JPH03221983A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent a fixing heater from excessive rise of the temp. and to reduce power consumption by controlling electric power in waiting and fixing so as to be lower than that at the time a driving power source is turned on and supplying the power the same as when the power source is turned on when the temp. is lowered during the fixing. CONSTITUTION:When the power source is turned on, a CPU 5 sends a signal to an AC phase control circuit 16, which energizes the heater 4 by a full wave AC, and the temp. of a fixing roller rises to a first set temp. When a thermister 13 detects that reaching the set temp. reaches the set temp., the energization to the heater 4 is switched to a half wave AC and the set temp. is maintained. When a printing signal is inputted during the waiting, the circuit 16 switches the energization to the heater 4 to the full wave AC again and the temp. of the fixing roller is raised to the set temp. When the rise of the temp. is detected, the energization is switched to the half wave AC again, which switching is repeated and the temp. required for the fixing is maintained. Thus, without excessive temp. rising during the waiting and fixing, the power consumption of the heater can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming apparatus such as a copying machine or a laser beam printer, which has a fixing means for heating and fixing an unfixed image using a heat generating member.

[Prior Art] An image forming apparatus, in particular, transfers a visible image formed by a Carlson electrophotographic process to a transfer material, and fixes the visible image to the transfer material to which the visible image has been transferred by a fixing means. In an electrophotographic copying apparatus that performs image formation, the fixing of the visible image to the transfer material is improved, the life of the fixing roller constituting the fixing means is extended, and the temperature inside the apparatus is increased. A number of measures have been taken to prevent this. For example,-”
(2) As temperature value data of the fixing roller constituting the fixing means, second temperature value data capable of fixing the image, that is, fixing temperature value data, and second temperature value data that is lower than the above fixing temperature value and that is a transfer material supplied to the above device. Between the time when the temperature reaches the 11th fixing means, the 11th temperature value data is set within a temperature range in which it is possible to rise to the 11th fixing temperature value. In the image forming process consisting of the Carlson electronic four-tool process, transfer process, etc., when the temperature of the fixing roller reaches the first temperature value, An example of this is one in which it is possible to start the rotational drive of the fixing roller. In such an image forming apparatus, the alternating current applied to the heater of the fixing roller is constantly applied to the fixing roller surface at the first set temperature immediately after the power is turned on, and then until the fixing temperature is reached and the transfer material is passed through. Full-wave continuous energization was used.

[Problem to be solved by the invention] However, in the above-mentioned conventional example, when sheets are passed continuously, the heat on the surface of the fixing roller becomes difficult to be absorbed by the outside, and the surface of the fixing roller exceeds the fixing temperature. There was a problem with it.

Therefore, in order to suppress the temperature ripple of the fixing roller during printing and prevent excessive temperature rise, the waveform of the alternating current applied to the heater is made half-wave, thereby lowering the heater power.
A method was proposed to eliminate sudden temperature changes. However, it has been found that according to this method, the fixing performance deteriorates due to insufficient power for the initial number of images after the driving power is turned on. This phenomenon was particularly noticeable in a low temperature environment of about 0°C to 20°C.

In other words, in the initial state after the drive power is turned on, the temperature of the pressure roller is at the shaded area far from the fixing roller or is low, close to room temperature, as shown in FIG. Since the temperature is low, close to room temperature, when the fixing device is driven and the transfer material is sent to the fixing device, the fixing roller loses heat to the pressure roller and the transfer material, and when the paper is not passing, the temperature shown in Figure 12 occurs. As shown, it takes longer to reach the fixing temperature than in the case of the ideal temperature rise curve shown by the broken line, and furthermore, if the transfer material is fed before the fixing temperature has been reached, As shown in FIG. 13, the temperature of the fixing roller dropped considerably as the paper passed through the paper, resulting in poor fixing.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that solves problem E, secures fixing performance in the initial state after power is turned on, and does not cause excessive temperature rise during continuous sheet feeding.

[Means for Solving the Problems] According to the present invention, the above object is to provide a fixing roller that has a heat generating member that generates heat by applying a voltage from a commercial power source and heats and fixes an unfixed image on a transfer material. In the image forming apparatus, the image forming apparatus includes: a temperature detection means for detecting the temperature of the fixing roller; and a phase control means for controlling the temperature of the fixing roller by controlling the phase of electric power from a commercial power source applied to the heat generating member. The phase control means maintains the temperature of the fixing roller during standby at a first set temperature which is a standby temperature set to a temperature lower by a predetermined value than the minimum fixing temperature necessary for fixing; Further, the temperature of the fixing σ-ra during fixing is set to be maintained between the above-mentioned minimum fixing temperature and a second set temperature which is higher than the above-mentioned minimum fixing temperature by a predetermined value. When the temperature is maintained between the minimum fixing temperature and the second set temperature, power is supplied to the L distribution member 8 less than the power when the power is turned on;
Further, when the temperature becomes lower than the minimum fixing temperature during fixing, the power is set to be supplied to the L heat distribution member at the time of power-on until at least the minimum fixing temperature is exceeded. distantly related to

[Function] The present invention adjusts the temperature of the fixing roller to the first standby temperature by applying a predetermined power to the heat generating member after the power is turned on.
Raise the temperature to the set temperature. When the first set temperature is reached, the power applied to the heat generating member is lower than the predetermined power to maintain the first set temperature without causing excessive temperature rise. Next, when a print signal is input during this standby, the predetermined power of 2 vS is applied to the heat generating section to raise the temperature from the minimum fixing temperature required for fixing to the second set temperature. When the temperature of the fixing roller reaches the above range, power less than the predetermined power is applied to the heat generating member to prevent excessive temperature rise and maintain the temperature within the above range.

However, if the initial state drops immediately after power is turned on,
Heat is taken away by the surrounding environment and the temperature of the fixing roller tends to drop gradually. Therefore, the present invention provides a system in which, when the temperature of the fixing roller becomes lower than the minimum fixing temperature during fixing, the power applied to the heat generating member is returned to the predetermined power after the power is turned on, so that the temperature exceeds at least the minimum fixing temperature. Raise the temperature. In this way, a predetermined temperature is maintained without excessive temperature rise during standby and fixing, and fixing performance is ensured in the initial state 43 after power is turned on.

[Embodiment] Next, a first embodiment to a sixth embodiment of the present invention will be described based on FIGS. 1 to 10 of the accompanying drawings. It should be noted that whether the image forming apparatus of this embodiment has an optical system, a conveyance system, a developing section, etc., the explanation of these will be omitted.
The fixing device of the present embodiment and its related control means will be explained below.

First, a first embodiment of the present invention will be described with reference to FIGS. 1 to 5.

FIG. 1 is a block diagram showing the fixing device l of this embodiment and the control means for controlling it.

The fixing device 1 includes a fixing roller 2 and a pressure roller 3 that is in pressure contact with the fixing roller 2 and rotates as a result. A fixing heater 4 (a halogen heater in the apparatus of this embodiment, hereinafter abbreviated as heater) is provided inside the fixing roller 2 as a heat generating member. Additionally, this heater 4 includes a fixing heater trilife circuit 6 that receives a signal from a CP [15 (central processing unit), which will be described later], and controls the amount of heat generated by the heater 4 within a predetermined range, and if the trife circuit 6 is malfunctioning. A thermoswitch 7 is also connected to cut off the electricity if this happens. Also,
A main motor 8 is disposed at the left end of the fixing roller 2 to rotate the fixing roller 2 in a predetermined direction via a gear or the like. A motor drive circuit 9 is connected to the main motor 8, which controls the rotation of the motor 8 in response to a signal from a CPU, which will be described later.

Next, the configuration of the control means related to the fixing device of the apparatus of this embodiment will be explained.

A CPU 5 (central processing unit), which is the core of the control means, is connected to a low voltage power source 11 that lowers the voltage of the commercial power source supplied from the outlet to a usable level. This low-voltage power supply 11 can be switched and used depending on the voltage of the commercial power supply supplied from the electrical outlets 1 to 10, and may be either a 100V system or a 200V system.

The CPU 5 also includes an ROH 12D as a storage device that stores the contents of the sequence of temperature control of the fixing unit for performing heat fixing, and a temperature detection unit 13 (circulator) that detects the surface temperature of the fixing roller 2. It is connected to the. The ROM 20 stores a block diagram for controlling the temperature of the fixing section, which sets the power supplied to the heater 4 to a value suitable for fixing in accordance with the commercial power supply voltage.

Next, the details of the configuration of the fixing heater drive circuit 6 will be explained in the second section.
As shown in the figure. The fixing heater trilife circuit 6 includes a noise filter 14, a circuit breaker 15, and an AC phase control circuit 16. The AC phase control circuit 16
is a circuit that controls the phase of alternating current supplied to the heater 4. The fixing heater trilife circuit 6 constitutes a phase control means together with the CI 115 and the ROM 21].

Here, a method of temperature control by an apparatus according to an embodiment of the present invention will be explained using FIG.

As shown in Fig. 3, if the timing of turning on the driving power of the image forming apparatus and the timing of inputting the print signal to execute the image forming process do not match, during the wait time from turning on the power to entering the standby state. 1. The CPt 15 sends a signal to the AC phase regulation circuit 16 to continuously perform full-wave energization of the AC applied to the heater 4 as shown in FIG. And the AC phase regulation circuit 16 is C1111
5. Receive A853 from [-J ROM2F] and energize the heater 41\AC continuously at full wave according to the sequence explained from [-J ROM2F].

After that, when it is detected by the thermistor 1:) that the temperature of the fixing roller 2 has reached the first set temperature, which is the standby temperature, the AC to the heater 4 is changed from full-wave continuous energization to half-wave continuous energization as shown in FIG. Switches to energized and supplies less power than when powered on. Here, the above-mentioned first set temperature is a standby temperature that is set to a predetermined value lower than the "IC minimum temperature required for fixing," and is a standby temperature that is set to a temperature lower than the "IC minimum temperature" required for fixing. The temperature required for this purpose can be raised in a short time, without causing fixing failure, and without wasting power.

When the temperature of the fixing roller 2 reaches the first set temperature, which is the standby temperature listed in L, the printer enters a waiting state for inputting a print signal.During this standby period, continuous half-wave energization is continued to prevent excessive temperature rise. and reduce wasteful power consumption.

When a power or a print signal is input, at the same time as the input, the AC phase control circuit 16 switches the AC that energizes the heater to full-wave continuous energization.
Raise the temperature to the set temperature of the machine. In this way, by supplying the power at power-on when raising the temperature, it is possible to shorten the time required for heating and prevent fixing failure. Here, the above-mentioned second set temperature is a temperature higher than the minimum fixing temperature necessary for fixing by a predetermined value, is a sufficient and appropriate temperature for fixing, does not cause high-temperature offset, and is set within the device. This is a temperature that does not cause the temperature to rise excessively.

Next, when it is detected that the temperature of the fixing roller 2 has reached the second set temperature, the energization to the heater 4 is switched to half-wave continuous energization. Since full-wave continuous energization is performed when heating the JJ to the second set temperature, if full-wave continuous energization is continued as it is, overshoot will occur and the temperature will rise excessively. Therefore, a lower power is supplied than when the power is turned on to prevent excessive temperature rise. However, if half-wave continuous energization is continued as it is, the temperature of the fixing roller 2 will gradually decrease as shown in FIG. 3 in a low-temperature, low-humidity environment. Therefore, the present invention
The temperature of the fixing roller 2 gradually decreases, increasing the temperature necessary for fixing.
When the temperature becomes lower than the minimum fixing temperature, full-wave continuous energization is immediately applied, that is, power is supplied to the heater using the power when the power is turned on, and the temperature of the fixing roller 2 is kept at or above the minimum fixing temperature. . Therefore, during fixing, the temperature of the fixing roller 2 is maintained between the second set temperature and the minimum fixing temperature, so that no fixing failure occurs.

Further, since the full-wave energization is performed only when the temperature of the fixing roller 2 is higher than the minimum fixing temperature, there is no excessive temperature rise and no unnecessary power consumption. In this embodiment, when the temperature of the fixing roller 2 reaches the second set temperature again, it is switched to half-wave continuous energization.

By performing the control described below, even if heat is taken away by the pressure roller and transfer material during the first few sheets after a print signal is input in a low temperature environment of 4 degrees Celsius, the temperature of the fixing roller surface will remain the same. The temperature required for fixing was maintained, and the fixing performance was good. In addition, when the pressure roller gradually warms up after the initial few sheets are passed through, the temperature does not drop below the minimum fixing temperature, so AC to the fixing heater becomes continuous half-wave current, which prevents excessive temperature rise of the fixing roller. In addition, the ability to efficiently consume power of the heater has become an important feature of σf.

In addition, in the first embodiment, half-wave energization is used when supplying less power than the power when the power is turned on, or half-wave energization is not particularly necessary, and during standby, as shown in FIG. 174 waves of electricity may be applied as in the second embodiment.

In the first embodiment, full-wave energization was applied from the minimum fixing temperature to the second set temperature, or as in the third embodiment shown in FIG. A similar effect can be obtained by switching to wave energization.

Furthermore, in the first embodiment, the phase of the alternating current was switched to 5 half waves to obtain half the power of the full wave, or as another method, the power was turned on as in the fourth embodiment, which is not shown in Fig. 8. A similar effect can be obtained by energizing the full wave at intervals of time T and non-energization time T2.

Alternatively, instead of 1/4-wave energization, half-wave energization may be performed with an interval of energization time T3 and non-energization time 'r4 as in the fifth embodiment shown in FIG. Even if half-wave energization is always performed with equally spaced non-energizing times of time 'r5 (-period and a half length) as in the embodiment, it is still possible to obtain 174 power.

[Effects of the Invention] According to the present invention, in an image forming apparatus having a fixing means for heating and fixing an unfixed image by a heat generating member to which a voltage from a commercial power supply is applied, the phase of the voltage applied to the heat generating member is controlled. The control means and the temperature detection means are provided to control the electric power during standby and fusing to be lower than the electric power when the drive power is turned on, and to control the temperature of the fusing roller during fusing to be lower than the minimum fusing temperature. When this occurs, the power at the time of turning on the drive power is supplied until the minimum fixing temperature is exceeded. Therefore, good fixing performance is maintained even in the initial state immediately after the drive power is turned on, and excessive temperature rise of the fixing heater due to excessive power during printing and thermal deterioration of the area around the fixing unit due to this can be prevented.
The power consumption of the fixing heater can now be used efficiently and effectively.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a device according to a first embodiment of the present invention, FIG. 2 is a schematic configuration diagram of a heater drive circuit of the device shown in FIG. 1, and FIG.
4 is a diagram showing the voltage phase of the first embodiment. FIG. 5 is a diagram showing the voltage phase of the first embodiment. The figure shows the AC voltage waveform of the fixing heater of the second embodiment, FIG. 7 is a diagram explaining the temperature control method of the third embodiment, and FIG. 8 shows the AC voltage waveform of the fixing heater of the fourth embodiment. FIG. 9 is a diagram showing the AC voltage waveform of the fixing heater of the fifth embodiment, FIG. 10 is a diagram showing the AC voltage waveform of the fixing heater of the sixth embodiment, and FIG. 11 is a diagram showing the AC voltage waveform of the fixing heater of the sixth embodiment. FIG. 12 is a diagram showing the temperature distribution of the pressure roller; FIG. 11 is a diagram showing the temperature change of the device;
FIG. 13 is a diagram showing a temperature change when paper is passed before the second set temperature is reached in the apparatus shown in FIG. 11. 2... Fixing roller 4... Heat generating member (fixing heater) 5...
CPU (phase control means) 6... Fixing heater drive circuit (phase control means)

Claims (5)

[Claims] (1) In an image forming apparatus equipped with a fixing roller that heats and fixes an unfixed image on a transfer material by having a heat generating member that generates heat by applying a voltage from a commercial power source, the temperature at which the temperature of the fixing roller is detected. and a phase control means for controlling the temperature of the fixing roller by controlling the phase of electric power from a commercial power supply applied to the heat generating member, the phase control means controlling the temperature of the fixing roller while the fixing roller is on standby. The temperature of the fixing roller is maintained at a first set temperature, which is a standby temperature that is set to a predetermined value lower than the minimum fixing temperature required for fixing, and the temperature of the fixing roller during fixing is maintained at the minimum fixing temperature and the corresponding temperature. The temperature is set to be maintained between the minimum fixing temperature and a second set temperature which is higher by a predetermined value, and when the temperature is maintained at the first set temperature, and between the minimum fixing temperature and the second set temperature. If the temperature is lower than the minimum fixing temperature during fixing, power is supplied to the heat generating member that is lower than the power when the power is turned on. An image forming apparatus characterized in that the image forming apparatus is configured to supply electric power to the heat generating member when the power is turned on. (2) The phase control means is set to supply power at power-on to the heat generating member when the temperature detection means detects that the temperature of the fixing roller has decreased to reach the minimum fixing temperature. The image forming apparatus according to claim (1). (3) Claim (1) wherein the phase control means is set to raise the temperature from the first set temperature during standby to the temperature required for fixing in synchronization with the input of the print signal.
The image forming apparatus described in . (4) The phase control means applies voltage to the heat generating member by repeatedly de-energizing or energizing intermittently, and controls by making the de-energizing time equal to the energizing time.
) to (3). (5) The phase control means applies a voltage to the heat-generating member by repeatedly de-energizing or energizing intermittently, and performs control by making the de-energizing time longer than the energizing time.
) to (3).