JPH11334100A - Ink jet printing system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine the run-out of ink in an ink jet pen efficiently with high reliability. SOLUTION: Ink tanks 20, 22, 24, 26 are arranged to be conducted with an ink jet print head while having a wall and a large number of particles are placed therein and filled with ink. The large number of particles exhibit first reflectance when it is saturated with ink and second reflectance when it is not saturated with ink. In order to provide the particles with an optical access, a transparent window is provided in the wall of the ink tank 20, 22, 24, 26. A photosensor is coupled optically with the ink tanks 20, 22, 24, 26 and delivers detection signals of first and second reflectances.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an ink jet printing system for detecting an ink level by utilizing a change in optical characteristics of a capillary ink storage member, and a method for detecting an ink level in an ink jet.

[0002]

2. Description of the Related Art Conventionally, an ink jet printer forms small letters and images by ejecting small droplets of ink from a print head onto a print medium. The printhead is mounted on an inkjet pen that is held in position relative to the media in the inkjet printer. The ink is
The printhead must be supplied with an appropriate "back pressure" (ie, less than ambient atmospheric pressure) to prevent ink from dripping from the printhead when the pen is not operating.

In order to contain this ink at a suitable back pressure, a resilient elastomeric bladder, porous foam
Various mechanisms have been used, including foams, internal accumulators, bubble generators, and spring-biased flexible bags. When the pen runs out of ink, it may be necessary to automatically detect an empty state of the pen. For example, the system is designed to be automatically refilled by a flexible follower or automatic refill. The pen can also damage the printhead if run when the ink is empty.

Various mechanisms have been proposed for detecting the ink level of an ink-jet pen. U.S. Patent No. 5,751,300, assigned to the assignee,
(Cowger et al.) Disclose an ink level sensor used in a driven tube printer. Here, a pair of electrical leads are embedded in the foam, and the current between the leads indicates the ink level. Using ink levels,
Operate a valve that controls the amount of ink that can supply ink to the pen. Also, U.S. Pat. No. 5,079,570 (Mohr et al.), Assigned to the assignee, discloses disposable printing using tubules and other components formed on the ink tank of an ink jet print cartridge. A dual fluid indicator for a cartridge is disclosed. The main ink tank of the print cartridge is filled with a porous substance such as polyurethane foam.

This patent also describes an alternative ink having components such as glass beads, felt pen fibers, capillaries, and rolled-up plastic film (columns 15-18). When the ink level drops to a certain level, the capillary member draws ink from the indicator, thereby dually indicating that the ink has dropped to the selected level. This low ink indicator can be read by a human or a machine.
No. 5,406,3, assigned to the assignee of the present invention.
No. 15 (Allen et al.) Discloses an example using an optical sensor to detect temperature and ink levels based on changes in the reflectivity of the phase change material near or within the pen body housing. .

[0006]

As described above, the above-mentioned prior art is well known for its ink level detecting system, but many of them are inexpensive for automatically detecting the ink level of the ink-jet pen. A highly reliable system is required.

SUMMARY OF THE INVENTION The present invention solves such problems in the prior art, and an ink jet printing system and an ink level in an ink jet capable of efficiently (reliably) determining (deciding) an out-of-ink state of an ink-jet pen. The purpose is to provide a detection method.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an ink jet print head having an ink jet print head and an ink tank having a wall and configured to be in flowable connection with the print head. Provide system. A large amount of particles are put in the ink tank, and ink is put between the particles. The particles have a first reflectivity when saturated with ink and a second reflectivity when not saturated with ink. On one of the walls of the ink tank,
A transparent window is provided that provides optical access to the particles. A photoelectric sensor is optically coupled to the ink tank, and the photoelectric sensor is configured to detect the first reflectance and the second reflectance and output a detection result. In a preferred embodiment, an ink reservoir is communicatively coupled to the ink tank and configured to add ink to the supply container.

[0009] The present invention also provides a method of supplying ink to an ink jet print head. This method
(A) filling the glass beads with ink for circulating the print head and supplying ink to the print head, (b) optically monitoring the reflectance of the glass beads, and (c). A step of optically detecting a change in the reflectance of the glass beads when the ink in the glass beads is consumed, and generating an electronic signal indicating the change in the reflectance; and (d) applying the ink to the glass beads based on the signal. Refilling.

Thus, the present invention provides a system and method for efficiently and reliably determining the out-of-ink condition of an ink-jet pen.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the ink jet printing system and the ink level detecting method in the ink jet according to the present invention will be described in detail with reference to the drawings.
FIG. 1 is an external perspective view showing an inkjet printing system of the present invention. In FIG. 1, the inkjet printing system includes a chassis 12, a carriage rod 14, a carriage 16, an ink cartridge storage 18, an ink tank 20, 22, 24, 26, and pens 28, 30, 32, 34.
(Shown by a dotted line), and a printer 10 having a control device 36.

A paper feed tray 38 and a paper discharge tray 40 are attached to the chassis 12. Control device 36
Is communicably connected to a host printing device (not shown) such as a personal computer, and receives an image and / or text data signal for printing from the host printing device. Further, the control device 36 includes the pens 28, 30, 3
Together with 2 and 34, they are communicably connected to a medium transport motor and a carriage transport motor (not shown). The carriage 16 is mounted on the carriage rod 14 so as to scan the print medium back and forth.

The control device 36 operates the carriage transport motor at an appropriate time to drive the carriage 16 in the direction of the carriage feed axis X, and the pens 28, 30, 32 over the scanning width of the print medium on the sheet at that time. , 34 are scanned. As the pens 28, 30, 32, and 34 scan across the print medium, the print head is designated by the controller 36 to fire droplets of ink in the desired dot matrix pattern across the page. You. After scanning is complete, the controller 36 sends a signal to the media transport motor to incrementally transport the sheet in the media transport direction Y, which causes the pen to begin scanning another path. In this way, a plurality of adjacent horizontal paths are printed, and printing of a desired image on a page is completed.

The ink is stored in the ink tanks 20, 22, 2
With the tubes 46 from 4, 26, the pens 28, 30, 32,
34. When any one of the ink tanks runs out of ink, this tank is replaced with a new ink tank. In some cases, one of the pens 28, 30, 32, 34 may deteriorate. In such a case, the deteriorated pen can be replaced by a user or a skilled technician.

FIG. 2 shows an outer housing 50, an ink jet print head 52, a mesh filter 54, and an inner wall 56.
And a pen 28 made of glass beads 58.
The outer wall of the outer housing 50 is made of transparent and high-density polyethylene or polypropylene. As shown, the inner wall 56 forms a small auxiliary cavity 66. Pen 2
8 has an input port 68 for receiving ink and a vent 70. Most of the pen body is filled with glass beads 58 as shown. The input port 68
It is connected so as to circulate with one of the tubes 46 (see FIG. 1) connected to the ink tank 20.

The mesh filter 54 is made of glass beads 5
8 is prevented from entering the spare chamber 72 just above the inkjet print head 52. Also, the mesh filter 54
Prevents foreign matter and air from entering the print head. After passing through the glass beads 58, the mesh filter 54
Is blocked by the mesh filter 54. The mesh filter 54 is preferably made of a stainless steel wire mesh and has pores of about 20 microns. The portion near the filter screen is glass beads filled with ink. Beads that are wet but only partially saturated are outside of this area. Partially saturated beads contain an air / ink boundary that creates a negative pressure. The boundary between partially saturated beads and saturated beads approaches the filter screen each time ink is ejected from the printhead. When the mesh filter 54 gets wet, the filter has a large "bubble pressure" that does not allow the bubbles to pass through. The ink preferably passes through the screen where the screen contacts the saturated beads.

The glass beads 58 have an average diameter of about 0.0
12 inches (about 0.3 mm) and about 0.01
0 to about 0.016 inch (about 0.25 to 0.41 mm)
Range. In the presence of a representative inkjet ink, these beads create a back pressure of about 1.5 inches (38.1 mm) of water. The size of the beads can be adjusted to match the required back pressure of the printhead.

As will be discussed later, the flow of ink from the tube into pen 28 is pressurized by a pump mechanism (not shown). The flow of ink to the pen 28 first enters a small chamber 60 from which it is absorbed by glass beads 58. It has been found that the flow of ink to the bottom of the pen does not increase the pressure of the ink provided to the inkjet printhead 52 than if the ink flows above the glass beads 58.

FIG. 3 shows pens 28, 30, 32, 34 connected to carriage 16. Ink level detector 60A is positioned to detect changes in reflectivity from glass beads 58 in each pen. The ink level detector 60 </ b> A includes two blue (481 nm) light emitting diodes (LEDs) 62 from Hewlett-Packard and an optical sensor 64. The optical sensor 64 is a Texas Instruments TLS 250 comprising a photodiode and an impedance conversion amplifier. Optical sensor 64 is electronically coupled to controller 36. The carriage 16 causes each pen 28, 30, 32 to scan so that the LED 62 is illuminated by the pen and the optical sensor 64 passes through a position where the reflectance of the glass beads can be detected. Optical sensor 64 and LED 62 are mounted near the right side of printer 10 as shown in FIG. 1, but are not shown.

An important feature of the glass beads selected is that the reflectivity changes depending on whether there is ink between the beads. When the glass beads are not saturated with ink, the glass beads are white in appearance and look like snow.
When saturated with ink, it takes on the appearance of the ink. When the beads are no longer saturated, the color of the beads becomes a very light color of the ink, and the reflectance increases. This change can be quite easily visually detected. As will be discussed below with respect to FIGS. 6-9, for each of the cyan, magenta, yellow, and black ink colors, there is a detectable change in reflectance of the glass beads from saturated to unsaturated. Tests have shown that this change in reflectivity can be optically detected by a photoelectric sensor.

Another important property of glass beads is that
The ability to maintain ink at an appropriate back pressure. The ability to provide capillary pressure by the action of capillary action is generated by the interaction of three physical compositions: liquid, solid and gas.
For this purpose, the liquid is an inkjet ink, the solid is a capillary member and the gas is air. Capillary pressure is
It depends on the surface tension of the liquid, the cohesion of the liquid molecules with each other, and the adhesion between the solid and liquid molecules forming the capillary element. An important way to measure the molecular interaction between a liquid and a solid with capillary pressure action is the contact angle θ when the liquid is on a solid.

The high-density polyethylene wall material has a larger contact angle with ink than glass beads. This means that polyethylene is less wettable with ink than glass beads. This is important for the function of the sensor that detects the out of ink. If the window is prone to wetting, the window may remain covered with a thin film of ink, thereby masking the reflectance of the glass beads (and thus the saturation of the ink).

When selecting the capillary member of the pen, it is desirable to consider not only the stationary differential capillary head, but also the dynamic resistance to ink flow. When refilling in the middle of a print job, it is important to refill the pen quickly. Generally, in order to reduce the resistance to the flow of a fluid, an extremely wet porous medium is required. A material having a very small contact angle and being very wet will reduce the resistance to flow at two points. First, the void size for a given capillary head can be increased, and in some cases, the permeability can be increased. The manner in which a capillary member, such as a capillary or porous material, lifts a liquid above a given height with respect to gravity is referred to as a "capillary head." Generally, a capillary head can be represented by the following equation (1).

H = (σ / ρg) (Lp / Ap) cos θ (1)

Where Lp = wet edge of void containing meniscus Ap = wet area of void occupied by meniscus σ = surface tension of liquid ρ = density of liquid θ = contact angle of liquid on capillary member g = universal gravitational constant

When the ratio Lp / Ap is reduced, the void size may be reduced and the permeability may be increased.
To achieve the same capillary head, a material that is not easily wetted (co
The material having a small term of sθ) has a lower Lp than a material which is easily wetted.
The ratio of / Ap should be large, the void size should be correspondingly small, and the permeability should be low. If the pore size is small and the permeability is low, the pressure loss cannot be tolerated when the ink flow rate is large, and the ink flow rate may be insufficient.

A second approach is to reduce the resistance to ink flow with extremely wet materials by reducing the critical pressure required to start moving the ink meniscus of the porous medium. It has been found that the meniscus of the porous medium tends to exhibit hysteresis that impedes the movement of the air-liquid interface until a critical pressure is reached. This phenomenon can be observed with raindrops on the windshield. The magnitude of this resistance increases as the contact angle increases. That is, for a given liquid (eg, ink), the resistance to meniscus movement is greater for a porous medium that is less wettable.

Glass beads are good porous media for inks. Glass has a small contact angle with liquids such as water, alcohol, carbon tetrachloride, xylene, glycerin, and acetic acid. The low advancing liquid contact angle is aided by the clean, smooth surface that is possible with glass beads. Testing has shown a more consistent capillary pressure between the suction and drainage than the blowing agent.

FIG. 4 is a schematic view showing a printing system according to the present invention, in which a pen 28, an optical sensor 60B, a pressurized ink tank 20, a valve 80, and a pipe 46 in the ink jet are used.
have. A personal computer 82 is communicatively coupled to control device 36. Optical sensor 60B
However, when a low ink level is detected, a corresponding signal is sent to the controller 36. Based on this signal, controller 36 opens valve 80 and pressurized ink is supplied to pen 28.

Controller 36 opens valve 80 and fills pen 28 with a preselected amount of ink. This amount is selected so that the pen can be refilled from a low state where a low ink level is detected to a full state. The amount required to refill the pen is approximately the same each time, since the lower level detection is performed at approximately the same lower level. The printing system can then print again until another low ink level is detected. When a low ink level is detected, controller 36 opens valve 80 again and refills pen 28. This process continues until the ink reservoir is empty. When the ink tank 20 is empty, the ink tank 20 is discarded and replaced with a new one.

FIG. 5 is an embodiment of an intermittent replenishment or "take-a-sip" of the printing system of the present invention. Although only one pen and ink tank are shown here, it should be understood that this consideration represents a plurality of pens, as discussed with reference to FIGS. The printing system includes a pen 90, an optical sensor 92, a control device 9
4. Carriage motor 96, valve 98 and ink tank 1
00.

Control unit 94 is also communicatively coupled to personal computer 102. Pen 90
Has transparent walls and is filled with glass beads.
The optical sensor 92 optically detects the ink level of the pen 90 by changing the reflectance of the glass beads. When a low ink level is detected, controller 94 sends a signal to carriage motor 96 to position pen 90 in fluid contact with ink tank 100. When the pen 90 is in this position, the controller 94 moves the valve 98 to fill the pen 90 from the ink tank 100.

FIGS. 6 to 9 show pens 28, 30, 32 and 34 for cyan, magenta, yellow and black, respectively.
7 is a graph of a voltage display from the optical sensor 60B as a function of ink consumption from the sensor. Here, ink consumption is shown in milliliter (ml), and sensor voltage is shown in millivolt (mV). As can be seen from these graphs, as ink flows through the pen, there is a finite change in sensor voltage. When the beads are completely saturated with ink and the ink tank is full, the voltage sensor level for all colors is about 350-400 millivolts. This low level represents the first reflectivity of the glass beads. As the ink runs out of the pen, the saturation of the beads decreases and the reflectivity increases, thereby increasing the voltage level of the sensor.

The controller can also be programmed to select a particular voltage level for an out-of-ink condition.
For example, 500 millivolts can be selected as the out-of-ink state for all colors. Alternatively, each color may have its own unique threshold level. For example, given the voltage output levels shown in FIGS. 6-9, it is possible to select a level of 1000 millivolts for cyan and 500 millivolts for other colors. This higher voltage level is the second voltage level of the glass beads.
Represents the reflectance.

The embodiments of the present invention will be summarized below. 1. An ink jet print head, an ink tank having a wall, the ink being connected to the ink jet print head such that ink can flow therethrough, a large number of particles arranged in the ink tank, and an ink put between the large number of particles. Wherein the plurality of particles have a first reflectivity when saturated with the ink and a second reflectivity when not saturated with the ink, and provide optical access to the particles. A transparent window formed in one of the walls of the ink tank to provide a, optically coupled to the ink tank;
An inkjet printing system comprising: a photoelectric sensor that outputs a detection signal that detects the first reflectance and the second reflectance. 2. The inkjet printing system of claim 1, further comprising an ink reservoir communicatively coupled to the ink tank and for supplying additional ink to the supply container based on the signal. 3. A flexible tube that communicatively couples the ink reservoir to the ink tank; and a flexible tube that is communicatively coupled to the ink reservoir and communicably connected to the optical sensor, wherein the optical sensor has the second reflectance. 3. The ink-jet printing system of claim 2, further comprising: a valve that opens upon detection of ink to allow ink to flow from the ink reservoir through the flexible tube to the ink tank. 4. The inkjet printing system according to claim 2, wherein the reservoir is connected to the ink tank so as to be able to intermittently flow when the optical detector detects the second reflectance. 5. The inkjet printing system according to claim 1, wherein the particles are beads. 6. The ink-jet printing system according to claim 1, wherein the particles are glass beads. 7. An ink-jet pen having a printer chassis, an ink tank having a print head and a wall, mechanically connected to the chassis, and positioning the ink-jet print head near a print medium; and A first bead when the glass beads are saturated with the ink, and a first reflectivity when the glass beads are saturated with the ink. A transparent window formed in one of the walls of the ink tank and providing optical access to the glass beads, and having a second reflectivity, and optically coupled to the ink tank; An inkjet printing system comprising: a photoelectric sensor that outputs a detection result signal that detects the first reflectance and the second reflectance. 8. 8. The inkjet printing system of claim 7, further comprising an ink reservoir communicatively coupled to the ink tank and for supplying additional ink to the supply container. 9. A flexible tube that communicatively couples the ink reservoir with the ink tank; a pliable tube that is communicatively coupled to the ink reservoir; communicably connected to the optical sensor; wherein the optical sensor detects the second reflectance A valve that opens when the ink flows to allow ink to flow from the ink reservoir through the flexible tube to the ink tank;
An inkjet printing system comprising: 10. 9. The ink jet printing system according to claim 8, wherein when the optical sensor detects the second reflectance, the ink jet printing system intermittently connects the reservoir to the ink tank. 11. A method for detecting an ink level in an ink jet when supplying ink to an ink jet print head, comprising filling the ink into a glass bead group communicably connected to the print head, and optically measuring the reflectance of the glass bead group. Monitoring and optically detecting a change in the reflectance of the glass beads when the ink in the glass beads is exhausted, and generating a detection signal indicating the change in the reflectance, Refilling the glass bead group with ink based on the signal. 12. Wherein the filling is performed from a reservoir by a tube communicatively coupled to the glass beads.
A method for detecting an ink level in an inkjet according to the above. 13. 12. The ink level detecting method according to claim 11, wherein the step of filling the ink is performed from a reservoir intermittently communicable with the glass beads.

[0036]

As is apparent from the above description, according to the ink jet printing system and the ink level detecting method in the ink jet according to the present invention, the ink-out state of the ink-jet pen can be determined efficiently and with high reliability. .

[Brief description of the drawings]

FIG. 1 is an external perspective view showing a configuration (a driven tube) in an embodiment of an inkjet printing system and an ink level detection method in an inkjet according to the present invention.

FIG. 2 is a cross-sectional view illustrating a configuration of a pen and an optical sensor according to the embodiment.

FIG. 3 is a perspective view showing a configuration of a pen, a carriage, and an optical sensor assembly in the embodiment.

FIG. 4 is a block diagram illustrating an electrical configuration of the inkjet printing system of FIG. 1;

FIG. 5 is a block diagram illustrating another electrical configuration of the inkjet printing system of FIG. 1;

FIG. 6 is a diagram (graph) showing a relationship between ink consumption of cyan ink and an ink level sensor voltage in the embodiment.

FIG. 7 is a diagram (graph) showing a relationship between ink consumption of magenta ink and an ink level sensor voltage in the embodiment.
It is.

FIG. 8 is a diagram (graph) showing a relationship between ink consumption of yellow ink and an ink level sensor voltage in the embodiment.

FIG. 9 is a graph (graph) showing a relationship between ink consumption of black ink and an ink level sensor voltage in the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Printer 16 Carriage 18 Ink cartridge accommodating part 20, 22, 24, 26, 100 Ink tank 28, 30, 32, 34, 90 Pen 36, 94 Control device 38 Paper feed tray 40 Paper discharge tray 46 Tube 50 Outer housing 52 Ink jet Print head 54 Mesh filter 58 Glass beads 60 Chamber 60A Ink level detector 60B, 64, 92 Optical sensor 62 Light emitting diode (LED) 80, 98 Valve 82, 102 Personal computer 96 Carriage motor

Claims (1)

[Claims] 1. An ink jet print head, an ink tank having walls, and an ink tank connected to the ink jet print head so that ink can flow therethrough; a large number of particles arranged in the ink tank; Wherein the plurality of particles have a first reflectance when saturated with the ink and a second reflectance when not saturated with the ink, A transparent window formed in one of the walls of the ink tank to provide optical access to particles; optically coupled to the ink tank, the first reflectance and the second reflectance And a photoelectric sensor that outputs a detection signal that has detected the following.