JPH026974A - Image forming device - Google Patents

Abstract

PURPOSE:To correctly detect the density of an original by moving a condenser lens moving upstream of a reference position to the reference position so that the condenser lens is not moved upstream of the reference position when a photosensor receives light from an original. CONSTITUTION:Before the photosensor 41 receives the light from the original 11, a moving means 36 moves the condenser lens 21 to the reference position without fail. Namely, even if the condenser lens 21 is moved upstream of the reference position to vary an original reading magnification, it is returned to the reference position without fail when the density of the original 11 is detected. As a result, with the condenser lens 21 located at the reference position, it does not shield light from the original 11 to the photosensor 41. Thus, the density of the original can be detected automatically and correctly all the time.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an image forming apparatus that has a mechanism for reading a document, such as an analog copying machine, a digital copying machine, or a facsimile machine, and performs various controls based on the document information. It is related to the device. In particular, the present invention relates to an image forming apparatus having an enlargement and/or reduction function that can vary the magnification of a document image to a desired magnification.

<Prior Art> Taking an analog copying machine as an example, in a conventional copying machine, a document is scanned with preliminary illumination, the intensity of the reflected light reflected from the document at that time is detected by a photo sensor, and the output of the photo sensor is detected. There are known document density detection devices that automatically detect the document density based on the
(See Publication No. 4).

FIGS. 8 and 9 are a perspective view and a plan view showing the optical path of exposure light of a conventional copying machine.

As shown in the figure, a light-receiving sensor 1 such as a photosensor in a conventional device is placed outside an optical path 4 of exposure light that is reflected by an original 2, focused by a condensing lens 5, and given to a photoreceptor 3. has been done. This is because if the light-receiving sensor 1 is placed in the optical path 4, a part of the exposure light that should be applied to the photoreceptor 3 will be blocked by the light-receiving sensor 1.

Therefore, the light receiving sensor 1 is placed at a position where it does not interfere with the exposure light.
In other words, it is arranged outside the optical path 4 and is able to detect light reflected from approximately the center of the document 2.

<Problem to be solved by the invention> By the way, in the case where the copying machine has an enlargement function or an enlargement and reduction function, the condenser lens 5 is configured to move along the optical path 4 on the upstream side (the document 2 side) or the downstream side (on the document 2 side). The photoreceptor 3 side) is movable. When copying at the same size, the condenser lens 5
is moved to the position shown by the solid line, and during enlargement copying, it is moved to the upstream side as shown by the two-dot chain line, and during reduction copying, it is moved to the downstream side.

On the other hand, the light receiving sensor 1 is attached to a lens unit (not shown), but its position is fixed regardless of movement of the condensing lens 5.

However, in a device in which the light receiving sensor 1 and the condensing lens 5 are arranged in the above-mentioned arrangement and the condensing lens 5 is movable in the optical path 4, the following problem occurs. That is, ■ When the condensing lens 5 is moved upstream for enlarged copying, there is a risk that part of the incident optical path 6 to the light receiving sensor 1 will be blocked (in the case of Fig. 9, the /X notch is attached). (The light in the exposed area is blocked.)

When the density of the original is detected under such circumstances, the amount of detected light decreases due to the fact that the light incident on the light receiving sensor 1 is partially blocked, and the density of the original 2 is incorrectly detected as being relatively high. It ends up.

■ To solve the above problem (■), the light receiving sensor 1 should be moved further to the side of the condensing lens 5, but this would make it difficult to adjust the light receiving of the light receiving sensor 1, and
It is necessary to increase the size of a lens unit (not shown) for mounting the light receiving sensor 1. Furthermore, when the light receiving sensor 1 is moved upstream, a new problem arises in that the light receiving sensor 1 may obstruct the movement of a reflecting mirror (not shown) that constitutes the optical path 4.

■Also, in order to solve the above-mentioned problem (■), it may be possible to make the light receiving sensor 1 movable together with the condensing lens 5, but the light receiving sensor 1 is connected to electrical wiring. For this reason, making the light receiving sensor 1 movable brings about another problem regarding the safety standards of the device.

The present invention has been made in view of the above-mentioned circumstances, and provides image formation that allows accurate document density detection without blocking the light given to the light receiving sensor 1 by the condenser lens 5 when detecting the document density. The purpose is to provide equipment.

Means for Solving the Problems> The present invention includes an optical path that guides light from an original to a photoreceptor, and a condenser lens that is movable upstream (original side) or downstream (photoreceptor side) in the optical path. In the image forming apparatus, the document image formed on the photoreceptor can be varied to a desired magnification by moving the condensing lens to a predetermined position in the optical path, comprising: a reference position of the condensing lens; a reference position setting means for determining the light from the original, a light receiving sensor disposed outside the optical path and capable of receiving light from the original; lens moving means for moving the condenser lens that has been moved upstream of the reference position to the reference position so that the condenser lens is not located upstream of the reference position; An image forming apparatus is characterized in that it includes:

Further, in the above-described document density detection device, if image formation is performed with the condenser lens located upstream of the reference position, the present invention provides a method for performing the next image forming operation after the completion of the operation. Preferably, the moving means moves the condenser lens to the reference position.

Furthermore, in the present invention, in the document density detection device described above, the moving means moves the condensing lens to the base position immediately before the light receiving sensor receives light from the document.

Function> Before the light receiving sensor receives light from the document,
The moving means always moves the condenser lens to the reference position. That is, even if the condenser lens is moved upstream from the reference position in order to vary the document reading magnification, the condenser lens is always returned to the reference position when detecting the document density. When the condenser lens is located at the reference position, the condenser lens does not obstruct light arriving from the document to the light receiving sensor.

<Embodiment> FIG. 2 is a sectional view showing a schematic configuration of an electrophotographic copying machine 10 to which an embodiment of the present invention is applied.

A transparent contact glass 12 for setting a document 11 is provided on the top surface of the copying machine 10, and a document cover 13 that can be opened and closed is provided on top of the transparent contact glass 12.

An exposure device 14 for reading a document is provided inside and above the copying machine 10, and a mechanism for detecting the density of the document is incorporated in the exposure device 14. The exposure device 14 has the following configuration.

A lamp unit 15 is provided for illuminating the document 11 placed on the contact glass 12. This lamp unit 15 is movable from a scanning start position at the left end indicated by a solid line to a scanning end position at the right end indicated by a two-dot chain line.By moving the lamp unit 15 from the left end to the right end, the document 11 is moved. , the illumination is scanned. The lamp unit 15 is equipped with a first mirror 16 for guiding the reflected light from the original 11 in a predetermined direction.

The light reflected by the first mirror 16 is further reflected by the second mirror 17 and the third mirror 18. The second mirror 17 and the third mirror 18 are attached to a common mirror frame 19, and in conjunction with the movement of the lamp unit 15, the second mirror 17 and the third mirror 18 are moved to the lamp unit 15 at a speed that is half the movement speed of the lamp unit 15. It is designed to follow. Therefore, when the lamp unit 15 reaches the scanning end position indicated by the two-dot chain line in the figure, the mirror frame 19 moves to approximately the center as indicated by the two-dot chain line.

The light reflected by the third mirror 18 passes through a condensing lens 21 inserted into the optical path 20 and is applied to the fourth mirror 22 so that it is reflected by the fourth mirror 22 and irradiated onto the photoreceptor drum 23. It has become. The copying machine 10 also has an enlargement and reduction function, and the condenser lens 21 is moved to a predetermined position in the optical path 20 during enlargement copying or reduction copying. Furthermore, a light receiving sensor (not shown in FIG. 2) for detecting the density of the original is provided outside the optical path 20 on the side of the condenser lens 21.

This mechanism will be described later.

Around the photoconductor drum 23, in order along the rotational direction of the photoconductor drum 23, there are a charger 24, an erase lamp 25, a developing device 26, a transfer/peel charger 27, a cleaner 28, a discharge lamp 29, etc. for image formation. Necessary equipment is in place.

Further, in accordance with the movement of the image forming device centered on the photosensitive drum 23, the paper 31 in the paper feed cassette 30 is moved to the paper feed roller 3.
The paper is taken out one by one at step 2, and the paper feeding timing is adjusted by the pair of registration rollers 33, and the paper is fed to the photosensitive drum 23 at a constant timing (so-called secondary paper feeding is performed).

A registration switch 44 is provided immediately before the registration roller pair 33 in order to detect the presence or absence of paper in the registration roller pair 33 for timing the secondary sheet feeding.

The toner image formed on the surface of the photoreceptor drum 23 is transferred to the secondary fed paper by the action of the transfer/separation charger 27, and the paper to which the toner image has been transferred is peeled off from the surface of the photoreceptor drum 23. It is sent to the joseki device 34. The paper on which the toner image has been fixed by the fixing device 34 is ejected to the ejection tray 35.

FIG. 3 shows the optical path 20 of the exposure device 14 in the copying machine 10.
FIG. As shown in FIG. 3, a condensing lens 21 is provided in the optical path 20, and the original 11
The light image is focused by a condensing lens 21, and the light image is
imaged above.

Further, during enlargement copying, the condensing lens 21 is moved along the optical path 20 toward the original 11 side (upstream side) and stopped at a predetermined position, as shown by the two-dot chain line, and during reduction copying, condensing lens 21 is moved toward the photosensitive drum 23 side during reduction copying. (downstream) and stopped at a predetermined position. For this purpose, a wire 38 hung on a pulley 37 is connected to the condensing lens 21, and the wire 38 is moved by a lens motor 36.

This lens motor 36 is constituted by, for example, a step motor.

In addition, in order to detect that the condensing lens 2 moved in this way has reached a predetermined reference position, specifically, the same magnification position indicated by the solid line, the lens position detection switch 3 is activated.
9 is provided. The lens position detection switch 39 is
For example, it is made of a photoelectric switch consisting of a light emitting element and a light receiving element, and the switching timing determines whether or not a blocking plate 40 provided in the condenser lens 21 blocks light from the light emitting element to the light receiving element. This is a mechanism that can detect whether or not the condenser lens 21 has reached the reference position. Note that operation control for this detection will be detailed later.

Furthermore, like the conventional apparatus, a light receiving sensor 4 for detecting the density of the original is provided outside the optical path 20 so as not to obstruct the exposure light.
1 is placed. The light receiving sensor 41 includes a photosensor such as a photodiode that converts incident light into an electrical signal, and is a cylindrical member that converts the light so that only the light reflected from the approximate center of the document 11 can be detected. The angle of incidence etc. are regulated.

In this embodiment, the document alignment is based on a so-called center reference, so the light receiving sensor 41 is configured to be able to detect the light reflected at approximately the center of the document 11. However, when the document alignment is based on a so-called one-sided basis, The light receiving sensor 41 may be configured to be able to detect light reflected from the reference end side of the original 11.

FIG. 4 is a block diagram showing the configuration of an electrical control circuit in the copying machine 10. As shown in FIG. The control circuit is mainly composed of a CPU 42, and includes an operation section 43 and a registration switch 4.
4 and three lens position detection switches are CP.
It is now given to U42. Further, the output of the light receiving sensor 41 is converted into a digital signal by an analog/digital converter 48 and is provided to the CPU 42. Note that the operation unit 43 is provided, for example, on the front side of the top surface of the copying machine 1o, and includes a print switch (not shown), an automatic exposure switch that switches whether or not automatic document density detection is performed,
It includes an enlargement copy instruction switch, a reduction copy instruction switch, a magnification specification key, etc.

The CPU 42 starts a control operation based on a signal from the operation unit 43. The drive control signal, rotation direction control signal, reference clock, etc. output from the CPU 42 are given to the motor controller 45, and the motor controller 45 controls the rotation timing, rotation time, rotation direction, etc. of the optical motor 46. The optical motor 46 is connected to the lamp unit 15 and the mirror frame 19 included in the exposure device 14.
It is useless to drive etc.

The CPU 42 also controls driving of the lens motor 36 via the driver 47. Furthermore, the cPU 42 adjusts the density adjustment section 49 based on the output from the light receiving sensor 41 and detects the document size.

FIG. 5 is a timing chart showing the operation of the control circuit shown in FIG. 4, and the timing chart drawn in the upper half shows the copying machine 10 when the automatic document density detection operation is not performed (the automatic exposure switch is off). The control operation depicted in the lower half is the control operation of the copying machine 10 when the automatic document density detection operation is performed (the automatic exposure switch is on).

FIG. 1 is a flowchart showing the operation of the above-mentioned control circuit.

Next, following the flow of FIG. 1 and referring to FIGS. 2 to 5, a copying machine 1 to which an embodiment of the present invention is applied.
The operation of 0 will be explained.

When the CPU 42 determines that the print switch of the operation unit 43 is turned on (step S1), it determines the state of the automatic exposure switch (step S2). When the automatic exposure switch is on, the exposure device 14 is operated and the original 11
The document density is detected based on the amount of light detected by the light receiving sensor 41 at that time by performing preliminary illumination scanning (step S3).
. Then, based on the detected document density, the density adjustment section 4
Make two adjustments. More specifically, the charger 24 as the density adjustment section 49, the developing bias voltage of the developing device 26, the lamp voltage of the lamp unit 15, etc. (see FIG. 2) are adjusted to automatically optimize the copy density. ,
a Adjust.

When the automatic exposure switch is on, after the above-described document density detection is performed, when the automatic exposure switch is off, the copy magnification specified on the operation unit 43 is immediately set.
The CPU 42 drives the lens motor 36 to move the condenser lens 21 (see FIG. 3) to a position corresponding to the designated copy magnification (step S4). Then, in step S, the sheet feed roller 32 (see FIG. 2) starts feeding the sheet.
5) Based on the ON of the registration switch 44, the optical motor 46 is rotated in the normal direction to perform image processing including illumination scanning of the original 11 (step S6, see FIG. 5). Eventually, as the registration switch 44 is turned off, the trailing edge of the supplied paper (in other words, the trailing edge of the document 11) is detected (step S7), the optical motor 46 is reversed, and the lamp unit 15 (see FIG. 2) is detected. reference) is returned to the illumination scanning start position (step S8).

Then, steps 85 to S8 are repeatedly controlled until the set number of copies have been completed, and when it is determined that the set number of copies has been completed, more specifically, the process is performed in order to copy the final copy. When the exposure operation is completed or when the last copy paper is ejected to the ejection tray 35 (
Step S9) Further, it is determined whether or not it is an enlarged copy (Step 510). If it is an enlarged copy,
The lens motor 36 returns the condensing lens 21 to the same magnification position as the reference position (step 5ll).

A feature of this embodiment is that the condenser lens 21 is always returned to the same magnification position after the enlarged copy is made. By doing this, when the document density is automatically detected in the next copy, the condenser lens 21 is always at the same magnification position, and there is no possibility that the condenser lens 21 blocks the light incident on the light receiving sensor 41.

FIG. 6 is a flowchart showing another control operation by the control circuit of FIG. 4. This control circuit controls the first
The control operation shown in FIG. 6 may be performed instead of the control operation shown in the figure.

To explain according to the flow shown in FIG. 6, when the CPU 42 determines that the print switch is turned on (step 52
1), determine the state of the automatic exposure switch (step 5)
22). If the automatic exposure switch is on, it is determined whether or not the condenser lens 21 is in the enlarged position (step 823). If the condenser lens 21 is in the enlarged position, the lens motor 36 causes the condenser lens 21 to is first moved to the same size position (step 524). If it is not the enlarged copy mode, the condensing lens 21 performs the document density detection operation while remaining in its current position (step 525).

As described above, when detecting the document density in the enlarged copy mode, the feature of this control operation is that the condenser lens 21 is temporarily moved to the same magnification position as a reference position.

After the original la degree detection operation is completed, the condenser lens 21 is moved to the position corresponding to the specified copy magnification (step 5).
26), the paper feeding operation and image processing are performed until the final copy is completed (steps 327 to 530), as described in the flowchart of FIG.

In the above control operation, immediately before copying is performed, that is, after the print switch is turned on, the condenser lens 2
1 to the position corresponding to the set copy magnification, but before the print switch is turned on, the condenser lens is moved to the position corresponding to the set copy magnification. In this case, if the automatic exposure switch is off (step 522), it is sufficient to immediately proceed to the paper feeding operation in step S27 (see the operation indicated by the dotted line in FIG. 6).

FIG. 7 shows that the control circuit of FIG. 4 moves the condenser lens to the reference position.
That is, it is a flowchart showing the control details of the lens motor 36 when moving to the same magnification position.

As shown in FIG. 3, the condenser lens 21 is equipped with a shielding plate 40, and the lens position detection switch 39 is turned on and off by the shielding plate 40. More specifically, when the condenser lens 21 is on the reduced copy side rather than the 1:1 magnification position, the shielding plate 40 always turns off the three lens position detection switches. Further, when the condensing lens 21 is on the enlarged copy side, the lens position detection switch 39 is not blocked by the shielding plate 40 and is therefore always on. Then, the condensing lens 21 moves from the reduction copying side to the enlarged copying direction, and at the moment it reaches the same magnification position, the lens position detection switch 39 is switched from off to on.

On this premise, the control operation according to the flow shown in FIG. 7 will be explained. The CPU 42 reads the state of the lens position detection switch 39 (step 541), and if the switch 39 is on (step 542), it determines that the condenser lens 21 is located on the enlarged copy side, and in step S43. The operations of S44 and S45 are performed. On the other hand, if the lens position detection switch 39 is not on, it is determined that the condenser lens 21 is located on the reduction copy side, and step S46. The operations of S47 and S48 are performed.

First, when the lens position detection switch 39 is on, the CP
U42 applies one pulse to the lens motor 36, which is a step motor, and rotates the lens motor 36 by one pulse so that the condenser lens 21 moves from the enlarged copy side to the reduced copy side (step 843). After rotating the lens motor 36 for one pulse, the lens position detection switch 3
Read the status of switch 9 (step 544), and read the status of switch 3
This control is repeated until the switch is turned off (step S43).
．． S44,545). As a result, the condenser lens 21 on the enlarged copy side passes past the same magnification position and moves to the reduced copy side.

When the lens position detection switch 39 is off (step S
42, S45 or 547), the CPU 42 rotates the lens motor 39 by one pulse so that the condensing lens 21 moves from the reduction copy side to the enlargement copy side (step 5).
48), the control for determining the state of the lens position detection switch 39 is repeated.

Then, the control operation is stopped the moment the lens position detection switch 39 is turned on.

As a result, the condenser lens 21 is always moved from the reduction copy side to the enlargement copy side and is stopped when it reaches the same magnification position, so that the reference stop position of the condenser lens 21 becomes accurate.

In particular, if the condenser lens 21 is moved from one direction and stopped at the reference position in this way, there is no fear that the reference position will shift due to backlash of the step motor 36 or the like. Further, according to this embodiment, when the enlarged copy mode is selected, the condenser lens 21 must be moved to the reference position at the end of copying (see Figure 1) or immediately before the original density detection operation (see Figure 6). Since the reference position of the condenser lens 21 can be automatically corrected each time, the position of the condenser lens 21 can be maintained accurately at all times.

In each of the embodiments described above, the same magnification position is used as the reference position of the condensing lens 21, and when the condensing lens 21 is moved to the enlarged copy side from that position, the condensing lens 21 is set to the same magnification position during the document density detection operation. However, the present invention also includes the following modifications.

That is, as shown in FIG. 3, due to the relationship with the light receiving sensor 41, when the condensing lens 21 moves toward the document side (upstream side) from a certain base position, the light incident on the light receiving sensor 41 is may hinder.

Therefore, in such a case, the condenser lens should be returned to the downstream side at least to its reference position.1. After that, the document density detection operation may be performed. Therefore, this is not limited to the enlarged copy mode, but due to the arrangement position of the light receiving sensor 41, when the condensing lens 21 moves relatively to the document side (upstream side),
If there is a possibility that the light entering the light receiving sensor 41 will be obstructed by the condenser lens 21, the condenser lens 21 may be moved to a predetermined reference position where there is no such possibility.

Although the above explanations have been made using an electrophotographic copying machine as an example, the present invention is widely applicable to the following devices. That is, it has an optical path that guides the light from the document to a photoreceptor (limited to the above-mentioned photoreceptor drum, but also includes a light-receiving element such as a CCD), and is movable upstream or downstream within the optical path. A document reading mechanism is provided with a lens and is configured to form an image of the set document on a photoreceptor at a desired magnification by adjusting the position of the condensing lens. The present invention can be applied to various devices such as the above-mentioned electrophotographic copying machine, digital copying machine, facsimile machine, and the like.

<Effects of the Invention> According to the present invention, it is possible to obtain a device that can always accurately and automatically detect the document density. Particularly, when the applied apparatus is capable of enlarging and reading a document to a desired magnification, accurate document density detection can be performed regardless of the magnification ratio when reading the document.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing the control operation of an electrophotographic copying machine 10 to which an embodiment of the present invention is applied. FIG. 2 is a sectional view showing a schematic structure of an electrophotographic copying machine 10 to which an embodiment of the present invention is applied. FIG. 3 is a plan view showing the optical path of exposure light in the electrophotographic copying machine 10. FIG. 4 is a block diagram showing a control circuit of the electrophotographic copying machine 10. As shown in FIG. FIG. 5 is a timing chart showing the operation of the control circuit of FIG. 4. FIG. 6 is a flowchart showing another operation of the control circuit of FIG. 4. FIG. 7 is a flowchart showing the control operation for moving the condensing lens 21 to the reference position. FIGS. 8 and 9 are a perspective view and a plan view of an exposure device in a conventional analog copying machine developed along an optical path. In the figure, 10...electrophotographic copying machine, 11...document, 12...contact glass, 14...exposure device, 20...optical path, 21...condensing lens, 23...
Photosensitive drum, 36... Lens motor, 39... Lens position detection switch, 40... Closing plate, 41...
A light receiving sensor, 42...CPU is shown. Patent Applicant 31) Industrial Co., Ltd.
Company representative Patent attorney Kamei
Hirokatsu (and 2 others)

Claims (1)

[Claims] 1. An optical path that guides light from an original to a photoreceptor, and an upstream side (original side) or a downstream side (photoreceptor side) in the optical path.
In an image forming apparatus, the image forming apparatus includes a condensing lens that is movable to a position, and is capable of changing a document image formed on a photoreceptor to a desired magnification by moving the condensing lens to a predetermined position in an optical path. , a reference position setting means for determining a reference position of the condensing lens; a light receiving sensor disposed outside the optical path and capable of receiving light from the document; and a light receiving sensor configured to receive light from the document. moving the condenser lens that has been moved upstream of the reference position to the reference position so that the condenser lens is not located upstream of the reference position when attempting to receive light; An image forming apparatus comprising: a lens moving means for moving the lens. 2. In the image forming apparatus according to claim 1, if an image forming operation is performed with the condenser lens located upstream of the reference position, the next image forming operation is performed after the end of the image forming operation. Therefore, the moving means moves the condensing lens to the reference position. 3. The image forming apparatus according to claim 1, wherein the moving means moves the condenser lens to the reference position immediately before the light receiving sensor receives light from the document.