JP2002331725A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus which electrically shuts off a laser without using a mechanical shut-off member and which does not apply a stress to the laser or the other electric component. SOLUTION: The image forming apparatus comprises an image signal modulator 205 for generating a modulation signal in response to image information, a laser drive means for driving the laser in response to the modulation signal, a door opening/closing sensing unit 200, a switch for opening/closing, a laser power source 204, and a power source shutting-off means for shutting off the laser power source supply. When the door is opened or the unit is drawn, the sensing unit 200 senses the state in which the door is previously opened or the unit is drawn, and disposed so that the switch is then opened. When the sensing unit 200 senses the door opening, the output of the modulator 205 is set to a GND level or a high impedance state. The power source shutting-off means is constituted to shut off the power to be supplied to the laser drive means, when the switch is opened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a laser beam printer, and more particularly, to an image forming apparatus related to a laser scanning device.

[0002]

2. Description of the Related Art In a conventional laser beam printer, a laser beam used for forming an image has a very high energy density despite being a very small spot. Is designed not to leak.

On the other hand, the optical path length of laser light has been shortened due to recent trends in miniaturization and cost reduction of apparatuses, and the necessity of mounting optical units and image forming units in the apparatus at high density has increased. I have.

[0004]

Therefore, as described above, when the inside of the apparatus is opened, there is no space for providing a mechanical blocking member between the optical unit and the image forming section. In other words, in order to secure a space for providing the blocking member between the optical unit and the image forming unit, it is necessary to increase the optical path length of the laser beam to secure a sufficient mechanical space. And the cost increases in the future.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and provides a means for reliably and electrically blocking a laser without using a mechanical blocking member. It is an object of the present invention to provide an image forming apparatus having a configuration that does not apply stress to the laser and other electric components.

[0006]

The present invention can solve the above-mentioned problems by providing the following constitution.

(1) An image forming apparatus for forming an image by scanning a laser beam modulated on the basis of image information, comprising: an image information modulating means for generating an image information modulation signal corresponding to the image information; Laser driving means for driving a laser in accordance with an information modulation signal; opening / closing detecting means for detecting the opening / closing state of a door of the image forming apparatus or the state of insertion / removal of a unit; A switch, a laser power supply to be supplied to the laser driving means, and a power cutoff means disposed between the laser power supply and the laser driving means to cut off the laser power supply to the laser driving means; When the unit is pulled out, the opening / closing detection means detects the state of the door being opened or the unit being pulled out first, and then the switch is opened. The detection means and the switch are arranged, and when the open / close detection means detects the opening of the door, the output of the image information modulation means is set to a GND level or a high impedance state, and when the switch is opened, the power cutoff means is the laser. An image forming apparatus, wherein power supplied to a driving unit is shut off.

(2) In the image forming apparatus as described in (1) above, the output of the image information modulating means is changed to a GND level or to a GND level after the opening / closing detecting means detects the opening / closing of the door of the image forming apparatus or the insertion / removal state of the unit. The time until the high impedance state is set to T1, and the power cutoff means cuts off the laser power supply to the laser drive means after the open / close detection means detects the opening / closing of the door of the image forming apparatus or the insertion / removal state of the unit. Time until T2, T
An image forming apparatus, wherein an inequality of 1 <T2 is satisfied.

(3) In the image forming apparatus according to the above (1) or (2), when the door is closed or the unit is inserted, the switch is closed first, and then the opening / closing detecting means is closed. Alternatively, the detection means and the switch are arranged to detect a state where the unit is inserted, and when the open / close detection means detects the door closing, the output of the image information modulation means is set to an output enabled state from a GND level or high impedance, and The image forming apparatus according to claim 1, wherein said power cutoff means supplies power to said laser driving means when said switch is closed.

(4) In the image forming apparatus described in (3), the time from when the switch is closed to when the laser power is supplied to the laser driving means is T3, and after the switch is closed, An image forming apparatus, wherein the time from when the output of the image information modulating means changes from a GND level or a high impedance state to an output enabled state is T4, and an inequality T3 <T4 is satisfied.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image forming apparatus according to the present invention will be described below.

FIG. 1 is a block diagram showing a schematic configuration of an image forming apparatus according to the present invention, FIG. 2 is a block diagram showing an example of a configuration of an electric laser cutoff unit in an embodiment, and FIG. FIG. 4 is a timing chart of each signal, and FIG.
8 is a timing chart when the door is closed in the embodiment.

This embodiment will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of an image forming apparatus provided with a laser drive circuit according to the present embodiment.

In FIG. 1, an image signal 1 sent from an external device such as an image scanner or a computer (not shown) is sent to an image writing timing control circuit 101.

An image writing timing control circuit 101 converts an image signal 2 of magenta (M), cyan (C), yellow (Y), and black (BK) into an ITOP which is a timing signal in the sub-scanning direction as shown in FIG. The laser drive control circuit 112 according to the timing of the signal (A in the figure) and the LSYNC signal (B in the figure) which is a timing signal in the main scanning direction.
To send to. The laser drive control circuit 112 uses the LSYNC signal and the image signal 2 to generate a laser lighting signal (L
As shown in FIG. The laser drive control circuit 112 responds to this Laser-ON signal,
The laser diode 100 is modulated and driven.

The laser light is reflected by the polygon mirror 103 rotating in the direction of the arrow shown in FIG. 1 when the polygon motor 106 is driven, fθ corrected by the f-θ lens 104, and scans the photosensitive drum 105. Thus, an electrostatic latent image is formed on the photosensitive drum 105. The BD sensor 107 is provided in the vicinity of the scanning start position of one line of the laser beam, detects the scanning of the line of the laser beam, and uses the image writing timing control circuit 101 to control the scanning start reference signal of each line of the same period as shown in FIG. An LPC signal (B in the figure) and an APC signal (Auto Pow) for performing a known laser APC
er Control signal, D) in the figure. La
The ser-ON signal is turned on for image formation (C-2 in the figure).
In addition, lighting for detecting the LSYNC signal is also performed (C-1 in the figure).

Around the photosensitive drum 105, magenta (M), cyan (C), yellow (Y), and black (BK) developing units (not shown) are provided. Three developing units alternately expose the photosensitive drum 105
, C, Y, and M formed on the photosensitive drum 105.
Develop with toner corresponding to the BK electrostatic latent image.

The recording paper 109 fed from a paper cassette (not shown) is wound around a transfer drum 108, and a toner image developed by a developing device is transferred. Transfer drum 108
A sensor 110 for generating an ITOP signal indicating the leading end position of the recording paper 109 on the transfer drum 108 is provided. The flag 111 fixed in the transfer drum 108 passes through the sensor 110 when the transfer drum 108 rotates. Thus, an ITOP signal (A in the figure) for each color as shown in FIG. 3 is created. The image writing position in the sub-scanning direction is determined based on the ITOP signal, and the image writing position in the main scanning direction is determined based on the LSYNC signal. Thus, M, C, Y,
After the four colors BK are sequentially transferred, the sheet is discharged through a fixing unit (not shown).

Next, a method of electrically shutting off the laser, which is a feature of this embodiment, will be described.

FIG. 2 shows an example of the configuration of the electric laser cutoff means. The door opening / closing detecting unit 200 includes a switch 201 and a photo sensor 202 including a light emitting and receiving element. The door opening / closing detection unit 200 is attached to all doors and units (not shown) that are accessed when opening the inside of the apparatus. When the door is opened, first, the light emitting element and the light receiving element of the photo sensor 202 are shut off. (Not shown) operates as described above, and then the switch 201 is opened (open).
It is arranged so that it becomes.

The switch 201 has one terminal connected to the + 24V power supply and the other terminal connected to the coil unit 203-1 of the relay 203.
It is connected to the. Also, the switch unit 2 of the relay 203
03-2 is connected to a laser power supply 204. When the door is closed, the coil unit 203-1 of the relay 203
Since the + 24V power is supplied to the switch unit 203,
-2 is closed, and when the door is opened, + 24V power is not supplied to the coil unit 203-1 of the relay 203, so the switch unit 203-2 is opened.

The laser drive control circuit 112 includes an image signal modulation section 205, a control signal generation section 206, and a laser drive circuit 20.
7. The image signal modulation unit 205 performs known pulse width modulation on the image signal 2 supplied from the image writing timing control circuit 101, and supplies the modulated image signal to the laser drive circuit 207. The control signal generation unit 206 generates a timing signal for performing laser APC based on the LSYNC signal supplied from the image writing timing control circuit 101 and supplies the timing signal to the laser drive circuit 207. Further, the image signal modulation unit 205 and the control signal generation unit 2
06 is supplied from the laser power supply 204. on the other hand,
The laser drive circuit 207 is connected to the switch unit 20 of the relay 203.
Since power is supplied from the laser power supply 204 via 3-2, when the door is opened, the switch 201 is opened (open).
The power supply to 7 is cut off. As a result, the laser light is forcibly cut off.

However, if the door is opened when the laser is turned on, such as during image formation, the light is forcibly turned off while the laser is turned on, giving stress to the laser diode 100. Furthermore,
When the door is opened, the power supply to the laser drive circuit 207 is cut off, but since the laser power is still supplied to the image signal modulation unit 205 and the control signal generation unit 206, a signal is supplied to the laser drive circuit 207. I will. That is, an electrical stress is applied to the laser drive circuit 207.

In the present invention, since the output enable signals of the image signal modulating unit 205 and the control signal generating unit 206 are connected to the output of the photo sensor 202 of the door open / close detecting unit 200, if the door is opened when the laser is turned on, the photo The output of the sensor 202 becomes L level, and the image signal modulating unit 20
5 and the output enable signal of the control signal generator 206 are disabled. That is, when the door is opened, the outputs of the image signal modulation unit 205 and the control signal generation unit 206 become L level (or high impedance state).

As described above, when the door is opened, the output of the photo sensor 202 becomes L and the switch 20 is turned off.
1 is open, the laser drive circuit 207
Therefore, the power supply input is interrupted after the control signal input to the L level (or high impedance state) becomes low, so that no electrical stress is applied to the laser drive circuit 207.

FIG. 4 shows this timing.

In FIG. 4, when the door is opened, the output of the photo sensor 202 goes low (401), that is, the output enable signal (EN signal) of the image signal modulation section 205 and the control signal generation section 206 goes low. Become. The image signal modulator 205 and the control signal generator 206 set the output (input of the laser drive circuit 207) to L level after T1 (402). The switch 201 is opened after T2 after the output of the photo sensor 202 becomes L level, and the voltage between the coil (203-1) of the relay 203 is + 24V.
To 0 V (403). Then, after T3, relay 2
03 is opened (open), the power supply to the laser drive circuit 207 is cut off (4).
04). Therefore, since the photosensor 202 and the switch 201 are mechanically arranged so that T1 <T2 + T3, power supply is performed after the input signal of the laser drive circuit 207 becomes L level (or high impedance state). The laser is shut off, and the laser can be turned off without giving an electrical stress to the laser diode 100 and the laser driving circuit 207.

Conversely, when the door is closed from the opened state, the photo sensor 202 detects that the door is closed after the switch 201 is closed.
After the laser power is supplied, signals from the image signal modulator 205 and the control signal generator 206 are output. That is, even when the door is opened and closed, the laser diode 10
0 or the laser drive circuit 207 is not electrically stressed.

FIG. 5 shows this timing.

In FIG. 5, when the door is closed, the switch 201 is opened and the coil (2
03-1) is changed from + 24V to 0V (50-1).
1). Then, after T4, the switch unit 20 of the relay 203
Since 3-2 is open, the laser drive circuit 2
07 is supplied (502).

After T5 after the voltage between the coils (203-1) of the relay 203 has changed from + 24V to 0V, the output of the photosensor 202 becomes H level (503). Then, after T6, the output enable signal (EN signal) of the image signal modulation unit 205 and the control signal generation unit 206 becomes H level. Therefore, since the photo sensor 202 and the switch 201 are mechanically arranged so that T4 <T5 + T6, a signal can be input after the power supply to the laser drive circuit 207 is started, so that the door is closed. Sometimes, no electrical stress is applied to the laser diode 100 or the laser drive circuit 207.

[0033]

As described above, since no mechanical blocking member is used, the size of the apparatus can be reduced, and the laser and other electric parts can be reliably electrically connected without applying any electric stress. Laser can be cut off,
This has the effect.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of an image forming apparatus according to the present invention.

FIG. 2 is a block diagram illustrating a configuration example of an electric laser cutoff unit according to the embodiment.

FIG. 3 is a timing chart of each signal of the image forming apparatus.

FIG. 4 is a timing chart of laser cutoff in the embodiment.

FIG. 5 is a timing chart when the door is closed in the embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 laser diode 101 image writing timing control circuit 103 polygon mirror 104 f-θ lens 105 photosensitive drum 106 polygon motor 107 BD sensor 107 108 transfer drum 109 recording paper 110 sensor 111 flag 112 laser drive control circuit 200 door open / close detection unit 201 switch 202 Photosensor 203 Relay 203-1 Coil section of relay 203 203-2 Switch section of relay 203 204 Laser power supply 205 Image signal modulation section 206 Control signal generation section 207 Laser drive circuit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 21/00 398 H04N 1/00 C 5C072 520 B41J 29/12 C H04N 1/00 3/00 D 1 / 113 H04N 1/04 104A F term (reference) 2C061 AP01 AQ06 AR01 AS02 BB02 BB17 CD01 CD16 HH01 HJ01 HV10 HV19 HV44 HV45 HV56 2C362 DA45 EA12 2H027 DA26 DA27 DA38 ED04 EE02 EF17 EJ17 ZA012BA13 DA17 AB49 AC04 AD02 5C072 AA03 CA06 HA02 XA05

Claims (4)

[Claims] 1. An image forming apparatus for forming an image by scanning a laser beam modulated based on image information, comprising: an image information modulating unit configured to generate an image information modulation signal according to the image information; Laser driving means for driving a laser according to a modulation signal; opening / closing detecting means for detecting the opening / closing state of a door of the image forming apparatus or the state of insertion / removal of a unit; A laser power supply to be supplied to the laser drive means; and a power supply cut-off means disposed between the laser power supply and the laser drive means to cut off the laser power supply to the laser drive means. When the switch is pulled out, the opening / closing detecting means detects the state of the door being opened or the unit being pulled out first, and then the switch is opened. The detection means and the switch are arranged, and when the opening / closing detection means detects the opening of the door, the output of the image information modulation means is set to a GND level or a high impedance state, and when the switch is opened, the power cutoff means is the laser. An image forming apparatus, wherein power supplied to a driving unit is cut off. 2. The image forming apparatus according to claim 1, wherein
The time from when the opening / closing detecting means detects the door opening / closing of the image forming apparatus or the insertion / removal state of the unit until the output of the image information modulating means is brought to the GND level or the high impedance state is T1, and the opening / closing detecting means is A time period from the detection of the opening / closing state of the door of the image forming apparatus or the insertion / removal state of the unit until the power cutoff means cuts off the laser power supply to the laser drive means is defined as T2, and the inequality T1 <T2 is satisfied. An image forming apparatus comprising: 3. The image forming apparatus according to claim 1, wherein when the door is closed or the unit is inserted, the switch is closed first, and then the opening / closing detecting means is closed or the unit is inserted. The detection means and the switch are arranged so as to detect a state in which the door is closed.
An image forming apparatus, wherein output is enabled from an ND level or high impedance, and the power supply shutoff means supplies power to the laser drive means when the switch is closed. 4. The image forming apparatus according to claim 3, wherein
The time from when the switch is closed to when the laser power is supplied to the laser driving means is T3, and the output of the image information modulating means is GN after the switch is closed.
An image forming apparatus, wherein a time period from the D level or the high impedance state to the output enabled state is T4, and an inequality T3 <T4 is satisfied.