US20150063968A1

US20150063968A1 - Flywheel excavator

Info

Publication number: US20150063968A1
Application number: US14/019,005
Authority: US
Inventors: Evan Earl Jacobson
Original assignee: Caterpillar Inc
Current assignee: Caterpillar Inc
Priority date: 2013-09-05
Filing date: 2013-09-05
Publication date: 2015-03-05

Abstract

A hybrid construction machine is provided. The machine includes a prime mover, at least one fluid pump, at least one fluid actuator, a swing motor, a first flywheel, and a second flywheel. The prime mover drives the at least one fluid pump. The fluid pump provides pressurized fluid to drive the at least one fluid actuator. The returning fluid from the at least one fluid actuator can be used to drive a swing motor, which in turn drives a swing structure. Further, the second flywheel is also coupled with the prime mover. The second flywheel can be configured to store the energy when the prime mover is driven by the at least one fluid pump. The at least one fluid pump is driven by the return fluid from the at least one fluid actuator.

Description

TECHNICAL FIELD

The present disclosure relates generally to a hybrid construction machine and in particular to a hybrid excavator having a swing structure operated by a flywheel.

BACKGROUND

A construction machine such as a hydraulic excavator uses engine as a prime mover to drive hydraulic actuators. Typically, the engine drives a hydraulic pump that in turn drives the hydraulic actuators such as hydraulic motors, hydraulic cylinders, steering motor, and wheel motors. The term “hydraulic actuator”, as used herein, generically refers to any device, such as a cylinder-piston arrangement or a rotational motor for example, that converts hydraulic fluid flow into mechanical motion.
During extension and retraction of a hydraulic cylinder assembly, pressurized fluid from the pump is usually applied by a valve assembly to one cylinder chamber and the fluid exhausting from the other cylinder chamber flows through the valve assembly into a return conduit that leads to the system tank. For example, high pressure fluid from the pump can be applied at a bottom chamber (cap end) of a hydraulic cylinder. Hence, the fluid from the upper chamber (rod end) can simultaneously exit to the tank. Under certain conditions, an external load or force acting on the machine enables extension or retraction of the cylinder assembly without significant fluid pressure from the pump. This is often referred to as an overrunning load. In an excavator for example, when the bucket is filled with heavy material, the boom can be lowered by the force of gravity alone. This external load drives fluid out of one chamber, say bottom chamber, of the boom's hydraulic cylinder, through the valve assembly, and into the tank. At the same time, an amount of fluid is also drawn from the pump through the valve assembly into the upper chamber which is expanding simultaneously. However because the incoming fluid is not driving the piston, it does not have to be maintained at a significant pressure for the boom motion to occur. In this. situation, the fluid is exhausted from the bottom chamber under relatively high pressure, thereby containing energy that normally is lost when the pressure is metered through the valve assembly.
To optimize efficiency and economical operation of the machine, it is desirable to recover the energy of the exhausting fluid. Some existing hydraulic systems store exhausting fluid in an accumulator, where it can be stored under pressure for later use in powering the machine. Other methods of recovering the energy are to drive a hydraulic motor via return fluid which will in turn drive an electric motor/generator. The electric energy thus generated can be stored in a battery for use in electrical system or driving an electric swing motor of an electric hybrid excavator. However, the electric and hydraulic storage and reuse systems are costly and are generally less efficient.
The present disclosure presents a solution to one or more of the problems set forth above.

SUMMARY

In one aspect, a hybrid construction machine is provided. The hybrid construction machine includes a prime mover. Further, the hybrid construction machine includes at least one fluid pump configured to be driven by the prime mover. The hybrid construction machine also includes at least one fluid actuator driven by the at least one fluid pump. Furthermore, the hybrid construction machine includes a swing motor driven by a return fluid from the at least one fluid actuator. Moreover, a first flywheel is included in the hybrid construction machine. The first flywheel can be configured for driving a swing structure. The first flywheel is driven by the swing motor. Additional, the hybrid construction machine includes a second flywheel. The second flywheel is coupled with the prime mover. The second flywheel is configured to store the energy when the prime mover is driven by the at least one fluid pump via the return fluid from the at least one fluid actuator.
In another embodiment, a hybrid construction machine having a swing structure, a lower travel structure, and an implement system having at least one work tool is provided. The swing structure can rotate with respect to the lower travel structure to rotate the work tool from a first position to a second position. The hybrid construction machine includes a prime mover. Further, the hybrid construction machine includes at least one fluid pump. The fluid pump is driven by the prime mover. Furthermore, the hybrid construction machine includes at least one fluid actuator. The fluid actuator is driven by the fluid pump. Moreover, the hybrid construction machine includes a swing motor. The swing motor is driven by a return fluid from the at least one fluid actuator. Further, the hybrid construction machine includes a first flywheel for driving a swing structure. The first flywheel is driven by the swing motor. Further, the first flywheel is coupled with the swing motor via a clutch. Additionally, the hybrid construction machine includes, a second flywheel coupled with the prime mover. The second flywheel is configured to store the energy when the prime mover is driven by the fluid pump via the return fluid from the at least one fluid actuator. Also, the second flywheel is configured to assist the prime mover during cold start and/or anti-idle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary hybrid construction machine; and

FIG. 2 illustrates is a schematic block diagram of an exemplary powertrain that may be used in conjunction with the hybrid construction machine of FIG. 1

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary hybrid construction machine 100 having multiple systems and components that cooperate to accomplish a task. The hybrid construction machine 100 may embody a fixed or mobile machine that performs various operations associated with an industry such as mining, construction, farming, transportation, or another industry known in the art. For example, the hybrid construction machine 100 may be an earth moving machine such as an excavator (shown in FIG. 1), a shovel, a backhoe, or another earth moving or construction machine.
The hybrid construction machine 100 may include a swing structure 102, a lower travel structure 104, and an implement system 106. The swing structure 102 may include a swing frame 108, a prime mover 110 mounted on the swing frame 108, and an operator station 112. The operator station 112 is configured for control of the implement system 106, the prime mover 110, the swing structure 102, and the lower travel structure 104. The swing structure 102 can be configured to rotate about a vertical axis X-X with respect to the lower travel structure 104.
The lower travel structure 104 includes a pair of tracks 114L and 114R. The track 114L may be driven by a travel motor 116L and the track 114R may be driven by a travel motor 116R. In an alternative embodiment, the lower travel structure 104 may include wheels, belts etc.
The implement system 106 may include a linkage structure acted upon by a plurality of fluid actuators 122, 126, 128 to operate a work tool 118. The implement system 106 includes a boom 120 configured to be pivoted about an axis by a boom cylinder 122. Further, the implement system includes a stick 124 configured to be pivoted about an axis by a stick cylinder 126. Further, the implement system includes a work tool cylinder 128 configured to pivot the work tool 118.
Numerous different work tools 118 may be attached to a single hybrid construction machine 100 and can be operator controllable. Work tool 118 may include any device used to perform a particular task such as, for example, a bucket (shown in FIG. 1), a fork arrangement, a blade, a shovel, a ripper, a broom, a propelling device, a cutting device, a grasping device, or any other task-performing device known in the art.
The prime mover 110 may include an engine such as, for example, a diesel engine, a gasoline engine, a gaseous fuel-powered engine, a dual fuel engine, or another type of combustion engine known in the art. The prime mover 110 can produce mechanical output that may then be converted to fluid power for fluid actuators (such as the aforementioned the travel fluid motors 116L and 116R, the boom cylinder 122, the stick cylinder 126 and the work tool cylinder 128) of the implement system 106.
The operator station 112 may include devices that receive input from a machine operator indicative of desired maneuvering of the hybrid construction machine 100. Specifically, the operator station 112 may include one or more operator interface devices for example a joystick, a steering wheel, or a pedal etc (none of which are shown but are well known in the industry). Operator interface devices may initiate movement of hybrid construction machine 100, for example travel and/or tool movement, swing structure movement by producing displacement signals that are indicative of desired maneuvering.
FIG. 2 illustrates a schematic block diagram of an exemplary powertrain 200 that may be used in conjunction with the hybrid construction machine 100. As shown in FIG. 2, the powertrain 200 includes the prime mover 110, at least one fluid pump 204, a set of control valves 206, the boom cylinder 122, the stick cylinder 126, and the work tool cylinder 128. The prime mover 110 can serve as a driving unit for the at least one fluid pump 204. It can be contemplated that one or more fluid pumps can be driven by the prime mover 110. It should be understood that the fluid pump 204 can operate as both a pump and a motor as will be further described. In one mode of operation, the at least one fluid pump 204 is powered by the prime mover 110 for pressurizing fluid to be supplied to one or more of the plurality of fluid actuators 122, 126, 128. In another mode of operation, the at least one fluid pump 204 can be driven by pressurized fluid returning from one or more of the plurality of fluid actuators 122, 126, 128 to generate mechanical motion. Thus, herein after, the at least one fluid pump 204 can simply be referred to as the pump motor 204. The at least one fluid pump 204 can be a variable displacement pump motor or a fixed displacement pump motor. The pressurized fluid, from the at least one fluid pump 204 is directed to the at least one fluid actuator through the control valves 206. The control valves 206 can be configured to control the quantity and the direction of fluid to the one or more actuators, such as the boom cylinder 122, the stick cylinder 126, and the work tool cylinder 128. For example, the operator may command to lower or raise the boom 120 of the hybrid construction machine 100. The control valves 206, accordingly, control the flow of pressurized fluid to the boom cylinder 122. The control valves 206 may also control the quantity and direction of the fluid to the travel motors 116L and 116R. Thus the control valves 206 can also be used for controlling the at least one fluid actuators (such as the aforementioned the travel motors 116L and 116R, the boom cylinder 122, the stick cylinder 126 and the work tool cylinder 128). It may be appreciated that there may be one control valve corresponding to each fluid actuator for controlling the quantity and direction of flow of fluid.
Each of the boom cylinder 122, the stick cylinder 126, and the work tool cylinder 128 includes a rod end chamber and a head end chamber. Consider the boom cylinder 122, for example, having a cap end chamber 122 a and a rod end chamber 122 b. Pressurized fluid can be supplied from the at least one fluid pump 204, through a fluid path 208 to the cap end chamber 122 a to extend the boom cylinder 122. The pressurized fluid causes a piston ‘P’ of the boom cylinder 122 to move towards the rod end chamber 122 b of the boom cylinder 122, hence exhausting the fluid from the rod end chamber 122 b through the fluid path 210. Similarly, while retracting the boom cylinder 122, the fluid can be exhausted from the head end chamber 122 a through the path 208. This exhausted fluid from the rod end chamber 122 b or the cap end chamber 122 a can be referred to as returning fluid or drained fluid, or discharge fluid.
In one embodiment, an external force may cause the exhausting fluid to exit at a pressure. In this embodiment, the boom cylinder 122 can be considered to be in an extended state and the work tool 118 of the machine 100 can be assumed be filled with heavy material. Hence, while lowering the boom 120, the load in the work tool 118 can cause the exhausting of the fluid from the cap end chamber 122 a through the fluid path 208. In such a scenario, the returning fluid from the cap end chamber 122 a can be exhausted in a pressurized state because of effect of gravity due to the load in the work tool 118.
In an embodiment the returning fluid or the drained fluid can be directed towards the at least one fluid pump 204 though fluid path 210 or fluid path 208. In this embodiment, the at least one fluid pump 204 can act as a motor and the returning fluid can be used to drive the pump motor.
It can be contemplated that stick cylinder 126 and the work tool cylinder 128, or any other fluid actuator, can also function in a similar manner and the returning fluid from the fluid actuator can be directed to drive the fluid pump 204.
The powertrain 200 further includes a swing motor 212. The swing motor 212 can be a fluid motor which can be driven by pressurized fluid supplied through the fluid path 214. In one embodiment, the swing motor 212 can be a hydraulic motor configured to be driven by high pressure hydraulic fluid similar to pump motor. In other words, the exhausting fluid or returning fluid can be directed towards the swing motor 212, through the fluid path 214. In one embodiment, the swing motor 212 can also be configured to be driven by drained or returned fluid from at least one fluid actuator such as the boom cylinder 122, the stick cylinder 126, and the work tool cylinder 128.
Further, the swing motor 212 can be coupled to a first flywheel 218 via a clutch 220. The clutch 220 can be configured to selectively engage or disengage the first flywheel 218 with the swing motor 212. Further, the first flywheel 218 can be configured to drive the swing structure 102. In other words, the swing motor 212 can be driven by the returning fluid from the one or more fluid actuators, such as the boom cylinder 122. The swing motor 212 in turn rotates the first flywheel 218. The first flywheel 218 can further rotate the swing structure 102, when engaged through clutch 220. Thus, the energy from the returning fluid can be conserved in the first flywheel 218 to drive the swing structure 102. In an embodiment, a clutch-able flywheel transmission 222 can also be disposed between the swing structure 102 and the first flywheel 218. The clutch-able flywheel transmission (CFT) 222 can be configured to vary the speed of the swing structure 102. Also, the swing structure 102 can be rotated in clockwise and anticlockwise direction during operation. The direction of rotation of the swing structure 102 is changed by controlling the CFT 222. In an embodiment, a reverser 224 can also be positioned between the CFT 222 and the swing structure 102. The reverser 224 can be configured to change the direction of rotation of the swing structure 102. In an exemplary embodiment, the reverser 224 can be a gearbox.
The powertrain 200 is also shown to include a second flywheel 226. The second flywheel 226 can be coupled with the prime mover 110. The second flywheel 226 can be coupled with the prime mover 110 via a gearing 228 for example a gearbox, a clutch, a mechanical coupling, a fluid coupling etc. The second flywheel 226 stores energy as kinetic energy when the prime mover 110 is driven by the at least one fluid pump 204 via the returning fluid from the at least one fluid actuator, such as the boom cylinder 122, the stick cylinder 126, and the work tool cylinder 128. In other words, the returning fluid from the fluid actuators (the boom cylinder 122, the stick cylinder 126, and the work tool cylinder 128) can drive the fluid pump 204. The fluid pump 204 acts as a motor thereby driving the prime mover 110. In an embodiment, when the boom cylinder 122 is operating in an overrunning load condition, the fluid discharged from the boom cylinder 122 may have a pressure elevated above an output pressure of the at least one fluid pump 204. In this situation, the elevated pressure of the return fluid can be directed through the at least one fluid pump 204 and may be used to drive the fluid pump 204. In this scenario, the fluid pump 204 drives the prime mover 110 which in turn may drive the second flywheel 226 through the gearing 228. Thereby, the second flywheel 226 stores the pressure energy of the return fluid of the boom cylinder 122 as kinetic energy. In addition, a speed up or reduction gear box 230 may be connected to the second flywheel 226. The gear box 230 may also be connected to a motor generator 232. When the second flywheel 226 is either driven by the prime mover 110 or by the overrunning load condition, the gear box 230 may rotate the motor generator 232 producing electrical energy that can be stored in a battery (not shown) or used to power electrical components of the hybrid construction machine 100. Alternatively, the motor generator 232 can be used to start the prime mover 110, to reducing idling of the prime mover 110 after low use time periods, or for cold starting.
Further, in an embodiment, the at least one fluid pump 204 can be connected to the swing motor 212 through a fluid path 216. In this embodiment, the at least one fluid pump 204 can be used to drive the swing motor 212 for the first swing. For example, the swing motor 212 can be driven by the at least one fluid pump 204 to start the rotation of the first flywheel 218.
Hence, the return fluid from the at least one fluid actuator, such as the boom cylinder 122, the work tool cylinder 128, and the stick cylinder 126, can be conserved as kinetic energy in the first flywheel 218 and/or the second flywheel 226. The energy stored in the first flywheel 218 can be used to drive the swing structure 102. On the other hand, the energy from the returning fluid can be stored in the second flywheel 226 via the at least one fluid pump 204, and further used to drive the prime mover 110 during cold start or managing excessive load. Also the at least one fluid pump 204 can be directly connected to the swing motor 212 to drive the first flywheel 218.
Further, the first flywheel 218 can also be configured to store energy as the swing structure 102 slows down during each working cycle. In an embodiment, the working cycle may be referred as a load dump cycle. For example, the hybrid construction machine 100 lifts earth in the work tool 118 and the swing structure 102 is rotated to dump the material in a dump truck. Now as the swing structure 102 is rotated, the brakes need to be applied to slow and eventually stop the swing structure 102 at a position over the dump truck. This braking energy may be stored in the first flywheel 218 as kinetic energy. Hence by operating the clutch 220 (de-clutching) the first flywheel 218 from the swing motor 212 the braking energy can be stored in the first flywheel 218. The energy stored in the first flywheel 218 can be used to accelerate the swing structure 102 in the next working cycle. Further, the swing motor 212 can be coupled with the first flywheel 218 to provide extra energy to the first flywheel 218 due to losses occurring in the working cycle. This may help in reducing the size of the swing motor 212.

INDUSTRIAL APPLICABILITY

The present disclosure applies generally to hybrid construction machine 100. The hybrid construction machine 100 is configured to perform a digging, loading and unloading during a typical work cycle. The hybrid construction machine 100 includes various actuators to execute their work. For example, the hybrid construction machine 100 can be excavator lifting earth in the bucket. The operator of the hybrid construction machine 100 can actuate a boom to lift the bucket. The boom can be actuated by a boom cylinder such as boom cylinder 122. The prime mover 110 of the hybrid construction machine 100 provides power to a fluid pump such as the at least one fluid pump 204. The pressurized fluid from the fluid pump 204 can be direct to the boom cylinder 122 to lift the work tool 118. While lowering the work tool 118, the pressurized fluid from the boom cylinder 122 can be direct to a swing motor 212. Hence, the returning fluid from the boom cylinder 122 can drive the swing motor 212 to rotate the swing structure 102 through the first flywheel 218. Also the returning fluid from the boom cylinder 122 can be directed to the fluid pump 204. The fluid pump 204 can act as motor and convert the energy from the returning fluid to rotate the prime mover 110. The prime mover 110 in turn can rotate the second flywheel 226. Thus the energy from the returning fluid can be also conserved in the second flywheel 226.
Thus the conserved energy can be used at a later stage to cold start the prime mover 110 or anti idle situation. Also the conserved energy help drive the swing structure 102 thus requiring less energy from the prime mover 110. Thus the flywheel 226 is configured to primarily support the functions of prime mover 110 hence a smaller prime mover 110 can be utilized. Since energy flow paths exist between all system components, the first flywheel 218 and the second flywheel 226 can be used in concert in a variety of ways.
It should be understood that the above description is intended for illustrative purposes only, and is not intended to limit the scope of the present disclosure in any way.

Claims

What is claimed is:

1. A hybrid construction machine having a swing structure, a lower travel structure, and an implement system having at least one work tool wherein the swing structure can rotate with respect to a the lower travel structure to rotate the work tool from a first position to a second position, the hybrid construction machine comprising:

a prime mover;

at least one fluid pump wherein the fluid pump is driven by the prime mover;

at least one fluid actuator wherein the fluid actuator is driven by the fluid pump;

a swing motor, the swing motor driven by a return fluid from the at least one fluid actuator;

a first flywheel for driving a swing structure, wherein the first flywheel is driven by the swing motor and wherein the first flywheel is coupled with the swing motor via a clutch; and

a second flywheel coupled with the prime mover, the second flywheel configured to store the energy when the prime mover is driven by the fluid pump via the return fluid from the at least one fluid actuator wherein the second flywheel is configured to assist the prime mover during cold start and/or anti-idle.