Microcomputer control for an inverter-driven heat pump

• US 4,257,238 A
• Filed: 09/28/1979
• Issued: 03/24/1981
• Est. Priority Date: 09/28/1979
• Status: Expired due to Term

• Current Assignee: York International Corporation (Johnson Controls International plc)
• Original Assignee: BorgWarner Incorporated
• Inventors: Cooper, Kenneth W., Abendschein, Frederic H., Kountz, Kenneth J., Sumner, Lee E. Jr.
• Primary Examiner(s): Wayner, William E.
• Assistant Examiner(s): Tanner, Harry
• Application Number:
  US06/080,363
• Time in Patent Office: 543 Days
• Field of Search: 62/180, 62/176 B, 62/228 B, 62/229, 62/176 E
• US Class Current: 62/176.3
• CPC Class Codes: F24F 11/30 for purposes related to the operation of the system, e.g. for safety or monitoring
• CPC Class Codes: F24F 11/67 Switching between heating and cooling modes
• CPC Class Codes: F24F 11/80 for controlling the temperature of the supplied air
• CPC Class Codes: F24F 11/81 by controlling the air supply to heat-exchangers or bypass channels
• CPC Class Codes: F24F 11/86 by controlling compressors within refrigeration or heat pump circuits
• CPC Class Codes: F24F 2110/10 Temperature
• CPC Class Codes: F24F 2110/20 Humidity
• CPC Class Codes: F25B 2600/021 Inverters therefor
• CPC Class Codes: F25B 2600/11 Fan speed control
• CPC Class Codes: F25B 49/02 for compression type machines, plants or systems
• CPC Class Codes: G05D 23/1917 using digital means
• CPC Class Codes: G05D 23/24 the sensing element having a resistance varying with temperature, e.g. a thermistor
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

An apparatus and method for controlling continuously and discretely the speed of an indoor evaporator fan motor and the speed of the compressor as a function of the fan speed for regulating the dry bulb temperature and relative humidity of a conditioned space includes a programmed control device which produces a first signal for driving a fan inverter connected to the evaporator fan motor. A second signal, which is a function of the first signal, is also provided by the control device to drive a compressor inverter coupled to the compressor. A microprocessor having a program is operatively connected to the programmed control device for controlling its operation to effect the measured temperature of the conditioned space.

Claims

1. A refrigeration system for conditioning a space and having a closed refrigerant circuit including a compressor, a condenser, an expansion device, and an evaporator connected respectively in series, said system comprising:

first sensing means for measuring the actual temperature of a space to be conditioned and generating an electrical signal representative of the measured temperature;

means for setting a reference temperature of the space to be conditioned and generating a second electrical signal representative of the reference temperature;

second sensing means for measuring the relative humidity and generating a third electrical signal representative of the reference temperature;

evaporator fan motor for driving a fan to direct air into the conditioned space;

first motor speed control means connectable to said evaporator fan motor for controlling continuously and discretely the speed thereof;

compressor motor for driving the compressor;

second motor speed control means connectable to said compressor motor for controlling continuously and discretely the speed thereof;

programmed control means for generating a first digital signal responsive to said measured temperature and said reference temperature to drive said first motor speed control means and a second digital signal which is a function of said first digital signal and said relative humidity to drive said second motor speed control means; and

data processor means having a program coupled to said programmed control means for controlling the operation thereof to affect a measured temperature and relative humidity of the conditioned space.

2. A refrigeration system as claimed in claim 1, further comprising third sensing means for measuring the temperature of the outdoor atmosphere and generating a fourth electrical signal representative of the outdoor atmospheric temperature, and wherein said programmed control means including means responsive to said fourth signal for modifying incrementally the functional relationship of said first and second digital signals.

3. A refrigeration system as claimed in claim 2, wherein said modifying means increases gradually and incrementally the compressor speed with respect to the fan speed when more dehumidification is required as sensed by said second sensing means.

4. A refrigeration system as claimed in claim 1, wherein said programmed control means includes a first summer which compares the actual measured temperature with the reference temperature to provide an error signal.

5. A refrigeration system as claimed in claim 4, wherein said control means further includes a second summer, a proportional gain amplifier and an integrator arranged in a closed loop and being responsive to said error signal for minimizing the steady-state error between the measured temperature and the reference temperature.

6. A refrigeration system as claimed in claim 5, wherein said control means further includes a digital filter connected to said second summer to remove noise within the system.

7. A refrigeration system as claimed in claim 1, wherein said data processor means comprises a microprocessor.

8. A refrigeration system as claimed in claim 1, wherein each of said first and second sensing means comprises a thermistor.

9. A method for use in a refrigeration system for conditioning a space having a closed refrigerant circuit including a compressor, a condenser, an expansion device, and an evaporator connected respectively in series, said method comprising the steps:

sensing the actual temperature of a space to be conditioned to generate an electrical signal representative of the measured temperature;

setting a reference temperature of the space to be conditioned to generate a second electrical signal representative of the selected reference temperature;

sensing the relative humidity to generate a third electrical signal representative of the relative humidity;

providing an evaporator fan motor for driving a fan to direct air into the conditioned space;

connecting a first motor speed control device to the evaporator fan motor for controlling continuously and discretely the speed thereof;

providing a compressor motor for driving the compressor;

connecting a second motor speed control device to the compressor motor for controlling continuously and discretely the speed thereof;

generating a first digital signal in response to the measured temperature and the reference temperature to drive the first motor speed control device and a second digital signal which is a function of the first digital signal and the relative humidity to drive the second motor speed control device; and

controlling through a microprocessor having a program the step of generating the first and second digital signals to affect the measured temperature and relative humidity of the conditioned space.