JP2002023554A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device which can prevent the temperature in an image forming device from rising and improve the productivity. SOLUTION: The fixing device has a heat fixation body equipped with a heat source inside, a pressure fixation body which is pressed against the heat fixation body, a detecting means which measures the surface temperature of the heat fixation body, a driving means which rotates the heat fixation body and pressure fixation body, and a control means which controls the heat source and driving means so that the surface of the heat fixation body is held at specific standby temperature in a nonoperation state and a sheet material is sandwiched and conveyed by the press-contact part between the heat fixation body and pressure fixation body. The control means rotates the heat fixation body and pressure fixation body for a prescribed time in arbitrary timing of the nonoperation state and controls the standby temperature in the nonoperation state according to variation in the surface temperature of the heat fixation body before and after the rotation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for an image forming apparatus using an electrophotographic system, such as a copying machine, a printer, a facsimile, and a multifunction machine thereof.
The present invention relates to a temperature control technique for a fixing device.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus using an electrophotographic system, such as a copying machine, a heating roll and a pressure roll are pressed and rotated, and a sheet material carrying a toner image is pressed and conveyed in the pressed portion. A fixing device that fixes a toner image on a sheet material by the action of heat and pressure is widely used. The surface temperature of the heating roll is maintained at a temperature sufficient to melt and fix the toner during the fixing operation, and the fixing can be performed immediately after the image forming instruction even when the fixing is not performed. It is kept at a predetermined standby temperature.

Conventional problems relating to such temperature control of the fixing device include, for example, appropriate setting of the standby temperature and appropriate return from the temperature at the end of the fixing operation to the standby temperature.

[0004] With respect to the appropriate setting of the standby temperature (described above), it is necessary to set the standby temperature so as to satisfy the following conflicting requirements. That is, on the other hand, the stand-by temperature is desirably low from the viewpoint of preventing a temperature rise in the image forming apparatus, thermal deterioration of the heating roll, and an increase in power consumption. On the other hand, at the time of fixing, since the heat of the heating roll is gradually removed by the sheet material, it is desirable that the standby temperature be high from the viewpoint of productivity when continuously fixing a large amount of sheet material.

In order to satisfy both of these requirements, Japanese Patent Laid-Open No. 5-127566 discloses a technique in which the standby temperature is changed based on the elapsed time after completion of fixing. According to this technique, when the elapsed time after completion of the fixing is short, it is determined that the heat storage amount in the heating / pressing roll is large,
The standby temperature is set relatively low with more emphasis on prevention of temperature rise in the image forming apparatus, and if the elapsed time after completion of fixing is long, it is determined that the heat storage amount in the heating / pressing roll is small, and production is started. The standby temperature is set relatively high with emphasis on performance.

[0006] With respect to the appropriate return from the temperature at the end of the fixing operation to the standby temperature (described above), it is necessary to perform temperature control so as to satisfy the following mutually contradictory requirements. That is, on the other hand, it is desirable to return to the standby temperature as quickly as possible in consideration of the case where the next fixing operation is started immediately after the fixing operation is completed, and to continue heating the heating roll after the fixing operation is completed. . On the other hand, if the heating of the heating roll is continued after the end of the fixing operation, the heat storage in the heating roll and the pressure roll,
Overshoot in which the surface temperature of the heating roll greatly exceeds the standby temperature is likely to occur. This overshoot should be avoided from the viewpoint of preventing temperature rise in the image forming apparatus.

In order to prevent such overshoot, Japanese Patent Application Laid-Open No. Hei 8-95420 discloses that heating of a heating roll is stopped after the fixing operation is completed, and the standby temperature is maintained after the surface temperature of the heating roll starts to decrease. A technique for starting such temperature control has been disclosed. According to this technique, since the heating of the heating roll is stopped after the fixing operation is completed, it is possible to prevent an overshoot in which the surface temperature of the heating roll greatly exceeds the standby temperature.

[0008]

However, all of these techniques still have room for improvement. That is, the technology described in Japanese Patent Application Laid-Open No. 5-127566 predicts the amount of heat stored in the heating / pressing roll based on “elapsed time from completion of fixing” and sets an appropriate standby temperature based on the prediction result. However, this "elapsed time since completion of fixing"
It is difficult to predict the amount of heat stored in the heating and pressurizing roll by using only the above. For example, even if the elapsed time from the completion of fixing is the same, the heat storage amount is large after a large amount of sheet material is continuously fixed for a long time, and the heat storage amount is small after a single sheet material is fixed. For this reason, the standby temperature is sometimes too high, causing a rise in the temperature inside the image forming apparatus, and sometimes the standby temperature is too low, which impairs the fixing productivity.

The technique described in Japanese Patent Application Laid-Open No. Hei 8-95420 can prevent overshoot, but immediately returns the surface temperature of the heating roll to the standby temperature to stop heating after the fixing operation is completed. It is difficult.
Therefore, when the next image forming instruction is issued immediately after the completion of a certain fixing operation, the surface temperature of the heating roll is not sufficiently recovered, and a waiting time occurs.

The present invention has been made in view of these problems, and a first object of the present invention is to provide a fixing device which can achieve both the prevention of temperature rise in an image forming apparatus and the improvement of productivity. To provide. It is a second object of the present invention to provide a fixing device that can achieve both quickness when returning from a temperature after completion of fixing to a standby temperature and prevention of overshoot at that time.

[0011]

In order to achieve the first object, the present invention provides a heat fixing member having a heat source therein, a pressure fixing member which is in pressure contact with the heat fixing member, and a heat fixing member. Detecting means for measuring the surface temperature of the heat fixing member, driving means for rotating the heat fixing member and the pressure fixing member, and maintaining the surface temperature of the heat fixing member at a predetermined standby temperature in a non-operating state and heating the fixing member in an operating state. And a control unit for controlling the heat source and the driving unit so that the sheet material is nipped and conveyed and fixed at a pressure contact portion between the heat source and the pressure fixing unit. In this method, the heat fixing member and the pressure fixing member are rotated for a predetermined time, and the standby temperature in the non-operation state is controlled based on a change in the surface temperature of the heat fixing member before and after the rotation. 1).

By configuring the fixing device in this manner, the surface temperature of the heated fixing body is measured before rotation in the non-operating state, and the heated fixing body and the pressure-fixing body are separated for a predetermined time at an arbitrary timing in the non-operating state. Is rotated, the amount of heat stored in the pressure fixing body is reflected on the surface temperature of the heat fixing body, and then the surface temperature of the heat fixing rotator is measured again, and based on the change in the surface temperature of the heating fixing body before and after the rotation. Predicting the heat storage amount of both fixing bodies including the pressure fixing body more accurately, and setting an appropriate standby temperature according to the heat storage amount, prevent the temperature rise in the image forming apparatus and improve productivity. Can be compatible.

Here, the timing of rotating the heat fixing member and the pressure fixing member may be, for example, a timing after turning on the power or a timing after the end of the operation (claim 2). The timing after the power is turned on refers to the timing when the power is turned on to the image forming apparatus, the heat source inside the heat fixing body generates heat, and its surface temperature is in the process of rising. Further, the timing after the end of operation refers to a timing at which after the last sheet material of a certain print job is fixed, the heat source inside the heat fixing body generates heat and its surface temperature is in the process of rising.

Incidentally, as one factor that affects the amount of heat stored in the fixing body, there is a power supply voltage supplied to a heat source inside the heating and fixing body. Therefore, the power supply apparatus further includes voltage detection means for detecting a power supply voltage supplied to the heat source, and the control means can control the standby temperature based on the power supply voltage detected by the power supply detection means. With such a configuration of the fixing device, it is possible to more accurately predict the heat storage amounts of both the fixing members, and to achieve a high degree of compatibility between prevention of temperature rise in the image forming apparatus and improvement in productivity.

When the predetermined time for rotating the heat fixing body and the pressure fixing body is changed, from the viewpoint of accurately estimating the heat storage amount of both fixing bodies, the standby temperature is determined based on the predetermined time. Is preferably controlled. Further, it is preferable that the control means controls the standby temperature based on an elapsed time of a non-operation state.

According to another aspect of the present invention, there is provided a heat-fixing member having a heat source therein, a pressure-fixing member in pressure contact with the heat-fixing member, and measuring a surface temperature of the heat-fixing member. Detecting means for rotating the heat-fixing member and the pressure-fixing member, and a surface temperature of the heat-fixing member at a predetermined standby temperature in a non-operating state and a heat-fixing member and a pressure-fixing member in an operating state. And a control unit that controls the heat source and the driving unit so that the sheet material is pinched and conveyed and fixed at the pressure contact portion with the control unit, wherein the control unit is in a non-operation state immediately after the end of the operation state.
The heat fixing body and the pressure fixing body are rotated for a predetermined time at an arbitrary timing before the overshoot of the surface temperature of the heat fixing body ends (claim 3).

With this configuration of the fixing device, the heat fixing member and the pressure fixing member are rotated for a predetermined time at an arbitrary timing before the overshoot of the surface temperature of the heat fixing member. Is transferred to the pressure fixing body, and overshoot when returning from the temperature after the fixing to the standby temperature can be prevented. Further, since the pressing of the pressure fixing member can be continued after the fixing, the surface temperature of the heat fixing member can be quickly returned to the standby temperature.

Here, the timing for rotating the heat fixing member and the pressure fixing member for a predetermined time includes, for example, a timing at which the surface temperature of the heat fixing member reaches the standby temperature (claim 4). Also in this case, in the non-operation state immediately after the end of the operation state, the control unit preferably continues heating the heat fixing body at least until the surface temperature of the heat fixing body reaches the standby temperature.

Further, when the surface temperature of the heat-fixed member does not drop so much immediately after the end of the operating state, it is unlikely that a large overshoot will occur in the first place. Therefore, the control unit may be configured to control the rotation of the heat fixing member and the pressure fixing member at the timing based on the surface temperature of the heat fixing member immediately after the end of the operating state. ).

[0020]

Embodiments of the present invention will be described below with reference to embodiments. FIG. 1 is a schematic sectional view of a fixing device according to an embodiment of the present invention. This fixing device includes a heating roll (heat fixing body) 1 having a halogen lamp (heat source) 3 therein, a pressure roll (pressure fixing body) 2 pressed against the heating roll 1, and a surface temperature of the heating roll. Temperature sensor (detection means) 4 for measurement, drive motor (drive means) 5 for rotating heating roll 1 and pressure roll 2
And Here, the heating roll 1 has a multilayer structure including a hollow pipe 11 made of aluminum, a Teflon (registered trademark) layer 12, and a surface layer (not shown) from the inside. The pressure roll 2 has a multilayer structure including a shaft 21 made of aluminum and an elastic layer 22 made of silicon rubber from the inside.

In such a fixing device, temperature control and drive control are performed as follows during operation and non-operation (when warming up and during standby), respectively.

First, during operation, the halogen lamp 3 generates heat by supplying power to the halogen lamp 3, and the surface temperature of the heating roll 1 is heated to a predetermined fixing temperature. In addition, when power is supplied to the drive motor 5, a rotational driving force is transmitted to the heating roll 1 via a drive transmission system (not shown), and the heating roll 1 is rotated in a direction indicated by an arrow A in the figure. Further, the pressure roll 2 pressed against the heating roll 2 at the pressure contact portion N follows the rotation of the heating roll 1 and is rotated in the direction of the arrow B in the figure.

When the sheet material S, on which the unfixed toner image T is electrostatically held on its surface by a predetermined electrophotographic process, passes through the pressure contact portion N between the heating roll 1 and the pressing roll 2, the heat S The unfixed toner image T is fused and fixed by the action of the pressure and the pressure, and the toner image T ′ is held on the sheet material S as a permanent image. The sheet material S holding the toner image T ′ is sequentially conveyed, discharged from the discharge port of the image forming apparatus (not shown) to the outside of the image forming apparatus, and the image forming operation ends.

Next, temperature control and drive control of the fixing device during non-operation will be described. First, in the fixing device according to the present embodiment, prevention of temperature rise in the image forming apparatus and improvement of productivity are achieved. Secondly, each of these controls is performed so that both quickness when returning from the temperature after completion of fixing to the standby temperature and prevention of overshoot at the same time can be achieved. We are devising. Less than,
The control for the first purpose will be described as a first embodiment, and the control for the second purpose will be described as a second embodiment.

First Embodiment The control according to the first embodiment aims at achieving both the prevention of temperature rise in the image forming apparatus and the improvement of productivity.

FIG. 2 is a block diagram illustrating a control system according to this embodiment. This control system includes a control unit (control means) 6
It is configured around 0. The detection target of this control system is
The surface temperature of the heating roll 1 sent from the temperature sensor 4;
The state of the fixing device sent from the main control unit 100 of the image forming apparatus and the voltage of the main power supply 70 of the image forming apparatus sent from the voltage detecting circuit (voltage detecting unit) 71. The control target of this control system is a halogen lamp 3 inside the heating roll 1 and a driving motor 5 for rotating the heating roll 1. Then, the control unit 60 sets each control target to the heater driver (control means) 6 based on the information from these detection targets.
1. Control via a motor driver (control means) 62. The heater driver 61 and the motor driver 62 are supplied with power from the main power supply 70.

FIG. 3 shows a control table stored in the control unit 60. FIG. 3A shows a temperature change ΔT accompanying rotation of both rolls 1 and 2 during warm-up.
Is a control table that defines the corresponding relation between the standard initial standby temperature T _S, the relationship between the standard initial standby temperature T _S and the corresponding temperature change [Delta] T 'associated with the rolls 1 and 2 rotate after completion of printing has a . For example, temperature change Δ
If T is in the range of T ₁ ≦ ΔT <T ₂ , it indicates that T _S2 is selected as the standard initial standby temperature T _{S at} that time. FIG. 3A is a control table that defines the relationship between the voltage V of the main power supply 70 detected by the voltage detection circuit 71 and the corresponding voltage correction coefficient α. For example, the voltage V
Is in the range of V ₁ ≦ V <V ₂ , it indicates that α ₂ is selected as the voltage correction coefficient α at that time. Note that the relations of these control tables are experimentally obtained.

4 to 7 are flowcharts for explaining the control operation of this control system. FIG. 4 shows the basic control operation, and FIGS. 5 to 7 show the control steps shown in FIG. 4 in more detail. This is shown as a simple control operation.

First, a basic control operation of this control system will be described with reference to FIG. First, the control unit 60 determines whether or not the fixing device is in the non-operation mode (S1). If the fixing device is in the non-operation mode, the control unit 60 determines whether or not the power is supplied to the image forming apparatus (S2). It is determined whether or not (S3).
Note that these determinations in S1 to S3 are made based on information indicating the state of the image forming apparatus sent from the main control unit 100 of the image forming apparatus.

If the operation mode is the non-operation mode, and the power has not been turned on or the printing has not been completed, the previous initial standby temperature is set (S8), and the initial initial standby temperature T _I is used as it is. Temperature control in the standby mode is performed (S9: described later). On the other hand, in the non-operation mode, after the power is turned on or after the printing is completed, a new initial standby temperature T _I is respectively obtained (S3, S4: described later), and the newly obtained initial standby temperature T _I is set (S8), and the temperature control in the non-operation mode is performed based on the newly obtained initial standby temperature T _I (S9: described later).

The initial standby temperature T _I predicts the amount of heat stored in the pressure roll 2 more accurately so that the prevention of temperature rise in the image forming apparatus and the improvement of productivity can be achieved at the same time. It is determined as a value that can be used (S3, S5).

FIG. 5 is a flowchart for explaining the control operation (S3, S5) for obtaining the initial standby temperature T _I in more detail. First, the control unit 60 idles the heating roll 1 and the pressure roll 2, and obtains a standard initial standby temperature T _S based on the temperature change (S31,
S51: described later).

Next, a voltage correction coefficient α is obtained from the power supply voltage V of the main power supply 70 sent from the voltage detection circuit 71 and a control table (see FIG. 3B) stored in the control section 60 in advance (S32, S52). Thereby, when the power supply voltage V is higher than the standard power supply voltage, the voltage correction coefficient α
Is selected as a correction coefficient smaller than 1. On the other hand, when the power supply voltage V is lower than the standard power supply voltage, a correction coefficient larger than 1 is selected as the voltage correction coefficient α. Further, the initial standby temperature T _I (= α × T _S ) is obtained based on the standard initial standby temperature T _S and the voltage correction coefficient α thus obtained (S33, S53).

Further, the standard initial standby temperature T _S is obtained as follows. FIG. 6 is a flowchart illustrating the control operation for obtaining the standard initial standby temperature T _S in more detail. First, the control unit 60 drives the motor driver 62 via the motor driver 62 after the power is turned on (S2: after a lapse of a predetermined time immediately after the power is turned on in this embodiment) or after the printing is completed (S4: immediately after the printing is finished in this embodiment). Electric power is supplied to the motor 5 to rotate the heating roll 1 and the pressure roll 2 idle (S311 and S511). At the same time, the control unit 60 stores the surface temperature H ₁ of the heating roll 1 at the start of idling of the both rolls 1 and 2 sent from the temperature sensor 4 (S312, S512).

After t seconds have passed since the storage of the surface temperature H ₁ (S 313, S 513), the controller 60 stores the surface temperature H ₂ of the heating roll 1 sent from the temperature sensor 4 (S 314, S 514). . At the same time, the control unit 60 stops supplying power to the drive motor 5 via the motor driver 62, and stops the idle rotation of the heating roll 1 and the pressure roll 2 (S315, S515). Here, the idle rotation time t of the two rolls 1 and 2 may be a fixed time regardless of whether the power is turned on (S3) or after printing is completed (S5). Then after power-on (S3)
The idle rotation time t = 1 (1) after the printing is different from the idle rotation time t = t (2) after the printing is completed (S5).

Next, a change in the surface temperature of the heating roll 1 during the idle rotation time t, ΔT (ΔT ′) = H ₂ −H _1, and a control table (FIG. a)
) To obtain the standard initial standby temperature T _S (S
316, S516). That is, a control table that defines the relationship between the temperature change ΔT due to the rotation of both rolls 1 and 2 at the time of warm-up, that is, after a lapse of a predetermined time immediately after the power is turned on, and the corresponding standard initial standby temperature T _S is actually set. The standard initial standby temperature T _S is obtained from the measured temperature change ΔT, and the relationship between the temperature change ΔT ′ associated with the rotation of the two rolls 1 and 2 immediately after printing is completed and the corresponding standard initial standby temperature T _S is defined. The standard initial standby temperature T _S is obtained from the control table and the actually measured temperature change ΔT ′.

Thus, when the temperature change ΔT (ΔT ′) is small (including a negative value), a relatively high standard initial standby temperature T _S is selected. On the other hand, when the temperature change ΔT (ΔT ′) is large (including a positive value), a relatively low standard initial standby temperature T _S is selected.

The temperature control in the non-operation mode (S9) is performed as follows based on the initial standby temperature T _I thus obtained. FIG. 7 is a flowchart illustrating the temperature control operation (S9) in the non-operation mode in more detail. Control unit 60, the temperature control in the non-operational mode starts counting the elapsed time until passage s seconds (S91), the on-off control of the halogen lamp 3 to the target temperature to the standby temperature T _W Perform (S92). Here, on-off control for the target temperature with the standby temperature T _W (S92), based on the surface temperature of the heating roll 1 sent from the temperature sensor 4, the control unit 60 to the halogen lamp 3 through the heater driver 61 by on-off controlling the supply of electric power, and controls to maintain the surface temperature of the heating roller 1 in the vicinity standby temperature T _W.

On the other hand, a certain standby temperature T_WON / OFF control
S seconds, the standby temperature T, which is the target temperature_WUpdate
(S93), the counter is reset (S94), and the counter is reset again.
Updated standby temperature T_WOn-off system with target temperature
Control and repeat this operation. Here, the standby temperature T_W
Is updated (S93) by, for example, setting the previous standby temperature to T
_W(N-1), the standby temperature after updating is T_W(N), pressure low
Temperature change taking into account the heat radiation of the_W(> 0) and
Then T_W(N) = T_W(N-1) + ΔT_WSeeking as
Is also good. In short, temperature control in this non-operation mode
(S9) is the standby temperature T _WBut first, the initial standby temperature
Degree T_IBut T every s seconds_W(1), T_W(2),
On and off with the target temperature while being sequentially updated
Control will be performed.

Up to now, the control operation of this control system has been described with reference to the flowcharts of FIGS. 4 to 7. Next, the control operation after the power is turned on and the control after the printing is completed will be described with reference to FIGS. The operation will be described over time.

FIG. 8 illustrates the control operation after the power is turned on over time. In the upper part of the figure, a graph in which the vertical axis is the surface temperature of the heating roll 1 and the horizontal axis is the elapsed time is described, and the lower part of the figure is the standby temperature, which is the target temperature of the on / off control, and the halogen. Both the ON / OFF timing chart of the lamp 3 and the ON / OFF timing chart of the drive motor 5 are described in such a manner that the horizontal axis of the upper graph coincides with the time axis.

When the power is turned on to the image forming apparatus at the time t ₀ , the control unit 60 simultaneously starts supplying power to the halogen lamp 3 via the heater driver 61. At this time, the drive motor 5 has stopped, and the standby temperature has not yet been determined. Thereafter, when the halogen lamp 3 generates heat, the surface temperature of the heating roll 1 increases, and when a predetermined time has elapsed and the time t ₁ has elapsed, the control unit 60 supplies power to the drive motor 5 via the motor driver 62. Is started, and the heating roll 1 and the pressure roll are idled (S31).
1) At the same time, the surface temperature H1 of the heating roll ₁ is measured and stored (S312).

After a lapse of a predetermined time t (1) (S31)
3) At time t ₂ , the controller 60 measures and stores the surface temperature H ₂ of the heating roll 1 (S 314), stops power supply to the drive motor 5 via the motor driver 62, and establishes a connection with the heating roll 1. The rotation of the pressure roll is stopped (S31).
5). At the same time, the temperature change ΔT of the surface temperature of the heating roll 1
(= H ₂ −H ₁ ) and the control table (see FIG. 3A) to obtain the standard initial standby temperature T _S (S 31).
6) The voltage correction coefficient α is obtained based on the voltage V of the main power supply 70 and the control table (S32), and finally the initial standby temperature T _I is obtained (S33, S3). Then, the initial standby temperature T _I is set as the standby temperature T _W (S8),
Non-operation mode control is started (S9).

[0044] Here, the surface temperature of H ₂ heating roll 1 at time t _2, since the standby temperature T _W (= T _I) in does not reach, the control unit 60 from time t ₂ to time t ₃ halogen Power is continuously supplied to the lamp 3. On the other hand, at time t ₃ , the surface temperature of the heating roll 1 becomes the standby temperature T _W (= T _I )
When reached, the control unit 60 is controlled to maintain the surface temperature of the heating roll 1 by turning on and off the halogen lamp 3 to the standby temperature T _W vicinity.

When the elapsed time from the time t ₂ becomes s seconds at the time t ₄ , that is, the on / off control (S 92) of the standby temperature T _W (= T _I ) continues for s seconds (S 9).
1), the standby temperature T _W is from T _I to T _W (1) (= T _I + ΔT _W )
(S93), and the updated standby temperature T _W (= T _W)
On / off control (S92) of (1)) is performed.

Here, the time t_FourOf the heating roll 1 in
Surface temperature T_IIs the standby temperature T after the update _W(= T_W(1))
Control unit 60 does not reach time t._FourFrom time
t_FiveUntil the above, the power is continuously supplied to the halogen lamp 3.
On the other hand, time t_FiveThe surface temperature of the heating roll 1 stands by
Temperature T_W(= T_WWhen (1)) is reached, the control unit 60
The on / off control of the gen lamp 3 controls the surface temperature of the heating roll 1
Degree waiting temperature T_WIt is controlled to keep it near. Less than
The same is true below.

FIG. 9 illustrates the control operation after printing is completed over time. In the upper part of the figure, a graph in which the vertical axis is the surface temperature of the heating roll 1 and the horizontal axis is the elapsed time is described, and in the lower part of the figure, the state of the fixing device, the heating roll 1
And the presence or absence of a sheet material in the nip portion N of the pressure roll 2, a standby temperature which is a target temperature for on / off control, an on / off timing chart of the halogen lamp 3, a drive motor 5
Are described in such a manner that the horizontal axis of the upper graph coincides with the time axis.

In the operation mode, the final image of a certain print job is electrostatically transferred onto the sheet material S, and the rear end of the sheet material S in the transport direction moves the nip N between the heating roll 1 and the pressure roll 2 for a time. Upon passing in t _1, the non-operation mode operation mode is finished (standby mode) starts.

Here, the control unit 60 does not immediately stop the rotation of the heating roll 1 and the pressure roll 2 but continues to supply power to the drive motor 5 via the motor driver 62 to connect the heating roll 1 and the pressing roll 2 with each other. The idle rotation of the pressure roll is performed (S31).
1) At the same time, the surface temperature H1 of the heating roll ₁ is measured and stored (S312).

After a lapse of a predetermined time t (2) (S31)
3) At time t ₂ , the controller 60 measures and stores the surface temperature H ₂ of the heating roll 1 (S 314), stops power supply to the drive motor 5 via the motor driver 62, and establishes a connection with the heating roll 1. The rotation of the pressure roll is stopped (S31).
5). At the same time, the temperature change Δ of the surface temperature of the heating roll 1
T ′ (= H ₂ −H ₁ ) and control table (see FIG. 3A)
Of the standard initial standby temperature T _S based on
6) The voltage correction coefficient α is obtained based on the voltage V of the main power supply 70 and the control table (S32), and finally the initial standby temperature T _I is obtained (S33, S3). Then, the initial standby temperature T _I is set as the standby temperature T _W (S8),
Non-operation mode control is started (S9).

[0051] Here, the surface temperature of H ₂ heating roll 1 at time t _2, since the standby temperature T _W (= T _I) in does not reach, the control unit 60 from time t ₂ to time t ₃ halogen Power is continuously supplied to the lamp 3. On the other hand, at time t ₃ , the surface temperature of the heating roll 1 becomes the standby temperature T _W (= T _I )
When reached, the control unit 60 is controlled to maintain the surface temperature of the heating roll 1 by turning on and off the halogen lamp 3 to the standby temperature T _W vicinity.

When the elapsed time from the time t ₂ becomes s seconds at the time t ₄ , that is, the on / off control (S92) of the standby temperature T _W (= T _I ) is continued for s seconds (S9).
1), the standby temperature T _W is from T _I to T _W (1) (= T _I + ΔT _W )
(S93), and the updated standby temperature T _W (= T _W)
On / off control (S92) of (1)) is performed.

Here, the time t_FourOf the heating roll 1 in
Surface temperature T_IIs the standby temperature T after the update _W(= T_W(1))
Control unit 60 does not reach time t._FourFrom time
t_FiveUntil the above, the power is continuously supplied to the halogen lamp 3.
On the other hand, time t_FiveThe surface temperature of the heating roll 1 stands by
Temperature T_W(= T_WWhen (1)) is reached, the control unit 60
The on / off control of the gen lamp 3 controls the surface temperature of the heating roll 1
Degree waiting temperature T_WIt is controlled to keep it near. Less than
The same is true below.

The control operation of the first embodiment has been described in detail. As described above, in the first embodiment, since the heat storage amount of the pressure roll 2 is predicted to set a more appropriate standby temperature T _W , the standby temperature T _W is too high and the temperature in the image forming apparatus is too high. Can be prevented, and continuous image formation can be prevented from being interrupted due to the standby temperature T _W being too low.

In this embodiment, the non-operation state is
The warm-up after power-on and the end of printing have been described. However, the present invention can be applied to, for example, warm-up after the preheating mode. Further, the idle rotation time t of both rolls 1 and 2 may be different between the warm-up after the power is turned on and the warm-up after the preheating mode. In this case, the control table (see FIG. 3A) ) Can be handled by increasing the number of columns.

Further, in this embodiment, the voltage of the main power supply 70 is
Initial standby temperature T in consideration of V _IWas determined (S
32, S52), it is not always necessary to consider this.
No. If the voltage V of the main power supply 70 is not considered,
The knowledge circuit 71 does not require the control table shown in FIG.
Therefore, the control operations of S32 and S52 in FIG.
Further, α = 1 in S33 and S53 of FIG.
Can be addressed.

Second Embodiment The control according to the second embodiment aims at achieving both quickness when returning from the temperature after fixing to the standby temperature and prevention of overshoot at that time. Hereinafter, the same configurations and operations as those of the first embodiment are denoted by the same reference numerals, and the description will be made focusing on the differences from the first embodiment.

FIG. 10 is a block diagram illustrating a control system according to this embodiment. This control system is a control unit (control means)
It is configured around 60. The control system detects the surface temperature of the heating roll 1 sent from the temperature sensor 4 and the state of the fixing device sent from the main control unit 100 of the image forming apparatus. The control target of this control system is a halogen lamp 3 inside the heating roll 1 and a driving motor 5 for rotating the heating roll 1. The control unit 60 controls each control target via a heater driver (control means) 61 and a motor driver (control means) 62 based on the information from these detection targets. The heater driver 61 and the motor driver 62 are supplied with power from a main power supply (not shown).

The basic control operation of this control system is almost the same as that of the first embodiment described with reference to FIG. Figure 1
FIG. 1 is a flowchart illustrating a difference from the basic control operation of the first embodiment. Hereinafter, the basic control operation of this control system will be described with reference to FIGS.

First, the control unit 60 determines whether the fixing device is in the non-operation mode (S1). If the fixing device is in the non-operation mode, the control unit 60 determines whether or not the power is supplied to the image forming apparatus (S1).
2) It is determined whether or not printing has been completed (S3). Note that these determinations in S1 to S3 are made based on information indicating the state of the image forming apparatus sent from the main control unit 100 of the image forming apparatus.

If the operation mode is the non-operation mode, and the power has not been turned on or the printing has not been completed, the previous initial standby temperature is set (S8), and the initial initial standby temperature T _I is used as it is. Temperature control in the standby mode is performed (S9: described above). On the other hand, in the non-operation mode, after the power is turned on, a new initial standby temperature T _I is obtained (S3: described above), and the newly obtained initial standby temperature T _I is set (S8). ,
Temperature control in the non-operation mode is performed based on the newly obtained initial standby temperature T _I (S9: described above).

If the operation mode is the non-operation mode and the printing is completed, the initial standby temperature T _I is newly obtained (S5: described above), and the initial standby temperature T _I and the heating roll 1 at that time are determined. comparing the surface temperature H ₂ (S
6) If the temperature difference (T _I -H ₂ ) is greater than 30 degrees, an overshoot prevention operation is performed (S7:
If the temperature difference (T _I -H ₂ ) is smaller than 30 degrees, the overshoot prevention operation is not performed, and the obtained initial standby temperature T _I is set (S
8) The non-operation mode temperature control is performed based on the newly obtained initial standby temperature T _I (S9).

FIG. 12 illustrates this overshoot preventing operation in more detail. The control unit 60 continues to supply power to the halogen lamp 3 via the heater driver 61 until the surface temperature of the heating roll 1 reaches the initial standby temperature T _I (S71, S72). When the surface temperature of the heating roll 1 reaches the initial standby temperature T _I , the timer is reset to reset the initial standby temperature T _I.
And the elapsed time from when the
3) The control unit 60 stops supplying power to the halogen lamp 3 via the heater driver 61 and starts supplying power to the drive motor 5 via the motor driver 62 (S74). Then, the heating roll 1 and the pressure roll 2 rotate in a state where they are in pressure contact with each other, and heat is efficiently transferred between the two rolls. That state continues for 2 seconds (S7
5) After that, the control unit 60 stops supplying power to the drive motor 5 via the motor driver 62 (S76), and ends the overshoot prevention operation.

Next, the control operation after the end of printing according to the present embodiment will be described with reference to FIGS.

FIG. 13 is a diagram for explaining the control operation after printing is completed over time. In the upper part of the figure, a graph in which the vertical axis is the surface temperature of the heating roll 1 and the horizontal axis is the elapsed time is described. In the lower part of the figure, the state of the fixing device, the heating roll 1 and the pressure are shown. The presence or absence of a sheet material in the nip portion N of the roll 2, a standby temperature which is a target temperature for on / off control, an on / off timing chart of the halogen lamp 3, a drive motor 5
Are described in such a manner that the horizontal axis of the upper graph coincides with the time axis.

In the operation mode, the final image of a certain print job is electrostatically transferred to the sheet material S, and the rear end of the sheet material S in the transport direction moves the nip portion N between the heating roll 1 and the pressure roll 2 in time. Upon passing in t _1, the non-operation mode operation mode is finished (standby mode) starts.

Here, the control unit 60 does not immediately stop the rotation of the heating roll 1 and the pressure roll 2 but continues to supply power to the drive motor 5 via the motor driver 62 and The idle rotation of the pressure roll is performed (S31).
1) At the same time, the surface temperature H1 of the heating roll ₁ is measured and stored (S312).

Further, after a predetermined time t (2) has elapsed (S31)
3) At time t ₂ , the controller 60 measures and stores the surface temperature H ₂ of the heating roll 1 (S 314), stops power supply to the drive motor 5 via the motor driver 62, and establishes a connection with the heating roll 1. The rotation of the pressure roll is stopped (S31).
5). At the same time, the temperature change Δ of the surface temperature of the heating roll 1
T ′ (= H ₂ −H ₁ ) and control table (see FIG. 3A)
Of the standard initial standby temperature T _S based on
6) The voltage correction coefficient α is obtained based on the voltage V of the main power supply 70 and the control table (S32), and finally the initial standby temperature T _I is obtained (S33, S3). Then, the initial standby temperature T _I is set as the standby temperature T _W (S8),
Non-operation mode control is started (S9).

Here, the time t_TwoOf the heating roll 1 in
Surface temperature H_TwoAnd initial standby temperature T _ICompared to
(S6), the temperature difference (H_Two-T_I) Is greater than 30 degrees
Therefore, an overshoot prevention operation is performed. Sand
The control unit 60 sets the time t_TwoFrom time t_ThreeUp to halogen
The power is continuously supplied to the pump 3. On the other hand, time t_Threesmell
The surface temperature of the heating roll 1 is the standby temperature T_W(= T_IReached)
Then, the control unit 60 turns off the halogen lamp 3 for 2 seconds.
While rotating the heating roll 1 and the pressure roll 2
You.

FIG. 14 explains in more detail the surface temperature of the heating roll 1 around the time t _{3 in} FIG. 13, and the on / off timing of the halogen lamp 3 and the drive motor 5. As shown in the figure, since power is constantly supplied to the halogen lamp 3 until the time t ₃ , the surface temperature of the heating roll 1 quickly changes from the temperature after completion of fixing to the standby temperature T _W (= T _I ) can return. On the other hand, time t
_For a predetermined time from 2 (in this embodiment, 2 seconds), the power supply to the halogen lamp 3 is stopped and the power is supplied to the drive motor 5, so that the heating roll 1 and the pressure roll 2 are pressed against each other. By rotating the pressure roller 2 at a relatively low temperature, the pressure roll 2 having a relatively low temperature quickly removes the heat of the high-temperature heating roll 1, so that the overshoot of the heating roll 1 can be prevented.

Thereafter, at time t ₄ , when the elapsed time from time t ₂ becomes s seconds, that is, the standby temperature T _W (= T _I )
When the on / off control (S92) of the control is continued for s seconds (S9)
1), the standby temperature T _W is from T _I to T _W (1) (= T _I + ΔT _W )
(S93), and the updated standby temperature T _W (= T _W)
On / off control (S92) of (1)) is performed.

Here, the time t_FourOf the heating roll 1 in
Surface temperature T_IIs the standby temperature T after the update _W(= T_W(1))
Control unit 60 does not reach time t._FourFrom time
t_FiveUntil the above, the power is continuously supplied to the halogen lamp 3.
On the other hand, time t_FiveThe surface temperature of the heating roll 1 stands by
Temperature T_W(= T_WWhen (1)) is reached, the control unit 60
The on / off control of the gen lamp 3 controls the surface temperature of the heating roll 1
Degree waiting temperature T_WIt is controlled to keep it near. Less than
The same is true below.

The control operation of the second embodiment has been described in detail. As described above, in the second embodiment, since the power supply to the halogen lamp 3 is continued after the fixing is completed, the surface temperature of the heating roll 1 quickly changes from the temperature after the fixing is completed to the standby temperature T.
_W (= T _I ) can be restored. On the other hand, the standby temperature T _W
(= T _I ), the heating roll 1 and the pressurizing roll 2 are pressed against each other and rotated, so that the heating roll 1
Overshoot can be prevented.

[0074]

As described above in detail, according to the present invention, it is possible to provide a fixing device capable of preventing the temperature in the image forming apparatus from rising and improving the productivity. Further, it is possible to provide a fixing device that can achieve both quickness when returning from the temperature after fixing to the standby temperature and prevention of overshoot at that time.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a fixing device according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a control system according to the first embodiment.

FIG. 3 schematically illustrates a table stored in a control unit.

FIG. 4 is a flowchart illustrating a basic control procedure.

FIG. 5 is a flowchart illustrating a control procedure when obtaining an initial standby temperature.

FIG. 6 is a flowchart illustrating a control procedure for obtaining a standard initial standby temperature.

FIG. 7 is a flowchart illustrating a control procedure in a non-operation mode.

FIG. 8 illustrates a control operation after power-on according to the first embodiment over time.

FIG. 9 illustrates a control operation after printing is completed according to the first embodiment over time.

FIG. 10 is a block diagram illustrating a configuration of a control system according to a second embodiment;

FIG. 11 is a flowchart illustrating a control procedure unique to the second embodiment;

FIG. 12 is a flowchart illustrating a control procedure.

FIG. 13 is a diagram for explaining a control operation after printing is completed according to the second embodiment over time.

FIG. 14 is a diagram for explaining a part of FIG. 14 in detail;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Heating roll (heat fixing body), 2 ... Pressure roll (pressure fixing body), 3 ... Halogen lamp (heat source), 4 ... Temperature sensor (detection means), 5 ... Drive motor (drive means), 60 ...
Control unit (control means), 61: heater driver (control means), 62: motor driver (control means), 70: main power supply, 71: voltage detection circuit (voltage detection means)

Claims (5)

[Claims] A heat fixing member having a heat source therein; a pressure fixing member in pressure contact with the heat fixing member; a detecting means for measuring a surface temperature of the heat fixing member; And a driving unit for rotating the sheet fixing device. In a non-operating state, the surface temperature of the heat fixing body is maintained at a predetermined standby temperature, and in the operating state, the sheet material is nipped and conveyed and fixed at a pressure contact portion between the heat fixing body and the pressure fixing body. As described above, in the fixing device having the heat source and the control means for controlling the driving means, the control means rotates the heat fixing body and the pressure fixing body for a predetermined time at an arbitrary timing in a non-operation state, A fixing device for controlling a standby temperature in a non-operating state based on a change in a surface temperature of a heated fixing body before and after. 2. The arbitrary timing is a timing after power-on or a timing after operation is completed.
3. The fixing device according to claim 1. 3. A heat-fixing member having a heat source therein, a pressure-fixing member in pressure contact with the heat-fixing member, detecting means for measuring a surface temperature of the heat-fixing member, a heat-fixing member and a pressure-fixing member. And a driving unit for rotating the sheet fixing device. In a non-operating state, the surface temperature of the heat fixing body is maintained at a predetermined standby temperature, and in the operating state, the sheet material is nipped and conveyed and fixed at a pressure contact portion between the heat fixing body and the pressure fixing body. As described above, in the fixing device having the heat source and the control unit for controlling the driving unit, the control unit is configured to perform the operation before the end of the overshoot of the surface temperature of the heat fixing member in the non-operation state immediately after the end of the operation state. A fixing device characterized in that the heat fixing body and the pressure fixing body are rotated at a desired timing for a predetermined time. 4. The fixing device according to claim 3, wherein the arbitrary timing is a timing at which the surface temperature of the heat fixing member reaches the standby temperature. 5. The fixing device according to claim 3, wherein the control unit controls the rotation of the heat fixing member and the pressure fixing member at the timing based on a surface temperature of the heat fixing member immediately after the end of the operating state.
3. The fixing device according to claim 1.