The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Nov. 12, 1996
Filed:
May. 25, 1995
Robert L Harrington, Eden Prairie, MN (US);
Alan D Gustafson, Eden Prairie, MN (US);
Thermo King Corporation, Minneapolis, MN (US);
Abstract
A method of controlling refrigerant pressure during elevated ambient temperature conditions in a refrigeration unit having a refrigerant compressor driven by a prime mover, and controllable suction line modulation. The method includes the steps of detecting the actual load PML on the prime mover, sensing the ambient temperature AA, and providing a dynamic load limit DLL as a function of the ambient temperature AA. The actual load PML is compared with the dynamic load limit DLL, and the suction line modulation is changed as a function of the comparison step to cause the actual load PML to follow the changing dynamic load limit DLL. The invention also includes a method of preventing excessive on-off cycling of a refrigeration unit during low ambient temperature conditions, with the refrigeration unit operating in a cycling start-stop mode to control the temperature of a conditioned space to a selected set point temperature SP. The latter method includes the steps of sensing the ambient temperature AA, and comparing the ambient temperature AA with the set point temperature SP. The on-off cycling rate of the refrigeration unit is determined when the comparison step finds the ambient temperature AA has a predetermined relationship with the set point temperature SP. A cycling rate upper limit is provided and compared with the actual on-off cycling rate. The suction line modulation is increased when the comparison step finds the cycling rate has reached the cycling rate upper limit.