Skid steer vehicle with self-leveling suspension

• US 6,633,804 B2
• Filed: 12/27/2001
• Issued: 10/14/2003
• Est. Priority Date: 12/27/2001
• Status: Expired due to Term

• Current Assignee: Blue Leaf IP Incorporated (CNH Industrial N.V.), CNH America Llc (CNH Industrial N.V.)
• Original Assignee: Case Corporation (CNH Industrial N.V.)
• Inventors: Dix, Peter J., Lin, Hong-Chin, Felsing, Brian E., Bateman, Troy D., Lamela, Anthony J., Shore, Daniel B.
• Primary Examiner(s): NGUYEN, TAN QUANG
• Application Number:
  US10/033,843
• Publication Number:
  US 20030125858A1
• Time in Patent Office: 656 Days
• Field of Search: 701/1, 701/36, 701/37, 701/38, 701/41, 701/49, 701/50, 280/5.503, 280/5.507, 280/5.515, 180/89.12, 180/89.13, 374/14
• US Class Current: 701/50
• CPC Class Codes: B60G 17/005 Suspension locking arrangements for retractable wheels B62D61/12
• CPC Class Codes: B60G 17/018 characterised by the use of a specific signal treatment or control method
• CPC Class Codes: B60G 17/056 Regulating distributors or valves for hydropneumatic systemsB60G17/044 - B60G17/048, B60G17/0416 take precedence; Fluid interconnection systems to control vehicle inclination B60G21/06, B60G21/10; valves per se F16K
• CPC Class Codes: B60G 21/10 not permanently interconnected, e.g. operative only on acceleration, only on deceleration or only at off-straight position of steering
• CPC Class Codes: B60G 2300/09 Construction vehicles, e.g. graders, excavators
• CPC Class Codes: B60G 2400/252 vertical
• CPC Class Codes: B60G 2600/02 Retarders, delaying means, dead zones, threshold values, cut-off frequency, timer interruption
• CPC Class Codes: B60G 2600/12 Sampling or average detecting; Addition or substraction
• CPC Class Codes: B60G 2600/20 Manual control or setting means
• CPC Class Codes: B60G 2800/012 Rolling condition
• CPC Class Codes: B60G 2800/014 Pitch; Nose dive
• CPC Class Codes: B60G 2800/164 Heaving; Squatting
• CPC Class Codes: B60G 2800/912 Attitude Control; levelling control
• CPC Class Codes: B60G 2800/914 Height Control System

Abstract

A skid steer vehicle has a sprung suspension system including four wheels mounted on four swing arms that are pivotally coupled to the chassis of the vehicle. An electronic controller is connected both to position sensors coupled to the swing arms to sense the position of the swing arms and wheels with respect to the chassis and also to hydraulic cylinders that control the position of the swing arms and wheels. The electronic controller determines the average position of each suspension and controls the flow of fluid to the cylinders to keep the swing arms and wheels at their proper target height when vehicle load changes.

Claims

1. A skid steer loader, comprising:

a chassis having a left side and an opposing right side, a front end and an opposing rear end, and a fore-and-aft center of gravity line;

a lift mechanism attached to the chassis and adapted to raise and lower and attachment relative to the chassis;

an engine fixed to the chassis;

a first hydraulic fluid pump driven by the engine to provide hydraulic fluid under pressure;

a second hydraulic fluid pump driven by the engine to provide hydraulic fluid under pressure;

a third hydraulic fluid pump driven by the engine to provide hydraulic fluid under pressure;

a first hydraulic motor in fluid communication with the first hydraulic fluid pump;

a second hydraulic motor in fluid communication with the second hydraulic fluid pump;

left front and left rear suspensions mounted in a fore-and-aft arrangement on the left side of the chassis for pivotal movement with respect thereto, each left suspension including;

a left ground-engaging wheel extending from the left side of the chassis and rotationally coupled to the first hydraulic motor to be driven in rotation thereby;

a left control arm assembly pivotably coupled to and between the left wheel and the chassis;

a left hydraulic cylinder disposed between the chassis and the left control arm such that movement of the left control arm with respect to the chassis causes the left cylinder to extend and retract;

a hydraulic valve coupled to and between the left hydraulic cylinder and the third hydraulic pump to regulate the flow of fluid from the third hydraulic pump to the left hydraulic cylinder; and

a left suspension sensor that is responsive to changes in the position of the suspension to generate a signal indicative of the position of the suspension with respect to the chassis;

right front and right rear suspensions mounted in a fore-and-aft arrangement on the right side of the chassis for pivotal movement with respect thereto, each right suspension including;

a right ground-engaging wheel extending from the right side of the chassis and rotationally coupled to the second hydraulic motor to be driven in rotation thereby;

a right control arm pivotably coupled to and between the right wheel and the chassis;

a right hydraulic cylinder disposed between the chassis and the right control arm such that movement of the right control arm with respect to the chassis causes the right cylinder to extend and retract;

a hydraulic valve coupled to and between the right hydraulic cylinder and the third hydraulic pump to regulate the flow of fluid from the third hydraulic pump to the right hydraulic cylinder; and

a right suspension sensor that is responsive to changes in the position of the suspension to generate a signal indicative of the position of the right suspension with respect to the chassis;

each pair of left front/right front and left rear/right rear wheels having a generally common axis of rotation;

each pair of left front/right front and left rear/right rear control arm assemblies having a generally common pivot axis extending between the left and right sides of the chassis, both pivot axes located between and generally parallel to vertical planes through the axes of rotation of the front and rear wheel pairs and generally adjacent the fore-and-aft center of gravity line of the chassis; and

an electronic controller electrically coupled to the left front, left rear, right front and right rear suspension sensors to receive the signals indicative of the positions of those suspensions and coupled to the left front, left rear, right front and right rear suspension hydraulic valves to regulate hydraulic fluid flow from the third hydraulic fluid pump into the cylinders responsive to signals received from the suspension sensors.

2. The skid steer loader of claim 1, wherein the electronic controller is configured to determine the height of each suspension, to compare the determined height of each suspension with a predetermined height value, and to fill the the hydraulic cylinder associated with any suspension that is below a predetermined height.

3. The skid steer loader of claim 2, wherein the electronic controller fills the hydraulic cylinder by opening the hydraulic valve associated with that suspension.

4. The skid steer loader of claim 3, wherein the electronic controller is configured to receive a plurality of the signals indicative of suspension position from each of the suspension sensors and to derive for each suspension a single position value indicative of suspension height from said plurality of signals.

5. The skid steer loader of claim 4, wherein the electronic controller is configured to repeatedly and automatically poll the position signals provided by the left front, left rear, right front and right rear suspension sensors at predetermined polling rate of no less than 1 Hertz.

6. A method for controlling the height relative to the ground of a skid steer loader having an electronic suspension controller, a chassis with a left side and a right side and four independent sprung suspensions, two disposed on each side of the vehicle in a fore-and-aft relation, each of the four suspensions including a hydraulic cylinder operatively coupled between the suspension and the chassis to raise and lower said each suspension with respect to the chassis, each suspension also including a suspension sensor configured to generate a signal indicative of suspension height with respect to the chassis, wherein the wheels on the left side of the vehicle are configured to be driven by at least a first hydraulic motor and the wheels on the right side of the vehicle are configured to be driven by at least a second hydraulic motor, and further wherein the wheels on the left side and the wheels on the right side can be driven in opposing rotational directions, the method comprising the steps of:

receiving a first position signal indicative of a first position of a first of the four suspensions with respect to the chassis from the suspension sensor of the first suspension, receiving at least a second position signal indicative of a second position of the first suspension with respect to the chassis from the suspension sensor of the first suspension, and averaging the first and at least second position signals to generate a first position value;

comparing the a first position value with a predetermined value indicative of a desired suspension position;

raising the first suspension when the step of comparing indicates that the first suspension is below the desired first suspension position;

lowering the first suspension when the step of comparing indicates that the first suspension is above the desired first suspension; and

substantially simultaneously performing each of the above steps for each suspension of the loader.

7. A work vehicle comprising:

a chassis having a left side and a right side;

an engine coupled to the chassis;

four non-steerable and ground-engaging wheels coupled to the chassis to drive the vehicle over the ground, wherein the wheels are disposed two on each side of the chassis in a fore-and-aft relation;

at least two hydraulic motors for driving the wheels wherein at least one motor drives the wheels on one side of the chassis and at least another motor drives the wheels on the other side of the chassis;

four position sensors, one associated with each of the four wheels, wherein each sensor is disposed to sense the vertical position of its associated wheel with respect to the chassis;

four hydraulic cylinders, each cylinder coupled to an associated one of the four wheels to control the position of said one of the four wheels with respect to the chassis;

an electronic controller coupled to both the position sensors and the cylinders to monitor the position of each wheel with respect to the chassis and to raise and lower said each wheel at least in response to position signals received from the position; and

the electronic controller configured to sequentially poll signals of the four position sensors at a repeating and predetermined time interval, and is further configured to calculate an average position for each of the four wheels based at least upon a plurality of sequentially polled signals for the sensor associated with said each of the four wheels, the electronic controller further configured to independently drive each of the four hydraulic cylinders based upon the average position for the position sensor associated with the wheel such that any combination of the cylinders can be engaged to raise or lower their respective wheels.

8. The work vehicle of claim 7, wherein the chassis is supported on the ground by only the four wheels, and further wherein the four wheels have the same outside diameter.

9. The work vehicle of claim 8, wherein the wheels on the left side of the vehicle are constrained to rotate at a first speed and wherein the wheels on the right side of the vehicle are constrained to rotate at a second speed, and further wherein the first speed and the second speed are independently selectable by the vehicle operator.