JP3558761B2 - Attachment overload protection device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an overload protection device for an attachment provided with a plurality of hydraulic actuators and used by being attached to a working device such as a construction vehicle.
[0002]
[Prior art]
Attachments attached to construction vehicles for performing various operations have become complicated and versatile in recent years, and a large number of hydraulic actuators have been used.
In such a hydraulically driven attachment, one operating valve is usually required to operate one actuator. Therefore, a work control valve of a construction vehicle to which the attachment is attached is provided with a standard operation valve which is standardly provided in the construction vehicle. It is necessary to provide the number of operation valves which is obtained by adding the number of actuators for attachment to the number of actuators for use.
[0003]
However, an increase in the number of operation valves causes an increase in the size of the multiple work control valves, and it becomes difficult to install the work control valves in relation to the mounting space of the construction vehicle. Also, the number of operation levers increases, so that the operability deteriorates.
Therefore, as shown in FIG. 5, the work control valve 20 is a standard work valve provided with standard work operation valves 62 and 63 for operating the standard work actuators 60 and 61 that are standard equipment of the construction vehicle. An attachment valve unit 25 having only one attachment operation valve 24 for operating the attachment actuators 64 and 65, and an attachment connected to a service port of the attachment operation valve 24. The actuator operating lines 41, 42, 43, and 44 are connected to the attachment actuators 64 and 65 via electromagnetic valves 39 and 40, respectively. Switching between 39 and 40 to operate desired attachment actuators 64 and 65 for attachment Those adapted to operate at 24 has come to be used. The standard operation actuators 60 and 61 are provided with overload relief valves 31, 32, 33 and 34, and the attachment operation pipelines 37 and 38 are also provided with overload relief valves 35 and 36.
[0004]
However, when the attachment operation conduits 37 and 38 and the attachment actuator 65 are in communication with each other by switching of the solenoid valve 40, if an overload occurs in the attachment actuator 65 due to an external force, the work control valve 20 may be used. The overload relief valves 35 and 36 provided in the valve portion 25 are operated to be protected, but the attachment actuator 64 not communicating with the attachment operation pipelines 37 and 38 is used for the attachment of the work control valve 20. It is not protected by the overload relief valves 35 and 36 provided in the valve section 25.
[0005]
Therefore, the overload relief valves 66, 67, 68, 69 dedicated to the respective attachment actuators 64, 65 are provided.
As described above, when the dedicated overload relief valves 66, 67, 68, 69 are provided for the respective attachment actuators 64, 65, a large number of relief valves are required, so that the cost increases and the hydraulic piping becomes complicated. .
[0006]
Also, normally, the work control valve 20 is located in the frame of the construction vehicle, and the attachment is attached to the tip of the boom arm. Therefore, in order to simplify the hydraulic piping from the work control valve 20 to the attachment, the solenoid valves 39, 40 and the overload relief valves 66, 67, 68, 69 of the attachment actuators 64, 65 are installed on the attachment. However, it is difficult to place them in a narrow space on the attachment.
[0007]
[Problems to be solved by the invention]
The present invention solves the above-described problem in the attachment of the working device, and it is not necessary to provide a dedicated overload relief valve for each of the plurality of attachment actuators, so that the hydraulic piping can be simplified, and the attachment actuator can be provided by an external force. An object of the present invention is to provide an attachment overload protection device that can protect any attachment actuator when an overload occurs.
[0008]
[Means for Solving the Problems]
In the attachment overload protection device of the present invention, in a working device used by attaching an attachment provided with a plurality of hydraulic actuators, the attachment valve portion for controlling the attachment actuator includes one attachment operation valve, A branch is made from an attachment operating line connected to the service port of the attachment operating valve, and an actuator operating line is connected to each of the attachment actuators via a solenoid valve, and the actuator operating line is connected to the actuator operating line. A pressure switch is provided for switching an electromagnetic valve so as to detect the overload of the actuator and connect the working pipe for attachment to the working pipe for actuator, and an overload of the working pipe for attachment is provided in the valve part for attachment. The Doririfu valve is provided.
[0009]
When the attachment is attached to the construction vehicle and the work is performed, the solenoid valve is switched so that the desired actuator for the attachment communicates with the operating pipe for the attachment, and then the operation is performed with the operation valve for the attachment.
If an overload is applied to the attachment actuator that is not in communication with the attachment operation conduit due to external force, the overload is detected by the pressure switch, and the solenoid valve is connected to the actuator operation conduit of the overloaded attachment actuator. The overload relief valve of the attachment operation pipeline operates to protect the attachment actuator in which an overload has occurred, since the communication is performed with the operation pipeline.
[0010]
Therefore, it is not necessary to provide a dedicated overload relief valve for each attachment actuator, and the hydraulic piping is simplified.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a hydraulic circuit diagram of an overload protection device for a wheel loader attachment according to one embodiment of the present invention, FIG. 2 is a side view of a wheel loader having an angling plow as an attachment, and FIG. It is a top view of a wheel loader.
[0012]
The wheel loader 1 is provided with a lift arm 4 at a front portion of a vehicle body 3 on which tires 2 are mounted so that the lift arm 4 can be moved up and down by a lift cylinder 5. ) Is supported by the tilt cylinder 6 and the tilt link 7 so as to be able to tilt forward and backward.
When the angling plow 8 is used as an attachment, the shovel is removed from the distal end portion 14 of the lift arm 4 and the base end 9 of the angling plow 8 is attached to the distal end portion 14 of the lift arm 4 as shown in FIG. Attach. At the base end 9 of the angling plow 8, left and right plows 10, 11 are provided so as to be rotatable independently of each other by left and right angling cylinders 12, 13.
[0013]
In the wheel loader 1, a work control valve 20 for controlling a lift cylinder 5 and a tilt cylinder 6 as standard work actuators and left and right angling cylinders 12 and 13 as attachment actuators is connected to the lift cylinder 5 and the tilt cylinder. A standard operation valve section 23 having a lift cylinder operation valve 21 and a tilt cylinder operation valve 22 which are standard operation valves for operating the cylinder 6, and an attachment for operating the angling cylinders 12 and 13. And an attachment valve section 25 having only one operating valve 24.
[0014]
The service port of the main relief valve 30, the lift cylinder operation valve 21, and the tilt cylinder operation valve 22 is provided between the discharge pipe 27 of the hydraulic pump 26 and the return pipe 29 to the tank 28 in the standard work valve section 23. The overload relief valves 31, 32, 33, 34 are provided between the valve and the return line 29.
The lift cylinder operation valve 21 and the tilt cylinder operation valve 22 are 6-port, 3-position manual operation valves. When both are in the neutral position, the discharge pipe 27 of the hydraulic pump 26 communicates with the pump port of the attachment operation valve 24. Is done.
[0015]
The attachment valve portion 25 is provided with overload relief valves 35 and 36 between each service port of the attachment operation valve 24 and the return pipe 29.
The attachment operation valve 24 is also a 6-port, 3-position manual operation valve, and when in the neutral position, the discharge pipe 27 of the hydraulic pump 26 communicates with the return pipe 29 to the tank 28.
[0016]
Attachment operation conduits 37, 38 connected to the service port of the attachment operation valve 24 branch off, and actuate the actuator operation conduits 41, 41 via electromagnetic valves 39, 40 to the left and right angling cylinders 12, 13, respectively. 42, 43, and 44 are connected.
[0017]
The solenoids 39S and 40S of the solenoid valves 39 and 40 are connected to the power supply 18 via the electric switch 19, and the solenoid 40S of the solenoid valve 40 is connected to the power supply 18 and excited as shown in FIG. Then, the actuator operation lines 43 and 44 for extending and contracting the right angling cylinder 13 communicate with the attachment operation lines 37 and 38, and the electric switch 19 is switched to connect the solenoid 39S of the solenoid valve 39 to the power supply 18. When connected and excited, the actuator operating lines 41 and 42 for expanding and contracting the left angling cylinder 12 communicate with the attachment operating lines 37 and 38.
[0018]
In the actuator operation lines 41 and 42, an overload of the left angling cylinder 12 is detected to excite the solenoid 39S of the electromagnetic valve 39, and the attachment operation lines 37 and 38 and the actuator operation lines 41 and 42 are detected. Pressure switches 45 and 46 are provided to communicate with the solenoid valve 40. The actuator operating conduits 43 and 44 detect overload of the right angling cylinder 13 and excite the solenoid 40S of the solenoid valve 40 to perform attachment. Pressure switches 47 and 48 are provided for connecting the operation pipes 37 and 38 to the actuator operation pipes 43 and 44.
The set pressure of these pressure switches 45, 46, 47, 48 is equal to the set pressure of the overload relief valves 35, 36.
[0019]
When a shovel is attached to the wheel loader 1 as a working device, the shovel is moved up and down and tilted by operating the standard work valve portion 23 of the work control valve 20 to perform a normal loading operation.
[0020]
When the angling plow 8 is attached to the wheel loader 1 to perform work, the angling plow 8 is moved up and down and tilted by the operation of the standard operation valve section 23 to position the angling plow 8. Further, for example, when the left plow 10 is operated, the electric switch 19 is switched to excite the solenoid 39S of the electromagnetic valve 39, and the attachment operation pipes 37, 38 and the actuator operation pipes 41, 42 are communicated. Therefore, the left-hand angling cylinder 12 is expanded and contracted by operating the attachment operation valve 24 of the attachment valve portion 25.
[0021]
When the right plow 11 is operated, the electric switch 19 is switched to excite the solenoid 40S of the solenoid valve 40, and the attachment operation pipes 37, 38 and the actuator operation pipes 43, 44 are connected to each other, so that the attachment The right-hand angling cylinder 13 may be expanded and contracted by manipulating the attachment operation valve 24 of the valve section 25.
[0022]
When the actuator operation lines 41 and 42 of the left angling cylinder 12 and the attachment operation lines 37 and 38 communicate with each other, an unexpected external force acts on the right plow 11 and the attachment operation lines 37 and 38. When an overload occurs due to an external force in the right angling cylinder 13 that is not in communication with 38, one of the pressure switches 47 and 48 is turned on, an overload is detected, and the solenoid valve 40 is overloaded. Since the actuator operation lines 43, 44 of the right angling cylinder 13 and the attachment operation lines 37, 38 communicate with each other, the overload relief valves 35, 36 are actuated and the right angling cylinder is overloaded. 13 is protected. When the hydraulic pressure is reduced by the operation of the overload relief valves 35 and 36, the pressure switches 47 and 48 are turned off and return to the original state.
[0023]
When the actuator operation lines 43, 44 of the right angling cylinder 13 and the attachment operation lines 37, 38 communicate with each other, an unexpected external force acts on the left plow 10 and the attachment operation lines 37, When an overload due to an external force occurs in the left angling cylinder 12 that is not in communication with 38, one of the pressure switches 45 and 46 is turned on, an overload is detected, and the solenoid valve 39 is overloaded. Since the actuator operating lines 41, 42 of the left angling cylinder 12 and the operating lines 37, 38 for attachment are communicated with each other, the overload relief valves 35, 36 are actuated and the left angling cylinder on which overload has occurred. 12 is protected. When the hydraulic pressure is reduced by the operation of the overload relief valves 35 and 36, the pressure switches 45 and 46 are turned off, and return to the original state.
[0024]
Therefore, it is not necessary to provide a dedicated overload relief valve for each of the angling cylinders 12 and 13, and the hydraulic piping is simplified.
[0025]
FIG. 4 is a hydraulic circuit diagram of an overload protection device for an attachment for a wheel loader according to another embodiment of the present invention.
Here, a shuttle valve 50 is provided between the actuator operation lines 41 and 42. The shuttle valve 50 detects an overload of the left angling cylinder 12 and connects the attachment operation lines 37 and 38 to the actuator operation lines. A pressure switch 51 for switching the electromagnetic valve 39 is provided so as to communicate with the solenoid valves 41 and 42. A shuttle valve 52 is provided between the actuator operation pipes 43 and 44. A pressure switch 53 is provided for switching the solenoid valve 40 so as to detect an overload of the solenoid valve 40 and connect the attachment operation pipes 37, 38 to the actuator operation pipes 43, 44.
Other configurations are the same as those of the overload protection device for the wheel loader attachment shown in FIG.
[0026]
If necessary, a slide cylinder may be provided between the distal end portion 14 of the lift arm 4 and the base end portion 9 of the angling plow 8 so that the angling plow 8 can slide left and right. In this case, a pressure switch may be provided by further branching and connecting the actuator operation pipeline to the slide cylinder.
[0027]
【The invention's effect】
As described above, the overload protection device for an attachment for a construction vehicle of the present invention can simplify the hydraulic piping without providing a dedicated overload relief valve for each of a plurality of attachment actuators, and can simplify the attachment actuator by an external force. When an overload occurs in any of the above, any of the attachment actuators can be protected.
[Brief description of the drawings]
FIG. 1 is a hydraulic circuit diagram of an overload protection device for an attachment for a wheel loader according to an embodiment of the present invention.
FIG. 2 is a side view of a wheel loader to which an angling plow is attached as an attachment.
FIG. 3 is a plan view of a wheel loader to which an angling plow is attached.
FIG. 4 is a hydraulic circuit diagram of an overload protection device for an attachment for a wheel loader according to another embodiment of the present invention.
FIG. 5 is a hydraulic circuit diagram of a conventional overload protection device for a construction vehicle.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Wheel loader 2 Tire 3 Body 4 Lift arm 5 Lift cylinder 6 Tilt cylinder 7 Tilt link 8 Angling plow 10 Plow 11 Plow 12 Angling cylinder 13 Angling cylinder 18 Power supply 19 Electric switch 20 Work control valve 21 Lift cylinder operating valve 22 Tilt cylinder operation valve 23 Standard operation valve unit 24 Attachment operation valve 25 Attachment valve unit 26 Hydraulic pump 35 Overload relief valve 36 Overload relief valve 37 Attachment operation line 38 Attachment operation line 39 Electromagnetic valve 40 Electromagnetic Valve 41 Actuator operating line 42 Actuator operating line 43 Actuator operating line 44 Actuator operating line 45 Pressure switch 46 Pressure switch 47 Pressure switch 48 Power switch

Claims (1)

In a working device in which an attachment having a plurality of hydraulic actuators is mounted and used, an attachment valve for controlling the attachment actuator is provided with one attachment operation valve, and is connected to a service port of the attachment operation valve. Branch from the attachment operating pipe, and connect the actuator operating pipe to each attachment actuator via a solenoid valve, and detect an overload of the attachment actuator in the actuator operating pipe to operate the attachment. Attachment wherein a pressure switch for switching an electromagnetic valve is provided so as to connect the pipe with the actuator operation pipe, and an overload relief valve of the attachment operation pipe is provided in the attachment valve section. Overload protection device.

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