Patent Grant
9297148
The present invention generally relates to the field of motorized machinery, and more specifically to a hydraulic circuit for a machine with a knuckle boom powered by hydraulic cylinders.
When operating conventional knuckle boom systems today, there are inefficiencies in the system whenever the boom and any lifted load is lowered, i.e. a reduction in their potential energy is dissipated by metering hydraulic oil through an orifice and converting the energy into heat which goes into the machine's hydraulic oil. Cooling systems need to be added to the machine to expel this heat to ambient air so the hydraulic oil does not overheat.
Mechanical-hydraulic systems have inherent kinematic limitations when operated by controlling cylinder speeds. The knuckle boom is a non-linear kinematic system where approximating constant boom system endpoint trajectories and velocities can be challenging. To raise a boom and load, typically diesel fuel or electricity is used as an energy source and converted to hydraulic power through diesel engines, electric motors and/or hydraulic pumps. This energy, in the form of hydraulic oil pressure and flow, is directed to the hydraulic cylinders by control valves which may be commanded by a human operator and/or an automated routine. There can be instances in a boom system where one or more booms are being raised and lowered simultaneously. It would be desirable to transfer energy from the lowering boom(s) and load(s) to the boom(s) and load(s) being raised in all operating modes.
A system is disclosed for improving the hydraulic operating efficiency of knuckle boom systems in all operating modes and/or simplifying the boom control inputs such that less skilled operators will be more productive and all operators will experience reduced fatigue from extended periods of operation, again resulting in productivity improvements.
An intelligent boom control hydraulic system is disclosed for a knuckle boom system including a main boom and a stick boom coupled at a knuckle. The intelligent boom control hydraulic system includes hoist and stick hydraulic cylinders, hoist and stick boom position sensors, a hydraulic fluid pump, a hydraulic reservoir with hydraulic fluid, a base end control valve, a hoist rod control valve, a stick rod control valve, an operator input device for input of operator commands, and a microprocessor. The hoist hydraulic cylinder raises and lowers the main boom, and the stick hydraulic cylinder raises and lowers the stick boom. Each of the hoist and stick hydraulic cylinders has a rod end and a base end. The hoist boom position sensor provides hoist boom position readings, and the stick boom position sensor provides stick boom position readings. The base end control valve controls flow from the hydraulic fluid pump to the base ends of the hoist and stick hydraulic cylinders, and controls flow from the base ends of the hoist and stick hydraulic cylinders to the hydraulic reservoir. The hoist rod control valve controls flow from the hydraulic fluid pump to the rod end of the hoist hydraulic cylinder, and controls flow from the rod end of the hoist hydraulic cylinder to the hydraulic reservoir. The stick rod control valve controls flow from the hydraulic fluid pump to the rod end of the stick hydraulic cylinder, and controls flow from the rod end of the stick hydraulic cylinder to the hydraulic reservoir. The microprocessor computes control signals to direct flow through the base end control valve, the hoist rod control valve and the stick rod control valve based on the operator commands and the hoist and stick boom position readings. During operation at least two of the base end control valve, the hoist rod control valve and the stick rod control valve can be activated, one of the activated valves coupling the stick or hoist hydraulic cylinder to the hydraulic fluid pump and the other of the activated valves coupling the stick or hoist hydraulic cylinder to the hydraulic reservoir.
The hoist boom position sensor can be a hoist cylinder position sensor that determines the length of the hoist hydraulic cylinder. The stick boom position sensor can be a stick cylinder position sensor that determines the length of the stick hydraulic cylinder.
The intelligent boom control hydraulic system can also include a hoist counter-balance valve that controls flow between the base end control valve and the base end of the hoist hydraulic cylinder. The intelligent boom control hydraulic system can also include a stick counter-balance valve that controls flow between the base end control valve and the base end of the stick hydraulic cylinder.
The intelligent boom control hydraulic system can also include an energy storage system that stores excess energy and releases the stored energy to the intelligent boom control hydraulic system when needed. The microprocessor can compute control signals to direct storage of excess energy to and release of stored energy from the energy storage system. The energy storage system can include a hydraulic accumulator, an accumulator control valve and a plurality of hydraulic pressure sensors. The microprocessor can receive readings from the plurality of hydraulic pressure sensors, and compute control signals for the accumulator control valve. When operation of the intelligent boom control hydraulic system results in excess energy, the excess energy can be routed through the accumulator control valve and stored in the hydraulic accumulator. When the hydraulic accumulator has stored energy and operation of the intelligent boom control hydraulic system needs additional energy, the stored energy from the hydraulic accumulator can be routed through the accumulator control valve to the hoist and stick cylinders. When the hydraulic accumulator has stored energy and operation of the intelligent boom control hydraulic system needs additional energy, the stored energy from the hydraulic accumulator can be routed through the accumulator control valve to the base end of the hoist cylinder and the base end of the stick cylinder. The accumulator control valve can be coupled between the base end control valve and the hoist and stick counter-balance valves. The intelligent boom control hydraulic system can also include a one-way valve that couples the hydraulic fluid pump to the hydraulic accumulator through the hydraulic control valve, where the one-way control valve allows fluid to flow from the hydraulic fluid pump to the hydraulic control valve for energy storage in the hydraulic accumulator. The plurality of hydraulic pressure sensors can include a pump line pressure sensor, a reservoir line pressure sensor, a work line pressure sensor and an accumulator pressure sensor.
When retracting the hoist cylinder and extending the stick cylinder simultaneously, the hoist rod control valve can couple the hydraulic fluid pump to the rod end of the hoist cylinder activating the hoist counter balance valve and allowing hydraulic fluid to flow from the base end of the hoist cylinder to the base end of the stick cylinder extending the stick cylinder and pushing hydraulic fluid from the rod end of the stick cylinder through the stick rod control valve to the hydraulic reservoir. Any difference in oil volume needed at the stick cylinder versus what is available from the hoist cylinder to achieve a commanded boom tip motion can be either: a) added by connecting the hydraulic fluid pump to the base end of the stick cylinder through the base end control valve, or conversely b) removed by directing excess to the hydraulic reservoir or an energy storage device. The actuation of the appropriate valves can be controlled by algorithms running on the microprocessor, based on the operator commands, boom position readings and hydraulic circuit pressure readings.
When retracting the stick cylinder and simultaneously extending the hoist cylinder, the stick rod control valve can couple the hydraulic fluid pump to the rod end of the stick cylinder activating the stick counterbalance valve and allowing hydraulic fluid to flow from the base end of the stick cylinder to the base end of the hoist cylinder extending the hoist cylinder and pushing hydraulic fluid from the rod end of the hoist cylinder through the hoist rod control valve to the hydraulic reservoir. Any difference in oil volume needed at the hoist cylinder versus what is available from the stick cylinder to achieve the commanded boom tip motion can be either: a) added by connecting the hydraulic fluid pump to the base end of the hoist cylinder through the base end control valve, or conversely b) removed by directing excess to the hydraulic reservoir or energy storage device. The actuation of the appropriate valves can be controlled by algorithms running on the microprocessor, based on the operator commands, boom position readings and hydraulic circuit pressure readings.
Energy can be transferred between the base end of the hoist hydraulic cylinder and the base end of the stick hydraulic cylinder through the hoist counter-balance valve and the stick counter-balance valve. Energy can be transferred between the hoist and stick hydraulic cylinders and the hydraulic accumulator through the accumulator control valve.
For the purposes of promoting an understanding of the principles of the novel invention, reference will now be made to the embodiments described herein and illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the novel invention is thereby intended, such alterations and further modifications in the illustrated devices and methods, and such further applications of the principles of the novel invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the novel invention relates.
A boom system can be operated in several different modes. The following table summarizes operational modes enabled by the exemplary knuckle boom hydraulic systems illustrated in
The operational mode of the boom system is typically selected by the operator. In some current machines, operation in RC mode (sometimes referred to as “energy recovery” (ER) mode) allows some energy transfer between the booms, but operation in joint mode does not allow energy transfer between the booms. It would be desirable to have energy transfer between booms in any operational mode and/or to have microprocessor assistance to simplify control of boom system endpoint trajectories and velocities for machine operators.
The knuckle boom system 100 can only be operated in “joint mode” (JM) with oil flow separately controlled to the main cylinder 122 and the stick cylinder 142. A proximal end of the main boom 120 is attached to the machine 102, and a distal end of the main boom 120 is attached to a proximal end of the stick boom 140 at the knuckle 130. The proximal end of the stick boom 140 is attached to the main boom 120 at the knuckle 130, and a distal end of the stick boom 140 includes a boom tip 150 which can include a stick pin where an attachment can be attached to the knuckle boom system 100. An operator of the machine 102 can direct hydraulic oil flow from an oil reservoir 112, through a pump 110 to a hoist control valve 124 to extend and retract the main boom cylinder 122 causing the main boom 120 to raise and lower. The operator of the machine 102 can direct hydraulic oil flow from the oil reservoir 112, through the pump 110 to a stick control valve 144 to extend and retract the stick boom cylinder 142 causing the stick boom 140 to raise and lower.
For the conventional boom hydraulic circuit 100 when operated in JM, the operator inputs that control raising and lowering of the booms are taken as hydraulic flow signals directed to two actuators with minimal manipulation (i.e. minimal ramping, curve shaping, etc). This arrangement results in inefficiency due to energy losses.
This arrangement also requires a significant level of operator skill to achieve linear constant velocity of the boom tip 150 since the tip velocity is constantly changing as a function of the cylinder speeds, as the tip moves through the boom operating envelope. In many applications, for example a feller buncher or an excavator, the operator wants to move the boom tip 150, and the attachment attached to the stick boom 140 at the stick pin, in a generally horizontal path. In these applications, it is desirable to make it easier for the operator to move the boom tip 150 in a generally horizontal path, and it would also be desirable to save energy while moving the boom tip 150 in the generally horizontal path. Moving the boom tip 150 in a generally horizontal path away from the machine 102 requires lowering the main boom 120 while simultaneously raising the stick boom 140. Thus, the operator would have to simultaneously coordinate movement of one joystick, or similar control mechanism, to control the main boom cylinder 122 through the hoist valve 124 and movement of another joystick, or similar control mechanism, to control the stick boom cylinder 142 through the stick control valve 144. The main boom 120 can be lowered by metering hydraulic fluid from the main boom cylinder 122 through an orifice in the hoist control valve 124 back into the oil reservoir 112. The energy released in lowering the main boom 120 is dissipated as heat into the hydraulic fluid. This then requires additional energy to be used for fans or other heat transfer apparatus to cool the hydraulic fluid as it passes through an oil cooling device. The stick boom 140 can be raised by pumping hydraulic fluid from the oil reservoir 112 through the pump 110 and the stick control valve 144 into the stick boom cylinder 142. This of course requires additional energy since the system 100 does not capture any of the energy from lowering the main boom 120 to raise the stick boom 140.
A proximal end of the main boom 220 is attached to the machine 202, and a distal end of the main boom 220 is attached to a proximal end of the stick boom 240 at the knuckle 230. The proximal end of the stick boom 240 is attached to the main boom 220 at the knuckle 230, and a distal end of the stick boom 240 includes a boom tip 250 that can include a stick pin where an attachment can be attached to the knuckle boom system 200. Hydraulic fluid is pressurized by a pump 210 which pulls the fluid from a reservoir 212. An operator of the machine 202 can direct hydraulic oil flow from the oil reservoir 212, through the pump 210 to a hoist control valve 224 to extend and retract the main boom cylinder 222 causing the main boom 220 to raise and lower. The operator of the machine 202 can also direct hydraulic oil flow from the oil reservoir 212, through the pump 210 to a stick control valve 244 to extend and retract the stick boom cylinder 242 causing the stick boom 240 to raise and lower.
The knuckle boom system 200 also includes a straight-line activation valve 262, a straight-line control valve 264 and a counter balance valve 266; the straight-line activation valve 262 and the counterbalance valve 266 directly coupling the hydraulic lines between the base end of the main boom cylinder 222 and the base end of the stick boom cylinder 242. With the straight line activation valve 262 activated, the operator can use the straight-line control valve 264 and counterbalance valve 266 to move the boom tip 250, and an attachment attached to the stick boom 240 at the boom tip 250, in a generally horizontal path while conserving energy.
Moving the boom tip 250 in a horizontal path away from the machine 202 requires lowering the main boom 220 while simultaneously raising the stick boom 240. This can be performed using one joystick mechanism controlling the straight line control valve 264. When the straight line activation valve 262 and control valve 264 are activated, pressurized hydraulic fluid from the pump 210 passes through the straight line control valve 264 into the rod end of the main boom cylinder 222, causing-the-main boom cylinder 222 to retract, pushing hydraulic fluid out of the base end of the main boom cylinder 222. When the straight-line activation valve 262 is activated and the hoist and stick control valves 224, 244 are in neutral position, the only available path for the hydraulic fluid exiting the base end of the main boom cylinder 222 is around the counterbalance valve 266 and straight-line activation valve 262 into the base end of the stick boom cylinder 242 which extends the stick boom cylinder 242 and raises the stick boom 240. Through kinematic design and optimization of cylinder sizes, the path of an attachment at the boom tip 250 can be configured to move in a near horizontal path parallel to the base of the machine 202. The velocity of the movement is determined by the hydraulic flow commanded through the straight line control valve 264 which is defined by the operator input.
Moving the boom tip 250 in a horizontal path towards the machine 202 requires raising the main boom 220 while simultaneously lowering the stick boom 240 which also can be performed using the joystick mechanism controlling the straight line control valve 264 along with the straight line activation valve 262 and the counterbalance valve 266.
In the knuckle boom system 200, functioning in RC mode, the operator controls the velocity of the boom tip with hydraulic fluid flow directed predominantly through one actuator which is hydraulically connected to a second actuator. The knuckle boom system 200 only provides straight-line operation in a narrow elevation range. When the straight-line activation valve 262 is not activated, the knuckle boom system 200 functions using the hoist and stick control valves 224, 244 as described with regard to
The knuckle boom system 300 also includes a hoist and stick base end control valve 324, a hoist rod control valve 344, a stick rod control valve 364, a hoist counter balance valve 366 and a stick counter balance valve 368. When operating the knuckle boom system 300, two of the control valves (base end control valve 324, hoist rod control valve 344, and stick rod control valve 364) are activated; one to let hydraulic fluid in and another to let hydraulic fluid out. Hydraulic fluid can be provided using a hydraulic pump 310 and released to a hydraulic reservoir 312 as needed.
The knuckle boom system 300 also includes operator input controls 372 coupled to a microprocessor 374. The microprocessor 374 can also receive inputs from sensors in the electro-hydraulic system including the hoist and stick cylinder position sensors 328, 348 and/or the main boom and stick boom angle sensors. For clarity, the connections between the microprocessor 374 and the individual sensors of the electro-hydraulic system are not shown. When operating the IBC system 300 in the kinematic control mode, the operator can input commands to define boom tip velocity using the operator input controls 372. To achieve smooth and constant velocities in this non-linear kinematic system, an algorithm running on the microprocessor 374 can receive the operator input commands from the operator input controls 372 and combine them with readings from the hoist and stick cylinder position sensors 328, 348, to compute input values for the control valves which direct hydraulic oil flow to achieve the commanded motion. The IBC system 300 can also be operated in joint mode (JM) with the efficiency advantages of the straight line hydraulic circuit (see
For example, to extend the hoist cylinder 322 (raising the main boom) alone, hydraulic fluid is pumped from the pump 310 through the base end control valve 324 (left position) around the hoist counter balance valve 366 and into the base end of the hoist cylinder 322 which pushes hydraulic fluid out of the rod end of hoist cylinder 322 through the hoist rod control valve 344 (right position) into the hydraulic reservoir 312. For example, to extend the stick cylinder 342 (raising the stick boom) alone, hydraulic fluid is pumped from the pump 310 through the base end control valve 324 (left position) around the stick counter balance valve 368 and into the base end of the stick cylinder 342 which pushes hydraulic fluid out of the rod end of the stick cylinder 342 through the stick rod control valve 364 (right position) into the hydraulic reservoir 312.
The knuckle boom system 300 enables the transfer of energy between the main boom system and the stick boom system in either joint mode or kinematic mode of operation. For example, to retract the hoist cylinder 322 (lowering the main boom) and extend the stick cylinder 342 (raising the stick boom) simultaneously, hydraulic fluid is pumped from the pump 310 through the hoist rod control valve 344 (left position) into the rod end of the hoist cylinder 322 which activates the hoist counter balance valve 366 and allows hydraulic fluid out of the base end of the hoist cylinder 322 through the hoist counter balance valve 366 around the stick counter balance valve 368 and into the base end of the stick cylinder 342 which extends the stick boom and pushes hydraulic fluid out of the rod end of the stick cylinder 342 through the stick rod control valve 364 (right position) and back to the hydraulic reservoir 312. The potential energy released by the lowering of the main boom is transferred through the hydraulic fluid to increase the potential energy of the stick boom.
For example, to retract the stick cylinder (lowering the stick boom) and simultaneously extend the hoist cylinder 322 (raising the main boom), hydraulic fluid is pumped from the pump 310 through the stick rod control valve 364 (left position) into the rod end of the stick cylinder 342 which opens the stick counterbalance valve 368 and pushes hydraulic fluid out of the base end of the stick cylinder 342 through the stick counterbalance valve 368 around the hoist counterbalance valve 366 and into the base end of the hoist cylinder 322 which extends the main boom and pushes hydraulic fluid out of the rod end of the hoist cylinder 322 through the hoist rod control valve 344 (right position) and back to the hydraulic reservoir 312. In this case the potential energy released by the stick boom is transferred to the main boom.
When operation of the knuckle boom system 400 results in excess energy, instead of releasing the energy as heat into the hydraulic oil returned to the reservoir 312, the system 400 can pass the energy through the accumulator control valve 484 to be stored in the hydraulic accumulator 482. In instances where the hydraulic accumulator 482 has stored energy, the IBC system 400 can use this energy instead of, or in addition to, energy from the pump 310. When the boom system is not in full use, the accumulator can be “charged” with energy through the one way valve 486 and the accumulator control valve 484 from the pump 310. The sequences for when to store and/or release energy can be controlled by the microprocessor 374 based on sensor inputs and programmed logic.
The exemplary IBC hydraulic knuckle boom systems illustrated in
While exemplary embodiments incorporating the principles of the present invention have been disclosed hereinabove, the present invention is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains.
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| Number | Date | Country | |
|---|---|---|---|
| 20150030424 A1 | Jan 2015 | US |
