Patent ID: 11898982
Assignee: DENSO WAVE INCORPORATED
Field: Measurement (Instruments)
Classification: CPC G  Y | IPC G

Claim 0:
1. A liquid heater apparatus comprising:
a water tank connected to a water inlet pipe and to a water outlet pipe so that water enters the water tank via the water inlet pipe and is supplied to outside the water tank via the water outlet pipe;
a heating tube installed in the water tank and connected to an injector so that mixed gaseous matter of air and gas is supplied to the heating tube, the mixed gaseous matter being ignited and burned in the heating tube and the water within the water tank being heated by the burned mixed gaseous matter;
an A/F sensor for detecting an oxygen density within the heating tube;
a heater for heating the A/F sensor;
a detector for measuring a current of the heater;
a timer for counting a time from a beginning of heating of the heater; and
a controller for controlling an electric energy for the heater, wherein the controller:
decides whether a gradient (ΔI/Δt) of a changed current detected by the detector over a predetermined time measured by the timer is smaller than a predetermined negative number β;
calculates a required temperature, which is a temperature difference between a target temperature on which the A/F sensor activates and a temperature of the A/F sensor at a drying time tα, which is counted by the timer and which is a time length from a beginning time when the heater starts to be heated to the drying time when the gradient (ΔI/Δt) of the changed current becomes smaller than the predetermined negative number β;
calculates a remaining heating time, which is a time difference between a target heating time, which is a time from the beginning time when the heater starts to be heated to a reaching time when a temperature of the A/F sensor reaches the target temperature, and the drying time tα;
calculates a required electric energy W1 for increasing the temperature of the A/F sensor to the target temperature at the target heating time by using a gradient T1 of the required temperature over the remaining heating time; and
controls the electric energy for the heater by using the required electric energy W1.