JPH0362080A - image forming device - Google Patents

Abstract

PURPOSE:To lower electric power consumed and an overall device by alternately controlling heating sources for a pair of rotors so as to prevent the simultaneous turning-on of both sources while an illuminating light source is lighting. CONSTITUTION:The device is provided with the illuminating light source 25 illuminating an original and a fixing device 18 fixing a toner image on a recording material. The fixing device 18 fixes a toner image in such a way that the pair of rotors brought into press-contact with each other by the heating of respective heating sources pinches and carries a recording material supporting the toner image. While the illuminating light source 25 is lighting, the heating sources are alternately controlled to prevent both from being simultaneously turned on. Consequently, electric power consumed by the overall image forming device having heaters for a fixing roller and a pressure roller can be lowered.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image forming apparatus that includes an illumination light source that illuminates a document and a fixing device that fixes a toner image on a recording material.

In particular, the present invention relates to an image forming apparatus in which the fixing device includes a pair of rotating bodies, each of which is heated by a heat source.

(Prior art) In a device that fixes a toner image by nipping and conveying a recording material supporting a toner image between a pair of rollers, the toner of an unfixed toner image on the recording material heats the toner and fuses it to the recording material. There is a problem called the so-called offset phenomenon in which the toner adheres to the fixing roller and is transferred to the next recording material.

In particular, full-color devices use high-temperature fixing, in which multiple types of toner are mixed in a nearly molten state, unlike single-color devices, which simply soften the toner and pressurize it to stick. The trend is stronger.

Therefore, in conventional full-color fixing devices, the pressure roller also has a heat source to effectively heat the toner image from the back side of the recording material to prevent offset to the fixing roller.
So-called backside heating has been practiced.

(Problems to be Solved by the Invention) However, when a so-called thermal light source such as a No. 10 Gen lamp is used as a light source for illuminating the original, there is a drawback that power consumption increases, and the power consumption of the image forming apparatus as a whole increases. there were. Further, heating for fixing must be performed at a temperature within a predetermined range; if the temperature is too high or too low, so-called offset occurs.

Therefore, highly accurate temperature control must be performed.

However, for this purpose, if a temperature detection member such as a thermistor is brought into contact with both the fixing roller and the pressure roller,
In addition to increasing the number of parts and increasing costs, the surface of the thermistor on the fixing roller side becomes dirty with toner, resulting in poor contact conditions and poor control, resulting in an excessive rise in roller temperature. Furthermore, if the toner adhering to the thermistor becomes stuck, it may damage the roller or cause a reduction in image quality.

However, if the thermistor is provided only on the pressure roller side, the above problem is solved, but since the temperature of the fixing roller is not controlled, the temperature of the fixing roller increases excessively, causing offset, as well as excessive power consumption, This also causes other problems such as temperature rise inside the machine.

(Means for Solving the Problems) The present invention for solving the above problems includes an illumination light source that illuminates the document, and a fixing device that fixes the toner image on the recording material.
This fixing device is a fixing device that fixes a toner image by sandwiching and conveying a recording material that supports a toner image between a pair of rotating bodies that are heated by a heat source and are in pressure contact with each other. is characterized in that each of the heat sources is controlled alternately so that both are not turned on at the same time, and that the energization to the heat source is switched to half-wave while the illumination light source is turned on. (Embodiments of the Invention) Hereinafter, the present invention will be described in detail based on the drawings.

FIG. 1 shows a full color electrophotographic copying machine which is an embodiment of an image forming apparatus according to the present invention.

An image carrier, that is, in this embodiment, a photosensitive drum 1 having an electrophotographic photosensitive layer on its surface is rotated in the direction of arrow X.

On the left side of the photosensitive drum 1 is a primary charger 4; on the left side of the photosensitive drum 1 is a primary charger 4 that uniformly charges the photosensitive drum 1;
Immediately below the photosensitive drum l, there is a developing device 100. which has a plurality of developing units, that is, in this embodiment, developing units 2M, 2C, 2Y, and 2B, and which moves in the left-right direction. Photosensitive drum 1
A transfer device 6 is disposed diagonally above and to the right of the photosensitive drum 1, and a cleaning device 5 is disposed diagonally above and to the left of the photosensitive drum 1.

Further, an optical system 3 is disposed above the copying machine, and is configured to project the original image on the platen 26 onto the photosensitive drum 1.

The optical system 3 can be any optical system, but in this embodiment, it includes a first scanning mirror 24, and second and third scanning mirrors 23 that move in the same direction at half the speed of the first scanning mirror.
, imaging lens 22, color separation B, G.

R filter 35 and CCD 34. It is composed of a laser scanner unit 31 and fixed mirrors 32 and 33. Here, the scanner unit 31 is a well-known device that polarizes laser light using a rotating polygon mirror, and detailed description thereof will be omitted.

Further, in the optical system 3, a halogen lamp 25 for illuminating the original is provided.
is configured to move together with the first scanning mirror 24.

Therefore, the reflected light image of the original scanned by the first to third scanning mirrors 24 and 23 passes through the lens 22 and is color-separated by the BGR color separation filter 35 and the CCD 34.
After the document information signal is converted into an electrical signal and subjected to various image processing, the laser unit oscillates a laser beam through a laser driver, and this laser beam is applied to the photosensitive drum 1 by the image signal. Image exposure is then performed.

Furthermore, in this embodiment, a fixing device 18 and a paper feed device 15 are provided on the right side of the copying machine. 16 is disposed between the transfer drum 6 and the fixing device 18, and a transfer paper conveyance system 7 for conveying a transfer paper serving as a recording material is disposed.

In the above configuration, the photosensitive drum 1 is subjected to charging, development, transfer, and cleaning processes for each separated color by the primary charger 4, the laser scanner unit 31, the transfer device 6, and the cleaning device 5.

The developing device 100 includes developing units 2M (magenta developing unit) and 2C (
cyan developing unit), 2Y (yellow developing unit)
, 2B (black developing unit), and each color-separated latent image formed on the photosensitive drum is developed into a toner image by the corresponding developing unit.

The transfer device 6 is typically a transfer drum configured to have a transfer material carrying sheet 6a around its periphery and to electrostatically hold the transfer paper on the sheet.

The transfer drum 6 grips the transfer paper fed at the same timing from the paper feeders 15 and 16, and rotates and transports the paper to transfer the toner images of each color on the photosensitive drum 1 in a superimposed manner at the transfer position T. .

At the transfer position T, a transfer charger 7 is arranged inside the transfer drum 6.

The transfer paper onto which the unfixed toner images of each color have been sequentially transferred is released from the transfer drum 6 and peeled off from the transfer drum 6 by a separation charger 8 or the like. Next, the transfer paper supporting this unfixed toner image is transferred to the fixing device 1 by the transfer paper conveyance system 17.
Sent to 8. The toner image on the transfer paper is fixed onto the transfer paper by the fixing device 18, and then the transfer paper is transferred to the tray 1.
It is released onto 9.

Next, referring to FIG. 2, the configuration of the fixing device 18 will be explained.

In FIG. 2, 201 is a rotating body on the side that comes into contact with the unfixed toner image. A pressure roller 202 is in pressure contact with the fixing roller from below. The fixing roller 201 is rotationally driven by means not shown, and is rotated by a pressure roller 20.
2 rotates as a result of this.

And both rollers 201. , 202 have built-in heaters 203 and 204 for heating, respectively.

A guide 205 for the transfer paper is provided on the entrance side of the rollers 201 and 202, that is, the introduction side of the transfer paper, and a guide 205 for the transfer paper is provided on the exit side, that is, the paper discharge side, to prevent the transfer paper from wrapping around both rollers. Separation claws 206 and 207 and a guide 209 for guiding the separation claws to a paper discharge roller 208 are provided.

A web for cleaning the roller surface is pressed against the upper surface of the fixing roller 201 by a web roller 210 . Further, a rubber blade 211 having a similar function is also in pressure contact with the lower surface of the pressure roller 202.

Heater 203 provided inside the fixing roller 201
In this embodiment, a heater 204 having the same output as the heater 204 provided inside the pressure roller 202 is used.

However, the thermal resistance R1 of the fixing roller 201 is set larger than the thermal resistance R2 of the pressure roller, and as a result, the heater 203. Even if the fixing roller 204 generates heat under the same conditions, the outer surface temperature of the fixing roller 201 is always lower than the outer surface temperature of the pressure roller 202.

In this embodiment, the fixing roller 201 has a rubber layer 201A made of RTV (room temperature vulcanization) silicone rubber or LTV (low temperature vulcanization) silicone rubber with a thickness of 3 mm as a release layer on the aluminum core tube 201B. has been set up. The pressure roller 202 is made of an aluminum core tube 202
On top of B, an HTV (thermally vulcanized) silicone rubber layer 202A with a thickness of I mm is provided, and a layer of 20 μm on the surface thereof is further provided.
It is coated with Daiel Latex (trade name of Daikin Industries, Ltd.), which is a mixture of fluororubber and fluororesin, to maintain the above thermal resistance relationship.

The thermal resistance of the roller is RH(2πKA)−”fn(r2/r,)+(−2π
KB)-'・6n (r3/r2)[Cm・SeCII
deg/Cal]. Here, KA is the thermal conductivity of the cored metal tube, KB is the thermal conductivity of the rubber layer, rl and r2 are the inner diameter and outer diameter of the cored metal tube, and r3 is the outer diameter of the rubber layer.

A thermistor 213, which is a temperature detection member, is placed in contact with the outer surface of the pressure roller 202, and the heaters 203 and 204 are independently controlled based on the detected temperature, which will be described in detail later.

However, - as an example, in the aforementioned roller, 1
When using a sharp-melt polyester resin toner with a softening point near 50°C, the heaters for both rollers are set to 400W and the outer surface temperature of the pressure roller 202 is controlled to 170°C. The outer surface temperature is maintained at approximately 155° C., slightly lower than the surface temperature of the pressure roller.

In addition, in FIG. 2, 212 is a pump roller 215.
This is a coating roller that uniformly coats the fixing roller 201 with silicone oil, which is a mold release agent, pumped up from the tank 214 by the fixing roller 201.

Now, here, the heaters 203 and 204 are both 40
0W, and the aforementioned halogen lamp 25 for document illumination also has an output of 230W, so the document illumination lamp 25 and
If both heaters 203 and 204 are all turned on, the power consumption of the machine becomes too large and exceeds the power supply capacity of 100V and 15A for general household use, which is very disadvantageous for the widespread use of the machine.

Therefore, in this embodiment, the halogen lamp 25 for illuminating the document is
When is lit, one of the heaters 2-03 and 204 is always turned off.

Next, in Figure 3, which explains this operation using Figures 3 to 5, 301 is a microcomputer (hereinafter abbreviated as CPU) that performs sequence control of this device, and 213 is the aforementioned A thermistor for fixing temperature detection that detects the surface temperature of the pressure roller.
3, and then converted to an 8-bit digital value through the A/D converter 302.
The information is input to the CPU 301 through the CPU 301.

The document illumination lamp 25 is a lamp regulator (hereinafter referred to as C).
(abbreviated as VR), both heaters are powered by 203
, 204 are independently driven by output ports 304, 306, and 308, respectively, using solid state relays (hereinafter abbreviated as SSR) 307 and 309.

4 and 5 are flowcharts relating to this embodiment.

FIG. 4 is a part of a subroutine of a copying operation sequence for a copying machine, which is when the document illumination lamp is turned on. First, in step 401, a flag LAMP indicating that the lamp is lit is set to "l". At 402, it is determined whether the counter flag CNT for controlling each scan is "1", and if CNT=1, CNT is set at 403.
0'', and if CNT=O, in step 404, CNT is inverted by 1''. Last 1:405 Turn on CVR305 and turn on lamp 25. On the other hand, FIG. 5 shows an interrupt routine for controlling the temperature of the fixing device.
It operates by a timer interrupt every msec.

First, in 501, the fixing temperature T detected by the thermistor 213 is determined. is higher than the lowest temperature TL to be controlled, and if it is higher than TL, in step 502, 5SR307, 309 are turned off, and both heaters 203
, 204 and exits from the routine. TL>
If To, it is determined in step 503 by looking at the flag LAMP indicating whether or not the original illumination lamp 25 is lit, and if the lamp is not lit, it is determined in step 504 that 5SR307,3
Turn on both heaters 203. Turn on 204 to raise the temperature of the fixing device. When it is determined in 503 that the lamp is lit, in 505 it is determined whether the counter flag CNT is "1" or "O", and C
If NT=1, 5SR307 is turned on at 506 and only the heater 203 is turned on; if CNT=0, 5SR309 is turned on at 507 and only the heater 204 is turned on.

With the above operation, when the document illumination lamp 25 is on, one of the two heaters of the fixing device is always turned off, thereby making it possible to reduce the power consumption of the device.

Furthermore, due to the configuration of the fixing roller and pressure roller as described above, while the document illumination lamp is on, power supply to one heater is interrupted, but when the document illumination lamp is turned off, power supply to both heaters is started. Because the control of the heater is switched alternately, especially every - scan,
Temperature control is sufficient.

When a transfer paper with unfixed toner is fed between both rollers under such conditions, it will be heated and pressed by both the fixing roller 201 and the pressure roller 202, but due to the surface temperature of the pressure roller 202. The fixing roller 201
Since the surface temperature of the pressure roller is higher than that of the fixing roller, and the thermal resistance of the pressure roller is also smaller than that of the fixing roller, the heat flow from the pressure roller side is greater than the heat flow from the fixing roller side, so the toner quickly adheres to the transfer paper. fixing roller 20
It is not offset to 1. This is because in the case of full-color copiers, there are many originals with high image ratios, and toners of two or more colors must be completely melted and mixed, making it easy to offset, but this example was effective in preventing offset. .

Note that one scan here refers to a scan in one movement of the optical system 3, and the copying apparatus of the embodiment shown in FIG. 1 requires four scans to copy one original. Let's do it.

The heaters 203 and 204 to be controlled may be switched every multiple scans, but it is preferable to switch every single scan since the fixing roller requires a very large heat capacity.

Next, another embodiment of the present invention will be described. In the above-mentioned embodiment, the fixing heater was controlled for each scan of the original illumination lamp by software, but by adding the circuit shown in FIG.
In the software, the input from the thermistor 213, which is a temperature detection member, is judged and the heater is turned on/off.
It is only necessary to control the software, and the burden on the software can be significantly reduced.

The operation will be explained using FIGS. 6 and 7.

In FIG. 6, the signal line 304 is connected to the document illumination lamp 25.
As shown in FIG. 7, ○N10FF is repeated at a constant cycle. In Figure 7 “
The “H” state indicates that the lamp 25 is on.Signal line 60
9 detects the surface temperature of the pressure roller 202 of the fixing device by input from a thermistor 25 (not shown), completely independent of the control of the lamp 25, and controls both heaters 203 and 204 based on the information. It's a signal.

A flip-flop 601 receives the signal 304 as a clock input and is connected to perform a toggle operation, and its output signal 610 is as shown in FIG. 7(c). Therefore, the AND gates 603, 604 and the NOTOR gate 605 cause the heater ON signal 609 from the CPU to turn ON.
N state (even if it becomes "H" level in Fig. 7, the state shown in Fig. 7 (
As shown in d) and (e), while the lamp 25 is on, only one of the heaters 203 and 204 is turned on.
The heater is controlled so that it does not turn on, and is turned on by the flip-flop 601 every time the lamp 25 scans.
Control to switch.

Furthermore, the NOTOR gate 605, the ND gate 608, and the OR gates 605 and 606 control both heaters so that when the lamp 25 is not lit, both heaters are lit.

As described above, by adding the circuit having the logic circuit shown in FIG. 6, the software can reduce the fixing performance in the same manner as in the previous embodiment without being aware that there are two heaters. It is possible to achieve energy savings without any effort.

Next, another embodiment of the present invention will be described.

If the thermal resistance of the fixing roller 201 is thicker than that of the pressure roller 202 as in the above embodiment, or if the thermal capacity of the fixing roller and the pressure roller is small, If one of the heaters is turned off every time the document illumination lamp 25 scans, the temperature may drop too much and offset may occur.

In this way, an embodiment that is effective when the thermal resistance of the fixing roller is smaller than that of the pressure roller or when the heat capacity of the fixing roller and the pressure roller is small will be described with reference to FIG.

As shown in Fig. 8, phototriac 801゜802
It is possible to reduce the power consumption of the device by controlling the power supply to the heater between full wave and half wave using the following devices.

In FIG. 8, 805 is the output board of the CPU, which is a signal line that controls the heaters 203 and 204, and turns on the LEDs 801a and 801b in the phototriac 801, thereby energizing the triac and turning on the heater 203. . (The same applies to the phototriac 802).

By turning on the transistors 803 and 804, the signal line 806 disables the LEDs 801b and 802b in the phototriacs 801 and 802 from turning on, and puts the phototriacs 801 and 802 into a half-wave energized state.

Therefore, when the original illumination lamp 25 is on, the signal line 806 is set to "L", and the transistors 803 and 804
is set to FF, and the heaters 203 and 204 are controlled in a state where the phototriacs 801 and 802 can conduct full-wave current,
When the lamp 25 is on, the signal line 806 is set to “H”.
, turn on transistors 803 and 804, and turn on the first transistor.
・With the triac 801.8C12 in a half-wave energized state, the heater 203. By controlling the lamp 204, the power consumption when the lamp 25 is lit is reduced.

(Effects of the Invention) As described above, the power consumption of the entire image forming apparatus having heaters for both the fixing roller and the pressure roller can be reduced.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an image forming apparatus that is an embodiment of the present invention. FIG. 2 is a sectional view of a fixing device used in the embodiment of FIG. 1. FIG. 3 is a circuit used in the embodiment of FIG. 1. 4 and 5 are flowcharts for controlling the embodiment of FIG. 1, respectively. FIG. 6 is a circuit diagram for explaining another embodiment of the present invention. Timing chart of the embodiment shown in FIG. 8 is a circuit diagram of still another embodiment of the present invention. 1 is a photosensitive drum, 2M, 2C, 2Y, 2Bk are developing units for each color, 3 is an optical system, 4 is a primary charger, 5 is a cleaning device, 6 is a transfer device, 6a is a transfer material carrying sheet,
7 is a transfer charger, 8 is a separation charger, 17 is a transfer paper transport system, 18 is a fixing device, 19 is a paper discharge tray, 22 is an imaging lens, 23 is a second . The third mirror, 24 is the first mirror, 25
26 is a halogen lamp for document illumination, and 26 is a platen glass.
31 is a laser scanner 32.331;! Folded mirror, 34 is ccD135 is color separation filter, 100
201 is a developing device, 201 is a fixing roller, 202 is a pressure roller, 203 and 204 are fixing heaters, 205 is a guide plate, 206 and 207 are separating claws, 208 is a paper ejection roller, 209 is a paper ejection guide, and 210 is a web roller, 21
1 is a cleaning blade, 212 is an oil application roller, 213 is a thermistor 214 is an oil tank, 21
5 is oil pump roller 3011t CPU,
302 Ha A/D: ] inverter, 305 is a lamp regulator (CVR), 307, 308 are solid state relays (SSR), 601 is a flip-flop, 602, 607 are NOT gates, 603, 604,
608 is an AND gate, 605 and 606 are OR gates, 801 and 802 are photo triacs, and 803 and 80
4 is a transistor. 100■ Figure 5

Claims (3)

[Claims] (1) It has an illumination light source that illuminates the document and a fixing device that fixes the toner image on the recording material. An image forming apparatus that is a fixing device that fixes a toner image by nipping and conveying the toner image, wherein while the illumination light source is turned on, each of the heat sources is controlled alternately so that both of the heat sources are not turned on at the same time. . (2) The image forming apparatus according to claim 1, wherein the control of each of the heat sources is performed alternately every time a document is scanned. (3) It has an illumination light source that illuminates the document, and a fixing device that fixes the toner image on the recording material, and the fixing device supports the toner image on the recording material with a pair of rotating bodies that are heated by heat sources and are in pressure contact with each other. An image forming apparatus that is a fixing device that fixes a toner image by nipping and conveying a toner image, wherein the image forming apparatus is characterized in that while the illumination light source is turned on, energization to the heat source is switched to half-wave.