JP3564635B2 - Pressure control valve - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pressure control valve, and more particularly to a structure of a spring chamber of a pilot poppet in a pilot operated type pressure control valve used for a direction switching valve for a hydraulic shovel.
[0002]
[Prior art]
The basic structure of a general hydraulic excavator will be described with reference to an external view shown in FIG. 3. A boom 55 is connected via a connecting pin 56 in front of a swivel 54 that is rotatably mounted on the upper surface of a traveling body 53. The arm 58 is attached to the tip of the boom 55 via a connecting pin 59 and is swingably supported by the arm cylinder 60. A bucket 61 is attached to a tip of the arm 58 via a connecting pin 62 and is swingably supported by a bucket cylinder 63. The hydraulic circuit for operating such a hydraulic excavator is provided with each pressure control valve for protecting each actuator with respect to the direction switching valve for controlling each actuator, and for controlling the pressure in the hydraulic circuit. A valve is provided.
[0003]
[Problems to be solved by the invention]
Conventionally, only a pressure control valve for protecting a boom cylinder is provided in a supply passage on a boom cylinder rod side of a boom directional switching valve in a hydraulic shovel, and it is necessary to obtain a high excavation force. For a certain operation, the set pressure is set to the maximum pressure at which the actuator can be protected, and the maximum pressure in the hydraulic circuit also needs to be high in consideration of the operation efficiency. By the mechanism of the hydraulic excavator described above, the behavior of the arm 58 during arm excavation moves clockwise in FIG. 3 around the connecting pin 59 at the tip of the boom, and the locus of the cutting edge at the tip of the bucket 61 is An arc is drawn with the lowest point in the vertical direction of the connecting pin 59 at the end of the boom. Therefore, the boom 55 receives the arm excavation reaction force upward, and the boom cylinder 57 attempts to move in the pushing direction. However, the pressure oil on the boom cylinder rod side is compressed and the pressure rises because the return port is closed, and when the pressure oil rises to a pressure equivalent to the weight of the vehicle body, the vehicle body is lifted from the front and the arm excavation is performed. Jack-up (a phenomenon in which the body of the hydraulic excavator is lifted) occurs due to the reaction force. This phenomenon is not preferable in the leveling operation (leveling the ground), and the leveling operation requires a constant boom pressing force against the ground. The skilled operator needed to be able to adjust the pressing force against the ground by performing the raising operation at the same time.
[0004]
The present invention has been made in view of the above points, and when performing a leveling operation in a hydraulic excavator, an operator does not need skilled skills and can switch to an operation requiring a high excavation force. Is to provide a pressure control valve for a hydraulic shovel that can be easily provided by an external signal, and can be mounted in a housing pocket of a directional control valve as in the related art.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, a pressure control valve according to the present invention has a spring in which a pilot pressure chamber is formed between a main poppet and a pilot poppet, and a pressure adjusting spring that presses against the pilot poppet is provided at a rear portion of the pilot poppet. The spring chamber communicates with the low-pressure section through the drain passage, and when the pressure of the high-pressure section rises above the set pressure, the pilot poppet opens to communicate the pilot pressure chamber with the spring chamber and the low-pressure section. In a pilot-operated pressure control valve configured to open the main poppet at the same time to communicate between the high-pressure section and the low-pressure section, a check valve is provided in a drain passage of the spring chamber, and the check valve is provided. Can be switched between opening and closing the main poppet by communicating and shutting off by an external signal through the piston And the pressure control valve.
[0006]
Further, this pressure control valve can be attached to the housing of the directional control valve of the hydraulic shovel, and is installed in the hydraulic circuit on the side of the boom cylinder rod. Switching can be performed by an external signal in correspondence with horizontal leveling work in which jack-up due to reaction force is prevented and a constant pressing force against the ground is obtained.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the pressure control valve according to the present invention will be described with reference to FIG. The pressure control valve 40 is mounted on a housing pocket of a directional control valve in a hydraulic shovel. That is, in FIG. 1, an outer sleeve 14 screwed to the housing 10 and a main poppet 15 slidably fitted to the outer sleeve 14 cause a high pressure in an oil passage communicating with the direction switching valve. The part 12 and the low-pressure part 13 are separated and shut off in a liquid-tight manner. The main poppet 15 receives the pressurized oil of the high pressure section 12 and moves the inner hole of the outer sleeve 14 against the spring force of the spring 16 (to the right in the figure), thereby changing the seat surface with the outer sleeve 14. An opening is provided to open and communicate between the high-pressure section 12 and the low-pressure section 13. At the rear side of the main poppet 15 inside the inner hole of the outer sleeve 14, a pilot seat 19 which is pressed against the end of the intermediate sleeve 21 screwed to the outer sleeve 14 is mounted. A poppet 17 is slidably fitted. A pilot pressure chamber 18 is formed between the main poppet 15 and the pilot poppet 17, and the pressure oil of the high-pressure section 12 is connected via an orifice 20 provided in an inner hole of the main poppet 15 and acts on the pilot pressure chamber 18. The pilot poppet 17 is pressed into the pilot sheet 19 via a pressure adjusting spring 22 and a spring receiver 23 by an inner sleeve 28 fitted into an inner hole of the intermediate sleeve 21 and screwed at an end. The pressing force can be arbitrarily adjusted according to the screwing amount of the inner sleeve 28, and the set pressure of the high-pressure section 12 can be adjusted arbitrarily. A spring chamber 24 in which a pressure adjusting spring 22 is disposed is formed between a rear portion of the pilot poppet 17 and a spring receiver 23 mounted on an end of the inner sleeve 28. The spring chamber 24 passes through an inner passage 25 formed in the spring receiver 23, an inner hole chamber (a spring chamber 26 of a check valve 27 described later) formed in the inner sleeve 28, and a lateral hole 29 through an intermediate sleeve. The low pressure passage 13 communicates with the low pressure portion 13 through a so-called drain passage which extends to a low pressure passage 31 formed inside the outer sleeve 21 and a low pressure passage 33 formed inside the outer sleeve 14.
[0008]
However, the pressure control valve 40 of the present invention is provided with the check valve 27 for communicating and shutting off between the inner hole chamber formed in the inner sleeve 28 and the lateral hole 29. The check valve 27 has a shaft portion 32 extending toward the head side slidably fitted in the inner sleeve 28, and the shaft portion 32 projects into a piston chamber 36 formed in the inner sleeve 28, and It is in contact with a piston 34 slidably fitted in the chamber 36. The piston chamber 36 is closed by a cap 35 screwed to the end of the inner sleeve 28, and the cap 35 is provided with an external signal port 38. A spring chamber 26 (inner hole chamber) in which a spring 37 is arranged between the check valve 27 and the spring receiver 23 is formed at the back of the check valve 27. When the pressure from the signal port 38 acts on the piston 34, it moves against the spring 37 (to the left in the figure) and opens the check valve 27, whereby the above-mentioned drain passage is communicated / blocked.
[0009]
Next, the operation of the pressure control valve 40 of the present invention having the above configuration will be described. When the pressure of the high-pressure section 12 rises above a set pressure, it acts on a pilot pressure chamber 18 connected through an orifice 20 provided in the inner hole of the main poppet 15 to open the pilot poppet 17 and further opens the spring chamber 24. And acts on the spring chamber 26 of the check valve 27 through the internal passage 25 of the spring receiver 23. Therefore, when there is no pressure signal at the external signal port 38, the check valve 27 is pressed against the seat surface of the inner sleeve 28 by the pressure of the spring 37 and the spring chamber 26, and the space between the spring chamber 26 and the side hole 29 is formed. To block the drain passage, the pressure oil in the high-pressure section 12 does not flow from the pilot pressure chamber 18 to the low-pressure section 13 via the drain passage. There is no pressure difference between the main poppets 15 and the main poppet 15 is closed. However, when the external signal port 38 has a pressure signal of a certain level or more, the piston 34 is moved (leftward in the figure), and the check valve 27 operates against the force of the spring 37 and the pressure of the spring chamber 26. The drain passage is opened (leftward in the figure), and the drain passage from the spring chamber 26 to the low pressure passage 31 inside the intermediate sleeve 21 and the low pressure passage 33 inside the outer sleeve 14 through the lateral hole 29 is communicated. A flow of the pressure oil of the high-pressure section 12 from the pilot pressure chamber 18 to the low-pressure section 13 through the drain passage is formed, and between the high-pressure section 12 and the pilot pressure chamber 18, an orifice 20 in the inner hole of the main poppet 15 is formed. Causes a pressure difference, and as a result, the main poppet 15 opens. Thus, depending on the presence / absence of a pressure signal exceeding a certain level to the external signal port 38, the check valve 17 is connected / disconnected and the drain path from the pilot pressure chamber 18 to the low pressure portion 13 is connected / disconnected. Thus, the main poppet 15 is opened and closed, and the switching between the relief function and the block function can be performed.
[0010]
FIG. 2 is a hydraulic circuit diagram of a hydraulic shovel using the pressure control valve 40 of the present invention. For convenience of explanation, illustration of parts that are not necessary in the description of the present invention is omitted. In general, a directional control valve of a hydraulic shovel is provided with two pump systems, and often requires a merge switch valve for each cylinder of a boom and an arm. That is, in the case of FIG. 2 as well, the two pumps 42 and 43 are used as hydraulic pressure sources, and the boom direction switching valve 44, the boom merging direction switching valve 45, the arm direction switching valve 46, and the arm merging direction switching valve 47 are used. Is provided. Further, a boom cylinder protection pressure control valve 48 and an arm cylinder protection pressure control valve 49 are provided as pressure control valves for protecting the boom and arm cylinders 57 and 60 with respect to the boom and arm direction switching valves 44 and 46. I have. Therefore, in addition to the pressure control valve 48 for protecting the boom cylinder, the pressure control valve 40 of the present invention is provided in the boom cylinder rod side supply passage 41. In the above-described embodiment, the pressure control valve 40 of the present invention is installed in the housing pocket of the directional switching valve 45 for boom confluence. However, the installation place is not limited to this, and the boom cylinder rod side supply passage 41 is provided. It may be installed anywhere as long as the pressure is applied. In addition, the pressure control valve 50 for circuit regulation is provided as a pressure control valve which regulates the pressure in a hydraulic circuit. In the hydraulic excavator constituting such a hydraulic circuit, during the arm excavation, the boom receives an arm excavation reaction force, and the boom cylinder 57 tends to move in the pushing direction. However, the pressure oil in the boom cylinder rod side supply passage 41 is compressed because the return port is closed, and the pressure increases. At this time, by inputting a signal to the external signal port 38, the pressure control valve 40 of the present invention is opened as described above, and the pressure in the boom cylinder rod side supply passage 41 rises. The pressurized oil returns to the tank 52 through the low-pressure passage 51, and the boom cylinder 57 can extend in the pushing direction, so that jack-up due to arm excavation reaction force is prevented and the boom cylinder rod side supply passage 41 is provided. The internal pressure becomes the set pressure of the pressure control valve 40 of the present invention, and the pressing force of the boom against the ground maintains a constant force. As described above in the operation of the pressure control valve 40 of the present invention, the set pressure of the pressure control valve 40 can be arbitrarily adjusted, and the pressing force of the boom against the ground can also be adjusted.
[0011]
【The invention's effect】
As described above, according to the pressure control valve of the present invention, the pressure control valve can be installed in the housing pocket of the conventional directional control valve. A constant pressing force against the ground can be obtained, leveling work can be easily realized, and switching to a work requiring high excavation force can be easily performed by an external signal.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an embodiment of a pressure control valve according to the present invention.
FIG. 2 is a hydraulic circuit diagram of a hydraulic shovel using the pressure control valve of the present invention.
FIG. 3 is an external view of a general hydraulic excavator.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Housing 12 High pressure part 13 Low pressure part 14 Outer sleeve 15 Main poppet 16 Spring 17 Pilot poppet 18 Pilot pressure chamber 19 Pilot seat 20 Orifice 21 Intermediate sleeve 22 Pressure adjusting spring 23 Spring receiver 24 Spring chamber 25 Internal passage 26 Spring chamber 27 Check valve 28 Inner sleeve 29 Side hole 31 Low pressure passage 32 Shaft 33 Low pressure passage 34 Piston 35 Cap 36 Piston chamber 37 Spring 38 External signal port 40 Pressure control valve 41 of the present invention Boom cylinder rod side supply passage 42 pump 43 pump 44 boom directional switching valve 45 boom merging directional switching valve 46 arm directional switching valve 47 arm merging directional switching valve 48 boom cylinder protection pressure control valve 49 arm cylinder protection pressure control valve 50 times Regulating the pressure control valve 51 low-pressure passage 52 tank 53 traveling body 54 swivel base 55 Bed - arm 56 connecting pin 57 Bed - arm cylinder 58 A - arm 59 coupling pin 60 A - arm cylinder 61 Bucket 62 connecting pin 63 bucket cylinder

Claims (2)

A pilot pressure chamber is formed between the main poppet and the pilot poppet, and a spring chamber is provided at the rear of the pilot poppet for arranging a pressure adjusting spring that presses against the pilot poppet, and this spring chamber is connected to the low pressure section via a drain passage. When the pressure in the high pressure section rises above the set pressure, the pilot poppet opens to communicate the pilot pressure chamber with the spring chamber and the low pressure section, and at the same time opens the main poppet to connect the high pressure section and the low pressure section. In a pilot operated type pressure control valve configured to communicate,
A check valve is disposed in the drain passage of the spring chamber, and the check valve is communicated / blocked by an external signal via a piston, so that opening and closing of the main poppet can be switched. And pressure control valve. The pressure control valve is attachable to a housing of a directional control valve of a hydraulic excavator, and is installed in a hydraulic circuit on a side of a bomber cylinder rod, which requires a high excavation force and an arm excavation reaction force. 2. The pressure control valve according to claim 1, wherein switching can be performed by the external signal in accordance with a horizontal leveling operation in which jacking-up caused by the pressure is prevented and a constant pressing force against the ground is obtained.

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