Vehicle electric power supply system

A vehicle electric power supply system includes: an electric power generating source; a battery; a first voltage converter configured to raise a voltage of the electric power generating source; a second voltage converter configured to raise a voltage of the battery; and an electric power converter configured to supply voltages, which are obtained by conversions by the respective first and second voltage converters, to a vehicle load. A power control unit, which includes the first voltage converter, the second voltage converter and the electric power converter, and the battery are integrated into a unitary component, and are placed in a front portion of a vehicle while isolated from a vehicle interior. Accordingly, it is possible to widen the vehicle interior and a luggage containing space in the vehicle's rear portion, and to avoid increase in the weight of the vehicle.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a vehicle electric power supply system comprising: an electric power generating source; a battery; a first voltage converter configured to raise a voltage of the electric power generating source; a second voltage converter configured to raise a voltage of the battery; and an electric power converter configured to supply voltages, which are obtained by conversions by the respective first and second voltage converters, to a vehicle load.

2. Description of the Related Art

Japanese Patent Application Laid-open No. 2006-345606 and Japanese Patent Application Laid-open No. 2008-193864 have made known hybrid vehicles in which: a power control unit is placed in an engine compartment; and a battery unit is placed under rear seats or in a trunk. In addition, Japanese Patent Application Laid-open No. 2007-39020 has made known a hybrid vehicle in which a power control unit and a battery are placed in or under the back of rear seats. Meanwhile, in fuel cell vehicles and electric vehicles, a power control unit is placed in a motor compartment in most cases because no engine is mounted thereon, while a battery is often placed under a vehicle interior or in a trunk. In some cases, the power control unit is placed in a space under the vehicle interior instead of in the motor compartment, depending on the configuration of the power control unit.

In the meantime, for the viewpoint of enhancing merchantability, it is desirable to widen the vehicle interior and also the luggage containing space in the vehicle's rear portion. However, there is a limit to the widening of the vehicle interior and the luggage containing space in the vehicle's rear portion, in the case of the configuration in which the battery unit is placed under the rear seats or in the trunk as disclosed in the above-described Japanese Patent Application Laid-open Nos. 2006-345606 and 2008-193864, and the configuration in which the power control unit and the battery are placed in or under the back of the rear seats as disclosed in the above-described Japanese Patent Application Laid-open No. 2007-39020. Furthermore, in a case where a vehicle has a configuration in which the power control unit and the battery are placed in their respective separate locations, a space in which to arrange electric wires and cooling pipes connecting the power control unit and the battery needs to be secured under the floor. The space in which to arrange the electric wires and the cooling pipes is likely to hinder a wider space from being secured for the vehicle interior. In addition, the electric wires and the cooling pipes need protection covers for the protection from protrusions and the like on the road surface. This entails increase in the weight of the vehicle. Moreover, from the viewpoint of securing the electricity safety, further safety measurements are needed for the protection covers of the electric wires and the cooling pipes. In the case where the power control unit and the battery are placed in their separated locations, consideration needs to be given to safety measurements such as the containing of the power control unit and the battery in their respective separated rigid cases. This entails increase in the weight of the vehicle as well.

SUMMARY OF THE INVENTION

The present invention has been made with the above-described situation taken into consideration, and an object of the present invention is to provide a vehicle electric power supply system which makes it possible to widen a vehicle interior and a luggage containing space in the vehicle's rear portion, and to avoid increase in the weight of the vehicle.

In order to achieve the object, according to a first feature of the present invention, there is provided a vehicle electric power supply system comprising: an electric power generating source; a battery; a first voltage converter configured to raise a voltage of the electric power generating source; a second voltage converter configured to raise a voltage of the battery; and an electric power converter configured to supply voltages, which are obtained by conversions by the respective first and second voltage converters, to a vehicle load, wherein a power control unit, which includes the first voltage converter, the second voltage converter and the electric power converter, and the battery are integrated into a unitary component, and are placed in a front portion of a vehicle while isolated from a vehicle interior.

Such a configuration makes it possible: to reduce lengths of electric wires and cooling pipes connecting the power control unit and the battery together; to widen the vehicle interior and a luggage containing space in the vehicle's rear portion; to protect the electric wires and the cooling pipes easily; to avoid increase in the number of parts needed for the protection; and to reduce the space needed to the protection. In addition, because the reduction in the lengths of the electric wires leads to reduction in radiation noise which occurs while an electric power is being supplied, it is possible to simplify the shielding measurements. Furthermore, because neither the electric wires nor the cooling pipes exist under the floor, no attention needs to be paid to contact which would otherwise occur between the electric wires and the ground as well as between the cooling pipes and the ground, or a collision which would otherwise occur between the electric wires and protrusions or the like on the road surface as well as between the cooling pipes and protrusion or the like on the road surface.

According to a second feature of the present invention, in addition to the first feature, a fuel cell unit including a fuel cell as the electric power generating source is placed in a location which is close to lateral sides of the battery and the power control unit, and which is isolated from the vehicle interior.

Such a configuration enables not only the power control unit and the battery but also the fuel cell unit to be compactly arranged while placing the power control unit, the battery and the fuel cell unit closer to one another, and thereby makes it possible to inhibit operating noise of the fuel cell unit from entering the vehicle interior.

According to a third feature of the present invention, in addition to the first feature, the vehicle load is a motor, and a cooling system including a pump configured to circulate coolant for cooling the power control unit and a radiator configured to cool the coolant by releasing heat from the coolant is configured in a way that, starting at the radiator, the coolant sequentially passes the power control unit, the battery and the motor in this order.

Such a configuration is capable of cooling the motor and the battery in addition to the power control unit. Furthermore, the configuration makes enables the power control unit, the battery, the motor and the radiator to be integrated into a unitary cooling system. In addition, the configuration makes it possible to construct the cooling system in a compact size, and to reduce the lengths of wires, pipes and the like which constitute part of the cooling system.

According to a fourth feature of the present invention, in addition to the third feature, a heater is interposed between an outlet side of the pump configured to suck the coolant from the radiator, and the power control unit.

Such a configuration heats the coolant by use of the heater interposed between the outlet side of the pump and the power control unit, and is thus capable of raising the temperature of the battery when the temperature thereof is low.

According to a fifth feature of the present invention, in addition to the third feature, individual bypass circuits are respectively connected to the power control unit, the battery, the motor and the radiator.

Such a configuration can make the coolant ready to flow in the individual bypass circuits respectively connected to the power control unit, the battery, the motor and the radiator, and accordingly can cause the coolant to flow to each of the power control unit, the battery, the motor and the radiator only when deemed necessary.

According to a sixth feature of the present invention, in addition to the fifth feature, the cooling system includes control valve means, respectively, for the power control unit, the battery, the motor and the radiator, the control valve means being configured to control flow of the coolant to the bypass circuits in accordance with a temperature of the coolant which is flowing in each of the power control unit, the battery, the motor and the radiator.

Such a configuration is capable of performing the cooling optimally in accordance with the conditions of the power control unit, the battery, the motor and the radiator, by controlling the amount of coolant to be flowed in each of the bypass circuits individually corresponding to the power control unit, the battery, the motor and the radiator by use of the control valve means in accordance with the temperature of the coolant which is flowing in each of the power control unit, the battery, the motor and the radiator.

According to a seventh feature of the present invention, in addition to the sixth feature, a lowest temperature to be maintained is set individually for the power control unit, the battery and the motor, and a controller configured to control operation of the pump stops the operation of the pump when the temperatures of the coolant in all of the power control unit, the battery and the motor are at or below the corresponding lowest temperature.

In accordance with such a configuration, the operation of the pump is stopped when all of the temperatures of the coolant do not reach the lowest temperatures individually set for the power control unit, the battery and the motor. Thereby, the configuration makes it possible to avoid wasteful energy loss which would occur if the pump would be operated while no cooling is necessary.

The above description, other objects, characteristics and advantages of the present invention will be clear from detailed descriptions which will be provided for the preferred embodiment referring to the attached drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring toFIGS. 1 to 6, descriptions will be hereinbelow provided for an embodiment of the present invention. First of all, referring toFIGS. 1 and 2, a unitary component including a battery16and a power control unit7placed above the battery16is placed in a motor compartment4in a front portion of a vehicle V as a fuel cell vehicle. The battery16and the power control unit7are contained in a common case8. A radiator9is forward of the battery16and the power control unit7. A motor17configured to produce a driving force for driving the driving wheels, for example, left and right front wheels WF is placed under the battery16.

A fuel cell unit10including a fuel cell15, which serves as an electric power generating source, is placed close to lateral sides of the battery16and the power control unit7. In this embodiment, the fuel cell unit10supported on a supporting mount11extending in a front-rear direction is placed close to the battery16and the power control unit7from the rear side.

Further, the battery16, the power control unit7, the radiator9and the motor17are placed in the motor compartment4which is isolated from a vehicle interior5of the vehicle V. The supporting mount11and the fuel cell unit10are placed under the vehicle interior5with a partition wall12interposed in between and thereby isolated from the vehicle interior5. The supporting mount11and the fuel cell unit10are placed, for example, between a driver's seat and a passenger seat in the vehicle interior5.

An air supplying unit13connected to the fuel cell unit10is placed in the motor compartment4while interposed between the battery16and the power control unit7, and the radiator9. A high-pressure hydrogen tank14connected to the fuel cell unit10is placed in a trunk6in the back of the vehicle interior5.

Referring toFIG. 3, the power control unit7includes: a first voltage converter18configured to raise a voltage of the fuel cell15; a second voltage converter19configured to raise a voltage of the battery16; an electric power converter20configured to supply voltages, which are obtained by the conversions by the respective first and second voltage converters18and19, to the motor17; and a direct-current link capacitor unit21serving as a peripheral circuit of the voltage converters18,19and the electric power converter20.

The first voltage converter18includes: a first input capacitor22; a first inductor24; a three-phase transformer26including a primary winding26A, a secondary winding26B and a tertiary winding26C; and first, second and third switching element modules27A,27B and27C.

A ground line28, which is common among the first voltage converter18, the second voltage converter19and the electric power converter20, is connected to the negative terminal of the fuel cell15. The first input capacitor22is provided between the ground line28and a first input positive line29, which is connected to the positive terminal of the fuel cell15. An end of the first inductor24is connected to the first input positive line29. In addition, ends of the respective primary, secondary and tertiary windings26A,26B and26C of the three-phase transformer26are connected in parallel to the other end of the first inductor24.

The first switching element module27A includes: a first positive-side switching element31A disposed between a common positive line30and the primary winding26A of the three-phase transformer26; and a first negative-side switching element32A disposed between the primary winding26A and the ground line28. The common positive line30is common among the first voltage converter18, the second voltage converter19and the electric power converter20. The second switching element module27B includes: a second positive-side switching element31B disposed between the common positive line30and the secondary winding26B of the three-phase transformer26; and a second negative-side switching element32B disposed between the secondary winding26B and the ground line28. The third switching element module27C includes: a third positive-side switching element31C disposed between the common positive line30and the tertiary winding26C of the three-phase transformer26; and a third negative-side switching element32C disposed between the tertiary winding26C and the ground line28.

The second voltage converter19includes: a second input capacitor23; a second inductor25; a two-phase transformer33including a primary winding33A and a secondary winding33B; and fourth and fifth switching element modules27D and27E.

The second input capacitor23is provided between a second input positive line34, which is connected to the positive terminal of the battery16, and the ground line28, which is connected to the negative terminal of the battery16. An end of the second inductor25is connected to the second input positive line34. In addition, ends of the respective primary and secondary windings33A and33B of the two-phase transformer33are connected in parallel to the other end of the second inductor25.

The fourth switching element module27D includes: a fourth positive-side switching element31D disposed between the common positive line30and the primary winding33A of the two-phase transformer33; and a fourth negative-side switching element32D disposed between the primary winding33A and the ground line28. The fifth switching element module27E includes: a fifth positive-side switching element31E disposed between the common positive line30and the secondary winding33B of the two-phase transformer33; and a fifth negative-side switching element32E disposed between the secondary winding33B and the ground line28.

The electric power converter20includes sixth, seventh and eighth switching element modules27F,27G and27H.

The sixth switching element module27F includes: a sixth positive-side switching element31F disposed between the common positive line30and a U-phase power line35U communicating with the electric motor17which is a three-phase alternating current motor; and a sixth negative-side switching element32F disposed between the U-phase power line35U and the ground line28. The seventh switching element module27G includes: a seventh positive-side switching element31G disposed between the common positive line30and a V-phase power line35V communicating with the electric motor17; and a seventh negative-side switching element32G disposed between the V-phase power line35V and the ground line28. The eighth switching element module27H includes: an eighth positive-side switching element31H disposed between the common positive line30and a W-phase power line35W communicating with the electric motor17; and an eighth negative-side switching element32H disposed between the W-phase power line35W and the ground line28.

In this embodiment, each of the first to eighth positive-side switching elements31A to31H and the first to eighth negative-side switching elements32A to32H of the first to eighth switching element modules27A to27H is made of an insulated gate bipolar transistor (IGBT) and a diode which is connected in parallel to the IGBT with the forward direction defined as a direction from the emitter to the collector.

The direct-current link capacitor unit21includes smoothing capacitors36which are provided between the common positive line30and the ground line28. Incidentally,FIG. 3shows only one smoothing capacitor36for the sake of simplicity. However, the direct-current link capacitor unit21includes the smoothing capacitors36which are provided between the common positive line30and the ground line28while respectively corresponding to the U, V and W phases of the electric motor17which is a three-phase alternating-current motor.

In addition, a series-connection circuit including paired discharging resistors37and37is connected between the common positive line30and the ground line28.

Referring toFIG. 4, the power control unit7is cooled by a cooling system40configured to circulate coolant such for example as cooling water. This cooling system40includes: a pump41configured to circulate the cooling water; and the radiator9configured to cool the cooling water by releasing the heat from the cooling water. The cooling system40is configured in a way that, starting at the radiator9, the cooling water sequentially passes the power control unit7, the battery16and the motor17in this order. An inlet side of the pump41is connected to an outlet of the radiator9. A heater42is interposed between an outlet side of the pump41and the power control unit7.

Further, individual bypass circuits43,44,45and46are connected to the power control unit7, the battery16, the motor17and the radiator9, respectively. Furthermore, the flow of the cooling water to the power control unit7, the battery16, the motor17and the radiator9as well as the flow of the cooling water to the bypass circuits43to46are switched and controlled by the operation of control valve means47,48,49and50which are configured to be controlled by a controller51in accordance with the temperature of the coolant which is flowing in each of the power control unit7, the battery16, the motor17and the radiator9.

The control valve means47corresponding to the power control unit7includes three-way solenoid selector valves V1and V2respectively provided to the inlet and outlet of the bypass circuit43. The control valve means48corresponding to the battery16includes three-way solenoid selector valves V3and V4respectively provided to the inlet and outlet of the bypass circuit44. The control valve means49corresponding to the motor17includes three-way solenoid selector valves V5and V6respectively provided to the inlet and outlet of the bypass circuit45. The control valve means50corresponding to the radiator9includes three-way solenoid selector valves V7and V8respectively provided to the inlet and outlet of the bypass circuit46.

It should be noted that the control valve means47to50may be thermostats configured to operate automatically without the control by the controller51.

In the meantime, a temperature range within which the temperature should be maintained is set for each of the power control unit7, the battery16, the motor17and the radiator9. A temperature range (TA<T<TB) in which the temperature T is higher than a temperature TA (for example, 40° C.) and lower than a temperature TB (for example, 100° C.) is set for the power control unit7. A temperature range (TC<T<TD) in which the temperature T is higher than a temperature TC (for example, 0° C.) and lower than a temperature TD (for example, 60° C.) is set for the battery16. A temperature range (TE<T<TF) in which the temperature T is higher than a temperature TE (for example, 0° C.) and lower than a temperature TF (for example, 100° C.) is set for the motor17. For the radiator9, the temperature T of the cooling water to be introduced thereto is set at a temperature TG (for example, 70° C.). The control valve means47to50are controlled in order that the temperatures of the power control unit7, the battery16, the motor17and the radiator9can be maintained within the respective temperature ranges set therefor.

By the setting of such temperature range, the temperature of the cooling water in the cooling system40changes as shown in, for example,FIG. 5. During the starting operation in a cool state, the temperature of the cooling water changes as shown by the chain line inFIG. 5. During the normal running operation, the temperature of the cooling water changes as shown by the continuous line inFIG. 5. When the temperature of the cooling water is higher, the temperature thereof changes as shown by the dash-dotted line inFIG. 5.

The operation of the pump41is controlled by the controller51as well. The lowest temperatures to be respectively maintained in the power control unit7, the battery16and the motor17, namely, the temperatures TB, TD, TF are individually set in this controller51. The controller51is configured to stop the operation of the pump41when the temperatures of the cooling water in all of the power control unit7, the battery16and the motor17are at or below the corresponding lowest temperature.

Referring toFIG. 6, the fuel cell15is supplied with the pressurized air from the air supplying unit13through a humidifier53, and with the high-pressure hydrogen from the high-pressure hydrogen tank14through a regulator54. The hydrogen sucked from the fuel cell15by a circulation pump55is returned to the downstream side of the regulator54through a check valve56. In addition, an on-off valve57is connected between the circulation pump55and the check valve56.

In this fuel cell system thus configured, the humidifier53, the regulator54, the circulation pump55and the check valve56are integrated into a unitary component as an accessory52. The accessory52and the fuel cell15constitute the fuel cell unit10. The accessory52is placed in the back of the fuel cell15, and is supported on the supporting mount11, as shown inFIGS. 1 and 2.

Next, descriptions will be provided for operations of this embodiment. The power control unit7, which includes the first voltage converter18, the second voltage converter19and the electric power converter20, and the battery16are integrated into the unitary component. The power control unit7and the battery16are placed in the front portion of the vehicle while isolated from the vehicle interior5. For this reason, it is possible to reduce the lengths of the electric wires and the cooling pipes connecting the power control unit7and the battery16together; to widen the vehicle interior5and the luggage containing space in the rear portion of the vehicle; to protect the electric wires and the cooling pipes easily; to avoid the increase in the number of parts needed for the protection; and to reduce the space needed for the protection. Furthermore, because the reduction in the lengths of the electric wires leads to reduction in radiation noise which occurs while an electric power is being supplied, it is possible to simplify the shielding measurements. Moreover, because neither the electric wires nor the cooling pipes exist under the floor, no attention needs to be paid to contact which would otherwise occur between the electric wires and the ground as well as between the cooling pipes and the ground, or a collision which would otherwise occur between the electric wires and protrusions or the like on the road surface as well as between the cooling pipes and protrusion or the like on the road surface.

The fuel cell unit10including the fuel cell15is placed in the location which is close to the lateral sides of the battery16and the power control unit7(in the back of the battery16and the power control unit7in this embodiment), and which is isolated from the vehicle interior5. For this reason, not only the power control unit7and the battery16but also the fuel cell unit10can be compactly arranged while placing the power control unit7, the battery16and the fuel cell unit10closer to one another, thereby making it possible to inhibit operating noise of the fuel cell unit10from entering the vehicle interior5.

Moreover, the cooling system40configured to cool the power control unit7by circulating the cooling water includes: the pump41configured to circulate the cooling water; and the radiator9configured to cool the cooling water by releasing the heat from the cooling water. The cooling system40is configured in a way that, starting at the radiator9, the coolant sequentially passes the power control unit7, the battery16and the motor17in this order. For these reasons, the motor17and the battery16can be cooled in addition to the power control unit7. Thus, it is possible to integrate the power control unit7, the battery16, the motor17and the radiator9into the unitary cooling system40. In addition, it is possible to construct the cooling system40in a compact size, and accordingly to reduce the lengths of wires, pipes and the like which constitute part of the cooling system40.

Additionally, the heater42is interposed between the power control unit7and the outlet side of the pump41configured to suck the cooling water from the radiator9. For this reason, it is possible to heat the cooling water by use of the heater42, and accordingly to raise the temperature of the battery16when the temperature thereof is low.

Besides, the individual bypass circuits43,44,45and46are connected to the power control unit7, the battery16, the motor17and the radiator9, respectively. For this reason, it is possible to make the cooling water ready to flow to the bypass circuits43to46, and accordingly to cause the coolant to flow to each of the power control unit7, the battery16, the motor17and the radiator9only when deemed necessary.

In addition, the cooling system40includes the control valve means47,48,49and50, respectively, for the power control unit7, the battery16, the motor17and the radiator9. The control valve means47,48,49and50are configured to control of the flow of the cooling water to the bypass circuits43,44,45and46in accordance with the temperature of the coolant which is flowing in each of the power control unit7, the battery16, the motor17and the radiator9. For this reason, it is possible to perform the cooling optimally in accordance with the conditions of the power control unit7, the battery16, the motor17and the radiator9, by controlling the amount of coolant to be flowed in each of the bypass circuits43to46individually corresponding to the power control unit7, the battery16, the motor17and the radiator9by use of the control valve means47to50in accordance with the temperature of the cooling water which is flowing in each of the power control unit7, the battery16, the motor17and the radiator9.

Furthermore, the lowest temperature to be maintained is set for each of the power control unit7, the battery16and the motor17. The controller51configured to control the operation of the pump41stops the operation of the pump41when the temperatures of the cooling water in all of the power control unit7, the battery16and the motor17are at or below the corresponding lowest temperature. For these reasons, it is possible to avoid wasteful energy loss which would occur if the pump41would be operated while no cooling is necessary.

An embodiment of the present invention is explained above, but the present invention is not limited to the above-mentioned embodiment and may be modified in a variety of ways as long as the modifications do not depart from the gist of the present invention.

The foregoing descriptions have been provided for the embodiment in which, for example, the fuel cell15is used as the electric power generating source. Nevertheless, the present invention can be applied to a hybrid vehicle in which an electric power generator configured to be driven by an engine is used as the electric power generating source.