Temperature regulating system for air conditioning or heating plants, preferably in railway vehicles

• US 4,379,520 A
• Filed: 08/05/1981
• Issued: 04/12/1983
• Est. Priority Date: 08/06/1980
• Status: Expired due to Fees

• Current Assignee: Alex Friedmann KG
• Original Assignee: Alex Friedmann KG
• Inventors: Tomsu, Peter
• Primary Examiner(s): Wayner, William E.
• Application Number:
  US06/290,211
• Time in Patent Office: 615 Days
• Field of Search: 73/362 AR, 364/557, 364/556, 236/94, 236/49, 165/11 R, 374/170, 374/184
• US Class Current: 236/49.3
• CPC Class Codes: B60H 1/00735 Control systems or circuits characterised by their input, i.e. by the detection, measurement or calculation of particular conditions, e.g. signal treatment, dynamic models
• CPC Class Codes: B61D 27/0018 Air-conditioning means, i.e. combining at least two of the following ways of treating or supplying air, namely heating, cooling or ventilating air-conditioning in general F24F
• CPC Class Codes: G05D 23/1917 using digital means
• CPC Class Codes: G05D 23/20 with sensing elements having variation of electric or magnetic properties with change of temperature G05D23/13 takes precedence

Abstract

In order to permit in a simple manner the use of a digital processing unit in a regulating system for an air conditioning or heating plant, each temperature sensor of a temperature-measuring device is connected to a capacitor so as to charge it with a current proportional to the measured temperature. The capacitor is connected to one input of a comparator, and a reference voltage is applied to the other input. The output of the comparator is applied to an input of a digital processing unit which, at the start of the temperature measurement, will discharge the capacitor over a predetermined period and will then, at uniform time intervals, check the output signal supplied by the comparator for change. The number of samplings from the end of capacitor discharge until the time a change in the comparator output occurs is available as a digital value corresponding to the measured temperature.

Claims

1. A temperature-regulating system for an air conditioning or heating plant which includes

a programmable digital processing unit which includes at least one input and at least one output, and

a value-measuring unit which includes at least one temperature sensor, a capacitor, a switching element, a switching means and a reference voltage-generating means, each temperature sensor being connected to a capacitor so as to charge the capacitor by a current proportional to the measured temperature, the switching element being connected to the output of the digital processing unit and to the capacitor so as to cause the capacitor to discharge at a rate determined by the digital processing unit, the switching means including an output connected to the input of the digital processing unit and two inputs, the capacitor being connected to one input of the switching means and the other input of switching means being connected to the reference voltage-generating means, the digital processing unit acting via the switching element to discharge the capacitor and also repeatedly checking the output of the switching means for a signal change, the number of such checks commencing from the beginning of measurement to a change in the signal representing digital values corresponding to the measured temperature, the switching means changing its output signal when the capacitor voltage reaches the reference voltage.

2. The temperature-regulating system as defined in claim 1 wherein the switching element is a discharging transistor, the base of which is connected via an electrical line to the output of the digital processing unit, and wherein the digital processing unit applies first a voltage "logical 1" to the discharge over a predetermined period and then a voltage "logical 0".

3. The temperature-regulating system as defined in claim 2 wherein said digital processing unit is a microprocessor.

4. The temperature-regulating system as defined in claim 2 wherein the reference voltage-generating means includes a variable resistor which acts to adjust the reference voltage supplied to the switching means and thus provides a calibration for the temperature-regulating system.

5. The temperature-regulating system as defined in claim 1 including multiple value-measuring units.

6. The temperature-regulating system as defined in claim 5 which is useful in conjunction with an air conditioning plant which supplies air to a number of rooms via a main duct and a supplementary duct, wherein the temperature-regulating system includes a fault-detecting means associated with the digital processing unit, and wherein the multiple value-measuring units of the temperature-regulating system include several external value-measuring units located outside of said rooms for determining the temperature of the air to be supplied to the rooms through the main duct and an internal value-measuring unit located inside each respective room for determining the temperature of the air to be supplied to the rooms through the supplementary duct, one of the external value-measuring units acting as an initially designated external pilot value-measuring unit for the digital processing unit and one of the internal value-measuring units acting as an initially designated internal pilot value-measuring unit for the digital processing unit, said fault-detecting means causing the microprocessor to change the external and internal value-measuring units acting as the pilot value-measuring units when the signals from the initially designated pilot value-measuring units deviate outside a predetermined tolerance range.