Stepper motor valve and method of control

• US 8,381,760 B2
• Filed: 07/14/2008
• Issued: 02/26/2013
• Est. Priority Date: 07/14/2008
• Status: Active Grant

• Current Assignee: Copeland Comfort Control LP (Emerson Electric Company)
• Original Assignee: Emerson Electric Company
• Inventors: Butler, William P., Jensen, Ryan, Santinanavat, Michael C., Atri, Jagdish
• Primary Examiner(s): Keasel, Eric
• Assistant Examiner(s): JELLETT, MATTHEW WILLIAM
• Application Number:
  US12/172,444
• Publication Number:
  US 20100009303A1
• Time in Patent Office: 1,688 Days
• Field of Search: 251/30.01, 251/30.02, 251/30.05, 251/129.01, 251/129.11, 251/30.04, 251/129.12, 137/485, 137/487.5, 700/281, 700/282
• US Class Current: 137/487.5
• CPC Class Codes: F16K 31/128 servo actuated
• CPC Class Codes: F16K 31/402 acting on a diaphragm
• CPC Class Codes: F16K 31/42 by means of electrically-actuated members in the supply or discharge conduits of the fluid motor F16K31/40 takes precedence
• CPC Class Codes: F23N 1/002 using electronic means F23N1/04 - F23N1/10 take precedence
• CPC Class Codes: G05D 16/202 actuated by an electric motor
• CPC Class Codes: Y10T 137/7761 Electrically actuated valve
• CPC Class Codes: Y10T 137/7764 Choked or throttled pressure type

Abstract

A stepper-motor gas valve control is disclosed that includes a main diaphragm in a chamber that controllably displaces a valve relative to an opening in response to changes in pressure, to adjust fuel flow through the valve. A servo-regulator diaphragm is provided to regulate flow to the main diaphragm, to thereby control the rate of fuel flow. A stepper motor is configured to move in a stepwise manner to displace the servo-regulator diaphragm, to control fluid flow to the main diaphragm. A controller mounted on the stepper-motor regulated gas valve control receives and converts an input control signal from a heating system to a reference value between 0 and 5 volts, and selects a corresponding motor step value. The control responsively moves the stepper-motor in a step wise manner to displace the servo-regulator diaphragm and thereby regulates the rate of fuel flow through the valve.

Claims

1. A stepper-motor regulated gas valve control, comprising:

an inlet, an outlet, and a flow path therebetween;

a main diaphragm chamber;

a main diaphragm coupled to a valve and configured to displace the valve relative to a valve opening in response to changes in pressure in the main diaphragm chamber;

a servo-regulator diaphragm configured to regulate fluid flow to the main diaphragm chamber, to control a rate of fuel flow through the valve opening, the servo-regulator diaphragm being fluidly disconnected from the outlet when the valve is closed;

a stepper motor coupled to the servo-regulator diaphragm and configured to move in a stepwise manner to displace the servo-regulator diaphragm to selectively block fluid flow into the main diaphragm chamber; and

a control circuit coupled to the stepper motor, the control circuit configured to receive an input control signal having a current between 0 and 180 milliamps, the control signal indicative of a requested fuel flow, the control circuit configured to convert the input control signal to a reference value having a voltage between 0 and 5 volts, the control circuit configured to determine a motor step value that corresponds to the converted reference value, and the control circuit configured to energize the stepper motor according to the determined motor step value, to thereby regulate the rate of fuel flow through the valve opening.

2. The stepper-motor regulated gas valve control of claim 1, wherein the control circuit includes a look-up table, which includes a set of motor step values that correspond to a number of reference values, wherein the control circuit is configured to select the motor step value from the look up table that corresponds to the converted reference value.

3. The stepper-motor regulated gas valve control of claim 2, wherein the set of motor step values correspond to a plurality of positions of the stepper motor, said plurality of positions ranging from a closed no-flow position to a full capacity position.

4. A heating system comprising the stepper-motor regulated gas valve control of claim 1 and a system controller that employs the control circuit for controlling the operation of the stepper-motor regulated gas valve control.

5. The heating system of claim 4, wherein the system controller is selectively configurable to control the movement of the stepper motor to provide an opening characteristic that is a function of the valve'"'"'s outlet pressure over time.

6. The heating system of claim 5, wherein the system controller is selectively configured such that each time the stepper-motor regulated gas valve is opened, the system controller incrementally moves the stepper motor to provide an initial low pressure supply of fuel and within an interval thereafter moves the stepper motor to provide an increased higher pressure supply of fuel, to thereby provide a step-opening characteristic.

7. The heating system of claim 5, wherein the system controller is selectively configured such that each time the stepper-motor regulated gas valve is opened, the system controller gradually moves the stepper motor from a closed no-flow position to a full-capacity supply of fuel flow over a minimum time interval of at least three seconds, to thereby provide a slow-opening characteristic.

8. The heating system of claim 5, wherein the system controller is selectively configured such that each time the stepper-motor regulated gas valve is opened, the system controller moves the stepper motor from a closed no-flow position to a full-capacity supply of fuel flow in less than a three second time interval, to thereby provide a fast-opening characteristic.

9. The heating system of claim 5, where the system controller is selectively configurable by a dip switch having a setting for at least one of a step-opening characteristic, a slow-opening characteristic, and a fast-opening characteristic.

10. The stepper-motor regulated gas valve control of claim 3, wherein said control circuit is disposed on the stepper-motor regulated gas valve.

20. The stepper-motor regulated gas valve control of claim 1, wherein the stepper motor is configured to move in a stepwise manner to displace the servo-regulator diaphragm to selectively block all fluid flow into the main diaphragm chamber.

21. The stepper-motor regulated gas valve control of claim 1, wherein the motor step value further corresponds to a valve outlet pressure in a first range of about 0.50 inches H₂O to about 4.0 inches H₂O for natural gas and a second range of about 5.0 inches H₂O to about 11.0 inches H₂O for liquid propane gas.

22. The stepper-motor regulated gas valve control of claim 1, wherein:

the stepper-motor regulated gas control valve is configured to be selectively operable with first and second different types of fuel sources; and

the control circuit is configured to determine the motor step value based on the type of fuel source, whereby the motor step value for the first type of fuel source is different than the motor step value of the second type of fuel source to account for differences in fuel densities and/or pressures.

23. The stepper-motor regulated gas valve control of claim 1, wherein the stepper-motor regulated gas control valve is configured to provide for adjustment of valve outlet pressure to set the valve for different altitudes.

11. A fuel-fired heating system comprising:

a burner for receiving a supply of fuel flow for combustion in a fuel-fired heating apparatus;

a furnace control for communicating a requested fuel flow;

a stepper-motor regulated gas valve control for supplying fuel flow to the burner;

the stepper-motor regulated gas valve control including;

an inlet, an outlet, and a flow path therebetween;

a main diaphragm chamber;

a main diaphragm in the main diaphragm chamber that controllably displaces a valve relative to a valve opening in response to changes in pressure in the main diaphragm chamber, to thereby permit adjustment of the flow of fuel through the valve opening;

a servo-regulator diaphragm configured to selectively block fluid flow into the main diaphragm chamber to thereby control the rate of fuel flow through the valve opening, the servo-regulator diaphragm being fluidly disconnected from the outlet when the valve is closed;

a stepper motor coupled to the servo-regulator diaphragm and configured to move in a stepwise manner to displace the servo-regulator diaphragm for regulating fluid flow to the main diaphragm chamber, to thereby regulate the rate of fuel flow through the valve opening; and

a system controller coupled to the stepper motor and the furnace control, the system controller configured to receive an input control having a current between 0 and 180 milliamps from the furnace control, the input control signal indicative of the requested fuel flow through the valve, the system controller configured to control the movement of the stepper motor, based on the input control signal, to provide an opening characteristic of the valve that is a function of the valve'"'"'s outlet pressure over time.

12. The fuel-fired heating system of claim 11, wherein the system controller is selectively configured such that each time the stepper-motor regulated gas valve is opened the system controller incrementally moves the stepper motor to provide an initial low pressure supply of fuel and within an interval thereafter move the stepper motor to provide an increased higher pressure supply of fuel, to thereby provide a step-opening characteristic.

13. The fuel-fired heating system of claim 11, wherein the system controller is selectively configured such that each time the stepper-motor regulated gas valve is opened the system controller gradually moves the stepper motor from a closed no-flow position to a full-capacity supply of fuel flow over a minimum time interval of at least three seconds, to thereby provide a slow-opening characteristic.

14. The fuel-fired heating system of claim 11, wherein the system controller is selectively configured such that each time the stepper-motor regulated gas valve is opened the system controller moves the stepper motor from a closed no-flow position to a full-capacity supply of fuel flow in less than a three second time interval, to thereby provide a fast-opening characteristic.

15. A method for controlling fluid flow through a stepper-motor gas valve of a heating system, the stepper-motor gas valve including a main diaphragm chamber, a main diaphragm coupled to a valve and configured to displace the valve relative to a valve opening in response to changes in pressure in the main diaphragm chamber, a servo-regulator diaphragm configured to regulate fluid flow to the main diaphragm chamber and to be fluidly disconnected from an outlet of the gas valve when the valve is closed, and a stepper motor coupled to the servo-regulator diaphragm, the method comprising:

receiving an input control signal from a furnace control of the heating system, the input control signal having a current in the range between 0 and 180 milliamps, the input control signal indicative of a requested fluid flow;

converting the input control signal to a reference value between 0 and 5 volts, the reference value representative of the input control signal;

determining a motor step value based on the reference value and a type of the fluid source coupled to the valve; and

based on the motor step value, causing the stepper motor to displace the servo-regulator diaphragm to selectively block fluid flow into the main diaphragm chamber, to thereby provide the requested fluid flow through the stepper-motor gas valve.

16. The method of claim 15, wherein determining the motor step value includes selecting the motor step value from a plurality of motor step values, the plurality of motor step values including a first motor step value associated with a closed no-flow position and a second motor step value associated with a full capacity position.

17. The method of claim 15, wherein determining the motor step value is further based on a fuel source.

18. The method of claim 15, wherein:

determining the motor step value includes selecting the motor step value from a plurality of motor step values, the plurality of motor step values including a first motor step value associated with a closed no-flow position and a second motor step value associated with a full capacity position; and

the method includes causing the stepper motor to displace the servo-regulator diaphragm in a closed position in which the servo-regulator blocks fluid flow to the main diaphragm chamber when the first motor step value associated with the closed no-flow position is selected.

19. The method of claim 15, wherein the method includes:

gradually moving the stepper motor from a closed no-flow position to a full-capacity supply of fuel flow over a minimum time interval of at least three seconds, to thereby provide a slow-opening characteristic; and

/or

moving the stepper motor from a closed no-flow position to a full-capacity supply of fuel flow in less than a three second time interval, to thereby provide a fast-opening characteristic.

24. The method of claim 15, wherein determining a motor step value based on the reference value and a type of the fluid source coupled to the valve comprises determining a motor step value that corresponds to a valve outlet pressure in a first range of about 0.50 inches H₂O to about 4.0 inches H₂O for a first type of fluid from the fluid source and a second range of about 5.0 inches H₂O to about 11.0 inches H₂O for a second type of fluid from the fluid source.