Voltage control using engine speed

Details Voltage control using engine speed Voltage control using engine speed

1999-03-26

2001-05-08

Tanner, Harry B. (Department: 3744)

Refrigeration

Automatic control

Refrigeration producer

C062S323300, C062S228400

Reexamination Certificate

active

06226998

ABSTRACT:

FIELD OF THE INVENTION
The field of the present invention relates to control systems for transport refrigeration systems. More specifically, the present invention is directed towards monitoring the generator current of a transport refrigeration system and, using a function derived from previous testing of operating conditions versus voltage, forcing the unit into low speed whenever high generator voltage conditions are predicted to occur.
DESCRIPTION OF THE PRIOR ART
A transport refrigeration system used to control enclosed areas, such as the box used on trucks, trailers, containers, or similar intermodal units, functions by absorbing heat from the enclosed area and releasing heat outside of the box into the environment. To accomplish this, a typical transport refrigeration unit requires a highly pressurized refrigerant is introduced into a low pressure environment such as an evaporator coil. The refrigerant is pressurized by flowing through a compressor, which can be powered by a generator run off of a diesel engine.
Refrigeration systems, including particularly refrigeration transport systems, require operation under a wide variety of ambient temperatures and operating loads. Excessive voltage generated by certain operating conditions is believed to be a significant factor in causing component failures on the transport refrigeration system. Currently available transport refrigeration systems include a speed solenoid for dropping or limiting engine speed to a preselected maximum rate. Unfortunately, the engine speed control systems that applicant is currently aware of involved manual selected activation of the speed solenoid or similar engine speed control.
The applicants have found that, in order to operate under acceptable voltage conditions, it is desirable to automatically monitor and control the voltage conditions of the system based upon the engine speed, generator temperature and current draw of the system.
SUMMARY OF THE INVENTION
The control method and process of this invention provides a refrigeration unit for a transport system having a controller for predicting and preventing high voltage conditions on the unit. The system includes sensors for monitoring engine speed, current draw and generator temperature (which reflects the ambient load). The data received from these sensors is loaded into the system controller, which utilizes a map, or more preferably an algorithm to predict voltage based upon those variable. If the algorithm or map predicts a voltage above preselected acceptable voltage levels programmed into the controller, then the system will drop the engine into low speed. Most preferably, this function would be accomplished by a digital signal generated by the controller to de-energize the speed solenoid connected to the engine, thus limiting engine speed.
Accordingly, one object of the present invention is to provide a microprocessor control for the regulation of transport refrigeration unit voltage levels.
It is another object of the present invention to provide a method or process for limiting or eliminating transport refrigeration unit component failure rates by automatically controlling voltage limits on the unit.
These and other objects, features, and advantages of the present invention will become more apparent in light of the following detailed description of a best mode embodiment thereof, and as illustrated in the accompanying drawings.


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