JP2020180997A - Image formation device - Google Patents

Abstract

To provide an image formation device which can prevent breakage of an element used by a conduction control unit and can precisely detect the state of connection to a heat generator in a fixation unit.SOLUTION: A fixation unit 30 in the image formation device includes a heater substrate 302 having a main heater 209a and a sub heater 209b. The main heater 209a is controlled in terms of conduction by a main conduction control unit 402. The sub heater 209b is controlled in terms of conduction by a sub conduction control unit 403. The main conduction control unit 402 is formed of an element with a larger rating than that of the sub conduction control unit 403. A CPU 702 determines the state of connection between a main heater 209a and a sub heater 209b by comparing a current value when the main heater 209a is made conductive and an expected value of the current value flowing in the main heater 209a.SELECTED DRAWING: Figure 3

Description

The present invention relates to an image forming apparatus that heat-fixes an image on a recording material.

Image forming devices such as electrophotographic copying machines and printers include on-demand film heating methods in which a developer image is thermally fixed to a recording material such as a transfer material or photosensitive paper. Such an image forming apparatus includes a heater in a fixing portion for heat fixing. The heater includes a heating element that generates heat when electric power is supplied to a ceramic substrate (for example, alumina, aluminum nitride) having electrical resistance, heat resistance, and good thermal conductivity. The heating element is composed of, for example, a resistor, and generates heat when electric power is supplied. On the substrate, a connector connection electrode pattern formed by printing, firing, or the like to supply electric power to the heating element, and a conductor pattern connecting the power feeding electrode and the heating element are formed. Electric power is supplied to the heating element via the connector connection electrode pattern and the conductor pattern.

When a plurality of heating elements (heating element groups) having different heating conditions depending on the parts are mounted in the fixing portion, the wiring for energizing each heating element may be erroneously connected. Incorrect connection of wiring hinders normal energization control to each heating element and makes proper temperature control difficult. If proper temperature control is not performed, an abnormal image is formed due to poor fixing. Further, if the detection result of the temperature of the heating element is abnormal, the image forming itself is not performed, and an error of the image forming apparatus is determined. Therefore, it is necessary to prevent erroneous connection of the wiring that energizes the heating element. Patent Document 1 detects an electric current value when energizing a plurality of heating elements having different resistance values, and determines whether or not the current ratio of each heating element is normal, thereby making an error in wiring to the heating element. An image forming apparatus for detecting a connection is disclosed.

JP-A-2017-37205

The power supply of each of the plurality of heating elements in the fixing unit is controlled by the energization control unit provided corresponding to each heating element. Each energization control unit may have different ratings and heat dissipation measures for the elements used. In this case, the power supplied to the heating element may exceed the rating of the element used in the energization control unit by detecting the current value at the time of energization of each heating element to detect the erroneous connection. Therefore, at the time of determining the incorrect connection, the element used for the energization control unit may be destroyed.

In view of the above problems, it is a main object of the present invention to provide an image forming apparatus that accurately detects a connection state to a heating element in a fixing unit while preventing destruction of elements used in an energization control unit. ..

The image forming apparatus of the present invention includes an image forming means for forming a developer image on a photoconductor, a transfer means for transferring the developer image formed on the photoconductor to a recording material, and a first heater and a second heater. A fixing means for fixing the developer image to the recording material by heating the recording material to which the developer image is transferred by the heating element, and to the first heater. A first energization control means for controlling energization, a second energization control means for controlling energization of the second heater, a current detection means for detecting the current value of a current flowing through the heating element when energized, and the first. A first terminal for connecting the energization control means and the first heater, a second terminal for connecting the second energization control means and the second heater, the first energization control means and the first The first energization control means includes a control means for controlling the temperature of the heating element by controlling the energization by the second energization control means, and the first energization control means is composed of an element having a higher rating than the second energization control means. The control means acquires a current value when the first heater is energized by the first energization control means from the current detection means, and obtains the acquired current value as a current flowing through the first heater. By comparing with the assumed value of the value, as a connection state of the heating element, the first energization control means and the first heater are connected by the first terminal, and the second energization control means is connected by the second terminal. It is characterized in that it is determined whether or not the second heater is connected to the second heater.

According to the present invention, it is possible to accurately detect the connection state to the heating element in the fixing unit while preventing the element used in the energization control unit from being destroyed.

The block diagram of the image forming apparatus. Explanatory drawing of fixing part. Explanatory drawing of control system of fixing part. A flowchart showing processing at the time of starting the image forming apparatus. The flowchart which shows the processing in the standby mode of an image forming apparatus. A flowchart showing the connection state detection process. A flowchart showing the connection state detection process.

An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram of an image forming apparatus of the present embodiment. The image forming apparatus 100 of the present embodiment forms an image on the recording material P by an electrophotographic method. The image forming apparatus 100 includes a recording material feeding unit 10, an image forming unit 20, a fixing unit 30, a recording material discharging unit 40, a recording material refeeding unit 50, and a control unit 600. The control unit 600 controls the operation of each unit in the image forming apparatus 100 to form an image on the recording material P.

The recording material feeding unit 10 includes a feeding cassette 11 on which the recording material P is placed and a manual feed tray 16. The recording material feeding unit 10 feeds the recording material P from the feeding cassette 11 or the manual feed tray 16 to the image forming unit 20. The feeding cassette 11 is provided with a recording material detection sensor S1 for detecting whether or not the recording material P is mounted.

A pickup roller 12, a separation roller pair 13, a feed roller pair 14, and a resist roller pair 15 are provided on the transport path PS1 for transporting the recording material P from the feed cassette 11 to the image forming unit 20. A resist sensor S2 is provided between the feed roller pair 14 and the resist roller pair 15. A supply roller 17, a separation pad 18, and a supply roller pair 19 are provided in a path for transporting the recording material P from the bypass tray 16 to the transport path PS1.

The recording material P stored in the feeding cassette 11 is fed to the separation roller pair 13 by the rotation of the pickup roller 12. The separation roller pair 13 separates the recording materials P fed by the pickup roller 12 one by one. The separation roller pair 13 is composed of, for example, a forward rotation roller and a reverse rotation roller. The feeding roller pair 14 conveys the recording material P separated by the separating roller pair 13 to the resist roller pair 15. When the rotation of the resist roller pair 15 is stopped, the tip of the recording material P collides with the nip portion, so that the skew of the recording material P is corrected. The resist sensor S2 detects the timing at which the tip of the recording material P reaches the nip portion of the resist roller pair 15. After the skew correction, the resist roller pair 15 starts rotating at a predetermined timing to convey the recording material P to the image forming unit 20.

The recording material P placed on the bypass tray 16 is fed one by one to the supply roller pair 19 by the supply roller 17 and the separation pad 18. The supply roller pair 19 conveys the recording material P to the supply roller pair 14 of the transfer path PS1. The feeding roller pair 14 conveys the recording material P conveyed from the supply roller pair 19 to the resist roller pair 15. The resist roller pair 15 corrects the skew of the recording material P. After the skew correction, the resist roller pair 15 rotates at a predetermined timing to convey the recording material P to the image forming unit 20.

The image forming unit 20 includes a photosensitive drum 21, a charging roller 22, a laser unit 23, a developing device 26, and a storage container 27 for storing a developing agent. The developer 26 includes a developing roller 24. The storage container 27 includes a stirring member 28 that stirs the developer inside. The storage container 27 is provided with a developer detection sensor S4. The image forming unit 20 includes a transfer roller 25 at a position sandwiching a transfer path through which the recording material P is conveyed. A transfer nip portion N1 is formed between the transfer roller 25 and the photosensitive drum 21.

The photosensitive drum 21 is a drum-shaped photosensitive member, and is rotated counterclockwise in the drawing about the axis of the drum. The charging roller 22 uniformly charges the surface of the rotating photosensitive drum 21. The laser unit 23 irradiates the charged surface of the photosensitive drum 21 with a laser beam modulated according to the image data. The image data is acquired from an external device such as a personal computer. The electric charge charged by the charging roller 22 is removed from the portion of the photosensitive drum 21 irradiated with the laser beam, and an electrostatic latent image corresponding to the image data is formed. The electrostatic latent image is visualized as a developer image by adhering the developer to the developing roller 24. The developer stored in the storage container 27 is supplied to the developer 26 by rotating the stirring member 28. The developer detection sensor S4 detects the amount of the developer in the storage container 27.

The developer image formed on the photosensitive drum 21 is conveyed to the transfer nip portion N1 by the rotation of the photosensitive drum 21. The resist roller pair 15 conveys the recording material P to the transfer nip portion N1 at the timing when the developer image is conveyed to the transfer nip N1. The recording material P is sandwiched and conveyed between the photosensitive drum 21 and the transfer roller 25 at the transfer nip portion N1, and the developer image formed on the photosensitive drum 21 is transferred by the transfer roller 25.

The recording material P to which the developer image is transferred is conveyed to the fixing unit 30. The fixing unit 30 of the present embodiment is an on-demand fixing method, and includes a fixing roller 31, a pressure roller 32, and a fixing sensor S3. The fixing roller 31 is configured by including a heat source such as a ceramic heater in an endless film. The fixing nip portion N2 is formed by the endless film of the fixing roller 31 and the pressure roller 32. By sandwiching and transporting the recording material P between the fixing nip portions N2, the recording material P and the developer image are heated and pressurized. As a result, the developer image is fixed on the recording material P. The fixing sensor S3 detects that the tip of the recording material P has passed through the fixing nip portion N2.

The fixing unit 30 may fix the developer image on the recording material P by a heating roller method instead of the on-demand fixing method. In the heating roller method, the fixing roller 31 is composed of an aluminum roller or the like, and is heated to a predetermined fixing temperature by a heat source arranged inside. The pressurizing roller 32 comes into contact with the fixing roller 31 and pressurizes the fixing roller 31 with a predetermined pressure. The fixing nip portion N2 is formed by the fixing roller 31 and the pressure roller 32. The recording material P to which the developer image is transferred is sent to the fixing nip portion N2, and is heated and pressurized while being sandwiched and conveyed between the fixing roller 31 and the pressure roller 32. As a result, the developer image is fixed on the recording material P.

The recording material P on which the developer image is fixed is conveyed from the fixing unit 30 to the recording material discharging unit 40. The recording material discharge unit 40 includes a discharge roller pair 41. When an image is formed on both sides of the recording material P by single-sided printing or double-sided printing, the discharge roller pair 41 discharges the recording material P to the discharge tray 42. When an image is formed on one side (first side) of the recording material P by double-sided printing, the discharge roller pair 41 temporarily stops before the rear end of the recording material P passes through the discharge roller pair 41, and in the opposite direction. Rotate. As a result, the recording material P on which the image is formed on the first surface is conveyed to the recording material refeeding unit 50 with the conveying direction reversed.

The recording material refeeding unit 50 includes refeeding rollers 51, 52, and 53 in the transport path PS2 to which the recording material P is transported. The recording material P is conveyed along the transfer path PS2 to the resist roller pair 15 by the refeed roller pairs 51, 52, 53. When the recording material P passes through the transport path PS2, the surface on which the developer image is transferred at the transfer nip portion N1 is inverted to the second surface opposite to the first surface. The recording material P1 conveyed to the resist roller pair 15 is processed in the same manner as when the image is formed on the first surface, an image is formed on the second surface, and the recording material P1 is discharged to the discharge tray 42.

(Fixing part)
FIG. 2 is an explanatory diagram of the fixing portion 30. In the figure, the recording material P is conveyed in the direction of arrow A. The fixing roller 31 is composed of a fixing film 207 which is a heat-resistant flexible member containing a heating element 209 which is a heat source. The fixing film 207 includes a rigid body stay 202 and temperature detection units 205 and 206 inside. The pressure roller 32 is arranged at a position where the recording material P is sandwiched so as to face the fixing film 207.

The rigid body stay 202 is a horizontally long member having heat resistance and heat insulating properties, whose longitudinal direction is orthogonal to the transport direction of the recording material P and parallel to the paper surface of the recording material P (depth direction in FIG. 2). is there. The rigid body stay 202 fixes the heating element 209 and functions as a guide when the fixing film 207 slides on the inner surface. The heating element 209 is a horizontally long member whose longitudinal direction is the same as that of the rigid body stay 202. A groove formed along the longitudinal direction is provided on the surface of the rigid body stay 202 on the side facing the recording material P. The heating element 209 is fitted into this groove and fixedly supported by a heat-resistant adhesive. The temperature detection units 205 and 206 are arranged at a plurality of positions in the longitudinal direction on the heating element 209, and detect the temperature of a plurality of parts of the heating element 209.

The fixing film 207 is a cylindrical heat-resistant film material, and is loosely fitted onto a rigid body stay 202 to which a heating element 209 is attached. The fixing film 207 is, for example, a cylindrical single-layer film such as PTFE, PFA, or FEP having heat resistance, releasability, strength, durability, etc., having a thickness of about 40 to 100 [μm]. Alternatively, the fixing film 207 may be a composite layer film in which the outer peripheral surface of a cylindrical film such as polyimide, polyamide, PEEK, PES, or PPS is coated with PTFE, PFA, FEP, or the like.

The pressure roller 32 is an elastic roller in which a heat-resistant elastic layer 204 such as silicon rubber is concentrically provided on the outer periphery of the core metal 203 in a roller shape. By sandwiching the fixing film 207 between the pressure roller 32 and the heating element 209 on the rigid body stay 202 side, a fixing nip portion N2 which is a range of pressure contact against the elasticity of the pressure roller 32 is formed.

The pressurizing roller 32 is rotationally driven at a predetermined peripheral speed in the direction of arrow B in the drawing. When the pressure roller 32 is rotationally driven, a rotational force acts directly on the fixing film 207 due to the frictional force between the pressure roller 32 and the outer surface of the fixing film 207 at the fixing nip portion N2. When the recording material P is conveyed in the direction of the arrow A and passes through the fixing nip portion N2, a rotational force indirectly acts on the fixing film 207 via the recording material P. By this action, the fixing film 207 moves while being in contact with the inner surface of the heating element 209, that is, is rotationally driven in the direction of arrow C while being pressure-welded and slid.

The rigid body stay 202 also functions as a film inner surface guide member of the fixing film 207, facilitating the rotation of the fixing film 207 around the rigid body stay 202. In order to reduce the sliding resistance between the inner surface of the fixing film 207 and the surface of the heating element 209 facing the pressure roller 32, a small amount of lubricant such as heat-resistant grease may be interposed between the two. Good.

In the fixing unit 30, the rotation of the fixing film 207 becomes steady according to the rotation of the pressure roller 32 before the fixing process is performed, and the temperature of the heating element 209 monitored by the temperature detection units 205 and 206 reaches a predetermined fixing temperature. To do. In this state, when the recording material P on which the developer image is transferred enters the fixing nip portion N2, the fixing portion 30 sandwiches and conveys the fixing film 207 and the recording material P at the fixing nip portion N2, and transfers the recording material P. Heat. As a result, the heat of the heating element 209 is efficiently transferred to the developer image of the recording material P via the fixing film 207, and the developer image is heat-fixed to the recording material P. The recording material P that has passed through the fixing nip portion N2 is separated from the surface of the fixing film 207 and conveyed in the direction of arrow A. The fixing process is performed in this way.

(Control system of fixing part)
FIG. 3 is an explanatory diagram of the control system of the fixing unit 30. In the figure, "SW" represents a switch. The fixing portion 30 has a heater substrate 302. The heating element 209 of FIG. 2 is mounted and arranged on the heater substrate 302. The heater substrate 302 is arranged so that the plate surface is parallel to the paper surface of the recording material P passing through the fixing nip portion N2. The heater substrate 302 is made of a ceramic material such as alumina and aluminum nitride. A heating element 209 (main heater 209a, subheater 209b), a plurality of electrodes (subheater electrode 308, main heater electrode 309, common electrode 310), and a conductor pattern 305-307 are printed and fired on the heater substrate 302.

The main heater 209a and the sub heater 209b are made of silver-palladium or the like, and generate heat when electric power is supplied. The sub-heater electrode 308, the main heater electrode 309, and the common electrode 310 are feeding electrodes that serve as electrical contacts to the connection terminals (sub-heater terminal 311, main heater terminal 312, common terminal 313). The conductor patterns 305 to 307 connect the main heater 209a and the subheater 209b to the subheater electrode 308, the main heater electrode 309, and the common electrode 310 to make them electrically conductive. The main heater 209a is connected to the main heater electrode 309 by the conductor pattern 305, and is connected to the common electrode 310 by the conductor pattern 307. The sub-heater 209b is connected to the sub-heater electrode 308 by the conductor pattern 306, and is connected to the common electrode 310 by the conductor pattern 307.

The fixing unit 30 is connected to the main heater energization control unit 402 and the sub heater energization control unit 403 via the interlock switch (SW) bundle wire 801. The main heater energization control unit 402 and the sub heater energization control unit 403 are connected to the commercial power supply 501. The interlock SW bundle wire 801 includes an interlock SW802. The interlock SW802 is used as a safety device for shutting off the energization so that even if the user touches the inside of the image forming apparatus 100, there is no electric shock.
The interlock SW802 is connected to the subheater terminal 311 of the fixing portion 30 via the subheater SW contact 806 and the subheater SW terminal 803. The interlock SW802 is connected to the main heater terminal 312 of the fixing portion 30 via the main heater SW contact 807 and the main heater SW terminal 804. The interlock SW802 is connected to the common terminal 313 of the fixing portion 30 via the common SW contact 808 and the common SW terminal 805.
The interlock SW802 is connected to the subheater energization control unit 403 via the subheater SW contact 809 and the subheater SW terminal 812. The interlock SW802 is connected to the main heater energization control unit 402 via the main heater SW contact 810 and the main heater SW terminal 813. The interlock SW802 is connected to the commercial power supply 501 via the common SW contact 811 and the common SW terminal 814.

The main heater 209a has a configuration in which the resistance value of the central portion of the heater substrate 302 is higher than the resistance value of both ends, and when energized, the central portion of the heater substrate 302 generates more heat than both ends. ing. The sub-heater 209b has a configuration in which the resistance values at both ends of the heater substrate 302 are higher than the resistance values at the central portion, and when energized, both ends of the heater substrate 302 generate more heat than the central portion. There is.

The recording material P that passes through the fixing portion 30 passes through the central portion of the heater substrate 302. Therefore, by controlling the energization ratio between the main heater 209a and the sub-heater 209b according to the width of the recording material P (the length in the direction orthogonal to the transport direction), the length of the heater substrate 302 after passing through the recording material P The heat distribution in the direction is controlled. When the recording material P whose size in the width direction orthogonal to the transport direction is equal to or smaller than a predetermined size (hereinafter referred to as “small size”) passes through, the fixing portion 30 increases the energization ratio of the main heater 209a to heat the heater. The central portion of the substrate 302 is heated more. In this embodiment, the predetermined size is A4R, but other sizes may be used. When the recording material P whose size in the width direction is larger than the predetermined size (hereinafter referred to as "large size") passes through, the fixing portion 30 sets the energization ratio of the subheater 209b as compared with the time when the small size recording material P passes through. It is controlled to be raised so that heat is evenly generated up to the end in the width direction. The main heater 209a has a smaller resistance value than the sub heater 209b, and a larger current flows through the main heater 209a.

The plurality of temperature detection units 205 and 206 are arranged along the longitudinal direction of the heater substrate 302. A temperature detection element such as a thermistor is used for the temperature detection units 205 and 206. The temperature detection unit 205 is a main thermistor arranged at the center of the heater substrate 302 in the longitudinal direction. The temperature detection unit 206 is a sub thermistor arranged at an end portion of the heater substrate 302 in the longitudinal direction. The detection results of the temperature detection units 205 and 206 are input as detection signals to the A / D port of the CPU (Central Processing Unit) 702 in the control unit 600. The CPU 702 controls the operation of the image forming apparatus 100. The control unit 600 has a memory 703, and stores various information related to processing in the memory 703.

The CPU 702 monitors the temperatures of the central portion and the end portion of the heater substrate 302 in the longitudinal direction by the detection signals acquired from the temperature detection units 205 and 206, respectively. The CPU 702 includes a main heater energization control unit 402 that controls energization of the commercial power supply 501 to the main heater 209a, a subheater energization control unit 403 that controls energization of the commercial power supply 501 to the sub heater 209b, based on the monitored temperature. To control. Thereby, the CPU 702 controls the energization ratio of the main heater 209a and the sub heater 209b.

The main heater energization control unit 402 and the sub-heater energization control unit 403 each have a switch element such as a triac, and the CPU 702 controls the conduction state of the switch element to control energization. The rating is different between the element used for the main heater energization control unit 402 and the element used for the sub heater energization control unit 403. In the present embodiment, since the main heater 209a flows a larger current than the sub heater 209b, the element used for the main heater energization control unit 402 is rated higher than the element used for the sub heater energization control unit 403. large. A current detection unit 401 for detecting the current value of the current flowing when the heating element 209 is energized is provided between the main heater energization control unit 402 and the sub-heater energization control unit 403 and the commercial power supply 501.

The current flowing through the main heater 209a is the main heater current Ia, the detection temperature of the temperature detection unit 205 is the temperature Ka1, and the detection temperature of the temperature detection unit 206 is the temperature Ka2. The values of the main heater current Ia, the temperature Ka1, and the temperature Ka2 are obtained from the detection results of the current detection unit 401, the temperature detection unit 205, and the temperature detection unit 206 when the main heater energization control unit 402 is energized.
The current flowing through the sub-heater 209a is the sub-heater current Ib, the detection temperature of the temperature detection unit 205 is the temperature Kb1, and the detection temperature of the temperature detection unit 206 is the temperature Kb2. The values of the sub-heater current Ib, the temperature Kb1, and the temperature Kb2 are obtained from the detection results of the current detection unit 401, the temperature detection unit 205, and the temperature detection unit 206 when the sub-heater energization control unit 403 is energized.
The CPU 702 determines the occurrence of an abnormality in the fixing unit 30 based on these current values and temperatures. A notification unit 601 is connected to the CPU 702. When the CPU 702 determines that an abnormality has occurred in the fixing unit 30, the notification unit 601 notifies the content of the abnormality.

As described above, when the small-sized recording material P is heated and fixed, the energization ratio of the main heater 209a becomes high. At this time, if the energization ratios of the main heater 209a and the sub heater 209b are exchanged and the temperature rise is reversed between the central portion and the end portion of the heater substrate 302, the temperature of the central portion of the heater substrate 302 is lowered and the temperature of the end portion is reduced. The temperature rises. A decrease in temperature at the center of the heater substrate 302 leads to poor fixing of the small-sized recording material P. An abnormal temperature rise at the end of the heater substrate 302 is determined to be an abnormality based on the detected temperature of the temperature detecting unit 206, and may cause an error to stop the image forming operation.

One of the objects of the present embodiment is to prevent the occurrence of erroneous connection of the wiring for energizing the heating element 209 (main heater 209a and sub-heater 209b). The details of the control will be described below.

(Operation of image forming device)
FIG. 4 is a flowchart showing the processing at the time of starting the image forming apparatus 100. This process is executed when a power switch (not shown) is operated to turn on the power of the image forming apparatus 100. When the power is turned on, the CPU 702 confirms the occurrence of an error before shifting the operation mode to the standby mode (S101). If an error has occurred (S101: N), the image forming operation may not be performed normally. Therefore, the CPU 702 determines to cancel the error until the error is cleared (S102: N). When no error has occurred (S101: Y) or when the error has been cleared (S102: Y), the CPU 702 shifts the operation mode to the standby mode.

FIG. 5 is a flowchart showing processing in the standby mode of the image forming apparatus 100.

When the CPU 702 receives a predetermined job in the standby mode (S201: Y), the CPU 702 determines whether or not the received job is the first job after the operation in which the fixing unit 30 may have been replaced. Judgment (S202). When the received job is not the first job (S202: N), the CPU 702 determines whether or not the unique information of the fixing unit 30 stored in the memory 703 matches the unique information of the fixing unit 30 currently mounted. Judgment (S203). When the unique information matches (S203: N), the CPU 702 determines whether or not the door of the housing of the image forming apparatus 100 has been opened or closed (S204). When the door is not opened / closed (S204: N), the CPU 702 determines that the fixing portion 30 may not have been replaced. If the control unit 600 is not equipped with the memory 703, the processing of S203 may not be performed.

If either the received job is the first job (S202: Y), the unique information does not match (S203: Y), or the door is opened / closed (S204: Y), the CPU 702 is satisfied. , It is determined that the fixing portion 30 may have been replaced. In this case, the CPU 702 executes a connection state detection process for determining whether or not the fixing unit 30 is accurately connected (S205). The details of the connection state detection process will be described later.

After executing the connection state detection process, or when it is determined that there is no possibility that the fixing unit 30 has been replaced, the CPU 702 determines whether or not the connection state of the fixing unit 30 is normal (S206). The CPU 702 makes this determination based on the execution result of the current connection state detection process or the information of the connection state at the time of the previous job execution.

When the connection state is normal (S206: Y), the CPU 702 executes the job and ends the process (S207). When the processing is completed, the CPU 702 sets the operation mode to the standby mode. When the connection state is abnormal (S206: N), the CPU 702 suspends the job (S208). The CPU 702 notifies the user that there is a connection abnormality of the fixing unit 30 by the notification unit 601 (S209). When the notification unit 601 is a display, the CPU 702 displays that the notification unit 601 has a connection abnormality (S209). After the notification, the CPU 702 ends the job and sets the operation mode to the standby mode.

(First connection status detection process)
FIG. 6 is a flowchart showing the connection state detection process. This process is a process of determining whether or not the fixing unit 30 (heating element 209) is normally connected. That is, it is determined whether or not the main heater 209a is connected to the main heater energization control unit 402 and the sub heater 209b is connected to the sub heater energization control unit 403.

When the connection state detection process is started, the CPU 702 energizes only the main heater 209a by conducting the main heater energization control unit 402 and shutting off the sub heater energization control unit 403 (S301). The CPU 702 acquires a detection result from the current detection unit 401 and detects the current value (main heater current Ia) of the current flowing through the main heater 209a (S302). After detecting the main heater current Ia, the CPU 702 shuts off the main heater 209a by shutting off the main heater energization control unit 402 (S303). The CPU 702 detects the current value by preferentially driving the main heater energization control unit 402, which has a relatively large rating.

The CPU 702 compares the detected main heater current Ia with the assumed value Ia'of the main heater current stored in advance in the memory 703, and determines whether or not the current is flowing as expected (S304). The CPU 702 is main when the main heater current Ia is within the first predetermined range including the assumed value Ia'(in the present embodiment, within the range of 0.9 to 1.1 times the assumed value Ia'). It is judged that the heater current Ia flows as expected and is normal.

When the main heater current Ia is within the first predetermined range (S304: Y), the CPU 702 determines that the connection state of the heating element 209 is normal (S305). The CPU 702 stores in the memory 703 the device state that the connection state of the heating element 209 is normal, and ends the connection state detection process (S309).

When the main heater current Ia is out of the first predetermined range (S304: N), the CPU 702 determines that the main heater current Ia is not normal. In this case, the CPU 702 compares the main heater current Ia with the assumed value Ib'of the sub-heater current stored in the memory 703 in advance, and determines whether or not the detected main heater current Ia is a value corresponding to the sub-heater current. Is determined (S306). The CPU 702 is main when the main heater current Ia is within the second predetermined range including the assumed value Ib'(in the present embodiment, within the range of 0.9 to 1.1 times the assumed value Ib'). It is determined that the heater current Ia is a value corresponding to the sub-heater current.

When the main heater current Ia is within the second predetermined range (S306: Y), the CPU 702 determines that the connection state of the heating element 209 is abnormal (misconnection) (S307). In this case, the CPU 702 determines that the connection of the main heater 209a and the connection of the sub heater 209b are reversed. The CPU 702 stores in the memory 703 the device state in which the connection of the main heater 209a and the connection of the sub heater 209b are reversed, and ends the connection state detection process (S309).

When the main heater current Ia is out of the second predetermined range (S306: N), the CPU 702 determines that the heating element 209 is out of order or disconnected (S308). In this case, the CPU 702 stores the device state that the heating element 209 is broken or disconnected in the memory 703, and ends the connection state detection process (S309).

(Second connection status detection process)
When it is known in advance that the resistance values of the main heater 209a and the sub heater 209b are different, the connection state of the heating element 209 can be detected by the first connection state detection process. However, the main heater 209a and the sub heater 209b do not have to have different resistance values. FIG. 7 is a flowchart showing a connection state detection process when it is unknown whether or not the resistance values of the main heater 209a and the sub heater 209b are different.

When the CPU 702 starts the connection state detection process, it acquires the detection results from the temperature detection units 205 and 206, and the temperature at the center of the current heater substrate 302 (center temperature K01) before heating the heating element 209. The end temperature (end temperature K02) is detected (S400). After the current temperature detection, the CPU 702 energizes only the main heater 209a by conducting the main heater energization control unit 402 and shutting off the sub heater energization control unit 403 (S401). The CPU 702 acquires the detection result from the current detection unit 401, detects the current value (main heater current Ia) of the current flowing through the main heater 209a, acquires the detection result from the temperature detection units 205 and 206, and obtains the detection result from the temperature detection units 205 and 206 to obtain the central temperature Ka1. And the end temperature Ka2 is detected (S402). After detecting the main heater current Ia, the center temperature Ka1, and the end temperature Ka2, the CPU 702 cuts off the power supply to the main heater 209a by shutting off the main heater power supply control unit 402 (S403). The CPU 702 detects the current value by preferentially driving the main heater energization control unit 402, which has a relatively large rating.

The CPU 702 compares the detected main heater current Ia with the assumed value Ia'of the main heater current stored in advance in the memory 703, and determines whether or not the current is flowing as expected (S404). The CPU 702 is main when the main heater current Ia is within the first predetermined range including the assumed value Ia'(in the present embodiment, within the range of 0.9 to 1.1 times the assumed value Ia'). It is judged that the heater current Ia flows as expected and is normal.

When the main heater current Ia is out of the first predetermined range (S404: N), the CPU 702 determines that the main heater current Ia is not normal. In this case, the CPU 702 compares the main heater current Ia with the assumed value Ib'of the sub-heater current stored in the memory 703 in advance, and determines whether or not the detected main heater current Ia is a value corresponding to the sub-heater current. Is determined (S406). The CPU 702 is main when the main heater current Ia is within the second predetermined range including the assumed value Ib'(in the present embodiment, within the range of 0.9 to 1.1 times the assumed value Ib'). It is determined that the heater current Ia is a value corresponding to the sub-heater current.

When the main heater current Ia is within the second predetermined range (S406: Y), the CPU 702 has different resistance values between the main heater 209a and the subheater 209b, and the connection state of the heating element 209 is abnormal (misconnection). It is determined that (S407). In this case, the CPU 702 determines that the connection of the main heater 209a and the connection of the sub heater 209b are reversed. The CPU 702 stores in the memory 703 the device state in which the connection of the main heater 209a and the connection of the sub heater 209b are reversed, and ends the connection state detection process (S409).

When the main heater current Ia is out of the second predetermined range (S406: N), the CPU 702 determines that the heating element 209 is out of order or disconnected (S408). In this case, the CPU 702 stores the device state that the heating element 209 is broken or disconnected in the memory 703 and ends the connection state detection process (S409).

When the main heater current Ia is within the first predetermined range (S404: Y), the CPU 702 assumes that the connection state of the heating element 209 is normal (S405). When the resistance values of the main heater 209a and the sub heater 209b are the same, the assumed current value is the same, and the connection state cannot be determined to be normal only by the current value. Therefore, the CPU 702 assumes that the connection is normal. To do.

The CPU 702 compares the detection results of the temperature detection units 205 and 206 with the temperature changes of the temperature detection points assumed when the main heater 209a is energized, and the temperature changes of the temperature detection points of the heating element 209 are normal. Whether or not it is determined (S410). The temperature change at each temperature detection location assumed when the main heater 209a is energized is stored in the memory 703 in advance. The CPU 702 acquires the current temperature of the heating element 209 detected by the temperature detection units 205 and 206. The CPU 702 acquires the actual temperature of each temperature detection position of the heating element 209 from the temperature change between the temperature acquired in the process of S400 and the current temperature. The CPU 702 makes this determination based on whether or not the actual temperature change at each temperature detection position corresponds to the expected temperature change.

When the actual temperature change is normal (S410: Y), the CPU 702 determines that the connection state of the heating element 209 is normal because the current value and the temperature change of the main heater 209a are normal (S411). The CPU 702 stores in the memory 703 the device state that the connection state of the heating element 209 is normal, and ends the connection state detection process (S415).

When the actual temperature change is abnormal (S410: N), the CPU 702 compares the temperature of the heating element 209 with the temperature assumed in advance when the sub-heater 209b is energized in the memory 703 (S412). When the actual temperature change corresponds to the assumed temperature change (S412: Y), the CPU 702 has the same resistance value between the main heater 209a and the sub heater 209b, and the connection state of the heating element 209 is abnormal (wrong connection). ) (S413). In this case, the CPU 702 determines that the connection of the main heater 209a and the connection of the sub heater 209b are reversed. The CPU 702 stores in the memory 703 the device state in which the connection of the main heater 209a and the connection of the sub heater 209b are reversed, and ends the connection state detection process (S415).

When the actual temperature change does not correspond to the expected temperature change (S412: N), the CPU 702 determines that the heating element 209 is out of order or disconnected (S414). In this case, the CPU 702 stores the device state that the heating element 209 is broken or disconnected in the memory 703 and ends the connection state detection process (S409).

As described above, when the resistance values of the main heater 209a and the sub heater 209b are different, the control unit 600 can determine the connection state of the heating element 209 only by the detected current value (FIG. 6). When the relationship between the resistance values of the main heater 209a and the sub heater 209b is unknown, the control unit 600 can determine the connection state of the heating element 209 according to the detected current value and the temperature of the heating element 209. (Fig. 7).

By the connection state detection process as described above, it is determined whether or not the heater substrate 302 of the fixing unit 30 is normally connected. When the connection is abnormal, the control unit 600 can notify the user that the connection is incorrect by the notification unit 601. The user can modify the connection in response to this notification. Therefore, it is possible to prevent the image forming apparatus 100 from operating while the temperature controls of the main heater 209a and the sub heater 209b are switched. Further, by detecting the erroneous connection of the wiring for energizing the heating element 209, it is possible to prevent the fixing portion 30 from failing due to overheating and the image not being fixed due to the temperature drop. In the present embodiment, the normal judgment of the current value is set to ± 10% of the assumed value, but it is not always necessary to judge within this range.

Further, the image forming apparatus 100 having a plurality of heating elements 209 (main heater 209a and sub-heater 209b) is preferentially driven from the main heater energization control unit 402 having a higher rating when detecting the connection of the heating element 209. When the main heater 209a is energized and an erroneous connection is detected, the CPU 702 does not energize the sub heater 209b. As a result, it is possible to prevent accidentally applying a large amount of electric power to the sub-heater energization control unit 403 having a small rating and destroying the elements in the sub-heater energization control unit 403.

Claims (14)

An image forming means for forming a developer image on a photoconductor, and
A transfer means for transferring the developer image formed on the photoconductor to a recording material, and
A fixing means having a heating element including a first heater and a second heater and fixing the developer image on the recording material by heating the recording material to which the developer image is transferred by the heating element. ,
A first energization control means for controlling energization of the first heater,
A second energization control means for controlling energization of the second heater,
A current detecting means for detecting the current value of the current flowing through the heating element when energized, and
A first terminal for connecting the first energization control means and the first heater,
A second terminal for connecting the second energization control means and the second heater,
A control means for controlling the temperature of the heating element by controlling the energization by the first energization control means and the second energization control means is provided.
The first energization control means is composed of elements having a higher rating than the second energization control means.
The control means acquires the current value when the first heater is energized by the first energization control means from the current detection means, and assumes the acquired current value to flow through the first heater. By comparing with the value, as the connection state of the heating element, the first energization control means and the first heater are connected by the first terminal, and the second energization control means and the second energization control means and the first by the second terminal. 2 It is characterized in determining whether or not a heater is connected.
Image forming device. The control means determines that the connection state of the heating element is normal when the acquired current value is within the first predetermined range, and when it is outside the first predetermined range, the control means determines. It is characterized in that the connection state of the heating element is determined by comparing the acquired current value with an assumed value of the current value flowing through the second heater.
The image forming apparatus according to claim 1. The control means determines that the connection state of the heating element is abnormal when the acquired current value is within the second predetermined range, and when it is outside the second predetermined range, the control means determines. It is characterized in that it is determined that the heating element is out of order.
The image forming apparatus according to claim 2. In the control means, when the acquired current value is within the second predetermined range, the first energization control means and the second heater are erroneously connected by the first terminal, and the second heater is used. It is characterized in that it is determined that the second energization control means and the first heater are erroneously connected by the terminal.
The image forming apparatus according to claim 3. Further, a temperature detecting means for detecting the temperature of the heating element is provided.
The control means is characterized in that it determines the connection state of the heating element by comparing the temperature change detected by the temperature detecting means with the temperature change assumed when the first heater is energized. To do,
The image forming apparatus according to any one of claims 1 to 4. The control means determines that the connection state of the heating element is normal when the actual temperature change corresponds to the temperature change assumed when the first heater is energized, and the actual temperature change is the first. When it does not correspond to the temperature change expected when the heater is energized, the connection state of the heating element is determined by comparing the actual temperature change with the temperature change expected when the second heater is energized. To
The image forming apparatus according to claim 5. The control means determines that the connection state of the heating element is abnormal when the actual temperature change corresponds to the temperature change assumed when the second heater is energized, and when the second heater is energized. It is characterized in that it is determined that the heating element is out of order when it does not correspond to the expected temperature change.
The image forming apparatus according to claim 6. In the control means, when the actual temperature change corresponds to the temperature change assumed when the second heater is energized, the first energization control means and the second heater are erroneously connected by the first terminal. The second terminal is used to determine that the second energization control means and the first heater are erroneously connected.
The image forming apparatus according to claim 7. The control means is characterized in that, when the connection state of the heating element is abnormal, a predetermined notification means notifies that the connection state is abnormal.
The image forming apparatus according to any one of claims 1 to 8. A storage means for storing the connection state determined by the control means is provided.
The image forming apparatus according to any one of claims 1 to 9. The control means is characterized in that it determines the connection state of the heating element when an operation that may have replaced the fixing means is performed between the previous job and the current job.
The image forming apparatus according to any one of claims 1 to 10. When the control means does not determine the connection state of the heating element after receiving the job, the control means determines whether or not the connection state is normal based on the connection state stored in the storage means, and connects. The job is executed when the state is normal, and the job is interrupted when the connection state is abnormal.
The image forming apparatus according to claim 10. When the control means detects that the connection state is abnormal, the control means does not energize the second heater by the second energization control means.
The image forming apparatus according to any one of claims 1 to 12. It is characterized by including an interlock switch including the first terminal and the second terminal.
The image forming apparatus according to any one of claims 1 to 13.