Flow rate sensor, flow meter, and discharge rate control apparatus for liquid discharge machines

A flow rate sensor comprising:

• a heating element;
• a flow rate detection temperature sensing element disposed so as to be affected by an effect of heating of the heating element;
• a flow passage for fluid to be detected which is formed so that the heat from said heating element is transferred to and absorbed by the fluid, wherein the temperature sensing which is affected by an effect of heat absorption of the fluid due to the heating of said heating element is executed in said flow rate detection temperature sensing element;
• and
• heating control means for controlling the heating of said heating element connected to a passage for supplying power to said heating element, wherein said heating control means controls the power to be supplied to said heating element on the basis of the temperature sensing result so that the temperature sensing result is coincident with a target value, and the flow rate of the fluid is detected on the basis of the control state of said heating control means;
• wherein said flow rate detection temperature sensing element is located outside said flow passage, the heat from said heating element is transferred through a heat transfer member extending into the inside of said flow passage in a direction about traversing a median of said flow passage, and the dimension of said heat transfer member in the direction of fluid flow in said flow passage is larger than the dimension of said heat transfer member in a direction perpendicular to the direction of fluid flow in said flow passage and perpendicular to the extending direction of said heat transfer member on the cross-section of said flow passage.

A flow meter comprising:

• a heating element;
• a flow rate detection temperature sensing element disposed so as to be affected by an effect of heating of the heating element;
• a flow passage for fluid to be detected which is formed so that the heat from said heating element is transferred to and absorbed by the fluid, wherein the temperature sensing which is affected by an effect of heat absorption of the fluid due to the heating of said heating element is executed in said flow rate detection temperature sensing element;
• and
• heating control means for controlling the heating of said heating element connected to a passage for supplying power to said heating element, wherein said heating control means controls the power to be supplied to said heating element so that the temperature sensing result is coincident with a target value, said heating control means performs ON-OFF control of the power to be supplied to said heating element on the basis of a pulse signal having the frequency corresponding to the temperature sensing result, and the flow rate of the fluid is detected by measuring the frequency of the pulse signal;
• wherein said flow rate detection temperature sensing element is located outside said flow passage, the heat from said heating element is transferred through a heat transfer member extending into the inside of said flow passage in a direction about traversing a median of said flow passage, and the dimension of said heat transfer member in the direction of fluid flow in said flow passage is larger than the dimension of said heat transfer member in a direction perpendicular to the direction of fluid flow in said flow passage and perpendicular to the extending direction of said heat transfer member on the cross-section of said flow passage.

A portable flow meter comprising:

• a casing comprising a body portion and a lid portion, said body portion having at both end portions thereof connection portions to be. connected to external pipes and containing a flow pipe line penetrating therethrough;
• a flow rate sensor which is accommodated in said casing and detects the flow rate of the fluid;
• a display portion for displaying a flow rate value;
• an operating portion for power-supplying and measuring the flow rate;
• and
• an electrical circuit for displaying on said display portion the flow rate detected by said flow rate sensor;
• wherein said flow rate sensor includes a flow rate detector having a heating element and a temperature sensing element formed on a substrate, a fin plate for transferring heat to fluid to be detected therethrough, and an output terminal for outputting the voltage value corresponding to the flow rate, wherein said flow rate detector, a part of said fin plate and a part of said output terminal are coated by molding;
• wherein said flow rate detector is located outside said flow pipe line, said fin plate extends into the inside of said flow pipe line in a direction about traversing a median of said flow pipe line and the dimension of said fin plate in the direction of fluid flow in said flow pipe line is larger than the dimension of said fin plate in a direction perpendicular to the direction of fluid flow in said flow pipe line and perpendicular to the extending direction of said fin plate on the cross-section of said flow pipe line.

A liquid discharge amount control apparatus for discharging a desired discharge amount of liquid from liquid discharge equipment for discharging to the outside the liquid supplied through a pipe line connected to a liquid supply source by a pump, comprising:

• a flow rate sensor for detecting the flow rate of the liquid flowing in said pipe line between said pump and said liquid discharge equipment;
• flow rate adjusting means for adjusting the flow rate of the liquid in said pipe line at the upstream side of said flow rate sensor;
• and
• a controller for controlling said flow rate adjusting means so that the flow rate value detected by said flow rate sensor is equal to the value corresponding to the desired discharge amount;
• wherein said flow rate sensor comprises:
• a flow rate detector having a heating function and a temperature sensing function;
• a flow passage which is in communication with said pipe line and formed so that heat from said flow rate detector is transferred to and absorbed by the liquid;
• and
• a heat transfer member provided to said flow rate detector and extending into the inside of said flow passage, wherein said heat transfer member extends to at least the vicinity of the central portion of a cross-section of said flow passage in a direction about traversing a median of said flow passage;
• wherein said flow rate detector is located outside said flow passage, and the dimension of said heat transfer member in the direction of liquid flow in said flow passage is larger than the dimension of said heat transfer member in a direction perpendicular to the direction of liquid flow in said flow passage and perpendicular to the extending direction of said heat transfer member on the cross-section of said flow-passage.

A liquid discharge amount control apparatus for discharging a desired discharge amount of liquid from liquid discharge equipment for discharging to the outside a part of the liquid supplied through a pipe line connected to a liquid supply source by a pump and returning the other part of the liquid through a return pipe to the pipe line, comprising:

• a first flow rate sensor for detecting the flow rate of the liquid flowing in said pipe line between said pump and said liquid discharge equipment;
• a second flow rate sensor for detecting the flow rate of the liquid returned through said return pipe;
• flow rate adjusting means for adjusting the flow rate of the liquid flowing in said pipe line at the upstream side of the first flow rate sensor;
• and
• a controller for controlling said flow rate adjusting means so that the value obtained by subtracting a second flow rate value detected by said second flow rate sensor from a first flow rate value detected by said first flow rate sensor is equal to a value corresponding to the desire discharge amount;
• wherein said first and second flow rate sensors each comprises:
• a flow rate detector having a heating function and a temperature sensing function;
• a flow passage which is in communication with said pipe line and formed so that heat from said flow rate detector is transferred to and absorbed by the liquid;
• and
• a heat transfer member provided to.said flow rate detector and extending into the inside of said flow passage, wherein said heat transfer member extends to at least the vicinity of the central portion of a cross-section of said flow passage in a direction about traversing a median of said flow passage;
• wherein said flow rate detector is located outside said flow passage, and the dimension of said heat transfer member in the direction of liquid flow in said flow passage is larger than the dimension of said heat transfer member in a direction perpendicular to the direction of liquid flow in said flow passage and perpendicular to the extending direction of said heat transfer member on the cross-section of said flow passage.