Patent Publication Number: US-6334668-B1

Title: Ink-jet recording apparatus

Description:
TECHNICAL FIELD 
     The present invention relates to an ink jet recording apparatus such as an ink jet printer or an ink jet plotter. More particularly, the present invention relates to the structure of a recording head in an ink jet recording apparatus. 
     BACKGROUND ART 
     Hitherto, in an ink jet recording apparatus such as an ink jet printer or an ink jet plotter, as shown in FIG. 12, in a drive signal generating circuit  8  formed in a apparatus main unit  2 , a drive signal COM generated by a waveform generating circuit  80  is amplified by a current amplification circuit  89  using push-pull-connected transistors, etc., for example, then is output to a recording head  10  mounted on a carriage. The recording head  10  is provided with a plurality of pressure generating elements  17  for jetting ink drops from nozzle openings by pressurizing ink in pressure generating chambers and a head drive circuit  18  for selecting which of the plurality of pressure generating elements  17  to drive based on recording data, and the drive signal COM is applied to the pressure generating element  17  selected by the head drive circuit  18 . As a result, the selected pressure generating element  17  pressurizes ink in the corresponding pressure generating chamber for jetting ink as an ink drop from the nozzle opening. 
     Here, the apparatus main unit  2  and the recording head  10  are connected by a flexible wiring board  100  having a length sufficient for the carriage to move, and the drive signal generating circuit  8  formed in the apparatus main unit  2  outputs a signal to the recording head  10  via the flexible wiring board  100 . 
     FIGS.  13 (A) and (B) show an example of a schematic structure of the recording head  10  in the conventional art. As shown in FIGS.  13 (A) and (B), the recording head  10  has a flow passage unit  230 , which comprises a nozzle plate  233  provided with a plurality of nozzle openings  231  as nozzle rows  232 , a flow passage formation board  237  comprising pressure generating chambers  234  communicating with the nozzle openings  231  and reservoirs  236  for supplying ink to the pressure generating chambers  234  through ink supply ports  235 , and an elastic plate  240  for abutting the tip of each piezoelectric vibrator  239  in a vertical vibration mode of piezoelectric vibration units  238  corresponding to the pressure generating elements  17  previously described with reference to FIG. 12 for expanding or shrinking the pressure generating chamber  234 , the nozzle plate  233 , the flow passage formation board  237 , and the elastic plate  240  being stacked in one piece. The flow passage unit  230  is connected to a holder  241  formed by injection molding, etc., of a polymeric material and each piezoelectric vibration unit  238  is connected to a flexible cable  242  for communicating an external drive signal, then they are housed in a housing chamber  243 , the abutment faces (not shown) against the holders  241  are fixed with an adhesive, and a frame  244  also serving as a shield material is inserted into the nozzle plate  233 , forming the recording head  10 . The holder  241  is provided with an ink lead passage  245  communicating with an external ink tank (not shown) and the tip is connected to an ink introduction port  246  of the flow passage unit  230  for supplying ink from the ink tank to the flow passage unit  230 . 
     Each piezoelectric vibrator  239  in the vertical vibration mode forming a part of the piezoelectric vibration unit  238  is formed by stacking an electrode as one pole and an electrode as an opposite pole like a sandwich via a piezoelectric material, exposing one electrode to the tip side and the opposite electrode to the rear end side, and connecting to a segment electrode and a common electrode on each end face with piezoelectric constant d 31 , for example, although not shown, and is fixed to a fix board  247  matching the arrangement pitch of the pressure generating chamber  234  as a part of the piezoelectric vibration unit  238 . 
     The segment electrode and common electrode (not shown) of each piezoelectric vibrator  239  of the piezoelectric vibration unit  238  are connected to a conductive pattern for drive signal transmission of the flexible cable  242  via a solder layer. With the flexible cable  242 , a window  248  is formed in an area facing the fix board  247 , a semiconductor IC (integrated circuit)  249  provided with the head drive circuit  18  (see FIG. 12) for converting a print signal into a drive signal for driving each piezoelectric vibrator  239  is installed in the window, and the print signal is transmitted to the semiconductor IC (integrated circuit)  249  according to conductive pattern from the external drive signal generating circuit  8  (see FIG. 12) and the head drive signal is supplied to each piezoelectric vibrator  239 . 
     Thus, a plurality of pressure generating elements  17  (piezoelectric vibration units  238 ) and head drive circuits  18  (semiconductor ICs  249 ) are formed on the recording head  10  and mainly the transistors of the head drive circuits  18  (semiconductor ICs  249 ) generate heat and therefore hitherto, a heat radiation measure has been taken for the recording head  10 . 
     That is, for the semiconductor IC (integrated circuit)  249  mounted on the flexible cable  242 , the area exposed from the window  248  is fixed to the fix board  247  with an adhesive via a thermal-conductivity fluid layer (for example, silicon grease, etc.,) not shown or is fixed with an adhesive having high thermal conductivity to the fix board  247 . The fix board  247  functions as a heat radiation member and is made of a material having high thermal conductivity such as metal or alumina. As shown in FIG.  13 (A), the fix board  247  is placed close to the ink lead passage  245 , whereby ink flowing through the ink lead passage  245  absorbs heat generated on the semiconductor IC  249  via the fix board  247 . 
     At the printing time, upon reception of input of a print signal via the flexible cable  242  from the external drive signal generating circuit  8  (see FIG.  12 ), the semiconductor IC (integrated circuit)  249  generates a drive signal for driving each piezoelectric vibrator  239  and supplies the drive signal to each piezoelectric vibrator  239 . Thus, mainly the transistors in the head drive circuit  18  generate heat and the heat has thermal conduction relationship with the semiconductor IC (integrated circuit)  249  forming the head drive circuit  18  and is absorbed by the heat sink action of the fix board  247  having a large heat capacity and is radiated through the fix board  247 , so that the semiconductor IC (integrated circuit)  249  can be prevented from leading to thermal runaway or damage. 
     In the conventional art example described above, the recording head  10  is provided with the head drive circuit  18 . However, if the drive signal COM is output from the apparatus main unit  2  to the recording head  10  with the long flexible wiring board  100 , there is a problem of distorting the waveform of the drive signal COM because of parasitic inductance, etc., of the flexible wiring board  100 . For the recording head  10 , characteristics vary from one head to another, thus previous inspection is executed for ranking for matching with the drive signal COM, but the characteristics of the semiconductor IC  249  forming the drive signal generating circuit  8  also vary from one product to another, thus the drive signal COM output from the drive signal generating circuit  8  and the recording head  10  do not match in some cases. 
     In the conventional art example described above, as shown in FIGS.  13 (A) and (B), the adjacent nozzle rows  232  and  232  each formed with a plurality of nozzle openings  231  are formed comparatively close to each other in the nozzle plate  233 , thus it is feared that to jet an ink drop from a predetermined nozzle opening  231  in one nozzle row  232 , vibration excited by the corresponding piezoelectric vibration unit  238  may affect the other nozzle row  232  (pressure generating chamber  234 ) and an ink drop whose amount is extremely small may be jetted from the nozzle opening  231  in the other nozzle row  232 , causing erroneous print to occur. 
     Further, combined with high image quality of print precision, the number of nozzle openings  231  in one nozzle row  232  is increased, for example, from  32  to  64  and can become  128  or more, thus it is expected that the number of transistors integrated in the semiconductor IC (integrated circuit)  249  will also never grow, thus a further heat radiation measure in the recording head  10  is desired. 
     It is therefore a first object of the present invention to provide an ink jet recording apparatus having a configuration wherein distorting the waveform of a drive signal can be prevented and a recording head also containing a drive signal generating circuit can be tested. 
     It is a second object of the present invention to provide an ink jet recording apparatus having a configuration wherein vibration excited by a piezoelectric vibration unit  238  can be effectively prevented from affecting another nozzle row, causing erroneous print to occur. 
     Further, it is a third object of the present invention to provide an ink jet recording apparatus having a configuration wherein the heat radiation effect in a recording head  10  can be more enhanced and particularly the detrimental effect when the configuration to accomplish the first object is adopted can be avoided. 
     DISCLOSURE OF THE INVENTION 
     To achieve the first object, according to the present invention, there is provided an ink jet recording apparatus comprising a recording head comprising a plurality of pressure generating elements for pressurizing ink in pressure generating chambers, thereby jetting ink drops from nozzle openings and a head drive circuit for selecting which of the plurality of pressure generating elements a drive signal is to be applied to based on recording data and a drive signal generating circuit for outputting the drive signal, the drive signal generating circuit comprising at least a waveform generating circuit for generating the drive signal and a current amplification circuit for executing current amplification of the drive signal generated by the waveform generating circuit and outputting the result, characterized in that the current amplification circuit is formed on a side of the recording head. 
     In the present invention, the current amplification circuit corresponding to the last stage, of the drive signal generating circuit is formed in the recording head, so that the drive signal after undergoing current amplification is output to the head drive circuit in the recording head and is not output via the flexible wiring board connecting the apparatus main unit and the recording head. Therefore, a problem of distorting the waveform of the drive signal after undergoing current amplification because of parasitic inductance, etc., of the flexible wiring board can be solved. When the recording head is tested for characteristics, the recording head also containing the current amplification circuit of the drive signal generating circuit is tested for characteristics, so that the characteristics of the recording head also containing those of the drive signal generating circuit can be determined properly. Therefore, a proper drive signal can be applied to each pressure generating element in the recording head. 
     Here, if the current amplification circuit is formed in the recording head, heat generation of the recording head becomes large. In the present invention, however, the heat radiation member is placed in the recording head to achieve the third object, so that a temperature rise in the recording head can be prevented. Therefore, in the recording head, each circuit can be prevented from malfunctioning or being degraded because of heat, and the detrimental effect of hastening drying of ink in the presence of heat or the like can be avoided. 
     In the present invention, preferably the waveform generating circuit is also formed on the side of the recording head. In such a configuration, the drive signal before undergoing current amplification is also output to the head drive circuit in the recording head and is not output via the flexible wiring board connecting the apparatus main unit and the recording head. Therefore, a problem of distorting the waveforms of the drive signals before and after undergoing current amplification because of parasitic inductance, etc., of the flexible wiring board can be solved. When the recording head is tested for characteristics, the recording head also containing the waveform generating circuit and the current amplification circuit of the drive signal generating circuit is tested for characteristics, so that the characteristics of the recording head also containing those of the drive signal generating circuit can be determined properly. Therefore, a proper drive signal can be applied to each pressure generating element in the recording head. 
     To achieve the second object, in the present invention, preferably the nozzle openings are formed in a flow passage unit as a plurality of nozzle rows in parallel and the heat radiation member is in contact with at least the area corresponding to the area between the plurality of nozzle rows in the flow passage unit. In such a configuration, interference occurring between the nozzle rows can be suppressed by means of the heat radiation member. 
     To achieve the third object, in the present invention, the heat radiation member may comprise at least a horizontal plate section in face contact with a carriage on which the recording head is mounted and a vertical plate section extended so as to be in contact with the area corresponding to the area between the nozzle rows in the flow passage unit from the horizontal plate section, and an IC, in which at least the head drive circuit and the current amplification circuit are formed, may be mounted onto the vertical plate section. In such a configuration, the carriage and the heat radiation member can be brought into contact with each other for escaping heat from the heat radiation member to the carriage, so that a temperature rise in the recording head can be prevented. Therefore, in the recording head, each circuit can be prevented from malfunctioning or being degraded because of heat, and the detrimental effect of hastening drying of ink in the presence of heat or the like can be avoided. 
     In the present invention, preferably heat radiation fins are formed in the carriage. In such a configuration, a temperature rise in the recording head can be suppressed furthermore effectively. 
     In the present invention, preferably, using the fact that the current amplification circuit is formed in the recording head, output of the waveform generating circuit is input into the current amplification circuit via switching elements of the switch circuit of the head drive circuit. In such a configuration, a signal before undergoing current amplification is input into the switching elements of the head drive circuit, thus heat generation of the switching elements of the head drive circuit is small. Therefore, small-sized elements can be used as the switching elements of the head drive circuit. 
     To achieve the third object, according to another aspect of the present invention, there is provided an ink jet recording apparatus comprising a recording head comprising a plurality of pressure generating elements for pressurizing ink introduced into pressure generating chambers via an ink lead passage, thereby jetting ink drops from nozzle openings and a semiconductor device containing a head drive circuit for selecting which of the plurality of pressure generating elements a drive signal is to be applied to based on recording data and a drive signal generating circuit for outputting the drive signal, the drive signal generating circuit comprising at least a waveform generating circuit for generating the drive signal and a current amplification circuit for executing current amplification of the drive signal generated by the waveform generating circuit and outputting the result, characterized in that 
     the current amplification circuit and the waveform generating circuit are also formed so as to be contained in the semiconductor device of the recording head, and 
     the recording head has a heat radiation member for the semiconductor device. 
     In the present invention, preferably the heat radiation member comprises at least a horizontal plate section in face contact with a carriage on which the recording head is mounted and a vertical plate section extended from the horizontal plate section to the flow passage unit, and 
     the semiconductor device is mounted onto the vertical plate section. 
     Further, in the present invention, preferably a first heat insulation material is attached between the vertical plate section of the heat radiation member and the area corresponding to the area between the nozzle rows in the flow passage unit. The first heat insulation material thermally insulates the vertical plate section and the flow passage unit and the heat generated by the semiconductor device of the recording head is escaped upwardly through the vertical plate section of the heat radiation member and is effectively radiated through the horizontal plate section of the heat radiation member. Since the heat insulation material is provided, the heat generated by the semiconductor device can be efficiently prevented from being transmitted to the ink flow passage. 
     In the present invention, preferably the heat resistance ratio between the first heat insulation material and the heat radiation member is at least larger than 4:1, because if the heat generated by the IC reaches 150° C., for example, the heat transmitted to the flow passage unit side can be suppressed to ⅕ or less. 
     In the present invention, preferably the ink lead passage is placed away from the semiconductor device. Further, in the present invention, the ink lead passage may be placed so as to be extended up and down between the semiconductor device and the pressure generating element. Since the ink lead passage is placed away from the semiconductor device (heat source), the heat generated by the semiconductor device (heat source) can be prevented from being transmitted to the ink flow passage. On the other hand, in the present invention, the surroundings of the semiconductor device may be covered with a second heat insulation material. Heat conduction to the ink lead passage is furthermore suppressed and it is also made possible to escape heat to the upper side more reliably. 
     In the present invention, first heat radiation fins may be formed in the carriage. Heat is radiated furthermore effectively through the first heat radiation fins of the carriage from the horizontal plate section of the heat radiation member. 
     In the present invention, second heat radiation fins may be formed on the upper surface side of the horizontal plate section of the heat radiation member. Thus, the heat radiation effect can be enhanced furthermore. 
     Preferably, in the present invention, the second heat radiation fins are formed in parallel in a move direction of the carriage, other fins are formed lower than the two fins at both ends so that only the two fins at both ends support an ink tank made of a resin for supplying ink to the ink lead passage of the recording head, and a space is provided between other fins and a bottom of the ink tank. While heat conduction to the ink tank is suppressed because the resin has a heat insulation effect, wind flows through the space between other fins and the bottom of the ink tank as the carriage is moved, so that the heat radiation effect is enhanced dramatically. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an ink jet recording apparatus according to a first embodiment of the present invention; 
     FIG. 2 is a functional block diagram of the ink jet recording apparatus shown in FIG. 1; 
     FIG. 3 is a block diagram to show the configuration of a drive signal generating circuit formed in the ink jet recording apparatus shown in FIG. 1; 
     FIG. 4 is a schematic representation to show the process of generating pulses contained in a drive signal in the drive signal generating circuit shown in FIG. 3; 
     FIG. 5 is a timing chart to show the timings of signals when a data signal is used to set a voltage change amount in memory in the drive signal generating circuit shown in FIG. 3; 
     FIGS.  6 (A) and (B) are a perspective view when a recording head and a carriage in the ink jet recording apparatus shown in FIG. 1 are disassembled and a bottom view to show a state in which the recording head is attached to the carriage, respectively; 
     FIGS.  7 (A) and (B) are a perspective view to show the main part of the recording head of the ink jet recording apparatus shown in FIG. 1 and a perspective view of a heat radiation member used with the recording head, respectively; 
     FIG. 8 is a functional block diagram of an ink jet recording apparatus according to a second embodiment of the present invention; 
     FIGS.  9 (A) and (B) are a sectional view and a bottom view of a recording head of the ink jet recording apparatus according to the second embodiment of the present invention respectively; 
     FIG. 10 is a drawing to describe a recording head and a carriage of an ink jet recording apparatus according to a third embodiment of the present invention; 
     FIGS.  11 (A) and (B) are a block diagram to show a general circuit configuration in an ink jet recording apparatus and a block diagram to show the feature of a circuit configuration in an ink jet recording apparatus according to a fifth embodiment of the present invention respectively; 
     FIG. 12 is a functional block diagram of an ink jet recording apparatus in a conventional art; and 
     FIGS.  13 (A) and (B) are a sectional view and a bottom view of a recording head of the ink jet recording apparatus in the conventional art respectively. 
    
    
     EMBODIMENTS 
     Referring to the accompanying drawings, ink jet recording apparatuses incorporating the present invention will be discussed 
     First Embodiment 
     General Configuration of Ink Jet Recording Apparatus 
     FIG. 1 is a perspective view to show the main part of an ink jet recording apparatus. 
     As shown in FIG. 1, in an ink jet recording apparatus  1 , a carriage  110  is connected to a carriage motor  13  of a carriage mechanism  12  by a timing belt  102  and is guided by a guide member  140  so as to be reciprocated in the paper width direction of recording paper  150 . The ink jet recording apparatus  1  is also provided with a paper feeding mechanism  11  using a paper feeding roller  160 . An ink jet recording head  10  is attached to the face of the carriage  110  opposed to the recording paper  150 , in the example shown in the figure, the lower face of the carriage. The recording head  10  receives supply of ink from an ink cartridge  170  placed on the upper portion of the carriage  110  and jets ink drops onto the recording paper  150  for forming dots for printing an image or a character as the carriage  110  is moved. A capping unit  180  is formed in a non-print area (non-recording area) of the ink jet recording apparatus  1  for sealing nozzle openings of the recording head  10  during quiescent operation of printing. 
     Therefore, an increase in the viscosity of ink or formation of an ink film because of scattering of a solvent from ink during the quiescent operation of printing can be suppressed for preventing the nozzles from being clogged during the quiescent operation of printing. The capping unit  180  receives ink drops from the recording head  10  produced by the flushing operation performed during the print operation. A wiping unit  19  is placed in the proximity of the capping unit  180  and wipes the surface of the recording head  10  with a blade, etc., thereby wiping out ink drops, paper powder, etc., deposited on the surface of the recording head  10 . 
     FIG. 2 is a functional block diagram of the ink jet recording apparatus  1  of the embodiment. 
     In FIG. 2, the ink jet recording apparatus  1  is made up of a apparatus main unit  2 , the carriage mechanism  12 , the paper feeding mechanism  11 , and the recording head  10 . The paper feeding mechanism  11  consists of a paper feeding motor (not shown), the paper feeding roller  160 , and the like as previously described with reference to FIG.  1  and feeds recording media of the recording paper  150 , etc., in order for executing subscanning. The carriage mechanism  12  consists of the carriage  110  on which the recording head  10  is mounted, the carriage motor  13  for running the carriage  110  via the timing belt  102 , and the like for executing main scanning of the recording head  10 . 
     The apparatus main unit  2  comprises an interface  3  for receiving recording data, etc., containing multilevel hierarchical information from a host computer (not shown), etc., RAM  4  for storing various kinds of data of recording data, etc., containing multilevel hierarchical information, ROM  5  storing routines, etc., for performing various types of data processing, a control section  6  consisting of a CPU, etc., an oscillation circuit  7 , and an interface  9  bearing the function of transmitting print data SI (recording data) expanded to dot pattern data to the recording head  10 , etc. 
     Here, the circuitry of the recording head  10  is connected to the apparatus main unit  2  by the flexible wiring board  100 . As the flexible wiring board  100 , a long wiring board is used so as not to hinder a move of the carriage  110 , as shown in FIG.  1 . 
     In the described ink jet recording apparatus  1 , recording data containing multilevel hierarchical information sent from the host computer, etc., is retained in a reception buffer  4 A in the recording apparatus via the interface  3 . The recording data retained in the reception buffer  4 A undergoes command analysis, then is sent to an intermediate buffer  4 B. In the intermediate buffer  4 B, the recording data in an intermediate format converted into intermediate code by the control section  6  (drive control circuit) is retained and processing of adding the print position of each character, qualification type, size, font address, etc., is executed by the control section  6 . Next, the control section  6  analyzes the recording data in the intermediate buffer  4 B and expands and stores binarized dot pattern data after hierarchical data is decoded in an output buffer  4 C as described later. 
     When dot pattern data corresponding to one scan of the recording head  10  is provided, the dot pattern data is serially transferred to the recording head  10  via the interface  9 . When the dot pattern data corresponding to one scan is output from the output buffer  4 C, the contents of the intermediate buffer  4 B are erased and the next intermediate code conversion is executed. Here, the print data expanded to the dot pattern data is made up of two bits, for example, as gradation data for each nozzle, as described alter. 
     The recording head  10  has a large number of nozzle openings, for example,  48  nozzle openings in the subscanning direction for jetting ink drops from the nozzle openings at a predetermined timing. The recording head  10  comprises a head drive circuit  18  consisting of a shift register  13 , a latch circuit  14 , a level shifter  15 , and a switch circuit  16 . The print data expanded to the dot pattern data by the apparatus main unit  2  is serially transferred from the interface  9  to the shift register  13  in synchronization with a clock signal (CLK) from the oscillation circuit  7 . The serially transferred print data (SI/recording data) is once latched by the latch circuit  14 . The latched print data SI is boosted by the level shifter  15 , which is a voltage amplifier, to a voltage capable of driving the switch circuit  16 , for example, a predetermined voltage of about several ten volts. The print data SI boosted to the predetermined voltage is given to the switch circuit  16 . A drive signal (COM) from a drive signal generating circuit  8  is applied to input of the switch circuit  16  and piezoelectric vibrators as pressure generating elements  17  are connected to output of the switch circuit  16 . 
     The print data SI controls the operation of the switch circuit  16 . For example, while the print data applied to the switch circuit  16  is “1,” the drive signal COM is applied to the pressure generating element  17  and the pressure generating element  17  is expanded or shrunk in response to the signal. As a result, ink in the pressure generating chamber is pressurized and is jetted from the nozzle opening. On the other hand, while the print data applied to the switch circuit  16  is “0,” supply of the drive signal COM to the piezoelectric vibrator  17  is shut off and thus no ink drop is jetted. 
     Configuration of Drive Signal Generating Circuit  8   
     FIG. 3 is a block diagram to show the configuration of the drive signal generating circuit  8 . FIG. 4 is a schematic representation to show the process of generating pulses contained in a drive signal in the drive signal generating circuit  8 . FIG. 5 is a timing chart to show the timings of signals when a data signal is used to set a voltage change amount in memory in the drive signal generating circuit  8 . 
     In FIG. 3, the drive signal generating circuit  8  is mainly made up of a waveform generating circuit  80  for generating the waveform of the drive signal COM and a current amplification circuit  89  for amplifying the current of the signal output from the waveform generating circuit  80  and outputting the result as the drive signal COM. The waveform generating circuit  80  is made up of memory  81  for receiving a signal from the control section  6  and recording the signal, a first latch  82  for reading and temporarily retaining the contents of the memory  81 , an adder  83  for adding output of the first latch  82  and output of a second latch  84  described later, a D/A converter  86  for converting output of the second latch  82  into analog data, a voltage amplification circuit  88  for amplifying the provided analog signal to the voltage of the drive signal, and the current amplification circuit  89  for amplifying the current of the drive signal output from the voltage amplification circuit  88  and outputting the result as the drive signal COM. Here, the memory  81  stores predetermined parameters for determining the waveform of the drive signal. The waveform of the drive signal COM is determined by the predetermined parameters previously received from the control section  6 , as described later. That is, the waveform generating circuit  80  receives clock signals  801 ,  802 , and  803 , a data signal  830 , address signals  810 ,  811 ,  812 , and  813 , and a reset signal  820 . 
     In the described drive signal generating circuit  8 , as shown in FIG. 4, before the drive signal COM is generated, some data signals indicating the voltage change amount of the control section  6  and the address of the data signal are output to the memory  81  of the drive signal generating circuit  8  in synchronization with the clock signal  801 . As shown in FIG. 5, serial transfer of the data signal  830  using the clock signal  801  as a synchronizing signal is executed to transfer data. That is, to transfer a predetermined voltage change amount from the control section  6 , first a data signal of a plurality of bits is output in synchronization with the clock signal  801 . Then, the address to store the data is output as the address signals  810  to  813  in synchronization with an enable signal  840 . The memory  81  reads the address signal at the timing at which the enable signal  840  is output and writes the received data into the address. Since the address signals  810  to  813  are four-bit signal, a maximum of 16 types of voltage change amounts can be stored in the memory  81 . The most significant bit of the data is used as a sign. 
     When address B is output to the address signals  810  to  813  after completion of setting the voltage change amount in each address A, B, . . . , the voltage change amount corresponding to the address B is retained in the first latch  82  based on the first clock signal  802 . In this state, if the clock signal  803  is next output, the value of output of the first latch  82  added to output of the second latch  84  is retained in the second latch  84 . That is, as shown in FIG. 4, once the voltage change amount corresponding to the address signal is selected, then output of the second latch  84  is incremented or decremented in accordance with the voltage change amount each time the clock signal  803  is received. The voltage change amount of the drive waveform is determined by voltage change amount ΔV 1  stored at the address B of the memory  81  and unit time ΔT of the clock signal  803 . Increment or decrement is determined by the sign of data stored at each address. 
     In the example shown in FIG. 4, a value of 0 as the voltage change amount, namely, the value for maintaining the voltage is stored at address A. Therefore, when the address A is validated by the clock signal  802 , the waveform of the drive signal is held flat with no increment or decrement. To determine the voltage change amount of the drive waveform, voltage change amount ΔV 2  per unit time ΔT is stored at address C. Therefore, after the address C is validated by the clock signal  802 , the voltage will be decremented by voltage ΔV 2 . 
     Thus, the waveform of the drive signal COM can be controlled as desired simply by thus outputting the address signals and the clock signals. 
     In the described drive signal generating circuit  8 , in the embodiment, as shown in FIG. 2, the waveform generating circuit  80  is formed in the apparatus main unit  2  and the current amplification circuit  89  is formed in the recording head  10 . Thus, in the drive signal generating circuit  8 , the drive signal COM before undergoing current amplification, output from the waveform generating circuit  80  is output to the current amplification circuit  89  in the recording head  10  via the interface  9  and the flexible wiring board  100 , but the drive signal COM after undergoing current amplification in the current amplification circuit  89  is not transmitted via the long flexible wiring board  100  connecting the recording head  10  and the apparatus main unit  2 . 
     Thus, in the ink jet recording apparatus  1  of the embodiment, the current amplification circuit  89  corresponding to the last stage in the drive signal generating circuit  8  is formed in the recording head  10 , so that the drive signal COM after undergoing current amplification is output to the head drive circuit  18  in the recording head  10  and is not output via the long flexible wiring board  100  connecting the apparatus main unit  2  and the recording head  10 . Therefore, the problem of distorting the waveform of the drive signal COM after undergoing current amplification because of parasitic inductance, etc., of the flexible wiring board  100  can be solved. When the recording head  10  is tested for characteristics, the recording head  10  also containing the current amplification circuit  89  of the drive signal generating circuit  8  is tested for characteristics, so that the characteristics of the recording head  10  also containing those of the drive signal generating circuit  8  can be determined properly. Therefore, a proper drive signal COM can be applied to each pressure generating element  17  in the recording head  10 . 
     Configuration of Recording Head and Carriage 
     However, when the current amplification circuit  89  is formed in the recording head  10 , heat generation in the recording head  10  grows, thus in the embodiment, the following heat radiation measure is taken for the recording head  10 : 
     FIGS.  6 (A) and (B) are a perspective view when the carriage  110  and the recording head  10  used with the ink jet recording apparatus  1  of the embodiment are disassembled and a bottom view in a state in which the recording head  10  is attached to the bottom of the carriage  110 , respectively. FIGS.  7 (A) and (B) are a perspective view to show the main part of the recording head  10  used with the ink jet recording apparatus  1  of. the embodiment and a perspective view of a heat radiation member (heat sink) used with the recording head, respectively. 
     As shown in FIGS.  6 (A) and (B), the carriage  110  comprises a metal case shaped like a rectangular parallelepiped opened in the upper surface thereof and stores an ink cartridge  17  (FIG. 1) inside. Here, a plurality rows of heat radiation fins  112  extended in the horizontal direction are formed on a side portion  111  parallel with the move direction (indicated by the arrow R), of the side portions of the carriage  110 . The recording head  10  is attached to the bottom of the carriage  110  and an upper surface portion  101  (attachment face to the carriage  110 ) of the recording head  10  is a part of the heat radiation member described with reference to FIGS.  7 (A) and (B). 
     As shown in FIGS.  7 (A) and (B), in the recording head  10  of the embodiment, a nozzle plate  115  provided with a plurality of nozzle openings  23  as nozzle rows, a flow passage formation board  116 , and an elastic board  117  are stacked in order, forming a flow passage unit  118 , and the pressure generating elements  17  are mounted on the upper surface of the flow passage unit  118  so as to abut the elastic board  117 . 
     A heat radiation member  200  comprising a metal plate shaped like T in cross section is mounted on the recording head  10 . The heat radiation member  200  comprises a horizontal plate section  220  in contact with the lower face of the carriage  111  and a vertical plate section  210  extended so as to be in contact with the area corresponding to the area between the nozzle rows in the flow passage unit  118  from the horizontal plate section  220 . Therefore, the heat radiation member  200  can be attached easily to the lower face of the carriage  111  with the horizontal plate section  220  brought into contact with the face of the carriage  111 . 
     Here, a semiconductor IC  300  provided with the head drive circuit  18  and the current amplification circuit  89  (see FIG. 2) is mounted on both faces of the vertical plate section  210  of the heat radiation member  200  and an end part of the flexible wiring board  100  passing through a slit  205  in the horizontal plate section  220  is connected to the semiconductor IC  300 . A flexible wiring board  105  considerably short as compared with the flexible wiring board  100  is connected to each row of the pressure generating elements  17  from the semiconductor IC  300 . 
     In the described recording head  10 , the current amplification circuit  89  of the drive signal generating circuit  8  installed in the apparatus main unit  2  in the conventional art is formed in the semiconductor IC  300  in the recording head  10 , thus the semiconductor IC  300  generates large heat. In the embodiment, however, the semiconductor IC  300  is mounted directly on the heat radiation member  200 , so that heat generated by the semiconductor IC  300  is escaped to the side of the carriage  110  through the vertical plate section  210  and the horizontal plate section  220  of the heat radiation member  200 , thus a temperature rise in the recording head  10  can be suppressed. Moreover, the carriage  110  is formed on the side portion  111  with the heat radiation fins  112 , so that the heat radiation property of the carriage  110  is also high. Therefore, if the semiconductor IC  300  generating large heat is installed in the recording head  10 , the heat of the semiconductor IC  300  is radiated efficiently, so that the reliability of the semiconductor IC  300  can be enhanced. Since a temperature rise in the recording head  10  is suppressed, a problem of drying ink in the recording head  10  because of heat of the semiconductor IC  300  or the like does not occur. 
     Moreover, the vertical plate section  210  of the heat radiation member  200  abuts the area corresponding to the area between the nozzle rows of the flow passage unit  118  and is fixedly secured. Thus, if the elastic plate  117  is vibrated on the side of one nozzle row, the vibration is not transmitted to the elastic plate  117  positioned on the adjacent nozzle row. Therefore, in the ink jet recording apparatus  1  of the embodiment, the heat radiation member  200  can prevent a temperature rise in the recording head  10  and can also prevent interference between the nozzle rows. 
     Second Embodiment 
     FIG. 8 is a functional block diagram of an ink jet recording apparatus of a second embodiment of the present invention. 
     In the first embodiment, in the drive signal generating circuit  8 , the waveform generating circuit  80  is formed in the apparatus main unit  2  and the current amplification circuit  89  is formed in the recording head  10 ; in the second embodiment, both a waveform generating circuit  80  and a current amplification circuit  89  are formed in a recording head  10 , as shown in FIG.  8 . Therefore, in the embodiment, the waveform generating circuit  80  receives the clock signals  801 ,  802 , and  803 , data signal  830 , address signals  810 ,  811 ,  812 , and  813 , and reset signal  820 , and the like previously described with reference to FIG. 3 from a control section  6  of a apparatus main unit  2  via a flexible wiring board  100 . In the embodiment, the waveform generating circuit  80  and the current amplification circuit  89  are formed in the semiconductor IC  300  shown in FIGS.  7 (A) and (B) together with a head drive circuit  18 . 
     Since in the ink jet recording apparatus  1  of the embodiment, both the waveform generating circuit  80  and the current amplification circuit  89  of a drive signal generating circuit  8  are formed in the recording head  10 , both drive signal COM before undergoing current amplification, output from the waveform generating circuit  80  and the drive signal COM after undergoing current amplification, output from the current amplification circuit  89  are output to the head drive circuit  18  in the recording head  10 . Therefore, the drive signals COM before and after undergoing current amplification are not output via a long flexible wiring board  100  connecting the apparatus main unit  2  and the recording head  10 . Therefore, the problem of distorting the waveforms of the drive signals COM before and after undergoing current amplification because of parasitic inductance, etc., of the flexible wiring board  100  can be solved. When the recording head  10  is tested for characteristics, the recording head  10  also containing the waveform generating circuit  80  and the current amplification circuit  89  of the drive signal generating circuit  8  is tested for characteristics, so that the characteristics of the recording head  10  also containing those of the drive signal generating circuit  8  can be determined properly. Therefore, a proper drive signal COM can be applied to each pressure generating element  17  in the recording head  10 . 
     In the recording head  10  of the first embodiment described above, the current amplification circuit  89  of the drive signal generating circuit  8  is formed in the semiconductor IC  300  in the recording head  10 , thus heat generation of the semiconductor IC  300  becomes large as compared with the conventional art example previously described with FIG.  12 . In the recording head  10  of the second embodiment described, both the waveform generating circuit  80  and the current amplification circuit  89  of the drive signal generating circuit  8  are formed in the semiconductor IC  300  in the recording head  10 , thus heat generation of the semiconductor IC  300  furthermore grows as compared with that in the first embodiment. In this case, if a structure of absorbing the generated heat in ink flowing through the ink lead passage  245  is adopted as one of the heat radiation measures against heat generation of the semiconductor IC  300  as described with reference to FIGS.  13 (A) and (B) for the conventional art example (conversely, both the waveform generating circuit  80  and the current amplification circuit  89  of the drive signal generating circuit  8  are placed in the semiconductor IC  249  in the conventional art example described with reference to FIGS.  13 (A) and (B)), heat generation of the semiconductor IC  300  reaches about three W (watts) to 15 W (watts), thus the temperature may become 100° C. to 150° C. and ink would come to a boil with no measures taken. As a result, a serious problem such that entirely separate pressure not corresponding to the drive signal occurs in the pressure generating chamber  234  because of a bubble produced by boiling the ink, jetting an ink drop, etc., may be incurred. 
     Then, in the second embodiment, the following heat radiation measure is taken for the recording head  10 : FIGS.  9 (A) and (B) show a schematic structure of recording head of the second embodiment. As shown in FIGS.  9 (A) and (B), in the recording head  90  of the second embodiment, a nozzle plate  915  provided with a plurality of nozzle openings  923  as nozzle rows  924 , a flow passage formation board  916 , and an elastic board  917  are stacked in order, forming a flow passage unit  918 , and pressure generating elements  97  are mounted on the upper surface of the flow passage unit  918  so as to abut the elastic board  917 . 
     A heat radiation member  1200  comprising a metal plate (for example, aluminum) shaped like T in cross section is mounted on the recording head  90 . The heat radiation member  1200  comprises a horizontal plate section  1220  in contact with the lower face of a carriage  911  and a vertical plate section  1210  orthogonal to the horizontal plate section  1220  and extended toward the flow passage unit  918 . The heat radiation member  1200  can be attached easily to the lower face of the carriage  110  (see FIG. 6) with the horizontal plate section  1220  brought into contact with the face of the carriage. 
     Here, a semiconductor IC  300 ′ provided with the head drive circuit  18 , the current amplification circuit  89 , and the waveform generating circuit  80  is mounted on both faces of the vertical plate section  1210  of the heat radiation member  1200  and an end part of a flexible wiring board  1100  passing through a slit  1205  in the horizontal plate section  1220  is connected to the semiconductor IC  300 ′. A flexible wiring board  1105  considerably short as compared with the flexible wiring board  1100  is connected to each row of the pressure generating elements  97  from the semiconductor IC  300 ′. 
     In the conventional art example shown in FIG.  13 (A), heat generated by the semiconductor IC  249  (heat source) is radiated mainly through the fix board  247 . In contrast, in the ink jet recording apparatus of the embodiment, heat is radiated through the heat radiation member  1200  having a larger surface area of heat radiation. A heat insulation material  1230  is attached to the lower end of the vertical plate section  1210  of the heat radiation member  1200 . The heat insulation material  1230  is in contact with the area corresponding to the area between the nozzle rows  924 . Therefore, the heat insulation material  1230  thermally insulates the vertical plate section  1210  and the flow passage formation board  916 . Thus, the heat generated by the semiconductor IC  300 ′ (heat source) is escaped upwardly (ink tank side) through the vertical plate section  1210  of the heat radiation member  1200  and is effectively radiated through the horizontal plate section  1220  of the heat radiation member  1200  and further heat radiation fins  112 , etc., of the carriage  110 . Since the heat insulation material  1230  is provided, the heat generated by the semiconductor IC  300 ′ (heat source) can be efficiently prevented from being transmitted to the ink flow passage. For example, if materials such that the heat resistance ratio between the heat insulation material  1230  and the heat radiation member  1200  becomes 9:1 are selected (if the heat radiation member  1200  is made of aluminum, a heat insulation material having heat resistance nine times that of aluminum is selected), the heat generated,by the semiconductor IC  300 ′ (heat source) can be escaped upwardly (ink tank side) at a ratio of 9:1 if other elements (portion circulated by convection into air from the surface of the semiconductor IC  300 ′ and radiated and the like) are not considered. Preferably, the heat resistance ratio between the heat insulation material  1230  and the heat radiation member  1200  becomes 4:1 or more, because even if the heat generated by the semiconductor IC  300 ′ becomes 150° C., the heat transmitted to the flow passage unit side can be suppressed to ⅕ or less if other elements are not considered. 
     As shown in FIG. 9A, an ink lead passage  245 ′ is formed away from the semiconductor IC  300 ′ (heat source) and extended up and down roughly midway between the pressure generating element  97  and the semiconductor IC  300 ′. In the conventional art example shown in FIG.  13 (A), the ink lead passage  245  is placed close to the semiconductor IC  249  (heat source) via the fix board  247  having high heat conductivity. In contrast, in the ink jet recording apparatus of the embodiment, the ink lead passage  245 ′ is placed away from the semiconductor IC  300 ′ (heat source), so that the heat generated by the semiconductor IC  300 ′ (heat source) can also be prevented from being transmitted to the ink flow passage according to the placement. To furthermore suppress heat conduction to the ink lead passage  245 ′, it is also possible to wind the surroundings of the semiconductor IC  300 ′ with heat insulation tape made of a resin, etc. In doing so, the above-mentioned portion circulated by convection into air from the surface of the semiconductor IC  300 ′ and radiated can be made extremely small, so that it is also made possible to escape heat to the upper side (ink tank side) more reliably. 
     In the nozzle plate  915 , the nozzle rows  924  each formed with a plurality of nozzle openings  923  are formed on the outer side from the ink lead passage  245 ′ (frame  244  side) and the adjacent nozzle rows  924  and  924  are placed largely away from each other, as shown in FIGS.  9 (A) and (B). As a result, if the ink lead passage  245 ′ is placed at the center, the ink flow passage to each nozzle opening  923  can be provided comparatively long, so that a temperature rise of ink can be easily avoided. The adjacent nozzle rows  924  and  924  are placed largely away from each other. Thus, if the elastic plate  917  is vibrated on the side of one nozzle row  924 , the vibration is not transmitted to the elastic plate  917  positioned on the other adjacent nozzle row  924 . Therefore, in the ink jet recording apparatus of the embodiment, interference between the nozzle rows can also be prevented. 
     As described above, in the recording head  90  of the embodiment, all of the head drive circuit  18 , the current amplification circuit  89 , and the waveform generating circuit  80  are formed in the semiconductor IC  300 ′ in the recording head  90 , thus heat generation of the semiconductor IC  300 ′ becomes very large, but the heat of the semiconductor IC  300  is radiated efficiently, so that the reliability of the semiconductor IC  300 ′ can be enhanced. Since a temperature rise in the recording head  90  is suppressed, boiling of ink due to heat of the semiconductor IC  300 ′ does not occur. 
     Third Embodiment 
     An ink jet recording apparatus according to a third embodiment of the present invention will be discussed with reference to FIG.  10 . 
     In the ink jet recording apparatus according to the embodiment, a plurality of rows of heat radiation fins  112  extended in the horizontal direction are formed on a side portion  111  parallel with a move direction of a carriage  110 ′ (direction perpendicular to the paper face in FIG.  10 ), of side portions of the carriage  110 ′, as in the first and third embodiments. A recording head  400  of the ink jet recording apparatus according to the embodiment is attached to the bottom of the carriage  110 ′ and an upper surface portion  402  of the recording head  400  (attachment face to the carriage  110 ′) is a portion similar to the horizontal plate section  1220  of the heat radiation member  1200  in the third embodiment described above and produces a heat radiation effect. The internal structure of the recording head  400  is similar to that of the recording head  90  in the third embodiment described above and therefore will not be illustrated or discussed again in detail. 
     As shown in FIG. 10, a plurality of rows of heat radiation fins  412  extended in the move direction of the carriage  110 ′ (direction perpendicular to the paper face in FIG. 10) are formed on the upper surface portion  402  (a horizontal plate section  1220 ′ of a heat radiation member  1200 ) of the recording head  400  in the embodiment. Fins  412   a  and  412   b  at both ends of a plurality of rows of heat radiation fins  412  are formed slightly higher than a plurality of other fins  412   c  and serve a function of supporting an ink cartridge  170  (see FIG. 1) mounted on the upper portion. Therefore, not only a gap  412   d  between other fins  412   c,  but also a space  412 E between a plurality of other fins  412   c  and the bottom of the ink cartridge  170  is formed. 
     In the recording head  400  of the embodiment, a plurality of rows of heat radiation fins  412  are also formed on the upper surface portion  402  (the horizontal plate section  1220 ′ of the heat radiation member  1200 ) and the heat radiation effect is more enhanced. In addition, when the carriage  110 ′ is moved (reciprocated in the direction perpendicular to the paper face in FIG. 10) by main scanning during printing, an air flow occurs (wind flows) in each gap  412   d  between the fins  412   c  and further the space  412 E between a plurality of fins  412   c  and the bottom of the ink cartridge  170  in response to the move speed of the carriage  110 ′, so that the effect of air cooling of the heat radiation member  1200  is produced because of the air flow. 
     The carriage  110 ′ has a structure with an opening in the front direction of the ink jet recording apparatus (front in the move direction of paper indicated by the arrow) for making it easy to remove an empty ink cartridge and attach a new ink cartridge at the replacement time of the ink cartridge  170 , etc. Recently, a general printer of an ink jet recording apparatus (printer), etc., has been often placed at the uppermost stage of a personal computer rack, etc. If a printer is placed at a high place, such as the uppermost stage of a personal computer rack, etc., replacement of an ink cartridge is facilitated by adopting the structure with an opening in the front direction of the carriage  110 ′. 
     Fourth Embodiment 
     FIGS.  11 (A) and (B) are a block diagram to show a general circuit configuration in an ink jet recording apparatus and a block diagram to show the feature of a circuit configuration of a fourth embodiment of the present invention respectively. The embodiment can be applied to both the first and second embodiments described above and other components are similar to those of the first and second embodiments. Therefore, FIG.  11 (B) shows only the feature of the embodiment. 
     In the ink jet recording apparatuses of the embodiments and the ink jet recording apparatus in the conventional art described above, as shown in FIG.  11 (A), output of the waveform generating circuit  80  is input into the current amplification circuit  89  and the signal after undergoing current amplification in the current amplification circuit  89  is input into each switching element  160  (analog switch) of the switch circuit  16  of the head drive circuit  18 . In the embodiment, as shown in FIG.  11 (B), using the fact that a current amplification circuit  89  is formed in a recording head  10 , output of a waveform generating circuit  80  is input into the current amplification circuit  89  via each switching element  160  (analog switch) of a switch circuit  16  of a head drive circuit  18 . The waveform generating circuit  80  may be formed in either main apparatus unit (in the first embodiment) or the recording head  10  (in the second embodiment). 
     In the described ink jet recording apparatus, a signal before undergoing current amplification is input into the switching elements  160  of the switch circuit  16  of the head drive circuit  18 , thus heat generation of the switching elements  160  is small. Therefore, the reliability of the switching elements  160  can be enhanced and small-sized elements can be used as the switching elements  160 . Although the present invention has been described in the specific embodiments, it is understood that the present invention is not limited to the specific embodiments and is applied to other embodiments within its spirit and scope as set out in the accompanying claims. 
     For example, in the above-described embodiments, piezoelectric vibrators are used as the pressure generating elements  17 , but the pressure generating elements  17  are not limited to the piezoelectric vibrators and magnetostrictive elements, etc., may be used. Further, the present invention can also be applied to an ink jet recording apparatus of so-called bubble jet type using heating elements as the pressure generating elements. 
     As described above, in the ink jet recording apparatus according to the present invention, at least the current amplification circuit of the drive signal generating circuit is formed in the recording head, so that the drive signal after undergoing current amplification is output to the head drive circuit in the recording head and is not output via the flexible wiring board connecting the apparatus main unit and the recording head. Therefore, the problem of distorting the waveform of the drive signal after undergoing current amplification because of parasitic inductance, etc., of the flexible wiring board can be solved. When the recording head is tested for characteristics, the recording head also containing the current amplification circuit of the drive signal generating circuit is tested for characteristics, so that the characteristics of the recording head also containing those of the drive signal generating circuit can be determined properly. Therefore, a proper drive signal can be applied to each pressure generating element in the recording head. 
     Since the current amplification circuit is formed in the recording head, heat generation of the recording head becomes large, but the heat radiation member is placed in the recording head, so that a temperature rise in the recording head can be prevented. Therefore, in the recording head, each circuit can be prevented from malfunctioning or being degraded because of heat, and the detrimental effect of hastening drying of ink in the presence of heat or the like can be avoided. Further, in the ink jet recording apparatus according to the present invention, the head drive circuit, the current amplification circuit, and the waveform generating circuit are formed so as to be contained in the semiconductor device of the recording head, the heat radiation member for the semiconductor device comprises at least a horizontal plate section in face contact with a carriage on which the recording head is mounted and a vertical plate section extended from the horizontal plate section to the flow passage unit, the semiconductor device is mounted on the vertical plate section, and further, a first heat insulation material is attached between the vertical plate section of the heat radiation member and the area corresponding to the area between the nozzle rows in the flow passage unit. The first heat insulation material thermally insulates the vertical plate section and the flow passage unit and the heat generated by the semiconductor device of the recording head is escaped upwardly through the vertical plate section of the heat radiation member and is effectively radiated through the horizontal plate section of the heat radiation member. Since the heat insulation material is provided, the heat generated by the semiconductor device can be efficiently prevented from being transmitted to the ink flow passage.