The present invention relates to an electric drive system in which an engine, a generator, converting devices, and a motor are arranged in series, and a series hybrid drive system that uses a capacitor along with the electric drive system.
Conventionally, there has been known a drive system of an electric vehicle that obtains power of a vehicle by driving a motor with electric power from a generator connected to an engine via electric-power converting devices, such as a converter and an inverter. An example of such drive system of an electric vehicle is a configuration of a series model in which a flow of energy from the generator to the motor is in series, and furthermore there has been known a drive system of a series hybrid electric vehicle that is provided with a capacitor in between the generator and the motor.
For example, Patent Document 1 mainly discloses a system configuration for a faulty situation of a failure in the converter or the inverter in the drive system of a series hybrid electric vehicle. According to Patent Document 1, the pole quantity of an alternating-current generator is configured to be fewer than the pole quantity of an alternating-current motor, and upon a failure in the converter or the inverter, the drive system disconnects the converter and the inverter from the alternating-current generator and the alternating-current motor, and connects the alternating-current generator directly to the alternating-current motor, so that the alternating-current motor is directly driven with alternating-current power supplied from the alternating-current generator. Thus, an object of Patent Document 1 is to improve operational reliability by providing a circuit to bypass the converter and the inverter arranged in between the alternating-current generator and the alternating-current motor, and ensuring a driving force even during a failure in the electric-power converting devices.
However, the conventional drive system of an electric vehicle, which includes a circuit that can connect the alternating-current generator directly to the alternating-current motor by bypassing the electric-power converting devices, has a problem that because an object of the drive system is to improve operational reliability in a faulty situation, if the drive system is applied to a movable body to be used for various purposes including situations other than a faulty situation, a wide range of the number of revolutions is required for operation of the engine, so that a fuel consumption of the engine and exhaust gas are worsened, and system efficiency cannot be improved. For this reason, the configuration using the bypass circuit is limited to use in a faulty situation.
Moreover, when producing vehicles in accordance with cruising speeds of the movable body to be used for various purposes so as to use the conventional drive system of an electric vehicle also during a cruise driving in situations other than a faulty situation, there is a problem that a plurality of types needs to be provided in a line-up of generators and motors.
The present invention has been made to solve the above problems, and an object of the present invention is to obtain an electric drive system and a hybrid drive system such that a driving force can be ensured during a failure in electric-power converting devices, favorable conditions of a fuel consumption of an engine and exhaust gas can be achieved during use in situations other than a failure, and the number of line-up of generator and motors can be reduced when producing movable bodies appropriate to purposed cruising speeds.
To solve the above problems and to achieve the object, an electric drive system according to the present invention is for driving a movable body, including an engine; an alternating-current generator that is connected to the engine and that generates alternating-current power; an AC/DC converter that converts the alternating-current power supplied from the alternating-current generator into direct-current power; a DC/AC converter that converts the direct-current power output from the AC/DC converter into alternating-current power; an alternating-current motor that is driven by the alternating-current power output from the DC/AC converter; a bypass unit that connects the alternating-current generator directly to the alternating-current motor by bypassing the AC/DC converter and the DC/AC converter; a bypass switching unit that switches a route from the alternating-current generator to the alternating-current motor to either one of a route through the bypass unit and a route through the AC/DC converter and the DC/AC converter; a generator pole-quantity changeover unit that changes over number of poles of the alternating-current generator; a motor pole-quantity changeover unit that changes over number of poles of the alternating-current motor; a cruising-speed determining unit that determines whether the movable body is running at a predetermined cruising speed; and a control unit that connects, when the cruising-speed determining unit determines that the movable body reaches the cruising speed, the alternating-current generator to the alternating-current motor through the bypass unit by switching the bypass switching unit, changes over at least one of the number of poles of the alternating-current generator and the number of poles of the alternating-current motor, and sets a frequency of the alternating-current generator and a frequency of the alternating-current motor to values corresponding to the cruising speed.
According to the present invention, when the cruising-speed determining unit determines that the movable body have reached a cruising speed, the drive system is configured to connect the alternating-current generator directly to the alternating-current motor via the bypass unit, to change over the pole quantity of the alternating-current generator and the pole quantity of the alternating-current motor, and to drive the movable body by setting the frequency of the alternating-current generator and the frequency of the alternating-current motor in accordance with the cruising speed, thereby improving a fuel consumption and exhaust gas even during a cruise driving.
Moreover, because the drive system is configured to drive the movable body during a cruise driving by setting the frequency of the alternating-current generator and the frequency of the alternating-current motor in accordance with a cruising speed determined based on a purpose of the movable body, the number of line-up of generators and motors can be reduced at the manufacturing stage, so that production can be simplified.
Exemplary embodiments of an electric drive system according to the present invention will be explained below in detail with reference to the accompanying drawings. The present invention is not limited to the embodiments.
As shown in
The embodiment describes the electric drive system that further includes a gear 7 for changing over the number of revolutions and torque of the induction motor 6, a drive shaft 8, a differential gear 9, and wheels 10 provided at the both ends of an axle connected to the differential gear 9, and is configured to be used in, for example, an automobile, a bus, and a truck.
The electric drive system according to the embodiment further includes generator pole-quantity changeover switches 19, 20 that can change over the pole quantity of the generator 2, and motor pole-quantity changeover switches 21, 22 that can change over the pole quantity of the induction motor 6. The generator 2 works as a generator of which pole quantity can be changed over, and the induction motor 6 works as a motor of which pole quantity can be changed over. The generator pole-quantity changeover switches 19 include three switches correspondingly to three phases U, V, and W, and the generator pole-quantity changeover switches 20 include three circuit breakers correspondingly to the three phases U, V, and W. The motor pole-quantity changeover switches 21 include three switches correspondingly to the three phases U, V, and W, and the motor pole-quantity changeover switches 22 include three circuit breakers correspondingly to the three phases U, V, and W. Section (a) of
The electric drive system according to the embodiment further includes a bypass unit 18, generator bypass switches 16, and motor bypass switches 17. The bypass unit 18 is configured, for example, as connecting lines, to connect the generator 2 directly to the induction motor 6 by bypassing the AC/DC converter 3, the capacitor 4, and the DC/AC converter 5. The generator bypass switches 16 and the motor bypass switches 17 are two kinds of changing switches that can switch a flow route of electric power from the generator 2 to the induction motor 6, into the bypass unit 18, or into a circuit that includes the AC/DC converter 3, the capacitor 4, and the DC/AC converter 5. The generator bypass switches 16 are changing switches provided in between the generator 2 and the AC/DC converter 3, and the motor bypass switches 17 are changing switches provided in between the DC/AC converter 5 and the induction motor 6. The generator pole-quantity changeover switches 19 are provided in between the generator 2 and the generator bypass switches 16, and the motor pole-quantity changeover switches 21 are provided in between the motor bypass switches 17 and the induction motor 6.
The electric drive system according to the embodiment further includes an engine control module (ECM) 13, a converter control circuit 14, a converter control circuit 15, a main controller 12, and a cab 11. The engine control module 13 controls the engine 1. The converter control circuit 14 is a driver that controls the AC/DC converter 3. The converter control circuit 15 is a driver that controls the DC/AC converter 5. The main controller 12 controls a system including the engine control module 13 and the converter control circuits 14 and 15. The cab 11 is connected to the main controller 12, includes various sensors, and can control the entire system.
The main controller 12 includes a function of a cruising-speed determining unit, which determines whether the movable body is driving at a cruising speed. The cruising speed is a speed that is substantially constant, frequently employed for long hours as a state of the movable body, and predetermined in accordance with each movable body based on specifications required by a customer and other requirements. For example, if the movable body is a bus that is operated mainly on a highway, the cruising speed is a typical speed during operation on a highway. Each of the generator bypass switches 16 and the motor bypass switches 17 is connected to the main controller 12, switching of each of them is controlled by the main controller 12. Although the main controller 12 includes the function of the cruising-speed determining unit according to the embodiment, the cruising-speed determining unit can be an individual unit.
The cab 11 is provided with various sensors, such as an accelerator sensor, a brake sensor, a shift lever, and a speed sensor, and control devices. A control instruction from the cab and information acquired by the sensors are input into the main controller 12.
Operations according to the embodiment are explained below with reference to
Operation of the movable body during a cruise driving is explained below. When the cruising-speed determining unit in the main controller 12 determines that the movable body is driving at the cruising speed, the generator bypass switches 16 and the motor bypass switches 17 are switched to connect the generator 2 to the induction motor 6 via the bypass unit 18. Furthermore, in accordance with the cruising speed, the generator pole-quantity changeover switches 19, 20 and the motor pole-quantity changeover switches 21, 22 are switched, windings, the gear 7, the differential gear 9 are set, the number of revolutions of the engine 1 is set to be appropriate to the cruising speed, and a generator frequency is made substantially equal to a motor frequency. In other words, the engine 1 shifts from the acceleration-deceleration mode A to a cruising mode B shown in
Similarly to the conventional technology, also when any of the converting devices fails, a driving force can be obtained by using the configuration that the generator 2 is directly connected to the induction motor 6 via the bypass unit 18.
According to the embodiment, the electric drive system is configured such that the generator pole quantity and the motor pole quantity can be changed over by the generator pole-quantity changeover switches 19, 20 and the motor pole-quantity changeover switches 21, 22, and is added with a function of determining a cruising speed of the movable body with the cruising-speed determining unit, accordingly, while driving the movable body at the cruising speed, the generator 2 is directly connected to the induction motor 6 via the bypass unit 18, and the movable body is driven by controlling the number of revolutions of the engine to be appropriate to the cruising speed. Consequently, losses made in the AC/DC converter 3 and the DC/AC converter 5 can be eliminated, a fuel consumption and exhaust gas can be improved, so that efficient driving can be achieved. Such configuration can improve the fuel consumption and exhaust gas during a cruising speed, in terms of which a series hybrid model has been considered as less efficient than a parallel hybrid model.
According to the conventional drive system of an electric vehicle (for example, see Patent Document 1) that drives the vehicle by connecting the alternating-current generator directly to the alternating-current motor via the bypass unit during a failure in the converting devices, when producing vehicles in accordance with cruising speeds of a movable body to be used for various purposes so as to employ the conventional configuration also in situations other than a failure in the converting devices, a plurality of types needs to be provided in the line-up of generators and motors. According to the embodiment, it only needs to change over an input frequency of the alternating-current motor and a generation frequency of the alternating-current generator in accordance with a cruising speed determined based on a purpose of each movable body, the number of line-up of the generators and the motors can be reduced, and production can be simplified.
Although the embodiment is explained above in the example of an electric vehicle, the present invention is not limited to this, but also can be applied to other movable bodies. For example, suppose a configuration in which the induction motor 6 or the drive shaft 8 is connected to a screw, the present invention can be applied to a ship. In such case, the electric drive system can cope with an emergency by using a bypassed direct connection during a failure on the sea.
Thus, according to the embodiment, because a function of manually specifying the cruising mode is provided, even during a movement under a situation that an automatic determination of the cruising mode is difficult, efficient driving in the cruising mode can be carried out with an intention of the driver.
According to the embodiment, the electric drive system uses a speed sensor signal detected by the speed sensor, which is provided on the cab as the cruising-speed determining unit in the configuration of the first embodiment.
According to the embodiment, the cruising mode is automatically determined in accordance with a detected speed by the speed sensor, so that the driver does not need to give an instruction of the cruising mode.
Thus, according to the embodiment, the cruising mode is determined by using the ETC 24, accordingly, a determination of the cruising mode can be reliably performed on a long-distance truck or a long-distance coach that frequently uses a highway or a motorway.
Thus, according to the embodiment, the cruising mode is determined based on output from the navigation system 25, so that efficient driving in the cruising mode can be carried out on a road with few traffic lights as well as on a highway and a motorway in the case that the movable body is an automobile, and efficient driving in the cruising mode can be carried out also in the case that the movable body is a ship.
Thus, according to the embodiment, the cruising mode is determined based on output from the traffic control system 26, efficient driving in the cruising mode can be carried out in a bus route or a railroad provided with a traffic control system.
When the movable body is a movable body that needs a plurality of patterns of driving at a constant speed, for example, a bus on a long-distance regular route that drives in an urban area and on a highway, the cruising-speed determining unit performs determination on a plurality of cruising speeds, for example, a cruising speed of driving in an urban area at 35 km/h, and a cruising speed of driving on a highway at 70 km/h. The electric drive system deals with a plurality of cruising modes by changing over the pole quantities of the generator 2 and the induction motor 6 in accordance with the determined speed, and substantially matching the generator frequency with the motor frequency.
According to the embodiment, when the movable body has a plurality of constant-speed driving patterns, the system configuration of the movable body can be switched into a system configuration appropriate to a cruising speed while driving, so that efficient driving in a cruising mode can be achieved at various speeds.
As described above, the electric drive apparatus according to the present invention can be applied to an electric drive model or a series hybrid drive model of a bus, a track, a ship, and the like.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2007/058851 | 4/24/2007 | WO | 00 | 4/14/2008 |