JPS6363067A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain a normal image by detecting a shift of a laser-radiated position, under a detection time interval of a reference image by an optical sensor, and correcting a shift of the timing for forming an image. CONSTITUTION:An interval measuring circuit 21 calculates a detection time interval based on a signal inputted from a toner concentration detecting sensor 18 and outputs its value to a comparing circuit 22, the comparing circuit 22 compares the detection time interval and a normal reference time, and subsequently, an arithmetic circuit 23 calculates a delay time and outputs its value to a delaying circuit 24. The delaying circuit 24 outputs a second image signal which has been inputted from an image control part 25, with a prescribed time delay. Subsequently, during its delay time, an electrostatic latent image of a first image which has been irradiated on a first exposure position X1 goes forward in the direction as indicated with an arrow (a) by a distance extending from the first exposure position to XaX2, therefore, a distance between the first image and the second image which are formed on a photosensitive drum 1 is corrected substantially to a normally level.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image forming apparatus that forms an image using a plurality of laser optical systems and a developing device, and particularly to control of the laser optical system.

(Prior Art and its Problems) Conventionally, as one aspect of the image forming apparatus, an image forming process including a charging means, a laser optical system, and a developing device around a photoreceptor drum, which is an electrostatic latent image carrier, is performed in a rotating direction. A plurality of developing units are arranged along the same line, each of the developing units contains toner of a different tone, and an image is first formed in a first image forming process, and then a second image forming process is performed. A printer has been proposed that forms a multicolor image by overlapping images in a third image forming process.

However, since the device is constructed by assembling a large number of parts, the bolts that secure each component may become loose due to vibration during transportation or long-term use. be.

Also, the environment in which it is used is not always constant;
For example, the ambient ambient temperature differs greatly between summer and winter.

For this reason, a shift occurs in the irradiation position of the laser beam irradiated from the optical system to form an electrostatic latent image on the surface of the electrostatic latent image carrier. However, in the case where characters and the like are formed using the second developing device, there is a problem in that an image is created in which the characters and ruled lines overlap.

Conventionally, this problem has been dealt with mechanically, for example, by adjusting the angle of a mirror while forming an image, or by adjusting the laser irradiation interval using a control switch or the like.

However, this method has the disadvantage that it must be carried out through repeated trial and error, the adjustment is troublesome, and defective images continue to be created without the user's knowledge.

Therefore, as a result of various studies in order to automatically correct the deviation of the laser irradiation position, the inventor of the present invention has discovered that the present inventors have found that, as a result of various studies to automatically correct the deviation of the laser irradiation position, the present inventors have discovered that the present inventors have discovered that the present inventors have found that, as a result of various studies, the present inventors have found that, as a result of various studies, the inventors have found that, as a result of various studies, the inventors have found that, as a result of various studies, the present inventors have found that, as a result of various studies, the present inventors have found that, as a result of various studies, the present inventors have found that, as a result of various studies to automatically correct the deviation of the laser irradiation position, the present inventor has found that the image forming method of a copying machine, etc. that conventionally uses a two-component developer consisting of a mixture of toner and carrier. In the device, the toner in the developer is consumed as the electrostatic latent image is developed, so in order to replenish new toner to match the amount used for development, an optical system is installed on the surface of the photoreceptor drum. Toner concentration: irradiating light to form a base latent image, developing this to form a reference image, and then measuring the toner content ratio in the developing device by detecting the density of the reference image with an optical sensor. We focused on the fact that it has a control mechanism.

That is, while measuring the detection time interval (T i ) at which the optical sensor detects each reference image formed by each developing device,
This is compared with the reference time ('r o) for one point on the photoreceptor drum to pass through the regular exposure position to determine whether the laser is being exposed at the regular position or not. Detect whether the state is set or not, and further,
By detecting the difference δ(T, -T.) and its sign, it is possible to detect what kind of relative positional shift has occurred in the optical system.

Then, by adjusting the laser irradiation timing based on this result, it becomes possible to irradiate the laser at a substantially regular position and obtain a normal image.

(Means for Solving the Problems) The present invention has been made based on the above-mentioned knowledge, and detects the deviation of the laser irradiation position based on the detection time interval of the reference image by the optical sensor, and the timing of image formation. A control mechanism is provided to correct the deviation.

(Example) The present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows the principle of a two-color printer, which is an image forming device according to the present invention.
), first optical system (3), first developing device (4), second charging gear (5), second optical system (6), second developing device (7)
, an eraser lamp (8), a transfer charger (9), a blade type cleaning device (10), and a main eraser lamp (11).

1st. The second chargers (2) and (5) uniformly apply a certain charge (positive polarity in this embodiment) to the surface of the photoreceptor drum (+) by its corona discharge.

1st. The second optical system (3), (6) is the first optical system. A predetermined image is created on the surface of the photoreceptor drum (1) using the laser light from the laser diodes (31) and (61) driven by the second laser diode driver circuits (32) and (62). It is formed as a latent image.

Hereinafter, the laser diode will be abbreviated as LD.

In addition, the eleventh second LD driver circuit (32), (62)
is connected to the image control section (25) via a delay circuit (24) of the timing control section (20), which will be described in detail later.
The image is exposed while a laser scans the surface of the photoreceptor drum (1) according to an image signal output from an image control section (25).

1st. Sensors (33) and (63) are installed at the scan start ends of the second optical systems (3) and (6), respectively.

The sensors (33) and (63) are used to instruct the driver circuits (32) and (62) when to start reading images, and the laser is the sensor (33).

(63), a signal is outputted when the laser beam is incident on the laser beam, and the timing of laser irradiation in the axial direction is adjusted.

1st. The second developing devices (4) and (7) are of the well-known magnetic brush type having developing sleeves (41) and (71) with built-in magnetic rollers, so the two-component developer consisting of toner and carrier is applied to the developing sleeves. (41) and (71) in a magnetic plan state, and rub it against the electrostatic latent image formed on the surface of the photoreceptor drum (1) to form a toner image. .

In the first developing device (4), a first developer made of a mixture of a color toner and a carrier is stored, for example, as a first toner, and in the second developing device (7), a second toner is stored. A second mixture of black toner and carrier as
A developer is stored therein, and in this embodiment, each toner is triboelectrically charged to a positive polarity and the carrier is triboelectrically charged to a negative polarity.

Each developing device (4), (7) is equipped with well-known toner replenishing means (42), (72), and a toner concentration control mechanism (50), which will be described later, is provided inside the developing device (4), (7). toner density is controlled.

The transfer charger (9) applies a negative charge to the transfer paper (P) that is conveyed from the direction of the arrow (b) to the transfer area (S) by a tractor (not shown) or the like, and electrostatically charges the surface of the photoreceptor drum. This is to transfer the toner image adsorbed onto the transfer paper (P). Note that the transport speed of the transfer paper (P) is set equal to the peripheral speed (V) of the photosensitive drum (1).

Next, the image forming operation of the image forming apparatus having the above configuration will be explained with reference to FIG.

Photosensitive drum (1) moves at a constant speed (V) in the direction of arrow (a)
While the photosensitive drum (1) is being rotationally driven, first charging is performed by the first mW charger (2), and the surface of the photosensitive drum (1) is charged to a potential of (Vo).

Subsequently, based on the image signal from the image control section (25), the first image signal is input to the first optical system (3) via the delay circuit (24).

In the first optical system (3), when the first image signal is input manually, the first optical system (3) drives the first LD driver circuit (32), and
At D (31), the surface of the photoreceptor drum (1) is irradiated with a laser beam from the first exposure position (X,) to expose the first image.

This laser beam scans the surface of the photoreceptor drum (1) in the axial direction, and the potential of the first image area is reduced to approximately OV, forming a negative electrostatic latent image.

Then, first development is performed in the first developing device (4).

This development is performed while applying a developing bias voltage of (Vbl) to the developing sleeve (41), and reverse development is performed in which positively charged color toner (Tc) adheres to the first image area (charge erased area). It is.

Subsequently, second charging is performed by the second charging gear (5), and the surface of the photosensitive drum (1) is returned to a potential of approximately (■.).

Next, a second image signal is input from the image control section (25) to the second optical system (6) via the delay circuit (24).

When the second image signal is input manually, the second optical system (6)
The LD driver circuit (62) drives the second LD (61)
At , a second image is exposed on the surface of the photoreceptor drum (1) from the second exposure position (X,), the potential of the image area is dropped to approximately OV, and a negative electrostatic latent image is formed. .

Subsequently, a second phenomenon is performed in the second phenomenon device (7).

This development is performed while applying a development bias voltage (Vbz) to the developing sleeve (71), and is a reversal development in which positively charged black toner (Tb) adheres to the image area (charge erased area). A second image is formed overlapping the first image.

In the above image forming operation, the laser irradiation timing in the axial direction of the photoreceptor drum (1) is determined by the sensor (33), (
63).

On the other hand, the transfer paper (P) is conveyed as a continuous paper in the direction of the arrow (b) at a speed (■゛) on the path shown by the dashed line in FIG. The toners ('I'c) and (Tb) are transferred, and then the toners (Tc) and (Tb) are melted and fixed by a fixing device (not shown).

Note that the charge on the photosensitive drum (1) is erased by an eraser lamp (8) immediately before the transfer process.

The photosensitive drum (1) continues to rotate in the direction of arrow (a) even after the transfer, residual toner is removed by a cleaning device (10), and residual charges are erased by a main eraser lamp (11). .

Next, the first. A toner concentration control mechanism (50) that detects the toner content ratio in the developer contained in the second developing device (4), (7'') and maintains it at an appropriate level will be described.

The toner concentration control mechanism (50) generally includes a concentration detection sensor (18), a toner replenishment control circuit (19), a first developer toner replenishment means (42), and a second developer toner replenishment means (7).
2).

As shown in FIG. 3, the concentration detection sensor (18) is an optical concentration detection sensor consisting of a light emitting element (18a) and a light receiving element (18b), and detects the reflected light of the light emitted from the light emitting element (18a). is detected by the light receiving element (18b), and the amount of reflected light is converted into an electrical signal and output to the toner replenishment control circuit (19).
) is placed so as to face the image plane.

Prior to the image forming operation of the desired image, lasers are simultaneously irradiated from the first optical system (3) and the second optical system (6) to form a reference latent image on the surface of the photoreceptor drum (1). Form. Subsequently, these reference latent images are transferred to the first developing device (4),
The toner density detection sensor (18) detects the density of the basic school images (Ml) and (M2) developed by the second developing unit (7) and further transferred to the transfer paper (P), and converts this into an electrical signal. It is converted and output to the toner supply control circuit (19).

If the toner density of the reference image (M,) or (M,) is lower than the base density, the toner replenishment control circuit (19) issues a toner replenishment signal to cause the first phenomenon device toner replenishment means (42) to output a toner replenishment signal.
) or the second developing device toner replenishing means (72) to replenish toner to the first developing device (4) or the second developing device (7). If not, the image forming operation continues.

The following is the gist of the present invention. Second optical system (3), (
Adjustment 6) will be explained.

In the image forming operation, the fixed state of the first and second optical systems (3) and (6) becomes loose due to long-term use, vibration during transportation, etc., and the direction of laser irradiation is distorted, causing the first optical system (
3), or the exposure position of the second optical system (6) deviates from the normal exposure position (Xa, (Xt), for example, the second optical system (
6) The laser beam is aligned with the dotted line (La) or the dashed-dotted line (
The second image is irradiated in the direction shown by Lb), and the second image deviates from the normal exposure position (X, ) (Xa).

(xb), the timing control unit (20) described below corrects the radiation and restores the normal state.

The timing control section (20) includes an interval measurement circuit (21),
It consists of a comparison circuit (22), an irradiation timing correction calculation circuit (hereinafter referred to as calculation circuit X23), and a delay circuit (24).

The interval measuring circuit (21) is connected to the toner concentration detection sensor (
18) and the toner concentration detection sensor (18).
This circuit detects the detection time interval (T 1X-c/V) of the reference images (Ml) and (M, ) detected in
(see figure).

Note that this detection time interval (T i) is the same as that of the first optical system (3
), and when the second optical system (6) is set at the normal position, the second exposure starts after a point on the photoreceptor drum (1) passes the first exposure position (X, ). This corresponds to the reference time ('ro) until reaching position 0 (,).

The comparison circuit (22) compares the reference time (T O) and the detection time interval (T i), and the calculation circuit (23) calculates the difference δ-TiTo, and the result is sent to the delay circuit ( 24).

The table below shows the control operation of the timing control unit (20) having the above configuration when the laser irradiation position of the second optical system (6) is shifted as shown by the dotted line or the dashed line in FIG. I will explain.

X, X, (no) To(=120/V)
--X, Xa=Ca (:12o) Ta (4a/V)
Second optical system δa (□XaL/V)X1Xb4b
(<(2o) Tb(4b/V) First optical system δ
b (=xbx, /v), where δa= T a T
o = ((!a-Qo)/V-(X1Xa-Xlx
2)/■ = X a X t/ V δb = T b To-(Cb (!o)/
V=(X,Xb-X,X,)/V-XbXt/V As shown in FIG. ), the interval (Qa) between the first exposure position (X, ) and the second exposure position (Xa) will be larger than the regular exposure interval (Q.), so the detection time interval ( Ti) is Ta(=
Qa/V), which is larger than the regular reference time ('r o).

The interval measuring circuit (21) then detects the detection time interval (21) based on the signal input from the toner concentration detection sensor (I8).
Ta) and outputs the value to the comparison circuit (22),
The comparison circuit (22) compares the detection time interval (Ta) with the regular reference time (To), and then the calculation circuit (23) calculates the delay time (δa) and applies the value to the delay circuit (2).
4), and also outputs a signal indicating that the second optical system (6) is to be delayed since δa>0.

The delay circuit (24) is connected to the image control section (25).
The second image signal inputted from the second optical system (6) is outputted to the second optical system (6) with a time delay of δa.

As a result, the delay circuit (24) is
) at the same time as the first one. The second image signal is output with a time delay of (δa). Then, during the delay time (δa), the first exposure position 1W (
Since the electrostatic latent image of the first image irradiated at X, ) advances in the direction of the arrow (a) by a distance of XaXt from the first exposure position (Xl), Image and second
The distance to the image is substantially corrected to normal (Q,).

On the other hand, if the laser irradiated from the second optical system (6) is irradiated at a position with an inclination (xb) in the direction indicated by the dashed-dotted line (Lb), the first exposure position (Xl) and the second exposure position (Xb
) and the distance G! b) is smaller than the regular exposure interval (C,), so the detection time interval (T i) is TbC=i2
b/V), which is smaller than the reference time ('r o).

Then, in the interval measuring circuit (21), the detection time interval (
Tb) is detected, and the comparator circuit (22) compares this with the regular reference time (T o), and then the arithmetic circuit (23) calculates the delay time (δb), and that value is used as the delay time. Since δb<o, a signal indicating that the first optical system (3) is to be delayed is outputted to the circuit (24).

The delay circuit (24) is connected to the image control section (25).
The first image signal inputted from the first image signal is outputted to the second optical system (6) with a time delay of (δb).

As a result, the delay circuit (24) is
) at the same time as the first one. The second image signal is output with a time delay of (δb). During the delay time (δb), the electrostatic latent image of the second image irradiated at the second exposure position (X, ) is moved in the direction of arrow (a) at a distance of xbx, from the second exposure position (X, ). Therefore, the distance between the first image and the second image formed on the photoreceptor drum (1) is corrected to be substantially normal (i2.).

By performing the above operations, the photoreceptor drum (
1) The first . There is no relative positional shift of the second image, and, for example, ruled lines and character images no longer overlap.

Moreover, since the above-mentioned operations are performed automatically, they are accurate and quick.

In addition, in the above description, the case where the position of the second optical system (6) is shifted is described, but it is not limited to this, and the case where the position of the first optical system (3) is shifted.
The same correction is made in the case where the laser irradiation position is shifted.

(Effects of the Invention) As is clear from the above explanation, the present invention can detect the toner density based on the detection time of the reference image by the optical sensor that detects the toner density.
It is equipped with a control mechanism that detects the positional deviation of the laser optical system and properly corrects the timing of image formation.

Therefore, vibrations during transportation of image forming devices such as copiers and printers, bolts fixing the optical system loosening due to long-term use, and changes in the environment may cause deviations in the laser irradiation position. However, the positional deviation will be corrected,
Since the image is formed in a normal state, there is no possibility of obtaining an image in which ruled lines and characters overlap.

In addition, since the writing correction operation is performed automatically, it is accurate and accurate.
And fast.

[Brief explanation of drawings]

The drawings show an embodiment of the two-color image forming apparatus according to the present invention, in which Fig. 1 is a schematic configuration diagram of the apparatus, Fig. 2 is an explanatory diagram of the image forming process, and Fig. 3 shows the arrangement of optical sensors. FIG. l...Photosensitive drum, 2...First charging charger,
3...First optical system, 4...First developing device, Death...Second
Charging charger, 6... Second optical system, 7... Second developing device, 9... Transfer charger, 18... Density detection sensor, 20... Timing control section, 21... Interval measurement circuit, 22... Comparison circuit, 23... Irradiation timing correction calculation circuit, 24... Delay circuit, 25... Image control unit. Patent applicant: Minolta Camera Co., Ltd. Representative: Patent attorney: Mr. Hajime and two others Figure 2, Figure 1B3

Claims (1)

[Claims] (1) A plurality of image forming processes consisting of a charging means, a laser optical system, and a developing device are arranged around the electrostatic latent image carrier along the moving direction of the electrostatic latent image carrier, and the image forming process is used. At the same time, a reference latent image is formed on the surface of the electrostatic latent image carrier, and this is further developed to form a reference image, and the density of the reference image is detected by an optical sensor. , in an image forming apparatus that detects a toner content ratio in a developer contained in each of the developing units, a shift in the laser irradiation position is detected based on a detection time interval of the reference image by the optical sensor. An image forming apparatus comprising: a control mechanism for correcting a timing shift in image formation;