JP2005315312A - Hydraulic cylinder drive device for construction machinery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To drive a hydraulic pump with an electric motor, to supply discharged oil of the hydraulic pump to a head side of the hydraulic cylinder, and to effectively perform the regeneration of energy by making the hydraulic pump absorb the working oil discharged from the head side of the hydraulic cylinder. <P>SOLUTION: The discharged oil of the hydraulic pump 22 driven by the electric motor 21 is supplied to a head-side oil chamber 18a of a boom cylinder 18 during boom lifting operation, and regeneration of energy is performed with reverse rotation of the electric motor 21 by making the hydraulic pump 22 absorb working oil discharged from the oil chamber 18a at a head side during boom lowering operation. A rod-side oil chamber 18b of the boom cylinder 18 is switchably connected with either of an oil pressure source 24 and a tank 25 via a selector valve 23, and a pressure sensor 27 is arranged on the head-side oil chamber 18a of the boom cylinder 18. When holding pressure of the boom cylinder 18 sensed by the pressure sensor 27 is under a designated pressure, working oil of the oil pressure source 24 is supplied to the rod-side oil chamber 18b of the boom cylinder 18 so that the selector valve 23 is switched to an offset position (A) by a control signal of a controller 30. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hydraulic cylinder drive device for a construction machine, and more particularly to a hydraulic cylinder drive device for a construction machine that is driven by an electric motor and is driven to extend and contract by the hydraulic pump.

  Conventionally, a hydraulic pump is driven by an electric motor, and discharge oil of the hydraulic pump is supplied to a head side oil chamber or a rod side oil chamber of a single rod type hydraulic cylinder via a direction control valve, and the hydraulic cylinder The direction of the external force acting on the engine is detected, and when the hydraulic cylinder is operated in the same direction as this external force, the oil in the cylinder oil chamber on the side where the external force acts is caused to flow into the hydraulic pump for energy regeneration. On the other hand, when the hydraulic cylinder is operated in a direction opposite to the external force, the hydraulic pump is driven by an electric motor as a normal operation mode so that oil is supplied to the cylinder oil chamber on the side where the pressure by the external force acts. Is known (for example, see Patent Document 1).

In the hydraulic cylinder circuit described in Patent Document 1, an external force based on the total weight of the attachment weight including the boom and the load acts as a force in the cylinder contraction direction on the boom cylinder during normal operation and is held in the head side oil chamber. Pressure is generated. When the cylinder is expanded or contracted, the direction control valve is switched to the first position by the control signal from the controller, and the electromagnetic valve is also energized and switched to the on position. Thereby, the head side oil chamber of the boom cylinder is connected to the hydraulic pump, and the rod side oil chamber is connected to the tank. When the boom cylinder contracts, the electric motor reverses and the hydraulic pump sucks the hydraulic oil in the head-side oil chamber and rotates in the direction in which the motor acts. At this time, hydraulic oil in the tank is sucked into the rod-side oil chamber through the tank line, and energy regeneration is performed when the boom cylinder contracts.
JP 2003-74517 A

  In the invention described in Patent Document 1, since a directional control valve is interposed between the hydraulic pump and the hydraulic cylinder, pressure loss when hydraulic oil passes through the directional control valve, and bleed-off during boom raising operation There are many.

  Therefore, the hydraulic pump is driven by an electric motor, and the oil discharged from the hydraulic pump is supplied to the head side of the hydraulic cylinder, and the hydraulic oil discharged from the head side of the hydraulic cylinder is absorbed by the hydraulic pump to regenerate energy. In a hydraulic cylinder drive device for a construction machine configured to perform, a technical problem to be solved in order to efficiently perform energy regeneration occurs, and the present invention solves this problem. With the goal.

The present invention has been proposed to achieve the above object, and the invention according to claim 1 drives a hydraulic pump by an electric motor and supplies the oil discharged from the hydraulic pump to the head side oil chamber of the hydraulic cylinder. In addition, in the hydraulic cylinder drive device of the construction machine configured to absorb the hydraulic oil discharged from the head side oil chamber to the hydraulic pump and perform energy regeneration,
A hydraulic cylinder driving device for a construction machine is provided in which a rod side oil chamber of the hydraulic cylinder is connected to either a hydraulic power source or a tank via a switching valve so as to be switchable.

  According to this configuration, when the hydraulic cylinder is driven to the rod side by switching the switching valve to the tank side, the pressure in the rod-side oil chamber is released and the hydraulic cylinder operates to the rod side. Also, when the hydraulic cylinder is driven to the head side, the hydraulic cylinder operates to the head side with the switching valve being switched to the tank side. On the other hand, when the hydraulic cylinder is driven to the head side, by switching the switching valve to the hydraulic source side, hydraulic oil from the hydraulic source is introduced into the rod side oil chamber of the hydraulic cylinder, and the rod side oil is The pressure in the chamber rises, and excavation and body jack-up can be performed in the boom lowering operation.

  According to a second aspect of the present invention, when a pressure detector is provided in the head side oil chamber of the hydraulic cylinder and the holding pressure of the hydraulic cylinder detected by the pressure detector is equal to or lower than a predetermined pressure, the switching valve is connected to the hydraulic source side. There is provided a hydraulic cylinder drive device for a construction machine configured to supply hydraulic oil to a rod-side oil chamber of a hydraulic cylinder.

  According to this configuration, the pressure detector provided in the head side oil chamber of the hydraulic cylinder detects the holding pressure of the hydraulic cylinder, and controls the switching valve according to the magnitude of the holding pressure. When the holding pressure is equal to or lower than a predetermined pressure, the switching valve is switched to the hydraulic source side to introduce hydraulic oil from the hydraulic source into the rod side oil chamber of the hydraulic cylinder, and excavation is performed by lowering the boom. At this time, the electric motor of the hydraulic pump facilitates the discharge of hydraulic oil by no-load rotation.

  According to the first aspect of the present invention, a switching valve is provided in the rod side oil chamber of the hydraulic cylinder so that it can be switched to either a hydraulic pressure source or a tank. In some cases, the switching valve is switched to the hydraulic pressure source side, and hydraulic oil from the hydraulic pressure source is introduced into the rod side oil chamber to perform excavation by lowering the boom.

  According to the second aspect of the present invention, when the holding pressure of the hydraulic cylinder detected by the pressure detector is equal to or lower than the predetermined pressure, the switching valve is switched to the hydraulic power source side and hydraulic oil is supplied to the rod side oil chamber of the hydraulic cylinder. In addition, it is possible to determine work conditions, for example, whether excavation is possible or jack-up is possible.

  Hereinafter, a hydraulic cylinder drive device for a construction machine according to the present invention will be described with reference to preferred embodiments. The hydraulic pump is driven by an electric motor, and the discharge oil of the hydraulic pump is supplied to the head side oil chamber of the hydraulic cylinder, and the hydraulic oil discharged from the head side oil chamber of the hydraulic cylinder is absorbed by the hydraulic pump to generate energy. For the purpose of enabling efficient regeneration, the rod side oil chamber of the hydraulic cylinder is connected to either a hydraulic source or a tank via a switching valve so as to be switchable, and further to the head side oil chamber of the hydraulic cylinder. A pressure detector is provided, and when the holding pressure of the hydraulic cylinder detected by the pressure detector is equal to or lower than a predetermined pressure, the switching valve is switched to the hydraulic power source side to supply hydraulic oil to the rod side oil chamber of the hydraulic cylinder. Realized by configuring.

  FIG. 1 shows a hydraulic excavator 10 as an example of a construction machine, and an upper swing body 13 is mounted on a lower traveling body 11 via a swing mechanism 12 so as to be rotatable. The upper swing body 13 is provided with a cab 14 on one front side thereof, and a boom 15 is attached to the front center portion so as to be able to be raised and lowered. Further, an arm 16 is attached to the tip of the boom 15 so as to be rotatable up and down, and a bucket 17 is attached to the tip of the arm 16. The boom 15 is rotated by the telescopic drive of the boom cylinder 18, and the arm 16 is rotated by the telescopic drive of the arm cylinder 19. Further, the bucket 17 is rotated by the expansion and contraction drive of the bucket cylinder 20.

  FIG. 2 shows a drive circuit of a boom cylinder 18 as an example of a hydraulic cylinder driving device. A bidirectional hydraulic pump 22 is driven by an electric motor 21 and the oil discharged from the hydraulic pump 22 is supplied to a head side oil chamber 18a of the boom cylinder 18. To supply. The rod side oil chamber 18b of the boom cylinder 18 is connected to a hydraulic pressure source 24 and a tank 25 via a switching valve 23 so as to be switchable. The switching valve 23 connects the rod side oil chamber 18b of the boom cylinder 18 and the tank 25 at the normal position (A), and the solenoid 26 is excited by the control signal of the controller 30 to switch to the offset position (B). At this time, the rod side oil chamber 18b of the boom cylinder 18 and the hydraulic pressure source 24 are connected.

  Further, a pressure detector 27 is provided in the head side oil chamber 18a of the boom cylinder 18, and the pressure detector 27 detects the pressure of the head side oil chamber 18a, that is, the holding pressure of the boom cylinder 18. The holding pressure detected by the pressure detector 27 is input to the controller 30. When the holding pressure of the boom cylinder 18 is higher than a predetermined pressure set in advance, a control signal is not output from the controller 30 to the solenoid 26 of the switching valve 23. When the holding pressure is lower than the predetermined pressure, the controller 30 A control signal is output to the solenoid 26 of the switching valve 23.

  The electric motor 21 is connected to a controller 30 via an inverter 31, and a battery 32 is connected to the inverter 31. When the operation unit 33 is operated, an operation signal is input to the controller 30, and a control signal is sent from the controller 30 to the inverter 31 in response to the operation signal to control the rotation / stop of the electric motor 21, the number of rotations, and the like. The As will be described later, when the electric motor 21 is reversely driven by the hydraulic pump 22, the electric motor 21 operates as a generator, and electric power generated by energy regeneration is stored in the battery 32.

  As shown in FIG. 2, when the operation unit 33 is not operated, a control signal is not output from the controller 30 to the solenoid 26 of the switching valve 23, and the switching valve 23 maintains the normal position (A). The rod side oil chamber 18b of the boom cylinder 18 and the tank 25 are connected. Further, since no control signal is sent from the controller 30 to the inverter 31, no power is applied to the electric motor 21 and the hydraulic pump 22 is not driven. Therefore, the hydraulic oil is not supplied to the boom cylinder 18, and the boom cylinder 18 does not extend and contract.

  As shown in FIG. 3, when the operation unit 33 is operated to the boom raising side, this operation signal is input to the controller 30, and a boom raising control signal is sent from the controller 30 to the inverter 31. 21 is controlled to rotate in the forward rotation direction (clockwise in the figure). The hydraulic pump 22 is driven in the forward rotation direction (clockwise in the figure) by the forward rotation of the electric motor 21, and the discharge oil from the hydraulic pump 22 is supplied to the head side oil chamber 18a of the boom cylinder 18, so that the boom cylinder 18 extends. It operates and the boom 15 rotates in the raising direction.

  If the operation unit 33 is returned to the neutral position in order to stop the boom 15 at a desired height position, the control signal from the controller 30 to the inverter 31 is interrupted, and the rotation of the electric motor 21 is stopped. Accordingly, the supply of hydraulic oil from the hydraulic pump 22 to the head side oil chamber 18a of the boom cylinder 18 is stopped, the extension operation of the boom cylinder 18 is stopped, and the boom 15 is held at a desired height position.

  In this state, as shown in FIG. 1, the external force due to the total weight of the attachments including the boom 15 and the load acts on the boom cylinder 18 as a force in the contraction direction, and the holding pressure is applied to the head side oil chamber 18a. Has occurred. This holding pressure is detected by the pressure detector 27 and input to the controller 30. When the holding pressure is higher than a predetermined pressure set in advance, a control signal is not output from the controller 30 to the solenoid 26 of the switching valve 23, the switching valve 23 holds the normal position (A), and the boom The rod side oil chamber 18b of the cylinder 18 and the tank 25 are connected.

  As shown in FIG. 4, when the operation unit 33 is operated to the boom lowering side, this operation signal is input to the controller 30, and a boom lowering control signal is sent from the controller 30 to the inverter 31. 21 is controlled to rotate in the reverse rotation direction (counterclockwise in the figure). Due to the reverse rotation of the electric motor 21, the hydraulic pump 22 is driven in the reverse rotation direction (counterclockwise in the figure), the hydraulic oil in the head side oil chamber 18a of the boom cylinder 18 is sucked into the hydraulic pump 22, and the boom cylinder 18 contracts. It operates and the boom 15 rotates in the downward direction.

  When the boom 15 is grounded (contacted) with the ground or the like and is held by an external force, the holding pressure of the boom cylinder 18 is reduced, and when the holding pressure becomes a predetermined pressure or less, the controller 30 sends the switching valve. A control signal is output to the solenoid 26 of 23. At that time, the switching valve 23 is switched to the offset position (B), and the rod side oil chamber 18b of the boom cylinder 18 and the hydraulic power source 24 are connected.

  Accordingly, hydraulic oil from the hydraulic source 24 can be introduced into the rod side oil chamber 18b and excavated by the boom cylinder 18.

  Thus, when the boom cylinder 18 is driven using the bidirectional hydraulic pump 22, the hydraulic source 24 and the tank 25 are connected to the rod-side oil chamber 18b via the switching valve 23 in a switchable manner. At the time of lowering, the switching valve 23 can be switched to introduce the hydraulic oil from the hydraulic source 24 into the rod side oil chamber 18b for excavation. Further, since no directional control valve is interposed between the hydraulic pump 22 and the boom cylinder 18, there is no pressure loss when hydraulic fluid passes through the directional control valve, and bleed-off during the boom raising operation is reduced. Furthermore, in a machine that does not need to apply pressure to the discharge side (rod side) such as jack-up, it is only necessary to connect the discharge side to the tank, which makes the configuration simpler.

  It should be noted that the present invention can be variously modified without departing from the spirit of the present invention, and the present invention naturally extends to the modified ones.

The figure shows an embodiment of the present invention.
The side view of a hydraulic excavator. The drive circuit diagram of a boom cylinder. The drive circuit diagram of the boom cylinder at the time of boom raising operation. The drive circuit diagram of the boom cylinder at the time of boom lowering operation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Hydraulic excavator 18 Boom cylinder 18a Head side oil chamber 18b Rod side oil chamber 21 Electric motor 22 Hydraulic pump 23 Switching valve 24 Hydraulic source 25 Tank 26 Solenoid 27 Pressure detector 30 Controller

Claims (2)

The hydraulic pump is driven by an electric motor, and the oil discharged from the hydraulic pump is supplied to the head side oil chamber of the hydraulic cylinder, and the hydraulic oil discharged from the head side oil chamber is absorbed by the hydraulic pump to perform energy regeneration. In the construction machine hydraulic cylinder drive device configured as follows:
The hydraulic cylinder driving device for a construction machine, wherein the rod-side oil chamber of the hydraulic cylinder is connected to either a hydraulic source or a tank via a switching valve so as to be switchable.   When a pressure detector is provided in the hydraulic chamber on the head side of the hydraulic cylinder, and the holding pressure of the hydraulic cylinder detected by the pressure detector is equal to or lower than a predetermined pressure, the switching valve is switched to the hydraulic source side and the rod side of the hydraulic cylinder is 2. The hydraulic cylinder driving device for a construction machine according to claim 1, wherein hydraulic oil is supplied to the oil chamber.

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