Electronic timepiece

An electronic timepiece has a case of which at least part is conductive; a clock chip that keeps and displays time on a time display means; a receiver chip that receives a radio signal through a GPS antenna; a storage battery; a timekeeping voltage conversion unit that converts output voltage from the storage battery to drive voltage for the clock chip; and a receiver voltage conversion unit that converts output voltage from the storage battery to drive voltage for the receiver chip. The output terminal of the timekeeping voltage conversion unit is connected to the clock chip and the case, and the output terminal of the receiver voltage conversion unit is connected to the receiver chip.

BACKGROUND

1. Technical Field

The present invention relates to an electronic timepiece, and relates more particularly to an electronic timepiece that can receive radio signals.

2. Related Art

Electronic timepieces having a timekeeping unit that keeps and displays time, and a heavy load system that has high power consumption compared with the timekeeping unit, are known from the literature. The electronic timepiece disclosed in Japanese Unexamined Patent Appl. Pub. JP-A-2007-101233, for example, has an electronic clock circuit as the timekeeping unit, and a keyless entry circuit as the heavy load system. In addition to a timekeeping unit, other electronic timepieces have a receiver circuit to receive radio signals such as time standard signals or satellite signals transmitted from GPS (Global Positioning System) satellites as the heavy load system.

In order to drive the heavy load system and timekeeping unit stably, an electronic timepiece with a heavy load system preferably uses separate power supplies to drive the heavy load system and timekeeping unit. More particularly, the receiver unit that receives radio signals is preferably driven using a stable voltage in order to improve reception sensitivity.

The electronic timepiece disclosed in JP-A-2007-101233 therefore has two batteries, a battery for the clock control circuit and a battery for the keyless entry circuit.

However, providing two batteries in an electronic timepiece increases the size of the electronic timepiece.

SUMMARY

The present invention is directed to reducing the size of an electronic timepiece that has a receiver circuit to receive radio signals while also improving reception sensitivity.

An electronic timepiece according to one aspect of the invention has a frame of which at least part is conductive; a timekeeping unit that keeps and displays time; a receiver unit that receives a radio signal; a battery; a first voltage conversion unit that converts output voltage from the battery to a first drive voltage; and a second voltage conversion unit that converts output voltage from the battery to a second drive voltage. The output terminal of the first voltage conversion unit is connected to the timekeeping unit and the frame, and the output terminal of the second voltage conversion unit is connected to the receiver unit.

The first drive voltage and the second drive voltage may be the same voltage or different voltages. The first drive voltage is preferably set to a voltage for driving the timekeeping unit (clock chip) in a common quartz timepiece. The output terminal of the first voltage conversion unit is connected to the frame. As a result, when the frame has a part that is made from a non-conductive material, the output terminal of the first voltage conversion unit is electrically connected to the part of the frame made from a conductive material.

By using a first voltage conversion unit and a second voltage conversion unit, this aspect of the invention can stably drive the timekeeping unit and the receiver unit using the voltage set by the respective voltage conversion units even when there is only one battery. Separate batteries for the timekeeping unit and receiver unit are therefore not needed, and the electronic timepiece can be made small.

The potential of the frame can also be held at the same voltage as the first drive voltage used for the timekeeping unit because the output terminal of the first voltage conversion unit is conductive to the frame (case). As a result, the system for detecting operation of an input unit, such as a button or pusher, disposed to the frame can be the same as used in a common quartz timepiece. More specifically, because the potential of the timekeeping unit and the frame is the same as the first drive voltage, the timekeeping unit and input unit can be the same as used in a common quartz timepiece.

The output terminal of the first voltage conversion unit is also conductive to the frame in the invention. The output terminal of the second voltage conversion unit therefore does not need to be conductive to the frame. Therefore, while the output voltage of the first voltage conversion unit tends to fluctuate due to external factors such as contact between the case and the user's skin (body), the output voltage of the second voltage conversion unit is not affected by such external factors and the receiver unit can therefore receive a stable voltage supply. The receiver unit in this aspect of the invention can therefore detect radio signals stably, and reception sensitivity can be improved.

In an electronic timepiece according to another aspect of the invention, the radio signal received by the receiver unit is a satellite signal transmitted from a positioning information satellite.

By receiving satellite signals as the radio signals, this aspect of the invention can acquire time information and positioning information for calculating the current location, adjust the internal time using the acquired time information and the current location information calculated from the positioning information, and display the time at the current location.

The satellite signals can also be received anywhere on Earth from positioning information satellites. The electronic timepiece according to the invention can therefore receive satellite signals and display the time at the current location anywhere on Earth.

In an electronic timepiece according to another aspect of the invention, the battery is preferably a lithium ion battery.

By using a lithium ion battery, which is a storage battery, as the battery, this aspect of the invention enables charging the battery. An electronic timepiece that does not require replacing the battery can therefore be provided by incorporating a generator that produces power by a rotor, a solar cell, or other type of generating means in the electronic timepiece.

A lithium ion battery has a high energy density, and enables using a small, high capacity battery. As a result, the receiver unit, which consumes more drive current than the timekeeping unit, can also be driven stably.

An electronic timepiece according to another aspect of the invention preferably also has a capacitor having one end connected to a line that is conductive to the negative terminal of the battery and the receiver unit, and the other end connected to the frame.

In this aspect of the invention the capacitor functions as a high frequency ground that removes high frequency noise caused by the radio signal, which is a high frequency electromagnetic wave, received by the receiver unit. The receiver unit can therefore detect radio waves more stably.

DESCRIPTION OF EMBODIMENTS

A preferred embodiment of the present invention is described below with reference to the accompanying figures.

Electronic Timepiece Construction

As shown inFIG. 1, an electronic timepiece1according to this embodiment of the invention receives satellite signals from a plurality of GPS satellites100(positioning information satellites) that orbit the Earth on specific known orbits. The electronic timepiece1receives satellite signals from at least one GPS satellite100to acquire time information, and receives satellite signals from at least three GPS satellites100to acquire positioning information. Multiple GPS satellites100are in orbit. There are currently approximately 30 GPS satellites100in the GPS constellation.

The electronic timepiece1in this embodiment is a wristwatch that is worn on the user's wrist, has a dial11and hands12, and keeps and displays the time.

The greater part of the dial11is made from a non-metallic material, such as plastic or glass, that is transparent to light and microwaves in the 1.5 GHz band.

The hands12are disposed on the exposed side of the dial11. The hands12include a second hand121, minute hand122, and hour hand123that rotate on a center pivot13.

The electronic timepiece1has a crown14and pushers15,16as input units. The electronic timepiece1executes specific processes according to operation of the crown14and pushers15,16. For example, when the crown14is operated, a manual adjustment process that adjusts the displayed time is executed as controlled by the crown14. If the one pusher15is pressed for a long time (such as 3 seconds or more), a reception process is executed to receive satellite signals (manual reception mode). If the other pusher16is pressed, a process that changes the reception mode is executed (selecting the timekeeping mode, positioning mode, or auto-reception cancellation mode). If the positioning mode is selected as a result of pressing the pusher16and changing the reception mode, the second hand121moves to the FIX position (at 1:00). If the timekeeping mode is selected, the second hand121moves to the TIME position (at 2:00). If the auto-reception cancellation mode (reception OFF mode) is selected, the second hand121moves to the OFF position (at 11:00). The user can therefore easily know which mode is set.

If pusher15is pressed for a short time (such as less than 3 seconds), a result display process that displays the result of the last reception process is executed. More specifically, if reception was successful in the positioning mode, the second hand121goes to the FIX (1:00) position. If reception was successful in the timekeeping mode, the second hand121goes to the TIME (2:00) position. If reception fails, the second hand121goes to the N position (at 4:00).

These indications are also made by the second hand121during reception. In the positioning mode, the second hand121goes to the FIX (1:00) position. In the timekeeping mode, the second hand121goes to the TIME (2:00) position. If a GPS satellite100cannot be locked onto, the second hand121goes to the N position (at 4:00).

As shown inFIG. 2, the electronic timepiece1has a case17made of stainless steel (SUS), titanium, or other metal. This case17is also referred to as the frame herein.

The case17is substantially cylindrical. A crystal19is attached to the opening on the face side of the case17with a bezel18. The bezel18is made of ceramic or other non-metallic material to improve satellite signal reception performance. A back cover20is attached to the opening on the back side of the case17.

A timekeeping mechanism21, solar cell22, GPS antenna23, storage battery24, and circuits for driving the electronic timepiece1are disposed inside the case17.

The timekeeping mechanism21includes a stepper motor and wheel train. The stepper motor includes a motor coil, stator, and rotor, and drives the hands12through the wheel train and center pivot13.

The solar cell22is disposed between the timekeeping mechanism21and dial11, or more specifically on the back side of (behind) the dial11. The solar cell22is a photovoltaic device that produces power by converting light energy to electrical energy. The solar cell22has an electrode for outputting the generated power. Because the greater part of the dial11is made from a material through which light passes easily, the solar cell22can receive light through the crystal19and dial11and produce power.

The GPS antenna23receives microwave signals in the 1.5 GHz band. The GPS antenna23is also disposed behind the dial11. The part of the dial11above the GPS antenna23in the direction perpendicular to the dial11is made of a material through which microwaves in the 1.5 GHz band can pass easily (such as a non-metallic material with low conductivity and permeability). The solar cell22with electrode is not between the GPS antenna23and the dial11. The GPS antenna23can therefore receive satellite signals passing through the crystal19and dial11.

The GPS antenna23can be a loop antenna, patch antenna (microstrip antenna), helical antenna, chip antenna, or an inverted-F antenna, for example.

The storage battery24is a battery according to the invention, and is the power supply of the electronic timepiece1. The electronic timepiece1has a charging control circuit that charges the storage battery24with power produced by the solar cell22, and the storage battery24stores the power generated by the solar cell22.

A lithium ion battery that is suitable for mobile devices is used as the storage battery24in this embodiment of the invention, but a lithium polymer battery or other type of storage battery can be used. A storage device other than a storage battery (such as a capacitive device) can also be used.

Because this embodiment uses a lithium ion battery as the storage battery24, a battery with greater capacity than a button battery commonly used in quartz timepieces can be used.

The electronic timepiece1according to this embodiment of the invention receives a satellite signal through the GPS antenna23, and adjusts the time kept by the electronic timepiece1based on the satellite signal. The electronic timepiece1therefore also has a receiver chip28described below and adjusts the time based on the received satellite signal. Driving this receiver chip28generally requires more current than driving the clock chip26described below. For example, while a few milliamperes is sufficient to drive the clock chip26, driving the receiver chip28requires several ten milliamperes of current. The receiver chip28can therefore be driven stably by using a high capacity battery.

This high capacity storage battery24normally has an output voltage (such as 3.7 V) that is higher than the drive voltage (such as 1.5 V) of the clock chip26.

Circuit Unit Configuration

As shown inFIG. 2, the circuit unit includes the storage battery24, a timekeeping voltage converter25as the first voltage conversion unit of the invention, the clock chip26, a receiver voltage converter27as the second voltage conversion unit of the invention, the receiver chip28, and a capacitor29. This circuit unit is mounted on a circuit board not shown that is disposed on the back side of the timekeeping mechanism21. The movement of the electronic timepiece1is rendered by the timekeeping mechanism21and circuit board.

The input terminal of the timekeeping voltage converter25is connected to positive terminal of the storage battery24, and the output terminal is connected to the clock chip26and case17. The timekeeping voltage converter25converts the output voltage of the storage battery24to the drive voltage (first drive voltage) of the clock chip26, and applies this drive voltage (VDD) to the clock chip26. Because the output terminal of the timekeeping voltage converter25is connected to the case17, the drive voltage (VDD) is used as the ground voltage, that is, the voltage of the case17.

The output voltage (battery voltage) of the storage battery24, which is a lithium ion battery, is normally approximately 3.7 V. The output voltage of a button battery typically used in a quartz timepiece is normally approximately 1.5 V. The clock chip26is the same type used in a quartz timepiece, and is driven at 1.5 V. As a result, the timekeeping voltage converter25converts the battery voltage (such as 3.7 V) of the storage battery24to the first drive voltage (such as 1.5 V) for driving the clock chip26.

The clock chip26is connected to the timekeeping voltage converter25and the negative terminal (VSS) of the storage battery24, and is driven by the first drive voltage output by the timekeeping voltage converter25.

The clock chip26executes a timekeeping process keeping the internal time, a process driving the hands12, and a reception control process.

More specifically, the clock chip26keeps the internal time by counting a reference signal generated using a crystal oscillator not shown, and outputs a motor drive pulse to the timekeeping mechanism21to drive the hands12and display the internal time.

When satellite time information contained in the satellite signal is acquired by the receiver chip28, the clock chip26receives this time information from the receiver chip28and adjusts the internal time.

To execute the automatic reception mode that acquires satellite time information at a specific time, the clock chip26sends a drive signal causing the receiver chip28to execute the automatic reception mode when a specific time is reached.

When in the positioning mode, the clock chip26also acquires orbit information and other information used to calculate the position in addition to the satellite time information, calculates the current location, and generates location information for the current position. The clock chip26also adjusts the internal time using the satellite time information and the positioning information. The clock chip26also has a storage unit that stores data for controlling the electronic timepiece1, including time zone information for calculating the time at the current location from the satellite time information.

The timekeeping unit of the invention is embodied by the dial11, hands12, timekeeping mechanism21, and clock chip26.

The input terminal of the receiver voltage converter27is connected to the positive terminal of the storage battery24, and the output terminal is connected to the receiver chip28. The receiver voltage converter27converts the battery voltage (such as 3.7 V) to the drive voltage (the second drive voltage of the invention, such as 1.5 V) of the receiver chip28, and applies the drive voltage to the receiver chip28.

The low voltage side of the receiver chip28is connected to the negative terminal (VSS) of the storage battery24. This line is also conductive to the case17through the capacitor29.

When operating in the timekeeping mode, the receiver chip28gets the satellite time information from the satellite signal received by the GPS antenna23, and passes the acquired satellite time information to the clock chip26.

When operating in the positioning mode, the receiver chip28gets the satellite time information and information for calculating the current location from the satellite signal received by the GPS antenna23, and outputs the acquired information to the clock chip26.

The receiver unit of the invention is therefore embodied by the GPS antenna23and receiver chip28.

The circuit unit also includes an operation detection circuit that detects operation of the pushers15,16. When a pusher is operated, the operation detection circuit detects the change in voltage from VDD (high voltage) to VSS (low voltage). The clock chip26detects a pusher was operated and applies control as described above based on the voltage change detected by the operation detection circuit.

Operational Effect of the Electronic Timepiece

The effect of an electronic timepiece1according to this embodiment of the invention is described below.

The electronic timepiece1according to this embodiment of the invention has a timekeeping voltage converter25that converts the output voltage of the storage battery24to a first drive voltage, and a receiver voltage converter27that converts the output voltage of the storage battery24to a second drive voltage, drives the clock chip26of the timekeeping unit with the first drive voltage, and drives the receiver chip28with the second drive voltage. As a result, the timekeeping unit and receiver unit can be driven using one storage battery24, there is no need to provide individual batteries for the timekeeping unit and receiver unit, and a small electronic timepiece1can therefore be easily achieved.

The output terminal of the timekeeping voltage converter25is connected to the case17, and the first drive voltage is used as the ground voltage (case potential) in this embodiment. Connecting the receiver voltage converter27to the case17is therefore not necessary.

The drive voltage of the receiver chip28(second drive voltage) will therefore not fluctuate even if the voltage on the output side of the timekeeping voltage converter25varies due to external factors such as contact between the frame (case17) and the body, and the receiver chip28can receive a stable power supply.

More specifically, the receiver chip28in this embodiment can stably detect radio signals, and can improve reception sensitivity.

Furthermore, because the output terminal of the timekeeping voltage converter25is electrically connected to the case17, the potential of the case17can be held at the same voltage, the first drive voltage, as the drive voltage of the clock chip26. As a result, the operation detection circuit of the input unit such as the pushers15,16disposed to the frame can be the same as used in a common quartz timepiece. More specifically, the operation detection circuit uses a common method for detecting a voltage change from the high voltage (VDD such as 1.5 V) when a pusher15,16is not operated to the low voltage (VSS) when a pusher15,16is operated. A common operation detection circuit can also be used and increased cost can be suppressed in this embodiment because the case17is set to the first drive voltage (such as 1.5 V).

Yet further, because the case17is conductive (connected) through the capacitor29to the low voltage side (VSS) of the receiver chip28, the capacitor29can be made to function as a high frequency ground, and the antenna sensitivity of the receiver chip28can be improved.

Other Embodiments

The invention is not limited to the foregoing embodiment, and can be changed in many ways without departing from the scope of the accompanying claims.

For example, a capacitor29that functions as a high frequency ground is disposed in the foregoing embodiment, but the invention is not so limited and a configuration not having a capacitor29is also conceivable.

The foregoing embodiments are described with reference to a GPS satellite as an example of a positioning information satellite, but the positioning information satellite of the invention is not limited to GPS satellites and the invention can be used with Global Navigation Satellite Systems (GNSS) such as Galileo (EU), GLONASS (Russia), and Beidou (China), and other positioning information satellites that transmit satellite signals containing time information, including the SBAS and other geostationary or quasi-zenith satellites.

The invention is also described above using a configuration that receives satellite signals as the radio signals, but the invention is not so limited and configurations that receive standard time signals transmitted from a standard time transmitter are also conceivable.

The receiver unit of the electronic timepiece1is also not limited to receiving satellite signals or time standard signals, and configurations that use a Bluetooth (R), Wi-Fi (R), or other radio frequency receiving means are also conceivable. A configuration having a radio signal transmitter function is also conceivable.

The drive voltage of the clock chip26and receiver chip28is 1.5 V in the foregoing embodiment, but the invention is not so limited. The drive voltage of the clock chip26can also differ from the drive voltage of the receiver chip28.

Furthermore, the foregoing embodiment describes an electronic timepiece having an analog time display means with hands12as an example of a time display means embodying the timekeeping unit, but the invention can also be used in an electronic timepiece that displays the time digitally using an LCD device, for example.

The foregoing embodiment also describes a configuration having a solar cell22as the charging means that charges the storage battery24, but the invention is not so limited. For example, the invention can also use a generator that produces power using a rotor as the charging means. Further alternatively, configurations that are charged from an external power source (such as a wall outlet) using a power cord, and configurations that are charged from an external power source by wireless charging using electromagnetic induction, are also conceivable.

The entire case17(frame) in the foregoing embodiment is made of a conductive material (metal), but part of the case could be made of a non-conductive material. More specifically, at least part of the frame (case) must be conductive. If part of the frame is made of a non-conductive material, the output terminal of the timekeeping voltage converter25is electrically connected and conductive to the part of the frame made of the conductive material.

The electronic timepiece1according to the invention is also not limited to a wristwatch, and can be broadly applied in devices having an electronic timepiece function and a receiver function. The invention is particularly well suited to mobile electronic timepieces driven by a storage battery.

The entire disclosure of Japanese Patent Application No. 2012-209259, filed Sep. 24, 2012 is expressly incorporated by reference herein.