JPH02146577A - Fixing device of image forming device - Google Patents

Abstract

PURPOSE:To save electric power while maintaining fixation efficiency by decreasing the peripheral speeds of fixing rollers below the peripheral speed of a photosensitive drum and lowering heating temperature when the rear end of recording paper separates from the photosensitive drum. CONSTITUTION:When the separation of the rear end of the recording paper from the photosensitive drum D is detected, the peripheral speeds of the fixing rollers R4 and R5 are decreased below the peripheral speed of the photosensitive drum D and the heating temperature is lowered correspondingly. Namely, when the rear end of the recording paper separates from the photosensitive drum D, the temperature of the heat fixing rollers R4 and R5 drop as the peripheral speeds of the fixing rollers R4 and R5 decrease below the peripheral speed of the photosensitive drum D. Consequently, the fixation efficiency of toner to the recording paper is held constant and the electric power consumed to heat the fixing rollers R4 and R5 is saved.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Industrial Application Field The second invention relates to a fixing device mainly used in electrophotographic copying machines, printers, and the like.

(B) Conventional technology Conventionally, in this type of fixing device, when the length of the recording paper in the traveling direction is smaller than the length from the separation position to the fixing position, the circumferential speed of the fixing roller is set to the circumferential speed of the photoreceptor drum. A device is known in which the speed is made slower than that (for fPL, see Japanese Patent Laid-Open No. 1983-78462).

(c) Problems to be solved by the invention However, in such a conventional fixing device,
If the length of the recording paper in the traveling direction is greater than the length from the separating position to the fixing position, there is a problem in that the circumferential speed of the fixing roller cannot be prevented from being lower than that of the photosensitive drum.

This invention was made in consideration of these circumstances,
When the length of the recording paper in the traveling direction is greater than the length from the separation position to the fixing position, the circumferential speed of the fixing roller is made slower than the circumferential speed of the photoreceptor drum, and the fixing roller is heated accordingly. By lowering the temperature,
It is an object of the present invention to provide a fixing device capable of reducing power consumed for heating a fixing S-ra while maintaining fixing efficiency at a constant level.

(d) Means for Solving the Problems This invention: An electrostatic latent image formed on a rotating photoreceptor drum is developed and transferred onto recording paper, and the recording paper is fixed by a fixing roller. In an image forming apparatus configured to eject, a driving means capable of rotating a fixing roller and changing its rotational speed, a heating means capable of heating the fixing roller and adjusting the heating temperature, and a fixing position direction. A detection means detects that the trailing edge of the recording paper has separated from the photoreceptor drum, and when the detection means detects that the trailing edge of the recording paper has separated from the photoreceptor drum, the circumferential speed of the fixing roller changes to the photosensitive drum. The present invention is characterized by comprising a control means for controlling the driving means so that the circumferential speed of the fixing roller is lower than the circumferential speed of the fixing roller, and controlling the heating means so that the heating temperature is reduced in response to a decrease in the circumferential speed of the fixing roller. This is a fixing device for an image forming apparatus.

Furthermore, the present invention provides an image forming apparatus configured to transfer an electrostatic latent image formed on a rotating photoreceptor drum onto recording paper, fix the recording paper with a fixing roller, and eject the image. A driving means capable of rotating the roller and changing its rotation speed, a heating means capable of heating the fixing roller and adjusting the heating temperature, and detecting the presence or absence of recording paper at a predetermined position on the conveyance path. a detection means; a timekeeping means that receives an output from the detection means to start timing and outputs an output a predetermined time before the time when the rear end of the recording paper separates from the photoreceptor drum; A detection means for detecting and outputting separation from the drum, a heating means so as to reduce the temperature of the fixing roller when the timing means outputs an output, and a heating means for controlling the circumferential speed of the fixing roller when the detection means outputs an output. The fixing device of the image forming apparatus is characterized in that it includes a control means for controlling the driving means so that the peripheral speed is lower than the circumferential speed of the photoreceptor drum.

(e) Operation When the trailing edge of the recording paper separates from the photoreceptor drum, the circumferential speed of the fixing roller becomes lower than the circumferential speed of the photoreceptor drum. At the same time, the temperature of the heat fixing roller decreases, so that the efficiency of fixing the toner onto the recording paper is maintained constant, and transfer misalignment does not occur. Furthermore, the power consumed in heating the fixing roller can be saved.

(f) Examples The present invention will now be described in detail based on examples shown in the drawings. This does not limit the invention.

FIG. 1 is a basic configuration diagram when an embodiment of the present invention is applied to an electrophotographic copying machine, in which M1 to M3 are mirrors that guide image light from a document (not shown) to an imaging lens;
is a mirror that forms an image of the image light from the imaging lens L onto a photosensitive drum D that rotates in the six directions of arrows; R1 is a photosensitive drum D;
A developing roller that develops the static 1i latent image formed on the toner, C is a cassette that stores the recording paper, and R2 is lf2.
A conveyance roller that conveys the green paper, R3 is a registration roller that conveys the recording paper in synchronization with the transfer position of the photosensitive drum D, and Gl is a registration roller that guides the recording paper conveyed by the registration roller R3 to the transfer position of the drum D. Guidance route, TC
is a transfer charger that is provided opposite to the transfer position of the photoreceptor drum D and transfers the toner image onto the recording paper; SC is the separation charger that separates the recording paper from the photoreceptor drum D; and G2 is the separation charger that is separated from the photoreceptor drum D. A conveyor belt that conveys the recording paper, R4 and R5 are fixing rollers that press and thermally fix the recording paper conveyed by the conveyor belt G2, H is a heater built into the fixing roller R4, and CL is the surface of the photoreceptor drum D. MC is a main charger that applies a -like charge to the surface of the photoreceptor drum D; M is a motor that rotates fixing rollers R4 and R5;
UE is a drive unit that drives the motor M, DU2 is an energization unit that energizes the heater H, SA is a switch that detects the presence or absence of recording paper provided in the guide path Gl, and SB is provided between the conveyor belt G2 and the fixing position. The switch CU is a control unit that receives the outputs of the switches SA and SB and outputs signals to the drive unit DUI and the energization unit DU2 to control the speed of the motor M and the amount of energization of the heater H. , control unit CU is ROM, RAM1CPU, I
It is equipped with a microcomputer consisting of 10 boats, etc.

The operation in such a configuration will be explained using the flowcharts shown in FIGS. 2 and 3 and the time charts shown in FIGS. 4 and 5. Note that TAL, TA2. T.B.
I and Ta2 are timers built into the control unit CU.

First, the copying operation of the electrophotographic copying machine shown in FIG. 1 is started (step 101), and the leading edge of the recording paper conveyed to the transfer position by the registration roller R3 via the conveyance path G1 reaches the position of the switch SA. When it comes, switch SAh
<ON, and switch SA is turned OFF at time TI when the trailing edge of the recording paper passes switch SA (step 102). At that time TI, timer TA1. T.A.
2 is set (step 103). As time passes, timers TA1, 7A2 change to set values TA, respectively.
I, TA2 (T, 1 = TA2 + ΔT) are subtracted (step 104. [05, 104a, IQ5a), and when the set time TA2 has elapsed, the IEI to the heater H is decreased.
is reduced and the heat down flag F2 is turned ON (steps 106 and 107). When time ΔT further passes,
The speed of the motor M is reduced so that the circumferential speed of the fixing rollers R4 and R5 becomes V2, which is lower than the circumferential speed V1 of the drum D (steps 106a and 107a). Here, timer T
The set time TAI of AI is set to the time from when the trailing edge of the recording paper passes the switch SA until it is separated from the drum D. That is, the recording paper is separated from the drum D when the timer TAI becomes 0. At the same time, the speed down flag Fl, 6 (turns ON (step 107a)), while the switch SB is turned on by the conveyor belt G2.
It has already been turned on by detecting the recording paper moving toward the fixing rollers R4 and R5, but when the trailing edge of the recording paper or time T2
When passing through switch SB at
FF (steps 108 and 109), timers TBI and TB2 are set at time T2 (step 110), and then timers TBI and TB are set as time passes.
2 set values TBI, TB2 (TBI>Ta2) are subtracted (steps 111, 112° 111a, 112a),
First, when the set time TB2 of the timer TB2 has elapsed, the energization to the heater H is increased and the heat down flag F2 is turned off.
becomes F (step 113114). Next, timer TBI
When the set time TBI has elapsed, the fixing rollers R4 and R5
Motor M so that the circumferential speed of drum D matches the circumferential speed V1 of drum D.
The rotation speed of increases and the speed down flag Fl turns off.
F (steps 113a, 114a). Note that the setting time of tie vTB1 is set to the time from when the trailing edge of the recording paper passes through switch SB until it is ejected by fixing rollers R4 and R5. In this way, after the recording paper is separated from the separation position of the drum D, the fixing roller R4,
Since the speed of R5 is reduced, no transfer deviation occurs.

In addition, since the time constant of the temperature change of the fixing roller is generally much larger than that of the motor, in order to keep the fixing efficiency constant by making the temperature change of the fixing roller correspond to the change in the circumferential speed of the fixing roller, this time constant is required. In the embodiment, the timing of switching the energization to the heater H and the timing of switching the speed of the motor are shifted by ΔT. In other words, as shown in FIG. 5, when the amount of electricity applied to the heater H is switched from HIGH to LOW, the temperature Ht of the fixing rollers R4 and R5 starts to gradually decrease, or the temperature change is Δ When . R5
By switching the circumferential speed from vl to v2, the fixing efficiency is maintained constant. Also, in the above explanation, the case where the length of the recording paper in the feeding direction is greater than the distance from the separation position to the fixing position is explained, or the length of the recording paper in the feeding direction is greater than the distance from the separation position to the fixing position. If the paper is small, the drum D will cover the entire length of the recording paper.
Needless to say, fixing is performed by a fixing roller having a peripheral speed lower than that of the fixing roller, and the temperature of the fixing roller is controlled accordingly.

FIGS. 6 and 7 are graphs showing examples of temporal changes in the rotational speed of the motor M and corresponding temporal changes in acceleration when decreasing the circumferential speed of the fixing rollers R4 and R5, and show examples of the temporal changes in the acceleration corresponding to the rotational speed of the motor M when the peripheral speed of the fixing rollers R4 and R5 is reduced. (several seconds), the motor M is controlled so that the rotational speed changes gradually, that is, there is no sudden change in acceleration. This reduces the impact of the speed change of the fixing roller on the recording paper, suppresses deflection and fluttering of the recording paper, and prevents distortion in the toner image.

(G) Effects of the Invention According to this invention, even if the length of the recording paper in the feeding direction is longer than the distance from the separation position to the fixing position, the circumferential speed of the fixing roller increases when the recording paper leaves the separation position. The circumferential speed of the drum is lower than that of the drum, and the current applied to the heater of the fixing roller is correspondingly reduced to maintain the fixing efficiency constant. Therefore, the power consumption of the heater of the fixing roller can be reduced without reducing the image forming ability.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a configuration in which an embodiment of the present invention is applied to an electrophotographic copying machine, FIGS. 2(a) to 2(c), and 3.
Figures (a) to 3(c) are respectively number ! FIG. 4 is a time chart explaining the operation shown in FIG. 1, FIG. 5 is a time chart explaining details of the main parts of FIG. 4, and FIGS. 6 and 7 are the fixing roller. 3 is a graph showing a sequence of temporal changes in rotational speed and acceleration of a motor that drives the motor. D: Photosensitive drum, TC: Transfer charger, SC: Separation charger, R3: Registration roller, G1: Guide path , G2... Conveyor belt, R4, R5... Fixing roller, M... Motor, H... Heater, DU i... Drive unit, DU2・・・・・・Electricity unit, CU・・・Control unit, SA, SB・
·····switch. Diagram (a) (b) (C) Diagram Diagram Diagram Diagram Diagram (C) Diagram Appropriate Rotation Diagram

Claims (1)

[Claims] 1. An electrostatic latent image formed on a rotating photoreceptor drum,
In an image forming apparatus configured to develop and transfer onto recording paper, fix the recording paper with a fixing roller, and discharge the recording paper, there is provided a drive means capable of rotating the fixing roller and changing its rotation speed, and a fixing roller. heating means capable of heating and adjusting the heating temperature; a detection means detecting when the trailing edge of the recording paper moving toward the fixing position is separated from the photoreceptor drum; When the detection means detects that the fixing roller is separated from the drum, the driving means is controlled so that the circumferential speed of the fixing roller is lower than the circumferential speed of the photosensitive drum, and in response to the decrease in the circumferential speed of the fixing roller. A fixing device for an image forming apparatus, comprising a control means for controlling a heating means so that a heating temperature is lowered. 2. The electrostatic latent image formed on the rotating photoreceptor drum,
In an image forming apparatus configured to develop and transfer onto recording paper, fix the recording paper with a fixing roller, and discharge the recording paper, there is provided a drive means capable of rotating the fixing roller and changing its rotation speed, and a fixing roller. a heating means capable of heating the recording paper and adjusting the heating temperature; a detection means for detecting the presence or absence of recording paper at a predetermined position on the conveyance path; a timer that outputs an output a predetermined time before the end of the recording paper separates from the photoreceptor drum; a detection device that detects and outputs that the trailing edge of the recording paper has separated from the photoreceptor drum; control means for controlling the heating means so that the temperature of the fixing roller is lowered at certain times, and controlling the driving means so that the circumferential speed of the fixing roller is lower than the circumferential speed of the photoreceptor drum when the detection means outputs an output. A fixing device for an image forming apparatus, characterized in that: