Matsushita Electric Industrial Co., Ltd.

Atsushi Fujita

Yuji Fujii

Izuo Hirota

Takahiro Miyauchi

Koji Niiyama

Akira Kataoka

Kouji Niiyama

Hideki Omori

Katsuyuki Aihara

Takeshi Kitaizumi

Nobuyoshi Makio

Hirofumi Inui

Manabu Takahashi

A detector is operable to detect a displacement of a load by an ascending force based on a period of time from a time a heating output of an inverter drops from a predetermined level to a first level, to a time the heating output returns back to a second level larger than first level. Thereby, the detector distinguishes an intentional removal of the load from the displacement of the load by the ascending force. An induction heater including the detector reduces the displacement of the load by the ascending force and stops the heating of the load when the load is removed intentionally.

Induction heater with controlled current to heating coil

In an induction heating apparatus, in order to decrease the buoyancy exerted on an object to be heated which is made of a material having high electrical conductivity and low magnetic permeability, such as aluminum, an electrical conductor is provided between a heating coil and the object to be heated, thereby increasing the equivalent series resistance of the heating coil. Hence, the current of the heating coil, which is required for obtaining a desired heating output, is decreased, whereby the buoyancy of the object to be heated can be decreased. In addition, the electrical conductor is divided into two halves, and they are arranged in a circular arc form with a clearance provided therebetween and made close contact with the bottom face of a plate, whereby the temperature rise of the electrical conductor can be restricted. Furthermore, the heat of the electrical conductor is transferred and dissipated to the object to be heated, whereby the heating coil and the like are not damaged even if the electrical conductor is heated. An electrical conductor temperature sensor for detecting the temperature of the electrical conductor is provided; when the detection temperature becomes a predetermined temperature, the heating output of a drive circuit is decreased, whereby the heat generation of the electrical conductor is decreased and the heating coil and the like are not damaged by heat.

Induction heating device

An induction heater having a safety function of lowering or stopping the heating power when an object to be heated moves, the safety function hardly interfering with the cooking activities of a user is provided. The induction heater includes an inverter circuit, an output detection section for detecting the magnitude of the inverter circuit, a first movement detection section, and a storage section for storing a control value before the first movement detection section detects a movement of the object. In a reach control mode, the output of the inverter circuit is gradually increased to a target. In a stable control mode, the output of the inverter circuit is maintained at the target. When the first movement detection section detects a movement of the object, a control section shifts to a first output mode in which a control value derived from the stored control value is output.

Induction heater

When a pan made of a non-magnetic material, such as aluminum, is used for cooking while the temperature is being controlled, a notice is made to the user to the effect that the temperature control function has been stopped and that the temperature should be manually adjusted, when the material detection section detects that the pan is made of a non-magnetic material or a pan floating phenomenon has occurred, in order to prevent abnormal increase in the temperature of the pan due to incorrect temperature detection caused by the pan floating phenomenon, a set temperature is lowered.

Induction heating apparatus

An induction heating device prevents an object to be heated from being displaced and buoyed from a mounting surface due to an mutual action of repulsive forces between the object to be heated and an induction heating coil. The induction heating device includes a source-current detector for detecting a source current input to a high-frequency inverter including the induction heating coil and an inverter circuit, a source-current change detector for measuring a change against time of a magnitude of the source current to detect a displacement and buoying of the object to be heated, such as a cooking pot, and a change examining unit. The controller controls an output of the high-frequency inverter in response to a detection result of the change examining unit. The induction heating device prevents the cooking pot from being displaced and buoyed even if the pot is not touched by a user at startup of heating or during the heating operation, and is inexpensive and safe.

An induction heating apparatus can heat aluminum pot etc. with pot vibration noise being suppressed. During a turn-on time of second switching device , an energy is accumulated at choke coil , and at the same time a resonant current with a shorter period than the turn-on time of second switching device or a driving time of first switching device is generated at heating coil , so that during turn-off of second switching device , i.e., during on-time of first switching device , the energy accumulated at choke coil is transferred to second smoothing capacitor . And then the output power is supplied from smoothing capacitor to heating coil , thereby reducing the pot vibration noise, which is caused by pulsating current of input voltage.

Growing community of inventors

Minoo, Japan

Atsushi Fujita