JP3158866B2 - Cooling system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus having a fixing device of this kind in a device, the temperature of the fixing device is controlled to a predetermined temperature at which a fixing operation can be performed by energizing a heater when performing a fixing operation. The inside of the apparatus is cooled by driving a cooling fan or the like so that the inside of the apparatus does not become higher than a predetermined temperature due to heat generation. However, maintaining the fixing device at the predetermined temperature during a standby state in which the fixing operation is not performed for a predetermined time or more not only wastes power but also significantly increases the temperature in the apparatus. During the standby state, the temperature of the fixing device is set low. Therefore, there is no need to continuously operate the cooling fan.

In consideration of the above points, the power supply to the heater of the fixing device is turned off in a standby state in which image formation is not performed for a predetermined time or more, and then cooling is performed when image formation is not performed for a predetermined time or more. A device that stops the operation of a fan is known (for example, Japanese Patent Publication No. 62-264).
No. 66). According to such a method, there is no unnecessary power consumption during standby, and the temperature inside the apparatus can be prevented from remarkably increasing.

[0004]

However, in the system disclosed in the above-mentioned publication, in which the cooling fan is turned off for a predetermined time after the power supply to the fixing device heater is turned off (a system in which only the time is turned off), the heater is turned off when the heater is turned off. Depending on the state and environment, there is a problem that the temperature inside the apparatus when the cooling fan is turned off cannot be kept constant and changes when the fan is wasted or stopped too quickly. In addition, if the cooling fan is turned off at a predetermined temperature by a method different from the above, it is necessary to detect the temperature, and the number of detection points in the temperature detection circuit increases accordingly, resulting in an increase in cost. I was The present invention has been made to solve the above-mentioned problem, and there is no needless power consumption during standby, and it is possible to suppress a rise in the temperature inside the machine, and to stop the cooling fan at a target temperature at a small number of temperature detection points. It is an object of the present invention to provide a cooling device which can reduce the cost, and does not fluctuate the internal temperature of the apparatus or the temperature of the fixing unit during standby depending on the state of the heat load of the fixing unit or the environment.

[0005]

According to a first aspect of the present invention, there is provided a cooling device for detecting a temperature of a heat load such as a fixing device or a peripheral temperature thereof which is controlled to be heated by energization control. Temperature control means for controlling the temperature of the heat load based on the temperature detected by the temperature detection means, and a cooling fan driven and controlled by the temperature control means for cooling the temperature around the heat load. A cooling device, wherein the temperature control means includes: a temperature determination means for determining whether a temperature detected by the temperature detection means has become equal to or lower than a predetermined value when power supply to the heat load is turned off; Time lapse determining means for determining whether a predetermined time has elapsed since the determination was made below, and driving of the cooling fan is stopped when the time lapse determining means determines that the predetermined time has elapsed. And a fan drive control means for,
The predetermined value determined by the temperature determination unit is determined by the heat load.
The temperature in standby mode or the heat load is operating normally
It is an error check temperature for checking whether or not it is.

Furthermore, the invention of claim 2, in the cooling apparatus according to claim 1, wherein said temperature detecting means and the temperature sensitive resistive element, with the temperature sensitive resistive element in series, and connected in parallel with each other A plurality of resistors, switching elements connected in series to the resistors, conduction selection control means for selectively controlling conduction of the switching elements, and a potential at a connection point between the temperature-sensitive resistance element and the resistance as a temperature detection signal. And a comparison means for comparing this potential with a reference voltage, and the detection temperature is switched by selecting conduction of the switching element by the conduction selection control means.

[0007]

According to the cooling device of the first aspect, the temperature of the heat load or the surrounding temperature is detected by the temperature detecting means, and the temperature of the heat load is detected by the temperature control means based on the detected temperature. The driving of the cooling fan for controlling the temperature around the thermal load is controlled. The temperature determination means in the temperature control means determines whether or not the detected temperature in the power-off state to the heat load has become equal to or lower than a predetermined temperature, and further, a predetermined time has elapsed since the detected temperature became equal to or lower than the predetermined temperature. It is determined by the time elapse determining means that the cooling fan has been driven by the fan drive control means when the predetermined time has elapsed. As the detected temperature in the power-off state to the heat load, the existing temperature detection point is a temperature for controlling the heat load to a standby state or a temperature for checking whether the heat load is operating normally. Used. With such control, the temperature detection point
Without increasing the heat load temperature or its surrounding temperature
To stop the cooling fan operation at almost constant temperature
Will be able to The switching of the detected temperature can be performed by the conduction selection control means selecting conduction of the switching element (corresponding to claim 2 ) .

[0008]

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

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

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

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

The switching of the detected temperature of the sensor circuit 20 can be performed as follows. Set ports 1 and 2 to “H”,
When “H” is set and the transistors Q2 and Q3 are turned on,
Since a parallel circuit of resistors R1, R2, and R3 is connected to the thermistor 13 and the divided potential drops, the temperature detected by the thermistor 13 is high, for example, a "print temperature" of 150.degree.
Becomes When the ports 1 and 2 are set to “H” and “L”, respectively, and the transistor Q2 is turned on, the resistance R
The parallel circuits 1 and R2 are connected, and the detected temperature level becomes low, for example, a "standby temperature" of 130C. Further, the ports 1 and 2 are set to “L” and “H”, respectively,
When the switch 3 is turned on, a parallel circuit of the resistors R1 and R3 is connected to the thermistor 13, and the detected temperature level further lowers, for example, to the “error check temperature” of 120 ° C.
Further, when the ports 1 and 2 are set to “L” and “L”, respectively, only the resistor R1 is connected to the thermistor 13, and the detected temperature level is low, for example, the “error check temperature” of 40 ° C. The “error check temperature” is a temperature at which the control circuit checks whether the fixing device or the device is operating normally.

The operation of the sensor circuit 20 at the "print temperature" will be described. If the temperature of the fixing device 5 is lower than the set value, the resistance value of the thermistor 13 is larger than the resistance value at the set temperature. The partial pressure between the resistors R1, R2 and R3 decreases. Since the resistors R1, R2, and R3 are selected so that the partial pressure becomes 2.5 V at the set temperature, the partial pressure value becomes 2.
5 V or less. Accordingly, the output of the comparator 21 becomes “H”, and unless it is forcibly turned off by the driver substrate 9, the heater of the fixing device 5, that is, the halogen lamp 5
c turns on and is heated to the set temperature. The above-mentioned detection temperatures can be arbitrarily set by selecting the resistance value, and the error check temperature and the like are not limited to the above-mentioned temperatures. In addition, since the temperature detection circuit is configured using the comparator and the resistor, the cost can be reduced as compared with a case where an expensive analog-digital converter or the like is used.

Next, the drive control of the cooling fan 18 in the laser printer having the above configuration will be described with reference to FIG. The driver board 9 controls the driving of the cooling fan 18 so that the temperature inside the apparatus does not rise significantly. When the power supply to the fixing device 5 is turned off, the internal temperature of the apparatus becomes a predetermined temperature, for example, 10
When the temperature is predicted to be 0 ° C. or lower, the driving of the cooling fan 18 is stopped in order to reduce noise and save energy. The details are described below. Note that the driver board 9 has a timer function, and can determine whether a predetermined time has elapsed.

First, the driver board 9 checks whether the power supply to the fixing device 5 is off (# 1). If the power supply is not off (NO in # 1), the cooling fan 18 is rotated (# 1).
2). When the power supply to the fixing device 5 is turned off (# 1)
Then, based on the temperature detection signal from the comparator 21 of the temperature detection circuit having the above configuration, it is determined whether or not the detected temperature has fallen below a predetermined value, for example, an “error check temperature” of 120 ° C. ( # 3), detection temperature is 120 ° C
If not below (NO in # 3), cooling fan 1
8 is kept rotated (# 2). Detection temperature is 120
° C or less (YES in # 3), it is then determined whether a predetermined time, for example, 2 minutes, has elapsed (# 4), and until the 2 minutes have elapsed (NO in # 4), the cooling fan 18 Although it is kept rotating (# 2), when 2 minutes have passed (Y in # 4)
ES), the driving of the cooling fan 18 is stopped (# 5).

The reason why the predetermined time is set to 2 minutes is as follows.
It is based on the prediction that the temperature will be around 100 ° C. if about 2 minutes have passed since the temperature fell below 20 ° C. In the above description, the drive of the cooling fan 18 is stopped at the time when the temperature in the apparatus is assumed to be about 100 ° C.
The existing “error check temperature” of 120 ° C., which is closest to 00 ° C., is used. If the “error check temperature” is, for example, 90 ° C., the “error check temperature” cannot be used. , 100 ° C., an existing temperature that is closest to 100 ° C., for example a “standby temperature” of 130 ° C., in which case the time lapse may be longer than the above two minutes.

As in the present embodiment, the rotation of the cooling fan is stopped after a predetermined time has elapsed since the temperature has been reached by using the existing detected temperature point, so that a new temperature detection circuit is provided. There is no need to set a temperature detection point, which is advantageous for an inexpensive temperature detection circuit using the comparator 21. In addition, by controlling not only the time but also the combination of the temperature and the time, the cooling fan 18 can be stopped at a temperature as close as possible to the target temperature.

The present invention is not limited to the configuration of the above-described embodiment, and various modifications are possible. For example, the combination of the predetermined temperature and the predetermined time to be determined is adjusted to the configuration of the temperature detection circuit and the cooling fan is stopped. What is necessary is just to set suitably according to the temperature to be made. Further, the heat load may be other than the fixing device.

[0019]

As described above, according to the cooling device of the first aspect of the present invention, a predetermined time has elapsed since the detected temperature became equal to or lower than the predetermined value when the power supply to the heat load such as the fixing device was turned off. When the cooling fan is stopped, wasteful power consumption is eliminated, the temperature inside the device can be suppressed, and the temperature inside the machine or the temperature of the fixing unit during standby depends on the state of the heat load and the environment. The cooling fan can be stopped at the target temperature without any change. here,
By using the standby temperature of the thermal load or the temperature for checking whether the thermal load is operating normally as the predetermined temperature, the cost can be reduced without increasing the number of temperature detection points. According to the cooling device of the second aspect of the present invention, in addition to the above effects, the temperature is detected by comparing the potential of the connection point between the temperature-sensitive resistance element and the resistor with the reference voltage, and the temperature is detected by selecting conduction of the switching element. Since the temperature is switched, the cost is lower than that of a conventional temperature detection circuit using an A / D converter.

[Brief description of the drawings]

FIG. 1 is a block diagram of a laser printer equipped with a cooling device according to one embodiment of the present invention.

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

FIG. 3 is a flowchart of a driving stop process of a cooling fan.

[Explanation of symbols]

 Reference Signs List 5 Fixing device 5a Heat roller 9 Driver substrate 10 Low voltage power supply 13 Temperature detection sensor 18 Cooling fan 20 Sensor circuit 21 Comparator R1, R2, R3 Resistance Q2, Q3 Transistor

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G03G 13/20 G03G 15/00 303 G03G 15/20 G03G 21/00 370-502 G03G 21/14

Claims (2)

(57) [Claims] A temperature detecting means for detecting a temperature of a heat load such as a fixing device or a temperature around the heat load which is controlled to be heated by an energization control; and detecting the temperature of the heat load based on the temperature detected by the temperature detecting means. A cooling device comprising: a temperature control unit for controlling; and a cooling fan that is driven and controlled by the temperature control unit and cools a temperature around the heat load. Temperature determining means for determining whether a temperature detected by the temperature detecting means has become equal to or lower than a predetermined value; and determining whether a predetermined time has elapsed since the temperature determining means has determined that the detected temperature is equal to or lower than the predetermined temperature. Time elapse determining means, and fan drive control means for stopping driving of the cooling fan when the time elapse determining means determines that a predetermined time has elapsed. The predetermined value determined by the temperature determining means is the heat load.
The temperature at which the load is in standby or the thermal load is operating normally
A cooling device characterized in that the temperature is an error check temperature for checking whether the temperature is high or not . 2. The temperature detecting means includes: a temperature-sensitive resistance element;
A plurality of resistances connected in series with the temperature-sensitive resistance element and in parallel with each other, switching elements respectively connected in series to the resistances, and conduction selection control means for selectively controlling conduction of the switching elements; Comparing means for setting a potential at a connection point between the temperature-sensitive resistance element and the resistor as a temperature detection signal and comparing the potential with a reference voltage, and detecting conduction by selecting conduction of the switching element by the conduction selection control means. 2. The cooling device according to claim 1, wherein the temperature is switched.