JP2000280687A - Electronic blackboard device - Google Patents

Abstract

(57) [Summary] [Problem] To detect the overheating of a recording means such as a thermal head with a quick response to prevent the destruction of members, and to stop the power supply only when it is predicted that abnormal overheating will occur, and to perform unnecessary operation. It is an object of the present invention to provide an electronic blackboard device capable of performing good printing without a stop. SOLUTION: A reading device for reading a drawing drawn on a screen 1c, a conveying device for conveying a recording medium, and a thermal head 4 as a recording device for printing data of a read image on a recording medium by a thermal method are provided. The electronic blackboard device includes a current supply interrupting unit that monitors the state of the current supplied from the current supplying unit to the reading unit, the transporting unit, and the recording unit and interrupts the current supply from the current supplying unit when an abnormality is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic blackboard device capable of recording and outputting information such as meeting minutes and drawings drawn on a screen of a board on paper, and more particularly to an electronic blackboard apparatus for printing a read image on paper. The present invention relates to an electronic blackboard device capable of reliably preventing a trouble due to overheating of a thermal head printer.

[0002]

2. Description of the Related Art In an electronic blackboard device, a screen incorporated in a loop in a board is used as a surface for drawing characters, drawings, and the like.
The basic configuration is to record such information and print it on recording paper when necessary, and output it. In this printing operation, information on the surface of the screen is read and stored by, for example, a CCD, and then printed by a printing device.

In such an electronic blackboard device, a thermal-type printing device equipped with a thermal head is generally used, mainly in order to reduce the cost and size of the device.

In the heat-sensitive method using heat generated by the thermal head, the higher the black printing rate, the larger the current supplied to the thermal head. That is, if the black printing rate is high,
Since the number of heating elements that are energized at the same time increases, the energizing current also increases, and when the black printing rate reaches 100%, the energizing current becomes the maximum value. In a very common use of an electronic blackboard device, the black printing ratio drawn on the screen is about 10% or more, and it is rare that an extremely high black printing ratio (for example, all black) is consciously drawn. Not in Therefore, in a very normal usage, no excessive current is supplied to the thermal head, and no trouble occurs due to heat generation.

On the other hand, when a table is drawn on the screen, ruled lines and the like are printed, so that short black printing may be a normal case. Therefore, the current value supplied to the thermal head becomes large although the time is extremely short.

As described above, the current supplied to the thermal head varies in various ways depending on the image drawn on the screen of the electronic blackboard device, and especially when the black printing rate is high, the current load may become abnormally large. is there.

If the current load on the thermal head becomes abnormally high, heat may damage parts and impair the safety for the user. Therefore, from the viewpoint of the current supply source (power supply unit), it is necessary to provide an overcurrent protection device. Is essential. Further, if continuous printing with a high black printing rate, that is, a situation where current consumption is high, continues under some abnormal conditions, the operating temperature of the thermal head itself rises, resulting in destruction of parts and smoke. Therefore, from the viewpoint of the thermal head itself, it is clearly determined that the continuation of the high current load is abnormal, and the printing operation is stopped, and some protection device is required so as to operate only within the specified operation guarantee temperature.

[0008] From such a viewpoint, conventionally, an overheat protection circuit for detecting the temperature of a heat-generating component by a thermistor attached to a common heat sink is generally used in a power supply portion. This overheat protection circuit is operable even in the event of an abnormality in the output system to the secondary side, and also indirectly detects and protects the temperature of the thermal head in the printing section. Further, a thermal head having a built-in thermistor, which detects the temperature of the thermal head and stops the printing operation when the thermal head reaches a certain level, has been widely adopted.

[0009]

However, in the case where the overheat protection circuit including the thermistor is provided in the power supply portion, the heat generation temperature of the heating element of the thermal head is indirectly detected. Therefore, when the temperature of the heating element rises rapidly and becomes an abnormal temperature, the temperature followability cannot be said to be good.

Further, in the case where the amount of energization is controlled by feedback of temperature detection by a thermistor incorporated in the thermal head, energization is stopped when the temperature of the thermal head reaches a certain critical temperature or higher, so that overheating can be prevented. However, there is a limit to the temperature followability when the heating element rapidly rises to an abnormal temperature, and it must be said that the reliability is low. In order to prevent the thermal head from being destroyed due to excessive heat generation, it is necessary to set the rated protection level of the thermistor. However, the setting is generally very difficult. For example, it is impossible to perform an optimal control to eliminate unnecessary malfunctions such as stopping before an excessive current value is reached and to prevent destruction at the same time.

On the other hand, the vertical ruled lines drawn on the screen are all black, although for a short time, when printed by the thermal head. In this case, if the protection circuit is activated and the stop is repeated because of the all black printing, the heating element is lower than the abnormally high temperature and can be operated without any trouble, but the useless stop is forced. Therefore, in order to print on the recording paper, manual operation such as canceling the operation of the protection circuit is required, which greatly affects usability.

The present invention detects the overheating of the thermal head with a fast response to prevent the destruction of the members, and stops the energization only when it is predicted that abnormal overheating is expected. It is an object of the present invention to provide an electronic blackboard device that can execute the method.

[0013]

According to the present invention, there is provided an electronic blackboard apparatus comprising: reading means for reading a drawing drawn on a screen; and conveying means for conveying a recording medium for recording information read by the reading means. Recording means for recording information read by the reading means on a recording medium conveyed by the conveying means; current supply means for supplying current to the reading means, the conveying means, and the recording means; Current supply interrupting means for interrupting the current supply to the current supply means when the state of the current supplied from the supply means to the reading means, the transport means, and the recording means is monitored and an abnormality is detected. Features.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall perspective view of an electronic blackboard device according to an embodiment of the present invention.

In FIG. 1, the electronic blackboard device 1 has a screen 1b disposed at the upper end of a leg 1a.
The screen b is provided with a screen 1c which moves leftward in the drawing in a loop in b. A printer 1d for recording the drawing drawn on the screen 1c is attached to the center of the lower end of the screen section 1b, and by operating the operation panel 1e, a recording paper on which the drawing is printed is output.

FIGS. 2A and 2B are schematic views showing main parts of the electronic blackboard device 1, wherein FIG. 2A is a perspective view of an optical reading system and a printing section, excluding a screen 1c, and FIG. 2B is a plan view.

As shown, the optical reading system disposed inside the screen section 1b and on the back side of the screen 1c includes a fluorescent lamp 2a and a mirror 2b, and an image on the screen 1c reflected by the mirror 2b. Image sensor 2 using a lens 2c for condensing light and a CCD which receives light from this lens 2c and reads it as an image signal
d. Further, a control board 3 having a control section for receiving a signal from the image sensor 2d and performing image processing, and a thermal head 4 electrically connected to the control board 3 are arranged as a printing section.

As is well known in the art, the thermal head 4 for printing has a large number of heating elements arranged in the width direction of the thermal paper P wound in a roll. Then, the thermal paper P is nipped between the thermal paper P and the platen roller 4a provided in the printing unit, and the thermal paper P is conveyed by rotating the platen roller 4a by a paper feed motor (not shown), and the image by the optical reading system is conveyed. Printing is performed on the thermal paper P based on the stored information. In the present embodiment, a heat-sensitive method using the heat-sensitive paper P is used, but a method of recording on plain paper via a transfer film may be used.

FIG. 3 is a block diagram of a monitoring circuit in the electronic blackboard device of the present invention, and FIG. 4 is a specific example of the monitoring circuit.
In FIG. 3, a solid line between blocks indicates a power system current path, and a broken line indicates a signal current path.

As shown in FIG. 3, 1 is a power supply source.
A power system current path between the next circuit A and the thermal head driving unit E for driving the thermal head 4 includes an overload detection unit B and a switch S, and a signal system current path to the primary circuit A is provided. An abnormal voltage detector C and a voltage monitor D are provided.

The overload detecting section B includes a controller (not shown) for controlling all operating devices of the electronic blackboard device, a driver for the fluorescent lamp 2a, a motor for driving the screen 1c, a thermal head driving section E, and a platen roller 4a. , And a total current supplied to the load side such as the image sensor 2d. When the overcurrent flows for a predetermined time or more, the input I to the switch S is changed to H (Hi).
gh), whereby the switch S is turned off and the power supply to the thermal head driving unit E is cut off.

As shown in FIG. 4, the overload detecting section B includes a positive temperature coefficient thermistor (PTC thermistor) 5a and a transistor 5b. As is well known, the positive-characteristic thermistor 5a has a resistance value increased by an overcurrent and a voltage drop increases. By utilizing this characteristic, the transistor 5b is turned on when an overcurrent flows. The input I becomes H. Therefore, when the overcurrent continuously flows for a predetermined time, the switch S is turned off, and the power supply to the thermal head 4 is stopped.

The change in the resistance value of the positive temperature coefficient thermistor 5a is reversible. When the overcurrent is eliminated, the resistance value returns to its original value. Is resumed.

Normally, the transistor 5b is off and the signal from the controller becomes the input I as it is. That is, during a non-printing period, the input I becomes H by a signal of H from the controller, and the switch S is in an off state. At the time of printing, the input I becomes L by a signal of L (Low) from the controller, and the switch S is turned on. Power is supplied to the thermal head driving unit E.

As shown in FIG. 4, the switch S is composed of a relay 6 comprising a switch and a coil, and a circuit for turning on and off a current to the coil. In the relay 6, when a current flows through the coil, the switch S is turned on. That is, when the input I is H, the current to the coil is turned off and the switch S is turned off. When the input I is L, the current to the coil is turned on and the switch S is turned on.

The voltage monitoring unit D monitors the voltage at the point P in FIGS. 3 and 4 so that the voltage at the point P becomes constant in order to stably drive the controller, the thermal head 4, and the like. The signal is fed back to the primary circuit A as a feedback signal S2. As shown in FIG. 4, the voltage monitoring unit D includes a photocoupler 7 in a circuit and a feedback signal S2 according to a current flowing through the photocoupler 7.
Are output to the primary circuit A. The supply voltage is controlled on the primary circuit A side in accordance with the value of the feedback signal S2, and as a result, the voltage at the point P is kept constant.

The abnormal voltage detector C detects a voltage rise at the point Q in FIGS. 3 and 4, and outputs the detected value to the primary circuit A as a primary circuit stop signal S1. That is, in the overload detection unit B, the resistance value of the positive temperature coefficient thermistor 5a increases due to the overcurrent, and the voltage drop increases. On the other hand, the voltage at the point P is energized so as to be kept constant by the operation of the voltage monitoring unit D.
The voltage at the point increases. Therefore, the abnormal voltage detector C
Detects an increase in the voltage at the point Q and outputs a primary circuit stop signal S1 to the primary circuit A when the overcurrent is still continued after the switch S is turned off by the overload detection unit B. Thus, the primary circuit A completely stops supplying the voltage.

As shown in FIG. 4, the abnormal voltage detector C comprises a Zener diode 8a and a photocoupler 8b. When the voltage at the point Q rises to a predetermined level or more, a current flows through the photocoupler 8b, and A next circuit stop signal S1 is output to the primary circuit A.

FIG. 5 is an operation flowchart of the control of the electronic whiteboard apparatus of the present invention, which will be described below in order.

When there is a command from the controller to read the information written on the screen 1c and read it by the optical system, after the voltage is supplied from the primary circuit A, the overload detector B detects the resistance by the positive characteristic thermistor 5a. The state of the current flowing to the point P is monitored by detecting the degree of the voltage drop due to the change in the value (S01). Where P
The criterion for determining that the current flowing to the point is abnormal is a case where a large current exceeding the rating continues for more than 10 seconds, and a positive temperature coefficient thermistor having characteristics meeting this criterion is used. Then, as long as the previous voltage drop is equal to or lower than a predetermined level (hereinafter, referred to as “first level”) and no abnormality is detected, the thermal head driving unit E is energized to perform a normal operation.

On the other hand, if the previous voltage drop becomes larger than the first level, it is detected as abnormal and the output from the overload detector B becomes H (S02). As a result, the input I to the switch S becomes H And the switch S is turned off (S0
3). That is, when the resistance value of the positive temperature coefficient thermistor 5a increases due to an overcurrent and the voltage drop becomes larger than a predetermined level, the transistor 5b turns on, and as a result, the input I to the switch S becomes H. Accordingly, the switch S is turned off, and the power supply to the heating elements of the thermal head 4 via the thermal head driving unit E is stopped. At this time, only the printing operation is stopped, and a driving motor for driving the screen 1c, an image sensor 2d, and a paper feeding motor (not shown) for driving the platen roller 4a via a point P maintained at a constant voltage. The voltage application to is continued. Therefore, the operation of reading the image on the screen 1c while moving the screen 1c and the operation of transporting the thermal paper P are continued as usual, as in the normal operation.

On the other hand, in order to confirm whether there is any trouble other than the overcurrent to the thermal head 4, the abnormal voltage detector C determines the voltage drop due to the increase in the resistance of the positive characteristic thermistor 5 a to a predetermined level different from the first level. Is compared with the second level (S04). This voltage drop is determined by the fact that the voltage at point P in FIG. 3 and FIG. 4 is always kept constant by the voltage monitoring unit D and the resistance value is increased by energizing the positive temperature coefficient thermistor 5a. It is sufficient to use the fact that the voltage drop increases corresponding to the above, and as a result, the voltage at point Q rises.

The voltage at point Q rises above the second level,
When an abnormality is detected, a current flows through the photocoupler 8b, and a primary circuit stop signal S1 is output to the primary circuit A (S1).
05) The primary circuit A is stopped, that is, the power supply to the entire electronic blackboard device is stopped (S06).

If no abnormality is detected by the abnormal voltage detecting section C, the state in which the power supply to the heating element of the thermal head 4 is stopped continues as long as an abnormal state is detected by the overload detecting section B (S04, S07). ). Then, when the abnormal state is resolved and the resistance value of the positive temperature coefficient thermistor 5a falls, the abnormal state is not detected by the overload detecting section B (S07), and the output of the overload detecting section B becomes L (S08). At this time,
If the operation of reading the image on the screen 1c while moving the screen 1c and the operation of transporting the thermal paper P, that is, the copying operation, have not been completed yet, since the output from the controller to the switch S is L, the input I to the switch S L. As a result, the switch S is turned ON, printing of the read image data on the thermal paper P is restarted from this point, and printing is continued until the copy operation is completed (S09, S09).
10). Therefore, even when the overcurrent is temporarily detected and the printing operation is stopped when a black solid portion is present in a part of the screen 1c, the reading process of the screen 1c and the transporting process of the thermal paper P are continued. Printing is resumed immediately after the current is eliminated.

On the other hand, when the overload detecting section B no longer detects an abnormal state, if the copying operation such as moving or reading the screen 1c has already been completed (S0).
9), the copy operation ends.

Of course, if the abnormal voltage detector C detects an abnormality while the power supply to the heating element of the thermal head 4 is stopped (S04), the primary circuit stop signal S1
Is output (S05), and the primary side completely stops (S0).
6).

Here, in the present invention, the criterion for determining that the thermal head 4 is in an overheated state and abnormal is based on the case where a large current exceeding the rating continues for more than ten seconds as described above. This criterion can easily be predicted to fluctuate depending on the characteristics of each device.
It is possible to know empirically by a device test how long it will be overheated at the time. For example, assuming that the black printing rate is 100%, a minimum time until overheating occurs is derived in advance, and a shorter time is set as a critical time by multiplying this by a safety coefficient. You just need to do the operation.

As described above, according to the present invention, the screen 1c
The protection circuit functions such as current limiting do not operate even during the short-time all black printing such as the ruled line printing illustrated in FIG. Therefore, the screen 1c
Even if there are a large number of ruled lines, the printing operation by the thermal head 4 is continued, and operations such as unnecessary stoppage and cancellation of the protection circuit function become unnecessary.

When the black printing ratio is high and the standard for determining the abnormality is exceeded, only the energization of the thermal head 4 is stopped, and the other functions are continued. Therefore, if a trouble is caused only by overheating of the thermal head 4, reading of the next image from the screen 1c to the image sensor 2d is not interrupted.
An operation such as re-reading becomes unnecessary.

Further, the current supply line is provided with a positive temperature coefficient thermistor 5a having a high resistance value due to an overcurrent or a rise in the ambient temperature. The degree of overheating of the head 4 is detected. Therefore, as compared with a conventional case where a thermistor for temperature detection and feedback control to a controller is built in the thermal head 4, a response delay can be remarkably shortened even when the temperature of the thermal head 4 suddenly rises. For this reason, even when the black printing rate of the screen 1c is high and an image is to be printed which is wide enough to energize all the heating elements of the thermal head 4 at the same time, the energization is performed before the thermal head 4 is overheated. Stopped. Therefore, it is possible to avoid destruction of the thermal head 4 itself and its peripheral circuit components.

Here, when the positive temperature coefficient thermistor 5a is incorporated in the current supply line, the voltage applied to the positive temperature coefficient thermistor 5a also reduces the energy applied to the thermal head 4 and adversely affects the print density. In contrast,
The positive temperature coefficient thermistor 5a is located in a voltage regulation feedback system upstream of a point P which is maintained at a constant voltage by the voltage monitoring unit D. By doing so, the voltage drop in the thermal head 4 is canceled, the energy applied to the thermal head 4 does not decrease, and the print density is properly maintained.

In the present embodiment, a heat-sensitive system is used. However, as long as there is a possibility that the temperature of the printing unit may rise due to an overcurrent, an electronic blackboard device using another recording system may be used. The present invention is applicable.

[0044]

According to the present invention, since the overcurrent supplied to the recording means such as a thermal head is integrated and the current supply is interrupted before the recording means becomes overheated, the conventional temperature measurement using a thermistor is performed. As compared with the case, the operation can be performed with higher responsiveness, and the thermal head and other components used as the recording means can be prevented from being destroyed.

Further, if the power supply is stopped when the current continues even after the supply of the current to the recording means is stopped, it is possible to detect an abnormality of a device other than the recording means and to avoid a trouble.

[Brief description of the drawings]

FIG. 1 is an overall perspective view of an electronic blackboard device according to an embodiment of the present invention.

FIGS. 2A and 2B are schematic views of an image reading system and a printing unit in the electronic blackboard device of the present invention, wherein FIG. 2A is a perspective view of a main part excluding a screen, and FIG.

FIG. 3 is a block diagram of a monitoring circuit in the electronic blackboard device of the present invention.

FIG. 4 is a diagram showing a specific example of a monitoring circuit of the electronic blackboard device of the present invention.

FIG. 5 is an operation float chart under the control of the electronic blackboard device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electronic blackboard device 1a Leg 1b Screen part 1c Screen 1d Printer 1e Operation panel 2a Fluorescent lamp 2b Mirror 2c Lens 2d Image sensor 3 Control board 4 Thermal head 4a Platen roller 5a Positive thermistor 5b Transistor 6 Relay 7 Photocoupler 8a Zener diode 8b Photo coupler

Claims (4)

[Claims] A reading unit for reading a drawing drawn on a screen; a conveying unit for conveying a recording medium for recording information read by the reading unit; and a conveying unit for reading the information read by the reading unit. A recording unit that records on a recording medium conveyed by a unit; a current supply unit that supplies a current to the reading unit, the conveyance unit, and the recording unit; and the reading unit, the conveyance unit, and the current supply unit. An electronic blackboard device comprising: a current supply cutoff unit that monitors a state of a current supplied to the recording unit and detects a current supply from the current supply unit when an abnormality is detected. 2. The current supply interrupting means, wherein when an overcurrent is supplied from the current supply means to the reading means, the transport means, and the recording means for a predetermined time or more, the current supply means transmits the current to the recording means. 2. The electronic blackboard device according to claim 1, wherein the current supply is interrupted. 3. An overcurrent supply to said reading means, said transport means, and said recording means is continued after said current supply interruption means interrupts the supply of current from said current supply means to said recording means. 3. The electronic blackboard device according to claim 1, further comprising a current supply stopping unit that stops current supply from the current supplying unit. 4. An electronic blackboard device according to claim 1, wherein said recording means includes a thermal head of a thermal recording system.