JP6888305B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus that forms an image with toner. More specifically, the present invention relates to an image forming apparatus having a fixing portion for fixing a toner image applied on a medium.

There are many fixing parts of the image forming apparatus, and the two rollers are opposed to each other. As a conventional example of an image forming apparatus provided with such a fixing portion, the one described in Patent Document 1 can be mentioned. In the image forming apparatus of the same document, the roller is rotated by a predetermined forced rotation time at a predetermined pause time interval during standby (claim 1 of Patent Document 1). As a result, it is possible to realize a significant cost reduction and prevent the start time of the fixing process from being delayed (Patent Document 1 [0050]).

Japanese Unexamined Patent Publication No. 2003-122177

However, the above-mentioned conventional technique has the following problems. The rollers of this type of fixing device are usually made of a material that has some flexibility. Therefore, at the positions where the two rollers face each other, each roller is slightly deformed by compression. If the rollers do not rotate for a long time, such as when the device is out of service, the same parts of each roller will be left in a deformed state. For this reason, a deformation habit may be attached to that part. If image formation is performed with the rollers still having deformation habits, improper fixing may occur when the deformation habits come into contact with the paper. Therefore, it is necessary to form an image without any deformation habit.

The "forced rotation" of Patent Document 1 is considered to be useful to some extent for preventing such deformation habits. However, the deformation habit becomes the most problematic at the start of operation after the image forming apparatus is paused for a certain period of time. In Patent Document 1, although there is a description about control during standby, there is no description about control at the start of operation after the device is stopped. Therefore, it cannot be said that it is appropriate as a control at the start of operation from a state with a deformation habit. On the other hand, the roller has a deformation habit when the rest period is long to some extent, but depending on the length of the rest period, it may not always be said that the roller already has a deformation habit. The optimum operation in such a case is not described in Patent Document 1.

The present invention has been made to solve the above-mentioned problems of the prior art. That is, the problem is an image forming apparatus that appropriately eliminates or prevents deformation habits according to the length of the pause period when the operation is resumed from the pause period, so as to quickly obtain a state in which an image can be formed. To provide.

The image forming apparatus according to one aspect of the present invention is composed of an image forming portion that forms a toner image and applies it on a medium, and two opposing rollers that fix the toner image applied on the medium by heating. An image forming apparatus having a fixing unit and a time measuring unit for measuring the stop time of a roller, and controls the operation of the fixing unit when the operation is resumed after a pause according to the time measuring time of the measuring unit when the operation is restarted. It has a restart control unit. Here, the restart control unit includes a pause period determination unit, a deformation recovery control unit, a deformation prevention control unit, and a normal restart control unit. The pause period determination unit shall set the timekeeping time to a long-term pause that is equal to or longer than the predetermined first reference time and a second reference time that is less than the first reference time and shorter than the predetermined reference time. It determines whether it is a certain medium-term pause or a short-term pause that is less than the second reference time. The deformation recovery control unit starts both a deformation recovery operation that recovers the deformation habit generated in the roller and a warm-up that raises the temperature of the roller to a predetermined fixing temperature in the case of a long-term pause, and recovers the deformation. When both the operation and the warm-up are completed, the image formation permission state is set. The deformation prevention control unit starts warm-up when it is in a mid-term pause, puts it in the image formation permission state when the warm-up is completed, puts it in the image formation permission state, and then progresses before the start of image formation. When the time reaches a predetermined third reference time, a deformation prevention operation is performed to prevent the roller from forming a deformation habit. Normally, the restart control unit starts warm-up when there is a short-term pause, and when the warm-up is completed, the image formation permission state is set. When the power is turned on, the restart control unit performs the above-mentioned operation control according to the time of the time measuring unit from the end of the rotation of the last roller before the power is stopped . Further, an image forming portion for forming a toner image and applying the toner image on the medium, a fixing portion composed of two opposing rollers for fixing the toner image applied on the medium by heating, and a stop time of the rollers are provided. It is an image forming apparatus having a time measuring unit for measuring, and has a restart control unit that controls the operation of the fixing unit when the operation is restarted after a pause according to the time measuring time of the time measuring unit when the operation is restarted. The department has a long-term pause that is equal to or longer than the predetermined first reference time and a medium-term pause that is less than the first reference time and shorter than the predetermined reference time and is greater than or equal to the second reference time. And a pause period determination unit that determines whether it is a short-term pause that is less than the second reference time, a deformation recovery operation that recovers the deformation habit that occurred in the roller in the case of a long-term pause, and a roller. A deformation recovery control unit that starts both warm-up to raise the temperature to a predetermined fixing temperature and puts the image formation permitted state when both the deformation recovery operation and the warm-up are completed, and when it is in the mid-term pause. , The warm-up is started, and when the warm-up is completed, the image formation permission state is set, and after the image formation permission state is set, the elapsed time before the start of image formation reaches the predetermined third reference time. In some cases, the deformation prevention control unit that performs the deformation prevention operation to prevent the roller from forming a deformation habit, and the warm-up is started in the case of a short pause, and the image formation permission state is set when the warm-up is completed. It has a normal restart control unit, and the third reference time is set longer when the environmental temperature at the time of restarting the operation is low than when it is high. The image forming portion that forms a toner image and applies it to the medium, the fixing portion that fixes the toner image applied to the medium by heating, and the fixing portion composed of two opposing rollers, and the stop time of the rollers are measured. It is an image forming apparatus having a time measuring unit, and has a restart control unit that controls the operation of the fixing unit when the operation is resumed after a pause according to the time measuring time of the timing unit when the operation is restarted. Regarding the timekeeping time, a long-term pause that is equal to or longer than the predetermined first reference time, and a medium-term pause that is less than the first reference time and shorter than the predetermined reference time and is greater than or equal to the second reference time. A pause period determination unit that determines whether it is a short-term pause that is less than the second reference time, a deformation recovery operation that recovers the deformation habit that occurs in the roller in the case of a long-term pause, and a roller are predetermined. A deformation recovery control unit that starts both warm-up to raise the temperature to the fixed fixing temperature and puts the image formation permission state when both the deformation recovery operation and warm-up are completed, and the warm-up when it is in the mid-term pause. When the up is started, the image formation permission state is set when the warm-up is completed, the image formation permission state is set, and the elapsed time before the start of image formation reaches a predetermined third reference time. ， Deformation prevention control unit that performs deformation prevention operation to prevent deformation habits of the rollers, and when there is a short pause, warm-up is started and image formation is permitted when warm-up is completed. It has a restart control unit, and the timekeeping unit has a warm-up timekeeping unit that measures the warm-up time, which is the time required for warm-up. The restart control unit sets the third reference time as the warm-up time. It has an expansion / contraction processing part that extends when it is long and shortens it when it is short. The image forming portion that forms a toner image and applies it to the medium, the fixing portion that fixes the toner image applied to the medium by heating, and the fixing portion composed of two opposing rollers, and the stop time of the rollers are measured. It is an image forming apparatus having a time measuring unit, and has a restart control unit that controls the operation of the fixing unit when the operation is resumed after a pause according to the time measuring time of the timing unit when the operation is restarted. Regarding the timekeeping time, a long-term pause that is equal to or longer than the predetermined first reference time, and a medium-term pause that is less than the first reference time and shorter than the predetermined reference time and is equal to or longer than the second reference time. A pause period determination unit that determines whether it is a short-term pause that is less than the second reference time, a deformation recovery operation that recovers the deformation habit that occurs in the roller in the case of a long-term pause, and a roller are predetermined. A deformation recovery control unit that starts both warm-up to raise the temperature to the fixed fixing temperature and puts the image formation permission state when both the deformation recovery operation and warm-up are completed, and warm-up when it is in the mid-term pause. When the up is started, the image formation permission state is set when the warm-up is completed, the image formation permission state is set, and the elapsed time before the start of image formation reaches a predetermined third reference time. ， Deformation prevention control unit that performs deformation prevention operation to prevent deformation habits of the rollers, and when there is a short pause, warm-up is started and image formation is permitted when warm-up is completed. It has a restart control unit and a non-volatile memory for storing the time when the rotation of the roller is completed.

The basic operation of the image forming apparatus in the above aspect is to form a toner image by the image forming portion, apply the toner image on the medium, and fix the toner image applied on the medium at the fixing portion. In the fixing portion, the medium is passed through the nip portions of the two opposing rollers, so that the toner image is fixed by heat. Here, when the operation is restarted after the pause, a specific process is performed by the restart control unit. The restart control unit not only warms up the roller to the fixing temperature, but also performs a deformation recovery operation or a deformation recovery operation depending on the time of the time measuring part, that is, the length of the stopping time when the image forming apparatus is in a dormant state. Performs deformation prevention operation. Therefore, the pause period determination unit determines whether the previous pause is a long-term pause, a medium-term pause, or a short-term pause.

In the case of a long pause, the deformation recovery control unit starts the deformation recovery operation in addition to warming up. The deformation recovery operation recovers the deformation habit of the roller. Then, when both the deformation recovery operation and the warm-up are completed, the image formation permission state is set. In the case of mid-term suspension, the deformation prevention control unit puts the image formation permission state when the warm-up is completed. After that, the deformation prevention operation is performed at a predetermined timing when the roller temperature is stable. The deformation prevention operation prevents the occurrence of deformation habits on the rollers. In the case of a short-term pause, the normal restart control unit sets the image formation permission state when the warm-up is completed. In the image forming apparatus of the above aspect, the restart control unit also performs the above-mentioned operation control according to the time of the time measuring unit from the end of the rotation of the last roller before the power is stopped when the power is turned on. desirable. This is because the elapsed time from the end of the previous rotation of the roller to the restart of the operation is a powerful factor for estimating the degree of occurrence of the roller deformation habit. In the image forming apparatus of the above aspect, it is desirable that the third reference time is set longer when the environmental temperature at the time of restarting the operation is low than when it is high. This is because it is desirable to perform the deformation prevention operation after the roller temperature has stabilized, and the time required to stabilize the roller temperature depends on the environmental temperature. In the image forming apparatus of the above aspect, or, the time measuring unit has a warm-up time measuring unit that measures the warm-up time, which is the time required for warming up, and the restart control unit warms the third reference time. It is desirable to have an expansion / contraction processing part that extends when the up time is long and shortens when the up time is short. The length of the warm-up time depends on the initial temperature of the rollers before the start of warm-up. Therefore, as in the case of the above-mentioned environmental temperature, it affects the time required to stabilize the roller temperature. In the image forming apparatus of the above aspect, it is also desirable that the time measuring unit has a non-volatile memory for storing the time when the rotation of the roller is completed. This is because the pause period is calculated from the time saved in the non-volatile memory and the current time when the operation is restarted.

In the image forming apparatus of the above aspect, it is desirable that the deformation recovery operation is forced rotation of the roller over a predetermined time. This is because the deformation habit can be eliminated by forcibly rotating the roller regardless of the image formation.

In the image forming apparatus of the above aspect, it is desirable that the deformation prevention operation is an operation of changing the facing portion by rotating the roller at a rotation angle of less than one rotation. This is because the occurrence of deformation habits can be prevented by changing the facing points.

In the image forming apparatus of the above aspect, as the temperature control method of the fixing portion, the standby method at the time of non-image formation and the execution method at the time of image formation execution, in which the degree of heating is stronger than that of the standby method, are used. The restart control unit performs temperature control to the heating control unit during the deformation recovery operation and the deformation prevention operation by a method for execution or a method in which the degree of heating is stronger than that. It is desirable to be able to do it. This is because the effect is greater when the fixing portion is heated under a strong condition during both the deformation recovery operation and the deformation prevention operation.

Among the above image forming devices, in the case where the deformation recovery operation is the forced rotation of the roller, it is desirable that the execution time of the forced rotation can be changed by the user's choice. This is because there are cases where it is desired to change the execution time of forced rotation from the normal setting, for example, at the start of the first operation after a long vacation.

According to this configuration, an image forming apparatus is provided that appropriately eliminates or prevents deformation habits according to the length of the pause period when the operation is resumed from the pause period, and promptly obtains a state in which an image can be formed. ing.

It is a block diagram of the image forming apparatus which concerns on embodiment. It is sectional drawing which shows the structure of the fixing part. It is a block diagram which shows the structure of the control system of the image forming apparatus which concerns on embodiment. It is a flowchart which shows the control content at the time of starting the operation of the image forming apparatus which concerns on embodiment. It is a graph which shows the rise state of a roller temperature in the case after a mid-term rest. It is a graph which shows two kinds of temperature control methods of a fixing part.

Hereinafter, embodiments embodying the present invention will be described in detail with reference to the accompanying drawings. In this embodiment, the present invention is applied to the image forming apparatus 1 shown in FIG. The image forming apparatus 1 shown in FIG. 1 is a tandem type digital color printer (hereinafter, simply referred to as “printer”). Of course, in addition to the printer, the present invention can be applied to a copier having a scanner, a multifunction device having a combination of these functions, and the like.

The image forming apparatus 1 is provided with an intermediate transfer belt 40 at a substantially central portion inside the image forming apparatus 1. The intermediate transfer belt 40 is hung on the drive roller 12, the tension roller 13, and the driven rollers 14 and 15. The intermediate transfer belt 40 circulates counterclockwise in FIG. 1 as the drive roller 12 is rotationally driven. Below the intermediate transfer belt 40, four imaging units 2Y, 2M, 2C, and 2K corresponding to each color of yellow (Y), magenta (M), cyan (C), and black (K) are arranged. .. The imaging unit 2K includes a photoconductor 21, a charging device 22, an exposure device 23, a developing device 24, a cleaning device 25, an eraser (static elimination device) 26, and a primary transfer roller 30. The other imaging units 2Y, 2M, and 2C are also configured in the same manner as the imaging unit 2K. As a result, a full-color toner image is formed on the intermediate transfer belt 40. Further, the secondary transfer roller 16 is pressure-welded to the portion of the intermediate transfer belt 40 supported by the drive roller 12.

A paper cassette 91 is detachably arranged at the lower part of the image forming apparatus 1. Paper P is drawn out one by one from the paper cassette 91 and supplied to the secondary transfer roller 16 via the transport path 93. The toner image is transferred to the paper P supplied to the secondary transfer roller 16. A fixing portion 94 is arranged at a position downstream of the secondary transfer roller 16 (upper in FIG. 1) in the transport path 93. The fixing unit 94 is a device for fixing an unfixed toner image on the paper P to the paper P. A paper ejection tray 98 is provided at a position further downstream from the fixing portion 94.

The fixing portion 94 will be described. FIG. 2 shows a cross-sectional view of the fixing portion 94. As shown in FIG. 2, the fixing portion 94 has a pressure roller 97 and a heating roller 92. The pressurizing roller 97 and the heating roller 92 are in pressure contact with each other to form a fixing nip 95. In the fixing nip 95, the pressure roller 97 and the heating roller 92 are locally compressed and deformed. A heater 99 is built in the heating roller 92. The heater 99 is a heat generating means such as a halogen lamp. As a result, the unfixed toner image is fixed by passing the paper P through the fixing nip 95. Further, a thermistor 96 is provided in the vicinity of the heating roller 92. The thermistor 96 detects the temperature of the heating roller 92.

The control system of the image forming apparatus 1 will be described with reference to FIG. The control system of the image forming apparatus 1 is mainly composed of the engine control unit 51. The engine control unit 51 has a built-in engine control CPU 56 and is a part that controls various parts related to toner image formation. The engine control unit 51 also controls the operation of the fixing unit 94 when the operation is resumed after the pause. The above-mentioned exposure device 23, eraser 26, fixing unit 94, and thermistor 96 are connected to the engine control unit 51. Of these, the engine control unit 51 controls the rotational drive of the pressurizing roller 97 and the heating roller 92 and the heat generation control of the heater 99 with respect to the fixing unit 94. The engine control unit 51 also receives information about the temperature of the heating roller 92 from the thermistor 96.

An MFP controller 52, a high-voltage unit 53, a timer 54, and a non-volatile memory 55 are further connected to the engine control unit 51. The MFP controller 52 controls the user interface, image data processing, and the like. The high-voltage unit 53 is a portion that controls the high voltage of the charging device 22, the developing device 24, the primary transfer roller 30, and the secondary transfer roller 16. The timer 54 has a timekeeping function, and in the present embodiment, it plays a role of measuring the length of the rest period of the image forming apparatus 1. The non-volatile memory 55 sets the time when the image forming apparatus 1 is stopped, more specifically, the time when the rotation of the pressurizing roller 97 and the heating roller 92 is stopped during the dormant period of the image forming apparatus 1 in order to measure the dormant period. Even so, it is something to remember. The circulation operation of the intermediate transfer belt 40 and the rotation operation of the photoconductor 21 in the image forming apparatus 1 are also controlled objects of the engine control unit 51, but since they are known matters, the description in FIG. 3 is omitted. There is.

The operation of the image forming apparatus 1 will be described below. A feature of the operation of the image forming apparatus 1 as this embodiment is the control of the fixing unit 94 when the operation is started from the hibernation state. At the start of operation, it is necessary to raise the temperature of the heating roller 92 of the fixing unit 94 to a predetermined fixing temperature. This temperature rise is called warm-up. Further, if the pressure roller 97 and the heating roller 92 in the fixing nip 95 have a deformation habit, it is necessary to eliminate the deformation habit.

Here, whether or not the deformation habit occurs at the start of the operation of the image forming apparatus 1 depends on the length of the rest period. If the rest period is a long period of time, it can be said that the deformity habit has definitely occurred. On the contrary, if the rest period is relatively short, it is unlikely that the deformity habit has occurred. And in the middle of them, there is a mid-term suspension in which it cannot be said that the deformity habit has definitely occurred, but the possibility that it has occurred cannot be denied. The boundary between these three types of pause periods is a design item that is predetermined in the image forming apparatus 1. For example, short-term pause is less than 3 hours, medium-term pause is 3 hours or more and less than 6 hours, and long-term pause is 6 hours or more. Can be.

In this embodiment, the processing at the start of operation is divided according to whether the pause period is long-term pause, medium-term pause, or short-term pause. Therefore, in the image forming apparatus 1, when the image forming apparatus 1 is stopped (more specifically, when the pressurizing roller 97 and the heating roller 92 are stopped rotating), the indicated time of the timer 54 at that time is stored in the non-volatile memory 55. Keep it. FIG. 4 shows the control contents at the start of operation. This flow is executed when the image forming apparatus 1 is turned on or when the image forming apparatus 1 shifts from the hibernation state to the operating state.

In the flow of FIG. 4, first, it is determined whether or not the rest period (leaving period in the figure) T is equal to or greater than the first reference time T1 (S1). The pause period T is the difference between the indicated time of the timer 54 at the start of operation and the stop time stored in the non-volatile memory 55. The first reference time T1 is 6 hours in the above-mentioned example. If the rest period T is less than 6 hours (S1: No), it is determined whether or not the rest period T is equal to or greater than the second reference time T2 (S2). The second reference time T2 is 3 hours in the above example. From the above S1 and S2, it is determined whether the rest period T is a long-term pause, a medium-term pause, or a short-term pause. If there is a long-term pause (S1: Yes), go to the row below S3, if there is a medium-term break (S2: Yes), go to the row below S8, and if there is a short-term break (S2: No). Goes to the columns below S14, respectively.

If it is a long-term pause (S1: Yes), the deformation recovery operation is started (S3). The deformation recovery operation is an operation for eliminating the deformation habit generated in the pressure roller 97 and the heating roller 92. Specifically, for example, the pressure roller 97 and the heating roller 92 are forcibly rotated for a predetermined time (for example, 1 minute to 3 minutes). Here, "forced" means that it has nothing to do with image formation. In addition, warm-up is also started in which the pressure roller 97 is heated to a predetermined fixing temperature by the heat generated by the heater 99 (S4). The order of S3 and S4 may be reversed.

Then, it is determined whether or not the pressure roller 97 has reached the fixing temperature, that is, whether or not the warm-up is completed (S5). This determination is based on the detection signal of the thermistor 96. Further, it is determined whether or not the deformation recovery operation is completed (S6). As a result, it waits until both of the determinations of S5 and S6 become Yes. When the deformation recovery operation is completed, the deformation habit is repeatedly passed through the fixing nip 95 while receiving heating, so that the deformation habit is eliminated. The determination order of S5 and S6 may be reversed. When the determinations of S5 and S6 are both Yes, image formation is permitted (S7). And this flow ends.

If it was a mid-term suspension (S2: Yes), warm-up is started (S8). However, in this case, the above-mentioned deformation recovery operation is not performed. Then, it is determined whether or not the warm-up is completed (S9). When the warm-up is completed (S9: Yes), image formation is permitted (S10). Since printing is possible without performing the deformation recovery operation in this way, image formation can be started earlier than in the case of a long pause. Deformation habits do not always occur after the mid-term pause, and even if they do occur, they are minor, so such treatment is desirable. The timing is started at the time of S10.

Then, it is determined whether or not the elapsed time t from S10 has elapsed the predetermined third reference time T3 (for example, 30 seconds to 1 minute) (S11). Further, it is determined whether or not there is an image formation instruction (S12). When the elapsed time t reaches the third reference time T3 without an image formation instruction (S11: Yes), the deformation prevention operation is performed (S13). The deformation prevention operation is an operation in which the pressure roller 97 and the heating roller 92 are rotated slightly (about 10 seconds), unlike the deformation recovery operation. The purpose is to change the location of the fixing nip 95 in the pressurizing roller 97 and the heating roller 92 to another location. Therefore, the amount of rotation less than one rotation of the pressure roller 97 and the heating roller 92 is sufficient. As a result, it is possible to prevent a new deformation habit from being generated at the portion of the fixing nip 95. When the deformation prevention operation is completed, this flow is terminated.

If an image formation instruction is given before the elapsed time t reaches the third reference time T3 (S12: Yes), this flow ends without performing the deformation prevention operation. In this case, image formation will be executed immediately thereafter. Since the pressure roller 97 and the heating roller 92 rotate as part of the image forming operation, there is no need to worry about the occurrence of deformation habits. If an image formation instruction is given before the deformation prevention operation (S13) is started and finished, the deformation prevention operation is immediately stopped and this flow is terminated. Then, image formation is executed.

If there is a short break (S2: No), warm-up is started (S14). Of course, the deformation recovery operation is not performed. Then, it is determined whether or not the warm-up is completed (S15). When the warm-up is completed (S15: Yes), image formation is permitted (S16). And this flow ends. In this case, of course, the deformation prevention operation is not performed. The above is the content of the flow of FIG.

Of the above, the processing in the case of mid-term suspension will be further described with reference to FIG. As shown in FIG. 5, the temperature of the heating roller 92 rises sharply in the period from the elapsed time of 0 seconds to about 8 seconds. This period is the warm-up execution period. Printing is permitted when the warm-up is completed. In FIG. 5, the control fixing temperature is set to 180 ° C. After that, the temperature of the heating roller 92 repeatedly rises and falls under temperature control to settle to the fixing temperature. As described above, it is possible to accept image formation instructions during this period as well.

Then, when the third reference time T3 (about 30 seconds in FIG. 5) elapses after the printing becomes possible and the temperature of the heating roller 92 settles down, the deformation prevention operation (about 10 seconds in FIG. 5) is performed. is there. As a result, the occurrence of deformation habits is prevented while the image formation permission state is set at an early stage. If the deformation prevention operation is performed without waiting for the third reference time T3 after the print becomes possible, the temperature of the fixing nip 95 may be lower than the fixing temperature immediately after the deformation prevention operation is completed. If an image formation instruction is given immediately in that state, fixing failure may occur. By waiting for the third reference time T3, such fixing failure can be prevented.

Subsequently, other detailed controls in the fixing unit 94 of the image forming apparatus 1 will be described. First, FIG. 6 is a graph showing a temperature control method of the fixing unit 94. As shown in the current waveform of FIG. 6, the image forming apparatus 1 can have two types of temperature control methods, one for standby and one for printing. In the standby method, only one-third of the AC waveform from the power supply is supplied as the current to the heater 99. On the other hand, in the printing method, two-thirds of the AC waveform is supplied as a current to the heater 99. Therefore, the printing method is stronger than the standby method in terms of the degree of heating. The standby method is mainly used during standby, and the print method is mainly used when image formation is executed. At the time of warm-up, the entire AC waveform (three-thirds of the wave) is supplied as a current to the heater 99.

Applying this to the flowchart of FIG. 4, it becomes as follows. First, after a long pause (row in S3), warm-up and deformation recovery operations are started with full-wave supply, and when printing is permitted in S7, the temperature control is switched to the standby method. Become. Here, if the warm-up is completed before the deformation recovery operation, the temperature control of the printing method is used during the subsequent deformation recovery operation, and the temperature of the standby method is used when the deformation recovery operation is completed. It will shift to the key. If the deformation recovery operation is completed before the warm-up, full-wave supply is performed throughout the warm-up, and when the warm-up is completed, the temperature control is shifted to the standby method. In other words, during the execution of the deformation recovery operation, the printing method or the heating degree is stronger than that. This is because the larger the calorific value, the more advantageous it is to eliminate the deformation habit.

In the case of after the mid-term pause (row in S8), heating with full-wave supply is started at the same time as the warm-up is started, and when the warm-up is completed, the temperature control is temporarily switched to the standby method. Then, when the deformation prevention operation is performed, the printing method is switched only during that time. This is also because the larger the calorific value, the more advantageous it is to prevent deformation habits. After a short pause (row in S14), full-wave supply is performed only during warm-up, and the standby method is used after warm-up is completed. In any case, if there is an image formation instruction after that, of course, the printing method is used during the execution.

Next, the execution time of forced rotation in the deformation recovery operation will be described. In the above explanation, it was only mentioned as a predetermined time, but it is desirable that this execution time can be changed by the user's choice. It is useful when the rest period extends for several days, for example, after a long vacation. In such a case, of course, on the flow of FIG. 4, it is the case after a long pause, but it is better to perform more forced rotation (for example, 1.5 times) than usual. It is also unhindered to give an option to reduce forced rotation than usual.

Next, the control for changing the third reference time T3 will be described. There are two ways to do this. The first is to expand and contract the third reference time T3 according to the environmental temperature. The second is that the third reference time T3 is expanded or contracted according to the length of time required for warming up. The control according to the environmental temperature is preferable because the time required for the temperature of the heating roller 92 to converge after the warm-up is completed (see FIG. 5) depends on the environmental temperature. In winter when the environmental temperature is low (for example, the environmental temperature is 5 ° C. or lower), it tends to take time for the temperature of the heating roller 92 to converge. Therefore, it is desirable to extend the third reference time T3 (for example, +10 seconds). On the contrary, in the summer when the environmental temperature is high (for example, the environmental temperature is 25 ° C. or higher), it is desirable to shorten the third reference time T3 (for example, -10 seconds). The temperature detected by the thermistor 96 before the start of warm-up can be used to detect the environmental temperature. Of course, a dedicated temperature sensor may be provided separately.

The control according to the time required for warm-up is preferable because the required time reflects the temperature of the heating roller 92 before the start of warm-up. When the initial temperature of the heating roller 92 is low, that is, when the heating roller 92 has cooled down due to the rest period, the warm-up time is naturally long (for example, 1 minute or more). In this case, it is desirable to extend the third reference time T3 because it is the same as when the environmental temperature is low. On the contrary, when the heating roller 92 has some residual heat remaining in the previous operation, the time required for warming up is naturally short (for example, less than 30 seconds). In this case, it is desirable to shorten the third reference time T3. The time required for warm-up can be measured by equipping the timer 54 with the necessary functions.

As described in detail above, according to the image forming apparatus 1 of the present embodiment, when the operation is resumed from the hibernation state, the fixing unit 94 is not only warmed up, but also according to the length of the hibernation period. , It is decided to appropriately perform the recovery operation or the prevention operation of the deformation habit of the fixing nip 95. In particular, when the rest period is medium in length, image formation is permitted at an early stage when the warm-up is completed, and the preventive action is performed at an appropriate timing thereafter. In this way, an image forming apparatus 1 has been realized in which an image-forming state can be quickly obtained while appropriately eliminating or preventing deformation habits according to the length of the rest period.

It should be noted that the present embodiment is merely an example and does not limit the present invention in any way. Therefore, as a matter of course, the present invention can be improved and modified in various ways without departing from the gist thereof. For example, the type of the heater 99 may be another type such as an IH heater or a Joule heater. Further, the configuration of the fixing portion 94 may be another type such as one having a fixing belt. The image forming apparatus 1 may also be a monochrome type or a double-sided printing type.

1 Image forming device 2K Imaging unit 16 Secondary transfer roller 40 Intermediate transfer belt 51 Engine control unit 54 Timer 55 Non-volatile memory 92 Heating roller 94 Fixing unit 95 Fixing nip 97 Pressurizing roller 99 Heater

Claims (8)

An image forming portion that forms a toner image and applies it to the medium, a fixing portion composed of two opposing rollers that fix the toner image applied to the medium by heating, and a stop time of the rollers are measured. It is an image forming apparatus having a time measuring unit and
It has a restart control unit that controls the operation of the fixing unit when the operation is resumed after the pause according to the time of the clock unit when the operation is resumed.
The restart control unit
About the timekeeping time
Long-term suspension, which is longer than the predetermined first reference time, and
A mid-term pause that is less than the first reference time and is greater than or equal to the second reference time, which is shorter than the first reference time and defined in advance.
A pause period determination unit for determining which of the short-term pauses is less than the second reference time, and
In the case of the long-term rest
Deformation recovery operation that recovers the deformation habit generated in the roller, and
A warm-up that raises the temperature of the roller to a predetermined fixing temperature is started together.
A deformation recovery control unit that enables image formation when both the deformation recovery operation and the warm-up are completed, and a deformation recovery control unit.
In the case of the above-mentioned mid-term suspension
Start the warm-up and
When the warm-up is completed, the image formation permission state is set.
Deformation that performs a deformation prevention operation to prevent the roller from deforming when the elapsed time before the start of image formation reaches a predetermined third reference time after the image formation permission state is set. Prevention control unit and
In the case of the short break
Start the warm-up and
Possess a normal resumption control unit to the image forming permission state when the warm-up is completed,
The restart control unit
When the power is turned on, the time of the timing section from the end of the last rotation of the roller before the power is stopped
An image forming apparatus characterized in that the above-described operation control is performed according to time. An image forming portion that forms a toner image and applies it to the medium, a fixing portion composed of two opposing rollers that fix the toner image applied to the medium by heating, and a stop time of the rollers are measured. It is an image forming apparatus having a time measuring unit and
It has a restart control unit that controls the operation of the fixing unit when the operation is resumed after the pause according to the time of the clock unit when the operation is resumed.
The restart control unit
About the timekeeping time
Long-term suspension, which is longer than the predetermined first reference time, and
A mid-term pause that is less than the first reference time and is greater than or equal to the second reference time, which is shorter than the first reference time and defined in advance.
A pause period determination unit for determining which of the short-term pauses is less than the second reference time, and
In the case of the long-term rest
Deformation recovery operation that recovers the deformation habit generated in the roller, and
A warm-up that raises the temperature of the roller to a predetermined fixing temperature is started together.
A deformation recovery control unit that enables image formation when both the deformation recovery operation and the warm-up are completed, and a deformation recovery control unit.
In the case of the above-mentioned mid-term suspension
Start the warm-up and
When the warm-up is completed, the image formation permission state is set.
Deformation that performs a deformation prevention operation to prevent the roller from deforming when the elapsed time before the start of image formation reaches a predetermined third reference time after the image formation permission state is set. Prevention control unit and
In the case of the short break
Start the warm-up and
It has a normal restart control unit that enables image formation when the warm-up is completed.
The image forming apparatus is characterized in that the third reference time is set longer when the environmental temperature at the time of resuming operation is low than when the environmental temperature is high. An image forming portion that forms a toner image and applies it to the medium, a fixing portion composed of two opposing rollers that fix the toner image applied to the medium by heating, and a stop time of the rollers are measured. It is an image forming apparatus having a time measuring unit and
It has a restart control unit that controls the operation of the fixing unit when the operation is resumed after the pause according to the time of the clock unit when the operation is resumed.
The restart control unit
About the timekeeping time
Long-term suspension, which is longer than the predetermined first reference time, and
A mid-term pause that is less than the first reference time and is greater than or equal to the second reference time, which is shorter than the first reference time and defined in advance.
A pause period determination unit for determining which of the short-term pauses is less than the second reference time, and
In the case of the long-term rest
Deformation recovery operation that recovers the deformation habit generated in the roller, and
A warm-up that raises the temperature of the roller to a predetermined fixing temperature is started together.
A deformation recovery control unit that enables image formation when both the deformation recovery operation and the warm-up are completed, and a deformation recovery control unit.
In the case of the above-mentioned mid-term suspension
Start the warm-up and
When the warm-up is completed, the image formation permission state is set.
Deformation that performs a deformation prevention operation to prevent the roller from deforming when the elapsed time before the start of image formation reaches a predetermined third reference time after the image formation permission state is set. Prevention control unit and
In the case of the short break
Start the warm-up and
It has a normal restart control unit that enables image formation when the warm-up is completed.
The timekeeping unit has a warm-up timekeeping unit that measures the warm-up time, which is the time required for the warm-up.
The restart control unit is an image forming apparatus including an expansion / contraction processing unit that extends the third reference time when the warm-up time is long and shortens it when the warm-up time is short. An image forming portion that forms a toner image and applies it to the medium, a fixing portion composed of two opposing rollers that fix the toner image applied to the medium by heating, and a stop time of the rollers are measured. It is an image forming apparatus having a time measuring unit and
It has a restart control unit that controls the operation of the fixing unit when the operation is resumed after the pause according to the time of the clock unit when the operation is resumed.
The restart control unit
About the timekeeping time
Long-term suspension, which is longer than the predetermined first reference time, and
A mid-term pause that is less than the first reference time and is greater than or equal to the second reference time, which is shorter than the first reference time and defined in advance.
A pause period determination unit for determining which of the short-term pauses is less than the second reference time, and
In the case of the long-term rest
Deformation recovery operation that recovers the deformation habit generated in the roller, and
A warm-up that raises the temperature of the roller to a predetermined fixing temperature is started together.
A deformation recovery control unit that enables image formation when both the deformation recovery operation and the warm-up are completed, and a deformation recovery control unit.
In the case of the above-mentioned mid-term suspension
Start the warm-up and
When the warm-up is completed, the image formation permission state is set.
Deformation that performs a deformation prevention operation to prevent the roller from deforming when the elapsed time before the start of image formation reaches a predetermined third reference time after the image formation permission state is set. Prevention control unit and
In the case of the short break
Start the warm-up and
It has a normal restart control unit that enables image formation when the warm-up is completed.
An image forming apparatus having a non-volatile memory for storing the time when the rotation of the roller is completed. The image forming apparatus according to any one of claims 1 to 4 , wherein the deformation recovery operation is performed.
An image forming apparatus characterized in that the roller is forcibly rotated over a predetermined time. The image forming apparatus according to any one of claims 1 to 5 , wherein the deformation prevention operation is performed.
An image forming apparatus characterized in that it is an operation of changing the facing portion by rotating the roller at a rotation angle of less than one rotation. The image forming apparatus according to any one of claims 1 to 6.
As the temperature control method of the fixing unit, a heating control unit having at least a standby method during non-image formation and a run-time method during image formation execution, which has a stronger degree of heating than the standby method, is provided. Have and
The restart control unit causes the heating control unit to perform temperature control by the run-time method or a method in which the degree of heating is stronger than that during the deformation recovery operation and the deformation prevention operation. An image forming apparatus characterized by. The image forming apparatus according to claim 5 , or the image forming apparatus according to claim 6 or 7, which has the matters specifying the invention of claim 5.
An image forming apparatus characterized in that the execution time of the forced rotation can be changed by the user's choice.

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