Patent Application
20080164084
The present disclosure relates to electric vehicles, such as golf cars and utility vehicles, and more particularly, to a locking differential for an electric vehicle.
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Electric vehicles have grown more and more popular for use as golf cars and utility vehicles. Electric vehicles are relatively low maintenance and emit zero environmentally harmful emissions. In addition, the electric vehicles are highly reliable.
Although electric vehicles have proven to be very popular and efficient, the need to improve the vehicle's manufacture and assembly still exists. One area of recent development for electrical vehicles relates to the braking system. Examples of such inventions are disclosed in U.S. Pat. Nos. 6,457,568 and 6,686,719 which are commonly assigned. In U.S. Pat. No. 6,457,568, a disc brake system for use with electric vehicles is provided. Electric vehicle disc brake systems are specially designed due to the limited ground clearance of the electric vehicle which has smaller wheels than a standard automotive vehicle. Additionally, U.S. Pat. No. 6,686,719 provides for regenerative braking, wherein electric energy is generated during braking so as to aid in the charging of the vehicle batteries.
The present invention utilizes the drive motor as a source of braking torque. Providing braking by the electric motor accomplishes two things: it returns energy back to the battery by using the electric motor 12 as a generator, and it reduces the cost and maintenance associated with a mechanical braking system. However, braking on slippery surfaces can be difficult when the drive motor is used for providing braking torque. In cases where one wheel loses traction, the other wheel is free to turn, resulting in no braking torque being applied to either of the wheels. This can also happen when an electro-mechanical brake on the motor shaft is used for emergency braking or for parking. To prevent this problem, the present disclosure provides a locking mechanism for locking both sides of the differential together so that both wheels will turn together, thus providing braking torque. In other words, when the first and second output shafts of the differential are locked together, and the input from the motor is braked, the differential is locked up and, therefore, the rear wheels are prevented from rotating. The locking differential can be actuated by a solenoid that will force the locking mechanism to lock. The lock signal is provided by a drive controller when a brake pedal is pressed a predetermined amount of its travel. The amount of the braking signal necessary to actuate the lock can be programmable.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.
With reference to
As shown in
The differential 16 includes the input shaft 14 which is connected to a drive gear 60. Drive gear 60 drivingly engages input gear 62 which drives the casing 64. As is typically known in a differential, the casing 64 supports a pair of beveled gears which rotate with the casing and drive a pair of output gears (only of which, 72, is shown) which are mounted to the first and second output shafts 18, 20, respectively. It should be understood that the locking mechanism can be utilized for locking any of the components of the differential 16 together. By locking any two components, the entire differential is locked-up to thereby engage the first and second output shafts together to prevent relative rotation therebetween. In particular, a locking mechanism may directly engage the first and second output shafts to one another, or may engage the differential housing 64 to one of the output shafts 18, 20 in order to engage the first and second output shafts together.
