JPS63153166A - Image forming system - Google Patents

Abstract

PURPOSE:To compensate the light to be emitted from a LED to a constant level, by calculating data correlating with the light to be outputted from LED based on a count in a counter and controlling the power supply time for the LED according to said data. CONSTITUTION:A temperature data for predicting the temperature rise of a LED head 28 calculated on the basis of data being stored in areas 80a, 80b of a memory 80 is loaded to a register in CPU 76' The count in a counter 84 is data for setting the power supply time rate or the power supply time data of LED elements to be lighted. Even if temperature rise of the LED head 28 causes lowering of the output from the LED elements, the output of light to be emitted can be maintained at a constant level by gradually lengthening the power supply time of the LED elements every minute, thereby a constant exposure light can be obtained within a range where the temperature of the LED elements does not exceed a limit level, resulting in a good print image at all times.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an image forming apparatus, and particularly to an image forming apparatus that selectively lights up an arbitrary LED element of an LED head having a large number of LED elements according to print data to form an image. Related to an image forming apparatus that performs (prior art)
For example, an image forming apparatus that detects the temperature of the D head with a temperature sensor and changes the intensity of the current of the LED head based on the detected temperature so as to always obtain a constant output light is disclosed in Japanese Patent Laid-Open No. 59 This is disclosed in, for example, Japanese Patent No.-202879.

(Problems to be Solved by the Invention) In the conventional device described above, since the temperature of the LED head is directly detected, the circuits associated with the temperature sensor and the temperature monitor become complicated, which impedes miniaturization of the entire device. It was not possible to reduce costs.

Therefore, a main object of the present invention is to provide an image forming apparatus that can compensate the output light of an LED head to a constant value with a simple and inexpensive configuration.

(Means for Solving the Problems) To put it simply, the present invention includes a photoreceptor, a plurality of LED elements, and an arbitrary LED element for each printing request.
An LED head for selectively lighting an element to irradiate the photoreceptor with exposure light, a counting means for counting the number of lit LED elements of the LED head, and a light output of the LED element based on the count value of the counting means. The image forming apparatus includes calculation means for calculating correlation data, and energization control means for controlling the energization time of the LED head according to the optical output correlation data.

(Operation) When an image formation request is made, the LED head is driven, and an arbitrary LED element is selectively turned on according to the image or print data. Exposure light corresponding to the data is generated by selectively lighting the LED elements, the exposure light is irradiated onto the photoreceptor, and the number of lit LED elements is counted by the counting means. Thereafter, the energization control means controls the energization time of the LED head based on the count value.

When the count value by the counting means is large, LE
Since the output light of the D element is probably decreasing, at this time, the energization control means lengthens the energization time of the LED element so as to keep the output light of the LED element constant. On the other hand, when the count value is small, the light output of the LED element has not decreased so much, and therefore a predetermined output light can be obtained in a short energization time, so the energization control means controls the energization time of the LED element. shorten.

(Effects of the Invention) According to the present invention, the lighting of the LED head can be controlled based on the count value of the counting means, without directly measuring the temperature with a temperature sensor as in the conventional case. Therefore, the temperature sensor and the circuit associated with the temperature sensor can be omitted, making it possible to downsize the entire image forming apparatus and reduce costs.

Based on the count value at each fixed time, it is possible to compensate for a decrease in output light due to a temporary rise in temperature of the LED element, and based on the accumulated count value, it is also possible to compensate for a decrease in output light due to aging. can do.

That is, when the temperature of the LED element increases due to continuous printouts, the output light of the LED element decreases, but this decrease in output light can be predicted by the count value of the counting means. Then, the output light of the LED element can be kept constant by controlling the energization control means to increase the energization time based on the count value.

Furthermore, if the characteristics of the LED element change over time, that is, if the accumulated count value is large, the output light of the LED element may have decreased due to long-term use. The decrease in output light can be compensated for by controlling the LED element to lengthen the energization time.

The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

(Example) FIG. 2 is an illustrative cross-sectional view showing one embodiment of the present invention.

Although the present invention will be described below as applied to an image forming apparatus, it should be understood that the present invention can also be applied to other image forming apparatuses other than such printers, such as copying machines and facsimile machines. Let me point this out in advance.

The printer 10 includes a main body 12. A cover 14 and a cover 16, which are separated at the center, are provided flush with the upper part of the main body 12. The cover 14 is fixed to the main body 12 with screws. The cover 16 is attached to the rotating wheel 18 when replenishing toner.
It is installed so that it can be opened upwards with the center at the center.

A paper feed section 22 is formed at one end of the main body 12 for removably mounting a paper feed cassette 20, and a discharge section 24 is formed at the other end for discharging the paper after the fixing process. It is formed.

A photosensitive drum 26 (its driving mechanism is not shown) is arranged approximately in the center of the main body 12 and rotates in the direction of the arrow (clockwise). The photoreceptor material of this photoreceptor drum 26 includes:
Amorphous selenium is used.

A light emitting diode (LED) is provided on the upper part of the photoreceptor drum 26.
) A head 28 is provided. The LED head 28 includes, for example, a red element with an emission wavelength of λ-660 nm, includes an LED head provided in parallel along the length direction of the photoreceptor drum 26, and further includes a groove between the LED head and the photoreceptor. A short focus lens such as a Cellhox lens is inserted between the drum 26 and the drum 26. Therefore, the LED head 28 is configured to
The D element is selectively driven, and the light from the LED element is focused by a lens system and irradiated onto the surface of the photoreceptor drum 26.

A charging corotron 30 is fixedly provided upstream of the LED head 28 in the rotational direction of the photoreceptor drum 26 to uniformly charge the photoreceptor drum 26 positively, for example to about 600 volts.

After being positively charged by the charging corotron 30, when light is irradiated from the LED head 28, an electrostatic latent image according to print data is formed on the surface of the photoreceptor drum 26.

A developing device 32 for developing the electrostatic latent image with toner is provided downstream of the LED head 28 . This developing device 32 stores a developer made of a mixture of toner and carrier. This developer is transferred toward the photosensitive drum 26 by the magnet roller 34 . At this time, a magnetic brush of the developer, that is, a spike is formed on the portion of the magnet roller 34 that faces the photoreceptor drum 26 . When the spikes come into contact with the photoreceptor drum 26, the negatively charged toner is attracted to the electrostatic latent image formed by the positively charged toner. In this way, the electrostatic latent image formed on the photoreceptor drum 26 is developed as a toner image by the developing device 32.

Transfer paper 36 is placed in a stacked manner in a paper feed cassette 20 that is removably attached to one end of the main body 12 . A support plate 38 for placing the transfer paper 36 thereon is provided at the bottom of the paper feed cassette 20 so as to be swingable in the vertical direction. An opening 40 is formed in the lower part of the support plate 38 . The upper part of the push-up lever 42, whose base end is swingably attached to the internal part of the main body 12, is inserted into the opening 40. In relation to this push-up lever 42, the support plate 3
A spring (not shown) is provided for biasing rotation of 8 clockwise. The support plate 38 supports this push-up lever 42
is pushed upward by. Therefore, the transfer sheets 36 stacked in the paper feed cassette 20 are pushed up by the push-up lever 42, and the uppermost transfer sheet 36 comes into contact with the paper feed roller 44 and is taken in. A size detector 46 is provided at a portion corresponding to the leading end of the attached paper feed cassette 20 in order to detect the size of the transfer paper 36 stored in relation to the paper feed cassette 20.

A register roller 48 is provided behind the paper feed roller 44 . The transfer paper 36 fed from the paper feed cassette 20 is temporarily stopped by the register roller 48 and is fed toward the photosensitive drum 26 in synchronization with the exposure by the LED head 28 . A transfer corotron 50 for transferring the toner image developed by the developing device 32 onto the transfer paper 36 is located near the circumferential side of the photosensitive drum 26 at a position where the transfer paper 36 is supplied from the register roller 48. provided. A separation corotron 52 is provided integrally with the transfer corotron 50. This separation corotron 5
2, the transfer paper 36 that is attracted by the residual charge,
By applying an alternating current discharge to neutralize the charge,
It is to be peeled off from the photoreceptor drum 26.

On the downstream side of the separating corotron 52, there is a vacuum conveyor 5 for conveying the transfer paper 36 onto which the toner image has been transferred.
4 is provided. The transfer paper 36 is conveyed toward the fixing device 56 by the vacuum conveyor 54 . The fixing device 56 includes a heating roller 58 with a built-in heater;
and a pressure roller 60 that is pressed against the heating roller 58. The transfer paper 36 on which the toner image has been transferred is inserted between the heating roller 58 and the pressure roller 60, and is heated and pressurized to fix the toner image. A paper discharge roller 62 is provided downstream of the fixing device 56 for discharging the fixed transfer paper 36 to the outside.

A cleaning device 64 is provided above the vacuum conveyor 54 and near the circumferential side of the photoreceptor drum 26 . This cleaning device 64 cleans the transfer paper 36
Toner remaining on the photosensitive drum 26 without being transferred is removed. The cleaning device 64 includes a blade 66 for scraping off residual toner on the photosensitive drum 26 and a screw conveyor 68 for conveying the toner scraped off by the blade 66 to a waste toner container.

An erase lamp 70 is provided upstream of the cleaning device 64 to remove residual charges on the surface of the photoreceptor drum 26 from which residual toner has been removed. The erase lamp 70 uses blue light having a wavelength of λ-4, for example, which causes little optical fatigue on the photoreceptor drum 26 but can completely remove residual charges.
A fluorescent glow lamp producing 50 nm light is used.

A main motor 72 for driving the photosensitive drum 26, the magnet roller 34 of the developing device 32, and the like is provided above the fixing device 56.

The photosensitive drum 26 and the magnet roller 34 are driven by a main motor 72 through a belt or chain.

A control box 74 is provided above the main motor 72. A control section for controlling the overall operation of the printer is provided within the control box 74.

FIG. 3 is a block diagram showing an example of the control system of this embodiment. The printer is controlled by a CPU 76 to which is connected an associated memory 80 through a pass line 78, as well as an I10 port 82 and a counter 84.

A print request signal is applied to the input of the I10 port 82 from a host a that uses such an image forming apparatus as an output device, such as a word processor or a personal computer. The LED head 28 is connected to the output of the I10 boat 82. Print data from a host machine such as a word processor is applied to the data input terminal Din of the LED head 28. A print synchronization clock from a clock source (not shown) is applied to the clock terminal CLK of the LED head 28. Print data is taken into the LED head 28 in a bit-serial manner by a synchronous clock. That is, the synchronization clock causes a shift register in the LED head 28 to be shifted, thereby converting the serial print data into image data for one row, that is, one column of LED elements. When one line of print data is captured, the LED head 28 selectively lights up the LED elements for one line corresponding to the print data. When printing one line like this,
Print data for the next line to be printed is taken into the LED head 28 by a synchronous clock. In this way, by sequentially lighting up the LED elements for each row, the LED head 28 lights up the photosensitive drum 26.
(Fig. 2) is exposed to light.

On the other hand, the print data and the synchronization clock are ANDed by an AND gate 86, and the clock terminal C of the counter 84 is
Also given to LK. That is, the counter 84 is
The number of LED elements lit in the D head 28 is continuously counted. Then, for example, one minute of count data is stored in area 80a of memory 80 every minute. Area 80a always stores count data for a certain past period of time, for example, 30 minutes. That is, when the latest 1-minute count data is supplied from the counter 84, the 1-minute count data from 30 minutes ago is cleared, and the newly stored 1-minute data is added to the past 29 minutes' data in its place. and stored.

In the area 80b of the memory 80, like the area 80a,
Data of the accumulated energization time for the past 30 minutes is always stored. However, the data is not updated every minute,
This is done for each printout.

The temperature of the LED head 28 increases approximately in proportion to the amount of power consumed by the LED head. Therefore, the LED head 2 is calculated based on the count data for the past 30 minutes stored in the area 80a and the accumulated energization time data for the past 30 minutes stored in the area 80b.
The current temperature state of 8 can be predicted. Based on this prediction, the LED head 2 will light up when the next printout occurs.
The energization time rate of the 8 LED elements is controlled by the CPU 76 for each row.

The area 80c of the memory 80 stores data on the allowable temperature of the LED element during use, that is, limit value data determined through experiments.

Next, referring to FIG. 3, the operation of this embodiment will be explained based on the flowchart shown in FIG. 1.

In the first step Sll, the CPU 76 first
It is determined whether a print request has been given to this image forming apparatus. When there is a print request, that is, when a print request signal is input from a host machine such as a word processor or a personal computer to which this image forming apparatus is connected to the input port of the I10 boat 82, the next step 3 is performed.
Proceed to step 13.

In step S13, a print sequence for executing printout is prepared.

That is, the main motor 72 for driving the photosensitive drum 26, the magnet roller 34 of the developing device 32, etc. is turned on.

Data calculated from the product of the respective data stored in areas 80a and 80b of memory 80, that is, temperature data predicting the temperature rise of LED head 28, is loaded into a register included in CPU 76.

In step 517, the temperature data of the LED head 28 loaded into the register in the previous step S15 is compared with the temperature data preset in the area 80c of the memory 80, that is, with the limit value.

If the temperature data loaded into the register of the CPU 76 is larger than the limit value set in the area 80c, that is, if the LED element continues to light up, the LE
If the temperature rise in the D head 28 reaches a temperature that would destroy the LED element, the process advances to step S19.

In step S19, the preparation for the print sequence started in the previous step S13 is terminated here. That is, the main motor 72, which was turned on to drive the photosensitive drum 26, the magnet roller 34 of the developing device 32, etc., is turned off in step S19.

Thereafter, in step 521, a certain delay time is counted. This delay time is a cooling time for lowering the temperature of the LED head 28, which has risen to a limit value due to continuous printing.

After a certain delay time in step S21, the routine returns to the first step Sll. Therefore, even if there is a print request in the first step Sll, step 51
If it is determined in step 7 that the temperature data loaded into the register of the CPU 76 is greater than the limit value stored in the area 80c, the print request at that time is not executed;
The process returns to the first step S11 via steps S19 and S21.

If it is determined in step S17 that the temperature data loaded into the register of the CPU 76 is not greater than the limit value set in the area 80c of the memory 80, the process advances to step S23.

In step S23, the energization time rate of the LED elements of the LED head 28, that is, the ratio of the energization time of the LED elements to the print cycle of one line by the LED head 28, is set according to the temperature data loaded into the register of the CPU 76. Ru. LED of LED head 28
As shown in FIG. 4, if the light emitting output of the element is 100% at 20° C., the light emitting output decreases as the temperature rises. Therefore, in this embodiment, the CPU 7
Depending on the temperature data loaded into register 6,
The energization time rate of the LED element is set so that a constant light emission output is obtained from the LED head 28.

For example, in FIG.
If it is at the position, the value is small, so it can be predicted that the temperature of the LED head 28 is low. Therefore, at this time, there is almost no decrease in the light emitting output of the LED element, and there is no need to increase the light emitting output by increasing the energization time, unlike when the temperature is rising. Therefore, in this case, the CPU 76 sets the energization time rate to 40%, as is clear from FIG. Then,
Since the cycle per row, that is, the printing cycle per column of LED elements is 0°75 m5ec, the energization time t is t+ = 0, as shown in Figure 6(A).
．． 75xO,4=0, 3+m5ec.

In Figure 5, if the temperature data is at the position ■,
LE from when the temperature data explained earlier is at position I.
It can be predicted that the temperature of the D head 28 is increasing. In other words, at this time, the cumulative number of LED elements lit is increasing, the lighting time is getting longer, and the temperature of the LED throat 28 is rising. Therefore, it is necessary to correct the light emission output of the LED element so that the energization time is increased by the amount of light emission output that has decreased due to the temperature rise. Therefore, in this case, the CPU
76 sets 60% as the energization time rate. Then, as shown in FIG. 6(B), the energization time t2 per row is Lz = 0.75XO, 6 = 0. 45m5e
c.

In Figure 5, if the temperature data is at the position ■,
It can be predicted that printing will be performed more continuously than in the state of the position (2) described above, and that the temperature of the LED head 28 will reach close to the usable limit value. Therefore, at this time, the light emitting output of the LED element is considerably reduced, and a predetermined light emitting output cannot be obtained unless the energization time is made longer than in the case of the position (3). Therefore, C
The PU 76 sets the energization time rate to 80%. Then, the energization time t3 at this time is tz = 0.75XO, 8 = 0, 6m, as shown in Fig. 6(C).
5ec, becomes.

In this way, the energization time rate is set according to the predicted temperature of the LED head 28, and the energization time 1. ．． 12 or t3 is determined, and the LED element is energized in the subsequent exposure process. For that purpose, the determined energization time rate is temporarily stored in a predetermined area of the memory 80.

Returning to FIG. 1, in the next step S25, a certain delay time is counted. This delay time is
4 and waiting for the leading edge of the transfer paper 36 to be conveyed to the register roller 48.

In the next step S27, the LED head 28 is turned on and exposure is started. That is, when print data and a synchronization clock as shown in FIG.
be taken in. Then, when the shift for one row, that is, one column of LED elements is completed, the previous step S2
One row of LED elements of the LED head 28 is lit based on the energization time determined in step 3.

On the other hand, the print data and synchronization clock are also provided to AND gate 86. The print data and the synchronization clock are logically ANDed by an AND gate 86 and also provided to a counter 84 .

As explained above, the number of pulses given to the counter 84 depends on the L of the LED head 28 that is lit for exposure.
This is the number of ED elements. The count value of the counter 84 is supplied to the memory 80 every minute, and the count value of the counter 84 is supplied to the memory 80 every minute.
Area 80a is updated every minute. In this way, the count value of the counter 84 is determined by the LED that is lit later.
This is data for setting the energization time rate of the element, that is, the energization time data.

When exposure is started in step S27, as described above, the LED elements of the LED head 28 are selectively turned on in accordance with the print data for each line.The generated output light is sent to the photoreceptor drum 26 as exposure light. irradiated. Also,
When exposure is started, a series of print sequences such as development, transfer, and fixing are also started.

At the next step S29, the exposure started at the previous step S27 is completed. That is, the LED head 28 was turned on and the LED elements were selectively lit according to the print data, but in step S29 the exposure is finished and the LED head 28 is turned off. Note that after turning on in step S27, the L is turned on until turning off in step S29.
The ED head 28 is turned on, and during this time, the LED elements are intermittently energized for selective lighting. By this energization, the LED head, strictly speaking, L
The temperature of the ED element will have increased since it started lighting in step S27. Based on this likely rising temperature, the energization time of the LED element, which is set first in the next printout, is set as described above.

In step S31, it is determined whether there is a print request. However, the print request determined in step S31 is different from the first step Sll and is determined in the case of continuous printing. Therefore, if it is determined in step S31 that there is a print request,
That is, if it is determined that continuous printing must be performed, the process returns to step S15 and repeats the loop from step S515 to step S31. Step S31
If it is determined that there is no print request, step S33
Proceed to.

In step S33, the main motor 72 was driven in the previous step S13 to prepare for the print sequence, but the main motor 72 is now stopped and the print sequence ends. Then, the process returns to the first step Sll and enters a standby state in which it waits for a print request through the external interface.

As described above, according to this embodiment, the LED head 2
Even if the output of the LED element decreases due to an increase in the temperature of the LED element 8, the light emitting output can be kept constant by increasing the energization time of the LED element little by little every minute. Therefore, constant exposure light can be obtained within a range where the temperature of the LED element does not exceed the limit value, so that a good printed image can always be obtained.

Next, with reference to FIG. 3 as well, the operation of another embodiment of the present invention will be described based on the flowchart shown in FIG. Below, the same steps 5111 and 51 as in FIG.
13 and 5125 to 5123 will be omitted to avoid duplication.

This embodiment differs from the embodiment shown in FIG. 1 in that, in step 5115, integrated data related to the total amount of energized power of the LED elements is loaded into the register of the CPU 76 instead of temperature data. That is, the first
In the example shown in the figure, temperature data based on the value calculated from the number of LED elements turned on in the past 30 minutes and the lighting time is loaded into the register of the CPU 76 in step S15. On the other hand, in this FIG. 8 embodiment,
In step 5115, the data from the start of use of the printer 10 to the present is loaded into the register of the CPU 76. Such integrated data is integrated data obtained from the product of the total number of lit LED elements and the total energization time, which has been integrated since the use of the printer 10 was started.

As shown in FIG. 9, the LED element light emission output also decreases depending on the past supplied power amount, that is, the usage time. The amount of power supplied is the value obtained by multiplying the lighting time by the applied voltage and the inflow current, so if you multiply the number of lighting times by the lighting time,
It can be calculated. In this way, the integrated data is derived from the value obtained by multiplying the total number of lighting times up to the present time by the total lighting time.

For this purpose, the area 80a of the memory 80 stores the count value accumulated since the start of use. Data corresponding to the accumulated lighting time is stored in the area 80b. Then, integrated data calculated from the data stored in areas 80a and 80b is temporarily stored in area 80c. Therefore, in this embodiment, the routine corresponding to steps 317 to S21 in FIG. .

Referring to FIG. 10, if the integrated data loaded in step 5115 was at position I, the LED element is still new. That is, in this case, the period after the image forming apparatus IO has been used is short (therefore, the light emitting output of the LED elements of the LED head 28 does not decrease much. In this case, even if the energization time of the LED elements is short, A predetermined light emission output can be obtained. Therefore, in this case, the energization time rate is set to 40%. Then, the energization time per row is t, as in FIG. 6(A), = 0.3m5ec in Figure 10, if the loaded integrated data is at position H, it can be expected that the LED element is older than at position ■.In other words, in this case, This is when the period of use is longer than in the position 2, and the light emitting output of the LED element has accordingly decreased.Therefore, the specified light emitting output cannot be obtained with the same energization time as in the position 3. In this case, set the energization time rate to 60%.Then, the energization time t2
As shown in FIG. 6(B), Lz =0.
It becomes 45m5ec.

In FIG. 1O, when the loaded integrated data is at the position ■, the LED element is considerably worn out. That is, at this time, since the image forming apparatus 10 has been used for a long period of time, the characteristics of the LED elements have significantly deteriorated. Therefore, in this case, the energization time rate is set to 80%. Then, the energization time t3 becomes t as shown in FIG. 6(C).
3 = 0. It becomes 6m5ec.

The embodiments in FIGS. 1 and 8 described above are respectively an embodiment for compensating for a decrease in the light output of an LED element due to temperature changes during use, and an embodiment for correcting a decrease in the light output of an LED element due to changes over time.
This was an example in which a decrease in the light emitting output of the element was corrected. However, in the present invention, it is also possible to keep the light emitting output of the LEDs and elements constant by simultaneously taking into account the factors of temporary temperature changes and the factors of changes in characteristics over time.

[Brief explanation of the drawing]

FIG. 1 is a flow diagram for explaining the operation of an embodiment of the present invention. FIG. 2 is a structural diagram showing an embodiment of the present invention. FIG. 3 is a block diagram showing an example of the control system of this embodiment. FIG. 4 is a graph showing the value of light emitting output versus temperature of the LED element. FIG. 5 is a graph showing the energization time rate with respect to temperature data. FIG. 6 is a diagram for explaining the set energization time per row. FIG. 7 is a timing diagram for explaining the operation of the LED head and counter in response to print data and synchronization clocks. FIG. 8 is a flow diagram for explaining the operation of another embodiment of the present invention. FIG. 9 is a graph showing the value of light emission output with respect to the total amount of energized power of the LED element. FIG. 1O is a graph showing the energization time rate with respect to integrated data. In the figure, 26 is an angry drum, 28 is an LED head, 76 is a CPU, 80 is a memory, 82 is an I10 port,
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Claims (1)

[Scope of Claims] 1. A photoconductor; an LED head that includes a plurality of LED elements and selects and lights up any LED element to irradiate the photoconductor with exposure light each time there is a print request; a counting means for counting the number of lighted LED elements; a calculation means for calculating light output correlation data of the LED elements based on the count value of the counting means; and a calculation means for calculating the light output correlation data of the LED elements according to the light output correlation data. An image forming apparatus comprising an energization control means for controlling energization time. 2. The calculation means calculates the optical output correlation data based on the count value of the counting means and the energization time.
An image forming apparatus according to claim 1. 3. The image forming apparatus according to claim 2, wherein the calculation means includes means for calculating the optical output correlation data based on the count value for each fixed time and the energization time. 4. Claim 2 or 3, wherein the calculation means includes means for calculating integrated data related to the total amount of energized power of the LED head, based on the integrated count value and energization time. The imaging device described. 5. The imager according to any one of claims 1 to 4, wherein the energization control means includes means for setting an energization time rate based on the optical output correlation data and thereby determining the energization time. Forming device.