JPH05165365A - Fixing device for electrophotographic printer - Google Patents

Abstract

PURPOSE:To improve printing quality without decreasing fixing intensity even in the case of thick paper by attaching a spring to a press-contact plate which presses a press-contact roller in contact with a heat roller and adjusting the pressing force of the spring according to the thickness of the paper. CONSTITUTION:The press-contact roller 6 and the heat roller 7 are respectively axially laid in a pair of bearing holes 2a and 2b provided on the side surface part 2 of a fixing device. In the case of the thick paper such as a post card, an adjusting lever 12 is rocked clockwise so as to fit and fix a lock pin 12b in a fitting hole 4c, so that a cam part 12a somewhat retreats from the press- contact plate 9. The plate 9 is rocked by the pressing force of the compressing spring 11 so as to increase the press-contact force against the roller 6. The roller 6 slides inside the bearing hole 2a formed in a long hole shape, so that the press-contact force to the thick paper is strengthened and the specified fixing intensity is maintained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermocompression type fixing device for fixing toner to a sheet in an electrophotographic printer.

[0002]

2. Description of the Related Art An electrophotographic printer mainly uses a laser light source and has an extremely high light-converging optical system and an electrophotographic recording system used in a general office copying machine. It is composed of a control unit that controls printing of this mechanism, and does not require special paper, and has the characteristic that paper can be used from business card size to A3, and from thin copy paper to postcard thickness. ing. In this electrophotographic printer, printing is performed by fixing a toner image formed on a sheet formed by each process of charging, exposure, development, transfer and cleaning arranged around a photoconductor.

As a method of fixing the toner image, generally, the toner having almost no adhesive force transferred onto the paper is melted by heat, and at the same time, pressure is applied to fix the toner on the paper. The fixing device has a structure in which one of a pair of rollers rotatably supported on the device frame is heated to form a heat roller, and the other roller is pressed against the heat roller to form a pressure contact roller. The paper was passed between the rollers to fix it.

[0004]

In the above-mentioned conventional fixing device, the pressure contact force of the pressure contact roller with respect to the heat roller is constant. Therefore, in the case of a postcard or a sheet having a thickness larger than that, However, the fixing strength is lower than other papers, and even though the electrophotographic printer has a feature that it can be used from thin copy paper to postcard thickness, it can be used effectively enough. There was a problem such as not.

Therefore, the present invention has been made in view of the above-mentioned conventional problems, and the object thereof is to cope with papers of various thicknesses, and particularly for thick postcards. Therefore, it is an object of the present invention to provide a fixing device for an electrophotographic printer that can obtain the fixing pressure of 1, and thus improve the printing quality.

[0006]

In order to achieve this object, a fixing device for an electrophotographic printer according to the present invention includes a heat fixing device for fixing a transferred image on a sheet, which is rotatably supported between side plates. In a fixing device of an electrophotographic printer comprising a roller and a pressure roller pressed against the roller, a bearing hole for axially supporting the pressure roller is an elongated hole, and the pressure roller is pressed against the heat roller by a biasing force of a spring. And a cam member that contacts the pressure contact plate and adjusts the biasing force of the spring.

[0007]

In the present invention, the urging force of the spring that presses the press roller against the heat roller is adjusted by changing the contact force of the cam member that contacts the press plate.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a front view of a main part of a fixing device of an electrophotographic printer according to the present invention. In the figure, reference numeral 1 is a frame, which is composed of a side surface portion 2, a bottom surface portion 3, and a back surface portion 4. The side surface portion 2 has a pair of upper and lower bearing holes 2
a and 2b are bored, and one bearing hole 2a is formed in a vertically elongated shape. The bottom part 3 has a dowel 3
a is formed in a protruding manner, and the rear portion 4 has a support shaft 4a at the center.
However, other support shafts 4b are respectively planted on the side slightly above the support shafts 4a, and at the upper part, three support shafts 4b are arranged on an arc locus centering on the support shafts 4b. Fitting hole 4c
Is recessed.

In the pair of bearing holes 2a, 2b, a pair of rollers 6, 7 are rotatably supported by a bearing hole between the other side surfaces (not shown), and one roller 6 is a pressure contact roller. The other roller 7 is a heat roller and has a built-in heater. A pressure contact plate 9 is swingably supported on the support shaft 4a. A dowel 9a is formed on one end of the pressure contact plate 9 so as to project therefrom, and the other end of the pressure contact plate 9 is attached to the shaft 6a of the pressure contact roller 6. An abutting portion that abuts is formed by being folded back, and the compression spring 11 fitted between the dowel 9a and the dowel 3a causes the pressure contact plate 9 to swing in the clockwise direction in the drawing around the support shaft 4a. The contact portion 9b presses the pressure roller 6 against the heat roller 7 with a constant pressure contact force.
An adjusting lever 12 is swingably supported on the other support shaft 4b, and the lower end surface of the adjusting lever 12 has a cam portion 12a.
a is formed, and is fitted into the fitting hole 4c on the upper end side,
A lock pin 12b having a sprocket structure whose tip is freely retractable is planted.

The fixing device of the electrophotographic printer according to the present invention has the above-described structure, and a method for adjusting the pressure contact force of the pressure contact roller according to the sheet thickness will be described below. In the case of relatively thin paper such as copy paper, as shown in FIG. 1, the lock pin 12b of the adjusting lever 12 is fitted into the leftmost fitting hole 4c of the three fitting holes 4c, and the cam is moved. The portion 12a brings the compression spring 11 into the most compressed state. Thereby, the pressure roller 6 of the pressure plate 9 is pressed.
The pressure contact force to is the smallest. Next, in the case of thick paper such as postcards, the fitting hole 4c for fitting the lock pin 12b of the adjusting lever 12 is fitted to the one located at the center or the right side in the drawing to move the adjusting lever 12 clockwise. When it is swingably fixed to, the cam portion 12a is slightly retracted from the press contact plate 9,
The urging force of the compression spring 11 to the pressure contact plate 9 is increased. As a result, the pressure contact force of the pressure contact plate 9 to the pressure contact roller 6 becomes large, and the predetermined fixing strength is maintained without reducing the pressure contact force to the postcard.

[0011]

As described above, according to the present invention, the bearing hole for axially supporting the pressure contact roller is an elongated hole, and the pressure contact plate is provided for pressing the pressure contact roller against the heat roller by the urging force of the spring. The urging force of the spring is adjusted by the thickness of the paper by the cam member that comes into contact with the press plate, so the fixing strength does not decrease even with relatively thick paper such as postcards, thus improving print quality. There is an effect that can be made.

[Brief description of drawings]

FIG. 1 is a front view of a main portion of a fixing device of an electrophotographic printer according to the present invention.

[Explanation of symbols]

 2a Bearing hole 4c Fitting hole 6 Pressure contact roller 7 Heat roller 9 Pressure contact plate 11 Compression spring 12 Adjustment lever

Claims (1)

[Claims] 1. A fixing device for an electrophotographic printer, comprising: a heat roller rotatably supported between side plates and fixing a transferred image on a sheet; and a pressure roller pressed against the heat roller. The bearing hole supporting the shaft is an elongated hole, and a pressure contact plate for pressing the pressure contact roller against the heat roller by a biasing force of a spring, and a cam member for contacting the pressure contact plate and adjusting the biasing force of the spring are provided. A fixing device for an electrophotographic printer, characterized by: