JPS60123874A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent laser exposing during maintenance and prolong the life of a laser element by stopping a laser driving signal by opening a door switch, and turning off a main switch once a scanner enters abnormal operation. CONSTITUTION:When the door switch 3 is opened, a power source 4 for driving an actuator and applying a voltage to a photosensitive body is turned off and the laser driving signal applied from a laser driving signal control circuit 7 to a laser driver 9 is cut off to prevent the exposure of a laser. On the other hand, a control circuit 6, scanner driver 8, etc., are powered on by a power source 5, so the door switch is closed to perform copying operation. When a signal READY goes down to L owing to abnormal rotation of a scanner motor 20, the main switch 2 is turned off. Consequently, the concentration of energy on a specific position is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an image forming apparatus such as a laser beam printer.

[Prior art] Laser beam printers use semiconductor lasers or He-Ne
A light emitting source such as a laser beam is used to scan a fixed width by reflecting it off a polygonal mirror of a polygon scanner, and the scanning light is irradiated onto a photosensitive drum.

The photosensitive drum uses an electrophotographic process, etc., and a charger, developer, cleaner, etc. are placed around the drum.
An image is formed using toner powder by changing the surface potential of the exposed area and the unexposed area, and the image is transferred to plain paper and printed.

Conventionally, this type of device often uses laser light. Whether it is a semiconductor laser or a He-Ne laser, the laser light has good focusing and straight propagation properties, and when exposing the photoreceptor L, the spot size can be reduced, and the light density can be increased. This is because it becomes possible to increase the height. Furthermore, if the semiconductor laser is used, the ON10FF of the laser lighting can be performed using a gate control signal, and if the laser is a laser, the ON10FF of the light source can be easily turned on using an optical modulator.

Therefore, printers using these laser beams are also collectively referred to as laser beam printers. Such image forming apparatuses often use cut paper of A size series such as A4 size and A3 size, B size series, and overseas series. The operation of taking out one sheet of paper from the paper cassette and feeding it according to the transfer process, transferring the image formed by the toner on the photoreceptor to the paper, and then guiding it to the second fixing unit to fix the transferred toner on the paper. This is done while transporting the paper. While transporting cut paper like this,
Since the toner image is transferred, errors in conveyance may occur at the joints of the conveyance section or at the paper feed section. In addition, this problem is more likely to occur if poor quality or deformed paper is sent. Furthermore, the high-voltage charger placed around the photoreceptor may be easily contaminated due to toner powder and paper powder flying around inside the machine. In case of such a symptom, the image forming apparatus as described in the present invention is usually not opened by the user or service personnel due to transportation error (hereinafter referred to as jam) or cleaning (hereinafter referred to as maintenance). It is designed with a mechanical structure in which the front door opens to facilitate maintenance such as removing paper jams that do not feed properly and cleaning the area around the charger. Because of this structure, there is a risk that the laser beam may hit the hands of the poet who is performing maintenance with the front door open, or that the laser beam may reflect on metal objects such as tools inserted from the outside and irradiate it to the outside of the machine. there were.

Therefore, for such cases, a method has been considered to mechanically install a shutter in front of the laser light source to shut off the laser beam when the front door is opened, but the position of the shutter depends on the optical arrangement as well. This has the disadvantage that the mounting position is limited because of the need to take this into consideration.

Furthermore, as an electrical method, attempts have been made to provide a switch that turns off according to the movement of the front door, control the laser drive power supply, and cut off the laser light. In this method, since the power is turned ON10F, the surge voltage at that time and the power ON10F
There was a drawback that the lifetime of the laser was shortened due to the unstable level caused by F. Furthermore, in order to avoid this disadvantage, the power supply is 0N10FF, and the laser drive signal is 0N10FF.
There is a method of protection using a circuit. However, this method has the disadvantage that when the ON10 FF circuit malfunctions, the laser beam is emitted and then goes out, making it less effective as a safety device.

[Objective] One object of the present invention is to provide an image forming apparatus that has a safe protection function without shortening the laser life.

[Example] FIG. 1 shows an example of the present invention. l is the input commercial power supply (
2 is the main switch (S W ), which is the AC switch that the user turns on when operating the machine.
This is an input 0N10F'F switch. This switch 2
The contacts that connect and disconnect the commercial power supply AC are mechanically operated by the user's operation, but at the same time, like a normal relay switch, a breaker can be turned off by supplying power from an external source. It's a switch.

Door switch 3 is a switch that operates when a user or service person opens the front door. This door switch 3 is not limited to the front door, but can be provided at a part that is opened when inspecting the inside of the machine, and it is of course also possible to connect a similar type of switch in series to the switch 3. Power source 4 is DC 24
This power source 4 is used as a high-voltage power source to drive actuators such as a solenoid and a DC motor inside the printer and to apply it to the photoreceptor for electrostatic processes. Therefore, opening the door switch 3 turns off the power supply 4, so even if the user opens the front door and touches the inside, the machine will not operate and cause injury, and furthermore, there will be no risk of electric shock from high-voltage parts. .

The power supply 5 supplies a DC voltage of +5V to the control circuit 6, laser drive signal control circuit 7, etc., laser driver 9, and scanner driver 88.
, -5V, and 24V are supplied to each. The voltage t5 is constantly operating and supplying an output voltage at the same time as the main switch 2 is turned on, and continues to operate as long as the main switch 2 is on, regardless of the ON10FF of the door switch 3.

The scanner motor 20 is composed of a DC motor and is controlled to rotate at a constant rate. A polygon mirror 21 is attached to the motor shaft, and the anticonductor laser beam is configured to strike this mirror 21 and further expose the photoreceptor. Therefore, the reflected light can operate the photosensitive drum under certain conditions. A detector FG 22 detects the rotational speed to keep the motor rotational speed constant, and is constructed using a photointerrupter or the like to extract the rotational speed as a pulse period.

The scanner motor driver 8 is a driver unit for controlling the scanner motor 20 to rotate at a constant rate.
LL (phased lock loop) control is performed. That is, the negative frequency phase from the detector FG22 is detected by the rotational phase detection circuit 8-1, and compared with the reference frequency aFR of the reference frequency oscillator 8-2, which is provided through a necessary frequency divider, by the phase comparator 8-3. The pulse waveform of the phase difference corresponding to this comparison value is filtered through a low-pass filter 8-4.
After converting it to DC and amplifying it with an amplifier (AMP) 8-5,
is applied to the scanner motor 20.

Therefore, the drive voltage increases until the phase difference disappears, and the rotational speed of the motor increases. Thereafter, the output of the AMP 8-5 is applied to the scanner motor 20 so that the reference frequency is maintained, and the constant rotation corresponding to the reference frequency is controlled with high precision. Further, the rotational phase detection circuit 8-1 is also a circuit that detects that the rotational speed of the scanner motor 20 has reached the target rotational speed, and outputs a READY signal to the control circuit 6 if the rotational speed is normal.

The drive signal control circuit 7 turns on the video signal, which is an image signal.
The video signal output to the laser driver 9 is the laser ON10F circuit from the control circuit 6.
Controlled by F output.

The laser driver 9 is a drive circuit that applies a constant current to the anticonductor laser and causes it to emit light with a constant power and a constant wavelength. The control circuit 6 receives READY input signals from the door switch 3 and the rotational phase detection circuit 8-1, and performs a logical operation to form output signals for turning off the laser and turning off the main switch 2.

An embodiment of the present invention applied to the laser beam printer configured as described above will be described in more detail with reference to the timing chart of FIG.

When the door switch 3 is closed normally, 24V from the power supply 4 is output and the door switch signal is "'H#".
level, and the laser ON signal from the control circuit 6 is at °
Since the level is high, the laser light emitting element can be driven whenever the video signal is received. When the door switch 3 is opened, the power @4 is turned off and the door switch signal becomes "L". Upon receiving this signal, the laser ON signal goes to the "°L°" level, and the laser drive signal applied to the relay laser driver 8 is completely turned off, so that the laser light emitting element no longer emits light. Therefore, even if the user or service person inspects the inside of the machine, exposure to laser light is prevented, thereby realizing safety protection for the user or service person.

The above protection state is when the door switch 3 is operating normally, the logic of the drive signal control circuit 7 and the control circuit 6 is operating perfectly, and the scanner motor is rotating normally. Considering the circumstances, it is possible that one of them may not work properly. For example, even if the drive signal control circuit 7 malfunctions and the laser drive signal is no longer output, if the scanner motor 20 is rotating normally, the laser light will be manipulated and the laser power will remain at a constant spot. There is no car that concentrates energy, so it works on the safe side, but if the scanner motor 20 rotates slowly or stops, energy will be concentrated in one point, which is very dangerous.

For such a case, the control circuit 6 performs a READY check to determine whether the aforementioned scanner motor 20 is rotating normally.
When the signal is received and the READY signal becomes "L", it outputs the main switch OFF signal, cuts off the AC input, completely turns off the power to the machine, and cuts off the laser light emission.This is used for this purpose. Persons will no longer be exposed to laser light.

FIG. 3 shows an example of a circuit configuration for realizing the timing chart of FIG. 2, which is composed of a logic circuit. Figure 3 (
a) is a laser control circuit, and an AND logic circuit 30 inputs a video signal and a door switch OFF (or laser
N) signal, the output laser drive signal is gated by the door switch OFF signal, and when the door switch 3 is open, the laser drive signal is stopped. Therefore, no laser light is emitted.

In addition, FIG. 3(b) shows that the READY signal is “H” or “L”.
Turn on breaker 3W2 in response to Pa.

FIG. 3 is a detailed circuit diagram of a part of the control circuit that is turned off.

The READY signal is connected to the inverting input terminal of the driver 32, so when the READY signal transitions from “H” to
The current flows to switch 2, which opens breaker switch 2. Therefore, when the rotational phase detection circuit 8-1 detects abnormal rotation (rotation stoppage, speed reduction) of the blade canner motor 20, the READY
The signal transitions to °'L power level and the breaker switch (
24V is driven to the main switch 2 through the resistor R1 of the breaker 5W2, and the AC input is completely cut off. Although not specifically stated in this embodiment, when the power is turned on, the rotation of the scanner motor does not immediately reach a predetermined rotation, so the READY signal is at L'°. As a result, the power supply may be turned on and off, so the breaker 5W2 is configured to stop driving for a certain period of time after the power is turned on.

Although the control circuit described in detail below is constructed from a logic circuit (an example is not shown), it is obvious that it may be implemented using a microprocessor. It is obvious that sequence control can be performed freely by using a microprocessor, and it can also be used in conjunction with an operation to immediately cut off the optical path of the laser beam to protect the photoreceptor when READY becomes low. It also becomes easier to do.

[Effects] As described above, according to the present invention, when the door switch is opened, the power supply of the laser driver is turned 0N10FF, thereby eliminating the need to shorten the life of the laser element. Furthermore, since the breaker 5W is not turned off at the same time as the door switch is opened, the scanner motor continues to rotate, and there is no rise time when the door is closed again. Furthermore, even if an abnormality occurs in the laser drive circuit, the condition of the scanner is constantly monitored, so there is an advantage that maintenance of the machine can be carried out with peace of mind without being exposed to laser radiation.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a timing chart showing the operation of the embodiment shown in FIG. Figure 3 is an example of a logic circuit that realizes the timing chart in Figure 2, and Figure 3 (a) shows the laser drive signal turned on.
, and FIG. 3(b) is a circuit diagram showing an example of a circuit that executes the logical operation of turning the breaker switch ON and OFF.

Claims (2)

[Claims] (1) A detection means for detecting a specific state of an image forming apparatus that has a light emitting source and forms an image on a photoreceptor by scanning light from the light emitting source with a scanning means; a control means for cutting off light emission from the light emitting source when a specific state is detected, and a monitoring means for monitoring a scanning state of the scanning means, and cutting off power to the image forming apparatus when the monitoring means determines a specific state. An image forming device characterized by: (2) The image forming apparatus according to claim 1, wherein the detection means is a door switch.