WO2010138029A1 - A hydraulic system and a working machine comprising such a hydraulic system - Google Patents
A hydraulic system and a working machine comprising such a hydraulic system Download PDFInfo
- Publication number
- WO2010138029A1 WO2010138029A1 PCT/SE2009/000282 SE2009000282W WO2010138029A1 WO 2010138029 A1 WO2010138029 A1 WO 2010138029A1 SE 2009000282 W SE2009000282 W SE 2009000282W WO 2010138029 A1 WO2010138029 A1 WO 2010138029A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- hydraulic
- pressure
- pump
- unit
- hydraulic system
- Prior art date
Links
Classifications
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02F—DREDGING; SOIL-SHIFTING
- E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
- E02F9/20—Drives; Control devices
- E02F9/22—Hydraulic or pneumatic drives
- E02F9/2217—Hydraulic or pneumatic drives with energy recovery arrangements, e.g. using accumulators, flywheels
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02F—DREDGING; SOIL-SHIFTING
- E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
- E02F9/20—Drives; Control devices
- E02F9/22—Hydraulic or pneumatic drives
- E02F9/2278—Hydraulic circuits
- E02F9/2292—Systems with two or more pumps
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02F—DREDGING; SOIL-SHIFTING
- E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
- E02F9/20—Drives; Control devices
- E02F9/22—Hydraulic or pneumatic drives
- E02F9/2278—Hydraulic circuits
- E02F9/2296—Systems with a variable displacement pump
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B13/00—Details of servomotor systems ; Valves for servomotor systems
- F15B13/02—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors
- F15B13/04—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor
- F15B13/042—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor operated by fluid pressure
- F15B13/043—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor operated by fluid pressure with electrically-controlled pilot valves
- F15B13/0433—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor operated by fluid pressure with electrically-controlled pilot valves the pilot valves being pressure control valves
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B21/00—Common features of fluid actuator systems; Fluid-pressure actuator systems or details thereof, not covered by any other group of this subclass
- F15B21/14—Energy-recuperation means
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
- F15B2211/205—Systems with pumps
- F15B2211/2053—Type of pump
- F15B2211/20546—Type of pump variable capacity
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/30—Directional control
- F15B2211/305—Directional control characterised by the type of valves
- F15B2211/3056—Assemblies of multiple valves
- F15B2211/30565—Assemblies of multiple valves having multiple valves for a single output member, e.g. for creating higher valve function by use of multiple valves like two 2/2-valves replacing a 5/3-valve
- F15B2211/3057—Assemblies of multiple valves having multiple valves for a single output member, e.g. for creating higher valve function by use of multiple valves like two 2/2-valves replacing a 5/3-valve having two valves, one for each port of a double-acting output member
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/30—Directional control
- F15B2211/31—Directional control characterised by the positions of the valve element
- F15B2211/3105—Neutral or centre positions
- F15B2211/3111—Neutral or centre positions the pump port being closed in the centre position, e.g. so-called closed centre
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/60—Circuit components or control therefor
- F15B2211/63—Electronic controllers
- F15B2211/6303—Electronic controllers using input signals
- F15B2211/6306—Electronic controllers using input signals representing a pressure
- F15B2211/6309—Electronic controllers using input signals representing a pressure the pressure being a pressure source supply pressure
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/60—Circuit components or control therefor
- F15B2211/63—Electronic controllers
- F15B2211/6303—Electronic controllers using input signals
- F15B2211/6306—Electronic controllers using input signals representing a pressure
- F15B2211/6313—Electronic controllers using input signals representing a pressure the pressure being a load pressure
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/60—Circuit components or control therefor
- F15B2211/63—Electronic controllers
- F15B2211/6303—Electronic controllers using input signals
- F15B2211/6336—Electronic controllers using input signals representing a state of the output member, e.g. position, speed or acceleration
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/60—Circuit components or control therefor
- F15B2211/63—Electronic controllers
- F15B2211/6303—Electronic controllers using input signals
- F15B2211/634—Electronic controllers using input signals representing a state of a valve
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/60—Circuit components or control therefor
- F15B2211/63—Electronic controllers
- F15B2211/6303—Electronic controllers using input signals
- F15B2211/6346—Electronic controllers using input signals representing a state of input means, e.g. joystick position
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
- F15B2211/71—Multiple output members, e.g. multiple hydraulic motors or cylinders
- F15B2211/7114—Multiple output members, e.g. multiple hydraulic motors or cylinders with direct connection between the chambers of different actuators
- F15B2211/7121—Multiple output members, e.g. multiple hydraulic motors or cylinders with direct connection between the chambers of different actuators the chambers being connected in series
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
- F15B2211/71—Multiple output members, e.g. multiple hydraulic motors or cylinders
- F15B2211/7114—Multiple output members, e.g. multiple hydraulic motors or cylinders with direct connection between the chambers of different actuators
- F15B2211/7128—Multiple output members, e.g. multiple hydraulic motors or cylinders with direct connection between the chambers of different actuators the chambers being connected in parallel
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/80—Other types of control related to particular problems or conditions
- F15B2211/88—Control measures for saving energy
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T137/00—Fluid handling
- Y10T137/0318—Processes
- Y10T137/0396—Involving pressure control
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T137/00—Fluid handling
- Y10T137/7722—Line condition change responsive valves
- Y10T137/7758—Pilot or servo controlled
- Y10T137/7762—Fluid pressure type
Definitions
- a hydraulic system and a working machine comprising such a hydraulic system
- the present invention relates to a hydraulic system in accordance with the preamble of the following claim 1.
- the invention also relates to a working machine comprising the hydraulic system.
- a working machine in the form of a wheel loader has a plurality of different work functions which are controlled hydraulically, such as lifting and tilting of an implement and steering (frame steering) of the working machine.
- the control of the respective work function is performed via hydraulic actuators, such as linear motors in the form of hydraulic cylinders.
- the invention will be described in connection with the operation of a wheel loader. This is a preferred, but by no means limiting application of the invention.
- the invention can also be utilized for other types of working machines or working vehicles having hydraulic work functions. It could for example also be an articulated hauler, a backhoe loader, an excavator, or an agricultural machine such as a tractor.
- the present hydraulic systems are preferably of a load sensing type (L S systems). This means that the pump supplying the system with hydraulic oil senses the pressure (via a L S signal) from the actuated hydraulic cylinder
- hydraulic cylinders (hydraulic cylinders).
- the pump then sets a pressure which is slightly higher than the pressure in the hydraulic cylinder. Thereby, a flow of hydraulic oil out to the hydraulic cylinder is obtained.
- a control valve also called a manoeuvre valve
- the magnitude of the flow to the hydraulic cylinder depends on how much the actuated control valve is modulated open. In the present hydraulic systems of load sensing type, energy which could be recovered is lost. Some examples of energy losses which may arise will be described below.
- An operation mode where an energy loss may arise is when lowering a work implement, such as a bucket or a container, wherein the intrinsic weight (and in some cases load) of the work implement drives the piston in the hydraulic cylinder.
- a pressure drop usually occurs across the control valve, since the returned hydraulic oil is drained to tank, which in its turn results in an energy loss (heat).
- Another operation mode where an energy loss may arise is with so-called back up pressure.
- the returned hydraulic oil is pressurized with a back pressure of the magnitude of approx. 10-40 bar with the purpose of obtaining a stable steering without jerks. This back up pressure, in its turn, leads to energy losses.
- Another operation mode where energy loss may arise is during so called parallel operation of different work functions.
- a single common pump is used for a plurality of work functions. These work functions may, however, require different pressures, meaning that the pump has to be adjusted according to the highest required pressure. This means that, during parallel operation of two work functions having different pressure requirements, the pressure has to be reduced for the work function requiring the lowest pressure. The pressure drop which arises across the control valve for the work function requiring the lowest pressure results in an energy loss,
- the pressure limiting means comprises a pilot-operated valve adapted to set a maximum allowable pressure at the return port of the control valve unit, which pressure is variable by controlling the pilot-operated valve by means of a control unit, an upper limit for the amount of energy desired to be recovered from the work function can be selected.
- the set maximum pressure also determines the smallest possible pressure drop across the control valve unit.
- a return flow of hydraulic oil from the work function will flow through the recovery unit and energy will be recovered as long as the recovery unit does not produce a higher back pressure than the set maximum allowable pressure.
- the invention creates conditions for controlling the energy recovery in a variable way depending on the actual operating mode. Within the range of the maximum allowable pressure, the pressure drop across the control valve unit will be determined by the resistance from the recovery unit. In many cases, the pressure drop across the control valve unit is preferably as small as possible in order to maximize the energy recovery, but sufficiently large to achieve the modulation of the requested return flow of hydraulic fluid.
- the recovery unit can, for example, be a hydraulic machine functioning as a hydraulic motor when recovering energy. The recovered energy can go directly to a consumer or be stored in a suitable manner.
- the recovery unit is adapted to the actual hydraulic system, in some cases it could happen that all energy which potentially can be recovered at a certain point in time cannot be stored or consumed instantaneously. In such a case, a certain amount of energy can still be emitted in a conventional manner in the form of heat resulting from a pressure drop across the control valve unit and/or the pilot-operated valve.
- the pilot-operated valve can be controlled so that the maximum allowable pressure at the return port is low (relative to the pressure of the work function in question) or, in the latter case, so that the maximum allowable pressure at the return port is essentially negligible.
- the pilot-operated valve can be controlled so that the maximum allowable pressure is high (of the same magnitude as, or higher than the pressure of the work function in question).
- the recovery unit is controlled so that the desired recovery is obtained, at the same time as it is ensured that the pressure drop across the control valve unit is sufficiently large to achieve the modulation of the requested return flow of hydraulic fluid.
- control valve unit can include a separate outlet from a valve (if the control valve unit comprises a valve with an outlet or a return port), as well as a common connection point for two or more outlets of one or several valves (if the control valve unit, for example, comprises two control valves).
- the expression "return port of the control valve unit” can include a separate outlet from a valve (if the control valve unit comprises a valve with an outlet or a return port), as well as a common connection point for two or more outlets of one or several valves (if the control valve unit, for example, comprises two control valves).
- the pilot-operated valve is preferably connected to the return port and connected in parallel with the recovery unit, which means that hydraulic fluid can be directed to the recovery unit and/or via the pilot-operated valve past the recovery unit and further for example to tank.
- the pilot-operated valve is preferably electrically controllable and, furthermore, the maximum allowable pressure at the return port of the control valve unit is preferably continuously variable by means of the pilot- operated valve.
- the pressure at the return port of the control valve unit can be adjusted and adapted to the actual operating situation in order to optimize the energy recovery.
- An electrically controllable valve creates conditions for controlling the energy recovery in an accurate manner.
- the pressure limiting means comprises a pilot-operated valve.
- This valve can, for example, be a pressure limiting valve or a proportional directional valve which, by means of a control unit and pressure sensors, functions as a pressure limiting valve.
- pilot-operated valve refers to a valve, the reference value of which (pressure or flow) is determined by an external signal (electric or hydraulic), preferably from a control unit. This in contrast to a valve which is direct acting, i.e. a valve which is adapted to respond to a specific condition
- such a direct acting valve can have a given pressure level which is determined by a preloaded spring.
- the invention has particular advantages in case the hydraulic fluid delivered by the main pump has a pressure which exceeds the pressure required for a certain work function in a given operating situation. Such an excessive pressure could be the result of the system having a pump operating at a constant pressure level, but it is more common when using one and the same pump for two or more work functions that different pressures are required for the work functions and the pump pressure then has to be adapted to the work function requiring the highest pressure. If, for example, hydraulic cylinders for lifting and steering are used simultaneously, the lift function may require a pressure of 200 bar and the steering may require 50 bar. With the system according to the invention, the control valve unit will not have to be used to reduce. the pressure to the steering to approx. 50 bar with associated energy losses.
- the pump pressure of 200 bar can be used both for the lift function and for the steering. Since the pressure drop instead occurs across the recovery unit, energy from the steering will be recovered and the recovered energy (with the exception of component-related losses) will be proportional to the product of the volume of hydraulic fluid passing the recovery unit multiplied by the pressure drop across the recovery unit.
- the invention can advantageously be applied to a hydraulic system comprising a plurality of work functions and, according to one embodiment of the invention, the hydraulic system comprises a plurality of work functions with associated respective control valve unit (which control valve units, however, in their turn can be integrated into a common overall fluid control means for two or more work functions), and one said pilot- operated valve is provided for the respective work function.
- control valve units which control valve units, however, in their turn can be integrated into a common overall fluid control means for two or more work functions
- one said pilot- operated valve is provided for the respective work function.
- the recovery unit is preferably arranged in parallel with all said pilot-operated valves, although it would also be possible to use a plurality of recovery units provided for different work functions. It shall be pointed out that the different variants of the hydraulic system described in connection with a work function of course also can be applied to two or more work functions.
- hydraulic fluid from the first work function will be directed to the hydraulic machine, while hydraulic fluid from other work functions instead will be directed to tank via the respective pilot-operated valve.
- an energy recovery system can be built as a separate unit and be ' offered as an option to a standard system.
- the expression "energy recovery system” will be used for the part of the hydraulic system capable of constituting such a separate unit which can be connected to a base system in a simple manner.
- the hydraulic system preferably comprises a pump, hereinafter also called a main pump or supply pump, for providing hydraulic fluid to said at least one work function.
- a pump can be adapted to supply one or several work functions with hydraulic fluid.
- the hydraulic system comprises a means for returning energy, recovered from a return flow from the work function, to the pressure side of the pump. This offers a possibility to recover energy which is then used to assist the main pump in supplying one or several work functions. This in its turn creates conditions for solving, or at least reducing, the problem of providing enough energy to drive the hydraulic system and the driveline at low engine speeds in a working machine.
- the main pump in a hydraulic system of the kind in question is namely usually mechanically connected to the engine of the working machine, such as a diesel motor, which is used to drive both the hydraulic system and the driveline for propelling the working machine.
- the speed of the main pump will thus become dependent on the speed of the diesel engine.
- the speed of the diesel engine in its turn, depends on the desired propulsion speed of the working machine and the torque determined by the actual operation mode.
- the recovery unit comprises a first hydraulic machine and a second hydraulic machine, and the first and second hydraulic machine are mechanically interconnected, and the first hydraulic machine is adapted to be driven by a flow of hydraulic fluid and the second hydraulic machine is adapted to pump hydraulic fluid by being driven by the first hydraulic machine.
- the first hydraulic machine is preferably connected to the return port to be driven by a return flow from the work function and the second hydraulic machine is adapted to pump hydraulic fluid from, for example, a tank to the pressure side of the main pump and/or to an accumulator and from the accumulator further to the pressure side (or suction side) of the pump.
- hydraulic fluid can be provided directly from the accumulator to the main g
- the accumulator supplies the first hydraulic machine and the second hydraulic machine pumps hydraulic fluid to the pressure side (or suction side) of the main pump.
- hydraulic fluid can be provided for supplying a work function in a way which is independent of the engine speed of the working machine.
- this flow together with the flow generated independently by the main pump, provides a sufficient flow to the work functions, also if the diesel engine is operating at a low speed causing the capacity of the main pump to be reduced.
- the recovered energy stored or used instantaneously can be used for supporting the diesel engine.
- a more simple recovery unit for example in the form of a simple hydraulic machine, energy can also be recovered and returned to the pressure side of the main pump. If there is a sufficiently high pressure on the return flow, at least part of the flow could be returned directly to the pressure side of the main pump. Should the pressure be too low, the hydraulic machine could be used as a pump to increase the pressure so that the return flow can be returned and, in some cases, if the pressure of the return flow exceeds the pressure on the pressure side of the main pump by some margin, part of the energy could first be recovered in the hydraulic machine, and thereafter the return flow could be returned to the pressure side of the main pump.
- the hydraulic system comprises a means for returning energy recovered from the work function to the suction side of the pump.
- a means for returning energy recovered from the work function to the suction side of the pump.
- the variants described above with respect to return of energy (or in other words hydraulic fluid) to the pressure side of the main pump can also be applied with respect to return to the suction side of the main pump.
- a certain amount can be directed to tank and/or be intermediately stored in an accumulator for successive return to the main pump.
- a pump preferably the main pump for supplying the work functions, is drivable by a driveline of a working machine and adapted to brake the driveline during deceleration of the working machine, and the system further comprises a hydraulic control means for controlling a flow of hydraulic fluid, from the pressure side of the pump to the recovery unit, for recovering energy during deceleration of the working machine.
- the recovery unit can also be used to decelerate the working machine, at the same time as deceleration energy is recovered during deceleration of the working machine.
- the recovery unit is adapted to dampen a relative movement caused by an external disturbance, at least in one direction, between a work implement and a machine body of the working machine, which work implement is moveable relative to the machine body by means of said work function.
- the hydraulic system comprises a sensor for determining a reference position for the work implement relative to the machine body.
- the recovery unit can recover energy at the same time as it is part of a suspension system for, for example, the lift arm of a wheel loader.
- a damped suspension system for a work implement can be achieved, at the same time as energy can be recovered with the recovery unit.
- the invention also relates to a method according to claim 31.
- energy can recovered with the recovery unit in a corresponding way as has been described above with respect to the hydraulic system. Since the maximum allowable pressure at the return port is controlled with a pressure limiting means through receiving signals, which preferably are electric, from a control unit, an upper limit for the amount of energy that is desired to be recovered from the work function can be selected.
- the set maximum pressure also determines the smallest possible pressure drop across the control valve unit.
- a return flow of hydraulic oil from the work function will flow through the recovery unit and energy will be recovered as long as the recovery unit does not generate a higher back pressure than the set maximum allowable pressure.
- the invention creates conditions for controlling the energy recovery in a variable way depending on the actual operating mode. Within the range of the maximum allowable pressure, the pressure drop across the control valve unit will be determined by the resistance from the recovery unit. In many cases, the pressure drop across the control valve unit is preferably as small as possible in order to maximize the energy recovery, but sufficiently large to achieve the modulation of the requested return flow of hydraulic fluid.
- the recovery unit can, for example, be a hydraulic machine functioning as a hydraulic motor when recovering energy. The recovered energy can go directly to a consumer or be stored in a suitable manner.
- the invention furthermore relates to a working machine provided with the hydraulic system according to the invention.
- Fig. 1 is a side view of a wheel loader
- Fig. 2 is a hydraulic system according to the invention
- Fig. 3 is a hydraulic system according to the invention comprising a plurality of work functions for a wheel loader
- Fig. 4 shows the hydraulic system of Figure 3 comprising a first example of an energy recovery system
- Figs. 5-9 show different variants of the first example of the energy recovery system
- Fig. 10 shows a second example of an energy recovery system
- Figs.ll-13 show different variants of the second example of the energy recovery system
- FIG. 1 shows a working machine in the form of a wheel loader 101.
- the wheel loader 101 should be seen as an example of a working machine to which the hydraulic system according to the invention can be applied.
- the wheel loader 101 comprises a front vehicle section 102 and a rear vehicle section 103.
- Each of these vehicle sections 102, 103 comprise a frame and wheels arranged on a drive axle 112, 113.
- the rear vehicle section 103 comprises an operator's cab 114.
- the vehicle sections 102, 103 are connected to each other in such a way that they can be pivoted relative to each other about a vertical axis by means of two hydraulic cylinders 104, 105, called steering cylinders, which are connected to the two vehicle sections 102, 103. Accordingly, the hydraulic cylinders 104, 105 are disposed on different sides of a centre line, extending in the longitudinal direction of the vehicle, for steering or turning the wheel loader 101 by means of the hydraulic cylinders. In other words, the wheel loader 101 is frame-steered.
- the wheel loader 101 comprises a lift arm assembly 111 for handling objects or (loose) material.
- the lift arm assembly 111 comprises a lift-arm unit 106 and an implement 107 in the form of a bucket, which is mounted on the lift arm unit 106.
- the bucket 107 is filled with material 116.
- a first end of the lift arm unit 106 is pivotally connected to the front vehicle section 102 in order to achieve a lifting movement of the bucket.
- the bucket 107 is pivotally connected to a second end of the lift arm unit 106 in order to achieve a tilting movement of the bucket.
- the lift arm unit 106 can be raised and lowered relative to the front section 102 of the vehicle by means of two hydraulic cylinders 108, 109.
- Each hydraulic cylinder 108, 109 is connected at a first end to the front vehicle section 102 and at the second end to the lift arm unit 106.
- the bucket 107 can be tilted relative to the lift arm unit 106 by means of an additional hydraulic cylinder 110, called a tilting cylinder, which is connected at a first end to the front vehicle section 102 and connected at the second end to the bucket 107 via a link arm system 115.
- FIG. 2 is a schematic illustration of one embodiment of the invention.
- the hydraulic system comprises at least one work function 1 and a control valve unit 2 for controlling hydraulic fluid to and from the work function.
- a supply unit such as a pump 3, is adapted to provide hydraulic fluid to the work function 1 via the control valve unit 2.
- the term hydraulic fluid used in the text is intended to include hydraulic oil as well as any other fluids which possibly may occur in a hydraulic system.
- the pump 3 can draw oil from a tank 4. (Although for reasons of simplicity different tank positions have been drawn in Figure 2, suitably, in practice it is a matter of one and the same tank.)
- the work function has a hydraulic cylinder 5 arranged on a working machine (not shown in Figure 2) for moving a work implement.
- the hydraulic cylinder 5 is preferably provided with a double- acting piston 6, which can be pressurized on both sides 7, 8.
- the schematically illustrated control valve unit 2 can contain one or several valves of different types. It can preferably comprise two control valves adapted to control the work function. A first one of these control valves can be adapted to connect the pump 3 to the piston side 7 of the hydraulic cylinder, and a second one of these control valves can be adapted to connect the piston rod side 8 of the hydraulic cylinder to tank 4, for piston displacement in a first direction.
- the first control valve can further be adapted to connect the piston side 7 of the hydraulic cylinder to tank and the second control valve can then be adapted to connect the pump 3 to the piston rod side 8 of the hydraulic cylinder, for piston displacement in a second direction opposite to the first direction.
- a recovery unit 9 is connected to a return port 10 of the control valve unit 2 for recovering energy from the work function 1.
- the recovery unit 9 is connected between the return port 10 and the tank 4.
- the hydraulic system also comprises a means 11 for limiting the pressure of the hydraulic fluid at the return port 10.
- the pressure limiting means 11 includes a pilot-operated valve 12 adapted to set a maximum allowable pressure at the return port 10 of the control valve unit 2, which pressure is variable by controlling the pilot- operated valve 12 by means of a control unit 13.
- the control unit 13 is further connected to the control valve unit 2 in order to control the magnitude of the flow of hydraulic fluid to and from the work function 1 by means of the control valve unit. This control, in its turn, is depending on the speed desired for the piston 6.
- An actuator 14 can be adapted to actuate the work function 1 and to request the desired speed of the work function 1.
- the recovery unit 9 is a hydraulic motor or a hydraulic machine, which can function both as a hydraulic motor and a pump.
- a return flow from the work function 1 drives the hydraulic machine 9, which results in a work W done on a shaft 15 of the hydraulic machine 9.
- This energy can then be used or stored.
- a generator can be connected to the hydraulic machine for converting the mechanical work into electrical energy.
- the work function 1 is connected in such a way that a return flow from either the piston side or piston rod side of the hydraulic cylinder can be used for energy recovery.
- the pilot-operated valve 12 is connected to the return port 10 of the control valve unit 2 and connected in parallel with the recovery unit 9. Furthermore, the pilot-operated valve 12 is suitably electrically controllable by means of the control unit 13 and so designed that the maximum allowable pressure at the return port 10 of the control valve unit 2 is continuously variable. Accordingly, a desired maximum pressure can be set at the return port 10 of the control valve unit 2 during energy recovery. At a pressure which exceeds the maximum allowable pressure, the pilot-operated valve 12 will open for a flow through the valve, which flow can be directed to tank 4. At a lower pressure of the return flow, the pilot-operated valve 12 will be closed, and the return flow will drive the hydraulic machine 9 as long as the resistance from the hydraulic machine 9 does not create a pressure which exceeds the maximum allowable pressure.
- the pressure drop across the control valve unit 2 can be adjusted in a flexible manner, which is adapted to the actual operating situation, in that the pressure limiting means 11 comprises the pilot-operated valve 12. Thereby, the energy recovery thus can be adapted to the actual operating situation.
- a pressure level which is also adapted to the pressure prevailing in the hydraulic fluid upstream of the control valve unit 2, is obtained at the return port 10 of the control valve unit.
- the recovery unit is preferably connected to the control unit 13 to enable control of the recovery unit 9. For instance, the displacement of the hydraulic machine can be varied by means of the control unit 13.
- the pressure drop across the control valve unit 2 can be reduced for recovering energy via the recovery unit 9, at the same time as the required modulation of requested flow (and the desired speed of the piston 6) can be achieved. Assuming that all recovered energy can be used or stored, the pressure drop across the control valve unit 2 is suitably kept as small as possible in order to maximize the energy recovery, but sufficiently large to achieve the modulation of the requested return flow of hydraulic fluid.
- the hydraulic system can further comprise a check valve 16, which is connected in series with the recovery unit 9 in a position between the return port 10 of the control valve unit and the recovery unit 9.
- the check valve 16 is connected in series with the recovery unit 9 and connected in parallel with the pilot-operated valve 12 in order to block flow in a direction from the recovery unit 9 toward the work function 1 and to allow flow in a direction from the control valve unit 2 toward the recovery unit 9.
- a check valve is used for the respective pilot-operated valve, so that it is ensured that hydraulic fluid from the work function from which energy is to be recovered is not drained to tank via the pilot-operated valve of another work function.
- the hydraulic system can preferably comprise one or several pressure sensors 17, 19, 20, 22 for measuring the pressure of the hydraulic fluid upstream and downstream of the control valve unit on the supply and/or return side.
- These pressure sensors can also be integrated into the control valve unit.
- a pressure sensor 20 can be used for measuring the pressure on the piston rod side of the hydraulic cylinder wherein the recovery unit is used to boost the pressure in order to ensure that the biasing pressure is the desired one.
- a position sensor 21 can be used for indicating the position of a work implement. This will be described in greater detail below in an example where the recovery unit is used for obtaining a damped suspension of a work implement with the purpose of controlling the position of the work implement relative to the machine body of the working machine.
- Figure 3 shows a hydraulic system 201. The hydraulic system is designed to perform the hydraulic work functions of the wheel loader 101 (see also Figure 1).
- Figure 4 shows the hydraulic system of Figure 3 comprising a first example of an energy recovery system 301 shown in detail.
- the hydraulic system 201 is provided with a first work function 203 for lifting and lowering the lift arm unit of the wheel loader.
- the work function comprises said two hydraulic cylinders 108, 109 for operating the lift arm unit 106.
- the system 201 further comprises a pump 205 adapted to supply said work function 203 with pressurized hydraulic fluid via a hydraulic circuit.
- the pump 205 is driven by the propulsion engine 206 of the vehicle, which can be e.g. a diesel engine.
- the pump 205 has a variable, preferably infinitely variable, displacement to provide the flow required for the work functions.
- the system 201 comprises a fluid control means 208 having a control valve unit for the respective work function.
- the respective control valve unit in its turn, can comprise a hydraulic circuit having one or several control valves adapted to control the delivery of pressurized hydraulic fluid from the pump 205 to the respective work function and from the respective work function to a tank 243.
- control valve unit 200b comprises two control valves 207, 209, in the form of flow valves, for the lifting and lowering movement. These control valves are arranged between the pump 205 and the lifting cylinders 108, 109 in the circuit, for controlling the lifting and lowering movement.
- the first 207 of these valves is adapted to connect the pump 205 to the piston side of the hydraulic cylinders 108, 109, and a second 209 one of these valves is adapted to connect the tank 243 to the piston rod side of the hydraulic cylinders.
- the first valve 207 When displacing the pistons in a second, opposite direction, the first valve 207 is adapted to connect the tank 243 to the piston side, and the second valve 209 is then adapted to connect the pump 205 to the piston rod side.
- the hydraulic system further comprises a control unit 213 which contains software for controlling the work functions.
- the control unit is also called a CPU (Central Processing Unit) or ECM (Electronic Control Module).
- the control unit 213 comprises a microprocessor.
- An operator-controlled element 211 in the form of a lift lever, is operatively connected to the control unit 213.
- the control unit 213 is adapted to receive controls signals from the lift lever and to control the control valves 207, 209 of the control valve unit 200b according to the lever position. This can occur directly from the control unit 213 or, as illustrated in Figure 3, via a valve control unit 215.
- the control unit 213 preferably controls more general control strategies for the working machine and the control unit 215 controls basic functions of the control valve units 200a, 200b 200c of the fluid control means 208.
- the control units 213, 215 can of course also be integrated into a single unit.
- the hydraulic system 201 further comprises a second work function 217 for steering the working machine.
- the work function comprises two hydraulic cylinders, hereinabove called the steering cylinders 104, 105 (see also Figure 1).
- An operator-controlled element 219 in the form of a steering wheel, is hydraulically connected to the steering cylinders 104, 105 via a valve unit in the form of an orbitrol unit 220a, for direct-control of the steering cylinders 104, 105.
- control valve unit 200c for the steering function comprises two control valves 210, 211, in the form of flow valves, arranged between the pump 205 and the steering cylinders 104, 105 in the circuit for steering the working machine.
- the steering cylinders can also be operated by means of an operator-controlled element 214 (shown in Figure 3), in the form of a steering lever, which is operatively connected to the control unit 213.
- the control unit 213 is adapted to receive control signals from the steering lever 214 and to control the control valves 210, 212 according to the lever position.
- the system 201 further comprises a third work function 221, for tilting the work implement, arranged on the lift arm unit.
- the work function comprises a hydraulic cylinder, hereinabove called the tilting cylinder 110.
- the control valve unit 200a for the tilt function comprises two control valves 223, 223 arranged between the pump 205 and the tilting cylinder 110 for controlling the forward and return movement of the implement relative to the lift arm unit.
- An operator-controlled element 227 in the form of a tilt lever, is operatively connected to the control unit 213.
- the control unit 213 is adapted to receive control signals from the tilt lever and to control the control valves 223, 225 according to the lever position.
- a prioritizing valve 220 is arranged on the output conduit 245 of the pump for automatically prioritizing the steering function over the lift function and the tilt function, with the purpose of ensuring that the steering always gets the required pressure and flow.
- the prioritizing valve 220 regulates on pressure and ensures that the steering receives the required pressure. When at correct pressure, also the required flow to the steering is obtained, which occurs at the expense of the other work functions if the total hydraulic fluid requirement would exceed what the system is capable of providing.
- the hydraulic system 201 is a load sensing system and, for this purpose, suitably comprises a plurality of pressure sensors 229, 231; 216, 218; 235, 237; 233, 239.
- the lift function of the system preferably comprises two pressure sensors 229, 231, out of which one 229 is adapted to measure the pressure on the piston side of the lifting cylinders (and is suitably arranged on a conduit to the piston side of the lifting cylinders) and the second one 231 is adapted to measure the pressure on the piston rod side of the lifting cylinders (and is suitably arranged on a conduit to the piston rod side of the lifting cylinders).
- the tilt function of the system comprises two pressure sensors 235, 237, out of which one 235 is adapted to measure the pressure on the piston side of the tilting cylinder (and is suitably arranged on a conduit to the piston side of the tilting cylinder) and the second one 237 is adapted to measure the pressure on the piston rod side of the tilting cylinder (and is suitably arranged on a conduit to the piston rod side of the tilting cylinder).
- the steering wheel control function comprises a pressure sensor 233 in a conduit connected to the steering cylinders 104, 105.
- the pressure sensor 233 is preferably placed on the L S conduit, which receives the same pressure as one cylinder side when steering in one direction and as the other cylinder side when steering in the other direction. In neutral, the L S conduit is connected to tank.
- the lever control function of the system comprises two pressure sensors 216, 218, out of which one 216 is adapted to measure the pressure on the piston rod side of a steering cylinder (and is suitably arranged on a conduit to the piston rod side of the steering cylinder) and the second one 218 is adapted to measure the pressure on the piston side of the steering cylinder (and is suitably arranged on a conduit to the piston side of the steering cylinder).
- the hydraulic system can further comprise an electrically controlled valve 241 adapted to control the pressure on the pressure side of the pump via a hydraulic signal.
- the system 201 can also comprise an additional pressure sensor 239 for sensing a pressure which is indicative of the pressure on the pressure side of the pump.
- the pressure sensor 239 is preferably adapted to sense the pressure in a position downstream of the electrically controlled valve 241.
- the control unit registers the pressure in the hydraulic cylinder in question.
- the control unit then adjusts the valve 241 to obtain the desired pressure in the L S conduit (which in its turn controls the pressure of the pump).
- the pressure sensor 239 is adapted to sense the pressure and the control unit 213 is adapted to receive a signal from the pump pressure sensor 239 with information about the pressure level.
- the pressure sensor 239 will sense the pump pressure directly, when the valve 241 is fully open, but in normal operation modes the pressure sensor 239 senses the modulated pressure from the valve 241. This function implies that the hydraulic system can be operated with a variable control pressure.
- control unit 213 is operatively connected to the pressure sensors 216, 218, 229, 231, 233, 235, 237, 239 and the electrically controlled valve 241.
- control unit 213 receives electrical signals from the pressure sensors and generates an electrical signal for controlling the electrical valve 241, which in its turn emits a hydraulic signal to the main pump 205.
- the control unit 213 is adapted to generate a control signal to the electrically controlled valve 241 corresponding to the highest sensed load pressure for any one of the work functions, so that the pressure on the pressure side of the pump becomes slightly higher than the required load pressure.
- the control unit 213 is adapted to receive signals from the control levers 211, 214, 227.
- the control unit receives a corresponding signal from the lift lever 211 and controls the control valves 207, 209 to such a position that the pump is connected to the piston side of the lifting cylinders 108, 109 and the piston rod side of the lifting cylinders is connected to the tank 243.
- the control unit further receives signals from the pressure sensor 229 on the piston side of the lifting cylinders and from the pressure sensor 239 downstream of the pump. Based on the received signals, a desired pump pressure at a level above the sensed load pressure is determined, and the electrically controlled pump control valve 241 is controlled accordingly.
- the control unit 213 is preferably adapted to coordinate the opening degree of the control valves 207, 209 and the output pressure of the pump 205 for optimum operation.
- the reversing valve 253 is adapted to receive hydraulic signals from the second work function 217 (for the steering) and the pump control valve 241.
- the reversing valve is further adapted to control the pump 205 according to the received signal indicating the highest pressure. Accordingly, the hydraulic means (reversing valve) 253 selects the higher pressure in an output signal made up of two input pressure signals.
- the respective control valve unit of the control means 208 is preferably adapted for double-acting hydraulic cylinders where the control valves are electrically controlled and have separated inlets and outlets and pressure sensors on both sides of the control valves and position sensors on the slides.
- FIG. 4 shows one said recovery unit 295 and a pressure limiting means 287b, 289b, 291b for the respective work function.
- Each pressure limiting means comprises one said pilot-operated valve 287, 289, 291.
- the recovery unit 295 suitably a hydraulic machine, is connected to a generator (or to an electric machine which can function both as a generator and a motor) in order to, together with the pilot-operated valves, produce a recovery system 301 for electrical energy.
- the respective pilot-operated valve 287, 289, 291 is connected to the return port 60a, 60b, 60c of the respective control valve unit.
- the energy recovery system 301 comprises a plurality of first conduits 280, 282, 284 on which the pilot-operated valves 287, 289, 291 are arranged.
- the respective said first conduit comprises a pilot-operated valve and is connected between a return conduit 281, 283, 285 from one of said work functions and the tank 243 in the hydraulic system.
- the energy recovery system 301 further comprises a second conduit 293, which is connected to each of the first conduits 280, 282, 284 upstream of the pilot-operated valves 287, 289, 291.
- the recovery unit 295 is arranged on the second conduit 293 for the purpose of being driven by a flow of hydraulic fluid from one or several of said work functions for recovering energy.
- the energy recovery system 301 comprises a plurality of branch conduits 303, 305, 307 on which check valves 297, 298, 299 are arranged.
- the respective branch conduit 303, 305, 307 is arranged between the respective first conduit 280, 282, 284 and the second conduit 293 in order to block flow in a direction from the recovery unit 295 toward the respective work function by means of the check valves.
- the energy recovery system 301 further comprises a pressure sensor 309 in the second conduit 293 upstream of the recovery unit 295.
- the first conduits 280, 282, 284 are further connected to the second conduit 293 downstream of the pilot-operated valves 287, 289, 291 and the recovery unit 295.
- the respective pilot-operated valve 287, 289, 291 is connected in parallel with the recovery unit.
- the electronic control unit 213 (shown in Figure 3) is adapted to control each of the pilot-operated valves 287, 289, 291 (shown in Figure 4) individually to achieve energy recovery from one of the work functions.
- the control unit 213 is further adapted to receive a signal with information about the pressure, sensed by the pressure sensor 309, resulting from the resistance from the recovery unit 295 (within the range of the maximum allowable pressure set by the pilot-operated valve in question). Accordingly, the return flows of the work functions pass via the energy recovery system 301. Naturally, more or fewer work functions can be connected to the energy recovery system.
- both piston side and piston rod side of the hydraulic cylinder are connectable to the energy recovery unit by means of the control valve unit, there is of course a possibility to choose to have only one cylinder side connectable for one or several work functions.
- the return flow from the other cylinder side then suitably has its outlet in tank.
- energy is recovered when lowering the lift arm assembly 111.
- the control unit registers that the operator wants to lower the assembly through receiving a signal from the lift lever.
- the control unit sets the pilot-operated valve 289, which is associated with the lifting cylinders 108, 109, to a pressure which is slightly higher than the pressure of the return flow which is desired, and opens the control valve 207 to allow a return flow from the return port.
- the desired pressure of the return flow is obtained by adjusting the resistance of the hydraulic motor 295.
- Hydraulic fluid can now flow from the piston side of the lifting cylinders 108, 109 through the control valve 207, via the check valve 298, and through the hydraulic motor 295 and further to the tank 243 via a counterpressure valve 311.
- Hydraulic fluid will only pass the pilot-operated valve 298 to the extent that temporary pressure peaks arise and/or flow peaks arise which the hydraulic motor cannot handle.
- the piston rod side of the lifting cylinders 108, 109 is filled via anticavitation valves in a conventional manner.
- the generator 313 which is driven by the hydraulic motor 295, can deliver the recovered energy in the form of electrical energy to, for example, an energy storing means 314, such as a battery or a capacitor.
- Different control options can be used for energy recovery when lowering the lift arm assembly;
- All flow passes through the pilot-operated valve 289, which is set to generate a minimum back pressure.
- the control of the magnitude of the return flow occurs by means of the control valve 207 in accordance with the desired lowering speed of the lift arm assembly.
- the pilot-operated valve 289 is controlled so that a maximum allowable pressure is obtained, which means that the entire return flow passes through the hydraulic motor 295.
- the magnitude of the return flow can now be controlled via the speed of the generator 313 in order to obtain the desired lowering speed of the lift arm assembly, or the flow control occurs by means of the control valve 207.
- the control unit can determine whether, in a particular operation mode, only part of the potentially recoverable energy can be recovered and how much energy/power can be recovered.
- the pilot-operated valve 289 is controlled so that a maximum allowable pressure is obtained at the return port, which pressure is adapted to the energy recovery level desired, (with the exception of losses in the recovery system, the recovered energy per unit of time is equal to the actual pressure drop across the hydraulic motor 295 multiplied by the flow through the hydraulic motor.)
- the flow through the hydraulic motor is determined by the speed of the generator 313. In this operation mode, hydraulic fluid flows in parallel via both the hydraulic motor 295 and the pilot- operated valve 289. There are different ways of controlling the speed of the hydraulic motor 295.
- the load (torque) from a generator connected to the hydraulic motor can be adjusted so that a desired speed is obtained.
- the load is kept constant and the speed is controlled via the pilot-operated valve 289.
- the total flow (which determines how fast the piston side of the hydraulic cylinder is emptied and thereby the lowering speed of the lift arm assembly) is controlled by means of the control valve 207.
- the pump is actuated when the return flow is below a specific level or, alternatively, when the flow (by some margin) is below the flow requested via the lift lever.
- the actual flow across the control valve 207 can be calculated on the basis of slide position and pressure drop across the control valve 207 or, alternatively, by means of time measurement and with information from a position sensor 50 indicating the position of the piston of the hydraulic cylinder.
- the actuation of the pump can take place when the pressure on the piston side of the hydraulic cylinder is below a certain specific level. This level can be fixed or be a level dependent on the requested lowering speed.
- both control valves 207, 209 can be controlled so that their outlets to the energy recovery system are opened, which means that both the piston side and the piston rod side are connected to the recovery unit. This, in its turn, will result in a reduced return flow to the recovery system (but a higher pressure), since the lowering operation will be carried out primarily by hydraulic fluid flowing from the piston side to the piston rod side. This can be used, for example, when the bucket is empty and a rapid lowering is to take place without risking overspeeding the hydraulic motor 295.
- the return side In order not to get a "nervous" and jerky steering, at the same time as the pump pressurizes the steering cylinders for the desired movement, the return side has to be boosted with a certain back pressure, which is capable of decelerating the load when the load tends to continue its movement without the influence of the pump on the steering cylinders.
- a biasing pressure on the return side the magnitude of which varies depending on the flow, is used. This back up pressure is usually within the range 10-40 bar.
- the required biasing pressure is controlled by means of the one of the control valves 210, 212 which controls the return flow to the pilot-operated valve 291.
- the pilot-operated valve 291 is controlled so that a suitable maximum allowable pressure is obtained, which means that the entire flow passes through the hydraulic motor 295.
- the biasing pressure can now be controlled by adapting the load from the generator 313 on the hydraulic motor 295.
- the control unit can determine whether, in a particular operation mode, only part of the potentially recoverable energy can be recovered and how much energy/power can be recovered.
- the pilot-operated valve 291 is controlled so that a maximum allowable pressure is obtained at the return port, which pressure is adapted to the desired biasing pressure.
- the biasing pressure can now be controlled (up to the maximum allowable pressure) by adapting the load from the generator 313 on the hydraulic motor 295.
- hydraulic fluid flows in parallel via both the hydraulic motor 295 and the pilot-operated valve 291.
- the load torque
- the load is kept constant and the speed is controlled via the pilot-operated valve 289.
- the level of the biasing pressure can be determined on the basis of one of the following criteria (or on the basis of a combination of them): o Utilization of a fixed predetermined biasing pressure. o Utilization of a variable biasing pressure being a function of:
- the biasing pressure is increased when there is an increased tendency to jerkiness in the steering, and is reduced according to a given time ramp or another type of filtration when there is less jerkiness.
- a jerky steering can be detected via the derivative of the steering rate which can be registered via the generator 313 or, alternatively, via position sensors on the steering cylinder (steering cylinders) 104, 105 or, alternatively, via a calculation of the flow across the outlet valves 210 or 212.
- Another way is that the control unit, via the pressure sensors 216, 218, registers that large pressure fluctuations arise in the steering cylinders.
- the pilot-operated valve 291 is controlled so. that the maximum allowable pressure corresponds to the desired biasing pressure.
- the load on the hydraulic motor from the generator 313 is adjusted to such a high level that the hydraulic fluid does not pass through the hydraulic motor 295, but substantially the entire flow passes through the pilot- operated valve 291.
- a shut-off valve can be added before or after the hydraulic motor 295 in order to prevent that a flow occurs through the hydraulic motor 295.
- FIG. 5 shows a further development of the embodiment in Figure 4.
- a pressure limiter 321 such as a hydraulic pressure limiting valve, is arranged on a conduit 323 connecting the return conduit 285 from the lever control function and the tank 243.
- the reliability is increased further since it can be ensured that the steering function will be supplied also in case of an electrical malfunction causing a stop in the return flow. If a malfunction should occur in the recovery system, the return flow of hydraulic fluid can still always reach the tank 243 via the pressure limiting valve 321.
- the opening pressure of the pressure limiting valve is suitably set slightly above the pressure level desired for use in the energy recovery system.
- This pressure limiting valve 321 could also, alternatively, be used with regard to the steering wheel steering.
- a check valve can be added in order to prevent that the biasing pressure for the lever steering reaches the pressure limiter and the orbitrol unit.
- energy is recovered when several work functions are used simultaneously. If, for example, lifting and steering are used simultaneously and the lift function requires the pump pressure 200 bar and the steering 50 bar, the energy recovery system can boost the return pressure to the steering with 150 bar. This means that the 200 bar pump pressure can be used both for lifting and for steering. The biased energy from the steering is recovered.
- the hydraulic system preferably comprises a sensor 50 for determining a reference position for the work implement which is mounted on the working machine.
- the work implement is movable relative to the machine body of the working machine by means of one said hydraulic work function.
- the work implement can, for example, be the lifting assembly or other types of functions where the undesired kinetic energy of the machine body and/or the work implement is recovered at the same time as the relative movement is damped.
- the recovery unit is adapted to dampen a relative movement, at least in one direction, between the work implement and the machine body. This is of importance when influenced by an external disturbance, which may occur, for example, when moving the working machine.
- suspension system of the lift function where damping of a lowering movement of the bucket relative to the machine body can take place while energy is recovered, will be described.
- a suspension system for the tilt function can function in a similar manner.
- the control unit Via the position sensor 50 (see Figure 4), which position sensor can be fitted on a lifting cylinder, the control unit registers the position of the lifting assembly relative to the machine body.
- the computer of the control unit stores into memory the position the lifting assembly had immediately before the suspension function was actuated and the actual pressure level on the piston and/or piston rod side of the hydraulic cylinder.
- the lift arm assembly is usually pivotally connected to the machine body of the working machine. This means that if the working machine drives on a bumpy surface, i.e. drives over a small elevation (a bump) and/or into a small hole, this is reflected in the hydraulic cylinders in the form of changes in pressure on the piston and piston rod sides.
- the control valve 209 opens the piston rod sides to the tank 243.
- the control valve 207 to the pump 205 is opened so that oil can be replenished and lifts the lift arm assembly a bit.
- the control valve 209 closes and the control valve 207 opens to the recovery system so that the assembly is lowered, wherein the flow of hydraulic fluid generates electrical energy in the recovery system.
- the generator 313 has a torque control, i.e. the load from the generator on the hydraulic motor can be increased until the lifting assembly stops because the back pressure from the hydraulic motor is sufficiently large.
- the piston stroke length and piston speed of the hydraulic cylinder will depend on the selected torque control strategy.
- the pilot-operated valve 289 is controlled to set a maximum allowable pressure which allows the desired pressure level for the recovery unit.
- the generator 313 has a speed control, wherein the piston stroke length and piston speed of the hydraulic cylinder will depend on the selected speed control strategy.
- the pilot-operated valve 289 is controlled to set a maximum allowable pressure which allows the desired pressure level for the recovery unit.
- the control can be performed such that the assembly stays around the initial position, which can registered by the position sensor 50.
- the maximum allowable amplitude relative to the initial position should be limited. This is for safety reasons, and so that the assembly does not fold up too much when pulling force is applied to the bucket.
- the system creates conditions for a variable "springing/damping" characteristic.
- the system essentially works like a spring with damping, i.e. if a disturbance pushes the lifting assembly down, electrical power is obtained by driving the generator, and at the same time the movement is decelerated (like a spring) by means of the above control strategies.
- a certain power level will be added, which then abates so that the lifting assembly stops.
- the form of this spring characteristic can be a function of the following, or parts thereof:
- the magnitude of the disturbance force The spring characteristic can be a function of the magnitude of the disturbance force.
- the difference in pressure of the hydraulic cylinder before and after the disturbance is a measure of the disturbance force.
- the spring characteristic can be a function of the load weight.
- the pressure on the piston side of the hydraulic cylinder is a measure of the load weight.
- the spring characteristic can be varied depending on which handling and/or work implement (bucket, pallet fork, timber grab etc.) which is to be utilized.
- the control unit can register the actual handling and select from a number of predetermined characteristics adapted for different work operations.
- Transport and work mode Different characteristics can be selected depending on whether the machine is only operated in transport mode or if work with the lifting assembly is in progress. This can, for example, be indicated by registration of the speed of the working machine and/or registration of any lever movements.
- the energy recovery system is used to add a pump function to the hydraulic system. See Figure 6.
- the hydraulic system comprises a means 520 for returning energy, recovered from a return flow from the work function, to the pressure side of the pump.
- An electric machine 513 is mechanically connected to the hydraulic machine 595.
- the electric machine can be driven by the hydraulic machine and thus be used as a generator when recovering energy, but it can also be used as a motor to drive the hydraulic machine as a pump. Accordingly, the hydraulic machine 595 can function both as a hydraulic motor and a pump.
- An electrically controlled valve 515 is arranged on a tank conduit 517 connecting the hydraulic machine 595 to the tank 243.
- the valve can be used to in order to be able to prevent flow of hydraulic fluid from the hydraulic machine to the tank 243.
- a pump conduit 521 is adapted to connect the hydraulic machine to the outlet side (pressure side) of the main pump 205.
- This pump conduit 521 is suitably connected at one of its ends to the tank conduit 517 in a position between the hydraulic machine 595 and the valve 517, and connected at its other end to the outlet side of the main pump 205.
- a check valve 519 can be arranged on the pump conduit 521. Thereby, hydraulic fluid is prevented from reaching the energy recovery system directly in a direction from the main pump 205.
- a check valve 523 can also be arranged on the outlet side of the main pump so that hydraulic fluid from the energy recovery system cannot pass to the tank 243 via the main pump 205.
- the recovery unit can also provide hydraulic fluid to the work functions of the hydraulic system.
- the recovery unit uses hydraulic fluid arriving from the return line of a work function.
- the check valve 523 at the main pump 205b has been eliminated.
- the main pump 205b is adapted to function both as a pump and a hydraulic motor.
- the pump is adapted to provide a torque when hydraulic fluid flows from the recovery unit 595b to the pressure side 50b of the pump and further through the pump to the suction side 51b of the pump, at the same time as the pump provides the required pressure on the pressure side for supplying the work functions.
- the hydraulic machine 595b can be connected to an electric machine 513 and can, in the same way as described previously, function as a hydraulic motor for recovering energy, or as a pump for increasing the pressure of the return flow.
- the main pump 205b is connected to the driveline 52b of the working machine (schematically illustrated in Figure 6b) for transferring a torque to the driveline when recovering energy.
- the driveline has a power take-off (PTO).
- PTO power take-off
- the power taken off at the PTO can then be used for an optional function of the working machine.
- the main pump 205b which in this case can operate both as a pump and a hydraulic motor, is adapted to maintain the required pressure on the pressure side at the same time as an excess flow of hydraulic fluid from the recovery unit 595b can flow via the conduit 521 and further through the main pump 205b and to the tank 243.
- the main pump which preferably is a variable load sensing pump of the type "over-centre variable displacement pump" is also mechanically connected to the driveline 52b, and can thus be used to generate a torque on the driveline in that hydraulic fluid flows "backwards" through the pump 205b to the tank 243.
- This can be particularly advantageous in operation modes where one or several work functions generate relatively large return flows, at the same time as the flow requirement on the supply side, at the moment in question, is relatively low. Also in case an energy storage connected to the electric machine 513 would be full, there is a possibility to recover energy via the main pump 205b instead.
- the pilot-operated valve 287 is controlled so that the required maximum allowable pressure is obtained, which means that the entire return flow of hydraulic fluid from the work function is directed to the hydraulic machine 595.
- Different strategies can be used depending on the pressure of the return flow relative to the pressure on the pressure side of the main pump:
- the valve 515 is closed and the entire flow of hydraulic fluid passes via the hydraulic machine 595.
- the electric machine 513 can recover an amount of energy, i.e. generate electrical power, corresponding to the pressure difference between the return pressure and the supply pressure.
- the valve 515 is closed and the entire flow of hydraulic fluid passes via the hydraulic machine 595.
- the electric machine 513 functions as a motor and supplies energy so that the pressure of the return flow can be raised to a level enabling hydraulic fluid to be supplied on the outlet side of the main pump.
- the recovered energy can be used for different needs. For example, at low diesel engine speeds, the electrical energy can be used to generate higher cylinder speeds in the work functions, or to release more engine power to the driveline.
- the recovery unit is used to provide the hydraulic system 201 with a function in the form of a standby steering pump. See Figure 7.
- a suction conduit 601 enabling the hydraulic machine 595 to draw hydraulic fluid from the tank 243, is added.
- the suction conduit 601 is preferably adapted to extend from the second conduit 293 to the tank 243 so that the hydraulic machine 595 can draw hydraulic fluid from the tank 243.
- a check valve 621 can be arranged on the suction conduit 601. By means of the suction conduit 601, the hydraulic machine 595 could deliver hydraulic fluid to the steering system in case the main pump 205, for some reason, would not be capable of providing hydraulic fluid.
- the energy recovery system is used to recover energy during a deceleration of the working machine 101.
- the main pump 205 is drivable by means of the driveline 205b of a working machine and is adapted to brake the driveline during deceleration of the working machine.
- the hydraulic system comprises a hydraulic control means 701b for controlling a flow of hydraulic fluid from the pressure side of the pump 205 to the recovery unit 595 to recover energy during deceleration of the working machine.
- the embodiment of the hydraulic system in Figure 8 comprises said control means 701b in the form of an electrically controlled valve 701 and a conduit 703.
- the valve 701 is arranged on the conduit 703 connecting the suction conduit 601 and the pump conduit 521.
- flow is driven from the pump 205 via the valve 701 to the recovery unit, where the hydraulic energy can be converted into electrical energy for direct consumption or storage in a storage unit.
- the machine will be decelerated to an extent corresponding to the energy required to drive the pump (and the hydraulic machine and the generator). Adjustment of the deceleration level can, for example, take place by modulating the maximum L S signal to the pump and to thereafter control the electric machine 513 by torque or speed control.
- the pressure level multiplied by the flow passing the recovery unit corresponds to the deceleration effect which can be achieved.
- the flow can be determined either by direct speed control of the electric machine, or by controlling the load (torque) which will correspond to a certain speed (and thereby a certain flow). If other functions are supplied simultaneously by the main pump, the electric machine 513 is controlled so that pressure and flow is continuously maintained to these other functions and the remaining part passes to the recovery unit.
- FIG 9 shows an alternative embodiment to the embodiment in Figure 8.
- the control means 801b comprises an electrically controlled valve 801 and a conduit 803 connecting the suction conduit 601 and a supply conduit 805.
- the supply conduit 805 extends from the pump to the prioritizing valve 220 and further to the work functions.
- the valve 801 is arranged on the conduit 803, which is connected to the supply conduit 805 in a position between the prioritizing valve 220 and the work functions.
- the prioritizing valve 220 will prioritize a flow from the main pump 205 to the steering at the expense of the supply to the work functions and/or the recovery unit.
- FIG 10 shows an alternative embodiment of the hydraulic system according to the invention.
- the energy recovery system 901 of the hydraulic system is provided in the hydraulic base system 201, which has already been described above with reference to Figures 3 and 4.
- the recovery unit comprises a first hydraulic machine 295 and a second hydraulic machine 903.
- the first and second hydraulic machine are mechanically interconnected, and the first hydraulic machine 295 is adapted to be driven by a flow of hydraulic flow and the second hydraulic machine 903 is adapted to pump hydraulic fluid by being driven by the first hydraulic machine.
- the energy recovery system 901 comprises said second hydraulic machine 903.
- the second hydraulic machine 903 will be referred to as a pump and the first hydraulic machine 295 as a hydraulic motor.
- This arrangement of pump and motor with an intermediate shaft for power transmission forms a hydraulic torque converter.
- a hydraulic energy storage 905, for example in the form of an accumulator, is connected to an outlet side of the pump 903.
- the outlet side of the pump 903 is further connected to the hydraulic system 201 via a conduit 907 which is connected to the suction side of the main pump 205. Accordingly, energy stored in the accumulator 905 can be delivered back to the system via the suction side of the main pump 205.
- the main pump 205 is preferably mechanically connected to the driveline of the working machine and is driven by the propulsion engine of the working machine, such as a diesel engine.
- the hydraulic system comprises a means 900 for returning energy, recovered from a return flow from the work function, to the suction side of the pump 205.
- Hydraulic fluid can be provided from the accumulator 905 to the main pump. Since the hydraulic fluid in the accumulator is pressurized, it can also contribute a torque that drives the main pump 205, which can be utilized to relieve the diesel engine load. Since the accumulator is connected to the suction side of the main pump, all energy stored in the accumulator 905 can be used in the system irrespective of the actual pressure level in the accumulator.
- the main pump will function as a hydraulic motor supporting the diesel engine.
- energy is recovered when lowering the lift arm assembly 111.
- the control unit registers that the operator wants to lower the lift arm assembly via the lift lever.
- the control unit sets the pilot-operated valve 289, associated with the lifting cylinders 108, 109, to a maximum allowable pressure, which means that the required pressure for the recovery unit can be achieved, and opens the control valve 207.
- Hydraulic fluid can now flow from the piston side of the lifting cylinders 108, 109 through the control valve 207, through the check valve 298, and further through the hydraulic motor 295 and then further to the tank 243 via the counterpressure valve 311.
- the piston rod side of the lifting cylinders 108, 109 is replenished in a conventional manner by means of the anticavitation valves arranged in the control valve unit.
- the pressure of the return flow passing through the motor 295 depends on the pressure in the hydraulic cylinder (which in its turn depends on the actual load).
- the pressure on the pressure side of the pump 903 is dependent on how much the gas in the accumulator 905 is compressed. This means that the pressure in the accumulator 905 and the pressure of the hydraulic fluid before the hydraulic motor 295 are essentially never equal.
- all recovered energy can be taken care of in the accumulator 905, irrespective of pressure levels.
- both the control valve 207 and control valve 209 can open the outlet to the recovery unit, which means that both the piston side and the piston rod side are connected to the recovery unit.
- the entire return flow passes through the pilot-operated valve 289, which is set to generate a minimum back pressure.
- the control of the magnitude of the return flow occurs by means of the control valve 207 according to the desired lowering speed of the lift arm assembly.
- the flow can be calculated on the basis of slide position and pressure drop across the slide of the control valve 207.
- Pressure sensors on the piston side of the hydraulic cylinder and the pressure sensor 309 at the recovery unit can be utilized.
- the reason which energy is not desired to be recovered can, for example, be because the accumulator 905 is fully charged, i.e. that the pressure in the accumulator has reached a maximum level. It can also be because the lift arm assembly is desired to be lowered with maximum force (through pushing by pumping force), and in such a case a back pressure in the return line would counteract the lowering movement. • Full recovery:
- the pilot-operated valve 289 is controlled so that a suitable maximum allowable pressure is obtained, which means that all flow passes through the hydraulic motor 295.
- the control of the magnitude of the return flow occurs by means of the control valve 207.
- the control unit has information about the pressure on the piston side of the hydraulic cylinder and preferably opens the control valve 207 as much as possible. A calculation of how high a back pressure should prevail after the control valve 207 in order to obtain the requested flow can be performed.
- the pressure can be measured by the pressure sensor 309.
- a calculation and modulation of the desired torque are performed by adjusting the displacement of the pump 903. This corresponds to a certain pressure in a position between the control valve and the hydraulic motor, i.e. at the pressure sensor 309.
- a sensor 909 is adapted to sense the speed on the shaft connecting the hydraulic motor 295 to the pump 903. With information from the speed sensor 909, it can be verified that the hydraulic motor 295 and the pump 903 are not overspeeding.
- the pilot- operated valve 289 can then adjust the maximum allowable pressure at the return port to a value such that overspeeding cannot arise. Accordingly, a flow of hydraulic fluid can be by-passed directly to the tank 243 via the pilot-operated valve.
- the control valve 207 is adjusted in a conventional manner so that the correct cylinder speed is obtained.
- energy is recovered when emptying the bucket (tilt-out). Recovery when emptying the bucket takes place in a corresponding manner as when lowering the lift arm assembly.
- energy is recovered when steering with the steering lever.
- Energy recovery during lever steering by means of a system according to the embodiment in Figure 10 takes place in substantially the same manner as for energy recovery during lever steering by means of the system according to the embodiment in Figure 4, with some differences:
- the biasing pressure is controlled by adjusting the torque on the pump 903 (according to the previous description).
- energy is recovered when steering with the steering wheel (via orbitrol unit).
- Energy recovery during steering wheel steering by means of a system according to the embodiment in Figure 10 takes place in substantially the same manner as for energy recovery during steering wheel steering by means of the system according to the embodiment in Figure 4, with some differences:
- FIG 11 shows a further development of the embodiment in Figure 9.
- This further development corresponds to the further development in Figure 5 of the hydraulic system in Figure 4.
- a pressure limiter 1021 is arranged on a conduit 1023 connecting the return conduit from the lever steering to the tank 243.
- energy is recovered when several work functions are used simultaneously, This works in substantially the same way as described above for the hydraulic system shown in Figure 4.
- the hydraulic system is used as an active suspension system for a work function, such as for example the lift function, where the undesired kinetic energy of the machine body and/or the work implement is at least partially recovered.
- a work function such as for example the lift function
- the pump 903 preferably has a torque control, i.e. the load from the pump on the hydraulic motor can be increased until the lifting assembly stops because the back pressure from the hydraulic motor is sufficiently large.
- the piston stroke length and piston speed of the hydraulic cylinder will depend on the selected torque control strategy.
- the pilot-operated valve 289 is controlled to set a maximum allowable pressure which means that the recovery unit can operate at the desired pressure level within the range of the maximum pressure.
- the hydraulic system is used to obtain energy recovery during a deceleration of the working machine 101. See Figure 12.
- an electrically controlled valve 1101 is arranged also on a conduit 1103 connecting the second conduit 293 of the recovery system and the tank 243.
- the main pump 205 is driven by the driveline at the same time as the main pump 205 brakes the drivel ⁇ ne. Thereby, the main pump pumps a flow of hydraulic fluid via the valve 1101 to the recovery unit.
- the working machine is decelerated to an extent corresponding to the energy required to drive the main pump 205 (and the recovery unit).
- the valve 1101 is preferably kept fully open. Adjustment of the deceleration level can take place by calculating and adjusting the L S signal to the main pump (since the L S signal constitutes a reference signal for the pressure regulator of the pump), and adjustment of the displacement of the pump 903.
- the flow can be calculated with input data from the speed sensor 909.
- the deceleration effect is proportional to the pressure multiplied by the flow.
- the L S signal to the main pump is determined by the highest pressure of the pressure required for the other work functions and the pressure required to obtain the desired deceleration effect (deceleration energy). Calculation of how much energy can be recovered is performed and the displacement of the pump 903 is adjusted accordingly.
- the flow across the hydraulic motor 295 is calculated (by means of the speed sensor 909) and the flow going out to other work functions is calculated (by means of slide position and pressure drop of associated control valves). If steering wheel steering with orbitrol unit is used, for example, a steering position sensor can be used to calculate the flow to the steering. If the recovery unit cannot receive a pressure and/or flow corresponding to the required amount of deceleration energy, a certain amount of energy can be dumped by controlling the control valve 1101 so that a corresponding pressure drop arises across it.
- Figure 13 shows an alternative embodiment to the embodiment in Figure 12.
- the electrically control valve 1201 is arranged on a conduit 1203 connecting the second conduit 293 in the recovery system to a supply conduit 805 arranged between the main pump 205 and the work functions.
- the conduit 1203 is connected to the supply conduit 805 in a position between the prioritizing valve 220 and the work functions.
- the prioritizing valve 220 will prioritize a flow from the main pump 205 to the steering at the expense of the supply to the work functions and/or the recovery unit.
- the hydraulic system is used to supply recovered energy from an accumulator to the main pump.
- the pressure in the accumulator is dependent on how much the gas is compressed, and the pressure required by the hydraulic cylinder depends on the actual load situation. Either the pressure in the accumulator is lower than the pressure requirement of the hydraulic cylinder, which will mean that the hydraulic cylinder does not move at all, or the pressure in the accumulator is higher than the pressure requirement of the hydraulic cylinder, which means that energy has to be throttled away via a valve to enable the speed of the hydraulic cylinder piston to be controlled.
- the accumulator 905 is connected to the suction side of the pump 205 via the valve 913.
- a check valve 915 on a conduit between the main pump 205 and the tank 243 prevents the pressurized oil from the accumulator 905 from passing to the tank 243.
- the valve 913 When the valve 913 is closed, the main pump draws oil in a conventional manner from the tank. The power required to drive the pump is proportional to the pressure difference between pressure and suction side of the pump multiplied by the flow through the pump.
- the valve 913 is opened, the pressure in the accumulator is supplied to the suction side of the pump, which reduces the pressure difference between pressure and suction side of the pump 205.
- the pressure in the accumulator is equal to the output pressure, virtually no energy has to be supplied from the diesel engine to drive the pump (with the exception of some energy consumption due to slip losses).
- the pressure in the accumulator 905 is lower than the output pressure from the main pump 205, only a power which increases the pressure prevailing in the accumulator 905 to the requested pressure on the pressure side of the pump is needed from the diesel engine.
- the main pump 205 will act as a hydraulic motor and drive the diesel engine and its auxiliary equipment.
- the term “electrically controlled valve” has been used for a direct electrically controlled valve in a hydraulic conduit, that is to say the valve is adapted to be controlled via an input electrical signal.
- electrically controlled valve such as an arrangement of several valves, out of which a first valve is arranged on the hydraulic conduit and a second direct electrically controlled valve is adapted to control the first valve via a hydraulic signal.
Landscapes
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Mining & Mineral Resources (AREA)
- Civil Engineering (AREA)
- Structural Engineering (AREA)
- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Mechanical Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Fluid-Pressure Circuits (AREA)
- Operation Control Of Excavators (AREA)
Abstract
Description
Claims
Priority Applications (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2012512999A JP5567663B2 (en) | 2009-05-29 | 2009-05-29 | Hydraulic system and work machine including such a hydraulic system |
EP09845306.1A EP2435717B1 (en) | 2009-05-29 | 2009-05-29 | A hydraulic system and a working machine comprising such a hydraulic system |
KR1020117028084A KR20120040684A (en) | 2009-05-29 | 2009-05-29 | A hydraulic system and a working machine comprising such a hydraulic system |
PCT/SE2009/000282 WO2010138029A1 (en) | 2009-05-29 | 2009-05-29 | A hydraulic system and a working machine comprising such a hydraulic system |
US13/322,941 US9074347B2 (en) | 2009-05-29 | 2009-05-29 | Hydraulic system and a working machine comprising such a hydraulic system |
CN200980159587.8A CN102449323B (en) | 2009-05-29 | 2009-05-29 | Hydraulic system and the engineering machinery comprising this hydraulic system |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PCT/SE2009/000282 WO2010138029A1 (en) | 2009-05-29 | 2009-05-29 | A hydraulic system and a working machine comprising such a hydraulic system |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2010138029A1 true WO2010138029A1 (en) | 2010-12-02 |
Family
ID=43222917
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/SE2009/000282 WO2010138029A1 (en) | 2009-05-29 | 2009-05-29 | A hydraulic system and a working machine comprising such a hydraulic system |
Country Status (6)
Country | Link |
---|---|
US (1) | US9074347B2 (en) |
EP (1) | EP2435717B1 (en) |
JP (1) | JP5567663B2 (en) |
KR (1) | KR20120040684A (en) |
CN (1) | CN102449323B (en) |
WO (1) | WO2010138029A1 (en) |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2012125320A1 (en) * | 2011-03-17 | 2012-09-20 | Parker Hannifin Corporation | Electro-hydraulic system for controlling multiple functions |
US20130126023A1 (en) * | 2011-11-22 | 2013-05-23 | Tam C. Huynh | Hydraulic system with energy regeneration |
WO2013082331A1 (en) * | 2011-11-29 | 2013-06-06 | Vanguard Equipment, Inc. | Auxiliary flow valve system and method for managing load flow requirements for auxiliary functions on a tractor hydraulic system |
WO2013095208A1 (en) | 2011-12-22 | 2013-06-27 | Volvo Construction Equipment Ab | A method for controlling lowering of an implement of a working machine |
US20130229272A1 (en) * | 2012-03-05 | 2013-09-05 | Caterpillar Inc. | Manual control device and method |
WO2013180605A1 (en) * | 2012-05-30 | 2013-12-05 | Volvo Construction Equipment Ab | A method for recovering energy and a hydraulic system |
EP2955389A1 (en) * | 2014-06-13 | 2015-12-16 | Parker Hannifin Manufacturing Finland OY | Hydraulic system with energy recovery |
Families Citing this family (44)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
BR112012026074A2 (en) * | 2010-04-12 | 2016-06-28 | Volvo Compact Equipment Sas | excavator and process for mounting or dismounting such excavator |
JP5817311B2 (en) * | 2011-08-08 | 2015-11-18 | ダイキン工業株式会社 | Hybrid hydraulic system |
EP2754758B1 (en) * | 2011-09-09 | 2018-03-07 | Sumitomo Heavy Industries, Ltd. | Excavator and control method for excavator |
US9644761B2 (en) | 2011-09-30 | 2017-05-09 | General Electric Company | Desalination system with energy recovery and related pumps, valves and controller |
US9387440B2 (en) | 2011-09-30 | 2016-07-12 | General Electric Company | Desalination system with energy recovery and related pumps, valves and controller |
US9279236B2 (en) | 2012-06-04 | 2016-03-08 | Caterpillar Inc. | Electro-hydraulic system for recovering and reusing potential energy |
US8807255B2 (en) * | 2012-09-24 | 2014-08-19 | Caterpillar Paving Products Inc. | Engine hot air deflector |
US9290912B2 (en) | 2012-10-31 | 2016-03-22 | Caterpillar Inc. | Energy recovery system having integrated boom/swing circuits |
US9638179B2 (en) | 2012-12-04 | 2017-05-02 | General Electric Company | Hydraulic control system for a reverse osmosis hydraulic pump |
US9897080B2 (en) | 2012-12-04 | 2018-02-20 | General Electric Company | Rotary control valve for reverse osmosis feed water pump with energy recovery |
US9476415B2 (en) | 2012-12-04 | 2016-10-25 | General Electric Company | System and method for controlling motion profile of pistons |
EP2955284B1 (en) * | 2013-02-08 | 2019-05-08 | Doosan Infracore Co., Ltd. | Apparatus and method for controlling oil hydraulic pump for excavator |
US9290911B2 (en) | 2013-02-19 | 2016-03-22 | Caterpillar Inc. | Energy recovery system for hydraulic machine |
US9850918B2 (en) | 2013-06-03 | 2017-12-26 | Volvo Construction Equipment Ab | Hydraulic system for a working machine and a method for controlling a hydraulic system |
US9204626B2 (en) * | 2013-10-23 | 2015-12-08 | Ms Gregson | Method and system for controlling an inclination of a boom carried by a vehicle |
WO2015094024A1 (en) * | 2013-12-19 | 2015-06-25 | Volvo Construction Equipment Ab | A hydraulic load sensing system |
JP2015137753A (en) * | 2014-01-24 | 2015-07-30 | カヤバ工業株式会社 | Control system of hybrid construction machine |
DE102014218886B3 (en) * | 2014-09-19 | 2015-11-12 | Voith Patent Gmbh | Hydraulic drive with fast lift and load stroke |
FR3026811B1 (en) * | 2014-10-03 | 2016-12-09 | Poclain Hydraulics Ind | HYDRAULIC ASSISTANCE METHOD FOR DRIVING A LOW-SPEED VEHICLE |
US9615499B2 (en) * | 2014-12-03 | 2017-04-11 | Cnh Industrial Canada, Ltd. | Hydraulic work unit leveling and calibration system for an agricultural implement |
US9402344B1 (en) * | 2015-01-20 | 2016-08-02 | Deere & Company | Power management for sugarcane harvesters |
WO2016190468A1 (en) * | 2015-05-28 | 2016-12-01 | 볼보 컨스트럭션 이큅먼트 에이비 | Method for controlling working device of construction equipment |
DE102015015858A1 (en) * | 2015-12-03 | 2017-06-08 | Sauter Feinmechanik Gmbh | Monitoring device for tool turrets |
DE102016002443A1 (en) * | 2016-02-29 | 2017-08-31 | Bomag Gmbh | Steering device, construction machine with a steering device and method for steering a steerable machine |
SE1600171A1 (en) | 2016-05-19 | 2017-11-20 | Flutron Ab | Electrohydraulic drive and control system |
DE102017100190B4 (en) | 2017-01-06 | 2018-11-15 | Danfoss Power Solutions Aps | Hydraulic steering arrangement |
US10029533B1 (en) * | 2017-01-23 | 2018-07-24 | Caterpillar Underground Mining Pty Ltd | Vehicle suspension control system |
DK179314B1 (en) * | 2017-02-08 | 2018-04-30 | Steeper Energy Aps | Pressurization system for high pressure treatment system |
US11105347B2 (en) * | 2017-07-20 | 2021-08-31 | Eaton Intelligent Power Limited | Load-dependent hydraulic fluid flow control system |
US10392774B2 (en) | 2017-10-30 | 2019-08-27 | Deere & Company | Position control system and method for an implement of a work vehicle |
US10663252B1 (en) | 2017-12-15 | 2020-05-26 | John M. Sprainis | Shoulder-fired firearm primary and secondary recoil attenuator |
CN108343651B (en) * | 2017-12-21 | 2021-03-16 | 中国神华能源股份有限公司 | Emergency rescue method for road maintenance mechanical operation device |
CN108298474A (en) * | 2017-12-26 | 2018-07-20 | 浙江大学 | A kind of fork truck energy saving system with speed-regulating function |
LT3761773T (en) * | 2018-03-08 | 2023-09-11 | Precision Planting Llc | Agricultural planter row unit with fluid control system |
AU2018431328A1 (en) * | 2018-07-06 | 2020-12-24 | Sandvik Mining And Construction G.M.B.H. | Hydraulic master and slave drive motor control system |
EP3908757A1 (en) | 2019-01-08 | 2021-11-17 | Parker Hannifin Corporation | Hydraulic control valve with duplicate workports and integrated actuator oscillation control features |
JP7460604B2 (en) * | 2019-03-28 | 2024-04-02 | 住友重機械工業株式会社 | excavator |
US11708106B2 (en) * | 2019-07-02 | 2023-07-25 | Cnh Industrial America Llc | Steering systems and methods using active braking |
CN110332163B (en) * | 2019-07-25 | 2024-04-19 | 中国铁建重工集团股份有限公司 | Hydraulic control system and scraper |
US11846086B2 (en) * | 2019-12-12 | 2023-12-19 | Volvo Construction Equipment Ab | Hydraulic system and a method for controlling a hydraulic system of a working machine |
US11716921B2 (en) | 2020-09-03 | 2023-08-08 | Deere & Company | Method of a variable steering response for different steering operations of a working machine and system thereof |
KR20220131389A (en) * | 2020-10-19 | 2022-09-27 | 히다치 겡키 가부시키 가이샤 | construction machinery |
KR20220091867A (en) * | 2020-12-24 | 2022-07-01 | 현대두산인프라코어(주) | Construction machine |
SE546159C2 (en) | 2022-01-10 | 2024-06-11 | Parker Hannifin Emea Sarl | A valve arrangement and a hydraulic actuator contol circuit |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2007239894A (en) * | 2006-03-09 | 2007-09-20 | Kayaba Ind Co Ltd | Energy conversion system |
JP2007263157A (en) * | 2006-03-27 | 2007-10-11 | Kayaba Ind Co Ltd | Energy conversion device |
US20080317574A1 (en) * | 2005-08-24 | 2008-12-25 | Shin Caterpillar Mitsubishi Ltd. | Swing Drive Device and Work Machine |
Family Cites Families (16)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0731221A4 (en) * | 1993-11-30 | 1997-12-29 | Komatsu Mfg Co Ltd | Linear excavating control device for a hydraulic power shovel |
US5933346A (en) * | 1996-06-05 | 1999-08-03 | Topcon Laser Systems, Inc. | Bucket depth and angle controller for excavator |
US6378301B2 (en) * | 1996-09-25 | 2002-04-30 | Komatsu Ltd. | Pressurized fluid recovery/reutilization system |
US6735888B2 (en) * | 2001-05-18 | 2004-05-18 | Witten Technologies Inc. | Virtual camera on the bucket of an excavator displaying 3D images of buried pipes |
JP2004011168A (en) * | 2002-06-04 | 2004-01-15 | Komatsu Ltd | Construction machinery |
JP3877307B2 (en) * | 2002-10-18 | 2007-02-07 | 株式会社小松製作所 | Pressure oil energy recovery device |
JP2004324742A (en) * | 2003-04-23 | 2004-11-18 | Saxa Inc | Hydraulic device |
US7565801B2 (en) * | 2005-06-06 | 2009-07-28 | Caterpillar Japan Ltd. | Swing drive device and work machine |
JP2007040393A (en) * | 2005-08-03 | 2007-02-15 | Shin Caterpillar Mitsubishi Ltd | Fluid pressure circuit |
ITTO20050629A1 (en) * | 2005-09-15 | 2007-03-16 | Cnh Italia Spa | HYDRAULIC ARRANGEMENT FOR A RAISED LIFTING ARM WITH A VEHICLE |
JP4762022B2 (en) * | 2006-03-27 | 2011-08-31 | カヤバ工業株式会社 | Energy converter |
JP4773883B2 (en) | 2006-05-26 | 2011-09-14 | 住友建機株式会社 | Control device for work machine |
EP1914353A3 (en) * | 2006-10-19 | 2011-04-20 | Hitachi Construction Machinery Co., Ltd. | Construction machine |
JP4844363B2 (en) * | 2006-11-28 | 2011-12-28 | コベルコ建機株式会社 | Hydraulic drive device and work machine equipped with the same |
JP2008275101A (en) * | 2007-05-01 | 2008-11-13 | Daikin Ind Ltd | Hybrid type construction vehicle |
US7634911B2 (en) * | 2007-06-29 | 2009-12-22 | Caterpillar Inc. | Energy recovery system |
-
2009
- 2009-05-29 WO PCT/SE2009/000282 patent/WO2010138029A1/en active Application Filing
- 2009-05-29 JP JP2012512999A patent/JP5567663B2/en not_active Expired - Fee Related
- 2009-05-29 US US13/322,941 patent/US9074347B2/en active Active
- 2009-05-29 KR KR1020117028084A patent/KR20120040684A/en not_active Application Discontinuation
- 2009-05-29 CN CN200980159587.8A patent/CN102449323B/en active Active
- 2009-05-29 EP EP09845306.1A patent/EP2435717B1/en active Active
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20080317574A1 (en) * | 2005-08-24 | 2008-12-25 | Shin Caterpillar Mitsubishi Ltd. | Swing Drive Device and Work Machine |
JP2007239894A (en) * | 2006-03-09 | 2007-09-20 | Kayaba Ind Co Ltd | Energy conversion system |
JP2007263157A (en) * | 2006-03-27 | 2007-10-11 | Kayaba Ind Co Ltd | Energy conversion device |
Cited By (16)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN103717911A (en) * | 2011-03-17 | 2014-04-09 | 派克汉尼芬公司 | Electro-hydraulic system for controlling multiple functions |
CN103717911B (en) * | 2011-03-17 | 2016-10-19 | 派克汉尼芬公司 | For controlling multi-functional electrohydraulic system |
WO2012125320A1 (en) * | 2011-03-17 | 2012-09-20 | Parker Hannifin Corporation | Electro-hydraulic system for controlling multiple functions |
US20130126023A1 (en) * | 2011-11-22 | 2013-05-23 | Tam C. Huynh | Hydraulic system with energy regeneration |
WO2013078213A1 (en) * | 2011-11-22 | 2013-05-30 | Eaton Corporation | Hydraulic system with energy regeneration |
WO2013082331A1 (en) * | 2011-11-29 | 2013-06-06 | Vanguard Equipment, Inc. | Auxiliary flow valve system and method for managing load flow requirements for auxiliary functions on a tractor hydraulic system |
CN104066897A (en) * | 2011-12-22 | 2014-09-24 | 沃尔沃建筑设备公司 | A method for controlling lowering of an implement of a working machine |
EP2795003A4 (en) * | 2011-12-22 | 2015-08-05 | Volvo Constr Equip Ab | A method for controlling lowering of an implement of a working machine |
WO2013095208A1 (en) | 2011-12-22 | 2013-06-27 | Volvo Construction Equipment Ab | A method for controlling lowering of an implement of a working machine |
US10125798B2 (en) | 2011-12-22 | 2018-11-13 | Volvo Construction Equipment Ab | Method for controlling lowering of an implement of a working machine |
US20130229272A1 (en) * | 2012-03-05 | 2013-09-05 | Caterpillar Inc. | Manual control device and method |
CN104160097A (en) * | 2012-03-05 | 2014-11-19 | 卡特彼勒公司 | Manual control device and method |
WO2013180605A1 (en) * | 2012-05-30 | 2013-12-05 | Volvo Construction Equipment Ab | A method for recovering energy and a hydraulic system |
EP2855784A4 (en) * | 2012-05-30 | 2016-06-01 | Volvo Constr Equip Ab | A method for recovering energy and a hydraulic system |
EP2955389A1 (en) * | 2014-06-13 | 2015-12-16 | Parker Hannifin Manufacturing Finland OY | Hydraulic system with energy recovery |
US9797419B2 (en) | 2014-06-13 | 2017-10-24 | Parker Hannifin Manufacturing Finalnd Oy | Hydraulic system with energy recovery |
Also Published As
Publication number | Publication date |
---|---|
US20120067432A1 (en) | 2012-03-22 |
CN102449323A (en) | 2012-05-09 |
JP5567663B2 (en) | 2014-08-06 |
JP2012528288A (en) | 2012-11-12 |
EP2435717A1 (en) | 2012-04-04 |
CN102449323B (en) | 2016-04-13 |
KR20120040684A (en) | 2012-04-27 |
US9074347B2 (en) | 2015-07-07 |
EP2435717A4 (en) | 2017-01-18 |
EP2435717B1 (en) | 2019-05-08 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
EP2435717B1 (en) | A hydraulic system and a working machine comprising such a hydraulic system | |
US9932721B2 (en) | System, working machine comprising the system, and method of springing an implement of a working machine during transport | |
US7712309B2 (en) | Arrangement and a method for controlling a work vehicle | |
KR101956959B1 (en) | Method for obtaining a full range of lift speeds using a single input | |
US8869520B2 (en) | Load sensing system, working machine comprising the system, and method for controlling a hydraulic function | |
US6748738B2 (en) | Hydraulic regeneration system | |
US7905089B2 (en) | Actuator control system implementing adaptive flow control | |
EP3154809B1 (en) | Energy recovery system for off-highway vehicles with hydraulic transformer coupled to transmission power take-off | |
US20070166168A1 (en) | Control system for a work machine and method for controlling a hydraulic cylinder in a work machine | |
US20080210505A1 (en) | Method for Damping Relative Movements Occurring in a Work Vehicle During Advance | |
CN109764027B (en) | Electro-hydraulic working vehicle with energy recovery function | |
US20140060018A1 (en) | Hydraulic control system | |
US7845458B2 (en) | Control system for frame-steering of a vehicle and method for controlling two steering cylinders in a frame-steered vehicle | |
US10655297B2 (en) | Hydraulic system and a method for moving an implement of a working machine | |
AU2023203412A1 (en) | Hydraulic retarding control system | |
US8209094B2 (en) | Hydraulic implement system having boom priority | |
US11814814B2 (en) | Hydraulic system for hydro-mechanical machines comprising rotary mechanism and boom cylinder | |
US20040249537A1 (en) | Machine tool and method for operating machine tool | |
US6076350A (en) | Hydrostatic drive system for a vehicle |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
WWE | Wipo information: entry into national phase |
Ref document number: 200980159587.8 Country of ref document: CN |
|
121 | Ep: the epo has been informed by wipo that ep was designated in this application |
Ref document number: 09845306 Country of ref document: EP Kind code of ref document: A1 |
|
WWE | Wipo information: entry into national phase |
Ref document number: 2009845306 Country of ref document: EP |
|
ENP | Entry into the national phase |
Ref document number: 20117028084 Country of ref document: KR Kind code of ref document: A |
|
WWE | Wipo information: entry into national phase |
Ref document number: 2012512999 Country of ref document: JP |
|
NENP | Non-entry into the national phase |
Ref country code: DE |
|
WWE | Wipo information: entry into national phase |
Ref document number: 13322941 Country of ref document: US |