Stand device for use in electric vehicle

Abstract: A stand device (41) for use in an electric vehicle (1), providing with a running motor (7) having an output shaft (7a) and which is operative on electric power from a storage battery (14a), and a stand (45) having a pivoting shaft (45a) and which is biased towards its retracted position, the stand device (41) comprising: one-way clutch (43) and gears (44) arranged such that the pivoting shall (45a) of the stand is idle when the motor (7) rotates in the forward direction so that the stand (45) remains biased towards its retracted position, and the pivoting shaft (45a) of the stand engages with the output shaft (7a) of the motor via the clutch (43) and gears (44) when the motor (7) rotates in the reverse direction to put the stand (45) in its parking position.

Description: The present invention relates to an assist device for use in an electric vehicle, and in particular to the assist device that provides a wide range of ease-of-use design improvements in the electric vehicle. Electric vehicles that use an electric motor as a prime mover recently draw attention as a next generation vehicle that is expected to replace a gasoline-powered vehicle employing an internal combustion engine. A diversity of technical proposals have been made in connection with the electric vehicle. The electric vehicle using a environmentally clean electrical energy solves entirely environmental problems associated with internal combustion engines, such as emissions of toxic exhaust gases and noise. It is estimated that 70% of air pollutants is given off by internal combustion engines. Also, it is believed that the full-scale introduction of electric vehicles effectively slows the current consumption rate of fossil fuels such as petroleum effectively doubling the currently expected remaining availability period of fossil fuels. As in the gasoline-powered vehicle, the electric vehicle is provided with running wheels suspended at shock absorbers by the vehicle body. The running wheels are driven by a power transmission device, the power source of which is an electric motor. The electric motor is power supplied by an electric power device. The electric power device is made up of a battery bank section having a plurality of storage batteries, a power supply circuit section for supplying electric power in a reliable manner, an electric motor for driving, a motor driving circuit, and a control circuit for issuing speed instructions or the like to the motor driving circuit. Driving power generated by the motor is then transmitted via the power transmission device to the running wheels to allow the electric vehicle to run. The battery bank section that feeds electric power to the running motor is constructed of the plurality of storage batteries connected in series to obtain a required voltage. The storage batteries have the following characteristics: the voltage across the battery terminals gradually drops with time elapse when the battery is used or discharged, as plotted by a discharge curve in FIG. 15. As soon as the battery voltage reaches a termination voltage at the rightmost end of the curve in FIG. 15, discharge is terminated to protect the storage battery. As FIG. 16 illustrates, the storage battery follows different discharge curves depending on the current in use. It is known that the operating discharge time of the battery varies as its operating current varies. For this reason, the electric vehicle is provided with a meter, indicative of power remaining unused, employing a diversity of techniques, to correctly know electrical energy remaining unused in the storage battery. The remaining capacity meter estimates electric power remaining and indicates it to a driver. As shown in FIG. 17, electric power from a battery bank section 91 is voltage-regulated by a power supply circuit section 92, and is distributed via unshown power lines to a diversity of devices including a remaining capacity meter 93. The main switch 94 to be operated by the driver is connected to the power supply circuit section 92. By operating the main switch 94, the power supply circuit section 92 is switched on or off. When the vehicle comes to a complete halt to park it, the key switch 94 is switched off cutting battery power to all devices on board including the remaining capacity meter to stop the operation of each device. The main key is detached from its switch and kept in the hands of the driver to prevent the vehicle from being stolen. Electric power regulated by the power supply circuit section 92 is fed to the motor via the motor driving circuit. The motor driving circuit in its chopper controlling mode controls the speed of the motor by raising or lowering the supply voltage to the motor. The chopper control duty ratio that raises or lowers voltage is controlled by the control circuit. The control circuit is electrically connected to an accelerator grip. The control circuit sets a duty ratio in response to the driver's opening setting of the accelerator. In response to the duty factor, the motor driving circuit raises or lowers the RMS voltage fed to the motor. The speed of the motor according to the opening of the accelerator is thus obtained. Since the electric vehicle does not have an idling state that is typical of the standard gasoline-powered vehicle, a ready-to-run state may go unnoticed. An erratic opening of the accelerator causes the vehicle to start running suddenly, while the driver is not ready to start in his driving position. A dismount sensor is disposed under a seat to sense the seating position of the driver. Even when a vehicle is ready to start, it gives off an alarm sound such as a buzzer sound in some known systems (for example, Japanese Patent Application No. Hei-6-115469). In another known system, a vehicle stops entirely the operation of the motor regardless of accelerator operation when a driver dismounts. In an electric two-wheel vehicle such as a two-wheel motorcycle or scooter, a motorcycle stand having at least two feet is provided in the vicinity of its rear running wheel. When such a vehicle is parked, the stand is set to its parking position. During parking, the vehicle is balanced on three ground points: one at its front wheel and two at the stand's feet. To charge a consumed storage battery, it is charged with a charging voltage that is typically higher than its nominal voltage. For example, for a 12 V storage battery, approximately 15 V is fed to the battery to charge it. The capacity of the battery is accurately determined based on the fact that the terminal voltage of the battery varies linearly with battery capacity when an open-circuit voltage is measured with the battery set for no load state upon completion of a charging operation. When the charging operation is completed, however, the terminal voltage rises temporarily (this state.is hereinafter referred to as "surface charge state") partly because the charging voltage is higher than the nominal voltage and partly because the battery interior remains electrochemically nonuniform at this moment. Terminal voltage measurement provides no accurate measurement of the battery capacity, therefore. For example, a 12 V storage battery is charged with a charging voltage of approximately 15 V. Immediately after the charging operation, the open-circuit voltage stays in the vicinity of 15 V regardless of actual capacity of the battery. Even when the charging operation is stopped before being fully charged, the battery may be mistakenly considered as fully charged because the measured terminal voltage is high. It is known that as time elapses, such a surface charge state indicating a high voltage is eliminated and the terminal voltage reaches to its equilibrium one reflecting actual charged battery capacity. In one of known methods of determining charged battery capacity immediately after charging, a regression equation that relates elapsed time after the completion of charging to open-circuit voltage is determined, the regression equation is used to estimate the open-circuit voltage at the equilibrium state after a sufficient duration of time has elapsed, and charged capacity is then calculated from the estimated open-circuit voltage (for example, Japanese Patent Application Hei-4-363679). In the electric two-wheel motorcycle such as a electric scooter, the ease of use as the motorcycle is greatly impaired by heavy weight, compared with an engine scooter. Namely, the electric scooter is relatively heavy because it has a number of batteries mounted on board. Heavy weight presents a handling difficulty to users. When transferring the two-wheel motorcycle from its stop position to its parking position in a parking lot, for example, or from its parking position to its start position, a driver usually dismounts and walks the two-wheel motorcycle there. The two-wheel motorcycle thus needs a great deal of human power. When walking the two-wheel motorcycle on a non-level road or a slope in particular, the driver has even more difficulty in this manual running operation. The running motor may be used to assist the driver in his manual running operation, but this may be very risky. An erratic accelerator manipulation may trigger a sudden start. From the safety standpoint, using the running motor for assistance is not preferable. In the already cited known system that triggers an alarm sound to alert the driver, the alarm sound may go unnoticed depending on the ambient conditions. In this case, stopping entirely the running motor is not perfectly acceptable, because it cannot be used to assist the driver in his manual run operation any more. Furthermore, another difficulty a heavy vehicle presents is that the driver needs more power and skill in putting the scooter on its stand for parking. As shown in Fig. 7, a known system comprises a stand device 106 having a dedicated motor 104 and its gear box 105 to put a stand 103 in its upright position, besides a running motor 101 and a power transmission device 102. The dedicated motor 104 provides driving power to put the stand 103 in its upright position. This stand device 106 employing the dedicated motor, however, renders the design of the vehicle more complicated and heavier. One such device is disclosed in JP 02063984, which relates to a scooter propelled by a petrol engine. The main switch turns on or off the power supply circuit that feeds power to all on-board devices in need. When the main switch is turned off with the vehicle parked, the remaining capacity meter is switched off as well. When the storage battery needs charging with an insufficient power remaining and when the main switch is turned off, the need for charging may escape the driver's attention. The driver unintentionally skips a charging operation not knowing the consumed storage battery. In the above described method in which charged battery capacity immediately after charging is determined using the regression equation from the terminal voltage, charge and discharge characteristics are different from battery to battery in terms of capacity and degree of ageing. Therefore, tests should be beforehand conducted to collect characteristics data. Such extra job is time consuming. In view of the above problems, the present invention has been developed. It is an object of the present invention to provide a lightweight electric vehicle power assist device that uses the running motor to drive a stand to its upright position with no dedicated stand motor employed. According to the present invention there is provided a stand device for use in an electric vehicle, said electric vehicle being provided with a stand, which has a pivoting shaft and is biased towards its retracted position, and with a running motor for propelling the electric vehicle, the motor having an output shaft and being operative on electric power from a storage battery, the stand device comprising: one-way clutch and gears arranged such that the pivoting shaft of the stand is idle when the motor rotates in the forward direction so that the stand remains biased towards its retracted position, and the pivoting shaft of the stand engages with the output shaft of the motor via the clutch and gears when the motor rotates in the reverse direction to put the stand in its parking position. Embodiments of the present invention will now be described with reference to the accompanying drawings, in which: FIG. 1 is a side view showing generally the electric motorcycle according to one embodiment of the electric vehicle of the present invention. FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1. FIG. 3 is a diagrammatic perspective view of one embodiment of the stand device of the present invention. FIG. 4 is a plane view of the stand device of the electric vehicle of the above embodiment. FIG. 5 is a side view of the stand device of the electric vehicle of the above embodiment. FIG. 6 is a front view of the stand device of the electric vehicle of the above embodiment. FIG. 7 is a perspective view showing the stand device of the prior art electric vehicle. Referring now to FIGS 1 through 6, an embodiment of the present invention is now discussed. The electric vehicle in the embodiment is illustrated using a two-wheel electric motorcycle (including an electric scooter) as an example. As in the known internal-combustion-engine driven motorcycle, an electric scooter 1 has on the front and rear sides of a vehicle body 2, running wheels 4, 5 suspended by a body main frame 3 and a driver's seat 2a on the approximately middle position of the vehicle body 2. The front wheel 4 is steered by a handle 6. The rear wheel 5 is driven by a running electric motor 7 rather than by an engine. A display panel 8 disposed in the middle of the handle 6 has an indicator device 9 for displaying a cruising speed, battery remaining capacity and the like and a plurality of switches for controlling on-board devices. Disposed below the display panel 8 on the main body 2 is a main switch 10 for turning on or off all on-board devices. The main frame 3 carries an electric power device 11 for supplying electric power required for running, a motor 7 that converts electric power from the electric power device 11 into mechanical force, and a power transmission device 12 for transmitting the mechanical force to the rear wheel 5. Accelerator grip 6a, a brake lever, a brake mechanism, suspension systems and some other unshown components remain unchanged from those used in the prior art two-wheel motorcycle. A diversity of switches including the accelerator grip 6a, the brake lever, the main switch 10 and the like are electrically connected to the electric power device 11. The electric power device 11 is made up of a battery bank section 14 disposed in an approximately middle lower position of the main frame 3 of the vehicle body 2, a remaining capacity meter 15, a power supply circuit 16, a control circuit 17, a charger 18 and a motor driving circuit 19 disposed beside the battery bank section 14, and a diversity of sensors disposed in the on-board devices. The battery bank section 14 comprises four batteries .14a secured onto the main frame by brackets. These batteries 14a are connected in series by heavy wire gauge cables to avoid voltage drop and to obtain a required voltage. Electric power from the battery bank section 14 is regulated by the power supply circuit 16 before it is distributed to each of the on-board devices. The motor driving circuit 19 is a circuit chiefly constructed of large-sized MOS FETs as high-power switching elements. Switching operation of the FET circuit in the form of chopper control raises or lowers the RMS voltage supplied to the running motor 7 to control the motor speed. Switching operation is performed according to speed instruction from the control circuit 17 in response to accelerator setting. The control circuit 17 comprises a microcomputer 31 that receives signals from the accelerator grip 6a and sensors mounted in the on-board devices and outputs signals to the motor driving circuit 19 and the indicator device 9 on the display panel 8. The microcomputer 31 is provided with an A/D converter for converting an input signal into a digital signal, an I/O port, a CPU, and memory. Under the control of the program stored in the memory, the microcomputer 31 processes sensor signals including the one regarding accelerator setting set by the operation of the accelerator grip 6a, and signals from other sensors, and issues required instructions 'such as a duty setting signal to the motor driving circuit 19. The power transmission device 12 is made up of the running motor 7 and a continuously variable transmission 20. The power transmission device 12 converts a rotary motion the motor 7 generates into an appropriate torque by means of the continuously variable transmission 20 and transmits the torque to the rear wheel 5. When the driver turns on the main switch 10, the power supply circuit 16 starts to operate, distributing electric power from the battery bank section 14 to the on-board devices and making the vehicle ready to start. Next, when the driver operates the accelerator grip 6a, the control circuit 17 in response issues a speed instruction to the motor driving circuit 19. In response to the speed instruction, the motor driving circuit 19 raises or lowers the driving power fed to the running motor 7 to control the speed of the running motor 7. The rotary motion generated by the running motor 7 is converted into an appropriate torque which is then transmitted to the rear wheel 5. The two-wheel electric scooter 1 thus starts to run at a speed the driver desires. The aspect of the electric vehicle in connection with the stand device is now discussed referring to the embodiment in Figs 3 through 6. In this embodiment of the electric vehicle in connection with the stand device, the pivoting shaft of the main stand is engaged with the output shaft of the running motor via a one-way clutch and a series of gears. Taking advantage of the reverse rotary motion of the running motor dispenses with a dedicated motor for the stand device. As shown in Figs 3 through 6, the stand device 41 in the embodiment of the electric vehicle comprises a gear box 42 integrally attached to the power transmission device 12 constructed of the running motor 7 and the continuously variable transmission 20, a one-way clutch 43 housed in the gear box 42, a series of gears 44, and a main stand 45, the rotation shaft of which is connected to the rotation shaft of the output gear of the series of gears 44. The continuously variable transmission (CVT unit) 20 comprises a driving pulley 47 supported by the output shaft 7a of the motor 7, a driven pulley 48 rigidly supported by the rear wheel shaft 5a, and a V-shaped belt 49. By changing the radius of rotation of the driving pulley 47, the transmission ratio is variably changed to convert the rotary motion of the motor 7 into an appropriate torque, which is then transmitted to the rear wheel 5. The one-way clutch 43 in the stand device 41 is supported by the output shaft 7a of the running motor 7. Attached onto the one-way clutch 43 is a first gear 51 which is the input gear of the series of gears 44. When .the running motor 7 rotates in the forward direction (as shown by continuous line arrows in FIG. 5, namely, when the running motor 7 rotates to move the vehicle forward, the one-way clutch 43 idles, not transmitting the motor rotary motion to the series of gears 44. On the other hand, when the running motor 7 rotates in the reverse direction (dashed line arrows in FIG. 5 , namely, when the running motor 7 rotates to move the vehicle backward, the one-way clutch 43 rotates integrally with the motor output shaft 7a to transmit the reverse rotary motion of the motor to the series of gears 44. At the same time, the one-way clutch 43 disengages the driving pulley 47 from the motor output shaft 7a, and thus reverse rotary motion is not transmitted to the rear wheel 5. The series of gears 44 comprises the first gear 51 rigidly attached onto the one-way clutch 43, a second gear 52 meshed with the first gear 51, and a third gear 53 meshed with the second gear 52. Meshed gears have their own predetermined gear reduction ratios. The pivoting shaft 45a of the main stand 45 is rigidly attached to the shaft 53a of the third gear 53. The stand 45 comprises the pivoting shaft 45a rigidly attached onto the third gear shaft 53a, a pair of feet 45b extending from both ends of the pivoting shaft 45a at substantially a right angle and gradually parted from each other toward their feet ends, and ground plates 45c attached onto the ends of the feet 45b. The stand 45 is constructed of mechanically strong material, and its tube portion has a large diameter so that it withstands the weight of the vehicle with a sufficient margin. The stand 45 is provided with retracting compression springs 55. Each of the retracting springs 55 is connected at one end to the middle of each foot 45b, and at the other end to the gear box 42. The retracting springs 55 constantly bias the stand 45 toward its retraction position. When the reverse rotary motion of the running motor 7 is not transmitted, the stand 45 stays retracted. The display panel 8 is provided with a stand upright switch, which is connected to the control circuit. When the stand upright switch is turned on, the control circuit issues an instruction that causes the motor to rotate in reverse, and then the stand 45 starts to shift to its upright position. The stand 45 has on its upright position a limit switch 57 which is also connected to the control circuit. The limit switch 57 senses the stand 45 put into its upright position. The control circuit stops the reverse rotation of the running motor 7 and locks the stand 45. The operation of the stand device 51 for the electric vehicle is now discussed. When the stand upright switch is turned on, the control circuit causes the running motor 7 to rotate in reverse. The one-way clutch 43 disengages the running motor 7 from the driving pulley 47 so that the reverse rotary motion of the running motor 7 is transmitted to the first gear 51 of the series of gears 44. The third gear 53 as the output gear of the gear series 44 rotates at a predetermined reduced speed. The stand 45 is pivoted around its own pivoting shaft 45a attached to the third gear shaft 53a in the direction of its upright position. With the stand 45 at its upright position as shown by imaginary lines in FIG. 5, it turns on the limit switch 57 and the control circuit stops the reverse rotation of the running motor 7. The stand 45 is locked, keeping the vehicle body 2 parked in a stable manner. To move the two-wheeled vehicle from its upright stand position, push the vehicle forward slightly. Then, the stand 45 is reverted to its retraction position by elasticity of the retracting springs 55. The two-wheeled vehicle is now ready start. This embodiment employs the upright stand device in which the pivoting shaft of the stand is rotated to force the stand to its upright position. The present invention is not limited to this type of stand device. A raise/lower type stand device with its stand capable of moving up and down is contemplated. The raise/lower stand device may employ a rotary/reciprocating motion conversion mechanism constructed of a combination of a rack and pinion and worm gears. In the upright type stand device, the vehicle is forward or backward moved slightly in the course of setting up the stand, and the vehicle may touch any object nearby, possibly damaging the rear light or some other thing. The raise/lower type stand device is free from such a damage, because it remains standstill in the course of setting up. By constructing the stand of planar plate rather than piping, the stand device may be used as an underguard. As described above, according to this embodiment of the electric vehicle in connection with the stand device, the pivoting shaft of the stand device idles while the running motor rotates in its forward direction, and is engaged with the output shaft of the running motor via the one-way clutch and the gear series while the running motor rotates in its reverse direction. The reverse rotary motion of the running motor is used to force the stand device to its upright position. No dedicated motor is required. The design of the vehicle is therefore simple, light-weight and low-cost. The aforegoing description has been given by way of example only and it will be appreciated by a person skilled in the art that modifications can be made without departing from the scope of the present invention as defined by the appended claims.

Claims: A stand device (41) for use in an electric vehicle (1), said electric vehicle being provided with a stand (45), which has a pivoting shaft (45a) and is biased towards its retracted position, and with a running motor (7) for propelling the electric vehicle (1), the motor (7) having an output shaft (7a) and being operative on electric power from a storage battery (14a), the stand device (41) comprising: one-way clutch (43) and gears (44) arranged such that the pivoting shaft (45a) of the stand is idle when the motor (7) rotates in the forward direction so that the stand (45) remains biased towards its retracted position, and the pivoting shaft (45a) of the stand engages with the output shaft (7a) of the motor via the clutch (43) and gears (44) when the motor (7) rotates in the reverse direction to put the stand (45) in its parking position. An electric vehicle (1) comprising one or more of the devices claimed in claim 1.

Inventors: KOIKE YOSHIKAZU, KOZAKI MINORU, TADOKORO KOHICHI, TAKAGI KUNIHIKO, KOIKE, YOSHIKAZU, KOZAKI, MINORU, TADOKORO, KOHICHI, TAKAGI, KUNIHIKO, Koike, Yoshikazu, c/o Seiko Epson Corporation, Kozaki, Minoru, c/o Seiko Epson Corporation, Tadokoro, Kohichi, c/o Tokyo R&amp;D Co. Ltd., Takagi, Kunihiko, c/o Seiko Epson Corporation
Applicants: SEIKO EPSON CORP, TOKYO R & D KK, SEIKO EPSON CORPORATION, TOKYO R&D CO., LTD.
Application year: 1996
Main classification: B62H1
IPC codes: G01R31, B60L15, B62M7, B60L11, B60L3, B62M23