JPH085208B2 - Recording head protector - Google Patents

Description

Description: TECHNICAL FIELD The present invention prevents excessive electric power from being transmitted to a recording head of a recording apparatus such as a printer or a facsimile machine during a transition period in which a driving voltage of the recording head is turned on and off. The present invention relates to a recording head protection device.

[Prior art]

A recording device such as a printer or facsimile is configured to form an image pattern on a recording medium such as paper while driving a plurality (for example, 32 or 128) of dot forming elements provided in a recording head based on recording information. ing.

The dot forming element is driven by an electrothermal converter such as a heating resistor in a thermal head or a bubble jet head, or an electromechanical converter such as a coil of a wire dot head or a piezoelectric vibrating electron of a mechanical inkjet head. The one driven by is used.

By the way, in particular, a recording head using a dot forming element composed of a heating resistor such as a bubble jet head is controlled in recording operation while applying a heating voltage at every fixed time regulated by a heat pulse width.

However, conventionally, in this type of recording head, the control logic becomes unstable in a transient state such as power on / off, and a heat pulse of a predetermined pulse width or more is input while the heating voltage is applied to the recording head. In this case, even if the heat inhibition circuit (head drive inhibition circuit) is provided, the control logic becomes unstable and the inhibition circuit does not operate properly, and the drive system such as the dot forming element of the recording head Damage could occur.

〔Purpose〕

The present invention has been made in view of the above prior art,
It is an object of the present invention to provide a recording head protection circuit which can prevent excessive power from being accidentally sent to the recording head even when the voltage is unstable when the power is off, and which can protect the recording head from damage. Is.

[Means for achieving the purpose]

The present invention relates to a recording head having a dot forming element, a head drive circuit for supplying a driving voltage to the dot forming element according to a control signal to drive the recording head, and a driving voltage for driving the dot forming element. In a recording head protection device in a recording device, the drive voltage generating device for controlling the head drive circuit and a control voltage generating device for generating a control voltage for controlling the head drive circuit are provided. A circuit, a discharging means for discharging the driving voltage generated by the driving voltage generating means in response to the reset signal, and a backup circuit for ensuring the input of the control voltage to the head driving circuit during the discharging period by the discharging means, The above object is achieved by adopting a structure having.

〔Example〕

 The present invention will be specifically described below with reference to the drawings.

FIG. 4 shows a bubble jet (BJ) type color ink jet recording apparatus suitable for carrying out the present invention.

In FIG. 4, a recording medium 1 such as a paper sheet or a plastic sheet is supported by conveying rollers 2 and 3 composed of a pair of rollers arranged above and below, and an arrow A is indicated by a conveying roller 2 driven by a sheet feeding motor 4. Is conveyed in the direction. Guide shafts 5 and 5 are provided in front of the conveying rollers 2 and 3 in parallel with the conveying rollers 2 and 3, and a carriage 6 is reciprocally driven in the direction of arrow B via a wire 8 by an output of a carriage motor 7 along the guide shafts. .

The carriage 6 is equipped with a bubble jet recording head unit 90 which is an inkjet head. The recording head unit 90 is for producing a color image, is arranged in the scanning direction, and has four recording heads 9 for recording with inks of cyan, magenta, yellow, and black.
It consists of 9A, 9B, 9C and 9D. On the front surface of each recording head 9, that is, the surface facing the recording medium 1 at a predetermined interval (for example, 0, 8 mm), a recording unit is provided in which a plurality of (for example, 32 or 128) ink ejection ports are arranged in one vertical column. There is.

FIG. 5 shows a partial vertical cross section of the ink ejection portion of the recording head 9 (the same applies to all recording heads 9A to 9D).

In FIG. 5, a plurality of ink ejection ports 10 are formed in a vertical direction at a predetermined pitch on the surface facing the recording medium 1. Based on the recording information, the electrothermal converters (heating resistors, etc.) of the respective ink ejection ports 10 are formed. ) 11 is driven (heating by energization) to generate bubbles 11A in the ink, and the pressure when flying ink drops 1
2 is formed, and recording is performed while attaching ink dots to the recording medium 1 in a predetermined pattern.

A circuit board of a drive circuit (driver) 13 for driving the recording heads as described above is attached to each recording head 9.

In FIG. 4, the control circuit (CPU) of the recording apparatus and the ROM, RAM, etc. attached to it are formed on the control board 15, and this control circuit is provided with a command signal and a data signal from the host machine 14 such as a computer. (Recording information) is received, and based on this, a heating voltage is applied to each of the recording heads 9A to 9D via the heat driver 13 together with a driving source such as various motors.

The operation panel 160 mounted on the outer case (not shown) of the recording device has an online / offline switching key 16
A, line feed key 16B, form feed key 16
In addition to keys such as C and the recording mode switching key 16D, some alarm lamps such as an alarm lamp 16E and a power lamp 16F are provided.

FIG. 3 is a block diagram showing a control system of the bubble jet type ink jet recording apparatus of FIG.

In FIG. 3, a CPU (microprocessor) 21
Is connected to a host machine 14 such as a computer via an interface 22, and the host machine 14 is connected to a data memory.
Command signals (recorded commands) and recorded information signals read in 23, lined up program memory 24, working memory 25, etc.
The recording operation is controlled based on the program stored in ROM.

CPU21 has output port 26 and motor driver 27
The carriage motor 7 (FIG. 4) and the sheet feeding motor 4 (FIG. 4) are controlled via the head and the recording head 9 is controlled via the head control circuit 29 based on the recording information stored in the data memory 23. To do.

The numeral 30 in FIG. 3 is a sheet sensor, which detects whether or not the recording medium 1 exists between the transport rollers 2 and 3 (FIG. 4), and sends a detection signal to the CPU 21 via the input port 31. Is transmitted.

Outputs from the operation keys 16A to 16D (FIG. 4) on the operation panel 160 described above are transmitted to the CPU 21 through the input port 32, and to warning lamps such as the alarm lamp 16E and the power lamp 16F. Electricity is supplied through the output port 36.

The number 33 in FIG. 3 is a DIP switch provided on the bottom surface of the exterior, and its output is CP via the input port 34.
Transmitted to U21.

In FIG. 3, from the power supply circuit 28, a logic drive voltage VCC (5 volts) for operating the control logic circuit, various motor drive voltages VM (30 volts), a reset voltage RESET, a dot forming element of each recording head 9 are provided. A heating voltage (head voltage) VH (25 V) for heating the recording head 9 and a backup voltage VDDH for protecting the recording head 9 are output.

The heating voltage VH is applied to the recording head 9 as a backup voltage VD.
DH is applied to the head control circuit 29 and the recording head 9, respectively.

FIG. 1 shows a circuit of a recording head protection device according to the present invention.

In FIG. 1, the power supply circuit 28 includes a first regulator 28-2 for 5V and a second regulator 28-5 for heat voltage (head voltage) (25V) in the rectifier circuit 28-1, as shown. Is connected to the first regulator 28-
2 includes a reset circuit 28-3 and a backup circuit 28-
4 is connected, and the reset voltage is output from the reset circuit 28-3.
RESET (5V), logic voltage VCC (5V) and moder drive voltage VM (30V) from the first regulator 28-2,
The backup voltage VDDH is output from the backup circuit 28-4.

A head voltage (heat voltage) VH is output from the second regulator 28-5, and an ON circuit Tr1 and an OFF circuit Tr2 for the head voltage VH are connected to the second regulator.

The head control circuit 29 is provided with a logic voltage monitoring circuit 29-1 and a head drive inhibition circuit 29-2. The logic voltage monitoring circuit 29-1 inputs the logic voltage VCC and the backup voltage VDDH, and outputs a logic stop signal to the head drive prohibiting circuit 29 when the logic voltage is unstable. On the other hand, the head drive prohibiting circuit 29-2 inputs the logic stop signal and the head drive signal, and outputs the head drive signal to the head drive circuit 13 of the head 9 if there is no logic stop signal.

The recording head 9 is provided with a head drive circuit (heat driver) 13 and a heater 11 for heating and driving each dot element. The head drive circuit 13 is a head drive signal,
Backup voltage VDDH and head voltage (heat voltage)
VH is input, and each heater 11 is energized based on the head drive signal.

As shown in FIG. 1 above, the recording head protection device according to the present invention includes circuits Tr1 and Tr2 that are composed of switching transistors that turn on / off the head voltage VH and a backup circuit 28-4 that outputs the backup voltage VDDH.
Logic voltage monitoring circuit 29-1, head drive prohibition circuit 29-
2 and the head drive circuit 13 to the backup voltage VDDH
The backup voltage VDDH is guaranteed until the capacitor discharge is completed when the head voltage VH is turned off, and the head drive prohibition circuit is driven by the backup voltage to stop the application of heat voltage to the head. At the same time, the logic monitoring circuit 29-1 is driven to perform the heat inhibition guarantee so that the application of the heat voltage by the head drive signal does not start.

As shown in FIG. 4, the power supply circuit 28 is mounted on the recording apparatus main body, the head control circuit 29 is mounted on the carriage 6, and the head drive circuit (heat driver) 13 is mounted on each recording head 9. Therefore, the power supply circuit 28 and the head control circuit 29 are connected by a flexible flat cable that absorbs the movement of the carriage 6.

FIG. 2 is a timing chart showing an operation sequence of each part of the recording head protection device of FIG.

The horizontal axis in FIG. 2 is a common time axis, graph [I] shows the power on / off, graph [II] shows the backup voltage VDDH, and graph [III] shows the logic voltage VCC.
The graph [IV] shows the head voltage (heat voltage) VH, the graph [V] shows the operation of the ON circuit Tr1 of the head voltage HV, and the graph [VI] shows the output of the logic voltage monitoring circuit 29-1, that is, the logic stop signal. Is output to the head drive prohibition circuit to guarantee the head heat inhibition, and graph [VII] shows the reset drive voltage RESET from the reset circuit 28-3.
Graph [VIII] shows the operation of the off circuit Tr2 for the head voltage VH.

In the example of FIG. 2, each operation when the power is turned on is program-controlled, and the backup voltage VDDH and the logic voltage VCC are applied at the same time when the power is turned on, but the head voltage (heat voltage) VH is the reset time a from the power on. And is applied from the time when the initialization time b has elapsed. In addition,
The graph [V] shows the operation of the ON circuit Tr1 of the head voltage VH, the graph [VI] shows the output state of the logic stop signal from the logic voltage monitoring circuit 29-1, and the graph [VII] is the reset voltage (RESET). The output status of the graph [VII
[I] indicates the operation timing of the discharge circuit Tr2 that turns the head voltage VH on and off.

On the other hand, when the power supply is turned off (graph [I]), the logic voltage VCC turns off at the fall of its time constant, and the head voltage VH switches to the off state while discharging with a unique time constant. However, as shown in the graph [II], the backup voltage VDDH is kept on for a predetermined time after power-off, that is, for a length of time covering the discharge time of the head voltage VH.

This backup voltage VDDH is the logic voltage monitoring circuit 29.
-1 is input to the head drive prohibiting circuit 29-2, the logic stop signal is supplied to the head as shown in the graph [VI] during the falling time of the logic voltage VCC as shown in the graph [III], that is, during the transient period. Drive inhibit circuit 29−
2 is output to the head 9, and therefore the application of the heating voltage to the head 9 is prohibited even when there is a head drive signal. That is, the heat prohibition guarantee function is given by the output of the logic voltage monitoring circuit 29-1.

Therefore, the head drive is prohibited when an abnormal voltage occurs while the head voltage VH is discharged when the power is off, and the recording head 9
Is reliably protected from abnormal voltage.

Further, the protection circuit of FIG. 1 backs up only the head control circuit 29 which is a part of the control system of the recording apparatus, and does not back up the whole but discharges the others, so that the backup capacity is kept small. You can

Note that the backup voltage VDDH is unnecessary when the discharge of the head voltage VH is completed. Therefore, it is sufficient to guarantee the backup voltage VDDH for a predetermined time until the discharge is completed and prohibit the head drive.

INDUSTRIAL APPLICABILITY The present invention is widely applicable to general recording apparatuses that drive a recording head with a head voltage VH, that is, various recording apparatuses such as a thermal type, a wire dot type, and an inkjet type. If it is applied to a jet type ink jet recording apparatus, a great effect can be obtained.

[Effect] As is apparent from the above description, according to the recording head protection circuit of the present invention, the head drive voltage is discharged when the power is off, and the backup circuit allows
The operation is performed to ensure the voltage for controlling the head drive circuit to be prohibited from being driven until the discharge is completed. Therefore, since the control voltage for recording control decreases after the driving voltage is discharged, it is possible to prevent excessive power from being accidentally sent to the recording head even when the voltage when the power is off is unstable. A printhead protection circuit is provided that can protect the printhead from damage.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a recording head protection device according to the present invention, FIG. 2 is a timing chart of the operation of the circuit of FIG. 1, and FIG.
FIG. 1 is a block diagram of a control system of a recording apparatus including the recording head protection device of FIG. 1, and FIG. 4 is a perspective view of a bubble jet type inkjet recording apparatus suitable for applying the present invention,
FIG. 5 is a partial vertical sectional view of the recording head of FIG. 9 ... Recording head, 11 ... Heater, 13 ... Head drive circuit, 28-4 ... Backup circuit, 29-1 ... Logic voltage monitoring circuit, 29-2 ... Head drive inhibition circuit, Tr1
...... Head voltage on circuit, Tr2 …… Head voltage off circuit, VH …… Head voltage, VCC …… Logic voltage, VDDH…
… Backup voltage.

Claims (1)

[Claims] 1. A recording head having a dot forming element, a head drive circuit for supplying a driving voltage to the dot forming element according to a control signal to drive the recording head, and a driving voltage for driving the dot forming element. In a recording head protection device in a recording device, comprising: a drive voltage generating unit for generating the voltage; and a control voltage generating unit for generating a control voltage for controlling the head drive circuit, a reset signal is generated when the power of the recording device is turned off. A reset circuit; a discharge circuit that discharges the drive voltage generated by the drive voltage generation circuit in response to the reset signal; and a backup circuit that ensures the input of the control voltage to the head drive circuit during the discharge period of the discharge circuit. A recording head protection device having: