JPH0199079A - Dry type electrophotographic device - Google Patents

Abstract

PURPOSE:To always obtain the best quality of printing even if the kind of paper is changed by detecting the kind of the paper feeding from a paper feeding mechanism and automatically changing the fixing temperature of a fixing part according to the kind. CONSTITUTION:A microswitch 16 functioning as a paper kind detector is attached in a cassette mounting port 11 into which a paper feeding cassette 7 is inserted. Meanwhile, pawls which abut on the microswitch 16 are selectively attached on the tip part of the paper feeding cassette 7 and the kind of the paper 8 housed in the paper feeding cassette 7 is specified with the attaching state thereof. It is specified whether the kind of the paper 8 at the time when the cassette 7 is mounted to the cassette mounting port 11 is regular paper or a post card and then the fixing temperature is automatically changed to the best fixing temperature with the action of the temperature control circuit of the respective fixing rollers 14a and 14b of the fixing part 14, so that it is unnecessary for an operator to perform the changing operation of the fixing temperature according to the kind of the paper.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a dry type electrophotographic device such as a laser printer, and in particular, to variable fixing temperature in a fixing unit depending on the type of paper fed from a paper feeding mechanism. The present invention relates to a controlled dry electrophotographic apparatus.

[Prior Art] Generally, in a dry type electrophotographic apparatus such as a laser printer, a charging unit that charges the photosensitive drum along the circumference of the photosensitive drum rotating at a constant speed is installed inside the case, and an input from the outside is installed inside the case. an exposure section that scans a laser beam in the axial direction of the photosensitive drum in response to an image signal corresponding to character data, a developing section that develops the image formed on the photosensitive drum, and a developing section that supplies the developed image from the outside. A transfer section that transfers images onto paper.

A static eliminating section and the like for erasing the image on the transfer section is provided.

Further, a paper feed cassette containing a large number of sheets is disposed at the bottom of the case, and a fixing section is provided on one side inside the case.

Then, when you press the start key on the operation panel provided on the outside of the case, the photosensitive drum starts rotating, an image is created in the exposure section on the photosensitive surface of the photosensitive drum whose static electricity has been removed, and this image is developed in the development section. Then, go to the transcription department. In the transfer section, the image is transferred onto the sheets of paper pulled out one by one from the paper feed cassette at the CF slot. The paper onto which the image has been transferred is transported to a fixing section by a transport roller, and the transferred image is thermally fixed by a fixing roller heated to a constant temperature. The paper that has passed through the fixing section is ejected from the paper ejection port to the outside of the case.

In general, a dry electrophotographic apparatus configured in this way has the following features:
A4. B5. Dedicated paper cassettes are prepared for each paper size such as letter size, and the operator inserts the paper cassette of the desired paper size into the cassette loading slot.
When the start switch is pressed, characters or images are printed on paper of the appropriate size.

[Problems to be Solved by the Invention] However, as described above, even in the dry electrophotographic apparatus configured to be able to select and print on a plurality of types of paper, the following problems still exist.

That is, in recent years, the types of paper that the operator can select are the aforementioned A4. B5. In addition to letter size, you can also choose postcard size. Therefore, it will naturally be printed on official and private postcards as well.

Generally, postcards are printed on A4 paper, which is used exclusively for copying machines and dry electrophotographic devices. B5. The paper used is thicker than standard sized plain paper such as letter size.

On the other hand, in the fixing section built into a dry electrophotographic device, the paper onto which the image has been transferred in the transfer section is thermally fixed using a fixing roller, etc., and the humidity at that time affects the quality of the thermally fixed image. In other words, it greatly influences the photo printing quality. Therefore, the fixing temperature is always controlled to provide the best print quality.

However, the print quality is greatly affected not only by the fixing temperature but also by the thickness and quality of the paper. For example, the above-mentioned postcards are thicker than standard size plain paper such as A4.85, so in terms of thermal efficiency, etc., a sufficient amount of heat cannot be obtained, resulting in poor fixing.

The present invention automatically changes the fixing temperature of the fixing unit according to the type of paper fed from the paper feeding mechanism, thereby constantly obtaining the best print quality even if the type of paper is changed. The purpose of the present invention is to provide a dry electrophotographic device that can perform

[Means for Solving the Problems] The present invention includes at least a charging section, an exposure section, a developing section, and a transfer section that are sequentially arranged along the circumference of a photosensitive drum, and the photosensitive drum charged by the charging section is The image formed on the photosensitive surface in the exposure section and developed in the development section is transferred to the paper fed from the paper feeding mechanism in the transfer section, and the paper with the image transferred is transferred in the transfer section. In a dry electrophotographic device that performs heat fixing in the fixing section,
a paper type detector that detects the type of paper fed from the paper feed mechanism; and a fixing temperature selection unit that selects the fixing density of the fixing unit in accordance with the paper type detected by the paper type detector. It is equipped with the following.

[Operation] In the dry type electrophotographic apparatus configured as described above, the type of paper fed from the paper feeding mechanism is detected by the paper type detector. Then, a fixing temperature corresponding to the detected paper type is automatically selected. Therefore, the best print quality can always be obtained.

[Example] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic cross-sectional view showing the general structure of a dry electrophotographic apparatus according to an embodiment. In the figure, reference numeral 1 denotes a case that covers the entire device, and a photosensitive drum 2 having a photosensitive surface formed on its outer peripheral surface is disposed at a central position within the case 1. The photosensitive drum 2 is rotated clockwise at a constant speed by a main drive motor (not shown). Along the outer periphery of the photosensitive drum 2, there is a charging section 39 consisting of a charging charger; an exposing section 5 which outputs a laser beam 4 in response to an image signal; a developing section 6 for developing the image formed on the photosensitive drum 2 in the exposing section 5; A transfer unit 9 consisting of a transfer charger that transfers the developed image onto the paper 8 fed from the paper feed cassette 7. A defrosting section 10 consisting of a static elimination lamp is provided for erasing the transferred image.

Further, at the bottom of the case 1, the paper feed cassette 7 for continuously supplying paper 8 to the transfer section 9 is inserted from the outside into a cassette mounting opening 11 formed in the case 1.

The paper 8 stored in the paper feed cassette 7 is transferred to the CF roller 12
The sheets are pulled out one by one from the paper feed cassette 7 and guided to the transfer section 9 via the conveyance roller 13. The image on the photosensitive drum 2 is transferred at this transfer section 9 . The paper 8 on which the image has been transferred is transferred to a fixing section 1 consisting of a pair of fixing rollers 14a and 14b.
The paper is discharged to the outside of the case 1 through the paper discharge port 15 via the paper outlet 15 .

A microswitch 16 having three contacts as a paper type detector is installed at a position where the front end surface of the paper feed cassette 7 comes into contact inside the cassette mounting port 11 into which the paper feed cassette 7 is inserted.

FIG. 2 is a perspective view showing the configuration of each paper feed cassette 7 inserted into the cassette mounting port 11. As shown in the figure, a partition plate 7 is provided in each paper cassette 7 so that only paper of the paper size assigned to that paper cassette 7 can be set.
a is provided, and it is impossible to set only one size of paper in one paper feed cassette 7. That is, as many paper feed cassettes 7 as there are paper types are prepared.

On the end surface 7b of each paper feed cassette 7 on the side to be inserted into the cassette mounting port 11, there are winter melons 17a, 17b that come into contact with the respective contacts of the microswitch 16.

17c is selectively attached. Zunawachi, winter melon 1
The type of paper 8 stored in the paper feed cassette 7 is determined depending on the attachment state of the paper feed cassettes 7a, 17b, and 17c. For example, all three claws 17a.

17b, 17G installed B5 if only is installed
A size-specific paper feed cassette 7 is shown. Figure 4 shows each contact point a.
, b, and c (◯ on, x off) and the relationship between the types of each paper 8. FIG. As shown in the figure, in this embodiment, five types of paper can be discriminated.

FIG. 3 is a block diagram showing a schematic configuration of a dry type electrophotographic apparatus. A CPU (central processing unit) 18 that executes various arithmetic processes is connected to a ROM 20 . A RAM 21 that stores variable data such as input character data. An interface 22 through which character data to be printed is input from an external host computer. It controls an input/output boat 23 that inputs and outputs various commands and data to various constituent members. The input/output boat 23 includes a main drive motor 24 for rotationally driving the photosensitive drum 2. Charging unit consisting of a charging charger 3. Transfer section 9 consisting of a transfer charger. A static eliminator 10 consisting of a static eliminator lamp, an exposure unit 5 that emits laser light 4. Drive motors for the PC roller 12 and conveyance roller 13, various sensors 25. A fixing unit 14 and the like are connected thereto. The fixing unit 14 also includes a microswitch 16 having the three contacts for specifying the type of the paper feed cassette 7, that is, the type of paper 8 to be fed.

FIG. 5 shows the fixing roller 14a of the fixing section 14.

14b is a temperature control circuit diagram. Fixing roller 14a, 1
The heater 31 embedded in the heater 31 is connected to an AC heater power source 33 via a fuse 31a and a solid state relay 32 that turns on/off AC using a zero cross switch. Further, a thermistor 34 for detecting the temperature of the fixing rollers 14a, 14b is disposed close to the fixing rollers 14a, 14b.
One end of 4 is connected to a DC control voltage terminal via a resistor 35. The other end of the thermistor 34 is connected to the +) side terminals of the first and second voltage comparators 37 and 38 via an integrating circuit 36 consisting of a capacitor and a resistor. That is, the fixing roller 14a.

14b is detected by the thermistor 34 and is applied to the first. The voltage is input to the (+) side terminals of the second voltage comparator 37, 38.

The (-) side terminal of the first heavy pressure comparator 37 has a control voltage V
A reference voltage obtained by dividing the voltage by resistors 39a and 39b is input. Note that this reference voltage is applied to the fixing rollers 14a and 14b.
The detection voltage of the thermistor 34 is set to correspond to a temperature of 150°C.

Therefore, the temperature of the fixing rollers 14a and 14b is 150.
℃, the first voltage comparator 37 sends an H-level preheating completion signal d to the turnout port 23 of the CPU 18.

The (-) side terminal of the second voltage comparator 38 has four resistors 40a, 4 resistors inserted in series between the control voltage terminal and the ground.
It is connected to the intermediate point C) between the resistor 40b and the resistor 40c in the temperature setting circuit 40 consisting of 0b, 40c, and 40d. Roughly speaking, the resistance 4 of this temperature setting circuit 40
A pnp transistor 41 is connected between both terminals of 0b. Furthermore, an npn type transistor 42 is interposed between both terminals of the resistor 40d, that is, between the connection point between the resistor 4oc and the resistor 40d, and the ground.

Usually, a resistor 4 is connected to the base of this transistor 42.
Since the control voltage V is applied through the transistor 3, this transistor 42 is in a conductive state. Then, the base potential is lowered by the L active print start signal e outputted from the input/output port 23 of the CPU 18, and the transistor 42 is cut off.

An output signal from a negative Nant gate 44 having three input terminals is input to the base of the transistor 41. Each input terminal of the Nandt gate 44 is connected to a control voltage terminal via a resistor 45, and is also grounded via contacts a, b, and c of the microswitch 16. Therefore, only when all the contacts a, b, and c of the microswitch 16 are opened (turned on), the Nant gate 44 is established and sends out an L-level output signal.

Next, the potential EC at the intermediate point C of the temperature setting circuit 40 is determined by the resistors 4Qa and 40t when the transistor 41 is in the cutoff state and the transistor 42 is in the conduction state.

Since the control voltage V is divided by 40c, the fixing roller 14a
, 141) is the set voltage corresponding to the temperature of 160°C.

Furthermore, when the print start signal e is output and the transistor 42 is cut off, the four resistors 40a, 40b, 40
c, 40dc Since the control voltage V is divided, the fixing roller 1
The set voltage corresponds to the temperature of 4a and 14b of 180°C.

Furthermore, with transistor 42 cut off and all contacts a, b of microswitch 16.

When C is turned on and the transistor 41 is conductive, the potential EC at the intermediate point C is the same as that at the resistors 40a and 40c.

Since the control voltage V is divided by 40d, the fixing roller 14a
, 14b is the set voltage corresponding to the temperature of 185°C.

Therefore, the fixing roller 14. The detected hot water temperature of a14b is (-
) When the set temperature indicated by the potential EC at the intermediate point C of the temperature setting circuit 40 inputted to the side terminal is reached, an H level output signal from the second voltage comparator 38 is output from the negative Nant gate 46. Sent to one input terminal.

The other input terminal of this Nant gate 46 is connected to the CP
An L active heater-on signal f is input from U18 via the input/output port 23. The output signal of this Nant gate 46 controls the operation of the solid state relay 32.

Next, each fixing roller 14a of the fixing section 14 shown in FIG.
The operation of the temperature control circuit 14b will be explained.

First, when the power switch of the operation panel 47 attached to the front of the case 1 is turned on, an L-level heater-on signal f is input from the CPU 18 via the input/output port 23. Then, the Nant gate 46 is established and sends an L level output signal to the solid state relay 32.

The solid state relay 32 becomes conductive and the fixing roller 1
4a.

The heater 31 of 14b starts to be energized. As a result, the temperature of fixing rollers 14a and 14b increases.

After a certain period of time has elapsed, the fixing roller 14a.

When the temperature of the thermistor 14b reaches 150°C, the terminal voltage of the thermistor 34, that is, the potential of the (+) side terminal of the first voltage comparator 37 becomes higher than the potential of the (-) side terminal, and this first voltage CP from the comparator 37 via the input/output port 23
A preheating end signal d at H level is sent to U18. Then, this dry type electrophotographic apparatus enters a standby state.

After that, when a paper feed cassette 7 other than the paper feed cassette 7 exclusively for postcards is attached to the cassette attachment slot 11, or when no paper feed cassette 7 is attached at all, and when the print start signal e is not input from the CPUIS, As mentioned above, the potential Ec at the intermediate point C of the temperature setting circuit 40 is 160°C.
Since the potential corresponds to the temperature of the thermistor 3
When the temperature detected at 4 reaches 160° C., an H level signal is applied from the second voltage comparator 38 to the Nandt gate 46. Then, the solid state relay 32 is cut off, and the power supply to the heater 31 is cut off.

Therefore, the temperature of the fixing rollers 14a and 14b starts to decrease. When the temperature falls below 160° C., the output signal of the second voltage comparator 38 returns to the L level, and the heater 31
is energized again. Therefore, fixing rollers 14a and 14b
The temperature is controlled at approximately 160°C.

Next, when the L level printing start signal e is input from the CPLJ 18, the potential EC at the intermediate point C of the temperature setting circuit 40 becomes the set voltage corresponding to the temperature of 180°C, so the heater 31 becomes conductive with the same operation as described above. - The temperature of the fixing rollers 14a and 14b is controlled to 180° C. under cut-off control.

Therefore, A4 items other than postcards. B5. When using plain paper such as letter size, the fixing temperature is 180℃.
controlled by.

Next, the case of printing on postcards will be explained.

When printing on postcards, a paper feed cassette 7 exclusively for postcards is installed in the cassette installation opening 11. Then, all contacts a, b, and c of the microswitch 16 are opened (turned on).

As a result, the Nant gate 44 is established and the output signal becomes L.
level, and the transistor 41 becomes conductive. Therefore, as described above, the potential E at the intermediate point C of the temperature setting circuit 40
C becomes a set voltage corresponding to a temperature of 185°C. Therefore, the temperature of the fixing rollers 14a and 14b is approximately 185°C.
controlled by. Therefore, when using postcards as paper, the fixing humidity is controlled at 180°C.

In this way, A4. B5. From the fixing temperature when printing on paper (plain paper) for regular printing such as letter size,
By automatically increasing the fixing temperature when printing on postcards that are thicker than plain paper, it is possible to print photographs on plain paper and postcards under the best conditions. Therefore, even if multiple types of paper with different thicknesses and qualities are used, the best photo printing quality can always be maintained.

Moreover, in the embodiment, when the paper feed cassette 7 is replaced, the best fixing temperature is automatically selected, so there is no need for the operator to change the fixing temperature depending on the type of paper. Therefore, operability can be improved.

[Effects of the Invention] As described above, according to the dry electrophotographic apparatus of the present invention, the fixed Wm degree of the fixing section is automatically changed depending on the type of paper fed from the paper feeding mechanism.

Therefore, even if the type of paper is changed, the best print quality can always be obtained.

[Brief explanation of the drawing]

The figures show a dry electrophotographic apparatus according to an embodiment of the present invention, and FIG. 1 is a schematic cross-sectional view showing the entire apparatus, and FIG.
The figure is a perspective view showing the paper feed cassette, Figure 3 is a block diagram showing the entire structure, Figure 4 is a diagram showing the relationship between the paper type and the state of each contact of the microswitch, and Figure 5 is a diagram showing the relationship between the paper type and the state of each contact of the microswitch. It is a temperature control circuit diagram. DESCRIPTION OF SYMBOLS 1... Case, 2... Photosensitive drum, 3... Charging section, 5... Exposure section, 6... Developing section, 7... Paper feed cassette, 8... Paper, 9... ... Transfer section, 10... Static elimination section, 11... Cassette mounting opening, 14... Fixing section, 1
4a, 14b...Fixing roller, 16...Micro switch, 17a. 17b, 17c...nail, 18...CPU, 23...
・Input/output port, 31... Heater, 32... Solid state relay, 34... Thermistor, 37...
First voltage comparator, 38...Second voltage comparator, 40
...Temperature setting circuit, 41.42...Transistor,
44.46... Nantes Gate. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Claims] Along the circumference of the photosensitive drum, at least a charging section, an exposing section,
A developing section and a transfer section are sequentially arranged, and an image formed at the exposure section and developed at the developing section is transferred to the photosensitive surface of the photosensitive drum charged at the charging section, at the transfer section, In a dry type electrophotographic device that transfers an image onto paper fed from a paper feeding mechanism and heat-fixes the paper onto which the image is transferred in this transfer unit in a fixing unit, the type of paper fed from the paper feeding mechanism 1. A dry electrophotography system comprising: a paper type detector for detecting a paper type; and a fixing temperature selection means for selecting a fixing temperature of the fixing unit in accordance with the paper type detected by the paper type detector. Device.