JP2014133359A - Printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent erroneous action due to noise overlapped on a flexible cable 30.SOLUTION: In a printer 1 moving a print head 20 performing printing in a predetermined direction to print on a recorded material, a flexible cable 30 transmits a plurality of control signals from a control substrate 10 to the print head 20 with an arc-shaped loop P. Low pass filters are electrically inserted in a transmission line of the control signals transmitted by the flexible cable 30, and the cut-off frequency of the low pass filter is set according to the level and frequency of noise overlapped on the flexible cable by contact discharge.

Description

  The present invention relates to a printing apparatus.

2. Description of the Related Art An inkjet printer that uses a piezoelectric element (for example, a piezo element) is known as an ink jet printer that prints an image or a document on a recording material by discharging droplets such as ink. Piezoelectric elements are provided corresponding to each of a plurality of nozzles in the print head, and each of them is used as a drive signal as the print head moves in the main scanning direction and the recording material is conveyed in the sub scanning direction. Therefore, by driving, a predetermined amount of liquid droplets are ejected from the nozzle at a predetermined timing.
In order to appropriately drive the piezoelectric element provided in the print head that reciprocates along the main scanning direction, a drive signal is supplied to the print head via a flexible cable from a control board attached to the casing of the printing apparatus. The configuration is general (see Patent Document 1). More specifically, the longitudinal direction of the conductor arrangement surface in the flexible cable, that is, the extending direction of the conductor coincides with the moving direction of the print head, and the conductor arrangement surface and the planar recording material are flexible so as to face each other. A configuration in which cables are arranged is common. With this configuration, it is possible to realize a printer in which the height of the housing is suppressed.

JP 2007-118436 A

By the way, when adopting a configuration in which a flexible cable is arranged as described in Patent Document 1 for a printer that prints on a large recording material such as A3 or A2, the size of the recording material is reduced. The operating area of the print head is proportionally increased, and the flexible cable must be lengthened accordingly. For this reason, the flexible cable may be bent and deformed due to the movement of the print head and the weight of the flexible cable, and may be slid (slid) while being in contact with each part of the printing apparatus to be charged. . When the flexible cable is in contact with a conductive member such as metal while being charged, noise is generated by contact discharge, which is superimposed on a signal transmitted by the flexible cable, which may cause malfunction in the printing apparatus.
Accordingly, one of the objects of some aspects of the present invention is to provide a printing apparatus that prevents noise from being superimposed on a flexible cable and suppresses malfunctions.

In order to achieve one of the above objects, a printing apparatus according to one aspect of the present invention moves a print head that performs printing in a main scanning direction, and moves a recording material relative to the print head in a sub scanning direction. A flexible cable for transferring a plurality of control signals from a control board to the print head, wherein at least a part of a flat surface faces the recording surface of the recording material A low-pass filter having a predetermined cutoff frequency and electrically inserted in a transmission path of at least one control signal among the plurality of control signals.
According to the printing apparatus according to the above aspect, even if noise is superimposed on the charged flexible cable due to contact discharge with another member, the noise is attenuated by the low-pass filter, so that malfunction due to the noise is prevented. can do. The cut-off frequency of this low-pass filter (frequency at which the attenuation is −3 dB) is set so that the noise can be sufficiently absorbed according to the level and frequency of noise superimposed on the flexible cable by contact discharge. Is done.

  In the printing apparatus according to the above aspect, the print head is provided corresponding to each of the plurality of nozzles, the nozzles, ejects droplets from the nozzles, and at least a driving pulse for driving the driving elements. A switch circuit that selects one of a plurality of drive signals each having a different waveform and supplies the selected drive signal to the drive element, wherein the one signal defines the supply timing of the drive pulse The structure which is a signal to do is preferable. According to this configuration, it is possible to prevent malfunction caused by noise mixed in the signal supply path that defines the supply timing of the drive pulse.

FIG. 3 is a perspective view illustrating a main part of a peripheral configuration of a print head in the printing apparatus. FIG. 3 is a block diagram illustrating an electrical configuration of the printing apparatus. It is a figure which shows the electrical structure in a print head. It is a figure which shows an example of a low-pass filter. It is a figure which shows an example of the decoding content in a decoder. 6 is a timing chart for explaining the operation of the print head. It is a figure which shows an example with the voltage waveform applied to a piezoelectric element. It is a figure which shows an example of the frequency characteristic of a low-pass filter. It is a figure which shows the relationship between the charging voltage and noise in a flexible cable. It is a figure which shows the position of a flexible cable, a deformation | transformation, etc. It is a figure which shows the position of a flexible cable, a deformation | transformation, etc. It is a figure for demonstrating the noise superimposed on a flexible cable.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
The printing apparatus according to the embodiment forms a group of ink dots on a recording material such as paper by ejecting liquid ink, whereby an image (characters, graphics, etc.) corresponding to image data supplied from a host computer. An ink jet printer. In the present application, the surface of the recording material on which the ink adheres and the image is formed is called a recording surface.

FIG. 1 is a perspective view illustrating a main part of a peripheral configuration of a print head in the printing apparatus 1.
In this figure, a control board 10 is fixed to a frame (not shown in the figure) of the printing apparatus 1 and generates various control signals for printing. The control signal generated by the control board 10 is transmitted to the print head 20 through the connector 12, the flexible cable 30 and the connector 22 in this order.
The print head 20 is mounted on a carriage 24 that can move in the X direction (main scanning direction) orthogonal to the Z direction, which is the conveyance direction (sub-scanning direction) of the recording material, and is integrated with the carriage 24. Then, it reciprocates along the X direction while keeping the distance from the surface of the recording material substantially constant. The print head 20 has a plurality of nozzles. Each of the nozzles ejects an amount of ink corresponding to the control signal transmitted through the flexible cable 30 toward the recording material at a timing defined by the control signal. In FIG. 1, the recording material is omitted in order to avoid the complexity of the configuration. In the present embodiment, the Y direction is the gravity direction.

  The flexible cable 30 is formed by arranging a plurality of conductors in parallel so as to form surfaces and covering them with an amount of an insulating material to form a band, and as the name suggests, the flexible cable 30 has flexibility. In the present application, a surface formed by arranging a plurality of conductors in parallel is called a flat surface. The flexible cable 30 is pulled out along the main scanning direction from the left side of the print head 20 in FIG. In other words, the flexible cable 30 is drawn out so that the extending direction of the conductor coincides with the main scanning direction, in other words, so as to intersect the sub scanning direction in plan view. Further, the flexible cable 30 is pulled out from the left side from the print head 20 and then reversed to the right side by an arc-shaped loop P to be connected to the control board 10. Therefore, the flexible cable 30 transmits the control signal from the control board 10 to the print head 20 while changing the size and position of the loop P as the print head 20 moves.

  An ink tube 40 is connected to each of the plurality of nozzles in the print head 20 so that, for example, ink for four colors is supplied from an ink tank provided on the housing side. Specifically, the print head 20 is pulled out in the direction opposite to the recording material arrangement side, and bent at the bent portion Q to the right side opposite to the drawing-out side of the flexible cable 30 and along the main scanning direction. In addition to being pulled out along substantially parallel, it is inverted to the left side by an arc-shaped loop R and connected to an ink tank (not shown) at the connection portion S. In the ink tube 40, a portion from the connection portion of the print head 20 to the bent portion Q is formed of a hard member, and the other portion is formed of a soft member. For this reason, the ink tube 40 supplies ink from the ink tank to the print head 20 while changing the size and position of the loop R as the print head 20 moves, similarly to the flexible cable 30.

FIG. 2 is a block diagram illustrating an electrical configuration of the printing apparatus 1.
As shown in this figure, the control board 10 is provided with a main control unit 120 and a drive signal generation unit 140.
Based on the image data acquired from the host computer, the main control unit 120 executes arithmetic processing for printing, such as image development processing, color conversion processing, ink color separation processing, and halftone processing, to perform printing. Clock signal SCK, print data SI, latch signal LAT, and change signal CH are generated and output to the print head 20. In the following description, the clock signal SCK, the print data SI, the latch signal LAT, and the change signal CH may be simply referred to as control signals without being distinguished. Details of these control signals will be described later.
The drive signal generator 140 generates drive signals COM-A and COM-B having different waveforms according to control by the main controller 120 and outputs them to the print head 20.

The print head 20 is provided with an LPF (Low Pass Filter) group 90, a selection control unit 200, a selection unit 250, and a plurality of piezoelectric elements (piezo elements) 50.
Control signals transmitted from the control board 10 via the flexible cable 30 are respectively supplied to the selection control unit 200 via the LPF group 90. The selection control unit 200 corresponds to each of the piezoelectric elements 50 with a selection signal that defines whether to select the drive signal COM-A or COM-B in accordance with the control signal supplied via the LPF group 90. And output.
The selection unit 250 selects the drive signals COM-A and COM-B according to the selection signals from the selection control unit 200 and supplies them to the piezoelectric elements 50. In other words, each of the piezoelectric elements 50 is configured to be driven by the drive signals COM-A and COM-B selected by the selection unit 250.

  Note that the contents of each arithmetic processing for printing executed on the control board 10 are well-known matters in the technical field of the printing apparatus, and a description thereof will be omitted. Further, the printing apparatus 1 includes a mechanism such as a carriage motor for moving the carriage on which the print head 20 is mounted in the main scanning direction, and a mechanism such as a conveyance motor for conveying the recording material in the sub-scanning direction. Further, the control board 10 includes a configuration for supplying a drive signal to these motors. However, since it is a well-known matter, the description thereof is omitted.

FIG. 3 is a block diagram showing the configuration of the print head 20.
As shown in this figure, the LPF group 90 includes LPFs 90a to 90d. Among these, the LPF 90 a cuts the high frequency component of the clock signal SCK transmitted through the flexible cable 30 and supplies the cut signal to the selection control unit 200. Similarly, the LPFs 90b, 90c, 90d. The high frequency components of the print data SI, the latch signal LAT, and the change signal CH are cut and supplied to the selection control unit 200, respectively.

  Note that each of the LPFs 90a to 90d is specifically an integration circuit including a resistance element 92 and a capacitance element 94 as shown in FIG. It is set to 5 MHz.

  Returning to FIG. 3 again, the selection control unit 200 includes a set of a shift register (S / R) 210, a latch circuit 220, and a decoder 230 corresponding to each of the piezoelectric elements 50 (nozzles).

Here, the print data SI defines the amount of ink ejected from one nozzle when forming one dot of an image. In the present embodiment, in order to express four gradations of non-recording, small dots, medium dots, and large dots, the print data SI is composed of two bits, an upper bit (MSB) and a lower bit (LSB). The print data SI is serially supplied from the main control unit 120 in synchronism with the main scanning of the print head 20 for each nozzle in synchronization with the clock signal SCK.
The shift register 210 is a configuration for temporarily holding the print data SI supplied serially for 2 bits corresponding to the nozzle. Specifically, the shift registers 210 corresponding to the number of stages corresponding to the piezoelectric elements 50 (nozzles) are cascade-connected to each other, and the serially supplied print data SI is sequentially transferred to the subsequent stage according to the clock signal SCK. ing.
Therefore, the print data SI is supplied to the selection control unit 200 in synchronization with the clock signal SCK, while the clock signal SCK is supplied when the print data SI corresponding to each of all the shift registers 210 is sequentially transferred. When stopped, each of the shift registers 210 maintains a state in which the print data SI corresponding to itself is held.
When the number of piezoelectric elements 50 is m (m is a plurality), in order to distinguish the shift register 210, the first, second,..., M stages in order from the upstream side to which the print data SI is supplied. It is written.

The latch circuit 220 latches the print data SI held by the shift register 210 at the rising edge of the latch signal LAT via the LPF 90c.
The decoder 230 decodes the 2-bit print data SI latched by the latch circuit 220 and selects it for each of the periods T1 and T2 defined by the latch signal LAT via the LPF 90c and the change signal CH via the LPF 90d. Signals Sa and Sb are output. Note that the decoding contents in the decoder 230 will be described later.

The selection unit 250 has m pairs of transmission gates 252a and 252b corresponding to each of the piezoelectric elements 50 (nozzles). The transmission gate 252a is turned on when the selection signal Sa is at the H level and turned off when the selection signal Sa is at the L level. Similarly, transmission gate 252b is turned on when selection signal Sb is at the H level and turned off when the selection signal Sb is at the L level.
A drive signal COM-A is supplied to one end of the transmission gate 252a, a drive signal COM-B is supplied to one end of the transmission gate 252b, and the other ends of the transmission gates 252a and 252b are commonly connected to one end of the piezoelectric element 50. Has been.
The other end of the piezoelectric element 50 is grounded to the ground G.

  Before describing operations of the selection control unit 200 and the selection unit 250 configured as described above, waveforms of the drive signals COM-A and COM-B generated by the drive signal generation unit 140 will be described.

FIG. 6 is a timing chart for explaining the waveforms of the drive signals COM-A and COM-B and the operation in the print head 20.
As shown in the figure, the drive signal COM-A includes the drive pulse Adp1 arranged in the period T1 from the rise of the latch signal LAT to the rise of the change signal CH in the print cycle Ta, and the print cycle Ta. It has a waveform in which the drive pulse Adp2 arranged in the period T2 from when the change signal CH rises to when the next latch signal LAT rises is continued. In the present embodiment, the drive pulses Adp1 and Adp2 have substantially the same waveform. If each of the drive pulses Adp1 and Adp2 is supplied to the piezoelectric element 50, a predetermined amount, specifically an intermediate amount, is supplied from the nozzles of the print head 20. The waveform is such that each ink is ejected.

The drive signal COM-B has a waveform obtained by continuing the drive pulse Bdp1 arranged in the period T1 and the drive pulse Bdp2 arranged in the period T2. In the present embodiment, the drive pulses Bdp1 and Bdp2 have different waveforms. Among these, the drive pulse Bdp1 has a waveform for preventing the increase in the viscosity of the ink by slightly vibrating the ink in the vicinity of the nozzle opening. For this reason, even if the drive pulse Bdp1 is supplied to the piezoelectric element 50, an ink droplet is not ejected from the nozzle. The drive pulse Bdp2 has a waveform different from that of the drive pulse Adp1 (Adp2). If the drive pulse Bdp2 is supplied to the piezoelectric element 50, the waveform is such that an amount of ink smaller than the predetermined amount is ejected from the nozzle.
Note that the level at the start timing and the level at the end timing of the drive pulses Adp1, Adp2, Bdp1, and Bdp2 are all common to Vc.

On the other hand, 2-bit print data SI for each nozzle is supplied serially from the main control unit 120 in synchronization with the clock signal SCK, and sequentially transferred in the shift register 210 corresponding to the nozzle. Then, the supply of the clock signal SCK is stopped and the print data SI corresponding to the nozzles is held in each of the shift registers 210. The print data SI is supplied in the order corresponding to the last m stages,..., 2 stages, and 1 stage nozzles in the shift register 210.
When the latch signal LAT rises at the start timing of the printing period Ta, each of the latch circuits 220 latches the print data SI held in the shift register 210 all at once. 3 and 6, L1, L2,..., Lm indicate the print data SI latched by the latch circuit 220 corresponding to the first, second,.

The decoder 230 defines and outputs the logic levels of the selection signals Sa and Sb as shown in FIG. 5 in each of the period T1 and the period T2 of the printing period Ta according to the 2 bits of the latched print data SI. To do.
In this figure, the latched 2-bit print data SI is expressed as (MSB, LSB). Although the logic levels of the selection signals Sa and Sb are not particularly shown, the level shifter is level-shifted to a higher amplitude logic than the clock signal SCK, the print data SI, the latch signal LAT, and the change signal CH.

  FIG. 7 is a diagram illustrating a voltage waveform supplied to the piezoelectric element 50 with respect to the print data SI. When the print data SI is (1, 1), since the selection signals Sa and Sb are at the H and L levels in the period T1, referring to FIG. 5, the transmission gate 252a is turned on and the transmission gate 252b is turned off. For this reason, the drive pulse Adp1 of the drive signal COM-A is selected. On the other hand, when the print data SI is (1, 1), the selection signals Sa and Sb are at the H and L levels even during the period T2, so the drive pulse Adp2 of the drive signal COM-A is selected. As described above, the drive pulse Adp1 is selected in the period T1, and the drive pulse Adp2 is selected in the period T2 and supplied to the piezoelectric element 50. Therefore, a medium amount of ink corresponding to each from the nozzle is divided into two times. Discharged. For this reason, the respective inks land and merge on the recording material, and as a result, large dots are formed.

  When the latched 2-bit print data SI is (0, 1), the selection signals Sa and Sb are at the H and L levels in the period T1, so that the drive pulse Adp1 of the drive signal COM-A is selected. During the period T2, the drive pulse Bdp2 of the drive signal COM-B is selected because it is at the L and H levels. In this way, the drive pulse Adp1 is selected in the period T1, and the drive pulse Bdp2 is selected in the period T2 and supplied to the piezoelectric element 50, so that the medium and small amounts of ink corresponding to each from the nozzles are 2 It is discharged in several times. For this reason, the respective inks land and merge on the recording material, and as a result, medium dots are formed.

  When the latched 2-bit print data SI is (1, 0), the selection signals Sa and Sb are at the L and L levels in the period T1, so that the drive pulse Adp1 and the drive signal COM- of the drive signal COM-A While none of the B drive pulses Bdp1 is selected, the drive pulses Bdp2 of the drive signal COM-B are selected because they are at the L and H levels in the period T2. For this reason, since a small amount of ink is ejected only once in the period T1, small dots are formed on the recording material as a result.

  If the print data SI is (0, 0), the selection signals Sa and Sb are L and H levels in the period T1, so that the drive pulse Bdp1 of the drive signal COM-B is selected, while the selection signals Sa and Sb are L in the period T1. Therefore, neither the drive pulse Adp2 of the drive signal COM-A nor the drive pulse Bdp2 of the drive signal COM-B is selected. For this reason, the ink in the vicinity of the opening of the nozzle only slightly vibrates in the period T1, and the ink is not ejected. As a result, no dots are formed on the recording material, that is, no recording is performed.

6 and 7, the selection of the drive signals COM-A and COM-B is performed simultaneously in the first stage, the second stage,.
When none of the drive pulses is selected, one end of the piezoelectric element 50 is in a high impedance state that is not electrically connected to any part. However, since the level Vc before the unselected state is maintained by the capacitive property of the piezoelectric element 50 itself, even if none of the drive pulses is selected, the potential at one end of the piezoelectric element 50 does not become indefinite. .

Next, the positional relationship of the flexible cable 30 accompanying the movement of the print head 20 will be described.
FIGS. 10 and 11 are side views of the main part showing the positional relationship of the flexible cable 30. FIG. In these drawings, the peripheral configuration of the print head 20 in the printing apparatus 1 is shown as observed in the Z direction in FIG.

As shown in these drawings, the control board 10 is fixed to a frame 80 having a substantially horizontal surface (XZ plane) in the housing, for example. Further, the recording material 5 is conveyed in the Z direction (the back side of the drawing) so that it is directly under the print head 20 and substantially parallel to the XZ plane. On the other hand, the nozzles in the print head 20 eject ink along the Y direction, which is the direction of gravity. Accordingly, the upper surface side of the recording material 5 is the recording surface 6.
On the other hand, a top plate 70 having a surface facing the frame 80 via the flexible cable 30 is provided above the print head 20. Further, on the left side of the print head 20 and inside the loop P, a plate-like support member 60 for suppressing the slack of the flexible cable 30 is provided on the housing with the plate surface horizontal.
In the present embodiment, the support member 60, the top plate 70, and the frame 80 are all made of a conductive metal plate such as iron. In addition, the ink tube 40 is omitted in this figure.

10 or 11, (a) shows the left end position in the movement range of the print head 20, and (b) shows the right end position. The present embodiment assumes a large printing apparatus 1 in which the length of a recording material in the main scanning direction is 1 meter or more. For this reason, the moving distance of the print head 20 exceeds 1 meter.
As the print head 20 moves, the position of the loop P moves or the shape of the loop P changes in the flexible cable 30. Further, with the movement of the print head 20, a part of the flat surface 31 of the flexible cable 30 is in a positional relationship facing the recording surface 6 of the planar recording material 5.
Here, when the repulsive force when the flexible cable 30 is deformed is small or relatively heavy, the flexible cable 30 hangs downward in the gravitational direction as shown by a broken line in FIG. . For this reason, the flexible cable 30 contacts the support member 60 and the frame 80 when the print head 20 is stationary.
On the other hand, when the repulsive force when the flexible cable 30 is deformed is large and relatively light, the flexible cable 30 is supported by the support member 60 and the frame when the print head 20 is stationary as shown by the broken line in FIG. 80 may contact the top plate 70 as well.

  10 and 11 merely show an example of the state of the flexible cable 30. FIG. Actually, the bending mode differs depending on the material, thickness, number of wires, wire length, weight, and the like of the flexible cable 30, and only the support member 60 or the frame 80 may be in contact.

  When the print head 20 moves, the flexible cable 30 contacts or peels without sliding against the frame 80 and slides with respect to the support member 60 and the top plate 70. Therefore, as the print head 20 moves, the flexible cable 30 is likely to be charged in the amount of insulating material that covers the surface of the conductor.

When the flexible cable 30 is charged as shown in (a) of FIG. 12 and contacts the conductive support member 60, the top plate 70 or the frame 80 as shown in (b) of FIG. Charge transfer occurs (contact discharge). Due to this contact discharge, noise is superimposed on the signal transmitted by the flexible cable 30 as shown in FIG.
The level of noise due to this contact discharge will be discussed below in comparison with air discharge.

FIG. 9 is a diagram illustrating the relationship between the charging voltage and the noise level superimposed on the transmission path of the flexible cable 30.
As shown in this figure, the charging voltage due to air discharge such as static electricity is in the range of approximately 5 kV to 7 kv, and the noise level superimposed on the flexible cable 30 having a transmission path length exceeding 1 meter is approximately 30 V to The noise generation frequency is also in the GHz band. Therefore, if only countermeasures against static electricity are taken, it is sufficient to set the cut-off frequency of the low-pass filter at about 7 GHz as shown in FIG.

However, the voltage generated by the contact discharge in question in this case is in the range of about 2 kV to 4 kv, and the noise level superimposed on the flexible cable 30 is not only in the range of about 2 V to 4 V, but also the generation of noise. The frequency is also about 100 MHz, which is lower than the air discharge. For this reason, the low-pass filter corresponding only to the countermeasure against static electricity has a problem in that noise due to contact discharge cannot be cut off, causing the print head 20 to malfunction and significantly reducing the printing quality.
Specifically, although the clock signal SCK, which is a logic signal, the print data SI, the latch signal LAT, and the change signal CH are output from the control board 10 at the L level, noise due to contact discharge is superimposed. If the threshold of the logical level is exceeded, the selection control unit 200 will be erroneously recognized as being at the H level. If the logic signal that should have been at the L level is recognized as being at the H level, ink is not ejected at the designated timing, and conversely, ink is ejected at a timing different from the designated timing. This causes the quality of printing to be significantly reduced, such as when an amount of ink different from the amount is ejected.

Therefore, in the present embodiment, the cutoff frequencies of the LPFs 90a to 90d are set so as to cut off noise having a frequency of about 2 to 4 V and a frequency of about 100 MHz generated by contact discharge in the flexible cable 30 that is a logic signal transmission path. In FIG. 8, it is set to 5 MHz as indicated by (a). If the cut-off frequency is 5 MHz, the attenuation amount at 100 MHz is about −26 dB (1/400), so that the noise can be sufficiently absorbed.
Therefore, according to the present embodiment, noise due to contact discharge is blocked, so that malfunction of the print head 20 can be prevented, and deterioration in printing quality can be suppressed.

  In order to prevent malfunction caused by noise superimposed on the flexible cable 30, it is conceivable to transmit the control signal in a differential (reverse phase), but the differential transmission is dedicated on the transmission side and the reception side. In addition to the need for the above circuit, a high cost is required such that two transmission lines are required for one control signal.

  Further, if a control signal other than the clock signal SCK, the print data SI, the latch signal LAT, and the change signal CH is used as a logic signal, a low-pass filter may be provided in the transmission path of the control signal.

DESCRIPTION OF SYMBOLS 1 ... Printing apparatus, 5 ... Recording material, 10 ... Control board, 20 ... Print head, 30 ... Flexible cable, 31 ... Flat surface, 50 ... Piezoelectric element, 60 ... Support member, 70 ... Top plate, 80 ... Frame, 90a to 90f ... LPF, 200 ... selection control unit, 250 ... selection unit.

Claims (2)

In a printing apparatus for printing on a recording material by moving a print head for printing in the main scanning direction and moving the recording material relative to the print head in the sub-scanning direction,
A flexible cable for transmitting a plurality of control signals from a control board to the print head, at least a part of the flat surface facing the recording surface of the recording material;
A low-pass filter having a predetermined cutoff frequency and electrically inserted in a transmission path of at least one control signal among the plurality of control signals;
A printing apparatus comprising: The printing apparatus according to claim 1,
The print head is
Multiple nozzles,
A piezoelectric element that is provided corresponding to each of the nozzles and ejects ink from the nozzle;
A selection unit that includes at least one drive pulse for driving the piezoelectric element, and selects any one of a plurality of drive signals each having a different waveform and supplies the selected one to the piezoelectric element;
Have
The printing apparatus according to claim 1, wherein the one control signal is a signal that defines a supply timing of the drive pulse.

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