JP2009127643A - Boom drive circuit of construction machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a boom drive circuit of a construction machine having good energy regeneration efficiency. <P>SOLUTION: A head side oil chamber 12a of a boom cylinder 12 is connected to an operating oil inlet of a hydraulic motor 23 via an energy regeneration valve 21, and an operating oil outlet of the hydraulic motor 23 is connected to a rod side oil chamber 12b of the boom cylinder 12 via a check valve 24. During boom lowering operation, a controller 28 opens the energy regeneration valve 21, and the operating oil in the head side chamber 12a to which the own weight of the boom is applied is made to flow into the hydraulic motor 23. Electric power output by a generator 26 connected to the hydraulic motor 23 is converted by an inverter 27 in the voltage and a storage battery is charged. The operating oil passed through the hydraulic motor 23 is separated through a conduit 25 into a portion for supplying to the rod side oil chamber 12b of the boom cylinder 12 and a portion for returning to a tank via a control valve. Discharging of a hydraulic pump 17 during the boom lowering operation is not required, consumed energy can be reduced, and energy can be regenerated. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a boom drive circuit for a construction machine, and more particularly to a boom drive circuit for a construction machine having an energy regeneration mechanism when the boom is lowered.

  2. Description of the Related Art Construction machines such as a hydraulic excavator and a hydraulic crane are known that include an energy regeneration mechanism that converts weight energy into electric energy and stores it in a storage battery when the boom is lowered.

  For example, in the hydraulic cylinder circuit described in Patent Document 1, one hydraulic pump motor that is driven by an electric motor and capable of normal / reverse rotation and a hydraulic cylinder are connected via a directional control valve. In the circuit that expands and contracts the hydraulic cylinder by switching the hydraulic oil supply to the head side oil chamber or the rod side oil chamber, when the hydraulic cylinder contracts (when the hydraulic pump motor reverses), the head side oil of the hydraulic cylinder depends on the weight of the boom, etc. Due to the pressure applied to the chamber, the reverse driving force applied to the hydraulic pump motor is converted into electric energy by the electric motor and returned to the storage battery.

  The hydraulic cylinder drive device described in Patent Document 2 directly connects one hydraulic pump motor that can be rotated / reversed and driven by an electric motor, and the hydraulic cylinder expands and contracts by switching the rotation direction of the hydraulic pump motor. Although the circuit configuration is different, the operation is similar, and the reverse driving force applied to the hydraulic pump motor is applied to the hydraulic pump motor by the pressure applied to the head side oil chamber of the hydraulic cylinder by the weight energy of the boom when the hydraulic cylinder contracts. Is converted into electrical energy and returned to the storage battery.

  The energy regeneration device described in Patent Document 3 is described as follows: “A branch portion that divides the return oil line from the boom cylinder when lowering the boom into two oil passages, and one of the divided flows into the tank via the regeneration means. A regenerative circuit for guiding and a flow rate adjusting circuit for guiding the other divided flow to the tank via the flow rate adjusting means.In other words, two hydraulic lines are connected to the head side oil chamber of the boom cylinder. Thus, a hydraulic pump or a hydraulic motor is connected to one hydraulic line via a directional control valve, and a hydraulic pump or tank is connected to the other hydraulic line via a directional control valve.

  When raising the boom, hydraulic oil from each hydraulic pump of the two hydraulic lines is supplied to the head side oil chamber of the boom cylinder, the boom cylinder is extended, and the boom is raised.

When lowering the boom, hydraulic oil is diverted from the boom-side oil chamber of the boom cylinder to two hydraulic lines. In one hydraulic line, the hydraulic motor and a generator connected to the hydraulic motor are driven to generate electricity. In addition, the storage battery is charged, and the working oil returns to the tank through the other hydraulic line.
JP 2003-74517 A JP 2005-315312 A JP 2006-312995 JP

  The technologies described in Patent Documents 1 and 2 perform driving of a hydraulic cylinder and regeneration of energy by a pair of electric motors and hydraulic pump motors, and have an advantage of being simple and small. However, it is difficult to reconcile the performance as a hydraulic pump and the performance as a hydraulic motor with a hydraulic pump motor for driving a hydraulic cylinder, and the energy regeneration performance must be compromised to a certain level. I am dissatisfied with the efficiency of energy regeneration. In addition, it is difficult to apply the configuration in which the expansion / contraction of the hydraulic cylinder is switched by switching the rotation direction of the hydraulic pump motor, to the configuration in which the hydraulic pump is driven by the engine. Limited to those driven by a motor.

  In the technique described in Patent Document 3, there is no limitation on the hydraulic pump drive source, but both of the two hydraulic lines connected to the head side oil chamber of the boom cylinder are provided with a directional control valve and a hydraulic pump. Further, a hydraulic motor and a generator are connected to the line, which is more complicated than the configurations described in Patent Documents 1 and 2, and has a large number of parts. Further, when the boom cylinder is contracted, it is necessary to drive the hydraulic pump to supply hydraulic oil to the rod-side oil chamber of the boom cylinder, and the driving energy of the hydraulic pump is consumed even during regeneration.

  As described above, the conventional technique has a problem to improve the energy regeneration efficiency, and the present invention aims to improve the energy regeneration efficiency regardless of whether the motor drive or the engine drive.

  The present invention is proposed in order to achieve the above object, and the invention according to claim 1 is directed to a hydraulic cylinder head side oil chamber driven by a hydraulic pump to raise and lower a boom of a construction machine. Control that connects to the hydraulic oil inlet via a control valve, connects the hydraulic oil outlet of the hydraulic motor and the rod side oil chamber of the hydraulic cylinder via a check valve, and opens the control valve during boom lowering operation A mechanism that opens the control valve during the boom lowering operation, drives the hydraulic motor to rotate by the hydraulic oil in the head side oil chamber of the hydraulic cylinder, and passes the hydraulic oil that has passed through the hydraulic motor to the rod side oil chamber of the hydraulic cylinder. The power is divided into the supply and the return to the tank through the control valve, and the generator connected to the hydraulic motor converts the rotation of the hydraulic motor into electric power to regenerate electric energy. And it is intended to provide a boom driving circuit of the construction machine.

  In the above configuration, during the boom lowering operation, hydraulic oil flows from the hydraulic chamber to the hydraulic motor from the hydraulic chamber head side of the hydraulic cylinder that is loaded by the weight of the boom, and the hydraulic motor and generator rotate to regenerate electrical energy. The The hydraulic oil that has passed through the hydraulic motor is sucked into the rod side oil chamber of the hydraulic cylinder as it is, and the hydraulic motor rotates with low loss and energy is efficiently regenerated.

  According to a second aspect of the present invention, there is provided a boom drive circuit for a construction machine provided with control means for reducing the discharge amount of the hydraulic pump to a minimum level during a boom lowering operation.

  In the above configuration, during the boom lowering operation, the hydraulic pump hardly discharges hydraulic oil, so that energy consumption is minimized.

  The invention according to claim 3 detects a pressure drop in the oil chamber on the head side of the hydraulic cylinder at the time of the grounding of the boom at the time of jack-up when the vehicle body of the construction machine is lifted by the reaction force of pushing down the boom. The discharge amount is increased to a desired discharge amount, and the electromagnetic induction load of the generator is released to reduce the rotational resistance of the generator due to electromagnetic induction and the pressure loss due to the hydraulic motor connected to the generator. A boom drive circuit for a constructed construction machine is provided.

  In the above configuration, during the jack-up operation, the boom and the bucket are lowered by their own weight until they come into contact with the ground. Since the discharge amount increases, jack-up operation becomes possible. In addition, when the jack is up, the generator is electrically disconnected to reduce the driving load.

  According to the first aspect of the present invention, the boom is lowered by its own weight, and at this time, the hydraulic motor is rotated to regenerate electric power, and the hydraulic oil is returned from the hydraulic motor to the rod-side oil chamber of the boom cylinder. The energy regeneration efficiency is good.

  According to the second aspect of the present invention, since the discharge amount of the hydraulic pump is lowered to the minimum level during the boom lowering operation, the driving load of the hydraulic pump is not applied, energy consumption is reduced, and the energy regeneration efficiency is further improved. Moreover, since the pushing pressure of the hydraulic pump does not stand in the rod side oil chamber at the time of boom lowering activation, the activation shock can be reduced.

  According to the third aspect of the present invention, during the jackup operation, the boom and the bucket are lowered by their own weight until they come into contact with the ground, and when the contact is made, the contact is detected and the discharge amount of the hydraulic pump increases to the desired discharge amount. Since it is jacked up, the boom lowering and jacking up for energy regeneration can be executed continuously without requiring any special operation, and the operability is good. In addition, when the jack is up, the generator is electrically disconnected, which reduces the driving load and is efficient.

  The present invention connects a hydraulic cylinder head side oil chamber that is driven by a hydraulic pump to raise and lower a boom of a construction machine to a hydraulic oil inlet of a hydraulic motor via a control valve. A control mechanism is provided that connects the hydraulic cylinder's rod side oil chamber via a check valve and opens the control valve when the boom is lowered, and opens the control valve when the boom is lowered. The hydraulic motor is rotationally driven by the hydraulic oil in the chamber, and the hydraulic oil that has passed through the hydraulic motor is divided into a supply to the rod-side oil chamber of the hydraulic cylinder and a return to the tank through the control valve. The boom drive circuit of a construction machine with good energy regeneration efficiency can be obtained by converting the rotation of the hydraulic motor into electric power and regenerating electric energy by the generator connected to To achieve the objective of providing.

  FIG. 1 shows a hydraulic excavator 1 as an example of a construction machine, and an upper swing body 4 is mounted on a lower traveling body 3 provided with a crawler 2. The front part of the upper swing body 4 is an operator room 5 and the rear part is an engine room 6 containing an engine, a hydraulic engine, etc. A counterweight 7 is attached to the rear end of the engine room 6. A fulcrum (not shown) of the boom 8 is provided beside the cab 5, and an arm 9 is attached to the tip of the boom 8 attached to this fulcrum, and a bucket 10 is attached to the tip of the arm 9. Hydraulic cylinders 12, 13, and 14 are interposed between the boom 8 and the upper swing body 4, the boom 8 and the arm 9, and the bucket link 11 attached to the bucket 10 and the arm 9, respectively. By expanding and contracting the cylinders 12, 13, and 14, the boom 8, the arm 9, and the bucket 10 are rotated around the respective pivot support points.

  FIG. 2 shows a drive circuit of a boom-driving hydraulic cylinder 12 (hereinafter referred to as a boom cylinder 12) and an energy regeneration circuit associated therewith. The boom-side oil chamber 12a and the rod-side oil chamber 12b each have 3 A pilot check valve 16 is provided in the oil passage to the head side oil chamber 12a of the main control valve 15 that is connected to the main control valve 15 that is a position direction control valve.

  In FIG. 2, the spool of the main control valve 15 is switched to the closed position a on the right side or the contracted position c on the left side according to the pilot pressure. In the closed position a, the discharge flow rate of the variable displacement hydraulic pump 17 is controlled to an idling level, and the hydraulic oil returns to the tank 19 through the main control valve 15 and the throttle valve 18.

  A pipe line 20 connecting the head side oil chamber 12a of the boom cylinder 12 and the main control valve 15 branches in the middle and is connected to a direction control valve 21 (hereinafter referred to as an energy regenerative valve 21). Are switched by pilot control by an electromagnetic proportional control valve 22. A hydraulic motor 23 is disposed downstream of the energy regenerative valve 21, and the hydraulic oil outlet of the hydraulic motor 23 is connected to the rod side oil chamber 12b of the boom cylinder 12 through a pipe line 25 provided with a check valve 24. .

  The hydraulic motor 23 is connected to a generator 26, and the electric power output from the generator 26 is converted into a direct current by the inverter 27 and converted into a direct current to charge a storage battery (not shown). In the lower left controller 28 in FIG. 2, signals such as the pipe pressure on the head side of the boom cylinder 12, the pilot pressure on the cylinder contraction side pilot port 15b of the main control valve 15, and the rotational speed of the generator 26 are respectively sent to the pressure sensor. 29, 30 and the rotational speed sensor 31, and the energy regeneration valve 21 and the inverter 27 are turned on and off in accordance with these signals.

  When the boom operation lever (not shown) in the cab 5 is operated to the up side, pilot pressure is applied to the extension side pilot port 15a of the main control valve 15, and the spool of the main control valve 15 is set according to the operation amount of the operation lever. 2 moves to the left in FIG. 2 and switches to the extension position b. At this time, the energy regenerative valve 21 is in the closed position in the figure, and the entire amount of hydraulic oil discharged from the hydraulic pump 17 is supplied to the head side oil chamber 12a of the boom cylinder 12, and the cylinder rod extends to expand the rod side oil. The hydraulic oil in the chamber 12b returns to the tank 19 through the main control valve 15.

  Contrary to the above, when the boom control lever is operated to the lower side, pilot pressure is applied to the contracting pilot port 15b of the main control valve 15, and the spool of the main control valve 15 is turned to the contracted position as shown in FIG. In addition, the pilot check valve 16 in the oil passage of the main control valve 15 opens, and the head side oil chamber 12a of the boom cylinder 12 communicates with the tank 19 through the main control valve 15. Further, the change of the pilot pressure is detected by the pressure sensor 29, and the controller 28 switches the energy regeneration valve 21 to the open position via the electromagnetic proportional control valve 22 by the signal.

  Pressure due to the weight of the boom 8, the arm 9, the bucket 10, etc. is applied to the head side oil chamber 12a of the boom cylinder 12. The hydraulic oil in the head side oil chamber 12a is transferred to the hydraulic motor 23 for energy regeneration by this load. The hydraulic motor 23 and the generator 26 are rotationally driven after being introduced. As a result, the electric power generated by the generator 26 is converted into a direct current after being converted into a voltage by the inverter 27 to charge a storage battery (not shown). The controller 28 monitors the rotational speed of the generator 26 via the rotational speed sensor 31 and adjusts the opening of the energy regenerative valve 21 via the electromagnetic proportional control valve 22 to make the rotational speed of the generator 26 appropriate. Control within range.

  The hydraulic oil that has passed through the hydraulic motor 23 is divided into a supply portion and a return portion to the tank through the control valve through the conduit 25 and the check valve 24 to the rod side oil chamber 12b. Therefore, when the boom is lowered, the hydraulic pump 17 does not need to be discharged. By controlling the discharge flow rate of the hydraulic pump 17 to the minimum, the hydraulic oil is pressed into the rod side oil chamber 12b of the boom cylinder 12 when the boom is lowered. Because it does not stand, there is almost no shock. The rod side oil chamber 12b of the boom cylinder 12 has a smaller cross-sectional area than the head side oil chamber 12a due to the presence of the rod, and therefore flows into the rod side oil chamber 12b more than the amount of oil discharged from the head side oil chamber 12a. Less oil. Therefore, the hydraulic oil that has passed through the hydraulic motor 23 is divided according to the pressure of each part. It is also possible to increase the amount of oil to the cylinder rod side by narrowing the opening of the control valve. As described above, during normal boom lowering, the hydraulic pump 17 hardly discharges hydraulic oil, and the drive energy of the hydraulic pump 17 is saved.

  In the case where the boom 8 is lowered to ground the bucket 10 from the state of FIG. 1 and the boom 8 is further lowered to jack up the front portion of the vehicle body of the hydraulic excavator 1, the hydraulic pump 17 needs to be driven. In this case, if the boom control lever is held in the lowered state, the boom 8 is not loaded on the boom cylinder 12 when the bucket 10 is grounded, so the hydraulic pressure in the head side oil chamber 12a of the boom cylinder 12 is reduced. To do. The controller 28 detects this pressure change via the hydraulic sensor 29, increases the discharge flow rate of the hydraulic pump 17, and turns off the inverter 27.

  The hydraulic oil is supplied from the hydraulic pump 17 to the rod side oil chamber 12b of the boom cylinder 12, and the boom cylinder 12 is further contracted to jack up the front portion of the vehicle body. At this time, since the inverter 27 is off and the generator 26 is electrically cut off, there is no rotational load due to the electromagnetic induction electromotive force of the generator 26, and the rotational resistance of the hydraulic motor 23 is reduced. The discharge resistance of the head-side oil chamber 12a of the boom cylinder 12 is reduced, so that no pressure is applied to the rod-side oil chamber 12b, and jack-up can be performed with little pressure loss.

  Here, a hydraulic excavator is taken as an example of the construction machine, and the case where it is applied to a boom cylinder that can be expected to regenerate large energy is described as an example. However, the present invention is not limited to the above embodiment, but other types of construction It is also possible to apply to a machine or a hydraulic machine. Further, various modifications are possible within the technical scope of the present invention, and the present invention naturally extends to those modified ones.

The side view of a hydraulic excavator. The hydraulic circuit diagram of the boom drive circuit of this invention. The hydraulic circuit diagram which shows the state at the time of boom lowering operation of the boom drive circuit of FIG.

Explanation of symbols

1 Hydraulic shawl
8 Boom
9 arm
10 bucket
12 Boom cylinder
15 Main control valve
16 Pilot check valve
17 Hydraulic pump
19 tanks
21 Energy regeneration valve
22 Proportional solenoid valve
23 Hydraulic motor
24 Check valve
26 Generator
27 Inverter
28 Controller
29 Pressure sensor
30 Pressure sensor
31 Speed sensor

Claims (3)

  A hydraulic cylinder head side oil chamber driven by a hydraulic pump to raise and lower the boom of the construction machine is connected to a hydraulic oil hydraulic oil inlet via a control valve, and the hydraulic motor hydraulic oil outlet and the hydraulic cylinder rod A control mechanism that connects the side oil chamber to a pipe line via a check valve and opens the control valve during a boom lowering operation, and opens the control valve during a boom lowering operation to operate the hydraulic oil in the head side oil chamber of the hydraulic cylinder. The hydraulic motor is driven to rotate, and the hydraulic oil that has passed through the hydraulic motor is divided into the supply to the rod-side oil chamber of the hydraulic cylinder and the return to the tank via the control valve, and power generation connected to the hydraulic motor. A boom drive circuit for a construction machine configured to regenerate electric energy by converting rotation of a hydraulic motor into electric power by a machine.   The boom drive circuit for a construction machine according to claim 1, further comprising control means for reducing the discharge amount of the hydraulic pump to a minimum level during a boom lowering operation. When jacking up the vehicle body of a construction machine by the reaction force of pushing down the boom, the pressure drop in the hydraulic chamber on the head side of the hydraulic cylinder at the time of boom contact is detected, and the discharge amount of the hydraulic pump is changed to a desired discharge amount. 2. The construction according to claim 1, wherein the construction is configured such that the electromagnetic induction load of the generator is released and the rotational resistance of the generator due to electromagnetic induction and the pressure loss due to the hydraulic motor connected to the generator are reduced. Mechanical boom drive circuit.

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