JPH06242699A - Image recorder - Google Patents

Abstract

PURPOSE:To provide an image recorder which can instantaeously discriminate the disconnection of a thermistor detecting the temperature of a fixing part from a low temperature and has high safety. CONSTITUTION:The fixing part and a control part 30 are electrically connected via plural thermistors 57, 58, etc. The temperature of the fixing part is detected by plural thermistors whose temperature detecting ranges are different from each other and a signal is sent to the control part 30 from the thermistors 57 and 58 according to the detected temperature. After that, the control part 30 selects the thermistor to be used. Thus, even if the image recorder is used under a low temperature environment, the disconnection of the thermistor can be surely and instantaneously detected. When the disconnection of the thermistor occurs, the disconnection can be instantaneously dealt with as an error and after that the thermistor is never heated. Therefore, a device having the high safety can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image recording apparatus.

[0002]

2. Description of the Related Art In recent years, an image recording apparatus has been developed which adheres toner charged to the same polarity as that of an image forming body to an electrostatic latent image.
It is used.

Conventionally, this type of image recording apparatus has been disclosed in Japanese Patent Application No.
The one disclosed in Japanese Patent No. 55223 was general. Less than,
The configuration will be described with reference to FIGS.

In FIG. 5, a main body 1 is provided with a paper feed unit 2 for supplying a transfer material, an electrophotographic process unit 3, a fixing unit 4, an optical unit 5, and the like. The sheet feeding unit 2 takes out the sheets 7 as transfer materials stacked on the sheet feeding table 6 one by one and conveys them to the process unit 3. The process unit 3 includes a photoconductor 8, a charging unit 9, a developing unit 10, a transfer unit 11, a cleaning unit 12, and the like. The charging unit 9 gives a charge to the photoconductor 8 and the optical unit 5 gives a charge. The photoconductor 8 is exposed to form an electrostatic latent image, the developing unit 10 adheres the toner 13 to the electrostatic latent image and develops it, and the transfer unit 11 conveys this development from the paper fed from the paper feeding unit 2. It is transferred to the fixing unit 4 and transferred to the fixing unit 4.
The developing unit 10 is provided with a developing roller 14 composed of a magnetic roller, and the toner 13 supplied from the toner case 15 is attached to the developing roller 14. The cleaning unit 12 is composed of a scraping member 16 and a waste toner box 17, and the scraping member 16 scrapes off the toner 13 adhering to the photoconductor 8 after the transfer is completed. 17 are removed. The sheet 7 transferred and conveyed in the process section 3 is fixed by heat and pressure in the fixing section 4 and then discharged onto a sheet discharge tray 18. The control unit 19 is electrically connected to the paper feeding unit 2, the process unit 3, and the optical unit 5, and also electrically connected to the fixing unit 4 via the temperature detecting unit 20, and is detected by the temperature detecting unit 20. The temperature of the fixing unit 4 is appropriately controlled according to the data. The temperature detector 20 is represented by an equivalent circuit including a thermistor 21 and a series resistor 22 as shown in FIG. 6, and has thermistor output characteristics as shown in FIG. 7 (the resistance value of the series resistor is R = 7. 100kΩ for 5kΩ
In the case of 2) is shown).

[0005]

However, in the conventional image recording apparatus, as shown in FIG.
Has a characteristic that the sensitivity is good only in a certain temperature range, and the sensitivity becomes dull when the temperature is out of the certain temperature range (for example, when the fixing unit 4 is set to 70 in the case of R = 7.5 kΩ).
If it is attempted to control with good sensitivity in the temperature range of −170 ° C., the sensitivity becomes dull in other temperature regions. ), Low temperature and disconnection of the thermistor (Vo = 25
The instantaneous discrimination of 5) becomes impossible, and the thermistor disconnection cannot be accurately discriminated unless it has been unconditionally heated for a certain time (tens of seconds unit). Therefore, even after the thermistor 21 is disconnected, the thermistor 21 must be heated. As a result, this heating may cause an accident, which is a safety issue.

In view of the above problems, it is an object of the present invention to provide an image recording apparatus capable of instantaneously and accurately discriminating between a low temperature and a thermistor disconnection.

[0007]

In order to achieve the above object, the present invention controls a plurality of thermistors having different temperature detection ranges for detecting the temperature of the fixing unit, and outputs of the thermistors are switched depending on the temperature. It is characterized in that it is configured with such a control unit.

[0008]

According to the structure of the present invention, the temperature of the fixing portion can be detected with high sensitivity in a wide temperature range, and the low temperature and the thermistor disconnection can be instantly discriminated, so that an image recording apparatus with high safety can be obtained. .

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS.
7 and FIG. 7.

First, the overall schematic structure of the image recording apparatus will be described with reference to FIGS. 23 is the main body of the image recording device,
A body cover 24 whose lower end is pivotably supported at its lower end is provided on the front surface inclined forward and backward, and an operation portion 25 is provided on the front portion of the upper surface of the body 23. The main body 23 is provided with a paper feed unit 26, a process unit 27, an optical unit 28, a fixing unit 29, a control unit 30, and the like. In the paper feed unit 26, as shown in FIG.
As shown in FIG. 3, the paper tray 31 is configured to be installed on the upper surface of the main body 23 in an obliquely upward inclined manner, and a pickup path 32 is formed so that a paper passage path is formed obliquely downward along the front surface of the main body 23. A feed roller 33, a paper sensor 34, a registration roller 35, etc. are provided. The process unit 27 includes a developing unit 36, a toner cartridge 37, a collecting unit 38, and the like. The collecting unit 38 is composed of a cleaning blade 40 that comes into contact with the photosensitive drum 39 to remove residual toner, a charging unit 41, and a collecting box 42. The developing unit 36 is arranged so as to face the photoconductor drum 40 between the charging unit 41 and the transfer unit 42 in the rotation direction of the photoconductor drum 39, and is located below the paper feed unit 26. Toner is supplied from the toner cartridge 37 to the developing unit. The optical unit 28 includes a semiconductor laser 43, a collimator lens 44, and a rotary reflecting mirror 45.
The optical scanning unit 46 and the reflecting mirror 47 using the
The light output from the optical scanning unit 46 toward the rear is reflected by the reflecting mirror 47 toward the upper front in the oblique direction. The photosensitive drum 39 is exposed between the charging unit 41 and the developing unit 36. The fixing unit 29 includes a heat roller 49, a pressure contact roller 50, a separating claw 51, and a plurality of thermistors that are temperature detecting units. The fixing unit 29 continuously heats and presses the paper sent from the process unit 27 to melt the toner. And fix it on the paper. Further, the paper sheet on which the fixing is completed is discharged onto the paper discharge tray 55 by the paper discharge roller 53 via the static elimination brush 54. As shown in FIG. 3, the control unit 30 includes a CPU including a microcomputer, and commands from the operation unit 25.
Alternatively, based on a command from an external device (not shown), the paper feed unit 26, the process unit 27, the optical unit 28, the fixing unit 29, and the like are comprehensively controlled to record the input image information on the paper.

The relationship between the fixing unit 29 and the control unit 30 will be described with reference to FIG. 3. The heat roller 49 of the fixing unit 29 has a first thermistor 57 and a second thermistor 57 having the same characteristics. The thermistors 58 are arranged close to each other, and both of these thermistors are the control unit 3.
0 is connected to the analog input port of the CPU 56. In addition, the first thermistor 57 has a resistance value of 100 kΩ.
, And a series resistor 60 having a resistance value of 7.5 kΩ is connected to the second thermistor 58.

As can be seen from FIG. 7, the first thermistor 57 has good sensitivity in the temperature range of 0 to 70 ° C, and the second thermistor 58 has good sensitivity in the temperature range of 70 to 170 ° C. . Based on the signals from these thermistors, the control unit 30 selects the first thermistor 57 when the temperature of the fixing unit 29 is 70 ° C or lower, and selects the second thermistor 58 when the temperature of the fixing unit 29 is 70 ° C or higher. The temperature of the fixing unit 29 is detected by the selected thermistor. CP
U56 performs AD conversion of the input analog signal and is recognized as a digital value. When the resistance value of the thermistor is r and the resistance value of the series resistor is R, this digital value V _o is V _o = 255r / (R + r) (see FIG. 7).

The control method of the control unit 30 will be described below with reference to FIGS. 3, 4 and 7. FIG. 4 shows the CPU 56
Is a subroutine that is executed by a timer interrupt and is executed at regular intervals such as 100 ms by a timer interrupt.

First, in S1, the output V _o 1 of the first thermistor 57 is read, and then in S2, the V _o 1 just read is 10
It is determined whether it is 0 or less. When V _o 1 is 100 or less, it can be seen from the graph of FIG. 3 that the temperature is 55 ° C. or higher. Therefore, in S3, the output V _o 2 of the second thermistor 58 having high sensitivity on the high temperature side is read.

On the other hand, if V _o 1 exceeds 100 at S2, the temperature is lower than 55 ° C. or the first thermistor 57 is used.
Is either broken. This is V at S9
It is determined by the _o 1 of value. The output V _o 1 in the case of disconnection is 255 from the above equation, and R = 100 kΩ in the graph of FIG. 3 showing the temperature characteristic of the first thermistor 57.
There is a big difference from the output value 228 of 0 degree C in the case of
Even if it is used in a low temperature environment of C and the reading error is taken into consideration, the judgment will not be wrong. 10 if R = 7.5 kΩ
Even at C, the output value is 252, and there is a sufficient possibility of making a mistake in determination when considering a reading error or the like. If it is determined in S9 that the first thermistor 57 has a disconnection error, S1
Error stop at 1. The first thermistor 42 in S9
When it is determined that the disconnection error is not generated, the temperature is simply low, so that the halogen lamp 61 is turned on for heating in S10 and the process returns to the main routine.

Next, in S2, it is determined that the temperature is 55 degrees C or higher, and in S3.
When the output V _o 2 of the second thermistor 58 is read with,
In S4, it is determined whether or not the output value V _o 2 is larger than 44. This is a determination as to whether the temperature is higher than 180 ° C. than in the case of R = 7.5 kΩ in the graph of FIG. 7 showing the temperature characteristic of the second thermistor 58. If it is higher, the high temperature error stop is performed in S12. If the temperature is lower than 180 degrees C, the disconnection check of the second thermistor 58 is performed in S5. Since it has already been determined by S2 that the temperature is 55 ° C. or higher, V _o 2 is 22 from the graph of FIG.
It can be seen that it is 9 or less. On the other hand, the second thermistor 58
If the line is broken, the output value V _o 2 is 255, and since the difference is large, there is no mistake in the determination. If the disconnection error of the second thermistor 58 is determined in S5, S1
Error stop at 3. If there is no error, the process proceeds to S6 and thereafter, the halogen lamp 61 is controlled so as to maintain the specified temperature, and the process returns to the main routine.

As described above, according to one embodiment of the present invention, a plurality of thermistors having different temperature detection ranges are provided, and the outputs of the thermistors are switched and input according to the detected temperature to be controlled. The temperature of 29 can be detected with good sensitivity in a wide temperature range, and the low temperature and the thermistor disconnection can be instantly discriminated, which can prevent the occurrence of an accident due to the heating of the thermistor after the thermistor disconnection, and the device safety. It is possible to improve.

In this embodiment, the thermistors having the same characteristics are used by changing the output characteristics depending on the series resistance value. However, thermistors having originally different characteristics may be used.

[0019]

As is apparent from the above description, according to the present invention, even if the image recording apparatus is used in a low temperature environment, the thermistor disconnection can be detected reliably and instantaneously. Even if occurs, it is never heated after that, so that it is possible to prevent the occurrence of an accident due to the heating of the thermistor after the thermistor is disconnected, and it is possible to provide a highly safe device.

[Brief description of drawings]

FIG. 1 is a side sectional view of an image recording apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view of the device.

FIG. 3 is a schematic configuration diagram of main parts of the device.

FIG. 4 is a flowchart showing control of a temperature detection unit of the same device.

FIG. 5 is a side sectional view of a conventional image recording device.

FIG. 6 is a circuit diagram of a temperature detector.

FIG. 7 is an output characteristic diagram of the temperature detection unit.

[Explanation of symbols]

 26 Paper Feeding Section 27 Process Section 28 Optical Section 29 Fixing Section 30 Control Section 57 First Thermistor 58 Second Thermistor

Claims (1)

[Claims] 1. A paper feed unit for feeding a sheet into an apparatus, a process unit for performing a process process until development of information to be recorded on the fed sheet, and a photosensitive member in the process unit for exposure. An optical unit, a fixing unit that fixes and discharges the paper that has been developed by the process unit, a plurality of temperature detection units having different temperature detection ranges of the fixing unit, and signals from the plurality of temperature detection units. An image recording apparatus including a control unit that selects the temperature detecting unit that actually detects the temperature of the fixing unit based on the above.