JP2022152446A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus that can prevent deterioration of a heater in a fixing unit through simple control.SOLUTION: An image forming apparatus 100 comprises a fixing unit 1 and a control unit 70. The fixing unit 1 has a fixing belt 10, a pressure member 20, a heater 31, and a thermo-sensitive body 34. The control unit 70 controls to start driving to heat the heater 31 through a heating driving circuit 50, and after the lapse of a certain time, start driving to rotate the pressure member 20 through a rotation driving circuit 40. The control unit 70 measures a first temperature gradient related to an increase in temperature of the heater 31 in a period after the start of heating drive and before the start of rotation drive and measures a second temperature gradient related to an increase in temperature of the heater 31 in a period after the start of rotation drive. When the difference between the first temperature gradient and the second temperature gradient is smaller than a predetermined threshold, the control unit 70 controls to stop, of the heating drive and the rotation drive, at least the heating drive.SELECTED DRAWING: Figure 4

Description

The present invention relates to an image forming apparatus.

The image forming apparatus described in Patent Document 1 includes a fixing section and a control section. The control unit detects mounting failure of the fixing unit based on the length of time required for the temperature of the heater of the fixing unit to rise from the first temperature to the second temperature and the ratio of the maximum suppliable power.

JP 2019-70772 A

If power is supplied to the heater while the pressure roller of the fixing unit is not rotating, the temperature of the heater excessively increases in a short period of time, accelerating deterioration of the heater.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of suppressing deterioration of a heater of a fixing section by simple control.

An image forming apparatus of the present invention includes an image forming section, a fixing section, and a control section. The image forming section forms a toner image on a recording medium. The fixing section fixes the toner image on the recording medium. The control section controls the operation of the fixing section. The fixing section includes a tubular fixing belt, a pressure member, a rotation driving section, a heater, a heating driving section, and a heat sensitive body. The pressing member presses the outer circumferential surface of the fixing belt to form a fixing nip area. The rotation driving section drives rotation of the pressing member. The heater faces the inner circumferential surface of the fixing belt and heats the recording medium passing through the fixing nip area. The heating driver drives the heater. The thermosensitive element senses the heat of the heater. The control unit controls to start rotating the pressure member via the rotation driving unit after a predetermined period of time from when the heating driving of the heater via the heating driving unit is started, and Based on the output of the thermosensitive body, a first temperature gradient related to the temperature rise of the heater is measured during a period after the start of the heating drive and before the start of the rotational drive, and based on the output of the thermosensitive body, the A second temperature gradient related to the temperature rise of the heater is measured during a period after the start of rotational driving, and if the difference between the first temperature gradient and the second temperature gradient is smaller than a predetermined threshold, the At least the heating drive out of the heating drive and the rotation drive is controlled to be stopped.

According to the present invention, there is provided an image forming apparatus capable of suppressing deterioration of a heater included in a fixing section with simple control.

1 is a schematic diagram showing an example of a configuration of an image forming apparatus according to an embodiment; FIG. 3 is a perspective view showing an example of a fixing section; FIG. 3 is a cross-sectional view taken along line III-III of FIG. 2; FIG. 2 is a block diagram showing an example of a control circuit of the image forming apparatus; FIG. 4 is a flow chart showing an example of the operation of a control unit; 4 is a timing chart showing an example of operation of a control unit;

An embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

An image forming apparatus 100 according to an embodiment will be described with reference to FIG. FIG. 1 is a schematic diagram showing an example of the configuration of an image forming apparatus 100. As shown in FIG. The image forming apparatus 100 is, for example, a copier, a printer, a facsimile machine, or a multifunction machine having these functions. An embodiment in which the image forming apparatus 100 is a monochrome MFP will be described below. In FIG. 1, for the sake of convenience, the direction from left to right is defined as the positive direction of the X axis, the direction from front to back is defined as the positive direction of the Y axis, and the direction from bottom to top is defined as the positive direction of the Z axis. do.

As shown in FIG. 1 , image forming apparatus 100 includes fixing section 1 , image forming section 2 , reading section 3 , feeding section 4 , conveying section 5 , and discharging section 6 .

The reading unit 3 reads the image of the document G. FIG. The reading unit 3 generates image data from the read image. The feeding unit 4 accommodates a plurality of sheets S and feeds the sheets S to the conveying unit 5 . The sheet S is made of paper or synthetic resin, for example. The transport unit 5 includes a plurality of pairs of transport rollers and transports the sheet S to the image forming unit 2 . The sheet S corresponds to an example of a "recording medium".

The image forming unit 2 forms a toner image on the sheet S by electrophotography. The image forming section 2 includes a photosensitive drum, a charging device, an exposure device, a developing device, a supply device, a transfer device, a cleaning device, and a static elimination device. The toner image indicates an image of the document G, for example. The fixing section 1 fixes the toner image on the sheet S by heating and pressing the toner image. The conveying portion 5 conveys the sheet S on which the toner image is fixed to the discharging portion 6 . The discharge unit 6 discharges the sheet S to the outside of the image forming apparatus 100 .

Next, the configuration of the fixing section 1 will be described with reference to FIGS. 2 and 3. FIG. FIG. 2 is a perspective view showing an example of the fixing section 1. As shown in FIG. FIG. 3 is a cross-sectional view along III-III in FIG.

As shown in FIGS. 2 and 3 , the fixing section 1 includes a fixing belt 10 , a pressure member 20 , a heating section 30 , a first belt holding member 61 and a second belt holding member 62 .

The fixing belt 10 is a flexible tubular belt and has an outer peripheral surface 101 and an inner peripheral surface 102 . The pressure member 20 is a pressure roller and has an elastic outer peripheral surface 201 . The outer peripheral surface 201 of the pressing member 20 contacts the outer peripheral surface 101 of the fixing belt 10 to press the fixing belt 10 . As a result, a fixing nip area N is formed between the outer peripheral surface 101 of the fixing belt 10 and the outer peripheral surface 201 of the pressing member 20 .

The pressure member 20 has an axis 24 . The pressurizing member 20 rotates around the rotation axis L with its axis 24 driven by a drive mechanism (not shown). The pressing member 20 rotates in a counterclockwise first rotation direction R1 in FIG. The fixing belt 10 is driven by the rotation of the pressing member 20 to rotate in the clockwise second rotation direction R2 in FIG. The sheet S moves along the sheet passing direction P intersecting the axial direction M parallel to the rotation axis L so as to pass through the fixing nip region N. As shown in FIG.

The heating unit 30 includes a heater 31 , a heater holding member 32 , a reinforcing member 33 and a heat sensitive member 34 and faces the inner peripheral surface 102 of the fixing belt 10 .

The heater 31 is in contact with the inner peripheral surface 102 of the fixing belt 10 to heat the fixing belt 10 . The heater 31 is, for example, an elongated plate-shaped ceramic heater that extends with the axial direction M as its longitudinal direction and the paper passing direction P as its lateral direction.

The heater holding member 32 holds the heater 31 . The heater holding member 32 is a heat-resistant resin member extending in the axial direction M and having a U-shaped cross section. The heater holding member 32 preferably has ribs 321 for shaping the fixing belt 10 .

The reinforcing member 33 is a metal stay member extending in the axial direction M and having a U-shaped cross section. The reinforcing member 33 is combined with the heater holding member 32 so as to reinforce the heater holding member 32 .

The heat sensitive element 34 contacts the heater 31 in the through hole provided in the heater holding member 32 and senses the heat of the heater 31 . The thermosensitive element 34 includes a thermistor element and a thermostat element.

Both ends of the fixing belt 10 in the axial direction M are held by a first belt holding member 61 and a second belt holding member 62 .

Next, the configuration of the control circuit of the image forming apparatus 100 will be described with reference to FIGS. 1 to 4. FIG. FIG. 4 is a block diagram showing an example of a control circuit of the image forming apparatus 100. As shown in FIG.

As shown in FIG. 4, the image forming apparatus 100 further includes a rotation drive circuit 40, a motor 41, a heating drive circuit 50, a control section 70, and a storage section . A rotation drive circuit 40 drives rotation of the pressure member 20 via a motor 41 . A heating drive circuit 50 drives the heater 31 . The rotation drive circuit 40 and the motor 41 correspond to an example of a "rotation drive section". The heating drive circuit 50 corresponds to an example of a "heating drive section".

The storage unit 80 includes a storage device and stores data and computer programs. The storage unit 80 includes a main storage device such as a semiconductor memory and an auxiliary storage device such as a hard disk drive.

Control unit 70 includes a processor such as a CPU (Central Processing Unit), and controls each component of image forming apparatus 100 by executing a computer program stored in storage unit 80 . Specifically, the control unit 70 controls rotation of the pressure member 20 via the rotation drive circuit 40 and the motor 41 . Also, the control unit 70 receives the output of the thermosensitive element 34 . Furthermore, the control unit 70 obtains information on the detected temperature T indicated by the output of the thermosensitive element 34 and controls heat generation of the heater 31 via the heating drive circuit 50 so that the detected temperature T matches the target temperature. The control unit 70 controls the operation of the fixing unit 1 by controlling the rotation of the pressure member 20 and the heat generation of the heater 31 .

Next, the operation of the control section 70 will be described with reference to FIGS. 1 to 5. FIG. FIG. 5 is a flowchart showing an example of the operation of the control section 70. As shown in FIG.

Step S11: As shown in FIG. 5, the controller 70 controls the heating drive circuit 50 to start driving the heater 31 for heating. When the process of step S11 is completed, the process of the control section 70 proceeds to step S13.

Step S<b>13 : The control unit 70 measures the first temperature gradient ΔT1/Δt related to the temperature increase of the heater 31 based on the output of the thermosensitive element 34 . The first temperature gradient ΔT1/Δt indicates the ratio of the minute change ΔT1 in the sensed temperature T to the minute time Δt. When the process of step S13 is completed, the process of the control section 70 proceeds to step S15.

Step S<b>15 : The control section 70 controls the rotation drive circuit 40 to start rotating the pressing member 20 . Smooth supply of the lubricant to the inner peripheral surface 102 of the fixing belt 10 is achieved by starting the rotational driving of the pressure member 20 after a certain period of time from the start of heating driving of the heater 31 . When the process of step S15 is completed, the process of the control section 70 proceeds to step S17.

Step S<b>17 : The control unit 70 measures the second temperature gradient ΔT/Δt related to the temperature rise of the heater 31 based on the output of the thermosensitive element 34 . The second temperature gradient ΔT/Δt indicates the ratio of minute change ΔT in sensed temperature T to minute time Δt. When the process of step S17 is completed, the process of the control section 70 proceeds to step S19.

Step S19: The control unit 70 calculates the incremental difference (ΔT1−ΔT) obtained by multiplying the difference between the first temperature gradient ΔT1/Δt and the second temperature gradient ΔT/Δt by the minute time Δt, and a predetermined threshold value A. compare. If the incremental difference (ΔT1−ΔT) is not smaller than the threshold A, the process of the control section 70 proceeds to step S21. If the incremental difference (ΔT1−ΔT) is smaller than the threshold A, the process of the control section 70 proceeds to step S23.

Step S<b>21 : The controller 70 continues both the heating drive by the heating drive circuit 50 and the rotation drive by the rotation drive circuit 40 and the motor 41 . When the process of step S21 is completed, the process of the control section 70 ends.

Step S23: The control section 70 stops both the heating drive by the heating drive circuit 50 and the rotation drive by the rotation drive circuit 40 and the motor 41 because there is concern about the mounting failure of the fixing section 1 . The control unit 70 may perform control to stop at least the heating drive out of the heating drive and the rotation drive. When the process of step S23 is completed, the process of the control section 70 ends.

Next, the operation of the control unit 70 will be further described with reference to FIGS. 1 to 6. FIG. FIG. 6 is a timing chart showing an example of the operation of the control section 70. As shown in FIG. The horizontal axis indicates time t (seconds), and the vertical axis indicates the detected temperature T (° C.) of the heater 31, respectively.

A curve L1 shown in FIG. 6 indicates a change process of the detected temperature T when the fixing unit 1 is not improperly mounted. Heating drive starts at time t0, and rotation drive starts at time t2 after a certain period of time. A first temperature gradient ΔT1/Δt at point P1 is measured at time t1 during a period after the start of the heating drive and before the start of the rotation drive. From the viewpoint of improving measurement accuracy, time t1 is preferably the time immediately before the start of rotational driving at time t2. Also, at time t3 during the period after the start of rotation driving, the second temperature gradient ΔT2/Δt at point P2 is measured. Since the heat of the heater 31 is taken away by the rotation of the fixing belt 10 following the rotation of the pressure member 20, the second temperature gradient ΔT2/Δt becomes smaller than the first temperature gradient ΔT1/Δt. Therefore, even if the heating drive and the rotation drive are continued, the detected temperature T does not reach the limit temperature Te of the heater 31 .

On the other hand, a straight line L2 shown in FIG. 6 indicates a change process of the detected temperature T when the fixing unit 1 is improperly mounted. Heating drive starts at time t0, and rotation drive starts at time t2 after a certain period of time. A first temperature gradient ΔT1/Δt at point P1 is measured at time t1 during a period after the start of the heating drive and before the start of the rotation drive. Also, at time t3 during the period after the start of rotation driving, the second temperature gradient ΔT3/Δt at point P3 is measured. Since the rotation of the fixing belt 10 does not remove the heat from the heater 31 due to the mounting failure of the fixing unit 1, the second temperature gradient ΔT3/Δt is substantially equal to the first temperature gradient ΔT1/Δt. Become. As a result, if the heating drive is continued as it is, the detected temperature T will exceed the limit temperature Te of the heater 31 . Therefore, as described in step S23, the control unit 70 performs control so as to at least stop the heating drive. In this manner, deterioration of the heater 31 is suppressed with simple control.

According to the embodiment, there is provided an image forming apparatus 100 capable of suppressing deterioration of the heater 31 of the fixing section 1 with simple control.

The embodiments of the present invention have been described above with reference to the drawings. However, the present invention is not limited to the above-described embodiments, and can be implemented in various aspects without departing from the gist of the present invention. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be omitted from all components shown in the embodiments. In order to facilitate understanding, the drawings mainly show each component schematically, and the number of each component shown in the figure may differ from the actual number for convenience of drawing preparation. Also, each component shown in the above embodiment is an example and is not particularly limited, and various modifications are possible within a range that does not substantially deviate from the effects of the present invention.

INDUSTRIAL APPLICABILITY The present invention can be used in the field of image forming apparatuses.

1 fixing section 2 image forming section 10 fixing belt 20 pressure member 31 heater 34 thermosensitive element 40 rotation drive circuit (rotation drive section)
41 motor (rotation drive part)
50 heating drive circuit (heating drive unit)
70 control unit 100 image forming apparatus N fixing nip area S sheet (recording medium)

Claims (2)

an image forming unit that forms a toner image on a recording medium;
a fixing unit that fixes the toner image onto the recording medium;
a control unit that controls the operation of the fixing unit;
The fixing section is
a cylindrical fixing belt;
a pressing member that presses the outer peripheral surface of the fixing belt to form a fixing nip area;
a rotation drive unit that drives the rotation of the pressure member;
a heater that faces the inner peripheral surface of the fixing belt and heats the recording medium passing through the fixing nip area;
a heating drive unit that drives the heater;
and a thermosensitive element that senses the heat of the heater,
The control unit
controlling to start rotating the pressure member via the rotation driving unit after a certain period of time after starting the heating driving of the heater via the heating driving unit;
measuring a first temperature gradient related to temperature rise of the heater during a period after the start of the heating drive and before the start of the rotation drive, based on the output of the thermosensitive element;
measuring a second temperature gradient related to the temperature rise of the heater during a period after the start of the rotational drive based on the output of the thermosensitive element;
An image forming apparatus configured to stop at least the heating drive out of the heating drive and the rotation drive when a difference between the first temperature gradient and the second temperature gradient is smaller than a predetermined threshold. 2. The image forming apparatus according to claim 1, wherein said controller measures said first temperature gradient immediately before said rotational drive is started.

Images