KR101808555B1 - Image forming apparatus and fixing unit control method thereof - Google Patents

Abstract

An image forming apparatus, and a control method of the fixing unit. An image forming apparatus includes: an image forming section that forms an image; A fixing unit for fixing the image transferred to the printing medium; A power supply unit for supplying operation power; A non-contact sensing unit including a pair of sensors for sensing the temperature of the fixing unit by a non-contact method and outputting a sensor sensing voltage and a sensor compensating voltage, respectively; And a noncontact sensing protector for shutting off the power supplied to the fixing unit from the power supply unit when the sensor sensing voltage is higher than the sensor compensation voltage. Thus, the noncontact sensing and protecting unit that detects the fixing temperature by the noncontacting method and cuts off the power by hardware can be provided, thereby preventing abnormal overheating and control errors and protecting the fixing unit.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an image forming apparatus,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an image forming apparatus and a fixing method thereof, and more particularly, to an image forming apparatus for preventing a malfunction of a non-contact sensor for sensing a temperature of a fixing unit and a fixing method.

The image forming apparatus forms an image to be printed on the printing medium. The image forming apparatus may be implemented by a printer, a copying machine, a facsimile, a multifunction peripheral having two or more functions, and the like.

1, the image forming apparatus includes an image carrier 121, an optical scanning knit 123 for forming a latent electrostatic image by scanning the image carrier 121 with a beam, A developing unit 125 for developing a toner image on an electrostatic latent image formed on the electrophotographic photosensitive member 121 and a transferring unit 130 for transferring the toner developed on the charged electrophotographic carrier 121 to a printing medium, Thereby performing image formation.

The image transferred to the printing medium is thermally compressed by the fixing unit 140 and output to the outside. The fixing unit 140 is heated by the power supply to fix the image on the printing medium.

The image forming apparatus includes a temperature sensing unit (temperature sensor) to prevent the fixing unit 140 from overheating, detects the temperature of the fixing unit 140, and controls the power supplied to the fixing unit 140 Control

In general, a temperature sensor is contacted with a fixing roller 141 of a fixing unit 140 to detect a temperature, and a contact sensor is often used.

When the fixing unit 140 to which power is supplied is abnormally overheated due to a reason such as a control error or an error occurs in the contact sensor, the fixing unit 140 A contact detection and protection unit for protecting the fixing unit 140 by turning off the power, that is, by turning off the power by hardware, is further provided.

However, in the case of the contact sensor, when the degree of smoothness of the surface of the fixing roller 141 is different from that of the sensor, or when the temperature sensed by adhesion of contaminants such as toner scum, A problem such as being measured may occur.

In recent years, a non-contact temperature sensor is provided as an auxiliary means for the contact sensor, and furthermore, a contact temperature sensor is used as an auxiliary temperature sensor such as the outer side of the fusing unit 140, and the non-contact sensor is used as a main temperature sensor of the fusing unit 140 Or the temperature of the fixing unit 140 is controlled using only the non-contact sensor.

However, in the conventional image forming apparatus, the contact detection and protection unit for preventing overheating, error, and the like of the fusing unit 140 due to the detection result of the contact sensor is used. However, when the fusing unit 140 is overheated due to the detection result of the non- In order to prevent errors, a circuit that cuts off the power by hardware is not used.

In addition, since the touch sensor is constituted by one sensor for sensing the temperature, the non-contact sensor is constituted to detect the temperature by the potential of the two sensors, that is, the infrared sensor and the temperature compensating device, The detection protection unit can not be applied to the noncontact detection protection unit.

Accordingly, as the demand of the noncontact sensor increases, the noncontact sensing and protecting unit that protects the abnormal fixing of the fixing unit 140 and the error caused by the malfunction of the control unit, There is a need to prepare.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an image forming apparatus capable of preventing abnormal overheating and control errors and protecting a fusing unit by providing a noncontact sensing and protecting unit that detects a fixing temperature by a noncontacting method and thereby cuts off power in hardware, And a sub control method.

It is another object of the present invention to provide a method of controlling a fusing unit more effectively by not only shutting off power by comparing a sensor detection voltage and a sensor compensation voltage but also shutting off the power even when at least one of a sensor sensing voltage and a sensor compensation voltage deviates from a temperature range. And an image forming apparatus capable of controlling the fixing unit.

The above object is achieved by an image forming apparatus comprising: an image forming section for forming an image; A fixing unit for fixing the image transferred to the printing medium; A power supply unit for supplying operation power; A non-contact sensing unit including a pair of sensors for sensing the temperature of the fixing unit by a non-contact method and outputting a sensor sensing voltage and a sensor compensating voltage, respectively; And a noncontact sensitive protection unit that disconnects the power supplied from the power supply unit to the fixing unit when the sensor detection voltage is higher than the sensor compensation voltage.

The noncontact sensing and protecting unit may include a first comparator receiving the sensor sensing voltage and the sensor compensation voltage and outputting a comparison result of the sensor sensing voltage and the sensor compensation voltage.

Further comprising a memory unit for storing a temperature characteristic table for the sensor sensing voltage and the sensor compensation voltage, wherein the non-contact sensing protection unit compares the sensor sensing voltage output from the non-contact sensing unit and the sensor compensation voltage with the temperature characteristic table And if the output of the sensor detection voltage and / or the sensor compensation voltage deviates from the temperature characteristic table stored in the memory unit, the power supplied from the power supply unit to the fixing unit may be cut off.

The noncontact sensing and protecting unit may include a plurality of comparators receiving either the upper limit value or the lower limit value of either the sensor sensing voltage or the sensor compensation voltage and the sensor sensing voltage or the sensor compensation voltage .

A second comparator receiving an upper limit value of the output sensor compensation voltage and the set sensor compensation voltage and outputting an error signal when the output sensor compensation voltage is greater than the upper limit value; A third comparator receiving a lower limit value of the output sensor compensation voltage and the set sensor compensation voltage and outputting an error signal when the output sensor compensation voltage is lower than the lower limit value; A fourth comparator receiving an upper limit value of the output sensor sensing voltage and the set sensor sensing voltage and outputting an error signal when the output sensor sensing voltage is greater than the upper limit value; And a fifth comparator receiving the output voltage of the sensor and a lower limit value of the set sensor sense voltage and outputting an error signal when the output sensed voltage is lower than the lower limit value, When an error signal is output from at least one of the comparators to the fifth comparator, the power supplied from the power supply unit to the fixing unit may be cut off.

And a control unit for receiving signals from the non-contact sensing and protecting unit and controlling the operation of the fixing unit.

A contact sensing unit sensing the temperature of the fixing unit by a contact method and outputting a contact sensing voltage; And a contact detection and protection unit for disconnecting the power supplied from the power supply unit to the fixing unit when the contact detection voltage is greater than a predetermined reference voltage.

The touch sensing and protecting unit may include a sixth comparator receiving the touch sense voltage and the reference voltage and outputting a result of comparing the input touch sense voltage with a reference voltage.

And a controller for receiving a signal from the non-contact sensing and protection unit and the contact sensing and protection unit and controlling an operation of the fixing unit, wherein the control unit is configured to control at least one of the non- So that the operation of the fixing unit can be stopped.

According to another aspect of the present invention, there is provided a method of controlling a fixing unit of an image forming apparatus including an image forming unit that forms an image, a fixing unit that fixes the image transferred to the printing medium, and a power supply unit that supplies operation power, Detecting a temperature of the fixing unit by a non-contact method, and outputting a sensor sensing voltage and a sensor compensating voltage; Comparing the sensor sensing voltage with a sensor compensation voltage; And blocking the power supplied from the power supply unit to the fixing unit when the sensor detection voltage is higher than the sensor compensation voltage as a result of the comparison.

Wherein the image forming unit further includes a memory unit for storing a temperature characteristic table for the sensor sensing voltage and the sensor compensation voltage and comparing the sensor sensing voltage and the sensor compensation voltage with the temperature characteristic table; And disconnecting the power supplied from the power supply unit to the fusing unit when at least one of the output of the sensor sensing voltage and the sensor compensation voltage is out of the range of the temperature characteristic table stored in the memory unit.

The comparing step with the temperature characteristic table may include comparing the voltage value set to either the upper limit value or the lower limit value of any one of the sensor detection voltage and the sensor compensation voltage and the sensor detection voltage and the sensor compensation voltage can do.

The comparison of the voltage value set to the upper limit value or the lower limit value may include comparing the upper limit value of the output sensor compensation voltage with the upper limit value of the set sensor compensation voltage and outputting an error signal when the output sensor compensation voltage is greater than the upper limit value Step 1; A second step of comparing the output sensor compensation voltage with a lower limit value of the set sensor compensation voltage and outputting an error signal when the output sensor compensation voltage is smaller than the lower limit value; A third step of comparing the output voltage of the sensor with an upper limit value of the set sensor sense voltage and outputting an error signal when the output sensed voltage is greater than the upper limit value; And a fourth step of comparing the output voltage of the sensor with a lower limit of the set sensor sensing voltage and outputting an error signal when the output sensed voltage is lower than the lower limit.

The step of interrupting the power supply may cut off the power supplied to the fixing unit from the power supply unit when the error signal is output in any one of the first to fourth steps.

And outputting a control signal for stopping the operation of the fusing unit when the sensor detection voltage is higher than the sensor compensation voltage as a result of the comparison.

Detecting a temperature of the fixing unit by a contact method and outputting a contact sensing voltage; Comparing the contact sensing voltage with a predetermined reference voltage; And disconnecting the power supplied from the power supply unit to the fixing unit when the contact detection voltage is greater than the reference voltage.

And outputting a control signal for stopping the operation of the fusing unit when the contact detection voltage is greater than the reference voltage as a result of the comparison.

As described above, the image forming apparatus and the fixing unit control method thereof according to the present invention provide a noncontact sensing and protecting unit that detects a fixing temperature by a non-contact method and cuts off power by hardware, thereby preventing abnormal overheating and control errors The fusing unit can be protected.

In addition, in the case where at least one of the sensor detection voltage and the sensor compensation voltage deviates from the temperature range as well as the power supply cutoff by comparing the sensor detection voltage and the sensor compensation voltage, the fusing unit can be more effectively protected by turning off the power.

1 is a view showing an image forming apparatus according to an embodiment of the present invention,
2 is an exploded perspective view showing the non-contact sensing unit 210 according to an embodiment of the present invention,
3 is a cross-sectional view showing a state in which the non-contact sensing unit 210 of the embodiment of FIG. 2 is assembled,
4 is a block diagram showing a configuration of an image forming apparatus according to an embodiment of the present invention,
5 is a circuit diagram of a noncontact sensing and protecting unit according to an embodiment of the present invention,
6 is a block diagram showing the configuration of an image forming apparatus according to another embodiment of the present invention,
FIG. 7 is a circuit diagram of a contact detection and protection unit according to another embodiment of the present invention,
8 is a flowchart showing a fixing unit control method of an image forming apparatus according to an embodiment of the present invention,
9 is a flowchart showing a fixing unit control method of an image forming apparatus according to another embodiment of the present invention,
10 is a flowchart showing a method of outputting an error signal of the touch sense protection unit of the embodiment of FIG.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a view showing an image forming apparatus according to an embodiment of the present invention.

The image forming apparatus of the present invention can be implemented by a printer, a copier, a fax machine, a multifunction peripheral having two or more functions, and the like.

1, an image forming apparatus according to an embodiment of the present invention is a tandem-type color image forming apparatus for forming a color image in a single pass manner. The apparatus includes a developing unit 125 including an image- A knit 123, and a transfer unit 130. The developing unit 125, the optical scanning unit knit 123 and the transfer unit 130 are included in the image forming unit 120 and the image forming unit 120 performs printing in accordance with the print command. Here, the printing is performed from the outside via the host device 300 including the server, including the printing for copying after the original is scanned, the printing of the received facsimile data, the inside of the image forming apparatus (HDD) Lt; / RTI >

The image forming apparatus further includes a fixing unit 140 for thermally compressing the image transferred to the printing medium, and a discharging unit 150 for discharging the printing medium to which the image is fixed.

A supply unit 111 on which a printing medium (also referred to as a print medium or a recording medium) M to be supplied is loaded is detachably provided inside the housing 10 constituting the outer shape of the image forming apparatus. The printing medium M loaded on the feeding unit 111 is picked up via the pick-up roller 113 and conveyed in the direction of the transfer unit 130 through the conveying path.

The photoreceptor 121 forms a latent image for each color in response to the light beam scanned by the optical scanning cutter 123. In this embodiment, the first to fourth conveying members arranged in this order from the feeding direction of the printing medium are exemplified as the plurality of the conveying members 121.

The developing unit 125 receives the toner and forms a toner image on the image carrier 121.

A plurality of developing units 125 may be provided for each color. 1 illustrates an example in which the first to fourth developing units are configured to respectively implement yellow (Y), magenta (M), cyan (C), and black (K) colors.

In this embodiment, the case where the toner is received in the developing unit 125 is shown as an example, but this is merely an example, and it is also possible to form the developer supplying portion separately. In this case, the developer supply portion includes the first to fourth developer supply portions in accordance with the developing portion for each color. In addition, although the configuration in which the image carrier 121 is provided in the developing unit 125 is shown as an example, the present invention is not limited thereto, and the image carrier may be provided outside the developing unit.

The optical scanning cutter 123 scans the beams to form a latent image on each of the plurality of image carriers 121. For this purpose, the light-guiding knit 123 includes a light source, a beam deflector for deflecting and scanning the beam irradiated from the light source, an imaging lens for scanning and imaging the light beam deflected in the beam scent, And a reflecting member for converting a traveling path of the emitted light.

The transfer unit 130 transfers the visible image formed on the image carrier 121 to the printing medium M supplied along the printing path. To this end, the transfer unit 130 may include a transfer belt 131 disposed to face a plurality of the image carrying bodies 101.

The image transferred to the printing medium M through the transfer unit 130 is fixed through the fixing unit 140. [

The fixing unit 140 forms a fixing nip N by a pressing force and fixes the transferred image by heating and pressing the printing medium M passing through the fixing nip. The fixing unit 140 includes a heat roller 141 having a heating unit 142 provided therein and generating heat and a pressure roller 143 closely contacting the heat roller 141 to form a fixing nip N do. The heat roller 141 and the pressure roller 143 are engaged with each other at a predetermined pressure to apply heat and pressure to the image transferred to the printing medium M and fix it on the printing medium M.

The heating means 142 provided in the heat roller 141 may be realized by a halogen lamp, a heat wire, an induction heater, or the like.

The image forming apparatus according to an embodiment of the present invention further includes a non-contact sensing unit 210 for sensing the temperature of the fixing unit 140 by a non-contact method.

The noncontact sensing unit 210 is disposed at a position spaced apart from the heat roller 141 of the fixing unit 140 by a predetermined distance to sense the temperature of the fixing unit 140 (i.e., the roller).

FIG. 2 is an exploded perspective view illustrating a non-contact sensing unit 210 according to an embodiment of the present invention, and FIG. 3 is a cross-sectional view illustrating a state where the non-contact sensing unit 210 of FIG. 2 is assembled.

As shown in FIG. 2, the non-contact sensing unit 210 is composed of a pair of sensors including an infrared sensing thermoelement element 21a and a temperature compensation thermoelement element 21b arranged at predetermined intervals.

The infrared sensing thermal element 21a outputs the sensor sensing voltage NCTH_D and the temperature sensing thermal element 21b outputs the sensor compensation voltage NCTH_C. The image forming apparatus senses the temperature of the fixing unit 140 by detecting the amount of infrared rays by the potential difference between the sensor sensing voltage and the sensor compensating voltage.

In the present invention, the infrared sensing thermosensitive element 21a and the temperature compensating thermostat 21b are implemented as a thermistor element, but a thermocouple or a resistance temperature detector (RTD) And the like can be applied as long as they can be used as temperature sensors. In the present invention, the infrared-sensitive thermal element 21a and the temperature-compensated thermal element 21b have the same shape and characteristics.

2 and 3, the non-contact sensing unit 210 includes a case 20, resin films 24a and 24b, a fixing frame 23 for fixing the resin films 24a and 24b, And a cover portion 25 including an infrared ray incident window 25a and an infrared ray shielding portion 25b. A protrusion 22 is formed in the case 20 so that the fixing frame 23 is fixed by a method such as adhesion. The case 20 and the fixed frame 23 are made of resin or metal having thermal conductivity and can be integrally formed.

The resin films 24a and 24b are formed by dispersing a carbon black or an inorganic pigment in a polymer material such as polyester having a predetermined thickness (for example, 0.2 mm).

The infrared-sensitive thermal element 21a and the temperature-compensated thermal element 21b are fixed to one surface of the resin films 24a and 24b in close contact with each other.

The cover section 25 has an infrared ray incidence window 25a at a portion of the resin film 24a provided with the infrared ray sensing element 21a and an infrared ray incident window 25b at a portion of the resin film 24b provided with the temperature- And a shielding portion 25b.

2, the resin films 24a and 24b correspond to the positions of the infrared ray-sensitive element 21a and the temperature-compensated element 21b, respectively. However, the resin films 24a and 24b may be composed of one resin film It is possible.

The infrared ray is incident on the infrared ray incidence window 25a provided in the cover portion 25 of the case 20 and is irradiated onto the resin film 24a. The temperature of the resin film 24a rises in accordance with the amount of infrared rays to be irradiated, thereby changing the resistance value of the infrared sensor 21a for infrared detection in close contact with the back surface of the resin film 25a. Therefore, the temperature rise of the resin film 24a according to the amount of infrared rays is outputted as a change in the resistance value. The change in the output resistance value may also include the influence of the ambient temperature of the infrared sensor 21a.

Since the temperature-compensating thermal element 21b is fixed to the resin film 25b and shields the infrared rays by the cover portion 25, the temperature-compensating thermal element 21b is not affected by the infrared rays, Is changed.

That is, since the resistance values of the infrared-sensitive thermal element 21a and the temperature-compensated thermal element 21b are both changed by the ambient temperature, if this change is canceled by using a separate bridge circuit (not shown) Can be detected accurately.

4 is a block diagram illustrating the configuration of an image forming apparatus according to an exemplary embodiment of the present invention. Referring to FIG. 4, the noncontact sensing unit 210 may sense the temperature change of the fixing unit 140 more accurately.

4, the image forming apparatus of the embodiment of the present invention further includes a non-contact sensing and protecting unit 230, a memory unit 280, a power supply unit 250, and a control unit 270. The image forming apparatus may further include an ADC (Digital Signal Processor) protection unit 260 for preventing electrostatic discharge (ESD) or electrical noise.

The noncontact sensing and protecting unit 230 compares the sensor sensing voltage sensed by the noncontact sensor 210 with the sensor compensating voltage and cuts off the power supplied from the power supplying unit 250 to the fixing unit 140 according to the comparison result.

The memory unit 280 stores a temperature characteristic table of the noncontact sensor.

Table 1 shows an example of the noncontact temperature characteristic table. The temperature characteristics shown in Table 1 are examples, and the values may vary depending on the characteristics of the sensor.

Compensation temperature (℃) The sensor compensation voltage Vc (V) Roller temperature (℃) 100 120 140 160 180 200 220 240 Sensor detection voltage Vd (V) One 3.2721 3.2690 3.2681 3.2669 3.2655 3.2637 3.2615 3.2590 3.2560 10 3.2472 3.2422 3.2407 3.2388 3.2364 3.2334 3.2299 3.2257 3.2207 20 3.2049 3.1974 3.1950 3.1920 3.1882 3.1835 3.1780 3.1714 3.1637 30 3.1366 3.1261 3.1226 3.1180 3.1123 3.1054 3.0972 3.0875 3.0763 40 3.0325 3.0189 3.0140 3.0075 2.9995 2.9897 2.9782 2.9648 2.9492 50 2.8832 2.8670 2.8605 2.8519 2.8413 2.8285 2.8134 2.7858 2.7757 60 2.6829 2.6657 2.6575 2.6469 2.6338 2.6181 2.5996 2.5784 2.5542 70 2.4333 2.4171 2.4077 2.3955 2.3805 2.3626 2.3418 2.3179 2.2909 80 2.1455 2.1327 2.1226 2.1097 2.0937 2.0749 2.0530 2.0282 2.0004 90 1.8387 1.8311 1.8210 1.8082 1.7925 1.7741 1.7529 1.7289 1.7023 100 1.5354 1.5354 1.5239 1.5120 1.4977 1.4808 1.4616 1.4400 1.4162 110 1.2545 1.2493 1.2389 1.2264 1.2119 1.1955 1.1771 1.1569 120 1.0084 1.0084 0.9997 0.9894 0.9775 0.9641 0.9495 0.9328 130 0.8019 0.7986 0.7904 0.7809 0.7703 0.7587 0.7459 140 0.6339 0.6344 0.6280 0.6207 0.6126 0.6037 0.5940 150 0.5001 0.4982 0.4926 0.4865 0.4799 0.4727

As shown in Table 1, the temperature characteristic table of the noncontact temperature sensor is configured in a two-dimensional form having a horizontal axis and a vertical axis. The horizontal axis represents the sensor sensing voltage (NCTH_D), and the vertical axis represents the sensor compensation voltage (NCTH_C). The voltage value is inversely proportional to temperature.

The temperature of the fixing unit 140 may be determined by comparing the sensor sensing voltage sensed by the non-contact sensor 210 and the sensor compensation voltage with the temperature characteristic table. For example, when the sensor sensing voltage is 3.1950 V and the sensor compensation voltage is 3.2049 V, the temperature of the fixing unit 140 becomes 120 deg.

As shown in Table 1, in a normal state, the sensor sensing voltage has a smaller or equal value with respect to the sensor compensation voltage. That is, the sensor compensation voltage is equal to or greater than the sensor detection voltage.

The power supply unit 250 supplies operating power to each configuration of the image forming apparatus. Specifically, the power supply unit 250 controls the supply of power to the fusing unit 140 under the control of the controller 270.

The control unit 270 controls on / off of the power source according to the fixing algorithm so that the fixing unit 140 maintains the proper fixing temperature based on the voltage sensed by the non-contact sensing unit 210. [

When the power supplied to the fixing unit 140 is turned on, an AC power source (AC power source) is applied to the fixing unit 140, and the temperature of the fixing unit 140 rises. The control unit 140 turns off the power supplied to the fixing unit 140 when the temperature is excessively increased according to the voltage sensed by the non-contact temperature sensor unit 210. [

The controller 270 is implemented by a CPU (Central Processing Unit) that controls the operation of the image forming apparatus 100. The controller 270 converts the sensed voltage values (for example, sensor sensing voltage and sensor compensation voltage) Block (ADC Block)

5 is a circuit diagram of the non-contact sensing and protecting unit 230 according to an embodiment of the present invention.

5, the non-contact sensing and protecting unit 230 includes a first comparator 31 receiving a sensor sensing voltage and a sensor compensation voltage, 33, 34, 35 receiving the voltage value set to any one of the upper limit value and the lower limit value of the sensor compensation voltage.

The first comparator 31 receives the sensor sensing voltage NCTH_D and the sensor compensation voltage NCTH_C from the non-contact sensing unit 210. When the sensor sensing voltage is higher than the sensor compensation voltage, And outputs an error signal (e.g., a low signal) for turning off the power supply.

Specifically, in a normal state as shown in Table 1, the sensor sensing voltage is equal to or less than the sensor compensation voltage, and the first comparator 31 outputs a high signal. When the sensor sensing voltage is higher than the sensor compensation voltage, the first comparator 31 outputs a low signal.

The second comparator 32 receives the sensor compensation voltage NCTH_C sensed by the non-contact sensing unit 210 and the upper limit value of the predetermined sensor compensation voltage. If the sensor compensation voltage is greater than the set upper limit value, the second comparator 32 outputs an error signal low) signal.

Here, the upper limit value of the sensor compensation voltage is determined by the temperature characteristic table of Table 1. That is, according to Table 1, when the output sensor compensation voltage is the highest, it is 3.2721V, so the upper limit value can be set to 3.2722V.

The third comparator 33 receives the sensor compensation voltage NCTH_C sensed by the non-contact sensing unit 210 and the lower limit value of the predetermined sensor compensation voltage, and outputs an error signal (for example, low) signal.

Here, the lower limit value of the sensor compensation voltage is determined by the temperature characteristic table in Table 1. That is, according to Table 1, when the output sensor compensation voltage is the lowest, it is 0.5001V, so that the lower limit value can be set to 0.5V.

The fourth comparator 34 receives the upper limit value of the sensor sensing voltage detected by the non-contact sensing unit 210 and the upper limit value of the predetermined sensor sensing voltage. If the sensor sensing voltage is greater than the set upper limit value, the fourth comparator 34 outputs an error signal low) signal.

Here, the upper limit value of the sensor sensing voltage is determined by the temperature characteristic table of Table 1. [ That is, according to Table 1, when the output voltage of the sensor is the highest, it is 3.2690 V, so the upper limit value can be set to 3.27V.

The fifth comparator 35 receives the sensor sensing voltage NCTH_D sensed by the non-contact sensing unit 210 and a lower limit value of a preset sensor sensing voltage. If the sensor sensing voltage is lower than the set lower limit, the fifth comparator 35 outputs an error signal low) signal.

Here, the lower limit value of the sensor sensing voltage is determined by the temperature characteristic table of Table 1. [ That is, according to Table 1, when the output voltage of the sensor is the lowest, it is 0.4727V, so that the lower limit value can be set to 0.4V. In some cases, the lower limit of the sensor compensation voltage and the sensor sense voltage may be set to 0V.

Accordingly, when at least one of the sensor sensing voltage NCTH_D and the sensor compensation voltage NCTH_C sensed by the non-contact sensing unit 210 is out of the range of the temperature characteristic table of Table 1, A low signal is outputted as an error signal in at least one of the first to fifth comparators 32, 33, 34, and 35, whereby the power supplied to the fusing unit 140 is cut off.

As a result, even if the output of the non-contact sensing unit 210 becomes high latch up (3.3V) or low latch up (0V), the second The power supplied to the fusing unit 140 is shut off by at least one of the first to fifth comparators 32, 33, 34, and 35 so that the fusing unit 140 can be protected.

In one embodiment of the present invention, when the first to fifth comparators 31, 32, 33, 34, and 35 are normal, a high signal is output, and when the temperature of the fixing unit 140 is abnormal, But is not limited thereto.

Meanwhile, the output of the non-contact sensing and protecting unit 230 is also input to the controller 270.

Specifically, when at least one of the first to fifth comparators 31, 32, 33, 34, and 35 generates the error signal nNCTH_ERROR, the ADC block of the controller 270 converts the error signal into a temperature value And the control unit 270 can control to stop the operation of the fixing unit 140 according to the fixing algorithm.

The noncontact sensing and protecting unit 210 detects an error signal in at least one of the first to fifth comparators 31 to 32 regardless of the control of the fixing unit 140 of the control unit 270 The power supplied from the power supply unit 250 to the fixing unit 140 is shut off by hardware.

Therefore, even if the control unit 270 can not normally perform the fixing algorithm due to an error, the fixing unit 140 is protected.

6 is a block diagram showing the configuration of an image forming apparatus according to another embodiment of the present invention.

The image forming apparatus according to another embodiment of the present invention shown in FIG. 6 may further include a contact sensing unit 220 and a contact sensing and protecting unit 240, as compared with the image forming apparatus 100 according to an embodiment. It is characterized by having prepared.

Therefore, components other than the touch sensing unit 220 and the contact sensing and protecting unit 240 are denoted by the same reference numerals and the same names as those of the embodiment, and a detailed description thereof will be omitted in order to avoid redundant description. .

Meanwhile, the image forming apparatus according to another embodiment of the present invention may further include an ADC (analog-to-digital) converter unit 260 for preventing electrostatic discharge (ESD) or electrical noise.

FIG. 7 is a circuit diagram of the contact detection and protection unit 240 according to another embodiment of the present invention.

7, the contact sensing unit 220 includes a thermistor Rth which is a thermal resistance in contact with the fixing roller. The contact sensing unit 220 senses the temperature of the fixing unit 140 by a contact method, And outputs a voltage.

The contact sensing unit 220 reads the resistance value of the thermistor Rth and senses the temperature of the fixing unit 140. The resistance value is converted into a voltage value (contact sensing voltage) ).

The controller 270 converts the contact sensing voltage into a temperature value and controls the fusing unit 140 to maintain the proper temperature by turning on / off the power supplied to the fusing unit 140 according to the fusing algorithm.

When the contact detection voltage is higher than a predetermined reference voltage, the contact detection protection unit 240 cuts off the power supplied from the power supply unit 250 to the fusing unit 140.

7, the contact sensing and protecting unit 240 receives a contact sensing voltage Vp and a reference voltage, and outputs a comparison result between the input contact sensing voltage and a reference voltage. . The sixth comparator 41 outputs an error signal (for example, a low signal) for interrupting power supply to the fixing unit 140 when the contact sensing voltage is higher than the reference voltage. Here, the reference voltage may be arbitrarily set (e.g., 1.65 V).

Meanwhile, the output of the contact detection protection unit 240 is also input to the control unit 270.

More specifically, when an error signal is output from the sixth comparator 41, the ADC block of the controller 270 converts the error signal into a temperature value and receives the error signal. The controller 270 controls the fusing unit 140, It is possible to control to stop the operation of the controller.

The contact detection and protection unit 240 receives the error signal from the sixth comparator 41 regardless of the control of the fusing unit 140 of the control unit 270 so that the fusing unit 140 The power supply to the power source is interrupted.

Therefore, even if the control unit 270 can not normally perform the fixing algorithm due to an error, the fixing unit 140 is protected.

When an error signal is output from at least one of the non-contact sensing protector 230 and the contact sensing protector 240 in the image forming apparatus of the present invention, the power supply to the fixing unit 240 is interrupted.

The control unit 270 controls the fixing unit 140 to stop the operation of the fixing unit 140 based on the output signal of at least one of the non-contact sensing unit 230 and the contact sensing unit 240.

Accordingly, overheating of the fusing unit 140 is prevented by the non-contact sensing and protecting unit 230 as well as the conventional contact sensing and protecting unit 240.

Since the fusing unit 140 can overheat the fusing power regardless of the fusing control signal of the controller 270, the fusing unit 140 can be powered off by at least one of the non-contact sensing unit 230 and the contact sensing unit 240, It is possible to more effectively protect the display unit 140. [

Hereinafter, in the image forming apparatus having the above-described structure, the fixing unit control method will be described with reference to Figs. 8, 9 and 10. Fig.

FIG. 8 is a flowchart illustrating a method of controlling a fixing unit of an image forming apparatus according to an embodiment of the present invention.

The image forming apparatus according to the embodiment of FIG. 8 includes a non-contact sensing unit 210 and a non-contact sensing and protecting unit 230 as shown in FIG.

As shown in Fig. 8, when the image forming apparatus receives the print command and performs printing, power is supplied to the fusing unit 140 for fixing the image (602).

When power is supplied to the fixing unit 140, the temperature rises, and the non-contact sensing unit 210 senses the sensor sensing voltage and the sensor sensing voltage and outputs the sensor sensing voltage and the sensor sensing voltage (604).

The non-contact sensing protection unit 230 compares the detected sensor sensing voltage with the sensor compensation voltage (606).

That is, the first comparator 31 of the non-contact sensing and protecting unit 230 receives the sensor sensing voltage NCTH_D and the sensor compensation voltage NCTH_C, and compares the sizes thereof with each other (608).

In step 608, when the sensor sensed voltage is greater than the sensor compensating voltage, a signal is output from the first comparator 31 and the power supplied from the power supply unit 250 to the fixing unit 140 is shut off (610). Thus, the fixing unit 140 is prevented from overheating regardless of the control of the control unit 270 by the software fixing unit 140.

In step 608, if the sensor sensing voltage is greater than the sensor compensation voltage, the controller 270 outputs a control signal to stop the operation of the fixing unit 140 (612).

Meanwhile, the non-contact sensing protection unit 230 compares the sensor sensing voltage sensed at step 604 and the sensor sensing voltage with a temperature characteristic table as shown in table 1 (614). Here, step 614 is performed in parallel with step 606 in accordance with the detection result of step 604 irrespective of the comparison result of step 608.

That is, the non-contact sensing protection unit 230 compares the sensor sensing voltage and the sensor compensation voltage with the upper and lower limit values, respectively, to determine whether the sensor sensing voltage is within the range of the temperature characteristic table (616). When a signal is outputted from at least one of the second to fifth comparators (32, 33, 34, 35) of the non-contact sensing and protecting unit 230, any one of the sensor compensation voltage and the sensor sensing voltage It is beyond the scope of the table.

If it is determined in step 616 that at least one of the sensor sensing voltage and the sensor compensating voltage deviates from the range of the temperature characteristic table, the power supplied from the power supplying unit 250 to the fixing unit 140 is shut off (610). Thus, the fixing unit 140 is prevented from overheating regardless of the control of the control unit 270 by the software fixing unit 140.

If both the sensor sensing voltage and the sensor compensation voltage are present in the temperature characteristic table in step 616 and the sensor sensing voltage is below the sensor voltage compensation in step 608, the fusing unit 140 operates normally under the control of the controller 270 (618). FIG. 9 is a flowchart illustrating a method of controlling a fixing unit of an image forming apparatus according to another embodiment of the present invention.

The image forming apparatus according to the embodiment of FIG. 9 further includes a non-contact sensing unit 210 and a contact sensing unit 220 and a non-contact sensing unit 240 in addition to the non-contact sensing unit 230

As shown in Fig. 9, when the image forming apparatus receives the print command and performs printing, power is supplied to the fusing unit 140 (step 702) to fix the image.

When power is supplied to the fixing unit 140, the temperature rises, the non-contact sensing unit 210 senses the sensor sensing voltage and the sensor compensation voltage, and the contact sensing unit 220 senses and outputs the contact sensing voltage 704).

The image forming apparatus determines whether an error signal is output from at least one of the non-contact detection protection unit 230 and the contact detection protection unit 240 by the voltage output at step 704 (706).

As shown in FIG. 8, the non-contact sensing and protecting unit 230 outputs an error signal when a signal is outputted from at least one of the first to fifth comparators 31, 32, 33, 34 and 35, The protection unit 240 outputs an error signal when a signal is output from the sixth comparator 41. The output of the error signal of the contact detection protection unit 240 will be described later in more detail with reference to FIG.

If an error signal is output from at least one of the noncontact sensing protector 230 and the touch sensing protector 240 at step 706, the power supplied from the power supplier 250 to the fixing unit 140 is interrupted (708). Thus, the fixing unit 140 is prevented from overheating regardless of the control of the control unit 270 by the software fixing unit 140.

If it is determined in step 706 that no error signal is output from both the non-contact sensing protection unit 230 and the contact sensing protection unit 240, that is, if the contact sensing voltage is lower than the reference voltage, If the sensor voltage is below the sensor voltage compensation, the fixing unit 140 normally operates according to the control of the controller 270 (712).

FIG. 10 is a diagram for explaining a control operation of the contact detection protection unit 240 in the embodiment of FIG.

The touch sensing unit 220 senses and outputs the contact sensing voltage (802).

The contact detection protection unit 240 compares the contact detection voltage sensed in step 802 with a predetermined reference voltage (804).

Specifically, the sixth comparator 41 receives the contact sensing voltage and the reference voltage, and outputs a low signal when the contact sensing voltage is greater than the reference voltage (806).

In step 806, the contact detection protection unit 240 outputs an error signal (808).

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.

100: Image forming apparatus 120: Image forming unit
140: fusing unit 210: non-contact sensing unit
220: contact sensing part 230: non-contact sensing protection part
240: contact detection protection unit 250: power supply unit
270: control unit 280: memory unit

Claims (17)

In the image forming apparatus,
An image forming section for forming an image;
A fixing unit for fixing the image transferred to the printing medium;
A power supply unit for supplying operation power;
A non-contact sensing unit including a pair of sensors for sensing the temperature of the fixing unit by a non-contact method and outputting a sensor sensing voltage and a sensor compensating voltage, respectively;
And a noncontact sensing protector for shutting off power supplied to the fixing unit from the power supply unit when the sensor sensing voltage is higher than the sensor compensation voltage,
The noncontact sensing /
A first comparator receiving the sensor sensing voltage and the sensor compensation voltage and outputting a comparison result of the sensor sensing voltage and the sensor compensation voltage;
A second comparator to a fifth comparator each receiving a voltage value set to either an upper limit value or a lower limit value of any one of the sensor detection voltage and the sensor compensation voltage and the sensor detection voltage and the sensor compensation voltage,
Wherein the power supply unit cuts off power supplied from the power supply unit to the fusing unit when an error signal is output from any one of the first comparator to the fifth comparator. delete The method according to claim 1,
Further comprising a memory unit for storing a temperature characteristic table for the sensor sensing voltage and the sensor compensation voltage,
Wherein the noncontact sensing and protecting unit compares the sensor sensing voltage output from the noncontact sensing unit and the sensor compensation voltage with the temperature characteristic table and if at least one of the sensor sensing voltage and the sensor sensing voltage output from the noncontact sensing unit matches the temperature characteristic stored in the memory unit And disconnects the power supplied from the power supply unit to the fixing unit when it is out of the range of the table. delete The method according to claim 1,
Wherein the second comparator receives an upper limit value of the output sensor compensation voltage and the set sensor compensation voltage and outputs an error signal when the output sensor compensation voltage is greater than the upper limit value,
Wherein the third comparator receives an output of the sensor compensation voltage and a lower limit value of the set sensor compensation voltage and outputs an error signal when the output sensor compensation voltage is less than the lower limit value,
Wherein the fourth comparator receives an upper limit value of the output sensor sensing voltage and the set sensing sensing voltage and outputs an error signal when the output sensing sensing voltage is greater than the upper limit value,
Wherein the fifth comparator receives an output of the sensor sensing voltage and a lower limit of the sensed sensing voltage, and outputs an error signal when the sensed sensing voltage is less than the lower limit. The method according to any one of claims 1, 3, and 5,
Further comprising a control unit for receiving a signal from the non-contact sensing and protecting unit and controlling the operation of the fixing unit. The method according to any one of claims 1, 3, and 5,
A contact sensing unit sensing the temperature of the fixing unit by a contact method and outputting a contact sensing voltage;
Further comprising a contact detection protector for shutting off power supplied from the power supply to the fixing unit when the contact detection voltage is greater than a predetermined reference voltage. 8. The method of claim 7,
Wherein the contact detection protector includes a sixth comparator that receives the contact sense voltage and the reference voltage and outputs a result of comparing the input contact sense voltage with a reference voltage. 8. The method of claim 7,
Further comprising a control unit for receiving a signal from the non-contact sensing protector and the contact sensing protector, and controlling an operation of the fixing unit,
Wherein the control unit controls to stop the operation of the fixing unit by an output signal of at least one of the non-contact detection protection unit and the contact detection protection unit. A fusing unit control method for an image forming apparatus including an image forming unit for forming an image, a fusing unit for fusing the image transferred to the printing medium, and a power supply unit for supplying operation power,
Detecting a temperature of the fixing unit by a non-contact method, and outputting a sensor sensing voltage and a sensor compensating voltage;
Comparing the sensor sensing voltage with a sensor compensation voltage;
And disconnecting the power supplied from the power supply unit to the fixing unit when the sensor sensing voltage is higher than the sensor compensation voltage,
Wherein the image forming apparatus further comprises a noncontact sensing protector for shutting off power supplied to the fixing unit from the power supply unit when the sensor sensing voltage is higher than the sensor compensation voltage,
The noncontact sensing and protecting unit includes a first comparator that receives the sensor sensing voltage and the sensor compensation voltage and outputs a comparison result of the sensor sensing voltage and the sensor compensation voltage, And a second comparator to a fifth comparator receiving a voltage value set to either the upper limit value or the lower limit value of any one of the sensor detection voltage and the sensor compensation voltage,
Wherein the step of interrupting the power supply cuts off the power supplied from the power supply unit to the fusing unit when an error signal is output from any one of the first comparator to the fifth comparator. Way. 11. The method of claim 10,
Wherein the image forming apparatus further comprises a memory unit for storing a temperature characteristic table for the sensor sensing voltage and the sensor compensation voltage,
Further comprising the step of comparing the sensor sensing voltage and the sensor compensation voltage with the temperature characteristic table,
The step of shutting off the power supply may include cutting off power supplied from the power supply unit to the fusing unit when at least one of the output of the sensor detection voltage and the sensor compensation voltage is out of the range of the temperature characteristic table stored in the memory unit Wherein the image forming apparatus further comprises: delete 12. The method of claim 11,
Comparing the sensor sense voltage and the sensor sense voltage,
Comparing the output voltage of the sensor with an upper limit value of the set sensor compensation voltage and outputting an error signal when the output voltage of the sensor is greater than the upper limit value;
A second step of comparing the output sensor compensation voltage with a lower limit value of the set sensor compensation voltage and outputting an error signal when the output sensor compensation voltage is smaller than the lower limit value;
A third step of comparing the output voltage of the sensor with an upper limit value of the set sensor sense voltage and outputting an error signal when the output sensed voltage is greater than the upper limit value;
And a fourth step of comparing the output voltage of the sensor with a lower limit value of the set sensor sense voltage and outputting an error signal when the output sensed voltage is lower than the lower limit value Sub control method. 14. The method of claim 13,
The method of claim 1,
Wherein when the error signal is output in any one of the first to fourth steps, the power supplied from the power supply unit to the fixing unit is cut off. The method according to any one of claims 10, 11, 13, and 14,
Further comprising the step of outputting a control signal for stopping the operation of the fusing unit when the sensor detection voltage is higher than the sensor compensation voltage as a result of the comparison. The method according to any one of claims 10, 11, 13, and 14,
Detecting a temperature of the fixing unit by a contact method and outputting a contact sensing voltage;
Comparing the contact sensing voltage with a predetermined reference voltage;
Further comprising the step of, when the comparison result indicates that the contact detection voltage is greater than the reference voltage, disconnecting the power supplied from the power supply unit to the fixing unit. 17. The method of claim 16,
Further comprising the step of outputting a control signal for stopping the operation of the fusing unit when the contact detection voltage is greater than the reference voltage as a result of the comparison.

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