US 5,493,867 A · Fuzzy logic adaptive defrost control

Abstract

A defrost cycle controller for modifying the total length of time a compressor operates before a defrost cycle is initiated, wherein the time the compressor is on between defrost cycles is referred to herein as a frost accumulation period. A microprocessor includes means for deenergizing the compressor and coupling the defrost heater to a power supply when a continuous compressor run time exceeds a predetermined demand defrost time. The microprocessor further includes means for determining the time required to actually defrost the evaporator during a defrost operation, referred to herein as a defrost time, and means for modifying the frost accumulation period in response to the time to complete the defrost operation. The present invention further provides a method for determining the time required to actually defrost the evaporator during a first defrost operation, referred to herein as a first defrost time, and for determining the time required to actually defrost the unit during a second defrost operation, referred to herein as a second defrost time, wherein the second defrost operation is immediately subsequent to the first defrost operation. An inference is made as to whether the frost accumulating period should be modified before initiating the next defrost operation in response to the first defrost time and the second defrost time are provided and the frost accumulating period is modified if required.

Claims12

Dependent claims

A method of controlling the defrosting of a heat transfer unit of a temperature conditioning system by initiating a defrost operation when a predetermined amount of frost has accumulated on the unit during a frost accumulating period that occurs between defrost operations, a known desired defrost time period being required to defrost said unit when it has the predetermined amount of accumulated frost thereon, said method comprising the steps:

(a) measuring the time required to actually defrost said unit during a first defrost operation, referred to herein as a first defrost time;
(b) measuring the time required to actually defrost said unit during a second defrost operation, said second defrost operation being the next defrost operation following the first defrost time, and referred to herein as a second defrost time;
and
(c) modifying said frost accumulating period in response to said first defrost time and said second defrost time.

1 more element

A defrost cycle controller for a refrigeration system, said system including a compressor, an evaporator and a defrost heater associated with the evaporator, said defrost cycle controller modifying the total length of time the compressor operates before a defrost cycle is initiated, wherein the cumulative time the compressor is energized between defrost cycles is referred to herein as a frost accumulation period, said defrost cycle controller comprising:

a relay operatively connected to mutually exclusively couple said compressor and said defrost heater to a power supply;
a first signal line providing a first signal indicative of the operating status of said compressor;
a second signal line providing a second signal indicative of the operating status of said defrost heater;
and
a microprocessor operatively coupled to said first and second signal lines and to said delay to control energization of said relay and to selectively couple said compressor and said defrost heater to said power supply, said microprocessor including:
means generating a signal for operating said relay for deenergizing said compressor and coupling said defrost heater to the power supply when a continuous compressor run time exceeds a predetermined demand defrost time,
means for measuring the time required to actually defrost said evaporator during a defrost operation, and
means for modifying said frost accumulation period in response to said time to actually defrost said evaporator during said defrost operation.

5 more elements

Dependencies are inferred from the claim text.

Fuzzy logic adaptive defrost control

Life of this patent

Fuzzy logic adaptive defrost control

Life of this patent

Abstract

Claims12