JPS5838317B2 - Ink pump servo pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an ink jet printing apparatus having a servo control device that maintains the velocity of an ink jet within a predetermined range.

[Background technology]

Conventionally, various types of ink jet printing devices have been proposed.

One is that a jet of ink, or a series of droplets, is formed from a nozzle, propelled toward the recording medium, charged by a variable amount according to a signal representing a graphic or character, and deflected by a deflection plate provided with a constant potential. It is something that will be done.

It is important that the velocity of the ink drops be within a predetermined range to ensure good drop positioning when forming graphics or characters.

If the speed is not within a predetermined range, synchronization with the signal of the charging means for charging the series of droplets will not be achieved and the droplets will not be charged to the desired amount.

Furthermore, even if a desired amount of charge is obtained, the time it takes for the series of droplets to pass through the deflection plate is too long or too short, making it impossible to obtain the desired degree of deflection.

As a result, desired figures or characters cannot be drawn. Furthermore, even when characters are drawn by relative movement between the recording medium and the nozzle, if the speed of the jet stream is not within a predetermined range, the quality of the print will deteriorate.

Conventionally, attempts have been made to maintain the ink pressure constant using a pump or the like.

However, even if the pressure is constant, the velocity of the jet may not always be maintained within a predetermined range due to other variables such as temperature.

[Summary of the invention]

The present invention aims to eliminate the above-mentioned drawbacks and improve the quality of printing by maintaining the speed of the ink jet within a predetermined range in an ink jet printing device.

That is, in the present invention, in order to maintain the velocity of the jet, the velocity of the jet is sensed near the jet and servo-controlled, thereby achieving the above object.

Although in the exemplary embodiment a voltage is induced in the sensor and a signal is generated as a charged droplet passes near the sensor, it will be appreciated that other sensing techniques may be used as appropriate.

As typified by the embodiments described in FIGS. 2 and 3 below, in this first invention, the time that the jet passes corresponds to its speed using a sensing means provided near the jet. Directly as a signal (Figure 2) or indirectly (Figure 3)
Sense.

Particularly, in the embodiment shown in FIG. 2, a counter 65 counts the time it takes to fly between the pair of sensors 48 and 49, and the counted value is converted into an analog signal and used for servo control of the pump pressure.

In the embodiment shown in FIG. 3, the flight time is directly converted into an analog signal by the ramp signal generating circuit 70 and used for servo control of the pump pressure.

Further, as represented by another embodiment described in FIG. 4 below, in this second invention, the deflection plates 78 and
A signal corresponding to the jet velocity is generated and used for servo control of the pump pressure, taking advantage of the property that the time for each droplet in one stream to pass changes depending on the velocity, and thus the degree of deflection.

That is, if the deflected jet approaches the sensor 82, this means that the degree of deflection has become excessive because the jet was slow.

If it is close to the sensor 83, this means that the degree of deflection is too small because the jet was high-speed.

[Explanation of Examples]

FIG. 1 is a schematic diagram of a typical servo control system to which various embodiments of the invention disclosed in detail in FIGS. 2-4 may be applied.

An ink jetting device 1, which typically includes an ink jetting printing device or the like, has a sensor 2, such as a speed sensor.

Ink ejection devices are well known in the art.

The output of the sensor 2 is applied to an amplifier circuit 3 and from there to a comparison circuit 4.

Another input to comparator circuit 4 is the reference signal on line 5.

The output of the comparison circuit 4 is given to the pump control circuit 7, and the output of the comparison circuit 4 is applied to the line 1
0 and 11 are utilized to generate a correction signal sent to the coil 12 of the pump 13.

Servo operations can be performed from the machine clock 16 via the machine logic 17 under normal conditions.

In this way, the operation of the servo device shown in FIG.
This is performed during non-printing periods, such as between printing characters and during carrier recovery periods.

《If the flow rate is too slow《, the pump pressure is low,
The rate of flow may be increased by a modification signal such as increasing the voltage or current applied to the coil 12 of the pump 13.

Additionally, the frequency of the signal applied to coil 12 may vary the pump pressure.

The pump arrangement 13 causes ink droplets 23 to be ejected from the nozzles 22 of the ink ejection device 1 toward a recording medium for printing characters or graphics.

If a drop is not needed during printing, it is guided into the groove.

Ink is supplied from the ink supply device 29 via conduit 30 and further via pump 13 to the nozzles.

Pump 13 may be a pump controlled by coil 12 such that its pressure is a function of the current flowing through the coil.

Instead of controlling coil current or the like to regulate pressure, an oscillator with constant current and varying frequency can be used to operate the pump.

If desired, pressure and/or temperature sensors may be used with the pump to monitor and vary pump pressure, thereby helping to control speed.

FIG. 2 shows an apparatus that directly monitors the droplet velocity and generates a signal to control the pump pressure to change the droplet velocity as necessary.

Figure 2 uses digital techniques.

Figure 2 uses basically the same sensing mechanism as Figure 3, but Figure 2 uses a digital signal and converts it to an analog signal, whereas Figure 3 uses a digital signal and converts it to an analog signal. Generates an analog signal to vary pump pressure.

In FIG. 2, a stream of drops 43 is ejected from a nozzle 44;
It passes through the charging electrode 45.

A groove 46 is positioned to receive the stream 430 drops.

Two sensors 48 and 49 are separated from each other by a predetermined distance and are located close to the path of travel of the droplets of stream 43.

Both sensors 48 and 49 send signals to associated comparator circuits 50 and 51, respectively.

A reference potential is provided to the comparator circuit by lines 53 and 54. This reference potential is used to identify that the passage of a drop has been sensed only when a potential greater than or equal to that potential is induced.

While testing drop velocity, such as while nozzle 44 is in the home position or between characters, gating circuit 56 is synchronously activated by clock pulses on line 58.

The outputs of both comparison circuits are provided to gate 56 by lines 60 and 61 through interface connectors 62 and 63, respectively.

In operation, a group of drops, on the order of six in number, are ejected from the nozzle 44.

When a group of droplets charged by charging electrode 45 pass through sensor 48, they induce a potential there and simultaneously actuate gate 56 to gate counter circuit 65 to begin a counting operation.

When a series of drops passes through sensor 49, another potential is induced which is applied to gate 56 which in turn switches counter 65 off.

In this way, a large number of count-pulses are sent to the counter 65.
The count in counter 65 represents the time required for a drop to pass from sensor 48 to sensor 49.

The count state of counter 65 is provided to digital-to-analog converter circuit 67 to later derive a corrected signal.

Normally this line 68 is fed to a comparison control circuit similar to circuit 4 of FIG. 1 and serves to vary the pump pressure as required.

As previously noted, the pump drive frequency or drive current may be varied to vary the pump pressure.

FIG. 3 shows an analog method using various elements in FIG.

The circuit of FIG. 3 replaces elements 56, 65 and 67 of FIG. 2, and appropriate interface connectors 62a and 63a are used in place of connectors 62 and 630 of FIG.

In this case, the outputs induced by the sensors 48 and 49 are applied to the slope signal generating circuit γ0.

Detecting the potential on line 60a in FIG. 3 energizes the ramp signal generation circuit.

Ramp signal generation circuit 70 generates a ramp signal at a known speed and over a range of voltage values.

Upon detection of another output on line 61a of FIG. 3, the output from ramp signal generation circuit 70 is deenergized.

The resulting value is stored in a holding circuit 71 and supplied by line 72 to vary the pump pressure in a manner similar to that previously described.

By using the techniques described above, the velocity of the ink stream 43 can be maintained constant.

As a result, the necessary deflection of the stream 43 during printing of information is maintained in a tightly controlled manner, since the deflection sensitivity of the stream 43 is proportional to 1/(velocity)3.

By using servo techniques as previously described, the tolerances, temperatures, etc. of other components of the device, such as the nozzle, do not need to be maintained as tightly as would otherwise be required.

In the embodiment of FIG. 4, the actual degree of deflection of the drop stream is tested to determine velocity characteristics.

Nozzle 75 passes through charging electrode 77 and deflection plates 78 and 7
A stream-like droplet 76 passing between 90 and 90 mm is ejected.

During printing of information, the stream-like droplets 76 are directed onto a recording medium, not shown.

When not needed for printing, the drops are directed into the groove 80.

Two adjacent sensors 8 to test the velocity of the flow
2,83 are located outside the normal deflection area.

This position is the position that the drop would arrive at if the maximum deflection was applied to the drop.

The droplets are thus suitably charged with the charging electrode 77 and deflected by the plates 78 and 79 so that they reach the areas of two adjacent sensors 82 and 83.

Note that the sensor is located outside the normal drop deflection area.

For example, a group of 6 drops can be used as before.

Groove 85 is positioned to receive drops directed between sensors 82 and 83.

When a stream of drops passes nearby, an electrical potential is induced by sensors 82 and 83.

When testing a flowing drop 76, it is assumed that a normal deflection will cause the drop to pass through the center of the sensors 82 and 83.

As the drop passes near sensor 830, indicating an increase in drop velocity, an output is provided to amplifier circuit 94, which in turn is provided to comparator circuit 91, which in turn provides an appropriate correction signal, appearing by line 92, to the pump. Control pressure.

In this case, the drop velocity is somewhat higher, so the pump pressure is reduced.

When a drop passes near the sensor 82, an output is presented to the amplifier circuit 94 which, if present, is also supplied to the comparator circuit 91.

In this case, the stream of drops moves at a relatively low velocity and the output signal on line 92 is of an appropriate value to increase the pump pressure.

As described above, the embodiment shown in FIG. 4 is a speed detection method that utilizes the property that when an ink droplet passes through a predetermined deflection voltage, if the speed is low, the ink droplet will be deflected greatly, and if the speed is high, it will be deflected only a little. Therefore, this is also shown in Figures 2 and 3.
Similar to the method of measuring the elapsed time of an ink jet explained with reference to the figure, this is one of the speed characteristics of the jet.

FIG. 5 shows a highly efficient pump structure 100 that can be used in various servo circuits such as those previously described.

Pump 100 includes a pump support structure 10 incorporating multiple elements.
It also becomes 1.

A flat spring member 102 is mounted for vibrational movement within structure 101.

Spring member 102 is driven by coil 104 being biased by oscillator 106 .

A connecting rod 108 coupled to a bellows 110 is attached to the member 102.

Pump 100 further includes an input conduit 112 through which ink is applied from an ink supply, not shown.

Output conduit 114 supplies ink to nozzles not shown but similar to those previously described.

Control of the ink passages and pumping is provided by input valve 115 and output valve 116.

The operation of the pump is similar to that of voice coils commonly found in radios, televisions, etc.

A metal diaphragm 102 and a bellows 110 that cooperates with it
changes the pump capacity 1200 volume.

Valves 115 and 116 control the flow of ink into and out of the pump.

The pressure generated by the pump 100 is applied to the diaphragm 1
02 to the bellows 110, and also to the frequency and current conditions established in the coil 104.

Pump 100 with these characteristics can be easily incorporated into various servo circuits, such as those previously described, and can be controlled as needed so long as a desired pressure range is maintained.

This controls the velocity of the drop as previously mentioned.

During operation, when the bellows 110 moves to the left in FIG.
Flap 115 opens, thereby drawing ink through conduit 112 into chamber 120.

Valve 116 remains closed at this time.

As bellows 110 moves to the right and expands, valve 115 remains closed and ink is forced against valve 116 and delivered by conduit 114 to the ink ejection nozzle.

〔summary〕

As mentioned above, the embodiments of the first and second inventions of the present invention have been described. Corresponding to the second invention) is shown below by the figure number in parentheses.

That is, the first invention comprises a nozzle means (44 in FIG. 2) for shaping an ink jet (43 in FIG. 2) and directing the jet so that it flies along a predetermined course; Pump means (13 in FIG. 1 and 100 in FIG.
), the ink jet printing apparatus further includes a sensing means (see FIG. 2, 84, 49 in FIG. 2), comparing means (4 in FIG. 1) for comparing the generated signal with a reference signal (5 in FIG. 1) and generating a correction signal, and the pumping means and means (7 in FIG. 1) for applying the correction signal to the pump means in order to control the pressure applied by the pump and maintain the velocity of the jet within a predetermined range. This is an ink jet printing device with special features.

The second invention also forms a jet of ink (76 in FIG. 4) and directs it so that it travels along a predetermined course.

a nozzle means (75 in FIG. 4), a pump means (13 in FIG. 1, 100 in FIG. 5) for applying pressure to the ink so that a jet of the ink is generated from the nozzle means, and charging the jet. In an ink jet printing apparatus comprising charging means (77 in FIG. 4) and deflection means (78, 79 in FIG. 4) for applying an electric field thereto to deflect the charged jet, Sensing means (2 in FIG. 1) that is provided near the deflected jet and generates a signal corresponding to the velocity of the jet by sensing the degree of deflection of the jet.
, 82, 83 in FIG. 4), comparison means (4 in FIG. 1) for comparing the generated signal with a reference signal (5 in FIG. 1) and generating a corrected signal; and means (1 in FIG. 1) for applying the correction signal to the pump means in order to control the pressure applied and maintain the velocity of the jet flow within a predetermined range. This is an ink jet printing device.

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing a general servo control system for a pump in an ink jetting device, and Figure 2 is an analog system that senses the speed of ink droplet flow and generates a digital count value to control the pump. FIG. 3 is also basically the same as FIG. 2, but shows the device in which the analog values are generated directly; FIG. 4 includes means for sensing the maximum deflection of the ink jet; A diagram showing the servo control mechanism, and the fifth
The figure is a cross-sectional view of a voice coil pump that may be used in embodiments of the present invention. 1... Ink injection device, 2, 48, 49, 82
, 83...sensor, 4...comparison circuit,
5...Reference signal, 7...Pump control device, 13,100...Pump, 4 4, 7
5-... Nozzle, 65... Counter, 70
..... Gradient signal generation circuit, 17 .... Charged electrode, 78, 79 ..... Deflection plate.

Claims (1)

Claims: 1. Nozzle means for forming a jet of ink and directing the jet to travel along a predetermined path; and applying pressure to the ink so as to produce the jet of ink from the nozzle means. an ink jet printing device further comprising: a sensing means disposed in the vicinity of the jet for generating a signal corresponding to the velocity of the jet by sensing the time during which the jet passes; comparing means for comparing the generated signal with a reference signal and generating a correction signal; What is claimed is: 1. An ink jet printing device comprising: a servo control device having means for providing a signal; 2. nozzle means for shaping and directing a jet of ink so that it travels along a predetermined path; and pump means for applying pressure to the ink so as to produce said jet of ink from said nozzle means; In the ink jet printing apparatus, the ink jet printing apparatus is provided with a charging means for charging the jet, and a deflection means for applying an electric field to the charged jet so as to deflect the charged jet; sensing means for generating a signal corresponding to the velocity of the jet by sensing the degree of deflection of the jet; comparison means for comparing the generated signal with a reference signal and generating a corrective signal; provided by the pumping means; an ink jet printing apparatus, comprising: means for applying said correction signal to said pump means for controlling the pressure and maintaining the velocity of said jet within a predetermined range;