Patent Application
20090112409
Industrial vehicles including construction and material handling trucks are typically required to transport and lift heavy loads. These loads may dramatically affect a balance or stability of the industrial vehicle during operation. To compensate for these effects on vehicle stability, various methods and systems may be employed to allow the vehicle to safely operate under these conditions. For example, dual drive tires may be mounted to the vehicle to improve side stability. Additional counterweight or a longer wheelbase may be provided to improve forward stability.
Some vehicles include stabilizers which can be provided at the front of the vehicle to improve vehicle stability. For example, some heavy duty construction vehicles include two hydraulic cylinders positioned on the frame in front of the drive axle, which extend when the stabilizer function is applied. The hydraulic cylinders are connected to the vehicle frame in order to exert a force on the ground, which lifts the front end of the vehicle, including the drive wheels, into the air.
By including the stabilizers in the front of the vehicle, a forward stability can be greatly improved. However, by removing the weight from the drive wheels, the side stability of the vehicle may be decreased. Reduced side stability combined with other factors such as windy weather conditions, an off-center load, or uneven terrain can present operational difficulties.
The present invention addresses these and other problems.
A stabilizer system for an industrial vehicle is disclosed as including one or more stabilizer cylinders mounted to the industrial vehicle, wherein the stabilizer cylinders are configured to contact the ground when deployed. The stabilizer system further includes a pressure sensor configured to determine a hydraulic system pressure, and a processor configured to calculate a stabilizing pressure to be applied to the one or more stabilizer cylinders. The stabilizing pressure is based on the hydraulic system pressure in order to improve a forward stability of the industrial vehicle when the one or more stabilizer cylinders are deployed.
An industrial vehicle is disclosed as comprising a drive wheel assembly located at a front end of the industrial vehicle, wherein the drive wheel assembly is in contact with the ground. The industrial vehicle further comprises one or more stabilizers mounted adjacent the drive wheel assembly, a lifting apparatus configured to lift a load, and one or more sensors configured to measure an operating condition of the lifting apparatus. A processor is configured to determine a stabilizing force of the one or more stabilizers based on the operating condition of the lifting apparatus, wherein the stabilizing force enables the one or more stabilizers to lift the front end of the vehicle while maintaining contact of the drive wheel assembly with the ground.
A method for stabilizing an industrial vehicle is disclosed. The method comprises determining a position of a load being transported by the industrial vehicle, measuring a weight of a load, and determining a load moment based on the position and the weight of the load. The method further comprises determining a stabilizing force to offset the load moment, and deploying one or more stabilizers to contact the ground with the stabilizing force.
A stabilizer system for an industrial vehicle is disclosed as including a stabilizer control assembly configured to control hydraulic operating pressure in the stabilizer system and one or more stabilizers mounted to the industrial vehicle. The one or more stabilizers are configured to contact ground when operating under a hydraulic stabilizer force. The stabilizer system further includes a hydraulic cylinder configured to lift a vehicle attachment when operating under a hydraulic lifting force, wherein the stabilizer control assembly is further configured to vary the hydraulic stabilizer force as a function of the hydraulic lifting force
The foregoing and other objects, features and advantages of the invention will become more readily apparent from the following detailed description of a preferred embodiment of the invention which proceeds with reference to the accompanying drawings.
The vehicle 10 is further illustrated as including a container handling attachment 12 mounted on an end of a boom 15. The attachment 12 may include a clamp, grapple, hook, scoop, shovel, fork, attachment pin or other types of apparatus capable of supporting a load or container. The boom 15 is able to extend and retract the position of the attachment 12 when handling a load. The boom angle 15A may be varied from an approximately horizontal position toward a vertical position by extending one or more derrick cylinders 5. In the manner, the attachment 12 may be raised and lowered, as well as extended and retracted. The derrick cylinders 5 may include one or more hydraulic actuated cylinders. Two derrick cylinders 5 are illustrated in
The stabilizers 20 may be deployed when a load is being lifted in an extended position. For example, the boom 15 and attachment 12 may be extended up and away from the vehicle 10 in order to handle a load which is stacked or located in an elevated position. The stabilizers 20 may be extended such that the stabilizer footing 22 is pressed against the ground with a stabilizing force. Where the stabilizers 20 include one or more hydraulic cylinders, a hydraulic circuit may be employed that provides a hydraulic force to extend the hydraulic cylinders or hold the stabilizers 20 in a rigid position. The stabilizers 20 and stabilizer footing 22 may be located in front of the drive wheels 2 for improved forward stability of the vehicle 10.
An increased loading condition (for example as the attachment 12 is extended or the load weight increases) typically causes the drive wheels 2 to deflect and the front end 4 to lower. This results in a loss of forward stability of the vehicle 10 of
The stability profile 31 may be evaluated in the context of a three dimensional model of the vehicle, taking into account the elevated position or height of the vehicle center of gravity, as well as the load if any. To ensure vehicle stability, a projection of the combined center of gravity of the vehicle and load must remain within the confines of the stability profile 31. If the center of gravity crosses the forward stability boundary line 32, the vehicle will tip over in the longitudinal or forward direction. If the center of gravity crosses the side stability boundary line 36, the vehicle will tip over in the lateral or sideways direction.
The side stability boundary line 37 of
The forward stability boundary line 34 of stability profile 35 lies along the stabilizer footing 22. By locating the stabilizer footing 22 in front of the drive axle of the drive wheels 2, the forward stability boundary line 34 provides for an increased forward stability as compared with the forward stability boundary line 32 of
Of the three stability profiles of
The following notation is used to describe the example forces and moments:
Fcog=Force center of gravity of the vehicle 10.
Fd=Drive axle reaction force acting on the drive wheels 2.
FL=Force center of gravity of the load 40.
FAC=Force center of gravity due to additional counterweight 6.
Arm A=Moment arm from the stabilizer footing 22 or stabilizers 20 to the drive axle 42. For illustrative purposes only, a dimension of 0.885 meters (m) is used for moment arm A.
Arm B=Moment arm from the stabilizer footing 22 or stabilizers 20 to the force center of gravity of the vehicle 10.
Arm C=Moment arm from the stabilizer footing 22 or stabilizers 20 to the steer axle 48. For illustrative purposes only, a dimension of 6.785 m is used for moment arm B.
Arm D=Moment arm from the stabilizer footing 22 or stabilizers 20 to the force center of gravity of the load 40. Moment arm D is understood as increasing in value when the boom 15 is extended in front of the vehicle 10.
MD=Drive axle moment, calculated as the product of the drive axle reaction force acting on the drive wheels 2 and moment arm A. The drive axle moment MD may be understood as reducing the forward tipping stability of the vehicle 10.
MV=Vehicle moment, calculated at the product of the force center of gravity of the vehicle 10 and the moment arm B.
MAC=Counterweight moment, calculated as the product of the reaction force due to the additional counterweight 6 acting on the steer wheels 8 and moment arm C. The counterweight moments MAC may be understood as counteracting the drive axle moment MD.
ML=Load moment, calculated at the product of the force center of gravity of the load 40 and the moment arm D.
ΣM=Sum of Moments. The sum of moments equates to zero for a static analysis.
For example, ΣM=MV+MD+ML=(Fcog×Arm B)+(Fd×Arm A)+(FL×Arm D)=0. The sum of moments may be calculated to provide a forward tipping point of the vehicle 10.
Through experience and industry safety standards, the minimum threshold drive axle force acting through the drive wheels 2 of the vehicle 10 may be determined that provides for sufficient force to enable the side stability boundary line 36 of
For illustrative purposes only, with reference again to
In one embodiment, the stabilizers 20 are deployed when the vehicle 10 is in the unloaded condition, or when the boom 15 is in a retracted position. A boom extension lockout switch may be provided which disallows an extension of the boom 15 unless the stabilizers 20 have been deployed. By deploying the stabilizers 20 before extending the boom 15, an amount of tire deflection that may occur to the drive wheels 2 is reduced when the boom 15 is extended. Reducing the amount of tire deflection of the drive wheels 2 improves forward stability, and maintains the force center of gravity Fcog of the vehicle 10 within the stability profile 35 of
Now assume that the drive axle reaction force Fd acting on the drive wheels 2 is 1,000,000 N when the vehicle 10 is operating in a loaded condition, for example when the boom 15 and load 40 is extended. Assume furthermore, that the stabilizers 20 were not deployed when the vehicle 10 was operating in an unloaded condition, but rather when the load 40 was already in an extended position. If the stabilizers 20 are set to provide the stabilizer force Fs of 173,913 N according to the unloaded condition requirements, then the drive axle reaction force Fd after the stabilizers 20 are applied may be calculated as ((1,000,000 N×(6.785 m−0.885 m))+(−173,913 N×6.785 m))/(6.785 m−0.885 m))=800,000 N. This 800,000 N of force may cause the drive wheels 2 to undergo significantly more tire deflection than if the stabilizers 20 had instead been deployed prior to handling the load 40 or extending the boom 15. The stabilizer force Fs of 173,913 N may be insufficient to fully alleviate the tire deflection. The increased tire deflection decreases the longitudinal stability of the vehicle 10, and may result in additional counter weight 6 being used. The additional counterweight 6 required may be calculated as follows:
MD=MAC
Fd×Arm A=FAC×Arm C
800,000 N×0.885 m=FAC×6.785 m
F
AC=800,000 N×0.885 m/6.785 m)=104,348 N, or 10,648 kg.
In order to provide the same longitudinal or forward stability provided by the stabilizers 30 of
The stabilizing pressure may be calculated to provide the one or more stabilizers 20 with sufficient force to lift the front end 4 of the vehicle 10 while maintaining contact of the two or more drive wheels 2 with the ground. The two or more drive wheels 2 may maintain at least a predetermined minimum threshold reaction force with the ground during deployment of the one or more stabilizers.
In one embodiment, the stabilizer system 50 includes a position sensor S2 configured to determine a distance that the boom 15 of
a illustrates an example hydraulic circuit of an embodiment of a novel stabilizer system 50. The stabilizer system 50 may include one or more stabilizer cylinders or stabilizers 20 mounted to the front end 4 of the vehicle 10. The stabilizers 20 may be configured to contact the ground when deployed. The stabilizer system 50 may include a stabilizer control valve assembly 56, which includes a stabilizer extend function 58, a stabilizer retract function 59, and a stabilizer pressure function 70. The stabilizer control valve assembly 56 may further include a high speed function 71. The stabilizer system 50 may include a pressure sensor S1 configured to determine a hydraulic system pressure. In one embodiment, the pressure sensor S1 measures a hydraulic pressure in the derrick cylinders 5. The stabilizer system 50 may further include an embedded controller or processor 55 configured to calculate a stabilizer pressure 60 to be applied to the stabilizers 20 based on the hydraulic system pressure in order to improve a forward stability of the vehicle 10 when the one or more stabilizers 20 are deployed.
The stabilizing pressure may be determined or calculated to provide the stabilizers 20 with sufficient force to lift the front end 4 of the vehicle 10 while maintaining contact of the two or more drive wheels 2 with the ground. The two or more drive wheels 2 may maintain at least a predetermined minimum threshold reaction force with the ground during deployment of the stabilizers 20. The stabilizer system may include an electro-proportional stabilizer pressure function 70 that limits the hydraulic system pressure to a calculated or determined stabilizer pressure 60. In one embodiment, the stabilizer pressure is stored in a look-up table or database, such as database 57, which may further be associated with or correspond to input values from the sensors S1, S2 and S3.
The stabilizer system 50 may include a position sensor S2 configured to determine a distance that the boom 15 of
Applying the Stabilizers
1. Operator presses stabilizer extend switch 63
2. Processor 55 checks the operating condition of the vehicle 10. For example, the processor 55 may check the vehicle travel speed, transmission and park brake status before activating the stabilizers 20. In one embodiment, the stabilizers 20 may only be applied when the vehicle travel speed is zero, the transmission is in neutral, and the park brake is activated.
3. Processor 55 determines a loading condition of the vehicle 10. For example, pressure sensor S1 may measure or transmit the hydraulic system pressure of the derrick cylinders 5. Position sensor S2 may measure or transmit the load position according to the extended distance of the boom 15. Angular sensor S3 may measure or transmit the load position according to the angular position of the boom 15.
4. Processor 55 calculates a minimum threshold stabilizing pressure corresponding to the loading condition of the vehicle 10. In one embodiment, the minimum threshold stabilizing pressure is a pressure that, when applied, will produce the minimum threshold drive axle force Fs (
5. Processor 55 applies a proportional control current to the electro-proportional stabilizer pressure function 70 corresponding to a target minimum threshold stabilizing pressure, or stabilizer pressure 60. Hydraulic pressure is applied to the stabilizers 20 until the stabilizer pressure 60 is achieved. The stabilizer pressure function 70 automatically limits the hydraulic pressure supplied to the stabilizers 20, for example according to feedback from the stabilizer pressure sensor S4.
6. When a stabilizer pressure 60 in the stabilizers 20 equals the calculated stabilizing pressure for a period of time, the processor 55 generates a signal that indicates that the stabilizers 20 are positioned correctly.
7. Operator releases the stabilizer extend switch 63.
8. Processor 55 turns off a proportional control current to the electro-proportional stabilizer pressure function 70 and turns off the stabilizer extend function 58 of the stabilizer control valve assembly 56. The connections to the stabilizers 20 may be blocked, preventing flow to and from the stabilizers 20.
9. The stabilizers 20 may remain extended at a fixed position or by applying the minimum threshold stabilizing force.
10. A Load Moment Indicator (LMI) system may be provided to determine a maximum allowable load based on sensor input and the operating condition of the vehicle 10 with the stabilizers 20 extended. In one embodiment, the LMI includes one or more charts, look-up tables or databases, such as database 57, which includes maximum allowable loads as a function of boom angle, position, or operating pressure. The LMI may interpolate data points provided in the database 57 to determine an interpolated maximum allowable load. The database 57 may include separate charts or look-up tables for the vehicle 10 both with and without the stabilizers 20 extended.
Retracting the Stabilizers
1. Operator presses a stabilizer retract switch 64.
2. Processor 55 identifies the loading condition and determines if the center of gravity of the vehicle 10 is within the stability profile, for example stability profile 31 of
3. The LMI system determines a maximum allowable load based on sensor input and the operating condition of the vehicle 10 with the stabilizers 20 retracted.
4. Processor 55 applies a control current to the stabilizer retract function 59 of the stabilizer control valve assembly 56 to open the necessary flow paths to retract the stabilizers 20 until a stabilizing retract pressure 61 is achieved or the stabilizers 20 are fully retracted. A position switch or sensor may be provided to determine the position of the stabilizers 20.
5. When the stabilizers 20 are fully retracted, the processor 55 may provide a signal to the operator to indicate the process has been completed.
6. Operator releases retract switch 64.
7. Processor 55 turns off the stabilizer retract function 59. The connections to stabilizers 20 may be blocked, preventing hydraulic flow to and from the stabilizers 20.
8. The stabilizers 20 may be fully retracted and locked in a retracted position.
A high speed function 71 may be used to increase the extension speed of the stabilizers 20. Oil pushed out of the rod side 81 of the stabilizers 20 when the stabilizers are being extended can be recycled to the base end 80 of the stabilizers 20. The base end 80 may include a piston. The high speed function 71 may be energized or activated during application of the stabilizers 20 by processor 55.
When the stabilizers 20 are operating in a high speed mode, the stabilizer pressure 60 may effectively act only on the rod end 81, instead of the base end 80. The processor 55 may calculate a higher stabilizer pressure to achieve the same down force on the stabilizers 20 as when the stabilizer system 50 is operating in a normal speed mode.
In one embodiment, the stabilizer system 50 is configured to vary the force of the stabilizers 20 such that, when applied, the drive axle reaction force Fd acting on the drive axle 42 of
The stabilizer force Fs to be applied to the stabilizers 20 may be calculated based on various vehicle operating conditions. In one embodiment, a hydraulically linked solution is provided, in which the pressure commanded in the stabilizers 20 is related to the pressure measured in the derrick cylinders 5. The hydraulic pressure in the derrick cylinders 5 may be used as a rough approximation of the stabilizer force Fs that is applied by the stabilizers 20 to compensate for the drive axle reaction force acting on the drive wheels 2. The stabilizer force Fs may be calculated as a predetermined percentage or ratio of the hydraulic pressure in the derrick cylinders 5. In one embodiment, the stabilizer force Fs is approximately 80% of the hydraulic pressure measured in the derrick cylinders 5.
In a further embodiment a load moment indicator system (LMI) is configured to control the stabilizer pressure 60. The LMI may include the processor 55, database 57 and any of the pressure sensor S1, the position sensor S2 and the angle sensor S3 of
Returning to the example force diagram of
MD=MAC
100,000 N×Arm A=FAC×Arm C
100,000 N×0,885 m=FAC×6.785 m
F
AC=100,000 N×0.885 m/6.785 m=13,043 N, or 1330 kg.
In order to provide the same longitudinal or forward stability provided by the stabilizers 30 of
While increasing the drive axle reaction force Fd on the drive axle 42 improves side stability, it reduces the forward stability of the vehicle 10. By calculating the stabilizer force Fs according to the vehicle operating conditions, a lower maximum drive axle reaction force Fd may be placed on the drive axle 42, thereby increasing a forward stability of the vehicle 10 and maintaining the improved side stability. The stabilizer force Fs may therefore be determined such that the drive axle reaction force Fd will be equal to the minimum threshold drive axle force when the load 40 is released and the vehicle 10 is operating in the unloaded condition. Regardless of when the stabilizer force Fs is applied, the drive axle reaction force Fd provides the minimum threshold drive axle reaction force. As a result, the boom 15 may be extended prior to deploying the stabilizers 20, and the desired forward and side stability may still be achieved.
The stabilizer system 50, 100 may provide an equivalent side and forward stability of the vehicle as compared to maximum stability values of vehicles employing stabilizers configured to exert a fixed stabilizer force that lifts the front end of a vehicle. Furthermore, the stabilizer system 50 accomplishes this using less counterweight 6. Less counterweight 6 decreases the cost of the vehicle 10, reduces tire wear on the steer wheels 8 due to reduced wheel loading, increases fuel efficiency, and improves vehicle handling.
At operation 610, a position of the load being transported by an industrial vehicle is determined. The position of the load may be determined according to one or both of an extended position of the load and an angle of a vehicle boom, for example.
At operation 620, a weight of a load is measured. In one embodiment, the weight of the load may be determined according to a hydraulic pressure, for example in one or more derrick cylinders.
At operation 630, a vehicle load moment is calculated based on the position and the weight of the load. In one embodiment, the load moment includes the weight of one or more of the boom 15, the attachment 12, and the load 40 (
At operation 640, a stabilizing force is calculated to offset the load moment. The stabilizing force may be calculated to maintain contact of a vehicle drive wheel assembly to the ground when the one or more stabilizers are deployed. In one embodiment, the stabilizing force is calculated to maintain a minimum threshold axle reaction of the vehicle drive wheel assembly when the load is released.
At operation 650, the one or more stabilizers are deployed to contact ground using the stabilizing force. In one embodiment, the stabilizers are deployed near a front end of the industrial vehicle. If no load is detected prior to deploying the stabilizers, a lower stabilizing force may be applied as compared to if a load is first detected.
In one embodiment, the stabilizing force is continuously varied according to the calculated load moment. The stabilizing force may be provided for or augmented by an accumulator which provides a hydraulic spring function. The stabilizing force may be varied in real-time by a processor or the accumulator, so that the stabilizing force automatically compensates for any change in load weight or position as it occurs.
The system and apparatus described above can use dedicated processor systems, micro-controllers, programmable logic devices, or microprocessors that perform some or all of the operations. Some of the operations described above may be implemented in software and other operations may be implemented in hardware.
For the sake of convenience, the operations are described as various interconnected functional blocks or diagrams. This is not necessary, however, and there may be cases where these functional blocks or diagrams are equivalently aggregated into a single logic device, program or operation with unclear boundaries.
Having described and illustrated the principles of the invention in a preferred embodiment thereof, it should be apparent that the invention may be modified in arrangement and detail without departing from such principles. We claim all modifications and variation coming within the spirit and scope of the following claims.
