JP3249680B2 - Image recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording apparatus such as a laser printer, a copying machine, and a facsimile machine having a heat fixing device for fixing a toner image on a recording medium.

[0002]

2. Description of the Related Art Conventionally, this type of fixing device is composed of a heat roller having a halogen heater therein and a pressure roller arranged opposite to the heat roller, and a sheet is pressed between these rollers. The toner on the sheet is fixed by passing while the toner image is passed. A thermistor for detecting the temperature of the fixing device is provided near the heat roller. In the image recording apparatus provided with the fixing device, when performing image recording, the halogen heater is energized to control the temperature to a temperature at which the fixing device can be fixed (printing temperature) and to rotate the heat roller. At the time of non-printing in which image recording is not performed for a predetermined time or more, the temperature of the fixing unit is controlled to be a predetermined standby temperature lower than the printing temperature, and the rotation of the heat roller is stopped, so that the image forming apparatus is in standby mode. To prevent unnecessary power consumption. However, if the standby temperature is high, the temperature of the apparatus during standby increases, and if the standby temperature is low, when the printing operation is restarted from standby, the time required for the fixing device to rise to the printing temperature becomes longer, Since the usability of the apparatus becomes poor, an appropriate temperature is naturally set as the standby temperature.

In such an image recording apparatus, usually, in order to check whether the fixing device is operating normally,
For each of the printing temperature and standby temperature, set an error check temperature that is lower than the temperature by an appropriate allowable amount, and detect an error when the temperature of the fixing unit falls below the error check temperature during printing and standby. Printing operation is prohibited. This check operation is performed in order to prevent a fixing failure that occurs when the temperature of the fixing device decreases during printing or to increase the time required to start reprinting when the temperature of the fixing device decreases during standby. ing.

[0004]

However, in such an image recording apparatus, when printing is started from standby, the temperature of the fixing device is increased from the standby temperature to the printing temperature, and the rotation of the heat roller is started. At this time, due to the rotation of the heat roller, the heat of the heat roller is taken by the pressure roller, and the temperature of the fixing device temporarily drops. In this case, depending on the situation, the temperature of the fixing unit may be lower than the error check temperature and an error may be detected, which is inconvenient. The present invention solves the above-described problem, and has a method in which an error occurs when the temperature of a fixing device falls below a predetermined temperature during an image recording operation. It is an object of the present invention to provide an image recording apparatus in which error detection is not unnecessarily caused by a necessary temperature change.

[0005]

According to one aspect of the present invention, there is provided an image forming means for forming an image by transferring toner on a recording medium, and a toner transferred on the recording medium. Heat fixing means comprising a heat roller and a pressure roller for fixing the temperature to the recording medium, a temperature detecting means for detecting the temperature of the heat fixing means, and a temperature of the heat fixing means based on the temperature detected by the temperature detecting means. And a temperature control unit that controls the temperature of the thermal fixing unit to be lower than that during image formation during standby. Error detection means for outputting an error signal when the temperature falls below a predetermined error detection temperature,
At the time of standby, the error detection temperature is set to an error during image formation.
Error detection temperature setting means for lowering from the error detection temperature, and when the image forming operation is started from the standby state, the heat roller and the pressure roller of the fixing means start rotating from a rotation stop state, and the error Detection temperature
The setting means forms an image of the error detection temperature for a predetermined period.
Lower from the error detection temperature at the time, or
The operation of the error detecting means is stopped .

According to a second aspect of the present invention, in the device according to the first aspect, the temperature detecting means includes: a temperature-sensitive resistance element; a plurality of resistors connected in series with the element and in parallel with each other;
A switching element connected in series to each of these resistors, conduction selection control means for selectively controlling conduction of these switching elements, a connection point potential between the temperature-sensitive resistance element and the resistance as a temperature detection signal, A comparison means for comparing with a reference voltage, wherein the conduction of the switching element is selected by the conduction selection control means, thereby switching the detected temperature.

[0007]

According to the image recording apparatus of the first aspect, the temperature of the heat fixing means is controlled based on the temperature detected by the temperature detecting means, and the temperature is lowered during standby in comparison with image formation. During normal image formation, when the temperature of the heat fixing unit falls below a predetermined error detection temperature, an error signal is output by the error detection unit. Error detection is performed by the error detection temperature setting unit during the period when
Lower the temperature setting or turn off the error detection
Stop. As a result, erroneous error detection caused by deprivation of heat due to the rotation of the roller of the heat fixing unit immediately after the transition to the image forming operation does not occur. As described above, in order to lower the setting of the error detection temperature immediately after the start of the image forming operation, for example, the switching of the error check temperature may be delayed in time. That is, in this method, the error check temperature for a predetermined period immediately after the start of the image forming operation is set to the error check temperature for standby, and the error check temperature for image formation after the lapse of the predetermined time.

According to the image recording apparatus of the present invention, the temperature of the heat fixing means is detected by comparing the potential at the connection point between the temperature-sensitive resistance element and the resistor with the reference voltage, so that the temperature can be detected during standby and during image forming operation. The detection temperature for the temperature control and the error check detection temperature are switched by selecting conduction of a switching element connected in series to the resistor.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image recording apparatus according to one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a laser printer. The laser printer 1 includes an image processing unit 2 including a photoconductor for forming an image by an electrophotographic method, a charger, a developing device, and the like; a laser scanner unit 3 for irradiating the photoconductor with a laser beam for image formation; And a heat roller 5a for fixing the image transferred on the paper by the image processing unit 2 and a fixing roller 5 comprising a pressure roller 5b.
And so on. The laser printer 1 includes, as a control system, a main board 8 which receives data from the outside via a Centronics interface (I / F) 7;
I which is connected to the main board 8 and controls each part of the printer
And a low-voltage power supply 10 for supplying a low voltage to each part of the printer and a high-voltage power supply 11 for supplying a high voltage for transfer, development and charging to the image processing unit 2 as a power supply system. .

The driver board 9 receives each detection signal from the paper feed sensor 12, the temperature detection sensor 13 of the fixing device 5, and the paper discharge sensor 14, receives the laser scanner unit 3, the high voltage power supply 11, and the paper feed registration clutch. 15, the paper supply solenoid 16, the main motor 17, and the cooling fan 18 are controlled. The driver board 9 receives signals from various switches SW operated by an operator to give an operation instruction to the printer, and displays the operation state of the laser printer 1 with LEDs. The low-voltage power supply 10 is connected to a power outlet and has an interlock function for opening a circuit when the main body cover is opened.
The power supply to the heater a is cut off. Main motor 17
Rotates the paper feed roller of the paper feed unit 4, the photoconductor of the image processing unit 2, and the heat roller 5 a of the fixing device 5. The cooling fan 18 is for suppressing an increase in the temperature inside the apparatus due to heat generated from the fixing device 5.

FIG. 2 is a diagram showing a control circuit configuration of the fixing device 5. The fixing device 5 is a heat load that is heated and controlled by controlling the energization of a halogen lamp 5c provided inside the heat roller 5a. The temperature is controlled using a sensor circuit 20 including a temperature detection sensor (a temperature-sensitive resistance element such as a thermistor, hereinafter, referred to as a thermistor) 13, a driver substrate 9, and a low-voltage power supply 10. The sensor circuit 20 includes a plurality of resistors R1, R2, R3 connected in series with the thermistor 13 and connected in parallel with each other.
And transistors Q2 and Q3 connected in series to the resistors R2 and R3, respectively.
Is controlled by a control signal for the ports 1 and 2 from the driver board 9 (conduction selection control means). The detection temperature is switched by selecting the conduction of the transistors Q2 and Q3 by using the potential of the connection point (voltage division) between the thermistor 13 and the resistors R1, R2 and R3 as a temperature detection signal. The other end of the thermistor 13 is connected to + 5V.

The temperature detection signal is inputted to a (-) input of a comparator 21, and a (+) input thereof is supplied with a reference voltage of 2.5.
V has been input. The “H” or “L” output of the comparator 21 and the forced off or “L” signal output from the driver board 9 in an abnormal situation are input to the AND circuit 22, and the output of the AND circuit 22 is supplied to the low-voltage power supply 10. Given. The low-voltage power supply 10 controls the temperature by controlling the power supply to the halogen lamp 5c.

The switching of the temperature detected by the sensor circuit 20 can be performed as follows. Set ports 1 and 2 to “H”,
When “H” is set and the transistors Q2 and Q3 are turned on,
Since a parallel circuit of resistors R1, R2, and R3 is connected to the thermistor 13 and the divided potential drops, the temperature detected by the thermistor 13 is high, for example, a "print temperature" of 150.degree.
Becomes When the ports 1 and 2 are set to “H” and “L”, respectively, and the transistor Q2 is turned on, the resistance R
The parallel circuits 1 and R2 are connected, and the detected temperature level becomes low, for example, a "standby temperature" of 130C. When the ports 1 and 2 are set to “L” and “H”, respectively, and the transistor Q3 is turned on, the parallel circuit of the resistors R1 and R3 is connected to the thermistor 13, and the detection temperature level is further lowered. Check temperature ". When the ports 1 and 2 are set to “L” and “L” respectively, the thermistor 13
, Only the resistor R1 is connected, and the detected temperature level is the lowest, for example, the “error check temperature” of 40 ° C.

The above-mentioned "error check temperature" is a temperature at which the driver board 9 as a control circuit checks whether or not the fixing device 5 is operating normally (abnormal detection). Is a temperature determined in consideration of the fact that when the temperature of the fixing device 5 falls below the temperature at which the image can be fixed at the time of printing, the toner is not completely melted and fixing failure occurs. The error check temperature during standby is
If the temperature of the fixing device 5 drops below a predetermined temperature during standby,
This is a temperature determined in consideration of an excessively long waiting time until the temperature becomes a fixable temperature when shifting from the standby state to the start of printing. In the sensor circuit 20, the detected temperature can be appropriately changed by selecting the values of the resistors R1, R2, and R3.

The operation of the sensor circuit 20 at the "print temperature" will now be described.
If the temperature is lower than the setting, the thermistor 13
Is greater than the resistance at 150 ° C.
The partial pressure between R2 and R3 decreases. Since the resistors R1, R2, and R3 are selected so that the partial pressure becomes 2.5 V when the set temperature is 150 ° C., the partial pressure value is 2.5 V or less. Accordingly, the output of the comparator 21 becomes "H", and unless the driver board 9 has forcibly turned off the heater, the heater of the fixing device 5, that is, the halogen lamp 5c is turned on, and is heated to the set temperature of 150.degree. Further, each resistance value is set so that the partial pressure becomes 2.5 V when the “standby temperature” is 130 ° C., and is set so as to be the same at other temperatures. The above-mentioned detection temperatures can be arbitrarily set by selecting a resistance value, and the error check temperature and the like are not limited to the above-mentioned temperatures. In addition,
Since the temperature detection circuit is configured using the comparator and the resistor, the cost can be reduced as compared with the case where an expensive analog-digital converter or the like is used.

The driver board 9 controls the driving of the cooling fan 18 so that the internal temperature does not rise significantly. In the case where the energization of the halogen lamp 5c of the fixing device 5 is turned off and the internal temperature is predicted to be a predetermined temperature, for example, 100 ° C. or less, based on the elapsed time since the off state. In order to reduce noise and save energy, the driving of the cooling fan 18 is stopped. Note that the driver board 9 has a timer function, and can determine whether a predetermined time has elapsed.

FIG. 3 is a flowchart showing the procedure of the abnormality detection processing of the fixing device 5. This abnormality detection is performed by the driver board 9. The driver board 9 checks whether the apparatus is in a printing state (# 1), and if it is in a printing state (YE in # 1).
S), the sensor circuit 20 is set to the above-mentioned “print temperature” of 150 ° C. (# 2). Next, it is checked whether 5 seconds have elapsed since the start of printing (# 3).
(NO in 3), the sensor circuit 20 is set to the “error check temperature” of 40 ° C., and an abnormality is detected (# 4).
The process returns. After 5 seconds (YE in # 3)
S), the temperature is set to the “error check temperature” of 120 ° C., an abnormality is detected (# 5), and then the process returns.
The detection of these abnormalities is performed as follows. That is, when the energization of the halogen lamp 5c is controlled so that the fixing device 5 becomes the printing temperature of 150 ° C., the levels of the ports 1 and 2 are instantaneously changed to set the detection temperature of the sensor circuit 20. When the temperature is lowered to 120 ° C., if the fixing device 5 is performing a normal heating operation and the temperature exceeds 120 ° C., the output of the comparator 21 becomes “L” to stop energizing the fixing device 5. Should be. Therefore, the driver board 9 determines that the operation of the fixing device 5 is normal if the output of the comparator 21 is “L”, and that the operation is abnormal if the output is “H”.

The reason why the "error check temperature" is raised after 5 seconds in # 3 to # 5 is that the heat roller 5a transfers the heat from the heat roller 5a to the pressure roller 5b after a lapse of time from the start of printing. This is because the conduction is stabilized, and even if the error check temperature is set to 120 ° C., there is no possibility of detecting an error. If it is not the printing state in # 1 (NO in # 1), the sensor circuit 20 is set to the "standby temperature" of 130 [deg.] C. (# 6), and it is checked whether it is in the standby state (# 7). If so, proceed to # 4 above. If it is not in the standby state (NO in # 7), it is determined that a warm-up has occurred and the abnormality detection processing is performed (# 8).
The process returns. In the abnormality detection process at the time of warm-up, for example, if the detected temperature of the fixing unit 5 does not become 40 ° C. or more after elapse of 20 seconds, it is determined that an error occurs.

FIG. 4A is a time chart before and after the start of printing in the above-described fixing unit abnormality detection processing of the present embodiment, and corresponds to # 3 to # 5 in FIG. When printing is started from the standby state, the halogen lamp 5c is energized so that the temperature of the fixing unit 5 becomes a printing temperature of 150 ° C. from the standby temperature of 130 ° C., and the heat roller 5a is rotated by driving the main motor 17. . Then, at the beginning of the rotation, the heat of the heat roller 5a is transmitted to the pressure roller 5b with the rotation, and the temperature of the fixing device 5 is temporarily reduced to 12 degrees.
The temperature may drop to 0 ° C or lower. However, in this embodiment, as shown in # 3 to # 5 in FIG. 3, the error check temperature is set to 40 ° C. for 5 seconds after the start of printing, and 1
Since the temperature is set to 20 ° C., even if the temperature of the fixing device 5 temporarily decreases as described above, no error is detected due to the decrease. On the other hand, conventionally, the timing of raising the error check temperature is set at the same time as the start of printing. Therefore, as shown in FIG. 4B, immediately after the start of printing, the temperature of the fixing device 5 is changed between the heat roller 5a and the pressure roller 5b. When the temperature drops below the error check temperature of 120 ° C. at the time when the temperature temporarily drops due to the heat conduction, the error is detected as an error although the error is not originally an error. In the above embodiment, when the printing is started from the standby state, the error check temperature is maintained at 40 ° C. for 5 seconds. However, this is because the error check temperature is set to 120 ° C. for 5 seconds after the printing is started. From 4
This is similar to lowering the temperature to 0 ° C.

The present invention is not limited to the configuration of the above-described embodiment, but can be variously modified. For example, the error check detection temperature and the predetermined time may be appropriately set according to the configuration of the temperature detection circuit and the characteristics of the device. . Also, instead of delaying raising the error check temperature at the start of printing as described above or lowering the error check temperature setting for a predetermined time immediately after the start of printing, an error check is performed for a predetermined time immediately after the start of printing. Is performed, that is, even if the error check operation is stopped, the same operation can be obtained.

[0021]

As described above, according to the image recording apparatus of the first aspect of the present invention, if the temperature of the heat fixing unit becomes lower than a predetermined temperature during the image recording operation, an error is generated in order to prevent defective fixing beforehand. In the apparatus for performing the processing, when shifting from the standby state to the image recording operation, the error check operation is stopped for a predetermined time immediately after the start of the image recording, or the error check temperature is set only for a predetermined time. Therefore, unnecessary error detection does not occur due to an inevitable temperature change of the heat fixing unit. According to the image recording apparatus of the second aspect, in addition to the above-described effects, the temperature is detected by comparing the potential at the connection point between the temperature-sensitive resistance element and the resistor with the reference voltage, and the conduction of the switching element is selected. Since the detection temperature is switched, the temperature is lower than that of a conventional temperature detection circuit using an analog-digital converter.

[Brief description of the drawings]

FIG. 1 is a block diagram of a laser printer as an image recording apparatus according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a fixing device of the laser printer.

FIG. 3 is a flowchart showing a procedure of an abnormality detection process for the identified dressing apparatus.

FIG. 4A is a time chart of a temperature detected by a fixing device at the start of printing according to the present embodiment, and FIG. 4B is a time chart equivalent to a conventional one.

[Explanation of symbols]

 5 Fixing Unit 9 Driver Board 10 Low Voltage Power Supply 13 Temperature Detection Sensor 20 Sensor Circuit 21 Comparator R1, R2, R3 Resistance Q2, Q3 Transistor

Claims (2)

(57) [Claims] An image forming means for transferring an image on a recording medium to form an image; and a heat fixing means comprising a heat roller and a pressure roller for fixing the toner transferred on the recording medium to the recording medium. Temperature detecting means for detecting the temperature of the heat fixing means, and controlling the temperature of the heat fixing means based on the temperature detected by the temperature detecting means,
A temperature control unit that controls the temperature of the thermal fixing unit to be lower than that during image formation during standby, wherein the temperature of the thermal fixing unit detected by the temperature detecting unit is a predetermined error. An error detecting means for outputting an error signal when the temperature becomes equal to or lower than the detected temperature ;
Error detection temperature setting means for lowering from the error detection temperature, when the image forming operation is started from the standby state, the heat roller and the pressure roller of the fixing means start rotating from a rotation stop state, and the error Detection temperature setting
Means for the predetermined period, the error detection temperature at the time of image formation
Lower the temperature from the error detection temperature, or
An image recording apparatus, wherein the operation of the error detection means is stopped . 2. The temperature detecting means includes: a temperature-sensitive resistance element;
A plurality of resistors connected in series with the element and in parallel with each other; switching elements connected in series to the resistors; conduction selection control means for selectively controlling conduction of the switching elements; A connection point potential between the temperature resistance element and the resistor is used as a temperature detection signal, and a comparison unit that compares this potential with a reference voltage.By selecting conduction of the switching element by the conduction selection control unit,
2. The image recording apparatus according to claim 1, wherein the detection temperature is switched.