JP2001021826A - Electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively and easily adjust the density of a recorded image by providing an adjusting means variably adjusting the moving position of an exposure unit. SOLUTION: A rotary knob 36 is provided at the upper part of the side surface of a main body 1, and a rod 37 is connected to the knob 36. Plural cams 38 are attached to the rod 37 and the housing of the exposure unit 2 abuts on the peripheral surface of the cam 38. The exposure unit 2 is moved up and down with the turning of the rod 37 and the cam 38 based on the operation of the knob 36. When the knob 36 is set to density set position height, the short part of the radial direction of the cam 38 abuts on the unit 2 and the unit 2 is pushed up by the biasing force of a spring. A distance between the unit 2 and a photoreceptor drum 3 is made longer than the focal distance of the lens system of the unit 2. In such a case, a laser beam is spread, so that the distribution of irradiation where a spot diameter is large is obtained on the drum 3 and the density of the image is made high.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus for recording an image by irradiating an image carrier with a laser beam from an exposure unit.

[0002]

2. Description of the Related Art A laser beam is emitted from an exposure unit to a photosensitive drum as an image bearing member to form an electrostatic latent image on the surface of the photosensitive drum, and the electrostatic latent image is visualized by development to form a paper. There is an electrophotographic device to transfer on.

In this electrophotographic apparatus, a photosensitive drum is rotatably provided below an exposure unit, and a charger, a developing device, a transfer device, and a cleaner are sequentially arranged around the photosensitive drum.

The surface of the photosensitive drum is charged by a charger, and the surface of the photosensitive drum is exposed and scanned by irradiating the surface with laser light from an exposure unit. By this exposure scanning, an electrostatic latent image is formed on the surface of the photosensitive drum.

[0005] The electrostatic latent image on the photosensitive drum is visualized by receiving a developer (toner) in a developing device, and moves to a transfer device position. A sheet is fed between the transfer unit and the photosensitive drum in synchronization with the rotation of the photosensitive drum, and a visible image on the photosensitive drum is transferred to the sheet.

The sheet on which the image has been transferred is peeled off from the photosensitive drum and sent to a fixing device. Here, the transferred image on the paper is heat-fixed, and the recording of the image is completed. The recorded paper is discharged to a paper discharge unit. After the transfer, the photosensitive drum is subjected to a removal treatment of the residual developer and the like by the cleaner, and charged again by the charger to prepare for the next recording.

In such an electrophotographic apparatus, the density of a recorded image can be changed by adjusting the intensity of a laser beam emitted from an exposure unit.

FIG. 13 shows the relationship between the intensity of the laser beam and the size of the distribution of the laser beam on the photosensitive drum. The intensity of the laser beam required for exposing the photosensitive drum is equal to or higher than a threshold value A, and the irradiation distribution of the laser beam having the intensity equal to or higher than the threshold value A has a spot diameter P1 in the axial direction (main scanning direction) of the photosensitive drum. The spot diameter becomes P2 in the circumferential direction (sub-scanning direction) of the body drum.

When the intensity of the laser beam is standard (above the threshold value A), the irradiation distribution is as shown in FIG. If the intensity of the laser beam is higher than the standard, as shown in FIG. 15, the spot diameter P1 of the irradiation distribution becomes larger than the standard time (the spot diameter P2 does not change). As a result, the dot size and the line thickness of the recorded image become larger than the standard time, and this appears as an increase in image density.

[0010]

In order to adjust the intensity of the laser beam, it is necessary to add a control system for controlling the output of the exposure unit, resulting in a problem that the cost is increased.

The present invention has been made in view of the above circumstances,
An object of the present invention is to provide an electrophotographic apparatus capable of easily and inexpensively adjusting the density of a recorded image.

[0012]

According to a first aspect of the present invention, there is provided an electrophotographic apparatus, wherein an image bearing member is irradiated with a laser beam from an exposure unit to form an electrostatic latent image on the image bearing member. Moving means for moving the exposure unit in the same direction as the optical axis of the laser beam emitted from the exposure unit, and moving the exposure unit by the moving means. Adjusting means for adjusting.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a main body of an electrophotographic apparatus, and an exposure unit 2 is provided in an upper portion of the main body 1. A photosensitive drum 3 serving as an image carrier is rotatably provided at a substantially central portion in the main body 1, and a charger 4, a developing device 5, a transfer device 9, and a cleaner 10 are provided around the photosensitive drum 3. Are sequentially arranged.

The exposure unit 2 irradiates the surface of the photosensitive drum 3 with a laser beam corresponding to the input image data, and performs exposure scanning on the surface of the photosensitive drum. By this exposure scanning, an electrostatic latent image is formed on the surface of the photosensitive drum 3.

A large number of sheets 11 are set on the bottom of the main body 1, and the sheets 11 are taken out one by one by a pickup roller 12. The taken out paper 11 is sent to the photosensitive drum 3 by the transport roller 13, the transport guide 14, and the transport roller 15.

The charger 4 applies a high voltage supplied from a high voltage power supply (not shown) to the photosensitive drum 3 to charge the surface of the photosensitive drum 3 with an electrostatic charge. The electrostatic latent image is formed on the photoconductor drum 3 by the charging and the irradiation of the photoconductor drum 3 with the laser beam from the exposure unit 2.

The electrostatic latent image on the photosensitive drum 3 is
The image is visualized by receiving the developer (toner), and moves to a position corresponding to the transfer device 9. The developing device 5 supplies the stored toner to the photosensitive drum 3 by the toner supply roller 6 and the developing roller 7. A toner regulating member 8 is in contact with the developing roller 7, and the toner regulating member 8
Thereby, an appropriate amount of toner layer on the developing roller 7 is formed.

A sheet 11 is sent between the photosensitive drum 3 and the transfer unit 9 in synchronization with the rotation of the photosensitive drum 3, and a visible image on the photosensitive drum 3 is transferred to the sheet 11.

The transferred paper 11 is separated from the photosensitive drum 3 and sent to a fixing device 16. Here, paper 11
The upper transfer image is heat-fixed, and the recording of the image is completed. The recorded paper 11 is transported by the transport roller 18 and the transport guide 1.
9 and a paper discharge roller 20 to discharge the paper to a paper discharge unit 21 on the upper surface of the main body 1.

The residual developer adheres to the photosensitive drum 3 after the transfer, and is removed by the cleaner 10. Thereafter, the photosensitive drum 3 is charged again by the charger 4, and the same image recording is repeated.

An operation panel 22 is provided near the paper discharge unit 21.
, And a rotary knob 36 is provided on the upper side of the main body 1. The rotary knob 36 is for moving the exposure unit 2 up and down, and as shown in FIG.
The following two density setting positions are provided.

On the other hand, the exposure unit 2 is shown in FIGS.
As shown in the figure, a laser generator 41, a rotating mirror 42, f-θ
Lenses 43, 44, 45 and a reflecting mirror 46 are provided.
The laser generator 41 includes a laser diode and a collimator lens, and emits a laser beam modulated according to an input signal. The laser light is deflected by the rotating mirror 42, and the deflected laser light is applied to the photosensitive drum 3 via the f-θ lenses 43, 44, 45 and the reflecting mirror 46.

As shown in FIGS. 1, 5, and 6, a fixing piece 31 and fixing pieces 32, 32 are attached to the side surface of the housing of the exposure unit 2 so as to protrude horizontally. The frames 33a and 33b are arranged at predetermined intervals at positions where the fixing piece 31 is vertically sandwiched, and the frames 34a and 33b are arranged at positions where the fixing pieces 32 are vertically sandwiched.
4b are arranged at a predetermined interval from each other. That is, the moving range of the fixing piece 31 is regulated by the frames 33a and 33b,
The moving range of each fixing piece 32 is different from each frame 34a, 34b.
, The exposure unit 2 can be moved up and down.

The pins 35a protrude from the lower surfaces of the fixing pieces 32, 32, and the pins 35b protrude from the upper surfaces of the fixing pieces 32, 32, respectively. Frames 34a, 34
b is formed with a pin insertion hole into which the pins 35a and 35b enter. The pin insertion holes and the pins 35a, 35
By the engagement with b, the positioning when the exposure unit 2 moves up and down is compensated.

The rotary knob 36 is provided on the upper side surface of the main body 1 as described above, and the rod 37 is connected to the rotary knob 36. The rod 37 penetrates the side surface of the main body 1 and is introduced above the exposure unit 2, and a plurality of cams 38 are attached to the introduction part. Then, the housing of the exposure unit 2 and the frame 3 are so arranged that the housing of the exposure unit 2 comes into contact with the peripheral surfaces of the cams 38, 38.
A spring 39 is mounted between the exposure unit 2a and the exposure unit 4a, and an upward biasing force is applied to the exposure unit 2.

The fixing pieces 31, the fixing pieces 32, 32,
The frame 33a, 33b, the frames 34a, 34b, the pins 35a, 35b, and the moving means for moving the exposure unit 2 in the same direction as the optical axis of the laser beam emitted from the exposure unit 2 are configured. Further, the rotating knob 36, the rod 37, and the cams 38, 38 constitute adjusting means for variably adjusting the moving position of the exposure unit 2 by the moving means.

That is, the exposing unit 2 moves up and down with the rotation of the rod 37 and the cams 38 and 38 based on the operation of the rotary knob 36. FIGS. 5 and 6 show the case where the rotary knob 36 is set to the density setting position “standard”. The long portions of the cams 38 and 38 in the radial direction abut the exposure unit 2 and the exposure unit 2 Is depressed against the biasing force. At this time, the distance between the exposure unit 2 and the photosensitive drum 3 corresponds to the focal length of the lens system of the exposure unit 2.

When the rotary knob 36 is set at the density setting position "high", short portions in the radial direction of the cams 38, 38 come into contact with the exposure unit 2 as shown in FIGS. 2 is pushed up by the biasing force of the spring 39. At this time, the distance between the exposure unit 2 and the photosensitive drum 3 is longer than the focal length of the lens system of the exposure unit 2.

The lens system of the exposure unit 2 is designed so that a laser beam forms an image on the photosensitive drum 3 with a designed focal length. When it is located at the position, the laser beam is narrowed down, so that an irradiation distribution with a small spot diameter P1 is obtained on the photosensitive drum 3 as shown in FIG.

When the exposure unit 2 is away from the focal length position as shown in FIGS. 5 and 6, the laser beam spreads, so that an irradiation distribution with a large spot diameter P1 is obtained on the photosensitive drum 3 as shown in FIG. Can be

As described above, when the spot diameter P1 of the irradiation distribution becomes larger than the standard time (the spot diameter P2 does not change), the dot size and line thickness of the recorded image become larger than the standard time. It appears as an increase.

FIG. 11 shows the relationship between the displacement of the exposure unit 2 with respect to the focal length position and the diameter of the laser beam irradiation distribution, ie, the beam system. The beam system becomes larger as the exposure unit 2 moves away from the focal length position.

As described above, the density of a recorded image can be adjusted at low cost and easily without adding a control system for controlling the output of the exposure unit 2.

In the above embodiment, two levels of "standard" and "high" are provided as the density setting positions. However, three or more levels of density setting positions may be provided.

Further, as the moving means and the adjusting means of the exposure unit 2, a motor drive may be employed. For example, as shown in FIG. 12, a belt 51 is hung on a rod 37, and the belt 51 is connected to a drive shaft 52 a of a stepping motor 52. The stepping motor 52 is connected to a control unit 53, and when the elevation switch (not shown) attached to the control unit 53 is operated, the stepping motor 52 rotates forward or backward. Accordingly, the rod 37 and the cams 38, 38 rotate, and the exposure unit 2 moves up and down. In this case, the density setting position can be set steplessly.

In addition, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the invention.

[0038]

As described above, according to the present invention, the moving means for moving the exposure unit in the same direction as the optical axis of the laser beam emitted from the exposure unit, and the moving position of the exposure unit by the moving means The provision of the variably adjusting means makes it possible to provide an electrophotographic apparatus capable of adjusting the density of a recorded image inexpensively and easily.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of an embodiment.

FIG. 2 is a view showing a rotary knob of the embodiment.

FIG. 3 is a view of the configuration of the exposure unit of the embodiment as viewed from above.

FIG. 4 is a side view of the configuration of the exposure unit of the embodiment.

FIG. 5 is a diagram illustrating a configuration of a moving unit according to the exposure unit of the embodiment and a state where the exposure unit is lowered.

FIG. 6 is a diagram illustrating a configuration of a moving unit according to the exposure unit of the embodiment and a state where the exposure unit is lowered as viewed from another direction.

FIG. 7 is a view showing a state in which the exposure unit of the embodiment is raised.

FIG. 8 is a view of a state in which the exposure unit of the embodiment is raised, as viewed from another direction.

FIG. 9 is a view showing an irradiation distribution of laser light of the exposure unit in FIGS. 5 and 6;

FIG. 10 is a view showing an irradiation distribution of laser light of the exposure unit in FIGS. 7 and 8;

FIG. 11 is a diagram showing the relationship between the displacement of the exposure unit with respect to the focal length position and the beam system in the embodiment, which has been experimentally confirmed.

FIG. 12 is a diagram showing a configuration of a modification of the embodiment.

FIG. 13 is a diagram showing the relationship between the intensity of laser light and the magnitude of the distribution of irradiation of the laser light on the photosensitive drum in the conventional apparatus.

FIG. 14 is a view showing an irradiation distribution when the intensity of a laser beam is standard in a conventional apparatus.

FIG. 15 is a view showing an irradiation distribution when the intensity of a laser beam is larger than a standard in a conventional apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Body 2 ... Exposure unit 3 ... Photoconductor drum (image carrier) 11 ... Paper 31, 32 ... Fixing pieces 33a, 33b, 34a, 34b ... Frame 36 ... Rotary knob 37 ... Rod 38 ... Cam

Claims (1)

[Claims] 1. An electrophotographic apparatus for irradiating a laser beam to an image carrier from an exposure unit to form an electrostatic latent image on the image carrier, developing the electrostatic latent image, and transferring the electrostatic latent image to paper. Moving means for moving the exposure unit in the same direction as the optical axis of the laser beam emitted from the exposure unit; and adjusting means for variably adjusting the moving position of the exposure unit by the moving means. Electrophotographic equipment.