Motor module, motor controller, temperature inferring device, and temperature inference method

A motor controller that controls an electric motor including a rotor and a stator that includes a plurality of windings, the motor controller comprising:

• a temperature inferring circuit that repeats processing to infer an electric resistance and a temperature of the plurality of windings;
• wherein
• the motor controller controls a rotation of the rotor by applying a voltage to the plurality of windings;
• the processing repeated by the temperature inferring circuit includes:
• calculating a tentative electric resistance of the plurality of windings according to an equation that defines a relationship between an electric resistance and a group of parameters that include a voltage, a current, and a rotor speed, the parameters being used to control the rotation of the rotor;
• calculating a resistance difference between the tentative electric resistance and an electric resistance inferred last time;
• inferring the electric resistance by adding an integrated value of calculated resistance differences to an initial value of the inferred electric resistance, a resistance difference, which is one of the calculated resistance differences, being excluded from the integrated value if the resistance difference exceeds a threshold;
• and
• inferring the temperature of the plurality of windings according to the inferred electric resistance.

A temperature inferring unit used in a motor controller that controls an electric motor including a rotor and a stator that includes a plurality of windings;

• the motor controller controls a rotation of the rotor by applying a voltage to the plurality of windings;
• the temperature inferring unit repeats processing to infer an electric resistance and a temperature of the plurality of windings;
• and
• the processing repeated by the temperature inferring unit includes:
• calculating a tentative electric resistance of the plurality of windings according to an equation that defines a relationship between an electric resistance and a group of parameters that include a voltage, a current, and a rotor speed, the parameters being used to control the rotation of the rotor;
• calculating a resistance difference between the tentative electric resistance and an electric resistance inferred last time;
• inferring the electric resistance by adding an integrated value of calculated resistance differences to an initial value of the inferred electric resistance, a resistance difference, which is one of the calculated resistance differences, being excluded from the integrated value if the resistance difference exceeds a threshold;
• and
• inferring the temperature of the plurality of windings according to the inferred electric resistance.

A method of inferring a temperature of a plurality of windings in a stator of an electric motor, the method comprising:

• repeating processing to infer an electric resistance and a temperature of the plurality of windings;
• wherein
• the processing includes:
• calculating a tentative electric resistance of the plurality of windings according to an equation that defines a relationship between an electric resistance and a group of parameters that include a voltage, a current, and a rotor speed, the parameters being used to control the rotation of the rotor;
• calculating a resistance difference between the tentative electric resistance and an electric resistance inferred last time;
• inferring the electric resistance by adding an integrated value of calculated resistance differences to an initial value of the inferred electric resistance, a resistance difference, which is one of the calculated resistance differences, being excluded from the integrated value if the resistance difference exceeds a threshold;
• and
• inferring the temperature of the plurality of windings according to the inferred electric resistance.

A motor module comprising:

• an electric motor including a rotor and a stator, the stator including a plurality of windings;
• a current sensor to monitor currents, each of which flows in one of the plurality of windings;
• a rotor angle inferring circuit to create a rotor position signal that indicates an angular position of the rotor;
• and
• a motor control circuit connected to the electric motor to control a rotation of the rotor by applying a voltage to the plurality of windings;
• wherein
• the motor control circuit includes a temperature inferring circuit that repeats processing to infer an electric resistance and a temperature of the plurality of windings;
• and
• the processing repeated by the temperature inferring circuit includes:
• calculating a tentative electric resistance of the plurality of windings according to an equation that defines a relationship between an electric resistance and a group of parameters that include a voltage, a current, and a rotor speed, the parameters being used to control the rotation of the rotor;
• calculating a resistance difference between the tentative electric resistance and an electric resistance inferred last time;
• detecting a change in a load state according to the group of parameters;
• inferring the electric resistance by adding an integrated value of calculated resistance differences to an initial value of the inferred electric resistance, a resistance difference, which is one of the calculated resistance differences, being excluded from the integrated value if the resistance difference is calculated when a change in the load state is detected;
• and
• inferring the temperature of the plurality of windings according to the inferred electric resistance.

A motor controller that controls an electric motor including a rotor and a stator that includes a plurality of windings, the motor controller comprising:

• a temperature inferring circuit that repeats processing to infer an electric resistance and a temperature of the plurality of windings;
• wherein
• the motor controller controls a rotation of the rotor by applying a voltage to the plurality of windings;
• and
• the processing repeated by the temperature inferring circuit includes:
• calculating a tentative electric resistance of the plurality of windings according to an equation that defines a relationship between an electric resistance and a group of parameters that include a voltage, a current, and a rotor speed, the parameters being used to control the rotation of the rotor;
• calculating a resistance difference between the tentative electric resistance and an electric resistance inferred last time;
• detecting a change in a load state according to the group of parameters;
• inferring the electric resistance by adding an integrated value of calculated resistance differences to an initial value of the inferred electric resistance, a resistance difference, which is one of the calculated resistance differences, being excluded from the integrated value if the resistance difference is calculated when a change in the load state is detected;
• and
• inferring the temperature of the plurality of windings according to the inferred electric resistance.

A temperature inferring unit used in a motor controller that controls an electric motor including a rotor and a stator that includes a plurality of windings, the motor controller comprising:

• a temperature inferring circuit that repeats processing to infer an electric resistance and a temperature of the plurality of windings;
• wherein
• the motor controller controls a rotation of the rotor by applying a voltage to the plurality of windings;
• and
• the processing repeated by the temperature inferring circuit includes:
• calculating a tentative electric resistance of the plurality of windings according to an equation that defines a relationship between an electric resistance and a group of parameters that include a voltage, a current, and a rotor speed, the parameters being used to control the rotation of the rotor;
• calculating a resistance difference between the tentative electric resistance and an electric resistance inferred last time;
• detecting a change in a load state according to the group of parameters;
• inferring the electric resistance by adding an integrated value of calculated resistance differences to an initial value of the inferred electric resistance, a resistance difference, which is one of the calculated resistance differences, being excluded from the integrated value if the resistance difference is calculated when a change in the load state is detected, and
• a step of inferring the temperature of the plurality of windings according to the inferred electric resistance.

A method of inferring a temperature of a plurality of windings in a stator of an electric motor, the method comprising:

• repeating processing to infer an electric resistance and a temperature of the plurality of windings including:
• calculating a tentative electric resistance of the plurality of windings according to an equation that stipulates a relationship between an electric resistance and a group of parameters that include a voltage, a current, and a rotor speed, the parameters being used to control the rotation of the rotor;
• calculating a resistance difference between the tentative electric resistance and an electric resistance inferred last time;
• detecting a change in a load state according to the group of parameters;
• inferring the electric resistance by adding an integrated value of calculated resistance differences to an initial value of the inferred electric resistance, a resistance difference, which is one of the calculated resistance differences, being excluded from the integrated value if the resistance difference is calculated when a change in the load state is detected;
• and
• inferring the temperature of the plurality of windings according to the inferred electric resistance.