JPH01130953A - Ink drop flight speed measuring apparatus - Google Patents

Abstract

PURPOSE:To provide an ink drop flight speed measuring apparatus that has a simple construction and a quick response speed by detecting the output from photo detector elements, finding a time needed for an ink drop to pass through the photo detector elements disposed at regular intervals and conducting a predetermined operation. CONSTITUTION:An ink drop D is designed to fly from a photo detector 11 to a photo detector 12. Due to this, the output from a comparator 16 comes earlier than that from a comparator 17: the former occurs at the time t1, while the latter occurs at the time t2. Therefore, a counter 19 counts the number of clock pulses generated from a clock generator 20 during a period of time when pulse signals are generated from the comparators 16, 17 at an interval of t2-t1 so as to find the time t2-t1 needed for the ink drop D to pass through the photo detectors 11, 12. A control circuit 21 operates the flight speed V of the ink drop D on the basis of the value counted by the counter 19 and controls a pump 22 on the basis of this flight speed V.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an ink droplet flight speed measuring device used in an inkjet printer or the like to measure the flight speed of ink droplets ejected from a nozzle.

[Prior Art] Conventionally, as this type of ink drop flight speed measurement device, there are the following devices. As shown in FIG. 9, ink droplets are continuously ejected from the nozzle 31 of the drop generator 30 at a period of 1/f, and n drops of the ejected ink droplets D are transferred to the charging electrode 31. After being charged to an appropriate amount, the ink droplet is deflected by an electric field formed by the deflection electrode 33, and is caused to fly away from the ink droplet detection means 34. At this time, the time t1 when the last ink droplet among the n droplets is charged plus 1/f is the time when the first ink droplet of the next m droplets passes the charging electrode 32. Therefore, if the time when the ink droplet detection means 34 captures the first ink droplet among m ink droplets is t2, and the distance from the charging electrode to the ink droplet detection means 34 is l, then the average flight speed of the ink droplets during this time is (2) becomes v=I/(t-(t1+1/f)).

However, this case has the following problems. That is, the charging electrode 32 that charges the ink droplets is
Since the ink droplet has a finite length, it is unclear where on the charging electrode 32 the ink droplet is charged, and the position where the ink droplet is charged changes over time. In other words, the distance l from the charged position of the ink drop to the ink drop detection means 34 is
It includes an unspecified error Δl, and the speed ■ obtained using this distance l is not an accurate value. In addition, the charging electrode 32
This method has the problem that it can only be applied to charge-controlled ink shed printers because the ink droplets are charged or uncharged and the speed of the ink droplets is detected.

Therefore, in order to solve the above problems,
As shown in Japanese Patent No. 4495, one or more first charge detection means integrally configured with a charging electrode, a gutter for collecting non-printing ink particles, and a second charge detection means connected to this gutter. a time measuring means for detecting the time until the charged particles collide with the gutter using the output of the first charge detecting means as a starting point; and an ink pressure instruction signal based on the measured time information to energize the pressurizing pump. A configuration has been proposed that includes an ink pressure adjusting means applied to the circuit. In order to accurately detect one position through which an ink droplet passes, this device is provided with a first charge detection means that detects the passage of an ink droplet integrally with a charging electrode.

[Problems to be Solved by the Invention] However, such prior art has the following problems. That is, the first charge detection means is
Since the charging electrode is integrated with the charging electrode and a high voltage is applied to the charging electrode, when the first charge detection means detects the passage of the ink droplet, it receives noise from the charging electrode. This method has a problem in that it is not possible to accurately detect the passage of ink droplets. Furthermore, the passage of an ink droplet is detected by the electric current induced in the charged ink droplet, but since the electric current generated as the ink droplet passes is small, the circuit for detecting this is complicated. There were problems in that the response speed was slow and the cost was high.

[Means for Solving the Problems] Therefore, the present invention was made to solve the problems of the above-mentioned prior art, and its purpose is to ensure that any type of inkjet printer can accurately Of course, it is possible to detect the flying speed of ink droplets,
To provide an ink droplet flying speed measuring device that is simple in configuration, quick in response speed, and inexpensive.

That is, the present invention includes a light source provided to illuminate the flight path of the ink droplets, and a plurality of photodetection elements installed to face the light source, and these photodetection elements illuminate the flight path of the ink droplets. The ink droplets are arranged at predetermined intervals along the direction, and detect the time required for the ink droplet to move between the photodetecting elements based on the output from the photodetecting elements,
The device is configured to measure the flight velocity of the ink drop.

As the light source, an LED or the like is used, for example, but the present invention is not limited to this, and of course, other light sources may be used.

As the photodetecting element, for example, a photodetector made of amorphous silicon is used, but the present invention is not limited thereto, and a PIN type silicon photodiode or the like may also be used.

The light source and the light detection element are arranged, for example, at a position corresponding to the position where the recording paper is arranged, but are not limited thereto, and may of course be arranged at other positions.

[Operation] In this invention, when an ink droplet passes through an area determined by a light source and a light detection element, a shadow of the ink droplet illuminated by the light source is formed on the light detection element. output changes. By detecting the output from this photodetection element, the passage of the ink droplet is detected,
The time required for an ink droplet to pass through photodetecting elements arranged at a predetermined interval is determined, and a predetermined calculation is performed to measure the flying speed of the ink droplet.

[Example] The present invention will be explained below based on illustrated embodiments.

FIG. 2 shows an inkjet printer to which the ink droplet flying speed measuring device according to the present invention can be applied. In the figure, reference numeral 1 denotes a drop generator that generates ink droplets, and this drop generator 1 introduces ink from an inlet hole 2 and discharges it from an outlet hole 3 by driving a pump (not shown). Ink droplets are ejected from the provided nozzles 4.4. The ink droplets ejected from the nozzles 4, 4, etc. are charged with a predetermined charge by the charging electrode 5, and then deflected by the electric field of the deflection electrode 6, and fly onto the recording paper (not shown). It is supposed to be done.

Ink droplet flying speed measuring device 7 according to an embodiment of the present invention
is disposed, for example, at a position corresponding to the position of the recording paper when the ink droplet flies straight without being charged.

Furthermore, since the speed of the ink droplet ejected from the drop generator 1 is uniformly determined by the pressure of the ink supplied to the drop generator 1 by driving the pump, the flying speed of the ink droplet is
What is necessary is to measure the flying speed of the ink droplets ejected from one nozzle 4 of the above. Therefore, one ink droplet flying speed measuring device 7 may be provided for each drop generator 1.

By the way, the ink droplet flight speed measuring device 7 according to this embodiment includes a light source provided to illuminate the flight path of the ink droplets, and a plurality of photodetecting elements installed to face the light source. These photodetecting elements are arranged at predetermined intervals along the flying direction of the ink droplets. That is, at a position corresponding to the position of the recording paper, as shown in FIG.
One light source 9 consisting of an ED is provided. Also, light 8
! First and second photodetectors 11 and 12 as photodetecting elements made of amorphous silicon are located at positions facing the light source 9 via the flight path 8 of the ink droplets.
The first and second photodetectors 11, 12 are arranged at a predetermined distance j11 along the flight path 8 of the ink droplets. Further, the length of the photodetector 11 in the ink droplet flight direction is d. In the figure, 13 indicates signal lines of photodetectors 11 and 12. Then, as shown in FIG.
．． Photodetector 11 by being formed on 12
．． 12 output changes are detected. It should be noted that it is preferable to use one light source as described above because it consumes less power, but as shown in FIG. . In such cases, photodetector 1
Since the interval 11 of 1.12 can be made large, the accuracy of detecting the flying speed of ink droplets can be improved.

FIG. 4 is a block diagram showing the control system. In the figure,
11.12 are the first and second photodetectors, 1
4.15 is the first and second photodetector 11.12
an IV converter that converts the output current from the 16.
17 is a comparator for comparing the output from the 1-V converter with the voltage from the reference voltage generator 18; 19 is for comparing the clock pulses outputted from the clock generator 20 while the outputs from the comparators 16 and 17 are respectively inputted; A counter 21 that counts the number is a control device that controls the drive of the pump 22 based on the count from the counter 19.

Based on the above configuration, the ink droplet flying speed measuring device according to this embodiment measures the flying speed of an ink droplet in the following manner. That is, the ink droplets ejected from the drop generator 1 fly straight without being charged by the charging electrode 5 and reach the ink droplet flying speed measuring device 7 . This ink dripping first blocks the light that is exposed onto the first photodetector 11 from the light m9.
As shown in FIG. 5, the output from the photodetector 11 falls sharply, then rises again and returns to the predetermined value. Thereafter, the ink dripping blocks the light exposed from the light source 9 onto the second photodetector 12, so the output from the second photodetector 12 rises rapidly as shown in FIG. After falling, it rises again and returns to the predetermined value.

The outputs from these photodetectors 11.12 are I
- The reference voltage V of the reference voltage generator 18 by the comparator 16.17 after being converted into a voltage by the V converter 14.15. compared to The reference voltage V of this reference voltage generator 18. As shown in FIG. 6, is set to a voltage slightly lower than the normal output value from the photodetectors 11, 12. Therefore, photodetector 11.12
The output of comparator 16.1 is converted into voltage.
7 to the reference voltage V. By comparing with
1 can be detected. By the way, ink drips are
In order to fly from the first photodetector 11 side to the second photodetector 12 side, the comparators 16 and 17
The output from the comparator 16 is shown in FIG.
is output earlier at time t1, and then]
7 outputs a pulse signal at time t2. Therefore, counter 19 receives time t2- from comparator 16.17.
While the pulse signals are output at intervals of t1, the number of clock pulses output from the clock generator 20 is counted, and the time 1-11 required for the ink droplet to pass between the photodetectors 11 and 12 is calculated. demand. Then, the control circuit 21 calculates the flying speed (■) of the ink droplet based on the count value from the counter 9 and the following equation, and controls the pump 22 based on this flying speed (■) to supply the ink droplets to the drop generator 1. The flying speed V of the ink droplets is kept constant by changing the ink pressure.

That is, at the above time t1, the shadow S of the ink drip is the first
is the time when the edge of photodetector 1 is reached,
Further, time t2 is the time when the shadow S of the ink drop reaches the edge of the second photodetector 1. By the way, the distance that an ink drop passes between time t 1 and t 2 is equal to j 2 + d 2 when the area of the light source is small (close to a point light source).

Also, f! , d2 can be easily calculated from the distance between the LED and the photodetector and d111 if the ink droplet is arranged so as to pass through the center of the light source and the photodetector. Therefore, the flying speed (■) of the ink droplet is given by V=(j2+d2)/(t2-tl).

In this way, since the position of the flying ink droplets is optically detected by a combination of a light source and a photodetector, the configuration of the detection circuit can be simple. Accurate detection is possible using the output, the detection part is not affected by the surrounding electric field, and there is no need to use a complicated circuit to obtain minute detection values, so the configuration of the detection circuit is unaffected by noise etc. It is simple, has a fast response speed, and can be constructed at low cost. Furthermore, since the position of the ink droplet is detected optically, the flying speed of the ink droplet can be detected regardless of whether the ink droplet is charged or not, making it suitable for inkjet printers other than charge control type. can also be applied.

FIG. 7 shows another embodiment of the ink droplet flying speed measuring device according to the present invention, and the same parts as in the previous embodiment are given the same reference numerals and explained as follows: = 14- This embodiment In this case, instead of using a photodetector made of amorphous silicon as a photodetection element, PI
An N-type silicon photodiode is used. That is, as shown in FIG. 7, the ink flight path 8 is provided with a PIN type silicon photodiode 25 having a planar rectangular shape so as to face the light source 9 via the flight path 8. The diode 25 is arranged so that its longitudinal direction is along the flying direction of the ink droplets.

Further, the photodiode 25 is covered by a shielding mask 26, and circular openings 27 and 28 are bored in the shielding mask 26 at a predetermined interval I3. The photodiode 25 can detect ink dripping as shown in FIG. 8 by receiving glare from the light source 9 through the openings 27 and 28 of the shielding mask 26.

In this way, when the photodetecting element is formed by the PIN type silicon photodiode 25, since this photodiode 25 has excellent sensitivity to infrared light, the light source 9
An LED or the like that emits infrared rays can be used as the sensor, and the passage of ink droplets can be detected without being affected by external light. In addition, silicon photodiode 2
No. 5 has good responsiveness, so the responsiveness is further improved and ink dripping can be detected with high precision. Since the other configurations and operations are the same as those of the previous embodiment, their explanations will be omitted.

[Effects of the Invention] This invention has the above configuration and operation, and it goes without saying that the flying speed of ink droplets can be accurately detected in any type of inkjet printer.
It is possible to provide an ink droplet flight speed detection device that is simple in configuration, has a fast response speed, and is inexpensive.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of essential parts showing an embodiment of an ink droplet flying speed measuring device according to the present invention, and FIG. 2 is a configuration diagram showing an inkjet printer to which the ink droplet flying speed measuring device according to the present invention is applied. Figure 3 is a perspective view showing another example of the light source;
FIG. 4 is a block diagram showing the control circuit, FIGS. 5 and 6 are graphs showing the operation of the control circuit, FIG. 7 is a perspective view showing another embodiment of the present invention, and FIG. 8 is the same side. FIG. 9 is a diagram showing the configuration of a conventional device. [Explanation of symbols] 7...Ink droplet flight speed measuring device 8...Flight path 9...Light source 11.12...Photodetector D...Ink droplet patent applicant Representative of Fuji Xerox Co., Ltd. Patent Attorney Tomohiro Nakamura (2 others) Figure 5 Figure 6 Figure 7 Figure 8 Figure 9

Claims (5)

[Claims] (1) A light source provided to illuminate the flight path of the ink droplets, and a plurality of photodetection elements installed to face the light source, and these photodetection elements are arranged along the flight direction of the ink droplets. The ink droplets are arranged at predetermined intervals, and the flying speed of the ink droplets is measured by detecting the time required for the ink droplets to travel between the photodetection elements based on the output from the photodetection elements. Ink droplet flight speed measuring device. (2) The ink droplet flying speed measuring device according to claim 1, wherein two photodetecting elements are provided for one light source. (3) The ink droplet flying speed measuring device according to claim 1, wherein the light sources are provided corresponding to the photodetecting elements. (4) The ink droplet flying speed measuring device according to any one of claims 1 to 3, wherein the photodetecting element is constituted by a photodetector made of amorphous silicon. . (5) Ink droplet flying speed according to any one of claims 1 to 3, wherein the photodetecting element is constituted by a photodetector made of a silicon PIN photodiode. measuring device.