JP2010184538A - Low floor type electric vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To lower a floor face as much as possible in a low floor type electric vehicle using an in-wheel motor. <P>SOLUTION: The low floor type electric vehicle includes: the in-wheel motor incorporated in a wheel; a nickel hydrogen battery supplying driving power to the in-wheel motor; an inverter converting output power from the nickel hydrogen battery into the driving power to output to the in-wheel motor, and regenerating the power generated in the in-wheel motor to the nickel hydrogen battery; a control part controlling the inverter; and a storage part storing the nickel hydrogen battery. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a battery-driven low floor electric vehicle.

  In recent years, from the viewpoint of barrier-free, low-floor riding vehicles such as low-floor buses have been recently developed and put into practical use for the purpose of safety, facilitation and smoothing of getting on and off for elderly people, persons with disabilities and wheelchair users. (For example, refer to Patent Document 1). The low-floor bus is designed so that the floor surface of a substantial part in the vehicle has the same height as the above-mentioned entrance / exit floor surface in consideration of the convenience of getting on and off by a wheelchair user. It is recommended that the height at the time of getting on and off the entrance / exit floor is 270 mm or less as a main standard to be satisfied by a low-floor bus that has been put into practical use ("Establishment of facilitation of movement related to public transport vehicles etc. Guideline (Supervised by Ministry of Land, Infrastructure, Transport and Tourism Policy Bureau, Safe Life Policy Division, Issued: Traffic Ecology and Mobility Foundation, issued in July 2007).

  Many existing buses are driven by a diesel engine, and are equipped with a diesel engine, a transmission, a differential mechanism, and the like. FIG. 7 shows (1) a schematic exploded plan view of a conventional low-floor bus 24 ′ driven by a diesel engine (that is, a plan view with the roof portion of the bus removed) and (2) a schematic longitudinal sectional view. is there. In addition, the longitudinal cross-sectional view of (2) is a longitudinal cross-sectional view by the surface which passes along AA 'shown in (1) and cuts a bus | bath vertically. The side on which the driver's seat 26 is provided is the front direction of the bus (the driver's seat is omitted in the longitudinal sectional view (2)). In the front half of the bus, the floor surface 25 is designed to be low, and the front seats 32r, 32l other than the seats 28r, 28l provided on the front wheel tire houses 42r, 42l are installed on the low floor surface 25. However, as shown in FIG. 7, in the rear half of the bus, the floor surface 27 is high and the entire floor surface is not low. This is because the space 48 under the floor 27 in the rear half of the bus and the space behind the rear seat contain various devices related to diesel engines, transmissions, and differential mechanisms. is there.

  On the other hand, there is an in-wheel motor technology that generates a driving force by a motor that is directly connected to a hub and incorporated in a wheel that supports a tire as a technology for securing a space for an occupant in a vehicle. For example, Patent Document 2 and Non-Patent Document 1 disclose a large bus equipped with an in-wheel motor. FIG. 8 shows a schematic configuration diagram of a drive system 2 ′ for a large vehicle using an in-wheel motor (IWM) 6. The drive system 2 ′ mainly includes a lithium ion battery 4 ′, a drive system 60, and a regeneration system 58. The drive system 60 includes an inverter 8, an in-wheel motor 6, and a drive torque command control unit 10. A drive system 60 is provided for each of the four wheels. Each inverter 8 receives control by the torque command from the drive torque command control unit 10, converts the DC input from the lithium ion battery 4 ′ to AC and outputs it to the in-wheel motor 6.

  The regeneration system 58 includes a chopper 52, a capacitor 54, and a charge / discharge control unit 56. The chopper 52 is provided for charging and discharging the capacitor 54. When the regenerative (deceleration) mode is entered and a current flows in the direction of charging the lithium ion battery 4 ′, the charge / discharge control unit 56 controls the current to flow to the chopper 52 to the capacitor 54 side, and the regenerative energy is absorbed by the capacitor 54. The When the power running (acceleration) mode is entered and a current flows in the direction in which the lithium ion battery 4 ′ is discharged, the charge / discharge control unit 56 controls to release the energy stored in the capacitor 54. One regenerative system 58 is provided in the entire drive system 2 '. “Power running” indicates a state in which an accelerator is normally depressed in the case of an automobile using an internal combustion engine, and a state in which electric power is supplied to a motor in the case of an electric vehicle.

  In the vehicle drive system that uses the in-wheel motor 6, since the driving force is generated by the motor built in the wheel that supports the tire, from the engine and motor mounted on the vehicle body to the tire, which is necessary for ordinary vehicles It is not necessary to mount driveline devices such as a transmission, a differential gear, a propeller shaft, and a drive shaft that transmit driving force on the vehicle body, and space for these devices can be secured.

  However, in the drive system 2 ′ using the in-wheel motor (IWM) 6 described above, a space for mounting the regenerative system 58 including the chopper 52 and the capacitor 54 is still necessary. Therefore, even if the drive system 2 ′ for a large vehicle using the in-wheel motor (IWM) 6 described above is used for a low floor bus, at least a part of the space 48 under the high floor surface 27 in the rear half of the bus. Is inevitable to leave as a space for mounting the regenerative system 58.

JP 2008-62680 A JP 2008-189118 A

“Development of in-wheel motor system for 22.5 inch wheel built-in type large bus”, Toyo Denki Technical Bulletin No. 113, 2006-3, pp. 9-14.

  As described above, the conventional engine-type low-floor bus is not flat on the entire floor surface. In consideration of user convenience, safety, etc., an all-low floor bus that does not have a high floor surface, that is, the entire floor surface is desired.

  Moreover, when using the in-wheel motor of patent document 2 for a vehicle, it is necessary to accommodate a regeneration system apparatus (apparatus included in the regeneration system 58) somewhere in the vehicle body. Therefore, it is conceivable to store in the rear half of the vehicle body like the conventional engine-type bus, and there is a problem that the entire floor cannot be made flat as in the conventional case.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electric vehicle having a full floor flat floor.

The present invention has been made to achieve the above object. The low floor electric vehicle according to the present invention is
An in-wheel motor built into the wheel,
A nickel metal hydride battery for supplying driving power to the in-wheel motor;
An inverter that converts output power from the nickel-metal hydride battery into drive power and outputs the drive power to the in-wheel motor, and regenerates power generated by the in-wheel motor to the nickel-metal hydride battery,
A control unit for controlling the inverter;
A storage unit for storing the nickel metal hydride battery.

  It is preferable that the storage portion is provided in a lower space of the passenger seat.

  The inverter is preferably a variable voltage variable frequency control inverter, and the allowable range of the input voltage is preferably configured such that the nominal voltage is the median value of the allowable range.

  It is preferable that there is no step on the floor of the vehicle.

The nickel metal hydride battery is composed of one or more battery modules,
The battery module is
A plate-like positive electrode current collector and a negative electrode current collector, which are provided to face each other, a separator disposed between the positive electrode current collector and the negative electrode current collector, and a positive electrode cell in contact with the positive electrode current collector And a plurality of unit cells having a negative electrode cell in contact with the negative electrode current collector are stacked so that the positive electrode current collector of one of the unit batteries adjacent to the negative electrode current collector of the other unit battery faces each other. It is preferable that a flow path of a heat transfer medium made of gas or liquid is provided between the unit cells adjacent to each other.

  According to the present invention, the floor surface of a passenger electric vehicle can be a full-flat, low-floor type over substantially the entire surface. In such a low-floor type riding electric vehicle, the range that can be used by elderly people, persons with disabilities and wheelchair users is wider than that of a normal low-floor bus, and it is possible to easily and smoothly get on and off.

1 is a schematic configuration diagram showing a drive system for a large vehicle using an in-wheel motor according to a preferred embodiment of the present invention. It is a more detailed block diagram which shows the drive system for the large sized vehicle using the in-wheel motor which concerns on suitable embodiment of this invention. (1) A schematic plan exploded view of a low floor bus equipped with a drive system for a large vehicle using an in-wheel motor according to a preferred embodiment of the present invention, with the roof portion of the bus removed (2) FIG. 2 is a schematic longitudinal sectional view. It is a SOC characteristic figure which shows the voltage change with respect to SOC (state of charge), such as various batteries. (1) It is a cross-sectional view of the battery module of one structural example, (2) The partial perspective view of the battery module of the same one structural example. In the perspective view of (2), the air flow direction in the heat transfer plate is shown. It is a perspective view of the heat exchanger plate used for the battery module of one structural example. FIG. 2 is a schematic plan exploded view of a conventional low-floor bus driven by a diesel engine, with the roof portion of the bus removed, and (2) a schematic longitudinal sectional view. It is a schematic block diagram of the drive system for the large vehicles using an in-wheel motor.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

Embodiment
FIG. 1 is a schematic configuration diagram showing a drive system 2 for a large vehicle according to a preferred embodiment of the present invention.

  A drive system 2 according to the present invention includes a nickel metal hydride battery 4, an in-wheel motor 6, a variable voltage variable frequency control inverter 8 (hereinafter abbreviated as "inverter 8"), and a drive torque command control unit 10. .

  When the vehicle is accelerating (powering mode), each inverter 8 receives control by a torque command from the drive torque command control unit 10, converts the DC input from the nickel-metal hydride battery 4 to AC and converts it to the in-wheel motor 6. Output. On the other hand, when the vehicle is decelerated (regeneration mode), the in-wheel motor 6 is used as a generator, and the inverter 8 converts AC power from the in-wheel motor 6 into DC power and outputs it to the nickel metal hydride battery 4. At this time, the nickel metal hydride battery 4 is charged. As will be described later, the inverter 8 and the in-wheel motor 6 are provided for each of the four wheels.

  FIG. 2 is a more detailed configuration diagram showing a drive system 2 for a large vehicle using an in-wheel motor according to a preferred embodiment of the present invention.

  In the drive system 2 shown in FIG. 2, the positive input terminal of the inverter 8 is connected to the positive external terminal of the nickel metal hydride battery 4 through the high-speed circuit breaker 12, the electromagnetic contactor 14, and the filter reactor 16. A negative external terminal of the nickel metal hydride battery 4 is connected to the negative input terminal of the inverter 8. A filter capacitor 18 that forms a low-pass filter together with the filter reactor 16 is connected in parallel with the inverter 8. An in-wheel motor 6 for driving the vehicle for driving the wheels 29 is connected to the output terminal of the inverter 8.

  The drive regeneration systems 20a, 20b, 20c, and 20d including the high-speed circuit breaker 12, the magnetic contactor 14, the filter reactor 16, the filter capacitor 18, the inverter 8, and the in-wheel motor 6 are provided for each of the four wheels 29. Provided. That is, the four wheels 29 can be controlled to operate freely independently of each other.

  Further, the positive side external terminal of the nickel metal hydride battery 4 is connected to the positive side input terminal of the inverter 9 via the high speed circuit breaker 13, the electromagnetic contactor 15, and the filter reactor 17, and the negative side input terminal of the inverter 9. Is connected to the negative external terminal of the nickel-metal hydride battery 4. A filter capacitor 19 that forms a low-pass filter together with the filter reactor 17 is connected in parallel with the inverter 9. A load 7 is connected to the output terminal of the inverter 9. The load 7 is an auxiliary device such as an air conditioner, a lighting device, a brake compressor, and a heating device, and the inverter 9 is an auxiliary power supply device that supplies power to the auxiliary device.

  The control device 11 has an inverter 8, a high-speed circuit breaker 12, and an electromagnetic device according to a command signal from a driving command stand by a driver's driving operation, a rotational speed from a speed sensor attached to the in-wheel motor 6, and the like. The contactor 14 is controlled separately for the drive regeneration systems 20a, 20b, 20c, and 20d. Further, the control device 11 controls the inverter 9, the speed breaker 13 and the electromagnetic contactor 15 connected to the auxiliary machine (load 7).

  The magnetic contactors 14 and 15 are turned on and off in response to turning on and off of the power switch of the operation command stand. The high-speed circuit breakers 12 and 13 are protection circuits for interrupting overcurrent.

  The direct current power from the nickel metal hydride battery 4 is supplied to the inverter 8, and the inverter 8 converts the supplied direct current power into three-phase alternating current power having a frequency and a voltage according to the command speed from the operation command table, and an in-wheel motor. Output to 6. The in-wheel motor 6 is driven by three-phase AC power supplied from the inverter 8.

  Further, the DC power from the nickel metal hydride battery 4 is supplied to an inverter 9, which converts the supplied DC power into three-phase AC power having a constant voltage and a constant frequency and outputs it to the load 7.

  When the drive system 2 decelerates, the in-wheel motor 6 is used as a generator, and the inverter 8 is operated as a converter to convert the three-phase AC power from the in-wheel motor 6 into DC power and output it to the nickel metal hydride battery 4. To do. At this time, the nickel metal hydride battery 4 is charged.

  The nickel metal hydride battery 4 is configured to have a battery voltage corresponding to a voltage within the allowable input voltage range of the inverters 8 and 9, and discharges and charges with regenerative power from the inverter 8 during regenerative braking.

  The nickel-metal hydride battery 4 has a pair of external terminals connected to the inverter 8 without a charge / discharge control device. The charge / discharge control device is, for example, a DC / DC converter (DC voltage converter).

[Large floor structure of large bus]
3 shows (1) a schematic plan exploded view (that is, a plan view with the roof portion of the bus removed) of the low floor bus 24 equipped with the drive system 2 of the present embodiment, and (2) a schematic longitudinal section. FIG. Note that the longitudinal sectional view of FIG. 3 (2) is a longitudinal sectional view of a surface that passes through AA ′ shown in FIG. 3 (1) and vertically crosses the bus. The side where the driver's seat 26 is provided is the front direction of the bus (the driver's seat is omitted in the longitudinal sectional view (2)).

  The low floor bus according to the present embodiment employs an in-wheel motor. As a result, it is necessary to mount driveline devices such as transmissions, differential gears, propeller shafts, drive shafts, etc., that are required for ordinary vehicles and that transmit drive power from the engine and motor to the tires, which are mounted on the vehicle body. Space for these devices can be secured.

  However, when the in-wheel motor is simply employed, there is a problem that a place for accommodating the regenerative system (the regenerative system 58 shown in FIG. 8) is required as described in the background art. In this embodiment, this problem is solved by using a nickel metal hydride battery as a secondary battery of a voltage supply source.

  Details of the nickel-metal hydride battery will be described later. However, the nickel-metal hydride battery has a very small voltage change (ΔV / ΔSOC) with respect to SOC (state of charge) variation, a small internal resistance, a high volume energy density, and the like. Compared with the secondary battery, the battery capacity can be reduced. In other words, since the voltage change of the nickel metal hydride battery is very small even if the SOC greatly varies, a large current can be instantaneously passed, and even if the nickel metal hydride battery is discharged, the decrease in the power supply voltage is suppressed. In addition, even if an instantaneous large current is generated and charged, an increase in battery voltage can be suppressed. Moreover, rapid and large current discharge can be performed even in a low SOC state, and rapid and large current charging can be performed even in a high SOC state. Since it has such a characteristic, the external mechanism (charge / discharge control apparatus) for controlling charging / discharging at the time of the charge and discharge of the electric power with respect to a nickel metal hydride battery becomes unnecessary. Therefore, it is not necessary to provide a regenerative system device (the chopper 52, the capacitor 54, and the charge / discharge control unit 56 included in the regenerative system 58 shown in FIG. 8) that is necessary in the configuration of the conventional in-wheel motor.

  Further, in the conventional in-wheel motor system as shown in FIG. 8, when the current enters the deceleration (regeneration) mode and the lithium ion battery 4 ′ is charged, the charge / discharge control unit 56 causes the chopper 52 to the capacitor. Control is performed so that the current is diverted to the side 54, and the regenerative energy is absorbed by the capacitor 54. When an acceleration (power running) mode is entered and a current flows in the direction of discharging the lithium ion battery 4 ′, control is performed so as to release the energy stored in the capacitor 54. That is, the electric power generated during regeneration is stored only in the capacitor 54, and the stored electric power is used during powering, and the regenerative system 58 functions as a temporary storage unit for regenerative power.

  On the other hand, the nickel metal hydride battery 4 used in the present embodiment also charges regenerative power from the motor. That is, the battery 4 'and the capacitor 54 shown in FIG. Also from this point, the use of the nickel metal hydride battery 4 eliminates the need for the capacitor 54 and the associated device such as a chopper, which are necessary for charging the regenerative power in the prior art. Generally, the volume of a device related to a chopper or a capacitor for using regenerative power is very large. Therefore, if these choppers and capacitors are omitted, the available space in the vehicle increases. In addition, since the regenerative power charged in the nickel-metal hydride battery 4 can be used not only during power running but also as auxiliary power, charging the regenerative power to the nickel-metal hydride battery 4 has an advantage that leads to effective use of the regenerative power. is there.

  Further, in the present embodiment, as shown in FIG. 3B, the nickel metal hydride batteries 4 are stored in the lower space 36 of the passenger seats 32r, 32l, 34r, 34l as appropriately dispersed. The nickel metal hydride battery 4 can be miniaturized because of its SOC characteristics, low internal resistance, and high volumetric energy density, so that it can be stored under the seat and the entire floor of the bus can be lowered. In the large bus shown in FIG. 3, the variable voltage variable frequency control inverter 8 is disposed, for example, in the space 40 behind the rear seat.

  Thus, in the low floor bus 24 equipped with the drive system 2 of the present embodiment, the increase in the space in the vehicle due to the provision of the in-wheel motor, the regeneration system portion due to the provision of the nickel metal hydride battery. Lowering the entire floor is achieved by eliminating the need and effectively using the space under the seat.

  Since the nickel metal hydride battery has a small volume and can be stored in a dispersed manner, the nickel hydride battery can be stored in a space other than the space 36 below the seat, such as a space where the thickness under the roof of the vehicle is not so large. It is also possible to store a nickel metal hydride battery.

[About nickel metal hydride batteries]
Hereinafter, the nickel metal hydride battery 4 used in the drive system 2 of the present embodiment will be described in detail.

  The nickel metal hydride battery 4 is constituted by a battery module in which a plurality of unit batteries are connected in series, and may be constituted by a single battery module, or a series battery module in which a plurality of battery modules are connected in series. It may be configured. Alternatively, the single battery module or the series battery module may be connected in parallel. When connected in parallel, the battery capacity increases and the equivalent internal resistance decreases.

  FIG. 4 is an SOC characteristic diagram showing a change in voltage with respect to SOC (state of charge) of various batteries. Curve a shows the voltage change of the nickel metal hydride battery, curve b shows the voltage change of the lead acid battery, curve c shows the voltage change of the lithium ion battery, and curve d shows the voltage change of the electric double layer capacitor.

  The voltage change (ΔV / ΔSOC) with respect to the SOC variation is about 0.1 for a nickel metal hydride battery, about 1.5 for a lead acid battery, about 2 for a lithium ion battery, and about 3 for an electric double layer capacitor. That is, with the same voltage change, the nickel-metal hydride battery can be reduced in battery capacity to 1/15 of the lead-acid battery, 1/20 of the lithium ion battery, and 1/30 of the electric double layer capacitor. Accordingly, the battery size can be reduced accordingly.

As shown in FIG. 4, the nickel metal hydride battery indicated by the curve a has a characteristic that the SOC variation range S with respect to the voltage fluctuation is wider than other batteries. That is, the nickel-metal hydride battery has a small battery voltage fluctuation with respect to the SOC fluctuation. Compared to this, in other batteries shown by the curves b, c, d, the voltage fluctuation is larger than the SOC fluctuation. For example, in terms of the median SOC, a nickel metal hydride battery can be used in almost the entire SOC range when the median voltage is V ₁ and the voltage fluctuation is within the range dV ₁ . The battery capacity can be used effectively. On the other hand, when the lead-acid battery is used so that the median voltage is V ₂ and the voltage fluctuation falls within the range dV ₂ , the SOC can be used only in a narrow range, and the battery capacity is effectively increased. Not available. Similarly, if a lithium ion battery using such a voltage fluctuation and a voltage of the median value and V ₃ is within a range dV _3, can not SOC is used only in a narrow range, it can not be utilized effectively battery capacity . The same applies to the electric double layer capacitor that the SOC range is narrow and the capacity cannot be effectively used within a predetermined voltage fluctuation range including the median voltage. Here, the magnitude of the voltage fluctuation _range, and _{dV 1 / V 1 = dV 2} / V 2 = dV 3 / V 3.

  Considering from the viewpoint of voltage fluctuation, when the SOC is in the middle of the range S (for example, SOC is 40 to 60%), the battery voltage is equal to or substantially equal to the rated input voltage of the inverters 8 and 9. When connected to the inverters 8 and 9 as shown in FIG. 2, even if the state of charge varies due to repeated charging and discharging of the nickel metal hydride battery 4, the variation in the battery voltage can be kept very small. On the other hand, in the case of other batteries (for example, lithium ion batteries), the battery voltage varies greatly. That is, the nickel metal hydride battery can effectively use the battery capacity.

  The allowable input voltage range of the inverters 8 and 9 is a range of about ± 20% with respect to the rated input voltage (for example, 600 V, 750 V, or 1500 V). More specifically, when the rated input voltage is 600V, the allowable input voltage range for which performance is compensated is 400V to 670V, and the maximum allowable range is −40% to + 20% (360V to 720V) of the rated input voltage. . When the rated input voltage is 750V, the allowable input voltage range for which performance is compensated is ± 20% (600V to 900V) of the rated input voltage, and the maximum allowable range is −40% to + 20% (450V to 900V) of the rated input voltage. ). When the rated input voltage is 1500 V, the allowable input voltage range for which performance is compensated is ± 20% (1200 V to 1800 V) of the rated input voltage, and the maximum allowable range is −40% to + 20% of the rated input voltage ( 900V to 1800V). The permissible input voltage range for which the performance is compensated is an input voltage range in which a predetermined performance can be exhibited. The maximum permissible range is an input voltage range that can be operated without a hardware failure.

In the nickel-metal hydride battery, even when almost the entire SOC range is used, the battery voltage fluctuation range can be within ± 20% of the median voltage V ₁ of the SOC.

  When the secondary battery is connected to the inverters 8 and 9 without using the charge / discharge control device, the range in which the entire battery can be charged / discharged is the fluctuation of the input voltage of the inverters 8 and 9. It is the range of the corresponding SOC, and the electric power in the battery is effectively utilized only within that range. Since the nickel-metal hydride battery covers most of the SOC range within the allowable input voltage range of the inverters 8 and 9, the capacity in the battery is effectively used.

  On the other hand, in the case of other types of secondary batteries compared to nickel-metal hydride batteries, the slope of the voltage change with respect to the SOC is large. Therefore, the batteries are effective within a range of about ± 20% allowed for the input voltages of the inverters 8 and 9. Capacity is reduced. That is, if secondary batteries such as lead-acid batteries and lithium ion batteries other than nickel metal hydride batteries are connected to the inverters 8 and 9 without using the charge / discharge control device, the result is compared with the nickel metal hydride battery. In addition, a large number of batteries are required, a large installation space is required, and the equipment cost is high.

  Compared to nickel metal hydride batteries, the internal resistance of lead-acid batteries with the same capacity is about 10 times that of nickel metal hydride batteries, and the internal resistance of lithium ion batteries with the same capacity is about twice that of nickel metal hydride batteries. . For this reason, the charge / discharge current flows more in the nickel metal hydride battery than in the lead storage battery or the lithium ion battery, and the amount of electricity charged / discharged is large. That is, in the nickel metal hydride battery, since the internal resistance is small compared to other secondary batteries having the same capacity, the amount of electricity that can be charged and discharged is large. However, even in the case of lead-acid batteries and lithium-ion batteries, the internal resistance can be reduced if they are connected in parallel, but a large installation space is required and expensive equipment costs are required.

  Since the space for mounting the secondary battery on the passenger vehicle, for example, the lower space 36 of the passenger seat, is limited, it is more advantageous to use the nickel-metal hydride battery 4 that can be miniaturized.

  As described above, if a lead storage battery or a lithium ion battery is to be connected to the inverters 8 and 9 without going through the charge / discharge control device from the point of voltage change with respect to the SOC or the point of internal resistance, a huge amount A large number of batteries are required, a large installation space is required, and an expensive equipment cost is required, which is not practical. In order to eliminate such inconvenience, in other types of secondary batteries, control is performed to use much of the battery capacity by controlling the charge / discharge voltage using an expensive and heavy charge / discharge control device. I must.

  Further, the SOC of the secondary battery changes when the charge / discharge is repeated many times. However, as shown by the curve a in FIG. 4, the nickel metal hydride battery has a stable voltage characteristic in a wide range S of the SOC, and Since the internal resistance is small, the voltage fluctuation can be reduced as a whole.

  For example, when a lithium ion battery is connected instead of the nickel metal hydride battery 4, the lithium ion battery has a large internal resistance. Therefore, when the discharge current increases during vehicle acceleration, the battery voltage drops greatly. Further, when the SOC varies, the voltage also varies greatly. For example, even if the internal resistance can be reduced by connecting a very large number of lithium ion batteries in parallel, the voltage largely fluctuates due to the fluctuation of the SOC as described above. Therefore, it is disadvantageous to use a lithium ion battery instead of the nickel metal hydride battery 2.

  Further, for example, in the case where long-distance traveling is performed using a lithium ion battery instead of the nickel metal hydride battery 4, the battery voltage fluctuation during traveling is within the allowable input voltage range of the inverters 8 and 9. In addition, it is necessary to set the amount of charge so that the increase / decrease in the SOC is within a narrow range including the optimum SOC, and to charge frequently using the charging facility.

  Also in the case of a lead storage battery, the internal resistance is very large, and when the SOC varies, the voltage varies greatly as shown by the curve b in FIG. Therefore, the lead storage battery is not suitable for use in place of the nickel metal hydride battery 2.

  That is, when a lithium ion battery, a lead storage battery, or the like is used in place of the nickel metal hydride battery 2, it is difficult to perform long-distance traveling with a large change in SOC while reducing the number of times of charging.

  As described above, since the nickel metal hydride battery 4 has a low internal resistance and a small voltage fluctuation due to the fluctuation of the SOC, the nickel metal hydride battery 4 is connected to the inverters 8 and 9 without using the charge / discharge control device. Even if the number of times of charging by the charging facility is reduced, long-distance traveling can be performed. In the present embodiment, the battery capacity is set so that a range in which voltage fluctuation due to SOC fluctuation is small (for example, range S in FIG. 4) can be used.

  In the present embodiment, the nickel metal hydride battery 4 is used as a power source for driving the vehicle, and the nickel metal hydride battery 4 has a small internal resistance and a small voltage fluctuation due to the fluctuation of the SOC, so that the battery capacity can be effectively used. Compared to the secondary battery, a small battery having a small capacity can be used, and a large installation space is not required. Further, since a charge / discharge control device such as a step-up / step-down chopper type DC / DC converter is not used, an installation space for the charge / discharge control device is not required. Moreover, since the nickel metal hydride battery 4 has a high volumetric energy density, a large installation space is not required. A very expensive and heavy charge / discharge control device is not required, and the use of a small nickel-metal hydride battery can reduce the overall weight and cost of the vehicle. In addition, since the nickel-metal hydride battery 4 is small and can have a high capacity, the use of the nickel-metal hydride battery 4 makes it possible to reduce the overall weight of the vehicle and to reduce the number of times of charging by the charging facility. Driving is possible.

  In addition, since a very expensive charge / discharge control device such as a step-up / step-down chopper type DC / DC converter is not used, the cost can be reduced. Moreover, there is no operation delay like the step-up / step-down chopper type DC / DC converter, and it has excellent rapid charge / discharge characteristics. Further, since the nickel metal hydride battery 4 has a small internal resistance and a small voltage fluctuation due to the fluctuation of the SOC, the in-wheel motor 6 instantaneously requires a large current when the vehicle is accelerated, and the nickel metal hydride battery 4 is discharged from the nickel hydride battery 4. In addition, the decrease in the battery voltage can be suppressed, and the increase in the battery voltage is suppressed even when the nickel-metal hydride battery 4 is charged by generating a momentary large current due to the regeneration of the in-wheel motor 6 when the vehicle decelerates. be able to.

  As described above, since the nickel metal hydride battery generally has a high volumetric energy density, even a high capacity nickel metal hydride battery 4 using a large number of unit batteries does not require a large installation space. Further, by configuring the nickel-metal hydride battery 4 using a battery module in which unit cells are stacked as in the configuration example described later, the size can be further reduced and the installation space can be further reduced.

  In addition, since the internal resistance is small like the nickel metal hydride battery 4, not only the amount of heat generated inside the battery is small and the heat loss is small, but also the heat dissipation device of the battery itself can be reduced.

  Next, the structural example of the battery module which comprises the nickel metal hydride battery 4 used for this Embodiment is described.

[One configuration example of battery module]
FIG. 5A is a cross-sectional view of a battery module of one configuration example. FIG. 5 (2) is a partial perspective view of the battery module of FIG. 5 (1), showing the flow direction of air in the heat transfer plate in the battery module (however, shown in FIG. 5 (1)). The insulating plates 107 and 108 are omitted). 6 is a perspective view of a heat transfer plate used in the battery module of FIGS. 5 (1) and 5 (2).

  The battery module 81 is formed by stacking a plurality of unit batteries. Each unit battery has a bellows-like separator between the positive electrode current collector 99 and the negative electrode current collector 100 provided opposite to each other, which does not change in corrosion or the like in an alkaline electrolyte, and transmits ions but does not transmit electrons. 101 are alternately arranged so as to be close to both current collectors. Further, in each unit battery, a positive electrode sheet 103 containing a positive electrode active material together with the electrolyte solution 102 is disposed in a space defined by the bellows-shaped separator 101 and the positive electrode current collector 99, and the bellows-shaped separator 101 and the negative electrode current collector are disposed. A negative electrode sheet 104 containing a negative electrode active material together with the electrolyte solution 102 is disposed in a space partitioned by the body 100, and the positive electrode sheet 103 and the negative electrode sheet 104 are alternately incorporated with the separator 101 interposed therebetween. In the unit battery, the separator 101 is formed in a bellows shape, whereby the positive electrode sheet 103 and the negative electrode sheet 104 can be stacked in the unit battery as a large number of cells. This makes it easy to increase the capacity of the unit battery. This also increases the electrode area and allows adjacent cells to be connected with a very small resistance, eliminating the need for a cable for connecting the cells and making the battery compact as a whole.

  The positive electrode sheet 103 is in contact with the positive electrode current collector 99, and the negative electrode sheet 104 is in contact with the negative electrode current collector 100. A heat transfer plate 96 shown in FIG. 6 is inserted between two adjacent unit cells so as to be in contact with the positive electrode current collector 99 of one unit cell and the negative electrode current collector 100 of the other unit cell. Has been. The direction of the air flow hole 97 of the heat transfer plate 96 coincides with the vertical direction of the positive electrode sheet 103 and the negative electrode sheet 104. Between the positive electrode current collector 99 and the negative electrode current collector 100 of each unit battery, the separator 101 is divided into a positive electrode cell and a negative electrode cell, and is divided by the separator 101 and the positive electrode current collector 99 to form the positive electrode sheet 103. The region in which the negative electrode sheet 104 is arranged is the positive electrode cell, and the region in which the negative electrode sheet 104 is divided by the separator 101 and the negative electrode current collector 100 is the negative electrode cell.

  As shown in FIG. 5 (1), the positive electrode current collector 99 and the negative electrode current collector 100 made of a metal having excellent conductivity and good thermal conductivity are in direct contact with the positive electrode sheet 103 and the negative electrode sheet 104, respectively. In addition, each current collector 99, 100 is in contact with a heat transfer plate 96 that serves to electrically connect the positive electrode current collector 99 and the negative electrode current collector 100. As a result, the heat generated as a result of the battery reaction is efficiently transferred to the air flowing through the air flow holes 97 of the heat transfer plate 96 along the direction indicated by the arrow in FIG. Released to the outside. In this way, the temperature of the battery module 81 is maintained in an appropriate range in which the battery reaction can be performed smoothly.

  As shown in FIG. 5 (1), an overall positive electrode current collector 105 is provided at the end of the positive electrode, and an overall negative electrode current collector 106 is provided at the end of the negative electrode. Insulating plates 107 and 108 are provided on the sides of the battery module 81. A connecting positive electrode terminal (not shown) is attached to the central portion of the overall positive electrode current collector 105, and a connecting negative electrode terminal (not shown) is attached to the central portion of the overall negative electrode current collector 106.

  The positive electrode sheet 103 is obtained by, for example, applying a paste obtained by adding a solvent to a positive electrode active material, a conductive filler, and a resin, applying the paste on a substrate, forming a plate, and curing the negative electrode sheet 104. For example, a paste obtained by adding a solvent to a negative electrode active material, a conductive filler, and a resin is applied onto a substrate, formed into a plate shape, and cured. As the positive electrode active material and the negative electrode active material, all known active material materials can be used. As the conductive filler, carbon fiber, carbon fiber nickel-plated, carbon particles, carbon particle nickel-plated, organic fiber nickel-plated, fibrous nickel, nickel particles, or nickel foil alone Or can be used in combination. As the resin, a thermoplastic resin having a softening temperature up to 120 ° C., a resin having a curing temperature from room temperature to 120 ° C., a resin that dissolves in a solvent having an evaporation temperature of 120 ° C. or less, a resin that dissolves in a solvent soluble in water, or Resins that are soluble in alcohol-soluble solvents can be used. As the substrate, a metal plate having electrical conductivity such as a nickel plate can be used.

  The heat transfer plate 96 is made of aluminum and nickel-plated, and has a large number of through holes 97 penetrating in the vertical direction as air flow paths. The heat transfer plate 96 can be inserted between the positive electrode current collector 99 and the negative electrode current collector 100 so that the air sucked by the intake fan 83a and the intake fan 83b can be passed through the flow hole 97. The heat transfer plate 96 is also a member for contacting the positive electrode current collector 99 and the negative electrode current collector 100 to electrically connect the positive electrode current collector 99 and the negative electrode current collector 100, and has electrical conductivity. In that respect, aluminum has a preferable property as the heat transfer plate 96 because it has a relatively low electrical resistance and a relatively high thermal conductivity, but has a drawback of being easily oxidized. Therefore, it is more preferable that the aluminum plate is nickel-plated as the heat transfer plate 96 because not only the oxidation is suppressed but also the contact resistance is lowered by the nickel plating.

  In the battery module 81 described above, since the heat transfer plate 96 provided with the flow holes 97 serving as the heat transfer medium flow path is provided between the unit batteries adjacent to each other, the battery module 81 is effectively cooled. Thus, heat generation of the battery can be effectively suppressed, deterioration of the battery can be suppressed, and the life of the battery can be extended. Further, by making the battery module 81 have a configuration in which unit cells are stacked as described above, the equivalent internal resistance of the battery module can be further reduced. In addition, by making the unit battery have the above-described structure, the positive electrode sheet 103 and the negative electrode sheet 104 become electrode plates, and it is possible to increase the electrode plate area and narrow the electrode plate interval, thereby further reducing the size and increasing the capacity of the battery. Therefore, the nickel-metal hydride battery can be further miniaturized and the installation space can be reduced.

  Instead of the heat transfer plate 96 provided with the flow holes 97, a heat transfer plate (hereinafter referred to as "porous heat transfer") made of a porous member (for example, a porous aluminum plate) not provided with the flow holes 97 is provided. You may use a board. If the heat transfer area is increased by making the porous heat transfer plate porous, the porous heat transfer plate plays a role as a heat transfer member and can sufficiently dissipate heat generated by the battery reaction. Thereby, deterioration of the battery can be suppressed. On the other hand, in addition to using this porous heat transfer plate as a heat radiating member, it can also be used as a heat storage member. In other words, it is not preferable that the heat generated by the battery reaction is trapped in the sealed battery because it promotes the deterioration of the battery. On the other hand, in order to smoothly execute the battery reaction, the battery components must be fixed. It is preferable that it exists in a temperature range (about 25 to 50 degreeC). Therefore, instead of forcibly radiating heat from the porous heat transfer plate, in some cases, in order to suppress the heat radiation in order to keep the battery component member at a certain temperature or higher, for example, about 25 ° C. or higher, A heat insulating material can also be stuck on the outer surface of the heat transfer plate. Similarly, in a structure in which the porous heat transfer plate is forcibly cooled by a fan, heat dissipation can be suppressed by not operating the fan when the battery component is at a certain temperature or lower.

  As the size of the battery increases, the surface area also increases, and cooling of the surface often results in insufficient cooling inside the battery. When the battery has a structure in which a plurality of unit cells are stacked as in the present embodiment, the positive electrode current collector 99 of one unit cell and the other unit are sandwiched between two adjacent unit cells. When the heat transfer plate 96 sandwiched between the negative electrode current collectors 100 of the battery is cooled, the inside of the battery can be effectively cooled.

  As another example of each unit battery to be stacked, an electrolyte solution is inserted between a positive electrode plate that is a positive electrode current collector and a negative electrode plate that is a negative electrode current collector, and the positive electrode cell and the negative electrode cell In the meantime, a separator that does not change in corrosion or alkaline in the alkaline electrolyte and that allows ions to pass through but does not transmit electrons is interposed, and the positive electrode active material is inserted into the positive electrode cell, and the negative electrode active material is inserted into the negative electrode cell. You may use the thing of the structure formed. In this configuration, the separator is planar, and the positive electrode cell and the negative electrode cell are partitioned by the planar separator. For example, a KOH aqueous solution is used as a common electrolyte solution for the positive electrode cell and the negative electrode cell. Nickel hydroxide powder is mixed in the electrolyte solution of the positive electrode cell as a positive electrode powder active material. As a powder active material, hydrogen-absorbing alloy powder is mixed.

[Other low-floor electric vehicles]
In the above-described preferred embodiment of the present invention, the large bus is taken up as an example of the electric vehicle. However, the present invention is applied to other types of electric vehicles, and the electric vehicles are constructed to have a low floor type. be able to. For example, the present invention is applied to a small electric bus, a wagon electric vehicle, an electric truck, an electric wheelchair, etc., and a low floor small electric bus, a low floor wagon electric vehicle, a low floor electric truck, a low floor electric Electric wheelchairs can be constructed.

DESCRIPTION OF SYMBOLS 4 ... Nickel metal hydride battery, 6 ... In-wheel motor, 7 ... Load, 8 ... Variable voltage variable frequency control inverter, 9 ... Inverter, 10 ... Drive torque command control part, 11 ... Control device, 12, 13 ... High-speed circuit breaker, 14,15 ... Electromagnetic contactor, 16,17 ... Filter reactor, 18,19 ... Filter capacitors, 20a, 20b, 20c 20d: Drive regeneration system, 24: Low floor bus, 25 ... Low floor surface, 27 ... High floor surface, 28r, 28l ... Seat on the front tire house, 29 ... Wheels, 30r, 30l ... seats on the front wheel tire house, 32r, 32l, 34r, 34l ... passenger seats, 36 ... space under the seats, 42r, 42l ... front wheel tire house, 44r 44l ... Rear wheel Ear house, 81 ... battery module, 82 ... air circulation space, 83a, 83b ... intake fan, 84 ... air circulation space, 96 ... heat transfer plate, 97 ... air flow hole , 99... Positive electrode current collector, 100... Negative electrode current collector, 101... Ion permeable separator, 102... Electrolyte solution, 103. ... General positive electrode current collector, 106 ... General negative electrode current collector, 107 ... Insulating plate, 108 ... Insulating plate.

Claims (5)

An in-wheel motor built into the wheel,
A nickel metal hydride battery for supplying driving power to the in-wheel motor;
An inverter that converts output power from the nickel-metal hydride battery into drive power and outputs the drive power to the in-wheel motor, and regenerates power generated by the in-wheel motor to the nickel-metal hydride battery,
A control unit for controlling the inverter;
A low-floor electric vehicle comprising a storage unit for storing the nickel metal hydride battery.   2. The low floor electric vehicle according to claim 1, wherein the storage portion is provided in a lower space of a passenger seat.   3. The low floor according to claim 2, wherein the inverter is a variable voltage variable frequency control inverter, and an allowable range of the input voltage is configured such that a nominal voltage is a median value of the allowable range. Electric vehicle.   The low-floor electric vehicle according to claim 1, wherein there is no step on the floor of the vehicle. The nickel metal hydride battery is composed of one or more battery modules,
The battery module is
A plate-like positive electrode current collector and a negative electrode current collector, which are provided to face each other, a separator disposed between the positive electrode current collector and the negative electrode current collector, and a positive electrode cell in contact with the positive electrode current collector And a plurality of unit cells having a negative electrode cell in contact with the negative electrode current collector are stacked so that the positive electrode current collector of one of the unit batteries adjacent to the negative electrode current collector of the other unit battery faces each other. The flow path of the heat transfer medium which consists of gas or liquid between said unit cells adjacent to each other is provided, and the unit battery according to any one of claims 1 to 3 Low floor electric vehicle.

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