JPH02286570A - Image formation device - Google Patents

Abstract

PURPOSE:To keep a lateral printing position constant, and prevent beforehand the formation of a defective image by detecting the length of a sheet material in both transfer and vertical directions on the basis of the shft amount of a transfer restriction guide upon detection of the side end of the sheet material. CONSTITUTION:When a transfer sheet 9 is inserted in transfer guides 1-a and 1-b, a closing operation starts. In this case, a ..D-cut roller 8 stops at a position for releasing the transfer sheet 9. Furthermore, the closing operation continues until micro switches 2-a and 2-b detects the edge of the sheet 9. As a base 10 is curved in a transfer direction, the sheet 9 is free from deflection and both edges thereof are caught with the micro switches 2-a and 2-b. During the aforesaid operation, a stepping motor 4 is turned in an arrow A direction and the excited pulse number of a PLMCNT signal up to the detection of both edges of the sheet 9 is counted. Upon completion of the closing operation, a sheet size in a transverse direction is calculated from the number of pulses.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus equipped with a conveyed paper size detection device.

[Prior Art] Conventionally, image forming apparatuses such as laser beam printers control image formation by determining various constants for image formation based on a standardized paper size. For example, a frame indicating paper size information is provided in a paper feed cassette determined for each paper size, and the device body reads the frame to obtain the paper size information of the paper being fed, and then sets the image width. Performs image formation control such as

In addition, when paper of irregular size is fed such as manual paper feeding, various constants are determined based on the maximum size that can form an image,
Perform image formation.

[The problem that the invention is trying to solve, however,
In the above conventional example, when paper of an irregular shape is fed, or when paper is fed with a conveyance deviation in the direction perpendicular to the conveyance direction (hereinafter referred to as the "horizontal direction"), the paper size in the horizontal direction,
Or, because the transport position is uncertain, (1) there is a mismatch between the size of the image to be formed and the fed paper, resulting in image loss.

(2) When an image is lost, for example in an electrophotographic printer, not only does the amount of developer (toner) consumed increase, but the toner also scatters inside the printer, adversely affecting the electrophotographic process.

■If the conveyance position shift is too large, paper jams will occur.

There were drawbacks such as.

[Means (and functions) for solving the problem] According to the present invention, there are provided a pair of conveyance guides provided along the paper conveyance direction, and a moving means for moving the conveyance guides in the lateral direction from a predetermined position. and a paper side edge detection means provided on the pair of conveyance guides, and a conveyance release means that enables movement of the paper when the conveyance guides are moved, and the paper side edge detection means detects the paper pile side. The paper size in the horizontal direction is detected from the amount of movement of the conveyance guide at the time the edge is detected.

Furthermore, the width of the image to be formed is controlled according to the detected paper size.

[Example] Fig. 1 shows an example in which the present invention is used in a paper feed port, and 1-a and 1-b indicate a pair of paper feed ports provided along the conveyance direction (arrow D in the figure). Microswitches 2-a and 2-b, which serve as conveyance guides and paper end detection means, are fixed.

The conveyance guides 1-a and 1-b are connected to a screw N3, and the screw shaft 3 is rotated by a stepping motor 4.

When the screw shaft 3 rotates in the direction of the arrow in the figure, the conveyance guides I-a and 1-b move as indicated by the arrows B-a and B- in the figure, respectively.
Pedestal i curved in direction b in the conveying direction.

move on. Note that the purpose of curving the paper is to increase the strength of the paper against compressive force.

A photointerrupter 5 detects passage of the conveyance guide 1-b and sets a home position.

In addition, the conveyance guide 1 provided on the same screw shaft 3
-A is regulated.

The stepping motor 4 is controlled by a control signal PLMCNT from a controller 7 via a drive circuit 6.

Reference numeral 9 denotes a conveyance sheet, which is conveyed by a D-cut roller 8 in the direction of the arrow in the figure, and sent to an image forming process means (not shown).

The operation will be explained using the time chart of FIG. 2 and the flow chart of FIG. 3.

First, before paper feeding and conveyance, the stepping motor 4 is rotated in the opposite direction to the arrow A in FIG.
Perform the release operation 1-b. This is preparation for the subsequent size detection and lateral alignment (horizontal registration of the sheet material and alignment with the reference position). Conveyance guide I-b
passes the photointerrupter 5 and moves to the home position by controlling the rotation of the stepping motor 4 until the Shp signal is detected.

Next, the conveyance paper (sheet material) 9 is moved to the conveyance guides 1a, 1-b.
The closing operation starts when it is inserted into the position (or transported). At this time, the D-cut roller 8 is stopped (or is on standby) at a position where the conveyed paper 9 is released.

The closing operation is performed until the microswitches 2-a and 2-b detect an etch in the conveyed paper 9. Since the pedestal 10 is curved in the conveying direction, the microswitches 2-a and 2-b can catch both ends of the conveyed paper 9 without bending it.

During this time, the stepping motor 4 is rotated in the direction of the arrow in FIG.
Count the number of excitation pulses of the CNT companion.

When the closing operation is completed, the paper size in the horizontal direction is calculated from the number of pulses. The paper size in the horizontal direction, the number of pulses n, the amount of transport guide movement per pulse d, and the distance between the Baum position and the transport center l.

Then It is calculated as L = 2 (ILo nd).

When the calculation is completed, the D-cut roller 8 is rotated in the direction marked C in the center of FIG. 1 to feed and transport the paper. At this time, the sheet material is aligned in the correct position by the guides la and lb.

In the above embodiments, the paper conveyance reference is set at the center in the lateral direction, but the present invention is not limited to this. For example, it goes without saying that if the conveyance guide 1-a is fixed at a predetermined position, the same effect can be obtained even if the control is performed based on the 414 registration direction end reference.

Alternatively, the amount of electricity proportional to the amount of movement may be measured by detecting the amount of movement of the conveyance guide by counting the number of excitation pulses of the stepping motor, or by directly using a variable resistor or the like.

Next, FIG. 4 shows an embodiment of a laser beam printer that controls the width of an image to be formed according to the horizontal and vertical size information obtained in the above embodiment.

The same parts as in FIG. 1 are given the same reference numerals.

21 is a photosensitive drum. A laser beam emitted from a laser diode 24 is scanned by a polygon mirror 22 rotating at a predetermined rotation speed, and a latent image based on the modulation signal LON of the laser diode 24 is formed on the photosensitive drum 21. The formed latent image is converted into a toner image by a developing device (not shown), and is transferred onto the conveyed paper 9 by a transfer device (not shown).

24 is a beam detector using a photoelectric conversion element such as a photodiode, and outputs a beam detector No. 3 BD which is a reference timing signal for rask scanning of a laser beam.

25 is an image mask control circuit, the specific configuration of which is shown in FIG.

31 is an oscillator that provides a clock pulse to the counter circuit 32;

The counter circuit 32 compares the clock pulse with the count value by comparing circuits 33 and 34 with the beam detect signal B.
The unblanking signal UNBL for forcibly turning on the laser diode 23 to detect D is applied to the generating circuit, and the count value is cleared by the beam detect signal BD.

The comparator circuit 33 is supplied with a first mask control value MASKI from the controller 7, and the comparator circuit 34 is supplied with a second mask control value MASK2 from the controller 7.

Each of the mask control values MASK1 and MASK2 is created according to the detected horizontal paper size.

The flip-flop circuit 36 sets an enable signal ENBL based on a match signal between the mask control value MASKI of the first comparator circuit and the count value of the counter circuit 32, and sets the enable signal ENBL by matching the mask control value MASK2 of the second comparator circuit with the count value of the counter circuit 32. A match signal resets the enable signal.

The enable signal ENBL is input to the AND circuit 37 together with the image signal VDO sent from an external device.

Therefore, the image signal VDO is gated by the enable signal ENBL.

The image signal VDO passed through the AND circuit 37 is combined with the unblanking signal UNBL by an OR circuit 38 and sent as a modulation signal LON to the laser diode 23.

The image mask control circuit 25 configured as described above generates an enable signal ENBL proportional to the paper size in the horizontal direction, as shown in the time chart of FIG. A latent image is formed according to the image.

[Other Embodiments] In the first embodiment described above, the width of the image to be formed is controlled according to the detected horizontal paper size. For example, when the width of the image to be formed is given in advance, that is, , a laser beam printer, etc., when an image width is specified by an external device such as a host computer, the following control is carried out to prevent image loss.

A flowchart is shown in FIG.

First, image width information is received from an external device and stored. When paper feeding is started, the paper size in the horizontal direction is detected by the operation described in the first embodiment. The paper horizontal size detection means is
Instead of the above-mentioned microswitch, an optical sensor such as a photointerrupter may be used.

Next, if the image width information and the detected paper size do not match, a warning to that effect is given to the outside, and if they match, a printing operation is started.

[Effect of the invention] As explained above, a pair of movable conveyance guides,
By having a paper side edge detection means provided on the conveyance guide and detecting the amount of movement of the conveyance guide until the paper side edge detection means detects both side edges of the paper, the printing position in the horizontal direction can be kept constant. It is maintained.

・Prevent image loss.

・Developer consumption becomes more efficient.

・There is no negative effect on the electrophotographic process due to unnecessary developer.

- Paper jams are less likely to occur.

There are effects such as

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of the paper feed section in the present invention, FIG. 2 is a time chart of paper size detection, and FIG.
Flowchart of paper size detection, FIG. 4 is a diagram showing an embodiment of the present invention in a laser beam printer, FIG. 5 is a block diagram of an image signal mask control circuit, and FIG. 6 is a time diagram in the image signal mask control circuit. Chart, FIG. 7 is a flowchart for warning in case of paper size mismatch. 1-a, 1-b... Conveyance regulation guide 2a, 2b.
... Sheet material side edge detection means 8 ... Roller (conveyance release means)

Claims (3)

[Claims] (1) In an image forming apparatus that conveys a sheet material and performs image formation, a pair of conveyance regulation guides are provided along the conveyance direction of the sheet material, and the conveyance regulation guide is moved from a predetermined position perpendicular to the conveyance direction. a movement control means for moving the sheet material in a direction perpendicular to the conveyance direction; a sheet material side edge detection means provided on the pair of conveyance regulation guides; and a conveyance release means, the sheet material is moved in the direction perpendicular to the conveyance direction based on the amount of movement of the conveyance regulation guide when the side edge of the sheet material is detected by the sheet material side edge detection. An image forming device characterized by detecting length. (2) The image forming apparatus according to claim 1, further comprising image mask control means for controlling the width of an image to be formed based on the sheet material size detected by the sheet material size detection means. (3) means for externally specifying the image width; comparison means for comparing the detected sheet material size with the image width; and warning means for warning the outside when the image width is larger than the sheet material size. An image forming apparatus according to claim 1, characterized in that it has the following.