JPH0566629A - Image forming device - Google Patents

Abstract

PURPOSE:To provide the image forming device where image density can be made thin and printing can be carried out with a small amount of developer when a test printing mode is selected. CONSTITUTION:In the image forming device forming an image on an outer periphery surface of a photosensitive body based on electrophotographic method by providing, a setting means 33 where selection between a normal printing mode and a test printing mode is carried out, and by providing an image density variation means 40 varying the image density on the photosensitive body by output of this setting means 33, when the test printing mode is set by the setting means 33, the image density on the photosensitive body is made thinner by the image density variation means 40, and thus, the running cost is saved by reducing the consumption quantity of the developer reducing the running cost, and also reducing bothersome replenishing frequency of the developer.

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 for forming an image on the outer periphery of a photoconductor based on an electrophotographic method.

[0002]

2. Description of the Related Art Conventionally, when a document or an image is input by a document input device such as a word processor, the layout of the document is determined by performing format setting. The width of the blank space on one page and the proofreading of the document can be confirmed on the display by setting the document input device to the layout mode, but it is easier to see on the document printed out for trial and there are few mistakes. .. Also, conventionally,
The pages to be printed and the number of prints can be set, but other printing conditions cannot be changed.

[0003]

If the test printing for calibration or the like is performed before the regular printing, the developer is consumed so much that the running cost is increased and the troublesome replenishment frequency of the developer is increased. There's a problem.

[0004]

According to the present invention, an image forming apparatus for forming an image on the outer periphery of a photosensitive member based on an electrophotographic method is provided with setting means for selecting a normal print mode and a test print mode. Image density changing means for changing the image density on the photoconductor by the output of the setting means is provided.

[0005]

When the test print mode is set by the setting means, the image density on the photoconductor can be made lighter by the image density changing means, so that the amount of developer consumed can be reduced.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. First, FIG. 3 shows the internal configuration of the laser printer. In the figure, reference numeral 1 denotes a housing, and a photosensitive member 2 is rotatably provided at the center of the housing 1. This photoconductor 2
A charging charger 3 for charging the photoconductor 2 and an exposure unit 4 for forming an electrostatic latent image by irradiating the charged portion of the photoconductor 2 with laser light based on image information around the periphery of the photoconductor 2.
A developing device 6 having a developing roller 5 for developing an electrostatic latent image on the photoconductor 2; a sheet 10 supplied from a sheet feeding cassette 7 by a sheet feeding roller 8 and a registration roller 9; A transfer charger 13 that transfers the developed image on the photoconductor 2 to the paper supplied from the conveyance roller 12 from the paper 11
A discharge lamp 14 for discharging the photoconductor 2 and a cleaning unit 15 for cleaning the photoconductor 2 are arranged. Further, the casing 1 is provided with a conveyor belt 16 that conveys the sheet 10 passing through the transfer charger 13 to a fixing roller 17, and the fixing roller 17 includes the press roller 1
8 is pressed.

As shown in FIG. 4, the exposure section 4 includes a laser light emitting element 19 which is turned on / off according to image information,
The rotary mirror 20 and the fθ lens 21 for scanning the laser light emitted from the laser light emitting element 19, and the rotary mirror 20.
The mirror 22 that reflects the laser light scanned from the photoconductor 2 to the photoconductor 2, the scanning start position sensor 23, the scanning end position sensor 24, and the rotary mirror 20 for these sensors 23 and 24.
And mirrors 25 and 26 that reflect the laser light from the.

Then, as shown in FIG. 1, the CPU 27
An RA having a ROM 28 in which a program for the CPU 27 to control the operation of each unit is written, an area for storing information for writing information for printing, and the like.
M29, character generator 30, interface 31 for taking in information from the outside, and I / O
The port 32 and the setting means 33 for selecting the normal print mode and the test print mode are connected on the bus line. Further, the I / O port 32 controls a driving device 34 for various sensors such as the scanning start position sensor 23 and the scanning end position sensor 24, a driving device 35 for various lamps, and a lighting operation of the static elimination lamp 14. Static elimination control circuit 36
A high voltage generator 37 for supplying a high voltage to the charging charger 3, a high voltage generator 38 for supplying a high voltage to the transfer charger 13, a motor for rotating the photoconductor 2 and a rotating mirror 20. Motor drive device 39 for driving various motors such as a motor, and this motor drive device 39
And an exposure power control circuit 40 for controlling the exposure power of the laser light emitting element 19
And are connected.

As shown in FIG. 2, the exposure power control circuit 40 includes a first operational amplifier 41, a second operational amplifier 42, and first, second, third, and fourth NPN-type operational amplifiers, respectively. It has transistors 42, 43, 44, and 45.
The negative input terminal of the first operational amplifier 41 is connected to one control terminal of the laser light emitting element 19, and the positive input terminal is connected to the + V power source. The output terminal of the first operational amplifier 41 is connected to the positive input terminal of the second operational amplifier 42 via the resistor 47, and the second operational amplifier 4
The second output terminal is connected to the base of the first transistor 43 via the resistor 48. The first transistor 43 has a collector connected to the other control terminal of the laser light emitting element 19 via a resistor 49, an emitter grounded, and a base connected to the collector of the second transistor 44. This second transistor 44
Has an emitter grounded, a base connected to a + V power source through resistors 50 and 51, and resistors 50 and 5
It is grounded through 2. Further, the exposure data DT is supplied to the base of the second transistor 44. The third transistor 45 has a collector connected to a + V power source via resistors 53 and 54 and an emitter grounded. The fourth transistor 46 has a collector connected to a + V power source via resistors 54 and 55,
The emitter is grounded. The resistors 53, 54, 55
Is connected to the second operational amplifier 42 via the resistor 56.
Connected to the negative input terminal of. The resistance value of the resistor 53 is set to a value larger than the resistance value of the resistor 54. In addition, the control signal SC is the third transistor 4
5 is supplied to the base of the fifth transistor via an inverter 57 and is supplied to the base of the fourth transistor 46 via inverters 58 and 59.

The operation of the exposure power control circuit 40 having such a configuration will be described with reference to the flow chart shown in FIG. At the time of printing, the setting means 33 sets the normal print mode or the test print mode. When the normal print mode is selected, the CPU 27 outputs the control signal SC at low level. This turns on the third transistor 45 and turns off the fourth transistor 46. In this state, the reference voltage supplied to the negative input terminal of the second operational amplifier 42 is determined by the voltage division of the resistor 53 and the resistor 54, so the level of the reference voltage is set relatively high. As a result, the first transistor 4
3 is deeply biased. Therefore, when the exposure data DT is supplied to the base of the first transistor 43, the laser light emitting element 19 is turned on, but the exposure power at this time becomes large.

When the test print mode is selected by the setting means 33, the control signal SC becomes high level, so that the third transistor 45 is turned off and the fourth transistor 46 is turned on. In this state, the reference voltage supplied to the negative input terminal of the second operational amplifier 42 is determined by the voltage division of the resistors 54 and 55,
The reference voltage is set relatively low. As a result, the first transistor 43 is biased shallowly, and when the exposure data DT is supplied to the base of the first transistor 43 in this state, the laser light emitting element 19 is turned on, but the exposure power at this time is small. Become.

As described above, when the test print mode is selected, the exposure power of the laser light emitting element 19 can be made smaller than when the normal print mode is selected. The concentration can be reduced,
As a result, the amount of developer consumed can be reduced. That is, the exposure power control circuit 40 functions as an image density changing unit that changes the image density of the photoconductor 2.

Next, a second embodiment of the present invention will be described with reference to FIG. The same parts as those in the above-mentioned embodiment are designated by the same reference numerals and the description thereof is omitted (the same applies hereinafter). The image density changing means 60 for changing the image density of the photoreceptor 2 in this embodiment has different potentials -Vb (-525V) and -Vbo (-250).
V) and a switch 64 having a movable contact 63 for selectively connecting two power sources 61, 62 having V) to the developing roller 5, and a switch 64 depending on the normal print mode or the test print mode set by the setting means 33. And a control device 65 that outputs a switching signal CHNG. This control device 65 is C
PU66, ROM67 where the program was written,
It also has a RAM 68 in which variable data is written, and also has a function of controlling the operation of the entire laser printer including the operation of the motor 66 for driving the photoconductor 2 and the laser light emitting element 19.

In such a configuration, when the photosensitive member 2 is driven clockwise and a voltage is applied to the charging charger 3, the CPU 66 causes the switch 64 to be L or H depending on the mode selected by the setting means 33. Output the switching signal CHNG. Switch 6 when the test print mode is selected
4 is an H switching signal CHNG output from the controller 65
Thus, the power source 62 of -Vbo (-250V) is applied to the developing roller 5. When the normal print mode is selected, the switch 64 outputs the L switching signal CH output from the controller 65.
The power source 61 of -Vb (-525V) is set to the photoconductor 5 by NG.
Connect to. The developing roller 5 supplies a small amount of developer to the photoconductor 2 when a bias voltage of -Vbo is applied to reduce the image density and develop. When a bias voltage of -Vb is applied, a relatively large amount of developer is supplied to the photoconductor 2 to increase the image density and develop.

As described above, when the test print mode is selected, the developing bias applied to the developing roller 5 is lowered to reduce the power consumption and the consumption amount of the developer can be reduced. The running cost can be reduced and the frequency of troublesome developer replenishment can be reduced.

Further, a third embodiment of the present invention will be described with reference to FIGS. 7 and 8. The image density changing unit 69 in the present invention changes the time for which the current is output from the drive circuit 70 according to the test print mode or the normal print mode, and the current output from the drive circuit 70 is passed through the buffer 71 to the laser light emitting element. It is applied to 19.

That is, when the normal print mode is selected, as shown in FIG. 8A, the energization time in one cycle is lengthened to form an electrostatic latent image on the photoconductor 2 and the test print mode is set. When selected, as shown in FIG.
The electrification time in one cycle is shortened to form an electrostatic latent image on the photoconductor 2. In this case, as compared with the case of the normal printing mode, the spot diameter of the laser light emitted from the laser light emitting element 19 to the photoconductor 2 in the main scanning direction can be made smaller. In other words, the pixel density per unit area of the photoconductor 2 can be made coarse and the image density can be made thin. Thereby, thin development can be performed.

When the test print mode is selected,
By thinning out the pixels of the electrostatic latent image formed on the photoconductor 2 to make the pixel density rough, it is possible to reduce the amount of developer consumed. In this case, a method of thinning out pixels in either the main scanning direction or the sub-scanning direction or thinning out pixels in both the main scanning direction and the sub-scanning direction can be considered.

[0019]

According to the present invention, in an image forming apparatus for forming an image on the outer periphery of a photoconductor based on an electrophotographic method, a setting means for selecting a normal print mode or a test print mode is provided, and the output of this setting means. Since the image density changing means for changing the image density on the photoconductor is provided, the image density on the photoconductor can be reduced by the image density changing means when the test print mode is set by the setting means. As a result, the amount of developer consumed can be reduced, running costs can be reduced, and the frequency of troublesome developer replenishment can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electronic circuit according to a first embodiment of the present invention.

FIG. 2 is an electronic circuit diagram of the exposure power drive circuit.

FIG. 3 is a front view showing the internal structure of the laser printer.

FIG. 4 is a perspective view of the exposure unit.

FIG. 5 is a flowchart showing an output control operation for the laser light emitting element.

FIG. 6 is a front view with a part in cross section according to the second embodiment of the present invention.

FIG. 7 is a block diagram showing an image density changing unit according to a third embodiment of the present invention.

FIG. 8 is a timing chart showing changes in energization time of the laser light emitting element.

[Explanation of symbols]

 2 photoconductor 33 setting means 40 image density changing means 60 image density changing means 69 image density changing means

Claims (1)

[Claims] 1. An image forming apparatus for forming an image on the outer periphery of a photoconductor based on an electrophotographic method, comprising setting means for selecting a normal print mode or a test print mode, and the photoconductor is output by the setting means. An image forming apparatus comprising an image density changing unit for changing the image density.