Control system for electric vehicle

• US 5,808,428 A
• Filed: 07/03/1996
• Issued: 09/15/1998
• Est. Priority Date: 07/03/1995
• Status: Expired due to Term

• Current Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Original Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Inventors: Kayano, Morio, Shibutani, Atsushi, Itoh, Tomoyuki, Tamenori, Koji, Ito, Hisahiro
• Primary Examiner(s): Ro, Bentsu
• Application Number:
  US08/674,841
• Time in Patent Office: 804 Days
• Field of Search: 318/139, 320/43, 320/48, 320/61, 324/425, 324/426, 324/427, 324/433, 340/636, 180/65.1, 364/424.026, 364/483
• US Class Current: 318/139
• CPC Class Codes: B60L 15/2045 for optimising the use of energy
• CPC Class Codes: B60L 50/51 characterised by AC-motors
• CPC Class Codes: B60L 58/10 for monitoring or controlling batteries
• 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 10/72 Electric energy management in electromobility

Abstract

When the voltage of a battery is dropped down to a first threshold value (9.5 V) or less, the driving force of a motor is decreased to a level Y(0)-Y(7) of a limit power determined in accordance with a remaining capacity of the battery. When the voltage is not restored even after a predetermined time is lapsed from the decreasing of the driving force to the level Y(0)-Y(7), the driving force is further decreased down to a lower level Y(0)-Y(7). When the voltage of the battery is restored to a second threshold value (10 V), the driving force of the motor is gradually increased up to a level Z(0)-Z(7) of a limit power determined in accordance with the capacity of the battery. Thus, it is possible to prevent a deep discharging of the battery, while minimizing the influence on the traveling of the vehicle.

Claims

1. A control system for an electric vehicle including a battery and a motor connected to driven wheels, said control system comprising:

motor control means for driving the motor by a driving force which is determined based upon an operational state of the vehicle;

voltage detecting means for detecting a voltage of the battery;

remaining capacity detecting means for detecting a remaining capacity of the battery;

timer means; and

driving-force control means connected to said motor control means, said voltage detecting means, said remaining capacity detecting means and said timer means for limiting the driving force of the motor in accordance with a condition of said battery, wherein said driving-force control means includes

first means which is operated such that when the voltage of said battery detected by the voltage detecting means is dropped down lower than a first threshold value, said first means decreases the driving force of said motor from a first level to a second level that is based upon the remaining capacity of said battery detected by the remaining capacity detecting means,

second means which is operated such that when the voltage of said battery is not restored after a predetermined time is lapsed set by said timer means from the decreasing of the driving force of the motor caused by said first means, said second means further decreases the driving force of the motor,

third means which is operated such that when the voltage of said battery is restored to a second threshold value which is higher than the first threshold value, said third means restores the driving force of the motor to a third level and

fourth means which is operated such that when the voltage of said battery is between said first and second threshold values, said fourth means maintains the driving force of the motor at the second level,

wherein an amount of decrease and an amount of restoration in the driving force of the motor are provided based on the remaining capacity of said battery and a resultant decreased or restored driving force of the motor is a maximum driving force the motor can output without causing damage to said battery.

2. A control system for an electric vehicle according to claim 1, wherein said driving force control means further includes a map for determining said amount of decrease in the driving force of the motor which is dependent upon the remaining capacity of the battery.

3. A control system for an electric vehicle according to claim 2, wherein said map for determining said amount of decrease in the driving force of the motor is formed to have step-wise values so that a driver can recognize a decrease in the capacity of the battery.

4. A control system for an electric vehicle according to claim 1, wherein said driving force control means further includes a map for determining said amount of restoration in the driving force of the motor which is dependent upon the remaining capacity of the battery.