Drive system for electrically driven dump truck

• US 8,265,849 B2
• Filed: 05/07/2007
• Issued: 09/11/2012
• Est. Priority Date: 06/06/2006
• Status: Active Grant

• Current Assignee: Hitachi Construction Machinery Company Limited (Hitachi, Ltd.)
• Original Assignee: Hitachi Construction Machinery Company Limited (Hitachi, Ltd.)
• Inventors: Tanaka, Yasuo, Yasuda, Tomohiko, Yagyu, Takashi, Watanabe, Yutaka
• Primary Examiner(s): Black, Thomas G.
• Assistant Examiner(s): LOUIE, WAE LENNY
• Application Number:
  US12/279,476
• Publication Number:
  US 20090048064A1
• Time in Patent Office: 1,954 Days
• Field of Search: 477/3, 180/65.265, 701/102, 701/50, 701/22, 701/84, 701/87, 701/90, 318/66, 318/34, 318/140
• US Class Current: 701/84
• CPC Class Codes: B60K 6/46 Series type
• CPC Class Codes: B60L 15/10 for automatic control superimposed on human control to limit the acceleration of the vehicle, e.g. to prevent excessive motor current electric devices for safety purposes B60L3/00
• CPC Class Codes: B60L 15/20 for control of the vehicle or its driving motor to achieve a desired performance, e.g. speed, torque, programmed variation of speed
• CPC Class Codes: B60L 2200/36 Vehicles designed to transport cargo, e.g. trucks
• CPC Class Codes: B60L 2220/12 Induction machines
• CPC Class Codes: B60L 2220/14 Synchronous machines
• CPC Class Codes: B60L 2220/44 Wheel Hub motors, i.e. integrated in the wheel hub
• CPC Class Codes: B60L 2260/28 Four wheel or all wheel drive
• CPC Class Codes: B60L 50/40 using propulsion power supplied by capacitors
• CPC Class Codes: B60L 50/61 by batteries charged by engine-driven generators, e.g. series hybrid electric vehicles
• CPC Class Codes: B60P 1/04 with a tipping movement of load-transporting element dredgers or soil-shifting machines E02F3/00
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 10/08 including control of electric propulsion units, e.g. motors or generators
• CPC Class Codes: B60W 20/00 Control systems specially adapted for hybrid vehicles hybrid vehicle design, B60K6/00; electric vehicles B60L
• CPC Class Codes: B60W 20/10 Controlling the power contribution of each of the prime movers to meet required power demand
• CPC Class Codes: B60W 2540/10 Accelerator pedal position
• CPC Class Codes: B60W 2710/0666 Engine torque
• CPC Class Codes: B60W 2720/30 Wheel torque
• CPC Class Codes: F02D 29/06 peculiar to engines driving electric generators
• CPC Class Codes: Y02T 10/62 Hybrid vehicles
• CPC Class Codes: Y02T 10/64 : Electric machine technologies in electromobility
• CPC Class Codes: Y02T 10/70 : Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 : Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y02T 10/72 : Electric energy management in electromobility

Abstract

A drive system of an electrically driven dump truck is capable of achieving an operational feeling in which the operation amount of the accelerator pedal is well balanced with the output horsepower of the electric motors, particularly at the time of slow traveling. To achieve this, the target motor output horsepower Pm0 corresponding to the operation amount of an accelerator pedal 1 is calculated. The target motor torque Tr1R, Tr1L is calculated on the basis of the target motor output horsepower Pm0 and the rotational speed ωR, ωL of electric motors 12R, 12L respectively. The acceleration torque limit values of the electric motors 12R, 12L corresponding to the operation amount of the accelerator pedal 1 are calculated, respectively. Then, smaller values are selected, as motor torque instruction values TrR, TrL, between the acceleration torque limit value and the target motor torque Tr1R, Tr1L to control inverters 73R, 73L, respectively.

Claims

1. A drive system of an electrically driven dump truck comprising:

a prime mover;

an alternating-current generator driven by the prime mover;

at least two electric motors for traveling, each of which is driven by the electric power supplied by the alternating-current generator;

at least two inverters, each of which is connected to the alternating-current generator, and each of which controls one of the electric motors; and

motor control means for controlling the inverters in response to the operation amount of an accelerator pedal to control the electric motors;

wherein the motor control means includes;

target motor output horsepower calculation means for calculating the target motor output horsepower corresponding to the operation amount of the accelerator pedal;

target motor torque calculation means for calculating the target motor torque on the basis of the target motor output horsepower and the rotational speed of the two electric motors;

acceleration torque limit value calculation means for calculating acceleration torque limit values of the two electric motors corresponding to the operation amount of the accelerator pedal;

motor torque instruction value determination means for, when the acceleration torque limit values are larger than the target motor torque, selecting the target motor torque as motor torque instruction values, and for, when the acceleration torque limit values become smaller than the target motor torque, selecting the acceleration torque limit values as motor torque instruction values; and

inverter control means for controlling the inverters on the basis of the motor torque instruction values.

2. The drive system of the electrically driven dump truck according to claim 1, wherein:

the acceleration torque limit value calculation means calculates the acceleration torque limit values on the basis of acceleration torque limit value characteristics that are configured as follows;

when the operation amount of the accelerator pedal is at 0, the acceleration torque limit values are the low range torque that is suitable for very slow traveling;

when the operation amount of the accelerator pedal falls within a range from 0 to the medium operation amount, which includes a small operation amount area, with the increase in the operation amount of the accelerator pedal, the acceleration torque limit values increase from the minimum torque up to a high range torque that is suitable for very slow traveling; and

when the operation amount of the accelerator pedal further increases, the acceleration torque limit values increase up to the maximum torque.

3. The drive system of the electrically driven dump truck according to claim 2, wherein:

the low range torque, which is suitable for very slow traveling, ranges from 15% to 30% of the maximum allowable motor torque that is predetermined in response to the rotational speed of the electric motors;

the high range torque, which is suitable for very slow traveling, ranges from 30% to 50% of the maximum allowable motor torque; and

the medium operation amount ranges 40% to 60% of the maximum operation amount.

4. The drive system of the electrically driven dump truck according to claim 1, wherein:

the acceleration torque limit value calculation means calculates, as the acceleration torque limit values, the motor acceleration torque corresponding to the operation amount of the accelerator pedal; and

the motor torque instruction value determination means compares among the target motor torque, the motor acceleration torque, and the maximum allowable motor torque, which is predetermined in response to the rotational speed of the electric motors, so that the minimum values are selected among them.

5. The drive system of the electrically driven dump truck according to claim 1, wherein:

the acceleration torque limit value calculation means calculates the maximum motor torque, as the acceleration torque limit values, the maximum motor torque being a value that is obtained by multiplying the maximum allowable motor torque, which is predetermined in response to the rotational speed of the electric motors, by a motor torque limit ratio that is calculated in response to the operation amount of the accelerator pedal; and

the motor torque instruction value determination means compares the target motor torque with the maximum motor torque so that each minimum value is selected between them.

6. The drive system of the electrically driven dump truck according to claim 1, further comprising:

maximum horsepower calculation means for, in response to the revolution speed of the prime mover, calculating an available maximum horsepower for the electric motors for traveling; and

motor output horsepower limiting means for limiting the target motor output horsepower calculated by the target motor output horsepower calculation means so that the target motor output horsepower does not exceed the maximum horsepower calculated by the maximum horsepower calculation means,

wherein;

the target motor torque calculation means calculates the target motor torque from the target motor output horsepower received from the motor output horsepower limiting means, and from the rotational speed of the two electric motors respectively.