device may be controlled at the fixing temperature, and may be controlled at the minimum fixing release temperature in order to prevent the temperature rise inside the apparatus when printing is not in progress.

Since the toner replenishment mode is provided in this manner, uneven density of images and blurring of images, which are caused by the toner not being distributed to the circulation path and the developing device after the toner tank is replaced, are prevented, and at the time of the first printing after the replacement. From this, good image quality was obtained. Further, if the toner does not reach the circulation path after the toner tank is replaced, the toner end sensor may erroneously determine that the toner is in the end state again. Did not occur. Particularly in the toner circulation method, the amount of toner in the circulation path decreases uniformly, so when the toner end is detected, the amount of toner decreases in the entire circulation path. Might continue for a long time.

(Embodiment 2) When the toner replenishing operation is long, for example, when the toner circulation path or the developing device is large and the toner replenishing amount is large, or when the operation speed of the apparatus is slow, the fixing device is raised during the toner replenishing mode. The temperature of the pressure roller is much higher than that during normal printing because not only is the power consumption increased due to being heated, which causes an undesirable rise in the machine temperature, but also the amount of heat flowing from the fixing roller to the pressure roller is large. Get higher To reduce the toner replenishment time, the device can be configured to operate faster than normal when replenishing toner, but the amount of heat flowing to the pressure roller is still large, and the temperature rise of the pressure roller is still caused. . When the temperature of the pressure roller rises, the joint between the core and the silicone rubber becomes weaker as the temperature rises, which causes a problem in durability. Further, when printing is performed immediately after replenishing toner, the heat of the pressure roller may cause wrinkles on the sheet. When it is not desirable to raise the temperature of the pressure roller in this way, after raising the temperature of the fixing device to a temperature at which toner fixation can be released and starting rotation, the fixing device is controlled at a temperature below the above temperature. It is recommended to stop energizing the heater. The second embodiment of the present invention performs such control in the toner replenishment mode, and FIG. 6 is a flowchart thereof. The structure of the apparatus is the same as that of the first embodiment, but the sheet passing speed is 18 mm / sec, and the operation speed of the apparatus is about 3/4 of that of the first embodiment. When the toner replenishing mode is entered, the heater control is started at the fixing roller surface set temperature of 90 ° C., and the cooling fan is started (S1 ′, S2 ′). Then
It is determined whether the temperature detected by the thermistor is 90 ° C. or higher (S3 ′), and if it is lower than 90 ° C., the heater control is continued.
When the temperature detected by the thermistor exceeds 90 ° C., it is determined that the toner fixation is released, and the drive system is started (S
4 '), and the toner supply maximum waiting time timer is started (S5'). The process up to this point is the same as in the first embodiment.
In the second embodiment, after the drive system is started in step S4 ', the heater control is stopped and the cooling fan is stopped in step S6' (S7 '). After that, the operation of the toner end sensor is restarted, and it is determined whether or not the toner end state is lost (S8 ′). If it is determined that the toner end state is not reached, the toner end display is canceled (S
9 ') The drive system is stopped (S10'), and the toner replenishing mode is ended. If it is determined that the toner end state is still maintained, it is determined whether the maximum waiting time timer has elapsed (S11 '). If not, the toner supply operation is continued. When the maximum waiting time timer has elapsed, the toner end display is not canceled and the process proceeds to step S10 'to stop the drive system, exit the toner replenishment mode, and return to the same state as when the toner end is detected. In this embodiment, the operation speed of the device is slower than that in the first embodiment, and accordingly, the maximum waiting time timer is set longer accordingly. In the second embodiment, since the heater is turned off during the toner replenishment and the fixing device generates less heat, the time for driving the cooling fan is short and the noise is reduced.

In the present embodiment, the temperature of the fixing roller during toner replenishment was sometimes lower than the toner fixation release temperature, but no adverse effect due to fixation occurred. The reason is considered as follows. For example, taking between the fixing roller and the pressure roller as an example, in order to fix between them, the toner softens and follows the unevenness of the surface of each roller,
It is necessary to eliminate voids between the toner surface and the roller surface, but the nip passage time during roller rotation is about 0.1 seconds, and during this short time the softened state that can follow the irregularities of the surface changes from the softened state to the solidified state. It cannot be changed, and passes through the nip in a softened state, or is solidified to the extent that unevenness cannot be traced before reaching the nip and passes through the nip as it is. In either case, the fixing roller and the pressure roller are not fixed to each other. The same applies to other contact members. It is considered that this is the same regardless of the toner used, unless the toner has a very high solidification rate.

Since the fixing roller of this embodiment has a small diameter and thin wall and a small heat capacity, the amount of heat accumulated is small even if the temperature is once raised to the toner fixing release temperature, and the control method of this embodiment is particularly effectively used. . Furthermore, since the temperature rise after toner replenishment can be done in a short time, the waiting time for temperature rise does not change much compared to the case where the toner fixation release temperature is maintained, and there is little difference in operability. It was good.

FIG. 7 is a control flowchart when the fixing device is controlled at a temperature lower than the toner fixation releasing temperature after the toner fixation is released. The flow is approximately the same as in Example 2, but instead of stopping the heater control after starting the drive system and the maximum waiting time timer, the set temperature is set to 60.
Control at ℃. Further, the heater control is stopped after the drive system is stopped. This method is particularly effective when the toner replenishment takes a long time or when the toner is replenished in a low temperature environment, and it is possible to prevent the temperature of the pressure roller from being lowered too much and to accumulate the electric charge due to friction on the surface. Noise caused by discharge of electric charges was prevented.

In the above description, the fixing device using the heat roller is taken as an example, but the same effect can be obtained by applying the present invention to a belt type fixing device in which one or both of the rollers is a belt. Obviously, the present invention can also be applied to a radiant fixing device having a roller for carrying a sheet or a shutter having a movable portion which may be fixed by toner.

Further, although the present invention has been described with respect to the image forming apparatus having the toner replenishing mode, the toner circulating operation may be performed independently of the image forming even in the apparatus having no toner replenishing mode. For example, the installation location is inclined,
If the toner is biased in the developing device or the toner circulation path due to being overturned during transportation of the device, there is a problem that uneven image density or blurring may occur if an image is formed as it is. By performing the circulation operation, it is possible to eliminate the bias of the toner. The present invention can be preferably applied to the toner circulation operation for eliminating the bias. That is, instead of shifting to the toner replenishment operation by closing the cover after toner replenishment, the inclination of the device is detected to start the toner circulation operation, or the user-operable button is provided on the operation panel and the button is pressed. It is sufficient to start the operation when it is given.

Further, the operation at the time of replenishing toner has been described so far, but it is also applicable to a device in which the entire device is driven when the transfer paper is automatically loaded, and the same effect can be obtained.

[0042]

As described above, according to the present invention, since the fixing device is heated when the toner replenishment is started, the members in the fixing device are not damaged by the fixing of the toner. The number of drive motors of the device can be one, and the heat exhaust efficiency can be improved. Further, since the fixing device is not driven in the state where the toner is fixed, the torque for releasing the fixing is not required, and the small motor can be used.
These were effective in reducing the size and cost of the device. Further, even if the toner is replenished in a low temperature environment, the electric charge is not abnormally accumulated in the pressure roller, and the generation of noise is prevented. Further, since heating of the heater is stopped or reduced during toner supply, power consumption is reduced, temperature rise in the device is prevented, and the pressure roller does not rise abnormally.
As a result, the durability of the pressure roller was improved and the occurrence of paper wrinkles was prevented.

[Brief description of drawings]

FIG. 1 is a main sectional view of an embodiment in which the present invention is applied to a printer.

FIG. 2 is a main cross-sectional view of a fixing device.

FIG. 3 is a partially cutaway perspective view showing a configuration of a toner circulation system and a toner tank.

FIG. 4 is a diagram showing a connection relationship between a control system and a fixing unit and other units related to a toner supply operation.

FIG. 5 is a flowchart showing a control flow when toner is replenished in the first embodiment.

FIG. 6 is a flowchart showing a control flow when toner is replenished in the second embodiment.

FIG. 7 is a flowchart showing a control flow at the time of toner replenishment in a modification of the second embodiment.

[Explanation of symbols]

 11 ... Paper feeding roller 12 ... Separation pad 13 ... Paper feeding tray 20 ... Exposure unit 21 ... Polarizing device 22 ... Folding mirror 30 ... Electrophotographic process unit 31 ... Photosensitive drum 32 ... Charging roller 33 ... Developing device 34 ... Transfer roller 35 ... Toner circulation path 351 ... Toner transport spring belt 352 ... Toner transport gear 353 ... Toner end sensor 354 ... Reflector plate 36 ... Toner tank 361 ... Lid 362 ... Opening 37 ... Cleaner 40 ... Fixing device 41 ... Fixing roller 42 ... Pressure roller 421 ... Metal core 422 ... Elastic material layer 43 ... Heater 44 ... Temperature detection element 441 ... Polyimide sheet 442 ... Elastic pad 443 ... Leaf spring 45 ... Cleaning pad 46 ... Separation Claw 461 ... Spring 50 ... Control circuit unit 51 ... Control system 52 ... SSR 53 ... Memory 54 ... AC power supply 60 ... Frame 61 ... Cover 62 ... Inter Lock switch 63 ... Display unit 64 ... Toner end display lamp 70 ... Drive system 71 ... Drive motor 72 ... Gear train 80 ... Paper ejection roller 81 ... Cooling fan

Claims (5)

[Claims] 1. A process unit for forming a toner image by an electrophotographic process, a toner reservoir, a replenishing unit for replenishing toner from the toner reservoir to the process unit, and unfixed toner mainly on a support. An image forming method comprising: a fixing device for fixing by heat; and when the fixing device is heated, a toner replenishing operation by the replenishing means is started. 2. A process section for forming a toner image by an electrophotographic process, a toner reservoir, a replenishing means for replenishing toner from the toner reservoir to the process section, and unfixed toner mainly on a support. An image forming method comprising: a fixing device for fixing by heat, wherein the toner replenishing operation by the replenishing means is started when the fixing device is at a predetermined temperature or higher. 3. The image forming apparatus according to claim 1, wherein after the toner replenishing operation is started, the temperature of the fixing device is controlled to be lower than the temperature at the start of the toner replenishing operation. Method. 4. The heating of the fixing device is stopped after starting the toner replenishing operation.
The image forming method described in 1 .. 5. The image forming method according to claim 2, wherein the toner replenishing operation is started when the temperature of the fixing device is higher than a predetermined temperature higher than room temperature.