JPH0556508B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to a temperature control monitoring device that monitors abnormalities in temperature control by a temperature detector of a heat roller such as a fixing roller.

<Prior art and its drawbacks> A fixing device installed in an electrostatic printing device such as a copying machine (hereinafter simply referred to as a copying machine) transfers a sheet of paper onto which a toner image has been transferred between a heated fixing roller and a pressure roller. This is a device that melts and presses the toner by passing it through the toner. When a copying machine is used, the fixing roller is heated to around 220°C and the pressure roller is heated to around 200°C. This temperature control is normally performed by turning on and off the current to the heater based on the detected value of a temperature sensor such as a thermistor installed inside the roller.

However, if there is an abnormality in the temperature detection part such as the temperature sensor and the heater remains on, the heat roller will overheat and the toner image will not be fixed properly, and there is a risk of damage to the entire copying machine. be. To prevent this risk, a temperature control monitoring device has been proposed that measures the continuous on time of the heater while the copying machine is in operation, and turns off the heater when this timer times up, regardless of the temperature detected by the temperature sensor. (Special Publication No. 58-55504, etc.) It has been put into practical use.

In such a temperature control monitoring device, the conventional device monitors temperature control when the copying machine is in a usable state. However, the reality is that copiers installed in general offices, etc. spend more time on standby when not in use than when they are in use. Nowadays, power-saving copying machines equipped with a power-down mode that sets the temperature to a low temperature and shuts down the copying machine are becoming popular, but the device that monitors the temperature control when the copying machine is ready for use does not have the above-mentioned danger prevention measures. It was insufficient for that purpose. Furthermore, since the set temperature of the heat roller when the copying machine is ready for use is set to a high temperature, the time that the heater is on is inevitably extended. Therefore, the timer's time-up time must be set long, and if there is an abnormality in the temperature control, by the time the abnormality is detected and the heater is turned off, the heat roller has reached a fairly high temperature, and various parts of the copier have already reached a high temperature. In many cases, damage was caused to the

<Object of the Invention> In view of the above-mentioned drawbacks, it is an object of the present invention to provide a temperature control monitoring device for monitoring temperature control of a heat roller when a copying machine is at rest.

<Structure and Effects of the Invention> The heat roller temperature control and monitoring device of the present invention is installed in a fixing device and controls a heat roller having a heater to a first set temperature at which a toner image can be fixed; , in a heat roller temperature control device that controls in a power down mode to control to a second set temperature lower than the fixing temperature, the heater is maintained at the first set temperature during control in the normal mode. a first timer that times up when a first predetermined time preset as a continuous on time is counted; and a first timer that is preset as a time shorter than the first predetermined time during control in the power down mode. the second
The heater is characterized by comprising: a second timer that times up when a predetermined time is counted; and heater-off means that forcibly turns off the heater when either the first or second timer times up. .

According to the present invention, with the above configuration, when the first and second timers measure the set time in each control of the normal mode and power down mode, it is determined that an abnormality has occurred in the temperature control by the temperature sensor or the like. It is possible to judge and forcibly turn off the heater. In power down mode, the control temperature of the heater is lower than in normal mode, so the continuous on time for proper control is different in both modes. The set time is set to the continuous on time necessary for proper heat retention temperature in normal mode, and the second set time measured by the second timer used in power down mode control is the same as the first set time above. It has been for a shorter time. As a result, in any mode, the heater is forcibly turned off when the continuous on time required to achieve the appropriate heat retention temperature has been exceeded, and the copier is always turned off regardless of the control mode in progress. This has the advantage of preventing overheating accidents.

In addition, normal mode control is executed during the copy machine's usage time, power down mode control is executed during the copy machine's down time, and under normal usage conditions, the Although the second timer measures a shorter time than the first timer used in the normal mode, an abnormality in temperature control is detected, so there is an advantage that the occurrence of an abnormality can be dealt with quickly.

<Embodiment> FIG. 2 is a block diagram of a control section of a copying machine equipped with a heat roller temperature control and monitoring device according to an embodiment of the present invention. Microcomputer 1 is
It consists of CPU, RAM, ROM, etc. ROM
Programs etc. are stored in the . The first part of the present invention is stored in the RAM to measure the time during which the heater is continuously turned on when the fixing roller is controlled to a temperature (first set temperature) at which the toner image can be fixed.
An area for storing the time-up time of a normal mode trouble timer (hereinafter referred to as N timer), which is a timer of An area for storing the time-up time of a power down mode trouble timer (hereinafter referred to as P timer), which is the second timer of the present invention, which measures the time during which the heater is continuously turned on when the heater is controlled to It is set. Each load 2, an operation section 3, each sensor 4, and a temperature detector 5 are connected to this microcomputer 1. load 2
includes the heater lamp of the fixing device. The operation section 3 includes a key switch on an operation panel.
The N timer and P timer are both subtraction timers, and are timers that subtract the elapsed time from the set time-up time and time up when the time reaches 0.

The temperature detector 5 is supplied with a DC voltage VD. This DC voltage is connected to the thermistor Th and resistor R1,
The voltage is divided by resistor R2 and resistor R3, and by resistor R4 and resistor R5. The divided voltages are respectively detected voltage Va, high temperature reference voltage V1, and low temperature reference voltage V.
Call it 2. The thermistor Th is installed inside the heat roller (fixing roller) of the fixing device. The detection voltage Va is the DC voltage VD from the positive side to the thermistor Th,
Since the voltage is divided by the resistor R1, the potential increases as the temperature detected by the thermistor Th increases and the internal resistance decreases. The high temperature reference voltage V1 is set to be equal to the detection voltage Va when thermistor Th detects 220°C, and the low temperature reference voltage V2 is set equal to the detection voltage Va when thermistor Th detects 150°C. It is set to be. The high temperature reference voltage V1 and the low temperature reference voltage V2 are provided by comparators OP1 and OP, which are operational amplifiers, respectively.
2 non-inverting input terminals, and the comparators
Detection voltage is applied to both the inverting input terminals of OP1 and OP2.
Va is entered. The signal outputs (WTLH, WTLL) of the comparators OP1 and OP2 are input to the microcomputer 1. WTLH is "H" when the temperature of the fixing roller is 200 degrees Celsius or less, and WTLL is "H" when the temperature of the fixing roller is 150 degrees Celsius or less. This temperature detector 5 and microcomputer 1 constitute a temperature control device.

FIG. 1 is a flowchart showing a temperature control monitoring subroutine during operation of the control section of the copying machine. When the main program calls this subroutine, it first determines at step n1 (hereinafter, step ni will be simply referred to as ni) whether the copier is ready for copying (nord mode) or is at rest (power down mode). When in power down mode, proceed to n2. At n2, the N timer that operates in normal mode is reset to stop its operation. At n3, judge the signal output WTLL of the temperature sensor 5 and set it to “L”.
If so, the temperature of the fixing roller is higher than the set temperature, so a time-up time is set in the P timer that starts when the heater lamp is turned on (n6), and the heater lamp is turned off (n8). If WTLL is "H", the process advances to n4 and determines whether the P timer has timed up. If the P timer has not timed up, the WTLL "H" is considered to be a normal heater lamp ON signal and the heater lamp is turned on (n5). If the P timer times up in n4, WTLL becomes “H”
It is assumed that the output is due to an abnormal operation of the temperature detection section 5, and a message indicating that an abnormality has occurred in the heat roller is displayed at n7, and the heater lamp is turned off (n8).

When it is determined in n1 that the normal mode is set, the operation is exactly the same as the operation when setting the power down mode described above. n9 resets the P timer that operates in power-down mode to stop its operation, and n10 outputs the signal of temperature detector 5.
Judging WTLH. If it is "L", the temperature of the fixing roller is higher than the set temperature, so a time-up time is set in the N timer that starts when the heater lamp is turned on (n12), and the heater lamp is turned off (n8).
If WTLH is "H", the process advances to n11 to determine whether the N timer has timed up. If the N timer has not timed up, the "H" of WTLH is considered to be a normal heater lamp ON signal, and the heater lamp is turned on (n5). If the N timer has timed up at n11, the WTLH "H" is output due to an abnormal operation of the temperature detection unit 5, and at n7 a message indicating that an abnormality has occurred in the heat roller is displayed and the heater lamp is turned on. Turn off (n8). n4 and n8 correspond to the heater-off means of the present invention.

As described above, in the copying machine equipped with the heat roller temperature control monitoring device according to the embodiment of the present invention, temperature control is performed when the fixing roller is kept warm in a copyable state (normal mode) when the copying machine is powered on. In addition to detecting temperature control abnormalities in the device, it is also possible to detect temperature control abnormalities during power down mode, which is set for a longer period of time than normal mode under normal usage conditions. It is possible to prevent heating accidents, and the set temperature can be lower than when the normal mode is set, and the timer time-up time can also be shortened. Therefore, it is possible to deal with abnormalities in temperature control during low temperature control. Further, since temperature control abnormalities can be detected even when the power down mode is set, it is often possible to detect and deal with them early.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing the operation of a control section of a copying machine equipped with a heat roller temperature control abnormality monitoring device according to an embodiment of the present invention, and FIG. 2 is a block diagram of the control section of the copying machine. 1...Microcomputer, 5...Temperature detector.

Claims (1)

[Claims] 1. A normal mode in which a heat roller installed in a fixing device and having a heater is controlled to a first set temperature at which a toner image can be fixed, or a second set temperature lower than the fixable temperature. In the temperature control device for a heat roller that is controlled in a power down mode, the first temperature control device is configured such that a first continuous on time is preset as a continuous on time for maintaining the heater at the first set temperature during control in the normal mode. a first timer that times up when a predetermined time is counted;
A second timer that times up when a second predetermined time that is preset as a shorter time than the first predetermined time is counted during control in the power down mode, and which one of the first and second timers A temperature control and monitoring device for a heat roller, comprising: a heater-off means for forcibly turning off the heater when the heater times out.