Power supply device for vehicle performing regenerative braking

Abstract

A power supply device comprises a lead-acid battery disposing a plurality of cells in a battery case of a rectangular parallelepiped shape having a pair of facing walls and a pair of end surface walls at the circumference of a rectangular bottom surface plate, and a power storage device connected in parallel to the lead-acid battery. The power storage device has a larger storage capacity by regenerative braking than that of the lead-acid battery, and the power storage device has an external case having a heat radiation plate disposed in a thermally connected state to the facing wall of the lead-acid battery, and the heat radiation plate is thermally connected to the facing wall of the lead-acid battery.

Claims

1. A power supply device for a vehicle performing regenerative braking, the power supply device comprising: a lead-acid battery disposing a plurality of cells in a battery case of a rectangular parallelepiped shape, the battery case having a pair of facing walls and a pair of end surface walls at the circumference of a rectangular bottom surface plate; and a power storage device connected in parallel to the lead-acid battery, wherein the power storage device has a larger capacity by regenerative braking than that of the lead-acid battery, wherein the power storage device has a plurality of condensers or a plurality of secondary batteries disposed in an external case, the external case being arranged adjacent to one of the facing walls of the battery case of the lead-acid battery, wherein the external case of the power storage device has a heat radiation plate disposed in a thermally connected state between (i) the one of the facing walls of the battery case of the lead-acid battery and (ii) the condensers or the secondary batteries of the external case of the power storage device, and wherein the heat radiation plate is thermally connected to the one of the facing walls of the battery case of the lead-acid battery.

2. The power supply device for a vehicle performing regenerative braking according to claim 1, wherein the secondary batteries are disposed in a horizontal posture and in vertically multiply stacked state in the external case, and each of the secondary batteries is connected by a bus bar of a metal plate, wherein the power storage device further comprises an output terminal connected to an electrode of one of the secondary batteries which is located on an upper surface located opposite a bottom surface of the external case of the power storage device, and wherein the output terminal is connected in parallel to an electrode terminal provided on an upper surface of battery case of the lead-acid battery through a connecting plate of a metal board.

3. The power supply device for a vehicle performing regenerative braking according to claim 2, wherein the secondary batteries are nickel hydride batteries.

4. The power supply device for a vehicle performing regenerative braking according to claim 2, wherein the secondary batteries are lithium ion secondary batteries or lithium polymer batteries.

5. The power supply device for a vehicle performing regenerative braking according to claim 2, wherein the connecting plate has a larger area facing to the battery case of the lead-acid battery than an area facing to the external case of the power storage device.

6. The power supply device for a vehicle performing regenerative braking according to claim 1, wherein the power storage device is a condenser.

7. The power supply device for a vehicle performing regenerative braking according to claim 1, wherein the lead-acid battery is connected in parallel to the power storage device through a connecting plate having a heat radiation fin.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a block diagram showing a state where a vehicle performing regenerative braking incorporates a power supply device related to one embodiment of the present invention.

(2) FIG. 2 is a schematic perspective view showing the power supply device related to one embodiment of the present invention.

(3) FIG. 3 is a plan view of the power supply device of FIG. 2.

(4) FIG. 4 is a vertical longitudinal sectional view of a power storage device of the power supply device of FIG. 2.

DESCRIPTION OF EMBODIMENTS

(5) Hereinafter, the embodiment of the present invention will be described referring to drawings. However, the following embodiments illustrate a power supply device for a vehicle performing regenerative braking which is aimed at embodying the technological concept of the present invention, and the present invention is not limited to the power supply device for a vehicle performing regenerative braking described below. Further, the members illustrated in Claims are not limited to the members in the embodiments.

(6) The power supply device shown in a block diagram of FIG. 1, is installed in the vehicle performing regenerative braking. Preferably, it is installed in the vehicle having a regenerative braking function and an idle stop (idle reduction) function. This power source device includes a lead-acid battery 1 and a power storage device 2. The lead-acid battery 1 and the power storage device 2 are connected in parallel, and are charged with regenerative generation power. The regenerative generation power is stored in both of the lead-acid battery 1 and the power storage device 2. In the power supply device installed in the vehicle having the idle stop function, power is supplied from both of the lead-acid battery 1 and the power storage device 2 to a starter motor 32, or from only the lead-acid battery 1 to the starter motor 32.

(7) The vehicle having the idle stop function rotates the alternator 33 by kinetic energy at deceleration. In the regenerative braking state, a wheel 34 rotates the engine 31, and the engine 31 rotates the alternator 33. A rotating torque of the alternator 33 brakes and decelerates the vehicle through the engine 31. Power generated from the alternator 33 by regenerative braking becomes large in direct proportion to kinetic energy of the vehicle. The kinetic energy of the vehicle becomes large in direct proportion to the product of the weight of the vehicle multiplied by the square of the speed. For example, a vehicle of the speed 60 km/h and 1 ton has the kinetic energy of approximate 40 Wh. Assuming that the battery is charged with an efficiency 50% of the kinetic energy, a standard size car of the speed 60 km/h can charge the battery with power of 20 Wh each time the vehicle is stopped due to waiting for a traffic light. Therefore, assuming that the vehicle driving at the speed 60 km/h stops by 20 seconds and the battery of 12 V is charged with a constant current, an output current of the alternator 33 at regenerative braking is 300 A, and it is very large.

(8) As mentioned above, in the regenerative braking, during a short time until stopping of the vehicle, the output current of the alternator 33 becomes very large, it is important that the output of the alternator 33 generated by the regenerative braking is efficiently stored. In the power supply device of FIG. 1, the lead-acid battery 1 is connected in parallel to the power storage device 2.

(9) The power storage device 2 comprises secondary batteries 2a or condensers. The power storage device 2 has a storage capacity of the regenerative braking larger than that of the lead-acid battery 1. The power storage device 2 of the secondary batteries 2A has a charging resistance smaller than that of the lead-acid battery 1 in order to get a larger storage capacity than that of the lead-acid battery 1. The secondary batteries 2A are nickel hydride batteries. As the nickel hydride battery has a nominal voltage 1.2 V, 10 series connection of the nickel hydride batteries has a nominal voltage 12 V of the power storage device 2. As the power storage device 2 of the nickel hydride batteries has the same nominal voltage as the lead-acid battery 1, the power storage device 2 can be connected in parallel to the lead-acid battery 1 without a circuit for adjusting voltage such as a DC/DC converter. Here, as the secondary batteries of the power storage device, the non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries or lithium polymer batteries which has charging resistance smaller than that of the lead-acid battery, can be used. The nickel hydride batteries have very small charging resistance and excellent charging characteristics by large current. The non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries have light weight and those can makes charging and discharging capacity large.

(10) The power storage device 2 of the secondary batteries 2A having charging resistance smaller than that of the lead-acid battery, is connected in parallel to the lead-acid battery 1, and charging current at the regenerative braking is made larger than that of the lead-acid battery 1, and then the storage capacity larger than the lead-acid battery 1 is made. In this power supply device, charging current of the power storage device 2 at the regenerative braking is made large, and charging current of the lead-acid battery 1 is made small, and then the degradation of the lead-acid battery 1 by large charging current can be suppressed.

(11) The condensers as the power storage device 2 are electric double layer capacitors having large electrostatic capacity. The power storage device 2 of the condensers has very small charging resistance, and storage capacity at the regenerative braking can be larger than that of the lead-acid battery 1. Further, as its discharging resistance is also small, it is connected in parallel to the lead-acid battery 1, and then power can be supplied to the starter motor 32. Here, as the voltage of the condenser is changed according to stored capacity, namely stored electrical charge, it is connected to the lead-acid battery 1 through a bidirectional DC/DC converter.

(12) A perspective view of FIG. 2 and a plan view of FIG. 3 show the lead-acid battery 1 and the power storage device 2 which are connected in parallel to each other. In the power supply device of these figures, the lead-acid battery 1 and the power storage device 2 are connected in parallel through connecting plates 3. In the power supply device having the power storage device of the condenser, not shown in figures, the bidirectional DC/DC converter is connected at the middle of the connecting plate which connects the positive sides of the lead-acid battery and the power storage device.

(13) In the lead-acid battery of FIG. 3, in each of cells 1A divided in a battery case 10, not shown in figures, the positive and negative electrode plates are stacked in an insulating state by separators and disposed, and the electrolyte is injected at a predetermined liquid surface level. The battery case 10 has a pair of facing walls 12 and a pair of end surface walls 13 at the circumference of a rectangular bottom surface plate 14, and an upper surface plate 11 closes an upper surface thereof, and has a rectangular parallelepiped shape. As the cell voltage of the lead-acid battery 1 is 2V/cell, in the lead-acid battery 1 having a nominal voltage 12V, the battery case 10 is divided in 6 cells, and the electrode plates disposed in the cells 1A are connected in series. Dividing walls 15 divide the battery case 10 into 6 cells, and are disposed in a parallel posture to the end surface walls 13, and both end edges thereof are coupled to the inner surfaces of the facing walls 12. The battery case 10 is made of an insulating plastic of ABS resin, and molded and made in a shape where the upper surface is opened and the plurality of the cells 1A are divided by the dividing walls 13. The upper opened portion of the battery case 10 is water-tightly closed by the upper surface plate 11. In this lead-acid battery 1, the positive and negative electrode terminals 19 are disposed and fixed at the upper surface plate 11.

(14) As shown in FIG. 3 and FIG. 4, in the power storage device 2, the secondary batteries 2A or the condensers are stored in an external case 20. The external case 20 has a rectangular parallelepiped shape, and a pair of heat radiation plates 22 which are disposed so as to face each other in the vertical surfaces. The secondary batteries 2A or the condensers are disposed between the pair of the heat radiation plates 22. In the external case 20, end portion plates 23 are coupled to both ends of the heat radiation plates 22, and then the rectangular parallelepiped shape is made. An upper surface plate 21 having output terminals 29 closes an upper opened portion, and a bottom surface plate 24 closes a lower opened portion.

(15) One of the radiation plates 22 in the external case 20 is disposed in a thermally connected state to the facing wall 12 of the battery case 10, and heat generation of the power storage device 22 is radiated to the lead-acid battery 1. Further, the plurality of the cells 1A of the lead-acid battery 1 are disposed in a thermally connected state to the facing wall 12 such that heat of the radiation plate 22 is radiated to the plurality of the cells 1A of the lead-acid battery 1. In the power storage device 2 of FIG. 2, the radiation plate 22 is disposed in a thermally connected state to the facing wall 12 of the 6 cells in the lead-acid battery 1. A thermal conductive sheet 4 or thermal conductive paste is sandwiched between the radiation plate 22 and the facing wall 12 of the lead-acid battery 1, and then they are disposed in the ideally thermally connected state. Here, in order that the facing wall and the radiation plate tightly contact, their surfaces are made in flat shapes, and then they directly, tightly contact and are disposed in the thermally connected state.

(16) In the power storage device 2 of FIG. 4, the plurality of the secondary batteries 2A are disposed in a horizontal posture and in vertically, multiply stacked state, and each of the secondary batteries 2A is connected in series by a bus bar 25 of a metal plate. In the power storage device 2 of this figure, the nickel hydride batteries of the cylindrical batteries are used as secondary batteries 2A, and the secondary batteries 2A are disposed in vertically 5 stacked and 2 rows, and each of the secondary batteries 2A is connected in series, and then its nominal voltage coincides with the lead-acid battery 1. The 5 pieces of the vertically stacked secondary batteries 2A are connected in series, and the 2 rows of the secondary batteries 2A are also connected in series, and then 10 pieces of the secondary batteries 2A are connected in series. The electrodes of the secondary batteries 2A of the uppermost stage are connected to the output terminals 29 by lead boards 26 of metal boards. In the power storage device 2 of FIG. 4, the cylindrical batteries are disposed in the horizontal posture and in multiply stacked state. However, in place of the cylindrical batteries, the plurality of the condensers can be also disposed in the horizontal posture and in multiply stacked state.

(17) In the power storage device 2 where the secondary batteries 2A are disposed in the multiply stacked state, a temperature of the secondary batteries 2A in the upper stages is higher than that in the lower stages. It is a reason why the air heated by the secondary batteries 2A rises in the external case 20. The heat energy of the secondary batteries 2A in the upper stages transmits to the output terminals 29 through the lead boards 26. The heat energy transmitted to the output terminals 29, is radiated by the connecting plates 3 which connect the output terminals 29 to the electrode terminals 19, and is transmitted to the electrode terminals 19 and is radiated.

(18) The connecting plates 3 connect the output terminals 29 of the power storage device 2 to the electrode terminals 19 of the lead-acid battery 1, and then the lead-acid battery 1 and the power storage device 2 are connected in parallel. In the power supply device of FIG. 2 and FIG. 3, as the electrode terminals 19 are provided at the upper surface of the lead-acid battery 1, and the output terminals 29 are provided at the upper surface of the power storage device 2, the connecting plates 3 are disposed at the upper surfaces of the battery case 10 and the external case 20. Each of the connecting plates 3 has predetermined width and thickness, and is a metal board having heat radiation fin 5 at the upper surface thereof. The connecting plates 3 radiate the heat transmitted from the output terminal 29 of the power storage device 2. The connecting plate 3 of FIG. 2 and FIG. 3 has a larger area facing to the battery case 10 of the lead-acid battery 1 than an area facing to the external case 20 of the power storage device 2, and then the heat is more efficiently radiated. As the connecting plates 3 can more efficiently radiate the heat at the lower ambient temperature, the area facing to the battery case 10 at the lower temperature of the lead-acid battery 1 is made larger than the area facing to the external case 20 at the higher temperature of the power storage device 2, and then the heat is more efficiently radiated.

(19) In the above power supply device, at the regenerative braking, generated power by the alternator 33 is stored in the lead-acid battery 1 and the power storage device 2. The stored power is used at restarting of the engine 31, and is supplied to operate the electrical equipment 30. The power storage device 2 and the lead-acid battery 1 generate heat, but the power storage device 2 having the larger storage capacity makes the larger heat generation amount than that of the lead-acid battery 1. Therefore, in the state of driving the vehicle, namely in the ON state of the ignition switch as the main switch, the temperature of the power storage device 2 becomes higher than that of the lead-acid battery 1. The heat generation energy of the power storage device 2 at the increased temperature is transmitted from the heat radiation plates 22 of the external case 20 to the facing wall 12 in the thermally connected state of the lead-acid battery 1. Further, the heat generation energy of the power storage device 2 is transmitted to the connecting plates 3 through the output terminals 29, and then the heat is also radiated from the connecting plates 3. In addition, as the connecting plates 3 are connected to the electrode terminals 19, the heat is transmitted from the connecting plates 3 to the electrode terminals 19, and the heat also radiated also from the lead-acid battery 1.

INDUSTRIAL APPLICABILITY

(20) The power supply device of the present invention is installed in the vehicle having the regenerative braking function, and improves a fuel efficiency, and prevents the abnormal temperature increase of the power storage device which stores regenerative generation power, and then can be safely used.