Weft insertion method and weft insertion device for air jet loom

A weft insertion method for an air jet loom, wherein

• the loom comprises a weft insertion device including:
• a first main nozzle for weft insertion;
• and
• a second main nozzle that is arranged upstream from the first main nozzle in a weft insertion direction and is configured to function as an auxiliary main nozzle,
• the first main nozzle is connectable to a first valve device by a first piping,
• the second main nozzle is connectable to a second valve device by a second piping shorter than the first piping,
• the weft insertion device is configured to supply compressed air to each main nozzle with each valve device being in an open state over a jet period from a predetermined jet starting timing,
• the second valve device includes a single lead-in flow path into which compressed air is supplied and is configured by combining:
• a valve for steady flow rate that implements a state in which the steady flow rate, which is a flow rate in a steady state of jet, is supplied;
• and
• a valve for small flow rate that implements a small flow rate state, which is a state in which a flow rate smaller than the steady flow rate is supplied,
• the second valve device is configured to switch an operating state of the second valve device between the state in which the steady flow rate is supplied and the small flow rate state,
• the weft insertion device further comprises:
• a storage unit configured to store a predetermined initial jet period that begins at the jet starting timing;
• and
• a control device configured to switch the operating state of the second valve device and to put the operating state of the second valve device into the small flow rate state in a period corresponding to the predetermined initial jet period, the period being in the jet period, and
• in the predetermined initial jet period that begins at the predetermined jet starting timing, the operating state of the second valve device is put into the small flow rate state, in which the flow rate smaller than the steady flow rate is supplied.