JPH10149051A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device in which eliminating waste warming-up time prevents working efficiency from reducing and saves energy. SOLUTION: The image forming device reads job data for past one week out of a history storing memory (831), and converts number of sheets copied for each job data to number of A4-sized recording sheets (832). The image forming device divides each number of jobs after the data conversion to classes by number of 100 copied sheets for each job and creates a Parate graph representing cumulative sum (833), sets a sheet class of the job number which occupies 80% of total job number in the Parate graph (834), and assumes the maximum number of sheets for the set class as number of sheets copied in the hereafter processed job (835). Then it calculates an optimum fixing temperature Ta for copying sheets sequentially by set number of copied sheets on the basis of pre-stored data (836), and finishes warming-up to allow copy when temperature of the fixing roller reaches the optimum fixing temperature Ta.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having a fixing device such as a copying machine or a laser printer.

[0002]

2. Description of the Related Art In a copying machine in which an image is formed by a normal electrostatic copying method, a toner image formed on a photosensitive drum is transferred onto a recording sheet such as copy paper by an electrostatic force of a transfer charger. The recording sheet is fixed by applying pressure while heating the recording sheet at a high temperature of, for example, about 160 ° C. by a fixing roller having a built-in heater.

[0003] However, since a general copying machine uses a household power source, there is a limit to the power supplied to the heater.
Since the amount of heat taken by the recording sheet is greater than the amount of heat generated by the heater, when a large number of recording sheets are continuously copied, the temperature of the fixing roller gradually decreases, and finally, Is below the lower limit of the fixing temperature (this temperature is hereinafter referred to as “fixing lower limit temperature”), which results in uneven fixing strength.

Recently, in order to increase the efficiency of office work, a copying machine capable of processing a large number of copies in a short time has been desired. In order to meet this demand, for example, an A3-size recording sheet is printed every minute. At a copying speed of 60 sheets (CPM),
Although a copying machine capable of continuously copying 500 sheets has appeared, as described above, since the temperature of the fixing roller is unavoidable to gradually decrease, the temperature of the fixing roller must be set in advance from the fixing lower limit temperature. The temperature is set to be higher by a predetermined temperature (the higher temperature is hereinafter referred to as a “maximum set temperature”), and after sufficient heat energy is accumulated in the fixing roller, the execution of the image forming operation is permitted. The temperature of the fixing roller does not become lower than the above-mentioned minimum fixing temperature even when sheets are continuously copied.

[0005]

However, usually,
At most 100 or 200 A4 size recording sheets
In spite of the fact that there are almost all requests to continuously copy about one sheet (hereinafter, such a copy request is referred to as “job”), in the above-described conventional copying machine, the fixing roller is uniformly A3 size. Since the image forming operation is not permitted until the maximum set temperature required for continuously copying 500 recording sheets is reached, the waiting time until the warm-up is completed becomes extremely long, and the efficiency of the copying operation is reduced. In addition, the fixing roller is heated more than necessary, which consumes extra power and contradicts energy saving.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an image forming apparatus capable of preventing a reduction in work efficiency by eliminating useless warm-up waiting time and saving energy. With the goal.

[0007]

In order to achieve the above object, in an image forming apparatus according to the present invention, there is provided a toner image forming means for forming a toner image on a recording sheet, and a toner image formed on the recording sheet. A fixing unit for fixing the image by heating the image to a first temperature or higher; and detecting a temperature of the fixing unit. When the detected temperature reaches a second temperature which is higher than the first temperature by a predetermined temperature. A permission unit for permitting execution of the image forming operation by the toner image forming unit, and a history of jobs processed in the past in the image forming apparatus capable of continuously processing a series of designated image forming operation jobs. And calculating the temperature of the fixing unit required to continuously process the job of the predicted amount based on the calculated temperature. Characterized in that it comprises a temperature setting means for setting as said second temperature.

Further, in the image forming apparatus of the present invention,
The prediction means includes a history storage means for storing, as job data, the size of the recording sheet and the number of times of image formation for each job, based on the stored job data, the amount of a job to be performed in one time in the future. Is converted into the number of times of image formation on a recording sheet having a predetermined reference size.

Further, in the image forming apparatus of the present invention,
The image forming speed controls the image forming speed such that the temperature of the fixing unit does not become lower than the first temperature when performing an image forming operation exceeding the predicted job amount. It may be characterized by having a control means.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a copying machine according to the present invention will be described below by taking a monochromatic 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 with reference to FIG. As shown in FIG. 1, the copying machine is roughly divided into an image reader section 10 for reading a document image, and an image reader section 10 for reading the original image.
And a printer unit 20 for reproducing the image read by the printer.

The scanner 11 of the image reader unit 10
An exposure lamp 12 for irradiating a document and a CCD image sensor (hereinafter, referred to as a CCD image sensor) for converting reflected light from the document to an electric signal
Simply called "CCD sensor". When the operator gives an instruction to start copying from the operation panel 60 (see FIG. 4), the scanner 11 moves in the direction of the arrow by a driving unit (not shown) and scans the original set on the original glass plate 15.

The image data thus obtained is subjected to A / D conversion in the image processing unit 110, and further subjected to necessary processing such as shading correction, density conversion, and edge enhancement, and then described later via the control unit 100. Exposure scanning unit 20
A is output to A. The printer unit 20 forms an image by a known electrostatic copying method, and includes an exposure scanning unit 20A.
And an image forming process unit 20B and a paper feeding unit 20C.

The laser diode 21 of the exposure scanning section 20A
Receives a drive signal from the control unit 100 and emits a laser beam. This laser light is reflected and deflected by the mirror surface of the polygon mirror 23 that is driven to rotate at a constant speed, and exposes and scans the surface of the photosensitive drum 27 in the image forming process unit 20B. The photosensitive drum 27 is cleaned by a cleaner 28 to remove residual toner before receiving the above-described exposure, and is further irradiated with an eraser lamp 29 to be neutralized. Thereafter, the photosensitive drum 27 is uniformly charged by a charging charger 30. When exposed to the laser beam in a state of being uniformly charged, an electrostatic latent image is formed on the surface of the photosensitive drum 27. The electrostatic latent image is developed by receiving toner supplied by the developing device 31, thereby forming a toner image on the surface of the photosensitive drum 27.

On the other hand, a predetermined recording sheet is supplied from one of the paper cassettes 40 to 42 of the paper supply section 20C in synchronization with the image forming operation of the photosensitive drum 27 by a paper supply roller 401 (4).
11, 421), the sheet is fed to a transfer position below the photosensitive drum 27 by a sheet feeding mechanism such as the timing roller 33 and the transport belt. At this transfer position, the toner image formed on the photosensitive drum 27 is transferred onto the recording sheet by the electrostatic force of the transfer charger 32 installed on the back of the transport belt 34.

Thereafter, the recording sheet onto which the toner image has been transferred is conveyed to a fixing device 36 by a conveying belt 35. FIG. 2 is an enlarged view of the vicinity of the fixing device 36. As shown in the figure, the fixing device 36 includes a pair of fixing rollers 36.
1, 362, and inside the upper fixing roller 361,
While a heater 363 is built in, a fixing temperature sensor 3 for detecting the surface temperature is provided on the surface of the roller 361.
64 are provided.

When the recording sheet S1 having the toner image transferred onto the upper surface thereof is conveyed to the fixing device 36 thus configured, the recording sheet S1 is further sandwiched between the rotating fixing rollers 361 and 362 and further pressed forward while being pressed against the same. . Fixing roller 36
1 is a predetermined fixing temperature (about 160
° C), and when pressed to such a high temperature, the toner particles on the surface of the recording sheet S1 are melted and adhered to the sheet surface and fixed. The recording sheet S <b> 1 fixed by the fixing device 36 is discharged onto a discharge tray 38 via a discharge roller 37.

The appearance of the copying machine is shown in FIG. 3. As shown in FIG. 3, an opening / closing door 50 for maintenance is provided on the front of the copying machine. Replenishment / replacement and paper jam processing can be performed. A main switch 51 is provided on the side of the copying machine, and an operation panel 60 is provided on the top of the copying machine for the user to input the number of copies, paper size, etc. and instruct the start of copying. (2) Configuration of Control Unit 100 FIG. 4 is a block diagram illustrating a configuration of the control unit 100.

The control unit 100 includes a CPU 101 and a timer 1 for setting the processing time of each routine described later.
04, a RAM 105 for temporarily storing various setting contents such as a copy mode, and an RO for storing a control program for each unit such as the image reader unit 10 and the printer unit 20.
M106, and a history storage memory 107 for storing, for each job processed based on an input operation from the operation panel 60, the sheet size and the number of copies of the recording sheet as job data.

The CPU 101 operates in accordance with a control program stored in the ROM 106 to control the image reader unit 1.
0. A smooth copying operation is achieved by uniformly controlling the operation of the printer unit 20. When the main switch 51 is turned on, the CPU 101 instructs the power supply unit 70 to cause the heater 363 to supply power by setting the ratio of the energizing time per unit time (duty ratio) to 100%, thereby starting warming up. Then, when the detected temperature T of the fixing temperature detecting sensor 364 rises and matches the predetermined set temperature Tp, it is determined that the warming-up is completed.

Thereafter, the CPU 101 appropriately changes the duty ratio so that the fixing roller 362 changes the set temperature T.
The temperature is controlled so as to be maintained at p. After the warm-up is completed, when the user operates the operation panel 60 to set a copy mode such as the number of prints or the paper size and presses the print key, the CPU 101 stores the copy mode in the RAM 105 and stores the copy mode in the RAM 105. Then, the image reader unit 10 and the printer unit 20 are controlled to execute a copy operation.

If a large number of recording sheets are continuously copied at a high speed, even if the duty ratio is set to 100% and the power is supplied to the heater 363, the amount of heat absorbed by the recording sheets per unit time is larger. The temperature T of the fixing roller 362 may gradually decrease from the set temperature Tp, and the detected temperature T of the fixing roller 362 may drop below the fixing lower limit temperature Th before copying to all of the recording sheets is completed. In this case, the CPU 101 performs control (hereinafter, referred to as “CPM control”) for changing the image forming speed in the printer unit 20, that is, the copy speed (CPM) so that the temperature does not become lower than the fixing lower limit temperature minimum Th. Like that. Details will be described later. (3) Control Operation in Control Unit 100 Next, the control operation of the control unit 100 will be described based on the flowcharts shown in FIGS.

FIG. 5 is a flowchart showing a main routine executed by CPU 101 of control unit 100. When the power of the copier 1 is turned on by turning on the main switch 51, the CPU 101
5 and so on are initialized (step S1). At this time, the maximum set temperature Tp stored in the ROM 106 is used as an initial value of the set temperature Tp of the heater 363 of the fixing device 36.
max is set, and various flags described later are set to initial values.

Then, the timer 104 is started (step S2), the predetermined processing of steps S3 to S8 is performed, and the completion of the timer 104 is monitored (step S2).
8) Then, the process returns to step S2, and thereafter from step S3
Steps S8 to S8 are executed at predetermined time intervals set in the timer 104. In step S3, the CPU 101
Calculates a fixing temperature Ta (described later) based on past job data stored in the history storage memory 107, and sets the optimum fixing temperature Ta to the set temperature Tp instead of the maximum set temperature Tmax. Execute

FIG. 6 is a flowchart showing a subroutine of the fixing temperature setting process in step S3. CP
U101 first reads job data performed in the past week from the history storage memory 107 (step S3).
1). FIG. 9 shows an example of the job data for one week, and shows the number of times of the job having the same number of copies for each used paper size. From this figure, it can be seen that, for example, the number of jobs for continuously copying 200 sheets on an A4 size recording sheet was 10 times in the past week.

By the way, when fixing the recording sheet,
The amount of heat absorbed by the recording sheet from the fixing roller 361 is
It depends on the size of the recording sheet and is proportional to the size (area). For this reason, in step S32, an operation of converting the number of copies in each job data into the number of A4 size recording sheets that can be used frequently is performed. That is, the number of copies is doubled for A3 size, 1.5 times for B4 size, and 0.5 times for A5 size. The data of the number of copies and the number of jobs converted into the A4 size are obtained as shown in FIG.

Next, the number of times of each job whose number of copies has been converted in this way is classified into the number of copies for every 100 copies, and the cumulative sum thereof is obtained.
Create a Pareto chart as shown in (step S33),
In this Pareto diagram, the number of copies of the number of jobs occupying 80% of the whole is set (step S34), and the maximum number of copies in the set number of copies is determined as the number of copies of jobs to be processed in the future (hereinafter, referred to as "set number of copies"). (Step S35). For example, in the Pareto diagram of FIG. 11, the number of jobs in the 1-100 sheet classification is less than 80% of the total, but the total number of jobs in the next 101-200 sheet classification is 95% in total. , The maximum number 200 in this number section is set as the set number of copies.

Next, the temperature of the fixing roller 362 (hereinafter referred to as "optimal fixing temperature") required to continuously copy the maximum number of recording sheets (set number of copies) is obtained (step S36). For this reason, the ROM 106 contains
For example, data indicating the correspondence between the number of copies when the A4 size recording sheet as shown in FIG. 12 is continuously copied at a copying speed of 60 CPM and the fixing temperature of the fixing roller 362 required at that time is stored in advance. And CP
U101 determines the optimum fixing temperature Ta required for continuously copying the set number of recording sheets based on the data.

Then, the optimum fixing temperature Ta is set as a set temperature Tp for controlling the temperature of the fixing roller 362 (step S37), and the process returns to the main routine. Returning to FIG. 5, in step S4, the CPU 101
Performs the fixing temperature control process by controlling the amount of current supplied to the heater 363 by the above-described duty ratio control so that the fixing roller 362 becomes the optimum fixing temperature Ta.

Next, in step S5, a key input process for setting a copy mode and receiving a copy start instruction is executed. FIG. 7 is a flowchart showing a subroutine of the key input process in step S5. In this key input processing, the CPU 101
When the temperature rises to the optimum fixing temperature Ta, printing is permitted (Yes in step S51), and the copy mode input from the operation panel 60, that is, the number of prints, the recording sheet size, other copy magnification, and the like are set. When the settings (steps S52, S53, S54) are received and the print key is turned on (Y in step S55)
es) The copy mode setting contents temporarily stored in the
It is stored in M105 (step S56), and the process returns to the main routine. If the print is not permitted in step S51 or if the print key is not turned on in step S55, the process returns to the main routine.

Returning to FIG. 5, after performing a document reading process of reading a document by the image reader unit 10 in step S6,
In step S7, a print process for printing on a recording sheet of a predetermined size is executed in accordance with the setting contents of the copy mode stored in the RAM 105.
In step 8, a job content storage process for storing the content of the job in the history storage memory 107 is executed.

FIG. 8 is a flowchart showing a subroutine of the printing process in step S7. CPU1
01 first determines whether the power-on flag is "0" (step S71). The power-on flag indicates whether or not the warm-up has been completed. In the initial setting in step S1, "0" indicating that the warm-up is being performed is set as an initial value.

If the power-on flag is "0" in step S71, it is next determined whether or not the detected temperature T of the fixing roller 363 is equal to or higher than the optimum fixing temperature Ta (step S71).
72) If the temperature is not equal to or higher than the optimum fixing temperature Ta, the warming-up has not been completed, so printing is prohibited (step S73), and the process returns to the main routine.

When the detected temperature T reaches the optimum fixing temperature Ta in step S72, the power-on flag is set to "1" (step S74), and printing is permitted (step S75). This allows the image forming operation to be performed when the fixing roller 362 has reached the optimum fixing temperature Ta (see FIG. 12) lower than the maximum set temperature Tmax. Can be improved. Also, A4
Since only the amount of heat capable of continuously processing 200 recording sheets of the size needs to be accumulated in the fixing roller, it is not necessary to heat the fixing roller 362 more than necessary, so that waste of energy can be eliminated and energy saving can be achieved. it can.

Next, it is determined whether or not the print key on the operation panel 60 has been turned ON (step S76). When it is turned ON, printing on a recording sheet is executed at a predetermined copying speed (step S77). In this step S77, based on the temperature of the fixing roller 361, the copying speed is set to the high speed mode (60 CPM) or the low speed mode (30 CP
M) is a CPM control process for executing printing by switching to M).

In this process, the CPU 101 first determines whether or not the copy speed flag is "0" (step S771). The copy speed flag indicates whether the current copy speed is the high-speed mode or the low-speed mode. In the initial setting in step S1, "0" indicating the high-speed mode is set as an initial value. Step S77
In step 1, if the copy speed flag is "0", then it is determined whether the detected temperature T of the fixing roller 361 exceeds the lower limit fixing temperature Th (step S772). Printing is performed with the settings (step S773), the number of copies is counted (step S774), and the process returns to the main routine.

On the other hand, if the user specifies more than the expected set number of copies of 200 or more copies, if the user continues to copy at more than 200 copies at 60 CPM, as described above. Since the heater 363 is heated only to a temperature at which continuous copying of 200 sheets is possible, the temperature will eventually fall below the fixing lower limit temperature Th. In order to avoid this, in the present embodiment, as shown in FIG. 13, the CPM control for switching the copying speed to the low speed mode from the time when the detected temperature T of the fixing roller 362 reaches the fixing lower limit temperature Th during copying. I do.

That is, if the detected temperature T of the fixing roller 362 has decreased to the fixing lower limit temperature Th in step S772, the copying speed flag is set to "1" (step S775), and the process returns to the main routine. When the routine circulates and reaches step S711 again, the copying speed flag is set to “1”, so the process proceeds to step S776, where the fixing roller 362 is first set.
It is determined whether or not the detected temperature T is equal to or higher than the optimum fixing temperature Ta. At this time, if the detected temperature is lower than the optimum fixing temperature Ta (No in step S776), the copy speed is set to 30.
Copy to CPM and continue copying (step S77
7) Count the number of copies (step S77)
8) Return to the main routine. When the copying speed is reduced in this manner, the amount of heat absorbed by the recording sheet per unit time at the time of fixing is reduced, and the amount of heat generated by the heater 363 is higher, and the temperature of the fixing device is increased while continuing copying. Becomes possible.

In step S776, the fixing roller 36
When the detected temperature T of No. 2 reaches the fixing optimum temperature Ta, the copy speed flag is reset to “0” (step S779),
Prepare to return the copy speed to 60 CPM and return to the main routine. By controlling the copying speed in this manner, it is possible to continuously process a large number of jobs that are rarely performed without interrupting the copying operation.

Returning to FIG. 5, in step S8, C
At the end of the job, the PU 101 determines the size of the recording sheet stored in the RAM 105 together with the number of copies.
The job data is stored in the history storage memory 107 as new job data, and the job content storage processing is executed. This job data is used for predicting the amount of the job after the next time (see FIG. 6, S
31) Therefore, it is possible to always set the optimum fixing temperature Ta based on the latest usage tendency. (4) Modifications Although the image forming apparatus according to the present invention has been described based on the embodiment, it goes without saying that the content of the present invention is not limited to the above-described embodiment. Modifications are possible.

(4-1) In the above embodiment, the warm-up is started by manually turning on the main switch 51. However, an automatic document feeder (ADF) is installed in the image reader section 10, and The apparatus power supply may be automatically turned on by detecting the setting of the document on the automatic conveyance device by an optical sensor or the like, and the warm-up may be started.

(4-2) In the above embodiment, after the fixing roller 361 has reached the optimum fixing temperature Ta, the operation panel 6
Although the setting of the copy mode from 0 has been received, these settings may be received before that. When an automatic document feeder is installed, the time required to read the document is calculated from the thickness of the document when the document is set in the automatic document feeder, and a fixing temperature detection sensor is set when warm-up starts. The temperature of the fixing roller 362 is measured by 364 to calculate the warming-up completion time, the warming-up completion time is compared with the document reading completion time, and the automatic document feeder starts reading the document at an optimal timing during the warming-up. May be instructed to the image reader unit 10.

(4-3) In the above embodiment, the total number of jobs in the past week is classified according to the number of jobs, and the maximum number of jobs in the number of jobs occupying at least 80% of the number of jobs is estimated as the amount of jobs expected in the future. However, this percentage may be appropriately changed according to the required ratio of power saving and work efficiency. (4-4) In the above embodiment, the set number of copies is obtained from the Pareto chart. However, the set number of copies may be obtained by another statistical method such as a histogram.

(4-5) In the above embodiment, the copying speed is reduced when the detected temperature of the fixing roller 362 reaches the fixing lower limit temperature Th during copying. However, the printing operation is temporarily stopped and the detected temperature is lowered. The printing operation may be resumed after the recovery of the print data. (4-6) In the above embodiment, the maximum set temperature Tmax is set as the initial value. However, the optimum set temperature Ta obtained last time is stored, and this optimum set temperature Ta is set as the initial value. You may do so.

(4-7) In the above embodiment, the amount of the job in the future is predicted from the job data of the past week, but the job data of the past month, the same day of the week, the same time zone, etc. You may make it predict. (4-8) Further, in the above-described embodiment, the present invention is applied to a single-color digital copying machine. However, the present invention can be applied to other image forming apparatuses including a fixing device such as a color or analog copying machine or a laser printer.

[0045]

As described above, according to the present invention, the amount of a job to be performed one time in the future is predicted based on the history of jobs processed in the past by the prediction means.
The temperature setting unit calculates the temperature of the fixing unit necessary for continuously processing the predicted amount of jobs, and when this temperature is reached, image formation is permitted. It is not necessary to raise the temperature, so that the waiting time until warm-up can be reduced, and unnecessary power consumption can be eliminated to save energy.

Further, according to the present invention, the prediction means comprises:
A history storage unit is provided for each job to store the size of the recording sheet and the number of image formations as job data. Based on the stored job data, the amount of a job to be performed in the future is determined according to a predetermined standard. Since it is obtained by converting the size into the number of times of image formation on the recording sheet, it is possible to accurately predict the amount of jobs in the future.

Further, according to the present invention, when the toner image forming means performs an image forming operation exceeding the predicted job amount, the temperature of the fixing means does not become lower than the first temperature. Since the image forming speed control means for controlling the image forming speed is provided as described above, even if a job is requested exceeding the predicted job amount, it can be processed continuously.

[Brief description of the drawings]

FIG. 1 is a diagram showing an entire configuration of a copying machine according to the present invention.

FIG. 2 is an enlarged view of the vicinity of a fixing device of the copying machine.

FIG. 3 is an external perspective view of the copying machine.

FIG. 4 is a block diagram of a control unit of the copying machine.

FIG. 5 is a flowchart showing the operation of the control unit.

FIG. 6 is a diagram showing a subroutine of a fixing temperature setting process (step S3) of FIG. 5;

FIG. 7 is a diagram showing a subroutine of a key input process (step S5) of FIG. 5;

FIG. 8 is a diagram showing a subroutine of the print processing (step S7) of FIG.

FIG. 9 is a diagram showing a history of jobs processed in the past week.

FIG. 10 is a diagram showing a state in which the number of copies of each job in FIG. 9 is converted into an A4 size number.

11 is a Pareto diagram in the case where the number of jobs in FIG. 9 is stratified into the number of copies every 100 copies.

FIG. 12 is a diagram illustrating a correlation between the number of continuous copies and an optimum fixing temperature.

FIG. 13 is a diagram illustrating a state of a temperature change of a fixing roller by CPM control.

[Explanation of symbols]

 Reference Signs List 10 image reader unit 20 printer unit 36 fixing device 51 main switch 60 operation panel 70 power supply unit 100 control unit 101 CPU 104 timer 105 RAM 106 ROM 107 history storage memory 361 fixing roller 363 heater 364 fixing temperature sensor

Claims (3)

[Claims] A toner image forming means for forming a toner image on a recording sheet; a fixing means for heating and fixing the toner image formed on the recording sheet to a first temperature or higher; Detecting a temperature, and the detected temperature is the first temperature.
A permission unit for permitting execution of the image forming operation by the toner image forming unit when the temperature reaches a second temperature which is higher than the temperature by a predetermined temperature. Means for predicting the amount of a job to be performed in the future based on the history of jobs processed in the past, and continuously processing the estimated amount of jobs. And a temperature setting unit that calculates a temperature of the fixing unit necessary to perform the fixing and sets the temperature as the second temperature. 2. The image processing apparatus according to claim 1, wherein the predicting means includes a history storing means for storing, as job data, the size of a recording sheet and the number of times of image formation for each job, based on the stored job data, 2. The image forming apparatus according to claim 1, wherein the amount of the job per hit is calculated by converting the number of image formations on a recording sheet of a predetermined reference size. 3. The image forming apparatus according to claim 1, wherein the toner image forming unit controls an image forming speed such that a temperature of the fixing unit does not become lower than the first temperature when performing an image forming operation exceeding the predicted job amount. The image forming apparatus according to claim 1, further comprising an image forming speed control unit for controlling.