JP2013087869A - Pressure oil energy recovery apparatus and construction machine employing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure oil energy recovery apparatus capable of improving fuel efficiency by allowing the stable recovery of pressure oil energy regardless of an effect such as a load condition of an actuator, and a construction machine using the same.SOLUTION: The apparatus includes: an accumulator 22 which accumulates pressure oil energy; a pressure converter 20 which supplies pressure-converted pressure oil to the accumulator 22; an accumulator duct line La which connects the outlet side of the pressure converter 20 to the accumulator 22; a branch duct line Lx which makes the inlet side of the pressure converter 20 communicate with a main circuit Lp; a throttle 18 provided at the downstream side of a center bypass circuit Lc; an accumulation change-over valve 19 provided in the branch circuit Lx and switched by pressure on the upstream side of the throttle 18; a first pressure detector 17 which detects the pressure of the main circuit Lp; a second pressure detector 23 which detects the pressure of the accumulator 22; and a control device 30 which acquires detection signals from the first and second pressure detectors 17, 23 and outputs an instruction to a capacity control unit 20C of a variable displacement hydraulic pump 20B in the pressure converter 20.

Description

  The present invention relates to a pressure oil energy recovery device provided in a hydraulic system such as a hydraulic excavator and a construction machine using the same.

  Generally, a hydraulic excavator has a plurality of hydraulic actuators including a hydraulic cylinder that drives each of a boom, an arm, and a bucket that are front working machines, and a hydraulic motor that drives each of a swiveling body and a traveling body. By appropriately operating these hydraulic actuators, operations such as excavation and movement of earth and sand are performed.

  In such a hydraulic excavator, a hydraulic pump, a plurality of actuators driven by pressure oil discharged from the hydraulic pump, and a plurality of directional control valves that respectively control the flow rate and direction of the pressure oil supplied to the plurality of actuators And a center bypass circuit communicating with the tank through the plurality of directional switching valves, and a relief valve that discharges hydraulic pump discharge oil to the tank when the pressure exceeds a predetermined pressure so that the circuit pressure of the hydraulic circuit does not become excessive. There is one using a hydraulic system equipped with.

  In such a hydraulic system, by arranging the energy recovery device in parallel with the relief valve and the circuit from the relief valve to the tank, the load pressure of the hydraulic circuit exceeds the set pressure of the relief valve and is discharged from the relief valve to the tank. Relieve the energy of the high-pressure pressure oil that is diverted to the energy recovery device and prevent the pressure of the circuit supplied from the hydraulic pump to the actuator from fluctuating due to the inertia, pressure loss, frictional resistance, etc. of the energy recovery device. There is one that improves the operation performance of the actuator by stabilizing the pressure of the circuit when the valve is operated (see, for example, Patent Document 1).

JP 2005-140143 A

  In the above-described prior art, since the high pressure oil discharged to the tank during the relief valve operation is discharged as surplus oil, recovering the energy of this pressure oil as generated electric energy is an effective use of energy. Can improve the efficiency of the system.

  However, the above-described prior art can recover the pressure oil energy as electric energy only when the relief valve is operated due to an increase in the actuator load. However, there are almost no cases where a light load operation with a small actuator load continues. Energy cannot be recovered. As described above, there is a problem that the degree of contribution to the system efficiency by energy recovery depends on the load condition of the actuator.

  In addition, the above-described conventional technique has a problem that the entire apparatus is expensive because an expensive electric device such as a generator, an inverter, or a battery is required as a component that uses electric energy. Further, in order to effectively use the large amount of collected electric energy, an electric device such as an electric motor that assists the torque of the engine and a turning electric motor that replaces the turning hydraulic motor is required. There was a problem that it could not be applied unless it was a construction machine.

  The present invention has been made on the basis of the above-mentioned matters, and the object thereof is applicable to construction machines not equipped with expensive electric motors, electric devices such as inverters and batteries, and the load conditions of actuators, etc. A pressure oil energy recovery device capable of recovering pressure oil energy irrespective of the influence of the above and improving the fuel efficiency of the construction machine and a construction machine using the same are provided.

  In order to achieve the above object, the first invention provides a hydraulic pump, a plurality of hydraulic actuators driven by pressure oil from the hydraulic pump, and a pressure supplied from the hydraulic pump to the plurality of hydraulic actuators. A plurality of direction switching valves for controlling the flow rate and direction of oil, a main circuit for supplying pressure oil from the hydraulic pump to the direction switching valves, and a center bypass circuit communicating with the tank through the plurality of direction switching valves A pressure oil energy recovery device that recovers excess oil that is not used in the hydraulic actuator as pressure oil energy, and supplies the pressure accumulator for accumulating the pressure oil energy and pressure oil that has been converted into pressure to the accumulator A pressure converter, a pressure accumulator pipe connecting the outlet side of the pressure converter and the pressure accumulator, a branch circuit communicating the inlet side of the pressure converter and the main circuit, A throttle provided downstream of the center bypass circuit, a pressure accumulation switching valve provided in the branch circuit and switched by a pressure upstream of the throttle, a first pressure detector for detecting the pressure of the main circuit, A second pressure detector for detecting the pressure of the pressure accumulator, and detection signals from the first and second pressure detectors are fetched, and a command is sent to a capacity control unit of a variable displacement hydraulic pump in the pressure converter. Is provided with a control device that outputs.

  According to a second invention, in the first invention, the control device is configured to control the pressure of the main circuit detected by the first pressure detector and the pressure accumulator detected by the second pressure detector. The target hydraulic pump capacity of the variable displacement hydraulic pump in the pressure converter is calculated using the pressure so that the discharge pressure of the variable displacement hydraulic pump in the pressure converter is equal to or higher than the pressure of the accumulator. An arithmetic unit, and an output unit that outputs the target hydraulic pump displacement calculated by the arithmetic unit as a command to a displacement control unit of the variable displacement hydraulic pump are provided.

  Furthermore, the third invention is the first or second invention, wherein a regenerative circuit that communicates the pressure accumulator and the inlet side of the plurality of direction switching valves, a regenerative valve provided in the regenerative circuit, A third pressure detector for detecting a command pressure to a pilot operating section for switching the direction switching valve; and opening the regenerative valve based on the command pressure to the pilot operating section detected by the third pressure detector. A control device is provided that includes a calculation unit that generates a command and an output unit that outputs an open command generated by the calculation unit to the operation unit of the regenerative valve.

  According to a fourth invention, in any one of the first to third inventions, the throttle is a variable throttle that changes a throttle amount of the center bypass circuit in accordance with a pressure of the pressure accumulator. When the pressure of the vessel is equal to or higher than a preset value, the throttle amount of the center bypass circuit is fully opened.

  Furthermore, the fifth invention is a construction machine, characterized in that it comprises any one of the first to fourth inventions.

  According to the present invention, the pressure converter that converts the pressure oil in the main circuit according to the flow rate of the surplus oil that is not used by the actuator led to the center bypass circuit, and the pressure oil that is converted by the pressure converter Since the accumulator to collect is provided, when surplus oil flows through the center bypass circuit, the pressure oil energy from the surplus oil can be reliably stored in the accumulator. As a result, stable recovery of pressure oil energy can be realized regardless of the influence of the load condition of the actuator.

It is a circuit diagram showing composition of a 1st embodiment of a pressure oil energy recovery device of the present invention and a construction machine using the same. It is a symbol figure which expands and shows the direction switching valve in 1st Embodiment of the pressure oil energy recovery apparatus of this invention shown in FIG. 1 and a construction machine using the same. It is a flowchart figure which shows the control flow of the pressure converter in 1st Embodiment of the pressure oil energy collection | recovery apparatus of this invention and a construction machine using the same. It is a flowchart figure which shows the control flow of the hydraulic pump and regenerative valve in 1st Embodiment of the pressure oil energy collection | recovery apparatus of this invention, and a construction machine using the same. It is a characteristic view which shows the characteristic of the pump capacity | capacitance command in 1st Embodiment of the pressure oil energy recovery apparatus of this invention and a construction machine using the same. It is a characteristic figure explaining the torque reduction control in 1st Embodiment of the pressure oil energy recovery apparatus of this invention and a construction machine using the same. It is a characteristic view which shows the characteristic of the torque reduction command in 1st Embodiment of the pressure oil energy collection | recovery apparatus of this invention and a construction machine using the same. It is a circuit diagram which shows the structure of 2nd Embodiment of the pressure oil energy recovery apparatus of this invention, and a construction machine using the same. It is a circuit diagram which shows the structure of 3rd Embodiment of the pressure oil energy recovery apparatus of this invention, and a construction machine using the same.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a pressure oil energy recovery device and a construction machine using the same according to the present invention will be described with reference to the drawings.

  FIG. 1 is a circuit diagram showing the configuration of a first embodiment of a pressure oil energy recovery device and a construction machine using the same according to the present invention, and FIG. 2 shows the pressure oil energy recovery device of the present invention shown in FIG. It is a symbol figure which expands and shows the direction switching valve in 1st Embodiment of the used construction machine. In this embodiment, the pressure oil energy recovery device of the present invention is applied to a hydraulic excavator. In FIG. 1, reference numeral 1 denotes an engine as a power source, and 2 denotes a variable displacement hydraulic pump driven by the engine 1. The hydraulic pump 2 has, for example, a swash plate as a variable displacement mechanism, and the displacement (displacement volume) of the hydraulic pump 2 is changed by adjusting the tilt angle of the swash plate with the displacement control device 2a. The discharge flow rate is controlled.

  The main circuit Lp for supplying the pressure oil discharged from the hydraulic pump 2 to the actuators of the swing motor 3, the arm cylinder 4 and the boom cylinder 5 includes direction switching valves 6 to 8 for controlling the direction and flow rate of the pressure oil, In order to prevent overload of the hydraulic pump 2, a relief valve 16 for limiting the pressure in the main circuit Lp and a pressure sensor 17 for detecting the pressure in the main circuit Lp are provided. The relief valve 16 allows the pressure oil in the main circuit Lp to escape to the tank 12 via the return circuit Lt when the pressure in the hydraulic piping rises above the set pressure.

  The direction switching valves 6 to 8 are three-position and six-port switching valves. Each spool position is switched by a pilot pressure supplied to each pilot operation unit, and pressure oil from the hydraulic pump 2 is supplied to each actuator. Supply to 3-5. Here, the turning direction switching valve 6 corresponds to the turning motor 3, the arm direction switching valve 7 corresponds to the arm cylinder 4, and the boom direction switching valve 8 corresponds to the boom cylinder 5. Further, as shown in FIG. 2, each of the direction switching valves 6 to 8 is connected to an inlet port 6 a, 7 a, 8 a to which pressure oil from the hydraulic pump 2 is supplied and a return circuit Lt communicating with the tank 12. Outlet ports 6b, 7b, 8b, center ports 6c, 7c, 8c communicating in the neutral position, connection ports 6d, 6e, 7d, 7e, 8d, 8e connected to each actuator 3-5 side, pilot It has operation parts 6f, 6g, 7f, 7g, 8f, 8g and neutral return springs 6h, 6i, 7h, 7i, 8h, 8i.

  When the pilot pressure to the pilot operating portions 6f, 6g, 7f, 7g, 8f, and 8g of the direction switching valves 6 to 8 is zero, the spools of these direction switching valves 6 to 8 are disposed in the neutral position. As a result, the center ports 6c, 7c, 8c communicate with each direction switching valve 6-8, so that the pressure oil supplied from the hydraulic pump 2 connects the main circuit Lp and each direction switching valve 6-8 in series. To the center bypass circuit Lc. The main circuit Lp is a circuit that supplies pressure oil discharged from the hydraulic pump 2 to the directional switching valves 6 to 8, and the hydraulic pump 2 and the center ports 6c, 7c, and 8c of the directional switching valves 6 to 8 are connected in series. Is connected to the return circuit Lt on the most downstream side.

  A center bypass circuit Lc is provided downstream of the direction switching valves 6-8. The center bypass circuit Lc is a circuit that guides the pressure oil of the main circuit Lp to the return circuit Lt, and is connected to the main circuit Lp. A fixed throttle 18 for increasing the pressure oil is provided on the downstream side of the center bypass circuit Lc. One end side that is the upstream side of the center bypass circuit Lc is connected to the direction switching valve 8 that is located on the most downstream side of the direction switching valves 6 to 8, and the other end that is the downstream side of the center bypass circuit Lc. The side is connected to a return circuit Lt communicating with the tank 12 via a fixed throttle 18. The return circuit Lt is connected to outlet ports 6b, 7b, 8b of the turning direction switching valve 6, the arm direction switching valve 7, and the boom direction switching valve 8 via pipe lines, respectively.

  The regenerative main circuit Lpy is connected to the inlet port 6a of the direction switching valve 6 via a load check valve 9 that prevents the flow of pressure oil from the swing motor side that is an actuator. In addition, the regenerative main circuit Lpy causes pressure oil to flow out from the arm cylinder 4 side and the boom cylinder 5 side as actuators to the inlet port 7a of the arm direction switching valve 7 and the inlet port 8a of the boom direction switching valve 8. The load check valves 10 and 11 to be prevented are connected to each other. The regenerative main circuit Lpy is a circuit that supplies the pressure oil of the regenerative circuit Ly described later to the directional switching valves 6-8. The regenerative circuit Ly and the inlet ports 6a, 7a, 8a of the directional switching valves 6-8 are respectively provided. Connected in parallel.

  An accumulator (pressure accumulator) 22 is connected to the downstream side of the regenerative main circuit Lpy via the regenerative circuit Ly. The regenerative circuit Ly is a circuit that supplies pressure oil accumulated in the accumulator 22 to the regenerative main circuit Lpy, and is a circuit that connects the accumulator 22 and the regenerative main circuit Lpy.

  A relief valve 24 for limiting the pressure of the regenerative circuit Ly is provided between the regenerative circuit Ly and the return circuit Lt. The relief valve 24 allows the pressure oil in the regenerative circuit Ly to escape to the tank 12 via the return circuit Lt when the pressure in the hydraulic piping rises above the set pressure. An accumulator line La is connected to the regenerative circuit Ly and the accumulator 22. A second hydraulic pump 20B constituting a pressure converter 20 described later is connected to the pressure accumulation line La via a check valve 21.

  The regenerative circuit Ly permits the regenerative valve 25, which is a 2-position 2-port electromagnetic switching valve, and the flow of pressure oil from the regenerative valve 25 to the inlet side of each direction switching valve 6-8 via the regenerative main circuit Lpy. The regenerative check valve 26 is connected.

  The regenerative valve 25 has a spring 25b on one end side, and is configured such that an electrical command from the controller 30 is output to the electromagnetic operation unit 25a. When the close command is output from the controller 30, the port is shut off, the regenerative circuit Ly is shut off, and when the open command is output, the port is connected and the regenerative circuit Ly is set in a communication state, and the accumulator 22 Pressure oil is caused to flow into the regenerative main circuit Lpy.

  In the main circuit Lp, one end side of the branch pipe Lx branched from the main circuit Lp is connected to the upstream side of the direction switching valve 6 arranged at the most upstream. A pressure accumulation switching valve 19 is provided in the branch pipe Lx, and a hydraulic motor 20A of the pressure converter 20 is connected to the other end.

  The pressure converter (pressure converting means) 20 is composed of a hydraulic motor 20A and a second hydraulic pump 20B, and is connected to each other by a drive shaft. When pressure oil is supplied to the hydraulic motor 20A side, drive torque due to the pressure oil Occurs, and the second hydraulic pump 20B is driven simultaneously. At this time, the pressure at the inlet of the hydraulic motor 20A can be converted into the pressure at the outlet of the second hydraulic pump 20B by changing the capacity of the second hydraulic pump 20B. The pressure oil discharged from the second hydraulic pump 20B is a conduit connecting the second hydraulic pump 20B of the pressure converter 20 and the accumulator 22, and only supplies the pressure oil from the second hydraulic pump 20B to the accumulator 22. The pressure is accumulated in the accumulator 22 through a pressure accumulating line La provided with an allowable check valve 21. The inlet side of the hydraulic motor 20A in the pressure converter 20 is connected to the main circuit Lp via the branch line Lx.

  The pressure accumulation switching valve 19 includes a spring 19b on one end side and an operation portion 19a on the other end side. One end of a pipe line Lca is connected to the operation unit 19a in order to use the pressure generated in the center bypass circuit Lc as a command pressure. The other end of the pipe line Lca is connected to the upstream side of the fixed throttle 18 provided in the center bypass circuit Lc. When the pressure on the upstream side of the fixed throttle 18 that is the command pressure is lower than a predetermined spring pressure (preset pressure) of the spring 19b, the pressure accumulation switching valve 19 shuts off the port, and the branch line Lx and the pressure The converter 20 is disconnected from the inlet side of the hydraulic motor 20A. On the other hand, when the command pressure exceeds a preset pressure, the port communicates and pressure oil is allowed to flow from the branch pipe Lx to the inlet side of the hydraulic motor 20A in the pressure converter 20. For example, when the flow rate of the center bypass circuit Lc increases, a pressure is generated on the upstream side due to a passage pressure loss of the fixed restrictor 18, and this pressure is supplied to the operation unit 19 a of the pressure accumulation switching valve 19. 19 is opened. As a result, the pressure oil in the main circuit Lp is guided to the hydraulic motor 20A in the pressure converter 20 via the branch pipe Lx.

  In the present embodiment, the hydraulic motor 20A is a fixed displacement type, the second hydraulic pump 20B is a variable displacement type, and an electric command is sent from the controller 30 to the second displacement control device 20C of the second hydraulic pump 20B. The output is being subjected to capacity control.

  An operation lever that is a command input means to each of the actuators 3 to 5 includes a turning lever 13, an arm lever 14, and a boom lever 15. Each operation lever has a pilot valve (not shown), and each generates a pilot pressure substantially proportional to the operation amount. The pilot pressure of the turning lever 13 is supplied to one of the pilot circuits connected to the two operation portions 6f and 6g of the turning direction switching valve 6 according to the operation direction. Similarly, the pilot pressure of the arm lever 14 is The pilot pressures supplied to the pilot circuits connected to the operation parts 7f and 7g of the arm direction switching valve 7 and the pilot pressure of the boom lever 15 are supplied to the pilot circuits connected to the operation parts 8f and 8g of the boom direction switching valve 8. To be supplied.

  Each pilot circuit of the turning lever 13 is provided with command pressure sensors 13a and 13b for detecting these pilot pressures, and each pilot circuit of the arm lever 14 is provided with command pressure sensors 14a and 14b for detecting these pilot pressures. And are provided. Similarly, each pilot circuit of the boom lever 15 is provided with command pressure sensors 15a and 15b for detecting these pilot pressures. Detection signals from these command pressure sensors 13 a to 15 b are input to the controller 30.

  The pressure sensor 17 detects the pressure of the main circuit Lp. The pressure sensor 23 is provided in the regenerative circuit Ly in order to detect the pressure of the accumulator 22. The pressure detection signal of the main circuit Lp from the pressure sensor 17 and the pressure detection signal of the accumulator 22 from the pressure sensor 23 are input to the controller 30.

  The controller (control device) 30 includes an input unit that takes in detection signals from the pressure sensors 13a to 15b, 17, and 23, an arithmetic unit that executes arithmetic processing described later based on these detection signals, and the hydraulic pump 2 The displacement control commands calculated by the calculation unit are output to the displacement control device 2a of the second pressure pump 20B and the second displacement control device 20C of the second hydraulic pump 20B constituting the pressure converter 20, and to the electromagnetic operation unit 25a of the regenerative valve 25. And an output unit that outputs an opening / closing command calculated by the calculation unit. The controller 30 includes a capacity control unit that performs capacity control of the second hydraulic pump 20B and the hydraulic pump 2 that constitute the pressure converter 20, and a regeneration control unit that performs opening / closing control of the regenerative valve 25.

Next, the operation | movement in 1st Embodiment of the pressure oil energy recovery apparatus of this invention and a construction machine using the same is demonstrated.
In FIG. 1, when the operation amounts of all the operation levers 13 to 15 are zero (non-operation), the pressure oil discharged from the hydraulic pump 2 to the main circuit Lp is the center ports 6c to 8c of the direction switching valves 6 to 8. The total flow rate is supplied to the center bypass circuit Lc. At this time, in response to the command signal from the controller 30, the displacement control device 2a of the hydraulic pump 2 minimizes the displacement of the hydraulic pump 2. In this state, when the engine 1 is operated at the low idle speed, the pressure of the spring 19b (the spring pressure of the spring 19b is prevented so that the pressure accumulation switching valve 19 does not open with the pressure generated on the upstream side of the fixed throttle 18 of the center bypass circuit Lc. Set pressure) is set.

  Next, when the arm lever 14 which is one of the operation levers is operated, the arm direction switching valve 7 is switched, the pressure oil in the main circuit Lp is guided to the arm cylinder 4, and the arm connected to the piston rod is driven. To do. In this state, surplus oil that has not been used in the arm cylinder 4 flows into the center bypass circuit Lc, and increases the pressure generated on the upstream side of the fixed throttle 18.

  When the pressure generated on the upstream side of the fixed throttle 18 of the center bypass circuit Lc rises and the pressure of the pressure oil supplied to the operation portion of the pressure accumulation switching valve 19 exceeds the set pressure, the pressure accumulation switching valve 19 opens and the main circuit Lp The pressure oil is guided to the hydraulic motor 20A in the pressure converter 20 through the branch pipe Lx.

  The controller 30 discharges the second hydraulic pump 20B to the second capacity control device 20C of the pressure converter 20 according to the pressure of the main circuit Lp detected by the pressure sensor 17 and the pressure of the accumulator 22 detected by the pressure sensor 23. The command signal which makes a pressure more than the pressure of the pressure accumulation line La is output. Accordingly, the pressure of the pressure oil discharged from the pressure converter 20 can be converted to be equal to or higher than the pressure of the pressure accumulation line La, regardless of the pressure of the pressure oil of the main circuit Lp supplied to the pressure converter 20. Since the pressure of the pressure oil discharged from the pressure converter 20 is higher than the pressure in the pressure accumulating line La, the check valve 21 is opened and guided to the pressure accumulating line La, and the accumulator 22 can accumulate the pressure oil. it can. As a result, the pressure oil energy can be reliably recovered when the excess oil in the center bypass circuit Lc increases.

Thus, the pressure oil energy stored by the operation of the pressure accumulation switching valve 19 and the pressure converter 20 is regenerated and used as follows.
For example, when the turning lever 13 is operated, the turning direction switching valve 6 is switched, and the pressure oil in the main circuit Lp is guided to the turning motor 3 and driven. The controller 30 inputs pilot pressure values generated by the operation of the turning lever 13, compares these values with a predetermined set value, and outputs an open command to the regenerative valve 25 when the input value exceeds the set value. To do. When the regenerative valve 25 is opened, the pressure oil stored in the accumulator 22 is supplied from the regenerative circuit Ly to the regenerative main circuit Lpy through the regenerative check valve 26.

  Thereby, since the flow volume of the pressure oil which the turning motor 3 requires is supplied from the regeneration circuit Ly and the regeneration main circuit Lpy, the discharge flow volume of the hydraulic pump 2 can be reduced. As a result, since the output of the engine 1 can be reduced, fuel consumption can be improved.

  Next, control of the pressure converter 20 will be described with reference to FIG. FIG. 3 is a flow chart showing a control flow of the pressure converter in the first embodiment of the pressure oil energy recovery device of the present invention and the construction machine using the same. In FIG. 3, the same reference numerals as those shown in FIGS. 1 and 2 are the same parts, and detailed description thereof is omitted.

  First, as a start state, for example, an operator turns on a key switch (not shown) of a hydraulic excavator.

  Thereby, the controller 30 takes in the data of the pressure Pm of the main circuit Lp from the pressure sensor 17 and the pressure Pac of the accumulator 22 from the pressure sensor 23 (step S101).

  Next, the calculation unit of the controller 30 calculates the target hydraulic pump capacity qp of the second hydraulic pump 20B of the pressure converter 20 (step S102). Specifically, as will be described in detail later, the second hydraulic pressure is detected using the detected pressure Pac of the accumulator 22, the detected pressure Pm of the main circuit Lp, and the capacity qm of the hydraulic motor 20A that is a fixed capacity. The target hydraulic pump capacity qp of the pump 20B is calculated.

  Next, the output part of the controller 30 outputs a command signal to the second displacement control device 20C of the second hydraulic pump 20B so as to achieve the target pump displacement (step S103). In this way, the capacity control of the second hydraulic pump 20B of the pressure converter 20 is executed.

Next, a calculation procedure of the target hydraulic pump displacement qp of the second hydraulic pump 20B calculated by the calculation unit of the controller 30 will be described. Assuming that the conversion loss of the pressure converter 20 set in advance by measurement or the like is η, the input hydraulic power (= Pm · qm) of the hydraulic motor 20A and the second hydraulic pump 20B connected to the hydraulic motor 20A by a drive shaft. Since the output power (= Pac · qp · η) is balanced, the equation Pm · qm = Pac · qp · η holds. As a result, the target hydraulic pump displacement qp of the second hydraulic pump 20B is calculated according to the following equation (1).
qp = (Pm · qm) / (Pac · η) (1)
Here, Pm is the pressure of the main circuit Lp, which is the motor inlet pressure, qm is the capacity of the hydraulic motor 20A, Pac is the pressure of the accumulator 22, qp is the target hydraulic pump capacity of the second hydraulic pump 20B, and η is the pressure converter 20 Conversion loss.

  The oil discharged from the second hydraulic pump 20B is guided to the pressure accumulating line La through the check valve 21, but the passage resistance of the check valve 21 is very small and can be ignored. Therefore, the discharge pressure when the second hydraulic pump 20B operates at the target hydraulic pump capacity qp is equal to the pressure Pac of the accumulator 22. The calculation unit of the controller 30 outputs a value slightly exceeding the target hydraulic pump displacement qp to the second displacement control device 20C of the second hydraulic pump 20B as a target command.

  Since the controller 30 controls the capacity qp of the second hydraulic pump 20B in this way, the pressure oil discharged from the pressure converter 20 is accumulated in the accumulator 22 regardless of the pressure at the inlet of the hydraulic motor 20A. be able to.

Next, control of the hydraulic pump 2 and the regenerative valve 25 will be described with reference to FIG. FIG. 4 is a flowchart showing a control flow of the hydraulic pump and the regenerative valve in the first embodiment of the pressure oil energy recovery device of the present invention and the construction machine using the same.
First, as a start state, for example, an operator turns on a key switch (not shown) of a hydraulic excavator.

  Thereby, the controller 30 takes in the data of each pilot pressure from each pressure sensor 13a-15b in order to detect the command pressure of each operation lever 13-15 (step S201).

  Next, the maximum value of the detected command pressure of each operation lever is calculated (step S202). Specifically, the maximum value Pi_max is calculated from the pilot pressure data acquired in (Step S201).

  Next, it is determined whether or not the maximum value Pi_max is higher than a predetermined set pressure Pi_set (step S203). Here, the case where the maximum value Pi_max is higher than the predetermined set pressure Pi_set is a case where any one of the operation levers is operated by a predetermined amount or more by the operator, and for driving any one of the actuators 3 to 5. This is a case where an increased flow rate of pressure oil is required. In such a case, the output torque of the hydraulic pump 2 can be reduced according to the regenerative flow rate by regenerating the pressure oil from the accumulator 22 to the regenerative main circuit Lpy. If the maximum value Pi_max is higher than the set pressure Pi_set, the process proceeds to (Step S204). Otherwise, the process proceeds to (Step S206).

  The controller 30 takes in the data of the pressure Pac of the accumulator 22 from the pressure sensor 23 (step S204).

  Next, it is determined whether or not the pressure Pac of the accumulator 22 is higher than a set pressure Pac_set necessary for regeneration in advance (step S205). If the pressure Pac of the accumulator 22 is higher than the set pressure Pac_set, the process proceeds to (Step S208). Otherwise, the process proceeds to (Step S206).

  In step S205, when it is determined that the pressure Pac of the accumulator 22 is equal to or lower than the set pressure Pac_set, the controller 30 outputs a close command to the regenerative valve 25 (step S206). Specifically, the excitation signal to the electromagnetic operation unit 25a of the regenerative valve 25 is blocked. As a result, the regenerative valve 25 is closed, and the regenerative main circuit Lpy and the regenerative circuit Ly are shut off.

  Next, the controller 30 outputs ΔT = 0 as a torque reduction command, which will be described later, to the displacement control device 2a of the hydraulic pump 2, and executes control without adding a correction signal (step S207). Return to start after executing this step.

  When it is determined in (Step S205) that the pressure Pac of the accumulator 22 is higher than the set pressure Pac_set, the controller 30 outputs an opening command to the regenerative valve 25 (Step S208). Specifically, an excitation signal to the electromagnetic operation unit 25a of the regenerative valve 25 is output. As a result, the regenerative valve 25 opens and communicates, and the pressure oil stored in the accumulator 22 is supplied from the regenerative circuit Ly through the regenerative check valve 26 to the regenerative main circuit Lpy.

  Next, torque correction control of the hydraulic pump 2 is executed (step S209). Specifically, a hydraulic pump reduction torque command value ΔT, which will be described later, is calculated, and a command value corresponding to this reduction torque command value is output to the displacement control device 2b of the hydraulic pump 2. After executing this step, the process returns to step S201.

  Next, capacity control and the like of the capacity control device 2a of the hydraulic pump 2 will be described with reference to FIGS. FIG. 5 is a characteristic diagram showing the characteristics of the pump displacement command in the first embodiment of the pressure oil energy recovery device and the construction machine using the same according to the present invention, and FIG. 6 shows the pressure oil energy recovery device of the present invention and the same. FIG. 7 is a characteristic diagram for explaining torque reduction control in the first embodiment of the construction machine used. FIG. 7 is a torque reduction command in the first embodiment of the pressure oil energy recovery device of the present invention and construction machine using the same. It is a characteristic view which shows the characteristic. 5 to 7, the same reference numerals as those shown in FIGS. 1 to 4 are the same parts, and the detailed description thereof is omitted.

The command value output to the capacity control device 2a of the hydraulic pump 2 is calculated by the controller 30 in the following steps.
(1) The pilot pressure data from the pressure sensors 13a, 13b, 14a, 14b, 15a, 15b, which are command pressures of all the operation levers 13-15, are taken into the controller 30.
(2) The maximum pressure Pi_max is calculated from these data.
(3) Based on the calculated maximum pressure Pi_max and the preset pump capacity command characteristic shown in FIG. 5, the command capacity q of the hydraulic pump 2 is calculated, and the command value realized by the command capacity q is calculated as a capacity control device. Output to 2a.

  Thus, the discharge capacity of the hydraulic pump 2 is determined from the maximum command pressure of all the operation levers 13 to 15.

  Next, torque reduction control will be described with reference to FIGS. Normally, the hydraulic pump 2 limits the pump absorption torque in order to prevent the engine 1 from stalling. FIG. 6 shows the characteristics of the pump capacity q corresponding to the pump discharge pressure P, where the vertical axis is the pump capacity q and the horizontal axis is the pump discharge pressure P (equal to the pressure of the main circuit Lp). Here, in the region where the pump discharge pressure P is low, the pump capacity q can be output at the maximum capacity qmax, but the pump capacity q is set so as not to exceed the limit torque T as the pump discharge pressure P increases. It is decreasing. By controlling the pump capacity q below this limit curve, the absorption torque of the pump does not exceed the limit torque T.

  FIG. 7 shows the characteristic of the reduced torque value ΔT corresponding to the pressure Pac of the accumulator 22 with the reduced torque value ΔT on the vertical axis and the pressure Pac of the accumulator 22 on the horizontal axis. The reduced torque value ΔT is a control for reducing the above-described limit torque T by ΔT and reducing the absorption torque of the pump when the pressure Pac of the accumulator 22 is higher than the preset set pressure Pac_set.

  Thus, the higher the pressure Pac of the accumulator 22, the greater the power that can be regenerated, and the output torque of the hydraulic pump 2 can be reduced accordingly. In the case of a hydraulic excavator, the engine 1 is operated at a constant rotational speed. Therefore, if the load torque is reduced, the output of the engine 1 is reduced as a result, and a fuel consumption reduction effect can be obtained.

  Further, the pressure fluctuation in the center bypass circuit Lc can be suppressed to a low level only by the degree of pressure increase due to the fixed throttle 18. As a result, the influence on the operability of the actuators 3 to 5 can be reduced.

  According to the above-described first embodiment of the pressure oil energy recovery device of the present invention and the construction machine using the same, according to the flow rate of surplus oil not used in the actuator led to the center bypass circuit Lc, the main circuit Since the pressure converter 20 for converting the pressure oil of the Lp and the accumulator 22 for recovering the pressure oil converted by the pressure converter 20 are provided, when the excess oil flows into the center bypass circuit Lc, The pressure oil energy can be reliably stored in the accumulator 22. As a result, stable recovery of pressure oil energy can be realized regardless of the influence of the load condition of the actuator.

  Further, according to the first embodiment of the pressure oil energy recovery device of the present invention and the construction machine using the same, the energy of the pressure oil stored in the accumulator 22 can be regenerated in the regenerative main circuit Lpy. As a result, the energy consumption efficiency is improved and the fuel efficiency of the construction machine can be greatly improved.

  Furthermore, according to the first embodiment of the pressure oil energy recovery device of the present invention and the construction machine using the same, the pressure fluctuation range of the center bypass circuit Lc can be kept low. The influence on the operability of 5 can be reduced. As a result, the burden on the operator is reduced and productivity is improved.

  Further, according to the first embodiment of the pressure oil energy recovery device of the present invention and the construction machine using the same, the pressure oil energy accumulated in the accumulator 22 is supplied to the regenerative main circuit Lpy when the operation lever is input. Regeneration is performed, and the output torque of the hydraulic pump 2 can be reduced according to the regenerative flow rate. As a result, the actuator power can be obtained with a small load of the hydraulic pump 2, and the fuel efficiency can be improved by reducing the torque.

  Furthermore, according to the first embodiment of the pressure oil energy recovery device of the present invention described above and the construction machine using the pressure oil energy, the pressure oil energy can be stored in the state of the pressure oil. No equipment is required and no conversion loss occurs. As a result, the energy consumption efficiency is improved, and the fuel efficiency of the construction machine can be greatly improved.

  Moreover, according to this Embodiment, since the torque reduction control based on the pressure Pac of the accumulator 22 is performed, the remarkable fuel consumption reduction effect can be acquired.

  In the present embodiment, the opening / closing operation of the pressure accumulation switching valve 19 is configured by connecting a pipe line to the operation portion 19a so that the pressure signal on the upstream side of the fixed throttle 18 of the center bypass circuit Lc is the command pressure. However, it is not limited to this. For example, it may be configured by an electromagnetic switching valve and opened and closed by a command from the controller 30. In this case, when the pressure Pac of the accumulator 22 detected by the pressure sensor 23 is equal to or higher than a set value, the pressure oil discharged from the hydraulic pump may be controlled to be cut off. As a result, it is possible to prevent excessive pressure oil from being supplied to the accumulator 22.

  Hereinafter, a second embodiment of a pressure oil energy recovery device of the present invention and a construction machine using the same will be described with reference to the drawings. FIG. 8 is a circuit diagram showing the configuration of the second embodiment of the pressure oil energy recovery device and the construction machine using the same according to the present invention. In FIG. 8, the same reference numerals as those shown in FIG. 1 to FIG.

  The second embodiment of the pressure oil energy recovery device of the present invention and the construction machine using the same shown in FIG. 8 is configured with a hydraulic pressure source, a work machine, and the like that are substantially the same as those of the first embodiment. The following configurations are different.

  The fixed throttle 18 in the first embodiment is omitted, and the switching valve 27 is provided in the center bypass circuit Lc as a variable throttle. One end side that is the upstream side of the center bypass circuit Lc is connected to the downstream side of the direction switching valves 6 to 8, and the other end side that is the downstream side of the center bypass circuit Lc is connected via the port of the switching valve 27. A return circuit Lt communicating with the tank 12 is connected.

  The switching valve 27 has a spring 27b on one end side, and is configured by connecting a pipe line from the upstream side of the relief valve 24 of the regenerative circuit Ly to the operation unit 27a so that the pressure Pac of the accumulator 22 is a command pressure. Yes. When the pressure Pac of the accumulator 22, which is a command pressure, is lower than a predetermined spring pressure (preset pressure) of the spring 27b, the switching valve 27 shuts off the port and connects the center bypass circuit Lc and the return circuit Lt. Block communication. On the other hand, when the command pressure rises and exceeds a preset pressure, the port communicates and pressure oil flows from the center bypass circuit Lc to the return circuit Lt. Thus, the switching valve 27 has a variable throttle function that changes the throttle amount of the center bypass circuit Lc according to the pressure of the accumulator 22. For example, if the set pressure at which the switching valve 27 is fully opened is a value that exceeds the cracking pressure of the relief valve 24, when the pressure Pac of the accumulator 22 exceeds this cracking pressure, the center bypassed pressure oil is fully opened. To escape to tank 12.

  As described above, since the throttle amount of the center bypass circuit Lc is variably controlled in accordance with the pressure Pac of the accumulator 22, when the pressure Pac of the accumulator 22 is sufficiently accumulated, the throttle amount is fully opened and the pressure accumulation switching valve 19 is opened. The command pressure is not generated in the pipe line Lca connected to the operation unit 19a. As a result, the pressure accumulation switching valve 19 does not open. As a result, the pressure accumulating switching valve 19 can be kept open to drive the pressure converter 20 with no load to prevent a fixed pressure loss.

According to the pressure oil energy recovery device of the present invention described above and the second embodiment of the construction machine using the same, the same effects as those of the first embodiment described above can be obtained.
Further, according to the present embodiment, when the pressure of the accumulator 22 is higher than the set pressure, the switching valve 27 that is a variable throttle is fully opened, so that waste of energy is reduced even when the work implement is in a standby state. be able to.

  Hereinafter, a third embodiment of a pressure oil energy recovery apparatus and a construction machine using the same according to the present invention will be described with reference to the drawings. FIG. 9 is a circuit diagram showing a configuration of a third embodiment of a pressure oil energy recovery device and a construction machine using the same according to the present invention. In FIG. 9, the same reference numerals as those shown in FIGS. 1 to 8 are the same parts, and detailed description thereof is omitted.

  The third embodiment of the pressure oil energy recovery device of the present invention and the construction machine using the same shown in FIG. 9 is composed of a hydraulic pressure source, a work machine, and the like that are substantially the same as those of the first embodiment. The following configurations are different.

  In the center bypass circuit Lc according to the first embodiment, a parallel pipe line is provided in the flow direction of the fixed throttle 18, and a relief valve 28 for limiting the pressure of the center bypass circuit Lc is provided in this pipe line. One end of one branch pipe is connected to the center bypass circuit Lc on the upstream side of the fixed throttle 18, and the other end of the one branch pipe is connected to the inlet side of the relief valve 28. The other end of the other branch line is connected to the center bypass circuit Lc on the downstream side of the fixed throttle 18, and one end of the other branch line is connected to the outlet side of the relief valve 28.

  The set pressure of the relief valve 28 is set to a pressure higher than the pressure of the center bypass circuit Lc that fully opens the pressure accumulation switching valve 19. As a result, even if the flow rate of the pressure oil flowing through the center bypass circuit Lc increases abruptly, it is possible to avoid excessive pressure in the center bypass circuit Lc.

According to the pressure oil energy recovery device of the present invention described above and the third embodiment of the construction machine using the same, it is possible to obtain the same effects as those of the first embodiment described above.
Further, according to the present embodiment, since the relief valve 28 is provided in parallel to the fixed throttle 18 in the center bypass circuit Lc, for example, suddenly from the state where the hydraulic pump discharges the maximum flow rate. Even if the operation lever is returned to the neutral position and a large amount of pressure oil flows into the center bypass circuit Lc, the relief valve 28 operates to discharge the pressure oil to the return circuit Lt. As a result, it is possible to avoid a sudden increase in the pressure of the main circuit Lp and an unnecessary increase in engine load.

DESCRIPTION OF SYMBOLS 1 Engine 2 Hydraulic pump 2a Capacity | capacitance control device 3 Direction switching valve 4 for rotations Direction switching valve 5 for arms Direction switching valve 6 for booms Turning motor 7 Arm cylinder 8 Boom cylinder 9 Load check valve 12 Tank 13 Turning lever 14 Arm lever 15 Boom Lever 16 Relief valve 17 Pressure sensor 18 Fixed throttle 19 Accumulation switching valve 20 Pressure converter 20A Hydraulic motor 20B Second hydraulic pump 20C Second capacity controller 21 Check valve 22 Accumulator 23 Pressure sensor 24 Relief valve 25 Regenerative valve 26 Regenerative check valve 27 Switching valve (variable throttle)
30 Controller Lp Main circuit Lc Center bypass circuit La Accumulation line Lt Return circuit Lx Branch line Ly Regenerative circuit Lpy Regenerative main circuit

Claims (5)

A hydraulic pump, a plurality of hydraulic actuators driven by pressure oil from the hydraulic pump, a plurality of directional control valves for controlling the flow rate and direction of pressure oil supplied from the hydraulic pump to the plurality of hydraulic actuators, A main circuit that supplies pressure oil from the hydraulic pump to the direction switching valve; and a center bypass circuit that communicates with the tank through the plurality of direction switching valves and pressurizes excess oil that is not used by the hydraulic actuator. A pressure oil energy recovery device for recovering oil energy,
A pressure accumulator for storing pressure oil energy;
A pressure converter for supplying pressure oil converted into pressure to the pressure accumulator;
An accumulator line connecting the outlet side of the pressure converter and the accumulator;
A branch circuit communicating the inlet side of the pressure converter and the main circuit;
A throttle provided downstream of the center bypass circuit;
An accumulator switching valve provided in the branch circuit and switched by a pressure upstream of the throttle;
A first pressure detector for detecting the pressure of the main circuit;
A second pressure detector for detecting the pressure of the accumulator;
And a control device that takes in detection signals from the first and second pressure detectors and outputs a command to a displacement control unit of a variable displacement hydraulic pump in the pressure converter. Energy recovery device. In the pressure oil energy recovery device according to claim 1,
The controller is
Using the pressure of the main circuit detected by the first pressure detector and the pressure of the accumulator detected by the second pressure detector, the discharge of the variable displacement hydraulic pump in the pressure converter A calculation unit that calculates a target hydraulic pump displacement of a variable displacement hydraulic pump in the pressure converter so that the pressure is equal to or higher than the pressure of the accumulator;
An output unit that outputs the target hydraulic pump displacement calculated by the arithmetic unit as a command to a displacement control unit of the variable displacement hydraulic pump;
A pressure oil energy recovery device. In the pressure oil energy recovery device according to claim 1 or 2,
A regenerative circuit communicating the pressure accumulator and the inlet sides of the plurality of direction switching valves;
A regenerative valve provided in the regenerative circuit;
A third pressure detector that detects a command pressure to a pilot operating unit that performs switching operation of the plurality of directional control valves;
A calculation unit that generates an opening command for the regenerative valve based on a command pressure to the pilot operation unit detected by the third pressure detector, and an opening command generated by the calculation unit is output to the operation unit for the regenerative valve A pressure oil energy recovery device comprising: a control device having an output portion for performing the operation. In the pressure oil energy recovery device according to any one of claims 1 to 3,
The throttle is a variable throttle that changes the throttle amount of the center bypass circuit according to the pressure of the pressure accumulator, and when the pressure of the pressure accumulator is equal to or higher than a preset value, the throttle amount of the center bypass circuit Is a fully-open pressure oil energy recovery device. A construction machine comprising the pressure oil energy recovery device according to any one of claims 1 to 4.

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