Cooling device for an internal combustion engine and method for controlling such a cooling device

Cooling device for an internal combustion engine which comprises:

• a heat exchanger, a cooling water pump coupled to the heat exchanger, a fan disposed adjacent to the heat exchanger for conveying cooling air through the heat exchanger, an electric motor coupled to at least one of the fan and the cooling water pump, and a motor circuit connected to the electric motor for controlling the rotational speed of the electric motor, the motor circuit including an operational amplifier, a power semiconductor coupled to the electric motor and responsive to an output signal of the operational amplifier, and a sensor that detects an engine temperature condition, the sensor including at least three switching contacts which are in each case actuated when predetermined temperature thresholds are reached, wherein the switching contact for the highest predetermined temperature threshold is coupled to the electric motor and provides a bypass of the power semiconductor and the remaining switching contacts are coupled via respective electronic components to an input of the operational amplifier, the electronic components influencing an input signal applied to the input of the operational amplifier in accordance with the actuation of the switching contacts to adjust the output signal of the operational amplifier;
• wherein the power semiconductor is an N-channel metal oxide field effect transistor (MOSFET) and the operational amplifier is a voltage-controlled frequency generator;
• and
• wherein said motor circuit further comprises a switching transistor, the base of which is connected to the output of the frequency generator via two inverting switching stages, is connected between a positive pole of the voltage source and the gate of the metal oxide field effect transistor.

Cooling device for an internal combustion engine which comprises:

• a heat exchanger, a cooling water pump coupled to the heat exchanger, a fan disposed adjacent to the heat exchanger for conveying cooling air through the heat exchanger, an electric motor coupled to at least one of the fan and the cooling water pump, and a motor circuit connected to the electric motor for controlling the rotational speed of the electric motor, the motor circuit including an operational amplifier, a power semiconductor coupled to the electric motor and responsive to an output signal of the operational amplifier, and a sensor that detects an engine temperature condition, the sensor including at least three switching contacts which are in each case actuated when predetermined temperature thresholds are reached, wherein the switching contact for the highest predetermined temperature threshold is coupled to the electric motor and provides a bypass of the power semiconductor and the remaining switching contacts are coupled via respective electronic components to an input of the operational amplifier, the electronic components influencing an input signal applied to the input of the operational amplifier in accordance with the actuation of the switching contacts to adjust the output signal of the operational amplifier;
• and
• a switch connected between the electric power and a rotational speed sensor, wherein the switch opens in response to a predetermined rotational speed of the electric motor.

Cooling device for an internal combustion engine which comprises:

• a heat exchanger, a cooling water pump coupled to the heat exchanger, a fan disposed adjacent to the heat exchanger for conveying cooling air through the heat exchanger, an electric motor coupled to at least one of the fan and the cooling water pump, and a motor circuit connected to the electric motor for controlling the rotational speed of the electric motor, the motor circuit including an operational amplifier, a power semiconductor coupled to the electric motor and responsive to an output signal of the operational amplifier, and a sensor that detects an engine temperature condition, the sensor including at least three switching contacts which are in each case actuated when predetermined temperature thresholds are reached, wherein the switching contact for the highest predetermined temperature threshold is coupled to the electric motor and provides a bypass of the power semiconductor and the remaining switching contacts are coupled via respective electronic components to an input of the operational amplifier, the electronic components influencing an input signal applied to the input of the operational amplifier in accordance with the actuation of the switching contacts to adjust the output signal of the operational amplifier;
• and
• wherein said motor circuit further comprises a relay having a normally open contact provided in a line branch connected in parallel with at least two of the switching contacts, the relay being responsive to at least one of a signal which is dependent on a particular rotational speed of the internal combustion engine and a voltage level of the dynamo of the internal combustion engine.

Cooling device for an internal combustion engine which comprises:

• a heat exchanger, a cooling water pump coupled to the heat exchanger, a fan disposed adjacent to the heat exchanger for conveying cooling air through the heat exchanger, an electric motor coupled to at least one of the fan and the cooling water pump, and a motor circuit connected to the electric motor for controlling the rotational speed of the electric motor, the motor circuit including an operational amplifier, a power semiconductor coupled to the electric motor and responsive to an output signal of the operational amplifier, and a sensor that detects an engine temperature condition, the sensor including at least three switching contacts which are in each case actuated when predetermined temperature thresholds are reached, wherein the switching contact for the highest predetermined temperature threshold is coupled to the electric motor and provides a bypass of the power semiconductor and the remaining switching contacts are coupled via respective electronic components to an input of the operational amplifier, the electronic components influencing an input signal applied to the input of the operational amplifier in accordance with the actuation of the switching contacts to adjust the output signal of the operational amplifier;
• and
• wherein said motor circuit further comprises a thermistor which is connected via a voltage divider to the non-inverting input of a second operational amplifier and the output of the second operational amplifier is connected to the non-inverting input of the first operational amplifier.

A method for controlling a cooling device for an internal combustion engine, said method comprising the steps of:

• successively switching contacts of a temperature sensitive sensor of a control circuit for said cooling device when predetermined switching thresholds are reached to change an input parameter to a non-inverting input of an operational amplifier provided in said control circuit;
• driving a power semiconductor device included in said control circuit with an output of said operational amplifier in such a manner that an electric motor connected to said semiconductor device coupled to at least one of a fan and cooling water pump is operated at certain rotational speeds allocated in steps to respective ones of said switching thresholds, and
• bypassing said power semiconductor device to drive said electric motor when a last switching contact closes by connecting said electric motor directly to said last switching contact;
• and
• generating a signal for exciting a relay when an idling speed of said internal combustion engine is reached, closing a contact of said relay to influence an input signal to said operational amplifier in such a manner that said power semiconductor device is driven with a pulse sequence which corresponds to a relative turn-on period of said power semiconductor device, during which said electric motor is driven at a minimum speed.