JPS62160327A - Controller for power shovel - Google Patents

Abstract

PURPOSE:To prevent the jumping of boom by a method in which a valve operable in an interlocking manner with a direction switch valve for raising or turning down the boom is connected between the servo cylinder of a discharge amount controller and a tank and a working pilot oil pressure is allowed to escape to the tank. CONSTITUTION:Direction switch valves 2 and 3 and a direction switch valve 20 for controlling slewing motor are provided to the first oil-pressure circuit 1. A resistance valve 22 to transmit the primary side pressure to the discharge amount controller 24 of a pump P1 is provided between a bypass 6' and a tank T. Direction switch valves 26 and 5 for controlling the bucket cylinder are provided to the second oil-pressure circuit 4, and a switch valve 7 is connected in series through the bypass 6. A resistance valve 27 is provided between the valve 7 and the tank T. The valves 5 and 2 are positioned on the middle between the neutral position and the boom-rising position, thereby allowing working oil pressure of the servo cylinder 9 to escape to the tank T. The leveling operation of the ground can thus be smoothly performed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a two-pump type power shovel using a variable displacement pump, and particularly to a power shovel in which the boom or arm can be driven at increased speed depending on the total discharge of both pumps. Regarding.

[Conventional technology]

Conventionally, the first pump is driven separately by a variable discharge type pump. The second hydraulic circuit is provided with a bypass passage whose opening and closing are controlled in conjunction with each of the directional switching valves, and the primary side pressure of the resistance valve is connected between each of the bypass passages and the tank.
A pump discharge amount control device that reduces or increases the pump discharge amount of the hydraulic circuit by nothing is attached to each of the pumps, and the first. a device for substantially synchronously switching the boom hoisting directional control valves connected to the second hydraulic circuit; A control circuit for a power shovel that is provided with a device that switches the arm rotation directional control valves connected to the second hydraulic circuit in substantially synchronized manner is known as a negative control system.

[Problem that the invention seeks to solve]

In order to be able to drive the boom and arm at the same time with this power excavator, the boom hoisting directional control valve 2 of the first hydraulic circuit 1 must be
and an arm rotation directional switching valve 6 are connected in parallel to the pump discharge port thereof, and the bypass oil passage 6 is connected to the downstream side of the boom hoisting directional switching valve 5 connected to the pump discharge port of the second hydraulic circuit 4. The arm rotation directional control valve 7 must be connected in series through the arm rotation direction switching valve 7. Then, when the boom and arm are simultaneously driven, the first hydraulic circuit 1 will supply pump discharge pressure oil to the arm rotation directional control valve 2, which has a small load, and the boom rotation directional control valve 2, which has a large load. This is because, while no pressure oil will flow through the second hydraulic circuit 4, only one pressure oil will be supplied to the boom rotation direction switching valve 5 on the upstream side.

However, since the directional control valves 5 and 7 of the second hydraulic circuit 4 are connected in series via the bypass oil passage 6, the spools of the boom hoisting directional control valves 2 and 5 can be moved between the neutral position and the boom raising position. By moving the boom to the middle, the boom can float up and down, and when the arm is pulled in by operating the directional valve 3.7t, it can be used for leveling horizontal or sloped land, and when the arm is not in operation. The directional valve 6,
7 is in the neutral position and the bypass passages are conducting, so the pump discharge amount is minimized due to the pilot oil pressure generated on the primary side of the resistance valve, but let's switch the two-way switching valve to pull the arm. In this case, since the pilot oil pressure on the primary side of the resistance valve becomes zero, the pump discharge amount of each hydraulic circuit 1, 4 increases rapidly at the same time. At this time, in the first hydraulic circuit 1, since the boom hoisting directional switching valve 2 is throttled, most of the pump discharge amount is supplied to the arm rotation directional switching valve 6, whereas the second hydraulic circuit 1 In the hydraulic circuit 4, since the bypass passage 6 in the boom hoisting directional control valve 5 is constricted and the flow rate to the directional control valve 7 is small, most of the flow is sent to the boom cylinder via the constricted directional control valve 5. If the pump discharge amount is supplied, the boom may jump up, making it impossible to perform leveling work on horizontal or sloped areas.

[Means for solving problems]

The present invention addresses this problem by connecting a valve that opens and closes in conjunction with the boom hoisting directional control valve between the servo cylinder 9 of the second hydraulic circuit side pump discharge amount control device 8 and the tank. and is configured such that when the spool of the boom hoisting directional control valve moves to an intermediate position between a neutral position and a boom raising position, the operating pilot hydraulic pressure of the pump discharge amount control device is released to a tank. shall be.

[For production]

According to the above configuration, in order to perform horizontal or sloped ground leveling work, first the spools of the boom hoisting directional control valves 2 and 5 are moved to an intermediate position between the neutral position and the boom raising position, and at that time the second hydraulic pressure is The operating pilot oil pressure of the pump discharge amount control device 8 in the circuit 4 is discharged to the tank, and the pump discharge amount rapidly increases. The pump discharge amount on the first hydraulic circuit 1 side only increases rapidly, and the boom hoisting directional control valve 2 on the first hydraulic circuit side is throttled, so that most of the temporarily increased pump discharge amount Since it is supplied to the arm cylinder side, there is no risk of the boom jumping up, and the ground leveling work can be carried out smoothly.

〔Example〕

1 to 3 show an embodiment of the present invention, and 1 in FIG.
Reference numeral 1 denotes a swivel base mounted on the crawler traveling device 12 so as to be rotatable by a swing motor, 16 a boom pivotably mounted on the swivel base 11 such that it can be raised and lowered by a boom cylinder 14, and 15 rotatably mounted by an arm cylinder 16. An arm 17 is pivoted at the tip of the boom 16, and is a packet pivoted at the tip of the arm 15 so as to be rotatable by a packet cylinder 18. The engine 19 with an all-speed governor on the swivel base 11 is an equivalent variable displacement type (axial piston type).
Pumps Pi and P2' are simultaneously driven, and the pump P1 supplies pressure oil to the first hydraulic circuit 1, and the pump P2 supplies pressure oil to the second hydraulic circuit 4. The first hydraulic circuit 1 is The directional switching valves 2 and 6, the swing motor control directional switching valve 20, and the left travel motor control directional switching valve 21 are connected in parallel to the discharge port of the pump P1 as shown in FIG. A resistance valve 22 is provided between the conductive bypass passage 6' and the tank T.
The primary side pressure of the resistance valve 22 is transmitted to the discharge amount control device 24 of the pump Pi via the pilot oil passage 26. A directional switching valve 25 for motor control, a directional switching valve 26 for packet cylinder control, and a directional switching valve 5 are connected in parallel, and a directional switching valve 7 is connected in series on the downstream side of the directional switching valve 5 via a bypass passage 6. A pilot oil passage 67 is connected to the primary side of a resistance valve 27 which is connected between a bypass passage 6 and a tank T, which conduct at the neutral position of the omnidirectional switching valve.

Only one boom cylinder 14 is shown as a representative in FIG.
The output side ports of the boom hoisting direction switching valves 2 and 5, which are switched synchronously by the operating lever 28, are connected in parallel to the arm cylinder 16. Output side boats of valves 6 and 7 are connected in parallel. Therefore, by operating one of the operating levers alone, the corresponding cylinder can be rapidly expanded or contracted by the pressure oil discharged from both pumps PL and P2.

Since the discharge amount control device 8.24 of each pump has the same configuration, the parent and child pistons are interlocked and connected to the pump swash plate so that the tilting angle thereof can be adjusted. 60 is always pressed in the direction C of decreasing the tilting angle or pump discharge amount by the discharge oil pressure (load oil pressure) of the pump P2 that is always supplied to the child cylinder 61, and the cylinder 60 in the parent cylinder 62 provided on the opposite side. The oil pressure is reversely controlled by a servo valve 66 that is switched depending on changes in load and a servo valve 64 that is switched depending on the presence or absence of the primary side pressure of the resistance valve a.

The servo valve 66 is controlled by the servo cylinder 65 to which the pump discharge oil pressure is constantly transmitted, and when the load increases, the communication boat A to the main cylinder 62 is connected to the tank T, and when the load decreases, the servo valve 66 The communication port B to 64 is connected to the pump discharge port. Therefore, as will be described later, the parent and child piston 60 is displaced in response to an increase or decrease in load, and the displacement is fed back to the outer casing of the servo valve 36 via the lever 66.

Furthermore, the servo valve 64 is connected to the resistance valve 2 via a pilot oil passage 67.
Controlled by a servo cylinder 9 connected to the primary side of 7,
When the bypass passage 6 is completely conductive as shown in Fig. 1, or when the directional control valve 5 is in the half-open position between the neutral position and the boom raised position (the right position in Fig. 1), there is no resistance. The servo valve 64 is switched to the position shown in FIG. 3 by the primary side pressure of the valve 27, and the main cylinder 62 is communicated with the tank T to minimize the pump discharge amount. When the servo valve 64 is switched to either the left or right position, the primary side pressure of the resistance valve 27 disappears, so the servo valve 64 is switched to the third position.
Switched to the lower end position in the figure, the parent cylinder 62 is connected to port B of the servo valve 66. In addition, 68 is parent and child piston 3
This is a lever that feeds back the zero displacement to the outer casing of the servo valve 64.

Therefore, if no pressure is generated on the primary side of the resistance valve 27,
Since the boat B of the servo valve 66 is connected to the parent cylinder 62 via the servo valve 64, the servo valve 66 returns to the neutral position shown in FIG. 3 when the discharge amount of the pump P2 reaches a discharge amount corresponding to the load. .

When the boom hoisting directional switching valves 5 and 2 are set to the half-open position between the neutral position and the boom raising position, the device that releases the operating pilot hydraulic pressure of the servo cylinder 9 to the tank T is a first hydraulic circuit side directional switching device. An oil passage 40 is provided to connect between the low pressure side oil passage (return 9 oil passage) 69 and the servo cylinder 9 on the output side of the valve 2 when the boom is raised, and the check valve 10 is installed in the oil passage 40. Insert it. In the illustrated case, in order to quickly discharge the operating pilot oil pressure of the servo cylinder 9, the throttle 41 is inserted into the pilot oil passage 67, and the oil passage 69
Although the check valve 42 is inserted between the connecting portion of the check valve 10 and the boom cylinder 14, it is not necessarily necessary if the length of the oil passage 40 or the flow passage resistance can be reduced.

For this reason, the reverse valve 10 is controlled in conjunction with the directional switching valve 2, and is opened or closed depending on whether the oil passage 69 is on the low pressure side or on the high pressure side.

The case where the valve block structure of the first hydraulic circuit 1 is simplified by controlling the servo cylinder 9 with the check valve 10 which is opened and closed by internal pilot pressure in conjunction with the directional control valve 2 has been described above. As shown in Figure 4, the servo cylinder 9 and the tank T are connected by a solenoid valve 46, and the boom hoisting direction switching valve 5 is set between the neutral position and the boom raised position, and between the neutral position and the boom tilted position. A switch device 44 may be provided which issues a signal when moving to any position in the middle, so that the solenoid valve 43 opens when the switch issues the signal.

Therefore, the boom hoisting directional control valves 5 and 2 are positioned between the neutral position and the boom tilted position (left position in Figure 4) to apply a slight lodging force to the boom 16, and the arm rotation directional control valves It is also possible to prevent the boom from jumping up when the rear surface of the packet 17 is pressed against the ground while operating the arms 6 and 7 in the arm tSt-pulling direction. Note that FIG. 4 does not show the first hydraulic circuit.

〔Effect of the invention〕

According to the present invention, when performing leveling work on horizontal or sloped land as shown in FIG. Since it is supported by the cylinder extension force, it is possible not only to reduce the grounding force of the packet 17, but also to operate the arm rotation directional control valve 6.7 to level the ground when the arm 15 rotates. Since the boom bounce-up phenomenon described above does not occur, the leveling work can be performed accurately and smoothly, and the boom 13 and arm 15 can be operated independently.
Alternatively, the fact that they can be operated simultaneously is very effective.

[Brief explanation of drawings]

Fig. 1 is a hydraulic circuit diagram of an embodiment of the present invention, Fig. 2 is a side view of a power shovel during ground leveling with a hydraulic system diagram, and Fig. 3 is a pump discharge amount control device on the second hydraulic circuit side. FIG. 4 is a hydraulic circuit diagram of the main parts of another embodiment. Pi, P2...variable discharge pump, 6,6'...
- Bypass passage, 16... Boom, 14... Boom cylinder, 15... Arm, 16... Arm cylinder, 17... Packet, 22, 27... Resistance valve, 2
3.37...Pilot oil line. Figure 1 Figure 2 λ Figure 3

Claims (2)

[Claims] (1) The first pump is driven separately by a variable discharge type pump,
The second hydraulic circuit is provided with bypass passages that are controlled to open and close in conjunction with the respective directional switching valves, and whether or not the primary side pressure of the resistance valves connected between the bypass passages and the tank is present or not. A pump discharge amount control device that reduces or increases the pump discharge amount of the hydraulic circuit is attached to each pump, and a boom hoisting directional control valve is connected to the first and second hydraulic circuits, respectively. In a power shovel equipped with a device for switching synchronously and a device for substantially synchronously switching directional control valves for arm rotation connected to the first and second hydraulic circuits, the boom of the first hydraulic circuit (1) Directional switching valve for elevation (2)
and a directional switching valve for arm rotation (3) are connected in parallel to the pump outlet thereof, and on the downstream side of the boom hoisting directional switching valve (5) connected to the pump outlet of the second hydraulic circuit (4),
An arm rotation directional control valve (7) is connected in series through the bypass passage (6), and is connected between the servo cylinder (9) of the second hydraulic circuit side pump discharge amount control device (8) and the tank. , when a valve that opens and closes in conjunction with the boom hoisting directional control valve is connected, and the spool of the boom hoisting directional control valve moves to an intermediate position between the neutral position and the boom raising position,
A control device for a power shovel, characterized in that the operating pilot hydraulic pressure of the pump discharge amount control device is configured to be released to a tank. (2) Configure the valve as a check valve (10), which is connected to the low pressure side oil path and servo cylinder (9) when raising the boom on the output side of the boom hoisting directional control valve (2) on the first hydraulic circuit side. ) A power shovel control device according to claim 1, wherein the power shovel control device is connected between the power shovel and the power shovel.