JPH04138485A - Image forming device - Google Patents

Abstract

PURPOSE:To increase the number of prints per an unit hour by independently changing the carrying speeds of a fixing/carrying body and a carrying means according to the thickness, quality, and size of a recording material. CONSTITUTION:The thickness of a transfer material is detected to change fixing speed. In other words, when the transfer material is housed in a cassette 7a, the size of the transfer material is detected according to the type of the cassette. When the transfer material is fed from the cassette 7a to a paper thickness detector 10 and it detects that the fed transfer material is thicker than the transfer material of a constant thickness, the speed Vp of a transfer belt 6a and the fixing speed VF are independently controlled, and speed is varied, to carry out copying. Thus, the number of prints per an unit hour can be increased without degrading the quality of an image, and efficiency are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming apparatus that can change the fixing speed, and particularly relates to an image forming apparatus that has a plurality of transfer stations and performs multiple transfers and then fixes.

[Prior art]

Conventionally, a heat roller fixing method has been popular as a fixing method for fixing an unfixed image.

In this heat roller fixing device, when the recording material to be nipped and conveyed is special paper such as cardboard or resin film, the rotational speed of the roller (
It is considered to slow down the fixing speed and apply more heat.

When this fixing speed is slowed down, in a transfer type image forming apparatus, the conveying speed of the recording paper before fixing is also reduced to the same speed as the fixing speed.

[Problems solved by the invention]

Therefore, if the size of the recording material is larger than the distance l between the transfer position and the fixing position, the fixing speed and transport speed are reduced to the same speed, which is effective in preventing image transfer misalignment. If the size of the recording material is smaller than the distance l between the position and the fixing position, the recording material will not hit the transfer position and the fixing position at the same time, and there is no risk of transfer misalignment in the image. %vp was slowing down and the number of prints per unit time was decreasing.

[Means to solve problems]

The present invention, which solves the above-mentioned problems, includes: an unfixed image forming unit that forms an unfixed image on a recording material; a pair of fixing conveyance bodies that nip and convey the recording material supporting the unfixed image and fix the image; In an image forming apparatus, the image forming apparatus includes a conveying means for conveying a recording material according to the size of the recording material, and a changing means for changing the conveyance speed of the fixing conveyance body and the conveying means according to the thickness or material of the recording material. It has a size detection means to detect, and depending on the thickness or material of the recording material and the size,
The present invention is characterized in that the conveyance speeds of the fixing conveyance body and the conveyance means are independently changed.

[Embodiments of the invention]

Embodiments of the present invention will be described below based on the drawings.

FIG. 4 is a sectional view of an image forming apparatus according to an embodiment of the present invention, showing a four-drum laser beam printer that is an example of a laser beam printer having a plurality of optical scanning means.

The printer is provided with four image forming stations including image forming means around an image bearing member which is an electrophotographic photoreceptor, and the image forming station formed on the image bearing member by each of the image forming stations is provided. The image is transferred onto a transfer material carried and conveyed by a moving body that moves and passes adjacent to the image carrier.

Mazetsu, cyan, yellow, and black image forming stations P m , P c , P y , P
Photosensitive drums IM, IC, IY, and IK are respectively arranged on Ic and rotated in the direction of the arrow. In addition, each photosensitive drum IM
, IC1IY, IK are surrounded by chargers 2M, 2C, 2.
Y, 2K.

Scanning optical bag fEf 3M, 3C1 as optical scanning means
3Y, 3, developing devices 4M, 4C that accommodate powder toner
,4,Y.

4, an image forming means consisting of cleaners 5M, 5C, 5Y, and 5K is disposed.

Furthermore, the transfer section 6 constituting one of the image forming means has a transfer belt 6a and transfer chargers 6M, 6C, 6Y, and 6K that are common to each image forming station, and the transfer belt 6 is used to form a full color image. This is achieved by sequentially transferring the toner images of each color formed on the photosensitive drum onto the transfer material P supported on the photosensitive drum 6a. The transfer material P is supplied from a paper feed cassette 7, its thickness is detected by a paper thickness detection device 10, and after the transfer process is completed, it is separated from the transfer belt and reaches a tray 9 via a fixing device 8.

The scanning optical devices 3M, 3C, 3Y, and 3 include a laser device (not shown) as a light source, a rotating polygon mirror that scans the laser device, and an fθ lens that focuses the scanning beam onto the generatrix of the photosensitive drum surface. , a reflection mirror that deflects a light beam, and a beam detection device that detects a specific position of the scanning beam.

FIG. 5 shows an enlarged sectional view of the fixing device.

A fixing roller 11 , a pressure roller 12 that rotates while being in pressure contact with the fixing roller 11 , a detachable coating device 13 that supplies a release agent to the surface of the fixing roller 11 , and a fixing roller 11 and pressure roller 12 . The cleaning web 14 is configured to clean toner and paper powder adhering to the surface. The fixing roller 11 has a structure in which the surface of a metal pipe is coated with silicone rubber or fluororubber. The pressure roller 12 is a metal roller whose surface is coated with silicone rubber, and whose surface is coated with a fluororesin.

A heater such as a halogen lamp is arranged inside the fixing roller 11 and the pressure roller 12. Further, a thermistor 15 is in contact with the pressure roller 12, and the temperature of the roller is controlled by controlling the voltage applied to the heater via a temperature control circuit. These rollers 11 and 12 are rotatably supported by the main body of the apparatus (not shown) so as to be rotatable in the direction of the arrow. The coating device 13 includes a mold release agent tank 13a that stores silicone oil as a mold release agent, a pumping roller 13b that pumps up the mold release agent from the mold release agent tank 13a, and a fixing roller 11 that pumps the mold release agent.
It is composed of an application roller 13c that applies the mold release agent to the surface of the mold, and a blade 13b that controls the amount of the release agent applied. The application roller 13c is rotatable, has a sponge rubber surface coated with silicone rubber, is removable from the fixing roller 11, and is coated with a release agent. The amount of mold release agent applied is blade 13d.
The amount of coating is adjusted from the leading edge to the trailing edge of the transfer material with a constant coating amount.

The cleaning web 14 has a nickel web 14a on the fixing roller 11 side and a Nomex felt 14b on the pressure roller 12 side to clean the rollers.

In this state, the transfer material is conveyed (then, the fixing roller 11 and the pressure roller 12 rotate at a constant speed, and when the transfer material passes between the rollers 11 and 12, it is rotated at a substantially constant rate from both the front and back sides. It is pressurized and heated with pressure and temperature, and the unfixed toner carried on the surface is melted and mixed and fixed to form a full-color image.

In this embodiment, both rollers are each provided with a heater, but it is preferable to provide a heater on at least one of the rollers, particularly at least the fixing roller 11 that is in contact with the unfixed image.

Here, the quality of fixing properties depends on the amount of heat given to the transfer material when it passes between the rollers 11 and 12. Therefore, in order to obtain the same fixing properties with thin and thick transfer materials, it is necessary to use thick transfer materials. When fixing, it is preferable to apply a larger amount of heat.

For this reason, in this embodiment, the thickness of the transfer material is detected and the fixing speed is changed.

FIG. 6 shows a mechanism for detecting the thickness of the transfer material.

In Fig. 6, 18 is a pivotally supported registration roller 19
is a vertically movable registration roller that is held down by a registration roller 18 from above with a spring 20. This 18.
When transfer materials of different thicknesses pass between the two registration rollers 19, the position of the registration rollers 19 changes, which is transmitted to a potentiometer 22 by a clutch 21, and the paper thickness is detected. In this way, when a thick transfer material is detected, the fixing speed is reduced to an appropriate speed according to the paper thickness so as to indicate good fixing performance, and fixing is performed.

Next, control of fixing speed and conveyance speed will be explained.

FIG. 1 shows a control diagram of one embodiment of the present invention.

This is a case where the transfer material is fed from a cassette in the storage section.

In FIGS. 1 and 4, first, the transfer material is placed in the cassette 7a.
When the transfer material is stored in the cassette, the size of the transfer material is detected depending on the type of cassette. Next, from the cassette 7a, the paper thickness detection device 10
When a transfer material is fed (then it is detected that the transfer material is thicker than a certain thickness), the speed of the transfer belt (in this embodiment, it matches the rotational speed of the photoreceptor) V+□ and the fixing speed V1.・are independently controlled, the speed is varied, and copying is performed.

First, a case will be described in which the size of the transfer material is detected to be longer than the distance l between the transfer position and the fixing position by the "force" setting, and the paper thickness detection device detects that the paper thickness is greater than a certain level.

If the length of the transfer material is longer than the distance l, the transfer material will cover both the transfer position and the fixing position, so the speed V1. and ■
If 1. is not made equal, a shift will occur in the image and the quality will deteriorate. Therefore, in this case, both ■) and Vl must be reduced to the same speed.

Next is distance! If the length of the transfer material is shorter and the paper is detected as thick paper, the transfer material will not be applied to both the transfer position and the fixing position, so there is no need to make the speeds V17 and Vll equal. Therefore, in this case, the speed V+ remains equal to the speed of the thin transfer material, and the fixing conveyance belt and fixing speed v1
By delaying only x, the number of copies per unit time was increased compared to the conventional method, and good fixing could be achieved without degrading the image quality.

Next, a second embodiment of the present invention will be described.

FIG. 2 is a control diagram showing this second embodiment.

In this embodiment, a paper thickness detection mechanism as shown in FIG. 6 is not provided.

In Fig. 2, since a paper thickness detection device is not provided, the paper fed from the transfer material storage cassette is judged to be plain paper, and when paper is fed from the cassette, the speed of the entire machine is V1. Fixing is performed without changing the fixing speed Vt, .

Next, when copying thick transfer materials other than plain paper, use the multi-manual feed setting, which allows you to print up to 30 sheets in succession. In the case of manual paper feeding, the paper is determined to be thick paper, and then the speed of the entire machine (V1), which detects the size of the transfer material, the fixing conveyance bell, and the fixing speed (Vh) are controlled independently, and the speed is varied, and the copying is performed. It will be done. First, a case will be described in which the size of the transfer material is detected to be longer than the distance l between the transfer position and the fixing position.

If the length of the transfer material is longer than the distance l, the transfer material will be applied to both the transfer position and the fixing position, so the speeds VF and Vp will be
If they are not made equal, the image will shift and the quality will deteriorate. Therefore, in this case, both Vl- and (1) must be reduced to the same speed.

Next, when it is detected that the length of the transfer material is shorter than the distance l, the transfer material does not cover both the transfer position and the fixing position, so there is no need to make the speeds VF and VP equal. Therefore, in this case, by keeping the overall machine speed Vp equal to the speed of the thin transfer material and slowing down only the fixing conveyance belt and the fixing speed V), the number of copies per unit time is increased compared to the conventional method, and the image quality is also improved. Good fixing was possible without any dropping.

A third embodiment of the present invention will be shown below. In a machine having a paper thickness detection device as shown in FIG. 1, when feeding paper from a transfer material storage cassette, as in the conventional case, when the paper thickness detection device detects a thick transfer material, the speed of the entire machine is v1.
and the fixing conveyance belt and fixing speed VF are reduced to the same speed. However, if this continues, the number of copies per unit time will also decrease when the transfer material length is shorter than the distance l between the transfer position and the fixing position. Therefore, when performing manual copying, the length is the distance between the transfer position and the fixing position! If you limit the transfer material to shorter lengths, and if the transfer material is thick and has the length shown above, set it so that the speed V1 remains the same and only the speed Vlr decelerates, so that it can print continuously for up to about 30 sheets. By using a multi-manual feeder that can feed paper at multiple speeds, the number of copies per unit time can be increased compared to conventional methods, and good fixing can be achieved without degrading image quality.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to increase the number of prints per unit time without degrading image quality, improving performance and efficiency.

[Brief explanation of drawings]

1 to 3 are control diagrams showing other embodiments of the present invention, FIG. 4 is a sectional view of an image forming apparatus according to an embodiment of the present invention, and FIG.
The figure is an enlarged sectional view of the fixing device used in the embodiment shown in FIG. 4, and FIG. 6 is a schematic perspective view showing the paper thickness detection mechanism. IM, IC, IY, IK...Photosensitive drums 2M, 2C,
2Y, 2K... Charger 3M, 3C, 3Y, 3K... Scanning optical device 4M, 4C
, 4Y, 4K...Developing device 5M, 5C, 5Y, 5K...
...Cleaner 6...Transfer section 6a...Transfer belt 6M, 6C, 6Y, 6K...Transfer charger 7a...Paper cassette 8a...Fixer 9...Tray 7b... Manual paper feed section 8b...Transfer material conveyance bell lO...Paper thickness detection device 11...Fixing roller 12...Pressure roller 13...Oil application device

Claims (3)

[Claims] (1) An unfixed image forming means that forms an unfixed image on a recording material, a pair of fixing conveyance bodies that nip and convey the recording material supporting the unfixed image and fix it, and a pair of fixing conveyance bodies that fix the recording material on the opposite side of the fixing conveyance body. In an image forming apparatus having a conveyance means for conveying the recording material, and a changing means for changing the conveyance speed of the fixing conveyance body and the conveyance means according to the thickness or material of the recording material, a size detection means for detecting the size of the recording material is provided. have,
An image forming apparatus characterized in that the conveyance speeds of the fixing conveyance body and the conveyance means are independently changed according to the thickness or material and size of the recording material. (2) The image forming apparatus according to claim 1, wherein the fixing conveyance body and the conveyance means are driven by separate driving means. (3) The apparatus has a plurality of image carriers, and the conveyance means conveys the recording material to each transfer position where an unfixed image on the image carrier is transferred. 1
2. The image forming apparatus according to item 2.