JPH05181329A - Safety device for image forming device - Google Patents

Abstract

PURPOSE:To prevent a failure of a device caused by the electrostatic noise even in the case where a user touches a fixing device when a user opens a door to remove paper jamming or the like by providing a means for releasing the electrostatic noise, which intrudes into a circuit for supplying the power to an opened heater when the door is positioned at an open position, to the grounding side. CONSTITUTION:A grounding pattern 1 is provided near a pattern on a circuit board, in which a circuit for connecting a heater 3 as a heat generator and a commercial power source 9 is formed. The grounding pattern 11 is provided so as to surround a power source line of the heater 3, and the insulating coating for protecting the pattern is scraped at neighboring parts of the pattern of the power source line and the grounding pattern 11 opposite to each other. In this case, the grounding pattern 11 is provided so as to be opposite to each phase of the power source supply side and the grounding side of the pattern a of the power source line, but, it can be provided so as to be opposite to any one of the phases. With this structure, the electrostatic noise, which intrudes the pattern of the power source line of the heater 3, is discharged to the grounding pattern 11 on the board.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a safety device for an image forming apparatus.

[0002]

2. Description of the Related Art A part of a conventional image forming apparatus is shown in FIG. In FIG. 5, 1 is a microcomputer,
It has a CPU, ROM, RAM, and I / O. The microcomputer 1 controls the surface temperature of a fixing roller 2 which is a part of a heat fixing device, and the fixing roller 2 is internally provided with a heater 3 as a heating element whose energization amount is controlled. The thermistor 4 for measuring the surface temperature is arranged so as to contact the surface of the fixing roller 2. Also,
The heater 3 is connected to a commercial power source 9 via a control circuit 5, and the control circuit 5 is connected to the microcomputer 1 via a buffer 6. That is, the microcomputer 1 takes in the voltage change corresponding to the change in the surface temperature of the fixing roller 2 by the thermistor 4,
The surface temperature of the fixing roller 2 is maintained at a predetermined temperature by controlling the amount of electricity supplied to the heater 3 by driving the control circuit 5 according to the taken-in voltage.

On the other hand, inside the closed circuit of the heater 3 and the commercial power source 9, there is provided a switch 7 as a disconnecting device for interrupting the power supply from the commercial power source 9 to the heater 3. The switch 7 is an image shown in FIG. It is in the closed state when it is pushed by the member 8 that moves in conjunction with the door 10, which is the door body of the forming apparatus. That is, when the door 10 is in the closed position, the member 8 pushes the switch 7, so that the switch 7 is also in the closed state.

However, when the door 10 is opened as shown in FIG.
Is opened, and the power supply from the commercial power supply 9 to the heater 3 is cut off. As a result, the temperature of the heat fixing device is lowered, and the user can safely perform paper jam processing and the like.

[0005]

However, according to the above conventional example, when the user touches the heat fixing device when the door 10 is opened, electrostatic noise enters the opened circuit of the heater 3 side. However, there is a problem that the control circuit 5 and the like fail.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a fixing device capable of preventing the device from being damaged due to the entry of electrostatic noise.

[0007]

According to the present invention, the above object is to provide a fixing device having a heating element, and a power supply device for connecting the heating element and a power source to supply power to the heating element. Electric power to be applied to the heating element by opening a door provided in the housing of the image forming apparatus and a closed circuit connecting the power source of the power supply device and the heating element when the door is in the open position. In a safety device of an image forming apparatus having a shutoff device for shutting off the supply of electricity, the open end of the circuit for supplying electric power to the heating element is grounded or brought close to the grounding side to enter the circuit. This is achieved by having a means for escaping electrical noise to the ground side.

[0008]

According to the present invention, when the door is opened for clearing a paper jam or the like, the shut-off means opens the closed circuit connecting the power source of the power supply device and the heating element, so that the electric power to the heating element is released. The supply is cut off. As a result, the temperature of the fixing device decreases and the user can safely work. However, when the user touches the fixing device during the work, electrostatic noise enters the circuit that supplies power to the opened heating element. There are cases. However, the means for escaping the electrostatic noise to the ground side causes the open end of the circuit to be grounded or brought close to the ground side, so that the electrostatic noise can escape to the ground side and damage the power supply device or the like. Absent.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First to third embodiments of the present invention will be described with reference to the drawings.

<First Embodiment> First, a first embodiment of the present invention will be described with reference to FIGS. The same parts as those of the conventional apparatus shown in FIGS. 5 and 6 are designated by the same reference numerals, and the description thereof will be omitted.

This embodiment is different from the conventional example in that a ground pattern 11 is provided in the vicinity of a pattern on a circuit board on which a circuit connecting a heater 3 as a heating element and a commercial power source 9 as shown in FIG. 1 is formed. The ground pattern 11 is provided so as to surround the power supply line pattern 12 of the heater 3 as shown in FIG. 2, and the adjacent portions of the power supply line pattern 12 and the ground pattern 11 which face each other are patterned as shown by diagonal lines in FIG. The insulating paint that protects the has been removed.

In the present embodiment, the ground pattern 11 is provided so as to face each of the phases on the power supply side and the ground side of the pattern 12 of the power line, but only one of the specific phases may be provided.

According to the present embodiment as described above, the heater 3
The electrostatic noise entering the pattern 12 of the power supply line is discharged to the ground pattern 11 on the substrate. Therefore, it is possible to prevent the device from being damaged due to electrostatic noise.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIG. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

This embodiment is different from the first embodiment in that a switch 13 as a breaking means is used as a means for releasing electrostatic noise to the ground. The switch 13 is pushed by the member 8 and connected to the commercial power source 9 when the door 10 is closed, but is connected to the ground side without being pushed by the member 8 when the door 10 is opened. As a result, the electrostatic noise that enters the pattern 12 of the power supply line of the heater 3 escapes to the ground and can prevent the breakdown of the device.

<Third Embodiment> Next, a third embodiment of the present invention will be described with reference to FIG. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

This embodiment is different from the first embodiment in that a relay 14 as a breaking means is used as a means for releasing electrostatic noise to the ground.

The microcomputer 1 has an LED
A light receiving element 16 such as a phototransistor paired with a light emitting element 15 such as a light emitting element 1 is connected to the light emitting element 1 when the door 10 is closed when a protrusion (not shown) provided on the door 10 is closed.
5 and the light receiving element 16 are blocked. When the light emission from the light emitting element 15 is blocked in this manner, the light receiving element 1
The output of 6 becomes low level. On the other hand, when the door 10 is opened, the protrusion does not block the space between the light emitting element 15 and the light receiving element 16, so that the level of the light receiving element 16 becomes high.

The microcomputer 1 includes a light receiving element 16
Relay 14 when the output of is at high level (when the door is open)
Is connected to the ground side, and when the output of the light receiving element 16 is at a low level (when the door is closed), the contact of the relay 14 is connected to the commercial power source 9 side.

Therefore, when the door 10 is opened, the power supply line of the heater 3 is connected to the ground side, and the device failure due to electrostatic noise can be prevented.

[0021]

As described above, according to the present invention,
When the door is in the open position, a means for escaping electrostatic noise that enters the circuit that supplies power to the open heating element to the ground side has been provided, so the user opens the door to clear paper jams, etc. Even when the fixing device is touched at times, the device failure due to electrostatic noise can be prevented.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a schematic configuration of a first embodiment device of the present invention.

FIG. 2 is a partially cutaway plan view showing a means for releasing electrostatic noise of the apparatus shown in FIG.

FIG. 3 is a circuit diagram showing a schematic configuration of a second embodiment device of the present invention.

FIG. 4 is a circuit diagram showing a schematic configuration of a third embodiment device of the present invention.

FIG. 5 is a circuit diagram showing a schematic configuration of a conventional device.

FIG. 6 is a perspective view showing a schematic configuration around a door body of a conventional device.

[Explanation of symbols]

3 Heater (heating element) 7 Relay (breaking means) 9 Commercial power supply (power source) 10 Door (door body) 11 Ground pattern (means for releasing electrostatic noise to the ground side)

Claims (4)

[Claims] 1. A fixing device having a heating element, a power supply device for connecting the heating element and a power source to supply electric power to the heating element, and an openable and closable door provided in a casing of the image forming apparatus. An image forming apparatus including a body and a shutoff device that opens a closed circuit that connects a power source of the power supply device and a heating element when the door is in the open position to shut off the power supply to the heating element. In the safety device described in (1) above, there is provided a means for grounding the open end of the circuit for supplying power to the heating element, or for bringing the open end close to the grounding side to release electrostatic noise entering the circuit to the grounding side. Image forming device safety device. 2. The means for releasing electrostatic noise to the ground side is a ground pattern arranged on the circuit board in the vicinity of the pattern for supplying electric power to the heating element so as to face the pattern. Item 2. A safety device for an image forming apparatus according to item 1. 3. The pattern for supplying electric power to the heating element and the ground pattern facing the pattern have insulating paints for protecting the pattern removed from each other in a predetermined area of the facing portion. Image forming device safety device. 4. The image forming apparatus according to claim 1, wherein the means for escaping the electrostatic noise to the ground side is a shutoff device set so as to ground the open end of a circuit for supplying electric power to the heating element. Device safety device.