JP6934783B2 - Inkjet recording device and its control method - Google Patents

Description

The present invention relates to an inkjet recording device and a control method thereof.

In Patent Document 1, a developing solution stored in a tank is mixed with a diluting solution at a certain ratio to generate a developing solution for detecting a toner concentration, which is diluted to a concentration within a measurable range of the amount of transmitted light. A method of measuring the amount of transmitted light in the transparent cell portion is disclosed.

Japanese Unexamined Patent Publication No. 11-198398

However, when the density of the ink used for image formation in the inkjet recording apparatus is measured by the measurement method of Patent Document 1, the diluted solution is mixed with the ink actually used for image formation, so that the ink density is detected. On the other hand, two density detection errors may occur: a mixing error of the diluent and a conversion error of the amount of transmitted light between the ink and the diluent. As a result, the density of the ink itself actually used is not measured, and there is a possibility that sufficient accuracy cannot be obtained in the measurement. Further, in the method of Patent Document 1, there is a possibility that the ink used for density detection may be wasted.

On the other hand, as a method of measuring the density of the ink itself used for image formation without using a diluent, a narrow portion is provided in the flow path of the ink for which the density is measured so that light can be transmitted, and the narrow portion is provided. There is a method of irradiating light and measuring the concentration from the transmitted light.

Here, in general, the absorption rate (hereinafter referred to as absorbance) Abs of ink is proportional to the concentration and the optical path length. The optical path length here corresponds to the width of the narrow portion to be irradiated with light. Expressing this as an expression,
Abs = constant 1 x concentration x optical path length ... (1)
Will be.

On the other hand, in the measurement of absorbance, if the amount of incident light before entering the optical path is Iin and the amount of light after passing through the optical path is Iout.
Abs = (-1) x log (Iout / Iin) ... (2)
There is a relationship. Here, log is a common logarithmic base of 10. However, in the actual Iin, the amount of light when the optical path (narrow portion) is filled with water having no ink component is defined as Iin, and the amount of light measured when the optical path is filled with ink for measuring the optical path is defined as Iout.

From the equations (1) and (2), it can be seen that the deviation of the optical path length has an exponential effect on the measurement result of the absorbance.

Further, when the optical path length is reduced, a negative pressure is generated in the flow path due to the pump operation for circulation when the ink is replaced in the flow path. As a result, the shape of the flow path (that is, the shape of the optical path) is deformed by the generated negative pressure, and the correct absorbance cannot be measured.

Therefore, an object of the present invention is to measure the ink density with high accuracy based on the above problems.

In order to solve the above problems, the present invention has the following configurations. That is, in an inkjet recording device, a tank for storing ink supplied to a recording head that ejects ink and a flow path for the ink are formed, and a density measuring unit for measuring the density of the ink in the flow path. The control means includes a pump for circulating ink in the flow path formed in the density measuring unit and the tank, and a control means for controlling the measurement of the ink density by the density measuring unit. After the ink circulation by the pump is completed, the ink density is measured by the density measuring unit at predetermined time intervals, and the difference between the latest measured value and the previous measurement becomes equal to or less than the predetermined threshold value. If so, the latest measured value is determined as an output value.

INDUSTRIAL APPLICABILITY According to the present invention, the density of ink used for image formation can be measured with high accuracy.

It is a schematic diagram of a recording system. It is a perspective view of a recording unit. It is a block diagram of the control system of the recording system of FIG. It is a block diagram of the control system of the recording system of FIG. It is a perspective view which shows the structural example of a recording head. It is a figure for demonstrating the mechanism which ink circulates in a recording head. It is a figure which shows the ink circulation mechanism between a recording head and a buffer tank. It is a figure explaining the circulation direction of ink in a recording head. It is a figure which shows the schematic structure of the concentration measuring part which concerns on this invention. It is a figure for demonstrating the structural example around the cell part of the concentration measuring part which concerns on this invention. It is a figure for demonstrating the flow path of ink which concerns on 1st Embodiment. It is a figure for demonstrating the switching of the ink flow path which concerns on 1st Embodiment. It is a figure for demonstrating the change of the shape of an optical path in a cell part. It is a figure for demonstrating the relationship between the optical path length and the amount of transmitted light. It is a flowchart of the process of the measurement operation which concerns on 1st Embodiment. It is a figure for demonstrating the relationship between the pressure in a cell part and the amount of transmitted light. It is a flowchart of the process of the measurement operation which concerns on 2nd Embodiment. It is a flowchart of the process of the measurement operation which concerns on 3rd Embodiment. It is a figure for demonstrating the change of the amount of transmitted light with the lapse of time.

An embodiment of the present invention will be described with reference to the drawings. In each figure, the arrows X and Y indicate the horizontal direction and are orthogonal to each other. Arrow Z indicates the vertical direction.

<Recording system>
FIG. 1 is a front view schematically showing a recording system 1 according to an embodiment of the present invention. The recording system 1 is a single-wafer inkjet printer that produces a recorded material P'by transferring an ink image to a recording medium P via a transfer body 2. The recording system 1 includes a recording device 1A and a transport device 1B. In the present embodiment, the X direction, the Y direction, and the Z direction indicate the width direction (total length direction), the depth direction, and the height direction of the recording system 1, respectively. The recording medium P is conveyed in the X direction.

In "recording", not only when significant information such as characters and figures is formed, but also images, patterns, patterns, etc. are widely formed on a recording medium or the medium is processed regardless of whether it is significant or unintentional. Cases are also included, and it does not matter whether or not it is manifested so that it can be visually perceived by humans. Further, in the present embodiment, sheet-shaped paper is assumed as the "recording medium", but cloth, plastic film, or the like may be used.

The components of the ink are not particularly limited, but in the present embodiment, it is assumed that a water-based pigment ink containing a pigment, water, and a resin as coloring materials is used.

<Recording device>
The recording device 1A includes a recording unit 3, a transfer unit 4, peripheral units 5A to 5D, and a supply unit 6.

<Recording unit>
The recording unit 3 includes a plurality of recording heads 30 and a carriage 31. See FIGS. 1 and 2. FIG. 2 is a perspective view of the recording unit 3. The recording head 30 ejects liquid ink to the transfer body 2 and forms an ink image of a recorded image on the transfer body 2.

In the case of the present embodiment, each recording head 30 is a full-line head extended in the Y direction, and nozzles are arranged in a range covering the width of the image recording area of the maximum usable recording medium. There is. The recording head 30 has an ink ejection surface having a nozzle opened on the lower surface thereof, and the ink ejection surface faces the surface of the transfer body 2 through a minute gap (for example, several mm). In the case of the present embodiment, since the transfer body 2 is configured to move cyclically on the circular orbit, the plurality of recording heads 30 are arranged radially.

Each nozzle is provided with a discharge element. The ejection element is, for example, an element that generates pressure in the nozzle to eject ink in the nozzle, and a technique of an inkjet head of a known inkjet printer can be applied. As the ejection element, for example, an element that ejects ink by causing a film to boil in the ink by an electric-heat converter to form bubbles, an element that ejects ink by an electric-mechanical converter, and an element that uses static electricity to eject ink. Examples include a discharge element. From the viewpoint of high-speed and high-density recording, a discharge element using an electric-heat converter can be used.

In the case of this embodiment, nine recording heads 30 are provided. Each recording head 30 ejects different types of ink from each other. The different types of ink are, for example, inks having different coloring materials, such as yellow ink, magenta ink, cyan ink, and black ink. Although one recording head 30 ejects one type of ink, one recording head 30 may be configured to eject a plurality of types of ink. When a plurality of recording heads 30 are provided in this way, ink (for example, clear ink) in which some of them do not contain a coloring material may be ejected.

The carriage 31 supports a plurality of recording heads 30. The end of each recording head 30 on the ink ejection surface side is fixed to the carriage 31. As a result, the gap between the ink ejection surface and the surface of the transfer body 2 can be maintained more precisely. The carriage 31 is configured to be displaceable while mounting the recording head 30 by the guidance of the guide member RL. In the case of the present embodiment, the guide members RL are rail members extending in the Y direction, and are provided in pairs separated in the X direction. Slide portions 32 are provided on each side portion of the carriage 31 in the X direction. The slide portion 32 engages with the guide member RL and slides in the Y direction along the guide member RL.

<Transfer unit>
The transfer unit 4 will be described with reference to FIG. The transfer unit 4 includes a transfer drum (transfer cylinder) 41 and an impression cylinder 42. These bodies are rotating bodies that rotate around a rotation axis in the Y direction, and have a cylindrical outer peripheral surface. In FIG. 1, the arrows shown in the figures of the transfer drum 41 and the impression cylinder 42 indicate the rotation directions thereof, and the transfer drum 41 rotates clockwise and the impression cylinder 42 rotates counterclockwise.

The transfer drum 41 is a support that supports the transfer body 2 on its outer peripheral surface. The transfer body 2 is provided continuously or intermittently in the circumferential direction on the outer peripheral surface of the transfer drum 41. When continuously provided, the transfer body 2 is formed in an endless band shape. When intermittently provided, the transfer body 2 is formed by dividing it into a plurality of segments in an endless band shape, and each segment can be arranged in an arc shape at an equal pitch on the outer peripheral surface of the transfer drum 41.

Due to the rotation of the transfer drum 41, the transfer body 2 moves cyclically on the circular orbit. Depending on the rotation phase of the transfer drum 41, the position of the transfer body 2 can be distinguished into a discharge pretreatment region R1, a discharge region R2, a discharge post-treatment region R3 and R4, a transfer region R5, and a transfer post-treatment region R6. The transcript 2 circulates through these regions.

The ejection pretreatment region R1 is an region in which the transfer body 2 is preprocessed before the ink is ejected by the recording unit 3, and is a region in which the peripheral unit 5A performs the treatment. In the case of this embodiment, the reaction solution is applied. The ejection region R2 is a forming region in which the recording unit 3 ejects ink to the transfer body 2 to form an ink image. The post-ejection processing areas R3 and R4 are processing areas for processing the ink image after the ink is ejected, the post-ejection processing area R3 is an area for processing by the peripheral unit 5B, and the post-ejection processing area R4 is the peripheral unit 5C. This is the area where the processing is performed. The transfer region R5 is a region in which the ink image on the transfer body 2 is transferred to the recording medium P by the transfer unit 4. The post-transcriptional processing region R6 is a region for post-treating the transfer body 2 after transcription, and is a region for processing by the peripheral unit 5D.

In the case of the present embodiment, the discharge region R2 is a region having a certain section. The other regions R1 and R3 to R6 have a narrower section than the discharge region R2. In the case of the present embodiment, the discharge pre-processing area R1 is approximately 10 o'clock, the discharge area R2 is approximately 11 o'clock to 1 o'clock, and the discharge post-processing area R3 is approximately 10 o'clock. It is the position at 2 o'clock, and the post-discharge processing area R4 is the position at about 4 o'clock. The transfer region R5 is at approximately 6 o'clock, and the post-transcriptional processing region R6 is approximately 8 o'clock.

The transfer body 2 may be composed of a single layer, or may be a laminated body having a plurality of layers. When composed of a plurality of layers, for example, a surface layer, an elastic layer, and a compression layer may be included. The surface layer is the outermost layer having an image forming surface on which an ink image is formed. By providing the compression layer, the compression layer can absorb the deformation, disperse the fluctuation with respect to the local pressure fluctuation, and maintain the transferability even at the time of high-speed recording. The elastic layer is the layer between the surface layer and the compression layer.

As the surface layer material, various materials such as resin and ceramic can be appropriately used, but a material having a high compressive elastic modulus can be used in terms of durability and the like. Specific examples thereof include an acrylic resin, an acrylic silicone resin, a fluorine-containing resin, and a condensate obtained by condensing a hydrolyzable organosilicon compound. The surface layer may be subjected to surface treatment in order to improve the wettability of the reaction solution, the transferability of the image, and the like. Examples of the surface treatment include frame treatment, corona treatment, plasma treatment, polishing treatment, roughening treatment, active energy ray irradiation treatment, ozone treatment, surfactant treatment, silane coupling treatment and the like. A plurality of these may be combined. Further, any surface shape can be provided on the surface layer.

Examples of the material of the compression layer include acrylonitrile-butadiene rubber, acrylic rubber, chloroprene rubber, urethane rubber, and silicone rubber. At the time of molding such a rubber material, a predetermined amount of a vulcanizing agent, a vulcanization accelerator, etc. are blended, and further, a foaming agent, hollow fine particles, a filler such as salt, etc. are blended as necessary, and the porous rubber material is blended. May be. As a result, since the bubble portion is compressed with a volume change in response to various pressure fluctuations, deformation in directions other than the compression direction is small, and more stable transferability and durability can be obtained. Porous rubber materials include those having a continuous pore structure in which each pore is continuous with each other and those having an independent pore structure in which each pore is independent, but any structure may be used, and these structures may be used in combination. You may.

As the member of the elastic layer, various materials such as resin and ceramic can be appropriately used. Various elastomer materials and rubber materials can be used in terms of processing characteristics and the like. Specific examples thereof include fluorosilicone rubber, phenylsilicone rubber, fluororubber, chloroprene rubber, urethane rubber, nitrile rubber and the like. Further, ethylene propylene rubber, natural rubber, styrene rubber, isoprene rubber, butadiene rubber, ethylene / propylene / butadiene copolymer, nitrile butadiene rubber and the like can be mentioned. In particular, silicone rubber, fluorosilicone rubber, and phenylsilicone rubber are advantageous in terms of dimensional stability and durability because they have a small compression set. In addition, the change in elastic modulus with temperature is small, which is advantageous in terms of transferability.

Various adhesives or double-sided tape can also be used between the surface layer and the elastic layer, and between the elastic layer and the compression layer to fix them. Further, the transfer body 2 may include a reinforcing layer having a high compressive elastic modulus in order to suppress lateral elongation when mounted on the transfer drum 41 and to maintain elasticity. Further, the woven fabric may be used as a reinforcing layer. The transfer body 2 can be produced by arbitrarily combining each layer made of the above-mentioned material.

The outer peripheral surface of the impression cylinder 42 is pressed against the transfer body 2. At least one grip mechanism for holding the tip of the recording medium P is provided on the outer peripheral surface of the impression cylinder 42. A plurality of grip mechanisms may be provided so as to be separated from each other in the circumferential direction of the impression cylinder 42. The recording medium P is conveyed in close contact with the outer peripheral surface of the impression cylinder 42, and when it passes through the nip portion between the impression cylinder 42 and the transfer body 2, the ink image on the transfer body 2 is transferred.
A drive source such as a motor for driving the transfer drum 41 and the impression cylinder 42 is common to these, and the driving force can be distributed by a transmission mechanism such as a gear mechanism.

<Peripheral unit>
Peripheral units 5A to 5D are arranged around the transfer drum 41. In the case of the present embodiment, the peripheral units 5A to 5D are, in order, an imparting unit, an absorption unit, a heating unit, and a cleaning unit.

The applying unit 5A is a mechanism for applying the reaction liquid onto the transfer body 2 before ejecting the ink by the recording unit 3. The reaction liquid is a liquid containing a component that increases the viscosity of the ink. Here, increasing the viscosity of the ink means that the coloring material or resin constituting the ink chemically reacts or is physically adsorbed by coming into contact with the component that increases the viscosity of the ink, thereby causing the ink to become highly viscous. An increase in the viscosity of the ink is observed. The increase in viscosity of the ink is not only when an increase in the viscosity of the entire ink is observed, but also when a part of the components constituting the ink such as a coloring material or a resin aggregates to cause a local increase in the viscosity. Is also included.

The component that increases the viscosity of the ink is not particularly limited, such as metal ions and polymer flocculants, but a substance that causes a change in the pH of the ink and aggregates the coloring material in the ink can be used, and an organic acid can be used. Can be used. Examples of the reaction liquid application mechanism include a roller, a recording head, a die coating device (die coater), and a blade coating device (blade coater). If the reaction solution is applied to the transfer body 2 before the ink is ejected to the transfer body 2, the ink that has reached the transfer body 2 can be immediately fixed. As a result, it is possible to suppress bleeding in which adjacent inks are mixed with each other.

The absorption unit 5B is a mechanism for absorbing a liquid component from the ink image on the transfer body 2 before transfer. By reducing the liquid component of the ink image, bleeding of the image recorded on the recording medium P can be suppressed. Explaining the decrease of the liquid component from a different viewpoint, it can be expressed as concentrating the ink constituting the ink image on the transfer body 2. Concentrating the ink means that the liquid component contained in the ink is reduced, so that the content ratio of the solid content such as the coloring material and the resin contained in the ink to the liquid component is increased.

The absorption unit 5B includes, for example, a liquid absorption member that comes into contact with the ink image to reduce the amount of liquid components in the ink image. The liquid absorbing member may be formed on the outer peripheral surface of the roller, or the liquid absorbing member may be formed in the shape of an endless sheet and travel in a cyclic manner. In terms of protecting the ink image, the liquid absorbing member may be moved in synchronization with the transfer body 2 by making the moving speed of the liquid absorbing member the same as the peripheral speed of the transfer body 2.

The liquid absorbing member may include a porous body that comes into contact with the ink image. In order to suppress the adhesion of ink solids to the liquid absorbing member, the pore size of the porous body on the surface in contact with the ink image may be 10 μm or less. Here, the pore diameter indicates an average diameter, and can be measured by a known means such as a mercury intrusion method, a nitrogen adsorption method, an SEM image observation, or the like. The liquid component is not particularly limited as long as it does not have a certain shape, has fluidity, and has a substantially constant volume. For example, water, an organic solvent, etc. contained in an ink or a reaction liquid can be mentioned as liquid components.

The heating unit 5C is a mechanism for heating the ink image on the transfer body 2 before transfer. By heating the ink image, the resin in the ink image is melted, and the transferability to the recording medium P is improved. The heating temperature can be equal to or higher than the minimum film forming temperature (MFT) of the resin. MFT can be measured by generally known methods such as JIS K 6828-2: 2003 and ISO2115: 1996 compliant devices. From the viewpoint of transferability and image fastness, heating may be performed at a temperature higher than MFT by 10 ° C. or higher, and further, heating may be performed at a temperature higher than 20 ° C. or higher. As the heating unit 5C, known heating devices such as various lamps such as infrared rays and a hot air fan can be used. Infrared heaters can be used in terms of heating efficiency.

The cleaning unit 5D is a mechanism for cleaning the transfer body 2 after transfer. The cleaning unit 5D removes ink remaining on the transfer body 2, dust on the transfer body 2, and the like. For the cleaning unit 5D, for example, a known method such as a method of bringing a porous member into contact with the transfer body 2, a method of rubbing the surface of the transfer body 2 with a brush, a method of scraping the surface of the transfer body 2 with a blade, or the like is appropriately used. Can be done. Further, as the cleaning member used for cleaning, a known shape such as a roller shape or a web shape can be used.

As described above, in the present embodiment, the imparting unit 5A, the absorbing unit 5B, the heating unit 5C, and the cleaning unit 5D are provided as peripheral units, but some of these units are provided with the cooling function of the transfer body 2 or are provided. , A cooling unit may be added. In the present embodiment, the temperature of the transfer body 2 may rise due to the heat of the heating unit 5C. If the ink image exceeds the boiling point of water, which is the main solvent of the ink, after the ink is ejected to the transfer body 2 by the recording unit 3, the absorption performance of the liquid component by the absorption unit 5B may deteriorate. By cooling the transfer body 2 so that the ejected ink is maintained below the boiling point of water, the absorption performance of the liquid component can be maintained.

The cooling unit may be a blowing mechanism that blows air to the transfer body 2 or a mechanism that brings a member (for example, a roller) into contact with the transfer body 2 and cools the member by air cooling or water cooling. Further, it may be a mechanism for cooling the cleaning member of the cleaning unit 5D. The cooling timing may be the period after the transfer and before the application of the reaction solution.

<Supply unit>
The supply unit 6 is a mechanism for supplying ink to each recording head 30 of the recording unit 3. The supply unit 6 may be provided on the rear side of the recording system 1. The supply unit 6 includes a storage unit TK for storing ink for each type of ink. The storage unit TK may be composed of a main tank and a sub tank. Each storage unit TK and each recording head 30 communicate with each other through a flow path 6a, and ink is supplied from the storage unit TK to the recording head 30. The flow path 6a may be a flow path for circulating ink between the storage unit TK and the recording head 30, and the supply unit 6 may include a pump or the like for circulating ink. A degassing mechanism for degassing air bubbles in the ink may be provided in the middle of the flow path 6a or in the storage portion TK. A valve for adjusting the hydraulic pressure of the ink and the atmospheric pressure may be provided in the middle of the flow path 6a or in the storage portion TK. The heights of the storage unit TK and the recording head 30 in the Z direction may be designed so that the ink liquid level in the storage unit TK is lower than the ink ejection surface of the recording head 30.

<Transport device>
The transport device 1B is a device that feeds the recording medium P to the transfer unit 4 and discharges the recorded material P'with the ink image transferred from the transfer unit 4. The transport device 1B includes a feed unit 7, a plurality of transport cylinders 8, 8a, two sprockets 8b, a chain 8c, and a recovery unit 8d. In FIG. 1, the inner arrow of the figure of each configuration of the transport device 1B indicates the rotation direction of the configuration, and the outer arrow indicates the transport path of the recording medium P or the recorded object P'. The recording medium P is transported from the feeding unit 7 to the transfer unit 4, and the recorded material P'is transported from the transfer unit 4 to the recovery unit 8d. The feeding unit 7 side may be referred to as the upstream side in the transport direction, and the recovery unit 8d side may be referred to as the downstream side.

The feeding unit 7 includes a loading unit on which a plurality of recording media P are loaded, and also includes a feeding mechanism for feeding the recording media P one by one from the loading unit to the most upstream transport cylinder 8. Each of the transport cylinders 8 and 8a is a rotating body that rotates around a rotation axis in the Y direction, and has a cylindrical outer peripheral surface. At least one grip mechanism for holding the tip of the recording medium P (or the recording object P') is provided on the outer peripheral surface of each of the transport cylinders 8 and 8a. The gripping operation and the releasing operation of each grip mechanism are controlled so that the recording medium P is passed between the adjacent transport cylinders.

The two transport cylinders 8a are transport cylinders for reversing the recording medium P. When recording on both sides of the recording medium P, after the transfer to the surface, the recording medium P is passed to the transport cylinder 8a without being passed from the impression cylinder 42 to the transport cylinder 8 adjacent to the downstream side. The recording medium P is turned upside down via the two transport cylinders 8a, and is passed to the impression cylinder 42 again via the transport cylinder 8 on the upstream side of the impression cylinder 42. As a result, the back surface of the recording medium P faces the transfer drum 41, and the ink image is transferred to the back surface.

The chain 8c is wound between the two sprockets 8b. One of the two sprockets 8b is the driving sprocket and the other is the driven sprocket. The rotation of the drive sprocket causes the chain 8c to travel cyclically. The chain 8c is provided with a plurality of grip mechanisms separated from each other in the longitudinal direction thereof. The grip mechanism grips the end of the recorded object P'. The recorded material P'is passed from the transport cylinder 8 located at the downstream end to the grip mechanism of the chain 8c, and the recorded material P'gripped by the grip mechanism is transported to the recovery unit 8d by the traveling of the chain 8c, and the grip is released. NS. As a result, the recorded material P'is loaded in the collection unit 8d.

<Post-processing unit>
The transport device 1B is provided with post-processing units 10A and 10B. The post-processing units 10A and 10B are arranged on the downstream side of the transfer unit 4 and are a mechanism for performing post-processing on the recorded material P'. The post-processing unit 10A processes the front surface of the recorded material P', and the post-processing unit 10B processes the back surface of the recorded material P'. Examples of the processing contents include a coating on the image recording surface of the recorded object P'for the purpose of protecting the image, polishing the image, and the like. Examples of the content of the coating include application of a liquid, welding of a sheet, laminating and the like.

<Inspection unit>
The transport device 1B is provided with inspection units 9A and 9B. The inspection units 9A and 9B are arranged on the downstream side of the transfer unit 4 and are a mechanism for inspecting the recorded material P'.

In the case of the present embodiment, the inspection unit 9A is an imaging device that captures an image recorded on the recorded object P', and includes, for example, an image pickup device such as a CCD sensor or a CMOS sensor. The inspection unit 9A captures a recorded image during a continuous recording operation. Based on the image taken by the inspection unit 9A, it is possible to confirm the change with time such as the color tone of the recorded image and determine whether or not the image data or the recorded data can be corrected. In the case of the present embodiment, the inspection unit 9A has an imaging range set on the outer peripheral surface of the impression cylinder 42, and is arranged so that the recorded image immediately after transfer can be partially captured. The inspection unit 9A may inspect all recorded images, or may inspect every predetermined number.

In the case of the present embodiment, the inspection unit 9B is also an imaging device that captures an image recorded on the recorded object P', and includes, for example, an image pickup device such as a CCD sensor or a CMOS sensor. The inspection unit 9B captures a recorded image in the test recording operation. The inspection unit 9B captures the entire recorded image, and can make basic settings for various corrections related to the recorded data based on the image captured by the inspection unit 9B. In the case of the present embodiment, it is arranged at a position where the recorded object P'carried by the chain 8c is photographed. When the recorded image is taken by the inspection unit 9B, the running of the chain 8c is temporarily stopped and the whole is taken. The inspection unit 9B may be a scanner that scans on the recorded object P'.

<Control unit>
Next, the control unit of the recording system 1 will be described. 3 and 4 are block diagrams of the control unit 13 of the recording system 1. The control unit 13 is communicably connected to the host device (DFE) HC2, and the host device HC2 is communicably connected to the host device HC1.

In the host device HC1, manuscript data that is the source of the recorded image is generated or saved. The manuscript data here is generated in the form of an electronic file such as a document file or an image file, for example. This manuscript data is transmitted to the higher-level device HC2, and the higher-level device HC2 converts the received manuscript data into a data format (for example, RGB data expressing an image in RGB) that can be used by the control unit 13. The converted data is transmitted from the host device HC2 to the control unit 13 as image data, and the control unit 13 starts the recording operation based on the received image data.

In the case of the present embodiment, the control unit 13 is roughly classified into a main controller 13A and an engine controller 13B. The main controller 13A includes a processing unit 131, a storage unit 132, an operation unit 133, an image processing unit 134, a communication I / F (interface) 135, a buffer 136, and a communication I / F 137.

The processing unit 131 is a processor such as a CPU, executes a program stored in the storage unit 132, and controls the entire main controller 13A. The storage unit 132 is a storage device such as a RAM, ROM, hard disk, SSD, etc., stores programs and data executed by the processing unit 131, and provides a work area to the processing unit 131. The operation unit 133 is, for example, an input device such as a touch panel, a keyboard, and a mouse, and receives a user's instruction.

The image processing unit 134 is, for example, an electronic circuit having an image processing processor. The buffer 136 is, for example, a RAM, a hard disk, or an SSD. The communication I / F 135 communicates with the host device HC2, and the communication I / F 137 communicates with the engine controller 13B. In FIG. 3, the broken line arrow illustrates the flow of image data processing. The image data received from the host device HC2 via the communication I / F 135 is stored in the buffer 136. The image processing unit 134 reads the image data from the buffer 136, performs predetermined image processing on the read image data, and stores the read image data in the buffer 136 again. The image data after image processing stored in the buffer 136 is transmitted from the communication I / F 137 to the engine controller 13B as recorded data used by the print engine.

As shown in FIG. 4, the engine controller 13B includes the control units 14, 15A to 15E, and acquires and controls the drive of the detection results of the sensor group and the actuator group 16 included in the recording system 1. Each of these control units includes a processor such as a CPU, a storage device such as a RAM or ROM, and an interface with an external device. Note that the division of control units is an example, and some controls may be executed by a plurality of control units that are further subdivided, or conversely, a plurality of control units may be integrated to combine the control contents. It may be configured to be performed by one control unit.

The engine control unit 14 controls the entire engine controller 13B. The recording control unit 15A converts the recorded data received from the main controller 13A into a data format suitable for driving the recording head 30, such as raster data. The recording control unit 15A controls the discharge of each recording head 30.

The transfer control unit 15B controls the imparting unit 5A, the absorption unit 5B, the heating unit 5C, and the cleaning unit 5D.

The reliability control unit 15C controls the supply unit 6, the recovery unit 12, and the drive mechanism for moving the recording unit 3 between the discharge position POS1 and the recovery position POS3.

The transfer control unit 15D controls the drive of the transfer unit 4 and the transfer device 1B. The inspection control unit 15E controls the inspection unit 9B and the inspection unit 9A.

Among the sensor group and the actuator group 16, the sensor group includes a sensor that detects the position and speed of a movable portion, a sensor that detects temperature, an image sensor, and the like. The actuator group includes a motor, an electromagnetic solenoid, an electromagnetic valve and the like.

Next, in the recording system having the above configuration, the ink circulation mechanism between the recording head 30 and the ink tank will be described.

<Detailed explanation of ink circulation mechanism>
[Detailed configuration of recording head]
FIG. 5 is a perspective view showing the configuration of the recording head 30.

FIG. 5A is a perspective view of the recording head 30 viewed from diagonally below, and FIG. 5B is a perspective view of the recording head 30 viewed from diagonally above.

The recording head 30 arranges 15 element substrates 10 capable of ejecting one color of ink on one element substrate 10 in a straight line (arranged in-line), and has a recording width corresponding to the width of the recording medium for full-line recording. The head.

As shown in FIG. 5A, the connection portions 111 provided at both ends of the recording head 30 are connected to the ink supply mechanism of the recording device. As a result, the ink is supplied from the ink supply mechanism to the recording head 30, and the ink that has passed through the recording head 30 is collected by the ink supply mechanism. In this way, the ink can be circulated through the path of the ink supply mechanism and the path of the recording head 30.

As shown in FIG. 5B, the recording head 30 includes a signal input terminal 91 and a power supply terminal 92 that are electrically connected via each element board 10, the flexible wiring board 40, and the electrical wiring board 90. .. The signal input terminal 91 and the power supply terminal 92 are electrically connected to the recording control unit 15A of the recording device, and supply the drive signal and the power required for discharge to the element substrate 10, respectively. By consolidating the wiring by the electric circuit in the electric wiring board 90, the number of signal input terminals 91 and power supply terminals 92 can be reduced as compared with the number of element boards 10. As a result, the number of electrical connections that need to be removed when the recording head 30 is attached to the recording unit 3 or when the recording head 30 is replaced can be reduced.

[Recording head ink circulation flow path]
FIG. 6 is a diagram illustrating a mechanism in which ink circulates in the recording head 30.

FIG. 6A is a side view of the recording head 30 including the liquid discharge unit 300, the liquid supply unit 220, and the negative pressure control unit 230. FIG. 6B is a schematic view showing the flow of the liquid. FIG. 6 (c) is a perspective view showing a cross section of the GG line portion of FIG. 6 (a).

As shown in FIG. 6A, the negative pressure control unit 230 is integrally formed below the liquid supply unit 220. Further, a flow path member 60 is attached to the liquid supply unit 220, and another flow path member 50 is attached below the flow path member 60. These two flow path members 50 and 60 form a part of the liquid discharge unit 300. Further, as shown in FIG. 6B, a connecting portion 111 and a filter 221 are provided in the liquid supply unit 220. With such a configuration, the distance between the negative pressure control unit 230 and the element substrate 10 in the height direction is shortened.

Further, since the water head difference between the negative pressure control unit 230 and the formation surface of the ink ejection port is relatively small, recording such that the tilt angle of the recording head 30 as shown in FIGS. 1 and 2 differs for each recording head. It can be suitably used for the unit 3. This is because the water arithmetic progression can be reduced, and even if a plurality of recording heads 30 are used at different inclination angles, the negative pressure difference applied to the ink ejection port of each element substrate can be reduced. Further, as the distance from the negative pressure control unit 230 to the element substrate 10 becomes smaller, the flow resistance between them becomes smaller, and the pressure loss difference due to the change in the flow rate of the liquid (ink) becomes smaller, so that stable negative pressure control can be performed. preferable.

Further, FIG. 6B shows the actual ink flow inside the recording head 30. A set of a common flow path (common supply flow path) 211 and a common flow path (common recovery flow path) 212 extending in the longitudinal direction of the recording head 30 are provided in the long flow path member 60. .. The common flow path 211 and the common flow path 212 are configured so that liquid (ink) flows in directions facing each other, and a filter 221 is provided on the upstream side of each flow path and penetrates from a connection portion 111 or the like. Trap foreign objects.

In this way, the common flow path 211 and the common flow path 212 flow the liquid in the directions facing each other, so that the temperature gradient in the longitudinal direction in the recording head 30 is reduced.

Negative pressure control units 230 are connected to the common flow path 211 and the downstream side of the common flow path 212, respectively. Further, there is a branch portion to a plurality of individual flow paths (individual supply flow paths) 213a in the middle of the common flow path 211, and to a plurality of individual flow paths (individual recovery flow paths) 213b in the middle of the common flow path 212. There is a branch of. The individual flow paths 213a and the individual flow paths 213b are formed in a plurality of flow path members 50, and each individual flow path communicates with an opening (not shown) provided on the back surface of the element substrate 10. ..

The negative pressure control unit 230 shown by H and L in FIG. 6B is a negative pressure control unit on the high pressure side (H) and a negative pressure control unit on the low pressure side (L). Each negative pressure control unit 230 is a back pressure type pressure adjusting mechanism set to control the pressure on the upstream side of the negative pressure control unit 230 with relatively high (H) and low (L) negative pressures. Is. The common flow path 211 is connected to the negative pressure control unit 230 (high pressure side), and the common flow path 212 is connected to the negative pressure control unit 230 (low pressure side), thereby between the common flow path 211 and the common flow path 212. A differential pressure is generated. Due to the differential pressure, the liquid flows from the common flow path 211 through the individual flow path 213a, each ink ejection port (not shown) in the element substrate 10, and the individual flow path 213b in this order to the common flow path 212.

Further, as can be seen from the configuration shown in FIG. 6A, the recording head 30 has a modular configuration including a plurality of units and members. As shown in FIG. 6C, each module is composed of a flow path member 50, an element substrate 10, and a flexible wiring substrate 40. In this embodiment, the element substrate 10 is directly connected to the flow path member 50. The common flow path 211 provided in the flow path member 60 is supplied from the communication port 61A formed on the upper surface thereof to the individual flow path 213a via the individual communication port 53 formed on the lower surface of the flow path member 50. NS. After that, the liquid is collected in the common flow path 212 via the individual flow path 213b, the individual communication port 53, and the communication port 61A in this order via the pressure chamber (not shown) of the element substrate 10.

Here, the individual communication port 53 on the lower surface of the flow path member 50 (the surface on the flow path member 60 side) has a sufficiently large opening with respect to the communication port 61A formed on the upper surface of the flow path member 50. With this configuration, even if the positions of each module are displaced when mounted on the flow path member 60, communication is reliably performed between the two flow path members 50 and 60, so that the yield during head manufacturing is improved. Cost reduction is planned.

[Ink circulation mechanism between the recording head and the buffer tank]
FIG. 7 is a diagram showing an ink circulation mechanism between the recording head 30 and the buffer tank. In FIG. 7, the same reference numbers and reference symbols as those already described with reference to FIG. 6 are assigned the same reference numbers and reference symbols, and the description thereof will be omitted. The ink circulation mechanism may be referred to as an ink supply device.

As shown in FIG. 7, five pumps 61 to 65 are used for the ink supply mechanism in this embodiment. In this embodiment, the storage unit TK for storing ink is composed of two tanks (main tank TK1 and buffer tank TK2), the buffer tank TK2 is connected to the recording head 30, and the buffer tank TK2 and the recording head 30 are connected. Ink circulates between them. On the other hand, a pump 61 is provided in the flow path between the main tank TK1 and the buffer tank TK2, and the pump 61 appropriately replenishes the buffer tank TK2 from the main tank TK1 with ink. The capacities of the main tank TK1 and the buffer tank TK2 are not particularly limited, and the relationship between the sizes is not particularly limited.

As shown in FIG. 7, the flow path 6a referred to in FIG. 1 includes a flow path 71 between the main tank TK1 and the buffer tank TK2, and four flow paths 72 between the buffer tank TK2 and the recording head 30. It is composed of ~ 75. Pumps 62 to 65 are provided in the flow paths 72 to 75, respectively.

The ink circulation mechanism can switch the ink circulation direction by controlling the drive of the four pumps 62 to 65.

FIG. 8 is a diagram illustrating circulation of ink in the recording head. When the ink is circulated, the pump 62 and the pump 65 are driven as described above, and the pump 63 and the pump 64 are stopped. In this case, the pressure reducing valve that operates as the negative pressure control unit 230 on the flow path 74 side is closed, and the pressure reducing valve that operates as the negative pressure control unit 230 on the flow path 75 side is opened. Therefore, as shown in FIG. 8, the ink passes through the flow path 72, passes through the filter 221 and reaches the common flow path 211, is supplied to each nozzle of the element substrate 10 via the individual flow path 213a, and is supplied to each nozzle of the element substrate 10 and is supplied to the individual flow path 213b. The common flow path 212 returns to the flow path 75.

Similarly, the pump 63 and the pump 64 are driven, and the pump 62 and the pump 65 are stopped. In this case, the pressure reducing valve operating as the negative pressure control unit 230 on the flow path 75 side is closed, and the pressure reducing valve operating as the negative pressure control unit 230 on the flow path 74 side is opened. As a result, the ink passes through the flow path 73, passes through the filter 221 and reaches the common flow path 212, enters each nozzle of the element substrate 10 via the individual flow path 213b, and enters the common flow path 211 via the individual flow path 213a. Return to the flow path 74.

In this way, the ink is circulated in the recording head 30. In the above, an example of a recording head having a configuration in which ink circulates in two directions has been shown, but the present invention is not limited to this, and a recording head that can circulate in only one direction may be used.

<First Embodiment>
Hereinafter, the first embodiment of the present invention will be described with reference to the drawings.

[Concentration measurement unit]
Hereinafter, a configuration example of a density measuring unit for measuring the density of ink provided in the inkjet recording apparatus according to the present invention will be described with reference to the drawings.

FIG. 9 is a diagram showing a schematic configuration of a concentration measuring unit according to the present embodiment. A plurality of concentration measuring units are provided according to the number of storage units TK shown in FIG.

The cell portion 901 is a portion made of a transparent member in which a flow path for passing the ink for measuring the density is formed. The cell portion 901 is made of, for example, quartz. The light emitting element 902 is a light source that irradiates light. The light emitting element 902 irradiates light with a predetermined amount of light based on the instruction from the measuring unit 909. The light emitting element 902 is composed of, for example, an LED or the like. The light receiving element 903 is a light receiving element that receives light transmitted through the cell portion 901, and is arranged at a position facing the light emitting element 902 with the cell portion 901 interposed therebetween. The information (signal) of the amount of light received by the light receiving element 903 is passed to the measuring unit 909. The light receiving element 903 is composed of, for example, a photodiode.

The flow paths 904 and 905 are connected to the cell portion 901 and the tank 906 so that the ink can be circulated. The tank 906 is a storage unit in which ink used for image formation is stored, and corresponds to the storage unit TK shown in FIG. More specifically, it corresponds to the buffer tank TK2 shown in FIG. The bypass flow path 907 is a flow path connecting the flow path 904 and the flow path 905, and ink can flow by opening and closing the installed valve. The bypass flow path 907 is used for the purpose of shortening the ink replacement time in the cell portion 901, eliminating the negative pressure at the time of density measurement, and the like. Pump 908 is controlled to circulate ink in the flow path and tank 906.

The measuring unit 909 functions as a control unit that controls the light emitting element 902 to emit light at a predetermined amount of light when measuring the density of the ink. Further, the measuring unit 909 also functions as a derivation unit that acquires the amount of light received by the light receiving element 903 in response to the light emitted by the light emitting element 902 and derives the ink density based on the value. It is assumed that the amount of light emitted by the light emitting element 902, the amount of light received by the light receiving element 903, and the density of the ink are associated with each other in advance and the information is retained. The correspondence here is defined for each ink color, for example, by a look-up table or the like.

FIG. 10 is a diagram showing a configuration example around the cell portion 901 according to the present embodiment.

The cell portion 901 is configured by using a transparent member, and a flow path 1001 through which ink flows is formed inside. Here, an example is shown in which ink flows from the lower side to the upper side of the figure. The light from the light emitting element 902 is irradiated to a predetermined position through which the ink flows as incident light. Then, the transmitted light transmitted through the predetermined position is configured to reach the light receiving element 903. In the flow path through which the ink of the cell portion 901 flows, a narrow portion is configured so that the predetermined position is narrower than the other portions. Here, it is assumed that the relationship between the width L1 (optical path length) at a predetermined position (narrow portion) in the cell portion 901 and the width L2 at other positions is defined according to the color and component of the ink. .. For example, the width L1 can be configured to be about 20 μm. The amount of light emitted by the light emitting element 902 at the time of density measurement is also defined in relation to the width L1 and the color (transmittance) of the ink. Here, the widths L1 and L2 refer to diameters in the flow path through which the ink passes, but the cross section is not limited to a circle and may have other shapes.

FIG. 11 is a diagram for explaining the overall concept of the ink flow path according to the present embodiment. As described above, since the cell portion 901 according to the present embodiment is configured so that a part of the flow path is narrowed, it takes time to circulate (replace) the ink, and the ink stays or foreign matter. Ink may be clogged. Therefore, in the present embodiment, this problem is solved by providing two flow paths for the concentration measuring unit 1101 so that the flow paths can be switched. Although the components for one color are shown in FIG. 11 for simplification of the description, the components of the set shown in FIG. 11 are shown according to the number of colors (types) of the inks supported by the recording device. Shall be provided.

The recording head 30 is a recording head that ejects ink to form an image. The ink used for image formation is supplied from the tank 906. Further, the recording head 30 and the tank 906 are configured so that ink circulates. As described above, the tank 906 corresponds to the buffer tank TK2 shown in FIG.

The tank 906 is a storage unit in which ink used for image formation is stored. The tank 906 may be provided with a stirring unit (not shown) for stirring the ink, a detecting unit (not shown) for detecting the amount of ink stored (remaining amount), and the like. Further, the tank 906 is provided with an atmospheric communication port 1110 for inflowing and discharging the air in the tank 906. Therefore, the outside air pressure and the air pressure inside the tank are usually configured to be the same (or substantially the same).

Ink supply tank 1102 for supplying ink to tank 906, diluted water supply tank 1103 for supplying diluted water to tank 906, and pumps 1104 and 1105 are provided around the tank 906. Pump 1104 corresponds to pump 61 shown in FIG.

Further, the tank 906 is provided with an ink flow path between the tank 906 and the recording head 30, and pumps 1106 and 1107 for circulating ink between the tank 906 and the recording head 30 are provided on the flow path. Provided. Two pumps 1106, 1107 are shown here for brevity, but they correspond to pumps 62-65 shown in FIG. The ink circulation between the recording head 30 and the tank 906 is as shown in FIGS. 6 to 8.

The ink supply tank 1102 is a supply unit in which the ink supplied to the tank 906 is stored when the amount of ink stored in the tank 906 decreases or the concentration of the ink in the tank 906 decreases. .. The ink supply from the ink supply tank 1102 to the tank 906 may be performed based on an instruction from the control unit (not shown), or may be performed when the ink supply tank 1102 is replaced. Ink is supplied from the ink supply tank 1102 to the tank 906 by driving the pump 1104 by the control unit (not shown). Further, inside the ink supply tank 1102, a stirring unit (not shown) for stirring the ink, a detecting unit (not shown) for detecting the amount of ink stored, and the like may be provided. The ink in the ink supply tank 1102 is replenished by a user or the like in a timely manner.

The diluted water supply tank 1103 is a supply unit in which diluted water for adjusting the concentration of the ink in the tank 906 is stored when the concentration of the ink in the tank 906 increases. As the diluted water, for example, pure water or the like is used. Since the density of the ink in the tank 906 fluctuates depending on the external environment, image forming operation, etc., the concentration is maintained at an appropriate level by supplying diluted water. The supply of the diluted water from the diluted water supply tank 1103 to the tank 906 may be performed based on an instruction from the control unit (not shown). Diluted water is supplied from the diluted water supply tank 1103 to the tank 906 by driving the pump 1105 by the control unit (not shown). Further, a detection unit (not shown) for detecting the stored amount of the diluted water may be provided inside the diluted water supply tank 1103. The diluted water in the diluted water supply tank 1103 is replenished by a user or the like in a timely manner.

The density measuring unit 1101 is a portion for detecting the density of the ink inside the tank 906. The concentration measuring unit 1101 corresponds to the configurations of 901 to 903 and 909 shown in FIG. The flow path 1108 is a flow path through which the ink whose density is measured by the density measuring unit 1101 passes. The flow path 1109 is a flow path through which the ink whose density is not detected by the density measuring unit 1101 passes. The flow path 1109 corresponds to the bypass flow path 907 shown in FIG. The pump 908 is controlled to circulate the ink in the tank 906 and the density measuring unit 1101 or the flow path 1109.

[Switching flow path]
FIG. 12 is a diagram for explaining switching of the ink flow path around the density measuring unit 1101 according to the present embodiment. In FIG. 12, the dashed line means that there is no ink flow.

FIG. 12A shows a state in which ink is flowing to the density measuring unit 1101 (that is, the cell unit 901) in the configuration shown in FIG. In other words, the ink in the density measuring unit 1101 has been replaced. In this case, the flow rate of the ink in a predetermined time unit will be described as Q1.

FIG. 12B shows a state in which ink is flowing through the flow path 1109 (that is, the bypass flow path 907) instead of the inside of the concentration measuring unit 1101 in the configuration shown in FIG. In other words, the ink in the flow path 1109 has been replaced. In this case, the flow rate of the ink in a predetermined time unit will be described as Q2.

As described with reference to FIG. 10, a part of the cell portion 901 is provided with a narrow portion on the flow path 1001 for measuring ink. Therefore, when the ink is circulated by the pump 908 with the same force, the flow rate becomes larger in the flow path shown in FIG. 12B. in short,
Q2> Q1
The relationship holds. In other words, the time required to circulate the same amount of ink is different. Specifically, the flow path shown in FIG. 12A takes longer to circulate the same amount of ink. Here, for the sake of simplicity, it is assumed that the length of each flow path is the same.

In the present embodiment, by switching the ink flow path, the ink density is appropriately measured and the time required for circulation is shortened.

[Change in channel shape due to change in negative pressure]
FIG. 13 is a diagram for explaining a state in which the shape of the narrow portion of the cell portion 901 changes with the change of the negative pressure. As described above, a pump is used to circulate the ink in the cell portion 901. As a result, a negative pressure is generated in the flow path. Here, the shape of the narrow portion (that is, the position where light for measuring the concentration is irradiated) provided in the cell portion 901 changes.

FIG. 13A shows a shape in which the pump is not operating and no negative pressure is generated. At this time, it is assumed that the width of the narrow portion is L1.

On the other hand, FIG. 13B shows a shape in which a negative pressure is generated as a result of operating the pump. At this time, the wall surface of the narrow portion is pulled toward the flow path side. At this time, it is assumed that the width of the most retracted position of the narrow portion is L3. The relationship of width at this time is
L1> L3
Will be.

When the same ink is measured along with this change, the amount of transmitted light fluctuates, resulting in a difference in the measurement result.

FIG. 14 shows the relationship between the time elapsed after the time when the shape of the narrow portion changes (the time when the pump is stopped) and the optical path length and the amount of light Iout after passing through the narrow portion. .. Here, it is assumed that the amount of light Iin of the incident light to the narrow portion is constant. As shown in FIG. 14, the optical path length approaches from L3 to L2 with the passage of time, reaches L2 at the time of T3, and then becomes constant thereafter. In addition, Iout also changes with the change of the optical path length, and after T3 when the change of the optical path length disappears, Iout also shows a constant value.

[Processing flow]
The figure shows a flow chart of control related to ink density measurement according to this embodiment. This processing is realized by the control unit (for example, the main controller 13A) included in the recording device reading and executing the program stored in the storage unit.

In S1501, the control unit controls the valve (not shown) so that the ink flow path is on the bypass flow path 907 side (FIG. 12A).

In S1502, the control unit drives the pump 908 to circulate the ink. That is, the ink in the bypass flow path 907 is replaced with the ink in the tank 906. Further, the control unit initializes and starts a timer (not shown), which is a time measuring means, with the start of driving the pump 908, and starts measuring the time.

In S1503, the control unit determines whether or not T1 has elapsed for a certain period of time since the start of driving the pump 908. It is assumed that the fixed time T1 here is defined in advance as the time required for replacing the ink in the bypass flow path 907 and is held in the recording unit or the like. Further, it is assumed that the time elapsed since the start of driving the pump 908 has been measured. When T1 has elapsed for a certain period of time (YES in S1503), the process proceeds to S1504, and when T1 has not elapsed for a certain period of time (NO in S1503), the process returns to S1502 and the operation of the pump 908 is continued.

At S1504, the control unit stops the pump 908. Further, the control unit controls the valve (not shown) so that the ink flow path is on the density measurement unit 1101 (cell unit 901) side (FIG. 12 (b)).

In S1505, the control unit drives the pump 908 to circulate the ink. That is, the ink in the cell portion 901 is replaced with the ink in the tank 906. Further, the control unit initializes and starts the timer with the start of driving the pump 908, and starts measuring the time.

In S1506, the control unit determines whether or not T2 has elapsed for a certain period of time since the start of driving the pump 908. It is assumed that the fixed time T2 here is defined in advance as the time required for replacing the ink in the cell unit 901 and is held in the recording unit or the like. Further, it is assumed that the time elapsed since the start of driving the pump 908 has been measured. When T2 has elapsed for a certain period of time (YES in S1506), the process proceeds to S1506, and when T2 has not elapsed for a certain period of time (NO in S1506), the process returns to S1507 and continues driving the pump 908.

At S1507, the control unit stops the pump 908.

In S1508, the control unit initializes the timer and then starts measuring the time by the timer. That is, the measurement of the time elapsed since the pump 908 in S1507 was stopped is started.

In S1509, the control unit determines whether or not T3 has elapsed for a certain period of time after the pump 908 is stopped. As shown in FIG. 14, the fixed time T3 is defined in advance as the time required for the deformation of the narrow portion (optical path length) to be completed, and is held in the storage unit or the like. If T3 has elapsed for a certain period of time (YES in S1509), the process proceeds to S1510, and if T3 has not elapsed for a certain period of time (NO in S1509), the process waits until it elapses.

At S1510, the control unit stops the timer.

In S1511, the control unit measures the ink density by the density measurement unit 1101. Then, this processing flow is terminated.

For the fixed time T1, T2, and T3 defined in the present embodiment, different values may be used depending on the type of ink having different characteristics and the like. Examples of the characteristics of the ink include the viscosity of the ink.

As described above, according to the present embodiment, by directly measuring the density of the ink used for image formation, it is possible to measure the density with higher accuracy without causing an error in detection. In addition, more accurate measurement is possible in consideration of the measurement error caused by the change in the shape of the ink flow path due to the negative pressure.

<Second embodiment>
Hereinafter, the configuration according to the second embodiment of the present invention will be described. The description of the configuration overlapping with the first embodiment will be omitted.

In the first embodiment, the description focuses on the change in the optical path length. In the present embodiment, a configuration focusing on a change in the internal pressure of the cell portion 901 will be described. The description will be given in consideration of the fact that when the internal pressure in the cell portion 901 is constant, the optical path length is also constant.

FIG. 16 shows the relationship between the elapsed time after the pump is stopped, the pressure in the cell portion 901, and the amount of light Iout after passing through the narrow portion. Here, it is assumed that the amount of light Iin of the incident light to the narrow portion is constant. As shown in FIG. 16, the pressure in the cell portion 901 rises with the passage of time and becomes constant after a certain point. In addition, Iout also changes with the change in pressure, and after the time when the change in pressure disappears, Iout also shows a constant value.

In this embodiment, it is assumed that a pressure sensor (not shown) is provided as a pressure measuring means for measuring the pressure in the cell portion 901.

[Processing flow]
FIG. 17 shows a flow chart of control related to ink density measurement according to the present embodiment. This processing is realized by the control unit (for example, the main controller 13A) included in the recording device reading and executing the program stored in the storage unit.

Since S1701 to S1707 are the same as S1501 to S1507 of FIG. 15 described in the first embodiment, the description thereof will be omitted.

In S1708, the control unit acquires and confirms the pressure inside the cell unit 901 by a pressure sensor (not shown).

In S1709, the control unit determines whether or not the pressure acquired in S1708 is equal to or higher than the threshold value P0. If the threshold value is P0 or more, the process proceeds to S1710 (YES in S1709), and if the threshold value is less than P0, the process returns to S1708 (NO in S1709) and the process is repeated. Here, it is assumed that the threshold value P0 is defined in advance and is held in a storage unit or the like. As shown in FIG. 16, the threshold value P0 does not necessarily have to be a value at which the pressure in the cell portion 901 is constant, and may be specified according to the speed of concentration measurement or the like.

In S1710, the control unit measures the ink density by the density measurement unit 1101. Then, this processing flow is terminated.

As described above, the configuration of the present embodiment makes it possible to obtain the same effect as that of the first embodiment.

<Third embodiment>
Hereinafter, the configuration according to the third embodiment of the present invention will be described. The description of the configuration overlapping with the first embodiment will be omitted.

In the first embodiment, the description focuses on the change in the optical path length. In this embodiment, a configuration focusing on the degree of change when the concentration is measured will be described.

FIG. 18 shows the relationship between the elapsed time after the pump is stopped and the amount of light Iout after passing through the narrow portion of the cell portion 901. Here, it is assumed that the amount of light Iin of the incident light on the narrow portion of the cell portion 901 is constant. As shown in FIG. 18, it is assumed that the ink density is measured at regular intervals ΔT after the pump 908 is stopped. At this time, Iout decreases with the passage of time, but the degree of decrease decreases. That is, the degree of decrease of T1 and T2 is larger than the degree of decrease of T4 and T5. In other words, as time goes by, it takes more time to stabilize Iout more. After a certain period of time has passed, Iout will show a certain value.

In the present embodiment, for example, when the fluctuation of the degree of decrease becomes small in consideration of the relationship between the time required for the value of Iout to become constant and the degree of decrease, and the degree of the fluctuation becomes equal to or less than the threshold value. , The measurement result at that time is used.

[Processing flow]
FIG. 19 shows a flow chart of control related to ink density measurement according to the present embodiment. This processing is realized by the control unit (for example, the main controller 13A) included in the recording device reading and executing the program stored in the storage unit.

Since S1901 to S1907 are the same as S1501 to S1507 of FIG. 15 described in the first embodiment, the description thereof will be omitted.

In S1908, the control unit initializes a timer (not shown) and then starts measuring the time by the timer. That is, the measurement of the time elapsed since the pump 908 in S1907 is stopped is started. Further, the control unit initializes a counter for counting the number of measurements by the concentration measuring unit 1101. The measurement result corresponding to the value of the counter and the number of measurements shall be stored in the storage unit each time.

In S1909, the control unit determines whether or not ΔT has elapsed for a certain period of time since the previous measurement. In the case of the first measurement, it is determined whether or not ΔT has elapsed for a certain period of time after the pump 908 is stopped. It is assumed that the fixed time ΔT here is defined in advance and is held in a storage unit or the like. If ΔT has elapsed for a certain period of time (YES in S1909), the process proceeds to S1910, and if it has not elapsed (NO in S1909), the process waits until ΔT has elapsed for a certain period of time.

In S1910, the control unit measures the ink density by the density measurement unit. Further, the counter is incremented by 1. That is, the concentration is measured at regular time intervals.

In S1911, the control unit calculates the difference between the measurement result measured this time (that is, the latest measurement result) and the measurement result measured last time. Then, the control unit determines whether or not the difference is within the threshold value ΔI. It is assumed that the threshold value ΔI here is described in advance and is held in a storage unit or the like. If the difference is within the threshold value ΔI, the process proceeds to S1912 (YES in S1911), and if the difference is larger than the threshold value ΔI, the process proceeds to S1913 (NO in S1911). In the case of the first measurement, it is treated as NO.

In S1912, the control unit stops the timer and determines the most recently measured concentration as the output value. Then, this processing flow is terminated.

In S1913, the control unit refers to the value of the counter and determines whether or not the number of measurements exceeds the threshold value. It is assumed that the threshold value here is defined in advance and is held in a storage unit or the like. If the number of measurements exceeds the threshold value (YES in S1913), the process proceeds to S1914, and if the number of measurements does not exceed the threshold value (NO in S1913), the process proceeds to S1915.

In S1914, the control unit stops the timer and notifies the error, assuming that the measurement cannot be performed with appropriate accuracy even if the concentration is measured a plurality of times. The notification method here is not particularly limited, but for example, the screen may be displayed via the user interface. Then, this processing flow is terminated.

In S1915, the control unit stores the measured value this time in the storage unit. In addition, the control unit initializes the timer and then continues timing. That is, the measurement of the elapsed time since the latest concentration measurement is performed is started.

The constant time ΔT, the threshold value ΔI, and the threshold value for the number of measurements defined in the present embodiment may be different values depending on the type of ink having different characteristics and the like.

As described above, the configuration of the present embodiment enables highly accurate concentration measurement in consideration of the elapsed time and accuracy required for measurement.

<Other Embodiments>
In the above embodiment, the recording unit 3 has a plurality of recording heads 30, but may have one recording head 30. The recording head 30 does not have to be a full-line head, and even if it is a serial system in which ink is ejected from the recording head 30 while the carriage on which the recording head 30 is detachably mounted is moved in the Y direction to form an ink image. good.

The transport mechanism of the recording medium P may be another method such as a method in which the recording medium P is sandwiched and conveyed by a pair of rollers. In a method in which the recording medium P is conveyed by a pair of rollers, a roll sheet may be used as the recording medium P, or the roll sheet may be cut after transfer to produce a recorded material P'.

In the above embodiment, the transfer body 2 is provided on the outer peripheral surface of the transfer drum 41, but another method such as a method in which the transfer body 2 is formed in an endless band shape and is circulated to run may be used.

Further, the present invention supplies a program that realizes one or more functions of the above-described embodiment to a system or a device via a network or a storage medium, and one or more processors in the computer of the system or the device read and execute the program. It can also be realized by the processing to be performed. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

901 ... cell unit, 902 ... light emitting element, 903 ... light receiving element, 904, 905 ... flow path, 906 ... tank, 908 ... pump, 909 ... measuring unit

Claims (14)

Inkjet recording device
A tank that stores ink supplied to the recording head that discharges ink, and a tank that stores ink.
A density measuring unit for measuring the density of the ink in the flow path after forming the ink flow path,
A pump for circulating ink in the flow path formed in the concentration measuring unit and the tank,
A control means for controlling the measurement of the ink density by the density measuring unit is provided.
The control means is an inkjet recording apparatus, characterized in that the ink density is measured by the density measuring unit when a predetermined time elapses after the ink circulation by the pump is completed. Inkjet recording device
A tank that stores ink supplied to the recording head that discharges ink, and a tank that stores ink.
A density measuring unit for measuring the density of the ink in the flow path after forming the ink flow path,
A pump for circulating ink in the flow path formed in the concentration measuring unit and the tank,
A control means for controlling the measurement of ink density by the density measuring unit, and
A pressure measuring means for measuring the pressure in the flow path formed in the concentration measuring unit is provided.
The control means is an inkjet recording apparatus characterized in that when the measurement result by the pressure measuring means exceeds a predetermined value, the density measuring unit measures the ink density. The inkjet recording apparatus according to claim 1 , wherein the predetermined time differs depending on the type of ink. Inkjet recording device
A tank that stores ink supplied to the recording head that discharges ink, and a tank that stores ink.
A density measuring unit for measuring the density of the ink in the flow path after forming the ink flow path,
A pump for circulating ink in the flow path formed in the concentration measuring unit and the tank,
A control means for controlling the measurement of ink density by the density measuring unit, and
With
The control means causes the density measuring unit to measure the ink density at predetermined time intervals after the ink circulation by the pump is completed, and the difference between the latest measured value and the previous measurement is predetermined. An inkjet recording apparatus characterized in that when the value falls below a threshold value, the latest measured value is determined as an output value. The inkjet recording apparatus according to any one of claims 1 to 4 , wherein the tank includes an air communication port. An adjusting means for adjusting the density of the ink stored in the tank is provided.
The inkjet recording apparatus according to any one of claims 1 to 5 , wherein the adjusting means adjusts the density of ink in the tank based on the density measured by the density measuring unit. The adjusting means
A first supply unit that supplies ink to the tank and
The inkjet recording apparatus according to claim 6 , further comprising a second supply unit for supplying diluted water for diluting the concentration of ink stored in the tank. A first flow path for circulating the ink stored in the tank through the concentration measuring unit, and
A second flow path for circulating the ink stored in the tank without going through the concentration measuring unit, and
With
The control means switches between the first flow path and the second flow path to circulate the ink.
The inkjet recording apparatus according to any one of claims 1 to 7 , wherein the flow rate in the second flow path is larger than the flow rate in the first flow path. The concentration measuring unit
The cell part, which is composed of transparent members and has an ink flow path,
A light emitting element that irradiates the ink passing through the cell portion with light,
A light receiving element that receives light transmitted through the cell portion and
Any one of claims 1 to 8 , further comprising a lead-out unit that derives the density of the ink based on the amount of light emitted by the light emitting element and the amount of light received by the light receiving element. The inkjet recording device described in 1. The inkjet recording according to claim 9 , wherein in the flow path formed in the cell portion, the position where the light is irradiated by the light emitting element is formed so that the diameter is smaller than the other positions. Device. The tenth aspect of claim 10, wherein the amount of light emitted by the light emitting element and the diameter of the position where the light is irradiated by the light emitting element are defined according to the type of ink stored in the tank. The inkjet recording device described. A tank that stores ink supplied to the recording head that discharges ink, and a tank that stores ink.
A density measuring unit for measuring the density of the ink in the flow path after forming the ink flow path,
A pump for circulating ink in the flow path formed in the concentration measuring unit and the tank,
It is a control method of an inkjet recording device equipped with
A control method for an inkjet recording apparatus, characterized in that the ink density is measured by the density measuring unit when a predetermined time elapses after the ink circulation by the pump is completed. A tank that stores ink supplied to the recording head that discharges ink, and a tank that stores ink.
A density measuring unit for measuring the density of the ink in the flow path after forming the ink flow path,
A pump for circulating ink in the flow path formed in the concentration measuring unit and the tank,
A pressure measuring means for measuring the pressure in the flow path formed in the concentration measuring unit, and
It is a control method of an inkjet recording device equipped with
A control method for an inkjet recording apparatus, characterized in that the ink density is measured by the density measuring unit when the measurement result by the pressure measuring means exceeds a predetermined value. A tank that stores ink supplied to the recording head that discharges ink, and a tank that stores ink.
A density measuring unit for measuring the density of the ink in the flow path after forming the ink flow path,
A pump for circulating ink in the flow path formed in the concentration measuring unit and the tank,
It is a control method of an inkjet recording device equipped with
After the ink circulation by the pump was completed, the ink density was measured by the density measuring unit at predetermined time intervals, and the difference between the latest measured value and the previous measurement became equal to or less than the predetermined threshold value. A method of controlling an inkjet recording apparatus, wherein the latest measured value is determined as an output value in the case of the case.

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