JP2579587Y2 - Hydraulic circuit of construction machinery - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit of a construction machine such as a hydraulic shovel having a boom and a stick.

[0002]

2. Description of the Related Art In a construction machine, for example, a hydraulic excavator, a boom is mounted on a vehicle body, and a stick (arm) is connected to a tip of the boom. A bucket is attached to the tip of the stick. Boom is by boom cylinder, stick is by stick cylinder,
Each bucket is driven by a bucket cylinder. Various works are performed using the working machine configured as described above. For this purpose, the hydraulic shovel is provided with a hydraulic circuit. There are various types of hydraulic circuits, some of which are capable of setting a boom priority mode, and are already in practical use. For example, in order to use the working machine to load earth and sand into a dump, it is necessary to increase the boom raising speed. In this case, the operation is performed in a state where the operation amount of the boom operation lever is a so-called boom raising full lever in which the operation amount is substantially maximum. The setting of the boom priority mode is performed for the purpose of preferentially supplying pressure oil to the boom cylinder at the time of such a boom raising full lever. When the boom priority mode is set, in the boom raising and stick-in (pulling) interlocking operation, the amount of oil supplied to the boom raising chamber of the boom cylinder when the boom raising full lever is increased is increased by the stick-in of the stick cylinder. The amount of oil supplied to the chamber is reduced.

As described above, there is known a hydraulic excavator having a hydraulic circuit capable of setting a boom priority mode. Hereinafter, a conventional hydraulic circuit of this type will be described with reference to FIG. explain. The first hydraulic pump 2 and the boom raising chamber 6 of the boom cylinder 4 are connected by a boom raising oil passage 8. A boom first control valve 10 is disposed in the boom raising oil passage 8. Normally, the boom first control valve 10 at the illustrated neutral position is supplied with a pilot secondary pressure (hereinafter simply referred to as “pilot pressure”) via a boom raising first pilot oil passage 12. This switches to the boom raising position. Thereby, the discharge pressure oil of the first hydraulic pump 2 is supplied to the boom raising chamber 6 of the boom cylinder 4 via the boom raising oil passage 8, and the boom (not shown) is raised. Boom raising first pilot oil passage 1
2 is connected to a pilot pump 16 via a boom operation valve (remote control valve) 14. The operation of the boom operation valve 14 is performed by a boom operation lever (not shown). Therefore, the driving of the boom cylinder 4 as described above is controlled by the operation of the boom operation lever (the operation of the boom operation valve 14). On the other hand, the second hydraulic pump 18 and the stick-in chamber 22 of the stick cylinder 20 are connected by a stick-in oil passage 24. A stick first control valve 26 is disposed in the stick-in oil passage 24. Normally, the stick first control valve 26 in the illustrated neutral position is switched to the stick-in position by supplying pilot pressure via the stick-in first pilot oil passage 28. As a result, the pressure oil discharged from the second hydraulic pump 18 is supplied to the stick-in chamber 22 of the stick cylinder 20 via the stick-in oil passage 24, and the stick (not shown) is stick-in (pulled to the boom side). The stick-in first pilot oil passage 28 includes a stick operation valve (remote control valve) 30.
Is connected to the pilot pump 16 via the. The operation of the stick operation valve 30 is performed by a stick operation lever (not shown). Therefore, the driving of the stick cylinder 20 as described above is controlled by operating the stick operating lever (operating the stick operating valve 30).

[0004] First hydraulic pump 2 and stick-in oil passage 2
4, the upstream position of the stick first control valve 26 is
They are connected by a stick junction oil passage 32. An on-off valve 34 and a second stick control valve 36 are arranged in the stick junction oil passage 32 in parallel. When the pilot pressure is supplied from the stick-in first pilot oil passage 28 via the stick-in second pilot oil passage 28 via the stick-in second pilot oil passage 38, the stick second control valve 36 operates the opening / closing valve from the neutral position, which is a position shown in the figure. Switch to position. When the stick second control valve 36 is switched to the open / close valve operating position, the pressure oil discharged from the first hydraulic pump 2 is supplied to the open / close valve 34 via the oil passage 40 as pilot pressure. As a result, the on-off valve 34 opens, and the stick junction oil passage 32 communicates. At the same time, the downstream and upstream positions of the on-off valve 34 in the stick joining oil passage 32
6 is communicated. As a result, the discharge pressure oil of the first hydraulic pump 2 is supplied to the stick-in oil path 24 via the stick junction oil path 32 (the discharge pressure oil of the second hydraulic pump 18 supplied to the stick-in oil path 24 is supplied to the stick-in oil path 24). Merged and added). An electromagnetic switching valve 42 is disposed in the stick-in second pilot oil passage 38. The electromagnetic switching valve 42 is normally in a deenergized state, and communicates with the stick-in second pilot oil passage 38. When the electromagnetic switching valve 42 is energized, the stick-in second pilot oil passage 38 on the stick second control valve 36 side is connected to the oil tank T while the stick-in second pilot oil passage 38 is closed. Thereby, the stick second control valve 36 is returned to the neutral position.

[0005] The second hydraulic pump 18 and the upstream position of the boom raising chamber 6 in the boom raising oil passage 8 are connected by a boom merging oil passage 44. A boom second control valve 46 is disposed in the boom joining oil passage 44. When the pilot pressure is supplied from the boom raising first pilot oil passage 12 via the boom raising second pilot oil passage 48, the boom second control valve 46 is moved from the neutral position shown in the drawing to the valve opening position. Is switched to. Boom second control valve 4
When the valve 6 is switched to the valve opening position, the boom joining oil passage 44 communicates. As a result, the discharge pressure oil of the second hydraulic pump 18 is supplied to the boom raising oil passage 8 at a position upstream of the boom raising chamber 6 through the boom merging oil passage 44 (the first oil supplied to the boom raising oil passage 8). Merge with the discharge pressure oil of hydraulic pump 2
Will be added). Boom raising first pilot oil passage 12
, A pressure switch 50 is arranged. When the pilot pressure in the boom raising first pilot oil passage 12 reaches the set value, the pressure switch 50 is turned on.
Becomes Pressure switch 50 and electromagnetic switching valve 42
Are connected in series via a boom priority mode switch (not shown) in an electric circuit (not shown). Therefore, when the boom priority mode switch is turned on in advance (when the boom priority mode is set), the electromagnetic switch valve 42 is energized by turning on the pressure switch 50. In a state where the boom priority mode switch is OFF (a state where the boom priority mode is not set), even if the pressure switch 50 is turned ON, the electromagnetic switching valve 42 is maintained in a deenergized state.

[0006]

Some of the operations performed by using a working machine of a hydraulic shovel having a hydraulic circuit configured as described above include a so-called "flattening" in which the ground is leveled evenly. Work "is included. This leveling operation is performed by pulling the bucket toward the driver's seat side of the vehicle body while keeping the bottom of the bucket substantially horizontal. in this case,
Boom raising and stick-in operations are performed simultaneously. This leveling operation is often performed with the boom priority mode set. The setting of the boom priority mode is performed by turning on the boom priority mode switch. During the leveling operation, the boom operation valve 14 and the stick operation valve 30 are simultaneously operated. By operating the boom operation valve 14, the boom first control valve 10 is switched to the boom raising position, and the boom second control valve 46 is switched to the valve opening position. As a result, the discharge pressure oil from the first hydraulic pump 2 and the second hydraulic pump 18 is combined and added to the boom raising chamber 6 of the boom cylinder 4. The boom starts to rise. On the other hand, by operating the stick operation valve 30, the first stick control valve 26 is switched to the stick-in position, and the second stick control valve 36 is switched to the on-off valve operating position. As a result, the discharge pressure oil of the second hydraulic pump 18 and the first hydraulic pump 2 is supplied to the stick-in chamber 22 of the stick cylinder 20 after being combined and added. The stick starts stick-in operation. The boom cylinder 4 and the stick cylinder 20 are operated at a speed corresponding to the spool opening of each valve and the pilot pressure. Since the boom priority mode is set, when the pilot pressure of the boom raising first pilot oil passage 12 reaches a predetermined value near the full lever of the boom operation lever, the pressure switch 5
0 turns ON. The electromagnetic switching valve 42 is energized, and the stick-in second pilot oil passage 38 on the stick second control valve 36 side is connected to the oil tank T. Since the stick second control valve 36 is in the neutral position, the stick joining oil passage 32
Is closed by the on-off valve 34. Accordingly, the amount of oil supplied to the boom raising chamber 6 of the boom cylinder 4 by the first hydraulic pump 2 through the boom first control valve 10 is increased, and at the same time, the stick cylinder is passed through the first stick control valve 26. The amount of oil supplied to the 20 stick-in chambers 22 is reduced. As a result, the boom raising speed of the boom cylinder 4 increases, and the stick-in speed of the stick cylinder 20 decreases.

As described above, in the boom raising and the stick-in interlocking operation by the boom operating valve 14 and the stick operating valve 30, the boom raising first pilot oil passage 1
When the pilot pressure of No. 2 reaches the set value and the pressure switch 50 is turned on, the stick second control valve 36 is immediately returned to the neutral position. Since the amount of oil to the boom raising chamber 6 of the boom cylinder 4 rapidly increases and the amount of oil to the stick-in chamber 22 of the stick cylinder 20 rapidly decreases, the boom cylinder 4 rapidly accelerates before and after the ON operation of the pressure switch 50, The stick cylinder 20 is rapidly decelerated. As a result, there arises a problem that the boom rises and the leveling work becomes difficult.

The present invention has been made based on the above facts, and an object of the present invention is to provide an improved construction machine capable of preventing sudden acceleration of a boom cylinder and sudden deceleration of a stick cylinder when a boom priority mode is set. Is to provide a hydraulic circuit.

[0009]

According to the present invention, a boom first control valve disposed in a boom raising oil passage connecting a first hydraulic pump and a boom raising chamber of a boom cylinder is provided according to the present invention. A first stick control valve disposed in a stick-in oil passage connecting the second hydraulic pump and the stick-in chamber of the stick cylinder; and a first stick control valve in the first hydraulic pump and the stick-in oil passage. A stick joining oil passage connecting the upstream position of the stick, an opening / closing valve arranged in the stick joining oil passage, a stick second control valve arranged in parallel with the opening / closing valve,
A boom joining oil passage connecting the hydraulic pump to an upstream position of the boom raising chamber in the boom raising oil passage; a boom second control valve disposed in the boom joining oil passage;
A boom raising first pilot oil passage for supplying a pilot pressure for switching a control valve to a boom raising position; and a boom raising first pilot oil for switching the boom second control valve to communicate with the boom merging oil passage. Boom raising second pilot oil passage for supplying pilot pressure from the passage, stick-in first pilot oil passage for supplying pilot pressure for switching the stick first control valve to the stick-in position, and stick second control valve And a stick-in second pilot oil path for supplying pilot pressure from the stick-in first pilot oil path to open the valve by applying pilot pressure to the on-off valve. A pressure reducing valve is disposed in the stick-in second pilot oil passage. A pressure-reducing pilot oil path for supplying pilot pressure to the pressure valve is provided, and a switching valve is disposed in the pressure-reducing pilot oil path. In a state where the switching valve is switched to the open position, the pressure-reducing valve moves the boom up. The pilot pressure of the stick-in second pilot oil passage is reduced according to the increase of the pilot pressure of the one pilot oil passage,
When the pilot pressure of the boom raising first pilot oil passage reaches a set value, the pilot pressure of the stick-in second pilot oil passage is reduced to an operating pressure of the stick second control valve or less. A hydraulic circuit for a construction machine is provided.

[0010]

When the boom priority mode is set, the switching valve arranged in the pressure reducing pilot oil passage is switched to the valve opening position, and the pressure reducing pilot oil passage is connected. Thus, the pilot pressure is supplied from the boom raising first pilot oil passage to the pressure reducing valve arranged in the stick-in second pilot oil passage. The pressure reducing valve is controlled to be reduced in pressure by the pilot pressure in the boom raising first pilot oil passage. In the boom raising and stick-in interlocking operation by the boom operating valve and the stick operating valve, as the pilot pressure of the boom raising first pilot oil passage increases, the pilot pressure to the stick second control valve is gradually reduced by the pressure reducing valve. go. The amount of oil to the boom raising chamber of the boom cylinder gradually increases, and the amount of oil to the stick-in chamber of the stick cylinder gradually decreases. When the pilot pressure of the boom raising first pilot oil passage reaches a set value near the full lever of the boom operation valve, the pressure reducing valve changes the pilot pressure of the stick-in second pilot oil passage to the operating pressure (opening) of the stick second control valve. Since the pressure is reduced to below (valve pressure), the stick second control valve returns to the neutral position, and the stick merging oil passage is closed by the on-off valve of the oil passage. As a result, discharge hydraulic oil is supplied from the first hydraulic pump and the second hydraulic pump to the boom raising chamber of the boom cylinder, and discharge hydraulic oil is supplied only from the second hydraulic pump to the stick-in chamber of the stick cylinder. That is, in the hydraulic circuit according to the present invention, when the boom priority mode is set, the amount of oil supplied from the first hydraulic pump supplied to the stick-in chamber of the stick cylinder via the stick junction oil passage is increased by the function of the pressure reducing valve. Since the pressure is gradually decreased in accordance with an increase in the pilot pressure in the raising first pilot oil passage, the occurrence of sudden acceleration of the boom cylinder and sudden deceleration of the stick cylinder are prevented. In addition, the operating speed of the boom cylinder is maintained at the same level as in the related art even near the full lever of the boom operation valve. As a result, the leveling operation is performed stably and reliably.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a hydraulic circuit of a construction machine constructed according to the present invention will be described with reference to FIG. In FIG. 1, the same parts as those in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted unless otherwise required. A pressure reducing valve 60 is disposed in the stick-in second pilot oil passage 38. Pressure reducing valve 60
Is constituted by a pilot operated pressure reducing valve in this embodiment. A pressure-reducing pilot oil path 62 for supplying pilot pressure from the boom raising first pilot oil path 12 to the pressure-reducing valve 60 is provided. A switching valve 64 is disposed in the pressure reducing pilot oil passage 62. The switching valve 64 is constituted by an electromagnetic switching valve in this embodiment. The switching valve 64 is turned on and off by a boom priority mode switch (not shown). That is, when the boom priority mode is not set, the boom priority mode switch is OFF, so that the switching valve 64 is also kept in the OFF state (valve closed position) as shown. The pressure reducing pilot oil passage 62 is closed, and the pilot side of the pressure reducing valve 60 is connected to the oil tank T. The pressure reducing valve 60 communicates with the stick-in second pilot oil passage 38, but the pressure reducing valve 60 is not affected by the pilot pressure of the boom raising first pilot oil passage 12.

When the boom priority mode switch is turned on, the switching valve 64 is also turned on, and can be switched from the illustrated position. That is, the switching valve 64 is switched to the valve opening position. The pressure reducing pilot oil passage 62 communicates with the boom
The pilot pressure is supplied from the pilot oil passage 12 to the pressure reducing valve 60. In this boom priority mode setting state, the pressure reducing valve 60 reduces the pilot pressure of the stick-in second pilot oil passage 38 in accordance with an increase in the pilot pressure of the boom raising first pilot oil passage 12. The pressure reducing valve 60 also reduces the pilot pressure of the stick-in second pilot oil passage 38 to the operating pressure of the stick second control valve 36 when the pilot pressure of the boom raising first pilot oil passage 12 reaches a set value. It is configured as follows. Switching valve 64
The pressure reducing valve 60 has a small capacity and a low pressure (maximum 45 kgf /
(approx. cm ² ).

As described above, the present invention has been described in detail based on the embodiments. However, the present invention is not limited to the above-described embodiments, but can be variously modified or modified within the scope of the present invention. is there.

[0014]

According to the hydraulic circuit for a construction machine constructed according to the present invention, it is possible to prevent sudden acceleration of the boom cylinder and sudden deceleration of the stick cylinder when the boom priority mode is set. As a result, the leveling operation is performed stably and reliably. Also, the present invention is the first boom raising
Practical application can be achieved easily and inexpensively simply by incorporating a small switching valve and a pressure-reducing valve of small capacity and low pressure into the pilot oil passage and the stick-in second pilot oil passage.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a hydraulic circuit of a construction machine configured according to the present invention.

FIG. 2 is a diagram showing a hydraulic circuit of a conventional construction machine.

[Explanation of symbols]

 2 First hydraulic pump 4 Boom cylinder 6 Boom raising chamber 8 Boom raising oil passage 10 Boom first control valve 12 Boom raising first pilot oil passage 14 Boom operating valve 16 Pilot pump 18 Second hydraulic pump 20 Stick cylinder 22 Stick-in chamber 24 stick-in oil passage 26 stick first control valve 28 stick-in first pilot oil passage 30 stick operation valve 32 stick merging oil passage 34 on-off valve 36 stick second control valve 38 stick-in second pilot oil passage 44 boom merging oil passage 46 Boom second control valve 48 Boom raising second pilot oil passage 60 Pressure reducing valve 62 Pressure reducing pilot oil passage 64 Switching valve

Claims (1)

(57) [Scope of request for utility model registration] 1. A boom first control valve disposed in a boom raising oil passage connecting a first hydraulic pump and a boom raising chamber of a boom cylinder, and a second hydraulic pump and a stick-in chamber of a stick cylinder are connected. A stick first control valve disposed in a stick-in oil passage, a stick merging oil passage connecting the first hydraulic pump and a position upstream of the stick first control valve in the stick-in oil passage, and the stick merging oil passage An on-off valve disposed on a passage, a stick second control valve disposed in parallel with the on-off valve, and a boom junction oil connecting the second hydraulic pump and an upstream position of the boom raising chamber in the boom raising oil passage. A boom second control valve disposed in the boom confluence oil passage; and a boom raising first for supplying pilot pressure to switch the boom first control valve to a boom raising position. A pilot oil passage, a boom raising second pilot oil passage for supplying pilot pressure from the boom raising first pilot oil passage for switching the boom second control valve to communicate with the boom merging oil passage, and A stick-in first pilot oil passage for supplying pilot pressure for switching one control valve to the stick-in position; and a stick for switching the stick second control valve to apply pilot pressure to the on-off valve to open the stick. In a hydraulic circuit of a construction machine having a stick-in second pilot oil passage for supplying pilot pressure from the first pilot oil passage, a pressure reducing valve is disposed in the stick-in second pilot oil passage, and A pressure reducing pilot oil passage for supplying a pilot pressure from one pilot oil passage to the pressure reducing valve is provided; A switching valve is disposed in the oil passage, and in a state where the switching valve is switched to the open position, the pressure-reducing valve operates the stick-in second pilot in response to an increase in the pilot pressure of the boom raising first pilot oil passage. When the pilot pressure of the first pilot oil passage reaches a set value, the pilot pressure of the stick-in second pilot oil passage is reduced by the operating pressure of the stick second control valve. A hydraulic circuit for a construction machine, wherein the hydraulic pressure is reduced as follows.