Heating systems – Automatic control – Heat source is a reverse cycle refrigerating system or heat...
Patent
1996-06-28
1998-08-04
Bennett, Henry A.
Heating systems
Automatic control
Heat source is a reverse cycle refrigerating system or heat...
237 123C, 236 78D, 236 21B, G05D 2300
Patent
active
057881480
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention pertains to a vehicle heater, with a combustion air blower and a fuel feed device, which feed combustion air and fuel to a burner, which generates a flame in a flame tube. A heat exchanger is included, which is separated by a gas jacket from the space accommodating the flame tube, and through which a heat carrier, e.g., water, is pumped. A heat carrier temperature sensor, measures the temperature of the heat carrier. A control device, controls the operation of the vehicle heater as a function of at least the measured heat carrier temperature and which an overheating monitoring device, which responds to a imminent overheating at the heat exchanger in order to stop the operation of the device by blocking the fuel feed or by other countermeasures.
BACKGROUND OF THE INVENTION
Such vehicle heaters, which are frequently also called auxiliary heaters, are used in passenger cars, trucks, buses, motor coaches, small airplanes, recreational vehicles, construction equipment, or the like. Gasoline or diesel fuel, which is taken from the fuel reserve of the vehicle or from an auxiliary tank, is used as the fuel. Water is usually used as the heat carrier and it is pumped by a water pump through the heat exchanger and a heating circuit in order to supply thermal energy to one or more radiators (vehicle heat exchangers). Air may also be used as the heat carrier.
The heat carrier temperature sensor is used in these vehicle heaters as the transducer to determine the actual temperature of the heat carrier, which is compared with a desired temperature in the control device to control the operation of the vehicle heater. The control device, which is usually equipped with a microprocessor, adjusts the heat carrier temperature to a constant value by switching the burner on and off. This is done by switching on and off the fuel feed device, which is usually designed as a fuel feed pump, and the combustion air blower, and/or by controlling the fuel feed pump such that a certain burner output is reached.
For safety reasons, these vehicle heaters have an overheating monitoring device, which operates as a function of the temperature at the heat exchanger.
A vehicle heater, in which the control device contains a microprocessor, which also stores parameters and threshold values for the control, besides a control program, has been known from DE 30 31 410. The overheating monitoring device is designed to such that the microprocessor receives a signal from an overheating sensor to compares that signal with an overheating threshold value. Where the overheating sensor is arranged and how it is designed are not stated in the document.
It used to be common practice to design the overheating monitoring device as a switch or as a fuse. The fuse or the switch responds to an increased heat exchanger temperature in the area of the rear end of the flame tube in order to interrupt the circuit of the fuel feed pump, if necessary. The fact that the fuse must be replaced if necessary or the switch must be reset can be considered to be drawbacks of such monitoring devices. This is laborious. These drawbacks are avoided by the above-described measure, according to which a sensor is provided, to compare its output signal with a threshold value.
If a vehicle heater is installed in a motor vehicle, e.g., a passenger car, the device is integrated within the cooling/heating water circuit of the vehicle. A bypass line is led to the vehicle heater in order to guarantee the circulation of the heat carrier in the heat exchanger of the vehicle heater when the vehicle heat exchanger (radiator) is switched off, i.e., when no heat is absorbed. The water inlet temperature now nearly corresponds to the water outlet temperature at the vehicle heater. When the burner is in operation, this temperature increases relatively rapidly, so that the heater is switched off when a threshold value, established for the controlled operation, is exceeded shortly thereafter.
If the bypass line is to be abandoned for cost reasons, the hea
Burner Erwin
Epple Jurgen
Humburg Michael
Koch Johannes
Bennett Henry A.
Boles Derek S.
J. Eberspacher GmbH & Co.
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