Abstract: An induction heating device is provided. The induction heating device comprises a plurality of induction heating devices disposed at intervals along the circumference of a ring-shaped workpiece, a setting unit for setting induction heating conditions, and a switching control unit. Each of the plurality of induction heating devices comprises heating coils disposed facing areas to be heated of the workpiece, a plurality of transformers connected to the heating coils in parallel, a plurality of matching units connected to any one of the plurality of transformers, an inverter unit having a rectifier unit and an inverter unit, an inverter control unit having a rectification control unit, and a group of switches.

Abstract: An induction heating power supply apparatus includes a smoothing section to smooth pulsating current of DC power output from a DC power supply section, and an inverter to convert the DC power smoothed by the smoothing section to AC power. The smoothing section includes a pair of bus bars connected to the inverter and a capacitor connected to the pair of bus bars. Each of the bus bars has an external surface extending in a current flow direction, the external surface including a flat face having a larger surface dimension than another face of the external surface in a direction perpendicular to the current flow direction. The bus bars are arranged in a layered manner such that the flat faces of the bus bars are opposed to each other and such that an insulator is sandwiched between the flat faces of the bus bars.

Abstract: A power conversion apparatus and a power conversion method are provided. The power conversion apparatus includes a rectifier configured to convert AC power to DC power, a smoothing filter configured to control the DC power received from the rectifier to be constant, an inverter configured to convert the DC power received from the smoothing filter into high-frequency power by turning the DC power on and off using a switching device, and a control unit configured to control the rectifier and the inverter. A rating of output power from the inverter is determined in accordance with a frequency of the high-frequency power output from the inverter, a current-applying time, and an operation rate obtained by dividing the current-applying time by a sum of the current-applying time and a non-current-applying time.

Abstract: A heating coil of a heat treatment apparatus is configured to inductively heat an elongated workpiece having a recessed lateral surface. The heating coil includes a base conductor and a projected conductor. A width of the projected conductor is narrower than a width of the base conductor. The projected conductor is arranged to project toward the recess from a position of the base conductor. The base conductor and the projected conductor are arranged to extend in a longitudinal direction of the workpiece. A heat treatment apparatus includes a cooling section and the heating coil. A heat treatment method uses the heating coil described above.

Abstract: An induction heating device and an induction heating method are provided. The entire areas to be heated of the workpiece can be uniformly heated to a predetermined high temperature, and uniform heating is possible even when the workpiece deforms in a non-uniform manner during heating. When areas to be heated are established on a workpiece so as to extend in one direction and the areas to be heated are induction-heated, the deformation amount on one edge of the areas to be heated is different from that on the other. This induction heating device includes; heating coils facing a portion of the areas to be heated when the workpiece is induction-heated; and a relative transfer means for transferring the workpiece and the heating coils along one direction in a relative manner, and the heating coils are disposed so as to correspond to the areas to be heated during the heating period.

Abstract: An induction heating device and an induction heating method are provided. The entire areas to be heated of the workpiece can be uniformly heated to a predetermined high temperature, and uniform heating is possible even when the workpiece deforms in a non-uniform manner during heating. When areas to be heated are established on a workpiece so as to extend in one direction and the areas to be heated are induction-heated, the deformation amount on one edge of the areas to be heated is different from that on the other. This induction heating device includes; heating coils facing a portion of the areas to be heated when the workpiece is induction-heated; and a relative transfer means for transferring the workpiece and the heating coils along one direction in a relative manner, and the heating coils are disposed so as to correspond to the areas to be heated during the heating period.

Abstract: An induction heating power supply apparatus includes a smoothing section to smooth DC power and an inverter section to convert the smoothed DC power into AC power. The inverter section has first and second modules, each having serially connected switching devices. Output bus bars are interposed between the first and second modules. The smoothing section has first bus bars connected to a DC power supply section and the first module, a capacitor connected to the first bus bars, second bus bars connected to the DC power supply section and the second module, and another capacitor connected to the second bus bars. The first and second bus bars extend parallel to the output bus bars. The first module is interposed between the first bus bars and the output bus bars. The second module is interposed between the second bus bars and the output bus bars.

Abstract: A power conversion apparatus includes a rectifier to convert AC power into constant-current DC power, a resonant inverter to convert the DC power into AC power to be output to a load, and a control unit to receive settings of an output current value of the inverter, a current-supplying time of the inverter, an operation rate defined by dividing the current-supplying time by a sum of the current-supplying time and a non-current-supplying time, and a resonance frequency of the load. The control unit operates the rectifier and the inverter only when it determines that it is operable to perform an output in accordance with the set conditions, based on data in which the output frequency, the current-supplying time and the operation rate are associated with an allowable output current value of the inverter at a temperature equal to or lower than a maximum operable temperature of a switching device.

Abstract: A steel plate to be heated is a blank having a first region and a second region adjacent to the first region. The blank is heated by direct resistance heating. A jet of cooling medium is applied to the first region during the direct resistance heating such that a temperature of the first region is kept lower than a quenching region while heating the second region to be equal to or higher than the quenching temperature. To provide a clear boundary between the first and second regions, the jet of cooling medium is applied along a slant direction such that the cooling medium expands along the boundary between the first and second regions. Alternatively, a partition member is provided along the boundary between the first and second regions. The heated blank is then press-formed and cooled in a press die to obtain a hot-pressed product.

Abstract: A direct resistance heating apparatus includes first and second electrodes arranged with a space provided therebetween, a power supply electrically connected to the electrodes, an electrode moving mechanism configured to move, in a state in which the electrodes are in contact with a workpiece and in a state in which current is applied from the power supply to the workpiece through the electrodes, at least one of the electrodes along an opposing direction in which the electrodes are opposed to each other, first and second holders configured to hold the workpiece such that, in a state in which the at least one of the electrodes is moved, a heating target region of the workpiece located between the electrodes is held between the holders in the opposing direction, and a holder moving mechanism configured to move at least one of the holders to pull the workpiece along the opposing direction.

Abstract: A load abnormality detecting circuit for an inverter to detect abnormality of a load during an operation of the inverter which has a switching element and a phase synchronizing loop controlling an output frequency to be a resonance frequency of the load, the load abnormality detecting circuit includes a phase shift detection part that detects a phase shift between an output voltage and an output current which are applied from the inverter to the load and sends an abnormal load signal based on the detected phase shift. The switching element including a self-arc-extinguishing element and a reflux diode connected in reversely parallel to the self-arc-extinguishing element. The phase shift detection part detects advance and delay of a phase of the output current with respect to the output voltage.

Abstract: An inverter of a power supply apparatus includes a smoothing circuit. The smoothing circuit includes a circuit body having a positive-side output terminal and a negative-side output terminal, and a plurality of capacitors mounted on the circuit body and connected in parallel between the positive-side output terminal and the negative-side output terminal. A difference between the maximum value and the minimum value among positive-negative electrical path lengths lnPNi=lnPi+lnNi (i=1, 2, and 3) for the respective capacitors is equal to or smaller than 30% of the minimum value.

Abstract: A method for setting conditions for a shaft diameter enlargement, a shaft diameter enlargement method, and a shaft diameter enlargement apparatus are provided. A controller of the shaft diameter enlargement apparatus controls a compressing section, a bending section, and a rotating section to enlarge an intermediate portion of a shaft workpiece to have a predetermined outer diameter by rotating the shaft workpiece about its axis with axial compressive force a bending angle being applied to the intermediate portion. The controller determines whether the shaft workpiece is acceptable, based on the number of rotations of die shaft workpiece required for enlarging the intermediate portion to have the predetermined outer diameter or based on an enlargement ratio of the intermediate portion.

Abstract: A load abnormality detecting circuit for an inverter to detect abnormality of a load during an operation of the inverter which has a self-arc-extinguishing element as a switching element and a phase synchronizing loop controlling an output frequency to be a resonance frequency of the load, the load abnormality detecting circuit includes a phase shift detection part that detects a phase shift between a gate voltage signal controlling ON/OFF of the self-arc-extinguishing element and an output current of the inverter which is applied to the load, and that sends a first abnormal load signal based on the phase shift.

Abstract: A rack bar blank material includes a rack portion configured to mesh with a pinion in an end side of a hollow shaft material in an axial direction, and an end portion which is provided closer to the end side of the hollow shaft material than the rack portion. The end portion has a diameter which is larger than that of a minimum circle embracing a section of the rack portion which is perpendicular to the axial direction and which is equal to that of a shaft portion at the other end side of the shaft material in the axial direction.

Abstract: A manufacturing method for a hollow rack bar made of a hollow shaft material and including a toothed section which has a rack on an outer surface and a shaft section which is formed thinner than the toothed section, the manufacturing method includes drawing the hollow shaft material by using a die and a plug, and preforming regions of the hollow shaft material including a toothed section forming region configured to form the toothed section and a shaft section forming region configured to form the shaft section to have thicknesses according to the regions respectively, and forming the rack at the toothed section forming region of the hollow shaft material which is preformed.

Abstract: A power supply apparatus for induction heating is provided. The power supply apparatus includes a smoothing filter configured to smooth a pulsating current of DC power output from a DC power supply, and an inverter configured to convert the DC power that has been smoothed by the smoothing filter into AC power. The smoothing filter includes a plurality of capacitors having different internal inductances and connected to each other in parallel between input terminals of the inverter, each of the capacitors being connected to the input terminals of the inverter directly or through a pair of bus bars. The plurality of capacitors includes a first capacitor and a second capacitor, the first capacitor having smaller internal inductance than the second capacitor and a shorter conductive path between the input terminals of the inverter than the second capacitor.

Abstract: An output current synthesizer that synthesizes output currents output from a plurality of power inverter circuits converting direct current power to alternating current power and outputs the synthesized output currents as synthesized current having a predetermined frequency, the output current synthesizer includes a pair of conductors which is provided with each of the power inverter circuits and to which the output currents of the power inverter circuits flow, a reactor which is provided on each of the pairs of conductors and generates magnetic flux corresponding to a difference between values of currents flowing to the pairs of conductors to reduce the difference between the values of currents, a pair of conductive members to which the pairs of conductors are connected in parallel, and a pair of output terminals which is provided on the pair of conductive members and output the synthesized currents.

Abstract: In preferred embodiments, a heating coil is provided that includes at least a set of heating conductors, one of which is arranged at a side of a work and the other one is arranged at an opposite side of the work. In addition, a plurality of connecting conductors are provided to connect an end of one of the heating conductors with an end of the other heating conductor, wherein each of the heating conductors is connected with at least two connecting conductors. The connecting conductors extend from an end of each of the heating conductor in a different direction from each other. In the preferred embodiments, the heating coil has a simple structure that enables an even heat treatment to a work in a width direction.

Abstract: To radially enlarge an intermediate portion of a shaft, the shaft is held by a pair of holders with a gap between the pair of holders in an axial direction of the shaft, compression force is applied in the axial direction to the intermediate portion arranged between the pair of holders, and alternating load is applied in a direction intersecting the axial direction to the intermediate portion to enlarge the intermediate portion. When enlarging the intermediate portion, a temperature of the intermediate portion is set to be above a blue brittleness temperature range of the shaft, and a temperature of the holders is set to be below a tempering temperature range of the holders.