JPH0519712B2 - - Google Patents

Description

[Detailed description of the invention] Technical field The present invention relates to an electrostatic recording device.

PRIOR ART Recently, as a means of writing addresses on a large number of envelopes, it has become common practice to read out a large number of address information stored in a storage means as electrical signals, input them to a printer, and print characters corresponding to the electrical signals. It became. Printers print at very high speeds, but the paper that can be printed on is usually limited to paper that is about the same thickness as ordinary recording paper, and paper that has multiple sheets stacked on top of each other, such as envelopes, and that is difficult to deform freely. It is difficult to write addresses on envelopes, and the common practice is to print on plain paper using a printer, cut it to an appropriate size, and paste it on the envelope, which hinders work efficiency. There was a problem.

Like a laser printer, a toner image corresponding to an information signal is formed on a photoreceptor, and this is transferred to transfer paper.
An electrostatic recording device that heats the transferred toner image and fuses it to the transfer paper. When printing on paper of considerable thickness, the following problems occur.

One of them is the problem of transferring toner images on the photoreceptor. Transfer of a toner image is usually performed by charging the transfer paper from the back side of the transfer surface with a corona discharger and electrostatically adhering the toner image on the photoreceptor to the surface of the transfer paper. When paper is stacked, not only does the total thickness of the paper become thicker, but there is also a layer of air between each paper, which makes it difficult for the toner to reach the required amount of charge to the surface to be transferred, resulting in poor transfer. It is something that happens. The same applies when the thickness of the transfer material is considerably thick.

Another problem is that when using a heating roller fixing device that has a roller pair consisting of a heating roller and a pressure roller that are in pressure contact with each other as a fixing device, there is a problem between the pair of rollers that are in pressure contact with each other with a fixing pressure suitable for fixing plain paper. When an envelope is passed through, there are problems in that the pressure causes wrinkles and the air inside accumulates at the rear end, causing the envelope to burst. Also, the tip part is difficult to be caught in the nip of the roller, which may cause a timing shift. Furthermore, there is a difference in temperature between the paper on the side that contacts the heat fixing roller and the paper on the side that contacts the pressure roller, and the difference in thermal expansion causes the envelope to become distorted, which causes wrinkles and creases to occur. I can do it.

Purpose The present invention solves the above-mentioned problems regarding fixing when recording on envelopes or transfer materials bound with multiple sheets of paper using an electrostatic recording device. An object of the present invention is to provide a fixing device that can perform good fixing even when recording images such as images.

Configuration In order to achieve the above object, the present invention provides a fixing device that performs fixing by passing an unfixed toner image through a transfer material carrying an unfixed toner image on a pair of rollers including a heating roller and a pressure roller. In the case of a product made by overlapping sheets of paper, the fixing pressure between both rollers is controlled to be weaker than the fixing pressure suitable for fixing plain paper.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing a schematic configuration of an example of a laser printer to which the present invention is applied.

This laser printer consists of a lower unit 1 and an upper unit 2, and both units are pivoted to each other at the back side when viewed from the operator, and the front side opens wide like the head of a lion dancer. . The chain line A-A in FIG. 1 is the boundary line between the upper and lower units, and the lower unit 1 accommodates a paper feed section 4 for transfer paper 3, a transfer device 5, and a conveyance section 6 for transferred paper. ing. The upper unit 2 includes an electrostatic recording section consisting of a photoreceptor unit 7, a developing unit 8, a toner tank 9, and a fixing device 10, a sequence board 11 for controlling the sequence of the machine, an interface with a host computer, and control of character generation. The two electrical boards of the controller 12, the laser optical system unit 13, and the power supply 1 that supplies power to all devices.
4. Electrical components such as a main motor 15 and a reversing sheet discharge unit 16 are housed. Upper unit 2
The cover 18 is removable, and its upper surface also serves as a paper discharge tray 19 for the transferred paper discharged from the reversing paper discharge unit 16.

The fixing device 10 is formed as a heated roller fixing device including a fixing roller 21 having a heater 20 inside and a pressure roller 22 that is in pressure contact with the fixing roller 21.

The fixing pressure between the fixing roller and the pressure roller is variable, and the fixing pressure when fixing envelopes and the like is lower than the fixing pressure when fixing plain paper.

Furthermore, as shown in Figure 2, not only is the fusing pressure of the envelope lower than that of plain paper, but also the fusing pressure at the front and rear edges of the envelope is lower than the fusing pressure between the active image fixing area of the entire length of the envelope. It is desirable to have an even lower pressure at the ends. This makes it easier for the front end of the envelope to be caught in the nip between the two rollers, and the pressure is lower at the rear end of the bag, where there is no relief from distortion, so there is no strain and wrinkles do not occur. It is possible to pass through the roller pair without any problems.

The above change in fixing pressure is achieved, for example, by a mechanism as shown in FIG. In Figure 3,
The fixing roller 21 is pivotally supported at a fixed position in the upper unit 2 of the recording apparatus, and the pressure roller 22 is supported by levers 23 at both ends. One end of the lever 23 is swingably supported by a pin fixed to the upper unit 2, and the other end is supported by a spring receiver 26 supported by one end of the lever 25, which swings around a fulcrum 24 fixed to the lower unit. The lever 23 is supported by a compression spring 27 whose lower end is supported, and when the upper and lower units 1 and 2 are closed, the lever 23 is supported by the compression spring 27.
7, both rollers 21 and 22
is pressurized. The left end of the lever 25 is connected to a worm 29 and a worm wheel 3 by a step motor 28.
It is engaged with a cam 31 that rotates through 0. Therefore, the compression spring 27 is compressed depending on the amount of protrusion of the cam 31 at the engagement point, and as a result, the fixing pressure between both rollers changes. As shown in FIG. 4, the cam 31
The fixing pressure is as shown in Fig. 2 at the position A of the minimum protrusion amount, the position C of the maximum protrusion amount, and the intermediate position B, respectively.
The value is set to . Therefore, for plain paper, the cam is held at position C, for envelopes, the cam is held at position A at the front and rear edges, and at position B in the effective image fixing area. By controlling the rotation, changes in fixing pressure as shown in FIG. 2 can be obtained.

The above control is performed as follows.

As a means for detecting whether the transfer material used is plain paper or an envelope, for example, as shown in FIGS. In addition to the size detection tongue piece 53 which is integrally provided with a side fence 51 that is moved according to the width of the transfer material and projects through a slit 52 provided at the front end of the cassette, there is also an envelope detection tongue piece which is fixed to the front end of the cassette. 54, and by mounting the envelope cassette 50, the envelope detection tongue 54 is detected by a sensor 55 provided at a corresponding position within the device. Although the plain paper cassette 56 is provided with a size detection tongue 53 that is displaced together with the side fence 51, an envelope detection tongue 54 is not provided, so that it is easy to detect whether or not it is an envelope. The size of the envelope is also detected.

The detection results of the sensor 55 are as shown in FIG.
The input is input to the CPU 57 and processed, and the envelope mode is selected and the leading edge of the envelope is detected by the sensor S provided upstream of the fixing device as shown in FIG. The rotational position of the stepping motor 28 is controlled. The sensor S may also be provided on the paper conveyance path for other purposes. As a result, in the envelope mode, the fixing pressure is lower than that for plain paper, so it is desirable to increase the temperature of the heater 20 via the relay 58 to ensure the fixing ability.

In addition, when transferring the toner image formed on the photosensitive drum to an envelope, the surface to be transferred is charged via multiple sheets of paper and an air layer, so a power pack is used to charge the toner image to a predetermined amount. 59 to increase the transfer current of the transfer charger 5.
Furthermore, in the case of envelope mode, the data writing timing is instructed to the controller 12 based on the size of the envelope and the paper feeding timing, and the display section 60 displays whether it is the envelope mode or the plain paper mode.

Switching of the fixing pressure between the envelope mode and the plain paper mode may be performed manually by an operator instead of being controlled by displacing a cam with a stepping motor via the CPU based on a transfer material type detection signal. In that case, the cam 61 (Fig. 7) provided at the same position as the cam 31 shown in Fig. 3 can be displaced by the operator turning a knob 62 provided on the outside of the device housing as shown in Fig. 8. I can do it. Around the knob 62, as shown in FIG.
It is preferable to indicate ``envelope'' and ``plain paper'' and the position of the tab. In this case, it is impossible to further reduce the pressure at the front and rear ends of the envelope manually, so the cam position is set to two points A and B as shown in Figure 10 to switch between plain paper and envelopes, and at the same time the fixing pressure is increased. In the low envelope mode, it is better to switch the heater to raise the fixing temperature. Further, as shown in FIG. 7, a switch 63 serving as an envelope mode sensor is turned on and off by the movement of a cam 61, and input is sent to the host machine. Note that in envelope mode, in the case of a fixing device in which the heater 20 is provided only on the fixing roller 21, the toner can be melted, but the heat is difficult to transfer to the pressure roller side, so the amount of thermal expansion between the top and bottom surfaces of the envelope, etc. This causes distortion, and when pressure is applied, wrinkles form. Therefore, as shown in FIG. 11, not only the fixing roller 21 but also the pressure roller 22
A heater 20 may also be provided for both, so that both generate heat in the envelope mode.

Also, since it is difficult to bend items such as envelopes, after fixing, make a U-turn and insert the paper into the paper output tray 19 at the top of the device.
Since it is not appropriate to eject the paper in the same direction, as shown in FIG. It is preferable to provide a foldable paper receiving tray 66 for receiving the paper. FIG. 12a shows the paper receiving tray 66 in use in envelope mode, and FIG. 12b shows the folded state. This switching is preferably carried out under control by the CPU by detecting the detection protrusion 53 of the paper feed cassette, or in conjunction with the rotation of the knob 62 shown in FIGS. 8 and 9.

Effects As described above, according to the present invention, a toner image transferred to a transfer material made of multiple sheets of paper, such as an envelope, can be well fixed by an electrostatic recording device. It becomes possible to directly record addressees using an electrostatic recording device, which has a significant effect on improving office efficiency.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the overall schematic configuration of an embodiment of an electrostatic recording device to which the present invention is applied, FIG. 2 is a curve diagram showing the fixing pressure in the case of fixing plain paper and envelopes according to the present invention, and FIG. The figure is a front view showing an embodiment of the fixing device according to the present invention, FIG. 4 is a curve diagram showing the relationship between the change in the cam shown in FIG. 3 and the fixing pressure, and FIGS. 6 is a control block diagram of this embodiment, FIG. 7 is a front view showing another embodiment of the fixing section of the present invention, and FIG. 8 is a front view of the housing thereof. FIG. 9 is an enlarged front view of the vicinity of the knob, FIG. 10 is a curve diagram showing the relationship between the displacement of the cam, fixing pressure, and fixing temperature, and FIG. 11 is a front view showing still another embodiment of the fixing device. FIG. 12 is a cross-sectional view showing an example of the paper ejection path after fixing, where a shows the envelope paper ejection tray in an open state, and b shows a closed state. 1, 2... Electrostatic recording device, 3... Transfer material, 10
... Fixing device, 20 ... Heat source, 21 ... Fixing roller, 22 ... Pressure roller, 31, 61 ... Cam (fixing pressure control means), 50, 56 ... Paper feed cassette, 53 ... Transfer paper Size detection means, 54...Transfer paper type detection means, 66...Envelope output tray.

Claims (1)

[Claims] 1 It has a fixing device that performs fixing by passing a transfer material carrying an unfixed toner image between a pair of rollers that are in pressure contact with each other and have a heat source inside one of them, and the transfer material is made by overlapping plain paper and multiple sheets of paper. In an electrostatic recording device capable of recording on paper, if the transfer material is made of multiple sheets of paper, the fixing pressure of the roller pair is lower than the fixing pressure suitable for fixing plain paper, and the fixing pressure is lower than that suitable for fixing plain paper. An electrostatic recording device characterized by comprising means for controlling the pressure so that it becomes lower at front and rear ends outside the effective image area of the transfer material than at the effective image area.