JP2009299719A - Construction machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a construction machine for efficiently regenerating potential energy of an arm body, when lowering the arm body by dead weight. <P>SOLUTION: This construction machine 1 is provided for operating the arm body 4 while operating a hydraulic actuator 7 by pressure oil delivered by a hydraulic pump 10R variable in a delivery quantity, and has a regenerative motor 55 rotated by the pressure oil flowing out of the hydraulic actuator 7 in response to operation in the dead weight direction of the arm body 4, and pressure oil regenerating parts 54, 70 and 71 for returning the pressure oil worked for rotating the regenerative motor 55 to the hydraulic actuator 7. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a construction machine that operates an arm body such as a boom, an arm, and a bucket while operating a hydraulic actuator by pressure oil discharged from a variable discharge hydraulic pump, and particularly lowers the arm body by its own weight. (Hereinafter referred to as “self-weight drop”) The present invention relates to a construction machine that efficiently regenerates the potential energy of the arm itself.

  Conventionally, a hydraulic motor (hereinafter referred to as a regenerative motor) that is rotationally driven by a return fluid discharged from a boom cylinder, a generator that is driven by the regenerative motor to generate electric power, and electric power generated by the generator A so-called hybrid hydraulic excavator including an accumulator that accumulates is known (for example, see Patent Document 1).

  The fluid pressure circuit described in Patent Document 1 includes a boom control circuit capable of controlling the circulation of pressure oil in the boom cylinder in a state disconnected from the main pump, and the boom control circuit is based on the regenerative motor and the boom's own weight. A drop prevention valve (holding valve) for preventing an unexpected descent, and a part of the pressure oil flowing out from the head side chamber (shrinking side chamber) when the boom is lowered by its own weight. A regeneration circuit is provided for returning (hereinafter referred to as “regeneration”) to the chamber (the chamber on the side of expansion).

With this configuration, the fluid pressure circuit described in Patent Document 1 regenerates the potential energy of the boom as electric energy by rotating the regenerative motor with the pressure oil flowing out from the boom cylinder when the boom is lowered by its own weight. While driving the assist pump with the obtained electrical energy, various hydraulic actuators are operated with the pressure oil discharged from the assist pump, so that the potential energy can be used effectively.
JP 2006-336848 A

  However, the fluid pressure circuit described in Patent Document 1 branches the pipe line continuing from the head side of the boom cylinder into a pipe line connected to the pressure oil tank and a pipe line connected to the regenerative motor. The rotational speed of the regenerative motor is controlled while controlling the flow rate ratio of the pressure oil flowing through each pipe using the solenoid valve installed in the path (the flow rate of the pressure oil flowing into the regenerative motor is limited. “Flow rate” means the amount of pressurized oil that flows per unit time.) Therefore, part of the pressurized oil (high energy) is discharged into the pressurized oil tank as it is, and the boom is lowered by its own weight. The regenerative motor does not sufficiently regenerate the potential energy of the boom when

  Further, the fluid pressure circuit described in Patent Document 1 uses the high pressure (high energy) pressure oil before the boom is rotated by the pressure oil flowing out from the head side of the boom cylinder when the boom is lowered by its own weight. Since the cylinder is returned (regenerated) to the rod side of the cylinder, the boom potential energy is not sufficiently regenerated by the regenerative motor.

  In view of the above points, an object of the present invention is to provide a construction machine that regenerates the potential energy of the arm body more efficiently when the arm body is lowered by its own weight.

  In order to solve the above-described problem, a construction machine according to a first aspect of the present invention is a construction machine that operates an arm body while operating a hydraulic actuator by pressure oil discharged from a hydraulic pump having a variable discharge amount. A regenerative motor rotated by pressure oil flowing out from a hydraulic actuator for operating the arm body in accordance with the movement of the body in its own weight direction, and a pressure oil that returns pressure oil that has rotated the regenerative motor to the hydraulic actuator And a reproducing unit.

  Further, the second invention is a construction machine according to the first invention, wherein operation detecting means for detecting that an operation for operating the arm body in its own weight direction and the arm body in its own weight direction are performed. And a discharge flow rate control means for reducing the discharge flow rate of the hydraulic pump when it is detected that an operation to be operated is performed.

  The third invention is a construction machine according to the first or second invention, wherein the regenerative motor rotates together with a generator whose rotational load is adjusted, and the flow rate of pressure oil flowing out from the hydraulic actuator. It is characterized by controlling.

  The fourth invention is a construction machine according to the first to third inventions, wherein the pressure oil regeneration unit is connected to the hydraulic actuator through a conduit through which pressure oil obtained by rotating the regenerative motor flows. A branch point that branches into a pipeline connected to the pressure oil tank and a flow rate of the pressure oil that is disposed between the branch point and the pressure oil tank and flows toward the pressure oil tank The flow rate control unit reduces the flow rate of the pressure oil flowing from the regenerative motor toward the pressure oil tank, thereby reducing the pressure oil flowing from the regenerative motor toward the hydraulic actuator. It is characterized by increasing the flow rate.

  A fifth invention is a construction machine according to the first to fourth inventions, wherein the hydraulic actuator has a first oil chamber and a second oil chamber defined by a piston, and the regeneration The motor is rotated by the pressure oil flowing out of the first oil chamber in accordance with the operation of the arm body in the direction of its own weight, and the pressure oil regeneration unit flows out of the regeneration motor after rotating the regeneration motor. The pressure oil is returned to the second oil chamber.

  By the means described above, the present invention can provide a construction machine that efficiently regenerates the potential energy of the arm body when the arm body is lowered by its own weight.

  Embodiments of the present invention will be described below.

  FIG. 1 is a diagram showing a configuration example of a hydraulic excavator on which a construction machine hydraulic pump control device according to the present invention is mounted. In FIG. 1, an excavator 1 has an upper swing body 3 mounted on a crawler-type lower traveling body 2 via a swing mechanism so as to be rotatable around the X axis.

  Further, the upper swing body 3 has a excavation attachment composed of a boom 4, an arm 5 and a bucket 6, and a boom cylinder 7, an arm cylinder 8 and a bucket cylinder 9 as actuators for driving the boom 4, the arm 5 and the bucket 6, respectively. Prepare.

  2 to 5 are hydraulic circuit diagrams of a hydraulic pump control device for construction machinery according to the present invention. The pump control device 200 is driven by an engine and the discharge amount (cc / rev) per rotation is variable. From the two hydraulic pumps 10L and 10R, the center bypass pipe line 30L which communicates the switching valves 12L, 16 and 17 or the center bypass pipe line 30R which communicates the switching valves 11, 12R, 13, 14 and 15. Pressure oil is circulated to the pressure oil tank 22.

  The switching valve 11 is a traveling straight valve, and is a traveling hydraulic motor 42L, 42R that drives the lower traveling body 2 and any hydraulic actuator of the upper swing body 3 (for example, boom cylinder 7, arm cylinder 8, bucket cylinder). In order to circulate the pressure oil from one hydraulic pump 10L to both the left and right traveling hydraulic motors 42L and 42R in order to improve the straightness of the lower traveling body 2. It is a spool valve that switches the flow of pressure oil.

  The switching valves 12L and 12R are spool valves that switch the flow of pressure oil so that the hydraulic oil discharged from the hydraulic pumps 10L and 10R is circulated by the traveling hydraulic motors 42L and 42R, respectively. This is a spool valve for switching the supply / discharge state of the pressure oil discharged from the hydraulic pump 10R to the bucket cylinder 9.

  Further, the switching valve 14 is a spool valve that switches the supply / discharge state of the pressure oil discharged from the hydraulic pump 10R to the boom cylinder 7, and the switching valve 15 is a hydraulic motor for turning the hydraulic oil discharged from the hydraulic pump 10R ( This is a spool valve that switches the flow of pressure oil in order to switch the supply / discharge state to (not shown).

  Further, the switching valve 16 switches the supply / discharge state of the pressure oil discharged from the hydraulic pump 10L to the boom cylinder 7 in addition to the supply / discharge of the pressure oil discharged from the hydraulic pump 10R to the boom cylinder 7. The switching valve 17 is a spool valve that switches the supply / discharge state of the pressure oil discharged from the hydraulic pump 10L to the arm cylinder 8 (not shown).

  The connection between the various switching valves and the various hydraulic actuators and the connection between the pilot valves of the various switching valves and the various operation levers (not shown) are omitted for the sake of clarity. However, conventional hydraulic control or electric control is appropriately adopted.

  The center bypass pipes 30L and 30R are respectively provided with negative control throttles 20L and 20R between the switching valves 15L and 15R on the most downstream side and the pressure oil tank 22, and the flow of the pressure oil discharged by the hydraulic pumps 10L and 10R. By controlling the above, the control pressure for controlling the hydraulic pump regulators 40L, 40R is generated upstream of the negative control throttles 20L, 20R.

  The control pressure lines 32L and 32R indicated by broken lines are control pressure lines for transmitting the control pressure generated upstream of the negative control throttles 20L and 20R to the hydraulic pump regulators 40L and 40R.

  The hydraulic pump regulators 40L and 40R flow pressure oil that tilts and drives a swash plate (yoke) for changing the pump capacity of the hydraulic pumps 10L and 10R to control the discharge amounts of the hydraulic pumps 10L and 10R, respectively. And a piston that is slidable in the cylinder and that defines the cylinder in two chambers. The piston is provided with a rod protruding outward along the cylinder axis, and displacement of the piston tilts and drives the swash plates of the hydraulic pumps 10L and 10R via the rod. A spring that constantly biases the piston is provided in one chamber of the cylinder, and the position of the piston is determined by the balance between the control pressure introduced into the other chamber and the biasing force of the spring.

  The hydraulic pump regulators 40L and 40R decrease the discharge amount of the hydraulic pumps 10L and 10R as the introduced control pressure increases, and increase the discharge amount of the hydraulic pumps 10L and 10R as the introduced control pressure decreases. To do.

  When any hydraulic actuator in the excavator 1 is not used (hereinafter referred to as “standby mode”), the pressure oil discharged from the hydraulic pumps 10L, 10R is negative through the center bypass pipes 30L, 30R. The control throttles 20L and 20R are reached, and the control pressure generated upstream of the negative control throttles 20L and 20R is increased.

  As a result, the hydraulic pump regulators 40L and 40R reduce the discharge amount of the hydraulic pumps 10L and 10R, and reduce the pressure loss (pumping loss) when the discharged pressure oil passes through the center bypass pipelines 30L and 30R. Like that.

  On the other hand, when any hydraulic actuator in the hydraulic excavator 1 is used, the pressure oil discharged from the hydraulic pumps 10L and 10R flows into the hydraulic actuator via the switching valve corresponding to the hydraulic actuator, and the negative control throttle 20L. , 20R is reduced or eliminated, and the control pressure generated upstream of the negative control throttles 20L and 20R is reduced.

  As a result, the hydraulic pump regulators 40L and 40R increase the discharge amount of the hydraulic pumps 10L and 10R, circulate sufficient pressure oil in each hydraulic actuator, and ensure the driving of each actuator.

  With the configuration as described above, the construction machine pump control apparatus 200, in the standby mode, wastes energy consumption in the hydraulic pumps 10L and 10R (the pressure oil discharged from the hydraulic pumps 10L and 10R is center bypass pipe lines 30L and 30R). In the case where various hydraulic actuators are operated while reducing the pumping loss generated in step 1), necessary and sufficient pressure oil can be supplied to the various hydraulic actuators from the hydraulic pumps 10L and 10R.

  A pipe connecting the head side of the boom cylinder 7 and the holding valve 43 branches in the middle, and the branched pipe is connected to the regenerative pump motor 55 via the holding valve 44.

  The holding valve 43 is a valve for stopping the flow of pressure oil flowing out from the head side of the boom cylinder 7 toward the switching valve 14 in order to prevent the boom cylinder 7 from being unexpectedly lowered.

  The holding valve 44 is a valve for stopping the flow of pressure oil flowing out from the head side of the boom cylinder 7 toward the regenerative pump motor 55 in order to prevent an unexpected lowering of the boom cylinder 7, similarly to the holding valve 43. is there.

  The control pump 50 is a hydraulic pump for discharging the control pressure oil flowing through the control pressure lines 35L, 35R, and 38, and continuously supplies the control pressure oil at a predetermined discharge pressure (for example, 4 MPa). This is a fixed displacement hydraulic pump that discharges.

  The electromagnetic valves 51L, 51R, 53 are electromagnetic proportional pressure reducing valves disposed on the control pressure lines 35L, 35R, 38, respectively, and the control pressure lines 36L, The control pressure in these control pressure lines is adjusted while flowing control oil into and out of 36R and 39.

  The shuttle valve 52L is a valve that causes the control pressure oil having a higher pressure out of the control pressure oil in the control pressure line 32L and the control pressure oil in the control pressure line 36L to flow into the hydraulic pump regulator 40L. The shuttle valve 52R is a valve that allows the control pressure oil having the higher pressure out of the control pressure oil in the control pressure line 32R and the control pressure oil in the control pressure line 36R to flow into the hydraulic pump regulator 40R. is there.

  The proportional throttle valve 54 is a valve for adjusting the flow rate of the pressure oil flowing in the pressure oil conduit 70 connecting the regenerative pump motor 55 and the pressure oil tank 22, and the control pressure in the control pressure conduit 39 is changed to the pilot port. Then, the flow rate of the pressure oil flowing in the pressure oil conduit 70 is adjusted steplessly while adjusting the throttle.

  The regenerative pump motor 55 is a device that functions as a hydraulic pump or a hydraulic motor, and its rotating shaft is connected to the rotating shaft of the generator motor 56.

  For example, the regenerative pump motor 55 is rotated by pressure oil flowing out of the boom cylinder 7 when the boom 4 is lowered by its own weight, and functions as a hydraulic motor. At the same time, the rotating shaft of the generator motor 56 is rotated to generate the generator motor 56. The electric energy generated is stored in a battery (not shown) via an inverter while functioning as a machine.

  Further, the regenerative pump motor 55 is rotated by the rotation of the generator motor 56 that functions as an electric motor, thereby pumping up the pressure oil in the pressure oil tank 22 and flowing the pressure oil into the boom cylinder 7 while functioning as a hydraulic pump. You may do it.

  The regenerative pump motor 55 may be a device having only a function as a hydraulic motor, and may be either a fixed capacity motor or a variable capacity motor.

  The generator motor 56 is a device that functions as a generator or an electric motor. The generator motor 56 stores the generated electric energy in a capacitor via an inverter, and rotates using the electric energy stored in the capacitor.

  The generator motor 56 also has a rotational speed when functioning as a generator in accordance with a control current output by the main controller 60 so that the lowering speed of the boom 4 becomes a lowering speed corresponding to an operation amount of a boom operation lever described later. Is controlled.

  The check valve 57 is a valve for preventing pressure oil from flowing from the boom cylinder 7 to the pressure oil pipeline 71.

  Each of the pressure sensors 58 and 59 is a sensor for measuring the cylinder pressure on the head side or the rod side of the boom cylinder 7, and outputs the measurement result to the main controller 60.

  The main controller 60 includes a computer having a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), etc., and corresponds to each of the operation detection means, the flow rate control means, and the discharge flow rate control means. While storing the program in the ROM, the CPU executes processing corresponding to each means.

  The operation detection means receives the outputs of the pressure sensors 58 and 59 and the outputs of various operation levers (remote control valves) such as a boom operation lever, an arm operation lever, a bucket operation lever, a turning operation lever, and a traveling operation lever. This is means for detecting the operation content of the arm body.

  Further, the flow rate control means controls the control current supplied to the holding valves 43 and 44, the electromagnetic valve 53, the generator motor 56, and the various switching valves based on the detection result of the operation detection means, while It is means for controlling the flow rate of the pressure oil flowing through each pressure oil pipe line and realizing the operation of the construction machine according to the detection result of the operation detection means.

  The discharge flow rate control unit controls the flow rate of the pressure oil discharged from the hydraulic pumps 10L and 10R while controlling the control current supplied to the solenoid valves 51L and 51R based on the detection result of the operation detection unit, thereby detecting the operation. It is means for realizing the operation of the construction machine according to the detection result of the means.

  FIG. 2 shows the state of the pump control circuit 200 in the standby mode. The hydraulic pumps 10L and 10R generate a control pressure upstream of the negative control throttles 20L and 20R, and as indicated by an arrow A, the control pressure line 32L. The control pressure oil is caused to flow into the hydraulic pump regulators 40L and 40R with the control pressure through the 32R. In addition, the black thick line which shows the flow of the pressure oil in a pressure oil pipe line represents that the flow volume is comparatively large.

  As a result, the hydraulic pump regulators 40L and 40R move their pistons according to the control pressure oil, and tilt drive the swash plates of the hydraulic pumps 10L and 10R, thereby minimizing the discharge amount of the hydraulic pumps 10L and 10R. The level is reduced to the level (a state in which the discharge amount of the hydraulic pump 10L is reduced is shown in FIG. 3).

  FIG. 3 shows the state of the pump control circuit 200 when the boom 4 is lowered by its own weight. For example, when the main controller 60 detects that the boom operation lever has been operated to the lowering side by the operation detection means, The control means and the discharge flow rate control means are configured not to supply a control current to the electromagnetic valve 53 and to prevent the holding valve 43 from being supplied with a signal pressure for opening generated in response to the operation of the boom operation lever (related). On the other hand, a control current is supplied to the electromagnetic valve 51R and a signal pressure for opening it is supplied to the holding valve 44, and the operation amount of the boom operation lever is supplied to the generator motor 56. By supplying a corresponding control current (relevant power line is shown in black), the boom 4 is provided while reducing the pumping loss of the hydraulic pump 10R. To be regenerated potential energy as electrical energy that. In addition, the gray dotted line which shows the flow of the pressure oil in a pressure oil pipe line represents that the flow volume is comparatively small.

  3 to 5 omit the control pressure pipes 35L and 36L, the electromagnetic valve 51L, the shuttle valve 52L, and the related power lines for the sake of simplification.

  The holding valve 43 to which no signal pressure for release is supplied blocks the flow of pressure oil from the head side of the boom cylinder 7 toward the switching valve 14, and the pressure oil flowing out from the head side of the boom cylinder 7 is supplied to the regenerative pump motor 55. Try to head.

  On the other hand, the holding valve 44 to which the signal pressure for release is supplied releases the flow of pressure oil from the head side of the boom cylinder 7 toward the regenerative pump motor 55, and the pressure oil flowing out from the head side of the boom cylinder 7 is released. It goes to the regenerative pump motor 55.

  Further, the solenoid valve 53 that is not supplied with the control current maintains the control pressure in the control pressure line 39 below a predetermined level, and maintains the throttle of the proportional throttle valve 54 at the maximum (the most easily flowable state). Let

  In addition, the solenoid valve 51R that has received the supply of the control current maintains the control pressure in the control pressure line 36R at a predetermined level or higher, and controls the hydraulic pump regulator 40R so that the discharge amount of the hydraulic pump 10R is minimized. (See arrow B in the figure.) This is to reduce the pumping loss of the hydraulic pump 10R.

  In addition, the generator motor 56 that has been supplied with the control current corresponding to the operation amount of the boom operation lever adjusts the rotational load of the generator motor 56 to a level corresponding to the operation amount of the boom operation lever, while Pressure oil flowing out from the head side is caused to flow into the regenerative pump motor 55, and the flow rate (corresponding to the lowering speed of the boom 4) is adjusted to a level corresponding to the operation amount of the boom operation lever.

  This is to maintain the lowering speed of the boom 4 according to the boom operation lever, so that the potential energy of the boom 4 can be regenerated as electric energy as much as possible.

  As a result, the pump control circuit 200 returns (regenerates) a part of the pressure oil that flows out from the regenerative pump motor 55 to the rod side of the boom cylinder 7, so that the pressure oil discharged from the hydraulic pump 10R is maintained at a low flow rate. However, the lowering of the weight of the boom 4 according to the operation amount of the boom operation lever can be realized, and the potential energy of the boom 4 can be regenerated as electric energy while reducing the pumping loss of the hydraulic pump 10R.

  In this way, the pump control circuit 200 causes a part of the pressure oil flowing out from the regenerative pump motor 55 and the low-flow pressure oil discharged from the hydraulic pump 10R to flow into the rod side of the boom cylinder 7 and the boom operation lever. The lowering of the weight of the boom 4 according to the operation amount is realized.

  FIG. 4 shows a state of the pump control circuit 200 when the boom 4 is lowered by its own speed faster than the case of FIG. 3. The main controller 60 is operated, for example, by the operation detecting means so that the boom operation lever is largely operated to the lowering side. Even when this is detected, the flow control means and the discharge flow control means do not supply the holding valve 43 with the signal pressure for opening generated in response to the operation of the boom operation lever (the related power line is grayed out). On the other hand, the opening signal pressure is supplied to the holding valve 44, the control current is supplied to the electromagnetic valve 51R, and the operation amount of the boom operation lever is supplied to the electromagnetic valve 53 and the generator motor 56. By supplying a control current in accordance with (the related power line is shown in black), the position error of the boom 4 is reduced while reducing the pumping loss of the hydraulic pump 10R. To be able to regenerate Energy as electric energy.

  The holding valve 43 to which no signal pressure for release is supplied blocks the flow of pressure oil from the head side of the boom cylinder 7 toward the switching valve 14, and the pressure oil flowing out from the head side of the boom cylinder 7 is supplied to the regenerative pump motor 55. Try to head.

  On the other hand, the holding valve 44 to which the signal pressure for release is supplied releases the flow of pressure oil from the head side of the boom cylinder 7 toward the regenerative pump motor 55, and the pressure oil flowing out from the head side of the boom cylinder 7 is released. It goes to the regenerative pump motor 55.

  In addition, the solenoid valve 51R that has received the supply of the control current maintains the control pressure in the control pressure line 36R at a predetermined level or higher, and controls the hydraulic pump regulator 40R so that the discharge amount of the hydraulic pump 10R is minimized. (See arrow B in the figure.) This is to reduce the pumping loss of the hydraulic pump.

  In addition, the solenoid valve 53 that has been supplied with the control current according to the operation amount of the boom operation lever continuously adjusts the control pressure in the control pressure line 39 to the level according to the operation amount of the boom operation lever, and is proportional. The throttle of the throttle valve 54 is reduced (a state in which it is more difficult to flow compared to the state of FIG. 3; see arrow C in the figure).

  Further, the generator motor 56 that has been supplied with the control current according to the operation amount of the boom operation lever adjusts the rotational load of the generator motor 56 to a level according to the operation amount of the boom operation lever, and the head of the boom cylinder 7. The pressure oil flowing out from the side is caused to flow into the regenerative pump motor 55 more than in the state of FIG.

  This is because the lowering speed of the boom 4 corresponding to the boom operating lever is made larger than the state shown in FIG. 3, so that the potential energy of the boom 4 can be regenerated as electric energy as much as possible.

  As a result, the pump control circuit 200 increases the pressure oil pressure in the pressure oil conduit 70 and returns (regenerates) most of the pressure oil flowing out from the regenerative pump motor 55 to the rod side of the boom cylinder 7 at a high flow rate. Therefore, while maintaining the pressure oil discharged from the hydraulic pump 10R at a low flow rate, the boom 4 can be lowered at a higher speed and the pumping loss of the hydraulic pump 10R can be reduced.

  In this manner, the pump control circuit 200 causes the high flow pressure oil flowing out from the regenerative pump motor 55 and the low flow pressure oil discharged from the hydraulic pump 10R to flow into the rod side of the boom cylinder 7 and the boom operation lever. A faster descent of the boom 4 according to the operation amount is realized.

  FIG. 5 shows a state of the pump control circuit 200 when excavation is performed while the excavation attachment is brought into contact with the ground and the boom 4 is lowered, and the main controller 60 operates the boom operation lever to the lower side by the operation detection means, for example. 3 is performed and the control described in FIG. 3 is performed, the pressure value output from the pressure sensor 58 on the head side of the boom cylinder 7 becomes less than a predetermined level, and the boom 4 is brought into contact with the excavation attachment on the ground. Is detected, the flow rate control means and the discharge flow rate control means do not supply the control current to the solenoid valves 51R and 53, and the generator motor 56 is set to a no-load state (free run state). (Related power lines are shown in gray.) On the other hand, a signal pressure for opening is supplied to the holding valve 43 and the holding valve 44. In (representing the associated power line in black.), (Do not load resistance to drop) does not interfere with the lowering of the boom 4 so.

  The holding valve 43 to which the signal pressure for opening is supplied is in a state that basically does not hinder the flow of pressure oil from the head side of the boom cylinder 7 toward the switching valve 14.

  The solenoid valve 51R not supplied with the control current maintains the control pressure in the control pressure line 36R below a predetermined level (for example, the tank pressure is at the minimum level), and thereby the control pressure line 32R. The control pressure oil in the control pressure oil in the control pressure line 36R becomes higher in pressure than the control pressure oil in the control pressure line 36R, so that the control pressure oil in the control pressure line 32R flows into the hydraulic pump regulator 40R by the shuttle valve 52R. Thus, the discharge amount of the hydraulic pump 10R is adjusted according to the control pressure oil in the control pressure line 32R.

  Further, the solenoid valve 53 that is not supplied with the control current maintains the control pressure in the control pressure line 39 below a predetermined level, and maintains the throttle of the proportional throttle valve 54 at the maximum (the most easily flowable state). Let

  The holding valve 44 to which the signal pressure for release is supplied releases the flow of pressure oil from the head side of the boom cylinder 7 toward the regenerative pump motor, and there is no pressure oil flowing out from the head side of the boom cylinder 7. The oil is discharged to the pressure oil tank 22 via the regenerative pump motor 55 that is in a loaded state (free-run state).

  In this way, the pump control circuit 200 causes the hydraulic oil discharged from the hydraulic pump 10R to flow into the rod side of the boom cylinder 7 to realize excavation by the boom 4.

  The main controller 60 detects that the boom operating lever has been operated to the lowering side by the operation detecting means and performs the control described in FIG. 3, and then the rod side of the boom cylinder 7 output by the pressure sensor 59. When the pressure value is maintained at a predetermined level or more, a state where the boom 4 is lowered while the excavation attachment is in contact with the ground (a state where the boom 4 cannot be lowered by its own weight) is detected. It is also possible to detect a state in which the boom 4 cannot be lowered by its own weight while detecting the displacement of the rod of the boom cylinder 7 with a displacement sensor.

  With the above configuration, the construction machine equipped with the pump control circuit 200 rotates the regenerative pump motor 55 before performing regeneration with high-pressure pressure oil flowing out from the head side of the boom cylinder 7 when the boom 4 is lowered by its own weight. Therefore, the potential energy of the boom 4 (the kinetic energy of the pressure oil flowing out from the head side of the boom cylinder 7) can be regenerated as electric energy more efficiently.

  The construction machine equipped with the pump control circuit 200 controls the rotation speed of the generator motor 56 while adjusting the magnitudes of the field current and the armature current so that the speed is in accordance with the operation amount of the boom operation lever. When the boom 4 is lowered by its own weight, the flow rate of the pressure oil flowing out from the boom cylinder 7 and the power generation amount of the generator motor 56 are controlled, so that the potential energy of the boom 4 can be regenerated more efficiently.

  The construction machine equipped with the pump control circuit 200 limits the flow rate in the pressure oil conduit 70 between the regenerative pump motor 55 and the pressure oil tank 22 by the proportional throttle valve 54, so that the regenerative pump motor 55 and the boom cylinder are limited. Since the flow rate in the pressure oil pipeline 71 between the boom 4 and the boom 7 is adjusted, the necessary and sufficient pressure oil can be returned (regenerated) to the rod side of the boom cylinder 7 when the boom 4 is lowered by its own weight. The pumping loss of the hydraulic pump 10R can be reduced while maintaining the discharge amount of the hydraulic pump 10R low.

  The “pressure oil regeneration unit” in the claims includes a regeneration circuit including the proportional throttle valve 54, the check valve 57, and the pressure oil pipes 70 and 71 in the above-described embodiment. The “flow rate control unit” includes the proportional throttle valve 54 in the above-described embodiment.

  Although the embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment, and various modifications and changes are within the scope of the gist of the present invention described in the claims. It can be changed.

  For example, in the above-described embodiment, the pump control circuit 200 regenerates the potential energy of the boom 4 as electric energy when the boom 4 is lowered by its own weight, but when the arm 5 or the bucket 6 is lowered by its own weight, The potential energy of the bucket 6 may be regenerated as electric energy.

  In the above-described embodiment, the pump control circuit 200 reduces the discharge amount of the hydraulic pump 10R and lowers the pumping loss when the boom 4 is lowered by its own weight. When the weight is lowered independently, the discharge amount of the hydraulic pump 10R may be reduced to reduce the pumping loss. When the plurality of arms are simultaneously lowered by their own weight, the discharge amounts of the hydraulic pumps 10L and 10R are reduced. The pumping loss may be reduced.

It is a figure which shows the structural example of a hydraulic shovel. 1 is a hydraulic circuit diagram of a pump control device mounted on a construction machine according to the present invention. It is FIG. (1) which shows the state of the pump control circuit in the case of carrying out the weight drop of a boom. It is FIG. (2) which shows the state of the pump control circuit in the case of carrying out a self-weight fall of a boom. It is a figure which shows the state of a pump control circuit in the case of lowering | hanging a boom, making an excavation attachment contact the ground.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Hydraulic excavator 2 ... Lower traveling body 3 ... Upper turning body 4 ... Boom 5 ... Arm 6 ... Bucket 7 ... Boom cylinder 8 ... Arm cylinder 9 ... Bucket cylinder 10L, 10R ... Hydraulic pump 11 ... Direct running valve 12L, 12R, 13,14,15,16,17 ... Switch valve 20L, 20R ... Negative control throttle 22 ... Pressure Oil tanks 30L, 30R ... Center bypass pipes 32L, 32R, 36L, 36R, 38, 39 ... Control pressure pipes 40L, 40R ... Hydraulic pump regulators 42L, 42R ... Traveling hydraulic motors 43 44 ... Holding valve 50 ... Control pump 51L, 51R, 53 ... Electromagnetic proportional pressure reducing valve 52L, 52R ... Shuttle valve 5 4 ... Proportional throttle valve 55 ... Regenerative pump motor 56 ... Generator 57 ... Check valve 58, 59 ... Pressure sensor 60 ... Main controller 200 ... Pump control device

Claims (5)

A construction machine that operates an arm body while operating a hydraulic actuator by pressure oil discharged from a hydraulic pump having a variable discharge amount,
A regenerative motor that is rotated by pressure oil flowing out of the hydraulic actuator in accordance with the operation of the arm body in the direction of its own weight;
A pressure oil regeneration unit that returns the pressure oil that has rotated the regenerative motor to the hydraulic actuator;
A construction machine comprising: Operation detecting means for detecting that an operation for moving the arm body in the direction of its own weight has been performed;
A discharge flow rate control means for reducing the discharge flow rate of the hydraulic pump when it is detected that an operation for operating the arm body in the direction of its own weight has been performed;
The construction machine according to claim 1, comprising: The regenerative motor rotates with a generator whose rotational load is adjusted, and controls the flow rate of the pressure oil flowing out from the hydraulic actuator.
The construction machine according to claim 1 or 2, characterized in that. The pressure oil regeneration unit is a branch point that branches a pipe line through which pressure oil obtained by rotating the regenerative motor flows into a pipe line connected to the hydraulic actuator and a pipe line connected to a pressure oil tank, and A flow rate controller that controls the flow rate of the pressure oil that is disposed between the branch point and the pressure oil tank and flows toward the pressure oil tank;
The flow rate controller increases the flow rate of pressure oil flowing from the regenerative motor toward the hydraulic actuator by decreasing the flow rate of pressure oil flowing from the regenerative motor toward the pressure oil tank.
The construction machine according to any one of claims 1 to 3, wherein The hydraulic actuator has a first oil chamber and a second oil chamber defined by a piston,
The regenerative motor is rotated by pressure oil flowing out of the first oil chamber according to the operation of the arm body in the direction of its own weight,
The pressure oil regeneration unit returns the pressure oil flowing out from the regenerative motor after rotating the regenerative motor to the second oil chamber,
The construction machine according to any one of claims 1 to 4, wherein