JP2008158083A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of shortening the warmup period, while properly detecting abnormal state. <P>SOLUTION: During a warmup period, it is monitored whether an abnormal state is detected (step S4). If an abnormal state is detected (step S4), an abnormal state table is referred to (step S5) and it is decided whether the detected abnormal state is an abnormal one written in the abnormal state table (step S6). If the detected abnormal state is one where the abnormal state table (YEs in step S6) is written, it is detected whether the abnormal state continues (step S9), after the elapse of a permissible period (YES in step S8). If the detection of an abnormal state is canceled in the subsequent check (YES in step S9), supply of power to a fixing heater is continued (step S10). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus including a fixing unit having a heat roller.

In an electrophotographic image forming apparatus, a heat roller type in which a pressure roller is pressed against a heat roller having a built-in fixing heater is widely used as a fixing unit. In this method, the toner on the transfer paper is melted and fixed on the transfer paper while the transfer paper is passed between the heat roller and the pressure roller.
The fixing heater is turned on by energization. When the power is turned on or when returning from the sleep mode, a warm-up operation for heating the heat roller to the fixing temperature is performed. During the warm-up, the energization state of the fixing heater is kept on. The time required for warm-up is preferably short.

On the other hand, many sensors are arranged in the image forming apparatus in order to detect various abnormal states. If an abnormality is detected by these sensors during the warm-up, the energization to the fixing heater is immediately stopped and the fixing heater is turned off. Then, after the abnormality is resolved, energization to the fixing heater is started again. In order to reliably detect an abnormality, it is required to improve the sensitivity of the sensor or to set detection conditions strictly.
JP-A-2005-3242

However, in such a case, there is a problem that abnormality is frequently detected by the sensor during warm-up, and the heater is frequently turned off. In particular, if the heater used for the fixing heater takes a long time until it is turned on once it is turned off, it may take a considerable amount of time to warm up.
SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of shortening warm-up time while appropriately detecting an abnormality.

  In order to achieve the above object, the invention according to claim 1 is characterized in that a heat roller (15) for thermally fixing toner to a recording material, a heater (18) for heating the heat roller, and detecting an abnormality. An abnormality detecting means (19, 20, 22) for turning on the heater and energizing the heater in order to heat the heat roller to a heat-fixable state by the heater when the power is turned on or when returning from the sleep mode. When an abnormality is detected by the abnormality detection means during energization of the heater by the warm-up control means (30) and the warm-up control means, whether the abnormality is of a predetermined type or not A determination means (30) for determining whether the abnormality is of a predetermined type by the determination means, the abnormality is resolved after a predetermined period of time has elapsed. , Without stopping the power supply to the heater, an image forming apparatus and a heater energizing continuing control means (30) to continue the energization to said heater.

The numbers in parentheses indicate corresponding components in the embodiments described later. The same applies hereinafter.
According to this configuration, even if an abnormality is detected, energization of the fixing heater is continued on the condition that the abnormality is of a predetermined type and that the abnormality is resolved after the elapse of a predetermined period. The That is, when an abnormality is detected, the energization to the fixing heater is stopped only when the abnormality needs to stop the energization to the fixing heater. Therefore, it is possible to shorten the warm-up time while appropriately detecting the abnormality.

  The predetermined type of abnormality discriminated by the discriminating means may include opening of a cover (21) constituting a part of the main body housing (2), as claimed in claim 2. As in Item 3, it may be included that the rotational speed of the drive motor (17) for rotationally driving the heat roller has reached a predetermined range.

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. FIG. 1 is a diagram schematically showing a configuration of an image forming apparatus 1 according to an embodiment of the present invention.
The image forming apparatus 1 is, for example, a printer, and includes a main body housing 2, an image forming mechanism 3 accommodated in the main body housing 2, and a cassette 4 in which paper P is accommodated. The image forming mechanism 3 includes an image forming / transfer unit 5 and a fixing unit 6.

  The image forming / transfer unit 5 forms a photoconductor 7 formed in a drum shape, a charger 8 for charging the surface of the photoconductor 7, and the surface of the photoconductor 7 charged by the charger 8 as a created image. An exposure device 9 for exposure corresponding to the above, a developing device 10 for developing the electrostatic latent image formed on the surface of the photoreceptor 7 by exposure with toner, and using the developed toner image as a recording material The transfer device 11 for transferring to the paper P, the cleaning device 12 for removing residual toner remaining on the surface of the photoconductor 7 after the toner image is transferred, and the photoconductor after removing the residual toner. 7 and a static eliminator 13 for neutralizing the surface of 7. The charger 8, the exposure device 9, the developing device 10, the transfer device 11, the cleaning device 12, and the static eliminator 13 are sequentially arranged along the rotation direction of the photoconductor 7 (direction indicated by the arrow 14) so as to surround the photoconductor 7. Has been placed. The paper P fed out from the cassette 4 is conveyed along a line indicated by an arrow in FIG. 1, and a toner image is transferred to the surface of the paper P when passing between the photosensitive drum 7 and the transfer device 11. . The paper P on which the toner image has been transferred is conveyed to the fixing unit 6.

  The fixing unit 6 heats and presses the paper P on which the toner image is transferred, thereby fixing the toner image on the paper P. The heat roller 15, the pressure roller 16 pressed against the heat roller 15, A drive motor 17 for rotating the heat roller 15 and the pressure roller 16 is provided. The heat roller 15 has a built-in fixing heater 18 for heating the heat roller 15. The fixing heater 18 is constituted by, for example, a halogen heater, and is a type of heater that takes a long time to be turned on once it is turned off. In the vicinity of the heat roller 15, a temperature sensor 19 for measuring the ambient temperature of the surface of the heat roller 15 is disposed. Further, a rotation speed sensor 20 for detecting the rotation speed of the drive motor 17 is provided in association with the drive motor 17. After the toner image is fixed on the paper P by the fixing unit 6, the paper P is discharged out of the apparatus.

A part of the upper surface of the main body housing 2 is constituted by a cover 21. When a paper jam occurs in the image forming / transfer unit 5, the user can open the cover 21 and perform an operation of removing the paper P from the image forming / transfer unit 5. A cover opening switch 22 for detecting the open state of the cover 18 is disposed in the main body housing 2.
FIG. 2 is a block diagram for explaining the electrical configuration of the image forming apparatus 1. The image forming apparatus 1 includes a control unit 30 having a configuration including a CPU 23, a memory 24, and an internal timer 25. The memory 24 includes a ROM, a RAM, a hard disk drive, and other external storage devices, and stores data necessary for controlling the image forming apparatus 1 in addition to a program executed by the CPU 23. The memory 24 stores an abnormality table 31 described later.

  Each drive member of the image forming mechanism 3, for example, the drive motor 17 and the fixing heater 18 of the fixing unit 6 are connected to the control unit 30 as control targets. The control unit 30 controls rotation driving of each driving member of the image forming mechanism 3, for example, the driving motor 17, according to a program stored in the memory 24. The control unit 30 also controls on / off switching of the energization state of the fixing heater 18 in accordance with a program stored in the memory 24.

  Further, the temperature sensor 19 of the fixing unit 6, the drive motor rotation speed sensor 20, and the cover opening switch 22 are connected to the control unit 30. For example, a limit switch is used as the cover opening switch 22. The control unit 30 is supplied with the measurement values output from the temperature sensor 19 and the drive motor rotation speed sensor 20 and the detection signal output from the cover opening switch 22. Based on the measured value (temperature) from the temperature sensor 19, the control unit 30 feedback-controls the fixing heater 15.

FIG. 3 is a flowchart for explaining the warm-up control of the fixing unit 6 when the power is turned on. FIG. 4 is a diagram for explaining an abnormality table stored in the memory 24.
Referring to FIG. 3, when the power is turned on, the target temperature of fixing heater 18 stored in memory 24 is read (step S1). Energization of the fixing heater 18 is started (step S2), and the fixing heater 18 is turned on. The energization to the fixing heater 18 is continued until the measured value (temperature) of the temperature sensor 19 reaches the target temperature (NO in step S3). During this warm-up period, it is monitored whether there is an abnormality detected (step S4). Various abnormalities are detected in the image forming apparatus 1. As warnings that can be detected, for example, the cover 22 is opened and the rotational speed of the drive motor 17 is outside a predetermined range. The abnormality in the rotational speed of the drive motor 17 and the overheating of the fixing heater 18 in a state where the fixing heater 18 is higher than a predetermined temperature. In addition, for example, abnormalities such as a disconnection to the fixing heater 18 and a state where the cassette 4 is not attached to the main body housing 2 are also detected.

  If an abnormality is detected (YES in step S4), the abnormality table 31 is then referred to (step S5), and it is determined whether or not the detected abnormality is an abnormality written in the abnormality table (step S6). . As shown in FIG. 4, a plurality of types of abnormality (abnormal items) and a grace period associated with each abnormal item are written in the abnormality table 31. In FIG. 4, the opening of the cover 22 and the rotation speed abnormality of the drive motor 17 are illustrated as the abnormality type (abnormal item). Further, the grace period corresponding to the opening of the cover 22 is 100 msec, and the grace period corresponding to the rotation speed abnormality of the drive motor 17 is 1000 msec. In the abnormality table 31, no overheating of the fixing heater 18 is written.

If the detected abnormality is an abnormality not written in the abnormality table 31 such as overheating of the fixing heater 18 (NO in step S6), the energization to the fixing heater 18 is stopped (step S7), and then warm-up control is performed. Finishes and moves to error handling.
When the detected abnormality is an abnormality written in the abnormality table 31 (YES in step S6), after the grace period has elapsed (YES in step S8), it is detected whether the abnormality continues (step). S9). For example, if the detection abnormality is the opening of the cover 22, the detection signal output from the cover opening switch 22 is checked again after a grace period of 100 msec has elapsed, and it is detected whether or not the opening of the cover 22 continues. Is done. If the detection abnormality is, for example, an abnormality in the rotational speed of the drive motor 17, the measurement value output from the drive motor rotational speed sensor 20 is detected after a grace period of 1000 msec has elapsed, and the rotational speed abnormality of the drive motor 17 is detected. Whether or not is continuing is detected.

  Even when the cover 22 is closed, the cover opening switch 22 may erroneously detect the opening of the cover 22 when vibration is applied to the image forming apparatus 1. Further, when the power is turned on, the rotational speed of the drive motor 17 may be unstable, and there is no abnormality in the drive motor 17 itself, but the measured value (rotational speed) detected by the drive motor rotational speed sensor 20 May deviate from the reference range. Such an abnormality is a type of abnormality that does not require the energization of the fixing heater 18 to be stopped. Nevertheless, if the energization is stopped immediately when an abnormality is detected, the fixing heater 18 is once turned off as described above, and therefore it takes a long time to turn on again. There was a problem that it took a considerable amount of time.

  In this embodiment, even if an abnormality is detected, the energization to the fixing heater 18 is continued on the condition that the abnormality is a predetermined abnormality and the abnormality is eliminated after the grace period has elapsed. That is, when an abnormality is detected, the energization to the fixing heater 18 is stopped only when the abnormality needs to stop the energization to the fixing heater 18. Therefore, it is possible to shorten the warm-up time while appropriately detecting the abnormality.

If the detection abnormality has not been eliminated by this re-check (NO in step S9), the energization to the fixing heater 18 is stopped (step S7), the warm-up control is terminated, and the process proceeds to error processing. .
If the detection abnormality is resolved by this re-check (YES in step S9), energization of the fixing heater 18 is continued (step S10). When the measured value (temperature) of the temperature sensor 19 reaches the target temperature (YES in step S3), the warm-up control at the time of power-on is completed, and then the control for maintaining the temperature of the heat roller 15 is performed. Transition is made (step S11).

In addition, this invention is not limited to embodiment mentioned above.
In the above description, examples of the abnormality written in the abnormality table 31 include the opening of the cover 22 and the abnormality in the rotational speed of the drive motor 17, but there are various other cases such as a state where the cassette 4 is not attached to the main body housing 2. An abnormality may be written. In addition, as an abnormality not written in the abnormality table 31, disconnection of the fixing heater 18 other than the fixing heater 18 can be cited.

Furthermore, in the above description, the warm-up control when the power is turned on has been described as an example. However, the present invention is not limited to when the power is turned on, but from the sleep mode where the power supply to the fixing unit 6 is suppressed to a low level. It can also be applied to warm-up control when returning.
In the above description, a printer has been described as an example of an image forming apparatus. However, the present invention can be applied to a copying machine, a facsimile machine, a multifunction machine, and the like in addition to a printer.

  In addition, various design changes can be made within the scope of matters described in the claims.

1 is a diagram schematically showing a configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a block diagram illustrating a configuration of an image forming apparatus. 6 is a flowchart for explaining warm-up control of the fixing unit when the power is turned on. It is a figure for demonstrating the abnormality table memorize | stored in memory.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Main body housing 15 Heat roller 17 Drive motor 18 Fixing heater (heater)
19 Temperature sensor (abnormality detection means)
20 Drive motor rotation speed sensor (abnormality detection means)
21 Cover 22 Cover release switch (abnormality detection means)
30 (warm-up control means, discrimination means, heater energization continuation control means)

Claims (3)

A heat roller for heat-fixing the toner on the recording material;
A heater for heating the heat roller;
An anomaly detection means for detecting an anomaly;
A warm-up control means for energizing the heater to heat the heat roller to a heat-fixable state by the heater at the time of power-on or return from the sleep mode;
A discriminating means for discriminating whether or not the abnormality is a predetermined type of abnormality when an abnormality is detected by the abnormality detecting means during energization of the heater by the warm-up control means;
If the abnormality is resolved after the elapse of a predetermined period when it is determined by the determination means that the abnormality is of a predetermined type, the energization of the heater is stopped without stopping the energization of the heater. An image forming apparatus comprising: heater energization continuation control means for continuing the process. A main body housing for housing the constituent members, and a cover that constitutes a part of the main body housing;
The image forming apparatus according to claim 1, wherein the predetermined type of abnormality determined by the determination unit includes opening of the cover. A drive motor for rotating the heat roller;
3. The image forming apparatus according to claim 1, wherein the predetermined type of abnormality determined by the determination unit includes that the rotational speed of the drive motor has reached a predetermined range.

Images