JP2784053B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus provided with a mechanism for detecting a mounting state of a developing device configured to be movable with respect to a photoconductor.

[Related Art] In various image forming apparatuses such as a copying machine, a printer, and a facsimile equipped with a photoconductor, a developing device is installed so as to develop and visualize an electrostatic latent image formed on the photoconductor. . The developing device is often configured to be detachable with respect to the main body, that is, movable with respect to the photoreceptor. When the developing device is configured to be detachable, the state of the developing device is determined by an electrical or mechanical sensor unit. That is, whether the developing device is new or in use,
Alternatively, it is detected whether or not it has been used. This is because grasping the state of the developing device is important on the device or management.

[Problems to be Solved by the Invention] However, in such a conventional image forming apparatus,
The device is complicated by a sensor unit for detecting the state of the developing device, and the provision of this sensor unit leads to an increase in size and cost of the device.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of simplifying a sensor unit for detecting a state of a developing device and achieving a reduction in size and cost of the device.

Means for Solving the Problems In order to achieve the above object, the present invention detects a developing device movable with respect to a photoreceptor and a toner density of a reference pattern visible image obtained by a developing action of the developing device. In an image forming apparatus including an image density detection mechanism, a toner density detection value of a reference pattern visible image obtained immediately after the start of driving of the developing device, and a reference pattern obtained after a predetermined time, obtained by the image density detection mechanism It has a configuration that includes a control mechanism that compares the detected toner density value of the visible image and determines the state of the developing device based on the comparison result.

[Operation] In the means having such a configuration, the state of the developing device is determined using an image density detection mechanism constituting the image density control device.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

First, the structure of the image forming apparatus according to the present invention will be described with reference to an embodiment of a copying machine shown in FIG.

As shown in FIG. 5, an original to be copied held on a contact glass 1 is irradiated by an exposure optical system 2 disposed below the contact glass 1, and a light image corresponding to an image is exposed. The body drum 3 is exposed.

The exposure optical system 2 includes a document illuminating light source 201, a first mirror 202, a second mirror 203, and a third mirror 204 constituting a first scanner, a through lens 205, and a fourth mirror 206 constituting a second scanner. And a fifth mirror 207. The first scanner is moved rightward in the figure at a speed of (V / m; m is a copy magnification) with respect to the peripheral speed (V) of the photosensitive drum 3, and at the same time, the second scanner is moved at a speed of (V / m It is driven by a drive motor (not shown) so as to move rightward in the figure at a speed of 2 m). The peripheral speed of the photosensitive drum 3 is constant irrespective of the magnification and the magnification.

An image forming system is provided at a slightly right side of the center of the copying machine body 1 with the photosensitive drum 3 as a center. That is, around the photosensitive drum 3, a charging charger 4 for uniformly charging the photosensitive drum 3, an eraser 5 for erasing unnecessary charges,
A developing device 6 for supplying a toner powder to the electrostatic latent image with a magnetic brush and developing the toner image to obtain a toner visible image, a transfer charger 7 for transferring the toner visible image on the photosensitive drum 3 to a recording sheet, A cleaning device 8 for cleaning the toner remaining on the photosensitive drum 3 without being transferred is provided.

The recording paper supply section 10 is provided with a paper supply cassette 101 provided in three stages and an intermediate tray 102 for double-sided copying, and only one recording paper is sent out by a call roller 103 and a paper supply roller 104. It is. The fed recording paper is temporarily stopped by the pair of registration rollers 105, and then fed to the transfer unit in synchronization with the leading end of the image on the photosensitive drum 3. The recording paper on which the toner visible image has been transferred by the transfer charger 7 after passing through the pair of registration rollers 105 is fused with the toner visible image by the heat roller pair of the fixing device 11. Recorded paper after fixing is
The paper passes through the fixing paper discharge roller pair and goes to the main body paper discharge tray or the re-feeding device.

As shown in FIG. 6, the photosensitive drum 3 as a latent image carrier is rotationally driven in a direction indicated by an arrow, that is, clockwise by a drive mechanism not shown. The photoconductor drum 3 is formed of, for example, an organic photoconductor (OPC). The photoconductor drum 3 is uniformly initially charged to a predetermined potential by the charging charger 4 and is statically formed by the exposure optical system 2 to form a light image. An electrostatic latent image is formed.

Further, a developing sleeve 602 made of a cylindrical member as a developer carrying member is provided in a developing casing 601 of the developing device 6 which is movably disposed in the vicinity of the photosensitive drum 3 with respect to the photosensitive drum 3. In addition, a part of the developing sleeve 602 is exposed from an opening provided in the developing casing 601 toward the photosensitive drum 3 side. The developing sleeve 602 is formed by forming a nonmagnetic material such as aluminum into a hollow cylindrical shape, and is rotationally driven in a counterclockwise direction by a driving mechanism (not shown). They are arranged to face each other with a certain gap. A transition area of the toner, that is, a development area is formed in a portion where the development sleeve 602 and the photosensitive drum 3 are opposed to each other.

On the other hand, a developing magnet roller (not shown) is provided inside the developing sleeve 602, and a magnetic carrier and toner are formed on the outer surface of the developing sleeve 602 by a magnetic force generated from each magnetic pole of the developing magnet roller. A magnetic brush consisting of The end portion of the magnetic brush is elastically in contact with the surface of the photosensitive drum 3 in the developing area described above.

The developer constituting the magnetic brush is initially a developing casing 60
1 and is pumped up to the developing sleeve 602 while being stirred by the paddle roller 603. The developer pumped up by the developing sleeve 602 is conveyed to the developing area as a magnetic brush as described above, and in the middle thereof, the magnetic brush is cut off by a developing doctor 604 arranged close to the developing sleeve 602. Is performed, whereby the amount of the developer is regulated.

The excess developer removed from the developing sleeve 602 by the developing doctor 604 reaches the inclined plate 605 of the separator along the inner curved surface of the developing doctor 604,
As shown in the figure, the paddle roller 603 is moved laterally forward (leftward in FIG. 7) by the guide action of a plurality of fins 606 erected on the inclined plate 605.
Has been dropped back to the area behind. A developer inlet 607 is provided at the left end of the inclined plate 605 in FIG.
The developer dropped through the developer inlet 607 is moved to the rear side in the lateral direction (right direction in FIG. 7) by the conveying action of the conveying screw 608, and the paddle roller 603 is moved from the right end portion in FIG. Is dropped into the upper region of the vehicle.

Further, a developer storage container 609 for storing unused new developer is attached to the side plate on the front side of the developing casing 601. A supply port 611 is formed through the developing device side mounting wall of the developer storage container 60, and a shutter 612 is provided between the wall surface of the developer storage container 609 and the side plate of the developing casing 601. I have. When the shutter 612 is pushed down to the state shown in FIG. 7,
The supply port 611 of the developer storage container 609 and the opening 613 formed in the side plate of the development casing 601 communicate with each other, so that the unused new developer in the developer storage container 609 flows into the development casing 601. It has become. The developer storage container 609 is provided with a handle portion 614 protruding to the front side. By pulling the handle portion 614, the entire developing device 6 is pulled out to the front side, and the handle portion 614 is pulled out. Developing device 6
Is mounted at a predetermined position on the back side.

On the other hand, on the photosensitive drum 3, a light reflection type sensor (P sensor) 20 of an image density detecting mechanism constituting the image density control device is disposed so as to face the axial direction of the photosensitive drum 1 and slightly toward the back side. I have. The light reflection type sensor 20 in the present embodiment is arranged at a position which is located a certain distance from the center of the developing device 6 toward the back side. At this time, the supply port 611 of the developer storage container 609 is set at a position farthest from the light reflection type sensor 20.

This light reflection type sensor 20 is an LED as a light emitting element.
And a phototransistor as a light receiving element, and has a function of detecting a toner density of a reference pattern visible image of a predetermined density formed on the photosensitive drum 3. Specifically, a sensor output VSG (for example, constant at about 4 V) obtained from an erase area before and after the reference pattern visible image and a sensor output VSP (for example, 0.3 to 1.2 V in a normal state) obtained from the reference pattern visible image ) Is compared. Then, the detected toner density of the reference pattern visible image is captured as the toner density in the developer, and a control operation such as toner supply is performed based on the detected toner density. In this embodiment, a control mechanism for detecting the state of the developing device 6 using the P sensor check by the image density detecting mechanism is provided.

That is, first, when the developer having a toner concentration sufficient for visualization exists on the developing sleeve 602 of the developing device mounted on the main body, the P sensor check results in that VSP / VSG is usually 0.08 to 0.30. Therefore, it is determined that the developing device is not an unused product but has already been used and can be developed.

When the replacement of the developing device 6 is performed, the replacement operation of the developing device 6 is determined by turning on the main switch or opening and closing the door cover. At this time, when the developing device 6 is replaced with a new one and mounted on the main body, the developer supply shutter 612 is pushed down to the state shown in FIG. The developer is supplied into the developing casing 601. At the same time, the P sensor check processing by the light reflection type sensor 20 of the image density detection mechanism constituting the image density control device is repeatedly performed a predetermined number of times as described later.

The developer replenished in the developing casing 601 is uniformly diffused by the rise of the drive of the developing device 6, but the developer immediately after the replenishment of the developer is unevenly distributed on the near side in the developing casing 601. The developer is also pumped only on the front side of the developing sleeve 602 as well. Therefore, at this time, the reference pattern visible image is not formed on the photosensitive drum 3, and the value of the sensor output VSP corresponding to the reference pattern visible image becomes the sensor output VSG (for example, about 4 V) corresponding to the drum surface. Are equal. As a result, it is determined that the developing device 6 is new.

On the other hand, if the developer exists on the developing sleeve 602,
The value of the sensor output VSP is, for example, 0.3 to 1.2 in a normal state.
Therefore, based on this, it is determined that the developing device 6 is not used but is already used.

In this case, since the developer supply port 611 is installed at a position away from the light reflection type sensor 20 of the image density detection mechanism, the detection operation of the image density detection mechanism is not affected by the supply of the developer. I have.

FIGS. 1 to 4 show a procedure for determining a state when such a developing device 6 is replaced. The normal copying operation is omitted because it is well known.

In mounting the developing device 6 on the main body, that is, detecting replacement of the developing device 6, the DT in FIG. 1 ST1 and FIG.
M detection FLAG is set up. If it is determined that the developing device 6 needs to be replaced, that is, if DTM detection FLAG = 1 is performed in ST3 in FIG. 2, the flow shown in FIG. 1 is executed.

In FIG. 1, first, a P sensor check process is performed (ST4), and when VSP / VSG ≧ 0.5 (ST5), the value becomes P
It is stored in the RPSV (ST6). When VSP / VSG <0.5, the mode is shifted to the normal copy mode (ST7). If VSP / VSG ≧ 0.5 in the above, the P sensor check processing is performed again (ST109) after the agitation processing of the developing unit is executed (ST8).

This is the case where VSP / VSG ≧ 0.5. In this case, there are two cases, that is, the case where the developing device is new and the case where the toner end is reached.

When the developing device 6 is new, unused new developer flows into the developing casing 601 from the developer storage container 609 disposed on the front side, and the first P sensor check processing is performed. At this point, almost no developer exists on the developing sleeve 602 except for the vicinity of the near side, so that a reference pattern visible image is not formed on the photosensitive drum 3. Therefore, the detection result at this time is VSP / VSG ≒ 1, and this detection value is stored in PRPSV. Next, with the start of the driving of the developing device, the developer existing on the front side in the developing unit is gradually diffused to the back side in about 30 seconds. Thereafter, the P sensor check processing is performed again, and the P sensor check processing is compared with the first stored value stored in the PRPSV. When the P sensor check processing is performed with a new developer, the value of VSP / VSG is normally 0.08 to 0.20, so that VRPPSV ≧ 2VSP / VSG. At this time, it is determined that the developing device 6 is an unused product. You.

On the other hand, even when the developing device in the toner end state is erroneously reused, the result of the first P sensor check processing is VSP / VSG ≧ 0.5, and the detected value is stored in PRPSV. The process up to this point is the same as the above-described case where the developing device is an unused product. However, in this case, even if the developer is stirred, the toner concentration in the developing section does not change.
The result of the P sensor check processing performed again after the developer is agitated is PRPSV <2V SP / VSG, whereby it is determined that the developing device 6 is a toner-end product. When the toner remaining in the hopper is replenished, the toner may be ready for development again. Therefore, the hopper is driven and the toner is replenished. Check processing is performed. As a result, if VPRPSV ≧ 2V SP / VSG, it is determined that the image can be developed and the mode is shifted to the normal copy mode. On the other hand, also in this case, if PRPSV <2V SP / VSG, it is determined that the toner has run out, and the toner end is displayed, and at the same time, the copying is disabled.

Looking at such a determination procedure in the flow shown in FIG. 1, a value twice as large as VSP / VSG detected by the second P-sensor check processing and already stored in the PRPSV by the first P-sensor check processing (ST10), and if PRPSV ≧ 2V SP / VSG, the installed developing device is determined to be new and the initial setting of the developing device 6 is executed (ST11 and ST11). ST12). PRPSV <2V
In the case of SP / VSG, the hopper drive of the developing device 6, that is, the toner replenishing operation and the agitating process of the developing unit are executed (ST
13) Then, a P sensor check process is performed (ST14).

Next, a value twice as large as VSP / VSG detected by the third P sensor check process described above is compared with a detected value already stored in the PRPSV (ST15), and the result is compared with the detected value.
If VPRPSV ≧ 2V SP / VSG, the mode is shifted to the normal copy mode (ST16). If PRPSV <2V SP / VSG, it is determined that the toner has run out, and it is determined that copying is not possible, that is, the developing device needs to be replaced (ST17).

In this embodiment, a light reflection type sensor is used as the toner density control device. However, other sensors such as a sensor that checks a change in magnetic permeability and a sensor that checks a change in inductance can be similarly used.

[Effects of the Invention] As described above, the present invention utilizes the image density detection mechanism constituting the image density control device to determine whether the developing device is used or unused, and whether the used product is usable or unusable. Since a control mechanism is provided to detect differences between products, there is no need to provide a special sensor unit, and the sensor unit that detects the state of the developing device can be simplified, and the size of the device can be reduced. In addition, it is possible to achieve cost reduction and prevent the photosensitive member from being damaged by unusable products.

[Brief description of the drawings]

1, 2, 3 and 4 are flowcharts showing control procedures by the control mechanism according to the present invention, and FIG. 5 shows a copying machine as an example of an image forming apparatus to which the present invention is applied. FIGS. 6 and 7 are a cross-sectional view and a vertical cross-sectional view, respectively, showing the structure of a developing device according to an embodiment of the present invention. 3 photoreceptor drum, 6 developing device, 20 P sensor, 602 developing sleeve, 609 developer storage container, 61
0: Developer supply port.

Claims (1)

(57) [Claims] An image forming apparatus comprising: a developing device movable with respect to a photoreceptor; and an image density detecting mechanism for detecting a toner density of a reference pattern visible image obtained by a developing action of the developing device. The toner density detection value of the reference pattern visible image immediately after the start of the driving of the developing device, and the toner density detection value of the reference pattern visible image after a certain period of time from the start of the driving of the developing device, obtained by the image density detecting mechanism And a control mechanism for determining the state of the developing device based on the comparison result.