Electrical drive system for a vehicle motor

Abstract: There is provided a vehicle motor switching apparatus having an armature coil, a series circuit including a series coil and connecting the armature coil and a battery and a shunt coil, comprising a switch for connecting the shunt coil to the series circuit in parallel to the armature coil to set up the motor as a compound-wound motor when the shunt coil is connected to the series circuit, while set up the motor as a series motor when disconnected therefrom. The apparatus further comprises a switch for disconnecting the series coil from the series circuit to set up the motor as a shunt motor when the shunt coil is connected to the series circuit and the series circuit is disconncted therefrom.

Description: BACKGROUND OF THE INVENTION This invention relates to an electrical drive system comprising a d.c. motor for driving a vehicle. The system has a motor-type selection means for selecting the type of the vehicle motor among a series motor, a compound-wound motor and a shunt motor. A vehicle motor is mostly driven by a battery installed in a vehicle, particularly an electric vehicle which has been developed for being free from oil resource and less pollution. Control of such a motor is one of the important factors in determining the vehicle performance. The Japanese Utility Model Publication No. 1983(58)-21284 discloses such motor control. The control apparatus disclosed therein comprises a feeder circuit including a controller for adjusting the voltage or current applied to the motor in response to an amount of depression of an accelerator. Also, the apparatus comprises a brake circuit for braking the motor by short-circuiting two terminals of the motor and a switch interlocked by the accelerator for switching the two circuits. The feeder circuit is driven to rotate the motor when the accelerator is depressed. On the other hand, the brake circuit is driven to brake the motor when the accelerator is released. As is already known, a motor driven by means of a d.c. current from a battery is roughly classified into a series motor, a compound-wound motor and a shunt motor according to a wiring configuration of coils for exciting field poles. Those motors are selectively used for their usage. However, only one type of a motor is sometimes not sufficient for a vehicle such as an electric vehicle which should be operated at various travelling conditions. The series motor produces a large starting torque and excellent starting acceleration but also has a large speed variation and increases the engine speed greatly when the load torque to the motor is made small. On the other hand, the shunt motor has a low speed variation or stable engine speed even if the load torque varies but also has relatively a small speed control region when a load is connected thereto. Furthermore, the compound-wound motor has characteristics intermediate between the series motor and the shunt motor and a slow response to the change of the operating state. An electrical drive system in accordance with the preamble of claim 1 is known from EP-A-0 129 319. In this electrical drive system the motor control circuit includes a second switching means connected in series with the series coil. Both switching means are implemented by choppers. The motor control circuit responds to speed selection settings to operate the second switching means intermittently while holding the first switching means closed over a lower speed range, and to operate the first switching means intermittently while holding the second switching means closed over a higher speed range, in order to provide a multiple-range speed control system for a compound motor. US-A-3,755,724 discloses a control circuit for a d.c. electric motor selectively operable as a series motor and as a shunt motor. The circuit includes means to switch connections of the motor armature and of the motor field to adapt such connections to assure the proper armature commutation under predetermined load conditions. SUMMARY OF THE INVENTION The object of the present invention is to provide an electrical drive system which switches the type of a vehicle motor according to travelling conditions to obtain best motor characteristics so as to improve vehicle performance. According to the present invention, this object is achieved by an electrical drive system as claimed in claim 1. The vehicle motor has an armature coil, a series circuit including a series coil and connecting the amature coil and a battery and a shunt coil, said system comprising a first switch for connecting the shunt coil to the series circuit in parallel to the armature coil to set up the motor as a compound-wound motor when the shunt coil is connected to the series circuit, while setting up the motor as a series motor when disconnected therefrom, and comprising a second switch for disconnecting the series coil from the series circuit to set up the motor as a shunt motor when the shunt coil is connected to the series circuit and the series circuit is disconneted therefrom. Other objects and features of this invention will become understood from the following description with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows the configuration of an electric vehicle; FIG. 2 shows a control system for a vehicle motor; FIG. 3 shows the characteristics of each type of a motor; FIGS. 4 and 5 show a preferred embodiment of the invention; FIG. 6 shows a preferred embodiment of the control system according to the present invention; FIG. 7 shows a functional block diagram of the control system shown in FIG. 6; FIG. 8 is a graph showing the relationship between the accelerator depression amount ϑ and adjusting resistances R₁ and R₂; FIGS. 9 to 11 are flowcharts showing a control procedure of the motor; and FIG. 12 shows a further preferred embodiment of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention will now be described in detail with reference to the accompanying drawings. Throughout the drawings, like reference numerals and letters are used to designate like or equivalent elements for the sake of simplicity of explanation. First in FIG. 1, an electric automobile 1 comprises an engine 2 having a crankshaft pulley 2a to which a pulley 4a of a generator 4 is connected through a belt 3. A battery 5 is charged by the generator 4. The generator 4 also acts as a starter when the engine 2 starts. A drive gear 1b mounted on an axle shaft 1a is connected to a drive gear 6d of a motor 6 through an idler gear 7. The motor 6 is a d.c. motor. The output of the engine 2 is converted into electrical energy. The battery 5 is then charged with the electrical energy. The motor 6 is thus driven by means of the charged electrical energy. Hence, the electric automobile 1 is a serial hybrid vehicle. The engine 2 is a gasoline engine. As is shown in FIG. 2, a carburetor 8 is provided in an intake pipe 7b. An air cleaner 9 is attached to the intake pipe 7b upstream the carburetor 8. Furthermore, a rotary actuator 10 composed of such as a stepping motor or a rotary solenoid is attached to a throttle valve 7a installed in the intake pipe 7b. There are provided protrusions on the outer periphery of the pulley 4a of the generator 4. A generator-rotating speed detection sensor 11 which is composed of such as an electromagnetic pickup detecting the protrusions is provided to face the protrusions. A controller 20 consisting of a microcomputer comprises a CPU (central processing unit) 21, a ROM (read only memory) 22, a RAM (random access memory) 23 and an I/O (input/output) interface 24 connected to each other through a bus line 25. A constant-voltage power supply 26 connected to the battery 5 through a relay contact of a control relay RY supplies electrical power to those components of the controller 20. The control relay RY is also connected to the battery 5 through a key switch 27 and an ignition circuit 2b of the engine 2. Furthermore, a generator control circuit 4b and a motor control circuit 6e are connected to the battery 5 to be supplied with the electrical power. Various sensors including the generator-rotating speed sensor 11 and an accelerator depression amount sensor 12 are connected to an input port of the I/O interface 24. Also, a positive terminal of the battery 5 is connected to the input port to supply a terminal voltage thereto. On the other hand, the rotary actuator 10, the ignition circuit 2b, the generator control circuit 4b and the motor control circuit 6e are connected to an output port of the I/O interface 24 through a drive circuit 28. FIG. 4 shows a preferred embodiment of the invention. A shunt coil 6b is connected in parallel to an armature coil 6a of the d.c. motor 6, and a series coil 6c is connected in series to the armature coil 6a. A switch SW4 is connected in series to the shunt coil 6b. A switch SW5 is connected in series to the series coil 6c. Furthermore, a switch SW6 is connected in parallel to a series circuit of the series coil 6c and the switch SW5. As is also shown in FIG. 5, a motor-type selection section 32 controls a switching means such as the switches SW4, SW5 and SW6 so that the motor 6 operates as a compound-wound motor, a shunt motor or a series motor according to the travelling state. The switch SW5 may be eliminated since it is to surely disconnect the series coil 6c from the battery 5. As is shown in FIG. 6, the engine 2 in this preferred embodiment of the present invention has a vehicle speed sensor 30 and a current sensor 14 connected to the battery 5 at its positive terminal. The sensors 14 and 30 are connected to the input port of the I/O interface 24. An alarm LED 15 is connected to the drive circuit 28. Other configuration in FIG. 6 is the same as that in FIG. 2. A motor control circuit 60e will be explained with reference to FIG. 7. In this figure, a field current/voltage adjusting resistor 16 is connected in series to a shunt coil 6b. Furthermore, a relay contact (corresponding to the switch SW4 in FIG. 4) of a relay switch SW10 is connected in series to the resistor 16. An armature voltage adjusting resistor 13 is connected in series to the series coil 6c. A relay contact (corresponding to the switch SW5 in FIG. 4) of a relay switch SW20 is connected in series to the resistor 13. A relay contact (corresponding to the switch SW6 in FIG. 4) of a relay switch SW30 is connected in parallel to the series circuit of the series coil 6c, the resistor 13 and the relay contact of the relay switch SW20. The values of the resistors 13 and 16 are adjusted by resistance-control actuators 13a and 16a, respectively. The ROM 22 is prestored with a control program and fixed data such as control data. On the other hand, the RAM 23 is stored with data obtained after calculating output signals from each of the sensors and also a monitored value of the terminal voltage of the battery 5. Signals from each of the sensors are processed by the CPU 21 according to the control program prestored in the ROM 22. Then, an engine-stop signal to the ignition circuit 2b, a control signal to the generator control circuit 4b, a drive signal to the rotary actuator 10 and a control signal to the control circuit 60e are calculated by the CPU 21. The opening of the throttle valve 7a of the engine 2 is controlled by the rotary actuator 10 which is driven by the CPU 21. Furthermore, charging to the battery 5 is controlled by the generator 4 whose rotation speed is adjusted to a specific value by the CPU 21. The motor 6 is also switched between the series, the shunt or the compound-wound motor-type by the CPU 21, according to the travelling state of the vehicle 1. As is also shown in FIG. 7, the controller 200 comprises a consumed-power calculation section 300, a consumed-power judging section 310, an alarm drive section 320, an accelerator depression amount calculation section 330, an accelerator depression amount judging section 340, a consumed current judging section 350, a vehicle speed judging section 360, a battery terminal voltage judging section 370, a motor-type selection section 380, an armature voltage adjusting resistance setting section 390, an armature voltage adjusting resistance map MR2, an armature voltage adjusting resistance-control actuator drive section 400, a field current adjusting resistance setting section 410, a field current adjusting resistance map MR1, a field current adjusting resistance-control actuator drive section 420. The consumed power W is calculated by means of a terminal voltage V B of the battery 5 and the consumed current A of the motor 6 detected by the sensor 14 (W = V B x A) in the calculation section 300. The consumed power W thus calculated is judged as to whether it is smaller than a specific preset value WSET in the judging section 310. The alarm LED 15 is then turned on by the alarm drive section 320 to warn a driver if it is judged in the judging section 310 that the calculated consumed power W exceeds the preset value WSET. On the other hand, a depression amount ϑ is calculated in the calculation section 330 based on a signal from the sensor 12. The depression amount ϑ thus calculated is judged as to whether it is smaller than a specific preset value ϑSET or not in the judging section 340 if the calculated consumed power W is judged smaller than the preset value WSET in the judging section 310. The consumed current A detected by the sensor 14 is judged as to whether it is larger than a specific preset value ASET or not in the judging section 350 if the calculated depression amount ϑ is judged larger than the preset value ϑSET in the judging section 340. Furthermore, a vehicle speed S detected by the sensor 30 is judged as to whether it is smaller than a specific preset value SSET in the judging section 360 if the detected consumed current A is judged to be larger than the preset value ASET in the judging section 350. The terminal voltage V B of the battery 5 is judged as to whether it is smaller than a specific preset value VSET in the judging section 370 if the calculated consumed power W is judged to be larger than the preset value WSET in the judging section 310. All the judging results of the judging sections 310, 340, 350, 360 and 370 are received by the selection section 380 to select the type of the motor 6 among the series motor-type, the shunt motor-type and the compound-wound motor-type. The relay switches SW10 and SW30 are turned off and the relay switch SW20 is turned on in the motor control circuit 60e if the series motor-type is selected. The relay switches SW10 and SW30 are turned on and the relay switch SW20 is turned off if the shunt motor-type is selected. Furthermore, the relay switches SW10 and SW20 are turned on and the relay switch SW30 is turned off if the compound-wound motor-type is selected. Namely, the motor 6 is set up as the compound-wound motor without any condition to reduce the power consumption if the present consumed power W is larger than the preset value WSET. The motor 6 is also set up as the compound-wound motor to restrict power reduction of the battery 5 if the consumed power W and the depression amount ϑ are smaller than preset values WSET and ϑSET, respectively. On the other hand, the motor 6 is set up as the series motor under the travelling state that the vehicle speed S is lower than the preset value SSET and a larger torque is required if the consumed power W is smaller than the preset value WSET and the depression amount ϑ is larger than the preset value ϑSET. Furthermore, the motor 6 is set up as the shunt motor under the travelling state that the vehicle speed S is higher than the preset value SSET and a large torque is not required but a stable vehicle speed is required. Therefore, the motor 6 can be driven under the best condition of the characteristics shown in FIG. 3 according to the travelling state to improve energy efficiency and the travelling performance greatly. In the setting section 390, an armature voltage adjusting resistance R2 of the motor 6 is retrieved from the map MR2 with the depression amount ϑ calculated by the calculation section 330 as a parameter ϑ when the motor 6 is set up as the series motor or the compound-wound motor in the selection section 380. The actuator 13a is then driven through the drive section 400 to adjust the resistor 13 connected in series to the series coil 6c of the motor 6 to the resistance R2. In the setting section 410, a field current adjusting resistance R1 is retrieved from the map MR1 with the depression amount ϑ calculated by the calculation section 330 as a parameter ϑ when the motor 6 is set up as the shunt motor or the compound-wound motor in the selection section 380. The actuator 16a is then driven through the drive section 420 to adjust the resistor 16 connected in series to the shunt coil 6b of the motor 6 to the resistance R1. As is shown in FIG. 8, the resistance R1 and R2 which are in inverse proportion to the depression amount ϑ - so as to produce the required torque and vehicle speed - are prestored in the maps MR1 and MR2, respectively. The larger the depression amount ϑ, the smaller the resistance R1 and R2 to boost voltages applied to the armature coil 6a and the series coil 6c in the case of the series motor-type. The current applied to the shunt coil 6b is made larger and the current applied to the armature coil 6a is made smaller with an increase of the depression amount ϑ in the case of the shunt motor. A combination of the above two cases are brought into the compound-wound motor-type when selected. The operation of the preferred embodiment according to the present invention will be explained with reference to the flowcharts shown in FIGS. 9 to 11. These flowcharts show a program which is repeated per specific period of time or cycle while the electric vehicle 1 is travelling by the motor 6 which is started by turning on the key switch 27. First in STEP 201 shown in FIG. 9, a terminal voltage V B of the battery 5 and the consumed current A of the motor 6 detected by the sensor 14 are accepted. In STEP 202, the consumed power W associated with the operation of the motor 6 is calculated by means of the terminal voltage V B and the consumed current A thus accepted (W = V B x A). Then, the program advances to STEP 203. The calculated consumed power W is compared with the preset value WSET in STEP 203. The program advances to STEP 219 shown in FIG. 11 if W > WSET. On the other hand, the program advances to STEP 204 in which a drive signal is stopped to turn off the alarm LED 15. Then, the program advances to STEP 205. The accelerator depression amount ϑ is accepted in STEP 205. The depression amount ϑ is compared with a preset value ϑSET in STEP 206 shown in FIG. 10. The program advances to STEP 207 if ϑ ≦ ϑSET, in which the relay switches SW10 and SW20 are turned on and the relay switch SW30 is turned off to set up the motor 6 as the compound-wound motor-type. Then, the program advances to STEP 208. In STEP 208, the resistances R1 and R2 are respectively retrieved from the maps MR1 and MR2 with the depression amount ϑ as a parameter. The program then advances to STEP 209. The actuators 16a and 13a are driven to set each of values of the resistors 16 and 13 to the resistances R1 and R2 determined in STEP 208. Then, the program returns to STEP 201. On the other hand, if ϑ > ϑSET in STEP 206, the program advances to STEP 210. The consumed current A accepted in STEP 201 and a preset value ASET are compared with each other in STEP 210. Then, the program advances to STEP 213 if A < ASET, while to STEP 211 if A ≧ ASET. The vehicle speed S is accepted from the sensor 30 in STEP 211. Then, the vehicle speed S and a preset value SSET are compared with each other in STEP 212. The program advances to STEP 213 if S ≦ SSET in STEP 212. In STEP 213, the relay switches SW10 and SW30 are turned off and the relay switch SW20 turned on in the motor control circuit 60e to select the series motor-type. Next in STEP 214, the resistance R2 is retrieved from the map MR2 with the depression amount ϑ as a parameter accepted in STEP 205. Then, the program advances to STEP 215. The actuator 13a is driven to set the resistor 13 to the resistance R2 determined in STEP 114. Then, the program returns to STEP 201. Furthemore if S > SSET in STEP 212, the program advances to STEP 216. In STEP 216, the relay switches SW10 and SW30 are turned on and the relay switch SW20 is turned off in the motor control circuit 60e to select the shunt motor-type. Then, the program advances to STEP 217. In STEP 217, the resistance R₁ is retrieved from the map MR1 with the depression amount ϑ as a paramemter accepted in STEP 205. The program advances to STEP 218. The actuator 16a is driven to set the value of the resistor 16 to the resistance R₁ determined in STEP 217. Then, the program returns to STEP 201. Still furthermore, the program advances to STEP 219 from STEP 203 if the calculated consumed power W is larger than the preset value WSET. In STEP 219, the alarm LED 15 is turned on and then in STEP 220 the relay swithes SW10 and 20 are turned on and the relay switch SW30 is turned off to select the compound-wound motor-type. Then, the program advances to STEP 221. A depression amount ϑ from the sensor 12 is accepted in STEP 221 and then in STEP 222, the resistance R₁ and R₂ are respectively retrieved from the maps MR1 and MR2 with the depression amount ϑ as a paramemter accepted in STEP 221. The program advances to STEP 223. The actuaters 16a and 13a are driven to set each of values of the resistors 16 and 13 to the resistance R₁ and R₂ determined in STEP 222. The program then advances to STEP 224. In STEP 224, the terminal voltage V B is again accepted and then in STEP 225, the terminal voltage V B and the preset reference voltage VSET are compared with each other. The program returns to STEP 220 to set the motor to the compound-wound motor-type if V B ≦ VSET and the program returns to STEP 201 to determine the motor-type again if V B > VSET. Next, FIG. 12 shows a further preferred embodiment according to the present invention. In this figure, a field current adjusting resistor 50 connected to the shunt coil 6b of the motor 6 and an armature voltage adjusting resistor 51 connected to the series coil 6c are linked to an accelerator 52 through wires 54a and 54b and a link 53. Connection of the armature coil 6a to the shunt coil 6b and also the series coil 6c are switched by a switching means composed of an interlocked switch SW40 which is operated by a motor-type selection section 380 according to travelling condition. FIG. 12 now represents the compound-wound motor-type. The motor 6 is then switched to the shunt motor-type when three contactors of the switch SW40 are switched one stage downward, respectively. The motor 6 is switched to the series motor-type when each contactor of the switch SW40 is switched one more stage downward. The wires 54a and 54b are pulled through the link 53 when the accelerator 52 is depressed to make values of the resistance 50 and 51 less so as to obtain the required torque and vehicle speed. As is understood from the foregoing, the present invention provides a switching means for switching connection between an armature coil and a series coil and a shunt coil of a vehicle motor according to travelling condition. One motor is thus switched to a compound-wound motor-type, a series motor-type or a shunt motor-type to obtain best motor characteristics matching with the travelling condition. Therefore, vehicle performance and cost performance are greatly improved.

Claims: An electrical drive system comprising a d.c. motor (6) and a battery (5), said motor (6) being mounted on a vehicle for driving said vehicle with electric power supplied from said battery, a motor control circuit (60e) for controlling said motor, an accelerator (52) for said vehicle and accelerator depression sensing means (12) for sensing the amount of accelerator depression, said motor (6) including an armature coil (6a) connected to said battery, a shunt coil (6b) connected to said battery in parallel to said armature coil and a series coil (6c) connected to said battery in series to said armature coil, said motor control circuit (60e) including first switching means (SW4; SW10) connected in series with said shunt coil, characterized by second switching means (SW6; SW30) connected in parallel to said series coil (6c), and motor-type selection means (32; 380) for selecting, according to travelling conditions, one of a shunt motor mode by turning both switches on, a series motor mode by turning both switches off, and a compound-wound motor mode by turning the first switch on and the second switch off. The electrical drive system according to claim 1, further comprising a third switching means (SW5; SW20) connected in series with said series coil (6c), said third switch being turned on in the series motor mode and compound-wound motor mode, while being turned off in the shunt motor mode. The electrical drive system according to claim 1 or 2, further comprising voltage detecting means for detecting the terminal voltage of said battery, current detecting means (14) for detecting the current supplied to said motor, power calculation means (300) for calculating the electrical consumed power of said motor (6) based on said terminal voltage and said current, power judging means (310) for judging whether said consumed power is larger than a predetermined power value, and said motor-type selection means (380) being adapted to select the compound-wound motor mode when said power judging means judges that said consumed power is larger than said predetermined power value. The electrical drive system according to claim 3, further comprising alarm (15) for warning an operator when said power judging means (310) judges that said consumed power is larger than said predetermined power value. The electrical drive system according to any one of the preceding claims, wherein said motor control circuit (60e) further includes a first variable resistor (16; 50) connected in series with said shunt coil (6a) and said first switching means (SW4; SW10) for varying the field current supplied to said shunt coil and a second variable resistor (13; 51) connected in series with said series coil (6c) for varying the voltage applied to said armature coil (6a) and said series coil (6c), both resistors being adapted for changing values thereof depending on the accelerator depression. The electrical drive system according to claim 5, further comprising: field current adjusting resistance setting means (410) for setting a first resistance value of said first variable resistor (16; 50) based on said accelerator depression when said compound-wound motor mode is selected, and voltage adjusting resistance setting means (390) for setting a second resistance value of said second variable resistor (13; 51) based on said accelerator depression when said compound-wound motor mode is selected, whereby said motor produces the required torque. The electrical drive system according to claim 6, wherein said field current adjusting resistance setting means (410) comprises a field current adjusting resistance map (MR1) which is set based on the inverse-proportional relationship of said first resistance value to said accelerator depression. The electrical drive system according to claim 6 or 7, wherein said voltage adjusting resistance setting means (390) comprises a voltage adjusting resistance map (MR2) which is set based on the inverse-proportional relationship of said second resistance value to said accelerator depression. The electrical drive system according to any one of the claims 5 to 8, further comprising connecting means (53) for connecting each of said first variable resistor (50) and said second variable resistor (51) to said accelerator (52) to change the values of each resistor depending on the accelerator depression. The electrical drive system according to any one of the claims 3 to 9, further comprising battery terminal voltage judging means (370) for judging whether said battery terminal voltage is larger than a predetermined voltage and imposing said motor-type selection means (380) to maintain said compound-wound motor mode when said battery terminal voltage is smaller than said predetermined voltage. The electrical drive system according to any one of the claims 3 to 10, further comprising: accelerator depression judging means (340) for judging whether said accelerator depression is larger than a predetermined amount when said power judging means (310) judges that said consumed power is smaller than said predetermined power value, said motor-type selection means (380) being adapted to select said compound-wound motor mode when said accelerator depression judging means judges that said accelerator depression is smaller than said predetermined amount. The electrical drive system according to any one of the claims 3 to 11, further comprising: current judging means (350) for judging whether said current is smaller than a predetermined current value when said accelerator depression judging means judges that said accelerator depression is larger than said predetermined amount, said motor-type selection means (380) being adapted to select the series motor mode when said current judging means judges that said current is smaller than said predetermined current value. The electrical drive system according to claim 12, wherein said voltage adjusting resistance setting means (390) is adapted to set said second resistance value of said second variable resistor (13; 51) based on said accelerator depression when said series motor mode is selected, whereby said motor produces the required torque. The electrical drive system according to claim 12 or 13, further comprising: vehicle speed sensing means (30) for sensing the vehicle speed, vehicle speed judging means (360) for judging whether said vehicle speed is higher than a predetermined speed when said current judging means (350) judges that said current is larger than said predetermined current value, said motor-type selection means (380) being adapted to select the shunt motor mode when said vehicle speed judging means judges that said vehicle speed is higher than said predetermined vehicle speed. The electrical drive system according to claim 14, wherein said motor-type selection means (380) is adapted to select said series motor mode when said vehicle speed judging means (360) judges that said vehicle speed is lower than said predetermined vehicle speed. The electrical drive system according to claim 14, wherein said field current adjusting resistance setting means (410) is adapted to set said first resistance value of said first variable resistor (16; 50) based on said accelerator depression when said shunt motor mode is selected, whereby said motor produces the required torque. The electrical drive system according to claim 3, further comprising vehicle speed sensing means (30) for sensing the vehicle speed, wherein said motor-type selection means (380) is adapted to select the shunt motor mode when the sensed vehicle speed is larger than a predetermined speed.

Inventors: KYOUKANE YASUAKI, NAGANO TOSHIHIRO, NAGANO, TOSHIHIRO
Applicants: FUJI HEAVY IND LTD, FUJI JUKOGYO KABUSHIKI KAISHA
Application year: 1990
Main classification: B60L11
IPC codes: B60L11, H02P7