US20040120800A1

US20040120800A1 - Method for controlling a raise/extend function of a work machine

Info

Publication number: US20040120800A1
Application number: US10/323,621
Authority: US
Inventors: Simon Litchfield; C. Johnson
Original assignee: Caterpillar Inc
Current assignee: Caterpillar Inc
Priority date: 2002-12-18
Filing date: 2002-12-18
Publication date: 2004-06-24
Also published as: FR2849075A1

Abstract

A method for controlling the raise/extend function of a work machine is provided. The method comprises sensing the position of a frame and the position of a telescopic boom of the work machine, comparing the sensed positions to a desired position and controlling the raise/extend operation in response to the actual verses the desired positions.

Description

TECHNICAL FIELD

The invention relates to a method of controlling the function of a work machine and more particularly to a method of controlling the raise/extend function of a telescopic material handler.

BACKGROUND

Material handling machines, such as telescopic material handlers are faced with stability problems during operation. These machines have these problems because of their high lifting capability, especially when heavy loads are being transported. These problems are even more troublesome when the material handlers are operated on work sites that have uneven terrain and are littered with debris. Many material handlers are provided with high ground clearance involving maintaining as much of the machine as possible elevated from the terrain, especially those elements which extend across the width of the vehicle, such as the axles. While high ground clearance facilitates maneuverability of the material handler it compounds the stability problem because of the elevated center of gravity. The stability problem is particularly acute when the material handlers are required to elevate substantial loads to considerable heights and move about on uneven terrain while balancing the load.

Heretofore in utilizing material handlers on or over uneven terrain or work surfaces, load spilling and machine stability have sometimes been major operational problems. Various attempts have been made to stabilize material handlers in such situations one example is disclosed in U.S. Pat. No. 3,937,339 issued Feb. 10, 1976 to Geis et al. and assigned to Koehring Company of Milwaukee, Wis. This stabilizing system uses two pair of mercury switches, mounted to the body of the machine, one of the pair being actuated at a time to select between coarse and fine adjustment settings. The system automatically, through the use of a solenoid valve, supplies pressurized fluid to a pair of cylinders to level the body of the machine during operation. This system allows for adjustments to counter act uneven terrain while traversing a work sight and during a load lifting operation. However, this system can cause a load to be dumped due to rapid adjustments, inadvertent contact with an obstacle during lifting, let alone the uneasiness in the ride felt by an operator during an adjustment while traversing a work site.

The present invention is directed to overcoming one or more of the following problems as set forth above.

SUMMARY OF THE INVENTION

In one aspect of the present invention a method for controlling a boom raise/extend function of a work machine is provided. The work machine has a longitudinal frame and a support member. The method includes sensing the pressure at both ends of at least one hydraulic cylinder positioned between the frame and the support member. Comparing the sensed force reacted by the at least one hydraulic cylinder to a desired predetermined limit and controlling the boom raise/extend in response to the sensed force being within a predetermined limit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation view of a work machine embodying the present invention; [0006]
FIG. 2 is a front elevation view of a work machine embodying the present invention; [0007]
FIG. 3 is a schematic diagram illustrating a portion of a hydraulic circuit of the present invention; and [0008]
FIG. 4 is a flowchart illustrating the various operational steps.[0009]

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2, a work machine such as a [0010] telescopic handler 10 is shown. It will be understood that this invention is equally applicable to other work machines, such as forestry machinery and other non-construction related machinery. In general, the work machine 10 comprises a frame 12, and a telescopic boom 14 that is pivotally mounted to the rear of the frame 12 for elevation to various angles relative to the frame 12. The telescopic boom 12 is extended and retracted by a hydraulic cylinder (not shown) and is raised and lowered by cylinders 15 (only one shown in FIG. 1). In addition, an operator cab 16 is provided on one side of the frame 12, and an engine enclosure 18 is provided opposite the boom 14, so that the boom 14, when lowered, extends between the cab 14 and the engine enclosure 18.
Front and rear support members such as [0011] axles 20,22 are pivotally mounted on the frame 12 for oscillating motion about a pivot point 24 parallel to the center-line of the frame 12. The axles 20,22 carry front and rear wheels 26 of equal size, steered by means of hydraulic cylinders in a known manner. At least one hydraulic cylinder 28 is pivotally connected between the frame 12 and the front axle 20 and used to level the frame 12 relative to the ground, one cylinder may be used on either side of pivot point 24 may be used as well, when the machine 10 is operating on uneven terrain. As an alternative, some work machines include a support member 21 attached to the frame 12. As shown in phantom in FIG. 2, support member 21 is an outrigger arrangement that includes a pair of legs 23 that are each controlled by cylinders 27. Graphically represented on the cab 14 in FIGS. 1 and 2 is an electronic control module 30. A first inclinometer 32 is shown attached to the cab 16 in FIG. 2 and a second inclinometer 34 is attached to the telescopic boom 15 in FIG. 1. Both inclinometers 32,34 are connected to the electronic control module 30 as by wire and receive signals therefrom related to the angular position of the frame 12 and the boom 15 respectively.
Referring now to FIG. 3 a portion of a lateral stabilization circuit [0012] 36 is shown. Lateral stabilization circuit 36 includes a supply conduit 38 that connects a source of pressurized fluid (not shown) to a control valve 40. A return conduit 42 drains the pressurized fluid back from the control valve 40 to a reservoir (not shown). Control valve 40 is a three position, four-way solenoid valve of any of a number of given configurations that is connected to hydraulic cylinder 28 via a conduit 44 and a conduit 46. It should be understood that at least one of hydraulic cylinders 27 may be used in the representative circuit as an alternative without departing from the gist of this disclosure. Positioned in each of the conduits 44,46 is a counter balance valve 48. In this example the counter balance valve 48 is used as a safety device that includes a pilot input 50 and a relief setting arrangement 52. The counter balance valve 48 positioned in conduit 46 includes a pilot line 54 connecting the pilot input 50 to conduit 44, while the counter balance valve 48 positioned in conduit 44 includes a pilot line 54 connecting the pilot input 50 to conduit 46. A check valve 56 is positioned in parallel to each of the counter balance valves 48 so that fluid flow from the cylinder 28 is blocked. Additionally, connected to conduits 44,46 between the counter balance valves 48 and the control valve 40 is a resolver 58 that drains to a signal line 60. Signal line 60 sends a fluid signal representative of load to a controller (not shown) such as a pump controller as is commonly known.
Referring now to FIG. 4 a method for controlling the lateral stability of [0013] work machine 10 is illustrated. The controller 30 receives signals from various operator inputs such as a joystick, control lever or similar input device (not shown) requesting a desired raise/extend operation of the telescopic boom 14 and from the first and second inclinometers 32,34. A calculation block 62 compares the actual position of the frame 12 and the telescopic boom 14 and compares the angular readings from the inclinometers 32,34 to stored data such as maps look up tables and the like in decision block 64. If the frame 12 is within a predetermined limit or the raise/extend request does not put the work machine 10 in an unstable position a control block 66 of the controller 30 allows signals from the operator controls (not shown) providing full functionality of the telescopic boom 14. Additionally, the level function is locked at this point in a control block 68. If the frame 12 is not within the predetermined limit the controller 30 compares the frame 12 position and the telescopic boom 14 position signals from inclinometers 32,34 respectively, in a decision block 70 to see if any movement of the telescopic boom 14 will place the machine in an unstable position. If the frame 12 is not within the predetermined limit and any raise/extend request places the work machine 10 in an unstable position, from block 70, a control block 72 of the controller 30 disables operator controls for raise/extend function. However, lower/retract functionality is still provided. At this point the operators options are provided in a control block 74 and allow the operator to send a signal through an operator input (not shown) to request the controller 30 to send a signal to control valve 34 to shift, allowing pressurized fluid to flow to either hydraulic cylinder 28 or at least one of hydraulic cylinders 27 to provide an automatic leveling function. If the frame 12 is not within the predetermined limit and a raise/extend request will not place the work machine 10 in an unstable position (i.e. the extend/raise is within a predetermined range) in block 70, a control block 76 always operator control to provide limited raise/extend function until the controller 30 receives signals from inclinometer 34 representative of an unstable position, the controller 30 then disables operator controls for raise/extend function in control block 72.

Industrial Applicability

In operation a raise/extend input command is provided to controller [0014] 30 from the operator to raise/extend the telescopic boom 14. To raise/extend the telescopic boom 14, the controller 30 receives signals from the first and second inclinometers 32,34. The controller 30 compares these signals to stored data related to the lateral orientation of the work machine 10 and position of the telescopic boom 14 in calculation block 62. The controller 30 then makes a determination of the work machine being in an unstable position in decision block 64. If the work machine 10 is found to be in a safe lateral orientation control block 66 allows for a load to be raised/extended (i.e. the cylinders 15 to raise telescopic boom 14 or the cylinder to extend telescopic boom 14) and the level function is blocked out in control block 68. The controller 30 determines if a raise/extend request will place the work machine 10 in an unsafe position in decision block 70. If the work machine 10 is not in a safe lateral orientation control block 72 disables the load raise/extend capability of the work machine 10. Control block 74 then allows the operator to maneuver the frame 12 by supplying a command to the hydraulic cylinder 27,28 to laterally position the work machine 10 in a safe position so that a load can be raised/extended. Or the operator can lower/retract the telescopic boom 14 and reposition the work machine 10 in a laterally stable position. If a raise/extend request will not place the work machine 10 in an un-safe lateral orientation control block 76 allows a limited amount of raise/extend capability of the work machine 10 until just before an un-safe condition then control block 72 disables the load raise/extend capability of the work machine 10. Control block 74 then allows the operator to maneuver the frame 12 by supplying a command to the hydraulic cylinder 27,28 to laterally position the work machine 10 in a safe position so that a load can be raised/extended.
In view of the foregoing it is readily apparent that the method provides a process for controlling the raise/extend function of a [0015] work machine 10. The method is for the most part automatic but does allow operator intervention so as to level the frame 12 of the machine 10 relative to the horizontal so as not to put the load or machine in an unstable situation.

Claims

What is claimed is:

1. A method for controlling a boom raise/extend function of a work machine, the work machine having a longitudinal frame, a telescopic boom and a support member, said method comprising:

sensing the position of the frame and the telescopic boom;

comparing the sensed positions of the frame and the telescopic boom to a desired predetermined limit;

controlling the boom raise/extend in response to the comparison between the sensed positions of the frame and the telescopic boom to the desired predetermined limit.

2. The method of claim 1, wherein controlling the boom raise/extend includes allowing the raise/extend function if the sensed positions of the frame and the telescopic boom is within the desired predetermined limit.

3. The method of claim 1, wherein controlling the boom raise/extend includes disabling the raise/extend function if the sensed positions is not within the predetermined limit.

4. The method of claim 3, including allowing the frame to be automatically leveled until the frame position is within the predetermined limit.

5. The method of claim 1, wherein controlling the boom raise/extend includes allowing limited raise/extend function if the sensed positions is not within the predetermined limit.

6. The method of claim 5, wherein controlling the boom raise/extend includes disabling the raise/extend function if further raise/extend of the telescopic boom will place the work machine in an unsafe position.