JP3355910B2 - Fixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for fixing an image recorded on transfer paper in a copying machine, a laser printer, or the like.

[0002]

2. Description of the Related Art For example, in a copying machine, a laser printer, or the like, a toner image formed on a photosensitive drum is transferred onto transfer paper by electrostatic force generated by a charge of a transfer charger. Since the transferred toner image is in an unstable state where the toner image is immediately peeled off when it is touched, the toner image is pressed at a predetermined temperature while being heated by a fixing roller having a built-in heater, so that the toner component is transferred to the fiber of the transfer paper. We let you penetrate inside and fix.

[0003] If the fixing temperature is not stable, the degree of fixing becomes uneven, which may cause image unevenness in a reproduced image. Therefore, the conventional fixing device controls the energization / de-energization of the heater to fix the image. The temperature is maintained at a predetermined temperature. However, since the heater is usually in the form of a coil, electromagnetic induction occurs at the time of switching between energization and non-energization, and the voltage greatly fluctuates, which has a considerable effect on other electric appliances. Lighting equipment such as a fluorescent lamp is particularly susceptible to such influences. Frequent switching between energization and non-energization causes flickering of the fluorescent lamp, which causes discomfort.

Therefore, conventionally, even if the heater temperature becomes equal to or higher than a predetermined temperature, energization is not stopped or started immediately, but if the required time has not elapsed since the start or stop of energization. The temperature of the fixing roller at the time of preheating (at the time of standby) and at the time of fixing (at the time of printing or copying) is controlled while controlling time so as not to switch between energization / deenergization.

[0005] According to such temperature control, generation of flicker can be prevented, and the life of the heater can be extended, so that a double effect can be obtained.

[0006]

However, according to the above-described conventional temperature control in which the time between the energization and the non-energization is switched, a time limit is set at the time of switching from preheating to fixing, or at the time of preheating at fixing. There were the following problems when switching to the hour. FIGS. 9 (a) and 9 (b) show a heater lighting signal and a heater lighting signal at the time of switching from preheating to fixing and at the time of switching from fixing to preheating, respectively, in the conventional temperature control method of a fixing device in a copying machine. It is a figure showing a situation of a temperature change.

[0009] As shown in FIG. 9 (a), at the time of preheating, a heater lighting signal which is output at a cycle of a predetermined time t or more with reference to a set temperature Tp at the time of preheating is turned on.
/ OFF, the temperature of the fixing roller is Tpu, Tp
It is controlled while changing to a waveform in the range of d. In this state, when the user gives an instruction to start copying from the operation panel, for example, the preheat signal is turned off and the temperature is raised to the set temperature Ta at the time of fixing.

However, if the heater lighting signal is in the OFF state at the time when the preheat signal is OFF as shown in the figure, the heater lighting OFF time is longer than the predetermined time t as described above. The heater is turned on only after the remaining time Δt1 has elapsed. Therefore, assuming that the temperature of the fixing roller at the time when the preheat signal is turned off is T1, once Tp
As a result, the time required to reach the fixing temperature Ta is delayed by a time Δt2 from when the heater temperature is decreased to d and when the heater is turned on to increase to T1.

[0009] Even though the user wants to copy immediately, he or she has to wait extra, and the work efficiency becomes very poor. In addition, extra power is required until the temperature once decreases to the temperature Tpd and then rises again to the temperature T1, resulting in waste of power. On the other hand, a similar problem occurs when the temperature changes from the time of fixing to the time of preheating.

That is, as shown in FIG. 9B, when a power saving switch is input from the operation panel, or in a copying machine having an automatic power saving function, a predetermined time ts elapses from the last copying operation. As a result, the preheat signal is turned ON. At this time, the heater lighting signal is ON.
In this state, the heater is turned off only after waiting for Δt3 as shown in FIG. As a result, unnecessary energization is performed by Δt3, and wasteful power is consumed.

SUMMARY OF THE INVENTION In view of the above-described problems, the present invention provides a fixing device that controls the temperature while controlling the switching time of energization / non-energization of a heater. It is an object to provide a fixing device that can be achieved.

[0012]

In order to achieve the above object, a fixing device according to the present invention comprises a fixing roller having a heat generating means, and a control unit which controls the energization / de-energization of the heat generating means to control the temperature of the fixing roller. A first temperature at the time of fixing and a second temperature at a standby time lower than the first temperature, wherein the temperature control means detects the temperature of the fixing roller. Temperature detecting means for setting, a reference temperature setting means for setting the first temperature and the second temperature as reference temperatures corresponding to a fixing time and a standby time, respectively, and a temperature detected by the reference temperature and the temperature detecting means. Comparing the power supply and the power supply to the heat generating means in a state where at least one cycle of the power supply / non-power supply does not become within a predetermined time based on the determination result of the determination means. / No electricity A first control unit for performing control; a standby signal output unit for outputting a standby start signal for instructing a start of a standby state; and a first control unit that receives the standby start signal and is energized during fixing by the first control unit. And immediately instructs the reference temperature setting means to change the reference temperature to the second temperature.
And control means.

Further, the fixing device according to the present invention includes a fixing roller having a heat generating means, and controlling a power supply to and a non-power supply to the heat generating means to control the temperature of the fixing roller at a first temperature at the time of fixing. A fixing device for controlling a temperature of the fixing roller to a second temperature lower than the temperature of the first fixing device during standby, wherein the temperature control device includes a temperature detecting device for detecting a temperature of the fixing roller; Correspondingly, a reference temperature setting means for setting the first temperature and the second temperature as reference temperatures, respectively, and a comparison between the reference temperature and the temperature detected by the temperature detection means to determine whether the current is supplied or not supplied And a first control for controlling the energization / de-energization of the heating means based on a result of the judgment by the determination unit, in a state where at least one energization / de-energization cycle does not fall within a predetermined time. Means and waiting A standby release signal output unit for outputting a standby release signal for instructing release of the state, and receiving the standby release signal, causing the first control unit to immediately start the power supply even when the power is not supplied during standby. And second control means for instructing the reference temperature setting means to change the reference temperature to the first temperature.

In this specification, "at the time of fixing" means a state in which the fixing roller is maintained at a predetermined fixing temperature for performing the fixing.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a fixing device according to the present invention will be described below by taking a fixing device in a digital copying machine as an example. (1) Overall Configuration of Digital Copier First, the overall configuration of the digital copier (hereinafter, simply referred to as “copier”) will be described.

FIG. 1 shows the overall configuration of the copying machine. As shown in FIG. 1, the copying machine includes an image reader section 10 for reading a document image and an image read by the image reader section 10. And a printer unit 20 for reproducing the same. A scanner 11 in the image reader unit 10 includes an exposure lamp 12 for irradiating a document, a rod lens array 13 for condensing light reflected from the document, and a contact type CCD color for converting the condensed light into an electric signal. Image sensor (hereinafter simply referred to as “CCD sensor”)
14 is provided.

When the user opens the document holder 16 upward, places the document on the document glass plate 15 with the document side down, and instructs the start of copying, the scanner 11 is driven by the scanner motor M2. The document is then moved in the direction of the arrow, and the document is scanned. The reflected light of the original by irradiation of the exposure lamp 12 of the scanner 11 is reflected by the CCD sensor 14.
The image data obtained by this is subjected to A / D conversion by the control unit 100 to become a digital signal, and further subjected to necessary processing such as shading correction, density conversion, and edge enhancement. Is output as a drive signal.

The laser light emitted from the laser diode 21 passes through a collimator lens 22 to become parallel light, and is further reflected and deflected by a mirror surface of a polygon mirror 23 driven to rotate at a constant speed by a polygon motor 24. . The deflected laser light passes through the fθ lens 25, is reflected by the folding mirrors 26a and 26b, and performs exposure scanning on the surface of the photosensitive drum 27.

Before the photosensitive drum 27 receives the exposure, the toner remaining on the surface of the photosensitive drum is removed by a cleaner 28.
Further, after being erased by irradiating the eraser lamp 29,
The photosensitive drum 27 is uniformly charged by the charging charger 30, and when exposed to light in such a uniformly charged state, an electrostatic latent image is formed on the photosensitive member on the surface of the photosensitive drum 27. The electrostatic latent image is developed by the developing device 31 to form a toner image on the surface of the photosensitive drum 27.

Transfer paper (not shown) placed on a paper cassette 34 in synchronization with the rotation of the photosensitive drum 27
Is fed to a transfer position below the photosensitive drum 27 by the feed roller 341, the timing roller 342, and the transport belt 33, and at this transfer position, the photosensitive drum is charged by the charge of the transfer charger 32 installed behind the transport belt 33. The toner image formed on the body drum 27 is transferred onto the transfer paper.

Since the toner image transferred to the copy paper is in an unstable state where it is immediately peeled off when it is touched,
The sheet is conveyed to a fixing device 36 by a reference numeral 5, where it is pressurized and fixed at a high temperature, and then discharged onto a discharge tray 38 by a discharge roller 37. An operation panel 17 is provided at a position on the front surface of the image reader unit 10 where the user can easily operate, for inputting, for example, the start of copying by the user. (2) Configuration of Fixing Device (Mechanical Portion) Next, the configuration of the mechanical portion of the fixing device 36 excluding the control system will be described.

FIG. 2 is an enlarged vertical sectional view of a mechanical portion of the fixing device 36. As shown in FIG.
Are a fixing roller 42 having a heater 41 therein, a pressing roller 43 disposed below the fixing roller 42 and rotating while contacting the outer peripheral surface of the fixing roller 42, and a fixing roller 42 or the pressing roller 43. Separation claws 44 and 45 for separating the transfer paper when it comes into close contact, a thermistor 46 for detecting the surface temperature of the fixing roller 42, a thermoswitch 47 for preventing overheating, and a heat retaining case 48 for accommodating these. Consists of

The separation claws 44, 45 are supported by support shafts 44a, 45a fixed to the inner wall of the heat retaining case 48,
The tension springs 44b and 45b respectively urge the fixing roller 42 and the pressure roller 43 toward each other. The thermistor 46 and the thermoswitch 47 are respectively fixed to the fixing roller 42 by the leaf springs 46a and 47a.
Urged to contact the surface of the

The fixing roller 42 and / or the pressure roller 43 are driven to rotate in the direction of the arrow by a rotary drive device (not shown), and when the transfer paper is conveyed along the guide plate 49, the fixing roller 42 The paper is sent out toward the discharge roller 37 while being nipped and pressed by the pressure roller 43. The surface temperature of the fixing roller 42 is maintained at a high temperature of about 190 ° C. by a temperature control device 60 (FIG. 3) described later, and when pressed with such high heat, the toner image adhered to the transfer paper surface However, it firmly enters between the fibers of the transfer paper and is fixed.

Even when the transfer paper comes into close contact with the fixing roller 42 or the pressure roller 43 during pressurization, the tips of the separation claws 44 and 45 urged against the surface of each roller as described above enter the gaps. The transfer paper is peeled off from the roller surface to prevent the transfer paper from being caught in the roller. The transfer paper on which the toner image is fixed in this manner is sent to the discharge roller 37 along the guide plates 50a and 50b, and is discharged onto the discharge tray 38 (FIG. 1). (3) Configuration of Temperature Control Device FIG. 3 is a block diagram of a temperature control device 60 for controlling the temperature of the fixing roller 42.

The temperature control device 60 includes a CPU 61,
It comprises a counter section 62, a RAM 63, a preheat signal generating section 64, an A / D converter 65, and an SSR (solid state relay) 66. One end of the thermistor 46 is grounded, and its resistance changes as the surface temperature of the fixing roller 42 changes, thereby changing the value of the output-side voltage Vs. The A / D converter 65 outputs the voltage V
The value of s is converted into a digital signal value and input to the CPU 61.

The RAM 63 has predetermined temperatures Ta, Tp (more precisely, digital signal values corresponding to the temperatures) at the time of fixing and at the time of preheating (at the time of standby) and predetermined initial values for time management of energization / de-energization. The count value Cs is stored, and the CPU 61 selects the above Ta and Tb as reference temperatures for temperature control according to the currently set operation state (whether preheating or fixing) and sets the reference temperature to this reference temperature. The corresponding digital signal value is compared with a digital signal value detected by the thermistor 46 and converted by the A / D converter 65 (hereinafter, in order to avoid such a roundabout expression, both digital signal values are used). Compare each other,
It is simply expressed as “compare the reference temperature and the detected temperature”. ).

On the other hand, the counter unit 62 initializes the initial counter number Cs stored in the RAM 63 each time the CPU 61 outputs a heater ON (energization start) signal and a heater ON (OFF) signal to the SSR 66. It is set as a value, and the count is decremented by "1". CPU6
1 compares the reference temperature with the detected temperature when the count value becomes “0” while the heater 41 is energized,
If it is determined that the detected temperature is higher than the reference temperature, S
A signal to turn off the heater is sent to SR66. SSR66
Receives this signal, opens the internal relay contact, and stops energizing the heater 41.

If the count value becomes "0" when the heater 41 is not energized (when the heater is not energized),
The above reference temperature is compared with the detected temperature, and if it is determined that the detected temperature is lower than the reference temperature, a signal for turning on the heater is sent to the SSR 66, and the SSR 66 receives this signal and closes the internal relay contact. Then, the power supply to the heater 41 is started.

If the count value of the counter section 62 does not become "0" in this way, the CPU 61 does not issue a heater ON / OFF signal to the SSR 66. The time does not become shorter than the predetermined time, which contributes to the prevention of the flicker described above and extends the life of the heater 41. The preheat signal generation unit 64 issues a preheat signal, changes the level of the signal from L to H when shifting from fixing to preheating (preheating signal ON), and when shifting from preheating to fixing. Change from H to L (preheat signal OFF).

The preheat signal generating section 64 starts counting time from the last copy operation using an internal timer, and when a predetermined time (for example, 10 minutes) has elapsed, or when the operation panel 1
7, when the power saving input operation is performed, the preheat signal is turned ON (changed from L to H).
When there is a copy start or other input operation from the above, the preheat signal is turned OFF (changes from H to L).

The CPU 61 detects the edge of the preheat signal that changes from L to H, executes the preheat, and immediately executes the preheat signal regardless of the counter value of the counter unit 62 when the heater 41 is being energized. Heater lighting O
A signal of the FF is issued to the SSR 66 to stop the energization, and RA
The set temperature Tp at the time of preheating is read from M63 and used as a reference temperature, and temperature control at the time of preheating is performed based on this temperature.

The set temperature Tp at the time of this preheating is
Is set to, for example, 160 ° C. Also, the CPU 61
Detects the edge at which the preheat signal changes from H to L, and if the power supply is currently stopped, immediately issues a heater ON signal to the SSR 66 regardless of the counter value of the counter section 62 to supply power. Start, RAM 63
, The set temperature Ta at the time of fixing is read out, and the temperature control at the time of fixing is performed using this temperature as a reference temperature.

The set temperature Ta at the time of fixing is set to, for example, 190 ° C. as described above. Next, a temperature control routine in the above-described temperature control device 60 will be described in detail with reference to the flowchart of FIG. The CPU 61 detects a level change (edge) of the preheat signal input from the preheat signal generation unit 64 and turns ON / O the preheat signal.
If the FF is determined (steps S1 and S2) and the edge is not detected, the process proceeds from the next step S3 to step S3.
Normal temperature control up to 16 is performed.

In this normal temperature control, first, it is determined whether or not the heater is currently in the OFF state (step S3). If the heater is OFF (that is, if the heater is not energized), the counter is turned off. It is determined whether or not the count value Coff of the unit 62 is 0 (step S4). The count value Coff is set to a predetermined time t after the power supply is stopped (such a predetermined time t is set to, for example, about 10 seconds. During this time, switching between power supply and non-power supply is limited in principle. This is counted down from the initial count Cs corresponding to the “switching limit time”. If the count value Coff = 0, the power supply is stopped and the switching limit time t has elapsed. Then, the reference temperature Ts is compared with the temperature T detected by the thermistor 46. If "T≤Ts", a heater lighting signal is output to the SSR 66 to turn on the heater (step S5).
5, S6), the count value Con set in the counter section 62 and subtracted from the time when the heater is turned on is reset to the initial count value Cs (step S7).

At step S4, the count value Cof
If f = 0, it means that the switching limit time t has not elapsed yet, so the count value is decremented by "1" (step S8) and the routine returns. If it is not “T ≦ Ts” in step S5, it is not necessary to start energization, and the process returns. If it is determined in step S3 that the heater is not currently in the OFF state, that is, if the power is being supplied, the process proceeds to step S9 to determine whether the count value Con of the counter unit 62 is 0 (step S9).

If the count value Con = 0, it means that the switching limit time t has elapsed since the start of energization, and thus the stop of energization is permitted. So, next,
The reference temperature Ts and the detected temperature T are compared, and if “T> Ts”, the SSR 6 is turned off so that the power supply to the heater 41 is stopped.
6 to turn off the heater (step S1).
0, S11), the count value Coff set in the counter section 62 is reset to the initial count value Cs (step S12).

In step S9, the count value Con
If it is not = 0, it means that the switching limit time t has not elapsed, so the count value is decremented by "1" (step 13) and the routine returns. If it is not "T>Ts" in step S10, there is no need to stop energization, and the process returns. In this way,
In the temperature control at the time of normal fixing or preheating, first, it is determined whether or not the switching limit time t has elapsed. If it is determined that the switching limit time has elapsed, the reference temperature Ts (described later) is started at that time. As described above, Ts = Ta at the time of fixing and Ts = Tp at the time of preheating.) Is compared with the detected temperature T, and ON / OFF control of the heater is performed as necessary. This is a priority control.

Of course, if the temperature difference (temperature ripple) becomes too large due to the temperature rising or falling too much before the switching limit time t elapses,
Since fixing unevenness occurs at the time of fixing, the switching limit time t is determined to be an optimum value in consideration of the heating capacity of the heater to be used so that the temperature ripple falls within an allowable range.

When the CPU 61 detects that the preheat signal has been turned on in step S1 while such normal temperature control is being performed, the process proceeds to step S14 to determine whether or not the heater is currently in the ON state. Then, if the heater is ON, regardless of the count value of the counter section 62, a signal to stop power supply is immediately issued to the SSR 66 to turn off the heater, and the reference temperature Ts is changed to the set temperature Tp at the time of preheating (step S14). Step S15, S1
6). If the heater is not turned on in step S14, it is not necessary to turn off the heater again, the reference temperature Ts is directly changed to the set temperature Tp at the time of preheating (step S16), and the process is returned. , The normal temperature control from step S3 to step S13 is performed.

By the interrupt control at the start of the preheating, the transition to the preheating state is quickly performed, and no wasteful power is consumed, which is effective as a power saving measure. If it is not detected in step S1 that the preheat signal has been turned ON, and if it is detected in step S2 that the preheat signal has been turned OFF, this means that the preheating is stopped (transition to fixing). In step S17, it is determined whether the heater is currently turned off (that is, the power is not supplied). If the heater is turned off, the SSR 66 is immediately transmitted to the SSR 66 regardless of the count value of the counter unit 62. The heater is turned on by issuing an energization start signal, and the reference temperature Ts is changed to the set temperature Ta at the time of fixing (steps S18 and S19).

Further, in step S17, the heater OF
If it is not the state of F (that is, if electricity is being supplied), it is not necessary to turn on the heater again, and the reference temperature Ts
Is changed to the set temperature Ta at the time of fixing (step S19).
Then, the temperature control from step S3 to step S13 is performed based on the set temperature Ta.

As described above, when the preheat OFF signal is detected, interrupt control is performed immediately to turn on the heater.
The transition to the state at the time of fixing is performed promptly, so that the user does not have to wait unnecessarily. FIG. 5A shows how the temperature of the fixing roller changes according to the temperature control routine described above.
(B).

FIG. 5A shows a state of a temperature change at the time of transition from preheating to fixing. When the preheating signal is turned off, the heater lighting signal is immediately turned on, and the temperature of the fixing roller is reduced. It can be clearly seen that the temperature rises toward the set temperature Ta at the time of fixing. FIG. 5 (b)
Shows the state of temperature change at the time of transition from fixing to preheating. When the preheating signal is turned ON, the heater lighting signal is immediately turned OFF, and the temperature of the fixing roller reaches the set temperature Tp during preheating. You can see that it is going down. (4) Modified Example of Temperature Control Device (First Modified Example) In the above-described temperature control device 60, the switching limit time during fixing and during preheating is set to the same t. As described above, the value of the switching limit time t is determined based on the balance between the temperature ripple allowed at the time of fixing and the amount of heat generated by the heater. However, at the time of preheating, the temperature control is more strict than at the time of fixing. This is not necessary, and it is only necessary to be within a certain temperature range lower than the fixing temperature. Therefore, in this modification, the value of the switching limit time t at the time of preheating is different from that at the time of fixing, and the switching limit time at the time of preheating is changed. t is set longer than that at the time of fixing.

FIG. 6A is a diagram showing an outline of the temperature control, in which the switching limit time t1 at the time of preheating is set to be considerably longer than the switching limit time t2 at the time of fixing, and flicker prevention at the time of preheating. And the heater life is given particular priority. Therefore, the configuration itself of the temperature control device 60 in the present modification is the same as that of FIG. 3, and only the contents of the initial count value stored in the RAM 63 and the temperature control routine by the CPU 61 are different as described below.

FIG. 7 shows a temperature control device 6 according to this modification.
7 is a flowchart illustrating a temperature control routine of 0. Steps S23 to S33 are a normal temperature control routine at the time of preheating or fixing, and are exactly the same as the control contents of steps S3 to S13 in the flowchart of FIG.

Further, the interrupt routine for switching to the preheating time following steps S21 and S34 to S36 is almost the same as steps S1 and S14 to S16 in FIG. However, step S37 is added after step S36, and in this step, the initial count value Cs is changed to the count value C1 corresponding to the switching limit time t1 in FIG. 6A.

Thus, the subtraction of the count values in steps S28 and S33 in the temperature control at the time of preheating is performed using the count value C1 as an initial value. On the other hand, the interrupt routine for switching to the fixing operation following steps S22 and S38 to S40 is also performed in steps S2 and S40 in FIG.
17 to S19, except that step S
Step S41 is added after step 40, and the initial count value Cs for switching prohibition is changed to the count value C2 corresponding to the switching limit time t2 in FIG. 6A.

As a result, the subtraction of the count values in steps S28 and S33 in the temperature control during fixing
2 is performed as an initial value. Of course, C1
> C2, whereby the switching limit time at the time of preheating is set longer than that at the time of fixing. These initial count values C1 and C2 are stored in RAM beforehand.
63, and read by the CPU 61 as necessary.

In the conventional temperature control method, if the switching time limit at the time of preheating is increased as described above, there is a possibility that the waiting time before shifting to the fixing time may be lengthened accordingly. Since the power can be supplied immediately by the interruption routine for time, there is no problem even if the switching limit time at the time of preheating is slightly increased. (Second Modification) In the second modification of the temperature control device, similarly to the first modification, the value of the switching restriction time t at the time of preheating and at the time of fixing is changed, and the switching restriction at the time of preheating is performed. The time t is set longer than that at the time of fixing.

However, the switching limit time is set for one cycle of energization / non-energization from the time when the heater is turned on to the time when the next heater is turned on. The only difference is that it depends. FIG. 6B is a diagram showing an outline of the temperature control. In FIG. 6B, the switching limit time of one cycle of heater ON / OFF at the time of preheating is set to t3, and the switching limit time of one cycle at the time of fixing is set to t3. It is set to t4.

Therefore, also in this modification, the configuration itself of the temperature control device 60 is the same as that of the embodiment of FIG. 3, and only the contents of the initial count value stored in the RAM 63 and the temperature control routine by the CPU 61 are different. Different as described below. FIG. 8 is a flowchart illustrating a temperature control routine of the temperature control device 60 according to the present modification.

What is substantially different from the flowchart of FIG. 7 is a normal temperature control routine of steps S43 to S49. When the count value C of the counter unit 62 becomes “0” in a state where ON / OFF of the preheat signal is not detected (steps S41, S42, S43),
Since the switching limit time has elapsed, the detected temperature T of the fixing roller is compared with the reference temperature Ts, and if “T ≦ Ts”, the heater is turned on and the count value Con is changed to the initial count value Cs (described later). As described above, when the temperature control at the time of fixing is currently performed, this Cs is equal to the time t4.
(See FIG. 6 (b)).
When the temperature control during preheating is performed, Cs is a count value C3 corresponding to time t3. ) And the process returns (steps S44 and S44).
45, S46).

If "T≤Ts" is not satisfied in step S44, that is, if "T>Ts", the heater is turned off and the process returns (step S50).
In step S43, if the count value C has not become "0" yet, the count value is further reduced by one (step S47), and the detected temperature T is compared with the reference temperature Ts (step S48).

In the case of "T>Ts", in the present embodiment, there is no restriction on the time for turning off the heater, so that the heater is immediately turned off (step S49) and the process is returned. Returns and waits until the temperature of the fixing roller further rises.
The interruption routine for switching to the preheating operation consisting of steps S41 and S51 to S54 is substantially the same as the interruption routine of FIG. 7 (steps S21 and S34 to S37), but the initial count value C in step S54 is not changed.
s governs the minimum time of one cycle of energization / de-energization as described above, and this value is C3 during preheating.
Is different.

Similarly, steps S42, S55 to S58
The interruption routine for switching to the fixing time is composed of the interruption routine of FIG. 7 (steps S22, S38 to S41).
However, the initial count value Cs in step S58 governs the minimum time of one cycle of energization / de-energization, and this value is set to C4 during fixing.

Of course, C3> C4, and these initial count values are stored in the RAM 63 in advance.
The data is read by the CPU 61 as needed. As described above, in the present modified example, one of energized / deenergized is
Since there is only a time constraint for the cycle,
The temperature control routine is simplified. For this reason, the restriction on the time from the energization to the stop of the energization is apparently eliminated, but the fact that the time of one cycle is equal to or longer than the predetermined time means that the temperature decreases by a certain amount after the energization is stopped. Since a time corresponding to the time from the re-energization to the rise to the predetermined reference temperature Ts is required, there is no concern that the switching from the energization to the non-energization becomes extremely short.

In this modification, the count value is reset and the subtraction count is performed from when the heater lighting signal is turned on. However, when the heater lighting signal is turned off, the count value is reset and the subtraction count is performed. Thus, the time of one cycle until the next heater lighting signal is turned off may be limited. As described above, the present invention has been described based on the embodiments and the modified examples. However, it is needless to say that the contents of the present invention are not limited to those described above, and the following modified examples can be considered.

By combining the first modification and the second modification of the temperature control device, the pre-heating
Is limited only by the time of one cycle of energization / non-energization as in the modification of the first embodiment. At the time of fixing, monitoring is performed by the switching limit time for each energization / non-energization switching as in the first modification. It may be finely controlled. Further, in the second modification of the temperature control device, the switching limit times t3 and t4 during fixing and preheating may be equal.

Further, in the above-described embodiment, a heater is provided only for the fixing roller, but a heater may also be provided for the pressure roller to perform similar temperature control. Accordingly, when the transfer paper is pressed by the fixing roller and the pressing roller, the temperature difference between the upper and lower rollers is almost eliminated, and the toner image can be more stably fixed. In the above embodiment, the temperature is controlled in two stages: the set temperature Tp (about 160 ° C.) at the time of preheating and the set temperature Ta (about 190 ° C.) at the time of fixing. For example, a standby state is set as needed. If the set temperature is set to 180 ° C. and the same control is performed, the time required to reach the temperature at the time of fixing can be further reduced.

The fixing device according to the present invention is not limited to the above-described digital copying machine, but may be any type of image forming apparatus such as an analog copying machine or a laser printer having a fixing unit for fixing while maintaining a predetermined temperature. Applicable to

[0062]

As described above, according to the fixing device of the present invention, energization / non-energization of the heat generating means of the fixing roller is controlled to control the temperature of the fixing roller to the first temperature at the time of fixing. And a temperature control means for controlling the temperature to a second standby temperature lower than the first temperature, the power supply / de-energization so that at least one cycle of power-on / power-off becomes a predetermined time or more. While controlling to contribute to preventing flicker and extending the life of the heater, on the other hand, the standby start signal immediately stops the energization even during energization at the time of fixing, and immediately enters the standby mode. Since the temperature is shifted to the above-mentioned temperature, unnecessary power consumption is eliminated, and it is possible to contribute to power saving.

Further, according to the fixing device of the present invention, energization / non-energization of the heating means of the fixing roller is controlled so that the temperature of the fixing roller is determined by the first temperature at the time of fixing and the first temperature at the time of fixing. In the fixing device including a temperature control unit that controls the second temperature at the time of low standby, at least one of energized / non-energized
The energization / de-energization is controlled so that the cycle time is equal to or longer than a predetermined time, thereby contributing to measures against flicker and extending the life of the heater. However, since the power can be immediately started and the temperature can be immediately shifted to the temperature at the time of fixing, the waiting time until copying can be performed in, for example, a copying machine does not needlessly become longer. .

Further, since energization can be started before the temperature of the fixing roller reaches the lower limit of the control temperature range, the temperature is once lowered to the lower limit of the control temperature range and then returned to the lower limit as in the conventional temperature control. Power is no longer required
This also contributes to power saving.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of a copying machine to which a fixing device according to the present invention is applied.

FIG. 2 is a longitudinal sectional view of a mechanical part of the fixing device according to the present invention.

FIG. 3 is a block diagram of a temperature control device in the fixing device according to the present invention.

FIG. 4 is a flowchart showing an operation of temperature control in the temperature control device.

FIG. 5 is a diagram showing how the temperature of the fixing roller changes under the control of the temperature control device.

FIG. 6 is a diagram illustrating a state of a temperature change of a fixing roller when a time limit for switching between energization and non-energization is changed between preheating and fixing.

FIG. 7 is a flowchart showing a temperature control operation in a first modification of the temperature control device.

FIG. 8 is a flowchart showing a temperature control operation in a second modification of the temperature control device.

FIG. 9 is a diagram illustrating a state of temperature control of a fixing roller in a conventional fixing device.

[Explanation of symbols]

 36 Fixing Device 41 Heater 42 Fixing Roller 43 Pressure Roller 60 Temperature Control Device 61 CPU 62 Counter 63 RAM 64 Preheat Signal Generator 65 A / D Converter 66 SSR

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 13/20 G03G 15/20

Claims (2)

(57) [Claims] A fixing roller having a heat generating means, a power supply to the heat generation means, and a power supply to the heat generation means for controlling a temperature of the fixing roller to a first temperature at the time of fixing and a standby temperature lower than the first temperature. A fixing device that includes a temperature control unit that controls a temperature of the fixing roller; a temperature detection unit that detects a temperature of the fixing roller; Temperature and second
Reference temperature setting means for setting the temperature as a reference temperature; determining means for comparing the reference temperature with the temperature detected by the temperature detecting means to determine energization / non-energization; Based on the condition, at least one cycle of energization / de-energization does not occur within a predetermined time,
A first control unit that controls energization / de-energization of the heating unit; a standby signal output unit that outputs a standby start signal for instructing a start of a standby state; A second control unit for immediately stopping the energization even during energization at the time of fixing by the control unit, and instructing the reference temperature setting unit to change the reference temperature to the second temperature;
A fixing device comprising: 2. A fixing roller having a heat generating means, and a first temperature at the time of fixing and a standby temperature lower than the first temperature when the temperature of the fixing roller is controlled by energizing / de-energizing the heat generating means. A fixing device that includes a temperature control unit that controls a temperature of the fixing roller; a temperature detection unit that detects a temperature of the fixing roller; Temperature and second
Reference temperature setting means for setting the temperature as a reference temperature; determining means for comparing the reference temperature with the temperature detected by the temperature detecting means to determine energization / non-energization; Based on the condition, at least one cycle of energization / de-energization does not occur within a predetermined time,
A first control unit for controlling energization / de-energization of the heating unit; a standby release signal output unit for outputting a standby release signal for instructing release of a standby state; A second control means for immediately starting energization even during non-energization during standby by the control means, and instructing the reference temperature setting means to change the reference temperature to the first temperature; And a fixing device.