JPH04172385A - Electrophotographic printing device - Google Patents

Abstract

PURPOSE:To enable an image to be fixed cleanly and accurately by changing the pressing force of a pressure roller in a roller pair, according to the detected temperature of a record body. CONSTITUTION:A carriage route 5c is laid next to the section of an image formation process, and a record body passes a fixing device 6 while being carried on the aforesaid carriage route 5c. In addition, the record body passes another carrier route 5d laid next to the route 5c and is discharged. In this case, a record body temperature detection means 1 for detecting the temperature of the record body is laid at the intermediate position of a carriage route 5b. Furthermore, a signal is sent from a control means to a pressing force variation means 2, according to a signal corresponding to the temperature of the record body detected with the means 1, thereby changing the pressing force of a pressure roller 8 to a heater roller 7. According to the aforesaid constitution, a properly fixed record image can always be obtained, regardless of environmental temperature and the temperature of the record body.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to electrophotographic printing devices.

[Conventional technology]

Conventionally, in this type of electrophotographic printing apparatus, the pressing force of the pressure roller of the fixing roller pair remains constant at the initially set pressing force.

[Problem to be solved by the invention]

In the above-mentioned conventional electrophotographic printing device, the pressure of the pressure roller in the pair of fixing rollers remains at the initial setting and does not change, so the temperature of the image recording medium changes when printing in a low-temperature environment. If the N is low, even if an attempt is made to fix the image on the recording medium by sandwiching and conveying the recording medium carrying an unfixed image between the pair of fixing rollers, the N formed by the pair of fixing rollers will
Since the NIP time during which the recording medium passes through the IP section is the same as in a room temperature or high temperature environment, the energy required for heating during the NI 2 hours is insufficient, making it impossible to fix the image cleanly and reliably. As a result, the image on the recording medium after printing is easily peeled off.

[Means to solve the problem]

The electrophotographic printing apparatus of the present invention includes a recording body temperature detecting means for detecting the temperature of the recording body, and a pressing force of the pressure roller of the roller pair according to the temperature of the recording body detected by the detecting means. and pressure variable means for changing the pressure.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the present invention.

A paper feed cassette 4 is installed on the recording medium (not shown) supply side of the printer main body 3. Inside the printer main body 3, a recording medium conveyance path 5a is disposed following the paper feed cassette 4, and a conveyance path 5b is disposed following it.

Next is a part called an image forming process, in which a photoreceptor drum 10 is disposed, and a cleaner 11. Erase Lamb 12. Charger 1
3. Exposure device 14. A developing device 15 and a transfer charging device 16 are disposed in contact with or in the vicinity, and an image is formed in this portion to create an unfixed image on the recording medium.

A conveyance path 5C is provided following this image forming process portion. The recording medium is conveyed on this conveyance path, passes through the fixing device 6, and then passes through the conveyance path 5d disposed.
is discharged through the

In this embodiment, a recording body temperature detection means 1 for detecting the temperature of the recording body is disposed in the middle of the recording body conveyance path 5b,
In response to a signal corresponding to the temperature of the recording medium detected by the recording body temperature detection means 1, a signal is sent from the control means (not shown) to the pressing force variable means 2, and the pressure roller 8 applies pressure to the heating roller 7. Change the pressure.

As a means for applying pressure to the pressure roller 8, for example, a roller bearing is pressurized from the bottom by a spring. For example, a solenoid is disposed at the bottom of the spring as the pressure variable means 2,
Push up or lower the spring from below.

Further, the recording body temperature detection means 1 may be disposed not in the middle of the conveyance path 5b but in the middle of the conveyance path 5a or the conveyance path 5C.

FIG. 2 is a schematic diagram showing the NIP portion of a pair of fixing rollers. In a normal state, the width of the NIP formed by the heating roller 7 and the pressure roller 8 can be increased to a width L□ by increasing the pressure in the direction of the arrow. increase

This increases the time it takes for the recording medium to pass through the NIP section, which increases the time required to supply the heating energy needed to fix the unfixed image onto the recording medium, resulting in good fixing. .

FIGS. 3(a) to 3(C) show recording medium temperature detection means 1 of the present invention.
It is a side view of the arrangement state of.

When the recording body temperature detection means 1 is disposed upstream of the image forming process section with respect to the conveyance direction of the recording body 17, the third
As shown in FIGS. (a) and (b), the recording medium temperature detection means 1
If the temperature of the recording medium 17 can be detected, the transport path 5
It may be placed above or below.

When the recording body temperature detection means 1 is disposed downstream of the image forming process section with respect to the conveyance direction of the recording body 17, the third
As shown in Figure (C), the recording body temperature detection means 1
The temperature is detected from below the recording medium 17.

By the way, as the recording medium temperature detection means, any device that can show an electrical change with respect to temperature can be used; for example, a thermistor or the like may be used.

As another example, instead of providing a means to detect the temperature of the recording medium in the conveyance path, a setting button can be provided on the operation panel of the printing device, and the operator can input data regarding the temperature of the recording medium himself. There is also a way to make it work.

〔Effect of the invention〕

As explained above, the present invention includes a recording body temperature detection means for detecting the temperature of the recording body, and a pressure roller of a pair of fixing rollers that adjusts the pressing force of the pressure roller in accordance with the temperature of the recording body detected by the detection means. By adding a variable pressure force means,
Even when the temperature of the image recording medium is low, such as when printing in a low-temperature environment or when printing using a recording medium that has been left in a low-temperature environment, sufficient NIP time can be taken. It is possible to supply the heating energy necessary to properly fix the printed image on the recording medium, allowing the operator to always maintain a well-fixed recorded image without worrying about the environmental temperature or the temperature of the recording medium. It has the effect of being able to obtain

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention, FIG. 2 is a schematic diagram showing the NIP portion of a pair of fixing rollers, and FIGS. 3(a) to (C)
FIG. 2 is a side view of the arrangement of the temperature detection means shown in FIG. 1; 1... Temperature detection means, 2... Pressure force variable means, 3.
...Printing device main body, 4...Paper feed cassette, 5a-5
d... Conveyance path, 6... Fixing device, 7... Heating roller, 8... Pressure roller, 9... Heating means, 10...
・Photosensitive drum, 11... Cleaner, 12... Eraser lamp, 13... Charger, 14... Exposure device, 1
5...Developer, 16...Transfer charger, 17...Recording body.

Claims (1)

[Claims] A recording medium is fed and conveyed, an unfixed image is formed on the recording medium through an image forming process, and then a heating roller is rotated by receiving driving force from a drive source, and a driven roller is placed in pressure contact with the heating roller. In an electrophotographic printing device, the recording medium is sandwiched and conveyed by a pair of fixing rollers and a rotating pressure roller, and the unfixed image is fixed on the recording medium, and then the recording medium is ejected. and a pressure variable means for changing the pressing force of the pressure roller of the roller pair in accordance with the temperature of the recording medium detected by the detection means. Characteristic electrophotographic printing device.