JPH0195070A - Image forming device - Google Patents

Abstract

PURPOSE:To control an image density without fogging variations on power loss, by controlling the on-time of an LED element according to an image density. CONSTITUTION:An LED head 28 is connected to a stabilizer power supply 111. An image data output section 112, controlled by a PU, outputs image data DATA based on an image data, a latch pulse LCH to control the LED head 28, and a constant shift clock SC. One-shot multi vibrator 113 generates, every time a latch pulse LCH is input to receive it, a strobe signal ST of which pulse width is determined by a density controlling variable resistor 114. The strobe signal ST is input to the head 28 to act as an on-time control signal so as to vary an image density only with fogging kept constant.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Industrial Application Field The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that selectively lights up arbitrary LED elements of an LED array according to print data to form an image. .

(B) Prior Art Generally, image density adjustment is often performed by making the developing bias variable.

In addition, especially in an image forming apparatus using an LED array as a light source, the image density can be adjusted by changing the current value of the LED element, as disclosed in, for example, Japanese Patent Laid-Open No. 59-202879. It is.

(c) Problems to be Solved by the Invention In the method in which the developing bias is variable, the density changes not only in the image area but also in the non-image area, so-called ground blur.
Even in JP 9-202879, there is a problem in that the power loss due to the current limiting resistor is large.

The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide an image forming apparatus that can adjust image density without causing a change in ground force blur or power loss.

(d) Means for Solving the Problems The present invention provides a photoreceptor, a plurality of LED elements for illuminating two selections each time a request is made to irradiate exposure light to the surface-printing photoreceptor, This image forming apparatus is characterized by comprising an image density adjusting means for adjusting the image density, and a lighting control means for controlling the lighting time of the LED element based on the value of the image density adjusting means.

(e) The lighting time of the LED element is controlled by the lighting control means according to the value of the action concentration adjusting means. For example, when the concentration is set high, the lighting time is lengthened, and conversely, when the concentration is set low. In some cases, the lighting time is controlled to shorten the lighting time. That is, by controlling the lighting time, the size of the tod in the sub-scanning direction (the rotational direction of the drum) is changed, and the density can be adjusted.

Kube) Example FIG. 2 is an illustrative cross-sectional view showing one embodiment of the present invention.

The present invention will be described below as being applied to an image forming apparatus, but it is understood that the present invention can also be applied to other image forming apparatuses other than printers, such as multifunction printers, facsimile machines, etc. Let me point this out in advance.

0 main bodies (12) including main bodies (12)
A cover (14) and a cover (16), which are partially cut out at the center, are provided on the top of the cover so as to be flush with each other. The cover (14) is
It is fixed to the main body (12) with screws. Cover (16
) is provided so that it can be opened upward about the rotation shaft (18) when toner is replenished.

A paper feed section (22) is formed on one end side of the main body (12) to removably attach a paper feed cassette (20).
On the other end side, a paper discharge section (24) is formed for discharging the paper that has undergone the standardization process.

Almost in the center of the main body (12), there is a mark in the direction of the arrow (clockwise).
The photosensitive drum (its driving mechanism is not shown) rotates to
26) is placed. Amorphous selenium is used as the photoreceptor material of this photoreceptor drum (26).

A light emitting diode (L
ED) head (28) is provided. LED head (2
8) includes, for example, a red element with an emission wavelength of -660 nm, and includes an LED head provided in parallel along the length direction of the photoreceptor drum (26). moreover,
A short focal length lens such as a Cellhox lens is inserted between the LED head and the photosensitive drum (26). Accordingly, the LED head (28) selectively drives the LED components in accordance with the provided image data;
The light from the LED element is focused by a lens system and irradiated onto the surface of the photoreceptor drum (26).

A charging roller I'l is provided on the current side of the photoreceptor drum (26) in the rotation direction of the photoreceptor drum (26) than the LED head (28) for uniformly positively charging the photoreceptor drum (26), for example, to approximately 600 volts. (30) is fixedly provided.

After being positively charged by this IT Flotron (30), when light is irradiated from the LED head (28), an electrostatic latent image corresponding to the DC data is formed on the surface of the photoreceptor drum (26). .

A developing device 32) for developing the electrostatic latent image with toner is provided downstream of the LED head (28). This developing device! A developer consisting of a mixture of toner and Kirlia is stored in (32). This developer is transferred toward the photoreceptor drum (26) by the magnet roller (34).

At this time, the photosensitive drum (
26), a magnetic brush or spike of developer is formed. This head is the photoreceptor drum (26)
By contacting the electrostatic latent image formed by the positive charges, the negatively charged toner is attracted to the electrostatic latent image formed by the positive charges.

In this way, the electrostatic latent image formed on the photoreceptor drum (26) is transferred to the developing device! (32) is developed as a toner image.

Transfer paper (36) is placed in 82 layers in a paper feed cassette (20) that is removably attached to one end of the main body (12). A support plate (38) for holding the transfer paper (36) thereon is provided at the bottom of the paper feed cassette (20) so as to be swingable in the vertical direction. Support plate (38
) is formed with an opening (40). This opening (
40) is inserted above a push-up lever (42) whose base end is swingably attached to the internal part of the main body (12). In connection with this push-up lever (42), there is a support lever.

A spring (not shown) is provided to urge the support plate (38) to rotate clockwise.The support plate (38) is pushed upward by the push-up lever (42).

Therefore, the transfer paper (36) stacked in the paper feed cassette (20) is pushed up by the push-up lever (42), and the uppermost transfer paper (36) is pushed up by the paper feed roller (42).
4) comes into contact with and is taken in. There is a paper feed cassette (20) in the part corresponding to the tip of the fully installed paper feed cassette (
A paper size detector (46) is provided for detecting the size of the transfer paper (36) stored in connection with the transfer paper (20).

Behind the paper feed roller (44), there is a register roller (44).
8) is provided. The transfer paper (36) fed from the paper feed cassette (20) is temporarily stopped by this register roller (48), and is fed in the direction of the photosensitive drum (26) in synchronization with the exposure by the LED head (28). be done. Near the circumferential side of the photoreceptor drum (26), at a position where the transfer paper (36) is supplied from the register roller (48), there is a
Developing equipment! A transfer flotron (50) is provided to transfer the toner image developed by (32) onto transfer paper (36). Integrally with this transcription corotron (50),
A separation flotron (52) is provided.

This separation Flotron (52) neutralizes the charge on the transfer paper (36), which is attracted by the residual charge, by applying an alternating current discharge to the photoreceptor drum (26).
It peels off from the surface.

A vacuum conveyor (54) for conveying the transfer paper (36) onto which the toner image has been transferred is provided downstream of the separation flotron (52). This vacuum conveyor (54) transfers the transfer paper (36) to the fixing device (56).
It is transported in the direction of. The fixing device (56) includes a heating roller (58) with a built-in heater and a heating roller 2 (
The pressure roller (60) is pressed against the roller (58). The transfer paper (36) on which the toner image has been transferred is inserted between the heating roller (58) and the pressure roller (60), and is heated and pressurized to fix the toner image. A paper discharge roller (62) for discharging the fixed transfer paper (36) to the outside is provided on the downstream side of the fixing device (56).

A cleaning device (64) is provided above the vacuum conveyor (54) and near the circumferential side of the photoreceptor drum (26). This cleaning device 64
) is not transferred to the transfer paper (36) and remains on the photosensitive drum (2).
6) Removes toner remaining on the surface. This cleaning outfit! (64) has a photosensitive drum (26
) for scraping off residual toner on the blade (66) and a screw conveyor (68) for conveying the toner scraped off by the blade (66) to a waste toner container.
) is included.

An erase lamp (70) is provided upstream of the cleaning device (64) to remove residual charges on the surface of the photoreceptor drum (26) from which residual toner has been removed. This erase lamp (70) uses blue light 1. which causes less light fatigue on the photoreceptor drum (26) but can completely remove residual charges. For example, a fluorescent glow lamp is used which generates a light beam with a wavelength λ of 1450 nm.

A main motor (72) for driving the photosensitive drum (26), the magnet roller (34) of the developing device (32), etc. is provided above the fixing device (56).

The photosensitive drum (26) and the magnet roller (34) are
It can be driven by a main motor (72) through a belt or chain.

At the top of the main motor (2), there is a control box (7).
4) is provided. Inside this control box (74),
A control section is provided to control the overall operation of the printer. Further, an operation panel can be arranged on the control box (74).

FIG. 3 is a block diagram showing an example of the control system of this embodiment. This printer can be controlled by the CPU (100), and this CPU (100) has a pass line (
101) to the I10 port (102).

A print request signal is applied to the input of the I10 baud (102) from a host machine, such as a word processor or a personal computer, which uses such an image forming apparatus as an output device. (2) An LED head (28) is connected to the output of the 10 boat (102). This LE
The D head (28) is supplied with image data DATA from a host machine such as a word processor. The LED head (28) is provided with a shift blocker SC. L
The 0 image data DATA to which the strobe signal ST is applied to the ED head (28) is taken into the LED head (28) in a bit tlL'e manner by the shift clock SC. That is, the shift clock SC causes a shift register in the LED head (28) to be shifted, and thereby the serial print data is converted to image data for one row, that is, one column of I and ED elements. When one line of zero image data DATA is captured, the LED head <28) reads image data D.
Selective lighting of one row of LED elements corresponding to ATA is performed. Control of this lighting time will be described in detail later. While one line is being printed, image data DATA for the next line to be printed is taken into the LED head (28) by the shift clock SC. By sequentially lighting up the LED elements for each row in this way, the LED head (
28) exposes the photosensitive drum (26) (FIG. 2).

FIG. 1 is a block diagram showing the connection state of the LED head (28). Funecta (11
0) to the stabilizing voltage tyX (111).

Referring to FIG. 4, the LED head (28) includes m LEDs arranged regularly.

and m driver chips IC, to IC, for controlling the power supplied to these LED arrays.

FIG. 5 is a circuit diagram for explaining the internal circuit configuration of the LED head. In FIG. 5, m LED arrays D
A, ~DA, each have n LED elements D
, ~D +-, -(D 1+ ~D, ,) are included. The LED arrays D A l to DA each include n LED elements D, to D1 . In order to control 0m driver chips IC, ~IC, to which m driver chips IC, ~IC, can be connected, n driver elements T I correspond to n LED elements, respectively. I ``”' T l m +...(T
1 to T, , ) are included. In the following description, for the sake of simplicity, the first LED array D A + and its corresponding driver chip IC+ will be described on behalf of the others.

A 7-bit shift register Sll~ having bits corresponding to each driver element TII''Tra
S1m converts serially input printing data into parallel data, and latches Lll to L1m temporarily store the contents of the bits of the corresponding shift registers S and S1m. AND gates G, ~G1m are LED elements D,, #
A gate that determines the lighting period of D Im, and a driver element T ll at the output terminal of each of these gates CII-G 1m.
” T I- (consisting of switching transistors, for example) are connected to each other, and further connected to the LED element D ++4 via current limiting resistors R0 to Rl++.
D,, can be connected.

In this way, these shift registers SII to S41
．． Latches LL1~°L0. Switch elements Tll to T1.
and current limiting resistors R1 to R, y can be configured as one driver chip IC.

In addition, in the following explanation, the L of this LED head (28)
The explanation will be given assuming that the number of ED elements is, for example, 2.048. The maximum output of the stabilized power source (111) is sufficient to light up all 2.048 elements, and this stabilized power source (10) has the following:
For example, a three-terminal regular rake is used.

The image data output section (112) is the CP shown in FIG.
U (100), as shown in FIG. 6, image data DATA and LED according to print data
It outputs a latch pulse LCH and a constant shift clock SC for controlling the head (28).

Further, (113) is a one-shot multi (lighting control means) to which the latch pulse LCH can be inputted, and each time the latch pulse LCH is applied, the density adjustment means (variable resistor)
A strobe signal ST whose pulse width is determined by (114) is generated. Note that the pulse width T of this strobe signal is expressed as Tl-KCR (K is a constant).

Such a strobe signal ST is shown in FIG.

The strobe signal ST is input to the LED head (2B) and becomes a control signal for controlling the lighting time of the LED element.

In the case of reversal development, the relationship between the exposure amount of the LED element and the image density is as shown in FIG. 8, and only the image density can be varied while the ground force blur remains constant.

(G) Effects of the Invention As is clear from the above description, since the present invention is provided with a lighting control means that controls the lighting time of the LED element based on the value of the image density adjustment means, changes in ground force blur can be prevented. Image density can be adjusted without power loss.

[Brief explanation of the drawing]

All drawings relate to embodiments of the present invention, and FIG. 1 shows an LED.
Figure 2 is a cross-sectional diagram of the printer, Figure 3 is a block diagram of the control system, Figure 4 is a perspective view of the LED head, and Figure 51iA is for explaining the internal configuration of the LED head. 6 is a timing diagram showing the waveform of the pulse output from the image data output section,
FIG. 7 is a timing diagram showing the waveform of a strobe signal that can be output from the lighting control means, and FIG. 8 is a diagram showing the relationship between exposure amount and density. (26)...Photoreceptor, (28)...LED head,
(100)...CPU, (111)...Stabilized power supply, (112)...Image data output unit, (113)
...Lighting control means, (114)...Concentration i14wJ
Means, <DA,) ~ (DA,)... LED array, (
D,,)~(D,,)...LED element.

Claims (1)

[Scope of Claims] 1. A photoconductor, a plurality of LED elements that are selectively turned on to irradiate the photoconductor with exposure light every time there is a print request, and image density adjustment means that adjusts image density; An image forming apparatus comprising: lighting control means for controlling the lighting time of the LED element based on the value of the image density adjusting means. 2. The image forming apparatus according to claim 1, wherein the image density adjusting means is provided on an operation panel.