Lower thread supply device of sewing machine

A lower thread supply device of a sewing machine which is arranged below a needle plate of a sewing machine, comprising:

• a bobbin which has a cylindrical portion for inserting into a spindle of a shuttle arranged below the needle plate, a shuttle side flange portion which is formed at an end portion at a shuttle side which is a side facing the shuttle of the cylindrical portion, and a front surface side flange portion which is magnetic and formed at an end portion at a front surface side which is a side opposite to the side facing the shuttle of the cylindrical portion, wherein a lower thread is wound around an outer circumference of the cylindrical portion between the shuttle side flange portion and the front surface side flange portion;
• a bobbin case which has a non-magnetic cover portion housing the bobbin and transmitting a magnetic force, wherein the cover portion has a front surface side part covering the front surface side of the bobbin and a side wall part covering an outer circumference side of the bobbin;
• a magnetic force member which is arranged at the front surface side of the bobbin case and attracts the front surface side flange portion of the bobbin by a magnetic force via the bobbin case;
• and
• a magnetic force change portion which changes the magnetic force of the magnetic force member acting on the front surface side flange portion,
• the bobbin case further comprises a first lower thread supply resistance mechanism which gives a resistance action to the supply operation of the lower thread wound around the bobbin,
• the first lower thread supply resistance mechanism is a contact member arranged in contact with the bobbin on an inner surface of the bobbin case,
• the bobbin further comprises a taper portion inclined toward the shuttle side in an outer circumference portion of the front surface side flange portion, and
• the contact member arranged in the bobbin case is arranged in contact with the taper portion in a region facing the taper portion on an inner surface of the front surface side part.