JPH0698754B2 - Recording device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording apparatus, and more particularly to a recording apparatus that drives a recording element by a control signal that controls application of a drive signal to the recording element.

[Summary of Disclosure] The present specification and the drawings show that a structure for providing a means for limiting the time width of a control signal for controlling the application of a drive signal to a recording element is used to prohibit and control the driving of the recording element for a predetermined time or longer. A technique for preventing destruction of a recording element due to a device failure or the like is disclosed.

[Prior Art] In recent years, a bubble jet printer has been known as a small-sized and low-noise recording device. A bubble jet printer is a kind of inkjet printer, and recording is performed by energizing a heating element provided in an ink ejecting nozzle to instantly boil the ink in the nozzle and eject the ink from the nozzle.

[Problems to be Solved by the Invention] Particularly in a small recording device such as a calculator with a printer, a recording head in which an ink cartridge, a nozzle, and a heating element are integrally formed is known. In a small recording head of such a device, the heating element is made very small, so if a drive signal with a long pulse width is applied to the head, the temperature of the heating element rises rapidly and the head may be destroyed. . In the cartridge type disposable bubble jet head, the element is destroyed with a pulse width of 2-3 times the normal pulse width of several microseconds. In particular, when the control circuit runs away due to electrostatic breakdown of the LSI composed of COMS, etc. due to noise when the power of the device is turned on and off, the energization time becomes longer and there is a risk of damage to the recording head.

[Means for Solving the Problems] In order to solve the above problems, the present invention outputs a plurality of recording heads and a plurality of recording signals supplied in parallel to each of the plurality of recording heads. Together with a recording control section for generating a strobe signal, a limiting circuit for limiting the time width of the strobe signal from the recording control section, a generating circuit for generating a reset signal when power is turned on, an output of the limiting circuit and the generation A configuration of a recording apparatus is provided that includes a logic unit that takes a logic with an output of a circuit, and a gate circuit that prevents the plurality of recording signals from being abnormally supplied to the plurality of recording heads by the output of the logic unit. Adopted.

[Operation] In FIG. 1, the recording head TH, which is composed of n heating elements, is driven and controlled by the controller 2 via the driver 4 composed of transistors and the like. The application of the drive signals S1 to Sn is controlled by the gates G1 to Gn. The gates G1 to Gn, which are NOR gates, are controlled by a strobe signal Ss output from the control unit 2 and a reset circuit 3 which initializes the operation of the control unit when the power is turned on and off. The strobe signal Ss output from the control unit 2 is input via an inverter G8 to a differentiation circuit composed of a capacitor CC, a resistor R and a diode DI. The differentiating circuit functions to adjust the time width of Ss within a predetermined time width.

As shown in FIG. 2, the drive signals S1 to Sn are strobe signals Ss.
Is output within a period in which the pulse width is set to a low level, and as a result, the rise of the time width of the drive signal applied to the recording head TH is defined by the drive signals S1 to Sn, and the fall is defined by the differential circuit. Will be synchronized with the falling edge of.

Therefore, the recording head TH is prohibited from being driven for a longer time than a predetermined time, and the reset circuit 3 shuts off the gates G1 to Gn when the power is turned on and off. For example, the recording head TH is prevented from being driven for a long time.

[Examples] The present invention will be described in detail below based on examples shown in the drawings. However, a bubble jet printer will be described below as an example.

FIG. 1 is a block diagram showing the configuration of a bubble jet printer or an electronic device including the same. In the figure, the reference numeral TH is a recording head including heating elements H1 to Hn. One side of each heating element is commonly connected, and a power supply voltage VH is supplied from the power supply circuit 1. Opposite sides of the heating elements H1 to Hn are connected to a driver 4 composed of transistors and the like, and each heating element is driven by applying a high level signal to the input of the driver 4. On the other hand, the reference numeral 2 is a control unit composed of an LSI or the like, which outputs drive signals S1 to Sn for causing the recording head TH to perform a recording operation. This drive signal
S1 to Sn are respectively connected to the inputs of the gates G1 to Gn which are respectively connected to the inputs of the driver 4. Gates G1 to Gn
Is composed of a NOR gate, and all of its remaining inputs are commonly connected to the output of the gate G5.

The gate G5 inverts the output of the gate G6 composed of a NOR gate. Gate to one input of gate G6
The reset signal output from the reset circuit 3 is input via G9. The reset circuit 3 outputs a reset signal for initializing each part of the apparatus in response to ON / OFF of the power switch or operation of the reset switch or the like. On the other hand, the remaining input of the gate G6 is connected via the gate G7 to the capacitor CC,
The output of a differentiating circuit composed of a resistor R and a diode D1 is connected. The strobe signal Ss of the control unit 2 is input to the capacitor CC of this differentiating circuit via the gate G8.

The strobe signal Ss is the driver 4 which is the above-mentioned drive signals S1 to Sn
To open gates G1 to Gn to give to.

Next, the operation of the above configuration will be described with reference to FIG. FIG. 2 is a waveform diagram showing signals at the connection points indicated by the reference numerals in FIG.

When the power of the device is turned on, first, in the period t1, the control unit 2
Alternatively, the power supply voltage Vcc for driving other logic circuits rises slowly. The reset circuit 3 outputs a low level reset signal during this period. Since this reset signal is inverted by the gate G9 and input to the gate G6, one input U1 of the gate G6 is set to a high level, and as a result, the output U2 of the other input of the gate G6 is set to any level. It becomes low level, and the control signal U3 of the inverted output of the gates G1 to Gn is made high level. Therefore, the high level output to the driver 4, that is, the driving of the recording head TH is prohibited.

When the reset signal becomes high level in the period t2, the input signal U1 of the gate G6 is made low level by the operation reverse to the above. As a result, the output U2 of the gate G6 will change according to the other input U8. That is, control by the strobe signal Ss of the control unit 2 becomes possible. When performing the recording operation, the control unit 2 first outputs the strobe signal Ss to open the gates G1 to Gn, and outputs the drive signals S1 to Sn in the time width in which the gates G1 to Gn are completely opened for recording. Drive head TH. When the control unit 2 outputs the strobe signal Ss, this signal is inverted by the gate G8 and becomes the signal U6 in FIG. Further, according to the time constants of the resistor R and the capacitor CC forming the differentiating circuit, the change of this signal is as shown by the symbol U7 in FIG. The output U8 of the gate G7 becomes low level in synchronization with the rising edge of the strobe signal Ss, or the signal U7 becomes the gate G7.
The signal U8 returns to the high level again when the output reversal level is reduced to. Therefore, the output U2 of the gate G6 becomes high level for the length of the inverted signal U8, and the signal U3 inverted by the gate G5 becomes a low level pulse of the same time width.

When the signal U3 falls, the gates G1 to Gn are opened and control by the drive signals S1 to Sn becomes possible, but the drive signal is output after the trailing edge of the strobe signal Ss.
As a result, the output U4 of G1 to Gn rises in synchronization with the drive signals S1 to Sn. Here, of the respective drive signals, only the drive signal S1 is shown.

When the drive signal S1 returns to low level, the gate is synchronized with this.
G1 to Gn are closed, the output U5 of the driver 4 returns to the high level, and the drive of the recording head TH is stopped.

Although the above is the normal operation, consider a case where the strobe signal Ss becomes longer than a predetermined time as indicated by a symbol P in FIG. 2 due to electrostatic breakdown of the control unit 2, runaway, and the like. When the strobe signal Ss is extended as indicated by the symbol P, the output U6 of the gate G8 is also extended. However, due to the time constant of the capacitor CC and the resistor R, the pulse width of this strobe signal is limited as indicated by symbol S. Therefore, the control signal U3 given to the gates G1 to Gn via the gates G6 and G5 has the same time width as that of the normal operation. At this time,
The drive signal S1 (to Sn) of the control unit 2 is synchronized with the symbol Q in FIG.
Even if it is extended as shown in, the output of the gates G1 to Gn returns to the low level in synchronization with the rising of the signal U3 due to the operation of the differentiating circuit, and as a result, it is applied to the recording head TH. The drive signal to be driven is limited at least within the time width of the normal strobe signal.

Then, when the power switch is turned off, the reset circuit 3 outputs the reset signal in the period t3 similarly to the above, so that the drive of the recording head TH via the gates G1 to Gn is prohibited.

As described above, since the time width of the strobe signal is limited by the differentiating circuit, the drive signal and the strobe signal due to noise around the power source, runaway due to electrostatic breakdown of the control unit 2, or the like is extended to a predetermined time or longer. Even in this case, it is possible to prevent the recording head TH from being damaged. Further, since the reset circuit prohibits the recording head from being driven when the power is turned on and off, it is possible to prevent the recording head from being driven for a predetermined time or longer due to an unstable operation when the power is turned on and off. In particular, in the above configuration, the drive voltage VH applied from the power supply circuit 1 to the print head TH is kept constant and the low-level logic circuit side limits the voltage. Therefore, the configuration of the power supply circuit 1 is simple and inexpensive. Can be

Although the bubble jet printer has been described as an example in the above, it goes without saying that the above configuration can be applied to a recording apparatus of another system. Further, in the above, the gate circuit is configured by using the inverter and the NOR gate, but the circuit may be configured by using other logic elements. Further, the differentiating circuit exemplifies a circuit using a capacitor and a resistor, but a circuit using an operational amplifier, a Schmitt trigger, or the like can be used.

[Effect] As is apparent from the above description, according to the present invention, a plurality of recording heads and a plurality of recording signals supplied in parallel to each of the plurality of recording heads are output and a strobe signal is generated. A recording control unit, a limiting circuit that limits the time width of a strobe signal from the recording control unit, a generating circuit that generates a reset signal when power is turned on, and a logic of an output of the limiting circuit and an output of the generating circuit. And a gate circuit for preventing the plurality of recording signals from being abnormally supplied to the plurality of recording heads by the output of the logic means. It is possible to provide an excellent recording apparatus which can surely prevent the recording head from being damaged even when the control apparatus is out of control and which can be simply and inexpensively constructed.

[Brief description of drawings]

FIG. 1 is a block diagram of a drive control circuit of a recording apparatus adopting the present invention, and FIG. 2 is a waveform diagram showing signals of respective parts of FIG. 1 ... Power circuit, 2 ... Control unit 3 ... Reset circuit, 4 ... Driver CC ... Capacitor, R ... Resistor TH ... Recording head

Claims (2)

[Claims] 1. A plurality of recording heads, a recording controller that outputs a plurality of recording signals supplied in parallel to each of the plurality of recording heads, and generates a strobe signal, and a strobe signal from the recording controller. A limiting circuit that limits the time width of the signal, a generating circuit that generates a reset signal when power is turned on, a logic unit that takes the logic of the output of the limiting circuit and the output of the generating circuit, and the output of the logic unit A recording device provided with a gate circuit for preventing a plurality of recording signals from being abnormally supplied to the plurality of recording heads. 2. The recording apparatus according to claim 1, wherein the plurality of recording heads include inkjet heads.