JPH0869206A - Image forming device - Google Patents

Abstract

PURPOSE: To provide an image forming device capable of restraining the rise of internal atmospheric temperature without providing a dedicated sensor. CONSTITUTION: The counter value N of the number of printed sheets after heater temperature reaches 180 deg.C is cleared (S1), and whether or not the temperature reaches 180 deg.C is judged (S2). When it does not reach 180 deg.C, operation is restored to the judgement of temperature (S11 to S2) after printing operation(S10 to S11). After reaching 180 deg.C, '1' is added to N(S3), and comparison whether or not N reaches the specified number of sheets X at the time of reaching the limit temperature of the internal atmospheric temperature is performed(S4). When it does not reach 180 deg.C, the printing operation is continued (S4 to S10), and when N reaches the specified number X, energizing a heater is stopped so as to stop the printing operation (S7) after the printing operation (S5 to S6). After waiting for Z1 seconds (S8), N is cleared (S9), the printing operation is permitted (S12), and startup temperature control is performed (S13). Then, the consecutive printing operation is repeated.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus using an electrophotographic process and having a heat fixing device is provided with a dedicated temperature sensor (thermistor or the like) as a means for monitoring the temperature of its internal atmosphere. Monitor control using a sensor was necessary.

[0003]

However, in the above-mentioned conventional example, since the dedicated internal atmosphere temperature detecting temperature sensor or its circuit components and the input port for monitoring this temperature sensor are added, the cost is reduced. It was up and uneconomical.

A first invention according to the present application solves the above problems and provides an image forming apparatus capable of suppressing an increase in the internal atmosphere temperature without providing a dedicated sensor for monitoring the internal atmosphere temperature. Is intended.

The second invention according to the present application solves the above-mentioned problems, and by means different from the first invention, the internal atmosphere temperature is not provided without providing a dedicated sensor for monitoring the internal atmosphere temperature. It is an object of the present invention to provide an image forming apparatus capable of suppressing a rise in the temperature.

[0006]

According to a first aspect of the present invention, the above object is to detect a fixing heater for heating and fixing a recording material carrying an unfixed image, and detecting the temperature of the fixing heater. In the image forming apparatus having the temperature detecting means for controlling the energization to the fixing heater so that the temperature detected by the temperature detecting means becomes substantially constant, the control means detects the temperature by the temperature detecting means. When the temperature drops to a predetermined temperature due to continuous image formation, it is achieved by setting the energization to the fixing heater for a predetermined time after the formation of a predetermined number of images thereafter. .

According to the second invention of the present application,
The above-mentioned object is to fix a fixing heater for heating and fixing a recording material carrying an unfixed image, temperature detecting means for detecting the temperature of the fixing heater, and temperature detected by the temperature detecting means to be substantially constant. An image forming apparatus having a control means for controlling energization to a fixing heater is provided with an exhaust fan, and the control means is provided when the temperature detected by the temperature detection means drops to a predetermined temperature due to continuous image formation. This is achieved by setting the exhaust fan to be driven for a predetermined time after the formation of a predetermined number of images thereafter.

[0008]

According to the first aspect of the present invention, when an image is formed while the temperature of the fixing heater is kept substantially constant by the temperature detecting means, the temperature of the fixing heater is gradually increased due to an increase in the number of recording materials. However, the ambient temperature inside the apparatus gradually rises. However, when the temperature of the fixing heater drops to a predetermined temperature, after that, the image formation is continued until a predetermined number of sheets at which the ambient temperature inside the apparatus is estimated to reach the limit temperature, and after the predetermined number of images are formed, the fixing is performed. Since the energization of the heater is stopped for a predetermined time, the temperature inside the device starts to drop immediately after reaching the limit temperature and drops to a sufficiently low temperature.

According to the second invention of the present application,
When an image is formed while the temperature of the fixing heater is kept substantially constant by the temperature detecting means, the temperature of the fixing heater gradually drops due to an increase in the number of recording materials, but the ambient temperature inside the apparatus gradually rises. . However, when the temperature of the fixing heater drops to a predetermined temperature, after that, the image formation is continued until a predetermined number of sheets at which the ambient temperature inside the apparatus is estimated to reach the limit temperature, and the exhaust gas is exhausted after the predetermined number of images are formed. Since the fan is driven for a predetermined time, the temperature inside the device starts to drop immediately after reaching the limit temperature and drops to a sufficiently low temperature.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing the overall configuration of a printer. In FIG. 1, reference numeral 1 denotes a printer main body, and in this embodiment, a case where a laser beam printer is used as an image forming apparatus is shown. The printer 1 is provided with an engine control unit 25 that controls the operation of each device, each unit, each device, etc. described below, and the video data sent via the video interface 40 is also included in the engine control unit 25. It is adapted to be input to the control unit 25.

Then, the laser light is modulated on the basis of the video data, and the polygonal mirror (not shown) of the optical unit 3 and the folding mirror 4 cause the photosensitive drum 2 uniformly charged by the charger 5. The surface is scanned to form an electrostatic latent image on the photosensitive drum 2, and the developing device 6 is driven to develop the electrostatic latent image as a toner image.

On the other hand, prior to such a printing operation, the paper feed roller 10 is driven to detect the presence / absence of paper as a recording material by the paper feed sensor 12, and the paper is loaded from the paper cassette 9 loaded with paper. Remove the paper one by one. Then, when the registration sensor 17 detects that the taken-out sheet has been conveyed to the registration roller 11, the sheet is once stopped at that position, and the registration roller 11 is rotated at a predetermined timing to be conveyed to the transfer position. Also, by checking this paper with the top sensor 16, the timing of starting the printing operation is determined,
A sub-scanning synchronization signal is sent out.

When the paper is conveyed to the transfer position as described above, the transfer device 7 is driven this time to transfer the toner image on the photoconductor drum 2 onto the paper, and the cleaner 8 is used to transfer the toner image on the photoconductor drum 2. The toner remaining on the toner is collected.

Then, the sheet on which the toner image has been transferred is conveyed to the fixing device 13, and the fixing device 13 is controlled at a predetermined temperature to heat and pressurize the toner image to fix it.
The paper is discharged to the paper discharge tray 15 while the paper discharge sensor 14 detects the presence or absence of the paper discharged from the sheet 3.

Next, the fixing device 13 in the apparatus of this embodiment
FIG. 2 shows a block configuration of the temperature control unit. In the figure, C1 is a hold capacitor, which transforms the input voltage from the commercial power source by the transformer TR1 and charges it through the diode D1. This voltage is
The commercial voltage is input to the A / D input port of the CPU 30 that is the control unit, and the CPU 30 monitors the input commercial voltage. Further, the fixing device 13 is provided with a ceramic heater R3 as a fixing heater, and the temperature of the heater R3 is controlled by the thermistor TH1 which is a temperature detecting means.
Is input to

When the CPU 30 monitors the voltage of the thermistor TH1 and determines that the temperature is lower than a predetermined temperature, it drives the transistor Q1 with the FSRD signal, and further the collector output thereof drives the triac coupler PC1.
And the triac Q2 to drive the ceramic heater R
Energize 3.

FIG. 3 shows the relationship between the temperature state of the heater and the temperature of the pressure roller in the temperature adjustment control during continuous printing by the temperature control unit as described above. In this example, from the seventh sheet, the internal temperature of the apparatus warms up and the surface temperature of the pressure roller reaches a temperature at which a high temperature offset is generated. From the seventh sheet and thereafter, the temperature control level for energizing the fixing heater is the lower limit (180 ° C). The cycle shown in A means a rising temperature control cycle, and the cycle shown in B means a falling temperature control cycle. Details of these are disclosed in Japanese Patent Laid-Open No. 5-165368.

FIGS. 4A to 4C show the relationship between the temperature state of the heater, the temperature of the pressure roller, and the internal atmosphere temperature in the temperature control for continuous printing shown in FIG. is there. As shown in the figure, as the number of continuous prints is increased, the pressure roller gradually warms, and the temperature of the internal atmosphere in the machine tends to rise. T1 shown in FIG. 4C represents a limit temperature, which means that the temperature is not allowed to rise any higher. In this example, T1 is reached when X sheets are printed after the heater temperature control temperature reaches 180 ° C (seventh sheet).

Therefore, in the present embodiment, when the printing of X sheets is completed after the heater temperature control temperature reaches 180 ° C., it is presumed that the internal atmosphere temperature reaches the above-mentioned limit temperature T1, and the predetermined time is exceeded. Only the heater is turned off.

The temperature control in this embodiment will be described below step by step with reference to the flow chart of FIG. 5 and the timing chart of FIG.

After the printing operation is started and the startup temperature control such as the cycle shown in FIG. 3A is performed, the counter value for counting the number of printed sheets after the heater temperature control temperature reaches 180 ° C. as described above. Initialization of N is performed (step S1), and it is determined whether the temperature of the thermistor TH has reached 180 ° C (step S2). If the temperature of the thermistor TH has not reached 180 ° C,
After the triac Q2 is turned on to perform the printing operation (step S10), the paper discharge sensor 14 detects the trailing edge of the sheet (step S11), the triac Q2 is turned off, and the temperature of the thermistor is adjusted to print the next sheet. The process returns to the determination routine (steps S11 and S2).

On the other hand, the temperature of the thermistor TH is 180 ° C.
When the counter value N is reached, 1 is added to the counter value N (step S3), and it is compared whether or not the counter value N reaches the specified number X when the internal ambient temperature limit temperature T1 is reached (step S4). If not reached, the printing operation is continued as described above (steps S4 to S10).

When the counter value N becomes equal to the specified number X and the temperature of the thermistor TH reaches 180 ° C. and the Xth sheet is printed, the triac Q2 is turned on. Thus, the heater R3 is energized to perform the printing operation (step S5), and after printing one sheet, that is, after printing the Xth sheet (step S6), the triac Q2 is turned off to stop the printing operation (step S5). S7).

In order to lower the internal temperature thereafter, Z
After waiting for 1 second (step S8), the counter value N
Is reset (step S9), and the printing operation is permitted (step S12).

Then, the triac Q2 is turned on, the startup temperature is controlled (step S13), the routine returns to the thermistor temperature determination routine to print the next sheet (steps S13 to S2), and the continuous printing operation is repeated. return.

As a result, as shown in the graph of FIG.
After the heater controlled temperature reaches 180 ° C, the internal atmosphere temperature reaches the limit temperature T1 after printing X sheets,
Immediately after printing X sheets, energizing the heater is stopped and an intermittent interval of Z1 seconds is provided to reduce the throughput, whereby the internal atmosphere temperature can be lowered to a sufficiently low temperature.

The prescribed number X described in this embodiment is
Since it depends on the type of heater, the size of the image forming apparatus, and the like, it is necessary to set it by conducting appropriate experiments.

As described above, according to the present invention, the internal atmosphere temperature can be appropriately lowered without providing a dedicated sensor for detecting the internal atmosphere temperature, so that the cost can be reduced.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

This embodiment is also an embodiment in which the present invention is applied to a laser beam printer as shown in FIG. 7, but differs from the first embodiment in that a fan 20 as an exhaust fan is provided.

The fan 20 is directly controlled by the CPU 30, as shown in FIG.

In this embodiment, after the printing of X sheets is completed after the heater temperature control temperature reaches 180 ° C., the fan 2 is operated for Z2 seconds without stopping the printing operation.
The difference from the first embodiment is that 0 is driven.

Next, the temperature control of the present invention will be described step by step with reference to the flowchart of FIG. 9 and the timing chart of FIG.

After the printing operation is started and the startup temperature control like the cycle shown in FIG. 3A is performed, the counter value for counting the number of printed sheets after the heater temperature control temperature reaches 180 ° C. as described above. Initialization of N is performed (step S1), and it is determined whether the temperature of the thermistor TH has reached 180 ° C (step S2). If the temperature of the thermistor TH has not reached 180 ° C,
After the triac Q2 is turned on to perform the printing operation (step S10), the paper discharge sensor 14 detects the trailing edge of the sheet (step S11), the triac Q2 is turned off, and the temperature of the thermistor is adjusted to print the next sheet. The process returns to the determination routine (steps S11 and S2).

On the other hand, the temperature of the thermistor TH is 180 ° C.
When the counter value N is reached, 1 is added to the counter value N (step S3), and it is compared whether or not the counter value N reaches the specified number X when the internal ambient temperature limit temperature T1 is reached (step S4). If not reached, the printing operation is continued as described above (steps S4 to S10). When the counter value N becomes equal to the specified number of sheets X and the temperature of the thermistor TH reaches 180 ° C. and the Xth sheet is to be printed, the triac Q2 is turned on.
By doing so, the heater R3 is energized to perform the printing operation (step S5), and after the printing of one sheet, that is, the printing of the Xth sheet (step S6), the fan 20 for Z2 seconds.
Is driven (step S20) to lower the internal atmospheric temperature. Then, the counter value N is reset (step S
9) Then, the process returns to the thermistor temperature determination routine to print the next sheet (steps S9 to S2), and the continuous printing operation is repeated.

As a result, as shown in the graph of FIG. 10, after the heater controlled temperature reaches 180 ° C., X
After printing the number of sheets, the internal atmosphere temperature reaches the limit temperature T1, but immediately after printing X sheets, the fan 20 is driven for Z2 seconds, so that the internal atmosphere temperature can be lowered to a sufficiently low temperature.

As described above, according to the present invention, the internal atmosphere temperature can be appropriately lowered without providing a dedicated sensor for detecting the internal atmosphere temperature, so that the cost can be reduced.

[0039]

As described above, according to the first invention of the present application, when the temperature of the fixing heater drops to a predetermined temperature due to continuous image formation, a predetermined number of sheets are printed thereafter. After forming the image, the energizing of the fixing heater is stopped for a predetermined time, thereby omitting the dedicated temperature sensor for monitoring the internal atmosphere temperature, its circuit part, and the input port for monitoring the temperature sensor. Also, it is possible to prevent the temperature of the internal atmosphere from rising and to reduce the cost.

According to the second invention of the present application,
When the temperature of the fixing heater drops to a predetermined temperature due to continuous image formation, the internal fan temperature is monitored by driving the exhaust fan for a predetermined time after forming a predetermined number of images. Even if the dedicated temperature sensor, its circuit portion, and the input port for monitoring the temperature sensor are omitted, it is possible to prevent the temperature of the internal atmosphere from rising and reduce the cost.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a temperature control unit of the apparatus shown in FIG.

FIG. 3 shows a heater temperature, a film temperature,
It is a figure which shows the change of the pressure roller temperature.

FIG. 4 is a diagram showing changes in pressure roller temperature and internal atmosphere temperature after the heater temperature reaches 180 ° C. in the apparatus of FIG. 1;

FIG. 5 is a flow chart of temperature control in the first embodiment of the present invention.

FIG. 6 is a diagram showing changes in heater temperature and internal atmosphere temperature in the first example of the present invention.

FIG. 7 is a diagram showing an overall configuration of an image forming apparatus according to a second embodiment of the present invention.

8 is a block diagram showing a configuration of a temperature control unit of the apparatus shown in FIG.

FIG. 9 is a flowchart of temperature control in the second embodiment of the present invention.

FIG. 10 is a diagram showing changes in heater temperature and internal atmosphere temperature in the second embodiment of the present invention.

[Explanation of symbols]

 1 Printer Main Body (Image Forming Device) 20 Fan (Exhaust Fan) 30 CPU (Control Unit) R3 Heater (Fixing Heater) TH1 Thermistor (Temperature Detection Unit)

Claims (2)

[Claims] 1. A fixing heater for heating and fixing a recording material carrying an unfixed image, temperature detecting means for detecting the temperature of the fixing heater, and temperature detected by the temperature detecting means being substantially constant. In the image forming apparatus having a control means for controlling the energization to the fixing heater, the control means controls the subsequent operation when the temperature detected by the temperature detection means drops to a predetermined temperature due to continuous image formation. An image forming apparatus characterized in that it is set to stop energizing the fixing heater for a predetermined time after the formation of a predetermined number of images. 2. A fixing heater for heating and fixing a recording material carrying an unfixed image, temperature detecting means for detecting the temperature of the fixing heater, and temperature detected by the temperature detecting means being substantially constant. An image forming apparatus having a control means for controlling energization to the fixing heater is provided with an exhaust fan, and the control means is provided when the temperature detected by the temperature detection means drops to a predetermined temperature due to continuous image formation. Is set to drive the exhaust fan for a predetermined time after the formation of a predetermined number of images thereafter.