Energy recovery device

Abstract

An energy recovery device according to one embodiment of the present invention is an energy recovery device installed in a construction machine comprising a tank, at least one hydraulic working device, at least one cylinder equipped with a large chamber and a small chamber for operating the working device, and an assist hydraulic motor for recovering and reusing the potential energy of oil discharged from the cylinder, wherein the large chamber, the small chamber, and the tank are connected to communicate with each other, and at least one control valve is provided to perform an energy recovery function, and an energy recovery hydraulic circuit is configured to operate such that oil discharged from the large chamber is supplied to an accumulator, pressurized, and then reused; wherein the control valve comprises: a tapered seat portion formed between an inlet side flow path and an outlet side flow path; a valve body formed on one side having an annular valve portion that selectively sits on the seat portion and a tubular protrusion protruding toward the outlet side flow path, and a control pressure chamber formed on the other side to supply control pressure from the outside for variably controlling the amount of raising and lowering of the valve body. It includes a valve spring provided within the control pressure chamber and pressurizing the valve body toward the seat portion in a closing direction.

Description

Technology Field

[0001] The present invention relates to an energy recovery device, and more specifically, to an energy recovery device capable of recovering potential energy of oil from a cylinder for operating a hydraulic work device equipped in a construction machine such as an excavator, storing it in an accumulator, and then reusing it. Background Technology

[0002] FIG. 1 is a general hydraulic excavator, wherein the hydraulic excavator comprises a lower driving body (1), an upper swivel body (2) swivelly mounted on the upper part of the lower driving body (1), and a work attachment (9) as a work device mounted on the upper swivel body (2).

[0003] The above work attachment (9) includes a boom (3), an arm (4), a bucket (5), and a boom cylinder (6), an arm cylinder (7), and a bucket cylinder (8) that operate them, respectively.

[0004] The above hydraulic excavator further includes left and right driving motors that drive the left and right driving means of the lower driving body (1) and a turning motor that drives the upper turning body (2) to turn.

[0005] The above hydraulic excavator is configured to include a plurality of hydraulic pumps, and the oil supplied from the plurality of hydraulic pumps is supplied to the boom cylinder (6), arm cylinder (7) and bucket cylinder (8), left and right driving motors and upper slewing body (2), etc., to enable operation.

[0006] A hydraulic excavator with the configuration described above consumes a lot of fuel to drive the boom because the boom has a heavy self-weight.

[0007] Meanwhile, with the rise of eco-friendly issues, various technological developments and research aimed at improving fuel efficiency are being conducted in the construction machinery sector, including hydraulic excavators.

[0008] For example, a technology has been proposed in which, when the boom of a hydraulic excavator is lowered, the boom's potential energy (e.g., potential energy) is recovered and temporarily stored, and then used for raising the boom or other operations.

[0009] However, these conventional technologies require the essential control of a very complex hydraulic circuit associated with the working motion of the boom, and as a result, there were difficulties in designing the hydraulic circuit and implementing the control algorithm.

[0010] (Prior Art) Korean Published Patent No. 10-2003-0084202 (Publication Date: Nov. 1, 2003) The problem to be solved

[0011] The objective of the present invention, which is to solve the problems according to the prior art described above, is to provide an energy recovery device capable of recovering potential energy of oil from a cylinder for operating a hydraulic work device equipped in a construction machine such as an excavator, storing it in an accumulator, and then reusing it. means of solving the problem

[0012] The energy recovery device of the present invention for solving the above technical problem comprises: a tank; at least one hydraulic working device; at least one cylinder equipped with a large chamber and a small chamber for operating the working device; and an assist hydraulic motor for recovering and reusing the potential energy of oil discharged from the cylinder; wherein the energy recovery hydraulic circuit is configured to operate such that the large chamber, the small chamber, and the tank are connected to communicate with each other, and at least one control valve is provided to perform an energy recovery function, and the oil discharged from the large chamber is supplied to an accumulator, pressurized, and then reused; wherein the control valve comprises: a tapered seat portion formed between an inlet side flow path and an outlet side flow path; a valve body formed on one side having an annular valve portion that selectively sits on the seat portion and a tubular protrusion protruding toward the outlet side flow path, and a control pressure chamber formed on the other side to supply control pressure from the outside for variably controlling the raising and lowering amount of the valve body. It includes a valve spring provided within the control pressure chamber and pressurizing the valve body toward the seat portion in a closing direction.

[0013] Preferably, a pair of first notch grooves having a first cross-sectional shape and a pair of second notch grooves having a second cross-sectional shape are formed at the end of the valve body, and the first notch grooves are formed to face each other symmetrically, and the second notch grooves can also be formed to face each other symmetrically.

[0014] Preferably, the control valve comprises: a cylindrical variable block having a plurality of through holes penetrating the inner surface of the tubular protrusion and the control pressure chamber, wherein the through hole comprises a first through hole having a first diameter and a second through hole having a diameter smaller than the first diameter and having a nut portion formed inside; a plurality of through holes penetrating the upper and lower surfaces, and a cylindrical variable block having a variable upper position to adjust the opening area of ​​the first notch groove and the second notch groove; and a plunger shaft having a lower portion connected to the upper portion of the cylindrical variable block, an upper portion extending to penetrate the first through hole and the second through hole and positioned in the control pressure chamber, having a screw thread formed on the upper outer surface to be fastened to the nut portion of the second through hole, and having an annular sealing portion formed on the lower outer surface corresponding to the inner diameter of the first through hole, and an O-ring provided between the annular sealing portion and the inner diameter of the first through hole. The apparatus further comprises a position fixing nut assembled to the threads of the plunger shaft inside the control pressure chamber to fix the position of the plunger shaft; and as the plunger shaft is rotated relative to the nut portion, the plunger shaft moves up and down, and the cylindrical variable block linked to the plunger shaft changes its up and down position, thereby allowing the opening area of ​​the first notch groove and the second notch groove to be adjusted.

[0015] Preferably, the system may further include a pressure-compensating flow stabilizing valve installed on the inlet side of the control valve and controlling the flow rate flowing to the outlet side of the control valve to be maintained in correspondence with the opening amount of the control valve by maintaining a constant pressure difference between the inlet side and the outlet side of the control valve.

[0016] Preferably, the control valve includes an LA control valve provided between the large chamber and the accumulator to allow or block oil flow from the large chamber to the accumulator, and the pressure-compensating flow stabilizing valve may be installed on the inlet side of the LA control valve.

[0017] Preferably, the hydraulic circuit for energy recovery comprises: a first line connecting the large chamber and the tank; an LT control valve provided on the first line to allow or block oil flow from the large chamber to the tank through the first line; a second line branched from the first line corresponding between the large chamber and the LT control valve and connected to the small chamber; and an LS control valve provided on the second line to allow or block oil flow from the first line to the small chamber; wherein the pressure-compensating flow stabilizing valve may be additionally installed on the inlet side of either or both of the LT control valve and the LS control valve.

[0018] Preferably, the hydraulic circuit for energy recovery is configured to further include a third line that is additionally connected to the connection point of the first line and the second line, branched off, and connected to the accumulator; and the LA control valve may be provided on the third line.

[0019] Preferably, the hydraulic circuit for energy recovery comprises: a fourth line branched from the third line corresponding between the LA control valve and the accumulator and connected to the assist hydraulic motor; and an AM control valve provided on the fourth line to allow or block oil flow through the fourth line; wherein the pressure-compensating flow stabilizing valve may be additionally installed on the inlet side of the AM control valve.

[0020] Preferably, the hydraulic circuit for energy recovery may further comprise: a fifth line connecting the third line and the fourth line; and an AL control valve provided on the fifth line to allow or block oil flow through the fifth line.

[0021] Preferably, the hydraulic circuit for energy recovery may further comprise: a sixth line branched from the fourth line and connected to the tank; a safety relief valve provided on the sixth line to discharge oil from the accumulator when the pressure of the accumulator exceeds a preset pressure; a seventh line connected to both sides of the sixth line corresponding to both sides of the safety relief valve; and a manual safety valve provided on the seventh line to be manually operated to discharge the pressure of the accumulator.

[0022] Preferably, the pressure-compensating flow stabilizing valve may be configured to include: a valve chamber having an inlet and an outlet; a flow control spool valve comprising a one-sided valve section and a other-sided valve section having a diameter corresponding to the inner diameter of the valve chamber, and a valve shaft section having a diameter smaller than the diameters of the one-sided valve section and the other-sided valve section and connecting the one-sided valve section and the other-sided valve section, wherein the one-sided valve section operates to open and close the inlet and the other-sided valve section operates to ensure that the outlet is always open; a spool spring provided in a other-sided pressure chamber that applies pressure to the side of the other-sided valve section and pressurizes the one-sided valve section of the flow control spool valve in a direction that opens the inlet; a first pressure line connecting a flow path between the outlet and the control valve and a one-sided pressure chamber that applies pressure to the side of the one-sided valve section; and a second pressure line connecting an outlet-side flow path of the control valve and a other-sided pressure chamber that applies pressure to the side of the other-sided valve section. Effects of the invention

[0023] The present invention, as described above, has the advantage of being able to recover and reuse oil from a cylinder for operating a work device of construction machinery such as a hydraulic excavator, and in particular, to configure an energy recovery device that can easily implement flow rate control through a pressure-compensating flow stabilization valve.

[0024] In addition, through a control valve having multiple notches formed, such as at least a first notch and a second notch, the flow rate according to the upward and downward movement of the valve body can be designed to have a desired characteristic curve, and in particular, there is an advantage that the characteristic curve can be adjusted into a desired shape by varying the upper and lower positions of the cylindrical variable block.

[0025] The effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by a person skilled in the art from the description below. Brief explanation of the drawing

[0026] Figure 1 is a diagram illustrating the schematic configuration of a conventional general hydraulic excavator. FIGS. 2a to 2d are drawings illustrating a hydraulic circuit diagram and an operating state of an energy recovery device according to an embodiment of the present invention. FIGS. 3a to 3c are drawings illustrating the operating state of the main parts of an energy recovery device according to an embodiment of the present invention. FIG. 4 is a perspective view illustrating a control valve configured in an energy recovery device according to an embodiment of the present invention. FIG. 5 is a cross-sectional view illustrating a control valve configured in an energy recovery device according to an embodiment of the present invention. FIG. 6 is a drawing showing the valve body of a control valve configured in an energy recovery device according to an embodiment of the present invention. FIG. 7 is a drawing illustrating a cylindrical variable block and a plunger shaft of a control valve configured in an energy recovery device according to an embodiment of the present invention. FIG. 8 is a cross-sectional view illustrating the change in the opening according to the vertical position adjustment of a cylindrical variable block of a control valve configured in an energy recovery device according to an embodiment of the present invention. FIG. 9 is a hydraulic circuit diagram of an energy recovery device according to another embodiment of the present invention. Specific details for implementing the invention

[0027] The present invention may be implemented in various other forms without departing from its technical concept or main features. Accordingly, the embodiments of the present invention are merely examples in all respects and should not be interpreted restrictively.

[0029] The energy recovery device of the present invention is installed in various construction machines equipped with a hydraulic working device, and is a device for recovering and reusing the potential energy (potential energy) of the oil in the cylinder used to operate the working device.

[0030] In the following, the case where the energy recovery device of the present invention is applied to a hydraulic excavator is described as an example, but it goes without saying that the energy recovery device can be applied to various construction machines such as hydraulic excavators, hydraulic loaders, and hydraulic cranes.

[0031] As shown in FIG. 2a, the hydraulic excavator of the present embodiment may include an energy recovery device (1) and an energy consumption unit (2).

[0032] Additionally, the hydraulic excavator comprises a tank (T), at least one working device, at least one cylinder (10) equipped with a large chamber (10L) and a small chamber (10S) for operating the working device, and an assist hydraulic motor (M) for reusing energy discharged from the cylinder (10).

[0033] The above working device may include a boom, an arm, and a bucket, and a boom cylinder, an arm cylinder, and a bucket cylinder that operate them, and in this embodiment, the boom cylinder (10) is described as an example.

[0034] The above energy consumption unit (2) is configured to include a power source (2a), a main pump (2b), a pilot pump (2c), an electronic proportional pressure reducing valve (2d), and a main control valve (MCV), and is connected between the tank (T) and the cylinder (10) to operate to supply oil stored in the tank (T) to the cylinder (10) or to return oil discharged from the cylinder (10) to the tank (T).

[0035] The above power source (2a) may be composed of an engine such as an internal combustion engine, an electric motor, etc., and the above power source (2a) drives the main pump (2b) so that the oil stored in the tank (T) can be supplied to the cylinder (10) by the operation of the main control valve (MCV).

[0036] The main pump (2b) is driven by the power source (2a) and operates to supply oil stored in the tank (T) to the main control valve (MCV).

[0037] An operator input device (OP) is provided to control the operation of the main control valve (MCV), and the operator can raise or lower the boom by operating the operator input device (OP) to extend or retract the boom cylinder (10).

[0038] Specifically, when an operation signal is transmitted from the operator input device (OP) to the control unit (ECU) by the operation of the driver, the control unit (ECU) sends the transmitted operation signal to the electronic proportional pressure reducing valve (2d) to operate the electronic proportional pressure reducing valve (2d). When the electronic proportional pressure reducing valve (2d) is operated to the first position, the pilot fluid supplied from the pilot pump (2c) is supplied to the main control valve (MCV), so that the main control valve (MCV) can be operated to perform a function corresponding to the driver's operation. When the electronic proportional pressure reducing valve (2d) is operated to the second position, the flow of the pilot fluid supplied from the pilot pump (2c) to the main control valve (MCV) is blocked, and the pilot fluid supplied to the main control valve (MCV) is returned to the tank (T).

[0039] The assist hydraulic motor (M) is rotated by oil supplied from the energy recovery device (1), and the rotational force generated at this time is transmitted to the power source (2a) to assist the power of the power source (2a).

[0040] Meanwhile, in order to transmit the rotational force of the assist hydraulic motor (M) to the power source (2a), a main shaft (405) connecting the power source (2a) and the main pump (2b), an assist shaft (2e) connected to the assist hydraulic motor (M), and a power transmission mechanism (2f) transmitting the rotational force of the assist shaft (2e) to the main shaft (405) may be provided.

[0042] The detailed configuration and operation of the energy recovery device (1) installed in the hydraulic excavator having the above configuration will be described.

[0043] The energy recovery device (1) is configured to connect the cylinder (10) and the tank (T) as shown in FIG. 2a, and can recover potential energy (potential energy) from the oil discharged from the cylinder (10).

[0044] The energy recovery device (1) is configured to connect the large chamber (10L) and small chamber (10S) of the cylinder (10) and the tank (T) to communicate with each other, and is equipped with a plurality of control valves to perform an energy recovery function.

[0045] The energy recovery device (1) includes a hydraulic circuit for energy recovery to reuse high-pressure oil stored in the accumulator (Acc), after which oil discharged from the large chamber (10L) is supplied to the accumulator (Acc) and then pressurized and stored.

[0046] Referring to FIG. 2a, the hydraulic circuit for energy recovery described above will be explained in detail.

[0047] The above-mentioned hydraulic circuit for energy recovery is configured to include a first line (L1) to a seventh line (L7) that enables the flow of oil.

[0048] The first line (L1) is configured to connect the large chamber (10L) and the tank (T), specifically allowing oil to flow between the large chamber (10L) ↔ holding control valve (HV) ↔ LT control valve (LT) ↔ tank (T).

[0049] The second line (L2) branches off from the first line (L1) corresponding to the space between the large chamber (10L) and the LT control valve (LT) and is connected to the small chamber (10S). Specifically, oil flows between the branch point (BP1) of the first line (L1) ↔ LS control valve (LS) ↔ LSC check valve (LSC) ↔ small chamber (10S).

[0050] The third line (L3) is additionally connected to the connection point of the first line (L1) and the second line (L2), branched off, and connected to the accumulator (Acc). Specifically, oil flows between the branch point (BP1) of the first line (L1) ↔ pressure-compensated flow stabilization valve (100) ↔ LA control valve (LA) ↔ LSC check valve (LSC) ↔ accumulator (Acc).

[0051] The fourth line (L4) branches off from the third line (L3) corresponding to the space between the LA control valve (LA) and the accumulator (Acc) and is connected to the assist hydraulic motor (M). Specifically, oil flows between the branch point (BP2) of the third line (L3) ↔ AM control valve (AM) ↔ assist hydraulic motor (M) ↔ tank (T).

[0052] The fifth line (L5) connects the third line (L3) and the fourth line (L4), and specifically, oil flows between the branch point (BP3) corresponding to the branch point (BP1) of the first line (L1) and the pressure-compensating flow stabilizing valve (100) ↔ AL control valve (AL) ↔ ALC check valve (ALC) ↔ the branch point (BP5) between the branch point (BP2) of the third line (L3) and the AM control valve (AM).

[0053] The 6th line (L6) branches off from the 4th line (L4) and is connected to the tank (T). Specifically, oil flows between the branch point (BP6) ↔ safety relief valve (SV1) ↔ tank (T), between the branch point (BP5) and the AM control valve (AM).

[0054] The 7th line (L7) is connected to both sides of the 6th line (L6) corresponding to both sides of the safety relief valve (SV1), specifically, so that oil flows between the inlet point of the safety relief valve (SV1) ↔ manual safety valve (SV2) ↔ the outlet point of the safety relief valve (SV1).

[0055] Although the first line (L1) to the seventh line (L7) have been described separately for convenience of explanation above, the sections or numbers of each line can be varied as long as the valve constituting the hydraulic circuit for energy recovery of this embodiment can be connected under the same conditions.

[0056] The above-described hydraulic circuit for energy recovery includes various valves for controlling the flow of oil flowing through the first line (L1) to the seventh line (L7).

[0057] For example, the above-mentioned hydraulic circuit for energy recovery may include a control valve composed of poppet valves such as an LA control valve (LA), an LT control valve (LT), an LS control valve (LS), and a holding control valve (HV).

[0058] In addition, the above-mentioned hydraulic circuit for energy recovery may include spool valves such as an AM control valve (AM) and an AL control valve.

[0059] In addition, the above-mentioned hydraulic circuit for energy recovery may include a safety relief valve (SV1) and a manual safety valve (SV2) to prevent explosion, leakage, or damage to the accumulator (Acc) caused by the internal pressure of the accumulator (Acc) becoming too high.

[0060] The above LA control valve (LA) is provided between the large chamber (10L) and the accumulator (Acc) and is a valve that allows or blocks oil flow from the large chamber (10L) to the accumulator (Acc), and is provided on the third line (L3).

[0061] Accordingly, when the LA control valve (LA) is switched to an open state and oil flows, the oil in the large chamber can be transferred to the accumulator (Acc) to be pressurized and stored.

[0062] The above LT control valve (LT) is provided on the first line (L1) and is a valve that allows or blocks oil flow from the large chamber (10L) to the tank (T) through the first line (L1). When the LT control valve (LT) is switched to an open state and oil flows, the oil in the hydraulic line connected to the upstream end of the LT control valve (LT) can return to the tank (T).

[0063] The above LS control valve (LS) is provided on the second line (L2) and is a valve that allows or blocks oil flow from the first line (L1) to the small chamber (10S). When the LS control valve (LS) is switched to an open state and oil flows, oil from the large chamber (10L) can be supplied to the small chamber (10S).

[0064] The holding control valve (HV) is provided at the outlet side of the large chamber (10L) and is a valve that allows or blocks the discharge of oil from the large chamber (10L). When the holding control valve (HV) is switched to a closed state and the flow of oil is blocked, the boom may be prevented from falling unintendedly due to its own weight.

[0065] The above AM control valve (AM) is provided on the fourth line (L4) and is a valve that allows or blocks oil flow through the fourth line (L4). When the AM control valve (AM) is switched to an open state and oil flows, the oil pressurized in the accumulator (Acc) is transferred to the assist hydraulic motor (M) to rotate the motor and then can be returned to the tank (T).

[0066] The above AL control valve is provided on the 5th line (L5) and is a valve that allows or blocks oil flow through the 5th line (L5). When the AL control valve is switched to an open state and oil flows, the oil pressurized in the accumulator (Acc) can be transferred to the large chamber (10L).

[0067] The above safety relief valve (SV1) is provided on the 6th line (L6) and operates to open when the pressure of the accumulator (Acc) exceeds a preset pressure, thereby discharging excess pressure and protecting the hydraulic circuit for energy recovery.

[0068] The above manual safety valve (SV2) is provided on the 7th line (L7) and is a spool valve that is manually operated to release pressure from the accumulator (Acc), and operates to open and close so that oil pressurized in the accumulator (Acc) returns to the tank (T).

[0070] The operation of each mode of the energy recovery device (1) equipped with the hydraulic circuit for energy recovery as described above will be explained.

[0071] < Eco Mode - Energy Storage >

[0072] FIG. 2b is a diagram illustrating a hydraulic circuit for energy recovery during an operation to lower the boom while the excavator equipped with the energy recovery device (1) of the present embodiment is set to an "eco mode" in which oil energy from the large chamber (10L) is compressed and stored in the accumulator (Acc).

[0073] When the boom is lowered in eco mode for energy storage, the holding control valve (HV) and LA control valve (LA) are switched to an open state to allow oil to flow, the LT control valve (LT), AL control valve (AL), and AM control valve (AM) are switched to a closed state to prevent oil from flowing, and the manual safety valve (SV2) remains in a closed state.

[0074] When the rod of the cylinder (10) contracts in accordance with the down operation of the boom while the valves are controlled in the state as described above, the oil inside the large chamber (10L) is discharged into the first line (L1).

[0075] The oil discharged through the first line (L1) can be introduced into the accumulator (Acc) through the third line (L3) to be pressurized and stored, and through this process, the potential energy of the oil can be stored in the accumulator (Acc).

[0076] Meanwhile, in this state, the LS control valve (LS) can be selectively controlled to an open or closed state. When the LS control valve (LS) is switched to an open state and operates to allow oil to flow, a portion of the oil discharged through the first line (L1) inside the large chamber (10L) can be introduced into the small chamber (10S) of the cylinder (10) through the second line (L2), and this introduction can occur simultaneously with the oil being pressurized in the accumulator (Acc).

[0077] That is, some of the oil from the first line (L1) flows into the accumulator (Acc), and the rest flows into the small chamber (10S), and as oil flows into the small chamber (10S), the lowering speed of the boom can be increased.

[0078] <Eco Mode - Fuel efficiency improvement through rotation of assist hydraulic motor (M)>

[0079] FIG. 2c is a diagram showing an energy recovery hydraulic circuit in a state where an excavator equipped with the energy recovery device (1) of the present embodiment is set to “Eco Mode” which improves fuel efficiency by supplying oil compressed in the accumulator (Acc) to the assist hydraulic motor (M).

[0080] The eco mode for improving fuel efficiency is a mode that uses oil compressed in the accumulator (Acc) to assist the output of the power source (2a).

[0081] When the boom rises in eco mode for fuel efficiency improvement, the AM control valve (AM) is switched to an open state to allow oil to flow, the AL control valve (AL) is switched to a closed state to prevent oil from flowing, and the manual safety valve (SV2) remains in a closed state.

[0082] As the valves are controlled in the above state, the oil pressurized in the accumulator (Acc) passes through the AM control valve (AM) and is supplied to the assist hydraulic motor (M), after which it returns to the tank (T); at this time, the oil passing through the assist hydraulic motor (M) rotates the assist hydraulic motor (M).

[0083] In this process, the rotational force of the assist hydraulic motor (M) generated assists the output of the power source (2a) through the assist shaft (2e) and the power transmission mechanism (2f), thereby increasing the fuel efficiency of the power source (2a).

[0084] <Power Mode - Boom-up Assist>

[0085] FIG. 2d is a diagram illustrating a hydraulic circuit for energy recovery during the operation of lowering the boom while the excavator equipped with the energy recovery device (1) of the present embodiment is set to a “power mode” which supplies oil compressed in the accumulator (Acc) to the large chamber (10L) to assist the boom raising operation.

[0086] The power mode for boom-up assistance is a mode that assists the power required for the boom's upward movement by using oil pressurized in the accumulator (Acc).

[0087] When the boom rises in power mode, the holding control valve (HV) and AL control valve (AL) are switched to an open state to allow oil to flow, the LS control valve (LS), LT control valve (LT), and AM control valve (AM) are switched to a closed state to prevent oil from flowing, and the manual safety valve (SV2) remains in a closed state.

[0088] As the valves are controlled in the above state, the oil pressurized in the accumulator (Acc) passes sequentially through the ALC check valve (ALC), AL control valve (AL), and holding control valve (HV) and is supplied to the large chamber (10L) of the cylinder (10).

[0089] Therefore, when the boom is raised in power mode, oil is simultaneously supplied from the accumulator (Acc) along with the oil supplied from the main control valve (MCV) to the large chamber (10L) by the operation of the main pump (2b) of the power source (2a), so the boom's raising speed can be increased compared to when the boom is raised without using power mode.

[0091] As previously explained, control valves such as the LA control valve (LA), LT control valve (LT), LS control valve (LS), and holding control valve (HV) may be composed of poppet valves, and the structure of such control valves will be described in detail.

[0092] The above control valve is configured to include a seat portion (210), a valve body (220), and a valve spring (230).

[0093] The seat portion (210) is a tapered portion formed between the inlet side flow path and the outlet side flow path, and is the portion where the valve portion (221a) of the valve body (220) is seated.

[0094] As illustrated in FIGS. 4 to 8, the valve body (220) is a part that operates to open or close the space between the inlet side flow path and the outlet side flow path. On one side of the valve body (220), a valve body (221) is formed having an annular valve part (221a) that selectively sits on the seat part (210) and a tubular protrusion part (221b) that protrudes toward the outlet side flow path. On the other side of the valve body (220), a control pressure chamber (222) is formed to supply control pressure from the outside to variably control the amount of movement of the valve body (221).

[0095] The above valve spring (230) is provided within the control pressure chamber (222) and operates to press the valve body (221) toward the seat portion (210) in a closing direction.

[0096] A control valve with a structure as described above is characterized by having a plurality of notches formed at the end of the valve body (221), as shown in FIGS. 4 and 6.

[0097] Specifically, at the end of the valve body (221), a pair of first notch grooves (h1) having a first cross-sectional shape, a pair of second notch grooves (h2) having a second cross-sectional shape, a pair of third notch grooves (h3) having a third cross-sectional shape, and a pair of fourth notch grooves (h4) having a fourth cross-sectional shape are formed.

[0098] As the cross-sectional shapes of the pair of first notch grooves (h1), the pair of second notch grooves (h2), the pair of third notch grooves (h3), and the pair of fourth notch grooves (h4) are formed with different cross-sectional shapes, the amount of oil flowing through the opening formed between the seat portion (210) and the notch grooves (h1, h2, h3, h4) during the lifting operation of the valve body (221) is configured to have a specific pattern (a curve corresponding to the amount of oil flowing according to the lifting height).

[0099] For example, if the valve body (221) is lifted to a position where only a portion of the upper side of the second notch groove (h2) is opened, the oil passing between the inlet side flow path and the outlet side flow path can only flow through the area formed by the second notch groove (h2), and only a small amount of oil can flow.

[0100] Additionally, for example, if the valve body (221) is lifted to a position where the upper portion of the second notch groove (h2), the fourth notch groove (h4), and the first notch groove (h1) is opened and the third notch groove (h3) is not opened, the oil passing between the inlet side flow path and the outlet side flow path flows through a larger area than in the example described above, and more oil can flow.

[0101] As described above, by forming the cross-sectional shape of the pair of first notch grooves (h1), the pair of second notch grooves (h2), the pair of third notch grooves (h3), and the pair of fourth notch grooves (h4) into a specific shape, the amount of oil flow according to the lift amount of the valve body (221) can be set, and thereby the operating characteristics of the control valve (corresponding curve of oil flow amount according to lifting height) can be set to a desired characteristic.

[0102] In other words, it can be configured to have corresponding curve characteristics in the form of a curve, rather than a simple linear curve.

[0103] Meanwhile, the first notch groove (h1) is formed to face each other symmetrically, the second notch groove (h2) is also formed to face each other symmetrically, the third notch groove (h3) is also formed to face each other symmetrically, and the fourth notch groove (h4) is also formed to face each other symmetrically.

[0104] For example, as shown in FIG. 6, the first notch (h1), second notch (h2), third notch (h3), and fourth notch (h4) can be arranged at equal angles at 45° intervals.

[0105] As described above, through the arrangement of the first notch groove (h1), second notch groove (h2), third notch groove (h3), and fourth notch groove (h4), the valve body (221) can be prevented from rotating due to vortices or asymmetric flow of oil when the valve body (221) is lifted.

[0106] Meanwhile, the control valve may optionally further include a configuration for adjusting the end-side opening area of ​​the first notch groove (h1), the second notch groove (h2), the third notch groove (h3), and the fourth notch groove (h4).

[0107] To this end, the control valve comprises a through hole (200H, including a first through hole (200h1) having a first diameter and a second through hole (200h2) having a diameter smaller than the first diameter and having a nut formed inside) penetrating the inner surface of the tubular protrusion (221b) and the control pressure chamber (222), a cylindrical variable block (240) disposed on the inner side of the tubular protrusion (221b) and having a plurality of through holes (240h) penetrating the upper and lower surfaces, and having a variable upper position to adjust the opening area of ​​the first notch groove (h1) and the second notch groove (h2), the lower part of which is connected to the upper part of the cylindrical variable block (240), and the upper part which is extended to penetrate the first through hole (200h1) and the second through hole (200h2) and is positioned in the control pressure chamber (222), and has screw threads formed on the upper outer surface so as to the second It is configured to include a plunger shaft (250) which is fastened to the nut portion of the penetration portion (200h2), has an annular sealing portion (252) formed on its lower outer surface corresponding to the inner diameter of the first penetration portion (200h1), and has an O-ring (253) between the annular sealing portion (252) and the inner diameter of the first penetration portion (200h1), and a position fixing nut (260) which is assembled to the thread (251) of the plunger shaft (250) inside the control pressure chamber (222) to fix the position of the plunger shaft (250).

[0108] According to the configuration described above, as the plunger shaft (250) is rotated relative to the nut portion, the plunger shaft (250) moves up and down, and the cylindrical variable block (240) linked to the plunger shaft (250) changes its up and down position, thereby allowing the end-side opening area of ​​the first notch groove (h1), second notch groove (h2), third notch groove (h3), and fourth notch groove (h4) to be adjusted.

[0109] Through this, the operating characteristics of the control valve are not determined as a single type, and can have variable operating characteristics depending on the height adjustment of the plunger shaft (250).

[0111] The hydraulic circuit for energy recovery of the present embodiment as described above is further equipped with a pressure-compensating flow stabilizing valve (100) to increase the controllability of control valves such as the LA control valve (LA), LT control valve (LT), LS control valve (LS), and holding control valve (HV). In this embodiment, as shown in FIG. 2a, the pressure-compensating flow stabilizing valve (100) is provided on the inlet side of the LA control valve (LA) to increase the controllability of the LA control valve (LA).

[0112] As shown in FIG. 2a, a pressure-compensating flow stabilizing valve (100) for increasing the controllability of the LA control valve (LA) is installed on the inlet side of the LA control valve (LA) and operates to maintain a constant pressure difference between the inlet side and the outlet side of the LA control valve (LA) so that the flow rate flowing to the outlet side of the LA control valve (LA) is maintained in correspondence with the opening amount of the LA control valve (LA).

[0113] For example, when the LA control valve (LA) is controlled to be open or maintained in a state where it is open to a certain degree, oil through the third line (L3) is continuously supplied to the accumulator (Acc) and pressurized, the internal pressure of the accumulator (Acc) gradually increases, and due to this increase in pressure, the flow rate of oil passing through the LA control valve (LA) decreases.

[0114] Therefore, if the flow rate of oil supplied to the accumulator (Acc) can be maintained at a constant value and stabilized according to the opening amount of the LA control valve (LA) regardless of changes in the internal pressure of the accumulator (Acc), the control of the hydraulic circuit for energy recovery can be configured simply, thereby improving controllability.

[0115] As described above, as the controllability of the LA control valve (LA) is improved, the hydraulic circuit for energy recovery or the control algorithm can be easily configured. In particular, by installing a pressure-compensating flow stabilization valve (100) on the inlet side of each of the control valves, such as the LA control valve (LA), LT control valve (LT), LS control valve (LS), and holding control valve (HV), the hydraulic circuit or the control algorithm can be configured even more easily.

[0116] FIG. 9 is a hydraulic circuit diagram of an energy recovery device according to another embodiment of the present invention, specifically, a hydraulic circuit diagram for rotating an upper pivoting body rotatably mounted on the upper part of a lower driving body.

[0117] The above pressure-compensating flow stabilization valve (100) can also be applied to a hydraulic circuit for swivel as described above.

[0118] The above-described hydraulic circuit for slewing is equipped with an energy recovery device (1') that stores rotational inertia energy generated during a stop operation after the rotational operation of the upper slewing body, and a control valve installed within the energy recovery device (1') is configured to supply oil discharged from the first swing line (SL1) or the second swing line (SL2) by the inertia rotation of the slewing motor to an accumulator to accumulate and store pressure.

[0119] At this time, the pressure-compensating flow stabilization valve (100) is installed at the tip of the control valve to maintain a constant pressure difference between the inlet side and the outlet side of the control valve within the energy recovery device (1'), thereby enabling operation so that the flow rate flowing to the outlet side of the control valve within the energy recovery device (1') is maintained in correspondence with the opening amount of the control valve within the energy recovery device (1').

[0121] Hereinafter, the configuration of the pressure-compensating flow stabilization valve (100) described above will be explained in detail.

[0122] The pressure-compensating flow stabilization valve (100) is configured to include a valve chamber (110), a flow control spool valve (120), a spool spring (130), a first pressure line (PL1), and a second pressure line (PL2), as shown in FIGS. 3a to 3c.

[0123] The above valve chamber (110) is provided with an inlet (111) and an outlet (112), and can be configured to be located, for example, in the middle of the third line (L3).

[0124] The above flow control spool valve (120) is composed of a one-sided valve part (121) and a other-sided valve part (122) having a diameter corresponding to the inner diameter of the valve chamber (110), and a valve shaft part (123) connecting the one-sided valve part (121) and the other-sided valve part (122) having a diameter smaller than the diameters of the one-sided valve part (121) and the other-sided valve part (122).

[0125] The above flow control spool valve (120) operates such that the one-side valve part (121) opens and closes the inlet (111), and the other-side valve part (122) operates such that the outlet (112) is always open.

[0126] The above spool spring (130) is provided in a pressure chamber (PS2) that applies pressure to the side of the other valve part (122), and operates to pressurize the one valve part (121) of the flow control spool valve (120) in a direction that opens the inlet (111).

[0127] The first pressure line (PL1) is a flow path connecting the flow path between the outlet (112) and the control valve and the one-sided pressure chamber (PS1) that applies pressure to the side of the one-sided valve section (121).

[0128] The second pressure line (PL2) is a flow path connecting the outlet side flow path of the control valve and the other side pressure chamber (PS2) that applies pressure to the side of the other side valve part (122).

[0129] The pressure-compensating flow stabilization valve (100) described above functions to maintain a constant flow rate of oil supplied to the accumulator (Acc) through the LA control valve (LA), and to this end, the flow control spool valve (120) automatically controls the opening amount of the inlet (111).

[0130] Specifically, when the above flow control spool valve (120) is at a specific position, the following [Equation 1] and [Equation 2] are established.

[0131] [Equation 1]

[0132] (P2×Ak1) = (P3×Ak2) + Fs, where Ak1 = Ak2 is the same

[0133] P2: Inlet side pressure of the above LA control valve (LA)

[0134] P3: Pressure on the outlet side of the above LA control valve (LA)

[0135] Ak1: Cross-sectional area of ​​one side valve part (121)

[0136] Ak2: Cross-sectional area of ​​the other valve part (122)

[0137] Fs: Elastic pressure of the spool spring (130)

[0138] That is, the force acting on the cross-section of the one-side valve part (121) within the one-side pressure chamber (PS1) becomes 'P2×Ak1', and the force acting on the cross-section of the other-side valve part (122) within the other-side pressure chamber (PS2) becomes '(P3×Ak2) + FS', and the flow control spool valve (120) is positioned so that the two forces are in a parallel state.

[0139] At this time, since the cross-sectional area of ​​the one-sided valve part (121) and the cross-sectional area of ​​the other-sided valve part (122) are the same, if Ak1 and Ak2 are substituted with Ak, the above [Equation 1] can be simplified into [Equation 2].

[0140] (P2 - P3) = Fs ÷ Ak

[0141] That is, the difference (△P) between the inlet side pressure and the outlet side pressure of the above LA control valve (LA) is expressed as a constant value (Fs ÷ Ak).

[0142] In conclusion, as illustrated in FIGS. 3a to 3c, when oil is continuously supplied to the accumulator (Acc) according to the opening amount of the LA control valve (LA), the valve body (221) operates to further open the inlet (111) so that the outlet side pressure of the LA control valve (LA) provided in the third line (L3) increases, and at the same time, the inlet side pressure of the LA control valve (LA) increases.

[0143] That is, as the valve body (221) further opens the inlet port (111), the outlet pressure of the LA control valve (LA) increases in response to the increased internal pressure of the accumulator (Acc), thereby allowing the flow rate of oil supplied to the accumulator (Acc) to be maintained at a constant level.

[0144] Here, there is a relationship of 'P1 pressure > P2 pressure > P3 pressure', a relationship of 'P2 pressure in Fig. 3a < P2 pressure in Fig. 3b < P2 pressure in Fig. 3c', and a relationship of 'P3 pressure in Fig. 3a < P3 pressure in Fig. 3b < P3 pressure in Fig. 3c'.

[0145] Through the pressure-compensating flow stabilization valve (100) described above, the oil flow rate corresponding to the opening amount of the LA control valve (LA) can be maintained constant regardless of the internal pressure of the accumulator (Acc) and supplied to the accumulator (Acc) to accumulate pressure.

[0147] Although the present invention has been described with reference to preferred embodiments with reference to the accompanying drawings, it is evident to those skilled in the art that many diverse and obvious variations are possible from this description without departing from the scope of the invention. Accordingly, the scope of the invention should be interpreted by the claims described to include such many variations. Explanation of the symbols

[0148] 1: Energy recovery device 10: Cylinder 10L: Large Chamber 10S: Small Chamber L1: Line 1 L2: Line 2 L3: 3rd line L4: 4th line L5: 5th line L6: 6th line L7: 7th Line T: Tank M: Assist hydraulic motor Acc: Accumulator LA:LA control valve LT:LT control valve LS:LS control valve AM:AM control valve AL:AL control valve SV1:Safety relief valve SV2: Manual safety valve 100: Pressure-compensated flow stabilization valve 110: Valve chamber 111: Inlet 112: Outlet 120: Flow control spool valve 121: One-side valve section 122: The other-side valve section 123: Valve shaft 130: Spool spring PS1: One side pressure chamber PS2: The other side pressure chamber PL1: 1st pressure line PL2: 2nd pressure line 200H: Penetration hole 200h1: First penetration part 200h2: Second penetration part 210: Sheet part 220: Valve body 221: Valve body 221a: Valve part 221b: Tubular protrusion 222: Control pressure chamber 230: Valve spring 240: Cylindrical variable block 240h: Through hole 250: Plunger shaft 251: Screw thread 252: Sealing part 253: O-ring 260: Position fixing nut h1: First notch groove h2: 2nd notch h3: 3rd notch h4:4th notch

Claims

Claim 1 An energy recovery device installed in a construction machine comprising a tank, at least one hydraulic working device, at least one cylinder equipped with a large chamber and a small chamber for operating the working device, and an assist hydraulic motor for recovering and reusing the potential energy of oil discharged from the cylinder, wherein the large chamber, the small chamber, and the tank are connected to communicate with each other and at least one control valve is provided to perform an energy recovery function, and an energy recovery hydraulic circuit is configured to operate such that oil discharged from the large chamber is supplied to an accumulator, pressurized, and then reused; wherein the control valve comprises: a tapered seat portion formed between an inlet side flow path and an outlet side flow path; a valve body formed on one side having an annular valve portion that selectively sits on the seat portion and a tubular protrusion protruding toward the outlet side flow path, and a control pressure chamber formed on the other side to supply control pressure from the outside for variably controlling the raising and lowering amount of the valve body. A valve spring provided within the control pressure chamber and pressurizing the valve body toward the seat portion in a closing direction; wherein a pair of first notch grooves having a first cross-sectional shape and a pair of second notch grooves having a second cross-sectional shape are formed at the end of the valve body, and the first notch grooves are formed to face each other symmetrically, and the second notch grooves are also formed to face each other symmetrically; the control valve includes a through hole penetrating the inner surface of the tubular protrusion and the control pressure chamber, wherein the through hole includes a first through hole having a first diameter and a second through hole having a diameter smaller than the first diameter and having a nut portion formed inside; and a cylindrical variable block disposed on the inner side of the tubular protrusion, having a plurality of through holes penetrating the upper and lower surfaces, and having a variable upper and lower position to adjust the opening area of ​​the first notch groove and the second notch groove;An energy recovery device comprising: a plunger shaft having a lower portion connected to the upper portion of the cylindrical variable block, an upper portion extending to penetrate the first and second through portions and positioned in the control pressure chamber, having a screw thread formed on the upper outer surface to be fastened to the nut portion of the second through portion, having an annular sealing portion formed on the lower outer surface corresponding to the inner diameter of the first through portion, and having an O-ring provided between the annular sealing portion and the inner diameter of the first through portion; and a position fixing nut assembled to the screw thread of the plunger shaft inside the control pressure chamber to fix the position of the plunger shaft; wherein, as the plunger shaft is rotated relative to the nut portion, the plunger shaft moves up and down, and the cylindrical variable block linked to the plunger shaft has its up and down position varied, thereby adjusting the opening area of ​​the first and second notch grooves. Claim 2 delete Claim 3 delete Claim 4 An energy recovery device according to claim 1, further comprising a pressure-compensating flow stabilizing valve installed on the inlet side of the control valve and controlling the flow rate flowing to the outlet side of the control valve to be maintained in correspondence with the opening amount of the control valve by maintaining a constant pressure difference between the inlet side and the outlet side of the control valve. Claim 5 An energy recovery device according to claim 4, wherein the control valve comprises an LA control valve provided between the large chamber and the accumulator to allow or block oil flow from the large chamber to the accumulator, and the pressure-compensating flow stabilizing valve is installed on the inlet side of the LA control valve. Claim 6 An energy recovery device according to claim 5, wherein the hydraulic circuit for energy recovery comprises: a first line connecting the large chamber and the tank; an LT control valve provided on the first line to allow or block oil flow from the large chamber to the tank through the first line; a second line branched from the first line corresponding between the large chamber and the LT control valve and connected to the small chamber; and an LS control valve provided on the second line to allow or block oil flow from the first line to the small chamber; wherein the pressure-compensating flow stabilizing valve is additionally installed on the inlet side of either or both of the LT control valve and the LS control valve. Claim 7 An energy recovery device according to claim 6, wherein the hydraulic circuit for energy recovery further comprises a third line connected to the connection point of the first line and the second line, branched off, and connected to the accumulator, and wherein the LA control valve is provided on the third line. Claim 8 An energy recovery device according to claim 7, wherein the hydraulic circuit for energy recovery comprises: a fourth line branched from the third line corresponding between the LA control valve and the accumulator and connected to the assist hydraulic motor; and an AM control valve provided on the fourth line to allow or block oil flow through the fourth line, wherein the pressure-compensating flow stabilizing valve is additionally installed on the inlet side of the AM control valve. Claim 9 An energy recovery device according to claim 8, wherein the hydraulic circuit for energy recovery further comprises: a fifth line connecting the third line and the fourth line; and an AL control valve provided on the fifth line to allow or block oil flow through the fifth line. Claim 10 An energy recovery device according to claim 9, wherein the hydraulic circuit for energy recovery further comprises: a sixth line branched from the fourth line and connected to the tank; a safety relief valve provided on the sixth line for discharging oil from the accumulator when the pressure of the accumulator exceeds a preset pressure; a seventh line connected to both sides of the sixth line corresponding to both sides of the safety relief valve; and a manual safety valve provided on the seventh line for manual operation to discharge the pressure of the accumulator. Claim 11 In claim 4, the pressure-compensating flow stabilizing valve comprises: a valve chamber having an inlet and an outlet; a flow control spool valve having a diameter corresponding to the inner diameter of the valve chamber, a valve shaft having a diameter smaller than the diameter of the valve chamber and the valve shaft connecting the valve chamber and the valve chamber, wherein the valve chamber operates to open and close the inlet and the valve chamber operates to keep the outlet always open; a spool spring provided in a pressure chamber that applies pressure to the side of the valve chamber and pressurizes the valve chamber of the flow control spool valve in a direction that opens the inlet; a first pressure line connecting the flow path between the outlet and the control valve and the pressure chamber that applies pressure to the side of the valve chamber; and a second pressure line connecting the flow path on the outlet side of the control valve and the pressure chamber that applies pressure to the side of the valve chamber.

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