JP4039261B2 - Natural vibration period measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a natural vibration period measuring apparatus that measures a flight speed of a droplet ejected from a liquid ejecting head and calculates a natural vibration period of a liquid in a pressure generation chamber using the obtained flight speed.
[0002]
[Prior art]
Examples of the liquid ejecting head for ejecting the liquid in the pressure generating chamber as droplets from the nozzle openings include, for example, an ink jet recording head used for an image recording apparatus such as a printer, and a color material ejecting used for manufacturing a color filter such as a liquid crystal display. There are an electrode material ejecting head used for forming electrodes such as a head, an organic EL (Electro Luminescence) display, and an FED (surface emitting display), and a bioorganic matter ejecting head used for manufacturing a biochip (biochemical element).
[0003]
In such a liquid ejecting head, there are those using a piezoelectric vibrator and those using a heating element as pressure generating means for applying pressure to the liquid in the pressure generating chamber.
For example, in a liquid ejecting head using a piezoelectric vibrator, the liquid pressure in the pressure generating chamber is changed by driving a pressure generating means such as a piezoelectric vibrator with an elastic plate that partially partitions the pressure generating chamber. A droplet is ejected from the nozzle opening by a change in pressure.
Further, in a liquid jet head using a heating element, the heating element is disposed in the pressure generating chamber, and the heating element is rapidly heated to boil the liquid and generate bubbles in the pressure generating chamber. Then, the liquid in the pressure generating chamber is pressurized by the bubbles, and droplets are ejected from the nozzle openings.
That is, all of these liquid ejecting heads eject droplets by changing the liquid pressure in the pressure generating chamber.
[0004]
In this type of liquid ejecting head, the liquid in the pressure generating chamber has a pressure vibration having a natural vibration period determined by, for example, the shape of the pressure generating chamber and the compressibility of the ink, as the pressure of the liquid is changed by the pressure generating means. Excited. In this type of liquid ejecting head, the droplet discharge timing is set based on the natural vibration period of the liquid in the pressure generating chamber, and the droplet discharge can be efficiently performed.
[0005]
By the way, this type of liquid jet head is configured by extremely fine processing and assembly. For this reason, factors that affect the natural vibration period of the liquid, such as the shape of the pressure generation chamber and the size of the nozzle opening, are likely to vary from one liquid ejecting head to another, and accordingly, the natural vibration period of the liquid in the pressure generation chamber also varies. It will occur. Accordingly, when all the liquid ejecting heads are driven with the drive signal having the same waveform shape, the droplet ejection characteristics vary depending on the liquid ejecting heads according to the variation in the natural vibration period.
Therefore, it is desirable to measure the natural vibration period excited by the liquid in the pressure generating chamber for each liquid ejecting head and set the drive signal based on the measured natural vibration period.
[0006]
As a method of measuring the natural vibration period, for example, droplets are ejected from the nozzle opening, the flight speed of the ejected liquid droplets is measured, and the natural vibration period is determined from the correlation between the obtained flight speed and the drive signal. There is a way to calculate.
[0007]
There are various apparatuses for measuring the flight speed of the droplet used for the measurement of the natural vibration period. For example, there is a system disclosed in Patent Document 1.
What is disclosed in this Patent Document 1 is provided with two sets of detection means (first and second detection means) consisting of a combination of a light emitting part and a light receiving part, and emits light emitted from the light emitting part of each detection means. The liquid droplets ejected from the liquid ejecting head (recording head) are sequentially blocked to detect the passage of the liquid droplets from the light receiving portion of each detecting means. The velocity of the droplet is derived based on the time from the passage of the first detection means to the passage of the second detection means and the distance between the detection means.
[0008]
There is also a configuration in which only one set of the detection means is provided so that the distance between the liquid jet head and the detection means can be controlled with high accuracy. In the case of this configuration, the distance between the liquid ejecting head and the detection means is set to a first distance and a second distance which are different from each other, and the passage of the ejected droplets is detected by the detection means at each set distance, and the detection is performed. The droplet velocity is derived based on the difference in time and the difference between the first distance and the second distance.
[0009]
[Patent Document 1]
Japanese Unexamined Patent Publication No. 3-71265 (page 3, FIG. 2)
[0010]
[Problems to be solved by the invention]
However, in the former case, since it is necessary to prepare two sets of detection means, there is a problem that the cost is correspondingly required.
In the latter case, a mechanism and control for moving the liquid ejecting head or the detection means with high accuracy are required, and there is a problem that the structure becomes complicated even if there is only one set of detection means.
[0011]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a natural vibration period measuring device capable of simplifying the device configuration and reducing the cost.
[0012]
[Means for Solving the Problems]
  The present invention has been proposed in order to achieve the above-described object. The liquid jet head is configured to be capable of ejecting liquid droplets from nozzle openings by causing pressure fluctuations in the liquid in the pressure generation chamber. In the natural vibration period measuring device for measuring the natural vibration period of the pressure vibration excited by the liquid,
  Speed measuring means for measuring the flight speed of droplets discharged from the nozzle opening;
  Natural vibration period calculating means for calculating the natural vibration period of the pressure vibration based on the flight speed of the droplet obtained by the speed measuring means;
An intersection distance table defining the relationship between the position of the nozzle opening and the intersection distance;With
  The speed measuring means includes
  Measurement light is emitted on a first trajectory that intersects the flight trajectory of the droplet at a first intersection, and on a second trajectory that intersects the flight trajectory of the droplet and a second intersection different from the first intersection. A light emitting part to be emitted;
  The measurement light emitted from the light-emitting unit is received, and the discharged droplets block the light on the first orbit to output a first pulse, and the droplets emit the light on the second orbit. A light receiving unit that outputs a second pulse by blocking;
  A speed calculation unit that calculates a flight speed of a droplet based on a time difference between the first pulse and the second pulse output from the light receiving unit and an intersection distance from the first intersection to the second intersection;
  While arranging the light emitting unit and the light receiving unit on one side of the flight trajectory of the droplet,The crossing distance varies depending on the nozzle opening.The light emitting unit and the light receiving unit reflect measurement light to the opposite side across the flight trajectory of the dropletOneA reflecting part is arranged, and the light on the first orbit emitted from the light emitting part is reflected on the second orbit by the reflecting part and received by the light receiving part,
  The velocity calculation unit selects an intersection distance corresponding to each nozzle opening with reference to the intersection distance table when calculating the flight speed of the droplet for each nozzle opening.It is characterized by that.
[0013]
  In the present invention, since the light emitting part, the reflecting part, and the light receiving part are configured as described above, the velocity of the droplet can be measured with a simple structure, thereby contributing to cost reduction of the apparatus. .
Also, when calculating the flight speed of droplets for each nozzle opening, the intersection distance corresponding to each nozzle opening is selected by referring to the intersection distance table, so the intersection distance corresponding to each nozzle opening can be easily selected. Furthermore, it is easy to cope with liquid jet heads having different specifications.
[0015]
Moreover, in the said structure, it is preferable that the said light emission part is comprised by the laser light source. Moreover, it is preferable that the said light-receiving part is comprised with the photodiode.
[0016]
In addition, the light emitting unit, the reflection, or the like, so that either the light on the first orbit or the light on the second orbit is closer to the liquid ejecting head is substantially parallel to the nozzle forming surface of the liquid ejecting head. And the light receiving unit can be arranged.
As a result, the light on the upper trajectory can be brought closer to the liquid ejecting head, so that even when the apparatus is installed in a narrow space, the intersection distance between the first intersection and the second intersection can be sufficiently taken, Measurement can be performed without any problem.
Note that “substantially parallel” does not necessarily mean that they are completely parallel, but also includes a range having a slight width from the parallel state.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0018]
FIG. 1 is a diagram showing a configuration of a natural vibration period measuring apparatus of the present invention. As shown in FIG. 1, the natural vibration period measuring apparatus 1 according to the present embodiment uses an ink jet recording head (hereinafter simply referred to as a recording head) 2 which is a kind of the liquid jet head of the present invention as a measurement target. The recording head 2 ejects liquid ink (a kind of liquid in the present invention) in the form of liquid droplets and records characters and images on a print recording medium such as recording paper (image recording apparatus). It is to be mounted on.
[0019]
The natural vibration period measuring apparatus 1 includes a plurality of types of driving for driving an optical system 6 including a light emitting unit 3, a reflecting unit 4, and a light receiving unit 5, and a piezoelectric vibrator 15 (see FIG. 2) in the recording head 2. It functions as a drive signal generator 7 that generates a signal COM and a speed calculator that calculates the flight speed of ink droplets (a type of droplet), and the natural vibration period Tc of ink in the pressure generation chamber 30 (see FIG. 2). The control unit 8 also functions as a natural vibration period calculating means for calculating
[0020]
Here, the structure of the recording head 2 will be described with reference to FIG. The illustrated recording head 2 includes a vibrator unit 18 in which a plurality of piezoelectric vibrators 15, a fixed plate 16, a flexible cable 17, and the like are unitized, a case 19 that can store the vibrator unit 18, The flow path unit 20 joined to the front end surface is provided.
[0021]
The case 19 is a block-shaped member made of synthetic resin in which a housing empty portion 21 for housing and fixing the vibrator unit 18 is formed. The storage empty portions 21 are empty portions that penetrate the height direction of the case 19 and are provided in the same number as the number of the vibrator units 18 to be stored. The vibrator unit 18 is housed in a state where the front end surface of the piezoelectric vibrator 15 faces the opening on the front end side of the housing space 21, and the fixing plate 16 is bonded to the inner wall surface of the case that partitions the housing space 21. ing.
[0022]
The piezoelectric vibrator 15 is a kind of pressure generating means, and is also a kind of electromechanical transducer that deforms in accordance with input electric energy. The piezoelectric vibrator 15 of the present embodiment is cut into comb teeth having a very narrow width of about 30 μm to 100 μm. The piezoelectric vibrator 15 is a laminated piezoelectric vibrator configured by alternately laminating piezoelectric bodies and internal electrodes, and is orthogonal to the electric field direction according to the potential difference between the piezoelectric bodies and the internal electrodes. Expand and contract in the direction of Each piezoelectric vibrator 15 is mounted on the fixed plate 16 in a so-called cantilever state. In other words, the base end side portion of each piezoelectric vibrator 15 is joined to the fixed plate 16, so that the free end portion protrudes outward from the edge of the fixed plate 16. And the front end surface of each piezoelectric vibrator 15 is joined to the island part 23 of the flow path unit 20, respectively. In addition, the flexible cable 17 is electrically connected to each piezoelectric vibrator 15 on the surface of the base end side portion that is opposite to the fixed plate 16.
[0023]
In the channel unit 20, the nozzle plate 26 is disposed on one surface of the channel forming substrate 25 with the channel forming substrate 25 interposed therebetween, and the elastic plate 27 is disposed on the other surface opposite to the nozzle plate 26. It is configured by arranging and bonding.
[0024]
The nozzle plate 26 is a thin plate made of stainless steel in which a plurality of nozzle openings 28-1 to 28-n are opened in a row at a pitch corresponding to the dot formation density, and is a kind of nozzle formation surface of the present invention. is there. In the present embodiment, for example, 96 nozzle openings 28 are opened at a pitch of 180 dpi, and these nozzle openings 28 constitute a nozzle row.
[0025]
The flow path forming substrate 25 is formed with a plurality of empty portions serving as pressure generation chambers 30 and groove portions serving as ink supply ports 31 at the same pitch as the nozzle openings 28 of the nozzle plate 26, and empty spaces serving as common ink chambers 32. It is the plate-shaped member which formed the part. The pressure generation chamber 30 is an elongated chamber in a direction orthogonal to the direction in which the nozzle openings 28 are arranged (nozzle row direction). The ink supply port 31 is a groove having a narrow channel width that communicates between the common ink chamber 32 and the pressure generation chamber 30. Further, a nozzle communication port 33 for communicating the nozzle opening 28 and the pressure generation chamber 30 is provided at a position farthest from the common ink chamber 32 in the pressure generation chamber 30 while penetrating in the plate thickness direction. Yes.
[0026]
The elastic plate 27 has a double structure in which an elastic film 36 such as a resin film is laminated on the surface of the support plate 35. The elastic plate 27 is provided with a diaphragm portion 37 that seals one opening surface of the pressure generating chamber 30 and a compliance portion 38 that seals one opening surface of the common ink chamber 32. Yes. The diaphragm portion 37 is manufactured by annularly etching the portion of the support plate 35 corresponding to the pressure generating chamber 30, and an island where the elastic portion 37 ′ including only the elastic film 36 and the piezoelectric vibrator 15 are joined. Part 23 is provided. In addition, the compliance unit 38 removes the support plate 35 corresponding to the common ink chamber 32 by etching and uses only the elastic film 36.
[0027]
In the recording head 2 configured as described above, the piezoelectric vibrator 15 expands and contracts in the longitudinal direction of the element based on the drive signal COM to change the volume of the pressure generating chamber 30. As a result, a pressure fluctuation is generated in the ink in the pressure generating chamber 30, and an ink droplet is ejected from the nozzle opening 28 using the pressure fluctuation.
[0028]
Here, it is considered that the flying speed of the ejected ink droplets changes in accordance with the state of the meniscus (the free surface of the ink exposed at the nozzle opening 28) at the ejection timing, specifically, the meniscus tension. It is done. For example, in a state where the meniscus is drawn largely toward the pressure generating chamber 30 side, the tension of the meniscus acting on the ejection direction side is large, and thus the flight speed increases when ink droplets are ejected at this timing. This is the same reason that the arrow's flying speed is faster when the bowstring is pulled more than when it is pulled smaller. Therefore, conversely, when the meniscus is greatly raised to the discharge side, the meniscus tension acts on the pressure generating chamber 30 side, and thus, when ink droplets are discharged at this timing, the flight speed decreases.
[0029]
Since the meniscus state changes in the natural vibration period Tc excited by the ink in the pressure generation chamber 30, the change period of the flying speed of the ink droplet corresponds to the natural vibration period Tc. In the present embodiment, ink droplets are ejected while the ejection timing is shifted little by little, the flying speed of the ink droplets at each timing is measured, and the period of change in the flying speed is used to calculate the inside of the pressure generating chamber 30. The natural vibration period Tc of the ink is calculated. Details of this point will be described later.
[0030]
A drive signal COM for driving the piezoelectric vibrator 15 of the recording head 2 to eject ink droplets is generated from the drive signal generator 7. As shown in FIG. 3, the drive signal generator 7 is configured to generate a drive signal COM having a waveform shape determined by the controller 8. The drive signal generator 7 generates a drive signal COM using the latch signal LAT from the controller 8 as a trigger and supplies the drive signal COM to the piezoelectric vibrator 15 of the recording head 2.
[0031]
The drive signal COM includes an expansion element s1 that increases the potential with a constant gradient from the minimum potential VL to the maximum potential VP, an expansion hold element s2 that maintains the maximum potential VP for a certain period of time, and a constant from the maximum potential VP to the minimum potential VL. The discharge element s3 lowers the potential with a gradient. When the piezoelectric vibrator 15 is driven by the drive signal COM, ink droplets are ejected from the nozzle openings 28.
[0032]
The duration of the expansion element s1, that is, the supply time to the piezoelectric vibrator 15 is set to a time during which the ink in the pressure generation chamber 30 can excite the pressure vibration of the natural vibration period Tc. For the purpose of efficiently exciting the pressure vibration, the supply time is preferably set to be equal to or less than the design value of the natural vibration period Tc, and more preferably set to be 1/2 or less of the design value. preferable.
[0033]
In addition, the drive signal generator 7 is configured to generate a plurality of types of drive signals COM. The duration of the expansion hold element s2, that is, the supply time of the expansion hold element s2 to the piezoelectric vibrator 15 is set to be slightly different for each drive signal COM. That is, the ejection timing is varied by changing the duration of the expansion hold element s2 for each drive signal COM. The duration of the expansion hold element s2 is set within a time range in which two maximum values (see FIG. 5) can be specified for the flying speed of the ink droplet to be measured.
[0034]
The drive signal COM is not limited to that shown in FIG. For example, a wave shape as shown in FIG. 4 may be used. The drive signal COM in FIG. 4 includes an expansion element ss1 that increases the potential with a constant gradient from the intermediate potential VM to the maximum potential VP, an expansion hold element ss2 that maintains the maximum potential VP for a certain time, and a minimum potential from the maximum potential VP. A discharge element ss3 that lowers the potential with a constant steep slope to VL, a contraction hold element ss4 that maintains this minimum potential VL for a certain period of time, and a damping element ss5 that increases the potential with a constant gradient from the lowest potential VL to the intermediate potential Vm It consists of and.
Even in this case, the drive signal generator 7 outputs a plurality of types of drive signals COM set so that the duration of the expansion hold element ss2 is slightly different.
[0035]
The flying speed of the ink droplets ejected from the recording head 2 is measured by a speed measuring means constituted by the optical system 6 and the control unit 8. In the present embodiment, the optical system 6 is a light emitting unit 3 that functions as a laser light source that emits measurement light (laser light), a reflecting unit 4 that reflects this light, and light reflected by the reflecting unit 4. The light receiving unit 5 is configured to receive light, and is characterized in that each unit is arranged so that the light from the light emitting unit 3 is reflected by the reflecting unit 4 and received by the light receiving unit 5. Details of the optical system 6 will be described below.
[0036]
In the optical system 6, the light emitting part 3 is constituted by a semiconductor laser, the light receiving part 5 is constituted by a photodiode, and the reflecting part 4 is constituted by a reflecting mirror. In the present embodiment, the flight trajectories L1... Ln of ink droplets ejected from the light emitting unit 3 and the light receiving unit 5 and the nozzle openings 28-1 to 28-n (hereinafter collectively referred to as ink droplet flight regions as appropriate). , And between the reflecting portion 4 and the ink droplet flying region, shielding plates 40a and 40b are respectively arranged so that the mist-like ink droplets (ink mist) are difficult to adhere to each portion. It has become. Each of the shielding plates 40a, 40b is provided with openings 41a, 41b, 41c so as not to hinder the passage of light.
[0037]
The light emitting unit 3 includes a first trajectory O1 that intersects the flight trajectory L (L1... Ln) at a first intersection P1 (P1-1... P1-n), and a first trajectory different from the first intersection P1. Measurement light is emitted to the second orbit O2 intersecting at two intersections P2 (P2-1... P2-n). And the position and direction of each part are set so that the light on the 1st track | orbit O1 inject | emitted from the light emission part 3 may be reflected on the 2nd track | orbit O2 by the reflection part 4, and the light-receiving part 5 light-receives.
[0038]
The light emitting unit 3 and the light receiving unit 5 are arranged on one side (left side in FIG. 1) with respect to the ink droplet flying region, and the reflecting unit 4 sandwiches the ink droplet flying region with the light emitting unit 3 and the light receiving unit 5. It is arranged on the opposite side (right side in FIG. 1). Since the light emitting unit 3 and the light receiving unit 5 are arranged on the same side in this way, the wiring is compared with the conventional configuration in which the light emitting unit and the light receiving unit are arranged on opposite sides of the ink droplet flight region. Is easy to handle.
[0039]
The light receiving unit 5 receives measurement light emitted from the light emitting unit 3 (light on the second orbit O2), and ink droplets ejected from the nozzle openings 28 block light on the orbits O1 and O2. When light reception is interrupted by this, a pulse waveform is output in response to this. Specifically, as shown in FIG. 3, an ink droplet is ejected by supplying a drive signal COM to the piezoelectric vibrator 15, and this ink droplet blocks light on the second trajectory O2 at the second intersection P2. Then, the light receiving unit 5 outputs the second pulse PL2. Thereafter, when the ink droplet that has flew a distance x (intersection distance) x between the intersections P2 and P1 blocks light on the first trajectory O1 at the first intersection P1, the light receiving unit 5 outputs the first pulse PL1. ing.
[0040]
By configuring the optical system 6 as described above, it becomes possible to measure the velocity of the droplets with a simpler configuration compared to the conventional one, thereby contributing to cost reduction of the apparatus.
[0041]
Next, the control unit 8 will be described. The control unit 8 is electrically connected to the drive signal generation unit 7, the light emitting unit 3, and the light receiving unit 5, and is configured to control each unit. The control unit 8 includes a CPU 10 that performs various controls and calculations, a ROM 11 that stores control routines for various data processing, a RAM 12 that stores various data, and a non-volatile information storage unit 13 (for example, an EEPROM). ) Etc.
The CPU 10 controls each part of the natural vibration period measuring device 1 based on the operation program stored in the ROM 11. The CPU 10 detects the ink droplets ejected from the nozzle openings 28 based on the pulses PL1 and PL2 output from the light receiving unit 5 when the ink droplets ejected from the nozzle openings 28 block the light on the tracks O1 and O2. Calculate the flight speed. Specifically, using the time Δt from the rising timing of the second pulse PL2 to the rising timing of the first pulse PL1 and the intersection distance x from the second intersection P2 to the first intersection P1, the calculation formula v = x The liquid drop velocity v is calculated from / Δt.
The method for obtaining the time Δt is not limited to the one based on the rising timings of the two pulses PL1 and PL2, as described above, but may be obtained based on other timings such as the falling timings of the two pulses PL1 and PL2. Also good.
[0042]
Here, the distance between the 1st track | orbit O1 and the 2nd track | orbit O2 becomes short gradually as it approaches the reflection part 4 side from the light emission part 3 and the light-receiving part 5 side. Accordingly, the intersection distances x1... Xn between the first intersections P1-1... P1-n and the second intersections P2-1. For this reason, the control unit 8 stores an intersection distance table that defines the relationship between the position of each nozzle opening 28 and the intersection distance x in the information storage unit 13. Then, when calculating the flight speed v of the ink droplet, the CPU 10 refers to this intersection distance table and selects the intersection distance x corresponding to each nozzle opening 28.
Thereby, the crossing distance x for each nozzle opening 28 can be easily selected, and it is possible to easily cope with the case where the specification of the head to be measured is changed.
[0043]
Further, the CPU 10, that is, the control unit 8 determines the natural vibration of the ink in the pressure generation chamber 30 based on the relationship between the calculated flying speed of the ink droplet and the duration of the expansion hold element s 2 (ss 2) of the drive signal COM. The period Tc is calculated.
[0044]
Hereinafter, an operation for measuring the natural vibration period Tc will be described.
First, the flying speed of ink droplets is measured. The control unit 8 controls the light emitting unit 3 to emit measurement light onto the ink droplet flight region, that is, the first trajectory O1. The light on the first orbit O <b> 1 emitted from the light emitting unit 3 is reflected on the second orbit O <b> 2 by the reflecting unit 4 and received by the light receiving unit 5. During the measurement period, light for measurement is always emitted from the light emitting unit 3.
[0045]
In this state, the drive signal generation unit 7 sends the drive signal COM to the piezoelectric vibrator 15 of the recording head 2 based on the control from the control unit 8. The piezoelectric vibrator 15 expands and contracts based on the drive signal COM, and ejects ink droplets from the nozzle openings 28.
The ejected ink droplets fly on the flight trajectory L, and first block the light on the second trajectory O2 at the second intersection P2. As a result, the light reception by the light receiving unit 5 is interrupted, and the second pulse PL2 is output from the light receiving unit 5. Thereafter, the ink droplets fly by a distance x from the second intersection P2 and block the light on the first trajectory O1 at the first intersection P1. In response to this, the light receiving unit 5 outputs the first pulse PL1. As a result, the control unit 8 obtains two pulses PL1 and PL2 as shown in FIG.
[0046]
Then, the control unit 8 (CPU 10), based on the time difference Δt between the rising timings of the two pulses PL1 and PL2 and the intersection distance x corresponding to each nozzle opening 28 in the intersection distance table, the ink droplet flight speed v ( = X / Δt).
[0047]
In this way, the flying speed of the ink droplet is measured for each drive signal COM having a different duration of the expansion hold element s2. Then, the control unit 8 creates a plot graph with the duration of the expansion hold element s2 as the horizontal axis and the flight speed as the vertical axis based on the measurement result. FIG. 5 shows an example of this plot graph.
[0048]
The control unit 8 specifies two maximum values for the flying speed v of the ink droplet based on the created plot graph. In the example of FIG. 5, E1 and E2 correspond to these two maximum values. The difference between the duration T1 corresponding to the maximum value E1 and the duration T2 corresponding to the maximum value E2 is output as the natural vibration period Tc of the pressure vibration excited by the ink in the pressure generating chamber 30.
[0049]
FIG. 6 is a diagram showing a configuration of the natural vibration period measuring device 1 in the second embodiment of the present invention. In the second embodiment, the layout of each part of the optical system 6 is different from that of the first embodiment. That is, either the light on the first orbit O1 or the light on the second orbit O2, which is closer to the recording head 2, that is, the light on the second orbit O2 is substantially parallel to the nozzle plate 26 in the example of FIG. Thus, the light emitting unit 3, the reflecting unit 4, and the light receiving unit 5 are arranged. Other configurations are the same as those in the first embodiment. In the present embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.
According to the second embodiment, since the upper light (light on the second orbit O2) can be brought closer to the recording head 2, even when the optical system 6 is installed in a narrow space, it is between the intersections P1 and P2. The distance x can be taken sufficiently and measurement can be performed without any trouble.
[0050]
By the way, the present invention is not limited to the above embodiment, and various modifications can be made based on the description of the scope of claims.
Regarding the light emitting unit 3 and the light receiving unit 5, in the above embodiment, the light receiving unit 5 is arranged closer to the recording head 2 (upper side), and the light emitting unit 3 is arranged farther from the recording head 2 (lower side). However, it is also possible to arrange them upside down, that is, the light emitting unit 3 is arranged closer to the recording head 2 and the light receiving unit 5 is arranged farther from the recording head 2.
[0051]
Although the example which comprised the reflecting part 4 by the reflective mirror in the said embodiment was shown, it can replace with a reflective mirror and can also be comprised by a prism. Thereby, the light on the first orbit O1 and the light on the second orbit O2 can be aligned in parallel with each other, and the intersection distance x between the intersections P1 and P2 is set to the same value for all the nozzle openings 28. I can do it. Therefore, it is possible to measure the flying speed of the ink droplet with higher accuracy, and it becomes unnecessary to refer to the crossing distance table when calculating the flying speed, and the control becomes easy.
[0052]
In the above, an ink jet recording head has been described as an example of a liquid jet head to be measured. However, the natural vibration period measuring device of the present invention can use another liquid jet head as a measurement target. For example, a color material ejecting head used for manufacturing a color filter such as a liquid crystal display, an electrode material ejecting head used for forming an electrode such as an organic EL (Electro Luminescence) display, FED (surface emitting display), and a biochip It can also be applied to bio-organic matter ejecting heads used in the production of
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of a natural vibration period measuring apparatus.
FIG. 2 is a partial enlarged cross-sectional view of a recording head.
FIG. 3 is a diagram illustrating a drive signal COM output from a drive signal generation unit and a pulse waveform output from a light receiving unit.
FIG. 4 is a diagram illustrating another example of a drive signal COM output from a drive signal generation unit.
FIG. 5 is a diagram showing an example of a plot graph showing the relationship between the duration of the expansion hold element of the drive signal COM and the flying speed of the ink droplet.
FIG. 6 is a diagram illustrating a configuration of a natural vibration period measuring device according to a second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Natural vibration period measuring apparatus, 2 ... Recording head, 3 ... Light emission part, 4 ... Reflection part, 5 ... Light reception part, 6 ... Optical system, 7 ... Drive signal generation part, 8 ... Control part, 10 ... CPU, 11 ... ROM, 12 ... RAM, 13 ... information storage unit, 15 ... piezoelectric vibrator, 16 ... fixed plate, 17 ... flexible cable, 18 ... vibrator unit, 19 ... case, 20 ... flow path unit, 21 ... housing space , 23 ... island part, 25 ... flow path forming substrate, 26 ... nozzle plate, 27 ... elastic plate, 28 ... nozzle opening, 30 ... pressure generating chamber, 31 ... ink supply port, 32 ... common ink chamber, 33 ... nozzle communication Mouth, 35 ... support plate, 36 ... elastic membrane, 37 ... diaphragm part, 38 ... compliance part, 40 ... shielding plate, 41 ... opening

Claims (4)

Natural vibration period measurement for measuring the natural vibration period of the pressure vibration excited by the liquid in the pressure generating chamber of the liquid ejecting head configured to cause the liquid fluctuation in the pressure generating chamber to cause the liquid droplet to be discharged from the nozzle opening. In the device
Speed measuring means for measuring the flight speed of droplets discharged from the nozzle opening;
Natural vibration period calculating means for calculating the natural vibration period of the pressure vibration based on the flight speed of the droplet obtained by the speed measuring means;
An intersection distance table that defines the relationship between the position of the nozzle opening and the intersection distance ;
The speed measuring means includes
Measurement light is emitted on a first trajectory that intersects the flight trajectory of the droplet at a first intersection, and on a second trajectory that intersects the flight trajectory of the droplet and a second intersection different from the first intersection. A light emitting part to be emitted;
The measurement light emitted from the light-emitting unit is received, and the discharged droplets block the light on the first orbit to output a first pulse, and the droplets emit the light on the second orbit. A light receiving unit that outputs a second pulse by blocking;
A speed calculation unit that calculates a flight speed of a droplet based on a time difference between the first pulse and the second pulse output from the light receiving unit and an intersection distance from the first intersection to the second intersection;
The light emitting unit and the light receiving unit are arranged on one side of the flight trajectory of the droplet, and the light emitting unit and the light receiving unit are measured on the opposite side of the droplet flight trajectory so that the crossing distance varies depending on the nozzle opening. One reflecting portion that reflects the light for use is arranged, and the light on the first orbit emitted from the light emitting portion is reflected on the second orbit by the reflecting portion and received by the light receiving portion,
The velocity calculation unit selects a crossing distance corresponding to each nozzle opening by referring to the crossing distance table when calculating a flight speed of a droplet for each nozzle opening. . The natural vibration period measuring device according to claim 1, wherein the light emitting unit is configured by a laser light source. The light receiving portion is the natural vibration period measuring device according to claim 1 or claim 2, characterized in that it is constituted by a photodiode. The light emitting unit, the reflecting unit, and the light on the first orbit, or the light on the second orbit, the one closer to the liquid ejecting head is substantially parallel to the nozzle forming surface of the liquid ejecting head, And the natural light period measuring device according to any one of claims 1 to 3 , wherein said light receiving part is arranged.

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