Control circuitry for multistage fans

• US 4,426,960 A
• Filed: 08/24/1982
• Issued: 01/24/1984
• Est. Priority Date: 10/09/1979
• Status: Expired due to Term

• Current Assignee: Square D Company (Schneider Electric SE)
• Original Assignee: Square D Company (Schneider Electric SE)
• Inventors: Hart, Robert E.
• Primary Examiner(s): Feinberg, Craig R.
• Assistant Examiner(s): Wolfe, W. R.
• Application Number:
  US06/411,136
• Time in Patent Office: 518 Days
• Field of Search: 123/41.15, 123/41.49, 123/41.12, 123/41.02, 123/41.11, 318/101, 318/102, 318/471
• US Class Current: 123/41.49
• CPC Class Codes: G05D 23/1912 whose output amplitude can take more than two discrete values
• CPC Class Codes: G05D 23/24 the sensing element having a resistance varying with temperature, e.g. a thermistor

Abstract

A solid-state, multistage temperature controller for automatically controlling the operation of fans to maintain the temperature of an associated engine within preselected limits.

Claims

1. A multistage temperature control circuit for maintaining engine manifold coolant at a selected temperature by selectively operating a plurality of cooling fans mounted to provide a flow of cooling air to said engine, said circuit comprising:

means to selectively energize said fans to operate to maintain the engine manifold cooling liquid below a selected temperature level;

sensing element means immersed in the manifold coolant for providing electrical signals proportional to the coolant temperature including a thermistor probe for sensing the coolant temperature, means responsive to said signals for enabling a first of said cooling fans at a predetermined temperature;

means for sequentially enabling additional fans as the coolant temperature increases including a differential circuit comprising a plurality of differential amplifiers means and a resistor bridge circuit, said thermistor providing a first input to each of said differential amplifiers, and said resistor bridge circuit providing selected level inputs as the second input to each of said differential amplifiers;

time delay circuitry for sequencing the operation of the cooling fans in accordance with a predetermined delay,

means for by-passing said time delay circuitry to selectively energize said fans sooner than said predetermined delay when the temperature cycles rapidly; and

a delay circuit connected to receive an input from a first fan, said delay circuit comprising an RC network, a logic AND gate having two inputs and input, the input from said first fan causing the RC network to charge to a high level after a first period of time delay and providing a first input to said AND gate, said thermistor providing a high logic level to said AND gate, and as the temperature rises to the energizing point of a succeeding fan, the other input to the AND gate goes high to turn ON said succeeding fan as the temperature decreases, the low logic level applied to the AND gate and said succeeding fan being turned OFF due to said first fan remaining engaged to enable said succeeding fan to be reactivated without the time delay when the temperatures again rises.

2. A multistage temperature control circuit for maintaining engine manifold coolant at a selected temperature by selectively operating in steps a plurality of cooling fans mounted to provide a flow of cooling air to the engine, the circuit comprising:

means to selectively energize the fans to operate to maintain the engine manifold coolant below a selected temperature level;

sensing element means immersed in the manifold coolant for providing electrical signals proportional to the coolant temperature;

means responsive to the signals for actuating one of the cooling fans at a first predetermined temperature;

means responsive to the signals for actuating another one of the fans at a second predetermined temperature higher than the first predetermined temperature;

time delay circuitry for sequencing the operation of the cooling fans in accordance with a predetermined delay to prevent simultaneous actuation of both of the cooling fans, the time delay circuitry including means responsive to actuation of the one cooling fan for disabling the other cooling fan actuating means for a preselected time period, the time delay circuit further including logic circuitry for presetting a minimum time period between steps and for re-energizing a fan within a shorter period than the predetermined time delay when the temperature cycles through the turn-on level of that fan, the logic circuitry including means for preventing the time delay circuitry from disabling the other cooling fan actuating means a second time again unless the one cooling fan is deactivated, and

means for bypassing the time delay circuitry to selectively energize the fans sooner than the predetermined delay when the temperature cycles rapidly.

3. A multistage temperature control circuit for maintaining engine manifold coolant at a selected temperature by selectively operating in steps a plurality of cooling fans mounted to provide a flow of cooling air to the engine, the circuit comprising:

means to selectively energize the fans to operate to maintain the engine manifold coolant below a selected temperature level;

a thermistor probe for sensing the coolant temperature;

means responsive to the signals for actuating one of the cooling fans at a first predetermined temperature;

means responsive to the signals for actuating another one of the fans at a second predetermined temperature higher than the first predetermined temperature;

time delay circuitry for sequencing the operation of the cooling fans in accordance with a predetermined delay to prevent simultaneous actuation of both of the cooling fans, the time delay circuitry including means responsive to actuation of the one cooling fan for disabling the other cooling fan actuating means for a preselected time period;

means for bypassing the time delay circuitry to selectively energize the fans sooner than the predetermined delay when the temperature cycles rapidly; and

means for testing the cooling fan actuating means including a test switch for connecting a resistor in parallel with the thermistor to simulate a temperature in excess of the second predetermined temperature, the time delay circuitry causing the cooling fans to turn on sequentially in response to actuation of the test switch.