JPH02219675A - Image recording device - Google Patents

Abstract

PURPOSE:To prevent an image of unnatural density from being output and from being unnecessarily recorded by determining the actual power supplied to the thermal element of a thermal head, and stopping data recording if the actual power supply exceeds the limits or the displacement speed of recording paper does not reach the constant level. CONSTITUTION:CPU 201 determines whether a line is final, and multiplies the voltage (v) by the pulse width (t) instructed to a recording control circuit 205, that is, the actual power supplied to the thermal element of a thermal head 11. The CPU 201 compares the limited power is a tolerable value of the supplied power with the calculated power. If the power supplied to the thermal head 11 exceeds the limits during recovering, a switching circuit 208 is turned off immediately. In the meantime, if a failure occurs on a drive device 14, or a paper feeder jams due to thermosensitive recording paper 13, the movement of the paper 13 stops. ln this case, a switching circuit 20 is turned OFF, and an error indicating the failure of the drive device 14 or paper jamming is displayed. Then an operator is called to suspend the operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image recording apparatus that records an image line by line on thermal recording paper using a thermal head.

[Prior Art] Image recording devices that record images on thermal recording paper using a thermal head are often used in recording units of facsimile machines, small printers, and the like.

In such an image recording apparatus, when recording an image line by line, a pulse current is applied to a heating element corresponding to a black pixel among the heating elements corresponding to each pixel of the thermal head. Also, when energizing this heating element, the temperature of the thermal head is detected, and if the temperature is low, the pulse width of one energization pulse is widened, and if the temperature is high, the pulse width is narrowed. A predetermined amount of thermal energy is supplied to the recording paper to obtain a recorded image with a constant density.

[Problems to be Solved by the Invention] By the way, the temperature of the thermal head is detected by a temperature sensing element such as a thermistor attached to the thermal head. However, there is a certain delay until the temperature of the heat generating part of the thermal head changes and the temperature of the temperature sensing element changes accordingly.

For this reason, for example, when a specific line is recorded, the thermal head generates a large amount of thermal energy, and a sudden temperature change that causes the image density to become thicker in that line is not detected by the temperature detection element. Therefore, in this case, an unnatural recorded image in which only a specific line has a high density is output.

As described above, in the past, there was a problem in that an image with unnatural image density was output as is because the temporary temperature rise of the heat generating part of the thermal head was not detected.

On the other hand, if a paper jam occurs in the recording paper conveyance path or the conveyance mechanism malfunctions during recording of one image, the movement of the recording paper may stop.

However, in the past, since the transport state of the recording paper was not detected, the recording operation continued even if the recording paper stopped. Therefore, there is a problem in that the recording operation is wasteful, and in the case of a paper jam, the paper jam condition becomes even worse.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image recording apparatus that solves one or more problems, prevents the output of images with unnatural density, and eliminates unnecessary recording operations.

[Means for Solving the Problems] For this purpose, the present invention detects the moving speed of the recording paper in the sub-scanning direction during image recording, and supplies the heating element of the thermal head according to the detected moving speed. While determining the limited amount of power to be used, determine the actual amount of power supplied to the heating element of the thermal head each time an image is recorded line by line.
That amount of electricity.

The present invention is characterized in that the recording operation is stopped when the above-mentioned limited power amount is exceeded or when the moving speed of the recording paper is less than a certain speed.

[Operation] By determining the amount of power supplied to the heat generating portion of the thermal head, a temporary temperature rise in the heat generating portion of the thermal head can be predicted. Therefore, by stopping the recording operation when the amount of power supplied exceeds a certain limit amount of power,
It is possible to prevent an unnatural image with partially high density from being output as is.

By the way, for example, when the moving speed of the recording paper is fast, the recorded density of the image becomes low even if the amount of heat generated by the thermal head is constant. Therefore, by determining the above-mentioned limited power amount according to the moving speed of the recording paper.

It becomes possible to more accurately determine whether the recorded image has reached a certain density or higher.

Further, since the recording operation is stopped when the moving speed of the recording paper is not constant, it is possible to eliminate unnecessary recording operations in the event of a paper jam of the recording paper or a malfunction of the transport mechanism.

[Example 1] Hereinafter, an example of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a block diagram of a facsimile machine according to an embodiment of the present invention. In the figure, a scanner 1 reads an original image and extracts image information of a predetermined resolution, and a plotter 2 records the image information on recording paper. The encoding/decoding unit 3 encodes image information to be transmitted and decodes received image information. The image memory 4 temporarily stores image information to be transmitted and received.

The network control device 5 performs predetermined call origination and incoming call operations by acquiring a line, sending out a selection signal which is an originating optical telephone number, and detecting an incoming call.

The modem 6 modulates and demodulates image information and transmits various procedure signals in transmission control procedures.
The communication control unit 7 controls the network control device 5 and the modem 6 to execute facsimile transmission according to a predetermined transmission control procedure.

The operation display section 8 displays the device status.

The operator performs various operations. The system control section 9 is composed of a microcomputer system, and controls each section mentioned above to execute predetermined operations of the facsimile machine.

FIG. 2 shows the ll118 configuration of plotter 2.

A thermal recording paper 13 is pressed against the thermal head 11 by a platen roller 12 . One end of the shaft of the platen roller 12 is driven by a drive device 14 composed of a step motor, gears, etc., and a circular slit plate 15 having radial slits is fixed to the other end.

A photo interrupter 1 is installed at the edge of the slit plate 15 to detect rotation of the slit plate 15 by light transmitted through the slit.
6 is installed. Also, a photosensor 1 consisting of a light emitting element and a light receiving element is placed on the conveyance path of the thermal recording paper 13.
7 is installed. This photosensor 17 irradiates the recording paper with light and extracts changes in the reflected light as an analog signal.

FIG. 3 shows a block diagram of a part of the plotter 2 and the system control section 9 that controls the plotter 2. In FIG. A detection signal from the photosensor 17 is input to a CPU 201 provided therein, and a detection signal from the photosensor 17 is input to a moving speed detection circuit 202 . Moving speed detection circuit 202
The thermal recording paper 13 is detected by the detection signal of the photosensor 17.
The detected moving speed information is input to the CPU 201.

Further, the thermistor 203 is fixed to the thermal head 11 in order to detect its temperature, and its detection signal is input to the CPU 205 via an A/D (analog-to-digital conversion circuit) 204. .

The recording control circuit 205 inputs image signals transferred one line at a time based on control information from the CPU 201, and drives the RAD 11 to thermally record the image. The step motor drive circuit 206 drives the step motor 207 in the drive device 14 to convey the thermal recording paper 13 in the sub-scanning direction. Note that the power supplies for operating the recording control circuit 205, the thermal head 11, the step motor drive circuit 206, and the step motor 207 are turned on and off by a switch circuit 208.

Further, the image signal is input to an integrating circuit 209 that integrates the signal line by line. This integrating circuit 20
9, the input image signal is input to the inverting input terminal of an operational amplifier 209b via a resistor 209a. The ratio inverting input terminal of the operational amplifier 209b is grounded. A capacitor 209C and an analog switch 209 are connected between the inverting input terminal and the output terminal of the operational amplifier 209b.
d is connected.

The output of the integrating circuit 209 is input to the A/D 210, and the output of the A/D 210 is input to the CPU 201.

The facsimile machine of this embodiment has the above configuration.

It has a memory reception function. That is, when the operator sets "memory reception" by a predetermined operation on the operation display section 8, the facsimile machine stores the received image in the image memory 4 as shown in FIG. It is stored once (processing 301).

When recording the received image, the operator performs a predetermined recording start operation. When this recording start operation is performed (Y in process 302), the CPU 201 starts the recording control operation and first sets a variable N for counting the number of interruptions in the recording operation.
is set to N=0 (processing 303).

By the way, when recording an image, a pulse of electricity is applied to the heating element of the thermal head 11. In this case, the temperature of the thermal head 11 is detected, and if the temperature is low, the pulse width of the energization pulse is widened. When the temperature is high, the pulse width is narrowed to supply a predetermined amount of thermal energy to the recording paper to obtain a recorded image with a constant density.

For this purpose, the CPU 201 next selects the thermistor 203.
detects the temperature of the thermal head 11, and instructs the recording control circuit 205 to apply the energizing pulse 1ef according to the detected temperature. Also, here, the step motor drive circuit 206 is activated.

Normally, the switch circuit 208 is turned on, and one operating power is supplied to the recording control circuit 205, the thermal radar 11, and the step motor drive circuits 206 and 207. The recording control circuit 205 reads one line of image signal from the image memory 4 and drives the thermal radar 11 with an energizing pulse having a pulse width t instructed by the CPU 201 .

As a result, one line of image is recorded on the thermal recording paper 13, and the thermal recording paper 13 is conveyed in the sub-scanning direction for 1542 minutes by the step motor 207, and a one-line recording operation is executed (process 304).

On the other hand, the CPU 201 controls the analog switch 209 immediately before the image signal of each line is input to the recording control circuit 205.
d is closed to discharge the charge in the capacitor 209c. Then, the integrating circuit 209 integrates the image signal of the l line. This image signal is 1. This is a signal that becomes high level when the recorded image has black pixels, and the integration circuit 209 outputs a voltage V proportional to the number of black pixels in one line due to the above integration operation.

Next, the CPU 201 determines whether it is the final line (process 305), and if it is not the final line (N in process 305).
, the product of the voltage V and the pulse lit instructed to the recording control circuit 205, that is, the amount of power supplied to the heating element of the thermal head 11 is calculated (process 306).

On the other hand, an initial value of the limit power amount, which is an allowable value of the power amount to be supplied to the heating element of the thermal head 11, is set in advance in the CPU 2O5. The CPU 201 compares the limited power amount with the calculated power amount (processing 307), and if the calculated power amount is less than the limited power amount (processing 30
7 Y) Next, the moving state of the thermal recording paper 13 is determined.

That is, first, in order to diagnose a failure of the drive device 14, it is checked whether the detection signal of the photointerrupter 16 has changed, and the rotational state of the platen roller 12 is determined.

By the way, the surface of the thermal recording paper 13 has minute irregularities like normal paper, and the intensity of the reflected light of the light irradiated by the photosensor 17 fluctuates in proportion to the moving speed of the thermal recording paper 13. do. The light receiving element of the photosensor 17 outputs a detection signal according to the intensity of one reflected light. The moving speed detection circuit 202 detects the moving speed of the thermal recording paper 13 based on the fluctuation of the detection signal and outputs it to the CPU 201 (
This concludes the process 308).

Next, the CPU 201 reads the moving speed and determines whether it is a predetermined speed (process 309).

The reason why both the photointerrupter 16 and the photosensor 17 are checked is to determine whether there is a failure in the drive device 14 or a paper jam in the recording paper.

By the way, for example, when the moving speed of the thermal recording paper 13 is fast, the recording density of one image becomes low even if the amount of heat generated by the thermal head 11 is one rectangle. Therefore, in order to determine whether the thermal recording paper 13 is being conveyed correctly (Y in process 309) and the density of the recorded image exceeds a certain density, a constant A limit power amount is determined (processing 310).

Repeat the above operation for each line of the image signal (
to process 304). Then, if you record up to the last line (
Step 305: Y), the above operation ends.

Additionally, during the above recording operation, if the amount of power supplied to the thermal head 11 exceeds the limited amount of power (processing 3 ()
i of N), immediately turns off the switch circuit 208 (processing 311), and compares the variable N with a preset constant number X (processing 311), and if the variable N is less than the constant number X ( At step 311 (Y), a message indicating that the recording operation is stopped is displayed (process 313), and the operation is stopped for a certain period of time, for example, 3 minutes (process 314).

If the temperature of the thermal radar 11 has increased, heat will be radiated during this certain period of time and the temperature will drop.

When the above-mentioned certain period of time has passed, next, in order to record from the first line of the same page again, the control state is set to the initial state (processing 315), and the variable N is +1 (processing 3).
16), restart the recording operation of each line (process 30).
4), this allows one page of images to be recorded from the beginning.

During this recording operation, if the amount of power supplied to the thermal head 11 exceeds the limited amount of power, the operation is stopped for a certain period of time and then restarted, similarly to the above. In this case, when the number of stops exceeds a certain number
), stop the operation.

On the other hand, if the drive device 14 fails or the thermal recording paper 13
If a paper jam occurs, the movement of the thermal recording paper 13 will stop. In this case (N in process 309), the switch circuit 208 is turned off (process 319), and the drive device 1
4 malfunction or paper jam (processing 317), and an operator call is made (processing 3).
18), stop the operation.

As described above, in this embodiment, by determining the amount of power supplied to the heat generating part of the thermal head 11, the temporary temperature rise of the heat generating part of the thermal head 11 is predicted without actually measuring it. Since the recording operation is stopped when the amount of power supplied exceeds the set limit amount of power, it is possible to prevent an image with unnatural density from being output as is. Furthermore, in this case, since the above-mentioned limited power amount is determined according to the moving speed of the recording paper, it becomes possible to more accurately determine that the density of the recorded image has reached a certain level or higher.

Furthermore, since the recording operation is stopped when the moving speed of the recording paper is not a predetermined speed, it is possible to eliminate unnecessary recording operations in the event of a paper jam of the recording paper or a malfunction of the transport mechanism.

In the above embodiment, the ratio of black pixels in one line is determined by integrating the image signal, but it is determined by counting the number of bits indicating black pixels per line of image information. Also, thermal recording paper 13
It goes without saying that the detection of the moving speed is not limited to an optical method such as the photosensor 17, and other means may be used.

Further, (2) Although it is determined whether or not to stop recording based on the amount of power supplied to the thermal head 11 for each line, it is also possible to make this determination based on the average amount of power supplied to each of a plurality of lines.

Further, the present invention is naturally applicable not only to facsimile machines but also to a wide range of image recording apparatuses using thermal heads.

[Effects of the Invention] As described above, according to the present invention, the moving speed of the recording paper is detected, the limited amount of power supplied to the heating element of the thermal head is determined according to the moving speed, and the image is Calculate the actual amount of power supplied to the heating element of the thermal head each time a line is recorded, and if the amount of power exceeds the limited amount of power, or.

Since the recording operation is stopped when the moving speed of the recording paper is not constant, it is possible to prevent unnatural images with high density in parts from being output as is, and also to prevent paper jams in the recording paper. No problem in case of failure or transport mechanism failure.
It is possible to eliminate unnecessary recording operations.

[Brief explanation of the drawing]

FIG. 1 is a block configuration diagram of a facsimile machine according to an embodiment of the present invention, FIG. 2 is a schematic configuration diagram of a plotter section, FIG. 3 is a block configuration diagram showing part of a plotter and a system control section, and FIG. The figure is an operation flowchart showing recording processing. 2... Plotter, 9... System control section, 11...
・Thermal head, 12...Platen roller, 13・
...Thermal recording paper, 14...Drive device, 15...Slit plate, 16...Photo interrupter, 17...
・Photo sensor, 201...CPU, 202...
Moving speed detection circuit, 203... thermistor, 204...
・・A/D (analog/digital conversion circuit), 205・
...Recording control circuit, 206...Step motor drive circuit, 207...Step motor, 208...Switch circuit, 209...Integration circuit Fig. 1 Fig. 2 Fig. 3

Claims (1)

[Claims] An image recording apparatus that records an image line by line on thermal recording paper using a thermal head includes a recording paper speed detection means that detects the moving speed of the recording paper in the sub-scanning direction during image recording, and a limited amount of power determining means for determining a limited amount of power to be supplied to the heating element of the thermal head according to the amount of electricity to be supplied to the heating element of the thermal head; and a supplied power calculating means for calculating the actual amount of electric power supplied to the heating element of the thermal head each time an image is recorded line by line. If the calculated amount of electric power exceeds the electric power limit determined by the electric power limit determining means, or if the moving speed of the recording paper detected by the recording paper speed detection means is not constant, the recording operation is stopped. What is claimed is: 1. An image recording device comprising a recording stop means.