EP0865921A2

EP0865921A2 - Piezoelectric element driving circuit and ink jet recording apparatus

Info

Publication number: EP0865921A2
Application number: EP97305778A
Authority: EP
Inventors: Shigeyoshi Nakamura; Jun Moroo; Hiroshi Nou
Original assignee: Fujitsu Ltd
Current assignee: Fujitsu Ltd
Priority date: 1997-03-18
Filing date: 1997-07-31
Publication date: 1998-09-23
Also published as: CN1210787A; JPH10250074A; EP0865921A3

Abstract

A piezoelectric element driving circuit drives a plurality of piezoelectric elements having common electrodes and independent electrodes which are driven independently. The piezoelectric element driving circuit includes a first switch circuit (25; 25-1 to 25-n) enabling each of a plurality of piezoelectric elements of a first piezoelectric element group (34) having the common electrodes coupled in common in response to a first enable signal, a second switch circuit (26) enabling each of a plurality of piezoelectric elements of a second piezoelectric element group (35) in response to a second enable signal, where the piezoelectric elements of the second piezoelectric element group are different from the piezoelectric elements of the first piezoelectric element group, and a driving circuit part (31, 32, 33-1 to 33-n) driving in common the independent electrodes of the corresponding piezoelectric elements of the first and second piezoelectric element groups based on recording data.

Description

BACKGROUND OF THE INVENTION

The present invention generally relates to piezoelectric element driving circuits and ink jet recording apparatuses, and more particularly to a piezoelectric element driving circuit for driving a piezoelectric element which is used as a pressure applying means of a recording head and to an ink jet recording apparatus having such a piezoelectric element driving circuit.

Ink jet recording apparatus can roughly be categorized into a first type having a first recording head which uses a piezoelectric element as a pressure applying means with respect to the ink so as to realize the ink jet, and a second type having a second recording head which uses a heating element to generate bubbles in the ink so as to realize the ink jet. According to the second recording head, it is difficult to control the size of the ink drop. On the other hand, the first recording head is constructed to realize the ink jet by mechanically deforming an ink chamber by the piezoelectric element, and for this reason, it is possible to control with relative ease the size of the ink drop by a driving signal waveform applied to the piezoelectric element.

FIG.1 is a circuit diagram showing an example of a conventional piezoelectric element driving circuit which drives the piezoelectric element of the ink jet recording apparatus. Since the piezoelectric element appears as a capacitor in the circuit, the piezoelectric element is shown as a capacitor in FIG.1.

The piezoelectric element driving circuit shown in FIG.1 includes

transistors

101 and 102 provided between a power supply voltage Vcc and ground,

diodes

103 and 105, and

resistors

104 and 106, and is connected as shown with respect to a piezoelectric element (capacitor) 107. The diode 103 and the resistor 104, and the diode 105 and the resistor 106 respectively determine charging and discharging time constants of the piezoelectric element 107. The piezoelectric element 107 is driven by applying pulse signals to the

transistors

101 and 102.

The piezoelectric element driving circuit shown in FIG.1 is provided with respect to each piezoelectric element. For this reason, the number of switching elements (transistors) within the piezoelectric element driving circuit increases depending on the number of piezoelectric elements, thereby making the piezoelectric element driving circuit complex and expensive.

FIG.2 is a circuit diagram showing another example of the conventional piezoelectric element driving circuit which drives the piezoelectric elements of the ink jet recording apparatus. The piezoelectric element driving circuit is constructed to drive a plurality of piezoelectric elements.

The piezoelectric element driving circuit show in FIG.2 includes

transistors

108 and 109 provided between a power supply voltage Vcc and ground, and a plurality of switch circuits 111-1 through 111-n provided with respect to a plurality of piezoelectric elements (capacitors) 107-1 through 107-n. Common electrodes of the piezoelectric elements 107-1 through 107-n are connected in common to a node which connects the

transistors

108 and 109, and independent electrodes of the piezoelectric elements 107-1 through 107-n are grounded via corresponding switch circuits 111-1 through 111-n. Each of the switch circuits 111-1 through 111-n includes a transistor Tr and a diode D. Each of the switch circuits 111-1 through 111-n is turned ON in response to a signal which is applied to the corresponding transistor Tr, so as to ground and enable driving of the corresponding one of the piezoelectric elements 107-1 through 107-n.

In the case of the piezoelectric element driving circuit shown in FIG.2, the increase in the number of switching elements (transistors) within the piezoelectric element driving circuit depending on the number of piezoelectric elements is slightly reduced compared to the piezoelectric element driving circuit shown in FIG.1 which requires a number of switching elements which increases considerably depending on the number of piezoelectric elements.

As a means of improving the recording speed of the recording head, it is effective to increase the number of nozzles which make the ink jet. In this case, one piezoelectric element is required with respect to each nozzle, and the increase in the number of piezoelectric elements cannot be avoided in order to realize a high-speed ink jet recording.

However, electrically, the piezoelectric element appears as a capacitor. For this reason, if the piezoelectric elements were connected in a matrix arrangement as in the case of the heating elements, a divided signal voltage would be applied to each of the piezoelectric elements. As a result, even the piezoelectric element which originally should not be driven would be driven by the applied divided signal voltage, and there is a possibility of this piezoelectric element making the ink jet. Therefore, in order to prevent erroneous operations of the piezoelectric elements, the piezoelectric elements cannot be connected in the matrix arrangement.

Hence, as may be seen from FIG.2, the conventional piezoelectric element driving circuit requires at least one switching element with respect to each piezoelectric element, and there were problems in that the piezoelectric element driving circuit becomes complex and expensive. Furthermore, there was another problem in that the power consumption of the piezoelectric element driving circuit increases due to the increase in the number of switching elements.

SUMMARY OF THE INVENTION

Accordingly it is a general object of the present invention to provide a novel and useful piezoelectric element driving circuit and ink jet recording apparatus, in which the problems described above are eliminated.

More particularly, it is an object of the present invention to provide a piezoelectric element driving circuit and an ink jet recording apparatus having a simple and inexpensive circuit construction, and capable of driving a plurality of piezoelectric elements at a low power consumption.

Another object of the present invention is to provide a piezoelectric element driving circuit for driving a plurality of piezoelectric elements having common electrodes and independent electrodes which are driven independently, said piezoelectric element driving circuit comprising a first switch circuit enabling each of a plurality of piezoelectric elements of a first piezoelectric element group having the common electrodes coupled in common in response to a first enable signal, a second switch circuit enabling each of a plurality of piezoelectric elements of a second piezoelectric element group in response to a second enable signal, said piezoelectric elements of the second piezoelectric element group being different from the piezoelectric elements of the first piezoelectric element group, and a driving circuit part driving in common the independent electrodes of the corresponding piezoelectric elements of the first and second piezoelectric element groups based on recording data. According to the piezoelectric element driving circuit of the present invention, it is possible to drive a plurality of piezoelectric elements at a low power consumption using a simple and inexpensive circuit construction.

Still another object of the present invention is to provide an ink jet recording apparatus for carrying out an ink jet recording by applying pressure on an ink by piezoelectric elements having common electrodes and independent electrodes which are driven independently, said ink jet recording apparatus comprising a first piezoelectric element group including a plurality of piezoelectric elements having common electrodes which are coupled in common and enabled in response to a first enable signal, a second piezoelectric element group including a plurality of piezoelectric elements having common electrodes which are coupled in common and enabled in response to a second enable signal, said piezoelectric elements of said second piezoelectric element group being different from the piezoelectric elements of said first piezoelectric element group, and driving means for driving in common independent electrodes of the corresponding piezoelectric elements of said first and second piezoelectric element groups based on recording data. According to the ink jet recording apparatus of the present invention, it is possible to drive a plurality of piezoelectric elements of the ink jet recording apparatus at a low power consumption using a simple and inexpensive circuit construction.

Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG.1 is a circuit diagram showing an example of a conventional piezoelectric element driving circuit for driving piezoelectric elements of an ink jet recording apparatus;

FIG.2 is a circuit diagram showing another example of the conventional piezoelectric element driving circuit for driving the piezoelectric elements of the ink jet recording apparatus;

FIG.3 is a system block diagram showing a part of a first embodiment of an ink jet recording apparatus according to the present invention;

FIG.4 is a circuit diagram showing an embodiment of the construction of a part of a head driver and a recording head in the first embodiment of the ink jet recording apparatus;

FIG.5 is a diagram showing head driving voltage waveforms; and

FIG.6 is a circuit diagram showing an embodiment of the construction of a part of the head driver and the recording head in a second embodiment of the ink jet recording apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A piezoelectric element driving circuit according to the present invention is provided with a first switch circuit which enables each of a plurality of piezoelectric elements of a first piezoelectric element group having common electrodes coupled in common in response to a first enable signal, a second switch circuit which enables each of a plurality of piezoelectric elements of a second piezoelectric element group in response to a second enable signal, where the piezoelectric elements of the second piezoelectric element group are different from the piezoelectric elements of the first piezoelectric element group, and a driving circuit part which drives in common independent electrodes of the corresponding piezoelectric elements of the first and second piezoelectric element groups based on recording data.

According to the piezoelectric element driving circuit of the present invention, only one of the corresponding piezoelectric elements of the first and second piezoelectric element groups is driven at each point in time. For this reason, it is possible to greatly reduce the number of switching elements that are required to positively drive only the selected piezoelectric element, and the power consumption is thereby reduced.

An ink jet recording apparatus according to the present invention carries out an ink jet recording by applying pressure on an ink by piezoelectric elements having common electrodes and independent electrodes which are driven independently. The ink jet recording apparatus is provided with a first piezoelectric element group which includes a plurality of piezoelectric elements having common electrodes which are coupled in common and enabled in response to a first enable signal, a second piezoelectric element group which includes a plurality of piezoelectric elements having common electrodes which are coupled in common and enabled in response to a second enable signal, where the piezoelectric elements of the second piezoelectric element group are different from the piezoelectric elements of the first piezoelectric element group, and a driving means for driving in common independent electrodes of the corresponding piezoelectric elements of the first and second piezoelectric element groups based on recording data.

According to the ink jet recording apparatus of the present invention, only one of the corresponding piezoelectric elements of the first and second piezoelectric element groups is driven at each point in time. For this reason, it is possible to greatly reduce the number of switching elements that are required to positively drive only the selected piezoelectric element, and the power consumption is thereby reduced. In addition, it is possible to realize a high-speed ink jet recording because a large number of piezoelectric elements can be selectively driven in this manner.

Next, a description will be given of embodiments of the piezoelectric element driving circuit and the ink jet recording apparatus according to the present invention, by referring to FIGS.3 through 6.

FIG.3 is a system block diagram showing a part of a first embodiment of the ink jet recording apparatus according to the present invention. This first embodiment of the ink jet recording apparatus employs a first embodiment of the piezoelectric element driving circuit according to the present invention. In addition, in this first embodiment of the ink jet recording apparatus, the present invention is applied to a color ink jet printer.

An ink jet printer generally includes a central processing unit (CPU) 1, a RAM 2, a ROM 3, a host interface 4, a mechanical interface 5, a head interface 6, a bus 7, a sensor group 11, a mechanical driver 12, a motor group 13, a head driver 14, and a recording head 15 which are connected as shown in FIG.3.

The CPU 1 controls the operation of the entire ink jet printer. The ROM 3 stores data and programs to be executed by the CPU 1. The RAM 2 stores intermediate data of computation processes carried out by the CPU 1 and the like. The CPU 1 is coupled to a host unit (not shown) via the bus 7 and the host interface 4. The host interface 4 supplies commands, recording data and the like from the host unit to the CPU 1, and also supplies information related to the operation mode or the like from the CPU 1 to the host unit.

The mechanical interface 5 notifies to the CPU 1 detection signals from the sensor group 11 which includes various sensors such as a sensor which detects the size of the recording paper used. In addition, the mechanical interface 5 supplies to the mechanical driver 12 information for controlling the mechanical driver 12 based on an instruction from the CPU 1. Accordingly, the mechanical driver 12 controls the motor group 13 based on the information from the mechanical interface 5, where the motor group 13 includes various motors for driving mechanisms such as a paper supply mechanism, a paper eject mechanism and head feed mechanism.

The head interface 6 controls the head driver 14 based on an instruction from the CPU 1, and controls nozzles which are to eject the ink out of the nozzles of the recording head 15 and to control an amount of the ink ejected from each of the nozzles. The recording head 15 has a known construction including a plurality of nozzles which eject a black ink that is used when making a single-color recording, a plurality of nozzles which eject yellow ink, magenta ink, cyan ink and black ink that are used when making a multi-color recording, and piezoelectric elements which are provided with respect to each of the nozzles. When making the single-color recording, the CPU 1 supplies a first enable signal which controls the plurality of nozzles which eject the black ink that is used when making the single-color recording to an enabled state to the head driver 14 via the head interface 6. On the other hand, when making the multi-color recording, the CPU 1 supplies a second enable signal which controls the plurality of nozzles which eject the yellow ink, magenta ink, cyan ink and black ink that are used when making the multi-color recording to an enabled state to the header driver 14 via the head interface 6. In this embodiment, the number of nozzles used when making the single-color recording is larger than the number of nozzles used when making the multi-color recording.

Next, a description will be given of the general operation of the ink jet printer. First, the CPU 1 notifies the host unit via the host interface 4 that the ink jet printer is in a ready state possible to carry out a recording operation. When the host unit receives a record instruction from an application program, the host unit issues commands related to the recording resolution, the image processing and the like with respect to the CPU 1 after confirming that the ink jet printer is in the ready state, and also transfer the recording data to the CPU 1 via the host interface 4.

In the ink jet printer, the CPU 1 sets various parameters in the mechanical interface 5 and the head interface 6 depending on the instructions of the commands from the host unit. In this state, the CPU 1 also sets in the head interface 6 a flag which indicates whether the recording data are to be recorded by the single-color recording or the multi-color recording, depending on the command from the host unit. The header interface 6 supplies the first enable signal to the head driver 14 depending on this flag when making the single-color recording, and supplies the second enable signal to the head driver 14 depending on this flag when making the multi-color recording. The recording data are supplied to the head driver 14 via the head interface 6 under the control of the CPU 1. Based on the recording data and the first or second enable signal, the head driver 14 supplies to the recording head 15 a head driving voltage for driving each piezoelectric element corresponding to the nozzle which is to eject the ink.

This embodiment is particularly characterized by the constructions of the head driver 14 and the recording head 15, and it is possible to use parts having known constructions with respect to other parts of the ink jet printer shown in FIG.3. For this reason, in the following description, a description will be given of the constructions and operations of the head driver 14 and the recording head 15 in particular.

FIG.4 is a circuit diagram showing an embodiment of the construction of a part of the head driver 14 and the recording head 15. In FIG.4, the head driver 14 includes waveform generators 21 through 23, a first switch circuit 25, and a second switch circuit 26. The first switch circuit 25 is made up of a transistor Tr1 and a diode D1, and the second switch circuit 26 is made up of a transistor Tr2 and a diode D2. An enable signal EN1 from the CPU 1 is supplied to the first switch circuit 25, and an enable signal EN2 from the CPU 1 is supplied to the second switch circuit 26.

On the other hand, the recording head 15 includes a shift register 31, a latch circuit 32, switches 33-1 through 33-n, a plurality of piezoelectric elements 34-1 through 34-n forming a first piezoelectric element group 34, and a plurality of piezoelectric elements 35-1 through 35-n forming a second piezoelectric element group 35. In this embodiment, the piezoelectric elements 34-1 through 34-n of the first piezoelectric element group 34 are used when making the single-color recording. Actually, if it is assumed that m > n, other piezoelectric elements 34-n+1 through 34-m the illustration of which are omitted in FIG.4 are actually also used when making the single-color recording. The piezoelectric elements 35-1 through 35-n of the second piezoelectric element group 35 are used when making the multi-color recording.

Independent electrodes of the piezoelectric elements 34-1 through 34-n of the first piezoelectric element group 34 are connected to output terminals of the corresponding switches 33-1 through 33-n. Similarly, independent electrodes of the piezoelectric elements 35-1 through 35-n of the second piezoelectric element group 35 are connected to the output terminals of the corresponding switches 33-1 through 33-n. On the other hand, common electrodes of the piezoelectric elements 34-1 through 34-n of the first piezoelectric element group 34 are connected in common to the first switch circuit 35. Similarly, common electrodes of the piezoelectric elements 35-1 through 35-n of the second piezoelectric element group 35 are connected in common to the second switch circuit 26. Accordingly, when the enable signal EN1 is active (has a high level), the common electrodes of the piezoelectric elements 34-1 through 34-n of the first piezoelectric element group 34 are grounded in common via the first switch circuit 25. In addition, when the enable signal EN2 is active (has a high level), the common electrodes of the piezoelectric elements 35-1 through 35-n of the second piezoelectric element group 35 are grounded in common via the second switch circuit 26.

The waveform generator 21 generates a head driving voltage having a waveform w1 shown in FIG.5 based on waveform data obtained from the CPU 1, and supplies this head driving voltage waveform w1 to each of the switches 33-1 through 33-n. In addition, the waveform generator 22 generates a head driving voltage having a waveform w2 shown in FIG.5 based on waveform data obtained from the CPU 1, and supplies this head driving voltage waveform w2 to each of the switches 33-1 through 33-n. Further, the waveform generator 23 generates a head driving voltage having a waveform w3 shown in FIG.5 based on waveform data obtained from the CPU 1, and supplies this head driving voltage waveform w3 to each of the switches 33-1 through 33-n. Rising edges of the waveforms w1 through w3 are the same, however, falling edges of the waveforms w1 through w3 have different slopes. As a result, the ink jet quantity from the recording head 15 is largest responsive to the waveform w1, second largest in response to the waveform w2, and smallest in response to the waveform w3. Of course, the number of waveform generators used and the number of head driving voltage waveforms supplied to each of the switches 33-1 through 33-n are not limited to three, and the head driving voltage waveforms are not limited to the waveforms w1 through w3 described above.

The recording data from the host unit that are obtained via the host interface 4 and the CPU 1 are input to the shift register 31 in response to a clock from the CPU 1. The recording data input to the shift register 31 are latched by the latch circuit 32 in response to a latch signal from the CPU 1. An output signal of the latch circuit 32 is supplied to each of the switches 33-1 through 33-n as a control signal. In each of the switches 33-1 through 33-n, one of the driving voltage waveforms w1 through w3 received from the waveform generators 21 through 23 depending on the recording data is selectively output based on the control signal from the latch circuit 32.

For example, when driving the piezoelectric elements 34-2 and 34-n of the first piezoelectric element group 34, the enable signal EN1 is active, and the common electrodes of each of the piezoelectric elements 34-1 through 34-n of the first piezoelectric element group 34 are grounded in common via the first switch circuit 25. On the other hand, the enable signal EN2 is inactive, and the common electrodes of each of the piezoelectric elements 35-1 through 35-n of the second piezoelectric element group 35 assume a floating state in common. In this case, potentials at the independent electrodes of the piezoelectric elements 34-2 and 34-n differ if the ink jet quantities of the two mutually differ, and there is a possibility of voltages being applied to the independent electrodes of the piezoelectric elements 35-2 and 35-n which are connected to the independent electrodes of the piezoelectric elements 34-2 and 34-n.

However, when sucking the ink, the head driving voltages applied to the independent electrodes of the piezoelectric elements 34-2 and 34-n have the same rising waveform, and thus, no voltage is applied to the independent electrodes of the piezoelectric elements 35-2 and 35-n. In addition, when ejecting the ink, although a slight potential difference exists between the head driving voltages applied to the independent electrodes of the piezoelectric elements 34-2 and 34-n, this slight potential difference is divided into a voltage which is 1/2 the slight potential difference at the maximum or less. For this reason, when the piezoelectric elements 34-2 and 34-n are driven and the ink is ejected from the corresponding nozzles, it is possible to positively prevent the piezoelectric elements 35-2 and 35-n from being driven and accordingly prevent ejection of the ink from the corresponding nozzles.

Therefore, according to this embodiment, it is possible to drive a plurality of piezoelectric elements at a low power consumption using a simple and inexpensive circuit construction.

Next, a description will be given of a second embodiment of the ink jet recording apparatus according to the present invention. The system block diagram of a part of this second embodiment of the ink jet recording apparatus is the same as that shown in FIG.3, and an illustration thereof will be omitted. This second embodiment of the ink jet recording apparatus employs a second embodiment of the piezoelectric element driving circuit according to the present invention. In addition, in this second embodiment of the ink jet recording apparatus, the present invention is applied to a color ink jet printer.

FIG.6 is a circuit diagram showing an embodiment of the construction of a part of the head driver 14 and the recording head 15 in this second embodiment of the ink jet recording apparatus. In FIG.6, those parts which are the same as those corresponding parts in FIG.4 are designated by the same reference numerals, and a description thereof will be omitted.

In FIG.6, the first piezoelectric element group 34 includes a first sub group made up of piezoelectric elements 34-11 through 34-1p, a second sub group made up of piezoelectric elements 34-21 through 34-2p, ..., and an n-th sub group made up of piezoelectric elements 34-n1 through 34-np. Independent electrodes of the p piezoelectric elements in each of the sub groups are connected to the output terminal of a corresponding one of the switches 33-1 through 33-n. Accordingly, in the case of the first sub group made up of the piezoelectric elements 34-11 through 34-1p, for example, each of the piezoelectric elements 34-11 through 34-1p are connected to the output terminal of the corresponding switch 33-1.

Common electrodes of the piezoelectric elements 34-11 through 34-1p of the first sub group are connected in common to a first switch circuit 25-1 which receives an enable signal EN11 from the CPU 1. Common electrodes of the piezoelectric elements 34-21 through 34-2p of the second sub group are connected in common to a first switch circuit 25-2 which receives an enable signal EN12 from the CPU 1. Common electrodes of the piezoelectric elements 34-n1 through 34-np of the n-th sub group are connected in common to a first switch circuit 25-n which receives an enable signal EN1n from the CPU 1. If it is assumed for the sake of convenience that i = 1, ..., n, the first switch circuit 25-i includes a transistor Tr1i and a diode D1i.

In this embodiment, the enable signals EN11 through EN1n which are supplied to the first switch circuits 25-1 through 25-n become active time-divisionally.

According to this embodiment, it is possible to realize a matrix drive of the piezoelectric elements because the piezoelectric elements of the first piezoelectric element group 34 are enabled time-divisionally for each of the sub groups. In addition, it is possible to reduce the required instantaneous power consumption.

In each of the embodiments described above, the first piezoelectric element group 34 is used for the single-color recording, and the second piezoelectric element group 35 is used for the multi-color recording. However, it is not essential to use the second piezoelectric element group 35 for the multi-color recording, and the second piezoelectric element group 35 may be used for the single-color recording, similarly to the first piezoelectric element group 34.

In addition, when ejecting the ink from the nozzle corresponding to the piezoelectric element which is driven using the distortion of the piezoelectric element, the direction of the distortion which is utilized may be the same as the direction of the electric field or, may be perpendicular to the direction of the electric field, and it is possible to cope with either case using similar circuits.

Further, the present invention is not limited to these embodiments, but various variations may be made without departing from the scope of the present invention.

Claims

A piezoelectric element driving circuit for driving a plurality of piezoelectric elements having common electrodes and independent electrodes which are driven independently, said piezoelectric element driving circuit comprising:

a first switch circuit (25; 25-1 to 25-n) enabling each of a plurality of piezoelectric elements of a first piezoelectric element group (34) having the common electrodes coupled in common in response to a first enable signal;

a second switch circuit (26) enabling each of a plurality of piezoelectric elements of a second piezoelectric element group (35) in response to a second enable signal, said piezoelectric elements of the second piezoelectric element group being different from the piezoelectric elements of the first piezoelectric element group; and

a driving circuit part (31, 32, 33-1 to 33-n) driving in common the independent electrodes of the corresponding piezoelectric elements of the first and second piezoelectric element groups based on recording data.
The piezoelectric element driving circuit as claimed in claim 1, wherein said first and second piezoelectric element groups (34, 35) have the same number of piezoelectric elements, and said driving circuit part (31, 32, 33-1 to 33-n) drives in common each corresponding pair of independent electrodes of the first and second piezoelectric element groups based on the recording data.
The piezoelectric element driving circuit as claimed in claim 1, wherein said first piezoelectric element group (34) comprises a plurality of sub groups, the common electrode of each of the piezoelectric element of the second piezoelectric element group (35) is coupled to a common electrode of a corresponding piezoelectric element of each of the sub groups, and said first switch circuit (25-1 to 25-n) time-divisionally enables the piezoelectric elements of the first piezoelectric element group for each of the sub groups.
An ink jet recording apparatus for carrying out an ink jet recording by applying pressure on an ink by piezoelectric elements having common electrodes and independent electrodes which are driven independently, said ink jet recording apparatus comprising:

a first piezoelectric element group (34) including a plurality of piezoelectric elements having common electrodes which are coupled in common and enabled in response to a first enable signal;

a second piezoelectric element group (35) including a plurality of piezoelectric elements having common electrodes which are coupled in common and enabled in response to a second enable signal, said piezoelectric elements of said second piezoelectric element group being different from the piezoelectric elements of said first piezoelectric element group; and

driving means (31, 32, 33-1 to 33-n) for driving in common independent electrodes of the corresponding piezoelectric elements of said first and second piezoelectric element groups based on recording data.
The ink jet recording apparatus as claimed in claim 4, wherein said first and second piezoelectric element groups (34, 35) have the same number of piezoelectric elements, and said driving means (31, 32, 33-1 to 33-n) drives in common each corresponding pair of independent electrodes of the first and second piezoelectric element groups based on the recording data.
The ink jet recording apparatus as claimed in claim 4 or 5, which further comprises:

a first switch circuit (25; 25-1 to 25-n) enabling each of the piezoelectric elements of said first piezoelectric element group (34) in response to the first enable signal; and

a second switch circuit (26) enabling each of the piezoelectric elements of said second piezoelectric element group (35) in response to the second enable signal.
The ink jet recording apparatus as claimed in claim 6, wherein said first piezoelectric element group (34) comprises a plurality of sub groups, the common electrode of each of the piezoelectric element of the second piezoelectric element group (35) is coupled to a common electrode of a corresponding piezoelectric element of each of the sub groups, and said first switch circuit (25-1 to 25-n) time-divisionally enables the piezoelectric elements of the first piezoelectric element group for each of the sub groups.
The ink jet recording apparatus as claimed in any of claims 4 to 7, wherein said first piezoelectric element group (34) forms a head for recording in a single color, and said second piezoelectric element group (35) forms a head for recording in multiple colors.
The ink jet recording apparatus as claimed in any of claims 4 to 8, wherein said driving means (31, 32, 33-1 to 33-n) controls an ink jet quantity by a slope of each driving signal waveform applied to the independent electrodes of the piezoelectric elements of said first and second piezoelectric element groups (34, 35).