Abstract:
According to one embodiment, a vehicle drive system has an engine to generate torque. The vehicle drive system has an alternator coupled to the engine. The alternator converts torque from the engine to magnetic flux and generate an AC voltage. The vehicle drive system has a PWM converter coupled to the alternator to convert AC voltage from the alternator to DC voltage. The vehicle drive system has a PWM inverter which is connected with the PWM converters, the PWM inverter is to transform DC voltage to AC voltage. The vehicle drive system has a filter capacitor between the PWM converter and the PWM inverter. The filter capacitor is configured to be charged by the PWM converter.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2010-207203, filed Sep. 15, 2010, the entire contents of which are incorporated herein by reference. 
       FIELD 
       [0002]    Embodiments described herein relate to drive systems for vehicles. 
       BACKGROUND 
       [0003]    An electric-powered rail car or other vehicle that operates in a location without sources of an electric power supply (such as from a power line) has an electric power unit to supply electric power to inverter or motor in vehicles. 
         [0004]    A power converter transforms the electric power supplied from this electric power unit. The electric motor operates with the alternating current electric power transformed by the power converter. In the drive system for vehicles, when this electric motor drives, vehicles run. 
         [0005]    As a rail car which runs a route without sources of an electric power supply, such as wire, the method which forms a battery in an electric power unit is known. However, in the drive system equipped with the battery for vehicles, it is necessary to maintain the charge of the vehicle battery. The charging of the vehicle battery increases the maintenance of the rail car. 
       SUMMARY 
       [0006]    According to one embodiment, a vehicle drive system has an engine to generate torque. The vehicle drive system has an alternator coupled to the engine. The alternator converts torque from the engine to magnetic flux and generate an AC voltage. The vehicle drive system has a converter coupled to the alternator to convert AC voltage from the alternator to DC voltage. The vehicle drive system has a inverter which is connected with the converter. The inverter is to transform DC voltage to AC voltage. The vehicle drive system has a filter capacitor between the converter and the inverter. The filter capacitor is configured to be charged by the converter, an inverter which is connected with the converter 
         [0007]    According to another embodiment, a vehicle includes an engine to generate torque, an alternator coupled to the engine, a converter coupled to the alternator, a filter capacitor between the converter and the inverter, a control circuit to regulate the speed of the engine, an electric motor that is coupled to the inverter, and one or more wheels attached to the at least one axle. The alternator converts torque from the engine to magnetic flux and generate an AC voltage. The converter converts AC voltage from the alternator to DC voltage. The inverter is to transform DC voltage to AC voltage. The filter capacitor is configured to be charged by the converter. The electric motor is configured to rotate and drive a vehicle. 
         [0008]    According to another embodiment, a method of driving a vehicle includes generating torque using an engine. The method further includes converting torque from the engine to magnetic flux and generate an AC voltage using an alternator. The method further includes converting AC voltage from the alternator to DC voltage. The method further includes transforming the DC voltage from the alternator to an AC voltage using an inverter. The method further includes providing a filter capacitor between the converter and the inverter, wherein the filter capacitor is configured to be charged by the converter. The method further includes regulating the speed of the engine using a control circuit. 
         [0009]    The features and advantages of the present disclosure will be readily apparent to those skilled in the art upon a reading of the description of exemplary embodiments, which follows. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a figure showing the vehicle drive system according to a first embodiment. 
           [0011]      FIG. 2  is a figure showing the vehicle drive system according to a second embodiment. 
           [0012]      FIG. 3  is a figure showing the vehicle drive-system according to a third embodiment. 
           [0013]      FIG. 4  is a figure showing a vehicle drive-system according to a fourth embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Various embodiments will be hereinafter explained with reference to the drawings. Throughout the embodiments, the same structures are attached with the same reference numerals, and redundant explanations thereabout are not repeated. Each figure is a schematic view illustrating the embodiments for helping the understanding thereof. In each figure, some of shapes, sizes, ratios, and the like may be different from those in an actual apparatus. As necessary, these may be changed in design in view of the following explanation and known techniques. 
         [0015]    One example embodiment of a drive system for vehicles is shown in  FIG. 1 . This example embodiment includes an engine  1 , alternators  2 , converter  3 , voltage sensor  4 , filter capacitor  5 , inverter  6 , electric motor  7 , control section  10 , voltage detector  11 , comparing element  12 , and engine rotation number commanding part  13 . 
         [0016]    In the example embodiment, engine  1  is connected with the rotor of alternator  2 . The stator winding of alternator  2  is connected with converter  3 . Converter  3  is connected with inverter  6  via filter capacitor  5 . inverter  6  is connected with electric motor  7 . In certain example embodiments converter  3  is a pulse-width modulation (PWM) controlled converter. In certain example embodiments inverter  6  is a PWM controlled inverter. Voltage sensor  4  is connected in parallel with filter  5 . Control section  10  is connected with voltage sensor  4 . Control section  10  has voltage detector  11 , comparing element  12 , and engine speed controller  13 . 
         [0017]    Voltage detector  11  connects with voltage sensor  4  and comparing element  12  within control section  10 . Comparing element  12  connects with voltage detector  11  and engine speed controller  13 . Engine speed controller  13  is connected with comparing element  12  and engine  1 . 
         [0018]    Engine  1  is engaged when the vehicle is on. Engine  1  generates torque, which is transmitted to the rotor of alternator  2 , rotating the rotor of alternator  2 . Alternator  2  is rotated and electric power is generated and sent to converter  3 . Filter capacitor  5  is charged by the electric power from converter  3 . Once filter capacitor  5  is charged, converter  3  supplies direct-current electric power to inverter  6 . inverter  6 , in turn, converts the direct-current electric power supplied from converter  3  into alternating current electric power. Electric motor  3  is driven with the alternating current electric power from inverter  6 . With the drive of electric motor  3 , torque is transmitted via coupling (not illustrated) to an axle to move the vehicle. 
         [0019]    To use an alternator  2  as a dynamo, it is necessary for converter  3  to maintain the voltage across filter capacitor  5  at or above a predetermined value. 
         [0020]    In order to maintain the voltage across filter capacitor  5  above a predetermined value, the magnetic flux of the rotor of alternator  2  is used. By rotating the rotor of alternator  2  voltage in induced in the stator of alternator  2 . Filter capacitor  5  is therefore charged by the output of by converter  3  from alternator  2 . By using the residual magnetic flux of a rotor and generating induction voltage, of the voltage across filter capacitor  5  is maintained above a default value, allowing alternator  2  to be used as a dynamo. In this case, filter capacitor  5  can be charged without a separate circuit by using residual magnetic flux. 
         [0021]    When alternator  2  is used as a dynamo as mentioned above, the voltage of filter capacitor  5  is controlled by control section  10 . The voltage value detected by voltage sensor  4  is relayed to voltage detector  11 . The voltage value inputted into voltage detector  11  is inputted into comparing element  12  from voltage detector  11  as voltage value (I). Voltage value (I) inputted into comparing element  12  is compared with a command value (A) previously set by comparing element  12 . The command value (A) may be set to the voltage value of the filter capacitor that will allow the drive system to operate. 
         [0022]    The comparison result of comparing element  12  is inputted into engine speed controller  13 . When the comparison result is “voltage value (I)&gt;command value (A)” (i.e., when the measured voltage is above the command voltage value), the voltage of filter capacitor  5  is assumed to be sufficient to operate the drive system, and engine speed controller  13  causes the engine rotation speed to decreases. When the comparison result is “voltage value (I)&lt;command value (A)” (i.e., when the measured voltage value is less than the command voltage value), the engine speed controller  13  causes the engine rotation speed to increases. 
         [0023]    Thus, the minimum voltage of filter capacitor  5  is maintained by the electric power generated with alternator  2  is supplied to electric motor  7 , and it enables it to run vehicles. 
         [0024]    According to embodiments of the vehicle drive system described above, it may be possible to provide the drive system for vehicles which can run in a location without available power by using engine  1  and converting its output with alternator  2 . 
         [0025]    A second example embodiment of a drive system for vehicles is shown in  FIG. 2 . 
         [0026]    In this example embodiment, a DC-to-DC converter  21  is connected with a backup power supply  22 . As shown in  FIG. 2 , between filter capacitor  5  and inverter  6 , a backup power supply  22  is connected by DC to DC converter  21 . 
         [0027]    When the magnetic flux of alternator  2  is insufficient to charge filter capacitor  5 , backup power supply  22  charges filter capacitor  5  by the DC-to-DC converter  21 . 
         [0028]    Alternator  2  can be used as a dynamo once filter capacitor  5  is charged. Thus, the drive system of the second example embodiment can extend a period of maintenance work by using the backup power source less frequency than an example system that relied more on the backup power supply  22 . 
         [0029]    A second example embodiment of a drive system for vehicles is shown in  FIG. 3  A third example embodiment is shown in  FIG. 3 . The third example embodiment differs from the second example embodiment in that it has a first gear  31 , a dynamo  32 , and a rectifier  33 . 
         [0030]    As shown in  FIG. 3 , the first gear  31  is connected to engine  1 . The other end of the first gear  31  is connected to, alternator  2  and dynamo  32 . Dynamo  3  is connected with rectifier  33 . Rectifier  33  is connected between filter capacitor  5  and inverter  6 . 
         [0031]    Engine  1  is engaged when control section  10  determines that the residual magnetic flux of alternator  2  is insufficient to charge filter capacitor  5 . When engine  1  is engaged, torque is transmitted to dynamo  32  by the first gear  31 . Dynamo  32  rotates by the torque transmitted from the first gear. Dynamo  32 &#39;s rotation generates alternating current electric power occurs. Alternating current electric power generated from dynamo  32  is rectified by rectifier  33  and is then supplied to filter capacitor  5 . Once filter capacitor  5  is fully charged, the vehicle drive system will operate. 
         [0032]    In certain example embodiments, a transformer may be inserted between dynamo  32  and rectifier  33  to adjust the output voltage of dynamo  32 . 
         [0033]    In certain embodiments from the output from alternator  32  is an alternating current. In other example embodiments a direct current generator is used. 
         [0034]    According to embodiments of the vehicle drive system described above, it may be possible to provide the drive system for electric-powered vehicles that will allow the vehicle to operate in a location that does not have external power. 
         [0035]    A fourth example embodiment of the drive system is show in  FIG. 4 . 
         [0036]    In this example embodiment, first gear  41  and second gear  42  are connected. 
         [0037]    The first gear is connected between engine  1  and alternator  2 . Electric motor  7  is mechanically connected with second gear  42 . The first gear  41  and second gear  42  are connected mechanically. 
         [0038]    Engine  1  is engaged when control section  10  determines the residual magnetic flux of alternator  2  is insufficient to charge filter capacitor  5 . When engine  1  is engaged, the first gear  41  is rotated. Torque is transmitted to second gear  42 . The rotation of the second gear  42  will, in turn, cause torque and rotation of electric motor  7 . The rotation of electric motor  7 , in turn, generates alternating current electric. In this example embodiment, electric power generated by electric motor  7  is then supplied to PWM inverter  6 . The alternating current electric power of electric motor  7  is transformed into direct-current electric power by PWM inverter  6 . This direct-current electric power charges filter capacitor  5 . Once filter capacitor  5  is fully charged, the drive system is set to operate. 
         [0039]    In this embodiment the filter capacitor  5  can be fully charged even when the residual magnetic flux of alternator  2  is insufficient to charge filter capacitor  2 . 
         [0040]    According to embodiments of the vehicle drive system described above, it may be possible to provide the drive system for electric-powered vehicles that will allow the vehicle to operate in a location that does not have external power. It may also be possible to avoid the maintenance of having to charge a power supply in the drive system. 
         [0041]    While certain embodiments of a vehicle drive system have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosure. Indeed, the novel systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the systems described herein may be made without departing from the spirit of the disclosure. The accompanying claims and their equivalent are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosure.