Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1998-06-16
2001-02-27
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
Reexamination Certificate
active
06193342
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet printer, and a method of and an apparatus for adjusting the ink discharge velocity in the ink jet printer.
2. Description of the Related Art
In such an ink jet printer, there is equipped an actuator of an ink jet head, which expands and restores the capacity of many ink storing chambers formed inside the actuator using a piezoelectric element installed corresponding to each of the ink storing chambers, and which applies pressure to the ink inside the ink storing chamber. In this way, the actuator discharges the ink from an ink discharge hole formed in each of the ink storing chambers to the external i.e., onto the recording sheet.
The ink discharge velocity of the actuator constructed in this manner varies depending upon the diameter of the ink discharge hole, the width or length of the ink storing chamber and the variation of the characteristics of the piezoelectric element and the like.
Hence, in order to correct this variance of the ink discharge velocity, either a driving voltage (i.e., a voltage of a wave for driving the piezoelectric element) or a driving voltage waveform (i.e., a waveform of a wave for driving the piezoelectric element) for expanding and restoring the piezoelectric element is adjusted or both of the driving voltage and the driving voltage waveform are adjusted.
However, according to the above mentioned ink jet head, since the driving voltage waveform and the driving voltage influence each other, it is a very cumbersome operation to adjust both of the driving voltage and driving voltage waveform.
In addition, in a case where the variance of the ink discharge velocity is corrected by adjusting only the driving voltage, the driving voltage needs to be adjusted over a wide range. However, in order to do this, the variable range of the power source voltage needs to be set very wide correspondingly, which caused a problem in the safety and the cost thereof.
SUMMARY OF THE INVENTION
Given these circumstances, it is an object of the present invention to provide an ink jet printer, and a method of and an apparatus for adjusting the ink discharge velocity in the ink jet printer, which can adjust the ink discharge velocity appropriately.
The above object of the present invention can be achieved by an ink jet printer provided with: an ink discharge device for discharging ink, having (i) a body prescribing an ink flow path through which the ink is supplied, a plurality of ink storing chambers each connected to the ink flow path in which the supplied ink is temporarily stored and a plurality of ink discharge holes connected to respective one of the ink storing chambers though which the temporarily stored ink is discharged, and (ii) a plurality of piezoelectric elements for selectively changing capacities of the ink storing chambers; a driving voltage generating device for generating a driving voltage having a pulse-like waveform, which causes the ink to be discharged from each of the ink discharge holes by deforming the respective one of the piezoelectric elements; a plurality of analog switching devices for selectively opening and closing each current-carrying path, through which the driving voltage is supplied to the respective one of the piezoelectric elements; a power source voltage supplying device for supplying a power source voltage to the analog switching devices; a driving voltage adjusting device for changing at least one of a slope and an amplitude of the waveform of the driving voltage; and a power source voltage adjusting device for changing the power source voltage.
According to the ink jet printer of the present invention, the driving voltage having the pulse-like waveform generated by the driving voltage generating device is supplied to respective one of the piezoelectric elements when the analog switching device closes the current-carrying path connected to the respective one of the piezoelectric elements. Thus, the ink is discharged from the ink discharge hole. At this time, the driving voltage adjusting device adjusts one or both of the slope and the amplitude of the waveform of the driving voltage, so as to generate a difference in the displacement velocity or the displacement amount of the piezoelectric element. As a result, the ink discharge velocity changes. On the other hand, when the power source voltage adjusting device changes the value of the power source voltage supplied to the analog switching devices, the ON resistance of the analog switching device changes, so that the waveform of the driving voltage is changed. As a result, the ink discharge velocity also changes in accordance with this change in the waveform. Therefore, the adjustment amount, which is necessary to be adjusted by the driving voltage adjusting device, decreases.
Consequently, the cost of the power source circuit can be reduced and the safety can be improved according to the ink jet printer of the present invention.
In one aspect of the ink jet printer of the present invention, the driving voltage adjusting device changes at least one of the slope and the amplitude of the waveform in accordance with the change in the power source voltage which is caused by the power source voltage adjusting device.
According to this aspect, when the power source voltage is changed by the power source voltage adjusting device, in accordance with this change, the driving voltage adjusting device changes at least one of the slope and the amplitude of the waveform. Therefore, the aforementioned driving voltage having the pulse-like shape is confined within a prescribed power source voltage range and does not destroy the analog switching device.
Consequently, the analog switching devices can be properly driven.
In this aspect, the driving voltage generating device may be provided with a first switching device for decreasing the driving voltage from a predetermined maximum value to a predetermined minimum value and a second switching device for increasing the driving voltage from the predetermined minimum value to the predetermined maximum value. And that, the first switching device and the second switching device may share the power source voltage, which is changed by the power source voltage adjusting device, with the analog switching devices.
In this case, the first switching device decreases the driving voltage from the predetermined maximum value to the predetermined minimum value, and the second switching device increases the driving voltage from the predetermined minimum value to the predetermined maximum value. At this time, since the first switching device and the second switching device share the power source voltage, which the power source voltage adjusting device changes, with the analog switching devices, even if the power source voltage adjusting device changes the power source voltage for the analog switching device as described above, the driving voltage is confined within a prescribed power source voltage range, and does not destroy the analog switching device. As a result, the analog switching devices can be properly driven.
In another aspect of the ink jet printer of the present invention, the power source voltage adjusting device is provided with a variable resistor and a Zener circuit for changing the power source voltage.
According to this aspect, by virtue of the variable resistor and the Zener circuit, the power source voltage can be appropriately adjusted. Thus, by employing a relatively simple construction, it is possible to adjust the ink discharge velocity.
In another aspect of the ink jet printer of the present invention, each of the analog switching devices is provided with a transmission gate, through which the driving voltage is supplied to the respective one of the piezoelectric elements, and whose ON resistance varies depending on the power source voltage supplied thereto.
According to this aspect, since the ON resistance of each transmission gate is certainly changed, it is possible to change the driving voltage by changing the ON resistance of the analog switc
Barlow John
Brother Kogyo Kabushiki Kaisha
Oliff & Berridg,e PLC
Stewart Jr. Charles W.
LandOfFree
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