JP2008023806A - Inkjet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To keep ink or an inkjet head in a suitable state by controlling an ink circulation volume. <P>SOLUTION: The inkjet recording device 10 is equipped with the inkjet head 17 having a common ink chamber which communicates with a nozzle for discharging the ink, ink tubes 35C, 35H passing the common ink chamber, a pump 21R which generates driving force for circulating the ink through the ink tubes 35C, 35H, a thermometer 29H for detecting the ink temperature in the common ink chamber and a circulation control apparatus 30 for controlling the pump 21R based on the result detected by the thermometer 29H. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an inkjet recording apparatus that forms an image on a recording medium by ejecting ink from an inkjet head.

  In this type of ink jet recording apparatus, when ink is ejected, a piezoelectric element (actuator) is driven to form an image on a recording medium. At that time, driving heat is generated. If this heat continues to be generated, the temperature of the ink jet head and the ink gradually rises and deviates from the temperature range in which proper ink discharge is possible. Therefore, it is necessary to maintain the ink jet head at a temperature at which ink can be suitably discharged. Further, if there are bubbles or foreign matter in the ink in the ink jet head, non-ejection occurs, so it is necessary to remove the bubbles or foreign matter in the ink.

  Patent Document 1 discloses a recording apparatus in which ink is circulated by a pump in an ink jet head and a cooling unit is disposed on the ink circulation path. According to this recording apparatus, the hot ink in the ink jet head is circulated by operating the pump.

  Moreover, the temperature of the ink discharged from the inkjet head is cooled by operating the built-in cooling means. Further, the cooled ink is circulated again to the ink jet head to control the ink temperature from being overheated.

Patent Document 2 discloses a liquid ejection apparatus in which ink is circulated by a pump in an ink jet head and a filter is disposed on the ink circulation path. According to this liquid ejecting apparatus, by operating the pump, it is possible to circulate ink containing bubbles and remove the bubbles with a filter.
JP 2003-182103 A JP 2006-68904 A

  Incidentally, for example, the amount of heat generated by the inkjet head depends on the driving conditions of the inkjet head. For example, if an inkjet head is driven, driving heat is generated in the head accordingly, and if it is driven at a high frequency, the amount of heat generation is increased accordingly.

  In an on-demand type ink jet head, the ink jet head is not always driven, and is driven only at a timing required for image formation. Therefore, for example, the amount of heat generated in the inkjet head differs between the standby state and the printing operation, and the degree of cooling of the head also differs.

  Therefore, in the technique disclosed in Patent Document 1, in order to cool the ink jet head to a predetermined temperature, ON / OFF control of ink circulation and ON / OFF control of the cooling means are performed. In such ON / OFF control, the apparatus is turned ON when the temperature is equal to or higher than the target temperature, and is turned OFF when the temperature is equal to or lower than the target temperature.

  For this reason, the transient state until the head temperature becomes stable is long, and it is difficult to keep the temperature of the inkjet head within a suitable range. In addition, since the amount of heat generated by the head changes in real time depending on the operating state / driving state of the head, it is difficult to adjust the temperature of the head with simple ON / OFF control.

  In addition, the bubbles in which the ink exists in the ink circulation path are not constant. For example, immediately after the ink is replenished to the ink tank, there are many bubbles. Since the ink circulation amount disclosed in Patent Document 2 is constant, when the number of bubbles temporarily increases, the bubble removal rate may be reduced, and it is not possible to prevent non-ejection.

  When the ink circulation amount is increased in accordance with the maximum amount of bubbles, the load on the ink circulation means becomes large. For example, in the case of circulation by a pump, the power consumption of the ink circulation pump becomes large and the life is shortened. In addition, there is a similar problem in the removal of foreign matter in the ink circulation path and the thickened ink in the ink head.

  The present invention has been made to solve such a problem, and an object of the present invention is to keep the temperature of the ink or the inkjet head in an appropriate state by variably controlling the ink circulation amount. An object of the present invention is to provide an ink jet recording apparatus capable of performing the above.

In order to achieve the object, the invention according to claim 1
An inkjet head having a nozzle for ejecting ink and an ink chamber communicating with the nozzle;
An ink circulation path through at least the ink chamber;
A circulation means for generating a driving force for circulating the ink in the ink circulation path;
Circulation control means for variably controlling the circulation flow rate of the ink in the ink circulation path.

The invention according to claim 2 is the ink jet recording apparatus according to claim 1,
The circulation control means has detection means for detecting information related to the state of the ink or the state of the inkjet head,
The ink circulation flow rate in the ink circulation path is variably controlled based on the detection result detected by the detection means.

The invention according to claim 3 is the inkjet recording apparatus according to claim 2,
The detection means is arranged on the ink circulation path.
The invention according to claim 4 is the ink jet recording apparatus according to claim 1,
An ink tank for supplying ink to the ink chamber;
An ink supply path extended from the ink tank with a predetermined water head difference is connected to a branch point of the ink circulation path.

The invention according to claim 5 is the ink jet recording apparatus according to claim 2,
A plurality of the ink jet heads are provided, the circulation means and the detection means are provided in each of the plurality of ink jet heads, and at least a part of the ink supply path is shared by the plurality of ink jet heads. And

The invention according to claim 6 is the inkjet recording apparatus according to claim 2,
The detecting means detects ink temperature in the ink chamber or information related to the ink temperature.

The invention according to claim 7 is the ink jet recording apparatus according to claim 1,
An ink temperature control means is disposed on the ink circulation path.
The invention according to claim 8 is the ink jet recording apparatus according to claim 7,
The circulation unit is a unit that circulates ink by convection resulting from a difference in ink temperature created by the ink temperature control unit.

The invention according to claim 9 is the inkjet recording apparatus according to claim 2,
The detection means is means for detecting a heat generation amount of the inkjet head based on a drive signal input to the inkjet head.

The invention according to claim 10 is the ink jet recording apparatus according to claim 1,
The ink jet recording apparatus has means for capturing and / or removing bubbles or foreign matters in the ink.

The invention according to claim 11 is the ink jet recording apparatus according to claim 2,
The detection means detects mixing of bubbles or foreign matters in the ink circulation path.

The invention according to claim 12 is the inkjet recording apparatus according to claim 2,
The detecting means detects an elapsed time from the latest recording operation.

  According to the present invention, it is possible to circulate an appropriate amount of ink through the ink circulation path of the ink jet recording apparatus and hold the ink or the ink jet head in an appropriate state.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 is a block diagram of an inkjet recording apparatus 10 to which the present invention is applied, and FIG. 2 is a cross-sectional view of an inkjet head 17.

  In FIG. 1, the ink jet recording apparatus 10 includes an ink jet head 17 in which a nozzle 50 is formed, and a recording medium 18 and a platen 19 are disposed at a position facing the ink ejection surface of the nozzle 50.

  One end of the ink tubes 35C and 35H is connected to the ink-jet head 17, and the other end is connected to a pump 21R as a circulation means to constitute an ink circulation system. In the present embodiment, the ink tubes 35C and 35H constitute an ink circulation path and an ink temperature control means.

  The ink tube 35C is connected to the other end of the ink tube 35P as an ink supply path having one end connected to the sub tank 15S at the branch point 36. The sub tank 15S is connected to the main tank 15M via the ink tube 35D.

  In FIG. 2, the inkjet head 17 has a piezoelectric element 55 as an actuator. By driving the piezoelectric element 55, ink is ejected from the plurality of nozzles 50. In the present embodiment, ink is ejected toward the recording medium 18 on the platen 19 that is opposed to the nozzle 50 at a position about 2.0 mm away.

  The ink jet head 17 has a configuration capable of forming an image that is equal to or larger than the width of the recording medium 18. Further, a meniscus (a concave liquid surface created by the surface of the liquid in the narrow tube by the interfacial tension) 59 is formed in the nozzle 50 of the inkjet head 17 so that ink can be ejected.

  The recording medium 18 is sequentially conveyed in the front and back direction of the paper surface of FIG. 2 by recording medium conveying means (not shown). The ink jet head 17 ejects ink based on the ejection signal synchronized with the conveyance of the recording medium 18, and an image is recorded on the recording medium 18. The ink jet head 17 can eject ink when the ink temperature is in the range of 10 ° C. to 50 ° C. In particular, it has very good ink ejection characteristics when the ink temperature is in the range of 25 ° C. to 35 ° C. Furthermore, when the ink temperature is 30 ° C., the ink ejection characteristics are optimum.

Next, the ink circulation path will be described.
The inkjet head 17 is located on the ink circulation path. The ink leaving the common ink chamber 58 circulates via the ink tube 35H, the pump 21R, and the ink tube 35C, and returns to the inkjet head 17 again. The pump 21R can circulate ink in forward and reverse directions. A thermometer 29H as a detecting means is provided on the path of the ink tube 35H, and an air buffer 37 and a filter 60 are provided on the path of the ink tube 35C.

  The thermometer 29H detects the temperature of the ink sent out from the common ink chamber 58. The air buffer 37 lifts the bubbles 51 mixed in the ink circulation path in the air buffer 37 and removes them from the circulation path. That is, when the bubbles 51 rise in the air buffer 37, the liquid level in the air buffer 37 is lowered by the pressure of the bubbles 51. When the liquid level detecting means 20B detects this decrease in the liquid level, the ink circulation is stopped and the valve 25B is opened.

  Subsequently, the pump 21S of the sub tank 15S is driven to pressurize the air in the sub tank 15S, thereby removing the air in the air buffer 37 from the valve 25B to the outside. At this time, the valve 25D between the main tank 15M and the sub tank 15S and the air release valve 25S of the sub tank 15S are closed. The filter 60 serves to eliminate foreign matter 52 such as gel and solid mixed in the ink circulation path.

  Next, when the pump 21R is driven so that ink flows in the clockwise direction (forward rotation direction) in FIG. 1 with the valve 25S opened and the valves 25B and 25D closed, the ink tube 35C, the common ink chamber 58, and the ink tube are driven. Ink circulates in the circulation path through 35H. In this embodiment, the ink exchanges heat with the outside air mainly through the ink tube 35C and the ink tube 35H during the ink circulation. When the ink temperature is higher than the outside air, the circulating ink is cooled by the outside air.

  For this reason, the ink tube 35C and the ink tube 35H are preferably made of a material having high thermal conductivity such as metal so that heat exchange efficiency is good. The thermometer 29H and the pump 21R are electrically connected to a circulation control device 30 as a circulation control means. For this reason, the pump 21 </ b> R is controlled by the circulation control device 30.

In the present embodiment, the circulation control device 30 controls the opening and driving of the various valves 25B, 25D, 25S, the pump 21S, and the like.
Next, ink supply to the ink circulation path will be described.

  The main tank 15M is connected to the sub tank 15S by an ink tube 35D. The main tank 15M is disposed at a position higher in the direction of gravity than the sub tank 15S. The valve 25D described above is located on the path of the ink tube 35D, and is closed except when ink is supplied from the main tank 15M to the sub tank 15S. The ink water level of the sub tank 15S is provided at a position lower than the nozzle 50 by a predetermined amount (water head difference) so that the meniscus 59 in the nozzle 50 of the inkjet head 17 is maintained.

  Further, the ink tube 35 </ b> P as an ink supply path is connected to a branch point 36 in the middle extending from the sub tank 15 </ b> S toward the inkjet head 17. When the ink jet head 17 ejects ink to the outside by a printing operation or the like, the ink in the sub tank 15S is supplied to the ink circulation path in the form of sucking ink from the sub tank 15S to the ink jet head 17. The liquid level detection means 20S in the sub tank 15S detects the ink amount in the sub tank 15S.

  When the liquid level detecting means 20S detects that the ink amount in the sub tank 15S is less than or equal to a predetermined amount, the valve 25D is opened, and the main tank 15M installed at a position higher than the sub tank 15S is changed to the sub tank 15S. Ink is fed down.

Next, the initial ink filling into the common ink chamber 58 will be described.
When the ink is initially filled, the pump 21R is driven with the valve 25S open and the valves 25B and 25D closed so that the ink flows in the counterclockwise direction (reverse direction) in FIG. That is, the ink flows from the pump 21R through the ink tube 35H, the ink jet head 17, the ink tube 35C, the branch point 36, the filter 60, the air buffer 37, and further into the pump 21R.

  Next, the valve 25S of the sub tank 15S is closed, and the pump 21S is driven to pressurize the air in the sub tank 15S. At this time, the valve 25B of the air buffer 37 is closed. Then, the ink in the sub tank 15S passes through the branch point 36 from the ink tube 35P, and is supplied to the inkjet head 17 from the ink tube 35C, the air buffer 37, and the ink tube 35H.

  In this case, the state in which the ink is filled in the inkjet head 17 side is detected by measuring time or the like. Next, the pump 21R is driven so that ink flows from the pump 21R in the forward rotation direction to the air buffer 37 side. In this process, bubbles remaining in the ink circulation path mix with the ink and circulate in the ink tube 35C, the inkjet head 17, and the ink tube 35H.

  The bubbles are trapped in the air buffer 37, and when a predetermined amount or more is accumulated, the pump 21R is stopped and the valve 25B is opened. Since the valves 25S and 25D are closed, the sub tank 15S is pressurized by the pump 21S and discharged from the valve 25B to the outside. Thereafter, the valve 25B is closed and the pump 21R is driven again. For this reason, bubbles gradually disappear, and only ink circulates at the end. In this state, the pump 21S of the sub tank 15S is stopped and the valve 25S is opened. In this way, the initial filling is completed and printing is possible.

FIG. 3 is a flowchart showing ink circulation in the present embodiment.
In step 1 (S1), when the power of the inkjet recording apparatus 10 is turned on, the printer is ready for printing after the initialization operation (S2). In S2, the printable state is used to include an ink filling process.

  Also, after this S2, the steps relating to ink circulation (S3 to S5) and the steps relating to printing (S6 to S9) proceed independently, and until a power-off operation is performed (S10), a print job input at any time is processed. Based on this, a printing operation is performed.

  That is, first, in S3 related to ink circulation, the ink temperature detected by the thermometer 29H is sequentially input to the circulation control device 30. In S4, the circulation control device 30 determines the operation output of the pump 21R based on the input ink temperature, and continues to increase or decrease the ink circulation amount.

  In this case, the circulation control device 30 includes the viscosity of the ink, the specific heat, the thermal conductivity of the ink and the piezoelectric element 55, other physical property parameters, the ink temperature history so far, the amount of heat generated by driving calculated from the recorded image, and the like. The control matrix (see FIG. 4) set from the above is input in advance. In the circulation control device 30, the operation output of the pump 21R is determined based on this control matrix.

Further, in S5, it is determined whether or not a power-off operation has been performed. If No, the process returns to S3. If Yes, the process proceeds to S9 to end printing, and the power-off operation is performed in S10.
On the other hand, in step S6 regarding printing, it is determined whether or not a print job has been input. If no print job is input, the process proceeds to S8. If there is, the print operation is performed in S7, and then the process proceeds to S8. In S8, it is determined whether or not a power OFF operation has been performed. If No, the process returns to S6, and if Yes, the process proceeds to S9.

As described above, the steps relating to ink circulation (S3 to S5) and the steps relating to printing (S6 to S9) proceed independently until the power is turned off.
FIG. 4 shows an example of the control matrix described above. Here, in this embodiment, about 30 ° C. is assumed as the optimum ink ejection temperature. The ink temperature may be cooled by removing heat from the outside air when the ink circulates, or a cooler with a fan may be used.

  In FIG. 4, for example, when the temperature of the ink detected by the thermometer 29H is sufficiently lower than the optimal ink ejection temperature, such as 10 ° C. to 20 ° C., the ink circulation flow rate causes the bubbles 51 and foreign matter 52 to flow. Set it as small as possible (50 ml / min). Then, the temperature of the ink rises due to heat generated by driving the inkjet head 17.

  In addition, when the ink temperature is 20 ° C. to 25 ° C., the optimum discharge temperature is closer to 30 ° C. than 10 ° C. to 20 ° C., so the ink circulation flow rate and cooling output are slightly higher than those of 10 ° C. to 20 ° C. (75 ml / min) is set. At this time, as in the case of 10 ° C. to 20 ° C., the temperature of the ink rises due to the heat generation of the piezoelectric element 55, but the temperature change is made slower than that in the case of 10 ° C. to 20 ° C. described above. That is, since the ink temperature is close to the optimum discharge temperature of 30 ° C., the ink circulation flow rate is slightly increased so that the temperature gradually rises.

  Furthermore, at 25 ° C. to 35 ° C. at which ink can be suitably discharged, the ink circulation amount (100 ml) is slightly higher than the amount of heat removed by ink circulation at 25 ° C. to 30 ° C. so as not to deviate from this temperature range. / Min). Furthermore, when the temperature of the ink is 30 ° C. to 35 ° C., the ink discharge amount (150 ml / min) is set so that the heat generation amount is slightly lower than the amount of heat removed by cooling, so that the ink jet head 17 has the optimum discharge temperature ( The circulation flow rate is set to be 30 ° C.

Further, in a slight overheating state where the ink temperature is 35 ° C. to 40 ° C., a slightly larger amount of ink circulation (250 ml / min) is set so that the ink temperature becomes 35 ° C. or lower.
Further, in the overheated state where the ink temperature is 40 ° C. to 50 ° C., the circulation flow rate is set to a sufficiently large value (400 ml / min), and the circulation flow rate is controlled so that the ink temperature quickly becomes 35 ° C. or less. When the power-off operation is executed, the power of the inkjet recording apparatus 10 is turned off after the already input print job is completed.

  In the above description, the case of controlling only by the temperature of the ink measured by the thermometer 29H has been described, but other parameters may be considered. For example, when the amount of heat generated by the piezoelectric element 55 at each time can be calculated from the image data to be recorded, the value of the control matrix may be corrected accordingly.

  For example, when it is known from the image data that the calorific value is doubled up to 10 seconds after 10 seconds, it is possible to control the circulating flow rate to be doubled after 10 seconds, for example. If it is not known that the calorific value doubles after 10 seconds, there is a time lag before it is fed back as the detection value of the thermometer 29H, so the thermometer 29H detects it after the calorific value has doubled. However, the control parameter becomes appropriate after, for example, 15 seconds. By calculating the calorific value from the image data, it is possible to set appropriate control parameters at appropriate timing without a time lag, so that the inkjet head 17 can be stably kept in a good state.

  Even after the control parameters are set appropriately, a certain time is required until the temperature of the ink contacting the piezoelectric element 55 reaches an appropriate temperature. By calculating in advance from the image data, it is possible to appropriately control the parameters without a time lag even if the amount of heat generation changes.

  In the present embodiment, the thermometer 29H connected to the ink tube 35H is used as the temperature detection means of the inkjet head 17, but the invention is not limited to this. For example, information related to the ink temperature in the common ink chamber 58 may be acquired, and ink circulation parameters may be determined therefrom.

  That is, a thermometer may be installed directly in the common ink chamber 58, or a thermometer may be installed in the piezoelectric element 55 that is in contact with the common ink chamber 58. Further, the ink temperature of the common ink chamber 58 may be derived from the amount of heat generated by driving the piezoelectric element 55 calculated from the ink discharge signal.

  Further, measurement of physical property parameters expressed as a function of temperature, such as ink viscosity, surface tension, density, electrical resistance, light transmittance or reflectance, or physical properties parameters of a member such as a tube in contact with the ink A device may be provided on the ink circulation path to replace the thermometer, and the measurement result may be used as information for determining the ink circulation parameter.

Alternatively, the ink circulation flow rate may be determined from information of these combinations.
Further, when heat is exchanged with the outside air via the ink tube 35C and the ink tube 35H as in the present embodiment, the efficiency of heat exchange varies depending on the outside air temperature. Therefore, the outside air temperature can be detected in addition to the ink temperature and the ink circulation amount can be controlled by the combination of the ink temperature and the outside air temperature.

  According to the present embodiment, the ink circulation flow rate is increased when the temperature of the inkjet head 17 is high, and the ink is cooled by increasing the ink circulation flow rate when the temperature of the inkjet head 17 is higher. Therefore, it has the following effects.

The temperature of the inkjet head 17 can be finely controlled, and can be maintained in a temperature range suitable for ink ejection. Also, no special ink cooling device is required.
So far, in this embodiment, the method of controlling the ink circulation flow rate based on the temperature of the ink jet head 17 has been described, but the parameter used for controlling the ink circulation flow rate is not limited to the temperature.

  For example, immediately after the main tank 15M is emptied and replaced with a new main tank 15M, bubbles are mixed into the connection between the main tank 15M and the ink tube 35D. Many of these bubbles are lifted and separated in the sub tank 15S, but some of them are mixed into the ink circulation path from the tube 35P.

  For this reason, immediately after the replacement of the main tank 15M, there are many bubbles in the ink circulation path. In such a case, it is possible to quickly collect bubbles in the air buffer 37 by detecting the replacement of the main tank 15M by the detection means and performing control to temporarily increase the ink circulation flow rate.

  Since a state where there are many bubbles in the ink circulation path is detected and the amount of ink circulation is increased only at this time, the average power consumption of the pump, which is the ink circulation means, can be reduced, and the life of the pump can be extended. When the ink circulation flow rate is temporarily increased, for example, if random time fluctuation of the ink circulation flow rate is applied to such an extent that the meniscus 59 is not destroyed, the stagnation point also moves randomly, and the stress acting on the bubbles Therefore, the air bubbles hardly stay at the stagnation point that can be formed in the bent portion or the uneven portion of the flow path, and even if the air bubbles stay, the air bubbles are immediately separated. It can flow.

  If air bubbles are sent to the air buffer 37 at a constant ink circulation flow rate or an ink circulation flow rate that fluctuates periodically with a relatively short period, the bubbles remain caught in the bent portion or uneven portion of the flow path. Alternatively, bubbles may be generated that vibrate at a certain interval in synchronization with the period of the ink circulation flow rate, so that the non-periodic fluctuation of the ink circulation amount as described above is added, or a relatively long period It is desirable to add periodic fluctuations.

  The above control is not necessarily limited when the main tank 15M is replaced. For example, the light source and the light receiving element are arranged in the ink circulation path, and the light from the light source is received by the light receiving element via the ink. Detecting means for detecting the amount of air bubbles by detecting the light transmittance of the air bubbles may be arranged, and when air bubbles mixed in from the nozzle 50 are detected by impact or the like, the air bubbles 37 may be sent to the air buffer 37 by the aforementioned control. .

  Another example of the parameter is a leaving time in a power-off state. When the power-off state is left for several days, for example, the ink solvent evaporates from the meniscus 59 that is a boundary with the outside air, and the ink near the meniscus 59 is thickened. If the ink is thickened, normal ink ejection is not performed.

  In such a case, for example, the power-off time is detected by the storage means for storing the power-off time every time and the detection means for comparing the current time with the previous power-off time when the power is turned on, and the power is turned off for a predetermined time or more. In this state, when the power is turned on, the ink circulation flow rate is increased, and the control is performed so that the thickened ink in the vicinity of the meniscus 59 is quickly removed, so that the ink discharge property can be recovered.

  The storage means for storing the power OFF time is deleted, and only the detection means for detecting the power ON every time is provided. When the power is turned ON, the ink circulation flow rate is increased each time, and the thickened ink in the vicinity of the meniscus 59 is quickly washed away. Control may be performed.

  Another example of the parameter is detection of non-ejection of ink. If a part or all of the nozzles 50 are blocked by the foreign matter 52, ink ejection from the nozzle 50 clogged with the foreign matter 52 may become impossible.

  Therefore, for example, an image of the recording medium 18 on which an image is formed is detected by a line sensor or the like, and provided with a detecting unit that detects ink non-ejection by comparing with the original data. In addition to the constant flow rate, for example, a sawtooth wave-like variation is added to increase the flow rate so that the foreign material 52 is peeled off from the nozzle 50 and trapped by the filter 60.

  In this embodiment, since air bubbles can be trapped by the air buffer 37, ink is circulated and the valve 25S is closed, and a negative pressure is generated in the sub tank 15S by the pump 21S to draw air from the nozzle 50. It is also effective to make the foreign matter 52 easier to separate from the nozzle 50 by using the momentum to shake the foreign matter 52.

According to the present embodiment, the temperature of the ink jet head 17, the bubbles in the ink, the foreign matter in the ink, and the non-ejection detection means of the ink jet head 17 are provided, and the ink circulation amount is appropriately changed so that an appropriate amount of ink is supplied. Since the ink is circulated, the ink or the inkjet head can be held in an appropriate state. Furthermore, the average power consumption of the ink circulating means such as a pump can be reduced, and the life of the ink circulating means can be extended.
(Modification 1)
FIG. 5 shows a modification of the present embodiment.

In addition, the same code | symbol is attached | subjected to the same or equivalent member as 1st Embodiment, and the description is abbreviate | omitted.
In this modification, a temperature control device 27 as an ink temperature control means is installed between the ink tube 35H and the ink tube 35C. The temperature control device 27 is used to cool the overheated ink to an appropriate temperature, and includes, for example, a cooling fan, a fin, a Beltier element, and the like. The cooling efficiency is variable by adjusting the fan rotation speed and the voltage of the Bercher element. In consideration of use in a cold region, the ink temperature may be set to an appropriate temperature by heating, such as sun storm, or a structure having both a cooling means and a heating means may be used.

  In this modified example, it is not preferable that the ink is affected by the environment to locally change the temperature. Therefore, unlike the first embodiment, the ink path 35H and the ink path 35C are preferably made of a material having high heat insulation. The ink path portion passing through the temperature control device 27 is preferably made of a metal having high thermal conductivity. At this time, output data of the temperature control device 27 is described in the control matrix (FIG. 4) described above, and the temperature control device 27 is controlled by the circulation control device 30.

According to this configuration, not only the ink circulation flow rate but also the ink temperature can be controlled. Therefore, the influence of the outside air temperature is small, the controllable temperature range is wide, and the temperature can be quickly stabilized. .
(Modification 2)
FIG. 6 shows a line head 17L configured by arranging a plurality of inkjet heads 17 side by side.

  That is, an ink circulation path is arranged in each of the plurality of ink jet heads 17, and the pump 21R, the thermometer 29H, and the circulation control device 30 are arranged in each. In this case, the ink circulation path needs to be provided in each inkjet head 17, but the number of parts can be reduced by using the sub tank 15S in common.

  In this modification, the circulation control device 30 is disposed in each of the plurality of inkjet heads 17. However, the present invention is not limited to this, and for example, the plurality of inkjet heads 17 can be controlled by one circulation control device 30. .

  In this case, even when the discharge states of the plurality of inkjet heads 17 are different, the temperatures of the plurality of inkjet heads 17 can be appropriately controlled.

According to this modified example, by constantly detecting the temperature of the ink, the circulating ink flow rate is sequentially determined according to the temperature of the inkjet head 17 that changes from time to time. The temperature can be stably maintained. Therefore, a good image can be formed on the recording medium 18.
(Second Embodiment)
FIG. 7 is a cross-sectional view of the ink jet head 17 according to the second embodiment. In addition, the same code | symbol is attached | subjected to the member which is the same as that of 1st Embodiment mentioned above, or it corresponds, and the description is abbreviate | omitted.

  In the present embodiment, the ink circulation path is formed inside the inkjet head 17. That is, the ink path 35H extends vertically upward from one end side (point A in the figure) of the common ink chamber 58, and is substantially parallel to the intermediate position (point C in the figure) from the uppermost position (point B in the figure). It extends to. In this substantially parallel portion (from the point B to the point C), a temperature control device 27 including a Beltier element as an ink temperature control means is provided. The temperature control device 27 has a function of heating or cooling the ink.

  The ink circulation path extends from the above-described intermediate position (point C in the figure) to the other end portion (point D in the figure) of the common ink chamber 58 through the downwardly inclined ink path 35C, and is slightly vertical from there. The configuration extends downward (point E in the figure). A thermometer 29H is provided at one end of the common ink chamber 58 (near point A in the figure), and a pump 21R including a gear pump is disposed in the middle of the ink path 35H.

According to the present embodiment, since most of the components necessary for ink circulation are collected in the ink jet head 17, ink circulation can be performed with a compact configuration.
Note that an air buffer similar to that of the first embodiment may be disposed in the ink circulation path, and bubbles mixed in the ink circulation path may be excluded from the ink circulation path. Further, a filter can be disposed in the ink circulation path to trap foreign matter in the ink.
(Third embodiment)
FIG. 8 is a cross-sectional view of the inkjet head 17 according to the third embodiment. Members that are the same as or correspond to those in the first embodiment described above are assigned the same reference numerals, and descriptions thereof are omitted. The present embodiment has a configuration close to that of the second embodiment.

  The difference from the inkjet head 17 shown in FIG. 7 is that the pump 21R is omitted. Further, the temperature control device 27 as the ink temperature control means has a cooling function. The density of the ink in the ink path 35 </ b> C cooled by the temperature control device 27 increases. Further, the density of the ink in the common ink chamber 58 heated by the heat generated by the piezoelectric element 55 is lowered.

  Due to these density differences, the low density ink in the common ink chamber 58 rises via the ink path 35H and then moves toward the inclined ink path 35C, and the high density ink in the ink path 35C is the common ink. Since heading to the chamber 58, convection occurs in the ink path. This convection is ink circulation.

  According to the present embodiment, precise control of the circulation flow rate is difficult and the controllable flow rate range is narrow, but the configuration is simple. And since there is no movable part, it has the characteristic that it is hard to break down.

The present invention is not limited to the first to third embodiments described above. For example, the following configuration may be used.
First, the ink circulation path is not limited to the above-described embodiment, and may be any circulation path that circulates ink including the ink chamber of the inkjet head. For example, the circulation means is not a pump, but may be a system in which pressure is applied to the sub-tanks disposed on the upstream side and the downstream side of the ink jet head in the ink circulation path as disclosed in JP-A-55-121074, for example. By circulatingly controlling the pressure in the two sub tanks, the ink circulation flow rate can be made variable.

  Further, the circulation means may be a system that uses a water head difference between sub-tanks arranged on the upstream side and the downstream side of the inkjet head and a pump as disclosed in, for example, JP-T-2002-533247. By variably controlling the water head difference between the two sub tanks, the ink circulation flow rate can be made variable. For example, it is possible to arrange a sensor for detecting a plurality of levels of the liquid level in the two sub tanks, to variably control the liquid level in the two sub tanks, and to vary the ink circulation flow rate.

  Alternatively, the liquid surface heights in the two sub tanks are made constant, and a height position variable mechanism that makes the height position of the two sub tanks variable with respect to the ink jet head is arranged to make the height positions of the two sub tanks variable. The ink circulation flow rate may be made variable.

Further, the configuration of the recording head is not limited to the above-described embodiment.
Further, the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment.

  For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

1 is a block diagram of an ink jet recording apparatus according to a first embodiment. It is sectional drawing of an inkjet head same as the above. It is a figure which shows the flowchart regarding operation | movement of an inkjet recording device. It is a figure which shows the control matrix regarding an ink circulation amount. It is a block diagram of the modification of an inkjet recording device. It is a block diagram of the modification of an inkjet recording device. It is sectional drawing of the inkjet head of 2nd Embodiment. It is sectional drawing of the inkjet head of 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Inkjet recording device 15M Main tank 15S Subtank 17 Inkjet head 18 Recording medium 19 Platen 21R Pump 21S Pump 25B Valve 25D Valve 25S Valve 27 Temperature control device 29H Thermometer 30 Circulation control device 35C Ink tube 35D Ink tube 35H Ink tube 35P Ink tube 36 Branch point 37 Air buffer 50 Nozzle 51 Bubble 52 Foreign material 55 Piezoelectric element 58 Common ink chamber 59 Meniscus 60 Filter

Claims (12)

An inkjet head having a nozzle for ejecting ink and an ink chamber communicating with the nozzle;
An ink circulation path through at least the ink chamber;
A circulation means for generating a driving force for circulating the ink in the ink circulation path;
Circulation control means for variably controlling the circulation flow rate of the ink in the ink circulation path,
An ink jet recording apparatus. The circulation control means has detection means for detecting information related to the state of the ink or the state of the inkjet head,
Based on the detection result detected by the detection means, the ink circulation flow rate in the ink circulation path is variably controlled.
The inkjet recording apparatus according to claim 1. The detection means is disposed on the ink circulation path.
The ink jet recording apparatus according to claim 2. An ink tank for supplying ink to the ink chamber;
An ink supply path extending from the ink tank with a predetermined water head difference is connected to a branch point of the ink circulation path;
The inkjet recording apparatus according to claim 1. A plurality of the inkjet heads, the circulation means and the detection means are provided in each of the plurality of inkjet heads, and at least a part of the ink supply path is shared by the plurality of inkjet heads;
The ink jet recording apparatus according to claim 2. The detecting means detects ink temperature in the ink chamber or information related to the ink temperature;
The inkjet recording apparatus according to claim 2. Ink temperature control means is disposed on the ink circulation path,
The inkjet recording apparatus according to claim 1. The circulation means is means for circulating ink by convection resulting from a difference in ink temperature created by the ink temperature control means;
An ink jet recording apparatus according to claim 7. The detection means is means for detecting a heat generation amount of the inkjet head based on a drive signal input to the inkjet head.
The ink jet recording apparatus according to claim 2. The ink jet recording apparatus has means for capturing and / or removing bubbles or foreign matters in the ink,
The inkjet recording apparatus according to claim 1. The detecting means detects mixing of bubbles or foreign matters in the ink circulation path;
The ink jet recording apparatus according to claim 2. The detection means detects an elapsed time from the latest recording operation;
The ink jet recording apparatus according to claim 2.