JP2013083293A - Hydraulic device for working machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic device for a working machine that can suppress and reduce energy loss by permitting relief to regenerate and reuse relieved working oil without including a means for actuating a hydraulic actuator in a direction of releasing a load to thereby reduce relief from a main relief valve.SOLUTION: The hydraulic device includes: a hydraulic pump 8 driven by a motor 4 to discharge operating oil; a control valve 12 for controlling the discharged oil to be supplied to and discharged from the hydraulic actuator 10; a main relief valve 16 disposed in an oil discharge path connecting the hydraulic pump and the control valve, and for defining a pressure of the hydraulic valve; and a hydraulic motor connected to the motor and driven by the operating oil in the oil discharge path of the main relief valve, and for assisting the drive of the hydraulic pump 20 by the motor.

Description

  The present invention relates to a hydraulic device for a work machine, and more particularly, to a hydraulic device including a system for regenerating a flow rate that has been relieved from a main relief valve.

  BACKGROUND ART A hydraulic device for a work machine, for example, a hydraulic device for a hydraulic excavator, includes a main relief valve that regulates the system pressure so as not to exceed a rated pressure when a hydraulic actuator is operated. Since the work machine has a heavy work load, the actuator is likely to be overloaded, and the relief valve operates frequently to release (relieve) the hydraulic oil.

  The relief hydraulic oil returns to the tank through the return oil passage. However, the relief of the high-pressure hydraulic oil causes energy loss and deteriorates the fuel consumption of the engine that drives the hydraulic pump. One way to suppress this energy loss is to reduce the hydraulic oil relief from the main relief valve by operating some hydraulic actuators in the direction of load relief when the load pressure reaches a specified warning pressure. It has been developed (see, for example, Patent Document 1).

JP 2010-190341 A (FIG. 1)

  As described above, the method of releasing the high-pressure hydraulic fluid by the main relief valve causes energy loss and deteriorates the fuel consumption of the engine that drives the hydraulic pump. On the other hand, the method of operating some actuators in the direction of releasing the work load may hinder the work because the operation of the actuator fluctuates.

  The present invention has been made in view of the above-mentioned facts, and its technical problem is that the main relief valve is provided without means for operating the hydraulic actuator in the direction of releasing the load in order to reduce the relief of hydraulic oil from the main relief valve. It is an object of the present invention to provide a hydraulic device for a work machine that allows the relief of the above-mentioned relief and recycles and uses the relief hydraulic oil to suppress and reduce energy loss.

  According to the present invention, as a hydraulic device for a work machine that solves the above technical problem, a hydraulic pump that is driven by a prime mover and sucks and discharges hydraulic oil in a tank, and controls the discharged oil to supply and discharge to a plurality of hydraulic actuators. Control valve, a main relief valve that is provided in the discharge oil passage connecting the hydraulic pump and the control valve and regulates the pressure of the hydraulic device, and a hydraulic motor that is connected to the prime mover and driven by hydraulic oil in the discharge oil passage of the main relief valve A hydraulic device for a working machine is provided, wherein the hydraulic motor assists the driving of a hydraulic pump by a prime mover.

  Preferably, the hydraulic motor is of a variable displacement type, and its capacity controller increases the capacity of the hydraulic motor when the amount of hydraulic oil flowing through the discharge oil passage is small and when it is large.

  Further, a check valve is provided between the return oil passage from the control valve to the tank and the discharge oil passage to allow a flow from the return oil passage to the discharge oil passage.

  A hydraulic device for a work machine configured according to the present invention includes a discharge oil passage of a main relief valve provided in a discharge oil passage connecting a hydraulic pump driven by a prime mover and a control valve for supplying and discharging the discharge oil to and from a hydraulic actuator. A hydraulic motor is provided that is driven by hydraulic oil and connected to the prime mover to assist the drive of the hydraulic pump.

  Therefore, without providing a means to operate the hydraulic actuator in the direction of load relief to reduce the relief of hydraulic oil from the main relief valve, the relief of the main relief valve is allowed, and the hydraulic oil that has been reclaimed is recycled to reduce energy loss. It can be suppressed and reduced. This is particularly effective for work machines with high relief frequency that operate at high load.

The circuit diagram of the hydraulic device of the working machine comprised according to this invention.

  Hereinafter, a hydraulic device for a working machine configured according to the present invention will be described in more detail with reference to the accompanying drawings illustrating a preferred embodiment of a hydraulic excavator that is a typical working machine.

  A description will be given with reference to FIG. A hydraulic apparatus for a work machine, generally indicated by numeral 2, is driven by an engine 4 as a prime mover, and a pair of hydraulic pumps 8 and 8 for sucking and discharging hydraulic oil in a tank 6 and a plurality of hydraulic pressures by controlling the discharged oil. Control valves 12 and 12 that supply and discharge to the actuators 10 and 10 respectively, and discharge oil passages 14 and 14 that connect the hydraulic pumps 8 and 8 and the control valves 12 and 12 respectively, and a main relief valve 16 that regulates the pressure of the hydraulic device. 16 and a hydraulic motor 20 connected to the engine 4 and driven by hydraulic oil in the discharge oil passage 18 of the main relief valves 16 and 16.

  The control valve 12 and the tank 6 are connected by a return oil path 22. The hydraulic oil that has passed through the hydraulic motor 20 flows to the tank 6 through an oil passage connected to the return oil passage 22.

  The hydraulic pump 8 is a variable displacement pump. In addition, as shown in FIG. 1, a hydraulic apparatus for a work machine having many hydraulic actuators to be operated such as a hydraulic excavator includes two systems of substantially the same hydraulic pump, control valve, main relief valve, and the like.

  The plurality of hydraulic actuators are collectively shown as two groups of hydraulic actuators 10 and 10. The hydraulic excavator is provided with at least a boom cylinder for operating a work arm, an arm cylinder, a bucket cylinder, a travel motor for airframe travel, and a swing motor for airframe rotation.

  These hydraulic pump 8, control valve 12, tank 6, discharge oil passage 14, return oil passage 22, etc. may be well-known ones. Therefore, the detailed description is abbreviate | omitted.

  The main relief valve 16 is a pilot operated type that is not easily affected by the pressure on the discharge side (discharge oil passage 18 side).

  The hydraulic motor 20 is a variable capacity type swash plate type piston motor, for example. The capacity controller 21 of the hydraulic motor 20 controls the motor capacity and the tilt angle of the swash plate based on the amount of hydraulic oil flowing through the drain oil passage 18. The capacity of the hydraulic motor 20 (tilt angle of the swash plate) is controlled to be small when the amount of hydraulic fluid flowing through the discharge oil passage 18 is small and large when it is large. That is, when the amount of hydraulic oil is small, the capacity is reduced so as not to become the rotational resistance of the engine 4 connected to the hydraulic motor 20, and when the amount of hydraulic oil is large, the capacity is increased so as to generate torque that assists the rotation of the engine 4. To do.

  The hydraulic motor 20 causes the engine 4 to match the rotational speed of the engine 4 and the rotational speed of the hydraulic motor 20 via a speed change coupling means (not shown) such as gears so that the hydraulic pump 8 is driven. Connected.

  Between the return oil path 22 from the control valve 12 to the tank 6 and the discharge oil path 18, a check valve 24 that allows a flow from the return oil path 22 toward the discharge oil path 18 is provided. The check valve 24 operates so that the hydraulic motor 20 does not become a rotational load of the engine 4 when the hydraulic motor 20 is rotated by the engine 4 in the relationship between the rotational speeds of the engine 4 and the hydraulic motor 20. Top up with oil. The hydraulic oil that passes through the check valve 24 is effectively supplied to the hydraulic motor 20 in a pressurized state, particularly when the tank 6 is of a sealed pressure type.

  With reference to FIG. 1, the effect of the hydraulic device 2 of the working machine as described above will be described.

  The hydraulic device 2 of the work machine is configured to discharge a main relief valve 16 provided in a discharge oil passage 14 that connects a hydraulic pump 8 driven by a prime mover 4 and a control valve 12 that supplies and discharges the discharged oil to and from a plurality of hydraulic actuators 10. A hydraulic motor 20 that is driven by hydraulic oil in the oil passage 18 and assists the drive of the hydraulic pump 8 is provided.

  Accordingly, the main relief valve 16 is allowed to be relieved without providing means for operating the hydraulic actuator 10 in the direction of releasing the load in order to reduce the relief of the hydraulic oil from the main relief valve 16, and this discharged oil is discharged to the discharged oil passage. By driving the hydraulic motor 20 connected to the engine 4 through 18, it is possible to recycle and relieve the hydraulic fluid that has been relieved and to suppress and reduce energy loss. Since the engine assist amount becomes large at the time of relief, fuel consumption at high load can be reduced. In particular, since the engine assist amount increases during relief, the fuel consumption during high loads can be reduced.

  The hydraulic motor 20 is a variable displacement type, and its capacity controller 21 reduces the capacity of the hydraulic motor 20 when there is little or no hydraulic oil flowing through the discharge oil passage 18, and increases it when it is large.

  Therefore, when the amount of hydraulic oil is small, the capacity is reduced, and the hydraulic motor 20 is brought into a state close to idling so as not to cause the rotational resistance of the engine 4 to which the hydraulic motor 20 is connected. A torque that assists rotation is generated.

  A check valve 24 is provided between the return oil path 22 from the control valve 12 to the tank 6 and the discharge oil path 18 to allow the flow from the return oil path 22 to the discharge oil path 18.

  Therefore, when there is no flow of the hydraulic fluid that has been relieved from the main relief valve 16 in the discharge oil passage 18, the hydraulic oil can be replenished so that the hydraulic motor 20 does not become a rotational load of the engine 4. The hydraulic fluid that passes through the check valve 24 is effectively supplied to the hydraulic motor 20 in a pressurized state, particularly when the tank 6 is of a sealed pressure type.

  The present invention has been described in detail based on the embodiments. However, the present invention is not limited to the above-described embodiments, and various changes or modifications can be made within the scope of the present invention, for example, as described below. Is.

  In the embodiment of the present invention, the prime mover 4 is an engine, but the prime mover 4 may be an electric motor.

  In the embodiment of the present invention, the hydraulic device 2 includes two systems of substantially the same hydraulic pump 8, control valve 12, main relief valve 16 and the like, but these may be one system.

2: Hydraulic device for work machine 4: Engine (motor)
6: Tank 8: Hydraulic pump 10: Hydraulic actuator 12: Control valve 14: Discharge oil passage 16: Main relief valve 18: Drain oil passage 20: Hydraulic motor 21: Capacity controller 22: Return oil passage 24: Check valve

Claims (3)

A hydraulic device for a work machine including a plurality of hydraulic actuators,
A hydraulic pump driven by a prime mover to suck and discharge the hydraulic fluid in the tank;
A control valve that controls the discharged oil to supply and discharge the hydraulic actuator;
A main relief valve that is provided in the discharge oil passage connecting the hydraulic pump and the control valve and regulates the pressure of the hydraulic device;
A hydraulic motor connected to the prime mover and driven by hydraulic oil in the discharge oil passage of the main relief valve;
This hydraulic motor assists the drive of the hydraulic pump by the prime mover,
A hydraulic device for a working machine. The hydraulic motor is a variable displacement type,
The capacity controller increases the capacity of the hydraulic motor when the amount of hydraulic oil flowing through the discharge oil passage is small and when it is large.
The hydraulic device for a working machine according to claim 1. A check valve is provided between the return oil path from the control valve to the tank and the discharge oil path to allow a flow from the return oil path to the discharge oil path.
The hydraulic device for a working machine according to claim 1 or 2, characterized in that

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