JPH11109785A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of detecting the abnormality of a relay, without providing special parts for detecting the abnormality of the relay. SOLUTION: When the temp. of a fixing heater 10 is low, the ON signal of a fixing heater current supplying TRIAC 14 and the OFF signal of an abnormal time power source interrupting relay 16 are outputted from a control part 20. Then, the initial temp. C of the fixing heater 10 is detected and after few seconds, the temp. of the fixing heater 10 is detected again. In the abnormal case, if power source interrupting relay 16 is normal, there is no change in the value of a fixing heater temperature detecting sensor 12. On the other hand, when the value of the temperature detecting sensor 12 is D and there is a difference E between the value D and the initial temp. C, during the turning off of the abnormal case power source interrupting relay 16, there is a possibility that heat is generated because a current flows through the fixing heater 10 for welding the contact of the relay 16. Thus, a repairing request to a serviceman is urged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, a relay for shutting off a power supply when an abnormality occurs in an OA device has been used. As a method of detecting an abnormality when the relay fails, the invention described in Japanese Patent Application Laid-Open No. 8-166826 can be mentioned. According to the present invention, the potential of the drive output port out which is data on the operation state of the energization control transistor for controlling the energization current to the relay coil of the control output relay, and the contact output of the relay contact according to the operation state The microcomputer determines whether the control output relay is normal or abnormal based on the combination of the potential of the contact output data input port, which is data, and the potential of the monitoring data input port, which is data corresponding to the energized state of the relay coil. Do. If an abnormality is detected, it is determined whether the cause is a failure of the conduction control transistor or a welding of the relay contact.

[0003]

By the way, when the relay for shutting off the power supply in the event of an abnormality of the image forming apparatus is not turned on (remains open), the temperature of the fixing heater does not rise, so that a failure can be detected. However, when the contact of the power-off relay at the time of abnormality is kept ON (contact mounted state) due to attachment or the like, the abnormality cannot be detected. For example, if the contact of the relay for shutting down the power supply in the event of an abnormal condition is a bearer and the copier or the like is being used, and the triac for supplying current to the fixed heater is short-circuited, current continues to flow to the fixing heater and the fixing heater generates heat. When the temperature becomes high, the thermal fuse 18 and the like are blown and the current supply to the fixing heater is cut off. Further, there is a possibility that an adjacent object is ignited by the heat generated by the fixing heater before the thermal fuse 18 or the like is blown, resulting in a fire. On the other hand, in the above-described related art, components such as a transistor, a microcomputer, and a potential sensor are used to detect an abnormality of the relay, and the cost is increased. Therefore, an object of the present invention is to provide an O
An object of the present invention is to provide an image forming apparatus capable of detecting an abnormality of a relay used in the device A.

[0004]

According to the first aspect of the present invention, a fixing heater for fixing an image, a switching element for supplying a current to the fixing heater for supplying a current to the fixing heater, and a current interruption when an abnormality occurs. In an image forming apparatus provided with a power-off relay for abnormal time and a fixing heater temperature detecting means for detecting the temperature of the fixing heater, it is detected that the temperature of the fixing heater is low by the fixing heater temperature detecting means. When the switching element for supplying the fixing heater current is turned on, the
By performing FF, the above-mentioned object is achieved by detecting the failure of the power-off relay at the time of abnormality.

According to a second aspect of the present invention, in the image forming apparatus of the first aspect, a current supplying triac is used as the switching element for supplying the fixing heater current.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below in detail with reference to FIGS. FIG.
FIG. 3 is a circuit diagram of a fixing heater used in the image forming apparatus according to the exemplary embodiment. The fixing heater 10 has an AC power supply (A
C), a power-off relay 16 at the time of abnormality, a triac 14 for supplying a fixing heater current, and a temperature fuse 18 are sequentially connected. Further, a fixing heater temperature detecting sensor 12 for detecting the temperature of the fixing heater 10 is provided, and a control unit 20 connected to the fixing heater temperature detecting sensor 12 controls the relay 16 for shutting down the power at the time of abnormality and the triac 14 for supplying the fixing heater current. ON / OFF is controlled.

Next, a process in which the fixing heater 10 generates heat will be described with reference to the circuit diagram of FIG. In the circuit shown in FIG. 1, an ON signal of the power-off relay 16 is output from the control unit 20 to close the contact of the power-off relay 16 or the ON signal of the triac 14 for supplying the fixing heater current is controlled. When the current is output from the unit 20 and the current flows through the fixing heater current supply triac 14, the current flows into the fixing heater 10, and the fixing heater 10 generates heat.

The procedure of the process of this embodiment will be described with reference to the flowchart of FIG. 2 and a graph of FIG. 3 showing the relationship between the fixing heater temperature and the fixing heater energizing time. First, the power of the image forming apparatus such as a copying machine is turned on (step 10). Then, the fixing heater temperature detection sensor 12 determines whether the temperature of the fixing heater 10 is low (FIG. 3A).
(Step 11). Here, the control unit 20 checks the temperature based on the output value of the fixing heater temperature detecting sensor 12. As a result, when the temperature of the fixing heater 10 is high (Step 11; N, FIG. 3B), since there is no abnormality in the power-off relay 16 at the time of abnormality, normal control is performed (Step 15).

On the other hand, when the temperature of the fixing heater 10 is low (step 11; Y), the control unit 20 outputs an ON signal of the triac 14 for supplying the fixing heater current and an OFF signal of the relay 16 for shutting down the power supply in the event of an abnormality (step 11). 1
2). Here, whether or not the fixing heater 10 generates heat is detected by the fixing heater temperature detecting sensor 12 (step 13). The temperature detection sensor 12 of the fixing heater 10
The initial temperature (C) of the fixing heater 10 is detected, and after a few seconds, the temperature of the fixing heater 10 is detected again (for example, D).

Since the power-off relay 16 is turned off, the value of the sensor 12 for detecting the temperature of the fixing heater should not be changed if the power-off relay 16 is normal (step 13; N). ). If the value does not change,
Proceed to normal control (step 15). On the other hand, if the value of the fixing heater temperature detecting sensor 12 is (D) and there is a difference (E) from the initial temperature (C) even though the abnormal-time power-off relay 16 is OFF (step S1). 13;
Y), for mounting the contact of the relay 16 for shutting down the power when abnormal,
There is a possibility that a current flows through the fixing heater 10 to generate heat. Therefore, SC (serviceman call) is displayed on the operation unit or the like (step 15), and the user is urged to request a serviceman for repair. According to the present embodiment, the user can easily detect a failure such as the attachment of a contact of the power-off relay 16 at the time of abnormality, and can quickly take measures against the failure.

[0011]

According to the first and second aspects of the present invention, it is possible to detect the attachment of the contact of the relay for shutting down the power supply in the event of an abnormality without providing a special device or the like. Accidents can be prevented.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an image forming apparatus according to an embodiment.

FIG. 2 is a flowchart illustrating a procedure of a process according to the embodiment;

FIG. 3 is a graph showing a relationship between a fixing heater temperature and a fixing heater energizing time according to the exemplary embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Fixing heater 12 Sensor for detecting fixing heater temperature 14 Triac for supplying fixing heater current 16 Relay for shutting off power in case of abnormality 18 Thermal fuse 20 Control unit

Claims (2)

[Claims] A fixing heater for fixing an image;
An image comprising: a switching element for supplying a current to the fixing heater for supplying a current to the fixing heater; a relay for shutting down the power supply in an abnormal state for interrupting the current in an abnormal state; and a fixing heater temperature detecting means for detecting the temperature of the fixing heater. In the forming apparatus, when the fixing heater temperature detecting means detects that the temperature of the fixing heater is low, the switching element for supplying the fixing heater current is turned on, and the relay for shutting off the power in the event of an abnormality is turned off. An image forming apparatus for detecting a failure of a power-off relay. 2. The image forming apparatus according to claim 1, wherein a current supply triac is used as the fixing heater current supply switching element.