JPS6118983A - Image forming device - Google Patents

Abstract

PURPOSE:To perform invariably stable fixation by detecting the surface temperature of a heat roller for fixation and varying the speed of an image forming process according to the detection result. CONSTITUTION:When copy information on a size, quantity, etc., is inputted from an operation part 42, a control part 41 controls a motors 48-50 for a photosensitive drum, conveying means, etc., electrifier 12, 23, and 24, and a destaticizing lamp 30 through drivers 44-47. Further, the temperature of the roll for fixation is detected 31, A/D-converted 40, and inputted to the control part 41. A processing speed setting part 43 increases or decreases speeds of the respective motors 48-50 according to whether the temperature detected by a temperature detector 31 rises of falls. A timer 51 makes the timing of form feeding from a paper feed cassette fast or slow. The driver 47 controls the operation periods of the destaticizing lamp 30 and electrifier 12, 23, and 24. Consequently, invariably stable fixation is carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an image forming apparatus such as a copying machine that uses a heat roller for fixing, for example.

[Technical background of the invention and its problems] In general, one development direction of copying machines is to increase the copying speed. The surface temperature of the heat roller drops significantly. In particular, under temperature conditions or high humidity conditions, the amount of heat taken away by the copy paper increases.
The temperature has dropped drastically, causing fusing failure. In order to prevent such problems, the power to the heat roller is increased to increase the amount of heat generated per unit time, but there is a method of increasing the heat capacity of the heat roller to reduce the rate of temperature drop.

However, increasing the power of the heat roller was not desirable because there is a limit to the current capacity of general household electrical outlets. Furthermore, increasing the heat capacity of the heat roller increases the warm-up time of the apparatus, making it necessary to hold the apparatus for a long time in order to make several copies, which is extremely unreasonable.

[Object of the Invention] This invention has been made in view of the above circumstances, and its purpose is to be able to always maintain a constant surface temperature of a fixing heat roller during high-speed image forming processing, and to An object of the present invention is to provide an image forming apparatus that can perform accurate fixing.

[Summary of the Invention] The present invention detects the surface temperature of a heat roller for fixing, and changes the speed of image forming processing according to the detection result.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 schematically shows the internal mechanism of a copying machine as an image forming apparatus. In other words, 1 is the copying machine main body,
A document table (transparent glass plate) 2 is provided on the top surface of the main body 1 to support a document.

On the lower surface side of the document table 2, there is an exposure optical system 1o consisting of an exposure lamp 4 that reciprocates in the direction of the arrow in the figure, a mirror 5, 6, 7, a lens block 8 that is movable in the optical axis direction, and a fixed mirror 9. By optically scanning the surface of the document using the optical system 10, an image of the document is formed on the surface! (slit exposure). The photosensitive drum 11 rotates in the direction of the arrow shown in the figure, and the surface is first charged by the charging device 12, and then the image is exposed to slit light to form an electrostatic latent image on the surface. This electrostatic latent image is turned into a pA image by applying toner by a developing device 13, and is then neutralized by a pre-transfer static elimination lamp 14.

On the other hand, the paper (image-forming object) P is taken out one by one from the selected upper paper feed cassette 15 or lower paper feed cassette 16 by a delivery roller 17 or 18, passes through a paper guide path 19 or 20, and is passed through a registration roller. 21, and is guided to the transfer section 22 by this registration roller 21.
You will be guided to. Here, the paper feed cassettes 15 and 16 are detachably provided at the lower right end of the main body 1, and one of them can be selected using an operation section (not shown). However, the transfer section 2
The paper P sent to the photoreceptor drum 2 comes into close contact with the surface of the photoreceptor drum 11 at the transfer charger 23, so that the toner image on the photoreceptor drum 11 is transferred by the action of the charger 23. The transferred paper P is electrostatically peeled off from the photoreceptor drum 11 by the action of the peeling charger 24 and conveyed through the paper conveyance path 25, and a heat roller 26 serving as a fixing device is provided at the end of the sheet conveyance path 25. The transferred image is fixed by passing through this area. After fixing, the paper P is discharged from the main body 1 through the discharge port 29 by the paper discharge roller 27 and guided to the tray 28/\. Further, after the transfer, the photosensitive drum 11 is returned to its initial state by removing residual toner on the surface by a cleaner 29 and erasing an afterimage by a static elimination lamp 30. The tray 28 is provided so as to be freely attachable.

Further, near the heat roller 26, its surface temperature (
A detector 31 is provided to detect the fixing temperature. This detector 31 is a well-known device consisting of a thermistor or the like.

FIG. 2 is a diagram showing the configuration of main parts of the control circuit.

That is, the control section 41 is responsible for controlling the entire copying operation, receives signals from the operation section 42 and signals supplied from the detector 31 via the A/D converter 40, and receives signals from the drivers 44, 45, 46. It is designed to control a drive process system consisting of a .47 etc. The control section 41
It is mainly composed of a microcomputer and its peripheral circuits, operates according to a program stored in advance in its internal memory (ROM), and controls the gods. The control section 41 also includes an A/D converter 40.
The speed information is read out from the processing speed 6-setting section 43 in response to a signal supplied from the processing speed 6 and set in the timer 51, and the interval at which the paper P is taken out is controlled, that is, the driver 45 is controlled in accordance with this speed information. That is, when the speed information is "T1", the next paper is started to be taken out after T1 time has elapsed since the previous paper was taken out, that is, the driver 45 is controlled in accordance with the timeout signal T1 from the timer 51. By driving the motor 49, the delivery roller 17 (18) starts rotating. Further, when the speed information is "T2", the next paper is started to be taken out 12 hours after the previous paper was taken out, that is, the driver 45 is controlled according to the timer 1 to signal T2 from the timer 51. Then, by driving the motor 49, the rotation of the delivery roller 17 (18) is started. As a result, the copying operation is performed at an interval for taking out the paper P according to the surface temperature of the roller 26, so that the fixing strip 1' is always properly adjusted.
Fixing is performed in step 1.

The processing speed setting section 43 is composed of, for example, RON=+, and stores a digital value corresponding to the surface humidity of the heat roller 26 and speed information indicating the take-out timing, and the relationship is It is as shown in Figure 3. For example, when the temperature of the heat roller 26 is low, the speed information "T1", which has a long take-out timing, is obtained for the digital value "Δ";
When the temperature of the roller 26 is high, the speed information is "T2", which has a short take-out timing, with respect to the digital value rBJ.
” can now be obtained. The A/D converter 40 converts the signal from the detector 31 into a digital value. The driver 44 drives a motor 48 that rotates the photosensitive drum 11.

The driver 45 is connected to the delivery roller 17 or 18.
It drives a motor 49 that rotates the . The driver 46 drives a motor 50 that moves the optical system 10. The driver 47 drives each of the chargers 12, 23, 2711, the static elimination lamp 30, and the conveyance system.

Next, the operation in such a configuration will be explained.

For example, now a document is placed on the document table 2, and the operation unit 42
The number of copies is set and copying starts (copy start key).
Suppose that the command is given. Then, the control unit 41 controls the driver 4
By controlling 4.47 and rotating the motor 48, the photoreceptor drum 11 is rotated in the direction of the arrow shown in the figure, and the charging charger 12, the static elimination lamp 30, the transfer charger 23, and the peeling charger 24 are rotated. and operating the transport system. Next, the control section 41 causes the driver 45 to rotate the motor 49, rotates the delivery roller '17 (18), and takes out the paper P. Then, the control unit 41 rotates the motor 50 with the driver 46, thereby
The optical system 10 is moved.

As a result, the original is scanned by the exposure lamp 4, and reflected light from the original is guided to the photosensitive drum 111 via the mirrors 5, 6, 7, the lens 8, and the mirror 9. Then, an electrostatic latent image for @ polarization is formed on the photosensitive drum 11, and as the photosensitive drum 11 rotates, this electrostatic latent image is developed by the imager 13 and made visible. Further, the paper P from the paper feed cassette 15 (16) is taken out by the rotation of the delivery roller 17-9 (18), and is sent to the transfer section 22 between the photosensitive drum 11 and the transfer charger 23 by the registration roller. It will be done. Here, the image on the photosensitive drum 11 is transferred to the surface of the paper P by the action of the transfer charger 23, and after this transfer, is peeled off by the action of the peeling charger 24. Then, the paper P on which the image has been transferred is sent to the heat roller 26 by the running of the conveyor belt 25, where the image is fixed, and the paper P is published onto the tray 28 by the paper ejection roller 27. At this time, the number of copies is counted by the control section 41. Further, after the transfer, residual toner on the surface of the photosensitive drum 11 is removed by a cleaner 29, and an afterimage is further erased by a static elimination lamp 30.

When the paper P is taken out, the control unit 41 rotates the motor 49 for the transport time required for the paper P to reach the registration rollers 21, and when the rotation is stopped, the timer 51 is activated.

At this time, if the surface temperature of the peeler 1-○-ra 26 is low,
A digital value rAJ is output from the A/D converter 40. Thereby, the control section 41 reads out the speed information T1 for the digital value rAJ from the processing speed setting section 43 and sets it in the timer 51. Further, when the surface condition of the heat roller 26 is high, the A/D converter 40 outputs a digital value rBJ.

Thereby, the control unit 41 reads out the speed information T2 for the digital value rBJ from the processing speed setting unit 43,
It is set in timer 51. Then, a timeout signal (T1 or T2, etc.) is sent from the timer 51 to the control unit 4.
1, the control unit 41 causes the driver 45 to rotate the motor 49, rotates the delivery roller 17 (18), starts taking out the paper P, and the copying operation is performed in the same manner as described above.

Thereafter, the speed information read from the processing speed setting unit 43 is set in the timer 51, and the sheets P are sequentially taken out and copied at the output timing of the timeout signal from the timer 51. Incidentally, a signal waveform diagram for explaining the above operation is shown in FIG.

As described above, since the paper P is taken out at time intervals depending on the surface temperature of the heat roller 26, the copying operation can always be performed under appropriate fixing conditions.

In the above embodiment, the fixing conditions were changed according to the surface temperature of the heat roller by changing the drive timing of the delivery roller, but the present invention is not limited to this, and the speed of the copying process such as exposure and development can be changed. You may also do so. Also,
The speed at which the paper passes through the peel roller may be changed. In this case, the toner fixing performance of the heat roller varies greatly depending on the speed of the paper passing through the heat roller or the temperature of the peeler 1-0- as shown in FIG. The above figure 5 shows P1
~It shows the relationship between the temperature of the roller and the fixing rate. Here, the fixing rate refers to the fixed solid image being rubbed with a non-woven cloth under a constant load, and the density of the remaining residual image being adjusted to the original image temperature. It shows the value divided by. As a result, when the paper passing speed is 300 mm, .sec, the temperature of the P1 roller is a and the [J fixing rate is × (%), but when the temperature drops to b, the fixing rate is Y (%). decreases to Therefore, the fixing performance of the heat roller is affected by the paper passing speed, but the fixing performance improves when the speed is reduced.

Therefore, at a speed of 300 mm/sec, the fixing rate x
(%), the temperature of the heat roller needs to be a, but if the temperature of the heat roller drops to b, the fixing rate drops to x (%).

However, at this time, if the speed is lowered to 150 mm/sec, a fixing rate of x(%) can be maintained.

[Effects of the Invention] As detailed above, according to the present invention, the surface temperature of the fixing heat roller can always be kept constant during high-speed image forming processing, and images can be reliably fixed. A forming device can be provided.

[Brief explanation of drawings]

Figures 1 to 4 show an embodiment of this invention.
Fig. 1 is a sectional view showing the overall configuration, Fig. 2 is a block diagram showing the main parts of the control circuit, and Fig. 3 is for explaining the relationship between the digital value for the temperature of the heat roller and the speed - 13 = information. , and FIG. 4 are signal waveform diagrams of main parts for explaining the operation, and FIG. 5 is for explaining the relationship between paper conveyance speed, fixing rate, and heat roller temperature in another embodiment. This is a diagram. 10...Optical system, 11...Photosensitive drum, P...
Paper (image forming body), 15.16... Paper feed cassette, 17.18... Sending roller, 26... Heat roller, 40... A/D converter, 41... Control unit,
42... Operation section, 43... Processing speed setting section, 44.
45.46.47... Driver, 48.49.50.
...Motor, 51...Timer.

Claims (5)

[Claims] (1) In an image forming apparatus that forms an image on an image forming body using a heat roller for fixing, there is provided a detection means for detecting the surface temperature of the heat roller, and an image is formed according to the detection result by the detection means. 1. An image forming apparatus comprising: changing means for changing processing speed. (2) The image forming apparatus according to claim 1, wherein the processing speed is slow when the surface temperature of the heat roller is lower than an appropriate temperature, and becomes faster when the surface temperature of the heat roller is higher than the appropriate temperature. (3) The image forming apparatus according to claim 1, wherein the processing speed is changed by controlling the timing at which the object to be imaged is taken out. (4) The image forming apparatus according to claim 1, wherein the processing speed is changed by changing the speed of the image forming process. (5) The image forming apparatus according to claim 1, wherein the processing speed is changed by changing the speed at which the image forming object passes through the heat roller.