Patent Application
20070093343
The present disclosure is directed generally to in-line drivetrains, more particularly to a four wheel drive vehicle that utilizes an in-line drivetrain powered by an electric motor.
In an ongoing effort to further reduce undesirable emissions from motor vehicles, engineers have begun to consider alternatives to internal combustion engines as a means of propelling the vehicle. One potential alternative is to employ one or more electric motors powered by an appropriate electrical source, such as a fuel cell. In the case of four wheel drive vehicles, such as articulated wheel loader work machines, there are many alternative potential strategies that each deserve consideration. For instance, a four wheel drive work machine could be constructed with a separate electrical motor on each of its four wheels. However, such a solution could be cost prohibitive and difficult to control. Another alternative might be to include separate electrical motors for each of the two axles such as that taught by Sakazaki in U.S. Patent Application US 2003/0116371. Although this strategy might be more attractive than the four motor strategy, it still requires two electrical motors, two sets of controllers, and likely duplicate pairs of other relatively expensive components, such as reduction gears to link the motors to their respective axles.
Another potential problem associated with some four wheel drive work machines relates to packaging the various power plant(s), motor(s), work implement, etc. in an envelope that renders the machine a realistic alternative to existing work machines that rely upon conventional internal combustion engines. These challenges can be especially difficult in relation to some applications, such as wheel loaders utilized in underground mining operations.
The present disclosure is directed to overcoming one or more of the problems set forth above.
In one aspect, a four wheel drive vehicle includes a motor, a first axle with a first differential, and a second axle with a second differential connected to a chassis. A first drive shaft is coupled between the first differential and the second differential. A second drive shaft is coupled between the motor and the first differential, on a side of the first differential opposite from the first drive shaft.
In another aspect, a drivetrain includes a first differential with a ring gear, a first side and a second side. A first pinion is meshed with the ring gear and has a first shaft extending toward the first side. In addition, a second pinion is meshed with the ring gear and has a second shaft extending toward the second side. A motor is operably coupled to one of the first and second pinions. A driven element is operably coupled to the other of the first and second pinions.
In another aspect, a method of operating a four wheel drive vehicle includes a step of torquing a ring gear of a first differential coupled to a first axle with a motor. Torque is transferred from the first differential to a second differential coupled to second axle via a drive shaft coupled to the ring gear.
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Referring now in addition to
The back differential 19 includes a first side 40 that faces electric motor 17, and a second face 41 that faces toward front differential 24. The electric motor is coupled to back differential 19 via a first pinion 33 that is meshed with a ring gear 34 and includes a drive shaft extending in the direction of side 40. Ring gear 34 is coupled to back axle 20 in a conventional manner, but also transfers torque to drive shaft 23 via a second pinion 35 that is meshed with ring gear 34 and includes a shaft extending in the direction of side 41. Thus, unlike many differentials, the ring gear 34 of back differential 19 not only is a driven element, but also transfers torque to drive shaft 23 via pinion 35. Although a differential substantially without modification could be utilized, its life could be extended in this application by substituting a ring gear 34 into the conventional differential that includes extra hardening over that of an identical differential that is only a driven element. In other words, since ring gear could be expected to experience substantially more and different stresses than that of a counterpart simply driven ring gear of a conventional differential, some additional hardening may be prudent in order to extend its life when it is utilized in a drivetrain application such as that illustrated, in which it not only is a driven element but also transfers torque to another pinion.
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The drivetrain of the present disclosure finds potential application in any instance where a motor is utilized to apply torque to an axle and at least one other thing, such as a second axle, via a differential. The second driven thing could be a pump or some other component. In addition, the illustrated embodiment shows the ring gear 34 transferring torque to one pinion, but the disclosure contemplates torque transfer to two or more pinions. In the illustrated embodiment, the motor is an electric motor that is arranged in-line and in sequence with a back axle and a front axle. Thus, in the illustrated embodiment which is applicable for use in a underground mine loader work machine, the motor and axles are arranged in series starting from back to front with the motor being first, the back axle second and the front axle third. In other potential applications, such as on the road vehicles, the arrangement might be just the opposite. In other words, a four wheel drive vehicle could have the electric motor being the forward most component followed from front to rear by the front axle and finally the rear axle and have a drivetrain substantially identical to that disclosed above.
Those skilled in the art will appreciate that the described in-line drive that utilizes an electric motor presents a more compact alternative that has fewer components and parts, and offers other further advantages relative to conventional designs that utilize a diesel engine, a transmission, U joints and drive shaft as well as a drop box. In addition, the differential that is directly coupled to the electric motor can be a nearly off-the-shelf component that is modified only be removing one of its front or rear panels and adding a symmetrical second pinion and support gear. The disclosed embodiment also offers advantages over other electrically driven four wheel drive vehicles in that only a single electric motor and single reduction gear are needed, which can provide a substantial cost savings over the multiple motor and multiple reduction gear alternatives described in the art. Thus, with fewer components and parts, there is reduced costs, and potentially reduced maintenance and reduced parasitic loses for any electrically driven vehicle employing the electrical in-line drive described above.
It should be understood that the above description is intended for illustrative purposes only, and is not intended to limit the scope of the present disclosure in any way. Thus, those skilled in the art will appreciate that other aspects, objects, and advantages of the disclosure can be obtained from a study of the drawings, the disclosure and the appended claims.
