Refrigeration – With indicator or tester – Operatively correlated with automatic control
Reexamination Certificate
2001-04-19
2002-04-09
Tanner, Harry B. (Department: 3744)
Refrigeration
With indicator or tester
Operatively correlated with automatic control
C062S210000, C062S217000
Reexamination Certificate
active
06367269
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to transport temperature control units, and more particularly to monitoring the operation of transport temperature control units.
BACKGROUND OF THE INVENTION
Straight trucks and tractor-trailers (hereinafter referred to as “vehicles”) frequently transport cargo that must be maintained at a predetermined temperature during transportation in order to preserve the quality of the cargo. Vehicles that transport such temperature-sensitive cargo have a conditioned space that is maintained at a predetermined temperature by a temperature control unit. The operation of the temperature control unit is monitored and controlled by an electronic controller.
SUMMARY OF THE INVENTION
One component of the temperature control unit is a compressor that raises the pressure of the refrigerant circulating through the temperature control unit. The mechanical throttling valve used to meter the refrigerant available to the suction end of the compressor has been replaced by an electronic throttling valve (ETV). The ETV provides a significant increase in system capacity, horsepower control, and temperature control because it can be adjusted between the fully opened position and the fully closed position with a large number of small, incremental steps. The mechanical throttling valve, on the other hand, has only a limited number of fixed positions between open and closed, and therefore does not offer the precision control available from the ETV.
The ETV is preferably controlled based on the system horsepower. For example, the ETV can be controlled based on the pressure ratio observed between the suction end of the compressor and the discharge end of the compressor. Pressure transducers at the suction end and the discharge end provide pressure data that is used by the controller to control the positioning of the ETV. If the pressure data from both the suction end and the discharge end is not available, the ETV can be controlled in other ways. For example, the ETV can be controlled based solely on suction pressure, solely on discharge pressure, or even as a function of the temperature differential across the evaporator. While these alternative control methods may not be as accurate as the preferred pressure ratio method, they are still preferable to shutting down the system until the pressure transducers can be replaced.
The present invention provides a method of monitoring the operation of the features used to control the ETV. The system analyzes whether the pressure transducers are functioning properly and, if not, switches control of the ETV to an alternative control method. These alternative control methods keep the temperature control unit running and minimize the occurrence of preventative shutdowns.
The system also monitors the functionality of the ETV itself to make sure the ETV is moving properly between the variable open and closed positions. If the system determines the ETV is stuck or otherwise non-responsive to the commands of the controller, the system determines whether the temperature control unit can still operate under these conditions or whether shutdown is needed.
Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings.
REFERENCES:
patent: 3794789 (1974-02-01), Bynum
patent: 3982664 (1976-09-01), Robbins et al.
patent: 4432210 (1984-02-01), Saito
patent: 4535598 (1985-08-01), Mount
patent: 4590576 (1986-05-01), Elpiner
patent: 4694390 (1987-09-01), Lee
patent: 4831866 (1989-05-01), Forkert et al.
patent: 4861231 (1989-08-01), Howard
patent: 4879901 (1989-11-01), Leon
patent: 4936105 (1990-06-01), Takechi et al.
patent: 4938663 (1990-07-01), Mitsuhashi et al.
patent: 4990057 (1991-02-01), Rollins
patent: 5006997 (1991-04-01), Reich
patent: 5115643 (1992-05-01), Hayata et al.
patent: 5123252 (1992-06-01), Hanson
patent: 5272647 (1993-12-01), Hayes
patent: 5658131 (1997-08-01), Aoki et al.
patent: 5664937 (1997-09-01), Takahashi et al.
patent: 5725358 (1998-03-01), Bert et al.
Hanson Jay Lowell
Helgeson Steven Bruce
Michael & Best & Friedrich LLP
Tanner Harry B.
Thermo King Corporation
LandOfFree
Electronic throttling valve diagnosis and preventative... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electronic throttling valve diagnosis and preventative..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electronic throttling valve diagnosis and preventative... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2896084