JPH09318520A - Ink viscosity measuring device and ink jet recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure the viscosity of ink circulating through an ink circulation system by filling the ink between opposed surfaces of a plurality of vertical concentric ribs formed concentrically on a drive rotor and a follower rotor. SOLUTION: A drive rotor 29 is provided with a plurality of vertical concentric ribs 29A opened downward and the vertical concentric ribs 29A are arranged to diametrically face vertical concentric ribs 28A concentrically in proximity thereto and positioned to overlap the vertical concentric ribs 28A. With the rotation of the drive rotor 29, ink in a measuring chamber 33 is rotated in the same direction by an adhesive strength with the drive rotor 29. The rotation of the ink transmits a rotating force to a follower rotor 28 to rotate the follower rotor. The frequency of the passage of a permanent magnet 35 made at the position of a detector 36 per fixed time is counted from an output signal of the detector 36 and an arithmetic processing is performed referring to a conversion table indicating a relationship of the viscosity with the rotational speed (number of revolutions) of the follower rotor 28 as predetermined to determine the viscosity of the ink.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus, and more particularly, to an ink viscosity measuring apparatus for keeping ink viscosity within a predetermined range to stabilize recording operation.

[0002]

2. Description of the Related Art An ink jet recording apparatus for recording by making ink particles ejected from nozzles adhere to a recording medium,
In order to maintain a stable recording operation, it is necessary to manage the viscosity of the ink within a predetermined range. For this,
The inkjet recording apparatus employs a method of measuring the speed of ink particles ejected from a nozzle and the amount of ink ejected within a fixed time, and indirectly determining the viscosity of the ink from these measured values. However, since the speed and the ejection amount of the ink particles differ depending on the ejection port diameter of the nozzle and the ejection pressure of the ink, if the ink viscosity is obtained from these measured values, an error will occur between the devices. For example, in the method of calculating the viscosity of ink by measuring the amount of ink ejected from a nozzle within a fixed time, it is determined that the ink having a large nozzle ejection diameter and a large ink ejection pressure has a low ink viscosity in use. Therefore, a nozzle having a small nozzle ejection diameter and a small ink ejection pressure is determined to have a high ink viscosity during use. Therefore, in order to obtain an appropriate value, it is necessary to change (adjust) the viscosity determination value or the coefficient setting at the time of calculation for each device. Moreover, it is difficult to realize high detection accuracy in such indirect ink viscosity measurement.

In order to directly measure the viscosity of ink,
The ink viscosity measuring device described in JP-A-56-37162 measures the depth of a rotation method surface of an ink liquid surface generated by rotating ink in a cylindrical liquid tank for viscosity measurement. The viscosity of the ink is measured by measuring. However, this device
There is a problem that the ink circulation system becomes complicated because a cylindrical liquid storage tank for inserting and rotating measurement ink, a temporary storage tank for temporarily storing recovered ink during measurement, and a switching valve are required.

The ink viscosity measuring device described in JP-A-56-66733 has a structure in which a viscosity sensor that directly responds to the viscosity of ink in the ink container is installed in the ink container. For models with different types, it is necessary to assemble a viscosity sensor according to the ink container for each model, and the versatility (mass productivity) is poor.

The ink viscosity measuring device described in Japanese Patent Application Laid-Open No. 56-126171 measures the viscosity of ink by the rotational speed of a rotating body to which a rotational force is given by the flow of ink circulating in an ink circulation system. I am configuring.
However, it is difficult to perform accurate measurement in an inkjet recording device in which the flow rate of ink circulating in the ink circulation system is extremely small.

[0006]

As described above, the ink viscosity measuring device in the conventional ink jet recording apparatus is
There are problems that the configuration is complicated, lacks versatility, and accurate measurement is difficult.

An object of the present invention is to provide a versatile ink viscosity measuring device having a simple structure capable of accurately measuring the viscosity of the ink circulating in the ink circulation system.

Another object of the present invention is to provide an ink viscosity measuring device which is small in size and has good responsiveness and which is versatile.

Still another object of the present invention is to provide an ink jet recording apparatus suitable for maintaining the viscosity of ink in a preferable state.

[0010]

SUMMARY OF THE INVENTION The present invention provides an ink viscosity for measuring the viscosity of ink by measuring the rotational state of the driven rotor with respect to the rotation of the driving rotor when the space between the driving rotor and the driven rotor is filled with ink. In the measuring device, a plurality of vertical concentric ribs formed in a concentric state on the drive rotor and the driven rotor are filled with ink between the facing surfaces that are close to each other in the concentric state, and the driven rotor is driven according to the viscosity of the ink. The viscosity of the ink is measured by utilizing the phenomenon that the rotating state of the rotor changes.

Such an ink viscosity measuring device according to the present invention can be implemented in the following modes.

A measuring chamber having an ink inlet portion and an ink outlet portion is formed concentrically with the driving rotor and the driven rotor, and the measuring chamber is concentrically located in the measuring chamber at a position where the measuring chamber and the driven rotor overlap with each other so as to face each other. A plurality of vertical concentric ribs that are rotatably installed, a synchronous motor that rotates the drive rotor, and a detection unit that detects a rotation state of the driven rotor are provided.

The plurality of vertical concentric ribs of the drive rotor and the driven rotor are opposed to each other in a state in which they are close to each other in the radial direction.

The synchronous motor comprises a rotor connected to the drive rotor in the measuring chamber, and a stator provided outside the measuring chamber on the outer circumference of the rotor.

The detection means generates a detection signal according to the rotation speed of the driven rotor.

An ink circulation system for supplying ink, which has been sucked by a pump from an ink container and pressurized, to a print head and ejecting it as ink particles to capture ink particles not used for recording and collect them in the ink container. In an ink jet recording apparatus equipped with an ink viscosity measuring device for measuring the viscosity of ink flowing in the ink circulation system and a control device for controlling the supply of a solvent to the ink container in accordance with the measured ink viscosity, A measuring device is installed between the ink container and the pump.

Further, the ink which is sucked by the pump from the ink container and pressurized and the foreign matter is removed by the filter is supplied to the print head and ejected as ink particles, and the ink particles not used for recording are trapped in the ink container. Inkjet recording provided with an ink circulation system for collecting, an ink viscosity measuring device for measuring viscosity of ink flowing in the ink circulation system, and a control device for controlling supply of a solvent to the ink container according to the measured ink viscosity In the apparatus, the ink viscosity measuring device is installed between the ink container and the filter.

Further, the ink which is sucked by the pump from the ink container, pressurized and adjusted, is supplied to the print head to be ejected as ink particles, and the ink particles not used for recording are captured and collected in the ink container. Circulatory system,
In an ink jet recording apparatus provided with an ink viscosity measuring device for measuring the viscosity of ink flowing in the ink circulation system and a control device for controlling the supply of a solvent to the ink container according to the measured ink viscosity, The ink is allowed to pass through the device. The ink viscosity measuring device as described above is used as the ink viscosity measuring device in these ink jet recording apparatuses.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an ink jet recording apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 shows circulation paths of ink and solvent in the ink jet recording apparatus according to the present invention.
The main body 1 of the ink jet recording apparatus contains an ink container 2 for storing new ink whose standard viscosity is adjusted, a solvent container 3 for storing a solvent 3, a circulation device 4 and a control device 5.

The print head 6 has nozzles 19 for ejecting ink particles 20 and ink particles 20 not used for recording.
An ink recovery port 21 for capturing and recovering the ink is provided.

The circulation device 4 is driven by a motor 12 to pump or suck ink or solvent under pressure.
0, 11 and solenoid valves 13, 14, 1 for opening and closing the pipeline
8, 22, 23, 24, a main ink container 15 for holding ink, filters 16, 25 for removing foreign matters mixed in the ink, and a pressure reducing valve for adjusting the pressure of the ink supplied to the nozzle 19. 17 and a viscosity sensor 7 for measuring the viscosity of the ink.

Ink particles 20 ejected from the nozzle 19
Are captured by the ink recovery port 21 except for the particles used for recording. The captured ink particles 20 are piped so as to return to the main ink container 15.

When the start command is input to the control device 5,
The motor 12 is rotated to cause the pumps 8, 9, 10 and 11 to start pressure feeding or suction operation. The pump 8 sucks the ink whose standard viscosity is adjusted from the ink container 2 and sends it to the main ink container 15 via the electromagnetic valve 13.
When there is a sufficient amount of ink in the main ink container 15, the solenoid valve 13 is closed to block the flow. Similarly, the pump 9 sucks the solvent in the solvent container 3 and sends it to the main ink container 15 via the electromagnetic valve 14. However, when the ink viscosity in the main ink container 15 is below a predetermined reference value, the solenoid valve 14 is closed to prevent the solvent from flowing in. The ink viscosity is constantly measured by a viscosity sensor 7 located near the main ink container 15 between the main ink container 15 and the pump 13 and input to the control device 5.

The pump 10 sucks up ink from the main ink container 15 via the viscosity sensor 7 and filters 1
Pump to 6. The pressure reducing valve 17 adjusts the liquid pressure of the ink that has passed through the filter 16 so as to drop it to an appropriate pressure and smooth it, and sends it to the nozzle 19 of the print head 6 via the electromagnetic valve 18.

The print head 6 excites ink by a piezoelectric element incorporated in the nozzle 19 to atomize the ink ejected from the nozzle 19 to form ink particles 20.
And Those of the ink particles 20 that have not been used for recording are captured by the ink recovery port 21 and are sucked by the pump 11 to be recovered in the main ink container 15. At this time, the electromagnetic valve 23 is opened, and the foreign matter contained in the ink is removed by the filter 25.

The solenoid valves 22 and 24 are used to open when the operation of the ink jet recording apparatus is stopped to release residual pressure in the ink circulation path.

The ink is adjusted to an appropriate standard viscosity by diluting it with a solvent such as methyl ethyl ketone. However, the methyl ethyl ketone easily volatilizes and becomes ink particles 20 to be volatilized during flight in the air. The viscosity tends to increase gradually. When the viscosity of the ink becomes a high value exceeding a certain range, it becomes impossible to adhere the ink particles to a predetermined position, which causes print disorder.

In order to prevent the occurrence of such print irregularity, the ink jet recording apparatus according to the present invention measures the viscosity of the ink with the viscosity sensor 7, and the control unit 5 determines whether the ink viscosity is relative to the reference value. Check if the value is
When it becomes higher than the reference value, the solenoid valve 14 is opened and the pump 9 is operated to supply the solvent in the solvent container 3 to the main ink container 15 to reduce the viscosity of the ink, and within a predetermined range. Control to keep on.

FIG. 2 is a vertical sectional side view showing an embodiment of the viscosity sensor 7. The base 26, which also serves as the entire mounting member, is provided with an ink inlet portion 26A in a part thereof. A fixed shaft 27, which stands upright in the center of the base 26, rotatably supports a driven rotor 28 and a drive rotor 29. A step portion 27A provided in the middle of the fixed shaft 27 regulates the position of the drive rotor 29 in the thrust direction to a predetermined position.

The driven rotor 28 is provided with a plurality of vertical concentric ribs 28A opened upward, and a plurality of small holes 28B for allowing ink to pass therethrough are formed at the bottom.
The driven rotor 28 is rotatably held by the fixed shaft 27, but its position in the thrust direction is restricted by the base 26 and the step portion 27A.

The drive rotor 29 has a plurality of vertical concentric ribs 29A opened downward, and a plurality of small holes 29B for passing ink and bleeding air are formed in the ceiling portion. The vertical concentric rib 29A is the vertical concentric rib 28.
The vertical concentric rib 28A is arranged at a position overlapping with the vertical concentric rib 28A so as to face the radial direction in the vicinity of the concentric state with A, thereby increasing the opposing area and preventing the axial dimension from increasing. One end of this drive rotor 29 is connected to a rotor 30 that constitutes a synchronous motor.

The case 31 has a seal 3 at the bottom open side.
It is fixed to the base 26 via 2. The base 26 and the case 31 are fixed by, for example, ultrasonic welding or the like so as to ensure airtightness.

A space formed by the base 26 and the case 31 in a closed state serves as a measuring chamber 33 for accommodating the driven rotor 28 and the driving rotor 29 in high density.
The rotor 30 is housed in the upper part of the measurement chamber 33, and the stator 34 separated by the partition wall 31A is installed to face the outer periphery of the rotor 30. The partition wall 31A is preferably as thin as possible in order to prevent loss of the rotating magnetic field generated in the stator 34. The lid 38 is provided in the measurement chamber 33 as shown in the cross section in FIG.
A plurality of ribs 38A that support the fixed shaft 27 while ensuring an ink passage connected to the ink outlet portion 38B.

The stator 34 is provided with an exciting coil and a magnetic pole member, and a rotating magnetic field is generated in the magnetic pole member by applying an alternating voltage to the exciting coil. The rotor 30 has an N pole and an S pole on its outer peripheral surface. By magnetizing the poles alternately at equal intervals, a self-starting synchronous motor that repeats the rotating magnetic field generated in the stator 34 and the attraction and repulsion to rotate is constructed.
Since this principle is the synchronous motor itself, as long as the period of the rotating magnetic field does not change, and unless an excessive load is applied to the rotor 30, the rotational speed (speed) of the rotor 30 becomes constant and the drive rotor 29 Is rotated at a constant rotation speed (speed).

The permanent magnet 35 is driven by the driven rotor 28.
The detector 36 receives the magnetic field generated by the permanent magnet 35 and generates a rotation detection signal.
The detector 36 uses an element that responds to the strength of the magnetic field, such as a Hall element or a reed switch.

The lid 38 and the case 31 are fastened with a screw 38 with an O-ring 37 for sealing interposed.

Since the base 26 and the case 31 are in contact with the ink (solvent), it is necessary to manufacture the base 26 and the case 31 with materials that are not affected by them. For example, if the solvent is methyl ethyl ketone (MEK), the material is polypropylene resin (PP) or polyphenylene sulfide resin (PP).
S) and the like are suitable.

Here, the circulation paths of the ink and the solvent will be described with reference to FIGS. When the pump 8 operates, the ink of standard viscosity in the ink container 2 is sucked into the pump 8 through the pipe from the ink container 2, is pressurized by the pump 8 and flows into the solenoid valve 13. At this time, if the solenoid valve 13 is open, the ink flows into the main ink container 15. Similarly, the solvent sucked from the solvent container 3 is sucked and pressurized by the pump 9, flows to the solenoid valve 14, and then to the main ink container 15.

The ink in the main ink container 15 is sucked by the pump 10 and is supplied to the ink inlet portion 26 of the viscosity sensor 7.
It is supplied from A to the measurement chamber 33, and after filling the measurement chamber 33, it exits from the ink outlet portion 38B and enters the pressure reducing valve 17 via the filter 16. The pressure reducing valve 17 adjusts this ink to an appropriate pressure and then supplies it to the nozzle 19 of the print head 6 via the electromagnetic valve 18. The pump 11 collects the ink captured by the ink recovery port 21 in the main ink container 15.

The viscosity sensor 7 is operated to measure the viscosity of the ink at preset time intervals. This viscosity measurement is performed as follows. An alternating voltage is applied to the stator 34 to generate a rotating magnetic field, and the rotor 30 is rotated at a constant rotation speed. As a result, the drive rotor 29 integrally connected to the rotor 30 also rotates, and the rotation of the drive rotor 29 causes the ink in the measurement chamber 33 to rotate in the same direction due to the adhesive force with the drive rotor 29. . The rotation of the ink transmits a rotational force to the driven rotor 28, causing the driven rotor 28 to rotate. In other words, due to the viscosity of the ink,
The drive rotor 29 and the driven rotor 28 are viscously connected or fluidly connected. This binding force changes depending on the viscosity of the ink. That is, the binding force is high when the ink viscosity is high, and the binding force is low when the ink viscosity is low.

Therefore, when the ink viscosity is high, the coupling force between the driving rotor 29 and the driven rotor 28 becomes large,
If the frictional resistance between the driven rotor 28 and the fixed shaft 27 is set to a constant value, the rotational speed of the driven rotor 28 becomes higher as the viscosity of the ink increases. When the viscosity of the ink is low, the rotation speed of the driven rotor 28 decreases.

In such a state, the number of the permanent magnets 35 passing through the position of the detector 36 (passage number) during a fixed time is counted and the detection signal output from the detector 36 is counted, so that the driven rotor 28 is rotated. The rotational speed (rotational speed) is measured, and the conversion table in which the relationship between the rotational speed (rotational speed) and the viscosity is obtained in advance is referred to based on the measurement result,
Alternatively, calculation processing for conversion is performed to obtain the ink viscosity, and whether the ink viscosity is higher or lower than the reference value is determined. The resistance to the rotation of the driven rotor 28 depends on the resistance of the driven rotor 28.
Since it is generated by friction between the driven rotor 28 and the fixed shaft 27, it is important to control the fitting dimensional accuracy between the driven rotor 28 and the fixed shaft 27. The controller 5 is adjusted so that the individual difference in the frictional resistance force caused by the processing error or the assembly error is corrected by changing the value of the conversion table or the coefficient of the arithmetic processing in the processing or assembling stage. .

In practice, the rotational speed (rotation speed) of the driven rotor 28 in the ink of standard viscosity is stored in the control device 5 as a reference value, and the driven rotor 2 is rotated at regular intervals.
8 rotation speed. The current ink viscosity is obtained from the rotational speed compared with the reference value over several degrees, and the solenoid valve 9 is opened to supply the required amount of solvent from the solvent container 13 to the main ink container 1.
Supply to 5. The controller 5 is made to calculate the required amount of solvent while comparing it with the reference value. For the supply amount, the flow rate of the solenoid valve 9 is input to the control device 5 in advance, and the ink amount in the main ink container 15 is detected by a sensor (not shown) and input to the control device 5. Control is performed while confirming the opening time of the solenoid valve 9 and the remaining ink amount.

If the rotation speed measurement time is lengthened, it is possible to measure even a minute difference in viscosity, and it is sufficient to confirm the rotation speed for a short time when it is desired to know a rough value.

In order to accurately measure the viscosity of the ink in the main ink container 15, the main ink container 15
It is necessary that the ink inside the ink and the ink inside the viscosity sensor 7 have the same viscosity. The viscosity of the ink in the main ink container 15 is supplied from the solvent container 13 for adjusting the viscosity, new ink of standard viscosity replenished from the ink container 12, high recovery ink recovered from the ink recovery port 21. It depends on the amount of solvent used. Viscosity sensor 7
It is desirable to be able to perform viscosity measurement sensitively following changes in the viscosity of the ink in the main ink container 15. For that purpose, the viscosity sensor 7 needs to be able to replace old ink in the ink circulation path with the ink sucked from the main ink container 15 by the pump 10 flowing in with a small time delay. Incidentally, in an ink jet recording apparatus used as an industrial marking apparatus, the flow rate of ink flowing through the ink circulation path is about 3 cc / minute, and the main ink container 15 to the outlet of the solenoid valve 18 (main body 1) in this ink circulation path. The flow path volume up to the outlet) is about 200 cc.

In this embodiment, the viscosity sensor 7 according to the present invention is installed by being inserted in a position near the main ink container 15 in the pipe between the main ink container 15 and the pump 10. Further, in order to shorten the exchange time of the ink in the measuring chamber 33 in the viscosity sensor 15, the viscosity sensor 7 has a plurality of vertical concentric ribs 2A and 29A of the driven rotor 28 and the driving rotor 29, which are coaxial with each other. The driven rotor 28 is configured to face each other in close proximity to the state.
The facing area for fluid coupling between the drive rotor 29 and the drive rotor 29 can be increased and the amount of ink for fluid coupling can be reduced. Therefore, the ink in the viscosity sensor 7 can be replaced with the ink supplied from the main ink container 15 within a relatively short time.

The installation position of such a viscosity sensor 7 is
The installation position is excellent not only when the viscosity sensor of the above-described form is used but also when the viscosity sensor of another form is used. The filter 16 in the ink circulation path of the ink jet recording apparatus used as the industrial marking apparatus has a filtration chamber having a volume of 180 cc, and therefore, it takes 60 minutes to replace the ink in this filtration chamber at a flow rate of 3 cc / min. Takes time. Therefore, in such an ink jet recording apparatus, it is desirable that the viscosity sensor 7 be installed before the filter 16.

However, the viscosity sensor 7 and the filter 16 having a small volume of the filtration chamber are not desired to be affected by the change in hydraulic pressure.
In the case of an ink jet recording apparatus including the above, as shown in FIG. 4, by installing the electromagnetic valve 18 in the subsequent stage, it is possible to supply stable ink that is decompressed by the decompression valve 17. Other configurations are the same as those of the above-described embodiment.

[0050]

According to the ink viscosity measuring device of the present invention, a plurality of vertical concentric ribs of a driving rotor and a driven rotor, which use ink flowing through an ink circulation system as a coupling fluid, are opposed to each other in a concentric state. The ink is filled between the surfaces, and the viscosity of the ink is measured by utilizing the phenomenon that the rotation state of the driven rotor changes according to the viscosity of the ink.
The viscosity of the ink can be accurately measured with a relatively simple configuration. In particular, a configuration in which a plurality of vertical concentric ribs are filled with ink between the facing surfaces that are closely opposed to each other in a concentric state,
Since the viscosity can be measured using a small amount of ink, even if the ink is arranged in the ink circulation path with a small circulation flow rate, it can respond quickly to changes in the viscosity of the ink, and is highly versatile.

Further, by installing the ink viscosity measuring device between the ink container and the pump or the filter for supplying the ink of the ink container to the print head, the response delay due to the volume of the ink flow path is reduced. It is possible to obtain an ink jet recording device that can be used.

Further, by installing the ink viscosity measuring device between the ink container and the pump or the filter for supplying the ink of the ink container to the print head, the response delay due to the volume of the ink flow path is reduced. be able to.

[Brief description of drawings]

FIG. 1 is a piping diagram showing a circulation path of ink and a solvent in an ink jet recording apparatus according to the present invention.

FIG. 2 is a vertical sectional side view of a viscosity sensor according to the present invention.

FIG. 3 is a sectional view taken along line AA in FIG. 2;

FIG. 4 is a piping diagram showing a circulation path of ink and solvent showing another embodiment of the inkjet recording apparatus according to the present invention.

[Explanation of symbols]

7 ... Viscosity sensor, 26 ... Base, 27 ... Fixed shaft, 28
... driven rotor, 28A ... vertical concentric ribs, 29 ... driving rotor, 29A ... vertical concentric ribs, 30 ... rotor, 31 ...
Case, 32 ... Seal plate, 33 ... Measuring chamber, 34 ... Stator, 35 ... Permanent magnet, 36 ... Detector.

Claims (10)

[Claims] 1. An ink viscosity measuring device for measuring the viscosity of ink by detecting the rotational state of a driven rotor with respect to the rotation of the driving rotor when the space between the driving rotor and the driven rotor is filled with ink. And a measurement chamber in which the ink outlet is formed, and the drive rotor and the driven rotor are concentrically formed, and are rotatably installed in the measurement chamber so as to face each other in a concentric state so as to face each other. An ink viscosity measuring device comprising: a plurality of vertical concentric ribs; a synchronous motor that rotates the drive rotor; and a detection unit that detects a rotation state of the driven rotor. 2. The ink viscosity measuring device according to claim 1, wherein the plurality of vertical concentric ribs of the driving rotor and the driven rotor are opposed to each other in a state of being close to each other in a radial direction. 3. The synchronous motor according to claim 1, further comprising a rotor connected to the drive rotor in the measurement chamber, and a stator provided outside the measurement chamber on an outer periphery of the rotor. Ink viscosity measuring device. 4. The ink viscosity measuring device according to claim 1, wherein the detection means generates a detection signal according to the rotation speed of the driven rotor. 5. An ink circulation system for supplying ink, which has been sucked by a pump from an ink container and pressurized, to a print head and ejecting the ink as ink particles to capture ink particles not used for recording and collect them in the ink container. An ink viscosity measuring device for measuring the viscosity of the ink flowing in the ink circulation system,
An ink jet recording apparatus comprising a control device for controlling the supply of a solvent to the ink container according to the measured ink viscosity, wherein the ink viscosity measuring device is installed between the ink container and a pump. Recording device. 6. An ink jet recording apparatus according to claim 5, wherein the ink viscosity measuring device uses the ink viscosity measuring device according to any one of claims 1 to 4. 7. An ink, which is sucked and pressurized by a pump from an ink container and has a foreign substance removed by a filter, is supplied to a print head and ejected as ink particles, and ink particles not used for recording are trapped in the ink container. Inkjet recording provided with an ink circulation system for collecting, an ink viscosity measuring device for measuring viscosity of ink flowing in the ink circulation system, and a control device for controlling supply of a solvent to the ink container according to the measured ink viscosity In the apparatus, an ink jet recording apparatus, wherein the ink viscosity measuring device is installed between the ink container and a filter. 8. An ink jet recording apparatus according to claim 7, wherein the ink viscosity measuring device uses the ink viscosity measuring device according to any one of claims 1 to 4. 9. An ink that is sucked by a pump from an ink container, pressurized, and pressure-adjusted is supplied to a print head to be ejected as ink particles, and ink particles not used for recording are captured and collected in the ink container. In an ink jet recording apparatus provided with a circulation system, an ink viscosity measuring device for measuring the viscosity of ink flowing in the ink circulation system, and a control device for controlling the supply of a solvent to the ink container according to the measured ink viscosity, An ink jet recording apparatus, characterized in that a pressure-adjusted ink is passed through the ink viscosity measuring apparatus. 10. An ink jet recording apparatus according to claim 9, wherein the ink viscosity measuring apparatus uses the ink viscosity measuring apparatus described in any one of claims 1 to 4.