Wheel loader

Details Wheel loader Wheel loader

1998-12-14

2001-01-16

Will, Thomas B. (Department: 3671)

Excavating

Scoop or excavating and transporting container

Supported on vehicle between longitudinally spaced ground...

C037S902000

Reexamination Certificate

active

06173513

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a wheel loader by which a higher acceleration, an energy-saving performance, and a higher traveling and working efficiency can be obtained.
BACKGROUND ART
A wheel loader has a traveling system and a hydraulic oil working system. The traveling system is driven by an engine, and the hydraulic oil working system is operated by receiving pressurized oil from a hydraulic pump which is driven by the engine. The engine of a wheel loader is set so that the maximum torque Te of the engine at each engine speed somewhat exceeds the total absorption torque (Th+Tr), which is obtained by adding the full absorption torque Th of the hydraulic working system to the absorption torque Tr of the traveling system at each engine speed in a low-to-medium engine speed range (Te>Th+Tr). A difference &Dgr;T[=Te−(Th+Tr)] between the maximum torque Te of the engine and the total absorption torque (Th+Tr) is set as excess torque &Dgr;T (hereinafter, called excess torque &Dgr;T).
The excess torque &Dgr;T ensures an acceleration to abruptly increase the engine speed from the low-to-medium engine speed range (specifically, a low-to-medium engine horsepower range) to a high engine speed range (specifically, a high engine horsepower range) in response to a hard increase in the pressure on the accelerator pedal provided adjacent a driver seat. The acceleration performance becomes higher as the excess torque &Dgr;T is greater. The traveling system has a speed change lever, with a plurality of speed change positions, located adjacent to the driver seat. The speed of the wheel loader is freely changed among a neutral (stopping) position, a forward position, and a reversing position, and among respective speed positions in the forward and reversing positions by the operator manipulating the speed change lever. In most cases, the hydraulic pump is a fixed displacement type, but a variable displacement type is used in some cases. A more specific explanation follows.
As is shown in
FIG. 3
, the wheel loader comprises a vehicle body A and a working machine B, which is located at the front portion of the vehicle body A. The working machine B includes a pair of arms B
2
and a bucket B
4
. The base (rear) end of each arm B
2
is pivotably attached to the front portion of the vehicle body A by a respective pivot pin, so that the bucket B
4
can be freely raised and lowered by a pair of arm hydraulic cylinders B
1
, each of which is connected between the vehicle body A and an intermediate portion of a respective one of the pair of arms B
2
. The distal (foremost) ends of the pair of arms B
2
are pivotably attached by respective pivot pins to the lower backside of the bucket B
4
, so that the bucket B
4
can be freely pivoted between a backwardly tilted position and a dump position by the bucket hydraulic cylinder B
3
, one end of which is connected to the vehicle body A and the other end of which is connected through a linkage to the backside of the bucket B
4
at a location above the pivot pins for the connection of the arms B
2
to the bucket B
4
.
The vehicle body A also includes a traveling system comprised of: a driver seat A
1
; an engine (not illustrated); a torque converter (not illustrated); a transmission (not illustrated); a drive shaft (not illustrated); a differential (not illustrated); four tires A
2
located at the right front, left front, right rear, and left rear of the vehicle body; a speed change lever (not illustrated); and the like. The vehicle body A further comprises a hydraulic working system which includes: a hydraulic oil circuit, having a hydraulic pump and which makes the hydraulic cylinders B
1
and B
3
extendable; the working machine B; a working machine operating lever (not illustrated), which is provided adjacent to the driver seat A
1
; and the like. The engine speed is controlled in response to the depression angle of an accelerator pedal (not illustrated). The traveling system can also include, for example, a steering hydraulic oil circuit, and the like. Further, various kinds of traveling systems can be used, for example, a system with the torque converter replaced by a damper mechanism, a system with the above mechanical traveling system replaced by a full hydraulic type, an electric type, or the like.
The wheel loader, constructed as described above, carries out a sole traveling operation, a sole working operation, and a joint operation which is a combination of the traveling operation and the working operation.
(1) The sole traveling operation is based on the operation of the speed change lever, the accelerator pedal, and the like, without operating the hydraulic working system (specifically, the working machine operating lever is in its neutral position). The sole traveling operation is conducted, for example, while traveling on a pavement, traveling between two sites, traveling a medium distance or a long distance with a load on the bucket B
4
(so-called, load-and-carry), or the like.
(2) The sole working operation is based on the operation of the working machine operating lever, the accelerator pedal, or the like, without operating the traveling system (specifically, the speed change lever is in its neutral position, and a brake pedal is operated). The sole working operation is conducted, for example, when raking and excavating natural ground with the bucket B
4
while the loader is in a non-traveling (stopped) condition.
(3) The combined operation is based on the simultaneous operations of the working machine operating lever, the speed change lever, the accelerator pedal, etc. For example, the vehicle body A is moved forwardly, the blade edge of the bucket B
4
is thrust into natural ground, and then while the working machine lever is being operated, the accelerator pedal is fully depressed. Thus, the purposes of the combined operations include obtaining a resultant force (a vector) of a greater thrusting force and raking force, produced by hydraulic oil pressure, and excavating with strong power at a higher speed, by increasing the discharge quantity of the hydraulic pump.
In the wheel loader conducting the above combined operations, with the speed change operation being by means of the speed change lever, and the oil quantity adjusting operation being by means of the working machine operating lever, the operator depresses the accelerator pedal hard. As for the operation of a wheel loader having an inching pedal or the like, an operation of depressing the inching pedal or the like can be also included. On the other hand, when an excavating force or a traveling force with smaller strength at a lower speed is desired, the operator only slightly depresses the accelerator pedal. Specifically, the operation mainly consists of a simple operation of obtaining engine horsepower corresponding to the load, in accordance with the depression angle of the accelerator pedal.
However, unless the engine horsepower quickly changes in response to an increase in the pressure on the accelerator pedal, excavation and travel with a high efficiency cannot be achieved. Especially in a wheel loader, a depressing operation to abruptly shift the engine speed from a low-to-medium engine speed range to a high engine speed range is frequently carried out by abruptly depressing the accelerator pedal. For example, in the combined operations described supra, when the vehicle body A is moved forwardly and the edge of the blade of the bucket B
4
is thrust into natural ground, some vehicle speed is sufficient until the moment at which it is thrust. Specifically, if there is vehicle speed to some extent, it is not necessary to depress the accelerator pedal so hard, that is, it is suitable if the engine speed is in a low-to-medium speed range.
However, when excavation with strong power at a higher speed is to be conducted next by abruptly and fully depressing the accelerator pedal while manipulating the working machine lever, the acceleration performance of the engine is decreased if there is no excess torque &Dgr;T.

Affiliated with

Also associated with

Rating

Wheel loader does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Wheel loader, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Wheel loader will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2516205