JP5257807B2 - Energy recovery and reuse technology for hydraulic systems - Google Patents

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a US Provisional Patent Application No. 60 / 865,710 filed on November 14, 2006 and a US Provisional Patent Application No. 60 / 913,457 filed on April 23, 2007. Claim the profit of the issue.
Federally commissioned research and development claims Not applicable

  The present invention relates to a hydraulic system that controls the flow rate to a hydraulic actuator that moves components on a machine, and more particularly to recovering energy from the hydraulic actuator and then utilizing the recovered energy to drive the hydraulic actuator.

  Construction agricultural equipment employs a hydraulic system to operate different mechanical elements. For example, an excavator is an ordinary construction machine that is pivotally coupled at one end to a tractor and has a bucket at the other end for skimming soil and other materials. The cylinder assembly is used to raise and lower the boom and includes a cylinder having a piston that forms two chambers within the cylinder. The rod connected to the piston is typically attached to the boom and the cylinder is attached to the body of the excavator. The boom is raised and lowered by extending and retracting the rod from within the cylinder.

  Other machinery uses different types of hydraulic actuators to move the mechanical elements. As used herein, the term “hydraulic actuator” generally refers to a cylinder-piston configuration, for example, a device such as a rotary motor that converts hydraulic fluid into mechanical motion.

  During the driving extension and retraction of the cylinder assembly, the pressurized fluid from the pump is usually added to one cylinder chamber by the valve assembly and all the fluid discharged from the other cylinder chamber leads to the system tank through the valve assembly Flow into. Under certain conditions, an external load or other force acting on the machine allows the cylinder assembly to extend or retract without sufficient fluid pressure from the pump. This is often referred to as overrun loading. For example, in an excavator, when a bucket is filled with heavy material, the boom is lowered only by gravity. This external force expels fluid through the valve assembly from one chamber of the boom hydraulic cylinder to the tank. At the same time, the flow rate is withdrawn from the pump through the valve assembly to the other cylinder chamber, but the incoming fluid does not drive the piston, so there is no need to maintain sufficient pressure to cause this boom movement. In this situation, the fluid is discharged from the cylinder at a relatively high pressure and contains energy that is normally lost when the pressure is metered through the valve assembly.

  In order to optimize the efficiency and economic operation of the machine, it is desirable to recover the energy of the exhaust fluid instead of releasing the fluid in the valve assembly. One conventional hydraulic system delivers discharged fluid to an accumulator that is stored under pressure for later use in mechanical drive. However, the challenge for effective energy recovery and reuse is that the accumulated hydraulic fluid must be at the proper pressure and volume to drive the actuator. The relationship between the pressure and volume of the discharged fluid and these parameters of the accumulator changes instantaneously and determines whether the fluid can accumulate. For example, if the external force acting on the cylinder assembly is insufficient to pressurize the exhaust fluid above the pressure level in the accumulator, the fluid cannot accumulate.

  At other times, if one wishes to utilize the fluid in the accumulator, the instantaneous relationship between the pressure and volume of the accumulator and the flow rate required to drive the fluid actuator determines whether the accumulator fluid can be used. For example, if the load of the hydraulic actuator requires a higher pressure than the accumulator, the recovered fluid cannot be employed. If the hydraulic actuator needs to move so as to require a larger fluid volume stored in the accumulator, it will be difficult to achieve effective operation. Another limiting factor is that as the hydraulic actuator consumes fluid from the accumulator, the accumulator pressure decreases, reducing the ability of the remaining fluid to drive the actuator.

  Accordingly, there is a need to provide effective technology for recovering and reusing energy in a hydraulic system.

  An energy regeneration method is provided for a hydraulic system including a first cylinder, a second cylinder, a supply conduit, a return conduit, and an accumulator. The first and second cylinders are operably connected in parallel to operate the components on the machine, each having first and second chambers.

  The energy recovery method includes a plurality of energy recovery modes, and various modes are used in a predetermined machine. The dual cylinder energy recovery mode consists of sending fluid from one chamber of the first and second hydraulic cylinders to the accumulator and directing fluid to the second chamber of the first and second hydraulic cylinders. In the split cylinder energy recovery mode, fluid is sent from the first chamber of the second hydraulic cylinder to the accumulator and the fluid is sent from the first chamber of the first hydraulic cylinder to at least one second chamber of the first and second hydraulic cylinders. It is done.

  In a preferred implementation of this method, directing fluid to the second chamber in dual cylinder energy recovery mode is accomplished by sending fluid from the supply conduit or return conduit to the second chamber of the first and second hydraulic cylinders. In this embodiment, the split cylinder energy recovery mode includes delivering fluid from a supply conduit to at least one second chamber of the first and second hydraulic cylinders.

  Preferred embodiments of the method also have at least one additional energy recovery mode. This additional energy recovery mode may include directing fluid from the first chambers of the first and second hydraulic cylinders to the second chambers of the first and second hydraulic cylinders.

  Another aspect of the present invention the feed conduit, return conduit, and either of two energy for use based on detecting the pressure at different locations, such hydraulic systems as in the first and second chambers of the hydraulic cylinders Determining a recovery mode.

  Several different modes are provided for reusing the fluid accumulated in the accumulator, and the accumulated fluid is directed to different chambers of the cylinder chamber.

  Although the present invention has been described in connection with use in an excavator, it can be implemented in other types of hydraulically operated devices.

  Referring first to FIG. 1, an excavator 10 includes a driver's seat 11 supported on a crawler (an endless track vehicle) and a boom assembly 12 attached to the driver's seat for vertical movement. The boom assembly 12 is subdivided into a boom 13, an arm 14, and a bucket 15 pivotally attached to each. The boom 13 coupled to the driver's seat 11 can pivot up and down when driven by a pair of hydraulic cylinder assemblies 16 and 17 mechanically connected in parallel between the driver's seat and the boom. In a typical excavator, the cylinders of these assemblies 16 and 17 are attached to the driver's seat 11, and when the piston rod is attached to the boom 13, the gravity acting on the boom tends to retract the piston rod into the cylinder. . Nevertheless, the cylinder assembly connection allows gravity to extend the piston rod from the cylinder, and many energy recovery techniques to be described can be used in this configuration. The arm 14 supported at the far end of the boom 13 can pivot forward and backward, and the bucket 15 is pivotally coupled to the tip of the arm. The other pair of cylinder assemblies 18 and 19 operate the arm 14 and bucket 15 independently. The bucket 15 can be replaced with another work head.

  Referring to FIG. 2, the cylinder assemblies 16, 17, 18 and 19 on the excavator 10 are part of a first hydraulic system 20 having a hydraulic fluid source 21 consisting of a first pump 22 and a tank 23. The first pump 22 draws fluid from the tank 23 and forcibly pumps the fluid through a check valve to a supply conduit 25 that supplies pressurized fluid to all hydraulic functions on the excavator. After being used to drive a hydraulic function, such as a function for raising and lowering the boom 13, the fluid returns to the tank 23 via a return conduit 26 where the fluid is pressurized by a spring loaded tank check valve 24. To do. The hydraulic system 10 drives several hydraulic function units on the excavator 10, but attention is paid to the boom function unit 30 in order to simplify the description of the energy recovery and reuse technique of the present invention.

  The boom function unit 30 raises and lowers the boom 13 by controlling the flow rate of the boom cylinder assemblies 16 and 17 each having a cylinder and a piston with a rod. The first boom cylinder assembly 16 has a first boom cylinder 31 having a slidingly received first piston 27 that divides the interior of the cylinder into a rod chamber 33 and a head chamber 34 opposite the piston. The second boom cylinder assembly 17 has a second boom cylinder 32 having a second piston 29 slidably received that divides the interior of the cylinder into another rod chamber 36 and a head chamber 38 opposite the piston. The volume of the rod and head chamber changes as the associated piston slides within the cylinder. In the example excavator 10 of FIG. 1, each boom cylinder 31 or 32 is attached to the driver's seat 11, and each piston 27 or 29 is attached to the boom 13 by a piston rod 35 or 37, respectively.

  The rod chambers 33 and 36 are directly connected together hydraulically. The bidirectional EHP cylinder separation control valve 39 is directly connected to the head chambers 34 and 38, preferably directly connected to each head chamber. Closing the cylinder separation control valve 39 separates the head chambers from each other, and opening the cylinder separation control valve provides a direct path between the two head chambers. Here, “control valve” is defined to mean a valve that is manually or electrically operated. As used herein, the term “direct connection” refers to a conduit without the use of intervening elements, such as valves, orifices, or other devices, where the associated component limits or controls the flow rate beyond the inherent limits of the conduit. Means that they are connected together. As used herein, a statement that a hydraulic component “directly connects” two other elements refers to the hydraulic component flowing through a control valve assembly or through a supply or return conduit through which fluid enters and exits other hydraulic functions. Without providing a path for fluid to flow between these two other elements. The statement that the control valve provides a “direct path” between two components or elements of the hydraulic system means that the path does not include other control valves.

  Control valve assembly 40 couples boom cylinder assemblies 16 and 17 to supply and return conduits 25 and 26 and controls the flow rate therebetween. As the control valve assembly 40 supplies pressurized fluid to the head chambers 34 and 38 in the boom cylinders 31 and 32 and drains fluid from the rod chambers 33 and 36, each piston rod 35 and 37 is extended from that cylinder, 13 is raised. Similarly, when pressurized hydraulic fluid is supplied from the supply conduit 25 to the rod chambers 33 and 36 and the fluid is discharged from the head chambers 34 and 38, the piston rods 35 and 37 are retracted to the boom cylinders 31 and 32 and the boom 13 is lowered. Let When commonly referred to as drive extension and drive retraction, the cylinder isolation control valve 39 opens and operates the two boom cylinder assemblies 16 and 17 in concert.

  The control valve assembly 40 consists of four electrohydraulic proportional (EHP) control valves 41, 42, 43 and 44 connected in a Wheatstone bridge configuration. As an alternative, solenoid operated spool valves can be used in place of the four EHP control valves 41-44. Preferably, each EHP control valve 41-44 is a pilot operated bi-directional control valve, such as the valve described in US Pat. No. 6,745,992, incorporating an anti-cavitation valve if necessary. The first EHP control valve 41 directs the flow rate of the hydraulic fluid from the supply conduit 25 to the first work port 46 connected to the node 51 between the head chamber 34 of the first cylinder 31 and the cylinder separation control valve 39 by the first actuator conduit 47. The head chamber 38 of the second boom cylinder 32 is connected to the first actuator conduit 47 and the head chamber 34 of the first cylinder 31 by the cylinder separation control valve 39, and the first work port 46 is separated from the head chamber 38 and the two head chambers. To do. The second EHP control valve 42 manages the flow rate between the first work port 46 and the return conduit 26. The third EHP control valve 43 controls the fluid path flowing between the cylinder rod chambers 33 and 36 connected to the second work port 48 by the supply conduit 25 and the second actuator conduit 49. A fourth EHP control valve 44 is connected between the rod chambers 33 and 36 and the return conduit 26.

  Similar to the cylinder separation control valve 39, the four EHP control valves 41-44 are solenoid operated independently by an electric signal from the system controller 50. By opening the first and fourth EHP control valves 41 and 44 together with the cylinder separation control valve 39, the pressurized fluid is added to the head chambers 34 and 38, the fluid is discharged from the rod chambers 33 and 36, and the piston rods 35 and 37 are moved. Extend and raise the boom 13. Similarly, when the second and third EHP control valves 42 and 43 are opened as in the cylinder separation control valve 39, the pressurized fluid is sent to the rod chambers 33 and 36, and the fluid is supplied to the head chamber 34 to retract the piston rods 35 and 37. 38, and the boom 13 is lowered.

  The system controller 50 is a microcomputer-based device in which a human operator receives control signals from several joysticks 52 that specify the desired operation of the hydraulic actuator on the excavator. System controller 50 receives signals from supply conduit pressure sensor 54 and return conduit pressure sensor 55. Separate pressure sensors 56 and 57 are provided for the cylinder head chambers 34 and 38 and another pressure sensor 58 measures the pressure in the rod chambers 33 and 36 of the boom cylinder assemblies 16 and 17. The rod chamber pressure sensor 58 is preferably located in the vicinity of the second workport 48 with the understanding that pressure measurements are affected by pressure loss in the second actuator conduit 49 to simplify electrical wiring. Pressure sensors 56, 57 and 58 for the cylinder chamber generate signals indicating the amount of force F acting on the boom 13. The system controller 50 responds to pressure measurements by operating the variable displacement first pump 22 to limit the pressure in the supply conduit 25 to satisfy the pressure requirements of different hydraulic actuators on the excavator.

  The first hydraulic system 20 includes several additional valves and other components that form a device that enables energy recovery and reuse for the boom function 30. Specifically, an accumulator 60 is provided for accumulating fluid collected from the boom cylinder assemblies 16 and 17. An additional pressure sensor 59 is located at the port 61 of the accumulator 60 and generates a signal to the system controller 50 indicating the pressure in the accumulator. The accumulator 60 is coupled to the head chamber 38 of the second boom cylinder assembly 17 by the bidirectional EHP recovery control valve 62 and is separated from the head chamber 34 of the first boom cylinder assembly 16. The electrohydraulic accumulator injection reuse control valve 66 provides a direct path between the supply conduit 25 and the port 61 of the accumulator 60. The electrohydraulic pump return control valve 68 connects the port of the accumulator 60 directly to the inlet of the first pump 22, and the relief control valve 70 connects the first node 64 directly to the tank return conduit 26 in the second cylinder head chamber 38. Connecting. The node 64 is separated from the head chamber 34 of the first cylinder 31 by the cylinder separation control valve 39. An EHP workport shunt control valve 65 provides a direct path between the first and second workports 46 and 48 and is preferably connected directly to each workport. All these additional control valves 39, 62, 65, 66, 68 and 70 are actuated by signals from the system controller 50.

  By selectively operating various combinations of these valves, fluid is routed to and from the boom cylinder assemblies 16 and 17, the first pump 22, the tank 23 and the accumulator 60. During the drop of the boom 13 due to gravity, the fluid discharged from the boom cylinder assembly can accumulate in the accumulator under pressure and is then used in place of the fluid from the first pump and is required to drive the pump. Accumulate energy. Different energy recovery modes resulting from the operation of the various valve combinations are described below.

  The recovery system of the present invention injects fluid directly from the first pump 22 into the accumulator 60 when the hydraulic function on the machine is not used or when the active hydraulic function requires only a relatively small amount of pump fluid. it can. At such times, the accumulator injection reuse control valve 66 opens and connects the supply conduit 25 directly to the port 61 of the accumulator 60. Pressure sensors 54 and 59 indicate when the pressure in the supply conduit is above the existing pressure in the accumulator 60 and an injection occurs.

  In another mode of reusing the accumulated energy, the pump return control valve 68 is opened, and the accumulated pressurized fluid is transferred from the accumulator 60 to the inlet of the first pump 22. This is particularly beneficial when the pump inlet has a high pressure inlet capability, this energy recovery even if the accumulator pressure is below the load pressure of the cylinder assemblies 16 and 17 and cannot be used to directly drive the cylinder assembly. The torque of the engine driving the first pump 22 is removed. In this case, only the first pump must use the torque from the engine to obtain a pressure difference between the load pressure of the accumulator 60 and the cylinder assembly.

  Still referring to FIG. 2, the first hydraulic system 20 also includes a swivel function 80 that bi-directionally rotates the excavator operator seat 11 and the boom assembly 12 relative to the crawler. The variable quantitative second pump 82 supplies the pressurized fluid to the swivel function unit 80 via the second supply conduit 83. A control valve assembly 84 similar to the control valve assembly 40 controls the flow rate of hydraulic fluid flowing from the second pump 82 to the motor 86 and from the motor to the tank 23. The motor 86 has two ports, and the valve assembly 84 selectively connects the second pump 82 to one port, and connects the other port to the tank. The direction of turning around the crawler 9 is determined.

  The two ports of the motor 86 are connected to the inlet of a shuttle valve 88 having an outlet connected to the outlet 61 of the accumulator 60 by a pressure operated valve 90. The pressure operated valve 90 opens when the pressure at the outflow portion of the shuttle valve 88 exceeds a predetermined level generated when the rotation of the driver's seat 11 stops. The pressurized fluid is then sent to the accumulator 60 instead of being sent to the tank 23 via the valve assembly 84. Therefore, the energy of the fluid discharged from the motor 86 at such time is stored in the accumulator 60.

  The accumulated fluid can be used by the boom function unit 30 as described above or can be used to drive the swing function motor 86. In order to accomplish the latter operation, the bi-directional electrohydraulic supply control valve 92 opens to deliver fluid from the accumulator 60 to the inlet of the valve assembly 84. This accumulator fluid is used in place of or as a trap for fluid from the second pump 82.

  By coupling the first and second boom cylinder assemblies 16 and 17 together, the load on these cylinders is evenly divided in the production system, but the degree of control freedom is lost. Greater efficiency is achieved by separating the head chambers 34 and 38 of the two boom cylinder assemblies 16 and 17 to minimize pressure compensation losses in the mechanical hydraulic system.

  FIG. 3 shows a modified second hydraulic system 96 that achieves greater degrees of freedom. The second hydraulic system 96 is similar to the first hydraulic system 20 of FIG. 2, and the same components are designated with the same reference numerals. The difference is replaced by a bi-directional electrohydraulic supply valve 98 in which the supply control valve 92 of the aforementioned system 20 provides a direct path between the second supply conduit 83 from the second pump and the head chamber 38 of the second boom cylinder 32. That is. Preferably, the supply control valve 98 is connected directly between the second supply conduit and the head chamber 38. This causes the boom to be raised using fluid from the first pump 22 to drive the first boom cylinder assembly 16 under the control of the control valve assembly 40, and the supply control valve 98 is moved from the second pump 82 to the second boom cylinder. Allows the flow of fluid into the assembly 17 to be controlled.

Example 1
It is assumed that the first pump 22 supplies fluid to the other hydraulic functions of the machine and is operating at 300 bar pressure to satisfy the maximum requirements of these functions. It is further assumed that yet another hydraulic function is connected to the second pump 82 operating at 200 bar pressure to satisfy the maximum flow requirement. It is further assumed that 250 bar pressure is required to increase the boom 13 load.

  In a conventional system, the first pump 22 remains at 300 bars and the extra 50 bars are “consumed” as pressure compensation losses. In this conventional system, the pressure of the second pump 82 rises to 250 bar, and the other hydraulic functions generate pressure compensation losses due to the greater pressure required by these functions.

  In the system shown in FIG. 3, the first pump 22 continues to operate at 300 bar and the second pump 82 continues to operate at 200 bar and thus at a combined average pressure of 250 bar. Each of these pumps supplies fluid to the boom cylinder assemblies 16 and 17, the first pump through the control valve assembly 40 and the second pump through the supply control valve 98. As a result, each cylinder assembly operates with a different amount of pressure, and thus a different pressure. Nevertheless, the net force acting on the boom 13 is similar to the conventional system.

Example 2
Assume that there is another hydraulic function connected to the first pump that has already consumed all the pump output flow. If raising of the boom 13 is commanded, the second pump 82 supplies all power to the boom through the supply control valve 98 and the second cylinder assembly 17, and the fluid in the head chamber 34 of the first cylinder 31 is controlled by the second EHP. It is discharged from the return conduit 26 via an anti-cavitation check valve in the valve 42.

  The functionality of Examples 1 and 2 is obtained by a third hydraulic system 100 that uses the solenoid operated spool valve shown in FIG. The hydraulic system 100 includes a boom function unit 102 in which the same components as those described above are identified with the same reference numerals. The head chambers 34 and 38 of the first and second cylinders 31 and 32 are hydraulically coupled by a bidirectional electrohydraulic cylinder separation control valve 39. The electrohydraulic shunt control valve 65 is connected between the rod of the first cylinder 31 and the port of the head chamber.

  The third hydraulic system 100 has a hydraulic fluid source 21 formed by first and second pumps 22 and 82 that draws fluid from the tank 23, and includes a boom function unit 102, a swivel function unit 80, and a machine not shown. Operate other functional units. The output of the first pump 22 supplies a first supply conduit 25 connected to the inlet of the three-position, four-way solenoid operated first spool valve 104 that constitutes the control valve assembly of the boom function unit. The outflow portion of the first spool valve 104 is connected to a return conduit 26 that leads to the tank 23. The first spool valve 104 has two work ports, that is, one work port 48 is directly connected to the rod chambers 33 and 36 of the two hydraulic cylinders, and the other work port 46 is connected to the head chamber 34 of the first hydraulic cylinder 31. Connected directly. The first relief valve 106 is connected between the first work port 46 and the return conduit 26.

  The outflow section of the second pump 82 supplies a second supply conduit 83 connected to a three-position four-way solenoid operated second spool valve 108 that forms a supply control valve. The outflow portion of the second spool valve 108 is connected to the return conduit 26. One of the second spool valves 108 is directly connected to the rod chambers 33 and 36 of the hydraulic cylinder, and the other work port has a pair of work ports directly connected to the head chamber 38 of the second hydraulic cylinder 32. A second relief valve 110 is coupled between the head chamber 38 and the return conduit 26. Two spool valves 104 and 108 deliver fluid from each of the two pumps 22 and 82 in approximately the same manner as the control valves 41-44 and 98 that function in the second hydraulic system 96 of FIG. Operates independently to supply cylinders 31 and 32.

  The third hydraulic system 100 also has an accumulator 112 connected to the head chamber 38 of the second cylinder 32 by a bidirectional electrohydraulic valve 114. This accumulator 112 can be used to store and reuse energy for the first and second hydraulic cylinders 31 and 32 in much the same manner as described for the accumulators in the hydraulic system of FIGS. .

Energy recovery The boom function operates in several modes, and in some modes energy is recovered from overload. An overload condition occurs in the exemplary excavator 10 when the load and weight of the boom assembly 12 affects the forces that tend to retract the piston rods 35 and 37 back into the boom cylinders 31 and 32, and the rod chambers 33 and 36. The fluid is forcibly discharged from the head chambers 34 and 38 without applying pressure to the head chamber 34. At that point, instead of sending the discharged fluid to tank 23, the fluid is directed into an accumulator 60 that accumulates the fluid under pressure. The energy recovery and reuse technique of the present invention includes operating the hydraulic circuit in several different energy recovery modes to lower the excavator boom 13. The selection of the specific energy recovery mode is based on the pressure in the head and rod chambers of the boom cylinders 31 and 32 and the existing pressure in the accumulator 60. The pressure relationship must allow the fluid to flow in the proper direction as described for each specific energy recovery mode, as described below. The accumulator pressure is indicated by pressure sensor 59, the pressure in head chambers 34 and 38 is measured by sensors 56 and 57, respectively, and the pressure in rod chambers 33 and 36 is measured by sensor 58.

  Some of the energy recovery modes are shown in FIGS. 5-9, which are simplified schematic diagrams of the second hydraulic system 96 of FIG. In these descriptions, the main fluid path is shown as a wide solid line, and the partial or selective flow path that occurs depending on the particular operating condition is shown as a bold dashed line. A thin solid line indicates a path through which fluid does not flow in the illustrated mode. This flow of conversion is utilized for the energy reuse mode shown in FIGS.

ここで、Ｐ_５９はセンサー５９から出力されたアキュムレータの圧力であり、Ｐ_５６はセンサー５６から出力された第１シリンダアセンブリ１６のヘッドチャンバー３４の圧力であり、Ｐ_５７はセンサー５７の圧力から第２シリンダアセンブリ１７のヘッドチャンバー３８の圧力であり、Ｐ_５８はセンサー５８から出力されたブームシリンダアセンブリ１６及び１７のロッドチャンバー３３及び３６内の圧力である（図３を参照）。Ｒはヘッドチャンバー３４及び３８とロッドチャンバー３３及び３６の面積比率である。シリンダ比率は下記方程式で与えられる。

ここで、ｒ_Ａはヘッドチャンバー３４及び３８の半径であり、ｒ_ＲＯＤはピストンロッド３５及び３７の半径であり、Ｒは油圧回路のために選択された選択シリンダアセンブリ１６及び１７の定数である。項（Ｐ_５６＋Ｐ_５７）／２Ｐ_５８／Ｒはデュアルシリンダエネルギー回収モード差分圧力と称される。さらに、上記不等式は摩擦及び他の要因による損失を含めるように変換できる。 Assume that the initial position of the boom assembly 12 is relatively high and has a relatively large amount of potential energy. As a result, the boom affects the forces acting on each cylinder assembly 16 and 17 that generate sufficient pressure in the head chambers 34 and 38 to inject the accumulator 60 shown in the dual cylinder energy recovery mode of FIG. Here, the pressure of the accumulator is below a threshold value given by the following inequality.

Here, P ₅₉ is the accumulator pressure output from the sensor 59, P ₅₆ is the pressure of the head chamber 34 of the first cylinder assembly 16 output from the sensor 56, and P ₅₇ is the first pressure from the pressure of the sensor 57. 2 is the pressure of the head chamber 38 of the cylinder assembly _{17, P 58} is the pressure in the rod chamber 33 and 36 of the boom cylinder assemblies 16 and 17 which are output from the sensor 58 (see Figure 3). R is an area ratio between the head chambers 34 and 38 and the rod chambers 33 and 36. The cylinder ratio is given by the following equation.

Where r _A is the radius of the head chambers 34 and 38, r _ROD is the radius of the piston rods 35 and 37, and R is the constant of the selected cylinder assembly 16 and 17 selected for the hydraulic circuit. The term (P ₅₆ + P ₅₇ ) / 2P ₅₈ / R is referred to as dual cylinder energy recovery mode differential pressure. In addition, the above inequality can be transformed to include losses due to friction and other factors.

この不等式の右辺はスプリットシリンダエネルギー回収モード差分圧力と称される。上記不等式は摩擦と他の要因による損失を含むように変更可能であることに留意すべきである。回収制御バルブ６２が開口しアキュムレータ３０を注入し続けると、第２ＥＨＰ制御バルブ４２はシリンダ分離制御バルブ３９が閉鎖するにつれて徐々に開く。この動作により、加圧流体は第２ＥＨＰ制御バルブ４２と第４ＥＨＰ制御バルブ４４内のキャビテーション防止バルブを介して第１ブームアセンブリ３１のヘッドチャンバー３４から両ブームアセンブリのロッドチャンバー３３及び３６に送られる。シリンダ分離制御バルブ３９を閉じることにより、２つのブームシリンダ３１及び３２が互いに分離し、２つのヘッドチャンバー３４及び３８を初期均等圧力状態からこれらのチャンバーが異なる圧力を有し異なる力を及ぼす状態に移行する。スプリットシリンダエネルギー回収モード１２２において、ブームからの力は第２シリンダアセンブリ１７のみにより支持され、第２シリンダ３２のヘッドチャンバー３８の圧力はブームの力が図５に示されるデュアルシリンダエネルギー回収モード１２１でのシリンダアセンブリ１６及び１７により支持された場合に較べてアキュムレータを注入するためのより高い圧力を有する。 In the dual cylinder energy recovery mode 121, the fluid discharged from the head chambers 34 and 38 is mixed by the opening cylinder separation control valve 39, flows through the opening recovery control valve 62, and is injected into the accumulator 60. The collection control valve 62 is adjusted to proportionally control the boom speed. The fluid required to fill the rod chambers 33 and 36 that extend as the boom descends is withdrawn through the control valve assembly 40. Specifically, fluid from other functional parts of the machine is drawn from the return conduit 26 to the fourth EHP control valve 44 via an anti-cavitation check valve. While gravity is descending the boom, the fluid drawn from the return conduit 26 need not be at high pressure. If this anti-cavitation flow is insufficient, the third EHP control valve 43 can be opened to supply fluid from the first pump 22 to the rod chambers 33 and 36. The force acting on the two cylinder assemblies 16 and 17 due to the lowering of the boom 13 reaches a position where sufficient pressure is not generated in the two head chambers to continue injecting the accumulator 60. If the accumulator pressure is below the threshold given by the following inequality, the energy recovery change to split cylinder energy recovery mode 122 shown in FIG. 6 will cause the pressure in one cylinder head chamber to inject the accumulator. Strengthen.

The right side of this inequality is called the split cylinder energy recovery mode differential pressure. It should be noted that the above inequality can be modified to include losses due to friction and other factors. As the collection control valve 62 opens and continues to inject the accumulator 30, the second EHP control valve 42 gradually opens as the cylinder separation control valve 39 closes. By this operation, the pressurized fluid is sent from the head chamber 34 of the first boom assembly 31 to the rod chambers 33 and 36 of both boom assemblies via the cavitation prevention valve in the second EHP control valve 42 and the fourth EHP control valve 44. By closing the cylinder separation control valve 39, the two boom cylinders 31 and 32 are separated from each other, and the two head chambers 34 and 38 are moved from the initial equal pressure state to a state where these chambers have different pressures and different forces. Transition. In the split cylinder energy recovery mode 122, the force from the boom is supported only by the second cylinder assembly 17, and the pressure in the head chamber 38 of the second cylinder 32 is the dual cylinder energy recovery mode 121 shown in FIG. Having a higher pressure for injecting the accumulator compared to that supported by the cylinder assemblies 16 and 17 of the present invention.

  The head chamber 38 of the second cylinder 32 generates a sufficiently high pressure to continue the accumulator 60 injection. The fluid from the head chamber 38 is directed to the accumulator 60 via the recovery control valve 62. During the split cylinder energy recovery mode 122, the recovery control valve 62 and the second EHP control valve 42 are adjusted to control the speed at which the boom 13 continues to descend.

  In the split cylinder energy recovery mode 122, if the head chamber fluid amount is insufficient to fill the rod chambers 33 and 36, the third EHP control valve 43 opens and can supply supplementary fluid from the first pump 22. it can. The supplemental fluid need not be a unique pressure as used to fill the expanding rod chamber, not to drive the cylinder assemblies 16 and 17. On the other hand, if the head chamber 34 of the first cylinder 31 contains more fluid than is needed to fill the rod chambers 33 and 36, as occurs with a large diameter piston rod, the excess fluid is subject to the second EHP control. It is possible to route the return conduit 26 by selectively opening the valve 42.

この不等式の右辺は疑似スプリットシリンダエネルギー回収差分圧力と称される。上記不等式は摩擦及び他の要因による損失を含むように変更できることに留意すべきである。 Since the flow rate from each head chamber 34 and 38 is controlled separately in the split cylinder energy recovery mode 122, the force on each side of the boom 13 may cause the torsional action to be uneven. In order to avoid this state, the pseudo split cylinder energy recovery mode 123 shown in FIG. 7 can be adopted. This mode can be selected directly from the dual cylinder energy recovery mode (FIG. 5) when the accumulator pressure falls below a threshold given by the following equation:

The right side of this inequality is referred to as the pseudo split cylinder energy recovery differential pressure. It should be noted that the above inequality can be modified to include losses due to friction and other factors.

  In this mode, the cylinder separation control valve 39 remains open to allow the pressure between the two head chambers 34 and 38 to communicate. The EHP workport shunt control valve 65 opens to send pressurized fluid from the head chamber 34 of the first boom cylinder 31 to the rod chambers 33 and 36.

  In a typical excavator, the boom cylinder assemblies 16 and 17 have large diameter piston rods 35 and 37 so that as the piston moves, the volume of each rod chamber 33 and 36 is, for example, half the change in volume of each head chamber. To change. That is, in the pseudo split cylinder energy mode 123, the flow rate discharged from the first cylinder head chamber 34 is sufficient to fill the expanding rod chambers 33 and 36. Thus, no fluid will flow to the open cylinder isolation control valve 39, but if one or two volume relationships do not exist, the additional fluid needed to fill the rod chambers 33 and 36 will be in the second cylinder head chamber. Flows from 38 through a cylinder separation control valve. Nevertheless, most (not all) of the fluid in the head chamber 38 of the second cylinder 32 flows to the accumulator 60.

ブーム動作は図８に示されるクロスチャンバーエネルギー回収モード１２４に変化する。この不等式の左辺はクロスチャンバーエネルギー回収モード差分圧力と称される。上記不等式を摩擦及び他の要因による損失を含むように変更できることを留意すべきである。クロスチャンバーエネルギー回収モード１２４において、回収制御バルブ６２は典型的にはアキュムレータ６０内の比較的高い圧力を保存するために閉じられる。それにもかかわらず、第２ブームシリンダ３２のヘッドチャンバー３８内に充分な残留圧力があり、圧力センサー５７及び５９（図３）により示されるようにアキュムレータを注入し続け、回収制御バルブ６２はこのモードで部分的に開く。どちらの場合でも、シリンダ分離制御バルブ３９はワークポートシャント制御バルブ６５と共に開くので、両ヘッドチャンバー３４及び３８からのいくらかの流体が送られ、伸張するロッドチャンバー３３及び３６を満たす。ヘッドチャンバーから排出する流体の総量はロッドチャンバーを満たすのに必要以上であるので、第２ＥＨＰ制御バルブ４２が開き、過剰流体を戻り導管２６に且つタンク２３に送る。 When the operation of split cylinder energy recovery mode 122 or 123 reaches the point where there is no sufficient pressure available from the head chamber 38 of the second cylinder 32 to inject the accumulator, but when it is above zero as given by the following equation: ,

The boom operation changes to the cross chamber energy recovery mode 124 shown in FIG. The left side of this inequality is referred to as the cross chamber energy recovery mode differential pressure. It should be noted that the above inequality can be modified to include losses due to friction and other factors. In the cross chamber energy recovery mode 124, the recovery control valve 62 is typically closed to store a relatively high pressure in the accumulator 60. Nevertheless, there is sufficient residual pressure in the head chamber 38 of the second boom cylinder 32 and it continues to inject the accumulator as indicated by pressure sensors 57 and 59 (FIG. 3) and the recovery control valve 62 is in this mode. Partially open with. In either case, the cylinder isolation control valve 39 opens with the workport shunt control valve 65 so that some fluid from both head chambers 34 and 38 is sent to fill the expanding rod chambers 33 and 36. Since the total amount of fluid draining from the head chamber is more than necessary to fill the rod chamber, the second EHP control valve 42 opens and sends excess fluid to the return conduit 26 and to the tank 23.

  It should be noted that the energy recovery modes 121, 122, 123 and 124 need not follow the above procedure. One of the energy recovery modes 121, 122, 123, and 124 should be selected based on the recovery efficiency benefits that each mode provides at a given time. Accordingly, any energy recovery mode is shifted to any other energy recovery mode, and an appropriate selection is made by the system controller 50 based on the equations provided herein.

  In the cross chamber energy recovery mode 124, the accumulator reaches its maximum storage capacity. Furthermore, as the cylinder separation control valve 39 opens, the pressure in the two head chambers 34 and 38 begins to equalize again. Although the preferred embodiment incorporates a workport shunt control valve 65, this valve is eliminated as a cost reduction measure if the split cylinder energy recovery mode 123 is not used. In that case, when the workport shunt control valve is opened, the control valve assembly 40 operates by opening the second and fourth EHP control valves 42 and 44, together with the opening of the isolation valve 39, the valve pair between the two workports 46 and 48. Carry fluid through one of the sides.

  Eventually, the boom 13 reaches a low position where the force due to gravity itself is insufficient and the boom lowering cannot be continued fast enough for the effective operation of the excavator. The pressure from the pump is necessary to further lower the boom. At this point, the operation transitions to the drive energy mode 125 shown in FIG. The third EHP control valve 43 is opened to apply pressurized fluid from the first pump 22 to the rod chambers 33 and 36 of both boom cylinders 31 and 32. The pressurized fluid advances the piston to further retract the piston rod and drives the boom 13 downward. At this time, the fluid discharged from the head chambers 34 and 38 is conveyed into the return conduit 26 by the opened cylinder separation control valve 39 and the second EHP control valve 42. Second and third EHP control valves 42 and 43 are adjusted to control the speed of the boom.

  The position of the boom 13 and arm 14 of the excavator 10 affects the amount of force that acts on the amount of energy that the boom can recover according to the cylinder assemblies 16 and 17. The amount of force corresponds to the cylinder chamber pressure measured by sensors 56, 57 and 58. Thus, the signal from these sensors along with the accumulator pressure sensor 59 determines that the system controller 50 can implement any of the energy recovery modes and which energy recovery mode can recover the most energy. to enable.

Energy reuse When the piston rod is extended from the boom cylinder 31 and the boom 13 is raised against the load force F acting downward, the fluid is used instead of using the pressurized fluid from the first pump 22. Or can be reused from the accumulator 60. In the first energy reuse mode 131 shown in FIG. 10, the fluid accumulated in the accumulator 60 is supplied to the cylinder head chambers 34 and 38 via the opening recovery control valve 62 and the cylinder separation control valve 39. The fluid discharged from the rod chambers 33 and 36 flows into the return conduit 26 through the open fourth EHP control valve 44.

  It should be understood that the accumulator 60 is often not injected at a pressure level sufficient to drive the cylinder assemblies 16 and 17. Further, the flow rate accumulated in the accumulator is not sufficient to fill the head chambers 34 and 38. In such an example, the second energy reuse mode 132 shown in FIG. 11 in which the recovery control valve 62 is opened and at the same time the cylinder separation control valve 39 is closed is performed. As a result, the fluid from the accumulator 60 is directed only to the head chamber 38 of the second cylinder 32. The recovery control valve 62 is typically fully open to eliminate flow measurement loss from the accumulator. The head chamber 34 of the first cylinder 31 receives pressurized fluid from the first pump 22 via the first EHP control valve 41. In this way, the first cylinder 31 is driven by the pump fluid, and the second cylinder 32 is driven by the fluid from the accumulator. The first EHP control valve 41 and the recovery control valve 62 are adjusted to control the boom raising speed. During adjustment, the fluid discharged from the two rod chambers 33 and 36 is returned to the return conduit 26 via the open fourth EHP control valve 44.

  The second pump 82 is connected to the port of the head chamber 34 for the first boom cylinder 31 by a second supply valve 99, and in either case, pressurized fluid from the second pump is supplied to the head chamber, The fluid from the pump 22 can be increased. In order to achieve this operation, the second supply valve 99 measures the flow rate to the head chamber 34 for the first boom cylinder 31, and at the same time, the first EHP control valve 41 is used to measure the flow rate.

  Eventually, the fluid from the accumulator 60 is drastically reduced and can no longer be used to drive the second cylinder 32. At that point, the hydraulic system operation enters a third energy reuse mode 133 shown in FIG. 12, where the fluid from the second pump 82 is used instead of or as a supplement to the fluid from the accumulator 60. This action is accomplished by opening the supply control valve 98 to direct fluid from the second pump 82 to the head chamber 38 of the second cylinder 32. The head chamber 34 of the first cylinder 31 continues to receive fluid from the first pump 22 via the control valve assembly 40 and the fluid discharged from the rod chambers 33 and 36 is also returned to the return conduit 26 via the control valve assembly. To be supplied. In the third energy reuse mode 133, the first EHP control valve 41 and the supply control valve 98 are adjusted to control the ascending speed of the boom 13.

  FIG. 13 shows a fourth energy reuse mode 134 in which the outputs of the first and second pumps 22 and 82 are coupled by a cylinder separation control valve 39 and flow into the head chambers 34 and 38. In the fourth energy reuse mode 134, fluid from the first pump 22 is sent by the first EHP control valve 41 to the head chambers 34 and 38, while the supply control valve 98 simultaneously delivers fluid from the second pump 82 to these same chambers. Send to. Some fluid flows from the accumulator 60 depending on the internal pressure level. The fluid discharged from the rod chambers 33 and 36 flows into the return conduit 26 through the open fourth EHP control valve 44.

  FIG. 14 illustrates a fifth energy reuse mode 135 in which fluid from only the first pump drives the head chambers 34 and 38 of the hydraulic cylinder assemblies 16 and 17. The second pump 82 does not supply the boom function unit 30 in this mode. The first EHP control valve 41 controls the flow rate from the first pump 22 to the head chambers 34 and 38 and the boom raising speed. The fourth EHP control valve 44 controls the flow rate from the rod chambers 33 and 36 to the return conduit 26.

  In the first to fifth energy reuse modes 131 to 135, the force acting on the boom 13 tends to lower the boom. In other operating states of the excavator 10, external forces tend to raise the boom 13. For example, referring to FIG. 1, the boom assembly 12 is fully extended from the excavator driver's seat 11 to the farthest reaching point, and the arm cylinder assembly 18 is driven to retract the bucket toward the driver's seat to dig the ground. Assuming that This resistance to excavation action applies an upward force that raises the boom without applying pressurized fluid from the pump 22 or 28 to the boom cylinder assemblies 16 and 17.

  While this upward force is acting on the boom 13, a portion of the hydraulic system for the boom cylinder assemblies 16 and 17 can be configured as shown in FIG. In this sixth reuse mode 136, the force acting on the boom 13 further extends the piston rod from the cylinders 31 and 32 that forces fluid from the rod chambers 33 and 36 to the second workport 48 of the control valve assembly 40. . The fourth EHP control valve 44 opens to control the boom to the desired speed and feeds the exhaust fluid into the return conduit 26. However, the expanding head chambers 34 and 38 generate a low pressure at the first work port 46 that opens the anti-cavitation valve in the second EHP control valve 42 and sends pressurized fluid from the return node to the first work port 46. This fluid continues to flow from the first work port 46 to the head chambers 34 and 38 via the currently open cylinder isolation control valve 39. Since the combined capacity of the head chambers 34 and 38 is larger than the two rod chambers 33 and 36, additional fluid is required to fill the head chamber. This additional fluid is drawn from the return conduit 26 into the control valve assembly 40, or if insufficient pressure is not present in that conduit as indicated by the pressure sensor 55, the first EHP control valve 41 opens and the second conduit is opened. A fluid is supplied from one pump 22. Since the fluid from the first pump does not drive the cylinder, it does not need to be delivered at a specific pressure, it simply fills the expanding chamber.

  Although the hydraulic system has been described as including a cylinder isolation control valve 39, as described above, the advantages of the present invention regarding the recovery and reuse of energy in the accumulator can also be achieved without the use of this valve. Here, the head chamber 34 of the first cylinder assembly 16 and the head chamber 38 of the second cylinder assembly 17 are coupled together so as to be in fluid communication without being coupled to the cylinder separation control valve 39. When overpressure is applied to the accumulator during the recovery operation, the circuit thus configured operates as described above in connection with FIGS. 5, 7, 8 and 9, and as described above. It operates through the modes of FIG. 5, FIG. 7, FIG. 8 and FIG. During reuse, referring to FIG. 2, fluid flows through the port 61 from the accumulator 60 to an injection reuse control valve 66 that opens to the supply conduit 25. The first pump 22 provides additional fluid to the supply conduit 25 in this reuse mode. Although two cylinders 16 and 17 are shown, a single cylinder can be used if the cylinder isolation valve 39 is removed. A single pressure sensor 56 or 57 can be used regardless of whether one or two cylinders are used.

  The above description has been primarily directed to a preferred embodiment of the present invention. While various variations are noted within the scope of the present invention, it is anticipated that those skilled in the art will realize additional variations that will be apparent from the disclosure of the embodiments of the present invention.

FIG. 1 is a perspective view showing an excavator incorporating a hydraulic system according to the present invention. FIG. 2 is a schematic view showing a portion of a hydraulic system for operating an actuator for raising and lowering a boom of an excavator. FIG. 3 is a schematic diagram showing an alternative part of a boom hydraulic system. FIG. 4 is a schematic diagram showing another alternative part of the boom hydraulic system. FIG. 5 is a simplified schematic diagram illustrating an alternative portion of the hydraulic system of FIG. 3 in different energy recovery modes. FIG. 6 is a simplified schematic diagram illustrating an alternative portion of the hydraulic system of FIG. 3 in different energy recovery modes. FIG. 7 is a simplified schematic diagram illustrating an alternative portion of the hydraulic system of FIG. 3 in different energy recovery modes. FIG. 8 is a simplified schematic diagram illustrating an alternative portion of the hydraulic system of FIG. 3 in different energy recovery modes. FIG. 9 is a simplified schematic diagram illustrating an alternative portion of the hydraulic system of FIG. 3 in different energy recovery modes. FIG. 10 is a simplified schematic diagram of an alternative portion of the hydraulic system of FIG. 3 in various recovered energy reuse modes. FIG. 11 is a simplified schematic diagram of an alternative portion of the hydraulic system of FIG. 3 in various recovered energy reuse modes. FIG. 12 is a simplified schematic diagram of an alternative portion of the hydraulic system of FIG. 3 in various recovered energy reuse modes. FIG. 13 is a simplified schematic diagram of an alternative portion of the hydraulic system of FIG. 3 in various recovered energy reuse modes. 14 is a simplified schematic diagram of an alternative portion of the hydraulic system of FIG. 3 in various recovered energy reuse modes. FIG. 15 is a simplified schematic diagram of an alternative portion of the hydraulic system of FIG. 3 in various recovered energy reuse modes.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Excavator 11 Driver's seat 12 Boom assembly 13 Boom 14 Arm 15 Buckets 16, 17, 18, 19 Hydraulic cylinder assembly 20 Hydraulic system 21 Hydraulic fluid source 22 Pump 23 Tank 25 Supply conduit 26 Return conduit 29 Piston 30 Functional parts 31, 32 Boom cylinder 33, 36 Rod chamber 34, 38 Head chamber 35, 37 Piston rod 39 EHP cylinder separation control valve 40 Control valve assembly 41, 42, 43, 44 Electrohydraulic proportional (EHP) control valve 46 Workport 49 Actuator conduit 50 System control Device 52 Joystick 54, 55, 56, 57, 58, 59 Pressure sensor 60 Accumulator

Claims (26)

Hydraulic pressure including a supply conduit, a return conduit, an accumulator, and first and second hydraulic cylinders mechanically connected in parallel to operate components on the machine, each having first and second chambers In an energy recovery method for a system,
Sending fluid from the first chamber of the second hydraulic cylinder to the accumulator only, and sending fluid from the first chamber of the first hydraulic cylinder to the second chambers of the first and second hydraulic cylinders. Split cylinder energy recovery mode;
Then reusing the fluid in the accumulator to drive at least one of the first hydraulic cylinder and the second hydraulic cylinder;
An energy recovery method comprising:   2. The energy recovery method of claim 1, wherein the split cylinder energy recovery mode further comprises the step of sending fluid from the supply conduit to the second chambers of the first and second hydraulic cylinders.   2. The energy recovery method according to claim 1, further comprising the step of selectively providing a path for fluid communication between the first chambers of the first and second hydraulic cylinders in the split cylinder energy recovery mode. . In order to fill the second chamber, comprising a cross-chamber recovery mode having a step of sending fluid from the first chamber of the first and second hydraulic cylinders to the second chamber of the first and second hydraulic cylinders 2. The energy recovery method according to claim 1, wherein an excess fluid amount greater than a required amount is sent to one of the accumulator and the return conduit.   The change from the split cylinder energy recovery mode to the cross chamber recovery mode is that the fluid from the first chamber of the second hydraulic cylinder no longer gives enough energy to inject the accumulator and the cross chamber energy recovery mode difference The energy recovery method according to claim 4, which occurs when the pressure is zero or more. A dual cylinder energy recovery mode comprising the steps of sending fluid from the first chambers of the first and second hydraulic cylinders to the accumulator and directing fluid to the second chambers of the first and second hydraulic cylinders; The energy recovery method according to claim 4, further comprising: Directing fluid to the second chamber in the dual cylinder energy recovery mode directing fluid from one of the supply conduit and the return conduit to the second chamber of the first and second hydraulic cylinders. The energy recovery method according to claim 6, further comprising:   A change from the dual cylinder energy recovery mode to at least one of the split cylinder energy recovery mode, pseudo split energy recovery mode, and cross chamber energy recovery mode is split cylinder energy recovery mode differential pressure, pseudo split energy recovery mode differential pressure, 6. The energy recovery method according to claim 5, wherein the energy recovery method is generated in response to an accumulator pressure equal to or lower than a pressure corresponding to the differential pressure in the cross chamber energy recovery mode.   The pressure of the accumulator is not more than at least two of the split cylinder energy recovery mode differential pressure, the pseudo split energy recovery mode differential pressure, and the cross chamber energy recovery mode differential pressure, and the change is a maximum efficiency for recovery. 9. The energy recovery method of claim 8, wherein the energy recovery method occurs in one of the split cylinder energy recovery mode, the pseudo split energy recovery mode, and the cross chamber energy recovery mode that provides a mode.   The step of reusing the fluid in the accumulator includes a first energy reuse mode comprising a step of sending fluid from the accumulator to the first chambers of the first and second hydraulic cylinders, and fluid from the accumulator to the second. At least one of a second energy reuse mode comprising a step of sending only the hydraulic cylinder to the first chamber and a step of sending fluid from the supply line to the first chamber of the first hydraulic cylinder. The energy recovery method according to claim 1. And further comprising a step of sending the return conduit at least one of fluid from said second chamber before Symbol first and second hydraulic cylinders of the first energy reuse mode and the second energy reuse mode The energy recovery method according to claim 10.   A first pump is connected to the supply line, further fluid is sent from the supply line to the first chamber of the first hydraulic cylinder, and fluid is supplied from at least one of the accumulator and second pump to the second hydraulic pressure. The energy recovery method according to claim 10, comprising a mode in which the cylinder is sent to the first chamber of the cylinder. Hydraulic pressure including a supply conduit, a return conduit, an accumulator, and first and second hydraulic cylinders mechanically connected in parallel to operate components on the machine, each having first and second chambers In an energy recovery method for a system,
A dual chamber energy recovery mode comprising the steps of sending fluid from the first chambers of the first and second hydraulic cylinders only to the accumulator and sending fluid to the second chambers of the first and second hydraulic cylinders;
Sending fluid from the first chamber of the second hydraulic cylinder to the accumulator and sending fluid from the first chamber of the first hydraulic cylinder to the second chambers of the first and second hydraulic cylinders. Split cylinder energy recovery mode;
Reusing fluid in the accumulator to drive at least one of the first hydraulic cylinder and the second hydraulic cylinder;
An energy recovery method comprising:   14. The energy recovery method according to claim 13, wherein the split cylinder energy recovery mode further comprises a step of sending fluid from the supply line to the second chambers of the first and second hydraulic cylinders.   14. The split cylinder energy recovery mode further comprises opening a valve to provide a path for fluid to flow between the first chambers of the first and second hydraulic cylinders. Energy recovery method.   Sending fluid to the second chamber in the dual cylinder energy recovery mode comprises sending fluid from one of the supply conduit and the return conduit to the second chamber of the first and second hydraulic cylinders. The energy recovery method according to claim 13.   In order to fill the second chamber, further comprising a cross chamber recovery mode comprising a step of sending fluid from the first chamber of the first and second hydraulic cylinders to the second chamber of the first and second hydraulic cylinders The energy recovery method according to claim 16, wherein an excessive flow rate exceeding that required for the gas is sent to one of the accumulator and the feed conduit.   Reusing the fluid in the accumulator; a first energy reuse mode comprising sending fluid from the accumulator to the first chambers of the first and second hydraulic cylinders; and fluid from the accumulator to the second At least one of a second energy reuse mode comprising a step of sending only the hydraulic chamber to the first chamber and a step of sending fluid from the supply line to the first chamber of the first hydraulic cylinder. The energy recovery method according to claim 13. And characterized by including the step of sending to said return conduit from the second chamber of the front Symbol at least one further fluid in the first energy reuse mode and the second energy reuse mode the first and second hydraulic cylinders The energy recovery method according to claim 13.   A first pump is connected to the supply line, further fluid is sent from the supply line to the first chamber of the first hydraulic cylinder and fluid is sent from the accumulator and second pump to the first of the second hydraulic chamber. The energy recovery method according to claim 13, further comprising a mode to be sent to the chamber. Hydraulic pressure including a supply conduit, a return conduit, an accumulator, and first and second hydraulic cylinders mechanically connected in parallel to operate components on the machine, each having first and second chambers In an energy recovery method for a system,
Sending fluid from the first chamber of the second hydraulic cylinder to the accumulator only and sending fluid from the first chamber of the first hydraulic cylinder to the second chamber of at least one of the first and second hydraulic cylinders. Split cylinder energy recovery mode consisting of processes;
A cross chamber recovery mode comprising the step of sending fluid from the first chambers of the first and second hydraulic cylinders to the second chambers of the first and second hydraulic cylinders;
Reusing fluid in the accumulator to drive at least one of the first cylinder and the second cylinder;
An energy recovery method comprising:   22. The energy recovery method of claim 21, wherein the split cylinder energy recovery mode further comprises the step of sending fluid from the supply conduit to the second chambers of the first and second hydraulic cylinders.   The energy recovery method of claim 21, wherein the split cylinder energy recovery mode further comprises selectively providing a path for fluid to flow between the first chambers of the first and second hydraulic cylinders. .   Directing fluid from the first chambers of the first and second hydraulic cylinders to the accumulator; and directing fluid to the second chambers of the first and second hydraulic cylinders. The energy recovery method according to claim 22, wherein   The step of reusing the fluid in the accumulator includes a first energy reuse mode comprising a step of sending fluid from the accumulator to the first chambers of the first and second hydraulic cylinders, and fluid from the accumulator to the second. At least one of a second energy reuse mode comprising a step of sending only the hydraulic cylinder to the first chamber and a step of sending fluid from the supply line to the first chamber of the first hydraulic cylinder. The energy recovery method according to claim 22.   A first pump is connected to the supply line, fluid is sent from the supply line to the first chamber of the first hydraulic cylinder, and fluid is fed from at least one of the accumulator and second pump to the second hydraulic cylinder. The energy recovery method according to claim 22, further comprising a mode sent to the first chamber.

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