JP6881963B2 - Liquid discharge device, liquid discharge head and liquid supply method - Google Patents

Description

The present invention relates to a liquid discharge device, a liquid discharge head, and a liquid supply method. Specifically, the present invention is a liquid that supplies a liquid by causing a pressure difference between the supply side and the recovery side with respect to the flow path of the liquid discharge head. It is about the supply mechanism.

Patent Document 1 describes that a liquid flow is generated in a liquid flow path in which an energy generating element is provided so as to communicate with a discharge port of a liquid discharge head. This prevents the liquid (ink) having an increased viscosity, for example, from being discharged in the vicinity of the discharge port and the ejection characteristics from being deteriorated. In Patent Document 1, two types of pressure adjusting tanks set to different control pressures are used for the liquid supply flow path and the liquid discharge flow path in the liquid discharge head, and the upstream side and the downstream side of the liquid discharge head in the liquid supply path, respectively. The pressure is controlled to be constant. As a result, a predetermined differential pressure between the supply flow path and the recovery flow path causes an ink flow in the flow path of the liquid discharge head.

Japanese Unexamined Patent Publication No. 2014-141032

By the way, in a long head such as a line type head, the number of ejection ports is large, so that the amount of ink supplied to the head increases. Therefore, the flow rate fluctuation and the pressure loss difference in the liquid discharge head caused by the fluctuation of the discharge duty according to the recorded data and the like become large. As a result, the negative pressure in the vicinity of the ejection port fluctuates greatly, and the volume of the droplets ejected changes, which may cause problems such as uneven density of the image.

On the other hand, in Patent Document 1, it is possible to generate a predetermined differential pressure between the supply flow path and the recovery flow path for the liquid discharge head by the action of the two pressure adjusting tanks. However, if there is an error in the resistance set for each of the supply flow path and the recovery flow path, or if there is an error over time (hereinafter, the error from these set values is referred to as "tolerance"), the above It becomes impossible to generate a predetermined differential pressure.

The present invention is a liquid discharge device capable of generating a predetermined differential pressure between the supply flow path and the recovery flow path with respect to the liquid discharge head even if the resistance set for each of the supply flow path and the recovery flow path fluctuates. And to provide a method of supplying a liquid.

In order to solve the above problems, the present invention is a liquid discharge device that discharges a liquid from the liquid discharge head by using a liquid discharge head provided with at least one recording element substrate, and supplies the liquid to the recording element substrate. A means having a flow path and a liquid recovery flow path from the recording element substrate, which causes a difference between the pressure of the liquid in the supply flow path and the pressure of the liquid in the recovery flow path to generate a liquid. A pair of differential pressure generating means for supplying and recovering, and a flow resistance adjusting means provided in the supply flow path and / or the recovery flow path, the differential pressure generating means having different set pressures from each other. It has a negative pressure control unit, the high pressure side is connected to the supply flow path, the low pressure side is connected to the recovery flow path, and the supply flow path and the recovery flow path are downstream from the supply flow path and the recovery flow path. It is characterized in that a liquid feeding pump for feeding a liquid from a recovery flow path to a liquid containing tank is connected.

According to the above configuration, in the liquid supply of the liquid discharge device, even if the resistance set for each of the supply flow path and the recovery flow path fluctuates, a predetermined value between the supply flow path and the recovery flow path for the liquid discharge head It is possible to generate a differential pressure.

It is a perspective view which shows the schematic structure of the inkjet recording apparatus which concerns on one Embodiment of the liquid ejection apparatus which ejects the liquid of this invention. It is a schematic diagram which shows the 1st circulation form of the circulation path applied to the recording apparatus of one Embodiment. It is a schematic diagram which shows the 2nd circulation form of the circulation path applied to the recording apparatus of one Embodiment. FIGS. (A) to (F) are diagrams for explaining the difference in the amount of ink flowing into the liquid ejection head 3 between the first circulation mode and the second circulation mode. (A) and (b) are perspective views which show the liquid discharge head which concerns on one Embodiment. It is an exploded perspective view which showed each component or unit which constitutes a liquid discharge head. (A) to (f) are views showing the front surface and the back surface of each of the first, second and third flow path members. FIG. 7A is a perspective view showing a part of FIG. 7A and is an enlarged view of a flow path in a flow path member formed by joining the first to third flow path members. It is a figure which showed the cross section in IX-IX of FIG. (A) and (b) are a perspective view and an exploded perspective view showing one discharge module. (A), (b) and (c) are a plan view, a partially enlarged view, and a plan view of the back side of the surface on the side where the discharge port of the recording element substrate is formed. It is a perspective view which shows the cross section of the XII-XII line in FIG. 11A. It is a top view which partially enlarged and showed the adjacent part of the recording element substrate in two adjacent discharge modules. (A) and (b) are perspective views which showed the liquid discharge head which concerns on another example of one Embodiment. It is a perspective exploded view which showed the liquid discharge head which concerns on another example of one Embodiment. (A) to (e) are diagrams showing each flow path member constituting the liquid discharge head according to another example of one embodiment. It is a perspective view which showed the connection relationship of the liquid between the recording element substrate and the flow path member in the liquid discharge head which concerns on another example of one Embodiment. It is a figure which showed the cross section in line XVIII-XVIII of FIG. (A) and (b) are a perspective view and an exploded view which showed the discharge module in the liquid discharge head which concerns on another example of one Embodiment. (A) is the surface on which the discharge port of the recording element substrate is arranged, (b) is the surface of the recording element substrate when the cover plate provided on the back surface side of the recording element substrate is removed, and (c) is the surface of the recording element substrate. , Is a schematic view showing the back surface of the surface on which the discharge port is arranged. It is a figure which showed the 2nd form of the inkjet recording apparatus which concerns on one Embodiment. (A) to (c) are diagrams showing a detailed structure of a negative pressure control unit suitable for use in the first circulation mode shown in FIG. 2 according to an embodiment of the present invention. It is a figure which shows the relationship between the flow resistance between a valve | opening, and a valve opening degree in the negative pressure control unit of embodiment. (A) to (c) are diagrams showing a detailed structure of a negative pressure control unit suitable for use in the second circulation mode shown in FIG. 3 according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing a circulation path using a negative pressure control unit suitable for use in the first circulation mode shown in FIG. It is a schematic diagram which shows the circulation path using the negative pressure control unit which concerns on another form. It is a schematic diagram which shows the circulation path using the negative pressure control unit which concerns on another form.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The liquid discharge head of the present invention for discharging a liquid such as ink and the liquid discharge device equipped with the liquid discharge head can be applied to devices such as printers, copiers, facsimiles having a communication system, and word processors having a printer unit. is there. Furthermore, it can be applied to an industrial recording device that is combined with various processing devices. For example, it can also be used for biochip manufacturing, electronic circuit printing, semiconductor substrate manufacturing, and the like.

In addition, since each of the embodiments described below is an appropriate specific example of the present invention, various technically preferable limitations are added. However, the present application examples and embodiments are not limited to the application examples, embodiments, and other specific methods of the present specification as long as they are in line with the ideas of the present invention.

(Inkjet recording device of the first form)
FIG. 1 is a diagram showing a schematic configuration of a liquid ejection device for ejecting a liquid of the present invention, particularly an inkjet recording apparatus (hereinafter, also referred to as a recording apparatus) 1000 for ejecting ink for recording. The recording device 1000 includes a transport unit 1 for transporting the recording medium 2 and a line-type liquid discharge head 3 arranged substantially orthogonal to the transport direction of the recording medium 2, and continuously or intermittently transports a plurality of recording media 2. This is a line-type recording device that continuously records in one pass while transporting the media. The liquid discharge head 3 is a page-wide type liquid discharge head having a length corresponding to the width of the recording medium 2. The recording medium 2 is not limited to cut paper, and may be a continuous roll medium. The liquid discharge head 3 supplies and discharges ink to the negative pressure control unit 230 that controls the pressure (negative pressure) in the circulation path, the liquid supply unit 220 that communicates with the negative pressure control unit 230, and the liquid supply unit 220. A liquid connecting portion 111 serving as an outlet and a housing 80 are provided. Although the details will be described later, the negative pressure control unit 230 as the differential pressure generating means creates a pressure difference between the supply flow path and the recovery flow path provided in the liquid discharge head 3, thereby circulating the liquid in the pressure chamber. I do. The liquid discharge head 3 of the present embodiment includes discharge port rows for discharging cyan C, magenta M, yellow Y, and black K inks, respectively, whereby full-color recording is possible. As will be described later in FIG. 2, the liquid discharge head 3 is fluidly connected to a liquid supply mechanism, a main tank, and a buffer tank (see FIG. 2 to be described later), which are supply paths for supplying the liquid to the liquid discharge head 3. Will be done. Then, four negative pressure control units 230 and a liquid supply unit 220 are provided corresponding to each of the four color inks. Further, an electric control unit that transmits electric power and a discharge control signal to the liquid discharge head 3 is electrically connected to the liquid discharge head 3. The liquid path and the electric signal path in the liquid discharge head 3 will be described later.

The recording device 1000 is an inkjet recording device in a form in which a liquid such as ink is circulated between a tank described later and a liquid discharge head 3. The inkjet recording apparatus of this embodiment can be configured in two circulation modes (configurations). That is, the first circulation mode in which two circulation pumps (for high pressure and low pressure) are operated on the downstream side of the liquid discharge head 3 and two circulation pumps (for high pressure and low pressure) are operated on the upstream side. Any of the two forms of the second circulation form to be circulated can be adopted. Hereinafter, the first circulation form and the second circulation form of this circulation will be described.

<Explanation of the first circulation form>
FIG. 2 is a schematic diagram showing a first circulation mode of a circulation path applied to the recording device 1000 of the present embodiment. The liquid discharge head 3 is fluidly connected to a first circulation pump (high pressure side) 1001, a first circulation pump (low pressure side) 1002, a buffer tank (liquid storage tank) 1003, and the like. In FIG. 2, for simplification of the explanation, only the path through which one color of the cyan C, magenta M, yellow Y, and black K inks flows is shown, but in reality, four colors are shown. Circulation paths are provided in the liquid discharge head 3 and the recording device main body.

In the first circulation mode, the ink in the main tank 1006 is supplied to the buffer tank 1003 by the replenishment pump 1005, and then to the liquid supply unit 220 of the liquid discharge head 3 via the liquid connection portion 111 by the second circulation pump 1004. Be supplied. After that, the ink adjusted to two different negative pressures (high pressure and low pressure) by the negative pressure control unit 230 as the differential pressure generating means connected to the liquid supply unit 220 is sent to the two flow paths on the high pressure side and the low pressure side. Divide and circulate. The ink in the liquid discharge head 3 circulates in the liquid discharge head by the action of the first circulation pump (high pressure side) 1001 and the first circulation pump (low pressure side) 1002 downstream of the liquid discharge head 3, and the liquid connection portion. The liquid is discharged from the liquid discharge head 3 via 111 and returns to the buffer tank 1003. The first circulation pump (high pressure side) 1001 and the first circulation pump (low pressure side) 1002 are not indispensable as supply means for generating a circulation flow, but are auxiliary ones for suppressing pressure loss and the like.

The buffer tank 1003, which is a sub tank, is connected to the main tank 1006, has an air communication port (not shown) that communicates the inside and the outside of the tank, and can discharge air bubbles in the ink to the outside. A replenishment pump 1005 is provided between the buffer tank 1003 and the main tank 1006. The replenishment pump 1005 transfers the ink consumed by ejecting (discharging) the ink from the ejection port of the liquid ejection head 3 from the main tank 1006 to the buffer tank 1005, such as recording by ejecting the ink and recovering suction.

The two first circulation pumps 1001 and 1002 draw liquid from the liquid connection portion 111 of the liquid discharge head 3 and flow it into the buffer tank 1003. As the first circulation pump, a positive displacement pump having a quantitative liquid feeding capacity is preferable. Specific examples thereof include a tube pump, a gear pump, a diaphragm pump, a syringe pump, and the like. For example, a general constant flow rate valve or relief valve may be arranged at the pump outlet to secure a constant flow rate. When the liquid discharge head 3 is driven, the first circulation pump (high pressure side) 1001 and the first circulation pump (low pressure side) 1002 are operated so that the common supply flow path 211 and the common recovery flow path 212 have a predetermined flow rate, respectively. Ink flows. By flowing the ink in this way, the temperature of the liquid ejection head 3 at the time of recording is maintained at the optimum temperature. The predetermined flow rate when the liquid discharge head 3 is driven is preferably set to a flow rate that can be maintained to such an extent that the temperature difference between the recording element substrates 10 in the liquid discharge head 3 does not affect the recording image quality. However, if the flow rate is set too large, the negative pressure difference between the recording element substrates 10 becomes large due to the influence of the pressure loss of the flow path in the liquid discharge unit 300, and the density unevenness of the image occurs. Therefore, it is preferable to set the flow rate while considering the temperature difference and the negative pressure difference between the recording element substrates 10.

The negative pressure control unit 230 is provided in the path between the second circulation pump 1004 and the liquid discharge unit 300. This negative pressure control unit 230 keeps the pressure on the downstream side (that is, the liquid discharge unit 300 side) of the negative pressure control unit 230 even when the flow rate of ink in the circulation system fluctuates due to a difference in the discharge amount per unit area or the like. It operates to maintain a preset constant pressure. As the two pressure adjusting mechanisms, the high pressure side (H) and the low pressure side (L), which constitute the negative pressure control unit 230, the pressure downstream of the negative pressure control unit 230 is constant around the desired set pressure. Any mechanism may be used as long as it can be controlled by fluctuations below the range. As an example, a mechanism similar to a so-called "decompression regulator" can be adopted. In the circulation flow path of the present embodiment, the second circulation pump 1004 pressurizes the upstream side of the negative pressure control unit 230 via the liquid supply unit 220. By doing so, the influence of the head pressure on the liquid discharge head 3 of the buffer tank 1003 can be suppressed, so that the degree of freedom in the layout of the buffer tank 1003 in the recording device 1000 can be expanded.

The second circulation pump 1004 may be a pump having a lift pressure equal to or higher than a certain pressure within the range of the ink circulation flow rate used when driving the liquid discharge head 3, and a turbo type pump, a positive displacement pump, or the like can be used. .. Specifically, a diaphragm pump or the like can be applied. Further, instead of the second circulation pump 1004, for example, a head tank arranged with a certain head difference with respect to the negative pressure control unit 230 can also be applied.

As shown in FIG. 2, the negative pressure control unit 230 includes two pressure adjusting mechanisms H and L, each of which is set with different control pressures. Of the two negative pressure adjusting mechanisms, the relatively high pressure setting side (denoted as H in FIG. 2) and the relatively low pressure side (denoted as L in FIG. 2) pass through the inside of the liquid supply unit 220. It is connected to the common supply flow path 211 and the common recovery flow path 212 in the liquid discharge unit 300, respectively. The liquid discharge unit 300 as a support member for supporting the plurality of recording element substrates 10 includes a common supply flow path 211, a common recovery flow path 212, and an individual flow path 215 (individual supply flow path 213) communicating with each recording element substrate. An individual recovery flow path 214) is provided. A pressure adjusting mechanism H is connected to the common supply flow path 211, and a pressure adjusting mechanism L is connected to the common recovery flow path 212, so that a differential pressure is generated between the two common flow paths. Since the individual flow path 215 communicates with the common supply flow path 211 and the common recovery flow path 212, respectively, a part of the liquid passes through the internal flow path of the recording element substrate 10 from the common supply flow path 211. A flow (arrow in FIG. 2) flowing into the common recovery flow path 212 is generated. The two negative pressure adjusting mechanisms H and L are connected to the path from the liquid connecting portion 111 via the filter 221 respectively.

Further, the supply side is between the common supply flow path 211 and the high pressure side pressure adjusting mechanism (H) of the negative pressure control unit 230, and between the common recovery flow path 212 and the low pressure side pressure adjusting mechanism (L), respectively. A flow resistance adjusting mechanism 222 and a recovery side flow resistance adjusting mechanism 223 are provided. Due to these flow resistance adjustment mechanisms, as will be described in detail later, there is a change in the ink flow resistance (hereinafter, also referred to as flow resistance) of the common supply flow path 211 and the common recovery flow path 212 from the set value such as a tolerance. Even in such a case, the above change can be corrected by adjusting the flow resistance adjusting mechanism in response to the change. As a result, deviation of the differential pressure between the common supply flow path and the common recovery flow path from the set value can be suppressed, and for example, it is possible to reduce variations in the flow rate of the ink flow in the flow path communicating with the ejection port. It becomes.

In this way, in the liquid discharge unit 300, a part of the liquid passes through each recording element substrate 10 while flowing the liquid so as to pass through the common supply flow path 211 and the common recovery flow path 212, respectively. A flow occurs. Therefore, the heat generated in each recording element substrate 10 can be discharged to the outside of the recording element substrate 10 by the ink flowing through the common supply flow path 211 and the common recovery flow path 212. Further, with such a configuration, when recording is performed by the liquid discharge head 3, it is possible to generate an ink flow even in a discharge port or a pressure chamber where the liquid is not discharged. As a result, the thickening of the ink can be suppressed by reducing the viscosity of the thickened ink in the ejection port. In addition, the thickened ink and foreign matter in the ink can be discharged to the common recovery flow path 212. Therefore, the liquid discharge head 3 of the present embodiment enables high-speed, high-quality recording.

<Explanation of the second circulation form>
FIG. 3 is a schematic diagram showing a second circulation mode, which is a circulation mode different from the first circulation mode described above, among the circulation paths applied to the recording device of the present embodiment. The main difference from the first circulation mode described above is that the two pressure adjusting mechanisms constituting the negative pressure control unit 230 as the differential pressure generating means both desire a pressure on the upstream side of the negative pressure control unit 230. It is a point to control by fluctuation within a certain range around the set pressure of. Further, the difference from the first circulation mode is that the second circulation pump 1004 acts as a negative pressure source for reducing the pressure on the downstream side of the negative pressure control unit 230. Further, the first circulation pump (high pressure side) 1001 and the first circulation pump (low pressure side) 1002 are arranged on the upstream side of the liquid discharge head 3, and the negative pressure control unit 230 is arranged on the downstream side of the liquid discharge head 3. There is also a difference.

In the second circulation mode, as shown in FIG. 3, the ink in the main tank 1006 is supplied to the buffer tank 1003 by the replenishment pump 1005. After that, the ink is divided into two flow paths, and is circulated through the two flow paths on the high pressure side and the low pressure side by the action of the negative pressure control unit 230 provided in the liquid discharge head 3. The ink divided into the two flow paths of the high pressure side and the low pressure side connects the liquid connection portion 111 of the liquid discharge head 3 by the action of the first circulation pump (high pressure side) 1001 and the first circulation pump (low pressure side) 1002. It is supplied to the liquid discharge head 3 via the liquid discharge head 3. After that, the ink circulated in the liquid discharge unit 300 by the action of the first circulation pump (high pressure side) 1001 and the first circulation pump (low pressure side) 1002 passes through the negative pressure control unit 230 and the liquid connection portion 111. The liquid is discharged from the liquid discharge head 3. The discharged ink is returned to the buffer tank 1003 by the second circulation pump 1004.

The negative pressure control unit 230 in the second circulation mode can change the pressure on the upstream side (that is, the liquid discharge unit 300 side) of the negative pressure control unit 230 even if the flow rate fluctuates due to the change in the discharge amount per unit area. It acts to stabilize within a certain range around a preset pressure. In the circulation flow path of the present embodiment, the second circulation pump 1004 pressurizes the downstream side of the negative pressure control unit 230 via the liquid supply unit 220. In this way, the influence of the head pressure of the buffer tank 1003 on the liquid discharge head 3 can be suppressed, so that the layout selection range of the buffer tank 1003 in the recording device 1000 can be widened. Instead of the second circulation pump 1004, for example, a head tank arranged with a predetermined head difference with respect to the negative pressure control unit 230 can be applied. In the second circulation mode, as in the first circulation mode described above, the negative pressure control unit 230 includes two pressure adjusting mechanisms H and L, each of which is set with different control pressures. Of the two negative pressure adjusting mechanisms H and L, the high pressure setting side (denoted as H in FIG. 3) and the low pressure setting side (denoted as L in FIG. 3) each discharge liquid via the inside of the liquid supply unit 220. It is connected to the common supply flow path 211 and the common recovery flow path 212 in the unit 300. By making the pressure of the common supply flow path 211 relatively higher than the pressure of the common recovery flow path 212 by the two negative pressure adjusting mechanisms, the pressure of the individual flow path 213 and each recording element substrate 10 is increased from the common supply flow path 211. An ink flow is generated to flow to the common recovery flow path 212 through the flow path.

In such a second circulation mode, the same ink flow state as in the first circulation mode can be obtained in the liquid ejection unit 300, but there are two advantages different from those in the first circulation mode. First, in the second circulation mode, since the negative pressure control unit 230 is arranged on the downstream side of the liquid discharge head 3, dust and foreign matter generated from the negative pressure control unit 230 flow into the liquid discharge head 3. There are few concerns. Second, in the second circulation mode, the maximum value of the required flow rate supplied from the buffer tank 1003 to the liquid discharge head 3 can be smaller than in the first circulation mode. The reason is as follows.

The total flow rate in the common supply flow path 211 and the common recovery flow path 212 when circulating during the recording standby is defined as the flow rate A. The value of the flow rate A is defined as, for example, the minimum flow rate required to keep the temperature difference in the liquid discharge unit 300 within a desired range when adjusting the temperature of the liquid discharge head 3 during recording standby. Further, the discharge flow rate when ink is discharged from all the discharge ports of the liquid discharge unit 300 (at the time of all discharges) is defined as a flow rate F (discharge amount per one discharge port x discharge frequency per unit time x number of discharge ports). ..

FIG. 4 is a diagram illustrating a difference in the amount of ink flowing into the liquid ejection head 3 between the first circulation mode and the second circulation mode. FIG. 4 (a) shows the standby time in the first circulation mode, and FIG. 4 (b) shows the total discharge time in the first circulation mode. 4 (c) to 4 (f) show the flow rate in the case of the second circulation flow path, and FIGS. 4 (c) and 4 (d) show the flow rate F <flow rate A, and FIG. 4 (e). ) And (f) are cases where the flow rate F> the flow rate A, and show the flow rates during standby and during full discharge, respectively.

In the case of the first circulation mode in which the first circulation pump (high pressure side) 1001 and the first circulation pump (low pressure side) 1002 having a quantitative liquid feeding capacity are arranged on the downstream side of the liquid discharge head 3 (FIG. 4 (FIG. 4). a), (b)), the total set flow rate of the first circulation pump 1001 and the first circulation pump 1002 is the flow rate A (FIG. 4 (a)). With this flow rate A, it is possible to control the temperature inside the liquid discharge unit 300 during standby. When the liquid discharge head 3 is used for full discharge, the total set flow rate of the first circulation pump 1001 and the first circulation pump 1002 remains the flow rate A. At this time, the negative pressure generated by the discharge in the liquid discharge head 3 acts, and the maximum flow rate supplied to the liquid discharge head 3 is the total set flow rate A plus the consumption amount (flow rate F) due to the total discharge. .. Therefore, the maximum value of the supply amount to the liquid discharge head 3 is the flow rate A + the flow rate F because the flow rate F is added to the flow rate A (FIG. 4B).

On the other hand, in the case of the second circulation mode in which the first circulation pump 1001 and the first circulation pump 1002 are arranged on the upstream side of the liquid discharge head 3 (FIGS. 4C to 4F), it is necessary during recording standby. The supply amount to the liquid discharge head 3 is the flow rate A as in the first circulation mode. Therefore, in the second circulation mode in which the first circulation pump 1001 and the first circulation pump 1002 are arranged on the upstream side of the liquid discharge head 3, the flow rate A is larger than the flow rate F (FIGS. 4C and 4d). )), The flow rate A is sufficient for the supply amount to the liquid discharge head 3 even at the time of full discharge. At that time, the discharge flow rate from the liquid discharge head 3 becomes the flow rate A − the flow rate F (FIG. 4 (d)). However, when the flow rate F is larger than the flow rate A (FIGS. 4 (e) and 4 (f)), if the supply flow rate to the liquid discharge head 3 is set to the flow rate A at the time of full discharge, the flow rate becomes insufficient. Therefore, when the flow rate F is larger than the flow rate A, it is necessary to set the supply amount to the liquid discharge head 3 as the flow rate F. At that time, when all the discharges are performed, the liquid discharge head 3 consumes the flow rate F, so that the discharge flow rate from the liquid discharge head 3 is hardly discharged (FIG. 4 (f)). When the flow rate F is larger than the flow rate A and the discharge is performed but not all discharges, the amount obtained by subtracting the amount consumed by the discharge from the flow rate F is discharged from the liquid discharge head 3.

As described above, in the case of the second circulation mode, the total value of the set flow rates of the first circulation pump 1001 and the first circulation pump 1002, that is, the maximum value of the required supply flow rate is the larger value of the flow rate A or the flow rate F. .. Therefore, as long as the liquid discharge unit 300 having the same configuration is used, the maximum value of the required supply amount (flow rate A or flow rate F) in the second circulation mode is the maximum value of the required supply flow rate (flow rate A + flow rate) in the first circulation mode. It is smaller than F).

Therefore, in the case of the second circulation mode, the degree of freedom of the applicable circulation pump is increased. For example, a low-cost circulation pump having a simple configuration can be used, or a load of a cooler (not shown) installed in the main body side path can be applied. There is an advantage that it can be reduced and the cost of the recording device can be reduced. This advantage increases as the value of the flow rate A or the flow rate F becomes relatively large, and is more beneficial for the line head having a longer length in the longitudinal direction.

However, on the other hand, there is also a point that the first circulation form is more advantageous than the second circulation form. That is, in the second circulation mode, since the flow rate flowing through the liquid discharge unit 300 during the recording standby is the maximum, the smaller the discharge amount per unit area (hereinafter, also referred to as a low duty image), the more the discharge port has. A high negative pressure is applied. For this reason, when the flow path width is narrow and the negative pressure is high, a high negative pressure is applied to the ejection port in a low duty image in which unevenness is easily visible, so that many so-called satellite droplets are ejected along with the main droplet of ink. It may occur and the recording quality may deteriorate. On the other hand, in the case of the first circulation mode, a high negative pressure is applied to the discharge port when an image having a large discharge amount per unit area (hereinafter, also referred to as a high duty image) is formed, so that satellite droplets are tentatively generated. However, it has the advantage that it is difficult to see and the effect on the image is small. The selection of these two circulation modes can be made in light of the specifications of the liquid discharge head and the recording device main body (discharge flow rate F, minimum circulation flow rate A, and flow path resistance in the head).

As shown in FIG. 3, also in the second circulation mode, as in the first circulation mode (FIG. 2), between the common supply flow path 211 and the high pressure side pressure adjusting mechanism (H) of the negative pressure control unit 230, and A supply side flow resistance adjusting mechanism 222 and a recovery side flow resistance adjusting mechanism 223 are provided between the common recovery flow path 212 and the low pressure side pressure adjusting mechanism (L), respectively. By these flow resistance adjusting mechanisms, it is possible to suppress the deviation from the set value of the differential pressure between the common supply flow path and the common recovery flow path, as described above in the first circulation mode.

<Explanation of liquid discharge head configuration>
The configuration of the liquid discharge head 3 according to the first embodiment will be described. 5 (a) and 5 (b) are perspective views showing the liquid discharge head 3 according to the present embodiment. In the liquid ejection head 3, 15 recording element substrates 10 capable of ejecting four color inks of cyan C / magenta M / yellow Y / black K on one recording element substrate 10 are arranged in a straight line (arranged in-line). This is a line-type liquid discharge head. As shown in FIG. 5A, the liquid discharge head 3 has a signal input terminal 91 and a power supply terminal 92 electrically connected to each recording element substrate 10 via the flexible wiring board 40 and the electrical wiring board 90. To be equipped. The signal input terminal 91 and the power supply terminal 92 are electrically connected to the control unit of the recording device 1000, and supply the discharge drive signal and the power required for discharge to the recording element substrate 10, respectively. By consolidating the wiring by the electric circuit in the electric wiring board 90, the number of signal output terminals 91 and power supply terminals 92 can be reduced as compared with the number of recording element boards 10. As a result, the number of electrical connections that need to be removed when assembling the liquid discharge head 3 to the recording device 1000 or when replacing the liquid discharge head can be reduced. As shown in FIG. 5B, the liquid connection portions 111 provided at both ends of the liquid discharge head 3 are connected to the liquid supply system of the recording device 1000 described above in FIGS. 2 and 3. As a result, cyan C / magenta M / yellow Y / black K4 color ink is supplied from the supply system of the recording device 1000 to the liquid ejection head 3, and the ink that has passed through the liquid ejection head 3 is supplied to the supply system of the recording device 1000. It is supposed to be collected. In this way, the inks of each color can be circulated through the path of the recording device 1000 and the path of the liquid ejection head 3.

FIG. 6 is an exploded perspective view showing each component or unit constituting the liquid discharge head 3. The liquid discharge unit 300, the liquid supply unit 220, and the electrical wiring board 90 are attached to the housing 80. The liquid supply unit 220 is provided with a liquid connection portion 111 (see FIG. 3), and the inside of the liquid supply unit 220 communicates with each opening of the liquid connection portion 111 in order to remove foreign matter in the supplied ink. Filters 221 for each color (see FIGS. 2 and 3) are provided. The two liquid supply units 220 are each provided with a filter 221 for two colors. The liquid that has passed through the filter 221 is supplied to the negative pressure control unit 230 arranged on the liquid supply unit 220 corresponding to each color. The negative pressure control unit 230 is a unit composed of pressure adjusting valves for each color, and is generated in the supply system of the recording device 1000 (generated by fluctuations in the flow rate of the liquid due to the action of valves and spring members provided inside each). The pressure loss change of the supply system on the upstream side of the liquid discharge head 3) is significantly attenuated. As a result, the negative pressure control unit 230 can stabilize the negative pressure change on the downstream side (liquid discharge unit 300 side) of the pressure control unit within a certain range. As described with reference to FIG. 2, two pressure adjusting valves for each color are built in the negative pressure control unit 230 for each color. The two pressure regulating valves are set to different control pressures, and the high pressure side is the common supply flow path 211 (see FIG. 2) in the liquid discharge unit 300, and the low pressure side is the common recovery flow path 212 (see FIG. 2) and the liquid supply unit. It communicates via 220.

The housing 80 is composed of a liquid discharge unit support portion 81 and an electric wiring board support portion 82, supports the liquid discharge unit 300 and the electric wiring board 90, and secures the rigidity of the liquid discharge head 3. The electric wiring board support portion 82 is for supporting the electric wiring board 90, and is fixed to the liquid discharge unit support portion 81 by screwing. The liquid discharge unit support portion 81 has a role of correcting warpage and deformation of the liquid discharge unit 300 to ensure the relative position accuracy of the plurality of recording element substrates 10, thereby suppressing streaks and unevenness in the recorded material. .. Therefore, the liquid discharge unit support portion 81 preferably has sufficient rigidity, and as the material, a metal material such as SUS or aluminum, or a ceramic such as alumina is preferable. The liquid discharge unit support portion 81 is provided with openings 83 and 84 into which the joint rubber 100 is inserted. The liquid supplied from the liquid supply unit 220 is guided to the third flow path member 70 constituting the liquid discharge unit 300 via the joint rubber.

The liquid discharge unit 300 includes a plurality of discharge modules 200 and a flow path member 210, and a cover member 130 is attached to the surface of the liquid discharge unit 300 on the recording medium side. Here, the cover member 130 is a member having a frame-like surface provided with a long opening 131 as shown in FIG. 6, and the recording element substrate 10 and the sealing included in the discharge module 200 are sealed from the opening 131. The stop material portion 110 (see FIG. 10 described later) is exposed. The frame portion around the opening 131 has a function as a contact surface of a cap member that caps the liquid discharge head 3 during recording standby. Therefore, an adhesive, a sealing material, a filler, or the like is applied along the periphery of the opening 131 to fill the irregularities and gaps on the discharge port surface of the liquid discharge unit 300, so that a closed space is formed at the time of capping. It is preferable to do so.

Next, the configuration of the flow path member 210 included in the liquid discharge unit 300 will be described. As shown in FIG. 6, the flow path member 210 is a stack of the first flow path member 50, the second flow path member 60, and the third flow path member 70, and the liquid supplied from the liquid supply unit 220 is supplied. Distribute to each discharge module 200. Further, the flow path member 210 is a flow path member for returning the liquid recirculated from the discharge module 200 to the liquid supply unit 220. The flow path member 210 is fixed to the liquid discharge unit support portion 81 with screws, whereby warpage and deformation of the flow path member 210 are suppressed.

7 (a) to 7 (f) are views showing the front surface and the back surface of each flow path member of the first to third flow path members. FIG. 7 (a) shows the surface of the first flow path member 50 on the side on which the discharge module 200 is mounted, and FIG. 7 (f) shows the liquid discharge unit support portion 81 of the third flow path member 70. The surface on the abutting side is shown. Further, the first flow path member 50 and the second flow path member 60 are joined so that FIGS. 7 (b) and 7 (c), which show the contact surfaces of the respective flow path members, face each other, and the second flow path member 50 and the second flow path member 60 are joined to each other. The flow path member and the third flow path member are joined so that FIGS. 7 (d) and 7 (e), which show contact surfaces of the respective flow path members, face each other. By joining the second flow path member 60 and the third flow path member 70, eight common flow path grooves 62 and 71 formed in each flow path member extend in the longitudinal direction of the flow path member. Common flow paths (211a, 211b, 211c, 211d, 212a, 212b, 212c, 212d) are formed. As a result, a set of the common supply flow path 211 and the common recovery flow path 212 is formed in the flow path member 210 for each color. Ink is supplied to the liquid discharge head 3 from the common supply flow path 211, and the ink supplied to the liquid discharge head 3 is recovered by the common recovery flow path 212. The communication port 72 (see FIG. 7 (f)) of the third flow path member 70 communicates with each hole of the joint rubber 100 and fluidly circulates with the liquid supply unit 220 (see FIG. 6). On the bottom surface of the common flow path groove 62 of the second flow path member 60, a communication port 61 (communication port 61-1 communicating with the common supply flow path 211, communication port 61-2 communicating with the common recovery flow path 212) is provided. A plurality of them are formed and communicate with one end of the individual flow path groove 52 of the first flow path member 50. A communication port 51 is formed at the other end of the individual flow path groove 52 of the first flow path member 50, and fluidly communicates with the plurality of discharge modules 200 via the communication port 51. The individual flow path groove 52 makes it possible to consolidate the flow paths toward the center of the flow path member.

The first to third flow path members are preferably made of a material having corrosion resistance to liquid and having a low coefficient of linear expansion. As the material, for example, a composite material (resin material) using alumina, LCP (liquid crystal polymer), PPS (polyphenyl sulfide) or PSF (polysulfone) as a base material and adding an inorganic filler such as silica fine particles or fibers is preferably used. be able to. As a method for forming the flow path member 210, three flow path members may be laminated and bonded to each other, or when a resin composite resin material is selected as the material, a joining method by welding may be used.

FIG. 8 shows the α portion of FIG. 7A, and the flow path in the flow path member 210 formed by joining the first to third flow path members is the flow path of the first flow path member 50. It is a perspective view showing a part enlarged from the surface side on which the discharge module 200 is mounted. In the common supply flow path 211 and the common recovery flow path 212, the common supply flow path 211 and the common recovery flow path 212 are alternately arranged from the flow paths at both ends. Here, the connection relationship of each flow path in the flow path member 210 will be described.

The flow path member 210 is provided with a common supply flow path 211 (211a, 211b, 211c, 211d) and a common recovery flow path 212 (212a, 212b, 212c, 212d) extending in the longitudinal direction of the liquid discharge head 3 for each color. Has been done. A plurality of individual supply channels (213a, 213b, 213c, 213d) formed by the individual channel grooves 52 are connected to the common supply channel 211 of each color via a communication port 61. Further, a plurality of individual recovery channels (214a, 214b, 214c, 214d) formed by the individual channel grooves 52 are connected to the common recovery channel 212 of each color via a communication port 61. With such a flow path configuration, ink can be concentrated on the recording element substrate 10 located at the center of the flow path member from each common supply flow path 211 via the individual supply flow path 213. Ink can be recovered from the recording element substrate 10 to each common recovery flow path 212 via the individual recovery flow path 214.

FIG. 9 is a diagram showing a cross section of FIG. 8 in IX-IX. Each individual collection flow path (214a, 214c) communicates with the discharge module 200 via a communication port 51. In FIG. 9, only the individual recovery channels (214a and 214c) are shown, but in another cross section, the individual supply channels 213 and the discharge module 200 communicate with each other as shown in FIG. The support member 30 and the recording element substrate 10 included in each ejection module 200 are formed with a flow path for supplying ink from the first flow path member 50 to the recording element 15 provided on the recording element substrate 10. .. Further, the support member 30 and the recording element substrate 10 are formed with a flow path for collecting (circulating) a part or all of the liquid supplied to the recording element 15 to the first flow path member 50.

Here, the common supply flow path 211 of each color is connected to the negative pressure control unit 230 (high pressure side) of the corresponding color via the liquid supply unit 220, and the common recovery flow path 212 is the negative pressure control unit 230. It is connected to (low pressure side) via a liquid supply unit 220. The negative pressure control unit 230 creates a differential pressure (pressure difference) between the common supply flow path 211 and the common recovery flow path 212. Therefore, as shown in FIGS. 8 and 9, in the liquid discharge head of the present embodiment in which each flow path is connected, the common supply flow path 211 to the individual supply flow path 213a to the recording element substrate 10 are used for each ink color. -Ink flow is generated in order from the individual recovery flow path 213b to the common recovery flow path 212.

<Explanation of discharge module>
FIG. 10A is a perspective view showing one discharge module 200, and FIG. 10B is an exploded view thereof. As a method of manufacturing the discharge module 200, first, the recording element substrate 10 and the flexible wiring substrate 40 are adhered to a support member 30 provided with a liquid communication port 31 in advance. After that, the terminal 16 on the recording element substrate 10 and the terminal 41 on the flexible wiring board 40 are electrically connected by wire bonding, and then the wire bonding portion (electrical connection portion) is covered with a sealing material 110 and sealed. .. The terminal 42 on the side of the flexible wiring board 40 opposite to the recording element board 10 is electrically connected to the connection terminal 93 (see FIG. 6) of the electrical wiring board 90. Since the support member 30 is a support that supports the recording element substrate 10 and is a flow path member that fluidly communicates the recording element substrate 10 and the flow path member 210, the flatness is high and sufficiently high. Those that can be reliably bonded to the recording element substrate are preferable. As the material, for example, alumina or a resin material is preferable.

<Explanation of the structure of the recording element substrate>
FIG. 11A shows a plan view of the surface of the recording element substrate 10 on the side where the discharge port 13 is formed, and FIG. 11B shows an enlarged view of the portion shown by A in FIG. 11A. 11 (c) shows a plan view of the back surface of FIG. 11 (a). Here, the configuration of the recording element substrate 10 in this embodiment will be described. As shown in FIG. 11A, the ejection port forming member 12 of the recording element substrate 10 is formed with four rows of ejection ports corresponding to each ink color. Hereinafter, the direction in which the discharge port row in which the plurality of discharge ports 13 are arranged extends is referred to as the "discharge port row direction". As shown in FIG. 11B, a recording element 15 which is a heat generating element for generating heat energy of a liquid and foaming the liquid is arranged at a position corresponding to each discharge port 13. The partition wall 22 partitions the pressure chamber 23 including the recording element 15 inside. The recording element 15 is electrically connected to the terminal 16 by an electric wiring (not shown) provided on the recording element substrate 10. Then, the recording element 15 generates heat based on a pulse signal input from the control circuit of the recording device 1000 via the electric wiring board 90 (see FIG. 6) and the flexible wiring board 40 (see FIG. 10) to generate a liquid. Bring to a boil. The liquid is discharged from the discharge port 13 by the force of foaming due to this boiling. As shown in FIG. 11B, a liquid supply path 18 extends on one side and a liquid recovery path 19 extends on the other side along each discharge port row. The liquid supply path 18 and the liquid recovery path 19 are flow paths extending in the discharge port row direction provided on the recording element substrate 10, and communicate with the discharge port 13 via the supply port 17a and the recovery port 17b, respectively.

As shown in FIG. 11C, a sheet-shaped cover plate 20 is laminated on the back surface of the surface of the recording element substrate 10 on which the discharge port 13 is formed, and the cover plate 20 is supplied with a liquid, which will be described later. A plurality of openings 21 communicating with the path 18 and the liquid recovery path 19 are provided. In the present embodiment, the cover plate 20 is provided with three openings 21 for one liquid supply path 18 and two openings 21 for one liquid recovery path 19. As shown in FIG. 11B, each opening 21 of the cover plate 20 communicates with the plurality of communication ports 51 shown in FIG. 7A. The cover plate 20 preferably has sufficient corrosion resistance against a liquid, and from the viewpoint of preventing color mixing, the opening shape and opening position of the opening 21 are required to have high accuracy. Therefore, it is preferable to use a photosensitive resin material or a silicon plate as the material of the cover plate 20 and to provide the opening 21 by a photolithography process. As described above, the cover plate 20 changes the pitch of the flow path by the opening 21, and it is desirable that the cover plate 20 is thin in consideration of the pressure loss, and it is desirable that the cover plate 20 is made of a film-like member.

FIG. 12 is a perspective view showing a cross section of the recording element substrate 10 and the cover plate 20 in XII-XII in FIG. 11A. Here, the flow of the liquid in the recording element substrate 10 will be described. The cover plate 20 has a function as a lid forming a part of the walls of the liquid supply path 18 and the liquid recovery path 19 formed on the substrate 11 of the recording element substrate 10. The recording element substrate 10 is formed by laminating a substrate 11 formed of Si and a discharge port forming member 12 formed of a photosensitive resin, and a cover plate 20 is bonded to the back surface of the substrate 11. A recording element 15 is formed on one surface side of the substrate 11 (see FIG. 11), and a liquid supply path 18 and a liquid recovery path 19 extending along the discharge port row are formed on the back surface side thereof. A groove is formed. The liquid supply path 18 and the liquid recovery path 19 formed by the substrate 11 and the cover plate 20 are connected to the common supply flow path 211 and the common recovery flow path 212 in the flow path member 210, respectively, and the liquid supply path 18 A differential pressure is generated between the liquid recovery path 19 and the liquid recovery path 19. When the liquid is discharged from the discharge port 13 and the recording is performed, at the discharge port where the liquid is not discharged, the liquid in the liquid supply path 18 provided in the substrate 11 due to this differential pressure is discharged from the supply port 17a. It flows to the liquid recovery path 19 via the pressure chamber 23 and the recovery port 17b (arrow C in FIG. 12). By this flow, in the discharge port 13 and the pressure chamber 23 which are not in the discharge operation, the thickening ink, bubbles, foreign matter and the like generated by evaporation from the discharge port 13 can be collected in the liquid recovery path 19. Further, it is possible to prevent the ink in the discharge port 13 and the pressure chamber 23 from thickening or increasing the density of the coloring material. The liquid collected in the liquid recovery path 19 is common to the communication port 51 in the flow path member 210 and the individual recovery flow path 214 through the opening 21 of the cover plate 20 and the liquid communication port 31 (see FIG. 10b) of the support member 30. It is collected in the order of the collection flow path 212, and is collected in the supply flow path of the recording device 1000. That is, the liquid supplied from the recording device main body to the liquid discharge head 3 flows in the following order, and is supplied and recovered.

The liquid first flows into the inside of the liquid discharge head 3 from the liquid connection portion 111 of the liquid supply unit 220. The liquid is the joint rubber 100, the communication port 72 and the common flow path groove 71 provided in the third flow path member, the common flow path groove 62 and the communication port 61 provided in the second flow path member, and the first flow path. It is supplied in the order of the individual flow path groove 52 and the communication port 51 provided in the member. After that, the liquid is supplied to the pressure chamber 23 through the liquid communication port 31 provided in the support member 30, the opening 21 provided in the cover plate 20, the liquid supply path 18 provided in the substrate 11, and the supply port 17a in this order. Of the liquids supplied to the pressure chamber 23, the liquids not discharged from the discharge port 13 are the recovery port 17b and the liquid recovery path 19 provided on the substrate 11, the opening 21 provided in the cover plate 20, and the support member 30. It flows through the liquid communication port 31 provided in the above in order. After that, the liquid is provided in the communication port 51 and the individual flow path groove 52 provided in the first flow path member, the communication port 61 and the common flow path groove 62 provided in the second flow path member, and the third flow path member 70. The common flow path groove 71, the communication port 72, and the joint rubber 100 flow in this order. Then, the liquid flows from the liquid connection portion 111 provided in the liquid supply unit 220 to the outside of the liquid discharge head 3.

In the first circulation mode shown in FIG. 2, the liquid flowing in from the liquid connection portion 111 is supplied to the joint rubber 100 after passing through the negative pressure control unit 230. Further, in the second circulation mode shown in FIG. 3, the liquid recovered from the pressure chamber 23 passes through the joint rubber 100 and then passes from the liquid connection portion 111 to the outside of the liquid discharge head via the negative pressure control unit 230. Flow to. Further, not all the liquid that has flowed in from one end of the common supply flow path 211 of the liquid discharge unit 300 is supplied to the pressure chamber 23 via the individual supply flow path 213a. That is, there is also a liquid that has flowed in from one end of the common supply flow path 211 and flows into the liquid supply unit 220 from the other end of the common supply flow path 211 without flowing into the individual supply flow path 213a. In this way, by providing the path for flowing without passing through the recording element substrate 10, even when the recording element substrate 10 having a fine flow path having a relatively large flow resistance as in the present embodiment is used. , The backflow of the circulating flow of the liquid can be suppressed. As described above, in the liquid discharge head 3 of the present embodiment, the thickening of the liquid in the pressure chamber 23 and the vicinity of the discharge port can be suppressed, so that the discharge twist and non-discharge can be suppressed, and as a result. High-quality recording can be performed.

<Explanation of positional relationship between recording element substrates>
FIG. 13 is a plan view showing a partially enlarged view of the adjacent portion of the recording element substrate in the two adjacent discharge modules 200. In this embodiment, a substantially parallelogram recording element substrate is used. The discharge port rows (14a to 14d) in which the discharge ports 13 of the recording element substrates 10 are arranged are arranged so as to be inclined at a constant angle with respect to the transport direction of the recording medium. Then, in the discharge port row in the adjacent portion between the recording element substrates 10, at least one discharge port overlaps in the transport direction of the recording medium. In FIG. 13, the two discharge ports on the line D overlap each other. With such an arrangement, even if the position of the recording element substrate 10 deviates slightly from the predetermined position, black streaks and white spots in the recorded image can be made inconspicuous by the drive control of the overlapping discharge ports. Even when the plurality of recording element substrates 10 are arranged in a straight line (in-line) instead of the so-called staggered arrangement, the configuration as shown in FIG. 13 suppresses an increase in the length of the recording medium of the liquid discharge head 10 in the transport direction. It is possible to take measures against black streaks and white spots at the joints between the recording element substrates 10. In the present embodiment, the main plane of the recording element substrate is a parallelogram, but the present invention is not limited to this, and even when a rectangular, trapezoidal, or other shaped recording element substrate is used, the configuration of the present invention can be used. It can be preferably applied.

(Inkjet recording device of the second form)
Next, the configurations of the inkjet recording device 2000 and the liquid ejection head 2003 of the second form, which are different from the inkjet recording device of the first form described above, will be described. In the following description, only the parts different from the recording device of the first form will be mainly described, and the description of the parts similar to the device of the first form will be omitted.

<Explanation of inkjet recording device>
FIG. 21 is a diagram showing an inkjet recording device 2000 of the second form. The recording device 2000 of the present embodiment performs full-color recording on a recording medium by arranging four single-color liquid ejection heads 2003 corresponding to each ink of cyan C, magenta M, yellow Y, and black K in parallel. Is different from the first embodiment. In the first embodiment, the number of discharge port rows that can be used per color is one row, whereas in the present embodiment, the number of discharge port rows that can be used per color is 20 rows. Therefore, by appropriately allocating the recorded data to a plurality of discharge port rows and recording the data, very high-speed recording becomes possible. Further, even if there is a discharge port that does not discharge, reliability is improved by interpolating discharge from a discharge port in another row located at a position corresponding to the discharge direction of the recording medium with respect to the discharge port. However, it is suitable for commercial records. Similar to the first embodiment, for each liquid discharge head 2003, the supply system of the recording device 2000, the buffer tank 1003 (see FIGS. 2 and 3) and the main tank 1006 (see FIGS. 2 and 3) are fluids. Is connected. Further, each liquid discharge head 2003 is electrically connected to an electric control unit that transmits electric power and a discharge control signal to the liquid discharge head 2003.

<Explanation of circulation route>
As in the first embodiment, as the liquid circulation path between the recording device 2000 and the liquid discharge head 2003, the first and second circulation modes shown in FIG. 2 or 3 are used as in the first embodiment. Can be done.

<Explanation of liquid discharge head structure>
14 (a) and 14 (b) are perspective views showing the liquid discharge head 2003 according to the present embodiment. The liquid discharge head 2003 is a line-type recording head including 16 recording element substrates 2010 arranged linearly in the longitudinal direction of the liquid discharge head 2003 and ejecting one color of ink. Similar to the first embodiment, the liquid discharge head 2003 includes a liquid connection portion 111, a signal input terminal 91, and a power supply terminal 92. However, since the liquid discharge head 2003 of the present embodiment has more discharge port rows than the head of the first form, signal output terminals 91 and power supply terminals 92 are arranged on both sides of the liquid discharge head 2003. As a result, it is possible to reduce the voltage drop and signal transmission delay that occur in the wiring portion provided on the recording element substrate 2010.

FIG. 15 is a perspective exploded view showing the liquid discharge head 2003, and each component or unit constituting the liquid discharge head 2003 is divided and shown for each function. The roles of each unit and member and the order of liquid flow in the liquid discharge head are basically the same as those in the first embodiment, but the functions for ensuring the rigidity of the liquid discharge head are different. In the first embodiment, the rigidity of the liquid discharge head is mainly ensured by the liquid discharge unit support portion 81, but in the liquid discharge head 2003 of the second embodiment, the second flow path member 2060 included in the liquid discharge unit 2300 is used. The rigidity of the liquid discharge head is ensured. The liquid discharge unit support portion 81 in the present embodiment is connected to both ends of the second flow path member 2060, and the liquid discharge unit 2300 is mechanically coupled to the carriage of the recording device 2000 to form a liquid discharge head 2003. Positioning. The liquid supply unit 2220 including the negative pressure control unit 2230 and the electrical wiring board 90 are coupled to the liquid discharge unit support portion 81. A filter (not shown) is built in each of the two liquid supply units 2220.

The two negative pressure control units 2230 are set to control the pressure with different, relatively high and low negative pressures. Further, as shown in FIG. 14, when the negative pressure control units 2230 on the high pressure side and the low pressure side are installed at both ends of the liquid discharge head 2003, a common supply flow path extending in the longitudinal direction of the liquid discharge head 2003, respectively. And the liquid flows in the common recovery flow path face each other. In such a configuration, heat exchange is promoted between the common supply flow path and the common recovery flow path, and the temperature difference between the two common flow paths is reduced. This has the advantage that the temperature difference between the plurality of recording element substrates 2010 provided along the common flow path is reduced, and recording unevenness due to the temperature difference is less likely to occur.

Next, the details of the flow path member 2210 of the liquid discharge unit 2300 will be described. As shown in FIG. 15, the flow path member 2210 is a stack of the first flow path member 2050 and the second flow path member 2060, and the liquid supplied from the liquid supply unit 2220 is transferred to each discharge module 2200. Distribute. Further, the flow path member 2210 functions as a flow path member for returning the liquid recirculated from the discharge module 2200 to the liquid supply unit 2220. The second flow path member 2060 of the flow path member 2210 is a flow path member in which a common supply flow path and a common recovery flow path are formed therein, and has a function of mainly carrying the rigidity of the liquid discharge head 2003. Therefore, as the material of the second flow path member 2060, a material having sufficient corrosion resistance against liquid and high mechanical strength is preferable. Specifically, SUS, Ti, alumina and the like can be used.

FIG. 16A is a view showing a surface of the first flow path member 2050 on which the discharge module 2200 is mounted, and FIG. 16B shows the back surface thereof, and FIG. 16B shows the back surface of the first flow path member 2060. It is a figure which showed the surface which comes into contact with. Unlike the first embodiment, the first flow path member 2050 in the present embodiment is formed by arranging a plurality of members corresponding to each discharge module 2200 adjacent to each other. By adopting the structure divided in this way, a plurality of modules can be arranged to correspond to the length of the liquid discharge head 2003, so that a relatively long scale corresponding to, for example, B2 size or longer can be used. It can be particularly preferably applied to the liquid discharge head of the above. As shown in FIG. 16A, the communication port 51 of the first flow path member 2050 fluidly communicates with the discharge module 2200, and as shown in FIG. 16B, the first flow path member 2050 is individually connected. The communication port 53 fluidly communicates with the communication port 61 of the second flow path member 2060. FIG. 16 (c) shows the surface of the second flow path member 60 that comes into contact with the first flow path member 2050, and FIG. 16 (d) shows a cross section of the second flow path member 60 at the center in the thickness direction. 16 (e) is a view showing a surface of the second flow path member 2060 that comes into contact with the liquid supply unit 2220. The functions of the flow path and the communication port of the second flow path member 2060 are the same as those for one color of the first form. One of the common flow path grooves 71 of the second flow path member 2060 is the common supply flow path 2211 shown in FIG. 17, which will be described later, and the other is the common recovery flow path 2212, respectively, in the longitudinal direction of the liquid discharge head 2003. The liquid is supplied from one end side to the other end side. In this embodiment, unlike the first embodiment, the liquid flows in the common supply flow path 2211 and the common recovery flow path 2212 are in opposite directions.

FIG. 17 is a perspective view showing the connection relationship of the liquid between the recording element substrate 2010 and the flow path member 2210. A set of a common supply flow path 2211 and a common recovery flow path 2212 extending in the longitudinal direction of the liquid discharge head 2003 are provided in the flow path member 2210. The communication port 61 of the second flow path member 2060 is connected in position with the individual communication port 53 of each first flow path member 50, and is a common supply flow path from the communication port 72 of the second flow path member 2060. A liquid supply path is formed that communicates with the communication port 51 of the first flow path member 2050 via 2211. Similarly, a liquid supply path that communicates from the communication port 72 of the second flow path member 2060 to the communication port 51 of the first flow path member 2050 via the common recovery flow path 2212 is also formed.

FIG. 18 is a diagram showing a cross section taken along line XVIII-XVIII of FIG. The common supply flow path 2211 is connected to the discharge module 2200 via a communication port 61, an individual communication port 53, and a communication port 51. Although not shown in FIG. 18, in another cross section, it is clear with reference to FIG. 17 that the common recovery channel 2212 is connected to the discharge module 2200 by a similar path. Similar to the first embodiment, each discharge module 2200 and the recording element substrate 2010 are formed with a flow path communicating with each discharge port, and a part or all of the supplied liquid pauses the discharge operation. It is possible to recirculate through the discharge port. Further, as in the first embodiment, the common supply flow path 2211 has a negative pressure control unit 2230 (high pressure side), and the common recovery flow path 2212 has a negative pressure control unit 2230 (low pressure side), respectively. Connected via. Therefore, due to the differential pressure, a flow is generated from the common supply flow path 2211 through the discharge port of the recording element substrate 2010 to the common recovery flow path 2212.

<Explanation of discharge module>
FIG. 19A is a perspective view showing one discharge module 2200, and FIG. 19B is an exploded view thereof. The difference from the first form is that a plurality of terminals 16 are arranged on both side portions (each long side portion of the recording element substrate 2010) along the plurality of discharge port row directions of the recording element substrate 2010. Along with this, two flexible wiring boards 40 that are electrically connected to the recording element substrate 2010 are also arranged with respect to one recording element substrate 2010. This is because the number of discharge port rows provided on the recording element substrate 2010 is 20 rows, which is significantly larger than the 8 rows of the first embodiment, and the maximum distance from the terminal 16 to the recording element is shortened. This is to reduce the voltage drop and signal delay that occur in the wiring portion in the recording element substrate 2010. Further, the liquid communication port 31 of the support member 2030 is provided on the recording element substrate 2010 and opens so as to straddle all the discharge port rows. Other points are the same as those in the first embodiment.

<Explanation of the structure of the recording element substrate>
20 (a) is a schematic view of a surface on which the discharge port 13 of the recording element substrate 2010 is arranged, and FIG. 20 (c) is a schematic view showing the back surface of the surface of FIG. 20 (a). FIG. 20 (b) is a schematic view showing the surface of the recording element substrate 2010 when the cover plate 2020 provided on the back surface side of the recording element substrate 2010 is removed in FIG. 20 (c). As shown in FIG. 20B, liquid supply paths 18 and liquid recovery paths 19 are alternately provided on the back surface of the recording element substrate 2010 along the discharge port row direction. Although the number of discharge port rows is significantly increased as compared with the first embodiment, the essential difference from the first embodiment is that the terminals 16 are oriented in the discharge port row direction of the recording element substrate as described above. It is arranged on both sides along the line. A set of a liquid supply path 18 and a liquid recovery path 19 are provided for each discharge port row, and the cover plate 2020 is provided with an opening 21 that communicates with the liquid communication port 31 of the support member 2030. , The basic configuration is the same as that of the first embodiment.

The description of the above embodiment does not limit the scope of the present invention. As an example, in the present embodiment, the thermal method of generating bubbles by a heat generating element to discharge the liquid has been described, but the present invention is also applied to a liquid discharge head in which the piezo method and various other liquid discharge methods are adopted. be able to.

Although the present embodiment has described an inkjet recording device (recording device) in which a liquid such as ink is circulated between the tank and the liquid ejection head, other embodiments may be used. As another form, for example, two tanks are provided on the upstream side and the downstream side of the liquid discharge head without circulating the ink, and the ink in the pressure chamber is made to flow by flowing the ink from one tank to the other tank. It may be in the form.

Further, in the present embodiment, an example of using a so-called line type head having a length corresponding to the width of the recording medium has been described, but a so-called serial type liquid discharge in which recording is performed while scanning the recording medium. The present invention can also be applied to the head. Examples of the serial type liquid ejection head include, but are not limited to, a configuration in which one recording element substrate for ejecting black ink and one recording element substrate for ejecting color ink are mounted. That is, a form in which a plurality of recording element substrates are arranged so that the discharge ports overlap in the discharge port row direction, a short liquid discharge head shorter than the width of the recording medium is created, and the liquid discharge head is scanned by the recording medium. It may be.

Next, an embodiment of the present invention relating to the configuration of the negative pressure control unit and the flow resistance adjusting mechanism in the liquid discharge heads of the first and second embodiments described above will be described below.

<Decompression type negative pressure control unit>
22 (a) to 22 (c) are views showing a detailed structure of a negative pressure control unit 230 suitable for use in the first circulation mode described above in FIG. 2 according to an embodiment of the present invention. The negative pressure control unit 230 is the same as what is generally called a "decompression regulator", and is also referred to as a decompression type negative pressure control unit in the present specification. 22 (a) shows the appearance of the negative pressure control unit, and FIGS. 22 (b) and 22 (c) show the cross sections of the XXIIb-XXIIb and XXIIc-XXIIc lines in FIG. 22 (a), respectively.

In the present embodiment, the negative pressure control unit 230 is configured by integrating a pair of negative pressure control mechanisms set on the high pressure side (H) and the low pressure side (L). In this case, as shown in FIG. 22 (c), the two negative pressure control mechanisms are arranged so as to be in a mating relationship with each other, whereby the negative pressure control unit 230 can be miniaturized. The two negative pressure control mechanisms set on the high pressure side and the low pressure side have the same basic structure and operating principle except that the urging force of the urging member 231 or the size of the pressure receiving plate is different from each other. Therefore, only the negative pressure adjusting mechanism on the high pressure side (H) will be described below with reference to FIG. 22 (b).

The flow of liquid will be described. The liquid that has entered the inflow port 230A (FIG. 22A) of the negative pressure control unit 230 from the outside enters the first pressure chamber 235 and passes through the gap between the valve 237 and the opening 238 to obtain the second pressure. It flows into the room 236. After that, the liquid in the second pressure chamber 236 is supplied from the outlet 230B (FIG. 22A) to the liquid discharge unit 300 (see FIG. 2).

As shown in FIG. 22B, a pressure receiving plate 232, a first pressure chamber 235, and a second pressure chamber 236 sealed with the pressure receiving plate and the flexible film 233 are provided in the negative pressure control unit 230. ing. Further, an opening 238 is provided as a communication portion for communicating the first pressure chamber 235 and the second pressure chamber. A valve 237 mechanically connected to the pressure receiving plate 232 by a shaft 234 is provided in the first pressure chamber. The shaft 234, the valve 237, and the pressure receiving plate 232 are configured to move integrally when the head is driven. Further, the pressure receiving plate 232 is urged by the urging member (spring) 231 in a direction in which the valve 237 is closed. In the present specification, the pressure receiving portion refers to a portion where the pressure receiving plate 232 and the flexible film 233 are combined.

However, not all of the flexible film 233 is displaced based on the pressure in the second pressure chamber, and the film portion near the pressure receiving plate 232 mainly functions as a pressure receiving portion and does not change based on the pressure change. It also has a portion of flexible film 233. The effective pressure receiving range of the film varies depending on the dimensions of each part and the pressure itself.

The valve 237 has a variable gap between it and the opening 238, which allows the flow resistance to be variable. Further, the valve 237 can be closed in contact with the opening 238 when the first circulation pump is stopped, and can be fluidly sealed. By fluidly sealing the valve 237 and the opening 238, it is possible to continue applying negative pressure to the discharge port when the circulation pump is stopped (that is, when the recording device is stopped), and ink leaks from the discharge port. Can be prevented. As the material of the valve 237, an elastic material such as rubber or an elastomer having sufficient corrosion resistance against a liquid is preferably used.

In the present embodiment, the pressure receiving portion is composed of the pressure receiving plate 232 and the flexible film 233, but other configurations may be used as long as the position of the valve 237 can be changed according to the pressure in the second pressure chamber. it can. For example, there may be a configuration in which the flexible film 233 is joined to the shaft 234 without the pressure receiving plate 232, or an elastic film-like member (diaphragm) may be used instead of the pressure receiving plate and the film as the pressure receiving portion. In this case, the diaphragm has not only a function as a pressure receiving portion but also a function as an urging means for urging the valve.

Further, in FIG. 22B, the spring as the urging member is two coupled springs, but if the synthetic spring force satisfies a desired negative pressure value, there is no problem in the pressure adjusting function. Therefore, one spring may be used, or a configuration using three or more springs may be used. Further, in the present embodiment, a coil spring is used as a mechanism for applying an urging force to the valve 237, but another mechanism, for example, a leaf spring may be used. Further, as described above, the valve 237 may be provided with an urging force by using a diaphragm which is a film-like elastic body instead of the pressure receiving plate and the flexible film.

As shown in FIG. 22 (b), of the two coupled springs, one urging member is separately provided in the second pressure chamber 236, and the pressure receiving plate 232 and the shaft 234 are configured to be separable. Has been done. Even when the pressure receiving plate 232 and the shaft 234 are separated from each other, the urging force of the urging member in the second pressure chamber acts on the pressure receiving plate 232. Therefore, even when the valve 237 is closed, the pressure receiving plate 232 can be separated from the shaft 234 by the action of the urging member in the second pressure chamber 236 and can be displaced in the direction of further increasing the volume in the second pressure chamber. Is. As a result, even if the liquid discharge head is not driven for a long period of time and air bubbles are taken into the liquid discharge head, the second pressure chamber 236 functions as a buffer and absorbs the volume increase of the air bubbles to keep the inside of the head. It is possible to suppress the positive pressure.

Further, in FIG. 22 (b), the valve 237 is provided on the upstream side of the opening 238, and when the pressure receiving plate is displaced upward in FIG. 22 (b), this displacement is transmitted to the valve to open the opening. The gap between 238 and valve 237 is reduced. The liquid entering from the inflow port 230A (FIG. 22A) of the first pressure chamber 235 flows into the second pressure chamber 236 through the gap between the valve 237 and the opening 238, and receives the pressure. Tell to board 232. After that, the liquid is supplied from the outlet 230B (FIG. 22 (a)) of the second pressure chamber 236 to the liquid discharge unit 300 (see FIG. 2).

The pressure P2 in the second pressure chamber 236 is determined from the following relational expression showing the balance of the forces applied to each part.
P2 = P0- (P1Sv + k1x) / Sd equation (1)

Here, Sd: the pressure receiving area of the pressure receiving plate, Sv: the pressure receiving area of the valve portion, P0: atmospheric pressure, P1: the pressure in the first pressure chamber 235, P2: the pressure in the second pressure chamber 236, k1: urging. The spring constant of the member 231 and x: the force of the spring displacement urging member 231 can be changed to set P2 to a desired control pressure. To change the force of the urging member, change the spring constant kl or change the spring length during operation.

Further, assuming that the flow resistance of the gap portion between the valve and the opening is R and the flow rate of the liquid passing through the negative pressure control unit 230 is Q, the following equation is established.
P2 = P1-QR equation (2)
Here, the flow resistance R and the gap between the valve and the opening (hereinafter referred to as “valve opening”) are designed to have the relationship shown in FIG. 23, for example. FIG. 23 is a diagram showing the relationship between the flow resistance between the valve and the opening and the valve opening degree in the negative pressure control unit according to the present embodiment. As shown in FIG. 23, the flow resistance R decreases as the valve opening degree increases. P2 is determined by determining the valve opening degree so as to satisfy the above-mentioned equations (1) and (2) at the same time.

That is, when the flow rate Q flowing into the negative pressure control unit 230 increases, the pressure of the second circulation pump (liquid feeding pump) 1004 (see FIG. 2) connected to the upstream of the negative pressure control unit is constant. P1 decreases by the amount of increase in flow resistance between the second circulation pump and the negative pressure control unit 220 due to the increase in the flow rate. Therefore, the force P1Sv that closes the valve decreases, and P2 increases instantaneously from the equation (1).

Further, R = (P1-P2) / Q is derived from the equation (2). Here, Q and P2 increase and P1 decreases, so R decreases. When R decreases, the valve opening degree increases due to the relationship shown in FIG. As can be seen from FIG. 22B, as the valve opening degree increases, the length of the urging member (spring) 231 decreases, so x, which is the displacement from the free length, increases. Therefore, the acting force k1x of the spring becomes large. As a result, P2 decreases instantaneously from the equation (1). On the contrary, when the flow rate Q decreases and P2 increases instantaneously, P2 decreases instantaneously due to the opposite action to the above. By repeating this instantaneously, P2 is controlled to be constant as a result of achieving both equations (1) and (2) while changing the valve opening degree according to the flow rate Q. As a result, the pressure downstream of the negative pressure control unit 230 (that is, the inlet of the liquid discharge unit) is autonomously and constantly controlled.

Further, as can be seen from the equation (1), the fluctuation width of P2 = the fluctuation width of P1 x (Sv / Sd). Therefore, by designing with a sufficiently small Sv / Sd ratio, the second circulation pump 1004 Even if P1 changes slightly due to the pulsation of FIG. 2 or the like, the fluctuation range of P2 can be sufficiently reduced. Therefore, the pressure sensor and the power for adjusting the negative pressure are not required, and the liquid discharge device main body can be simplified.

<Back pressure type negative pressure control unit>
24 (a) to 24 (c) are views showing a detailed structure of a negative pressure control unit 230 suitable for use in the second circulation mode described above in FIG. 3 according to an embodiment of the present invention. The negative pressure control unit 230 is the same as what is generally called a "back pressure regulator", and is also referred to as a back pressure type negative pressure control unit in the present specification. 24 (a) and 24 (b) show the appearances of the high pressure side (H) and the low pressure side (L) of the negative pressure control unit of this embodiment, respectively, and FIG. 24 (c) shows C in FIG. 24 (a). The cross section of the -C'line is shown.

In this embodiment, unlike the decompression type pressure adjusting mechanism shown in FIGS. 22 (a) to 22 (c), the two negative pressure control units on the high pressure side (H) and the low pressure side (L) are configured as separate bodies. As shown in FIG. 14, one negative pressure control unit 2230 is arranged at each end of the liquid discharge unit 300. It should be noted that this separate form is an example, and the high-pressure side and the low-pressure side may be integrally formed as in the decompression type negative pressure control unit shown in FIGS. 22 (a) to 22 (c). Of course. FIG. 3 according to this embodiment shows this integrated negative pressure control unit. The two negative pressure control mechanisms set on the high pressure side and the low pressure side differ in the urging force acting on the valve or the pressure receiving area of the pressure receiving plate, and have the same basic structure and operating principle.

The pressure receiving unit, the pressure receiving unit and the urging mechanism other than those described below are the same as those of the decompression type negative pressure control unit described above in FIGS. 22 (a) to 22 (c).

As shown in FIG. 24 (c), the difference from the negative pressure control unit of the pressure reducing valve type is that the valve 237 is arranged in the first pressure chamber 235, and the pressure receiving plate 232 is shown in FIG. 24 (c). ), The gap between the opening 238 and the valve 237 expands when moving downward, and the liquid flow in the negative pressure control unit 230 is reversed, so the side where the pressure receiving plate is placed is upstream. It is the point that is the first pressure chamber of. The flow of liquid will be described. The liquid that has entered the inflow port 230A of the negative pressure control unit 230 from the liquid discharge unit 300 enters the first pressure chamber 235, passes through the gap between the valve 237 and the opening 238, and enters the second pressure chamber 236. Inflow. After that, the liquid in the second pressure chamber 236 is supplied to the outside of the liquid discharge unit 300 from the outflow port 230B.

The pressure adjusting mechanism can be described as being substantially the same as the case of the decompression type pressure adjusting mechanism described above. That is, the pressure P1 in the first pressure chamber 235 is determined from the following equation (3) showing the balance of the forces acting on each part. Unlike the decompression type negative pressure control unit, in the back pressure type negative pressure control unit of this embodiment, the second urging member 239 is arranged on the opposite side of the pressure receiving plate 232 from the first pressure chamber 235. Therefore, when the spring constants of the urging member 231 and the second urging member 239 are k1 and k2, respectively, and the displacements at zero valve opening are x0 and y0, respectively, when the opening a increases, the first urging member The displacement from the free length decreases by a, and the displacement of the second urging member increases by a. As a result, the following equation is derived from the equilibrium relationship of the forces acting on each part.
P1Sd + k1 (x0-a) + P2Sv = P0Sd + k2 (y0 + a)
The following equation is obtained by modifying the above equation.
P1 = P0- (P2Sv / Sd) + (k1 + k2) a / Sd-PL equation (3)

Here, Sd: the pressure receiving area of the pressure receiving plate, Sv: the pressure receiving area of the valve portion, P0: atmospheric pressure, P1: the pressure in the first pressure chamber, P2: the pressure in the second pressure chamber, k1: the spring of the urging member 231. Constant, k2: Spring constant of the second urging member 239, a: Valve opening, x0: Displacement of the first urging member from the free length at zero valve opening, y0: Second urging at zero valve opening The displacement of the member from the free length, PL (Preload) = (k1x0-k2y0) / Sd.

Further, the above-mentioned equation (2) for the decompression type negative pressure control unit is similarly established for the back pressure type negative pressure control unit of the present embodiment. Here, the relationship between the valve opening degree and the gap portion flow resistance R between the valve and the opening portion is designed as shown in FIG. 23. That is, the flow resistance R decreases as the valve opening degree increases. In this embodiment, P1 is determined by determining the valve opening degree so that the equations (3) and (2) are satisfied at the same time.

When the flow rate Q flowing out of the negative pressure control unit 230 increases, the pressure of the second circulation pump 1004 (see FIG. 3) connected to the downstream of the negative pressure control unit is constant, so that the negative pressure due to the increase in the flow rate increases. P2 rises by the amount of increase in flow resistance between the pressure control unit 220 and the second circulation pump. Therefore, the force P2Sv for opening the valve increases, and P1 decreases instantaneously according to the equation (3). Further, R = (P1-P2) / Q is derived from the equation (2).

Here, since Q and P2 are increasing and P1 is decreasing, R is decreasing. Then, when R decreases, the valve opening degree increases due to the relationship shown in FIG. As shown in FIG. 24 (c), as the opening degree of the valve 237 increases, the lengths of the urging member 231 and the second urging member 239 increase and decrease, respectively, so that the displacement from the free length decreases and increases. It becomes. As a result, the valve acting force of the first urging member and the valve acting force of the second urging member decrease and increase, respectively. From this, the acting force in the direction of opening the valve decreases as the valve opening degree increases. Therefore, from the equation (3), P1 increases instantaneously. On the contrary, when the flow rate Q decreases and P1 increases instantaneously, P1 decreases instantaneously due to the opposite action to the above.

By repeating these momentarily, P1 is controlled to be constant as a result of achieving both equations (3) and (2) while changing the valve opening degree according to the flow rate Q, so that the negative pressure control unit 230 The pressure upstream (that is, the outlet of the liquid discharge unit) is controlled to be autonomous and constant. Further, as can be easily understood from the equation (3), since the fluctuation width of P1 = the fluctuation width of P2 x (Sv / Sd), the second circulation pump can be designed by keeping the Sv / Sd ratio sufficiently small. Even if P2 changes slightly due to the pulsation of P1, the fluctuation range of P1 can be sufficiently reduced. Therefore, a pressure sensor and power for adjusting negative pressure are not required, and the recording device main body can be simplified.

<Other forms of negative pressure control unit>
FIG. 25 is a diagram showing another form of the negative pressure control unit suitable for use in the first circulation form shown in FIG. As shown in FIG. 25, the negative pressure control unit 230 contains two negative pressure control mechanisms whose inside is divided into a liquid chamber 234 and an air chamber 235 by a flexible film 233. A pressure sensor S and air pumps PH and PL are connected to each air chamber 235. Although not shown in FIG. 25, the respective pressure sensors S, air pumps PH, and PL are electrically connected to the control unit of the apparatus main body. The control unit drives and controls the air pumps PH and PL as the high pressure side and the low pressure side, respectively, based on the pressure value from the pressure sensor S and the pressure set value stored in the control unit in advance. By this control, the pressure of each liquid chamber 234 can be maintained at a desired pressure, and a desired differential pressure can be generated between the common supply flow path 211 and the common recovery flow path 212.

Further, as in the case of the negative pressure control unit shown in FIG. 2, in the negative pressure control unit shown in FIG. 25, the deviation of the flow resistance is adjusted by operating the supply side flow resistance adjusting mechanism 222 and the recovery side flow resistance adjusting mechanism 223. It can be corrected. That is, even if the flow resistance of the common supply flow path 211 or the common recovery flow path 212 deviates from the set value, the deviation of the flow resistance between the negative pressure control unit and the common flow path is corrected and the common flow path is corrected. A desired pressure can be applied at a desired flow rate at the inlet of the. As a result, the tolerance between the design value of the differential pressure between the common supply flow path and the common recovery flow path can be reduced, and the variation in the flow rate of the circulating flow flowing through each liquid discharge head can be reduced.

(Variable pressure type (decompression type) pressure tolerance adjustment of negative pressure control unit)
One embodiment of the present invention corrects the tolerance of the control pressure by the decompression type negative pressure control unit described above in FIG. 22. As described above, since the negative pressure control unit has the same mechanism as the force-balanced pressure-reducing pressure regulating valve, generally, the control pressure / flow rate has a negative gradient (so-called drove, the control pressure decreases as the flow rate increases. There can be tolerances for its gradient. In the present embodiment, the gradient of the control pressure / flow rate is made positive, and the gradient is adjusted by adjusting the flow resistance in the flow resistance adjusting mechanism to suppress the pressure change due to the flow rate fluctuation at the inlet of the common flow path. ..

Further, in a general pressure reducing type pressure regulating valve, a tolerance occurs in the control pressure value itself at a certain flow rate due to the tolerance of the pressure receiving plate area and the spring force. In this embodiment, the control pressure tolerance and the control pressure / flow gradient tolerance are corrected at the same time.

The following description describes the negative pressure adjusting mechanism on the high pressure side shown in FIG. 22B, but the same applies to the negative pressure adjusting mechanism on the low pressure side, so the description thereof will be omitted. In FIG. 22B, the negative pressure adjusting member 240 has an outside air communication port and is fixed to the main body of the negative pressure control unit. As the fixing method, either a mechanical method or an adhesive method can be preferably used.

Here, the spring constant of the urging member 231 is k1, and the displacements at zero valve opening are x0 and y0, respectively. As the opening degree a increases, the displacement of the urging member 231 from the free length increases by a, so the following equation is derived from the balance of the forces applied to each part.
P2Sd + k1 (x0 + a) + P1Sv = P0Sd
The following equation is obtained by modifying the above equation.
P2 = P0- (P1Sv / Sd) -k1a / Sd-PL equation (4)
Here, a: valve opening degree, x0: displacement of the urging member 231 from the free length at zero opening degree, PL (Preload) = (k1x0) / Sd.

<Adjustment of P2 tolerance>
As shown in FIG. 22 (c), the negative pressure adjusting member 240 is in contact with the urging member on the first pressure chamber side via the flexible film 233. Here, the displacement of the urging member can be changed and the control pressure P2 can be adjusted by changing the shape such as the thickness and height of the negative pressure adjusting member. Specifically, if the shape of the negative pressure adjusting member 240 is changed so that the length of the urging member on the first pressure chamber side is shortened, x0 in the above equation becomes large, so the PL of the equation (4) Decreases and P2 rises. On the other hand, if the length of the urging member on the first pressure chamber side is increased, x0 becomes smaller, so that the PL of the equation (4) increases and P2 decreases. In this way, the tolerance of the control pressure P2 can be corrected so that the desired control pressure P2 can be obtained at a desired flow rate.

The following equation is obtained by differentiating both sides of equation (4) with respect to the flow rate Q.
dP2 / dQ =-(Sv / Sd) dP1 / dQ- (k1 + k2) / Sdda / dQ equation (5)

Here, as the flow rate Q increases, the pressure loss between the second circulation pump and the negative pressure control unit in FIG. 2 also increases, so that P1 decreases. Therefore, dP1 / dQ is negative. On the other hand, since the opening degree a increases as the flow rate Q increases, da / dQ is positive. Here, if the design is made so as to satisfy the following equation (6), as can be seen from the equation (5), the gradient of the control pressure P2 / flow rate Q of the negative pressure control unit becomes positive. That is, as the flow rate Q increases, the control pressure P2 rises. At this time, the flow rate change rate R2 of the valve working pressure P1 satisfies the following equation.
R2> (k1 + k2) / Sv · (da / dQ) (R2: −dP1 / dQ) Equation (6)

<Adjustment of P2 / Q gradient>
The negative pressure control mechanism shown in FIG. 22 capable of the above correction is used in the negative pressure control unit 230 shown in FIG. In this case, the change in the positive gradient of P2 / Q is offset by increasing the flow resistance by adjusting the supply side flow resistance adjustment mechanism 222 and the recovery side flow resistance adjustment mechanism 223 downstream of the negative pressure control unit 230. Can be done. As a result, even if there is a tolerance in the P2 / Q gradient, this tolerance can be corrected by adjusting the supply side flow resistance adjusting mechanism 222 or the recovery side flow resistance adjusting mechanism 223.

As a specific adjustment method, for example, the following can be performed.
1) Measure the pressure at the inlet of the common supply flow path and / or the common recovery flow path at the minimum flow rate that passes through the negative pressure control unit, which is assumed in the specifications of the liquid discharge device.
2) Similarly, the pressure at the inlet of the common supply flow path and / or the common recovery flow path is measured at the maximum flow passing through the negative pressure control unit, which is assumed in the above specifications.
3) While maintaining the flow rate in the step 2) above, the supply side flow resistance adjusting mechanism 222 and the recovery side flow resistance adjusting mechanism 223 downstream of the negative pressure control unit 230 approach the pressure measured in the step 1) above. , Adjusted by the negative pressure adjusting member 240.

Either of the steps of adjusting the absolute value of the control pressure P2 by adjusting the negative pressure adjusting member 240 and the steps of adjusting the P2 / Q gradient in the above steps 1) to 3) may come first. However, the resolution of the pressure sensor used at the time of adjustment is generally higher as the measurement range full scale is smaller and lower as the scale is larger. Considering this point, first, in the vicinity of atmospheric pressure, the adjustment steps of steps 1) to 3) above are performed using a pressure sensor with a small measurement pressure range but high accuracy to achieve a high resolution of P2 / Q gradient. Correct the tolerance. After that, it is more accurate to adjust the control pressure P2 in the vicinity of the desired pressure value by the negative pressure adjusting member 240 and at the same time adjust the tolerance of P2 by using a pressure sensor having a large measurement pressure range but low resolution. High adjustment is possible.

As can be easily understood from the equation (6), the P2 / Q gradient can also be adjusted by adjusting R2. Specifically, as shown in FIG. 26, R2 can be adjusted by arranging the flow resistance adjusting mechanisms 222 and 223 between the negative pressure control unit and the second circulation pump 1004. In the example shown in FIG. 26, the flow resistance adjusting mechanism is built in the liquid supply unit 220 constituting the liquid discharge head, but the same effect can be obtained even if it is arranged outside the liquid discharge head. Of course. Further, instead of the second circulation pump, a pressure source whose pressure can be controlled (for example, a head tank or a bag having a flexible wall and an air pump) can be used.

(Variable pressure type (back pressure type) pressure tolerance adjustment of negative pressure control unit)
One embodiment of the present invention corrects the tolerance of the control pressure by the back pressure type negative pressure control unit described above in FIG. 24. As described above, since the negative pressure control unit has the same mechanism as the force-balanced back pressure type pressure regulating valve, the control pressure generally has a positive gradient to the control pressure / flow rate (so-called drove, the control pressure increases as the flow rate increases. There can be tolerances for its gradient. In this embodiment, the gradient of the control pressure / flow rate is made negative, and the gradient is adjusted by adjusting the flow resistance in the flow resistance adjusting mechanism to suppress the pressure change due to the flow rate fluctuation at the inlet of the common flow path. ..

Further, in a general back pressure type pressure regulating valve, a tolerance occurs in the control pressure value itself at a certain flow rate due to the tolerance of the pressure receiving plate area and the spring force. In this embodiment, the control pressure tolerance and the control pressure / flow gradient tolerance are corrected at the same time.

The adjustment of the pressure tolerance of this embodiment will be described with reference to FIG. 24 (c). The negative pressure adjusting mechanism of this form is basically the same as that shown in FIGS. 22 (a) to 22 (c), but as shown in FIG. 24 (c), the first pressure of the pressure receiving plate 232. The difference is that the second urging member whose one end is fixedly supported by the negative pressure adjusting member 240 is in contact with the surface opposite to the chamber 235. The negative pressure adjusting member 240 has an outside air communication port, and is configured to be movable within the movable mechanism 241 of the negative pressure control unit. In the present embodiment, a male screw is formed on the side surface of the negative pressure adjusting member 240 and a female screw is formed on the movable mechanism 241, and the position of the negative pressure adjusting member 240 can be changed by engaging with each other.

<Adjustment of P1 tolerance>
In FIG. 24C, the negative pressure adjusting member 240 is moved in the vertical direction to change y0 of the second urging member 239. Thereby, the control pressure P1 can be adjusted. When the negative pressure adjusting member 240 is moved so as to be close to the valve 237, y0 becomes large, so that the PL of the equation (3) decreases and P1 increases. On the contrary, when the negative pressure adjusting member 240 is moved away from the valve 237, y0 becomes smaller, so that PL increases and P1 decreases. In this way, it is possible to correct the tolerance of the control pressure P1 and obtain a desired control pressure P1 at a desired flow rate.

Since the position of the negative pressure adjusting member 240 of this embodiment is adjusted by a screw-shaped member, if the recording device is used for a long period of time after adjusting the P1 tolerance, the negative pressure adjusting member 240 and the negative pressure adjusting member 240 may be affected by vibration or the like. There is a risk that the relative position with the valve 237 will change. Therefore, it is more preferable that there is a mechanism for fixing the negative pressure adjusting member 240 to the negative pressure control unit after the adjustment. Specifically, a caulking structure that prevents the negative pressure adjusting member 240 from rotating, or a method of fixing with an adhesive or the like is preferably used.

Also in this embodiment, the following equation differentiated by the flow rate Q can be obtained, which is the same as the equation (5) described above. dP1 / dQ =-(Sv / Sd) dP2 / dQ + (k1 + k2) / Sdda / dQ (7)
As the flow rate Q increases, as can be seen from FIG. 3, the pressure loss between the negative pressure adjusting mechanism and the second circulation pump increases, so that P2 rises. Therefore, dP2 / dQ is positive. On the other hand, since the opening degree a increases as the flow rate Q increases, da / dQ is positive. Here, if the design is made so as to satisfy the following equation (8), as can be seen from the equation (7), the gradient of the control pressure P2 / flow rate Q of the negative pressure adjusting mechanism becomes negative. That is, as the flow rate Q increases, the control pressure P1 decreases. At this time, the flow rate change rate R3 of the valve working pressure P2 satisfies the following equation.
R3> (k1 + k2) / Sv · (da / dQ) (R3: dP2 / dQ) Equation (8)

<Adjustment of P1 / Q gradient>
When the negative pressure adjusting mechanism having such characteristics is applied to the back pressure type negative pressure control unit of FIG. 3, the flow is caused by the supply side flow resistance adjusting mechanism 222 and the recovery side flow resistance adjusting mechanism 223 downstream of the negative pressure control unit 230. The resistance can be adjusted, thereby changing the negative gradient of P1 / Q. As a result, even if there is a tolerance in the P1 / Q gradient, this tolerance can be corrected by adjusting the supply side flow resistance adjusting mechanism 222 and the recovery side flow resistance adjusting mechanism 223.

As a specific adjustment method, for example, the following can be performed.
1) Measure the pressure at the inlet of the common supply flow path and / or the common recovery flow path at the minimum flow rate that passes through the negative pressure control unit, which is assumed in the specifications of the liquid discharge device.
2) Similarly, the pressure at the inlet of the common supply flow path and / or the common recovery flow path is measured at the maximum flow passing through the negative pressure control unit, which is assumed in the specifications of the above device.
3) While maintaining the flow rate in the above step 2), the pressure is adjusted so as to approach the pressure obtained in the step 1) by the adjustment in the supply side flow resistance adjusting mechanism 222 and the recovery side flow resistance adjusting mechanism 223.

The order of the step of adjusting the absolute value of the control pressure P1 by the negative pressure adjusting member 240 and the step of adjusting the P1 / Q gradient of the above 1) to 3) is the same as that of the embodiment of the decompression type negative pressure control unit. is there.

As can be easily understood from the equation (8), the P1 / Q gradient can also be adjusted by adjusting R3. Specifically, as shown in FIG. 27, a flow resistance adjusting mechanism is arranged between the negative pressure control unit and the second circulation pump 1004. This makes it possible to adjust R3. In the configuration shown in FIG. 27, the flow resistance adjusting mechanism is built in the liquid supply unit 220 constituting the liquid discharge head, but the same effect can be obtained even if it is arranged outside the liquid discharge head. Further, instead of the second circulation pump, a pressure source whose pressure can be controlled (for example, a head tank or a bag having a flexible wall and an air pump) can be used.

(Flow resistance adjustment mechanism)
The flow resistance adjusting mechanism described in each of the above embodiments has a movable portion capable of changing the cross-sectional area of the flow path or the length of the flow path. Among such mechanisms, a mechanism that changes the cross-sectional area of the flow path, for example, a needle valve or a mechanism that has a flexible film in a part of the flow path and can change the cross-sectional area of the flow path can be preferably used. ..

Specifically, as shown in FIG. 24 (c), the flow resistance adjusting mechanism 222 has an adjusting bolt 224 attached so that the sealing material 226 can slide, and a flow having a female threaded portion 225 cut in advance. It is a form that is inserted into the road. In this configuration, by increasing the amount of the bolt tip inserted into the flow path, it is possible to create a portion (high flow resistance portion) having a small flow path cross-sectional area. On the contrary, if the bolt insertion amount is reduced, the flow resistance becomes low. In the configuration shown in FIG. 24 (c), the screw shape is shown, but a slidable O-ring or the like can also be used. Further, although not shown in FIG. 24 (c), it is preferable that there is a mechanism for fixing the adjustment bolt 224 after the adjustment in order to prevent a change in the adjustment amount of the flow resistance. Specifically, a caulking structure that prevents the adjustment bolt 224 from rotating, or a method of fixing with an adhesive or the like is preferably used.

In FIG. 24C, the flow resistance adjusting mechanism is arranged in the negative pressure control unit, but as shown in FIGS. 2, 3, 26, and 27, the flow of the liquid supply unit. The effect of the present invention can be obtained even if it is arranged in the path or in the flow path on the recording device main body side outside the liquid discharge head.

211 Common supply flow path 212 Common recovery flow path 220 Liquid supply unit 222 Supply side flow resistance adjustment mechanism 223 Recovery side flow resistance adjustment mechanism 224 Adjustment bolt 225 Female thread 226 Seal member 230 Negative pressure control unit 231 Biasing member 232 Pressure receiving plate 233 Flexible film 234 Shaft 235 First pressure chamber 236 Second pressure chamber 237 Valve 238 Opening 239 Second urging member 240 Negative pressure adjusting member 241 Movable mechanism 3 Liquid discharge head

Claims (19)

A liquid discharge device that uses a liquid discharge head provided with at least one recording element substrate and discharges a liquid from the liquid discharge head.
A means having a liquid supply flow path to the recording element substrate and a liquid recovery flow path from the recording element substrate, and between the liquid pressure in the supply flow path and the liquid pressure in the recovery flow path. A differential pressure generating means that supplies and recovers the liquid by making a difference in
With the flow resistance adjusting means provided in the supply flow path and / or the recovery flow path,
With
The differential pressure generating means has a pair of negative pressure control units having different set pressures, and the high pressure side is connected to the supply flow path and the low pressure side is connected to the recovery flow path, and the supply flow path and the recovery flow path are connected to each other. A liquid discharge device characterized in that a liquid feeding pump for feeding liquid from the supply flow path and the recovery flow path to a liquid storage tank is connected to the downstream side of the flow path. The liquid discharge device according to claim 1, wherein the differential pressure generating means circulates the liquid to the liquid discharge head through the supply flow path and the recovery flow path. The liquid discharge head includes a plurality of discharge ports, the supply flow path includes a common supply flow path common to the plurality of discharge ports, and the recovery flow path is common to the plurality of discharge ports. The liquid discharge device according to claim 1, further comprising a recovery flow path. At least one of the pair of negative pressure control units is applied with a pressure higher than the set pressure of the negative pressure control unit from the upstream side of the negative pressure control unit.
The first pressure chamber that communicates with the liquid storage tank,
A second pressure chamber having a variable volume and connected to the common supply flow path or the common recovery flow path,
An opening that communicates the first pressure chamber and the second pressure chamber,
A valve provided in the first pressure chamber, the flow resistance between the first pressure chamber and the second pressure chamber is variable, and the valve is urged to close the gap between the first pressure chamber and the opening.
A pressure receiving portion that is displaceable based on the pressure fluctuation of the second pressure chamber and that transmits the displacement to the valve to change the position of the valve in combination with the urging force acting on the valve. ,
The liquid discharge device according to claim 3, wherein the liquid discharge device comprises. At least one of the pair of negative pressure control units includes a spring that urges the pressure receiving portion.
The spring constant of the spring is k1, and the flow rate change rate of the pressure acting on the valve from the upstream of the valve is R2.
Then, the following formula R2 > k1 / Sv ・ da / dQ
Here, a is the valve opening degree, Q is the flow rate, and Sv is the pressure receiving area of the pressure acting on the valve.
The liquid discharge device according to claim 4, wherein the liquid discharge device meets the requirements. The liquid discharge device according to claim 5, further comprising a second flow resistance adjusting means in at least one of the flow paths between the liquid storage tank and each of the pair of negative pressure control units. A liquid discharge device that uses a liquid discharge head provided with at least one recording element substrate and discharges a liquid from the liquid discharge head.
A means having a liquid supply flow path to the recording element substrate and a liquid recovery flow path from the recording element substrate, and between the liquid pressure in the supply flow path and the liquid pressure in the recovery flow path. A differential pressure generating means that supplies and recovers the liquid by making a difference in
With the flow resistance adjusting means provided in the supply flow path and / or the recovery flow path,
With
The differential pressure generating means has a pair of negative pressure control units having different set pressures, and the high pressure side is connected to the supply flow path and the low pressure side is connected to the recovery flow path, and the supply flow path and the recovery flow path are connected to each other. A liquid discharge device characterized in that a liquid delivery pump for feeding liquid from a liquid storage tank to the supply flow path and the recovery flow path is connected to the upstream side of the flow path. The liquid discharge head includes a plurality of discharge ports, the supply flow path includes a common supply flow path common to the plurality of discharge ports, and the recovery flow path is common to the plurality of discharge ports. The liquid discharge device according to claim 7, further comprising a recovery flow path. At least one of the pair of negative pressure control units is applied with a pressure lower than the set pressure of the negative pressure control unit from the downstream side of the negative pressure control unit.
A first pressure chamber having a variable volume and connected to the common supply flow path or the common recovery flow path,
A second pressure chamber that communicates with the liquid storage tank,
An opening that communicates the first pressure chamber and the second pressure chamber,
A valve provided in the first pressure chamber, which has a variable flow resistance between the first pressure chamber and the second pressure chamber and is urged in a direction to open a gap between the first pressure chamber and the opening.
A pressure receiving portion that is displaceable based on the pressure fluctuation of the first pressure chamber and that transmits the displacement to the valve to change the position of the valve in combination with the urging force acting on the valve. ,
The liquid discharge device according to claim 8, wherein the liquid discharge device comprises. At least one of the pair of negative pressure control units includes a spring that urges the pressure receiving portion.
The spring constants of the springs are k1 and k2, and the flow rate change rate of the pressure acting on the valve from the downstream side of the valve is R3.
Then, the following formula R3> (k1 + k2) / Sv ・ da / dQ
Here, a is the valve opening degree, Q is the flow rate, and Sv is the pressure receiving area of the pressure acting on the valve.
The liquid discharge device according to claim 9, wherein the liquid discharge device satisfies. The liquid discharge device according to claim 10, further comprising a second flow resistance adjusting means in at least one of the flow paths between the liquid storage tank and each of the pair of negative pressure control units. The liquid discharge device according to any one of claims 1 to 11, wherein the flow resistance adjusting means includes a movable portion capable of changing the cross-sectional area of the flow path or the length of the flow path. The liquid discharge device according to claim 4 or 9, wherein at least one of the pair of negative pressure control units further includes a negative pressure adjusting member that changes the urging force acting on the valve. A liquid discharge device that uses a liquid discharge head to discharge liquid from the liquid discharge head.
A means having a liquid supply flow path to the liquid discharge head and a liquid recovery flow path from the liquid discharge head, between the liquid pressure in the supply flow path and the liquid pressure in the recovery flow path. A liquid supply method in a liquid discharge device including a differential pressure generating means for supplying and recovering a liquid by causing a difference between the two, and a flow resistance adjusting means provided in the supply flow path and / or the recovery flow path. And
The first step of measuring the pressure at the inlet of the supply channel and / or the recovery channel at the first flow rate, and
A second step of measuring the pressure at the inlet of the supply channel and / or the recovery channel at a second flow rate higher than the first flow rate.
The flow resistance adjusting means adjusts the flow resistance from the negative pressure control unit of the differential pressure generating means to the inlet of the supply flow path and / or the inlet of the recovery flow path, and adjusts the flow resistance to the first. A third step of bringing the pressure at the inlet of the supply channel and / or the recovery channel at the second flow rate closer to the pressure at the first flow rate.
The liquid supply method, which comprises supplying a liquid by the differential pressure generating means at a pressure adjusted in the third step. A liquid discharge device that uses a liquid discharge head to discharge liquid from the liquid discharge head.
A means having a liquid supply flow path to the liquid discharge head and a liquid recovery flow path from the liquid discharge head, between the liquid pressure in the supply flow path and the liquid pressure in the recovery flow path. A liquid supply method in a liquid discharge device including a differential pressure generating means for supplying and recovering a liquid by causing a difference between the two, and a flow resistance adjusting means provided in the supply flow path and / or the recovery flow path. And
The first step of measuring the pressure at the outlet of the supply channel and / or the recovery channel at the first flow rate, and
A second step of measuring the pressure at the outlet of the supply channel and / or the recovery channel at a second flow rate higher than the first flow rate.
The flow resistance adjusting means adjusts the flow resistance from the negative pressure control unit of the differential pressure generating means to the outlet portion of the supply flow path and / or the outlet portion of the recovery flow path, and adjusts the flow resistance to the first. A third step in which the pressure at the outlet of the supply flow path and / or the recovery flow path at the second flow rate approaches the pressure at the first flow rate.
The liquid supply method, which comprises supplying a liquid by the differential pressure generating means at a pressure adjusted in the third step. A recording element substrate including a recording element that generates energy used for discharging a liquid.
When,
Liquid supply flow path to the recording element substrate and liquid recovery flow from the recording element substrate
A means having a path, the pressure of the liquid in the supply flow path and the liquid in the recovery flow path.
A differential pressure generating means that supplies and recovers the liquid by creating a difference between the pressure and the pressure of
With the flow resistance adjusting means provided in the supply flow path and / or the recovery flow path,
It is a liquid discharge head equipped with
The page-wide type liquid discharge head is a support in which a plurality of the recording element substrates are arranged.
Equipped with holding members
The support member includes the supply flow path and the recovery flow path.
The supply flow path includes a common supply flow path for supplying a liquid to the plurality of recording element substrates.
The recovery flow path includes a common recovery flow path for recovering liquid from the plurality of recording element substrates.
The differential pressure generating means is provided on the upstream side of the common supply flow path and the common recovery flow path.
The differential pressure generating means is
The first pressure chamber and
A second pressure chamber provided on the downstream side of the first pressure chamber and having a variable volume,
An opening that communicates the first pressure chamber and the second pressure chamber,
A valve urged in a direction in which the flow resistance of the communication portion between the first pressure chamber and the second pressure chamber is variable and the gap between the first pressure chamber and the second pressure chamber is closed.
A pressure receiving portion that is displaceable based on the pressure fluctuation of the second pressure chamber and that transmits the displacement to the valve to change the position of the valve in combination with the urging force acting on the valve. ,
A liquid discharge head characterized by containing. The differential pressure generating means includes a spring for urging the valve.
When the spring constant of the spring is k1 and the flow rate change rate of the pressure acting on the valve from the upstream side of the valve is R2, the following formula R2 > k1 / Sv · da / dQ
Here, a is the valve opening degree, Q is the flow rate, and Sv is the pressure receiving area of the pressure acting on the valve.
16. The liquid discharge head according to claim 16. The differential pressure generating means is provided on the downstream side of the common supply flow path and the common recovery flow path.
The differential pressure generating means is
The first pressure chamber with variable volume and
A second pressure chamber provided on the downstream side of the first pressure chamber and
An opening that communicates the first pressure chamber and the second pressure chamber,
A valve provided in the first pressure chamber, which has a variable flow resistance between the first pressure chamber and the second pressure chamber and is urged in a direction to open a gap between the first pressure chamber and the opening.
A pressure receiving portion that is displaceable based on the pressure fluctuation of the first pressure chamber and that transmits the displacement to the valve to change the position of the valve in combination with the urging force acting on the valve. ,
16. The liquid discharge head according to claim 16. The differential pressure generating means includes a spring for urging the valve.
When the spring constants of the spring are k1 and k2 and the flow rate change rate of the pressure acting on the valve from the downstream side of the valve is R3, the following formula R3> (k1 + k2) / Sv · da / dQ
Here, a is the valve opening degree, Q is the flow rate, and Sv is the pressure receiving area of the pressure acting on the valve.
18. The liquid discharge head according to claim 18.

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