JPS62115472A - Abnormality detector for image forming device - Google Patents

Abstract

PURPOSE:To detect the abnormality of a main deriving system (failure in rotation at a normal rotating speed, etc.) by detecting the rotating condition of a magnetic roller by a magnetic sensor provided near the magnetic roller of a developing device. CONSTITUTION:Magnets 3a-3d are fixed to the magnetic roller 2 provided in the developing device 12. The magnetic roller 2 rotates according to the rotation of a main motor 24 and the resistance value of a Hall element 1 provided near the magnetic roller 2 changes. The main motor 24 is driven and the timer constituted by a RAM 22 is started by the control of a CPU 20. The CPU judges that the rotating speed of the magnetic roller 2 is decreased if the period of the output signal from the magnetic sensor HS has the period of the valve exceeding the specified value. The abnormality of the main deriving system by the main motor 24 is then displayed on a display part 27.

Description

[Detailed Description of the Invention] Technical Field> The present invention relates to a copying machine, etc., which has a developing device incorporating a magnetic roller having a plurality of magnetic poles, and a main drive system that drives a photoreceptor and a document scanning device together with the magnetic roller. The present invention relates to a device for detecting an abnormal state of a main drive system in an image forming apparatus.

<Prior Art and Its Disadvantages> Electrophotographic copying machines and the like have conventionally been provided with a main motor that interlocks and drives a photoreceptor document scanning device, a fixing roller, and the like. If an abnormality occurs in the main drive system including the main motor and the main motor locks up or stops rotating at the normal speed, there is a risk of serious damage to the system, such as deterioration of the photoreceptor.

Conventionally, in order to detect such abnormal conditions,
A slit disk and a photo ink club are installed in the main motor drive system, and abnormalities in the main drive system are detected by determining whether the rotation speed of this slit disk has reached a set speed. .

For this reason, a slit disk, a photo ink clubter, and a complicated circuit for controlling the same are required, which increases the cost.

<Object of the Invention> The object of the invention is to detect an abnormality in the main drive system (such as not rotating at the normal rotation speed) with a simple configuration without using the slit disk or photo ink acter as described above. An object of the present invention is to provide an abnormality detection device for an image forming apparatus.

<Configuration and Effects of the Invention> The present invention provides an image forming apparatus that includes a developing device incorporating a magnetic roller having a plurality of magnetic poles, and a main drive system that drives a photoreceptor and a document scanning device together with the magnetic roller. The present invention is characterized in that it includes a magnetic sensor provided near the roller, and an abnormality detection means that outputs an abnormality signal when the output signal of the magnetic sensor does not change for a certain period of time after the main drive system starts driving.

Electrostatic photocopiers and printers use a developer tank that stores toner and agitates the toner as a developing device.
It has a built-in magnetic roller that generates a magnetic brush to bring the toner into contact with the photoreceptor.

A plurality of magnetic poles are formed on the magnetic roller, and the plurality of magnetic poles rotate as the magnetic roller rotates. Therefore, with the above configuration, the magnetic sensor can detect the rotational state of the magnetic roller, and thereby can detect whether the main drive system is being driven normally.

This eliminates the need for an expensive slit disk as in the prior art, and can reduce costs accordingly. Further, since no space is required for providing the slit disk, it is possible to downsize the device.

<Embodiment> FIG. 2 is a diagram showing the structure of a copying machine to which this invention is applied. Reference numeral 19 denotes a document table, and 17 and 18 denote mirror units that scan the lower surface of the document table 19. The photosensitive drum 10 is controlled by these mirror units and other optical systems.
An image of the original is formed on the image. Various units necessary for the copying process are arranged around the photosensitive drum 10. 1
1 is a charger, 12 is a developing device, 13 is a transfer charger,
14 is a peeling charger, 15 is a cleaner unit, 16
is a static elimination charger.

The original scanning device comprising the mirror units 17 and 18 and the photosensitive drum 10 are rotated by a main motor (not shown), and a magnetic roller built into the developing device 12 is also rotationally driven by the main motor.

FIG. 1 is a diagram showing the structure of the developing device 12 shown in FIG. 2 in detail. 6 is a developer tank, and a magnetic roller 2 is provided inside the developer tank. The magnetic roller 2 includes magnetized magnets 3a, 3b, and 3c.

3d is fixed. The shaft 2a of the magnetic roller is connected to a main drive system using a main motor as a drive source, and rotates with the rotation of the main motor. A stirring roller 5 stirs toner and magnetic powder (not shown).

A sleeve 4 is provided around the magnetic roller,
The magnetic material forms a magnetic brush on the surface of the sleeve 4 along the lines of magnetic force. The sleeve 4 is fixed, and the magnetic brush ears move together with the rotation of the magnetic roller 2. As a result, toner adheres to the surface of the photosensitive drum 10 shown in FIG. 2, and development is performed.

1 is a magnetic sensor installed near the magnetic roller;
Built-in Hall element. As the magnetic roller 2 rotates, the resistance value of this Hall element changes.

FIG. 5 is a diagram showing the relationship between the drive signal of the main motor and the detection signal of the magnetic sensor. As is clear from the figure, the output signal of the magnetic sensor changes at a constant period t as the main motor rotates.

FIG. 3 is a block diagram of the control section of the copying machine. The overall control is performed by program processing by the CPU 20, and the control program is stored in the ROM 21 in advance.

The RAM 22 is a memory used as a working area when executing the program, and timers TMI, 7M2, etc. are also configured here as described later. 1 is a Hall element (magnetoresistive element), and 28 is a detection circuit that converts a change in the resistance value of the Hall element 1 into a change in voltage and outputs it as a signal at a logical level.

This detection circuit 28 and the Hall element 1 constitute a magnetic sensor H3. The CPU 20 reads the output signal of the magnetic sensor H3 via 1023.

The motor control circuit 25 drives or stops the main motor 24 under the control of the CPU. The key manual device 26 is an input device for various settings including a copy button. The display unit 27 displays information such as that the main drive system is in an abnormal state.

FIGS. 4(A) and 4(B) are flowcharts showing the processing procedure of the CPU.

First, when the power of the copying machine is turned on, the main motor (MM) is turned off and the heater (HL) of the fixing device is turned on to enter the warming-up mode, as shown in FIG. 4(A). When the temperature TX of the fixing device reaches the steady temperature Ta, this mode is ended, the main motor is turned on, and the timer TM1 is started (n14→n16), n
At 1B, it is determined whether the drive system by the main motor, that is, the main drive system is in an abnormal state. This routine is configured as a subroutine shown in FIG. 4(B).

As shown in FIG. 4(B), first, it is determined whether the value of the timer TM2 exceeds a predetermined time period β (n100). Now, considering the case where it has not been exceeded,
At n102, the output signal of the magnetic sensor H3 is determined. H
3 is at the "L" level, flag FF is set and the process returns to the main routine (n102-=n104).

If there is no abnormality as described above, initialization (idling cycle) of the photosensitive drum and document scanning device is started (n20).

This process is repeated until the timer TMI reaches the predetermined time α (n22-=n18).

If the main motor stops or the main drive system does not rotate at the regular rotation speed, the driving of the developing device is also stopped, so the output signal of the magnetic sensor H3 will not change at the regular cycle. As shown in FIG. 4(B), signal H3 is 1.
When the flag FF reaches the set state, the timer TM2 is reset and timing is started (n108-nllo).
After starting time measurement in step n100, the next time this subroutine is called, timer TM is started in step n100.
If the value of 2 has reached a value exceeding the constant value β, it is assumed that the magnetic roller of the developing device is not rotating at the normal rotation speed, and the process returns to step n24 in FIG. 4(A). As a result, the display section displays that the main drive system is in an abnormal state, the main motor and all other loads are turned off, and the process ends (n24-"n26).

In this way, the subroutine shown in Figure 4 (B) uses timer TM2 to measure the period from when the output signal of the magnetic sensor rises until the next rise, and detects an abnormality depending on whether the value exceeds a certain value β. do. As shown in Fig. 5, the period t of the output signal of the magnetic sensor is a constant value β
A value exceeding this value indicates that the number of rotations of the magnetic roller of the developing device has decreased, and it is thereby detected that the main drive system using the main motor is in an abnormal state.

As shown in Figure 4 (A), if no abnormal condition occurs during the idling cycle, the main motor is turned off after the idling cycle ends and the start of the copy cycle is waited (n2B-=n
30). If the copy button or the like is operated here, the main motor is turned on and an abnormal state is determined in the same manner as in step nl & above (n 30-n 32-n 3
4). If it is normal at this time, normal copying is performed by copy cycle control (n36). After copying is complete, turn off the main motor and wait for the next copy cycle (n38-n
40). If an abnormal state occurs during copy cycle control, an abnormality display will be displayed in the same way as above, and the entire load will be turned off (n34→n
24→n26).

As described above, by detecting a change in the output signal of the magnetic sensor provided near the magnetic roller built into the developing device, it is possible to detect the occurrence of an abnormal state in the main drive system. This can prevent serious defects in the system.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the structure of a developing device in a copying machine to which the present invention is applied, and FIG. 2 is a diagram showing the overall structure of the copying machine.
Figure 3 is a block diagram of the control section of the copying machine, Figure 4 (A)
, (B) is a flowchart showing the processing procedure of the CPU in the control section, and FIG. 5 is a diagram showing the relationship between the drive signal of the main motor and the detection signal of the magnetic sensor. 1-Hall element, 2-M1 roller, 3a, 3b, 3c, 3d-7 magnet, 12-developing device, H5-magnetic sensor.

Claims (1)

[Claims] (1) In an image forming apparatus having a developing device incorporating a magnetic roller having a plurality of magnetic poles, and a main drive system that drives a photoreceptor and a document scanning device together with the magnetic roller, a magnetic roller provided near the magnetic roller. An abnormality detection device for an image forming apparatus, comprising: a sensor; and abnormality detection means for outputting an abnormality signal when the output signal of the magnetic sensor does not change for a certain period of time after the main drive system starts driving.