Honda Giken Kogyo Kabushiki Kaisha

Kenji Miyanaga

Fumitomo Takano

Hitoshi Saito

Yuji Kanai

Kazuo Isogai

Manabu Maruyama

Izuru Hori

Kouki Mizutani

Nobuo Kobayashi

Yuko Suzuki

Gen Tujii

A process for forming a tubular member is provided which includes a pre-forming process for tube-expanding (bulge) forming and bending forming a tubular material using first and second molds and a final forming process for crush forming a preformed tube using a third mold so as to give its cross section a desired shape, the pre-forming step being carried out using the first and second molds heated at temperatures equal to or higher than the recrystallization temperature of the tubular material and the final forming step being carried out using the third mold heated at temperatures equal to or lower than the recrystallization temperature of the tubular material. The process enables a tubular material of aluminum alloy to be formed into a tubular member of high precision and high quality which has expanded portions as well as bent portions and whose cross section varies across its length.

Process for forming tubular member

A process is provided for producing a hollow member having a wall thickness, in a cross section orthogonal to the longitudinal direction, that varies in the longitudinal direction, the process including a heating step of heating a tubular material (Pa) so that the tubular material (Pa) is given a temperature variation in the longitudinal direction, and a stretching step of axially stretching the tubular material (Pa) that has been heated in the preceding step. In this way, a hollow member having a cross-sectional wall thickness that is variable in the longitudinal direction can be easily produced.

Process for producing hollow member

Before a deterioration of a secondary current sensor is detected, a controller effects a feedback control process based on a secondary current from the secondary winding of a welding transformer which is energized by an inverter, for thereby controlling a welding current with a high degree of accuracy, e.g., an accuracy level of .+-.1%. At the same time, it is monitored whether a detected value of a primary current from the primary winding of the welding transformer, which is detected by a primary current sensor, exceeds a predetermined allowable range with respect to a reference value of the primary current. If the detected value of the primary current exceeds the predetermined allowable range, then it is decided that the secondary current sensor is deteriorated. When the secondary current sensor is deteriorated, the controller switches from the feedback control process based on the secondary current to a feedback control process based on the primary current to control the welding current with a certain degree of accuracy, e.g., an accuracy level of .+-.3%, without interrupting the welding process.

Method of controlling welding current and inverter-controlled DC

A direct current resistance welding machine and a method of controlling the direct current resistance welding machine wherein primary current of a welding transformer is detected when a plurality of switching devices of an inverter are controlled based on corresponding pulses having a predetermined frequency and each having a time width corresponding to the value of a required secondary current. Rise and fall times of the detected primary current are detected. An upper limit frequency Of the primary current is computed based on the time width of each pulse and on the rise and fall times. Thus, the primary current of the welding transformer is controlled by controlling the switching devices based on pulses having a frequency falling within the computed upper limit frequency.

Direct current resistance welding machine and method of controlling the

A direct-current resistance welding apparatus includes pneumatic actuators for pressurizing welding guns, respectively, to grip respective workpieces, an inverter composed of a plurality of parallel-connected switching device units each comprising a pair of series-connected switching devices, and a plurality of welding transformers connected to the welding guns, respectively, and also connected between the switching device units. A timer circuit applies an energization signal to energize the switching device units. The pneumatic actuators are actuated by a control circuit to pressurize the welding guns and successively energize the switching device units according to s sequence read from a sequence memory circuit.

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Sayama, Japan

Kenji Miyanaga