JP3296941B2 - Control method of ink pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling an ink pump used in a continuous jet type ink jet recording apparatus, and more particularly, to a method for controlling a discharge flow rate of ink from a nozzle (hereinafter, simply referred to as a flow rate). And a control method of a discharge pressure of an ink pump (hereinafter, may be simply referred to as a pressure).

[0002]

2. Description of the Related Art As a conventional ink pump control method, there has been a constant pressure control method for controlling the pressure of an ink pump at a constant pressure during printing (for example, Kent).
Bladh, "The three-color i
nk jet plotter, a new devi
ce for the presentation o
fgeophysical data ", Report
1/182, Dept. Electr. Mea
s. , Lund Inst. Tech. , P. 70-8
3).

Further, a pressure (hereinafter, referred to as an equilibrium pressure) that balances with a desired flow rate (hereinafter, referred to as a prescribed flow rate) is predicted from a pressure rising speed in a rising process of the ink pump, and constant pressure control is performed at the predicted equilibrium pressure. There has been a method for printing one recording medium (see, for example, JP-A-62-32289 and JP-A-62-85185).

Further, there is a method by the present inventor who measures the relationship between the pressure and the flow rate during the rising process of the ink pump, calculates an equilibrium pressure that balances with the specified flow rate based on the measured value, and prints one sheet at the equilibrium pressure. (Japanese Unexamined Patent Publication No.
294155).

Furthermore, an equilibrium pressure that balances with a specified flow rate is predicted from the ambient temperature at the start of printing, a flow rate is measured at the predicted equilibrium pressure, and a difference between the specified flow rate and the measured flow rate is calculated. There has also been a method by the present inventor for correcting the pressure so that a specified flow rate is obtained (Japanese Patent Application No. Hei 6 (1994)).
-115967).

[0006]

In the conventional method of controlling an ink pump described above, in the case of controlling the pressure of the ink pump at a constant pressure during printing, the discharge flow rate of the ink from the nozzles is equal to the ambient temperature. There is a problem that the image density changes in accordance with the ambient temperature since the image density greatly changes due to the change.

Further, in the method of controlling the constant pressure at the predicted equilibrium pressure, in order to solve the problem of the method of controlling the constant pressure at a constant pressure, the equilibrium pressure at which the specified flow rate is equilibrated is predicted. Although control is performed so as to print one sheet of the recording medium, the equilibrium pressure is predicted from the rate of pressure rise during the rising process of the ink pump.
For the ink tubes and the like that form the ink flow path between the ink pump and the nozzles, materials that are easily plastically deformed, such as plastic and rubber, are frequently used, so the pressure prediction algorithm is complicated. Do not fit,
Material characteristics vary among individuals, and the error between the predicted equilibrium pressure and the actual equilibrium pressure is large and impractical (for this reason, in Japanese Patent Laid-Open No. 62-85185, the equilibrium pressure during the previous printing is Referenced).

Further, according to the ink pump control method of the present inventor (see Japanese Patent Application Laid-Open No. 4-294155),
In the rising process of the ink pump, instead of measuring the rate of pressure rise, constant pressure control is performed at _two different pressures P ₁ and P _2, and the flow rates Q ₁ and Q
₂ is measured, the equilibrium pressure P ₀ that balances with the specified flow rate Q ₀ is determined from these values, and furthermore, the printing is performed after confirming the stabilization of the flow rate Q with the equilibrium pressure P _0. By performing the control, a stable pressure P, which is extremely accurate compared to the above two methods, can be obtained, which has greatly contributed to the improvement of the print image quality. There is a problem that it takes a long time.

Further, in another control method of the ink pump by the inventor of the present invention (see Japanese Patent Application No. 6-115967), at the start of printing, an equilibrium pressure at which a specified flow rate is equilibrated from the ambient temperature is predicted and started. By measuring the flow rate at that time and correcting the pressure based on the difference between the specified flow rate and the measured flow rate, more precise pressure control for improving the quality of a printed image has become possible. However, since the temperature of the ink flowing through the nozzle does not match the measured ambient temperature, a correction step is required in most cases,
Therefore, there has been a problem that the rising speed of the ink pump cannot be sufficiently increased. In addition, since the discharge flow rate of the ink pump is measured indirectly by measuring the moving speed of the piston, there is a problem that the measurement takes a long time and the flow rate measurement accuracy is not sufficient for the following reasons. Was. That is, when the ink pump is operated by a control such that the discharge pressure of the ink pump is constant, that is, a so-called constant pressure control, the discharge pressure of the ink pump and the discharge flow rate from the nozzle respond at high speed. However, since the discharge flow rate from the nozzle cannot be directly measured, the flow rate is indirectly measured by measuring the moving speed of the piston (the average step rate of the stepping motor driving the piston). However, when the pressure rises, the plastic tube connecting the cylinder and nozzle of the ink pump and the sealing O-ring cause transient elastic deformation, so the flow rate is controlled by the piston moving speed before the transient phenomenon is settled. When the measurement is performed, the deformation value is included in the measured value, and the measured value is not an accurate value. In order to obtain an accurate flow rate, it is necessary to wait for this transient phenomenon to settle, but this time has empirically taken several tens of seconds.

In view of the above, an object of the present invention is to measure the jet current by charging the ink jet with a constant DC voltage and utilizing the property that the jet current (the charge carried by the charged ink jet) is proportional to the flow rate. Accordingly, it is an object of the present invention to provide a method of controlling an ink pump in which the flow rate is directly measured and the value is used to precisely control the ink pump.

It is another object of the present invention to provide a method of controlling an ink pump in which an ink pump is controlled at a high speed by utilizing a high-speed response of a jet current.

[0012]

According to the present invention, there is provided a method of controlling an ink pump, which operates to guide a pressurized ink to a nozzle and discharge a specified flow rate of ink from an orifice thereof. The ink jet is charged with a constant DC voltage, and a jet current (I ₀ ) corresponding to a specified flow rate (Q ₀ ) is measured. The measured jet current (I ₀ ) is used as a nozzle parameter, and a discharge pressure is calculated using the nozzle parameter. Is controlled.

Further, according to the ink pump control method of the present invention, in the ink pump control method which operates to guide the pressurized ink to the nozzle and discharge the ink at a specified flow rate from the orifice, A nozzle parameter setting step of preliminarily measuring a jet current (I ₀ ) corresponding to a specified flow rate (Q ₀ ) by charging with a DC voltage and storing the measured jet current (I ₀ ) in a memory as a nozzle parameter; Is charged with a constant DC voltage and the ink pump is started up while measuring the jet current (I), and constant pressure control is performed at a pressure at which the jet current (I) becomes the jet current (I ₀ ) corresponding to the nozzle parameter. And an ink pump start-up step.

Further, according to the ink pump control method of the present invention, there is provided a method of controlling an ink pump which operates so as to guide pressurized ink to a nozzle and discharge a specified flow rate of ink from an orifice thereof. A nozzle parameter setting step of preliminarily measuring a jet current (I ₀ ) corresponding to a specified flow rate (Q ₀ ) by charging with a DC voltage and storing the measured jet current (I ₀ ) in a memory as a nozzle parameter; Before the start, the ink jet is charged with a constant DC voltage and the ink pump is started up while measuring the jet current (I), and the pressure at which the jet current (I) becomes the jet current (I ₀ ) corresponding to the nozzle parameter. Ink pump start-up process with constant pressure control at the The charged was to define the flow rate (Q ₀₎ in the corresponding jet current (I ₀ ") again measured, characterized in that it comprises a nozzle parameter modification step of rewriting the nozzle parameters of the memory.

[0015]

In the control method of the ink pump the present invention, to measure the jet current corresponding to the charges the ink jet at a constant DC voltage prescribed flow rate _{(Q 0) (I 0)} , the measured jet current (I ₀ ) Is a nozzle parameter, and the discharge pressure is controlled using the nozzle parameter.

In the method of controlling an ink pump according to the present invention, in a nozzle parameter setting step, the ink jet is charged with a constant DC voltage, and a jet current (I ₀ ) corresponding to a specified flow rate (Q ₀ ) is measured in advance. The measured jet current (I ₀ ) is stored in a memory as a nozzle parameter, and the ink jet is charged with a constant DC voltage in the ink pump start-up process, and the ink pump is started while measuring the jet current (I), and the jet pump is started. Constant pressure control is performed at a pressure at which the current (I) becomes the jet current (I ₀ ) corresponding to the nozzle parameter.

Further, in the ink pump control method of the present invention, in the nozzle parameter setting step, the ink jet is charged with a constant DC voltage, and the jet current (I ₀ ) corresponding to the specified flow rate (Q ₀ ) is measured in advance. The measured jet current (I ₀ ) is stored in a memory as a nozzle parameter in the memory, and the ink pump is charged with a constant DC voltage before the printing process in the ink pump start-up process, and the ink pump is operated while measuring the jet current (I). Start-up, constant pressure control is performed with the pressure at which the jet current (I) becomes the jet current (I ₀ ) corresponding to the nozzle parameter, and after the printing process is completed in the nozzle parameter correction process, the inkjet is charged with a constant DC voltage and the specified flow rate (Q ₀₎ corresponding jet current (I ₀ ") and re-measure the write nozzle parameters of memory It is.

[0018]

Next, the present invention will be described in detail with reference to the drawings.

FIG. 7 is a main part configuration diagram showing an example of a continuous jet type ink jet recording apparatus to which the ink pump control method of the present invention is applied. This continuous jet type ink jet recording apparatus includes an ink bottle 1 for storing ink, a cylinder 2 for sucking ink from the ink bottle 1, a piston 3 reciprocating in the cylinder 2, and opening and closing the ink bottle 1 and the cylinder 2. An electromagnetic valve 4 communicating freely, an ink tube 5 for guiding ink discharged from the cylinder 2,
A nozzle 6 for ejecting the ink guided by the ink tube 5 as a jet, a pressure sensor 7 for measuring the pressure in the cylinder 2, an ink electrode 8 for setting the ink potential in the nozzle 6 to the ground potential, and concentric with the nozzle 6 A control electrode 11 having a circular opening or a slit-like opening for inductively charging an ink-jet by being supplied with a potential, a DC power supply 12 for supplying a DC potential to the control electrode 11, and an output of the DC power supply 12 A switch 13 for connecting either the image signal at the time of printing to the control electrode 11 in accordance with a command from a central processing unit (hereinafter abbreviated as CPU) of the continuous ejection type ink jet recording apparatus.
A conductive particle catcher 14 for capturing the electric charge of the ink jet; a current detector 15 connected thereto for detecting a jet current; a piston driving mechanism 9 for reciprocating the piston 3 in the cylinder 2; And a pump control device 10 for controlling the solenoid valve 4 and the piston drive mechanism 9 based on the output of the pressure sensor 7 and the current detector 15.

The cylinder 2 and the piston 3 form an ink pump, and the capacity of the cylinder 2 for one stroke of the piston 3 is larger than the capacity for discharging ink for one print.

Although not specifically shown, the pump control device 10 has a built-in nonvolatile random access memory (hereinafter simply referred to as a memory) in which stored contents are not lost even when the power is turned off.

The conductive particle catcher 14 is disposed at a home position (an area not related to recording) behind (rightward in FIG. 7) the control electrode 11, which is an essential element in the continuous jet type ink jet recording apparatus. It also serves as a detection electrode (for details, see Japanese Patent Application Laid-Open No.
No. 36, etc.).

The current detector 15 is constituted by an integrating circuit. For example, the integration time is 2 × 10 ⁴ times or more of the particle formation period, that is, 2 × 10 ⁴ or more electric charges of the ink particles are integrated. A typical value of the particleization period of the inkjet to which the present invention is applied is 1
Since it is 0 ^-6 seconds, the minimum time required for one integration is 2 ×
This is on the order of 10 ^-2 seconds (for details of the integration circuit, see Japanese Patent Application Laid-Open No. H5-246036).

As shown in FIG. 8A, the ink particles are
It is inductively charged by a charging control voltage φ applied between the control electrode 11 and the ink electrode 8 in the nozzle 6 and a capacitance C between an ink piece forming one ink particle and the control electrode 11. . The charge amount q of one ink particle is given by q = Cφ.

Now, the particleization frequency (1
If the number of particles generated per second) is f, the jet current I is I = fq = fCφ. Here, when the discharge flow rate of the ink from the nozzle 6 is Q and the discharge flow rate Q is changed, fC changes in proportion to the discharge flow rate Q. This is because in the case of spontaneous particle formation in which the vibrator is not attached to the nozzle 6, the capacitance C is constant with respect to the change in the discharge flow rate Q, and the particle formation frequency f is proportional to the discharge flow rate Q. On the other hand, in the case of particle formation by excitation when a vibrator is attached to the nozzle 6, the particleization frequency f is constant with respect to the change in the discharge flow rate Q, and the volume of one ink particle forming one ink particle is proportional to the discharge flow rate Q. This is because the capacitance C changes in proportion to the discharge flow rate Q. Therefore, assuming that the charging control voltage φ is constant, as shown in FIG.
Holds. K in this equation is a constant unique to the nozzle.

The relationship of I = KQ indicates that if the constant K is determined in advance, the discharge flow rate Q can be determined by measuring the jet current I. Therefore, the piston 3 of the ink pump is operated so as to discharge the specified flow rate Q ₀ in advance, and the jet current I ₀ at that time is measured. From the measured jet current I ₀ , K ₀ = I ₀ / Q
_If a constant K ₀ specific to the nozzle 6 is determined by ₀ and the constant K ₀ is stored in the memory of the pump control device 10, the constant K ₀ and the measured jet current will be used in the subsequent operation of the ink pump. From I, the discharge flow rate Q = I / K ₀ can be known. Alternatively, instead of storing the constant K ₀ in the memory, the jet current I ₀ itself may be stored in the memory as a parameter unique to the nozzle 6 (hereinafter, simply referred to as a nozzle parameter).

The processing procedure of the ink pump control method according to the first embodiment of the present invention is, as shown in FIGS. The process includes two processes: a nozzle parameter setting process S1 that is started once at the time of replacement, and an ink pump start-up process S2 and a printing process S3 that are started for each printing operation.

Referring to FIG. 2A, the nozzle parameter setting step S1 includes an ink pump constant flow rate mode starting step S11, a jet current measuring step S12, a jet current difference determining step S13, and a nozzle parameter storing step S14. Consists of

Referring to FIG. 3A, the ink pump start-up step S2 includes a high-speed pressurizing step S21, a jet current measuring step S22, a jet current comparing step S23, and a constant pressure control step S24.

Next, the processing of the control method of the ink pump according to the first embodiment will be described.

At the time of initial use of the continuous jet type ink jet recording apparatus or at the time of replacement of the nozzle 6, the CPU sets the switch 13 to DC when the print head (carriage) mounting the nozzle 6 faces the conductive particle catcher 14. The pump is switched to be connected to the power supply 12, a constant DC voltage φ is applied to the control electrode 11, and the pump controller 10 starts the nozzle parameter setting step S1.

[0032] In the nozzle parameter setting step S1, the pump control unit 10 drives the piston driving mechanism 9 at a piston speed of discharge flow rate Q is first ejected from the nozzle 6 is defined flow rate Q _0, ink constant flow mode The pump is started (step S11). Then, the ink in the cylinder 2 is ejected as ink jet from the nozzle 6 through the ink tube 5 because the electromagnetic valve 4 is closed.
The ink jet ejected from the nozzle 6 is split into ink particles, and is inductively charged to a charge q = Cφ with a constant DC voltage φ applied from the DC power supply 12 to the control electrode 11,
The conductive particles are captured by the catcher 14. Charge = q = C of ink particles captured by conductive particle catcher 14
φ is detected by the current detector 15 as a jet current I in units of 2 × 10 ⁻² seconds, for example.

Next, the pump control device 10 measures the jet current I detected by the current detector 15 at a constant cycle (step S12), and measures the jet current I _n (n =
It is determined whether or not the difference ΔI = I _n −I _n−1 between the previously measured jet current I _n−1 and the previously measured jet current I _n−1 is smaller than the specified minute value δ (step S13). The difference ΔI is a specified minute value δ
If it is not smaller, the pump control device 10 determines in step S1
The control is returned to step 2, and steps S12 and S13 are repeated.

If the difference ΔI is smaller than the specified minute value δ in step S13, the jet current I is stabilized at the jet current I ₀ , and the discharge flow rate Q from the nozzle 6 becomes the specified flow rate Q _0. The control device 10 stores the jet current I = I ₀ measured last in the memory as the nozzle parameter of the nozzle 6 (step S14), and ends the nozzle parameter setting step S1.

In the nozzle parameter setting step S1, when the piston is started at the piston speed (constant flow mode) corresponding to the specified flow rate Q ₀ from the start of the start (step S11), the jet current I is represented by the curve A in FIG. Changes as shown in FIG.
In this case, the nozzle parameter setting step S1 requires, for example, about 7 minutes in total, but the curve B in FIG.
As shown in the figure, if the start-up is started at a high speed, and if the piston speed is switched to the piston speed corresponding to the specified flow rate Q ₀ halfway, the jet current I can be started at a high speed, and the nozzle parameter setting step S1 Can be reduced to, for example, about 3 minutes.

After the nozzle parameters are set in the nozzle parameter setting step S 1, at the start of printing by the continuous jet type ink jet recording apparatus, the CPU determines that the print head having the nozzles 6 faces the conductive particle catcher 14. Switch 1 in the home position
3 is connected to the DC power supply 12, and the pump control device 10 starts the ink pump start-up step S2.

In the ink pump start-up step S2, as shown in FIG. 3B, the pump control device 10 increases the piston speed by the piston drive mechanism 9 so that the jet current I corresponds to the specified flow rate Q _0. The jet current I is measured while increasing the pressure at a high speed until the current I ₀ (step S21) (step S22), and the measured jet current I is stored in the jet current I as the nozzle parameter.
_It is determined whether it is ₀ or more (step S23). If the jet current I is not equal to or greater than the jet current I ₀ , the pump control device 10 returns the control to step S21 and returns to steps S21 to S21.
Repeat 23.

If the jet current I becomes equal to or greater than the jet current I _{0 in} step S23, the specified flow rate Q ₀ is obtained, and the pump control device 10 outputs the output of the pressure sensor 7 as shown in FIG. , The piston drive mechanism 9 is driven to perform constant pressure control with the pressure at that time (step S24), and control is transferred to the printing step S3. The time required for the ink pump start-up step S2 is, for example, about 20 seconds in total.

FIG. 4A is a flowchart showing another example of the ink pump start-up step S2 shown in FIG. 3A. The ink pump start-up step S2 of this example includes a high-speed pressurization step S31, a jet current measurement step S32, a jet current comparison step S33, a constant pressure control step S34, a jet current re-measurement step S35, and a pressure correction step S36. When,
It comprises a constant pressure control step S37.

In such an ink pump start-up step S2, the pump control device 10 controls the step S21 in FIG.
If the process proceeds to the constant pressure control by starting up the ink pump as in steps S24 to S24 (steps S31 to S34), as shown in FIG.
Second), the jet current I ₀ ′ is measured again (step S3).
5) When I ₀ ′ ≠ I ₀ , the pressure is corrected so that the jet current I ₀ ′ measured with reference to the output of the pressure sensor 7 becomes the jet current I ₀ corresponding to the nozzle parameter (step S36). ), Constant pressure control is again performed with the corrected pressure (about several seconds) (step S37), and the printing step S3
Transfer control to.

In the ink pump start-up step S2 of this embodiment,
Jet current I in step S35 is performed to check whether became jet current I ₀ corresponding to the nozzle parameters, the correction of the pressure is performed in step S36, more precise defined flow rate Q ₀ is obtained.

FIG. 5A is a flowchart showing a control method of the ink pump according to the second embodiment of the present invention. Second
The control method of the ink pump of the embodiment includes a nozzle parameter setting step S1 (same as the step S1 in the first embodiment shown in FIG. 1A), an ink pump start-up step S2, and a printing step S3 (FIG. a) The same as steps S2 and S3 in the first embodiment shown in a), and a nozzle parameter correction step S4. That is, the control method of the ink pump of the second embodiment is such that after the printing process S3 is completed,
In the nozzle parameter correcting step S4, the nozzle parameters are measured again each time, and the nozzle parameters in the memory are rewritten to new nozzle parameters.

Referring to FIG. 6, the nozzle parameter correcting step S4 includes an ink pump constant flow rate operation step S41, a jet current measuring step S42, and a nozzle parameter rewriting step S43.

In the control method of the ink pump according to the second embodiment, when the print head equipped with the nozzle 6 returns to the home position facing the conductive particle catcher 14 after the printing step S3, the CPU is stopped. Switches the switch 13 to connect to the DC power supply 12,
The pump control device 10 starts the nozzle parameter correction step S4.

In the nozzle parameter correcting step S4, the pump controller 10 controls the ink pump to the specified flow rate Q _0.
(Step S4)
1) After the jet current I is stabilized, the jet current I
₀ "is measured (Step S42), the measured jet current I _0" rewrites the nozzle parameters of the memory (I ₀
← I ₀ ″) (Step S43) As a result, at the start of the next print, the ink current is controlled in the ink pump start-up step S2 so that the jet current I becomes the latest nozzle parameter, the jet current I ₀ .

[0046]

As described above, according to the present invention,
Utilizing the relationship between the jet current and the discharge flow rate when the inkjet is charged with a constant DC voltage, the ink pump is controlled so that the discharge flow rate from the nozzles becomes a specified flow rate by detecting the jet current. As a result, there is an effect that it is possible to control the ink pump to obtain an extremely precise discharge flow rate.

Further, by utilizing the high-speed response of the jet current, there is an effect that high-speed control of the ink pump becomes possible.

[Brief description of the drawings]

FIG. 1 is a flowchart showing each step of an ink pump control method according to a first embodiment of the present invention, wherein (a) shows a nozzle parameter setting step, and (b) shows an ink pump start-up step and a printing step. Shown respectively.

FIG. 2A is a flowchart showing a nozzle parameter setting step in FIG. 1 in further detail, and FIG. 2B is a graph showing a change in jet current with time.

3A is a flowchart showing the ink pump start-up process in FIG. 1 in further detail, and FIG. 3B is a graph showing a time change of a jet current.

FIG. 4A is a flowchart illustrating another example of the ink pump start-up process in FIG. 1, and FIG. 4B is a graph illustrating a temporal change of a jet current.

FIGS. 5A and 5B are flowcharts showing steps of a method for controlling an ink pump according to a second embodiment of the present invention, wherein FIG. 5A shows a nozzle parameter setting step, and FIG. Each of the nozzle parameter correction steps will be described.

FIG. 6 is a flowchart showing a nozzle parameter correcting step in FIG. 5 in further detail;

FIG. 7 is a main part configuration diagram showing an example of a continuous jet type ink jet recording apparatus to which the ink pump control method of the present invention is applied.

FIG. 8A is a diagram for explaining the charge of the ink particles, and FIG. 8B is a graph showing the relationship between the flow rate and the jet current.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ink bottle 2 Cylinder 3 Piston 4 Solenoid valve 5 Ink tube 6 Nozzle 7 Pressure sensor 8 Ink electrode 9 Piston drive mechanism 10 Pump controller 11 Control electrode 12 DC power supply 13 Switch 14 Conductive particle catcher 15 Current detector S1 Nozzle parameter setting Step S2 Ink pump start-up step S3 Printing step S4 Nozzle parameter correction step S11 Ink pump constant flow rate mode start-up step S12 Jet current measurement step S13 Jet current difference determination step S14 Nozzle parameter storage step S21 High-speed pressurization step S22 Jet current measurement step S23 Jet current comparison process S24 Constant pressure control process S31 High-speed pressurization process S32 Jet current measurement process S33 Jet current comparison process S34 Constant pressure control process S35 Jet current measurement process S36 pressure correction step S37 the constant pressure control step S41 ink pump constant flow operation step S42 jet current measuring step S43 nozzle parameter rewriting step

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B41J 2/175 B41J 2/045 B41J 2/055

Claims (5)

(57) [Claims] 1. A method for controlling an ink pump which operates to guide a pressurized ink to a nozzle and discharge a specified flow rate of ink from an orifice thereof. _A method for controlling an ink pump, comprising: measuring a jet current (I ₀ ) corresponding to a jet current (I ₀ ), using the measured jet current (I ₀ ) as a nozzle parameter, and controlling a discharge pressure using the nozzle parameter. 2. A method for controlling an ink pump, which operates to guide a pressurized ink to a nozzle and discharge a specified flow rate of ink from an orifice thereof. _A nozzle current setting step of previously measuring a jet current (I ₀ ) corresponding to the jet current (I ₀ ) and storing the measured jet current (I ₀ ) in a memory as a nozzle parameter; Starting the ink pump while measuring the current (I), and starting the ink pump to perform constant pressure control at a pressure at which the jet current (I) has become the jet current (I ₀ ) corresponding to the nozzle parameter. Characteristic ink pump control method. 3. A method of controlling an ink pump which operates to guide a pressurized ink to a nozzle and discharge a specified flow rate of ink from an orifice thereof. the jet current corresponding to ₀₎ (I ₀₎ was previously measured, the measured jet current (I ₀₎ and the nozzle parameter setting step of storing in the memory as the nozzle parameter, the ink jet before starting the printing process at a constant DC voltage An ink pump start-up step in which the ink pump is started up while measuring the jet current (I) by charging, and a constant pressure control is performed at a pressure at which the jet current (I) becomes the jet current (I ₀ ) corresponding to the nozzle parameter; After the printing process, the ink jet is charged with a constant DC voltage, and the ink jet corresponding to the specified flow rate (Q ₀ ) is charged. A nozzle parameter correction step of re-measuring the jet current (I ₀ ″) and rewriting the nozzle parameters of the memory. 4. The method according to claim 1, wherein the step of setting the nozzle parameters comprises charging the ink-jet with a constant DC voltage,
₀ ) an ink pump constant flow rate mode start-up step of pressurizing the ink at a constant piston speed corresponding to ₀ ), a jet current measurement step of measuring the jet current (I) at that time,
A convergence determining step of confirming that the jet current (I) has converged to a constant value, and a nozzle parameter storing step of storing the jet current (I ₀ ) when the convergence is confirmed in the memory as the nozzle parameter. Item 2 or 3
The control method of the ink pump described in the above. 5. The ink pump start-up step starts the ink pump while charging the ink jet with a constant DC voltage and measuring the jet current (I), and the jet current (I) corresponds to the nozzle parameter. a pressure control step of pressure control by the pressure became jet current (I _0), and the jet current remeasurement step transients to measure the jet current waiting to settle (I ₀ ') at the constant pressure control process the jet current remeasurement step is measured jet current (I ₀ ') is the jet current corresponding to the nozzle parameters (I ₀₎ jets when not match the current (I _0') is a jet current (I 4. The method according to claim 2, further comprising a pressure correcting step of correcting the pressure so as to satisfy ₀ ) and a constant pressure controlling step of performing a constant pressure control with the pressure corrected in the pressure correcting step. How to control the pump.