JP2013002122A - Pressure oil energy recovery device and construction machine using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure oil energy recovery device that is applicable to a construction machine including no device for electric motor, and recovers energy of pressure oil of minimum flow rate discharged from a hydraulic pump and discarded into a tank through a center bypass circuit, and regenerates and uses the energy of the recovered pressure oil when a plurality of direction changeover valves are all at neutral positions; and a construction machine using the same.SOLUTION: There is provided the pressure oil energy recovery device which recovers the energy of pressure oil produced by the hydraulic pump, the pressure oil energy recovery device including a pressure accumulator connected to a duct downstream from a plurality of direction changeover valves of the center bypass circuit, pressure detection means of detecting the pressure of the pressure accumulator, and pressure accumulation changing means of changing a flow-out destination of the pressure oil of the center bypass circuit to the pressure accumulator or the tank. The pressure accumulation changing means makes the pressure oil of the center bypass circuit flow out to the side of the pressure accumulator when the pressure of the pressure accumulator detected by the pressure detection means does not exceed a previously set value.

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, control is performed by switching a hydraulic pump, a plurality of hydraulic actuators driven by pressure oil discharged from the hydraulic pump, and pressure oil that supplies operating directions and operating speeds of the plurality of hydraulic actuators. Some use a hydraulic system including a plurality of direction switching valves and a center bypass circuit communicating with the tank through the plurality of direction switching valves.

  When all of the plurality of directional control valves are in the neutral position, the energy of the pressure oil discharged from the hydraulic pump and discarded to the tank via the center bypass circuit is recovered. There is a center bypass circuit located downstream of the direction switching valve in which a device for converting the energy of the pressure oil flowing out to the tank through the center bypass circuit into electrical energy is arranged (see, for example, Patent Document 1).

JP 2003-049810 A

  In the above-described prior art, since the pressure oil that has passed through the direction switching valve in the center bypass circuit is surplus oil, recovering the electrical energy generated by the energy of this pressure oil can be used effectively. Increase system efficiency.

  As described above, the above-described conventional technology can improve the efficiency of the system, but requires an expensive electric device such as a generator, an inverter, or a battery as a component that uses electric energy. As a result, there was a problem that the cost would be high. Further, in order to effectively use a large amount of collected electric energy, an electric device such as an electric motor that assists engine torque 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 based on the above-mentioned matters, and the object thereof is applicable to a construction machine not including an expensive electric motor, an electric device such as an inverter or a battery, and a plurality of direction switching valves. When all of the oil is in the neutral position, the pressure oil energy that can be recovered and recovered by recovering the energy of the minimum amount of pressure oil discharged from the hydraulic pump and thrown into the tank via the center bypass circuit An apparatus and a construction machine using the same are provided.

  In order to achieve the above object, the first invention includes a hydraulic pump, a plurality of hydraulic actuators driven by the hydraulic pump, and a plurality of control units for controlling the flow rate and direction of pressure oil discharged from the hydraulic pump. A pressure oil energy recovery device that recovers energy of pressure oil generated by the hydraulic pump of a hydraulic device having a direction switching valve and a center bypass circuit communicating with the tank through the plurality of direction switching valves; A pressure accumulator connected to pipes downstream of the plurality of direction switching valves in the center bypass circuit; a pressure detection means for detecting a pressure of the pressure accumulator; and a pressure oil outlet of the center bypass circuit as the pressure accumulation. Pressure accumulation switching means for switching to the tank or the tank, and the pressure accumulation switching means presets the pressure of the pressure accumulator detected by the pressure detection means. When the set pressure does not exceed the set value, the center bypass circuit causes the pressure oil in the center bypass circuit to flow out to the accumulator side, and when the pressure in the accumulator detected by the pressure detection means exceeds a preset set value, the center bypass circuit The pressure oil is allowed to flow out to the tank side.

  According to a second aspect, in the first aspect, a discharge circuit that connects the hydraulic pump and the plurality of direction switching valves, and a regenerative unit that controls communication / blocking between the discharge circuit and the pressure accumulator. Each of the operation command input means for controlling the plurality of directional control valves to drive the plurality of hydraulic actuators, and the regeneration means includes the discharge circuit and the discharge circuit based on an input value of the operation input means. The pressure accumulator is controlled in a communication state.

  Furthermore, a third invention is the variable displacement hydraulic pump according to the second invention, wherein the hydraulic pump is provided with a variable displacement mechanism, further comprising torque command means for outputting a command to the variable displacement mechanism, The torque command means outputs a torque reduction command when the regeneration means controls the discharge circuit and the pressure accumulator in a communication state.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the pressure accumulation switching means further comprises a prime mover that drives the hydraulic pump, and a state detection means that detects start / stop of the prime mover. Is characterized in that, when the state detecting means detects the stoppage of the prime mover, the pressure oil in the center bypass circuit is caused to flow out to the tank side.

  Furthermore, the fifth invention is the first hydraulic pump according to any one of the first to fourth inventions, the second hydraulic pump disposed on the pressure accumulator side of a pipe line connecting the center bypass circuit and the pressure accumulator, A power conversion device comprising a hydraulic pump and a hydraulic motor connected by a drive shaft and disposed on the center bypass circuit side of the pipe, wherein the second hydraulic pump is a variable displacement hydraulic having a variable displacement mechanism. It is a pump.

  The sixth invention is a construction machine, comprising any one of the first to fifth inventions.

  According to the present invention, when all of the plurality of directional control valves are in the neutral position, the accumulator that collects all the hydraulic oil corresponding to the minimum flow rate discharged from the hydraulic pump and discarded into the tank via the center bypass circuit is provided. It can be applied to a construction machine not equipped with an electric device, and a hydraulic system can be manufactured at a low cost. Also, without converting the pressure oil energy into electrical energy, it can be stored in the accumulator as it is, and the energy of the pressure oil stored in the accumulator can be regenerated in the main circuit, so there is no loss of conversion to electric energy and energy consumption The efficiency is improved and the fuel efficiency of the construction machine can be greatly improved.

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 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 flowchart figure which shows the control flow of the hydraulic pump and regenerative valve in 2nd 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 instruction | command in 2nd Embodiment of the pressure oil energy recovery apparatus of this invention and a construction machine using the same. It is a characteristic view explaining the torque reduction control in 2nd 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 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. It is a flowchart figure which shows the control flow of the pressure accumulation solenoid valve in 3rd 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 4th Embodiment of the hydraulic 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 pressure converter in 4th Embodiment of the pressure oil energy collection | 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 the first 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 that supplies 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 has a relief valve 16 and a pressure for limiting the pressure of the pressure oil in the main circuit Lp. Direction switching valves 6 to 8 for controlling the direction and flow rate of oil 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. A center bypass circuit Lc is provided downstream of the direction switching valves 6-8.

  The direction switching valves 6 to 8 are three-position and six-port switching valves. Each spool position is switched by the pilot pressure supplied to both pilot operation portions, and pressure oil from the hydraulic pump 2 is supplied to each actuator 3. -5 to be driven. 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.

  In addition to the center port 6c of the turning direction switching valve 6, the main circuit Lp is connected to the inlet port 6a via a load check valve 9 that prevents the flow of pressure oil from the side of the turning motor 3 that is an actuator. ing. Further, the main circuit Lp prevents pressure oil from flowing out from the arm cylinder 4 side and the boom cylinder 5 side, which are 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 are connected to each other.

  One end 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 of the center bypass circuit Lc allows only inflow of pressure oil from the direction switching valves 6 to 8 side. It is connected to an accumulator 18 via a check valve 17. The check valve 17 and the accumulator 18 are connected by a pressure accumulation circuit La. The center bypass circuit Lc is connected to a return circuit Lt that communicates with the tank 12 via a pressure accumulation switching valve 19 that is a 2-position 2-port switching valve.

  The pressure accumulation switching valve 19 has a spring 19b on one end side, and is configured by connecting a pipe line from the pressure accumulation circuit La to the operation portion 19a so that the pressure of the pressure accumulation circuit La is a command pressure. When the pressure of the pressure accumulation circuit La, which is the command pressure, is lower than a predetermined spring pressure (preset pressure) of the spring 19b, the port is blocked and the center bypass circuit Lc and the return circuit Lt do not communicate with each other. On the other hand, when the command pressure exceeds a preset pressure, the port communicates and pressure oil flows from the center bypass circuit Lc to the return circuit Lt.

  A regenerative valve 20 that is a two-position / two-port switching valve is connected to the other end of the pipe line having one end connected to the pressure accumulating circuit La, and only inflow of pressure oil from the pressure accumulating circuit La in series with the regenerative valve 20 is performed. One end side of the regenerative check valve 21 that permits the above is connected. The other end side of the regenerative check valve 21 is connected to the main circuit Lp.

  The regenerative valve 20 has a spring 20b on one end side, and is configured by connecting a pipe line from a shuttle circuit, which will be described later, to the operation portion 20a so that the maximum pressure of the operation lever, which will be described later, will be a command pressure. When the maximum pressure of the operating lever, which is the command pressure, is lower than a predetermined spring pressure (preset pressure) of the spring 20b, the port is blocked and the pressure accumulation circuit La and the main circuit Lp are not communicated. On the other hand, when the command pressure exceeds a preset pressure, the port communicates and pressure oil flows from the pressure accumulation circuit La to the main circuit Lp.

  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 generated in the pilot circuit 13a or 13b connected to the two operation portions 6f and 6g of the turning direction switching valve 6, and the pilot pressure of the arm lever 14 is operated by the operation of the arm direction switching valve 7. It occurs in the pilot circuit 14a or 14b connected to the sections 7f and 7g. Similarly, the pilot pressure of the boom lever 15 is generated in the pilot circuit 15a or 15b connected to the operation portions 8f and 8g of the boom direction switching valve 8.

  The pilot circuits 13a and 13b of the swivel lever 13 are respectively connected to one end side of pipes for detecting the pilot pressure, and the other end side of the pipe is connected to a shuttle valve 22 for selecting a high value. The pilot circuits 14a and 14b of the arm lever 14 are connected to one end sides of pipes for detecting the pilot pressure, respectively, and the other end side of the pipes is connected to a shuttle valve 23 for selecting a high value. Similarly, the pilot circuits 15a and 15b of the boom lever 15 are respectively connected to one end sides of pipes for detecting the pilot pressure, and the other end side of the pipes is connected to a shuttle valve 24 for selecting a high value. .

  The detection pipe of the shuttle valve 25 is arranged so that the high value selected by the shuttle valve 22 and the shuttle valve 23 can be selected, and the high value selected by the shuttle valve 25 and the shuttle valve 24 is selected. The detection pipe of the shuttle valve 26 is arranged so as to make it possible. By arranging in this way, a shuttle circuit that can select the highest value of all the operation levers is configured. This maximum pressure is guided to a capacity control device 2a that controls the discharge capacity of the hydraulic pump 2, and is also controlled as a command pressure of the regenerative valve 20 while controlling the pump capacity.

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, the case where the operation amounts of all the operation levers 13 to 15 are zero will be described. The hydraulic oil discharged from the hydraulic pump 2 to the main circuit Lp is supplied at its full flow rate to the center bypass circuit Lc via the center ports 6c to 8c of the direction switching valves 6 to 8. At this time, the capacity control device 2a receives the command pressure from the shuttle circuit to minimize the capacity of the hydraulic pump 2.

  In this state, when the pressure of the pressure accumulation circuit La is lower than the set pressure of the pressure accumulation switching valve 19, since the pressure accumulation switching valve 19 is cut off, the pressure oil introduced from the main circuit Lp to the center bypass circuit Lc 17 through the pressure accumulating circuit La. Moreover, since the input of the operation levers 13-15 is zero, the regenerative valve 20 will be in a cutoff state. As a result, as the pressure oil flows in, the pressure in the pressure accumulation circuit La starts to rise. When the pressure exceeds the set pressure of the pressure accumulation switching valve 19, the pressure accumulation switching valve 19 is switched to the communication state. Thereby, the pressure oil of the center bypass circuit Lc flows into the tank 12 through the pressure accumulation switching valve 19 and the return circuit Lt. As a result, the pressure of the hydraulic pump 2 is reduced, and wasteful energy consumption is prevented. The set pressure of the pressure accumulation switching valve 19 is preferably a pressure that can drive at least one actuator alone, for example.

  Normally, the hydraulic pump 2 discharges a pressure oil having a minimum flow rate that is not zero even if the operation levers 13 to 15 are not input. Therefore, even if the operation levers 13 to 15 are not input, the pressure oil corresponding to the minimum flow rate is guided to the center bypass circuit Lc, so that the pressure oil can be accumulated in the accumulator 18 without waste.

  Next, the case where the turning lever 13 which is one of the operation levers is input will be described. 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. When the pilot pressure generated in the pilot circuits 13a and 13b by operating the swivel lever 13 rises above the set pressure of the regenerative valve 20, the regenerative valve 20 communicates, so the pressure oil stored in the pressure accumulating circuit La is regenerated. It passes through the valve 21 and joins the main circuit Lp.

  Thereby, since the flow volume of the pressure oil which the turning motor 3 requires is supplied from the pressure accumulation circuit La, the discharge flow volume of the hydraulic pump 2 can be reduced. As a result, the output of the engine 1 can be reduced, so that fuel efficiency can be improved.

  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, when all of the plurality of direction switching valves 6 to 8 are in the neutral position, the hydraulic pump 2 The accumulator 18 that collects all of the minimum amount of pressure oil that is discharged and discarded into the tank 12 via the center bypass circuit Lc is provided, so it can be applied to construction machines that do not have an electric device and is manufactured at low cost. can do. In addition, since the pressure oil energy can be stored in the accumulator 18 as it is without being converted into electric energy and the pressure oil can be regenerated to the main circuit Lp as appropriate, there is no loss of conversion into electric energy, and energy consumption efficiency is improved. In addition, the fuel efficiency of construction machinery can be greatly improved.

  In addition, according to the first embodiment of the pressure oil energy recovery device of the present invention and the construction machine using the same, control is performed without using an electrical device such as a controller, thus avoiding electrical troubles. can do. As a result, a highly reliable pressure oil energy recovery device can be provided.

  In the present embodiment, the maximum pilot pressure in all the operating levers is configured as the command pressure of the regenerative valve 20, but the pilot pressure of a specific actuator may be configured as the command pressure of the regenerative valve 20. .

  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. 3 is a circuit diagram showing the configuration of the second embodiment of the pressure oil energy recovery apparatus and the construction machine using the same according to the present invention, and FIG. 4 shows the pressure oil energy recovery apparatus and the construction machine using the same according to the present invention. It is a flowchart figure which shows the control flow of the hydraulic pump and regenerative valve in 2nd Embodiment. 3 and 4, the same reference numerals as those shown in FIG. 1 and FIG. 2 are the same parts, and detailed description thereof is omitted.

  The second embodiment of the pressure oil energy recovery device of the present invention and the construction machine using the same shown in FIG. 3 is composed of a hydraulic power source, a work machine, and the like which are substantially the same as those of the first embodiment. The following configurations are different.

  The shuttle valves 22 to 26 in the first embodiment are omitted, the pilot circuits 13a and 13b of the turning lever 13 are provided with command pressure sensors 13c and 13d for detecting these pilot pressures, and the arm lever 14 The pilot circuits 14a and 14b are provided with command pressure sensors 14c and 14d for detecting these pilot pressures. Similarly, the pilot circuits 15a and 15b of the boom lever 15 are provided with command pressure sensors 15c and 15d for detecting these pilot pressures. Detection signals from these command pressure sensors 13c to 15d are input to the controller 30 described later. A pressure sensor 18 a that detects the pressure of the pressure accumulation circuit La is provided, and a detection signal is input to the controller 30.

  From the controller 30, an electrical command is output to the displacement control device 2 b of the hydraulic pump 2, and an electrical command is output to the electromagnetic operation unit 31 a of the regenerative valve 31. Thus, the controller 30 performs capacity control of the hydraulic pump 2 and opening / closing control of the regenerative valve 31.

Next, control of the hydraulic pump 2 and the regenerative valve 31 will be described with reference to FIG.
First, as a start state, for example, an operator turns on a key switch (not shown) of a hydraulic excavator.

  In step (S101), command pressures of the operation levers 13 to 15 are detected. Specifically, the pilot pressure data from the pressure sensors 13 c to 15 d is taken into the controller 30.

  In step (S102), the detected maximum value of the command pressure of each operation lever is calculated. Specifically, the maximum value Pi_Max is calculated from each pilot pressure data captured in step (S101).

  In step (S103), it is determined whether or not the maximum value Pi_Max is higher than a predetermined set pressure Pi_set. If the maximum value Pi_Max is higher than the set pressure Pi_set, the process proceeds to step (S104). Otherwise, the process proceeds to step (S106).

  In step (S104), the pressure of the pressure accumulating circuit La is detected. Specifically, the data of the pressure Pac of the pressure accumulation circuit La from the pressure sensor 18 a is taken into the controller 30.

  In step (S105), it is determined whether or not the pressure Pac of the pressure accumulating circuit La is higher than a set pressure Pac_set necessary for regeneration. When the pressure Pac of the pressure accumulation circuit La is higher than the set pressure Pac_set, the process proceeds to step (S108), and otherwise, the process proceeds to step (S106).

  In step (S106), a close command is output to the regenerative valve 31. Specifically, the excitation signal from the controller 30 to the electromagnetic operation part 31a of the regenerative valve 31 is cut off. As a result, the regenerative valve 31 is closed and the main circuit Lp and the pressure accumulation circuit La are shut off.

  In step (S107), torque correction control of the hydraulic pump 2 is not executed. Specifically, since T = 0 is output from the controller 30 to the displacement control device 2b of the hydraulic pump 2 as a torque reduction command to be described later, no correction signal is added. After executing step (S107), the process returns to the start.

  In step (S108), when the pressure Pac of the pressure accumulation circuit La is determined to be higher than the set pressure Pac_set, in step (S108), an opening command is output to the regenerative valve 31. Specifically, an excitation signal is output from the controller 30 to the electromagnetic operation unit 31a of the regenerative valve 31. As a result, the regenerative valve 31 opens and communicates, and the pressure oil stored in the pressure accumulation circuit La passes through the regenerative check valve 21 and joins the main circuit Lp.

  In step (S109), torque correction control of the hydraulic pump 2 is executed. 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 step (S109), the process returns to step (S101).

  Next, capacity control and the like of the capacity control device 2b 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 second 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 second embodiment of the construction machine used, and FIG. 7 is a torque reduction command in the second 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 2b of the hydraulic pump 2 is calculated by the controller 30 in the following steps.
(1) The pilot pressure data from the pressure sensors 13c, 13d, 14c, 14d, 15c, and 15d, which are command pressures of all the operation levers 13 to 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 by the capacity control device. To 2b.

  Thus, also in 2nd Embodiment, the discharge capacity | capacitance of the hydraulic pump 2 is determined from the highest pressure of the command pressure of all the operation levers 13-15.

  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 characteristics of the reduced torque value ΔT corresponding to the pressure accumulation circuit pressure Pac, with the vertical axis representing the reduced torque value ΔT and the horizontal axis representing the pressure accumulation circuit pressure Pac. The reduced torque value ΔT is obtained by reducing the above-described limit torque T by ΔT and reducing the pump absorption torque when the pressure Pac of the pressure accumulation circuit La is higher than the preset pressure Pac_set of the pressure accumulation circuit La. It is control to do.

  Thus, the higher the pressure Pac of the pressure accumulating circuit La, 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.

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.
Moreover, according to this Embodiment, since the torque reduction control based on the pressure Pac of the pressure accumulation circuit La is performed, a remarkable fuel consumption reduction effect can be obtained.

  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. 8 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, and FIG. 9 is a pressure oil energy recovery device of the present invention and a construction machine using the same. It is a flowchart figure which shows the control flow of the pressure accumulation solenoid valve in 3rd Embodiment. 8 and 9, the same reference numerals as those shown in FIGS. 1 to 7 are the same parts, and the detailed description thereof will be 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. 8 is composed of a hydraulic power source, a work machine, and the like that are substantially the same as those of the second embodiment. The following configurations are different.

  The hydraulic switching accumulator switching valve 19 in the second embodiment is replaced with an electromagnetic switching accumulator solenoid valve 40, and a rotation sensor 41 for detecting the rotational speed Neng of the engine 1 is attached to the engine 1. A detection signal from the rotation sensor 41 is input to the controller 30. From the controller 30, an electrical command is output to the electromagnetic operation unit 40 a of the pressure accumulating electromagnetic valve 40, and opening / closing control of the pressure accumulating electromagnetic valve 40 is performed.

Next, control of the pressure accumulating electromagnetic valve 40 will be described with reference to FIG.
First, as a start state, for example, an operator turns on a key switch (not shown) of a hydraulic excavator.

  In step (S201), the rotational speed of the engine 1 is detected. Specifically, data of the rotational speed Neng of the engine 1 detected from the rotation sensor 41 is taken into the controller 30.

  In step (S202), it is determined whether or not the rotation speed Neng is higher than a predetermined engine rotation lower limit value Nmin. If the rotational speed Neng is higher than the engine rotation lower limit Nmin, it is determined that the engine 1 is in an operating state, and the process proceeds to step (S203). Otherwise, the process proceeds to step (S206). Here, the engine rotation lower limit Nmin is a value set lower than the low idle rotation speed of the engine 1, and is set in consideration of a decrease in the rotation speed when a sudden load is applied from the low idle time. .

  In step (S203), the pressure of the pressure accumulation circuit La is detected. Specifically, the data of the pressure Pac of the pressure accumulation circuit La from the pressure sensor 18 a is taken into the controller 30.

  In step (S204), it is determined whether or not the pressure Pac of the pressure accumulating circuit La is higher than a preset pressure Pac_max for protecting the accumulator 18 determined in advance. When the pressure Pac of the pressure accumulation circuit La is higher than the set pressure Pac_max, the process proceeds to step (S206), and otherwise, the process proceeds to step (S205).

  In step (S205), since the pressure Pac of the pressure accumulation circuit La is not higher than the set pressure Pac_max, a close command is output to the pressure accumulation electromagnetic valve 40. Specifically, the excitation signal from the controller 30 to the electromagnetic operation unit 40a of the pressure accumulating electromagnetic valve 40 is cut off. As a result, the pressure accumulating electromagnetic valve 40 is closed, the center bypass circuit Lc and the return circuit Lt are shut off, and all the pressure oil from the center bypass circuit Lc flows into the pressure accumulating circuit La.

  In step (S206), since the pressure Pac of the pressure accumulating circuit La is higher than the set pressure Pac_max, an open command is output to the pressure accumulating electromagnetic valve 40. Specifically, an excitation signal is output from the controller 30 to the electromagnetic operation unit 40 a of the pressure accumulating electromagnetic valve 40. As a result, the pressure accumulating electromagnetic valve 40 is opened to be in a communicating state, and surplus oil stored in the pressure accumulating circuit La flows into the tank 12 via the return circuit Lt. As a result, when the accumulator 18 does not need to accumulate pressure in the full state and the operation levers 13, 14, and 15 are not operated, the pressure of the main circuit Lp does not increase, so that deterioration of the fuel consumption of the engine 1 can be suppressed. .

  On the other hand, even when it is determined in step (S202) that the rotational speed Neng is not higher than the predetermined engine rotation lower limit Nmin, it is determined that the engine 1 is stopped and the pressure accumulation solenoid valve 40 is determined in step (S206). The opening command is output.

  After executing either step (S205) or step (S206), the process returns to the start.

  In the present embodiment, it is determined that the engine 1 is stopped and the accumulator electromagnetic valve 40 is controlled to open, so that an excessive load can be prevented from acting on the starter motor when the engine 1 is started.

  For example, assuming that the accumulator electromagnetic valve 40 is not controlled to be opened by determining that the engine 1 is stopped, and the pressure Pac of the accumulator circuit La is equal to or lower than the upper limit value Pac_max when the engine 1 is stopped, the accumulator solenoid valve In 40, a closing command is output. Since the hydraulic pump 2 is directly connected to the engine, the hydraulic pump 2 is also driven when the engine 1 is started. As a result, a pressure Pac is generated in the pressure accumulating circuit La communicating with the hydraulic pump 2, and a large starting torque corresponding to the load torque of the hydraulic pump 2 is required when the engine 1 is started. As a result, an excessive load torque is generated in the starter motor. In particular, when the ambient temperature is low, the viscosity of the hydraulic oil is large, so that there is a possibility that the engine 1 cannot be started if there is a high residual pressure of the accumulator 18.

According to the above-described pressure oil energy recovery device of the present invention and the third embodiment of the construction machine using the same, it is possible to obtain the same effects as those of the second embodiment described above.
Further, according to the present embodiment, it is not necessary to increase the capacity of the starter motor of the engine 1, and it is possible to suppress the cost increase and secure stable engine startability.

  Hereinafter, a fourth 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. 10 is a circuit diagram showing a configuration of a fourth embodiment of a pressure oil energy recovery device and a construction machine using the same according to the present invention, and FIG. 11 is a pressure oil energy recovery device of the present invention and a construction machine using the same. It is a flowchart figure which shows the control flow of the pressure converter in 4th Embodiment of this. 10 and 11, the same reference numerals as those shown in FIGS. 1 to 9 are the same parts, and detailed description thereof is omitted.

  The fourth embodiment of the pressure oil energy recovery device of the present invention and the construction machine using the same shown in FIG. 10 is configured with a hydraulic pressure source, a work machine, and the like that are substantially the same as those of the third embodiment. The following configurations are different.

  In the center bypass circuit Lc in the third embodiment, a power conversion device 42 is additionally arranged on the upstream side of the check valve 17. The power conversion device 42 includes a hydraulic motor 43 and a second hydraulic pump 44, and is connected to each other by a drive shaft. When pressure oil is supplied to the hydraulic motor 43 side, a drive torque is generated by the pressure oil, Two hydraulic pumps 44 are driven simultaneously. At this time, the pressure at the outlet of the second hydraulic pump 44 can be converted from the pressure at the inlet of the hydraulic motor 43 by changing the capacities of the hydraulic motor 43 and the second hydraulic pump 44. Pressure oil discharged from the second hydraulic pump 44 is accumulated in the accumulator 18 via the check valve 17.

  In the present embodiment, the hydraulic motor 43 is a fixed displacement type, the second hydraulic pump 44 is a variable displacement type, and an electric command is output from the controller 30 to the displacement control device 44a of the second hydraulic pump 44. Capacity control is performed.

Next, control of the pressure converter 42 will be described with reference to FIG.
First, as a start state, for example, an operator turns on a key switch (not shown) of a hydraulic excavator.

  In step (S301), the pressure of the pressure accumulating circuit La is detected. Specifically, the data of the pressure Pac of the pressure accumulation circuit La from the pressure sensor 18 a is taken into the controller 30.

  In step (S302), the target hydraulic pump displacement qp of the second hydraulic pump 44 of the pressure converter 42 is calculated. Specifically, as will be described in detail later, the detected pressure Pac of the accumulator circuit La, the capacity qm of the hydraulic motor 43 that is a fixed capacity, and the preset target motor inlet pressure Pm are used to A target hydraulic pump displacement qp is calculated.

  In step (S303), a command signal is output to the displacement control device 44a of the second hydraulic pump so as to achieve the target pump displacement. In this way, the capacity control of the second hydraulic pump 44 of the pressure conversion device 42 is executed.

Next, calculation of the target hydraulic pump capacity qp of the second hydraulic pump 44 will be described. If the conversion loss of the power conversion device 42 set in advance by measurement or the like is η, the input hydraulic power (= Pm · qm) of the hydraulic motor 43 and the output power of the hydraulic pump 44 connected to the hydraulic motor 43 by a drive shaft. Since (= Pac · qp · η) is balanced, the equation Pm · qm = Pac · qp · η holds. As a result, the target hydraulic pump capacity qp of the second hydraulic pump 44 is calculated according to the following equation (1).
qp = (Pm · qm) / (Pac · η) (1)
Here, Pm is a preset target motor inlet pressure, qm is the capacity of the hydraulic motor 43, Pac is the pressure of the accumulator circuit La, qp is the target hydraulic pump capacity of the second hydraulic pump 44, and η is the power converter 42. Conversion loss.

  The oil discharged from the second hydraulic pump 44 is guided to the accumulator circuit La through the check valve 17, but the passage resistance of the check valve 17 is very small and can be ignored. Therefore, the discharge pressure of the second hydraulic pump 44 is equal to Pac.

  Further, the inlet set pressure Pm of the hydraulic motor 43 is set in advance, and the capacity qp of the second hydraulic pump 44 is controlled based on the equation (1), so the pressure at the inlet of the hydraulic motor 43 is the accumulator circuit. Regardless of the pressure Pac of La, it is controlled to be constant. As a result, the pressure of the center bypass circuit Lc is controlled to be constant, so that even if the pressure of the accumulator 18 fluctuates, the operability of the actuators 3 to 5 is not affected.

According to the pressure oil energy recovery device of the present invention described above and the fourth embodiment of the construction machine using the same, the same effects as those of the above-described third embodiment can be obtained.
Further, according to the present embodiment, the energy of the pressure oil can be recovered even when the pressure of the center bypass circuit Lc in the first to third embodiments described above is lower than the accumulator pressure Pac. Therefore, even when the pressure oil energy is recovered when there is no input from the operation levers 13 to 15, the pressure of the center bypass circuit Lc can be reduced to the preset inlet set pressure Pm of the hydraulic motor 43, The pressure oil pressure in the main circuit Lp can also be suppressed to about the inlet set pressure Pm. As a result, the hydraulic pump 2 can be operated without increasing the load torque of the engine 1, so that the fuel efficiency of the construction machine can be greatly improved.

  Furthermore, according to the present embodiment, the pressure of the center bypass circuit Lc can be kept constant at the preset inlet set pressure Pm of the hydraulic motor 43, so that it is affected by operability due to fluctuations in the pressure of the accumulator 18. Absent. As a result, stable operability can be realized.

  Although the present embodiment has been described with the configuration in which the inlet pressure of the hydraulic motor 43 is not detected, the present invention is not limited to this. It is possible to further improve control accuracy by detecting the inlet pressure of the hydraulic motor 43 and performing feedback control.

DESCRIPTION OF SYMBOLS 1 Engine 2 Hydraulic pump 3 Turning direction switching valve 4 Arm direction switching valve 5 Boom direction switching valve 6 Swing motor 7 Arm cylinder 8 Boom cylinder 9 Load check valve 12 Tank 13 Swing lever 14 Arm lever 15 Boom lever 16 Relief valve 17 Check valve 18 Accumulator 19 Accumulation switching valve 20 Regenerative valve 21 Regenerative check valve 22 Shuttle valve Lp Main circuit Lc Center bypass circuit La Accumulation circuit Lt Return circuit

Claims (6)

A hydraulic pump, a plurality of hydraulic actuators driven by the hydraulic pump, a plurality of directional switching valves for controlling the flow rate and direction of pressure oil discharged from the hydraulic pump, and a tank through the plurality of directional switching valves A pressure oil energy recovery device for recovering the energy of the pressure oil generated by the hydraulic pump in a hydraulic device having a center bypass circuit communicating with
A pressure accumulator connected to pipes downstream of the plurality of direction switching valves in the center bypass circuit;
Pressure detecting means for detecting the pressure of the accumulator;
Pressure accumulation switching means for switching the outlet of the pressure oil of the center bypass circuit to the accumulator or the tank,
When the pressure of the pressure accumulator detected by the pressure detection means does not exceed a preset set value, the pressure accumulation switching means causes the pressure oil of the center bypass circuit to flow out to the pressure accumulator side, and the pressure detection means When the detected pressure of the pressure accumulator exceeds a preset set value, the pressure oil in the center bypass circuit is caused to flow out to the tank side. In the pressure oil energy recovery device according to claim 1,
A discharge circuit connecting the hydraulic pump and the plurality of directional control valves;
Regenerative means for controlling communication / blocking between the discharge circuit and the pressure accumulator;
Each operation command input means for controlling the plurality of direction switching valves to drive the plurality of hydraulic actuators,
The regenerative unit controls the discharge circuit and the pressure accumulator to be in communication with each other based on an input value of the operation input unit. In the pressure oil energy recovery device according to claim 2,
The hydraulic pump is a variable displacement hydraulic pump having a variable displacement mechanism, further comprising torque command means for outputting a command to the variable displacement mechanism,
The torque command means outputs a torque reduction command when the regeneration means controls the discharge circuit and the pressure accumulator to communicate with each other. In the pressure oil energy recovery device according to any one of claims 1 to 3,
A prime mover for driving the hydraulic pump;
A state detecting means for detecting start / stop of the prime mover,
The pressure oil energy recovery device, wherein the pressure accumulation switching means causes the pressure oil of the center bypass circuit to flow out to the tank side when the state detection means detects the stop of the prime mover. In the pressure oil energy recovery device according to any one of claims 1 to 4,
A second hydraulic pump disposed on the pressure accumulator side of a pipe line connecting the center bypass circuit and the pressure accumulator, and connected to the second hydraulic pump by a drive shaft and disposed on the center bypass circuit side of the pipe line. A power conversion device comprising a hydraulic motor,
The pressure oil energy recovery device, wherein the second hydraulic pump is a variable displacement hydraulic pump provided with a variable displacement mechanism. A construction machine comprising the pressure oil energy recovery device according to any one of claims 1 to 5.

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