JPH03100584A - Image forming device of electrophotographic method - Google Patents

Abstract

PURPOSE:To always obtain a good image quality by temporarily inhibiting the image forming operation and making a state of standby when a surface temperature of a fixing roll is discriminated by a temperature range discriminating means to be out of the range of an appropriate operation temperature. CONSTITUTION:When the surface temperature of the fixing roll detected by a surface temperature detecting means A is discriminated to be out of the range of the appropriate operation temperature by the temperature range discriminating means B, the image forming operation is temporarily inhibited by an image forming operation inhibiting means C and the device is made to be a state of standby until the surface temperature of the fixing roll reaches the appropriate operation temperature again. Therefore, toner is heat-fixed on paper only by the fixing roll which is heated and retained at the appropriate fixing temperature. Thus, the good image quality can always be obtained.

Description

[Detailed description of the invention] [Industrial application field] This invention is a laser printer and an LED printer.

The present invention relates to an electrophotographic image forming apparatus equipped with a fixing device such as an electrophotographic copying machine and a facsimile machine.

[Conventional technology]

2. Description of the Related Art Electrophotographic image forming apparatuses such as laser printers generally use a fixing device that uses a fixing roller to fix a toner image transferred from a photoconductor surface onto a sheet of paper.

In this fixing device, the fixing roller is heated by a heater provided inside the fixing roller, and the temperature is controlled so that the surface temperature of the fixing roller falls within a proper operating temperature range suitable for image formation.

For this temperature*J control, the lower and upper limits of the above-mentioned proper operating temperature range are set in advance, and the surface temperature of the fixing roller is generally detected by a temperature sensor such as a thermistor placed near it. The heater is energized when the temperature is lower than the lower limit of the proper operating temperature, and is turned off when the temperature is higher than the upper limit of the proper operating temperature.
This refers to off control.

Incidentally, temperature abnormalities in a fixing device that performs such temperature control can be broadly classified into the following two types.

■ High temperature abnormality where the surface temperature of the fixing roller continues to rise even if it exceeds the upper limit of the proper operating temperature.

■ When the power is turned on or when the surface temperature of the fixing roller falls below the lower limit of the proper operating temperature, the lower limit of the proper operating temperature must be lowered within a certain time to ensure that the surface temperature does not reach the proper operating temperature within a certain time. (not exceeded) low temperature abnormality.

Therefore, when such a temperature abnormality occurs in the fixing device, it is impossible to continue normal image forming operation, and for safety reasons, the entire image forming device must be completely stopped and repaired by a service person. For example, a display to that effect is displayed on the display device so that the request can be made.

[Problem to be solved by the invention]

In such conventional electrophotographic image forming apparatuses, the image forming operation is not immediately stopped even if the surface temperature of the fixing roller of the fixing device falls outside the proper operating temperature range, and the image forming apparatus is not controlled as described above. Since the image forming operation was stopped only when the temperature was abnormal, fixing offset due to abnormal temperatures, that is, the toner image on the paper was not fixed reliably,
There was a problem that image quality deteriorated.

This invention has been made in view of the above points, and aims to solve the above-mentioned problems and to always obtain good image quality.

[Means to solve the problem]

In order to achieve the above object, the present invention provides an electrophotographic image forming apparatus equipped with a fixing device for thermally fixing a toner image transferred to paper. A surface temperature detection means A for detecting the surface temperature of the roller; a temperature range determination means B for determining whether the surface temperature of the fixing roller detected by the means A is within a proper operating temperature range; An image forming operation inhibiting means C is provided which temporarily inhibits the image forming operation and puts the image forming apparatus into a standby state when it is determined that the surface temperature of the fixing roller is out of the proper operating temperature range.

[For production]

According to the electrophotographic image forming apparatus configured as described above, the surface temperature of the fixing roller detected by the surface temperature detection means A is determined to be out of the proper operating temperature range by the temperature range determination means B. Sometimes, the image forming operation inhibiting means C temporarily prohibits the image forming operation and puts the fixing roller into a standby state until the surface temperature of the fixing roller reaches the proper operating temperature again. Only the toner on the paper is thermally fixed.

Therefore, good image quality is always obtained.

〔Example〕

Hereinafter, embodiments of the present invention will be specifically described with reference to FIG. 2 and subsequent figures.

FIG. 2 is a sectional view showing a schematic configuration of a laser printer which is an embodiment of the present invention.

This laser printer consists of a main body 1 and a table 2.
The main body 1 is removably equipped with upper and lower two paper feed trays (cassettes) 3.4 each capable of storing 250 sheets of cut paper, and a first paper stacker 6 and a second paper stacker 7 in two stages at the top. A third paper ejection stacker 8 is installed at the rear of the paper ejection port 9.
It is provided so that it can be opened and closed in the direction of arrow A in FIG.

Furthermore, inside the main body 1, there is a photosensitive drum 10 that constitutes the image forming section of the printer engine. Electric charger 11. Laser writing device 12. Developing device 13. Transfer charger 14. A cleaning unit 15, a fixing device 16, a pair of registration rollers 17, a paper ejection conveyance section 18 consisting of a large number of conveyance rollers, a paper guide plate, etc., and a power supply unit (PSU).
It is equipped with 19.

Also, within the main body 1, various data such as image data sent from a host system such as a computer or a word processor are stored as laser modulation data and a paper feed path.

and an image information processing device (controller) 21 that converts into a selection signal for selecting a paper ejection path, print mode (single-sided mode, double-sided mode, etc.), and the like.

Each board of a sequence driver 30 that controls the printing operation by receiving a print request signal from the image information processing device 21 is installed, and externally of the main body 1 there are multiple keys for operation and the operation of this laser printer. An operation display section (not shown) consisting of a display device and the like that displays the status and the like is provided.

On the other hand, the table 2 is equipped with a bulk paper feed tray 5 that can store 1000 sheets of cut paper, and inside is a reversing section for double-sided printing, which consists of a large number of conveyance rollers and paper guide plates that make up the duplex unit. 22 and reversing paper feeding section 2
It is equipped with 3rd class.

Next, the operation of each part mentioned above will be briefly explained.

The image information processing device 2 uses data from the host system.
When all the data for printing is completed in step 1, the image information processing device 21 sends a print request signal to the sequence driver 30 along with selection signals for the paper feed path, paper ejection path, print mode, etc. When the driver 30 receives the print request signal, it starts print sequence control.

When the print sequence is started by the sequence driver 30, paper feed starts from the selected paper feed trays 3 and 4 or the large quantity paper feed tray 5 at a predetermined timing, and the leading edge of the paper reaches the pair of registration rollers 17. Pause while it is being held in place.

Meanwhile, the photosensitive drum 10 rotates in the direction of the arrow in FIG.
The surface charged by the f-electric charger 11 is exposed by being irradiated with a laser beam modulated according to video data by a laser writing device 12 while main scanning in the direction of the drum axis, thereby forming an electrostatic latent image.

Developing the latent image with toner from the developing device 13,
The transfer charger 14 transfers the image onto a sheet of paper fed by a pair of registration rollers 17 at a predetermined timing.

The paper on which the toner image has been transferred is peeled off from the photoreceptor drum 10 and conveyed to the fixing device 16, where the toner image on the paper is transferred while being sandwiched between a fixing roller 18a with a built-in heater and a pressure roller 16b. Heat and fix.

In order to detect the surface temperature of the fixing roller 18a, that is, the fixing temperature, a thermistor TH is fixedly disposed close to the surface of the fixing roller 18a as a temperature detection element (temperature sensor).

The printed paper that has passed through the fixing device 16 is transferred to the first paper stacker 6 or the second paper stacker 7 located at the top of the printer, or to the second paper stacker 7 located at the rear of the printer via the paper transport section 18 as a paper discharge section. The paper is ejected to one of the three paper ejection stackers 8 selected.

On the other hand, the toner remaining on the photoreceptor drum 10 after the transfer is removed by the cleaning unit 15 and collected into an internal toner collection chamber.

Note that 1 usually the first stray paper stacker 6 and the second paper output stacker 7
However, in special cases, such as when using paper that easily curls, such as envelopes and postcards, the third paper stacker 8 is selected.

However, when the paper ejection port 9 is closed and the paper cannot be ejected, the third paper ejection stacker 8 cannot be selected.

By the way, when the double-sided mode is selected as the print mode, the sheet printed on one side is sent to the table 2 by changing the conveying path.

Then, after first feeding it into the reversing section 22 for double-sided printing, the conveying direction is reversed and conveyed to the reversing paper feeding section 23, where it is kept on standby, and then fed into the main body 1 at a predetermined timing, and the same process as described above is carried out. Print on the other side, and then output the paper to one of the paper output stackers.

FIG. 3 is a diagram showing an example of a fixing temperature detection mechanism in the fixing device 16 shown in FIG.

In this figure, the thermistor TH for detecting the surface temperature of the fixing roller 168 with built-in heater 1f3c is
The plate spring 2 together with the thermistor holding member 24 that holds this
5 toward the fixing roller 1Ba side, and lightly contacts the surface of the fixing roller 1Ba.

In order to control the fixing temperature in a heating roller type fixing device such as this fixing bag W16, each temperature detection element including a thermistor is brought into contact with the surface of the fixing roller as shown in FIG. 3, or placed close to it. The fixing temperature is measured by the output of the temperature detection element and controlled to maintain an appropriate operating temperature, or an infrared sensor or the like is used to detect infrared rays emitted from the fixing roller to ensure proper operation. A common method is to control the temperature so as to maintain it.

FIG. 4 is a circuit diagram showing the configuration of a fixing temperature control circuit that controls power supply to the heater 16c of the fixing device 16. The fixing temperature control circuit is installed on the substrate of the sequence driver 30 shown in FIG. A microcomputer (
(hereinafter abbreviated as rCPUJ) 31, comparator 32.
It is composed of an AND gate 33, a plurality of resistors, etc., and controls the power supply from the power supply unit (PSU) 19 to the fixing heater 18c in a 0N10FF manner.

CPUE! ;1 is microprocessor, ROM, RAM
, timer, Ilo, etc., and this cptr31 has a power supply voltage Vcc (+5 V
) and ground (GND), the fixing temperature is measured from the connection point a of the bridge circuit, which is composed of a series circuit of a volume (variable resistor) VR and a resistor R1, and a series circuit of a thermistor TH and a resistor R2, which are connected in parallel between The voltage signals of a reference voltage vO corresponding to a target value and a detection voltage v1 serving as a detection value of the fixing temperature from the connection point S are input.

The inverting input terminal and the non-inverting input terminal of the comparator 62 are supplied with a detection voltage signal V] from the above-mentioned connection point, respectively.
A reference voltage Vr from a connection point C, which is divided by voltage dividing resistors R3 and R4 connected in series between the power supply voltage Vcc and the ground, is input.

In addition, thermistor TH, volume V Rt each m resistance R
1* R2 and CPU 31 constitute surface temperature detection means A and temperature range determination means B shown in FIG.

It also functions as image forming operation inhibiting means C.

Next, the operation of this embodiment configured as described above will be explained with reference to FIG. 5 and subsequent figures.

FIG. 5 shows the proper operating temperature range as the surface temperature of the fixing roller 16a shown in FIG. 3, that is, the fixing temperature T. This corresponds to the temperature range of the fixing temperature T during image forming operation.

Note that To in the proper operating temperature range is the target set temperature, and by changing the resistance value of the volume VR shown in FIG. 4, the reference voltage Vo can be changed and set to any corresponding temperature value. can.

In addition, T1 and T2 are the lower limit temperature and upper limit temperature, respectively, of the appropriate operating temperature range, and the corresponding voltage values are VD
and VU, and each voltage value is RO in the CPU 51.
Store it as data in M.

Furthermore, To' is a temperature slightly higher than the target set temperature To, which means that when the CPU 31 malfunctions due to noise or the like and becomes uncontrollable, the comparator 32 shown in FIG. The target set temperature corresponds to the reference voltage Vr when controlling T (corresponding to the detected voltage v1), and this control will be explained in detail later.

FIG. 6 is a flowchart showing the fixing temperature control operation by the CPU 31 of this embodiment.

In this routine, when the power is turned on and the initial settings are completed, the sequence driver 3 is set to star 1 in step 1.
0 (see FIG. 2) sends an image formation prohibition signal to the main CPU (not shown) above to prohibit the image formation operation and put it into a standby state, and in step 2 it is determined whether Vl<Vo.

That is, the fixing temperature T, which is the surface temperature of the fixing roller IF3a shown in FIG. 3, is the target temperature T at which the fixing temperature T is the center of the proper operating temperature range shown in FIG.

If the fixing temperature T is not Vl<Vo,
has reached the target set temperature To, proceed to step 3.

Note that if the power is turned on again soon after the power is turned off, the fixing temperature T will maintain approximately the same temperature as before the power was turned off, so in some cases it may exceed the target set temperature To. Yes, so you may proceed to step 3.

Then, when proceeding to step 3, Vl>VU
In other words, if the fixing temperature T exceeds the upper limit temperature of the proper operating temperature range, the process proceeds to step 18; otherwise, the process returns to step 2 and repeats this process.

If Vl<Vo in step 2, the process proceeds to step 4, and the heater 16c built in the fixing roller 16a in FIG.
Turn on.

Note that, as shown in FIG. 5, since the temperature To' is higher than the target set temperature To, the reference voltage Vr input to the comparator 32 shown in FIG. The voltage value is higher than the voltage Vo.

However, if Vt < Vo, the CPU 51 sets one input terminal of the AND gate 33 to 1°, and at this time Vt
Since x<Vr, the comparator 32 is also the AND gate 3.
Since the other input terminal of 3 is set to 1'', the AND gate 33 performs the logical product and outputs 1°, and the power supply unit 1
-19, the power to the heater 18c in FIG. 3 is turned on.

Next, in step 5, start the timer in the CPU 711 to 1.
-, and in step 6 it is determined whether v1≧VD, that is, the fixing temperature T is the lower limit temperature T1 of the proper operating temperature range shown in FIG.
Determine whether it has been reached.

If Vl≧VD and the fixing temperature T is lower than the lower limit temperature T1, it is determined in step 7 whether the timer value t exceeds the set value ta, and if t > t a, the process returns to step 6. This process is repeated, and if t) ta, the timer is reset in step 8, and then AN in step 9.
By outputting O° to one input terminal of the D gate 33, the heater 16c is turned off.

Next, in step 10, a low temperature abnormality notification signal is sent to the operation display unit (not shown) via the image information processing device 21 shown in FIG. 2 to display information to that effect, and the process ends.

Furthermore, as the timer setting value ta, data on the expected time until the heater 16c reaches the target setting temperature To is used as CPtJ.
It is stored in the ROM in ESt.

On the other hand, if ■1≧VD and the fixing temperature T reaches the lower limit temperature T1 of the proper operating temperature range in step 6, step 1
Step 1 resets the timer, step 12 cancels the transmission of the image formation prohibition signal, and proceeds to step 13, and ■1≧Vo
In other words, it is determined whether the fixing temperature T has reached the target set temperature To shown in FIG.

If v1≧VO and the fixing temperature T has not yet reached the target set temperature To, proceed to step 14 for reconfirmation; if V1≧VD, return to step 13; otherwise, the fixing temperature T is operating properly. Lower limit temperature T1 of temperature range
If it has fallen further, the process advances to step 28.

Also, Vl≧Vo and the fixing temperature T becomes the set temperature To.
When the temperature reaches VU, the heater 16c is turned off by outputting °O゛ to one input terminal of the AND gate 33 in step 15, and then in step 16 it is determined whether Vl>VU, that is, the fixing temperature T is shown in FIG. upper limit temperature T2 of the proper operating temperature range
Determine whether or not the value has been exceeded.

Then, if Vl>VU is not satisfied and the fixing temperature T is lower than the upper limit temperature T2 of the proper operating temperature range, the process proceeds to step 25, and Vl
> At VU, the fixing temperature T is the upper limit temperature T of the proper operating temperature range.
If it exceeds 2, an image formation prohibition signal is sent to the main CPU in step 17 to prohibit the image formation operation and put it into a standby state.

Next, after starting the timer in step 18, it is determined in step 19 whether v1≦VU, and if v1≦VU and not Vx>Vt+, then the fixing temperature T exceeds the upper limit temperature TU of the proper operating temperature range. Therefore, the process proceeds to step 20, and if the timer value t exceeds the set value tb, the timer is reset in step 21, and then, in step 22, the operation display section (not shown) is sent via the image information processing device 21 shown in FIG. A high temperature abnormality notification signal is sent to the device, information to that effect is displayed, and the process ends.

Incidentally, appropriate arbitrary time data is stored in the ROM in the CPU 61 as the timer setting [tb.

On the other hand, if v1≦VU in step 19, the fixing temperature T is lower than the upper limit temperature T2 of the proper operating temperature range, so the sending of the image formation prohibition signal is canceled in step 23, and in step 24
After resetting the timer, proceed to step 25 and set Vl<
If it is not VO, the process returns to step 16, and if Vl<VO, the heater 16Q is turned on.

Next, in step 27, it is determined whether Vl<VD, and -V
If l<VD, return to step 13.

If vl or vD, an image formation prohibition signal is sent to the main CPU in step 28 to prohibit the image formation operation, a timer is started in step 29, and then step 30 is performed again.
It is determined whether Vl<VD.

Then, if Vl<VD, the process returns to step 11 and V
If l<VD, proceed to step 31, and if the timer value t exceeds the set value tc, proceed to step 8.9, and send a low temperature abnormality notification signal to the operation display section (not shown) in the same manner as described above. Display the information and end the process.

Note that any suitable time data is set as the timer setting value tc by CPtJ! It is stored in ROM in il.

Next, fixing temperature control by the comparator 32 shown in FIG. 4 will be briefly explained.

However, due to a malfunction of the CPU"51, even though the fixing temperature T exceeded the target set temperature TO shown in FIG.
It is assumed that the output from the CPU 31 to the AND gate 33 remains at 1° and the heater 18C is turned on.

When the fixing temperature T reaches TO' shown in FIG. The output of the gate 33 also becomes 0°, and the power supply unit 19 turns off the heater 18Q.

After that, when the fixing temperature becomes lower than TO', Vx<V
r, so that the output of the comparator 32 becomes °l
Since the angle becomes 1°, the output of the AND gate 33 also becomes 1°, turning on the heater 18c.

Therefore, 'ro' becomes the target temperature, and the energization of the heater 16c is controlled on and off with this as the target.

As described above, according to this embodiment, the fixing roller 18a in FIG.
The CPU 31 in the fixing temperature control circuit in the sequence driver 30 shown in FIG. 2 detects that the surface temperature of the fixing roller 16a, that is, the fixing temperature When the temperature falls outside the proper operating temperature range shown in Figure 5, an image formation prohibition signal is sent to the main CPU in the sequence driver 30, and the image forming operation is temporarily stopped until the fixing temperature falls within the proper operating temperature range again. is prohibited and placed on standby.

For example, when the fixing temperature changes over time as shown in FIG. 7, the time t.

(when the power is turned on) to time t1, from time t2 to time t
During each time from t4 to time t5, the fixing temperature is outside the proper operating temperature range, so the image forming operation is prohibited by sending an image forming prohibition signal from the CPU 31 only during that time.

Therefore, the toner on the paper is thermally fixed by the fixing roller heated and maintained at the optimum fixing temperature, so that good image quality can always be obtained.

The present invention is not limited to laser printers, and is applicable to other optical printers such as LED printers and liquid crystal shutter printers, as well as various electrophotographic image forming apparatuses such as electrophotographic copying machines and facsimile machines.

〔Effect of the invention〕

As explained above, in the electrophotographic image forming apparatus according to the present invention, the toner on the paper is thermally fixed only by the fixing roller heated and maintained at the optimum fixing temperature.
Good image quality can always be obtained.

[Brief explanation of drawings]

FIG. 1 is a functional block diagram showing the basic configuration of the present invention. FIG. 2 is a schematic sectional view showing the internal mechanism of a laser printer which is an embodiment of the present invention, FIG. 3 is a diagram showing an example of a fixing temperature detection mechanism in the fixing device, and FIG. 4 is a diagram showing an example of the fixing temperature detection mechanism in the fixing device. FIG. 5 is a circuit diagram showing the configuration of the fixing temperature control circuit; FIG. 5 is an explanatory diagram for explaining its operation; FIG. 6 is a flowchart of the fixing temperature control operation by the CPU 51 in FIG. 4; FIG. 7 is according to this embodiment. 5 is a diagram illustrating an example of a change in fixing temperature over time and an image formation prohibition period; FIG. 1... Laser printer main body 1... Fixing device 1
6a... Fixing roller 18b... Pressure roller 16c... Heater 19... Power supply unit (PSU) 21... Image information processing device 24... Thermistor holding member 25... Leaf spring 30
...Sequence driver 31...Microcomputer (CPU) 32...
Comparator 33...AND gate TH...
・Thermistor VR...Volume m2 diagram Proper operating temperature range (Vo) (Vo) Vr) Edition 3

Claims (1)

[Claims] 1. In an electrophotographic image forming apparatus equipped with a fixing device for thermally fixing a toner image transferred to paper, a surface temperature detection means for detecting the surface temperature of a fixing roller of the fixing device, and a temperature detected by the means are provided. temperature range determining means for determining whether or not the surface temperature of the fixing roller is within a proper operating temperature range; and when the means determines that the surface temperature of the fixing roller is outside the proper operating temperature range; An electrophotographic image forming apparatus comprising: an image forming operation inhibiting means for temporarily prohibiting an image forming operation to enter a standby state.