JP2001175118A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make rising time after releasing jamming as short as possible while securing stability at the time of jamming disposal. SOLUTION: When jamming occurs (S11), control target temperature lower than fixing control target temperature at the ordinary time is set (S12). Thus, the temperature of a fixing roller falls and energizing control that the low- temperature control target temperature is maintained is performed, so that a state where the jamming disposal is safely performed is obtained (S13). When the finish of jamming disposal is informed (S14), the control target temperature is restored to a normal state (S15), whereby the energizing control that the control target temperature at the ordinary time is maintained is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to fixing control in an image forming apparatus such as a copying machine, a printer, and a facsimile.

[0002]

2. Description of the Related Art As a fixing device in an image forming apparatus such as a copying machine, a printer, a facsimile, etc., a fixing roller for heating a sheet carrying an unfixed image and a pressure roller pressed against the fixing roller are provided. A heat roller type fixing device for nipping and conveying a sheet between a fixing roller and a pressure roller and fixing an unfixed image on the sheet by heat and pressure is well known.

Conventionally, in a fixing device of a heat roller type,
A halogen lamp or the like as a heater is provided inside the fixing roller, and the halogen lamp heats the inside of the fixing roller.

[0004] However, such a heating method using a heater requires a long time until the fixing roller is heated to a required temperature and a large loss of the heater itself. Has been requested.

In such a situation, the fixing device using the induction heating method can instantly heat the fixing roller by the eddy current caused by the electromagnetic induction, so that the start-up time can be shortened remarkably. . For this reason, the induction heating type fixing device requires the preheating that was required in the conventional halogen lamp method (the temperature of the fixing unit is maintained even during non-image formation because the temperature of the fixing unit quickly rises to a predetermined temperature when reused). Is unnecessary, unnecessary power is not required, and the heating efficiency is excellent.

[0006] Reducing the rise time of the fixing device can be achieved not only by starting up the image forming apparatus from a low temperature state when the power is turned on, but also by resuming the power supply to the fixing apparatus (mode). It is also required at the start. For example, restart from jam release, restart by opening and closing the body door (cover),
Alternatively, it is desirable to start up in a short time even when returning from power-off at night.

Japanese Patent Application Laid-Open No. 5-281805 discloses an image forming apparatus in which power supply to a fixing device is stopped when a jam occurs for safety during jam processing. . In the above publication,
It describes that the power supply to the fixing device is stopped when a paper jam is detected.

[0008] Indeed, from the viewpoint of workability and safety during jam clearance, it is very dangerous to keep the fixing roller in a high temperature state in a steady state, and if the fixing unit is jammed with jammed paper. Could be ignited.

[0009]

However, in the case of a non-feeding jam or the like that occurs due to slippage of the rollers of the feeding section, it is not necessary to remove the jammed paper, and it is released only by a certain procedure such as opening and closing the main body door. In this case, stopping the power supply to the fixing device in this case unnecessarily lowers the fixing temperature, resulting in a longer rise time after the jam is cleared.

The present invention solves the above-mentioned problems in the conventional image forming apparatus, and provides an image forming apparatus capable of shortening the rising time after the jam is released while ensuring the safety during the jam processing. That is the task.

[0011]

According to the present invention, there is provided an image forming apparatus including an induction heating type fixing device, comprising a high frequency generating circuit and a high frequency power supply for supplying a high frequency current to an induction heating coil. Temperature detecting means for detecting a fixing roller surface temperature of the fixing device, and means for controlling a level signal supplied to the high frequency generating circuit so that the fixing roller temperature detected by the temperature detecting means becomes a predetermined target temperature. In the case where paper jam in the image forming apparatus is detected, the problem is solved by performing the fixing energization control by lowering the target temperature from a steady state.

According to another aspect of the present invention, there is provided an image forming apparatus including an induction heating type fixing device, comprising: a high frequency generation circuit and a high frequency power supply for supplying a high frequency current to an induction heating coil; Temperature detecting means for detecting the surface temperature of the fixing roller of the fixing device; and means for controlling a level signal given to the high frequency generating circuit so that the temperature of the fixing roller detected by the temperature detecting means becomes a predetermined target temperature. It is proposed that the level signal given to the high-frequency generation circuit be set lower than in a normal state when paper jam is detected in the image forming apparatus.

According to another aspect of the present invention, there is provided an image forming apparatus including an induction heating type fixing device, comprising: a high frequency generating circuit and a high frequency power supply for supplying a high frequency current to an induction heating coil; Temperature detecting means for detecting a surface temperature of a fixing roller of the fixing device; and means for controlling a level signal given to the high frequency generating circuit so that the fixing roller temperature detected by the temperature detecting means becomes a predetermined target temperature. Means for identifying a position where a paper jam has occurred in the paper transport path, and when the identification means detects a paper jam near the fixing device, it is proposed to cut off the power supply to the fixing device.

Further, in order to solve the above-mentioned problem, the present invention is to perform fixing energization control by lowering the target temperature than normal when the paper jam occurrence position identified by the identification means is not near the fixing device. Suggest.

According to another aspect of the present invention, a level signal applied to the high-frequency generating circuit is set to be lower than a steady state when a paper jam occurrence position identified by the identification means is not near the fixing device. Propose that.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. The image forming apparatus according to the present embodiment employs a well-known electrophotographic system, and the description of the overall configuration thereof will be omitted, and the configuration and control of the fixing unit according to the present invention will be mainly described.

FIG. 1 is a schematic diagram showing a main part of a fixing device in an example of an image forming apparatus according to the present invention. FIG. 2 is a control block diagram of the fixing device, and the fixing roller 1 and the pressure roller 2 are shown as sectional views taken along line AA ′ in FIG.

In FIG. 2, a sheet P carrying unfixed toner T is conveyed in the direction of arrow B and enters the nip between the fixing roller 1 and the pressure roller 8. The fixing roller 1 and the pressure roller 8 pinch and transport the sheet, and the toner is melted by the heat of the fixing roller 1 and fused to the sheet P.

As shown in FIGS. 1 and 2, the fixing roller 1 has a release layer 1b formed on the outer peripheral surface of a metal core 1a, and a heat insulating layer 2 provided on the inner peripheral side of the metal core 1a. This fixing roller 1
The induction heating unit 3 is disposed in the internal space of the first embodiment. In the induction heating section 3, an induction heating coil 5 is wound around an outer periphery of a bobbin 4, and the outside thereof is covered with a heat insulating member 6.

The fixing roller 1 is rotatably supported on a structure (or a frame of the fixing device) 9 of the image forming apparatus by a fixing roller bearing 10 having high heat resistance. A gear 7 is attached to one end of the fixing roller 1, and a driving force from a drive system (not shown) is transmitted to the gear 7 to rotate the fixing roller 1. In the fixing device of the present embodiment, which is an induction heating system, the induction heating unit 3 inside the fixing roller does not rotate, and only the fixing roller 1 rotates.

In the present embodiment, the core metal 1a of the fixing roller is made of a good magnetic metal such as iron or magnetic stainless steel. The release layer 1b on the outer periphery of the fixing roller is formed of a fluororesin or silicon rubber having excellent heat resistance to a thickness of about several tens of microns to about 1 mm. The pressure roller 8 pressed against the fixing roller 1 is made of a pressure roller shaft made of a non-magnetic metal such as aluminum, copper, and non-magnetic stainless steel, and a silicone rubber with excellent surface release and heat resistance on its outer periphery. It is composed of a release layer having a thickness of about 1 mm to 5 mm.

An induction coil 5 disposed close to the inside of the fixing roller 1 is wound around the outer periphery of a hollow bobbin 4 molded of a resin having excellent heat resistance and insulation.
a and 5b are connected to an externally disposed inverter circuit 15 (FIG. 2) so that high-frequency current can pass therethrough. A high-frequency magnetic flux is generated by the high-frequency current, and the generated magnetic flux is generated in the space inside the central portion of the induction coil 5 →
Space on the inner surface of the end of induction coil 5 → fixing roller core member 1
a end → the center of the fixing roller core member 1a → the other end of the fixing roller core member 1a → the space inside the other end of the induction coil 5 →
A loop of the space on the inner surface of the center of the induction coil 5 is formed.

The magnetic flux passing through the fixing roller core member 1a at this time generates an eddy current inside the fixing roller core member 1a, and heats the entire circumference of the fixing roller 1 by heat generated by eddy current loss. At this time, the surface temperature of the fixing roller 1 is set to the thermistor 11.
, And is fed back to the fixing control unit 13 to be controlled and maintained at a predetermined temperature.

The control unit 13 for implementing the fixing control is constituted by a microcomputer, and functions by executing a program written in the ROM in advance. Also,
The control unit 12 of the image forming apparatus main body is in charge of controls such as scanner control, image forming control, paper sheet transport control, high-voltage power supply control, input / output device control, etc. I have.

The high-frequency power supply section is the same as a conventionally known high-frequency power supply section, so that illustration and description are omitted. FIG. 3 is a flowchart showing a basic part of the power supply control in the fixing control unit 13.

As shown in this flowchart, the fixing energization control always forms a loop at regular intervals and monitors whether there is a factor for turning OFF the fixing (S1). If there is a fixing OFF factor such as “door open”, “night mode”, or “main unit failure” in response to a command from the image forming apparatus control unit 12, the fixing control unit 13 turns off the relay (S
2) The set value of the PWM register is set to 0% (S3), and the power supply to the induction coil is stopped. If there is no fixing OFF factor in S1, the surface temperature of the heating roller detected by the thermistor 11 is acquired (S4), and the amount of energization is determined from the difference between the obtained current temperature and the control target temperature (S5).

As a well-known technique, the PID
A method such as an arithmetic method is used, and a multiplier (gain) of an arithmetic expression including three terms of a proportional term, a differential term, and an integral term is used to determine a heat capacity of a fixing roller, a W (watt) number of a heating element, and the like. Considering the conditions, it is possible to achieve an optimum temperature control without overshoot and control ripple. Next, the energization amount is set in the PWM register as OUTPUT from the control unit 13 (S6). The PWM generation means 14 rewrites the value of the PWM register (by controlling the level signal applied to the high frequency generation circuit) to 20K to 30K.
A KHz pulse is generated, output to the inverter circuit 15, and finally the amount of high-frequency current supplied is adjusted.
As described above, when there is no fixing OFF factor, a certain WAI
T is set (S7), and the amount of energization is updated.

By the way, according to the present invention, when a paper jam occurs, the jammed paper can be safely removed by immediately lowering the temperature of the fixing unit, and the fixing start-up time after the jam is cleared is reduced as much as possible. It is intended for. The control in the present embodiment for achieving this will be described with reference to the flowchart in FIG.

As shown in the flowchart of FIG. 4, in the energization control at the time of a jam, when a jam occurs, the image forming apparatus main body control unit 12 notifies the occurrence of the jam (S11). Normally, the fixing target temperature for fixing is 180 ° C
Although the temperature is set to about 200 ° C., the control target temperature is changed to a low temperature state (to the extent that there is no danger even if a user touches the paper at the time of jam clearance) with the occurrence of a jam (S12). Thereby, the energization is temporarily stopped (the duty of PWM is 0).
%), And the temperature decreases. Then, when the temperature is lowered to the low-temperature control target temperature, low-duty energization is performed. Thereafter, energization control for maintaining the low-temperature control target temperature is performed according to the flowchart of FIG. 3, so that the user can safely perform the jam-paper removal operation. (S1
3).

When the jam-paper removing operation is completed and the main body door is closed, a clearing of the jam is notified from the image forming apparatus main body control unit 12 (S14). At this point, by returning the control target temperature to the steady state (S15), the energization control for maintaining the steady-state control target temperature is performed according to the flowchart of FIG. 3, and the fixing state is established.

As described above, in the present embodiment, when a jam occurs, the fixing target temperature is set to the steady state target temperature (180).
C. to 200.degree. C.) to a low temperature (for example, a level that does not cause danger even if a user touches the paper during the jam processing) and control the energization, thereby preventing the temperature inside the image forming apparatus from rising and safely jamming. The paper can be removed.
In addition, since the power supply to the fixing device is not completely stopped, the temperature of the fixing roller can be reduced without reducing the temperature of the fixing roller more than necessary, and the time required for fixing to rise after the jam is cleared can be reduced.

Next, an embodiment according to the second aspect of the present invention will be described. The hardware configuration of the fixing device in the image forming apparatus of this embodiment is the same as that of the above-described embodiment, and the description will be made with reference to FIGS. Note that the basic energization control in the present embodiment is the same as the flowchart in FIG. 3, and redundant description will be omitted.

FIG. 5 is a flowchart showing the energization control at the time of a jam in this embodiment. As shown in the flowchart, when a jam occurs, the image forming apparatus main body control unit 12 notifies the occurrence of the jam (S
21), and change to a fixed value of low PWM duty (duty for generating a pulse that makes the roller temperature such that there is no danger even if the user comes into contact with the fixing device during jam processing) (S22). As a result, the energization amount becomes lower than the PWM duty in the steady state, and the fixing roller temperature decreases slowly.

Then, the user can safely remove the jammed paper (S23). When the jam-paper removing operation is completed and the main body door is closed, the image forming apparatus main body control unit 12 notifies the user of the jam release (S24).
At this time, the PWM set value (duty) is changed from the low-temperature fixed value to the energization control updated according to the flowchart of FIG. 3 (P which is updated and set based on the target temperature and the detected temperature).
By returning to the WM duty control (S2
5), fixing is possible.

As described above, in this embodiment, when a jam occurs, the level signal (PWM duty) given to the high frequency generation circuit (inverter circuit 15) is set to be low to control the energization, so that the temperature inside the image forming apparatus can be controlled. The jam paper can be safely removed by preventing the paper from rising. In addition, since the power supply to the fixing device is not completely stopped, the temperature of the fixing roller can be reduced without reducing the temperature of the fixing roller more than necessary, and the time required for fixing to rise after the jam is cleared can be reduced.

Next, an embodiment according to the third aspect of the present invention will be described. In the image forming apparatus of this embodiment,
A plurality of paper sensors are arranged in the paper transport path so that it is possible to identify at which position in the transport path a jam has occurred (the arrangement of the sensors is not shown). Other configurations of the fixing device are the same as those of the above-described embodiments, and the description will be made with reference to FIGS. In addition,
The basic energization control in the present embodiment is the same as the flowchart in FIG. 3, and a duplicate description will be omitted.

FIG. 6 is a flowchart showing the energization control at the time of a jam in this embodiment. As shown in this flowchart, when a jam occurs, the image forming apparatus main body control unit 12 notifies the jam position information identified by a plurality of paper transport sensors (not shown) (S31). The fixing control unit 13 determines from the notified jam position information whether or not this is a paper jam in the fixing unit (S32). If there is a jammed paper in the fixing unit, the relay is turned off (S33). Then, the fixing control is stopped through the procedure of setting the energization amount to 0% (S34).

On the other hand, if there is no jammed paper in the fixing section in S32, there is no danger that the jammed paper will be scorched due to high temperature, and the fixing temperature is kept at a constant low temperature even when the user removes the jammed paper. Since it can be determined that the safety can be ensured if the temperature is maintained in such a manner, the process of shifting the fixing temperature to a low temperature state is performed according to the flowchart of FIG. 4 or FIG.

As described above, in the present embodiment, it is determined whether or not jammed paper is in the fixing section when a jam occurs, and if the jammed paper is in the fixing section, power to the fixing device (inverter circuit 15) is determined. By turning off the supply, it is possible to prevent the risk that the jammed paper will be ignited due to the high temperature state of the fixing unit.

If no jammed paper is present in the fixing section when a jam occurs, the fixing target temperature is changed from the steady-state target temperature to a lower temperature to control the energization, or to provide a high frequency generating circuit (inverter circuit 15). By setting the level signal (PWM duty) low and controlling the energization,
The jammed paper can be safely removed by preventing the temperature inside the image forming apparatus from rising, and the power supply to the fixing device is not completely stopped. Fixing rise time can be shortened.

[0041]

As described above, according to the image forming apparatus of the present invention, when a paper jam is detected in the image forming apparatus, the fixing temperature is controlled to lower the target temperature than in the steady state, so that the image forming apparatus is controlled. The jam paper can be safely removed by preventing the temperature inside the apparatus from rising. In addition, since the power supply to the fixing device is not completely stopped, the temperature of the fixing roller can be reduced without reducing the temperature of the fixing roller more than necessary, and the time required for fixing to rise after the jam is cleared can be reduced.

According to the second aspect of the present invention, when a paper jam in the image forming apparatus is detected, the power supply is controlled by setting the level signal applied to the high frequency generating circuit to be lower than that in the normal state, so that the temperature inside the image forming apparatus rises. The jam paper can be removed safely. In addition, since the power supply to the fixing device is not completely stopped, the temperature of the fixing roller can be reduced without reducing the temperature of the fixing roller more than necessary, and the time required for fixing to rise after the jam is cleared can be reduced.

According to the third aspect of the present invention, there is provided a means for identifying a position where a paper jam has occurred in the paper transport path. When the identification means detects a paper jam in the vicinity of the fixing device, power is supplied to the fixing device. Since the blocking is performed, it is possible to prevent a risk that the jammed paper is ignited due to a high temperature state of the fixing unit.

According to the fourth or fifth aspect, when the paper jam occurrence position identified by the identification means is not in the vicinity of the fixing device, the fixing temperature control is performed by lowering the target temperature from the steady state, or the level given to the high-frequency generation circuit. By setting the signal to be lower than the steady state and controlling the power supply, it is possible to prevent the temperature inside the image forming apparatus from rising and safely remove the jammed paper, and to completely stop the power supply to the fixing device. The fixing rise time after the jam is cleared can be shortened without lowering the fixing roller temperature more than necessary.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a main part of a fixing device in an example of an image forming apparatus according to the present invention.

FIG. 2 is a control block diagram of the fixing device.

FIG. 3 is a flowchart illustrating a basic part of fixing power supply control according to the embodiment.

FIG. 4 is a flowchart illustrating fixing energization control during a jam according to the embodiment.

FIG. 5 is a flowchart illustrating fixing energization control during a jam in the embodiment according to the second embodiment of the present invention.

FIG. 6 is a flowchart showing fixing power supply control during a jam in the embodiment according to the third aspect of the present invention.

[Explanation of symbols]

 Reference Signs List 1 fixing roller 1a fixing roller core metal 1b fixing roller release layer 3 induction heating unit 5 induction heating coil 8 pressure roller 11 thermistor 12 image forming apparatus main body control unit 13 fixing control unit 14 PWM generation circuit 15 inverter circuit (high frequency generation circuit) )

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H033 AA03 AA37 AA42 BA24 BA30 BA34 BE06 CA02 CA07 CA22 CA23 CA30 CA34 CA48 3K059 AA02 AB00 AB19 AB27 AB28 AC09 AC33 AC37 AC73 AD07 AD10 AD26 BD17 BD19 CD05 CD10 CD14 CD23 CD44 CD77

Claims (5)

[Claims] 1. An image forming apparatus comprising an induction heating type fixing device, comprising: a high frequency generating circuit and a high frequency power supply for supplying a high frequency current to an induction heating coil; and a temperature for detecting a fixing roller surface temperature of the fixing device. Detecting means for controlling a level signal given to the high frequency generating circuit so that the fixing roller temperature detected by the temperature detecting means becomes a predetermined target temperature, and detecting a paper jam in the image forming apparatus. In this case, the image forming apparatus performs the fixing energization control by lowering the target temperature from a normal state. 2. An image forming apparatus comprising an induction heating type fixing device, comprising: a high frequency generator and a high frequency power supply for supplying a high frequency current to an induction heating coil; and a temperature for detecting a fixing roller surface temperature of the fixing device. Detecting means for controlling a level signal given to the high frequency generating circuit so that the fixing roller temperature detected by the temperature detecting means becomes a predetermined target temperature, and detecting a paper jam in the image forming apparatus. In this case, the level signal given to the high-frequency generation circuit is set lower than in a normal state. 3. An image forming apparatus having an induction heating type fixing device, comprising: a high frequency generating circuit and a high frequency power supply for supplying a high frequency current to an induction heating coil; and a temperature for detecting a fixing roller surface temperature of the fixing device. Detecting means; controlling means for controlling a level signal to be supplied to the high frequency generating circuit so that the fixing roller temperature detected by the temperature detecting means becomes a predetermined target temperature; and identifying a paper jam occurrence position in a paper transport path. And a power supply to the fixing device when a paper jam near the fixing device is detected by the identification device. 4. An image according to claim 3, wherein when the paper jam occurrence position identified by said identification means is not in the vicinity of the fixing device, the target energization is controlled by lowering the target temperature than in a steady state. Forming equipment. 5. The apparatus according to claim 3, wherein a level signal applied to said high-frequency generation circuit is set lower than in a steady state when the position of occurrence of a paper jam identified by said identification means is not near the fixing device. Image forming device.