JPH0260752A - Ink jet recording device - Google Patents

Abstract

PURPOSE:To enable an ink particle to be generated always at appropriate timing by a method wherein a first timing value obtained by a first test means is not established immediately as a new timing value, and the new timing value is established based on a specific comparison result. CONSTITUTION:Firstly, found out excitation voltage M1 is compared with excitation voltage M0 established before a test of this time. When a difference of the value M0 from the value M1 is judged to be outside a specific range, the previously found out value M1 is once stored in a memory. Then, new excitation voltage M2 is again found out, and the value M0 is compared with the value M2. When the value M0 is judged to be almost equal to the value M2, a value M0-M2 is established as appropriate excitation voltage. When a deviation of the value M0 to the value M2 is outside the specific range, it is highly possible that the value M1 is significant, and the stored value M1 is taken out to be compared with the value M2. When the value M1 is almost equal to the value M2, a value M1-M2 is established newly as appropriate excitation voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inkjet recording apparatus that causes ink particles to collide with the surface of a recording medium to perform arbitrary recording on the recording medium.

[Prior Art] In an inkjet recording apparatus, when environmental conditions such as temperature change, the physical properties of the ink change, making it impossible to perform good recording. Therefore, in order to always perform good recording, measures such as those described in Japanese Patent Application Laid-Open No. 191158/1983 are employed. This means will be explained using figures.

FIG. 3 is a system diagram of a conventional inkjet recording apparatus. In the figure, 1 is a nozzle, to which ink is supplied at a predetermined pressure by a pressure device (not shown). 2 is a piezoelectric element that excites the ink within the nozzle 1; 3a and 3b are ink particles separated from the ink column ejected from the nozzle 1; The ink particles 3a are large-diameter ink particles, and the ink particles 3b are small-diameter ink particles.

Reference numerals 4a and 4b are charged deflection electrodes (hereinafter simply referred to as electrodes) that charge the ink particles 3b and deflect them, and are plate-shaped and placed opposite each other.

5 is a rotating drum, 6 is a recording sheet stretched on the drum 5, and 6g is a gap between the edges of the stretched recording i6.

7 is a gutter that collects undeflected ink particles.

8 is a gap detector for detecting the gap 6g of the recording paper 6;
9 is a level conversion circuit that converts the output of the gap detector 8 into a high level or low level signal according to the output; 10 is an excitation voltage variable circuit that changes the voltage (excitation voltage) applied to the piezoelectric element to an arbitrary voltage; be. 11 is a recording signal source that outputs a recording signal to the recording paper 6; 12 is a test signal source that outputs a test signal for performing a test to be described later; 13 is a switching device that switches between the recording signal source 11 and the test signal source 12. The circuit 14 is a video amplifier for amplifying recording signals and test signals. 15 is a sense amplifier that detects and amplifies the amount of charge on the ink droplet 3b during testing; 16 is an electrode switching circuit that switches the connection to the electrodes 4a and 4b during recording and testing. Reference numeral 17 denotes a control device that controls the operation of the inkjet recording apparatus.

Next, the operation of the above inkjet recording apparatus is shown in FIG.
), (c), and (c), the flowchart shown in FIG. 5, and the graph shown in FIG. 6. First, the operation when recording on the recording paper 6 using the ink particles 3b will be described. When a command is given from the control device 17 to the excitation voltage variable circuit 10, the excitation voltage variable circuit 10 applies a voltage corresponding to the command to the piezoelectric element 2. As a result, the pressurized ink is excited and ejected from the nozzle 1. The ejected ink initially forms an ink column with a small constriction, and the constriction breaks off at the tip of the ink column to form ink particles. , the diameter of the ink particles, etc. are determined by the excitation voltage applied to the piezoelectric element.

In the above inkjet recording device, large-diameter ink particles 3
The excitation voltage is selected so that ink particles 3b and small-diameter ink particles 3b are generated alternately at predetermined times.

On the other hand, voltages -V and 10V, which have equal absolute values and opposite polarities, are applied to the electrodes 4a and 4b, respectively, as shown in FIG. 4(a). In this state, the electrodes 4a, 4b
The central part C between (Fig. 4(a)).

In the middle of (b), the potential (indicated by a dashed line) is 0, and the generated ink particles 3a and 3b fly straight without being affected in any way and are collected in the gutter 7. The electrode switching circuit 16 switches the electrode 4a according to a command from the control device 17.
, 4b are switched so that the voltages -V, , +V are applied to them.

In this state, when the control device 17 gives a command to the recording signal source 11, the recording signal source 11 outputs a recording signal, and the switching circuit 13 (switched to the recording signal source 11 side by the control device 17) The period T shown in FIGS. 4(a) and 4(b) is transmitted via the amplifier 14 and the electrode switching circuit 16.
During this period, a recording signal is applied to the electrodes 4a and 4b. Electrode 4a
The voltage of the recording signal applied to the electrode 4 is voltage -■2, which has a larger absolute value than voltage -■1 and has the same polarity.
The voltage of the recording signal applied to b is a voltage of 10v1, which is lower than the voltage of 10v1. When the small-diameter ink droplet 3b leaves the ink column while such a recording signal is being applied, the ink droplet 3b becomes positively charged. Then, this charged ink particle 3b has a voltage of -
V,,+V.

is deflected toward the electrode 4a and collides with the recording paper 6.

Since the drum 5 is continuously rotating, by outputting a recording signal according to the recording command, a dot is created by the ink particles 3b at a desired location on one line of the recording paper 6 during one rotation of the drum 5. will be recorded.

During the above operation, the correct amount of charge must be applied to the ink droplet 3b in order for the ink droplet 3b to be deflected correctly. In order for such charging to occur, it is necessary that the ink particles 3b separate from the ink column approximately in the middle of the recording signal flat period shown in FIGS. 4(a) and 4(b). Therefore, the excitation voltage for exciting the ink is set so that the ink particles 3b are separated at the above timing. However, as mentioned above, the timing of the generation of the ink particles 3b is greatly influenced by changes in environmental conditions such as temperature and is not constant, so if the excitation voltage is fixed, the amount of charge on the ink particles 3b, and therefore the amount of deflection, will change. Things change, and it's impossible to hope for a good record. For this reason, the apparatus described in the above-mentioned publication has no problem with the ink particles 3 even during the above-mentioned recording operation.
The configuration is such that the amount of charge of b is tested. below,
This configuration will be explained.

In the above inkjet recording apparatus, the excitation voltage is significantly changed prior to recording, and the amount of charge is checked for each excitation voltage, so that ink particles 3a, 3b of large diameter and small diameter are generated, and ink particles of small diameter are generated. An excitation voltage suitable for generating the particles 3b at approximately the middle of the period t is found, and this excitation voltage is stored as a set value in the storage section of the control device (step S shown in FIG. 5). Next, the recording operation is started (step S2). During this recording operation, the gap detector 8 constantly outputs the detection result to the control device 17 via the level conversion circuit 9. The control device 17 looks at the detection result and determines whether recording of one line on the recording paper 6 has been completed, that is, whether the gap detector 8 has detected the gap 6g (step 11if (S3). 1 line When it is determined that the recording of has been completed, it is then determined whether or not that one line is the last line to be recorded (step S4).
, if it is the last line, stop the operation (step S,)
.

If it is not the last line, charge amount data is collected (step S6).

Collection of this charge amount data is performed as follows. That is, the control device 17 switches the switching circuit 13 to the test signal source 12 side, and also switches the electrode switching circuit 16 so that the voltage of the test signal is applied to the electrode 4a, and the electrode 4b is selectively connected to the ground and the sense amplifier 15. Switch to connect.

Next, the test signal source 12 outputs a test signal as shown in FIG. 4(C), and the switching circuit 13. Video amplifier 14. A test voltage is applied to the electrode 4a via the electrode switching circuit 16. The test signal is a signal synchronized with the recording signal as shown in FIG. 4(C). This test signal is transmitted multiple times (for example, 30 times) during the period in which the gap detector 8 detects the gap 6g (within the recording stop period).
During this output, the electrode 4b is grounded by the electrode switching circuit 16. As a result, the ink particles generated for each test signal are positively charged in accordance with the generation timing, and a negative charge corresponding to this charge is accumulated in the electrode 4b each time the test signal is output. After outputting the test signal a predetermined number of times (30 times), 17 outputs a command to the electrode switching circuit 16 to switch the connection of the electrode 4b from the ground to the sense amplifier 15.

Therefore, the charge accumulated in the electrode 4b is transferred to the sense amplifier 1.
5 and is detected as a current. This current is proportional to the amount of charge of a predetermined number (30) of ink particles 3b, and therefore also proportional to the amount of charge of one ink droplet 3b.

The above charge data was collected for a certain excitation voltage, for example, the excitation voltage set in step S1. Then, by collecting such data for excitation voltages near the excitation voltage set above and comparing the collected data, an appropriate excitation voltage is determined. For this reason, the above data collection must be performed at a plurality of different excitation voltages and is performed on a plurality of consecutive lines. Control device 17
Each time data collection is completed, it checks the number of times and determines whether a predetermined number (for example, 9 times) of data has been collected (step S7). If the predetermined number has not been reached, step 82~
The process of S is repeated.

If it is determined in step S7 that data collection has been completed a predetermined number of times, the process moves to step S. In step SL+, the maximum value of all collected data (for example, nine pieces of data) is searched for.

This state is shown in FIG. In the figure, the horizontal axis represents the excitation voltage, and the vertical axis represents the particle charge amount, that is, the above data. If the excitation voltage when the maximum value data is generated is vo, this excitation voltage V may can be considered to be the excitation voltage that generates the ink particles 3b at the optimal timing, and from then on during the next test period. The excitation voltage for the recording operation in is corrected to the excitation voltage V n+ax regardless of the current excitation voltage. That is, recording in step S2 is performed using the excitation voltage determined by the previous test.

With the above configuration, the excitation voltage is checked and corrected every predetermined number of lines (for example, nine) (at a predetermined rotational speed of the drum 5), so that an appropriate excitation voltage can be maintained during the recording operation, resulting in good recording. can be done.

[Problem to be solved by the invention]

In the test of the inkjet recording apparatus described above, data collection in step S shown in FIG. 5 is performed by outputting a test signal a plurality of times (for example, 30 times) for each excitation voltage, as described above.

This is because the amount of charge on the ink particles 3b by one test signal is extremely small, and detection by the sense amplifier 15 is virtually impossible. For example, depending on the amount of charge of 30 ink particles 3b, the amount detected by the sense amplifier 15 is about several nanoamperes. Since the above-mentioned data acquisition is performed using such a small current, the influence of electrical noise generated from the surroundings is extremely large, and it is difficult to avoid it even with strict electrical shielding. Therefore, when the above-mentioned noise is collected as data and becomes the maximum data, in many cases, a voltage that deviates greatly from the appropriate excitation voltage is adopted as the appropriate excitation voltage, which may end up making the test ineffective. In fact, the result is that it is better not to perform the test at all.

Furthermore, temporary inappropriate data as described above also occurs when dust is mixed between the electrodes or when air bubbles are present inside the nozzle 1. Particularly in the latter case, when a bubble pops out from the nozzle, no ink droplets come out during that time, resulting in a large error in the amount of charge, or a situation where the timing is off due to the bubble popping and the large-diameter ink droplets 3a are charged. also occurs.

In this way, with conventional equipment, transient erroneous data not only renders the test meaningless, but also causes the determination of an excitation voltage that is significantly off, causing discrepancies in the recording. A situation was occurring.

The purpose of the present invention is to solve the problems in the above-mentioned prior art,
An object of the present invention is to provide an inkjet recording device that can reliably generate ink particles at appropriate timing and can perform good recording.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a nozzle that ejects ink to generate ink particles, an electrode that deflects charge of the ink particles, a charge amount detection means that detects the amount of charge of the ink particles, and a recording operation. In the inkjet recording apparatus, the timing control means controls the optimum generation timing of ink particles based on the amount of charge detected by the amount of charge detected by the amount of charge detected during the discontinuation period. a first test means for determining a first timing value based on the first timing value; a first comparison means for comparing the first timing value with a setting value set in a previous test; If the deviation is outside the predetermined range, repeat the test based on the amount of charge again and perform the second test.
a second test means for determining a timing value of the second test means;
a second comparing means for comparing the timing value of and the set value; and a second comparing means for comparing the first timing value and the second timing value when the deviation obtained by the second comparing means is outside a predetermined range. and a setting means that sets a new timing value based on the comparison result of each comparison means.

[Effect]

The first test means determines a first timing value for the generation of the ink droplet based on the amount of charge of the ink droplet, and compares this first timing value with a previously set timing value (setting value). When the deviation between the two is within a predetermined range, it is determined that the first timing value is not a value based on transient data, and one of the two values or a value in between is set as the new timing value. If the deviation is outside the predetermined range, the second test means repeats the test to obtain a second timing value. And this second
The timing value is compared with the set value, and if the deviation between the two is within a predetermined range, it is determined that the first timing value was due to temporary data and this is eliminated, and the second timing value is determined to be due to temporary data.
The timing value or the set value or an intermediate value between the two is set as the timing value. If the deviation between the two is outside the predetermined range in the above comparison, compare the first timing value and the second timing value, and if the deviation between the two is within the predetermined range, the setting should be made due to changes in environmental conditions, etc. It is determined that the timing value has changed, and one of the two values or an intermediate value is set as the new timing value.

〔Example〕

Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 1 is a system diagram of an inkjet recording apparatus according to an embodiment of the present invention. In the figure, parts that are the same as those shown in FIG. 3 are given the same reference numerals, and explanations thereof will be omitted. 18 is a control device corresponding to the control device 17 shown in FIG. This embodiment differs from the conventional device only in the configuration of the control device, and the other configurations are the same as the conventional device shown in FIG.

Next, the operation of the control device 18 of this embodiment will be explained with reference to the flowchart shown in FIG.

The processes of steps 31 to S7 shown in FIG. 5 are the same in this embodiment, and are denoted by the same reference numerals in FIG. In the conventional device, the excitation voltage that gives the maximum amount of charge is found in step S8, and this excitation voltage is set as the appropriate excitation voltage. In contrast, in this embodiment, a new excitation voltage M1 is simply found (step SI+'), and the next process is performed without immediately setting this as an appropriate excitation voltage.

First, we convert the found excitation voltage M1 to the excitation voltage that was set before this test (this excitation voltage is M).

(step S9). If the excitation voltage Mo
, M+ are approximately equal, it is safe to judge that the excitation voltage M obtained in this test is not a temporary value but a reliable value. Therefore, the value M. or value M
1 or an intermediate value between the two is set as the new excitation voltage (step S1°), and the process returns to step S2 to start a new test. Note that the value M0 and the value M1 do not have to match exactly. This is because if the excitation voltage to be tested is set in small steps, there may be one or more values that can be considered optimal, and the detected amount of charge includes an error within a certain range. Therefore, if the deviation between the value M and the value M1 is within a certain range, they can be considered to be equal, and the newly set excitation voltage can also be determined as shown in the above procedure SIO (the following procedure 5lff~S
The same applies to I6).

Next, consider the case where it is determined in step S that the deviation between the value M0 and the value M is outside the predetermined range.

In this way, both values M0. Possible reasons for the difference in M+ are that the optimum excitation voltage has changed due to changes in environmental conditions and the like, and that the value M1 is a temporary value as described above. Therefore, it is not appropriate to set the value M0 or the value M- as the appropriate excitation voltage here. Therefore, in this embodiment, the following process is executed to determine an appropriate excitation voltage.

That is, the value M found earlier is temporarily stored in memory (
Step Sz), then steps 82 to 3 again. + processing is performed to find a new excitation voltage M2 (step s, 2). Then, the value M0 and the value M2 are compared (procedure 5Iff).

Procedure SI! If it is determined that the value M0 and the value M2 are approximately equal, the previously found value MI can be considered to be a temporary value, and it can be excluded.

Therefore, the value M0, the value M2, or an intermediate value thereof is set as the appropriate excitation voltage (step 314), and the next test is started again from step S2. On the other hand, step s
If the deviation between the value M0 and the value M2 in rs is outside the predetermined range, there is a high possibility that the value M is a significant value, and this cannot be excluded. Therefore, the stored value M1
is extracted and compared with the value M2 (step S+s).

If the value M+ and the value M2 are almost equal, it can be considered that the value M0 is no longer the appropriate excitation voltage due to changes in environmental conditions, etc., and the value M, the value M2, or a value in between them can be considered as the appropriate excitation voltage. Newly set 11pS
za), the next test starts again from step S2.

If it is determined in step SI5 that the deviation between the value M1 and the value M2 is outside the predetermined range, that is, the value M,,M,.

This is a case where all of M2 have different values, but such a situation almost never occurs.

Possible cases in which this occurs are when temporary data occur consecutively by chance, or when some kind of accident occurs in the device. The former case can be handled by returning to step S2 again and repeating the above process. Furthermore, if it is clear that an accident has occurred, the device is stopped by a stopping means (not shown).

In this way, in this embodiment, the excitation voltage first obtained in the test is not directly set as the next appropriate excitation voltage, but is compared with the previously set value, and if the deviation between the two is outside the predetermined range, further adjustment is made. We performed a test to obtain an excitation voltage, and compared this excitation voltage with the set value and the excitation voltage obtained from the first test to set a new excitation voltage, so it is possible to set a new excitation voltage based on transient data. Excitation voltage can be eliminated and ink droplets can be generated at appropriate timing.

In addition, in the description of the above embodiment, each comparison means (step S1.
S+! . In addition, in the explanation of the above embodiment, an example was explained in which the excitation voltage is changed in order to obtain the appropriate ink droplet generation timing. can be controlled.

〔Effect of the invention〕

As described above, in the present invention, the first timing value obtained by the first test means is not immediately set as a new timing value, but is compared with the set value of the previous test, and if the deviation between the two is large, the first timing value is compared with the set value of the previous test. In this case, the second timing value is determined by the second test means, and this is compared with the set value. If the deviation between the two is large, the first timing value and the second timing value are compared, and the result of these comparisons is determined. Since a new timing value is set based on the data, it is possible to eliminate the timing value based on temporary data, and it is possible to always generate ink particles at the appropriate timing, resulting in good recording. Can be done.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of an inkjet recording apparatus according to an embodiment of the present invention, FIG. 2 is a flowchart explaining the operation of the control device shown in FIG. 1, and FIG. 3 is a system diagram of a conventional inkjet recording apparatus. Figure 4(a). (b) is the electrode voltage, FIG. 4 (C) is a waveform diagram of the test voltage, FIG. 5 is a flowchart explaining the operation of the control device shown in FIG. 3, and FIG. 6 is a graph of the detected particle charge amount. It is. 1-----Nozzle, 2-----1 piezoelectric element, 3
a, 3 b-・-ink particle, 4 a, 4
b-----Electrode, 5--Drum, 6-
---Recording paper, 6g---1111 gap, 8-
・−・−・−Gap detector, 10−・・−・・Excitation voltage variable circuit, 11−・・−Recording signal source, 12−・・・
-・Test signal source, 13-・-Switching circuit, 15
----1...Sense amplifier, 16-----Electrode switching circuit, 18---Control device Fig. 4 Fig. 6B max #h Post-voltage 294- Section 5

Claims (6)

[Claims] (1) A nozzle that ejects ink to generate ink particles, an electrode that charges and deflects the ink particles, a charge amount detecting means that detects the amount of charge of the ink particles, and a charge amount that detects the amount of charge during a period when recording operation is stopped. In the inkjet recording apparatus, the timing control means controls the optimum generation timing of the ink particles based on the amount of charge detected by the detection means, the timing control means controlling the optimum generation timing of the ink particles based on the amount of charge detected by the detection means. a test means for determining a timing value; a comparison means for comparing the new timing value with a set value set in a previous test; and when the deviation obtained by the comparison means is within a predetermined range, the set value and the new timing are compared. an inkjet recording device comprising a selection means for selecting a value within the predetermined range including the value as a set value. (2) In claim (1), when the deviation obtained by the comparison means is outside a predetermined range, the test based on the charge amount is executed again to obtain another new timing value. means, another comparison means for comparing the other new timing value and the set value, and when the deviation obtained by the other comparison means is within a predetermined range, the set value and the other new timing are compared. an inkjet recording apparatus characterized in that it is provided with another selection means for selecting a value within the predetermined range including the value as a set value. (3) In claim (2), there is a further method for comparing the new timing value and the other new timing value when the deviation obtained by the other comparison means is outside a predetermined range. and a comparison means, and when the deviation obtained by the further comparison means is within a predetermined range, a value within the predetermined range including the new timing value and the other new timing value is selected as a set value. An inkjet recording device characterized by being provided with a selection means. (4) The inkjet recording according to claim (3), further comprising repeating means for executing the test means again when the deviation obtained by the further comparison means is outside a predetermined range. Device (5) In claim (1), (2), (3), or (4), the timing value is an excitation voltage that excites the ink. Inkjet recording device (6) In claim (1), (2), (3), or (4), the timing value is the pressure of a pressurizing means that pressurizes the ink. An inkjet recording device featuring