JP3885812B2 - Ink jet recording apparatus and driving method of ink jet recording apparatus - Google Patents

Description

  The present invention relates to a method for driving an ink jet recording apparatus such as an ink jet printer or an ink jet plotter. More specifically, the present invention relates to a driving technique for ejecting ink droplets from a nozzle opening of an ink jet recording apparatus to eject minute ink droplets.

  As an ink jet head used in various ink jet recording apparatuses such as an ink jet printer and an ink jet plotter, a type in which ink droplets are ejected by changing the volume of a pressure generating chamber communicating with a nozzle opening is known. In this type of ink jet recording apparatus, a diaphragm that is elastically deformable in an out-of-plane direction is formed on a part of a peripheral wall that defines a pressure generating chamber, and the diaphragm is vibrated by a pressure generating element such as a piezoelectric vibrator. As a result, the volume of the pressure generating chamber is changed.

  In the ink jet recording apparatus, it is necessary to reduce the recording dot diameter in order to realize high quality recording. As a method for reducing the recording dot diameter, a so-called “strike” method has been used in which an ink chamber communicating with a nozzle opening is expanded and then contracted. According to this method, since the weight of the ink droplet can be reduced, the recording dot diameter can be reduced. In this “pulling” type ink jet recording apparatus, as shown in FIG. 6B, the drive signal for operating the piezoelectric vibrator maintains the intermediate potential Vm for a predetermined time (hold pulse 113). After falling to a minimum potential VLS with a constant gradient (first signal / discharge pulse 114), and maintaining this minimum potential VLS for a predetermined time (second signal / hold pulse 115), a constant gradient to the maximum potential VP And rise again (third signal / charge pulse 116).

  According to such a drive signal, in the recording head shown in FIG. 3, as shown in FIGS. 9A and 9B, the ink meniscus after ejecting ink droplets with the previously applied charge pulse is used. While the hold pulse 113 is applied, the ink surface tension causes a vibration centered on the nozzle opening 23 with a predetermined period of vibration, and the meniscus attenuates the vibration with the passage of time. After a while, it will be in a stationary state. Here, when the charging pulse 114 is applied, the piezoelectric vibrator 17 bends in the direction of expanding the volume of the pressure generating chamber 32, and a negative pressure is generated in the pressure generating chamber 32.

  As a result, the meniscus causes a movement toward the inside of the nozzle opening 23, and the meniscus is drawn into the nozzle opening 23. When this state is maintained while the hold pulse 115 is being applied and then the charge pulse 116 is applied, a positive pressure is generated in the pressure generating chamber 32 and an ink droplet is ejected.

Japanese Patent Laid-Open No. 4-251749

  However, in the ink jet recording apparatus, further improvement in recording quality is desired, and in order to respond to such a request, it is necessary to further reduce the recording dot diameter. It is not possible to respond by simply adopting the “pulling” method.

In order to solve the above problem, the present invention operates a pressure generating element corresponding to each of a plurality of nozzle openings to contract a pressure generating chamber communicating with the nozzle openings and discharge ink droplets from the nozzle openings. An inkjet recording apparatus,
The driving signal for operating the pressure generating element includes at least a first signal for expanding the pressure generating chamber, a second signal for maintaining the expanded state of the pressure generating chamber, and the expansion state from the expanded state. A third signal for causing the pressure generation chamber to contract and ejecting ink droplets,
Temperature detection means for detecting temperature, and the first potential difference between the first signal and the second signal at the start of expansion of the pressure generation chamber is the first potential difference at the end of contraction of the pressure generation chamber. When the detected temperature is higher than the second potential difference between the third signal and the second signal, the difference between the first potential difference and the second potential difference is increased. .

  In order to solve the above problems, in the present invention, by operating a pressure generating element corresponding to each of a plurality of nozzle openings, the pressure generating chamber communicating with the nozzle openings is contracted to eject ink droplets from the nozzle openings. In the driving method of the ink jet recording apparatus, the driving signal for operating the pressure generating element includes at least a first signal for expanding the pressure generating chamber and a second signal for maintaining the expanded state of the pressure generating chamber. And a third signal for contracting the pressure generating chamber to eject ink droplets, and a first of the first signal and the second signal at the start of expansion of the pressure generating chamber The potential difference is larger than a second potential difference between the third signal and the second signal at the end of contraction of the pressure generating chamber.

  In the present invention, since the first potential difference between the first signal and the second signal at the start of expansion of the pressure generation chamber is large, the ink meniscus is drawn to a large extent from the nozzle opening. is there. Therefore, if the pressure generating chamber is contracted from this state, the weight of the ink droplet is small, so that the recording dot diameter can be reduced. Further, since the second potential difference between the third signal and the second signal at the end of contraction of the pressure generating chamber is small, the degree of contraction of the pressure generating chamber is small. Therefore, since the weight of the ink droplet can be further reduced, the recording dot diameter can be further reduced, and the display quality can be improved.

  In the present invention, based on the temperature detection result of the temperature detection means, the difference between the first potential difference and the second potential difference is increased when the temperature is high, and when the temperature is low, the first potential difference and the second potential difference are increased. It is preferable to compress the difference from the potential difference. For example, by adjusting the potential of the third signal at the end of contraction of the pressure generating chamber based on the temperature detection result of the temperature detecting means, the difference between the first potential difference and the second potential difference is obtained. adjust. That is, in the present invention, the first potential difference between the first signal and the second signal at the start of expansion of the pressure generation chamber, the third signal at the end of contraction of the pressure generation chamber, and the Since the fact that the weight of the ink droplet changes due to the magnitude relationship between the second signal and the second potential difference is utilized, if such a magnitude relationship is adjusted, the ink viscosity increases with temperature change. It is possible to compensate for a change in the weight of the ink droplet.

  As described above, in the ink jet recording apparatus according to the present invention, since the potential difference of the drive signal before and after the expansion of the pressure generating chamber is large, the ink meniscus is in a state of being largely drawn from the nozzle opening. Therefore, if the pressure generating chamber is contracted from this state, the weight of the ink droplet is small, so that the recording dot diameter can be reduced. Further, since the potential difference before and after contraction of the pressure generation chamber is small, the degree of contraction of the pressure generation chamber is small. Therefore, since the weight of the ink droplet can be further reduced, the recording dot diameter can be further reduced, and the display quality can be improved.

  An ink jet printer (ink jet recording apparatus) to which the present invention is applied will be described with reference to the drawings.

(Overall configuration of inkjet printer)
FIG. 1 is a functional block diagram of the ink jet recording apparatus of the present embodiment.

  In FIG. 1, the inkjet recording apparatus includes a print controller 1 and a print engine 2. The print controller 1 includes an interface 3 that receives recording data including multilevel hierarchical information from a host computer (not shown), and a RAM 4 that stores various data such as recording data including multilevel hierarchical information. A ROM 5 storing routines for performing various data processing, a control unit 6 including a CPU, an oscillation circuit 7, a drive signal generation circuit 8 for generating a drive signal to a recording head 10 described later, A power generation unit 80 that generates a power for generating a drive signal by the drive signal generation circuit 8, and an interface 9 for transmitting print data and drive signals developed in dot pattern data to the print engine 2 are provided. Yes.

  Recording data including multi-level hierarchical information sent from a host computer or the like is held in the reception buffer 4A inside the recording apparatus via the interface 3. The recording data held in the reception buffer 4A is sent to the intermediate buffer 4B after command analysis is performed. In the intermediate buffer 4B, the recording data in the intermediate format converted into the intermediate code by the control unit 6 is held, and the process for adding the print position, modification type, size, font address, etc. of each character is controlled. This is executed by the unit 6. Next, the control unit 6 analyzes the recording data in the intermediate buffer 4B and develops and stores the binarized dot pattern data after decoding the hierarchical data in the output buffer 4C as will be described later.

  When dot pattern data corresponding to one scan of the recording head 10 is obtained, this dot pattern data is serially transferred to the recording head 10 via the interface 9. When dot pattern data corresponding to one scan is output from the output buffer 4C, the contents of the intermediate buffer 4B are erased and the next intermediate code conversion is performed. Here, the print data developed into the dot pattern data is composed of, for example, 2 bits as gradation data for each nozzle, as will be described later.

  The print engine 2 includes a recording head 10, a paper feed mechanism 11, and a carriage mechanism 12. The paper feed mechanism 11 includes a paper feed motor, a paper feed roller, and the like, and sequentially feeds a recording medium such as recording paper to perform sub-scanning. The carriage mechanism 12 includes a carriage on which the recording head 10 is mounted and a carriage motor that travels the carriage via a timing belt. The carriage mechanism 12 causes the recording head 10 to perform main scanning.

  The recording head 10 has a large number of nozzles such as 48 in the sub-scanning direction, and ejects ink droplets from each nozzle at a predetermined timing. The print data developed into the dot pattern data is serially transferred from the interface 9 to the shift register 13 in synchronization with the clock signal (CLK) from the oscillation circuit 7. The serially transferred print data (SI) is once latched by the latch circuit 14. The latched print data is boosted to a voltage that can drive the switch circuit 16, for example, a predetermined voltage of about several tens of volts, by a level shifter 15 that is a voltage amplifier. The print data boosted to a predetermined voltage is given to the switch circuit 16. A drive signal (COM) from the drive signal generating circuit 8 is applied to the input side of the switch circuit 16, and a piezoelectric vibrator 17 as a pressure generating element is connected to the output side of the switch circuit 16. .

  The print data controls the operation of the switch circuit 16. For example, while the print data applied to the switch circuit 16 is “1”, a drive signal is applied to the piezoelectric vibrator 17 and the piezoelectric vibrator 17 expands and contracts in response to this signal. On the other hand, during the period when the print data applied to the switch circuit 16 is “0”, the supply of the drive signal to the piezoelectric vibrator 17 is cut off.

(Configuration of inkjet recording head)
FIG. 2 specifically shows the configuration of the recording head 10. The shift register circuit 13, the latch circuit 14, the level shifter 15, the switch circuit 16, and the piezoelectric vibrator 17 in FIG. 1 are elements 13A to 13N, 14A to 14N, 15A to 15N, and 16A corresponding to the nozzles of the recording head 10, respectively. To 16N and 17A to 17N. The print data is composed of 2-bit data for each nozzle as in (10), (11), and the like. Then, the bit data of each digit for all the nozzles is serially transferred to the shift registers 13A to 13N within one recording cycle. When the bit data applied to the switch elements 16A to 16N configured as analog switches is “1”, the drive signal COM is directly applied to the piezoelectric vibrators 17A to 17N, and the piezoelectric vibrators 17A to 17N are driven. It is displaced according to the signal waveform of the signal. Conversely, when the bit data applied to each switch element 16A to 16N is “0”, the drive signal to each piezoelectric vibrator 17A to 17N is cut off, and each piezoelectric vibrator 17A to 17N holds the previous charge. .

  FIG. 3 shows an example of a mechanical cross-sectional structure of the recording head 10. In this figure, the first lid member 30 is composed of a thin plate of zirconia (ZrO) having a thickness of about 6 μm, and a common electrode 31 serving as one pole is formed on the surface, as will be described later. A piezoelectric vibrator 17 (any one of the piezoelectric vibrators 17A to 17N) made of PZT or the like is fixed to the surface, and a drive electrode 34 made of a relatively flexible metal layer such as Au is formed on the surface thereof.

  The piezoelectric vibrator 17 constitutes a flexural vibration type actuator together with the first lid member 30. When the piezoelectric vibrator 17 is charged, the piezoelectric vibrator 17 contracts to reduce the volume of the pressure generating chamber 32, and the piezoelectric vibration. When the child 17 is discharged, it expands and deforms in a direction that expands the volume of the pressure generating chamber 32.

  The spacer 35 is formed by forming a through hole in a ceramic plate such as zirconia having a thickness suitable for forming the pressure generating chamber 32, for example, 100 μm. The second lid member 36 and the first lid member 30 described later are used. Thus, both surfaces are sealed to form the pressure generating chamber 32 described above.

  The second lid member 36 is also a ceramic plate such as zirconia, and has a communication hole 38 that connects an ink supply port 37 and a pressure generation chamber 32, which will be described later, a nozzle opening 23, and the other end of the pressure generation chamber 32. A nozzle communication hole 39 to be connected is formed and fixed to the other surface of the spacer 35.

  These members 30, 35, and 36 are gathered together in the actuator unit 21 without using an adhesive by forming a viscous ceramic material into a predetermined shape, laminating them and firing them.

  The ink supply port forming substrate 40 also serves as a fixed substrate for the actuator unit 21, and a nozzle communication hole 44 connected to a common ink chamber 41 and a nozzle opening 23 described later is formed on one end side of the pressure generating chamber 32 side. The other surface is sealed with a nozzle plate 45 to form a common ink chamber 41.

  The ink supply port forming substrate 40, the common ink chamber forming substrate 43, and the nozzle plate 45 are fixed to each other by adhesive layers 46 and 47 such as a heat welding film and an adhesive and are collected in the flow path unit 22. ing.

  The flow path unit 22 and the above-described actuator unit 21 are fixed by an adhesive layer 48 such as a heat welding film or an adhesive to constitute the recording head 10.

  In the recording head 10 configured as described above, when the piezoelectric vibrator 17 is discharged, the pressure generation chamber 32 expands, and the pressure in the pressure generation chamber 32 decreases, so that ink from the common ink chamber 41 enters the pressure generation chamber 32. Flows in. On the other hand, when the piezoelectric vibrator 17 is charged, the pressure generating chamber 32 is reduced, the pressure in the pressure generating chamber 32 is increased, and the ink in the pressure generating chamber 32 is ejected to the outside through the nozzle opening 23. The

(Relationship between each drive pulse and gradation display)
The ink jet recording apparatus according to the present embodiment is a gradation display, and an operation for performing this will be described with reference to FIG.

  FIG. 4 is an explanatory diagram showing the relationship between the waveform of the gradation signal, the magnitude relationship between the ejected ink droplets, the gradation value, and the like.

  As shown in FIG. 4, the drive signal generated by the drive signal generation circuit 8 shown in FIG. 1 has time on the horizontal axis and voltage on the vertical axis, and the first drive pulse as the “first drive pulse” for small dots. 1 drive pulse and a second pulse as a “second drive pulse” for large dots. The first pulse is for ejecting a small ink droplet of 5 ng, for example. This first pulse is selected when recording small dots, and a small dot diameter is obtained. When recording a large dot, the first and second pulses are selected in succession, thereby ejecting a large ink droplet of, for example, 20 ng (5 ng + 15 ng), thereby obtaining a large dot diameter.

  Regarding gradation expression, there are three patterns: no dot forming no dot (gradation value 1), forming only a small dot (gradation value 2), and forming a large dot (gradation value 3). Thus, if the recording dots are formed on the recording paper, three gradations of dot gradation can be performed. Each gradation value can be represented by 2-bit data such as (00), (01), and (10).

  For example, in the case of a gradation value 2 of a small dot that discharges only a small ink droplet, “1” is applied to the switch circuit 16 in synchronization with the generation of the first pulse, and “0” is generated when the second pulse is generated. Is applied, only the first pulse can be supplied to the piezoelectric vibrator 17. That is, by translating (decoding) 2-bit data (01) indicating a gradation value of 2 into 2-bit data (10), only the first pulse can be applied to the piezoelectric vibrator 17 and small dots A gradation value of 2 can be realized. In addition, if the decoded 2-bit data (11) is applied to the switch circuit 16, the first pulse and the second pulse are applied to the piezoelectric vibrator 17, so that two large and small ink droplets continue on the recording paper. In this case, the inks are mixed and substantially large dots are formed, and a gradation value of 3 can be realized. Further, in the case of a dot-free gradation value of 1 that does not eject ink droplets, if 2-bit data (00) is supplied to the switch circuit 16, no pulse is applied to the piezoelectric vibrator 17, so a dot-free gradation. A value of 1 can be realized.

  One-bit data assigned to each drive pulse corresponds to a pulse selection signal. The print data is generated by the control unit 6, and the generated print data is stored in the output buffer 4C. For example, the control unit 6 generates print data and stores it in the output buffer 4C so as to give 2-bit data (11) to the switch circuit 16 of the piezoelectric vibrator 17 that records large dots.

  Next, a specific configuration for giving each 2-bit print data to the switch circuit 16 will be described with reference to the waveform diagram of FIG.

  In FIGS. 1, 4 and 5, first, the output buffer 4C stores 2-bit print data (D1, D2) translated by the control unit 6. Here, D1 is a selection signal for the first pulse, and D2 is a selection signal for the second pulse. This 2-bit print data is given to the switch circuit 16 corresponding to each nozzle of the recording head 10 within one recording period.

  Specifically, the number of nozzles of the recording head 10 is n, the print data of the first nozzle at a certain position in the sub-scanning direction is (D11, D21), and the print data of the second nozzle is (D12, D22). In this case, the data (D11, D12, D13,... D1n) of the first pulse selection signal D1 for all the nozzles are serially input to the shift register 13 in synchronization with the clock signal. Similarly, the data (D21, D22, D23,... D2n) of the second pulse selection signal D2 for all nozzles is transferred to the shift register 13 within one recording cycle.

  More specifically, as shown in FIG. 5, print data for selecting the drive pulse is transferred to the shift register 13 before the timing at which the target drive pulse is generated. The print data set in the shift register 13 is transferred to the latch circuit 14 and stored in synchronization with the generation of the target pulse. The print data of the latch circuit 14 is boosted by the level shifter 15 and input to the switch circuit 16.

  Next, drive pulses constituting the drive signal will be described.

  First, the voltage of the first pulse for small dots starts from the intermediate potential Vm (hold pulse 111) and rises to the first maximum potential VPS with a constant gradient (hold pulse 112). The potential VPS is maintained for a predetermined time (hold pulse 113). Next, the first pulse falls at a constant gradient to the first lowest potential VLS (first signal / discharge pulse 114), and the first lowest potential VLS is maintained for a predetermined time (second signal / hold). Pulse 115).

  Then, the voltage value of the first pulse rises again with a constant gradient to the second maximum potential VPL (third signal / charge pulse 116), and the second maximum potential VP is maintained for a predetermined time (117). Thereafter, the first pulse falls at a constant gradient to the intermediate potential Vm (discharge pulse 118).

  3 and 5, when the charging pulse 112 is applied to the piezoelectric vibrator 117, the piezoelectric vibrator 17 bends in the direction of contracting the volume of the pressure generating chamber 32 and generates a positive pressure in the pressure generating chamber 32. . As a result, the meniscus rises from the nozzle opening 23.

  While the hold pulse 113 is being applied, the meniscus that has risen due to the charge pulse 112 turns into a movement that returns to the inside of the nozzle opening 23 with a predetermined period of vibration due to the ink surface tension.

  Next, when the discharge pulse 114 is applied, the piezoelectric vibrator 17 bends in the direction of expanding the volume of the pressure generating chamber 32, and a negative pressure is generated in the pressure generating chamber 32. As a result, the movement of the meniscus toward the inside of the nozzle opening 23 is superimposed, and the meniscus is largely drawn into the nozzle opening 23. In this way, by applying the discharge pulse 114 at the timing when the meniscus moves toward the inside of the nozzle opening 23, the meniscus can be largely drawn into the nozzle opening 23 even with a relatively small potential difference of the discharge pulse 114. Such a state is maintained while the hold pulse 115 is applied.

  Next, when the charging pulse 116 is applied, a positive pressure is generated in the pressure generating chamber 32 and the meniscus rises from the nozzle opening 23. At this time, since the pressure change in the positive pressure direction occurs in a state where the meniscus is largely drawn into the nozzle opening 23, the ejected ink droplets are minute ink droplets.

  The discharge pulse 118 is a pulse for suppressing the vibration of the meniscus excited by the discharge pulse 114 and the charge pulse 116.

  Next, the second pulse for large dots will be described.

  The second pulse starts from the intermediate potential Vm following the first pulse (hold pulse 119). The voltage falls at a constant gradient to the second lowest potential VLL (discharge pulse 121), and the second lowest potential VLL is maintained for a predetermined time (hold pulse 122). The second lowest potential VLL of the second pulse is higher than the lowest potential VLS of the first pulse. Then, the voltage value of the second pulse rises with a constant gradient to the maximum potential VP (charging pulse 123), and the second maximum potential VPL is maintained for a predetermined time (hold pulse 124). Thereafter, the second pulse falls with a constant gradient to the intermediate potential Vm (discharge pulse 125).

  When the discharge pulse 121 is applied, a negative pressure is generated in the pressure generating chamber 32 as described above, and the meniscus is drawn into the nozzle opening 23. However, by setting the potential difference of the discharge pulse 121 to be smaller than the potential difference of the discharge pulse 114 of the first pulse, the meniscus is not greatly drawn into the nozzle opening 23 compared to the first pulse.

  When the charging pulse 123 is applied, a positive pressure is generated in the pressure generating chamber 32 and the meniscus rises from the nozzle opening 23. At this time, a pressure change in the positive pressure direction occurs in a state where the meniscus is not drawn so much into the nozzle opening 23, so that the ejected ink droplet becomes a larger ink droplet than the first pulse.

  The discharge pulse 125 causes the meniscus to be directed toward the inside of the nozzle opening 23 at the timing when the vibration of the meniscus excited by the discharge pulse 121 and the charge pulse 123 moves toward the outlet of the nozzle opening 23.

(Measures to reduce the size of dots)
Among the drive signals having such a waveform, the first pulse for small dots is optimized as shown in FIG. 6A to further reduce the weight of the ink droplet at the gradation value 2 and perform recording. Make the dot diameter smaller.

  In this embodiment, as shown in FIG. 6A, the potential difference ΔV1 of the discharge pulse 114 (the first potential difference between the first signal and the second signal at the start of expansion of the pressure generating chamber 32) is the charge pulse. 116 is greater than the potential difference ΔV2 (second potential difference between the third signal and the second signal at the end of contraction of the pressure generating chamber 32). That is, when comparing the first maximum potential VPS and the second maximum potential VPL, the first maximum potential VPS is higher. For example, if the potential difference ΔV1 of the discharge pulse 114 is 100%, the potential difference ΔV2 of the charge pulse 116 is 83%. Therefore, in this embodiment, since the potential difference ΔV1 of the discharge pulse 114 is large, the ink meniscus is largely drawn from the nozzle opening 23, and there is a portion where no ink exists in the nozzle opening 23. Therefore, if the pressure generating chamber 32 is contracted from this state, the weight of the ejected ink droplet is small even if the speed at which the ink droplet is ejected is the same. Further, since the potential difference ΔV2 of the charging pulse 116 is small, the degree of contraction of the pressure generating chamber 32 is small and the amount of ink discharged is small.

  As described above, in this embodiment, when a small dot is formed, the ink meniscus is largely drawn through the nozzle opening 23 and the ink is ejected small, so that the weight of the ink droplet can be reduced. Therefore, the recording dot diameter can be further reduced at the gradation value 2, and the display quality (resolution) can be improved.

  FIG. 7 is a functional block diagram of the ink jet recording apparatus of the present embodiment. Since the basic configuration of the ink jet recording apparatus of the present embodiment is the same as that of the first embodiment, portions having common functions are denoted by the same reference numerals and description thereof is omitted.

  In an ink jet recording apparatus, if the ink viscosity changes with temperature and the ink droplet weight fluctuates when the dot size is small, the effect appears remarkably in the recording quality. Therefore, in the present embodiment, for the purpose of preventing the display quality from being lowered due to such a temperature change, as shown in FIG. 7, first, for the print controller 1 of the ink jet recording apparatus, a temperature sensor 91 and AD conversion are performed. A temperature detecting means 90 comprising a vessel 92 is configured. The temperature detection result of the temperature detection means 90 is input to the temperature compensation means 93. The temperature compensation means 93 receives from the temperature compensation condition storage means 94 in which the temperature compensation conditions corresponding to the relationship between the temperature and the ink viscosity are stored. Set the compensation condition corresponding to the current temperature. Next, the temperature compensation means 93 optimizes the power generation condition in the power generation unit 80 based on the compensation condition set here, and based on the optimized power supply, the drive signal generation circuit 8 A predetermined drive signal (first pulse for small dots) is generated.

  That is, in this embodiment, as shown in FIG. 8 (A), the temperature compensation means 93 has the potential difference ΔV1 of the discharge pulse 114 (the first time at the start of expansion of the pressure generating chamber 32) if the current temperature is 25 ° C. When the first potential difference between the signal and the second signal is 100%, the potential difference ΔV2 of the charging pulse 116 (the second difference between the third signal and the second signal at the end of contraction of the pressure generating chamber 32). The power source generation unit 80 generates a power source such that the potential difference between the power source and the power source is 83%.

  On the other hand, in the temperature detection result of the temperature detecting means 90, when the current temperature is 40 ° C., the ink viscosity is small and the weight of the ink droplet is too large. Thus, the temperature compensation means 93 is charged when the potential difference ΔV1 of the discharge pulse 114 (the first potential difference between the first signal and the second signal at the start of expansion of the pressure generating chamber 32) is 100%. A power source (optimal at 25 ° C. when the potential difference ΔV2 of the pulse 116 (the second potential difference between the third signal and the second signal at the end of contraction of the pressure generating chamber 32) is 66%. The power supply generation unit 80 generates a power supply corresponding to the second highest potential VPL ′ that is lower than the second highest potential VPL. Therefore, the drive signal generation circuit 8 generates the charge pulse 116 and the hold pulse 117 using the temperature compensated power source. Therefore, when the current temperature is 40 ° C., the drive condition of the recording head 10 is automatically changed in the direction in which the weight of the ink droplet is reduced, so that the situation where the weight of the ink droplet is excessive is prevented. can do.

  On the other hand, in the temperature detection result of the temperature detecting means 90, when the current temperature is 10 ° C., the ink viscosity is large and the weight of the ink droplet is too small. Therefore, as shown in FIG. The temperature compensator 93 sets the potential difference ΔV1 of the discharge pulse 114 (the first potential difference between the first signal and the second signal at the start of expansion of the pressure generation chamber 32) to 100%. The power source (the second optimal that was optimal at 25 ° C.) with a potential difference ΔV2 (second potential difference between the third signal and the second signal at the end of contraction of the pressure generating chamber 32), for example, 100%. The power supply generation unit 80 generates a power supply corresponding to the second highest potential VPL ″ that is higher than the maximum potential VPL. Based on the power supply, the drive signal generation circuit 8 generates a predetermined drive signal (for small dots). First pulse) generate.

  That is, the drive signal generation circuit 8 generates the charge pulse 116 and the hold pulse 117 using a power supply corresponding to the first highest potential VPS. As a result, when the current temperature is 10 ° C., the drive condition of the recording head 10 is automatically changed in the direction in which the weight of the ink droplet increases, thus preventing the situation where the weight of the ink droplet is too small. can do.

  Thus, in this embodiment. Based on the temperature detection result of the temperature detecting means 90, when the temperature is high, the potential difference ΔV1 of the discharge pulse 114 (the first potential difference between the first signal and the second signal at the start of expansion of the pressure generating chamber 32) and The potential difference ΔV2 of the charging pulse 116 (the second potential difference between the third signal and the second signal at the end of contraction of the pressure generating chamber 32) is enlarged, and the potential difference ΔV1 of the discharging pulse 114 is low when the temperature is low. And the potential difference ΔV2 of the charging pulse 116 are compressed, so that temperature compensation for small dots can be performed. Further, in this embodiment, since the setting of the second highest potential VPL lower than the first highest potential VPS is changed, the first highest potential VPS is not increased. Therefore, the drive voltage does not increase.

[Other Embodiments]
In the above embodiment, the flexural vibrator type PZT is used as the piezoelectric vibrator 17. However, the vertical vibration lateral effect PZT may be used. It will replace the discharge. Further, the pressure generating element is not limited to the piezoelectric vibrator, and a magnetostrictive element or the like may be used.

1 is a functional block diagram of an ink jet recording apparatus according to Embodiment 1 of the present invention. FIG. 2 is a circuit diagram illustrating a main part of a recording head driving circuit of the ink jet recording apparatus illustrated in FIG. 1. It is explanatory drawing which shows the mechanical structure of the recording head of the inkjet recording device shown in FIG. FIG. 2 is an explanatory diagram showing a drive waveform in the ink jet recording apparatus shown in FIG. 1 and a magnitude relationship between ejected ink droplets. FIG. 2 is an explanatory diagram illustrating a relationship between a driving pulse and print data transfer timing in the ink jet recording apparatus illustrated in FIG. 1. (A) is a waveform diagram of drive pulses for ejecting ink droplets for small dots in the ink jet recording apparatus shown in FIG. 1, and (B) is a waveform diagram of drive pulses of a conventional ink jet recording apparatus. It is a functional block diagram of the inkjet recording device which concerns on Embodiment 2 of this invention. (A), (B), and (C) are waveform diagrams of drive pulses for ejecting ink droplets for small dots at 25 ° C., 40 ° C., and 10 ° C. in the ink jet recording apparatus shown in FIG. It is. (A), (B) is a waveform diagram of a drive signal for ejecting ink droplets in the ink jet recording apparatus, and an explanatory diagram showing the movement of the ink meniscus corresponding to this waveform.

Explanation of symbols

6 Control Unit 8 Drive Signal Generating Circuit 10 Recording Head 16 Switch Circuit 17 Piezoelectric Vibrator (Pressure Generating Element)
23 Nozzle opening 32 Pressure generation chamber 80 Power generation unit 90 Temperature detection means 91 Temperature sensor 92 AD converter 93 Temperature compensation means 94 Temperature compensation condition storage means 114 Discharge pulse (first signal)
115 Hold pulse (second signal)
116 Charging pulse (third signal)
ΔV1 First potential difference between the first signal and the second signal at the start of expansion of the pressure generation chamber ΔV2 Second potential difference between the third signal and the second signal at the end of contraction of the pressure generation chamber

Claims (4)

An ink jet recording apparatus that operates a pressure generating element corresponding to each of a plurality of nozzle openings to contract a pressure generating chamber communicating with the nozzle openings and discharge ink droplets from the nozzle openings.
The driving signal for operating the pressure generating element is selected within one recording cycle when a small pulse is recorded and a driving pulse selected when recording a small dot and when selecting a small dot. Drive pulses that are not
The drive pulse selected when recording the small dots is at least a signal for contracting the pressure generating chamber, a signal for maintaining contraction of the contracted pressure generating chamber for a certain time, and a contraction maintaining for a certain time. A first signal for expanding the pressure generating chamber, a second signal for maintaining the expanded state of the pressure generating chamber, and a third signal for contracting the pressure generating chamber from the expanded state and ejecting ink droplets Including
The first potential difference between the first signal and the second signal at the start of expansion of the pressure generating chamber is the difference between the third signal and the second signal at the end of contraction of the pressure generating chamber. Greater than the second potential difference,
The ink jet recording apparatus increases the difference between the first potential difference and the second potential difference when the temperature detected by the temperature detecting means for detecting the temperature is higher than when the temperature is low. Inkjet recording apparatus.   2. The inkjet recording apparatus according to claim 1, wherein the first potential difference is adjusted by adjusting a potential of the third signal at the end of contraction of the pressure generation chamber based on a temperature detection result of the temperature detection unit. An ink jet recording apparatus, wherein a difference from the second potential difference is adjusted. A method of driving an ink jet recording apparatus, wherein a pressure generating element corresponding to each of a plurality of nozzle openings is operated to contract a pressure generating chamber communicating with the nozzle openings and eject ink droplets from the nozzle openings,
The driving signal for operating the pressure generating element is selected within one recording cycle when a small pulse is recorded and a driving pulse selected when recording a small dot and when selecting a small dot. Drive pulses that are not
The drive pulse selected when recording the small dots is at least a signal for contracting the pressure generating chamber, a signal for maintaining contraction of the contracted pressure generating chamber for a certain time, and a contraction maintaining for a certain time. A first signal for expanding the pressure generating chamber, a second signal for maintaining the expanded state of the pressure generating chamber, and a third signal for contracting the pressure generating chamber from the expanded state and ejecting ink droplets Including
The first potential difference between the first signal and the second signal at the start of expansion of the pressure generating chamber is the difference between the third signal and the second signal at the end of contraction of the pressure generating chamber. Greater than the second potential difference,
The inkjet recording apparatus is characterized in that the difference between the first potential difference and the second potential difference is enlarged when the temperature detected by the temperature detecting means for detecting the temperature is higher than when the temperature is low. A method for driving an inkjet recording apparatus.   4. The method for driving an ink jet recording apparatus according to claim 3, wherein the first signal potential is adjusted by adjusting a potential of the third signal at the end of contraction of the pressure generating chamber based on a temperature detection result of the temperature detecting means. And adjusting the difference between the second potential difference and the second potential difference.

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