JPH07266564A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device with the capability of correcting the irregularity of an image density by correctly detecting the temperature of a printing head and thus properly controlling the temperature. CONSTITUTION:The image forming device includes printing means 3 for forming an image on the recording paper 4, heating means 32 for jetting out ink on the printing means 3, pulse signal generating means 21 for controlling the temperature of the heating means 32, detecting means 33 for the temperature of the printing means, and means for detecting the disenablling period of the pulse signals. In addition, the device is provided with means 22 for sampling the temperature data from the temperature detecting means of the printing means during the detected disenabling period. and means 20 for variably controlling pulse signals for controlling the temperature of the heating means on the basis of the sampled temperature data.

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 using an ink jet recording system, and more particularly to an image forming apparatus capable of controlling temperature accurately by monitoring the temperature of a printing means at an appropriate timing.

[0002]

2. Description of the Related Art Generally, an ink jet type printer, which is a kind of image forming apparatus, has a print head for forming an image on a recording paper and a print head which holds the print head in a recording paper conveyance direction (sub-scanning direction). A carriage which is scanned in a direction perpendicular to the carriage (main scanning direction), a linear scale provided in parallel with the scanning direction of the carriage, a linear sensor installed in the carriage for detecting slits of the linear scale, and a printer device. And a control unit for controlling the whole. While the recording paper is being conveyed, a print signal is output from the control unit in response to the slit detection signal of the linear sensor, the image data is transmitted to the print head together with the print signal, and the ink is ejected from the print head by an inkjet method. An image is formed on the recording paper.

In such an ink jet type image forming apparatus, several heaters are mounted in a nozzle in which ink is immersed, and by applying a pulse signal to this heater, the heater is heated to boil the ink, Ink is ejected by the bubble pressure generated thereby. Normally, when used as an image forming apparatus, a plurality of nozzles are arranged to form one print head to form an image. And
The conventional image forming apparatus, mainly the control of the print head, has the configuration shown in FIG. In FIG. 8, the image forming apparatus includes an external device 1 such as an image scanner for reading and generating image data, a control unit 2, a print head 3, and a recording paper 4. The control unit 2 includes a CPU 20 for controlling the entire apparatus, image data VD sent from the external apparatus 1, a print signal CLK from a slit detection signal from the linear sensor, and a control circuit 31 for the print head 3.
AMP2 that amplifies the detection signal from the head drive signal generation unit 21 and the temperature detection sensor 33 of the print head 3 that are transmitted to
8 and an A / D converter 29 for converting the amplified analog signal into a digital signal. When the nozzles are divided into blocks, the head drive signal generator 21 has a block enable signal Ben for enabling each block, a heater drive signal Hen for enabling the heater, and a latch signal LAT. Is generated and transmitted to the control circuit 31. The print head 3 is
It is composed of the control circuit 31, the heater 32, and the temperature detection sensor 33. The heater 32 is controlled by various signals sent from the head drive signal generation unit 21 to eject ink to form an image. And the temperature detection sensor 3
3, the CPU 20 monitors and detects the temperature of the print head 3 to generate a temperature control signal for the heater 32.

The structure of the control circuit 31 for driving the print head 3 will be described with reference to FIG. In FIG. 9, reference numeral 901 indicates a shift register, reference numeral 902 indicates a latch circuit, and reference numeral 903 indicates
906 is an AND circuit, 907 to 910 are transistors,
Reference numeral 32 indicates a heater. The print head 3 is composed of 128 nozzles, which are divided into eight blocks. Therefore, the AND circuit and the transistor are shown for 8 blocks each, and ×
16 means that each block is provided with 16 pieces. Also, eight block enable signals Ben are generated and sent from 1 to 8.

These operate and operate as follows. Image data VD from external device 1 is serial binary data 1
It is transmitted in synchronization with 28 transfer clocks CLK and serial-parallel converted by the shift register 901. When the latch signal LAT is input after the image data VD is transferred to each nozzle, the image data is
The VD is held on each nozzle. In addition, the block enable signals Ben 1 to 8 of one pulse and the heater drive pulse signal Hen are transmitted from one head drive signal generation section 21 to one block, and the block is enabled and the image data VD is enabled and held in the nozzles. Only the transistor is turned on and the heater is heated to eject ink.

In the case of an image in which ink is printed in this manner, but ink is continuously ejected such as a solid image as shown in FIG. 10A, ideally, as shown in FIG. As shown, the densities at both ends of the image should be the same (a = a in the figure), but since the heater is continuously heated, the temperature of the print head 3 is actually as shown in (B). At first, it rises gradually low (like U to D in the figure). Therefore, since the ink ejection amount changes at both end portions of the image (as in the figure from O to F), uneven density may occur at both end portions.
In order to correct this density unevenness, the temperature detection sensor 33 of the print head 3 is provided as described with reference to FIG.
Is monitoring the detection signal. As a result, when the temperature rises, the pulse signal Hen for driving the heater is changed from the pulse signal Hen shown in FIG. 11 (a) to s1, s2, s3, or as shown in FIG. 11 (b). s4
Of the short pulse signal Hen, or a combination of these pulse signals to obtain a divided pulse signal Hen. As a result, the heating time of the heater is shortened, the temperature rise of the print head is suppressed, and the ink ejection amount is controlled to be constant. When the pulse signal Hen is H, it is in the enable state, and when it is L, it is in the disenable state.

[0007]

However, in the conventional image forming apparatus of this type, the temperature rise of the print head is controlled as described above. However, as shown in FIG. Fig.12 during the output period of the pulse signal Hen
As shown in (b), the temperature sensor output Sen is the pulse signal He.
Induces noise due to the influence of n. In particular, when the pulse Hen shown in FIG. 12 rises, the noise is large, an accurate temperature cannot be detected, and a problem may occur in the division of the heater driving pulse signal Hen, making it impossible to perform accurate temperature control. Further, in order to perform high-speed printing, the generation of the heater driving pulse signal Hen is normally performed by hardware, without being controlled by the CPU 20 via software. Therefore, the CPU 20 drives the heater drive pulse signal Hen.
It was not possible to recognize whether or not was output, and it was impossible to monitor the temperature sensor output Sen during the disenable period of the heater driving pulse signal Hen. If the state of the pulse signal Hen for driving the heater is changed to the CPU
Even if it can be recognized by 20, the disable period may be short (several μsec).
There is also a problem that monitoring by the PU 20 is impossible.

The present invention has been made in view of the above circumstances, and an object of the present invention is to accurately detect the temperature of the print head and perform appropriate temperature control to correct the image density unevenness. To provide a forming apparatus.

[0009]

To achieve the above object, in the present invention, a printing means for forming an image on a recording paper, a heating means for ejecting ink of the printing means, and A means for generating a pulse signal for controlling the temperature of the heating means, a means for detecting the temperature of the printing means, a means for detecting a disable period of the pulse signal, and a temperature of the printing means during the detected disable period. The gist of the present invention is to include means for sampling the temperature data from the detecting means and means for variably controlling the pulse signal for controlling the temperature of the heating means based on the sampled temperature data.

Further, a plurality of printing means for forming an image on the recording paper, heating means for ejecting ink provided in each of the printing means, and a pulse signal for controlling the temperature of these heating means are provided. Generating means, means for detecting the temperature provided in each printing means, means for detecting the disenable period of the respective pulse signals, and detecting that all of these pulse signals are disabled. It is provided with means for sampling the temperature data from the temperature detecting means of any printing means, and means for variably controlling the pulse signal for controlling the temperature of the heating means of the printing means based on the sampled temperature data. It is what

Further, in these image forming apparatuses, the temperature detecting means of the printing means is provided by a synchronizing signal generated based on a signal from a linear encoder generated by scanning of the printing means or a signal for holding image data in the printing means. And a means for variably controlling a pulse signal for controlling the temperature of the heating means based on the sampled temperature data.

[0012]

According to the above construction, the temperature data from the temperature detecting means provided in the printing means is sampled during the disenable period of the pulse signal for controlling the temperature of the heating means of the printing means, and the sampled temperature data is used for the above The temperature of the printing means is controlled by changing the pulse width of the pulse signal for controlling the temperature of the heating means or by controlling the pulse division.

When there are a plurality of printing means such as multicolor printing, the temperature data from the temperature detecting means of any printing means is sampled during a period in which all of the plurality of pulse signals are disabled, and this sampling is performed. Since the pulse signal for controlling the temperature of the heating means of the printing means is variably controlled by the temperature data thus obtained, the temperature of each printing means can be controlled independently.

Further, in these image forming apparatuses, unlike the above-mentioned two, the linear encoder which is generated by scanning the printing means rather than sampling the temperature data from the temperature detecting means of the printing means during the period when the pulse signal is disabled. The temperature data is sampled by a synchronizing signal generated on the basis of the signal from or a signal for holding the image data in the printing means.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. The same components as those described in the section of the prior art are designated by the same reference numerals.

FIG. 1 is a schematic block diagram of an embodiment of the image forming apparatus of the present invention. In FIG. 1, a print head 3, which is a printing unit for forming an image, is held by a carriage and scanned while facing a recording paper 4 being conveyed on a conveyance table of the apparatus main body. Then, there is a control unit 2 for controlling the apparatus main body including the print head 3, and this control unit 2 is an image scanner, a personal computer or a CAD (Computer Aided D).
It is connected to an external device 1 such as esign). An image image is formed on the recording paper 4 using the print head 3 from the image data VD sent from the external device 1. The control unit 2 performs the control. The control unit 2 receives the image data VD sent from the CPU 20, which is the central processing unit, and the external device 1, generates various signals, and outputs them to the control circuit 31 of the print head 3 together with the image data VD. The drive signal generator 21, the temperature detection sensor output monitor 22 to which the output signal Sen from the temperature sensor 33 for detecting the temperature of the print head 3 is input, and the image data VD from the print head drive signal generator 21 are stored. An image memory 23 to be read out, a work RAM 24 connected to the CPU 20 for temporarily storing data and the like, and similarly the CPU 20
CPU via the ROM 25 and I / O port 26 that are connected to
20 and each load unit 27 connected thereto.
The load of each load unit 27 includes a motor for driving the carriage, a motor for transporting the recording paper 4, and the like. It is important that the linear scale detection signal LS by the linear sensor accompanying the carriage scanning is the print head drive signal generation unit 21. Is to be output to. The print head drive signal generation unit 21 and the temperature detection sensor output monitor unit 22 are also CPUs.
The CPU 20 interfaces with the external device 1 to which the image data VD is sent and the signal Sen from the temperature detection sensor output monitor unit 22.
Is also monitored and read requests are output. It also controls the operation of each memory and the entire device.

Further, the print head 3 comprises the control circuit 31, the heater 32, and the temperature detection sensor 33 as in the conventional case. The configuration, operation and action of the print head 3, particularly the control circuit 31, are the same as those described with reference to FIG. Therefore, redundant description will be omitted.

Next, the operation and action of the control section 2 will be mainly described. When the serial image data VD is sent from the external device 1, the print head drive signal generation unit 21 temporarily holds the image data VD for several bands in the image memory 23 according to an instruction from the CPU 20. Various image processes are applied to the held image data VD, the image data VD is read out in accordance with the scanning of the print head 3, and the image data VD is output to the print head 3. In the present embodiment, the clock signal CLK is generated by using the slit detection signal LS output from the linear encoder in synchronization with the scanning of the print head 3 as described above to generate the image data.
Various controls such as VD output are synchronized. Also,
Also in this embodiment, the print head 3 is composed of 128 nozzles, which is divided into eight blocks, as in the conventional case. Therefore, the print head drive signal generation unit 21 generates eight enable signals Ben 1 to Ben 8 for each block, and also generates the heater drive pulse signal Hen which is a signal necessary for ink ejection. Image data VD output from the print head drive signal generation unit 21, block enable signals Ben 1 to 8, heater drive pulse signal Hen
Etc. are transmitted to the print head 3, and the internal control circuit 31
Then, the heater 32 is turned on only for the nozzles for which the enable signals Ben and Hen are enabled, ink is ejected, and an image image is formed on the recording paper 4. The temperature detection sensor 33 is arranged inside the print head 3 as described above, and the output Sen is controlled by the temperature detection sensor output monitor unit 22. The temperature detection sensor output monitor unit 22 is where the characteristic processing of this embodiment is performed. Print head drive signal generator 21
There is a request from the CPU 20 to read the temperature data of the print head 3 by detecting the disenable period of the heater driving pulse signal Hen output from the CPU 20 and sampling the output Sen of the temperature detection sensor 33 only during this disenable period. Only when the temperature data is held is controlled. Since noise is induced in the output Sen of the temperature detection sensor 33 by the heater driving pulse signal Hen, the output Sen of the temperature detection sensor 33 is sampled at the timing when no noise occurs. The temperature detection sensor output monitor unit 22 will be described in detail later.

FIG. 2 shows the print head drive signal generating section 2 described above.
2 is a configuration diagram of the inside of FIG. In FIG. 2, the print head drive signal generation unit 21 mainly includes an image memory control unit 211, an image synchronization signal generation unit 212, and a head block selection signal generation unit 213.
, A heater drive signal generation unit 214, and a CPU interface I / F 215. Image memory control unit 21
Reference numeral 1 denotes generation of an address signal for temporarily holding (inputting) the serial image data VD sent from the external device 1 in the image memory 23 for several bands as described above, and the held image data VD for the print head 3 An address signal to be output in synchronization with the clock signal CLK is generated in accordance with the scanning of. The generation of the address signal at the time of input is generated at the transmission timing of the image data VD from the external device 1, and the generation of the address signal at the time of output is generated at the synchronization timing from the image synchronization signal generation unit 212 described later. It The image synchronization signal generation unit 212 generates the synchronization signal Hsync for generating the address signal when the image data VD is output from the image memory 23 by the slit detection signal LS from the linear sensor of each load unit 27 as described above. The latch signal RAT is generated when the print head 3 holds the image data VD. The head block selection signal generation unit 213 also generates block enable signals Ben 1 to 8 for selecting which block of the print head 3 is driven in synchronization with the synchronization signal Hsync. The heater drive signal generation unit 214 generates the heater drive pulse signal Hen and stores it in the register of the CPU I / F 215 as shown in FIG.
The width of the heater driving pulse signal Hen is set by setting any of the pulses s1 to s4 shown in FIG. The width of the pulse signal Hen can be variably controlled depending on which is set or which is combined. For this setting, the value of the temperature detection sensor 33 of the print head 3 is monitored by the CPU 20 using the temperature detection sensor output monitor unit 22,
The sequence is set from the result.

FIG. 3 is an internal block diagram of the temperature detection sensor output monitor unit 22. In FIG. 3, the temperature detection sensor output monitor unit 22 includes a heater drive signal detection unit 221,
It is composed of a sensor output sampling unit 222 and a CPU interface I / F 223. The heater drive signal detector 221 is the print head drive signal generator 21 (214).
The heater driving pulse signal Hen output from the sensor is detected as a disenable period, and the sampling timing signal T 1 is generated when the output Sen of the temperature detection sensor 33 is sampled. Further, the sensor output sampling unit 222 samples the output Sen of the temperature detection sensor 33 by the timing signal T 1 and the CPU I / F 2
When a read command is issued from the CPU 20 via 23, control is performed to temporarily hold the sampling result. CP
The temperature data read by U20 is reflected in the variable pulse width and pulse division of the heater drive pulse signal Hen by the heater drive signal generation unit 214 of the print head drive signal generation unit 21 as described above, and is reflected in the print head 3. It is a sequence to adjust the temperature.

FIG. 4 is a circuit diagram of the inside of the temperature detection sensor output monitor unit 22. In FIG. 4, the heater drive pulse signal Hen output from the heater drive signal generation unit 214 of the print head drive signal generation unit 21 by the clock C16M is output by the flip-flop circuit 401 to the internal reference clock C16M of the apparatus main body. Re-hold and adjust timing to generate sampling clock SMPCLK.
In addition, a minute analog electric signal is output from the temperature detection sensor 33.
Sen is output. Therefore, the signal is amplified by the amplifier AMP402 in order to increase the resolution at the time of A / D conversion by the analog-digital converter 403 in the subsequent stage. After that, A / D converter
At 403, it is converted into a digital signal by the sampling clock SMPCLK. Eight flip-flop circuits 404 for each block are provided as digital signalized temperature data.
Input to the D terminal of the sampling clock SMPCLK
Is input to the D terminals of the eight latch circuits 405. On the other hand, the CPU 20 sends the address bus AB to the decoder 406.
When the temperature data read request SenRD is output from the decoder 406 and the read request RD is output from the CPU 20, the AND circuit 407 inputs it to the E terminal of the latch circuit 405. When the read request RD is input to the E terminal, the latch circuit 405 temporarily holds the sampled temperature data. The retained temperature data is C via the data bus DB.
Based on the temperature data read by the PU 20, the CPU 20 causes the heater drive signal generator 214 of the print head drive signal generator 21 to drive the heater drive pulse signal Hen.
It is used for variable pulse width and pulse division control.

FIG. 5 is a diagram showing the above operation timing. In FIG. 5, C16M, which is the internal reference clock of the apparatus main body, is always output. Print head drive signal generator 21
The synchronization signal Hsyn output from the image synchronization signal generation unit 212 of
Various signals are output during c. The image data VD is output in synchronization with the clock signal CLK. Further, enable signals Ben 1 to Ben 8 are selectively output to each block, and a heater driving pulse signal Hen is also output during this period. As can be seen from the output Sen of the temperature detection sensor 33, noise is generated at the rise of the heater drive pulse signal Hen, so the sampling clock SMPCLK is disabled for the heater drive pulse signal Hen after the fall of the pulse signal Hen. It is released at. As a result, the temperature data of the print head 3 is sampled at the sampling timing T indicated by the arrow in the figure, and the pulse signal He for driving the heater is generated as described above based on the read data of this temperature data.
It becomes possible to feed back to n to control the temperature of the print head 3.

Next, FIG. 6 is a diagram showing another embodiment of the internal circuit configuration of the temperature detection sensor output monitor section 22. In the embodiment shown in FIG. 4, an example in which one print head 3 is used has been described. However, when performing multicolor printing, there are cases where two or more print heads 3 are used. When the output Sen of the normal temperature detection sensor 33 is not influenced by the heater driving pulse signal Hen of each print head 3, it can be realized by simply increasing the number of print heads 3 in the circuit configuration of the above embodiment. Is. However, since the print heads 3 are close to each other, the print heads 3 may be affected by the noise of the pulse signals Hen for driving the heaters. In that case, the circuit configuration shown in FIG. 6 is used. In FIG. 6, this embodiment is an example in which full-color printing including cyan C, magenta M, yellow Y, and black B is performed. The pulse signals Hen C, Hen M, Hen Y, and Hen B for driving the heaters of the respective colors output from the print head drive signal generation unit 21 by the clock C16M are AN.
When all the signals are input to the D circuit 600 and all signals are disabled (when the pulse is L), the flip-flop circuit 601 holds them again with the internal reference clock C16M of the main body of the device and adjusts the timing. Generates sampling clock SMPCLK. The output Sen of each of the four temperature detecting sensors 33 of the print heads 3 is an amplifier AMP602.
Is amplified by. The amplified temperature data Sen is
Which color is selected by the switch SW by the latch circuit 610 described later, and the selected temperature data Sen is temporarily held by the sample hold circuit 609 and A / D converted by the analog-digital converter 603. The A / D converter 603 converts it into a digital signal by the sampling clock SMPCLK. The temperature data converted into a digital signal is input to the D terminals of the eight flip-flop circuits 604 for each block and also input to the D terminals of the eight latch circuits 605 by the sampling clock SMPCLK. On the other hand, CPU2
Address bus AB is output from 0 to decoder 606,
When the decoder 606 outputs the temperature data read request SenRD and the CPU 20 outputs the read request RD, the AND circuit 607 inputs it to the E terminal of the latch circuit 605. When a read request RD is input to the E terminal, the latch circuit 605
Holds the sampled temperature data temporarily. The held temperature data is read by the CPU 20 via the data bus DB, and the CPU 2 based on the read temperature data.
0 is used by the heater drive signal generator 214 of the print head drive signal generator 21 to change the pulse width of the heater drive pulse signal Hen and to control the pulse division. Also, C
The data bus DB from the PU 20 is input to the D terminal of the latch circuit 610, and the switch signal Sen SW indicating which color temperature data Sen is selected from the decoder 606 is input to the E terminal of the latch circuit 610. Then, the Q terminal of the latch circuit 610 outputs to the analog switch SW which color temperature data Sen is to be selected. In this way we detect when all signals are disabled,
It is possible to monitor the sensor output of the desired color, that is, the temperature data Sen while no print head 3 is being driven. By sampling in time division like this,
It is possible to achieve the same effect as that of the above-described embodiment with a circuit configuration that is smaller than the number of independent circuit configurations.

Finally, FIG. 7 is a diagram showing another embodiment of the sampling timing. In the above two embodiments, the output Sen of the temperature detection sensor 33 is sampled during the period when the heater driving pulse signal Hen is disabled, and CP
An example of monitoring the pulse signal Hen for driving the heater by monitoring with U20 is shown. However, the print head 3 used in the present invention drives the heater after converting the image data VD serially transmitted from the print head drive signal generator 21 into a parallel signal (Ben and Hen are enabled. Since the transistor 32 is turned on), the heater is not driven when the latch signal RAT, which is the timing for holding the parallel data, is output. Therefore, even if the output Sen of the temperature detection sensor 33 is sampled by using the latch signal RAT, it is possible to avoid the noise generated by the influence of the heater driving. Further, the same effect as above can be obtained by using the 1-line synchronization signal Hsync generated from the slit detection signal LS output from the linear encoder in synchronization with the scanning of the print head 3. This synchronization signal Hsyn
c is the original signal when the latch signal RAT is generated, and is output at almost the same timing as the latch signal RAT.
Even if this synchronization signal Hsync is used, noise generated by the influence of the heater driving can be avoided. An example of sampling using these signals is shown in FIG. Sampling timing T shown by the dashed arrow in FIG.
Is an example. In this way, the 1-line synchronization signal Hsyn
Even if sampling is performed using c and the latch signal RAT, the accurate temperature of the print head 3 can be monitored.

In the above embodiment, the number of nozzles in the print head is 128, but the number of nozzles in one print head is not limited to this. Further, although an example in which 128 nozzles are divided into 8 blocks has been described, any number may be used. If divided into n blocks, the print head drive signal generator 21
The block enable signals output from Ben 1 to n
Becomes

[0026]

As described above, according to the image forming apparatus of the present invention, the output Sen of the temperature detection sensor 33 is sampled while the heater driving pulse signal for ejecting ink of the print head is disabled. CPU20
Since the pulse signal width and division are controlled based on the results of the monitoring, the temperature of the print head can be monitored accurately without being affected by noise in the heater drive pulse signal, and accurate printing can be performed. The temperature of the head can be controlled. As a result, it becomes possible to form an image without uneven density.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of an image forming apparatus of the present invention.

FIG. 2 is an internal configuration diagram of a print head drive signal generation unit.

FIG. 3 is an internal configuration diagram of a temperature detection sensor output monitor unit.

FIG. 4 is a circuit configuration diagram inside a temperature detection sensor output monitor unit.

FIG. 5 is a diagram showing an operation timing of the present embodiment.

FIG. 6 is a diagram showing another embodiment of the internal circuit configuration of the temperature detection sensor output monitor unit.

FIG. 7 is a diagram showing yet another embodiment of sampling timing.

FIG. 8 is a schematic configuration diagram of an embodiment of a conventional image forming apparatus.

FIG. 9 is a diagram showing a configuration of a control circuit that drives a print head.

FIG. 10 is a diagram for explaining the influence of temperature during printing.

FIG. 11 is a diagram illustrating an example of a heater driving pulse signal.

FIG. 12 is a diagram for explaining a drawback of the conventional technique.

[Explanation of symbols]

 1 External device 2 Control unit 3 Print head 4 Recording paper

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location B41J 3/10 114 A 114 E (72) Inventor Nobuaki Ando 6-3-3 Shimorenjaku, Mitaka City, Tokyo No. Copia Co., Ltd. (72) Inventor Lee Suiwei 6-3-3 Shimorenjaku, Mitaka-shi, Tokyo Copier Co., Ltd. (72) Masayuki Mori 6-3-3 Shimorenjaku, Mitaka-shi, Tokyo Copier Within the corporation

Claims (4)

[Claims] 1. A printing unit for forming an image on a recording sheet, a heating unit for ejecting ink of the printing unit, a unit for generating a pulse signal for controlling the temperature of the heating unit, and the printing unit. Means for detecting the temperature of the means, means for detecting the disable period of the pulse signal, means for sampling the temperature data from the temperature detecting means of the printing means during the detected disable period, and the sampled temperature data And a means for variably controlling a pulse signal for controlling the temperature of the heating means based on the image forming apparatus. 2. A plurality of printing means for forming an image on recording paper, heating means for ejecting ink provided in each of these printing means, and a pulse signal for controlling the temperature of these heating means. Generating means, means for detecting the temperature provided in each printing means, means for detecting the disenable period of the respective pulse signals, and detecting that all of these pulse signals are disabled. It is provided with means for sampling the temperature data from the temperature detecting means of any printing means, and means for variably controlling the pulse signal for controlling the temperature of the heating means of the printing means based on the sampled temperature data. Image forming apparatus. 3. The temperature detection of the printing means according to claim 1, wherein a synchronizing signal generated based on a signal from a linear encoder generated by scanning of the printing means or a signal for holding image data in the printing means. An image forming apparatus comprising: means for sampling temperature data from the means; and means for variably controlling a pulse signal for controlling the temperature of the heating means based on the sampled temperature data. 4. The image forming apparatus according to claim 1, wherein the pulse signal is variably controlled to change the pulse width or divide the pulse.