JPS61258758A - Recording device - Google Patents

Abstract

PURPOSE:To prevent breaking of a recording element due to failure or the like of a control device by providing a means which limits a time width of a control signal to control an application of a driving signal for a recording element. CONSTITUTION:A recording head TH which consists of (n) pieces of heat generating elements is controlled to be driven by a control portion 2 through a driver 4. Application of driving signals S1-Sn is controlled by gates G1-Gn. The gates G1-Gn are controlled by strobe signal Ss to be put out from the control 2, a making current and a reset circuit 3 which brings back a controlling operation to its initial stage during cutoff. The above stated strobe signal Ss is put into a derivative network and is adjusted to the fixed time width or less. Within the network, the rise time for the time width of a driving signal to be applied to the recording head TH is synchronized with driving signals S1-Sn, and that of finishing is with the finishing of pulse regulated by the derivative network. Therefore, a driving time of the recording head TH longer than the fixed time is prohibited and, additionally, the gates G1-Gn are closed at times of making current and cutoff by the reset 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a printing apparatus, and particularly to a printing apparatus that drives a printing element using a control signal that controls the application of a driving signal to the printing element.

[Summary of the Disclosure] This specification and the drawings have a structure that is provided with means for limiting the time width of a control signal that controls the application of a drive signal to a recording element, thereby prohibiting the recording element from being driven for a predetermined period of time or more, and controlling the drive signal. This invention discloses a technique for preventing destruction of recording elements due to equipment failure or the like.

[Prior Art] In recent years, bubble jet printers have become known as small, low-noise recording devices. Bubble jet printers are a type of ink jet printer, and perform recording by energizing a heating element provided in an ink jet nozzle to instantaneously boil ink in the nozzle and jetting it from the nozzle.

[Problems to be Solved by the Invention] Particularly in small-sized recording devices such as calculators with printers, recording heads in which an ink cartridge, a nozzle, and a heating element are integrated are known.

In the case of compact recording devices like this, 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 will rise rapidly and the head will be destroyed. There is a danger. In a cartridge type disposable bubble jet head, the device is destroyed by a pulse width two to three times the normal pulse width of several microseconds. CMO especially due to noise when powering on and off equipment
If a control circuit goes out of control due to electrostatic damage to an LSI made up of S or the like, the current supply 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 adopts a configuration in which means is provided for limiting the time width of the control signal that controls the application of the drive signal to the recording element. .

[Operation] In FIG. 1, the recording head TH, which is made up of n heating elements, is driven and controlled by the control section 2 via the driver 4, which is made up of transistors and the like. Application of the drive signals S1 to Sn is controlled by gates Gl-Gn. The gates 01 to Gn, which are NOR gates, are controlled by a strobe signal Ss output from the control section 2 and a reset circuit 3 that initializes the operation of the control section when the power is turned on or off.

The strobe signal Ss output from the control section 2 is sent to the inverter G.
8 through capacitor CC9 resistor R and diode DI
is input to a differentiator circuit consisting of The differentiating circuit functions to adjust the time width of SS to within a predetermined time width.

As shown in FIG. 2, the drive signals 31 to Sn are output during the period when the strobe signal Ss is at a low level, so that the rising edge of the time width of the drive signal applied to the recording head TH is By S1-Sn,
Further, the falling edge is synchronized with the falling edge of the pulse defined by the differentiating circuit.

Therefore, the recording head TH is prohibited from being driven for a longer time than a predetermined period of time, and the reset circuit 3 shuts off the gates Gl-Gn when the power is turned on and off, so unstable operation of the control section or electrostatic noise may occur during this period. This prevents the 12-dot TH from being driven for a long time to record.

[Example] The present invention will be described in detail below based on embodiments shown in the drawings.

explain. However, below, a bubble jet printer will be explained as an example.

FIG. 1 is a block diagram showing the configuration of a bubble jet printer or an electronic device including the bubble jet printer. In the figure, a recording head indicated by the symbol TH is composed of heating elements H1 to Hn. One side of each heating element is commonly connected, and a power supply voltage VH is supplied from a power supply circuit l. The opposite side of each heating element H1 to Hn is connected to a driver 4 made of a transistor or 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, what is indicated by the reference numeral 2 is a control section composed of an LSI or the like, and is a control section for controlling the recording head TH.
Drive signals 51 to Sn for causing the recording operation to be performed are outputted. These drive signals 51 to Sn are provided by the driver 4, respectively.
Gl to Gn are connected to the inputs of Gl to Gn. Gate Gl-Gn is composed of a NOR gate, and all of its remaining inputs are commonly connected to the output of gate G5.

Gate G5 inverts the output of gate G6, which is a NOR gate. A reset signal output from the reset circuit 3 is input to one input of the gate G6 via the gate G9. Reset circuit 3 is set to O of the power switch.
A reset signal for initializing each part of the device is output in response to the operation of the N, OFF or reset switch. On the other hand, the remaining inputs of the gate G6 are connected via a gate G7 to the output of a differentiating circuit composed of a capacitor CC2 resistor R and a diode D1. The capacitor CC of this differentiating circuit is connected to the control unit 2 via the gate G8.
A strobe signal Ss is input.

The strobe signal Ss is used to open the gates G1 to Gn in order to provide the drive signals S1 to Sn to the driver 4.

Next, the operation of the above configuration will be explained with reference to FIG. FIG. 2 is a waveform diagram showing signals at connection points indicated by respective symbols in FIG. 1.

When the power of the device is turned on, first, during period t1, the power supply voltage V for driving the control unit 2 or other logic circuits is turned on.
cc rises slowly. The reset circuit 3 outputs a low-level reset signal during this period. Since this reset signal is inverted by gate G9 and input to gate G6, one input U1 of gate G6 is set to high level, and as a result, no matter what level the other input of gate G6 is, its output U2 becomes low level, and the control signal U3 of G1-Gn, which is this inverted output, becomes high level. Therefore, high level output to the driver 4, that is, driving of the recording head TH is prohibited.

When the reset signal becomes high level during period t2,
By the operation opposite to the above, the input signal U1 of the game controller G6 is brought to a low level. As a result, the output U2 of the game G6 changes in accordance with the other input U8. That is, control using the strobe signal Ss of the control section 2 becomes possible. When performing a recording operation, the control section 2 first outputs a strobe signal SS to open the gates Gl-Gn,
Drive signal 3 during the time period when G1 to Gn are completely open.
1-3n is output to drive RAD TH for recording. When the control section 2 outputs the strobe signal Ss, this signal is inverted by the gate G8 and becomes as indicated by the symbol U6 in FIG. Furthermore, the signal changes as indicated by reference numeral U7 in FIG. 2 in accordance with the time constants of the resistor R and capacitor CC constituting the differentiating circuit.

The output U8 of the gate G7 becomes a low level in synchronization with the rise of the strobe signal SS, or the signal U7 becomes a low level (G).
When the signal U8 falls to the inverted output level of No.7, the signal U8 returns to high level again. Therefore, the output U2 of the gate G6 becomes high level by the length of the inverted signal U8,
The inverted signal U3 becomes a low-level pulse with the same time width.

When the signal U3 falls, the gates Gl to Gn open and control by the drive signals 3l to 3n becomes possible, but the drive signals are output with a delay from the fall of the strobe signal SS. As a result, the output U4 of G l = G n rises in synchronization with the drive signals S1 to Sn. Here, only the drive signal S1 of each drive signal is illustrated.

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

The above is a normal operation, but let us consider a case where the strobe signal SS becomes longer than a predetermined time as indicated by P in FIG. 2 due to electrostatic damage or runaway of the control section 2. If the strobe signal S3 is extended as indicated by the symbol P, the output U6 of the gate G8 is also extended in the same way. However, the pulse width of this strobe signal is limited as indicated by the symbol S due to the time constant of the capacitor CC and the resistor H. Therefore, game) G6. Gate 01~G via G5
The control signal U3 given to n has the same time width as the normal operation described above. At this time, the drive signal SL (
~Sn) is similarly extended as shown by the symbol Q in FIG.
The output of -Gn returns to a low level in synchronization with the rising edge of signal U3, and as a result, the drive signal applied to recording head TH is limited to at least the time width of a normal strobe signal.

Subsequently, when the power switch is turned off, the reset circuit 3 outputs a reset signal in the same manner as described above during the period t3, so that driving of the recording head TH via the gates 01 to Gn is prohibited.

As described above, since the time width of the strobe signal is limited by the differentiating circuit, the drive signal or strobe signal may be extended beyond the predetermined time due to noise around the power supply, runaway due to electrostatic damage in the control unit 2, etc. Even in such a case, damage to the recording head TH can be prevented. Furthermore, 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 more than a predetermined time due to unstable operation when the power is turned on and off. In particular, in the above configuration, the drive voltage V applied from the power supply circuit 1 to the recording head TH
Since H is kept constant and limited on the low-level logic circuit side, the configuration of the power supply circuit 1 can be made simple and inexpensive.

Although the bubble jet printer has been described above as an example, it goes without saying that the above configuration can be applied to recording apparatuses of other types. Further, although the gate circuit is configured using an inverter and a NOR gate in the above example, it is also possible to configure the circuit using other logic elements. Furthermore, although a circuit using a capacitor and a resistor is illustrated as the differential circuit, it is also possible to use a circuit using an operational amplifier, a Schmitt trigger, or the like.

[Effects] As is clear from the above description, according to the present invention, the control device is prevented from being damaged by electrostatic discharge, etc., due to the configuration provided with means for limiting the time width of the control signal that controls the application of the drive signal to the recording element. It is possible to provide an excellent recording device which can reliably prevent damage to the recording head even in the event of runaway, and which can be constructed easily and inexpensively.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a drive control circuit of a recording apparatus employing the present invention, and FIG. 2 is a waveform diagram showing signals of various parts in FIG. l...Power supply circuit 2...Control unit 3...Reset circuit 4...Driver CC...Capacitor
R...Resistance TH...Recording head Fig. 1 Fig. 2

Claims (1)

[Claims] In a recording apparatus that is provided with a means for limiting the time width of a control signal that controls the application of a drive signal to a recording element, a means is provided for prohibiting the application of the control signal whose time width is limited when the power is turned on and off. A recording device characterized by: