Vehicle safety device
A vehicle safety device installed in a hybrid electric vehicle or an electric vehicle is provided to be capable of interrupting a current supplied from a power supply to a load via a supply line. The vehicle safety device includes first interrupting mechanism adapted to set the supply line in an interrupted condition when a temperature of the load reaches a first set temperature and second interrupting mechanism adapted to set the supply line in the interrupted condition such that the supply line cannot be returned to an energized condition when the temperature of the load reaches a second set temperature that is higher than the first set temperature.
1. A vehicle safety device that is installed in a hybrid electric vehicle or an electric vehicle having an electric heater serving as a heat source of a heating apparatus housed in a warm water tank and that is configured to interrupt a current supplied from a power supply to the electric heater via a supply line, comprising:
a first interrupting mechanism adapted to set the supply line in an interrupted condition when a temperature of the electric heater or a temperature within the warm water tank reaches a first set temperature, and to return the supply line to an energized condition when the temperature of the electric heater or the temperature within the warm water tank decreases to a third set temperature that is lower than the first set temperature; and
a second interrupting mechanism adapted to set the supply line in the interrupted condition such that the supply line cannot be returned to the energized condition when the temperature of the electric heater or the temperature within the warm water tank reaches a second set temperature that is higher than the first set temperature,
wherein the second interrupting mechanism interrupts the supply line differently from the first interrupting mechanism, and the second interrupting mechanism interrupts the supply line at a position that is closer to the power supply than is a position at which the first interrupting mechanism interrupts the supply line.
2. The vehicle safety device as defined in claim 1 , wherein the second interrupting mechanism includes:
a short-circuit line configured to short-circuit the supply line upstream and downstream of the electric heater;
a second bimetal switch that short-circuits the short-circuit line when the temperature of the electric heater or the temperature within the warm water tank reaches the second set temperature; and
a power fuse provided on the supply line between the power supply and the short-circuit line,
wherein the first interrupting mechanism includes a transistor connected in series with the electric heater so as to be arranged on the supply line between the electric heater and the short-circuit line.
3. The vehicle safety device as defined in claim 2 , wherein:
the transistor is provided to interrupt the current supplied to the electric heater when a control current thereof is interrupted or applied; and
the first interrupting mechanism further includes a switching mechanism adapted to switch between interruption and application of the control current in accordance with the temperature of the electric heater or the temperature within the warm water tank.
4. The vehicle safety device as defined in claim 3 , wherein the switching mechanism interrupts the control current when the temperature of the electric heater or the temperature within the warm water tank reaches the first set temperature and applies the control current when the temperature of the electric heater or the temperature within the warm water tank decreases to the third set temperature, and
the transistor interrupts the current supplied to the electric heater when the control current is interrupted and applies the current supplied to the electric heater when the control current is applied.
5. The vehicle safety device as defined in claim 3 , wherein:
the switching mechanism applies the control current when the temperature of the electric heater or the temperature within the warm water tank reaches the first set temperature and interrupts the control current when the temperature of the electric heater or the temperature within the warm water tank decreases to the third set temperature, and
the transistor interrupts the current supplied to the electric heater when the control current is applied and applies the current supplied to the electric heater when the control current is interrupted.
6. The vehicle safety device as defined in claim 3 , wherein the switching mechanism is a first bimetal switch to which heat from a first part of the electric heater is transmitted,
a heat from a second part of the electric heater is transmitted to the second bimetal switch, and
the second part of the electric heater has a lower temperature than the first part.
7. The vehicle safety device as defined in claim 5 , wherein a current that bifurcates from the supply line downstream of the power fuse is supplied from the power supply to a load that is different from the electric heater, and
the power fuse is shared by the electric heater and the load.
8. The vehicle safety device as defined in claim 7 , wherein the load is an electric compressor in a vehicle air-conditioning device.
9. The vehicle safety device as defined in claim 1 , wherein the second set temperature is set at a higher temperature than a maximum temperature of the electric heater or the temperature within the warm water tank, which is generated when the temperature of the electric heater or the temperature within the warm water tank increases due to overshoot after reaching the first set temperature such that the first interrupting mechanism sets the supply line in the interrupted condition.
10. The vehicle safety device as defined in claim 1 , wherein:
the first interrupting mechanism comprises:
a transistor provided on the supply line to interrupt the current supplied to the electric heater when a control current thereof is interrupted and apply the current supplied to the electric heater when the control current is applied; and
a first bimetal switch that contacts the electric heater to permit heat transfer, interrupts the control current when the temperature of the electric heater or the temperature within the warm water tank reaches the first set temperature, and applies the control current when the temperature of the electric heater or the temperature within the warm water tank reaches the third set temperature that is lower than the first set temperature, and
the second interrupting mechanism comprises:
a short-circuit line configured to short-circuit the supply line upstream and downstream of the electric heater;
a second bimetal switch that is provided on the short-circuit line, contacts the electric heater to permit heat transfer, and short-circuits the short-circuit line when the temperature of the electric heater or the temperature within the warm water tank reaches the second set temperature that is higher than the first set temperature; and
a power fuse provided on the supply line between the power supply and the short-circuit line.
11. The vehicle safety device as defined in claim 9 , wherein:
the first interrupting mechanism comprises:
a transistor provided on the supply line to apply the current supplied to the electric heater when a control current thereof is interrupted and interrupt the current supplied to the electric heater when the control current is applied; and
a first bimetal switch that contacts the electric heater to permit heat transfer, applies the control current when the temperature of the electric heater or the temperature within the warm water tank reaches the first set temperature, and interrupts the control current when the temperature of the electric heater or the temperature within the warm water tank reaches the third set temperature that is lower than the first set temperature, and
the second interrupting mechanism comprises:
a short-circuit line configured to short-circuit the supply line upstream and downstream of the electric heater;
a second bimetal switch that is provided on the short-circuit line, contacts the electric heater to permit heat transfer, and short-circuits the short-circuit line when the temperature of the electric heater or the temperature within the warm water tank reaches the second set temperature that is higher than the first set temperature; and
a power fuse provided on the supply line between the power supply and the short-circuit line.
12. A vehicle safety device that is installed in a hybrid electric vehicle or an electric vehicle having an electric heater serving as a heat source of a heating apparatus housed in a warm water tank and that is configured to interrupt a current supplied from a power supply to the electric heater via a supply line, comprising:
first interrupting means for setting the supply line in an interrupted condition when a temperature of the electric heater or a temperature within the warm water tank reaches a first set temperature, and for returning the supply line to an energized condition when the temperature of the electric heater or the temperature within the warm water tank decreases to a third set temperature that is lower than the first set temperature; and
second interrupting means for setting the supply line in the interrupted condition such that the supply line cannot be returned to the energized condition when the temperature of the electric heater or the temperature within the warm water tank reaches a second set temperature that is higher than the first set temperature,
wherein the second interrupting means interrupts the supply line differently from the first interrupting means, and the second interrupting means interrupts the supply line at a position that is closer to the power supply than is a position at which the first interrupting means interrupts the supply line.
13. A vehicle safety device installed in a hybrid electric vehicle or an electric vehicle configured to interrupt a current supplied from a power supply to a load via a supply line, comprising:
a first interrupting mechanism adapted to set the supply line in an interrupted condition when a temperature of the load reaches a first set temperature; and
a second interrupting mechanism adapted to set the supply line in the interrupted condition such that the supply line cannot be returned to an energized condition when the temperature of the load reaches a second set temperature that is higher than the first set temperature,
wherein the first interrupting mechanism includes
a transistor provided on the supply line to interrupt the current supplied to the load when a control current thereof is interrupted or applied; and
a switching mechanism adapted to switch between interruption and application of the control current in accordance with the temperature of the load, and
wherein the first interrupting mechanism returns the supply line to the energized condition when the temperature of the load decreases to a third set temperature that is lower than the first set temperature.
14. The vehicle safety device as defined in claim 13 , wherein:
the switching mechanism interrupts the control current when the temperature of the load reaches the first set temperature and applies the control current when the temperature of the load decreases to the third set temperature, and
the transistor interrupts the current supplied to the load when the control current is interrupted and applies the current supplied to the load when the control current is applied.