Liquid dispensing head, liquid dispensing unit, and device for dispensing liquid

Abstract

To provide a liquid ejection head that is able to reduce a temperature difference between ejected droplets, caused by a difference in an amount of ejection, is able to reduce a temperature change of an ejected droplet immediately after a change in the amount of ejection, and is able to reduce a time difference between timing of the change in the amount of ejection and timing of detection of the change in the amount of ejection.SOLUTION: A liquid ejection head includes: a flow passage in which liquid flows from a liquid inlet toward a nozzle; a heating member 230 that heats the liquid at a predetermined heating point in the flow passage; a pressure measuring member that measures a difference in pressure between two points in the flow passage; and a temperature measuring member 240 provided on a downstream side of the flow passage from the heating member and configured to measure a temperature of the liquid in the flow passage. The difference in pressure between the two points, measured by the pressure measuring member, is used to calculate a flow rate. The heating member is controlled so that the temperature measured by the temperature measuring member becomes a predetermined value. The predetermined value is changed based on the calculated flow rate.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a liquid ejection head, a liquid ejection unit, and a device for ejecting a liquid.

Background Art

[0002] In an image forming apparatus using an inkjet method, it is known to heat ink, which is a liquid ejected from a nozzle (for example, ink), using a heat source such as a heater so that the ink reaches a desired state. In such a device, a technique for controlling the heating amount by obtaining the flow rate of ink in order to heat the ink to a desired temperature has been proposed. <W

[0003] Patent Document 1 discloses a liquid viscosity control device for controlling the viscosity of a liquid ejected from a nozzle. Patent Document 1 discloses a liquid viscosity control device that controls the output of a heater so that the measured flow rate measured by a flow rate measuring device approaches an ideal flow rate, thereby controlling the viscosity of the liquid. According to Patent Document 1, viscosity control for obtaining an ideal flow rate can be directly performed based on the actual flow rate, and it is said that the responsiveness of viscosity control can be enhanced. Also, in Patent Document 1, a temperature sensor is provided downstream of the flow path from the heating point where the heater heats the liquid, and the output of the temperature sensor is used to measure the flow rate of the liquid flowing through the flow path, and it is disclosed that the output of the heater is controlled so that the measured flow rate approaches the ideal flow rate for ejecting the liquid from the nozzle.

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in conventional technology, when determining the flow rate, information from a temperature sensor located downstream of the heater is used. Therefore, changes in the heater's heating amount need to be transmitted downstream, resulting in a time lag between the time the heater is controlled and the time the result of that control is detected. Consequently, it was necessary to wait between controlling the heater and detecting the result of that control. In such cases, a period of time occurs during which liquid at an unintended and inappropriate temperature flows, and this liquid reaches the nozzle, causing image distortion due to variations in discharge.

[0005] Furthermore, in conventional technology, the amount of heating from the heater was controlled solely by the temperature information from the temperature sensor. In this case, even if the detected temperature was the same, if the discharge rate was different, the average temperature of the liquid flowing through the fluid would differ, making it impossible to bring the liquid to the target temperature. For example, if the discharge rate is high, the liquid flows quickly, causing uneven heating of the liquid. However, since the temperature sensor cannot acquire information on the temperature distribution, it was not possible to control the fluid while taking into account the difference in discharge rate. As a result, temperature differences occurred in the discharged droplets due to differences in discharge rate.

[0006] Therefore, the present invention aims to provide a liquid dispensing head that can reduce the temperature difference of dispensed droplets due to differences in dispensing volume, reduce the temperature change of dispensed droplets immediately after a change in dispensing volume, and reduce the time difference between the timing of a change in dispensing volume and the timing of detecting that change in dispensing volume. [Means for solving the problem]

[0007] To solve the above problems, the liquid discharge head of the present invention comprises a flow path through which liquid flows from a liquid inlet toward a nozzle, a heating member that heats the liquid at a predetermined heating point in the flow path, a pressure measuring member that measures the pressure difference between two points in the flow path, and a temperature measuring member provided downstream of the heating member in the flow path that measures the temperature of the liquid in the flow path, wherein the pressure difference between the two points measured by the pressure measuring member is used to calculate the flow rate, the heating member is controlled so that the temperature measured by the temperature measuring member is a predetermined value, and the predetermined value is changed based on the calculated flow rate. [Effects of the Invention]

[0008] According to the present invention, it is possible to reduce the temperature difference of discharged droplets due to differences in discharge volume, reduce the temperature change of discharged droplets immediately after a change in discharge volume, and reduce the time difference between the timing of the change in discharge volume and the timing of detecting that change in discharge volume. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic perspective view showing an example of a liquid dispensing head according to the present invention. [Figure 2] This is an exploded perspective schematic diagram showing an example of a liquid dispensing head according to the present invention. [Figure 3] This is a schematic front view showing an example of a liquid dispensing head according to the present invention. [Figure 4] This is a schematic diagram illustrating an example of a flow path. [Figure 5] This is another schematic diagram illustrating an example of a flow path. [Figure 6] Figure 5 shows a schematic cross-sectional view of AA'. [Figure 7] This is a schematic diagram illustrating an example of a heated area. [Figure 8] This is a schematic diagram illustrating an example of ink temperature distribution. [Figure 9] This is a schematic diagram (A) illustrating an example of a method for measuring a pressure difference (Example 1), and a diagram (B) illustrating an example of a pressure measurement area. [Figure 10A] It is a diagram for explaining measurement examples of P1 and P2 at Q = 0. [Figure 10B] It is a diagram for explaining measurement examples of P1 and P2 at Q = Q1. [Figure 10C] It is a diagram for explaining measurement examples of P1 and P2 at Q = Q2. [Figure 11] It is a diagram showing the discharge droplet temperature in Comparative Example 1. [Figure 12] It is a diagram showing the discharge droplet temperature in Example 1. [Figure 13] It is a schematic diagram for explaining another example (Example 2) of the method for measuring the pressure difference. [Figure 14] It is a schematic diagram (A) for explaining another example (Example 3) of the method for measuring the pressure difference and a diagram (B) for explaining another example of the pressure measurement region. [Figure 15] It is a schematic diagram (A) for explaining another example (Example 4) of the method for measuring the pressure difference and a diagram (B) for explaining another example of the pressure measurement region. [Figure 16] It is a schematic diagram for explaining another example (Example 5) of the method for measuring the pressure difference. [Figure 17] It is a schematic diagram for explaining another example (Example 6) of the method for measuring the pressure difference. [Figure 18] It is a schematic diagram for explaining another example (Example 7) of the method for measuring the pressure difference. [Figure 19] It is a schematic diagram for explaining another example (Example 8) of the method for measuring the pressure difference. [Figure 20] It is a schematic diagram in an example of a device for discharging a liquid. [Figure 21] It is a schematic diagram in another example of a device for discharging a liquid. [Figure 22] It is a schematic diagram in an example of a liquid discharge unit.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, a liquid ejection head, a liquid ejection unit, and a device for ejecting a liquid according to the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments shown below, and can be changed within the scope that those skilled in the art can conceive, such as other embodiments, additions, modifications, deletions, etc. As long as the functions and effects of the present invention are achieved in any aspect, it is included in the scope of the present invention.

[0011] The liquid ejection head of the present invention has a flow path through which a liquid flows from a liquid inlet toward a nozzle, a heating member that heats the liquid at a predetermined heating point in the flow path, a pressure measurement member that measures a pressure difference between two points in the flow path, and a temperature measurement member that is provided on the downstream side of the flow path from the heating member and measures the temperature of the liquid in the flow path. The pressure difference between the two points measured by the pressure measurement member is used for calculating the flow rate, and the heating member is controlled so that the temperature measured by the temperature measurement member becomes a predetermined value, and the predetermined value is changed based on the calculated flow rate.

[0012] FIG. 1 is a schematic external perspective view of the liquid ejection head of the present embodiment, and FIG. 2 is a schematic exploded perspective view of the liquid ejection head of the present embodiment.

[0013] As shown in FIG. 1, the liquid ejection head 1 of the present embodiment has, for example, a nozzle cover 110, a base member 120, actuator units 130a and 130b, and a manifold member 140. Although not shown, the liquid ejection head 1 has an electrical member, a cover member, and the like.

[0014] The manifold member 140 is composed of, for example, manifold members 140a, 140b, and 140c. The manifold member 140a has liquid inlets 202a and 202b. The manifold member 140b has a damper member 210, a heat transfer member 220, a heater 230, and a temperature measurement member 240.

[0015] In this embodiment, liquid (e.g., ink) flows in through liquid inlets 202a and 202b, and the liquid flows through a channel formed in the manifold 140. The liquid then flows to actuator units 130a and 130b, and further to the base member 120. A nozzle is formed in the base member 120, and the liquid that has flowed into the base member 120 is discharged as droplets from the nozzle when a discharge force is applied by the actuator units 130a and 130b.

[0016] The heater 230 is an example of a heating element and heats the liquid at a predetermined heating point in the flow path. The predetermined heating point may be a single point such as the center or center of gravity of the heater 230, or it may be a region in which the heater 230 is provided. The heater 230 also heats the liquid in the flow path via the heat transfer element 220. The region in which the heater 230 is provided may be called the heating region, but since the heater 230 heats the liquid in the flow path via the heat transfer element 220, in this embodiment, the region in which the heat transfer element 220 is provided is called the heating region. The heat transfer element 220 and the heater 230 together may also be called the heating means.

[0017] Figure 3 is a schematic diagram of the liquid discharge head 1 as viewed from the front (or side). While not particularly limited, when viewed from the front, the heat transfer member 220, heater 230, and temperature measuring member 240 are provided on the left side, and the damper member 210 is provided on the right side. In this embodiment, the heat transfer member 220, heater 230, temperature measuring member 240, and damper member 210 are also provided on the back side (the side opposite to the front) of the liquid discharge head 1. Furthermore, in this embodiment, the damper member 210 is provided on the opposite side of the flow path from the heating member. That is, when viewed from the back side, the heating member is provided on the left side and the damper member 210 is provided on the right side, similar to when viewed from the front.

[0018] By providing the damper member 210 on the opposite side of the flow path from the heating element, compliance can be more easily ensured. This makes it easier to respond to changes in flow rate and liquid pressure due to heating, and allows for efficient damping.

[0019] Figure 4 is a schematic diagram illustrating the flow path within the manifold 140. The liquid flowing in from the liquid inlet 202a flows through the flow path 201 towards the nozzle. In the figure, the direction of liquid flow is schematically indicated by white arrows. Although not particularly limited, in this embodiment, heating elements and damper elements 210 are provided in areas where the width of the flow path widens. By providing heating elements and damper elements 210 in areas where the width of the flow path widens in this way, heating and damping can be performed efficiently.

[0020] Note that the heater 230 and the damper member 210 are shown with different dashed lines, which means they are located on different surfaces. The heater 230 and the damper member 210 are located on opposite sides of the flow path.

[0021] Furthermore, in the diagram, the direction of liquid flow is indicated by reference numeral 130. The direction of liquid flow can be either actuator unit 130a or 130b, or the left side of the diagram may be configured to flow to actuator unit 130a and the right side to flow to actuator unit 130b, or 130a and 130b may be reversed, and can be changed as appropriate. For this reason, it is indicated by reference numeral 130 instead of reference numerals 130a and 130b. Also, when circulating the liquid, on the recovery side, the liquid flows through the flow path shown in the diagram, so the direction of the white arrow is reversed.

[0022] Figure 5 is another schematic diagram illustrating the flow path within the manifold 140. The flow path 201 is shown schematically in the same way as in Figure 4. In the figure, the dashed line R1 indicates the pressure measurement area. In this embodiment, the pressure measurement area is located upstream of the area heated by the heating element (also referred to as the heating area, etc.). This improves the accuracy of flow rate calculation. Pressure measurement and flow rate calculation will be described later.

[0023] Figure 6 is a schematic cross-sectional view along the line A-A' in Figure 5. As shown in the figure, the heating element and the damper element 210 are located on opposite sides of the flow path 201. As described above, this arrangement makes it easier to respond to changes in flow rate and liquid pressure due to heating, and allows for efficient damping.

[0024] As shown in the figure, a temperature measuring member 240 is also provided. The temperature measuring member 240 is located downstream of the heater 230 (heating member) in the flow path and measures the temperature of the liquid in the flow path. For example, a temperature sensor can be used as the temperature measuring member 240.

[0025] Here, we will explain an example of temperature measurement using Figures 7 and 8. Figure 7 is a diagram illustrating the flow path 201, similar to Figure 6, but without the damper member 210. Figure 8 is a diagram showing the temperature distribution of the liquid (ink) at point x=a in Figure 7. Figures 7 and 8 illustrate an example where no control is performed in this invention.

[0026] As shown in Figure 7, when a liquid is heated, the temperature of the liquid at x=a will have a temperature distribution as shown in Figure 8, for example. The transfer of heat in the z direction due to heating by the heater 230 travels further in the z direction the longer the liquid stays near the heater 230. When the liquid discharge rate is high, the speed at which the liquid flows through the channel increases, and the time it stays near the heater 230 decreases. On the other hand, when the liquid discharge rate is low, the speed at which the liquid flows through the channel decreases, and the time it stays near the heater 230 increases. Therefore, when the discharge rate is high, the distance over which heat from the heater 230 is transferred in the z direction is shorter. As a result, as shown in Figure 8, when the discharge rate is high (solid line), the temperature distribution is lower than when the discharge rate is low (dashed line).

[0027] Therefore, when averaging the liquid temperature with respect to the z direction at point x=a, the average temperature of the liquid in the flow path will be lower when the liquid discharge rate is higher compared to when the discharge rate is lower. In other words, when averaging the liquid temperature with respect to the z direction at point x=a, the average temperature of the liquid in the flow path will be higher when the liquid discharge rate is lower compared to when the discharge rate is higher.

[0028] In conventional technology, the heating amount of the heater 230 was controlled so that the temperature measured by the temperature measuring member 240 was the desired temperature at the measuring section of the temperature measuring member 240, based solely on the temperature information measured by the temperature measuring member 240, so that the temperature of the liquid at the time of discharge was the desired temperature. In this case, even if the measured temperature is the same, if the amount of liquid discharged is different, there is a problem that the average temperature of the liquid after heating (average temperature in the z direction), that is, the temperature of the liquid at the time of discharge, will be different. For example, when a temperature measuring member 240 is provided as shown in Figure 7, the temperature measuring member 240 can only measure the temperature at one point, so it is not possible to measure the temperature distribution as shown in Figure 8. Therefore, even if the temperature of the temperature measuring member 240 is the same, the average temperature at point x=a will differ depending on the discharge amount. In other words, if the desired temperature at the measuring section of the temperature measuring member 240 is the same regardless of the flow rate, a liquid at an inappropriate temperature that is outside the target will flow through the flow path and be discharged from the nozzle, making it difficult to achieve the desired discharge.

[0029] Furthermore, if the temperature measuring member 240 is located downstream of the region heated by the heater 230, a time lag occurs between the timing of the change in flow rate and the timing of detecting the effect of that change in flow rate. When controlling the heating amount of the heater 230 based on the temperature measuring member 240, this time lag can lead to ineffective control of the heating amount of the heater 230, resulting in liquid at an inappropriate temperature flowing through the flow path.

[0030] Therefore, in this invention, when controlling heating by the heating element so that the temperature measured by the temperature measuring element 240 becomes a predetermined value in the temperature measuring element 240 measuring section, the predetermined value in the temperature measuring element 240 measuring section is changed based on the calculated flow rate.

[0031] Detailed examples will be described later, but as for the control of the heating element, for example, the control is made so that the temperature measured by the temperature measuring element is the same regardless of the flow rate, and when the liquid temperature at discharge is lower when the flow rate is higher than when the flow rate is lower, the system determines that the discharge volume is high when the flow rate is high and makes the temperature measured by the temperature measuring element higher than when the flow rate is low. On the other hand, when the flow rate is low, the system determines that the discharge volume is low and makes the temperature measured by the temperature measuring element lower than when the flow rate is high. For example, by doing this, it is possible to control the heating element while taking the discharge volume into consideration, and the difference in the average temperature of the heated liquid due to differences in discharge volume can be reduced.

[0032] To ensure that the temperature measured by the temperature measuring element reaches a predetermined value, one method is to control the amount of heat applied to the heating element. For example, increasing the amount of heat applied to the heating element can increase the temperature measured by the temperature measuring element. The predetermined temperature can be set in advance.

[0033] Furthermore, in this invention, the flow rate of the liquid in the flow path is calculated by determining the pressure difference between two points in the flow path (also referred to as the pressure difference between the two points). Since the pressure difference between the two points is determined by the flow rate flowing between those two points, there is no time lag between the timing of a change in flow rate and the timing of the effect appearing in the pressure difference between the two points. In other words, by measuring the pressure at two points in the flow path and calculating the flow rate from this pressure difference, it is possible to immediately detect the timing of a change in the flow rate in the flow path. By immediately detecting changes in flow rate, the heating element can be controlled with high precision, making it easier to bring the temperature of the liquid in the flow path to the target temperature, and also making it easier to bring the temperature of the discharged droplets to the target temperature.

[0034] The following explains how to determine the flow rate from the pressure difference between two points, using several examples. The region for measuring the pressure difference (also referred to as the pressure measurement region) can be selected as appropriate; for example, region R1 in Figure 5 is one such region. It is preferable that the pressure measurement region be upstream of the heating region. When the pressure measurement region is upstream of the heating region, the influence of changes in liquid viscosity can be reduced.

[0035] Figure 9 illustrates an example (Example 1) of a method for determining the flow rate from the pressure difference between two points. Figure 9(A) is a schematic cross-sectional view of the flow path. In this example, pressure measuring members 270a and 270b are provided on the side surface of the straight section of the flow path 201 so that only static pressure can be measured. The pressure measuring members 270a and 270b in this example measure the pressure at points a and b, thereby allowing the pressure difference between the two points to be determined.

[0036] Note that the axes (x, z) shown in Figure 9(A) are merely an example provided for illustrative purposes; other cases involving axes (x, y) are also possible and can be changed as appropriate. The same applies to Figures 13, 16, 17, etc., described later.

[0037] Figure 9(B) is a diagram illustrating examples of the positions where pressure measuring members 270a and 270b are installed, in other words, the positions of points a and b. As shown in the figure, examples of the positions of points a and b include regions R2, R3, and R4. Figure 9(A) is, for example, region R2 or region R4. It is preferable that points a and b are located upstream of the heating region, for example, the region where the heater 230 is installed. In this case, the influence of changes in the viscosity of the liquid due to heating can be avoided, and the flow rate can be calculated from the pressure difference with greater accuracy.

[0038] If P1 is the pressure at point a, P2 is the pressure at point b, μ is the viscosity of the liquid at the assumed liquid temperature during inflow, and Ph is the pressure due to the difference in water head between the sensor surfaces of pressure measuring members 270a and 270b, then the pressure loss ΔP between point a and point b is expressed as follows. Note that the following equation does not include dynamic pressure, Q represents the flow rate, and B1 is a constant. ΔP = B1 × μ × Q =P1-P2+Ph Equation (1)

[0039] Rearranging the above equation yields the following: Q=(P1-P2+Ph) / (B1×μ) Equation (2) Therefore, by determining B1 and Ph in advance, the flow rate of the liquid in the flow path can be determined using the pressure difference between the two points.

[0040] The head of the sensor surface refers to the energy of the liquid at the sensor surface of the pressure measuring member when the liquid in the flow path is flowing, expressed as the height of the liquid. The head difference Ph at the sensor surface is the difference between the head of pressure measuring member 270a and the head of pressure measuring member 270b. The head difference Ph at the sensor surface can be determined from P1 and P2 when the flow rate is 0 with the sensor filled with liquid.

[0041] Furthermore, μ represents the viscosity of the liquid at the assumed liquid temperature at the time of inflow. This liquid temperature represents the temperature of the liquid as it flows into the liquid discharge head. Therefore, by determining the temperature and viscosity of the liquid to be used in advance, the above value can be substituted for μ. Note that μ may be determined using the liquid temperature at the time of inflow, which is measured directly, or it may be determined from the liquid temperature at the time of inflow estimated from the ambient temperature around the liquid discharge head, or from the detected value of a temperature measuring element, although there may be some differences. Also, as explained below, viscosity μ may be treated as a constant.

[0042] Therefore, in this embodiment, by measuring the pressure at two points using two pressure measuring members 270a and 270b, the pressure loss between the two points can be measured and the liquid flow rate can be calculated. As a general phenomenon, the pressure loss between two points increases as the liquid flow rate increases, so in this embodiment, the liquid flow rate is calculated by measuring the pressure at two points.

[0043] Note that the "pressure difference between two points" corresponds to P1-P2 in equation (1), and the "pressure loss between two points" corresponds to B1×μ×Q in equation (1), and these are considered separately.

[0044] In equations (1) and (2) above, the values ​​of P1 and P2 themselves change depending on the flow rate and other settings (for example, the location where the reference pressure is set and the pressure value at that location). Therefore, there are several possible cases in which the flow rate Q changes. For example, when the flow rate Q increases, the behavior of P1 and P2 can be categorized into the following three cases. (a) P1 increases AND P2 increases (i) P1 becomes larger and P2 becomes smaller. (c) P1 becomes smaller AND P2 becomes smaller However, in all cases (a) to (c), P1-P2 changes in proportion to the flow rate.

[0045] As an example, the case of (c) above will be explained using Figures 10A to 10C. The example shown in Figures 10A to 10C is an example where the head difference Ph is 0 for illustrative purposes. Also, Figures 10A to 10C show the relationship between the pressures at point a and point b when a reference pressure is set upstream of point a and the pressure is fixed regardless of the flow rate. In this example, as shown in the figure, both P1 and P2 decrease as the flow rate increases.

[0046] First, Figure 10A shows an example where the flow rate Q is 0 (zero), in which case P1 and P2 are equal. The value of P1 (pressure) when Q=0 is represented as P1(0), and the value of P2 (pressure) when Q=0 is represented as P2(0).

[0047] Figure 10B shows an example where the flow rate Q changes from 0 to Q1. In other words, it shows an example where the flow rate increases. In this case, for example, the pressure P1 at point a decreases, from P1(0) to P1(Q1). Also, the pressure P2 at point b decreases, from P2(0) to P2(Q1). In the figure, the values ​​of P1 and P2 when Q=0 are represented by white circles, and the values ​​of P1 and P2 when Q=Q1 are represented by black circles.

[0048] As shown in Figure 10B, the pressure P2 at downstream point b is lower than the pressure P1 at upstream point a. Therefore, when Q=Q1, P1-P2, i.e., ΔP(Q1), is greater than 0. By substituting the measured P1-P2 into equation (2), the absolute or relative value of Q1 can be determined.

[0049] Figure 10C shows an example of a change in flow rate from Q1 to Q2, which is an example of an increase in flow rate. In the figure, the values ​​of P1 and P2 when Q=Q1 are represented by white circles, and the values ​​of P1 and P2 when Q=Q2 are represented by black circles. As shown in the figure, the pressure P1 at point a is even smaller than when Q=Q1, and the pressure P2 at point b is even smaller than when Q=Q2. Therefore, P1-P2, i.e., ΔP(Q2), when Q=Q2 is larger than ΔP(Q1).

[0050] Then, by substituting the measured P1-P2 into equation (2), the absolute or relative value of Q2 can be determined. If Q2 falls within a predetermined range, it can be determined that the flow rate has increased, and therefore the discharge volume has increased. In such a determination, if Q2 is greater than Q1, it can also be determined that the discharge volume has increased by comparing Q2 and Q1.

[0051] Furthermore, as with (c) above, ΔP increases as the flow rate increases for (a) and (b).

[0052] Furthermore, as in this embodiment, we believe that by calculating the flow rate based on the pressure loss between two points, the influence of the temperature of the liquid flowing into the liquid discharge head can be reduced, even if viscosity is considered a constant. This will be explained below. To bring a liquid to a desired temperature, if the temperature of the liquid flowing into the liquid discharge head is low, the amount of heating by the heating means needs to be increased. On the other hand, the viscosity of a liquid increases as the liquid temperature decreases, so if viscosity is considered a constant, the pressure loss will increase. In other words, if viscosity is considered a constant, a low temperature of the liquid flowing into the liquid discharge head is equivalent to an increase in flow rate. An increase in flow rate raises the heater temperature, which in turn increases the amount of heating by the heating means. Therefore, even if the flow rate is calculated using viscosity as a constant, if the temperature of the liquid flowing into the liquid discharge head is low, the heating means will be controlled to increase the amount of heating, so the influence of the temperature of the incoming liquid is small.

[0053] In Example 1, pressure measuring members 270a and 270b were provided on the side of the straight section of the flow path, and the static pressure at each point was measured. However, they could also be provided in a section affected by dynamic pressure. In that case, the pressure difference between point a and point b is calculated from the following formula, taking into account the dynamic pressure which is proportional to the square of the flow rate. Here, B2 is a constant and ρ is the density of the liquid. P1 - P2 = B1 × μ × Q + B2 × ρ × Q 2 -Ph formula (3) Compared to measuring static pressure, the number of constants increases, thus increasing the effort required to identify them. However, by pre-determining B1, B2, and Ph, the flow rate of the liquid in the flow path can be determined using the pressure difference between two points.

[0054] Furthermore, when measuring static pressure while eliminating the influence of dynamic pressure, one example is to install pressure measuring members 270a and 270b on the side of the straight section of the flow path. In addition, the "pressure difference between two points" corresponds to P1-P2 in equation (3), and the "pressure loss between two points" corresponds to B1×μ×Q in equation (3), and these are considered separately.

[0055] Furthermore, as explained in Figure 9(B), it is preferable that the pressure measuring member be located upstream of the heating member in the flow path. The pressure loss between the two points is affected by the flow rate and viscosity. When the pressure measuring area is upstream of the heating area, the influence of viscosity changes due to heating can be avoided. Therefore, the viscosity of the liquid flowing between the two pressure measuring points can be determined from the liquid temperature at the liquid inlet, thereby improving the accuracy of flow rate calculation.

[0056] While this invention does not exclude the case where the pressure measurement area is downstream of the heating area, if the pressure measurement area is downstream of the heating area in the flow path, it becomes difficult to improve the accuracy of flow rate calculation. When the pressure measurement area is downstream of the heating area in the flow path, the liquid temperature changes due to heating, and the liquid temperature is affected by the flow rate and the history of the overheating state, so the accuracy of liquid temperature estimation decreases. For this reason, it becomes difficult to improve the accuracy of flow rate calculation.

[0057] Figure 11 illustrates Comparative Example 1, which is not included in the present invention. In Figure 11, the horizontal axis represents time and the vertical axis represents temperature. The detected temperature (target temperature) of the temperature measuring member 240 is plotted as a black circle, and the temperature of the droplet discharged from the nozzle (discharged droplet temperature) is plotted as an ×.

[0058] Comparative Example 1 is an example in which the pressure measuring member is not present in Example 1. Comparative Example 1 is an example in which the heating member is controlled so that the temperature of the temperature measuring member 240 remains constant, without considering the flow rate. In other words, Comparative Example 1 is an example in which the heating member is controlled so that the temperature of the temperature measuring member 240 remains constant at a predetermined value, without considering the discharge volume.

[0059] As shown in the diagram, the left side of the figure represents a small discharge volume, the center represents a large discharge volume, and the right side represents a small discharge volume. In other words, these are the measurement results when droplets are discharged with a small discharge volume first, then with a large discharge volume, and finally with a small discharge volume again.

[0060] As shown in the figure, it can be seen that the discharge droplet temperature decreases when the discharge rate is increased. In other words, the point plotted with an "x" in the center of the figure is lower than the point plotted with an "x" on the left side of the figure. The second "x" in the center of the figure is lower than the first "x", and the line connecting the first and second "x" has a negative slope. Also, although gradual, there is a negative slope from the second "x" to the fourth "x". As mentioned above, when the discharge rate is high, the time the liquid stays near the heater 230 is shortened, so the average temperature in the z direction decreases. When the discharge droplet temperature changes significantly, variations occur in the discharge, causing distortion in the image.

[0061] Figure 12 illustrates Embodiment 1 included in the present invention. In Figure 12, as in Figure 11, the horizontal axis represents time and the vertical axis represents temperature. The measured temperature of the temperature measuring member 240 is plotted as a black circle, and the temperature of the droplet discharged from the nozzle (discharged droplet temperature) is plotted as an "x".

[0062] In Example 1, the heating element is controlled considering the flow rate. That is, the heating element is controlled so that the predetermined temperature measured by the temperature measuring element 240 changes to a value corresponding to the flow rate, depending on the discharge rate. For example, if the discharge rate is high, the amount of heating from the heater 230 is increased so that the measured temperature of the temperature measuring element 240 becomes higher. On the other hand, if the discharge rate is low, the amount of heating from the heater 230 is decreased so that the measured temperature of the temperature measuring element 240 becomes lower.

[0063] As shown in the figure, Example 1 (Figure 12) is able to suppress the decrease in discharge droplet temperature even when the discharge volume is increased, compared to Comparative Example 1 (Figure 11). For example, the decrease in the second × relative to the first × in the center (high discharge volume) of the figure is suppressed. Also, the decrease in the first × on the left side (low discharge volume) of the figure is suppressed compared to Comparative Example 1. Example 1 is able to suppress variations in discharge droplet temperature compared to Comparative Example 1. Therefore, even if the discharge volume changes, variations in discharge can be suppressed, and image quality can be stabilized.

[0064] Furthermore, in Example 1, since the flow rate is calculated based on the pressure difference between two points, there is no time difference between the timing of the flow rate change and the timing of detecting the change in flow rate. Therefore, the timing of a change in the flow rate in the channel can be detected immediately. This reduces the time delay in controlling the heating means. This also helps to prevent a large difference between the first and second ×s in the center of the figure, and also prevents a large difference between the first and second ×s on the left side of the figure.

[0065] In Example 1, control and measurement are performed by considering viscosity μ as a constant. As mentioned above, even if the flow rate is calculated by considering viscosity μ as a constant, the influence of the temperature of the liquid flowing into the liquid discharge head can be reduced.

[0066] As described above, this embodiment reduces the temperature difference of discharged droplets due to differences in discharge volume, reduces the temperature change of discharged droplets immediately after a change in discharge volume, and reduces the time difference between the timing of the change in discharge volume and the timing of detecting that change in discharge volume. Furthermore, as this embodiment reduces the temperature difference of discharged droplets due to differences in discharge volume, variations in discharge can be suppressed and image quality can be stabilized.

[0067] The heating element is controlled, for example, by a control unit. The control unit may be located on the liquid discharge head or outside the liquid discharge head. For example, a control unit may be provided in a liquid discharge device equipped with a liquid discharge head. The control unit calculates the flow rate based on the pressure difference between the two points and controls the heating element based on the calculated flow rate. When controlling the heating element, the control unit uses the calculated flow rate and controls the temperature measured by the temperature measuring element to a predetermined value. The intended effects of the present invention are obtained when the heating element is controlled in this manner. As the control unit, for example, known DFEs, CPUs, etc., can be used.

[0068] One way to control the heating element is to control the amount of heat the heating element has been heated. In this embodiment, when controlling the amount of heat the heating element has been heated, a predetermined value of the temperature measured by a temperature measuring element is changed according to the flow rate. Specifically, the amount of heat the heating element has been controlled so that the predetermined value of the temperature measured by the temperature measuring element increases as the flow rate increases.

[0069] As in Example 1, it is preferable that the heating element is controlled so that when the calculated flow rate changes, the temperature measured by the temperature measuring element changes to a predetermined value. Furthermore, it is preferable that the heating element is controlled so that when the calculated flow rate changes to an increased level, the temperature measured by the temperature measuring element increases, and when the calculated flow rate changes to a decreased level, the temperature measured by the temperature measuring means decreases. By performing such control, appropriate heating according to the flow rate can be performed, and variations in the discharge droplet temperature can be suppressed. This further suppresses image distortion.

[0070] Figure 13 is a schematic diagram illustrating Example 2, and is a diagram illustrating a method for calculating the flow rate with a different configuration than that shown in Figure 9. Example 2 is an example in which one pressure measuring member 270 is provided in the flow path of the manifold member 140a. In Example 2, a differential pressure gauge is used as the pressure measuring member 270, and the pressure difference between point a and point b is measured with one pressure measuring member 270. In Example 2, since the pressure difference is measured using one pressure measuring member, the measurement error can be reduced compared to the case where two pressure measuring members are used and the pressure difference is determined from the difference in measured values ​​(Example 1). When the pressure at two locations is measured separately and the pressure difference is determined from those values ​​(Example 1), measurement errors occur at each of the two pressure locations. For this reason, the measurement error can be reduced when the differential pressure is measured directly (Example 2).

[0071] Furthermore, the range of the pressure difference between point a and point b is smaller than the range of absolute pressure between point a and point b. The range of differential pressure between two points (at most a few kPa or less) is smaller than the range of absolute pressure between the two points (for example, it can reach tens of kPa during filling). Generally, the narrower the range of pressure measured by a pressure measuring element, the better the sensitivity of the element. Therefore, as in Example 2, directly measuring the pressure difference by using a differential pressure type pressure measuring element can improve measurement accuracy.

[0072] In Example 2, a differential pressure type pressure measuring member is used, so the values ​​of P1-P2 in equations (1) and (2) above can be obtained directly. When a differential pressure gauge is used as the pressure measuring member, the head difference Ph can be determined from the value of the differential pressure gauge when the flow rate is 0 with the container filled with liquid. The head difference Ph can be determined in the same manner in Example 4, which will be described later.

[0073] In Example 2, it is preferable to provide a side passage 201a for flow rate measurement in the flow path 201, as shown in the figure. It is preferable to provide one pressure measuring member 270 in this side passage 201a to determine the pressure difference between point a and point b.

[0074] The location of the pressure measurement area, as in Example 2, can be selected as appropriate, for example, areas R2 to R4 shown in Figure 9(B). Figure 13 aligns the x and y axes with areas R2 and R4 shown in Figure 9(B). If area R3 is selected, the axes in Figure 12 should be changed as appropriate. As mentioned above, the shape of the flow path is not limited to those shown.

[0075] Figure 14 is a schematic diagram illustrating Example 3, and is a diagram illustrating a method for calculating the flow rate with a different configuration than that of Figure 13 (Example 2). As shown in Figure 14(A), in Embodiment 3, the manifold member 140a is formed from manifold member 140d and manifold member 140e, and the pressure measuring member 270 is installed on the joint surface between manifold member 140d and manifold member 140e. Installing the pressure measuring member 270 on the joint surface between manifold member 140d and manifold member 140e, as in Embodiment 3, has the advantage of making it easier to install wiring and other components.

[0076] In Example 3, as in Example 2, the pressure difference between point a and point b can be determined using a single pressure measuring member 270.

[0077] Figure 14(B) illustrates an example of the location where the pressure measurement area of ​​Example 3 is provided. While not particularly limited, area R5 is an example. Furthermore, the shape of the flow path is not limited to that shown.

[0078] Figure 15 is a schematic diagram illustrating Example 4, and is a diagram illustrating a method for calculating the flow rate with a different configuration than that shown in Figure 13 (Example 2). As shown in Figure 15(A), in Example 4, the pressure measuring member 270 is installed on the joint surface of the manifold member 140a and the manifold member 140b. Installing the pressure measuring member 270 on the joint surface of the manifold member 140a and the manifold member 140b, as in Example 4, has the advantage of making it easier to install wiring and other components.

[0079] In Example 4, as in Example 3, the pressure difference between point a and point b can be determined using one pressure measuring member 270. Also, since both point b and point c are in the region where the width of the flow path 201 is widened, if the pressure at point c is P3, then P3 ≈ P2 can be considered. Therefore, the pressure loss between point a and point b can be considered to be the same as the pressure loss between point a and point c. This pressure loss ΔP can be expressed as follows using the above equations (1) and (2). Equation (2)' is the same as equation (2). ΔP = B1 × μ × Q =P1-P2+Ph ≒P1-P3+Ph Equation (1)' Q=(P1-P2+Ph) / (B1×μ) Equation (2)'

[0080] Figure 15(B) illustrates an example of the location where the pressure measurement area of ​​Example 4 is provided. While not particularly limited, for example, area R6 is an example. Furthermore, the shape of the flow path is not limited to that shown.

[0081] Next, other embodiments of the present invention will be described with reference to several examples. In this embodiment, a fluid resistance section is provided between two points where the pressure difference in the flow path is measured. By providing the fluid resistance section, the measurement performance of flow rate changes can be improved.

[0082] Figures 16 to 19 are schematic diagrams illustrating embodiments 5 to 8 included in this embodiment, and each shows embodiments 1 to 4 shown in Figures 9(A), 13, 14(A), and 15(A) with the fluid resistance section 280 added. As shown in Figures 16 to 19, the fluid resistance section 280 is provided between point a and point b.

[0083] In Figure 17, the fluid resistance section 280 is not located in the side passage 201a where the pressure measuring member 270 is provided. However, even in this case, the fluid resistance section is still considered to be located between the two points where the pressure difference is measured. Furthermore, in Figure 19, the fluid resistance section 280 can be said to be located between point a and point b, or between point a and point c. In this case as well, the fluid resistance section is still considered to be located between the two points where the pressure difference is measured.

[0084] The pressure loss due to flow rate increases as the resistance between point a and point b increases. Therefore, the greater the resistance, the easier it is to detect changes in flow rate as a pressure difference. In other words, by providing a fluid resistance section, the measurement performance of flow rate changes can be improved even if the performance of the pressure measuring element remains the same.

[0085] The fluid resistance section 280 may be, for example, a throttling structure or it may be formed of a number of holes. When the fluid resistance section 280 consists of a number of holes, it is preferable that the size (diameter) of the holes is smaller than the nozzle diameter. In this case, the fluid resistance section 280 can be given the function of a foreign matter filter, and nozzle clogging due to foreign matter can be reduced.

[0086] Next, an example of a liquid dispensing apparatus according to the present invention will be described with reference to Figures 20 and 21. Figure 20 is a plan view illustrating the main part of the apparatus, and Figure 21 is a side view illustrating the main part of the apparatus.

[0087] This device is a serial type device, and the carriage 403 reciprocates in the main scanning direction by the main scanning movement mechanism 493. The main scanning movement mechanism 493 includes a guide member 401, a main scanning motor 405, a timing belt 408, etc. The guide member 401 is stretched across the left and right side plates 491A and 491B and holds the carriage 403 in a movable position. The carriage 403 is then reciprocated in the main scanning direction by the main scanning motor 405 via the timing belt 408 stretched between the drive pulley 406 and the driven pulley 407.

[0088] The carriage 403 is equipped with a liquid discharge unit 440 that integrates a liquid discharge head 404 and a head tank 441 according to the present invention. The liquid discharge head 404 of the liquid discharge unit 440 discharges liquids of various colors, such as yellow (Y), cyan (C), magenta (M), and black (K). The liquid discharge head 404 is also mounted with a nozzle row consisting of multiple nozzles arranged in a sub-scanning direction perpendicular to the main scanning direction, and with the discharge direction facing downwards.

[0089] A supply mechanism 494, which supplies liquid stored outside the liquid discharge head 404 to the liquid discharge head 404, supplies the head tank 441 with the liquid stored in the liquid cartridge 450.

[0090] The supply mechanism 494 consists of a cartridge holder 451, which is a filling section for mounting the liquid cartridge 450, a tube 456, a liquid delivery unit 452 including a liquid delivery pump, and the like. The liquid cartridge 450 is detachably mounted in the cartridge holder 451. Liquid is delivered from the liquid cartridge 450 to the head tank 441 via the tube 456 by the liquid delivery unit 452.

[0091] This device includes a transport mechanism 495 for transporting paper 410. The transport mechanism 495 includes a transport belt 412, which is a transport means, and a sub-scanning motor 416 for driving the transport belt 412.

[0092] The conveyor belt 412 attracts the paper 410 and transports it to a position opposite the liquid discharge head 404. This conveyor belt 412 is an endless belt and is stretched between the conveyor roller 413 and the tension roller 414. Attraction can be performed by electrostatic attraction or air suction.

[0093] Then, the conveyor belt 412 moves in a circular motion in the sub-scanning direction as the conveyor rollers 413 are rotationally driven by the sub-scanning motor 416 via the timing belt 417 and timing pulley 418.

[0094] Furthermore, a maintenance and recovery mechanism 420 is positioned on one side of the carriage 403 in the main scanning direction, to the side of the conveyor belt 412, for maintaining and recovering the liquid discharge head 404.

[0095] The maintenance and recovery mechanism 420 consists of, for example, a cap member 421 that caps the nozzle surface (the surface on which the nozzle is formed) of the liquid discharge head 404, and a wiper member 422 that wipes the nozzle surface.

[0096] The main scanning movement mechanism 493, the supply mechanism 494, the maintenance and recovery mechanism 420, and the transport mechanism 495 are mounted on a housing that includes side plates 491A, 491B, and a back plate 491C.

[0097] In this configured device, the paper 410 is fed onto the transport belt 412 and picked up, and the paper 410 is transported in the sub-scanning direction by the circumferential movement of the transport belt 412.

[0098] Therefore, by moving the carriage 403 in the main scanning direction and driving the liquid ejection head 404 in accordance with the image signal, liquid is ejected onto the stationary paper 410 to form an image.

[0099] Thus, since this device is equipped with a liquid discharge head according to the present invention, it can stably form high-resolution images.

[0100] Next, another example of the liquid dispensing unit according to the present invention will be described with reference to Figure 22. Figure 22 is a plan view illustrating the main parts of the unit.

[0101] This liquid discharge unit consists of a housing portion comprising side plates 491A, 491B and a back plate 491C, a main scanning movement mechanism 493, a carriage 403, and a liquid discharge head 404, which are components of the device that discharges the liquid.

[0102] Furthermore, a liquid dispensing unit can also be configured by further attaching, for example, the side plate 491B of this liquid dispensing unit to at least one of the aforementioned maintenance and recovery mechanism 420 and supply mechanism 494.

[0103] In this application, "liquid dispensing device" refers to a device that includes a liquid dispensing head or liquid dispensing unit and drives the liquid dispensing head to dispense liquid. A liquid dispensing device includes not only devices that can dispense liquid onto objects to which liquid can adhere, but also devices that dispense liquid into air or into liquid.

[0104] This "liquid dispensing device" may also include means for feeding, transporting, and dispensing paper onto materials to which liquid can adhere, as well as pre-treatment devices, post-treatment devices, etc.

[0105] For example, "devices that dispense liquids" include image forming machines, which dispense ink to form images on paper, and three-dimensional molding machines, which dispense molding liquid into a powder layer formed in layers to create three-dimensional objects.

[0106] Furthermore, the term "liquid dispensing device" is not limited to devices that visualize meaningful images such as letters or figures through the dispensed liquid. For example, it also includes devices that form patterns that do not have meaning in themselves, or devices that create three-dimensional images.

[0107] The term "materials to which liquid can adhere" above refers to materials to which liquid can adhere, at least temporarily, including materials that adhere and solidify, or materials that adhere and penetrate. Specific examples include recording media such as paper, recording paper, film, and cloth; electronic components such as electronic circuit boards and piezoelectric elements; powder layers; organ models; and inspection cells. Unless otherwise specified, it includes all materials to which liquid can adhere.

[0108] The materials referred to as "materials to which liquid can adhere" above include paper, thread, fibers, fabrics, leather, metal, plastic, glass, wood, ceramics, building materials such as wallpaper and flooring, and textiles for clothing, as long as liquid can adhere to them, even temporarily.

[0109] Furthermore, "liquid" also includes inks, processing solutions, DNA samples, resists, patterning materials, binders, molding fluids, or solutions and dispersions containing amino acids, proteins, calcium, etc.

[0110] Furthermore, "liquid dispensing devices" include devices in which the liquid dispensing head and the surface to which the liquid can adhere move relative to each other, but are not limited to these. Specific examples include serial-type devices in which the liquid dispensing head moves, and line-type devices in which the liquid dispensing head does not move.

[0111] Other examples of "devices that dispense liquids" include processing liquid coating devices that dispense processing liquid onto the surface of paper for purposes such as modifying the surface of the paper, and injection granulation devices that granulate fine particles of raw materials by spraying a composition liquid, in which raw materials are dispersed in a solution, through a nozzle.

[0112] A "liquid dispensing unit" is a collection of components related to liquid dispensing, in which functional parts and mechanisms are integrated with a liquid dispensing head. For example, a "liquid dispensing unit" may include a combination of a liquid dispensing head with at least one of the following components: a head tank, carriage, supply mechanism, maintenance and recovery mechanism, and main scanning and moving mechanism.

[0113] Here, integration includes, for example, cases where the liquid dispensing head and functional components or mechanisms are fixed to each other by fastening, bonding, engaging, etc., or where one is held movably relative to the other. Furthermore, the liquid dispensing head and functional components or mechanisms may be configured to be detachable from each other.

[0114] For example, some liquid dispensing units, such as the liquid dispensing unit 440 shown in Figure 21, have a liquid dispensing head and a head tank integrated into one unit. Others have a liquid dispensing head and head tank integrated into one unit, connected to each other by tubes or similar means. It is also possible to add a unit containing a filter between the head tank and the liquid dispensing head of these liquid dispensing units.

[0115] Additionally, some liquid dispensing units have an integrated liquid dispensing head and carriage.

[0116] Furthermore, some liquid dispensing units integrate the liquid dispensing head and the scanning mechanism by movably holding the liquid dispensing head in a guide member that constitutes part of the scanning mechanism. Additionally, as shown in Figure 22, some liquid dispensing units integrate the liquid dispensing head, carriage, and main scanning mechanism.

[0117] Furthermore, some liquid dispensing units integrate the liquid dispensing head, carriage, and maintenance / recovery mechanism by fixing a cap component, which is part of the maintenance / recovery mechanism, to a carriage to which the liquid dispensing head is attached.

[0118] The main scanning movement mechanism shall include the guide member alone. The supply mechanism shall also include the tube alone and the loading section alone.

[0119] Furthermore, the "liquid discharge head" is not limited to any particular pressure generating means. For example, in addition to the piezoelectric actuator described in the above embodiment (which may use a multilayer piezoelectric element), a thermal actuator using an electrothermal conversion element such as a heating resistor, or an electrostatic actuator consisting of a diaphragm and a counter electrode may also be used.

[0120] Furthermore, in the terminology used in this application, image formation, recording, printing, copying, printing, and shaping are all considered synonymous.

[0121] The liquid discharge unit of the present invention can be configured to integrate a liquid discharge head with at least one of the following: a head tank for storing liquid supplied to the liquid discharge head; a carriage on which the liquid discharge head is mounted; a supply mechanism for supplying liquid to the liquid discharge head; a maintenance and recovery mechanism for maintaining and restoring the liquid discharge head; and a main scanning movement mechanism for moving the liquid discharge head in the main scanning direction.

[0122] Examples of the present invention are as follows: <1> A flow path through which liquid flows from the liquid inlet towards the nozzle, A heating member that heats the liquid at a predetermined heating point in the flow path, A pressure measuring member for measuring the pressure difference between two points in the aforementioned flow path, It includes a temperature measuring member provided downstream of the heating member in the flow path for measuring the temperature of the liquid in the flow path, The pressure difference between the two points measured by the pressure measuring member is used to calculate the flow rate. The heating element is controlled so that the temperature measured by the temperature measuring element reaches a predetermined value. A liquid dispensing head characterized in that the predetermined value is changed based on the calculated flow rate. <2> The two points for measuring the pressure difference are provided on the side surface of the straight portion of the flow path. <1> The liquid dispensing head described above. <3> The pressure measuring member is characterized by being a differential pressure gauge. <1> The liquid dispensing head described above. <4> The pressure measuring member is characterized in that it is provided upstream of the heating member in the flow path. <1> from <3> A liquid dispensing head as described in any of the following. <5> The heating element is If a change occurs that increases the calculated flow rate, the temperature measured by the temperature measuring member is controlled to increase. If a change occurs that causes the calculated flow rate to decrease, the temperature measured by the temperature measuring means is controlled to decrease. Characterized by <1> from <4> A liquid dispensing head as described in any of the following. <6> The flow path is characterized by having a liquid resistance section between the two points. <1> from <5> A liquid dispensing head as described in any of the following. <7> The liquid resistance section is characterized by comprising a plurality of holes, the size of which is smaller than the diameter of the nozzle. <6> The liquid dispensing head described above. <8> <1> from <7> A liquid dispensing unit characterized by having a liquid dispensing head as described in any of the following. <9> <1> from <7> A liquid dispensing head as described in any of the following, <8> A device for dispensing liquid, characterized by being equipped with the liquid dispensing unit described above. [Explanation of symbols]

[0123] 110 Nozzle Cover 120 Base member 130a, 130b Actuator Unit 140 Manifold components 140a~140e Manifold components 201 Flow channel 201a Side road 202a, 202b Liquid inlet 210 Damper component 220 Heat transfer components 230 Heater 240 Temperature measuring element 270 Pressure measuring member 280 Liquid resistance section [Prior art documents] [Patent Documents]

[0124] [Patent Document 1] Patent No. 5024413

Claims

1. A flow path through which liquid flows from the liquid inlet towards the nozzle, A heating member that heats the liquid at a predetermined heating point in the flow path, A pressure measuring member for measuring the pressure difference between two points in the aforementioned flow path, It includes a temperature measuring member provided downstream of the heating member in the flow path for measuring the temperature of the liquid in the flow path, The pressure difference between the two points measured by the pressure measuring member is used to calculate the flow rate. The heating element is controlled so that the temperature measured by the temperature measuring element reaches a predetermined value. A liquid dispensing head characterized in that the predetermined value is changed based on the calculated flow rate.

2. The liquid discharge head according to claim 1, characterized in that the two points for measuring the pressure difference are provided on the side surface of the straight portion of the flow path.

3. The liquid discharge head according to claim 1, characterized in that the pressure measuring member is a differential pressure gauge.

4. The liquid discharge head according to claim 1, characterized in that the pressure measuring member is provided upstream of the heating member in the flow path.

5. The heating element is If a change occurs that increases the calculated flow rate, the temperature measured by the temperature measuring member is controlled to increase. If a change occurs that causes the calculated flow rate to decrease, the temperature measured by the temperature measuring means is controlled to decrease. The liquid dispensing head according to feature 1.

6. The liquid discharge head according to claim 1, characterized in that the flow path has a liquid resistance portion between the two points.

7. The liquid discharge head according to claim 6, characterized in that the liquid resistance portion consists of a plurality of holes, and the size of the holes is smaller than the diameter of the nozzle.

8. A liquid dispensing unit characterized by comprising a liquid dispensing head according to any one of claims 1 to 7.

9. A liquid dispensing device characterized by comprising a liquid dispensing head according to any one of claims 1 to 7.

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