JP3786891B2 - Hydraulic circuit of excavator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydraulic circuit of a hydraulic excavator, and particularly to a hydraulic circuit of a hydraulic excavator that can be switched between an excavator specification and a crane specification by a switch operation.
[0002]
[Prior art and problems to be solved by the invention]
A hydraulic excavator that can be switched between a shovel specification and a crane specification by a switch operation is known. In this type of hydraulic excavator, when switching to the crane specification by operating the switch, the engine speed is drastically lowered to reduce the discharge amount of the hydraulic pump, and the rotation speed of the swing motor is reduced to ensure a safe swing speed. Is controlled to ensure. However, not only does the turning motor rotate at a low speed, but also the operating speed of other actuators becomes slow, so the workability is remarkably deteriorated.
[0003]
Therefore, in hydraulic excavators that can be switched between excavator specifications and crane specifications by switch operation, safety is ensured by suppressing the operating speed only during turning operations when switching to crane specifications, and during other operations. There is a technical problem to be solved in order to improve workability at a normal work speed, and the present invention aims to solve this problem.
[0004]
[Means for Solving the Problems]
The present invention has been proposed in order to achieve the above-described object. In a hydraulic excavator that can be switched between a shovel specification and a crane specification by a switch operation, means for changing the discharge amount of the hydraulic pump, and a turning operation In a state where the switch operation is switched to the crane specification, the discharge amount of the hydraulic pump is set to the same large flow rate as the excavator specification, the switch operation is switched to the crane specification, and When a turning operation is detected, a hydraulic circuit of a hydraulic excavator provided with a control means for changing the discharge amount of the hydraulic pump to a small flow rate, and a means for changing the discharge amount of the hydraulic pump include a pump tilt A hydraulic cylinder for changing the angle, and a shuttle valve for selecting high pressure pressure oil from a hydraulic pressure source and pressure oil from a negative control oil passage and introducing it into the hydraulic cylinder; Rannahli, further an electromagnetic switching valve disposed between the hydraulic source and the shuttle valve is switched to the crane specifications in the switch operation, and, upon detection of the turning operation, the electromagnetic response to a command signal from said control means Provided is a hydraulic circuit of a hydraulic excavator configured to change a discharge amount of the hydraulic pump to a small flow rate by opening a switching valve and introducing pressure oil from a hydraulic source into the hydraulic cylinder via a shuttle valve. To do.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, the control valve 13, 14, 15 for each actuator is provided in the discharge oil passage 12 of the variable displacement hydraulic pump 11. The control valve 14 for the swing motor 16 will be described. By operating the remote control valve 17 for the swing motor 16, the spool of the control valve 14 is switched, and the pressure oil discharged from the hydraulic pump 11 is switched. Is supplied to the turning motor 16, and the turning motor 16 rotates in either the left or right direction.
[0006]
Secondary oil passages 18 and 19 of the remote control valve 17 are connected via a shuttle valve 20, and a pressure switch 21 is installed in an outlet oil passage of the shuttle valve 20. When the remote control valve 17 is operated in either the left or right direction, either pilot pressure is selected to be high by the shuttle valve 20 and the pressure switch 21 is turned on. Therefore, the controller 22 as the control means can determine that the turning remote control valve 17 has been operated by the ON signal of the pressure switch 21. The shuttle valve 20 and the pressure switch 21 constitute means for detecting a turning operation.
[0007]
On the other hand, the hydraulic pump 11 is a variable displacement type, and the discharge amount can be increased or decreased by changing the pump tilt angle by the expansion and contraction of the hydraulic cylinder 23. The hydraulic cylinder 23 is connected to a shuttle valve 26 that selects and introduces either the pressure oil from the hydraulic source 24 or the pressure oil from the negative control oil passage 25 at a high pressure. The valve 26 constitutes means for changing the discharge amount of the hydraulic pump 11.
[0008]
Further, a pressure reducing valve 27 and an electromagnetic switching valve 28 are provided between the hydraulic power source 24 and the shuttle valve 26. After the pressure oil from the hydraulic power source 24 is reduced to a predetermined pressure by the pressure reducing valve 27, the electromagnetic switching is performed. When the valve 28 is opened, it is configured to be introduced into the hydraulic cylinder 23 via the shuttle valve 26. As shown in FIG. 1, when the pressure rod is not introduced into the hydraulic cylinder 23 and the piston rod is retracted, the tilt angle of the hydraulic pump 11 becomes large and the discharge amount becomes a large flow rate. .
[0009]
Reference numeral 29 denotes a changeover switch for switching from the excavator specification to the crane specification. When the changeover switch 29 is off as shown by a solid line, the controller 22 is determined to be the excavator specification and is indicated by a chain line. Thus, when the changeover switch 29 is on, it is determined that the controller 22 has been switched to the crane specification. Then, when the changeover switch 29 is turned on to switch to the crane specification, the rotational speed of the engine (not shown) is not lowered extremely as in the prior art, and the turning operation is performed as described later. The presence or absence is detected and controlled to ensure a safe turning speed.
[0010]
Unless the turning operation is performed in a state where the changeover switch 29 is turned on and switched to the crane specification, the electromagnetic switching valve 28 remains at the illustrated position, so that the pressure oil from the hydraulic source 24 is transmitted by the electromagnetic switching valve 28. It is shut off and is not led to the shuttle valve 26. Accordingly, the tilt angle of the hydraulic pump 11 is the same as that of the excavator specification, and the discharge amount of the hydraulic pump 11 is set to a large flow rate state.
[0011]
Here, as shown in FIG. 2, when the changeover switch 29 is turned on and the turning remote control valve 17 is operated, for example, to the left side to turn the machine body under the crane specification state, the secondary oil The pilot pressure is led to the path 18 and the control valve 14 for turning is switched to the left position, and the pressure oil discharged from the hydraulic pump 11 is supplied to the turning motor 16, and the turning motor 16 rotates, so that the airframe is turned to the left. Turn.
[0012]
At this time, since the pilot pressure in the secondary oil passage 18 turns on the pressure switch 21 via the shuttle valve 20, the controller 22 detects that a turning operation has been performed, and the controller 22 detects the electromagnetic switching valve 28. Is output to the solenoid, and the electromagnetic switching valve 28 is switched to the open position as shown. Therefore, after the pressure oil from the hydraulic source 24 is reduced to a predetermined pressure by the pressure reducing valve 27, it passes through the electromagnetic switching valve 28 and is sent to the shuttle valve 26. Pressure oil and pressure oil from the negative control oil passage 25 are selected to be high pressure and introduced into the hydraulic cylinder 23.
[0013]
Accordingly, the piston rod of the hydraulic cylinder 23 is pushed out, the tilt angle of the hydraulic pump 11 becomes small, and the discharge amount becomes a small flow rate. That is, when the controller 22 detects a turning operation under a crane specification state, the discharge amount of the hydraulic pump 11 is changed to a small flow rate under the control of the controller 22. For this reason, the supply amount of the pressure oil to the turning motor 16 is reduced, the rotation of the turning motor 16 is reduced, and a safe turning speed suitable for crane work can be ensured.
[0014]
On the other hand, as shown in FIG. 3, the control valve 13 is operated so as to operate the other actuator 30 such as a boom cylinder instead of the swing motor 16 under the crane specification state with the changeover switch 29 turned on. Is switched, the pilot pressure is not derived to the shuttle valve 20, so that the pressure switch 21 is turned off. For this reason, no signal is output from the controller 22 to the solenoid of the electromagnetic switching valve 28, and the electromagnetic switching valve 28 holds the closed position as shown. The pressure oil from the hydraulic source 24 is blocked by the electromagnetic switching valve 28 and is not led to the shuttle valve 26. Therefore, the tilt angle of the hydraulic pump 11 is large, and the discharge amount of the hydraulic pump 11 is set to a large flow rate state.
[0015]
Thus, the amount of pressure oil supplied to the other actuators 30 is increased, and a high working speed similar to that of the excavator specification can be obtained despite the crane specification, so that the workability is remarkably improved. Although not shown, the same effect can be obtained even if the hydraulic pump itself is provided with a maximum discharge amount limiting port and the solenoid valve is switched to apply the pilot pressure.
[0016]
Thus, 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.
[0017]
【The invention's effect】
As described in detail in the above-described embodiment, the invention according to claim 1 sets the discharge amount of the hydraulic pump to the same large flow rate as that of the excavator specification when the crane specification is switched by the switch operation. When switching to crane specifications by switch operation and turning operation is detected, the discharge amount of the hydraulic pump is controlled to be changed to a small flow rate. The flow rate is large, and the work speed is remarkably improved because the work speed is the same as that of the excavator, although it is a crane. And at the time of turning, the discharge amount of the hydraulic pump is changed to a small flow rate, and the rotation of the turning motor becomes low, so that a safe turning speed suitable for crane work can be ensured.
[0018]
According to a second aspect of the present invention, the means for changing the discharge amount of the hydraulic pump comprises a hydraulic cylinder and a shuttle valve for changing the pump tilt angle, and the hydraulic source is controlled by a command signal from the control means. Since the hydraulic oil is introduced into the hydraulic cylinder via the shuttle valve, the switch to the crane specification is performed by switch operation, and when the turning operation is detected, the discharge amount of the hydraulic pump becomes a small flow rate. In addition to the effect of the invention described in item 1, the invention provides various effects such as the ability to automatically and reliably reduce the turning speed and contribute to the improvement of safety and workability.
[Brief description of the drawings]
The figure shows an embodiment of the present invention.
FIG. 1 is a hydraulic circuit diagram in a shovel specification state.
FIG. 2 is a hydraulic circuit diagram during a turning operation in a crane specification state.
FIG. 3 is a hydraulic circuit diagram during an operation other than turning in a crane specification state.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Hydraulic pump 16 Swing motor 17 Remote control valve 20 Shuttle valve 21 Pressure switch 22 Controller 23 Hydraulic cylinder 24 Hydraulic source 25 Negative control oil path 26 Shuttle valve 28 Electromagnetic switching valve 29 Changeover switch

Claims (2)

In a hydraulic excavator that can be switched between excavator specifications and crane specifications by switch operation, the hydraulic excavator has means for changing the discharge amount of the hydraulic pump and means for detecting turning operation, and switching to crane specifications by the switch operation. In this state, the discharge rate of the hydraulic pump is set to the same high flow rate as that of the excavator specification, switched to the crane specification by the switch operation, and when the turning operation is detected, the discharge amount of the hydraulic pump is set to the low flow rate. A hydraulic circuit for a hydraulic excavator, characterized by comprising control means for changing to The means for changing the discharge amount of the hydraulic pump selects a high pressure from a hydraulic cylinder for changing the pump tilt angle and pressure oil from a hydraulic source and pressure oil from a negative control oil passage and introduces it into the hydraulic cylinder. And a solenoid switching valve between the hydraulic pressure source and the shuttle valve. When switching to the crane specification by the switch operation and detecting a turning operation, a command of the control means is provided. 2. The discharge amount of the hydraulic pump is changed to a small flow rate by opening the electromagnetic switching valve by a signal and introducing pressure oil from a hydraulic source into the hydraulic cylinder via a shuttle valve. Hydraulic circuit of the described excavator.

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