JPH04371985A - Temperature control over fixing unit of electrophotographic printer - Google Patents

Abstract

PURPOSE:To provide temperature control over the fixing unit which can holds the temperature in the machine in a normal state without lowering the temperature of a heat roller at the start of printing even right after the power source is turned on and a warm-up ends. CONSTITUTION:The heat roller fixing unit of the electrophotographic printer has the heat roller 11 and a thermistor 15 which detects its surface temperature and performs fixing operation while holding the surface temperature of the heat roller 11 within a certain temperature range. After the printer is powered ON, the fixing operation of the fixing unit is inhibited and the surface temperature of the heat roller 11 is raised up to the upper-limit of a temperature range higher than normal fixation temperature. Then the fixing operation of the fixing unit is allowed and the surface temperature of the heat roller 11 is held within the temperature range higher than the normal fixation temperature for a specific time. The surface temperature of the heat roller 11 is held within the normal temperature range the specific time later.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] This invention relates to a fixing device used in an image forming apparatus using electrophotography, and more specifically, the present invention relates to a fixing device used in an image forming apparatus using electrophotography. Regarding control.

0002

2. Description of the Related Art Conventionally, electronic copying machines, laser beam printers, and the like have been known as image forming apparatuses that utilize so-called electrophotography. In electrophotography, a photoreceptor on the surface of a uniformly charged photoreceptor drum is first exposed to light based on image information to form a latent image, and toner is attached to the latent image to form a toner image (development). . Next, this toner image is transferred to recording paper and then fixed by a fixing device. As the fixing device described above, a so-called heat roll fixing device is generally used, which uses a heated roller (heat roller) to heat and press a toner image to fix it on a recording paper.

[0003] The heat roll fixing device has a heat roller that is heated to a predetermined temperature by inserting a heating element such as a halogen lamp inside the cylindrical roller. A pair of fixing rollers is constructed by placing press rollers made of a material having This applies pressure to fix the toner on the recording paper. This heat roll fixing device has the advantage of high thermal efficiency and high speed fixing operation.

FIG. 5 is a diagram schematically showing a pair of fixing rollers configured as described above and a drive circuit for maintaining the temperature of the heat roller at a predetermined value. The fixing roller pair 10 is composed of a heat roller 11 and a press roller 12, and a halogen lamp 11A as a heating element is inserted inside the heat roller 11.

The halogen lamp 11A is driven by an AC power source 13 to generate heat, and a thyristor 14 as a switching element is inserted into its drive circuit. Further, a thermistor 15 as a temperature detection element is arranged in contact with the surface of the heat roller. heat roller 11
When the surface temperature of the thermistor 15 changes, the resistance value of the thermistor 15 changes, so that the temperature can be detected. The data obtained by the thermistor 15 is sent to the CPU 16. Based on the data from the thermistor 15, the CPU 16 determines whether or not to energize the halogen lamp 11A, and turns the thyristor 14 ON/OFF via the gate terminal of the thyristor 14. That is, the temperature is kept constant by controlling the energization of the halogen lamp 11A based on the temperature of the surface of the heat roller 11 detected by the thermistor 15.

[0006]

[Problems to be Solved by the Invention] However, in an image forming apparatus using a pair of fixing rollers configured as described above, if a printing request is made immediately after the apparatus is turned on and warm-up is completed, the press roller The temperature of the entire fuser unit, including the fuser unit, has not risen sufficiently.
There has been a problem in that when printing is started and the pair of fixing rollers are brought into pressure contact, the temperature of the heat roller drops, resulting in poor toner fixing performance.

[N]Alternatively, even if the pair of fixing rollers are pressed together and the temperature of the press roller at the pressure contact point has risen sufficiently,
If the temperature of the surface of the press roller other than the pressure contact area has not increased, the temperature of the heat roller will decrease when the pair of fixing rollers starts rotating, which may also result in poor toner fixing performance.

However, if the control temperature of the fixing device is increased to prevent this, not only does power consumption increase, toner may adhere to the heat roll, and the temperature inside the machine increases, causing damage to the members constituting the fixing device. This may cause problems such as deformation due to heat, which may adversely affect image quality.
Measures such as installing a cooling fan are required to lower the temperature inside the aircraft.

[0008] In view of the above-mentioned circumstances, the present invention is designed to prevent the temperature of the heat roller from dropping at the start of printing even immediately after the power is turned on and the warming-up is completed, and to maintain the internal temperature at the normal state after the start of printing. The purpose is to provide temperature control of the fuser that is possible.

[Means for Solving the Problem] Therefore, in the present invention, there is provided a detection means for detecting the temperature of the heat roller and the surface of the heat roller.
In the heat roller fixing device of an electrophotographic printer, which performs the fixing action by maintaining the temperature within a predetermined temperature range, first, after turning on the power of the printer, the fixing action by the fixing device is prohibited, and the surface temperature of the heat roller is a second heat roller whose surface temperature is higher than the first predetermined temperature range;
The fixing device is allowed to perform the fixing action from the time when the temperature reaches the upper limit of the second predetermined temperature range, the surface temperature of the heat roller is maintained within the second predetermined temperature range for a predetermined time, and after the predetermined time elapses, The surface temperature of the heat roller is maintained within the first predetermined temperature range. Furthermore, the fixing device includes a heat roller and a heater means for increasing the temperature of the heat roller, and the surface temperature of the heat roller is adjusted to maintain the surface temperature of the heat roller within the second predetermined temperature range. is above the upper limit of the second predetermined temperature range, the heater means is turned off, and when the surface temperature of the heat roller is below the lower limit of the second predetermined temperature range, the heater means is turned on; Further, in order to maintain the surface temperature of the heat roller within the first predetermined temperature range, the heater means is turned off when the surface temperature of the heat roller exceeds the upper limit of the first predetermined temperature range.
The heater means is turned on when the surface temperature of the heat roller falls below the lower limit of the first predetermined temperature range.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a control section for controlling the temperature of a fixing device according to the present invention. The temperature data detected by the thermistor 15 as temperature detection means is A/D.
It is converted and input to CPU1. The drive circuit 2 is driven based on the A/D converted temperature data, and the halogen lamp 11A is turned on/off. Note that the timer 3 is a timer for measuring the time interval of the high temperature setting section, which will be described later.

FIG. 2 is a flowchart showing the printing process of an electrophotographic printer to which the fixing device temperature control of the present invention is applied. Step S1 (hereinafter simply S1, S2...
), the CPU is initialized, a memory test, variable initialization, etc. are performed. Here, initial values 0 and 1 are set to a heater READY flag and a heater high temperature setting flag, which will be described later, respectively. In S2, a self-check of the printer mechanism is performed, and if the check is completed normally, warming up of the heater is started. When the warm-up of the heater is completed, the process moves from S3 to S4 and waits until there is a printing request, and when there is a printing request, printing is started in S5.

FIG. 3 is a flowchart illustrating temperature control of the fixing device according to the present invention. This process is executed as an interrupt process at predetermined time intervals (for example, every 200 ms). This interrupt processing becomes interruptible when the processing of S2 in FIG. 2 is completed and heater warming-up is started. When this interrupt process is executed for the first time after the power is turned on, the initial value of the heater READY flag is 0, so S1
The process advances from 0 to S20. At S24, the heater is turned on and the interrupt processing is exited. In the subsequent interrupt processing, the temperature data detected by the thermistor 15 is
Until the temperature exceeds 0 degrees, the interrupt processing is exited through steps S10, S20, and S24. When the temperature data exceeds 200 degrees, the heater READY flag is set to 1, 60 second timer 3 is started, and the heater is temporarily turned off.
F (S21 to S23).

Next, interrupt processing after the heater READY flag is turned ON will be explained. Since the initial value of the heater high temperature setting flag is 1, in S12 to S15, ON/OFF of the heater is controlled so that the temperature data is 190 degrees or more and 200 degrees or less. This process is performed every time the interrupt process is executed until the timer 3 started in S22 times out. When the 60 second timer 3 times out, the heater high temperature setting flag is set to 0.
is set. From this point on, interrupt processing is performed in S10.
, S11, S30 to S33, and is a normal temperature control routine in which ON/OFF of the heater is controlled so that the temperature data is 180 degrees or more and 190 degrees or less.

[0013] With the above control, after turning on the power, 20
The temperature of the heat roller surface is increased until it exceeds 0 degrees. After that, the temperature is controlled within the range of 190 degrees to 200 degrees for 60 seconds.

FIG. 4 is a graph showing the temperature of the heat roller under the above control. In the conventional control method, as shown by the broken line, the temperature control is performed in the same way as during normal printing even when the press roller etc. have not warmed up immediately after the power is turned on, so the area shown as the high temperature setting section in the figure When printing starts, the temperature of the heat roller surface drops. On the other hand, according to the temperature control of the present invention, as shown by the solid line in the figure, the temperature is maintained higher than the normal control temperature within the high temperature setting section, so even if printing is started in this section, The toner fixability does not deteriorate due to a decrease in the temperature of the heat roller.

[0015]

As described above, according to the temperature control method for an electrophotographic printer of the present invention, immediately after the printer is turned on, when the temperature of the entire fixing device including the press roller has not risen sufficiently, Even when the fixing action starts and the heat roller and press roller come into contact and the heat roller is deprived of heat, the temperature of the heat roller is set in advance to be maintained higher than the normal fixing temperature. The surface of the heat roller has a temperature at which it can perform a good fixing action, and problems such as deterioration in toner fixing performance can be prevented. In addition, even if the fuser roller pair is in pressure contact and the temperature of the press roller at the pressure contact point has risen sufficiently, if the temperature of the press roller surface other than the pressure contact point has not risen, the fuser roller pair The temperature of the heat roller will drop when it starts rotating, but even in this case, by setting the control temperature of the heat roller higher than usual when the fixing roller starts rotating from a stopped state, the same problem as above can be achieved. It is possible to prevent problems caused by a drop in the temperature of the heat roller. Furthermore, the heat roller's high temperature setting period is limited to a predetermined period of time after the heat roller's surface temperature reaches the upper limit of the predetermined temperature range. It does not cause problems in image formation or deformation of the components of the fixing device due to overheating.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a control unit that controls the temperature of a fixing device according to the present invention.

FIG. 2 is a flowchart showing the printing process of an electrophotographic printer to which the temperature control of the fixing device of the present invention is applied.

FIG. 3 is a flowchart illustrating temperature control interrupt processing according to the present invention.

[Fig. 4] Graph showing the temperature of the heat roller according to the temperature control of the present invention.

FIG. 5 is a diagram schematically showing a pair of fixing rollers and a drive circuit for keeping the temperature of the heat roller at a predetermined value.

[Explanation of symbols]

1 CPU 2 Drive circuit 3. Timer 15 Thermistor

Claims (2)

[Claims] 1. An electronic device comprising a heat roller and a detection means for detecting a surface temperature of the heat roller, and performs a fixing action by maintaining the surface temperature of the heat roller within a first predetermined temperature range. In the heat roller fixing device of a photo printer, (1) after the power of the printer is turned on, (a) the fixing action by the fixing device is prohibited, and (b)
) increasing the surface temperature of the heat roller; (2) from the time when the surface temperature of the heat roller reaches the upper limit of a second predetermined temperature range higher than the first predetermined temperature range; (a) fixing by the fixing device; (b) maintaining the surface temperature of the heat roller within the second predetermined temperature range for a predetermined period of time; (3) after the elapse of the predetermined time, the surface temperature of the heat roller is 1. Temperature control of a fixing device in an electrophotographic printer characterized by maintaining the temperature within a predetermined temperature range. 2. The fixing device includes heater means for increasing the temperature of the heat roller, (1) in order to maintain the surface temperature of the heat roller within the second predetermined temperature range; a) when the surface temperature of the heat roller exceeds the upper limit of the second predetermined temperature range, the heater means is turned off; and (b) when the surface temperature of the heat roller exceeds the lower limit of the second predetermined temperature range. (2) In order to maintain the surface temperature of the heat roller within the first predetermined temperature range, (a) the surface temperature of the heat roller is kept within the first predetermined temperature range; (b) when the temperature exceeds the upper limit of the temperature range, the heater means is turned off; and (b) when the surface temperature of the heat roller falls below the lower limit of the first predetermined temperature range, the heater means is turned on. The temperature control method according to claim 1.