Quartz crystal unit, quartz crystal oscillator having quartz crystal unit, and electronic apparatus having quartz crystal oscillator

An electronic apparatus comprising:

• at least one oscillating circuit having an amplifier;
• a capacitor;
• a resistor;
• and a quartz crystal unit comprised of a quartz crystal tuning fork resonator having an overall length, a case having a mounting portion and a lid;
• wherein the quartz crystal tuning fork resonator vibrates in a flexural mode and has a quartz crystal tuning fork base, and first and second quartz crystal tuning fork tines connected to the quartz crystal tuning fork base, each of the first and second quartz crystal tuning fork tines having a first main surface and a second main surface opposite the first main surface and a first side surface and a second side surface opposite the first side surface, the first side surface of the first quartz crystal tuning fork tine confronting the second side surface of the second quartz crystal tuning fork tine;
• wherein at least one groove having a length, a first surface opposite the first side surface and a second surface connected to the first surface through a third surface, is formed in each of the first and second main surfaces of each of the first and second quartz crystal tuning fork tines so that a width of at least one of the grooves formed in the first and second main surfaces of each of the first and second quartz crystal tuning fork tines is greater than a distance in the width direction of the at least one groove measured from an outer edge of the at least one groove to an outer edge of the corresponding one of the first and second quartz crystal tuning fork tines;
• wherein a first electrode is disposed on the first surface of the at least one groove formed in each of the first and second main surfaces of each of the first and second quartz crystal tuning fork tines and a second electrode is disposed on the first side surface of each of the first and second quartz crystal tuning fork tines so that the first electrode disposed on the first surface of the at least one groove formed in each of the first and second main surfaces of the first quartz crystal tuning fork tine has an electrical polarity opposite to an electrical polarity of the second electrode disposed on the first side surface of the first quartz crystal tuning fork tine, and the first electrode disposed on the first surface of the at least one groove formed in each of the first and second main surfaces of the second quartz crystal tuning fork tine has an electrical polarity opposite to an electrical polarity of the second electrode disposed on the first side surface of the second quartz crystal tuning fork tine;
• wherein each of the overall length of the quartz crystal tuning fork resonator and the length of the at least one groove formed in each of the first and second main surfaces of each of the first and second quartz crystal tuning fork tines is determined so that a series resistance R1 of a fundamental mode of vibration of the quartz crystal tuning fork resonator is less than a series resistance R2 of a second overtone mode of vibration thereof;
• wherein the quartz crystal tuning fork resonator is mounted on the mounting portion of the case and the lid is connected to the case;
• wherein the quartz crystal tuning fork resonator of the quartz crystal unit is electrically connected to the amplifier, the capacitor and the resistor;
• and
• wherein an output signal of the at least one oscillating circuit having the amplifier, the resistor, the capacitor and the quartz crystal unit is a clock signal for use in operation of the electronic apparatus.

A quartz crystal unit comprising:

• a quartz crystal tuning fork resonator having an overall length;
• a case having a mounting portion;
• and a lid;
• wherein the quartz crystal tuning fork resonator vibrates in a flexural mode and has a quartz crystal tuning fork base, and first and second quartz crystal tuning fork tines connected to the quartz crystal tuning fork base, each of the first and second quartz crystal tuning fork tines having a first main surface and a second main surface opposite the first main surface and a first side surface and a second side surface opposite the first side surface, the first side surface of the first quartz crystal tuning fork tine confronting the second side surface of the second quartz crystal tuning fork tine;
• wherein at least one groove having a length, a first surface opposite the first side surface and a second surface connected to the first surface through a third surface, is formed in each of the first and second main surfaces of each of the first and second quartz crystal tuning fork tines so that a width of at least one of the grooves formed in the first and second main surfaces of each of the first and second quartz crystal tuning fork tines is greater than a distance in the width direction of the at least one groove measured from an outer edge of the at least one groove to an outer edge of the corresponding one of the first and second quartz crystal tuning fork tines;
• wherein a first electrode is disposed on the first surface of the at least one groove formed in each of the first and second main surfaces of each of the first and second quartz crystal tuning fork tines and a second electrode is disposed on the first side surface of each of the first and second quartz crystal tuning fork tines so that the first electrode disposed on the first surface of the at least one groove formed in each of the first and second main surfaces of the first quartz crystal tuning fork tine has an electrical polarity opposite to an electrical polarity of the second electrode disposed on the first side surface of the first quartz crystal tuning fork tine, and the first electrode disposed on the first surface of the at least one groove formed in each of the first and second main surfaces of the second quartz crystal tuning fork tine has an electrical polarity opposite to an electrical polarity of the second electrode disposed on the first side surface of the second quartz crystal tuning fork tine;
• wherein each of the overall length of the quartz crystal tuning fork resonator and the length of the at least one groove formed in each of the first and second main surfaces of each of the first and second quartz crystal tuning fork tines is determined so that a series resistance R1 of a fundamental mode of vibration of the quartz crystal tuning fork resonator is less than a series resistance R2 of a second overtone mode of vibration thereof;
• wherein the quartz crystal tuning fork resonator is mounted on the mounting portion of the case and the lid is connected to the case;
• and
• wherein the quartz crystal tuning fork resonator is electrically connected to an amplifier, a capacitor and a resistor to form a quartz crystal oscillating circuit.