JPH09325619A - Image recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a print of sharp image even in the vase of carious liner images and gradation images by providing nip width switching mechanism for freely switching an amount of nip according to a transfer mode. SOLUTION: A developing roller 14 is provided in a developing unit 16, attaches toner in which negative charges are electrified to an electrostatic latent image to develop the image, and a transfer roller 15 supplies positive charges to a printing medium 2 to attach the developed toner to the printing medium 2. The transfer roller 15 is equipped with the nip width-switching mechanism 17 which supports a shaft 15a freely rotatably and switches the amount of nip by shifting the shaft 15a in relation to a photoreceptor drum 11 according to the transfer mode. The mechanism 17 supports the shaft 15a of the transfer roller 15 freely rotatably, also makes a bearing 18 sliding toward the photoreceptor drum 11 about on a can having an outline matching amounts of shifts, and rotates the cam the amount of shift by means of a cam-rotating drive part. Thus, because the minute amount of nip can be set, the recorder can cope with the types of images.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic printer,
The present invention relates to an image recording device used for a facsimile or the like.

[0002]

2. Description of the Related Art Conventionally, in an image recording apparatus, for example, an electrophotographic printer, a photoreceptor for forming a toner image and a toner are used.
A nip is provided at the contact portion with the transfer roller that transfers the image from the photoconductor to the print medium.

By the way, there is a relation between the nip amount and the transfer efficiency of the toner, and the transfer efficiency of the toner is 0.2 mm when the nip amount is 0.2 mm.
Up to the neighborhood, it is proportional to the nip amount, and thereafter reaches saturation. Therefore, in the conventional image recording apparatus, the nip amount is 0.2 to 0.
It was fixed at about 3 (mm).

[0004]

In the conventional image recording apparatus, since the nip amount is constant, the transfer mode is a character centered on a fine line or requires a smooth gradation. However, there was a problem in that it was not possible to clearly respond to a picture like a photograph.

An object of the present invention is to provide an image recording apparatus capable of printing a clear image even in the case of various line drawings and gradation images.

[0006]

In order to achieve the above object, the image recording apparatus of the present invention is provided with a nip amount switching mechanism capable of switching the nip amount according to the transfer mode.

[0007]

Embodiments of the present invention will be described with reference to the drawings. Elements common to the drawings are given the same reference numerals. FIG. 1 is a schematic diagram showing a schematic configuration of an image recording apparatus according to an embodiment. The image recording apparatus 1 includes a medium feeding unit 4, a registration roller unit 5, an image forming unit 6, and a heat fixing unit 7 along a medium carrying path 3 for carrying a print medium 2 in a direction of an arrow A, which is a medium carrying direction. It is set up. A cassette 8 accommodating the print medium 2 is detachably provided at one end of the medium transport path 3, and a stacker 9 for ejecting the printed print medium 2 is provided at the other end.

The medium feeding unit 4 has a medium feeding roller 10 which rotates in the direction of the arrow and feeds the print medium 2 from the cassette 8 one by one. The registration roller unit 5 has registration rollers 5a and 5b which rotate in the directions of the arrows, respectively. The skew of the print medium 2 fed by the medium feeding roller 10 is corrected by the pressure contact portion, and the print medium 2 is arrowed. It is conveyed in the A direction. The image forming unit 6 includes a photoconductor 1 that rotates in the direction of the arrow.
A charging roller 12, a recording head 13, a developing roller 14, and a transfer roller 15 are arranged in contact with each other along the circumference of 1 (hereinafter referred to as a photosensitive drum 11).

The charging roller 12 rotates in the direction of the arrow to uniformly charge the surface of the photosensitive drum 11 with negative charges, and the recording heads 13 are arranged in a line in a direction intersecting at right angles with the direction of the arrow A. An electrostatic latent image is formed by the LED element on the surface of the photoconductor drum 11 having a negative charge.

The developing roller 14 is provided in the developing unit 16, and a toner charged with a negative charge is attached to the electrostatic latent image for development, and the transfer roller 15 is positively charged on the print medium 2. Is supplied to attach the developing toner to the print medium 2.

The transfer roller 15, as shown in FIG.
The shaft 15a is rotatably supported, and a nip amount switching mechanism 17 that switches the nip amount by shifting the shaft 15a with respect to the photosensitive drum 11 according to the transfer mode is provided.

The heat fixing section 7 has a fixing roller 7a and a pressure contact roller 7b which rotate in the directions of the arrows. Fixing roll
A heat source such as a halogen lamp is internally provided in the roller 7a, and the developing toner adhered to the print medium 2 is thermocompression bonded at a pressure contact portion with the pressure contact roller 7b.

FIG. 2 is a perspective view showing the nip amount switching mechanism, and FIG. 3 is a sectional view taken along line BB of the nip amount switching mechanism shown in FIG. The nip amount switching mechanism 17 is the shaft 1 of the transfer roller 15.
Bearings 18 and 19 for rotatably supporting 5a, and bearing 1
8 and 19 are brought into contact with the cam surface to rotatably support the cams 20 and 21, and the cams 20 and 21 are rotated to transfer the transfer roller.
And a cam rotation drive unit 22 for moving the roller 15 toward the photoconductor drum 11.

The bearings 18 and 19 are the shaft 15 of the transfer roller 15.
V-shaped grooves 18a and 19a for rotatably supporting a are provided at one end, and V-shaped protrusions 18b and 19b that come into contact with the cam surfaces of the cams 20 and 21 are provided at the other end. It is slidably disposed toward the photoconductor drum 11 in a groove provided in the side frame.

The cams 20 and 21 are fixed to both ends of a shaft 23 rotatably supported by a side frame (not shown). The cam rotation drive unit 22 includes a motor 25 that rotates the drive gear 24, a driven gear 26 that meshes with the drive gear 24,
The home position of the cams 20 and 21 is set to the sensor lever 27.
And a home position detection sensor 28 for detecting The driven gear 26 and the sensor lever 27 are fixed to one end of the shaft 23. The motor 25 rotates the cams 20 and 21 in the directions of the arrows C and D by the shift amount, and
On the other hand, the transfer roller 15 is moved in the directions of arrows E and F.

In the contours of the cams 20 and 21, as shown in FIG. 3, 360 ° is divided into angles θ1, θ2, and θ3, and the bearing 1
Positions P1, P2, P3 for positioning the convex portions 18b, 19b of Nos. 8 and 19 are provided.
2 and P3 are provided with a step portion with which the edges of the convex portions 18b and 19b abut. Positions P1 and P2 from the axis of shaft 23
, P3 are r1, r2, and r3, and the nip amount s1 between the photosensitive drum 11 and the transfer roller 15, which will be described later, is s1.
, S2, s3. In this embodiment, the position P1 is the home position.

FIG. 4 is a block diagram of the transfer mode changeover control unit. The control unit 30 has a transfer mode changeover unit 31 (for example, a transfer mode changeover switch provided in the operation unit).
The cam rotation drive unit 22 of the nip amount switching mechanism 17 is connected. The control unit 30 includes a central processing unit 32 (hereinafter CPU
32) and a memory 33. The CPU 32 operates as a transfer mode discriminating means 32a and a nip amount changing means 32b according to a control program, and a memory 33 stores a shift amount table in which the transfer mode and the shift amount (pulse number) are associated with each other. It operates as an amount table storage means 33a and a transfer mode storage means 33b for storing the current transfer mode.

The transfer mode discriminating means 32a compares the output contents of the transfer mode switching portion 31 with the contents of the transfer mode storing means 33b to judge that the transfer mode has been switched. The nip amount changing means 32b is a transfer mode determining means 32.
Based on the output of a, the content of the shift amount table storage means 33a is referred to, the shift amount corresponding to the output content of the transfer mode switching unit 31 is selectively output, the cam rotation drive unit 22 is driven, and the nip amount is set. And transfer mode storage means 3
The content of 3b is updated to the output content of the transfer mode switching unit 31.

The transfer mode includes a standard mode, a thin line mode,
There is a gradation image mode. Shift amount table storage means 33
The number of pulses m1 and m2 for driving the motor 25 of the cam rotation drive unit 22 corresponding to the fine line mode and the gradation image mode are shown in a.
Is remembered.

When the contact position between the cam surface and the convex portions 18b, 19b of the bearings 18, 19 is changed from the home position P1 to the position P2, the pulse number m1 is
The number of pulses for driving the motor 25, and similarly, the number of pulses m2 is the number of pulses for driving the motor 25 when changing from the position P1 to the position P3.

FIG. 5 is an explanatory diagram showing the relationship between the transfer mode and the nip amount. (A) to (C) correspond to the gradation image mode, the standard mode, and the thin line mode, and the nip amounts s3, s1, and s2 corresponding to each mode have a magnitude relationship of s3 <. s1
<S2.

Next, the operation will be described with reference to FIG. FIG. 6 is a flow chart for explaining the operation of the present invention. When the power switch is turned on, C in step S1
The PU 32 initializes the device. CP as a part of initialization
U32 sets the standard mode in the transfer mode storage means 33b, drives the motor 25, rotates the cams 20 and 21 in the direction of arrow C, and detects the home position detecting sensor 2
The sensor lever 27 is sensed via 8.

When the home position detecting sensor 28 detects the sensor lever 27, the CPU 32 further rotates the cams 20 and 21 in the direction of arrow C to some extent, and then reverses the motor 25 to rotate the Vs of the bearings 18 and 19. Shaped convex portion 18b,
The motor 25 is stopped by rotating until 19b contacts the stepped portions of the cams 20 and 21. The V-shaped convex portions 18b and 19b of the bearings 18 and 19 are positioned at the position P1,
The nip amount between the photosensitive drum 11 and the transfer roller 15 is set to s1 as shown in FIG. 5 (B).

At step S2, the CPU 32 (transfer mode discriminating means 32a) compares the output contents of the transfer mode switching portion 31 with the contents of the transfer mode storing means 33b to determine whether the transfer mode has been switched. Whether or not it is checked, if it is switched, the process branches to step S6, and if not, the process branches to step S3.

In step S3, the CPU 32 checks whether or not a print start command is input. If a print start command is input, the process branches to step S5.

In step S4, the CPU 32 feeds out one sheet of the print medium 2 from the cassette 8 based on the print control program, forms a toner image on the photosensitive drum 11, and transfers it as shown in FIG. A positive charge is supplied to the print medium 2 by 15 to transfer the toner image to the print medium 2, and the heat fixing unit 7 heat-fixes the toner on the print medium 2.

In step S5, the CPU 32 checks whether or not the printing is completed. If the printing is completed, the process branches to step S2.

In step S6, the CPU 32 (transfer mode discriminating means 32a) checks whether or not the output content of the transfer mode switching section 31 is the thin line mode, and if it is the thin line mode, the process branches to step S7. , No, the process branches to step S8.

In step S7, the CPU 32 (nip amount changing means 32b) refers to the contents of the shift amount table storing means 33a based on the output contents of the transfer mode switching portion 31,
The pulse number m1 is read as the shift amount, the motor 25 is driven, and the cams 20 and 21 are rotated in the arrow C direction. The V-shaped convex portions 18b and 19b of the bearings 18 and 19 are positioned at the position P2, and the photosensitive drum 11 and the transfer roller 1 are positioned.
The nip amount with 5 is set to s2, as shown in FIG. When the CPU 32 sets the nip amount to s2,
The contents of the transfer mode storage means 33b are updated to the thin line mode, and the process returns to step S3.

In step S8, the CPU 32 (transfer mode discrimination means 32a) checks whether or not the output contents of the transfer mode switching section 31 is a gradation image mode. If not, the process branches to step S10.

At step S9, the CPU 32 (nip amount changing means 32b) refers to the contents of the shift amount table storing means 33a based on the output contents of the transfer mode switching portion 31,
The number of pulses m2 is read as the shift amount, the motor 25 is driven, and the cams 20 and 21 are rotated in the direction of arrow C. The V-shaped convex portions 18b and 19b of the bearings 18 and 19 are positioned at the position P3, and the photosensitive drum 11 and the transfer roller 1 are positioned.
The nip amount with 5 is set to s3, as shown in FIG. When the CPU 32 sets the nip amount to s3,
The contents of the transfer mode storage means 33b are updated to the gradation image mode, and the process returns to step S3.

In step S10, the CPU 32 determines the motor 2 based on the output contents (standard mode) of the transfer mode switching unit 31.
5 to rotate the cams 20 and 21 in the direction of arrow C,
Sensor lever via home position detection sensor 28
Senses 27.

When the home position detecting sensor 28 detects the sensor lever 27, the CPU 32 further rotates the cams 20 and 21 in the direction of arrow C to some extent and then reverses the motor 25 to rotate the V of the bearings 18 and 19. Shaped convex portion 18b,
The motor 25 is stopped by rotating until 19b contacts the stepped portions of the cams 20 and 21. The V-shaped convex portions 18b and 19b of the bearings 18 and 19 are positioned at the position P1,
The nip amount between the photosensitive drum 11 and the transfer roller 15 is set to s1 as shown in FIG. 5 (B). CPU32
When the nip amount is set to s1, the setting mode storage means 3
The contents of 3b are updated to the standard mode, and the process returns to step S3.

When switching from the fine line mode to the gradation image mode, the contents of the shift amount table storage means 33a are referred to and the pulse numbers m1 and m2 are read out as the shift amount.
The motor 25 is driven by calculating the pulse number difference (m2-m1).

When switching from the gradation image mode to the fine line mode, the standard mode is set, the pulse number m1 is read out, and the motor 25 is driven.

In the present embodiment, three modes of gradation image mode, standard mode, and fine line mode are designated as transfer modes,
The cam surface is also provided with a contour corresponding to it, but the cam surface may be stepless as shown in FIG. If the cam surface is made stepless, it is possible to set a finer nip amount, and it is possible to deal with various types of images.

Further, in the present embodiment, the nip amount switching mechanism is provided with a cam and a cam rotation driving unit, and the bearing that rotatably supports the shaft of the transfer roller is moved toward the photosensitive member. However, a rotatable lever is provided, one end of the lever is engaged with the bearing, and the other end of the lever is manually rotated.
The transfer may be stopped depending on the nip amount, or the electromagnetic solenoids may be engaged at the positions of the other ends for moving the bearings according to the nip amount, respectively, and the transfer mode switching unit as in this embodiment may be used. May be operated according to the output of.
Further, when the photoconductor is a belt, the photoconductor may be moved toward the transfer roller.

In this embodiment, the monochrome image recording apparatus has been described, but the present invention can be applied to a multi-color image recording apparatus such as a tandem system or an intermediate transfer system.

Further, in the present embodiment, the mode switching is performed by the type of image, but it may be performed by the resolution of the data to be printed. For example, when printing at 600 DPI (dots / inch), 300 DPI, and 150 DPI, the modes are thin line mode, standard mode, and gradation image mode.
Switch to do.

Further, the mode switching may be performed at the printing speed. For example, 12PPM (page / min), 8PP
When printing in M or 4PPM, the mode is switched to the thin line mode, the standard mode, and the gradation image mode.

[0041]

Since the present invention is configured as described above, it has the following effects. The image to be printed is centered on the thin line because the transfer roller shaft is rotatably supported and a nip amount switching mechanism that moves the shaft relative to the photosensitive drum by a shift amount according to the nip amount is provided. Also, the SMOOTH can print a clear image even when it is a picture like a photograph that requires gradation.It also supports the axis of the transfer roller rotatably and faces the photoconductor drum. It is possible to set a fine nip amount by providing a sliding bearing and contacting it with a cam having a contour corresponding to the shift amount, and rotating the cam by the shift amount by the cam rotation drive unit. It can correspond to various image types.

By changing the transfer mode and selectively outputting the shift amount corresponding to the nip amount of the changed transfer mode to drive the cam rotation drive unit, the shift amount table is set. You can set a fine nip amount without changing the mechanism simply by changing the contents of the bull.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a schematic configuration of an image recording apparatus according to an embodiment.

FIG. 2 is a perspective view showing a nip amount switching mechanism.

3 is a cross-sectional perspective view taken along line BB of FIG.

FIG. 4 is a block diagram of a transfer mode switching controller.

FIG. 5 is an explanatory diagram showing a relationship between a transfer mode and a nip amount.

FIG. 6 is a flowchart for explaining the operation of the present invention.

FIG. 7 is an explanatory view showing an embodiment of another cam.

[Description of Reference Signs] 1 image recording device 11 photoconductor drum 15 transfer roller 17 nip amount switching mechanism 18, 19 bearings 20, 21, 40 cam 22 cam rotation drive unit 30 control unit 32 CPU 33 memory

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuichiro Ogata 4-11-22 Shibaura, Minato-ku, Tokyo In the Oki data of the stock company

Claims (3)

[Claims] 1. A toner for forming a toner image, and a toner.
An image recording apparatus having a nip at a contact portion with a transfer means for transferring an image from a photoconductor to a printing medium, characterized by having a nip amount switching mechanism capable of switching the nip amount according to a transfer mode. Image recording device. 2. The nip amount switching mechanism is the transfer roller.
Bearing rotatably supporting the shaft of the rotor and slidable toward the photoconductor drum, and the bearing is brought into contact with a cam surface having a contour corresponding to the nip amount to allow the shaft to rotate freely. The image recording apparatus according to claim 1, further comprising: a supported cam and a cam rotation drive unit that rotates the cam according to the transfer mode. 3. The image recording apparatus according to claim 2,
A transfer mode switching section for switching the transfer mode, and a transfer mode switching control section for selectively outputting a shift amount corresponding to the nip amount of the switched transfer mode to drive the cam rotation drive section. An image recording apparatus comprising: