High frequency induction and method with temperature control

• US 5,477,035 A
• Filed: 04/08/1994
• Issued: 12/19/1995
• Est. Priority Date: 04/09/1993
• Status: Expired due to Term

• Current Assignee: Denki Kogyo Company Limited, Fuji Heavy Industries Limited (Subaru Corp.)
• Original Assignee: Denki Kogyo Company Limited, Fuji Heavy Industries Limited (Subaru Corp.)
• Inventors: Matsumoto, Isao, Kimura, Fumitoshi, Fusato, Tetsuo, Matsui, Fujio
• Primary Examiner(s): Leung, Philip H.
• Application Number:
  US08/225,154
• Time in Patent Office: 620 Days
• Field of Search: 219/666, 219/667, 219/665, 219/635, 219/663, 60/272, 60/286, 60/303
• US Class Current: 219/635
• CPC Class Codes: F01N 3/2013 using electric or magnetic heating means
• CPC Class Codes: F01N 9/00 Electrical control of exhaust gas treating apparatus monitoring or diagnostic devices for exhaust-gas treatment apparatus F01N11/00; conjoint electrical control of two or more combustion engine functions F02D43/00
• CPC Class Codes: G01K 7/38 the variations of temperature influencing the magnetic permeability
• CPC Class Codes: H05B 2213/07 Heating plates with temperature control means
• CPC Class Codes: H05B 6/06 Control, e.g. of temperature, of power
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A resonance circuit including a high frequency induction heating coil is set to a resonance state and a heating temperature of an object to be heated (for example, catalytic converter or the like) is controlled on the basis of a resonance frequency varied with an increased temperature of the object under the resonance state.

Claims

1. A high frequency induction method with temperature control using a high frequency induction coil and a high frequency power source directly connected to said coil via a condenser for supplying an alternating current with high frequency, comprising the steps of:

(a) starting high frequency induction for heating a workpiece by supplying high frequency electricity, from said high frequency power source, to a series resonance circuit including said high frequency induction coil for heating said workpiece by high frequency induction heating, and said condenser;

(b) unifying the phases of a high frequency voltage and current output respectively from said high frequency power source, thereby maintaining said resonance circuit in a resonance state at a resonance frequency corresponding to the temperature of said workpiece; and

(c) controlling the temperature of said workpiece on the basis of a resonance frequency, said resonance frequency varying with the increase in the temperature of said workpiece in said resonance state.

2. A heating temperature control method in high frequency induction heating, according to claim 1, wherein said workpiece is a catalytic converter for purifying exhaust gas of an automobile.

3. A high frequency induction heating temperature control apparatus comprising:

(a) a high frequency power supply unit;

(b) a resonance circuit including a series circuit of a high frequency induction heating coil for high frequency induction heating an object to be heated and a condenser to be supplied with high frequency electric power from said high frequency power supply unit;

(c) a phase control circuit for controlling the power supply frequency of said high frequency power supply unit so that a phase of a high frequency voltage produced by said high frequency power supply unit is substantially coincident with a phase of a high frequency current flowing through said high frequency induction heating coil to always set said resonance circuit to a resonance state; and

(d) a flag signal generating circuit for detecting that the power supply frequency of said high frequency power supply unit reaches a predetermined frequency to generate a predetermined flag signal;

whereby said object is high frequency induction heated continuously while said resonance circuit is always set to the resonance state by said control circuit in response to variation of an impedance of said high frequency induction heating coil due to increased temperature of said object and the supply of electric power to said resonance circuit from said high frequency power supply is cut off on the basis of said flag signal generated by said flag signal generating circuit when a resonance frequency of said resonance circuit reaches a predetermined frequency.