JP2023157197A - inkjet head - Google Patents

Abstract

To provide an inkjet head that can finely adjust discharge volumes of ink droplets.SOLUTION: The inkjet head comprises: a pressure chamber that stores ink; a nozzle plate equipped with a nozzle in communication with the pressure chamber; an actuator that displaces the volumes of the pressure chamber; and a driving circuit that generates a driving signal for driving the actuator. A waveform of the driving signal has a first pulse at which the pressure chamber is varied from a steady state to an expanded state and the expanded state is maintained for a certain time, a second pulse at which the pressure chamber is returned from the expanded state to the steady state and the steady state is maintained for a certain time, a third pulse at which the pressure chamber is varied from the steady state to a contracted state and the contracted state is maintained for a certain time, and a fourth pulse at which the pressure chamber is returned from the contracted state to the steady and the steady state is maintained for a certain time, in order of time. The driving circuit has a third pulse width adjusting part that adjusts a pulse width of the third pulse for the actuator and a first pulse width adjusting part that adjusts a pulse width of the first pulse for the actuator.SELECTED DRAWING: Figure 12

Description

Embodiments of the present invention relate to an inkjet head.

2. Description of the Related Art Inkjet heads are known that eject ink droplets from nozzles by expanding and contracting pressure chambers containing ink using actuators. The drive circuit generates a waveform drive signal including a pulse that expands and contracts the pressure chamber, and drives the inkjet head by supplying the drive signal to an actuator.

The size of the ink chamber and the diameter of the nozzle are not necessarily uniform. Therefore, even if the same drive pulse signal is applied to each actuator, the ejection volume of ink droplets ejected from each nozzle is not necessarily constant.

Inkjet heads are known that adjust the ejection volume of ink droplets for each nozzle by adjusting the pulse width of the pulse that expands the pressure chamber in order to suppress variations in the ejection volume of ink droplets from each nozzle. .

JP2013-59961

The problem to be solved by the present invention is to provide an inkjet head that can finely adjust the ejection volume of ink droplets.

The inkjet head driving device drives an inkjet head that uses an actuator to expand and contract a pressure chamber containing ink to eject ink droplets from a nozzle. The inkjet head driving device includes a drive signal generation circuit that generates a drive signal for the actuator. The waveform of the drive signal includes a first pulse that changes the pressure chamber from a steady state to an expanded state, a second pulse that returns the pressure chamber from an expanded state to a steady state, and a third pulse that changes the pressure chamber from a steady state to a contracted state. A pulse and a fourth pulse for returning the pressure chamber from a contracted state to a steady state are sequentially arranged in time. The drive signal generation circuit includes a third pulse width adjustment section that adjusts the pulse width of the third pulse for the inkjet head, and a first pulse width adjustment section that adjusts the pulse width of the first pulse for each nozzle.

FIG. 1 is a partially exploded perspective view of an inkjet head. FIG. 2 is a cross-sectional view of the front part of the inkjet head. FIG. 3 is a longitudinal sectional view of the front part of the inkjet head. FIG. 4 is a schematic diagram showing a pressure chamber in a steady state. FIG. 5 is a schematic diagram showing a pressure chamber in an expanded state. FIG. 6 is a schematic diagram showing a pressure chamber in a contracted state. FIG. 7 is a block diagram showing the hardware configuration of an inkjet printer. FIG. 8 is a diagram showing the waveform of a drive signal supplied to the actuator of one pressure chamber. FIG. 9 is a diagram showing a waveform of a drive signal in which the Push pulse width is changed in a state where the Draw pulse width is not adjusted. FIG. 10 is a graph showing the relationship between the adjustment value of the Push pulse width, the fine adjustment level of Draw, and the ejection volume of ink droplets. FIG. 11 is a graph showing the amount of decrease in the ejection volume of ink droplets with respect to changes in the fine adjustment level when the adjustment value of the Push pulse width is 1.8 microseconds and 2.55 microseconds. FIG. 12 is a diagram showing a waveform of a drive signal in which the pulse width of Push supplied to the actuator of one pressure chamber is adjusted to 1.8 microseconds. FIG. 13 is a flowchart illustrating the operation of the inkjet head according to the embodiment.

First, the configuration of the inkjet head 100 will be explained using FIGS. 1 to 3. FIG. 1 is a partially exploded perspective view of the inkjet head 100, FIG. 2 is a cross-sectional view of the front portion of the inkjet head 100, and FIG. 3 is a longitudinal cross-sectional view of the front portion of the inkjet head 100. Note that, in the inkjet head 100, the longitudinal direction is the vertical direction, and the direction orthogonal to the longitudinal direction is the horizontal direction.

As shown in FIG. 1, the inkjet head 100 has a rectangular base substrate 9. In the inkjet head 100, a first piezoelectric member 1 is bonded to the upper surface of the front side of the base substrate 9, and a second piezoelectric member 2 is bonded onto the first piezoelectric member 1. The joined first piezoelectric member 1 and second piezoelectric member 2 are polarized in opposite directions along the thickness direction, as shown by arrows in FIG.

The base substrate 9 is formed using a material that has a small dielectric constant and a small difference in coefficient of thermal expansion between the piezoelectric members 1 and 2. Examples of suitable materials for the base substrate 9 include alumina (Al203), silicon nitride (Si3N4), silicon carbide (SiC), aluminum nitride (AlN), and lead zirconate titanate (PZT). On the other hand, as the material for the piezoelectric members 1 and 2, lead zirconate titanate (PZT), lithium niobate (LiNbO3), lithium tantalate (LiTaO3), etc. are used.

The inkjet head 100 is provided with a large number of elongated grooves 3 from the leading end to the rear end of the joined piezoelectric members 1 and 2. Each groove 3 has a constant interval and is parallel. Each groove 3 has an open front end and an upwardly inclined rear end. A cutting machine can be used to form such a large number of grooves 3.

As shown in FIGS. 2 and 3, the inkjet head 100 is provided with electrodes 4 on the partition walls of each groove 3. As shown in FIGS. The electrode 4 has a two-layer structure of nickel (Ni) and gold (Au). The electrode 4 is uniformly formed in each groove 3 by, for example, a plating method. The method for forming the electrode 4 is not limited to the plating method. Besides, sputtering method, vapor deposition method, etc. can also be used.

As shown in FIG. 1, the inkjet head 100 has an extraction electrode 10 extending from the rear end of each groove 3 toward the rear upper surface of the second piezoelectric member 2. As shown in FIG. The extraction electrode 10 extends from the electrode 4 .

As shown in FIGS. 1 and 3, the inkjet head 100 includes a top plate 6 and a nozzle plate 7. The top plate 6 closes the upper part of each groove 3. The nozzle plate 7 closes the tip of each groove 3. The inkjet head 100 forms a plurality of pressure chambers 15 by each groove 3 surrounded by the top plate 6 and the nozzle plate 7. The pressure chambers 15 have a shape of, for example, a depth of 300 μm and a width of 80 μm, and are arranged in parallel at a pitch of 169 μm. However, the shape of each pressure chamber 15 is not necessarily uniform due to variations during manufacturing due to the characteristics of the cutting machine. For example, a cutting machine forms 16 pressure chambers 15 at once, and repeats this process 20 times to form 320 pressure chambers 15. At this time, if the machining blades forming the 16 pressure chambers 15 have individual differences, the shape of each pressure chamber 15 will have periodicity. Moreover, the shape of the pressure chamber 15 changes slightly due to changes in processing temperature during repeated processing 20 times. These minute changes in the pressure chamber 15 ultimately become one of the causes of minute periodic changes in print density.

The top plate 6 includes a common ink chamber 5 at the rear inside thereof. The nozzle plate 7 has nozzles 8 formed at positions facing each groove 3. The nozzle 8 communicates with the opposing groove 3, that is, with the pressure chamber 15. The nozzle 8 has a tapered shape from the pressure chamber 15 side toward the opposite ink ejection side. One set of nozzles 8 corresponds to three adjacent pressure chambers 15, and are formed at regular intervals in the height direction of the groove 3 (in the vertical direction of the plane of the paper in FIG. 2). In addition, in FIG. 2, the nozzle 8 is schematically illustrated so that the position of the nozzle 8 can be understood. The nozzle 8 can be formed using a laser processing machine, for example. When a laser processing machine forms nozzles 8 at predetermined positions, there are two methods for determining the processing position of each nozzle 8: one is to optically set the position of the laser beam, and the other is to mechanically set the workpiece, that is, the nozzle plate 7 side. There are ways to move. When the number of nozzles 8 is large, it is convenient to use the two methods together. However, when hole machining is performed using both an optical positioning method and a mechanical positioning method, periodicity occurs in the hole shape due to minute changes in the hole shape for each machining process. The periodicity of this hole shape is also one of the causes of minute periodic changes in print density.

As shown in FIG. 1, in the inkjet head 100, a printed circuit board 11 on which a conductive pattern 13 is formed is bonded to the rear upper surface of the base substrate 9. The inkjet head 100 has a drive IC 12 mounted on the printed circuit board 11 with a drive circuit described later. The drive IC 12 is connected to the conductive pattern 13. The conductive pattern 13 is connected to each extraction electrode 10 by a conductive wire 14 by wire bonding. One drive IC 12 may drive the electrodes corresponding to all the nozzles 8. However, if the number of circuits per driver IC becomes too large, several disadvantages arise. For example, the yield rate decreases as the chip size increases, wiring for output circuits becomes difficult, heat generation concentrates during driving, and it is not possible to respond to increases or decreases in the number of nozzles by increasing or decreasing the number of driver ICs. . Therefore, for example, for a head having 320 nozzles 8, four driver ICs 12 each having 80 output circuits may be used. However, in that case, the output waveform has a spatial period depending on the direction in which the nozzles 8 are arranged due to differences in wiring resistance within the driver IC 12 and the like. The strength of the periodicity changes depending on individual differences in the drive IC 12 and the like. This spatial periodicity of the output waveform is also one of the causes of minute periodic changes in print density.

Next, the principle of operation of the inkjet head 100 configured as described above will be explained using FIGS. 4 to 6.

FIG. 4 shows a state in which the potentials of the electrodes 4 disposed on the walls of the central pressure chamber 152 and the pressure chambers 151 and 153 on both sides adjacent to the pressure chamber 152 are both at the ground potential GND. ing. In this state, the partition wall 161 sandwiched between the pressure chambers 151 and 152 and the partition wall 162 sandwiched between the pressure chambers 152 and 153 are not subjected to any strain action. In this specification, the state shown in FIG. 4 is referred to as a steady state.

FIG. 5 shows a state in which a negative voltage -V is applied to the electrode 4 of the central pressure chamber 152, and the potentials of the electrodes 4 of the pressure chambers 151 and 153 on both sides remain at the ground potential GND. . In this state, an electric field of voltage V acts on each of the partition walls 161 and 162 in a direction perpendicular to the polarization direction of the piezoelectric members 1 and 2. Due to this action, each of the partition walls 161 and 162 deforms outward so as to expand the volume of the pressure chamber 152. In this specification, the state shown in FIG. 5 is referred to as an extended state.

FIG. 6 shows a state in which a positive voltage +V is applied to the electrode 4 of the central pressure chamber 152, and the potentials of the electrodes 4 of the pressure chambers 151 and 153 on both sides remain at the ground potential GND. In this state, an electric field of voltage V acts on each of the partition walls 161 and 162 in the opposite direction to that in FIG. Due to this action, each of the partition walls 161 and 162 deforms inward so as to contract the volume of the pressure chamber 152. In this specification, the state shown in FIG. 6 is referred to as a contracted state.

Now, when ejecting ink droplets from the nozzle 8 communicating with the pressure chamber 152, the inkjet head 100 first changes the pressure chamber 152 from a steady state to an expanded state as operation 1. In the expanded state, as shown in FIG. 5, the partition walls 161 and 162 on both sides of the pressure chamber 152 deform outward to expand the volume of the pressure chamber 152. Due to this deformation, the pressure within the pressure chamber 152 decreases, and ink flows into the pressure chamber 152 from the common ink chamber 5.

Next, in operation 2, the inkjet head 100 returns the pressure chamber 152 from the expanded state to the steady state. When the steady state returns, as shown in FIG. 4, the partition walls 161 and 162 on both sides of the pressure chamber 152 are restored to the steady state. Due to this restoration, the pressure within the pressure chamber 152 increases, and ink droplets are ejected from the nozzle 8 corresponding to the pressure chamber 152. Thus, the partition wall 161 that separates the pressure chambers 151 and 152 and the partition wall 162 that separates the pressure chambers 152 and 153 serve as actuators for applying pressure vibrations to the inside of the pressure chamber 152 whose walls are the partition walls 161 and 162.

Next, in operation 3, the inkjet head 100 changes the pressure chamber 152 from a steady state to a contracted state. When the pressure chamber 152 is in the contracted state, the partition walls 161 and 162 on both sides of the pressure chamber 152 deform inward to reduce the volume of the pressure chamber 152, as shown in FIG. This deformation further increases the pressure within the pressure chamber 152. Therefore, the pressure drop that occurs within the pressure chamber 152 after the ink droplet is ejected is alleviated, and the pressure vibration remaining within the pressure chamber 152 is canceled.

After that, the inkjet head 100 returns the pressure chamber 152 from the contracted state to the steady state in operation 4. When the steady state returns, as shown in FIG. 4, the partition walls 161 and 162 on both sides of the pressure chamber 152 are restored to the steady state.

Next, the configuration of the inkjet printer 200 (hereinafter abbreviated as printer 200) will be described using FIG. 7. FIG. 7 is a block diagram showing the hardware configuration of the printer 200. The printer 200 is applied to, for example, an office printer, a barcode printer, a POS printer, an industrial printer, and the like.

The printer 200 includes a CPU (Central Processing Unit) 201, a ROM (Read Only Memory) 202, a RAM (Random Access Memory) 203, an operation panel 204, a communication interface 205, a transport motor 206, a motor drive circuit 207, a pump 208, and a pump drive. A circuit 209 and a head 100 are provided. The printer 200 also includes bus lines 211 such as an address bus and a data bus. The printer 200 connects the CPU 201, ROM 202, RAM 203, operation panel 204, communication interface 205, motor drive circuit 207, pump drive circuit 209, and drive circuit 101 of the head 100 to this bus line 211, either directly or via an input/output circuit. Connect.

The CPU 201 corresponds to the central part of the computer. The CPU 201 controls each unit to realize various functions of the printer 200 according to the operating system and application programs.

The ROM 202 corresponds to the main memory portion of the computer. The ROM 202 stores the above operating system and application programs. The ROM 202 may also store data necessary for the CPU 201 to execute processing for controlling each unit.

RAM 203 corresponds to the main memory portion of the computer. The RAM 203 stores data necessary for the CPU 201 to execute processing. The RAM 203 is also used as a work area where information is appropriately rewritten by the CPU 201. The work area includes an image memory in which print data is developed.

The operation panel 204 has an operation section and a display section. The operation unit has function keys such as a power key, paper feed key, and error release key arranged thereon. The display unit can display various states of the printer 200.

The communication interface 205 receives print data from a client terminal connected via a network such as a LAN (Local Area Network). For example, when an error occurs in the printer 200, the communication interface 205 sends a signal notifying the client terminal of the error.

A motor drive circuit 207 controls driving of the transport motor 206. The conveyance motor 206 functions as a drive source for a conveyance mechanism that conveys a recording medium such as printing paper. When the transport motor 206 is driven, the transport mechanism starts transporting the recording medium. The conveyance mechanism conveys the recording medium to a printing position by the head 100. The transport mechanism discharges the printed recording medium to the outside of the printer 200 from an unillustrated discharge port.

A pump drive circuit 209 controls the drive of the pump 208. When the pump 208 is driven, ink in an ink tank (not shown) is supplied to the head 100.

The drive circuit 101 drives the channel group 102 of the head 100 based on print data. A set of the pressure chamber 15, electrode 4, and nozzle 8 that the head 100 has is called a channel. The channel group 102 is a plurality of channels included in the head 100. The drive circuit 101 includes a Push adjustment section 103 and a Draw adjustment section 104. The Push adjustment section 103 and the Draw adjustment section 104 will be described later.

The waveform of the drive signal generated by the drive circuit 101 has a first pulse, a second pulse, a third pulse, and a fourth pulse in time order. The first pulse changes the pressure chamber 15 from a steady state to an expanded state, and maintains the expanded state for a certain period of time. The second pulse returns the pressure chamber 15 from the expanded state to the steady state and maintains the steady state for a certain period of time. The second pulse is provided after the first pulse. The third pulse changes the pressure chamber 15 from a steady state to a contracted state, and maintains the contracted state for a certain period of time. The third pulse is provided after the second pulse. The fourth pulse returns the pressure chamber 15 from the contracted state to the steady state and maintains the steady state for a certain period of time. Note that the fourth pulse maintains a steady state for a certain period of time until the next drive signal is applied. The fourth pulse is provided after the third pulse.

By supplying a waveform drive signal having a first pulse, a second pulse, a third pulse, and a fourth pulse in time order to the actuator of each nozzle 8, the inkjet head 100 ejects one ink droplet from each nozzle 8. do.

By supplying a waveform drive signal having a first pulse, a second pulse, a third pulse, and a fourth pulse repeatedly in time order to the actuator of each nozzle 8, the inkjet head 100 ejects a plurality of ink droplets from each nozzle 8. Discharge continuously.

The first pulse is a pulse for drawing ink into the pressure chamber 15. Therefore, the first pulse is also referred to as a Draw pulse. The second pulse is a pulse for releasing ink from the nozzle 8. Therefore, the second pulse is also referred to as a Release pulse. The third pulse is a pulse for pushing the ink out of the nozzle 8 as one ink droplet. Therefore, the third pulse is also referred to as a Push pulse. The fourth pulse is a pulse for maintaining the pressure chamber 15 in a steady state in preparation for ejecting the next ink droplet. Therefore, for convenience, the fourth pulse is also referred to as a steady pulse.

The drive circuit 101 includes a Push adjustment section 103 that adjusts the pulse width of the third pulse, that is, the Push pulse, and a Draw adjustment section 104 that adjusts the pulse width of the first pulse, that is, the Draw pulse. The Push adjustment section 103 is a third pulse width adjustment section, and the Draw adjustment section 104 is a first pulse width adjustment section. The pulse width of the Push pulse is the time required to change the pressure chamber 15 from a steady state to a contracted state and maintain the contracted state for a certain period of time. The pulse width of the Draw pulse is the time required to change the pressure chamber 15 from a steady state to a contracted state and maintain the contracted state for a certain period of time.

In addition to adjusting the pulse width of the first pulse, that is, the Draw pulse, the drive circuit 101 adjusts the pulse width of the third pulse, that is, the Push pulse. Below, the adjustment of the pulse width of the Draw pulse will be explained first, and then the adjustment of the pulse width of the Push pulse will be explained.

Here, with reference to FIG. 8, the waveform of the drive signal supplied to the actuator of one pressure chamber 152 will be described. FIG. 8 is a diagram showing the waveform of a drive signal supplied to the actuator of one pressure chamber 152. In FIG. 8, "Draw" represents a Draw pulse, "Release" represents a Release pulse, and "Push" represents a Push pulse. Hereinafter, for convenience, the Draw pulse will be simply referred to as Draw, the Release pulse will be simply referred to as Release, and the Push pulse will be simply referred to as Push.

One waveform length is the time required to eject one ink droplet. One waveform length includes a Draw pulse width, a Release pulse width, and a Push pulse width.

FIG. 8 shows a waveform of a drive signal in which the Draw pulse width is not adjusted and a waveform of a drive signal in which the Draw pulse width is adjusted in 16 steps. By adjusting the pulse width of Draw, the ejection volume of ink droplets ejected from the nozzles 8 of the inkjet head 100 can be finely adjusted.

The waveform at the top level, that is, at the first level, is a waveform of a drive signal in which the Draw pulse width is not adjusted. Although the Draw pulse width of the first-stage waveform is not adjusted, it is described as fine adjustment level 0 for convenience. In the waveform of fine adjustment level 0, the pulse width of Draw is UL defined by the inkjet head and ink used. UL is half the time of the natural vibration period of the liquid in the pressure chamber. Further, the pulse width of Release and the pulse width of Push are both equal to UL. That is, the ratio of the pulse widths of Draw, Release, and Push is 1:1:1. For this reason, the waveform of the drive signal is indicated as a 111 waveform in FIG.

Here, first, the operation of the actuator using a drive signal of 111 waveforms with a fine adjustment level of 0 will be described with reference to FIGS. 4 to 6.

Before the 111 waveform is switched to Draw, the voltage of the drive signal is at the ground potential GND, and the ground potential GND is applied to the electrode 4 of the pressure chamber 152. As a result, the pressure chamber 152 is in a steady state (FIG. 4).

When the 111 waveform is switched to Draw, the voltage of the drive signal becomes a negative voltage -V during the Draw, and the voltage -V is applied to the electrode 4 of the pressure chamber 152. As a result, the pressure chamber 152 changes from the steady state (FIG. 4) to the expanded state (FIG. 5) (operation 1). During this time, ink is drawn into the pressure chamber 152.

When the 111 waveform is switched to Release, the voltage of the drive signal becomes the ground potential GND during Release, and the ground potential GND is applied to the electrode 4 of the pressure chamber 152. As a result, the pressure chamber 152 returns from the expanded state (FIG. 5) to the steady state (FIG. 4) (operation 2). During this time, ink is ejected from the nozzle 8.

When the 111 waveform is switched to Push, the voltage of the drive signal becomes a positive voltage +V during Push, and the voltage +V is applied to the electrode 4 of the pressure chamber 152. As a result, the pressure chamber 152 changes from a steady state (FIG. 4) to a contracted state (FIG. 6) (operation 3). As a result, the ink is separated from the nozzle 8 and is ejected as a single ink droplet.

Thereafter, the voltage of the drive signal becomes the ground potential GND, and the ground potential GND is applied to the electrode 4 of the pressure chamber 152. As a result, the pressure chamber 152 returns from the contracted state (FIG. 6) to the steady state (FIG. 4) (operation 4). This maintains the pressure chamber 15 in a steady state in preparation for ejecting the next ink droplet.

Thereafter, a plurality of identical ink droplets can be continuously ejected from the nozzle 8 by supplying a drive signal with the same waveform to the actuator. This is known as gradation printing using the multi-drop method.

In the multi-drop method, the density of printing is adjusted by the number of ink droplets. However, even if the same number of ink droplets are ejected from each nozzle 8, density unevenness may occur due to manufacturing variations. Even if the number of ink droplets is adjusted, such density unevenness is too rough and cannot be eliminated.

Therefore, it is desirable to finely adjust the ejection volume of ink droplets. It is known that the ejection volume of an ink droplet depends on the time it takes to draw the ink into the pressure chamber 152. That is, it is known that by adjusting the pulse width of Draw, the ejection volume of ink droplets ejected from each nozzle 8 can be finely adjusted.

Next, fine adjustment of the ejection volume of ink droplets by adjusting the pulse width of Draw will be explained. In FIG. 8, the waveforms in the second and subsequent stages are drive signal waveforms in which the Draw pulse width is finely adjusted in 16 steps. The 111 waveforms in the second and subsequent stages are each delayed in switching time to Draw by a predetermined fixed period of time compared to the 111 waveforms in the upper stage. In other words, in order to finely adjust the ejection volume of ink droplets ejected from each nozzle 8, each of the 111 waveforms in the second and lower stages is compared with the 111 waveform in which the pulse width of the top Draw is not adjusted. In each case, the switching time to Draw is delayed by a multiple corresponding to the fine adjustment level of a certain time width.

Therefore, the 111 waveforms in the second and subsequent rows are labeled as fine adjustment level 1 to fine adjustment level 16, respectively, depending on the level of fine adjustment of the ejection volume of ink droplets. That is, compared to the 111 waveform at fine adjustment level 0, the switching time from the steady pulse to Draw, in other words, the start time of Draw, in the 111 waveform at fine adjustment level 1, is delayed by one time by the above-mentioned constant time width. , the 111 waveform at the fine adjustment level 16 is delayed by 16 times the constant time width described above.

The fixed time width of this delay is, for example, 0.05 μs or 0.05 microseconds. However, the fixed time width of this delay is not limited to this. The fixed time width of this delay may be set arbitrarily.

Next, adjustment of the Push pulse width will be described with reference to FIG. Here, the adjustment of the Push pulse width when the Draw pulse width is at fine adjustment level 0 will be described first, and then the adjustment of the Draw pulse width after the Push pulse width adjustment will be described. FIG. 9 is a diagram showing a waveform of a drive signal in which the Push pulse width is changed in a state where the Draw pulse width is not adjusted.

In FIG. 9, the pulse width of Draw is in a state where it has not been adjusted for fine adjustment of the ejection volume of ink droplets. Therefore, as described above, the pulse width of Draw is the UL defined by the inkjet head and ink used. The time width between the median value of the Draw pulse width and the median value of the Push pulse width is equal to twice the Draw pulse width UL when no adjustment is made.

In FIG. 9, "DRP" represents the waveform of a drive signal including Draw, Release, and Push. Moreover, "P0.9", "P1.2", "P1.5", "P1.8", "P2.1", and "P2.55" respectively represent the pulse width of Push. That is, P0.9, P1.2, P1.5, P1.8, P2.1, and P2.55 have Push pulse widths of 0.9 microseconds, 1.2 microseconds, and 1.5 microseconds, respectively. It represents microseconds, 1.8 microseconds, 2.1 microseconds, and 2.55 microseconds.

Adjustment of the Push pulse width is performed by increasing or decreasing the Push pulse width equally before and after the median value of the Push pulse width. Therefore, the pulse width of Release is 2UL-(pulse width of Draw/2+pulse width of Push/2).

By changing the Push pulse width, the length of one waveform changes. The shorter the Push pulse width is, the shorter the length of one waveform is, and the longer the Push pulse width is, the longer the length of one waveform is. The maximum length of the Push pulse width is 2.55 microseconds, which is equal to UL. The waveform in this case, that is, the waveform of the P2.55 drive signal, is a 111 waveform in which the pulse widths of Draw, Release, and Push are equal.

FIG. 10 is a graph showing the relationship between the adjustment value of the Push pulse width, the fine adjustment level of Draw, and the ejection volume of ink droplets. In FIG. 10, the adjustment values of the Push pulse width are 0.9 microseconds, 1.2 microseconds, 1.5 microseconds, 1.8 microseconds, 2.1 microseconds, and 2.55 microseconds, respectively. The relationship between the fine adjustment level of Draw and the ejection volume of ink droplets in seconds is shown.

When the adjustment value of the Push pulse width was 0.9 microseconds, 1.2 microseconds, and 1.5 microseconds, the ejection volume of ink droplets increased once as the Draw fine adjustment level increased. It has decreased since then.

On the other hand, when the adjustment value of the Push pulse width is 1.8 microseconds, 2.1 microseconds, or 2.55 microseconds, the ejection volume of ink droplets increases as the fine adjustment level of Draw increases. It decreases monotonically.

Furthermore, the amount of decrease in the ejection volume of ink droplets with respect to the increase in the fine adjustment level of Draw is smaller when the adjusted value of the Push pulse width is 2.1 microseconds than when the adjusted value of the Push pulse width is 2.55 microseconds. The number of cases where the adjustment value of the Push pulse width is 1.8 microseconds is smaller than the case where the adjustment value of the Push pulse width is 2.1 microseconds.

This embodiment reduces the amount of change in the ejection volume of ink droplets by adjusting the Push pulse width without changing the number of Draw fine adjustment levels, that is, the number of Draw pulse width adjustment stages. It is an object.

By shortening the Draw pulse width, the ejection volume of ink droplets is reduced. Therefore, a suitable adjustment value for the Push pulse width is preferably one that monotonically and minutely decreases the amount of decrease in the ejection volume of ink droplets in response to an increase in the Draw fine adjustment level.

That is, in the example shown in FIG. 10, regarding the increase in the fine adjustment level of Draw, the adjustment value of the Push pulse width that increases the ejection volume of ink droplets, although initially temporarily, is 0.9 microns. seconds, 1.2 microseconds, and 1.5 microseconds are not appropriate.

On the other hand, the adjustment value of the Push pulse width, in which the ejection volume of ink droplets monotonically decreases as the Draw fine adjustment level increases, is 1.8 microseconds, 2.1 microseconds, and 2.55 microseconds. , 1.8 microseconds is the most preferable, since the amount of decrease in the ejection volume of ink droplets is the smallest.

FIG. 11 is a graph showing the amount of decrease in the ejection volume of ink droplets with respect to changes in the fine adjustment level when the adjustment value of the Push pulse width is 1.8 microseconds and 2.55 microseconds. Further, Table 1 is a table showing the ejection volume and ejection volume reduction amount of ink droplets at each fine adjustment level when the adjustment value of the Push pulse width is 1.8 microseconds and 2.55 microseconds. .

In the graph of FIG. 11 and Table 1, when the Push pulse width adjustment value is 1.8 microseconds, it is written as P1.80μs, and when it is 2.55 microseconds, it is written as P2.55μs. .

In both the graph of FIG. 11 and Table 1, the amount of decrease in ejection volume of ink droplets is greater when the adjusted value of the Push pulse width is 1.8 microseconds than when it is 2.55 microseconds. It can be seen that there are consistently fewer

When the adjustment value of the Push pulse width is 1.8 microseconds, the volume reduction step amount at fine adjustment level 14 is 0.24 pL. When the adjustment value of the Push pulse width is 2.55 microseconds, the volume reduction step amount at fine adjustment level 9 is 0.26 pL. When the adjustment value of the Push pulse width is 1.8 microseconds, the volume reduction step amount is small even if the fine adjustment level is increased.

When the adjustment value of the Push pulse width is 1.8 microseconds, if the range from fine adjustment level 1 to fine adjustment level 7 is used, the volume reduction step amount is 0.061 pL or less, and the ejection of ink droplets is Volume can be adjusted in minute units.

Next, with reference to FIG. 12, the waveform of the drive signal supplied to the actuator of one pressure chamber 152 in which the Push pulse width is adjusted to 1.8 microseconds will be described. FIG. 12 is a diagram showing a waveform of a drive signal in which the Push pulse width supplied to the actuator of one pressure chamber 152 is adjusted to 1.8 microseconds.

The meanings of "Draw", "Release", "Push", "fine adjustment level", and "1 waveform length" are as explained in relation to FIG. 8. Further, the meanings of "DRP" and "P1.8" are as explained in relation to FIG. 9.

Similar to FIG. 8, FIG. 12 shows the waveform of the drive signal with the Draw pulse width not adjusted (fine adjustment level 0) and the waveform of the drive signal with the Draw pulse width adjusted in 16 steps (fine adjustment level 1 to 16). It shows.

The operation of the actuator of the pressure chamber 152 by the drive signal having the waveform of FIG. 12 is similar to that described in connection with FIG. 8 . Further, by adjusting the pulse width of Draw, the ejection volume of ink droplets ejected from the nozzles 8 of the inkjet head 100 is finely adjusted, as described in connection with FIG. 8 .

However, the waveform of the drive signal shown in FIG. 12 and the waveform of the drive signal shown in FIG. 8 are different in the push pulse width. Specifically, the waveform of the drive signal shown in FIG. 8 is a 111 waveform in which the pulse widths of Draw, Release, and Push are equal. On the other hand, the waveform of the drive signal shown in FIG. 12 is a waveform in which the Push pulse width is adjusted to 1.8 microseconds.

Also, the waveform of the drive signal with the Push pulse width adjusted to 1.8 microseconds and the waveform of the drive signal with the Push pulse width adjusted to 2.55 microseconds, which were performed with reference to FIGS. 10 to 12. That is, the following will be easily understood from the comparative explanation with the 111 waveform.

The Draw pulse width is adjusted in the drive signal waveform with the Push pulse width adjusted to 1.8 microseconds compared to the drive signal waveform with the Push pulse width adjusted to 2.55 microseconds, that is, the 111 waveform. As a result, the ejection volume of ink droplets ejected from the nozzles 8 of the inkjet head 100 can be finely adjusted.

That is, by appropriately adjusting the Push pulse width, the inkjet head 100 according to the embodiment can eject from each nozzle 8 of the inkjet head 100 without increasing the number of adjustment stages of the Draw pulse width, that is, the number of fine adjustment levels. The ejection volume of one ink droplet can be finely adjusted.

Finally, the operation of the inkjet head 100 will be described with reference to FIG. 13. FIG. 13 is a flowchart illustrating the operation of the inkjet head 100 according to the embodiment.

First, in Act 1, the push adjustment unit 103 adjusts the push pulse width of the drive signal for the actuator of each pressure chamber 15 of the inkjet head 100. The Push pulse width is adjusted for all actuators in at least one inkjet head 100 driven by a drive signal generated by the drive circuit 101.

Next, in Act 2, the Draw adjustment unit 104 adjusts the Draw pulse width of the drive signal for the actuator of each pressure chamber 15 of the inkjet head 100. The draw pulse width is adjusted for each actuator of each pressure chamber 15 of the inkjet head 100.

Subsequently, in Act 3, the drive circuit 101 generates a waveform drive signal having a Push pulse width adjusted by the Push adjustment unit 103 and a Draw pulse width adjusted by the Draw adjustment unit 104.

Next, in Act 4, the drive circuit 101 supplies the generated drive signal to the actuator of each pressure chamber 15 of the inkjet head 100 to drive the inkjet head 100.

According to the embodiment, an inkjet head 100 is provided in which the amount of adjustment of the ejection volume of ink droplets can be finely adjusted.

Note that the present invention is not limited to the above-described embodiments, and can be variously modified at the implementation stage without departing from the gist thereof. Moreover, each embodiment may be implemented in combination as appropriate, and in that case, the combined effect can be obtained. Furthermore, the embodiments described above include various inventions, and various inventions can be extracted by combinations selected from the plurality of constituent features disclosed. For example, if a problem can be solved and an effect can be obtained even if some constituent features are deleted from all the constituent features shown in the embodiment, the configuration from which these constituent features are deleted can be extracted as an invention.

DESCRIPTION OF SYMBOLS 1... First piezoelectric member, 2... Second piezoelectric member, 3... Groove, 4... Electrode, 5... Common ink chamber, 6... Top plate, 7... Nozzle plate, 8... Nozzle, 9... Base substrate, 10 ... Extraction electrode, 11... Printed circuit board, 12... Drive IC, 13... Conductive pattern, 14... Conductive wire, 15... Pressure chamber, 51... Image memory, 100... Inkjet head, 101... Drive circuit, 102... Channel group, 103... Push adjustment section, 104... Draw adjustment section, 151, 152, 153... Pressure chamber, 161, 162... Partition wall, 200... Inkjet printer, 201... CPU, 202... ROM, 203... RAM, 204... Operation panel, 205... Communication Interface, 206...Transportation motor, 207...Motor drive circuit, 208...Pump, 209...Pump drive circuit, 211...Bus line.

Claims (5)

a pressure chamber containing ink;
a nozzle plate including a nozzle communicating with the pressure chamber;
an actuator provided corresponding to the pressure chamber and displacing the volume of the pressure chamber;
a drive circuit that generates a drive signal to drive the actuator;
Equipped with
The waveform of the drive signal includes a first pulse that changes the pressure chamber from a steady state to an expanded state and maintains the expanded state for a certain period of time, and a first pulse that changes the pressure chamber from the expanded state to a steady state and maintains the steady state for a certain period of time. a second pulse that changes the pressure chamber from a steady state to a contracted state and maintains the contracted state for a certain period of time; and a third pulse that changes the pressure chamber from the contracted state to a steady state and maintains the steady state for a certain period of time. having a fourth pulse in time order;
The drive circuit includes:
a third pulse width adjustment section that adjusts the pulse width of the third pulse for the actuator;
comprising a first pulse width adjustment section that adjusts the pulse width of the first pulse for the actuator;
inkjet head. The first pulse width adjustment unit adjusts the pulse width of the first pulse in multiple stages by delaying the start time of the first pulse by a constant value.
The inkjet head according to claim 1. The time width between the median pulse width of the first pulse when no adjustment is made and the median pulse width of the third pulse is equal to twice the pulse width of the first pulse when no adjustment is made.
The inkjet head according to claim 1 or 2. The pulse width of the third pulse is adjusted to a time width that monotonically decreases as the ejection volume of the ink droplet decreases due to the multistep decrease in the pulse width of the first pulse.
The inkjet head according to claim 3. The pulse width of the third pulse is adjusted to a time width in which the amount of decrease in the ink droplets is small with respect to the decrease in the ejection volume of the ink droplets.
The inkjet head according to claim 4.