JPH0637781B2 - Control device for power shovel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a two-pump power shovel using a variable discharge type pump, and more particularly to a power shovel capable of driving a boom or an arm to be accelerated by the total discharge amount of both pumps. Regarding

[Conventional technology]

Conventionally, first and second hydraulic circuits that are separately driven by variable discharge pumps are provided with bypass passages that are controlled to open and close in conjunction with the respective directional control valves, and the bypass passages and the tank are connected to each other. With the primary pressure of the resistance valve connected between the
By attaching a pump discharge amount control device for reducing and increasing the pump discharge amount of the hydraulic circuit to each of the pumps, and connecting a boom hoisting direction switching valve to each of the first and second hydraulic circuits. A power shovel control circuit provided with a device for switching in a substantially synchronous manner and a device for switching the arm circuit directional switching valves respectively connected in the first and second hydraulic circuits in a substantially synchronous manner is known as a negative control system. There is.

[Problems to be solved by the invention]

To enable the boom and the arm to be driven simultaneously by this power shovel, the boom hoisting direction switching valve 2 of the first hydraulic circuit 1 is used.
And the arm rotation direction switching valve 3 are connected in parallel to the pump discharge port thereof, and the bypass oil passage 6 is provided downstream of the boom up / down direction switching valve 5 connected to the pump discharge port of the second hydraulic circuit 4. The arm rotation direction switching valve 7 must be connected in series via the arm rotation direction switching valve 7. Then, during the simultaneous drive operation of the boom and the arm, the pump discharge pressure oil is supplied to the arm rotation direction switching valve 3 having a small load in the first hydraulic circuit 1, and the boom rotation direction switching valve 2 having a large load is supplied. This is because the pressure oil does not flow to the second hydraulic circuit 4, whereas the pressure oil is supplied only to the boom rotation direction switching valve 5 on the upstream side in the second hydraulic circuit 4.

However, since the direction switching 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 direction switching valves 2 and 5 are placed between the neutral position and the boom raising position. By moving the boom in the middle, the boom can be floated vertically, and when the direction switching valves 3 and 7 are operated to pull the arm, horizontal or inclined leveling work is performed. Switching valve 3,7
Since the bypass passages are in conduction at the neutral position, the pump discharge amount is minimized by the pilot hydraulic pressure generated on the primary side of the resistance valve. Then, since the pilot hydraulic pressure on the primary side of the resistance valve becomes zero, the pump discharge amounts of the hydraulic circuits 1 and 4 simultaneously increase rapidly. At that time, in the first hydraulic circuit 1, since the boom up-and-down direction switching valve 2 is throttled, most of the pump discharge amount is supplied to the arm rotation direction switching valve 3, whereas the second direction. In the hydraulic circuit 4, since the bypass passage 6 in the boom hoisting direction switching valve 5 is throttled and the flow rate to the direction switching valve 7 is small, most of the boom cylinder is connected to the boom cylinder via the throttled direction switching valve 5. When the pump discharge amount is supplied, the boom bounces up and horizontal or inclined ground leveling work cannot be performed.

[Means for solving problems]

The present invention addresses this problem by connecting a valve that is opened / closed in conjunction with the boom up / down direction switching valve between the servo cylinder 9 of the second hydraulic circuit side pump discharge amount control device 8 and the tank. Then, when the spool of the boom up-and-down direction switching valve moves to an intermediate position between the neutral position and the boom up position, the operating pilot oil pressure of the pump discharge control device is released to the tank. And

[Work]

According to the above configuration, in order to perform horizontal or inclined ground leveling work, first, if the spools of the boom up-and-down direction switching valves 2 and 5 are moved to an intermediate position between the neutral position and the boom up position, the second hydraulic pressure is applied at that time. The operation pilot hydraulic pressure of the pump discharge amount control device 8 in the circuit 4 is discharged to the tank, and the pump discharge amount increases rapidly.

Therefore, even if the arm rotation direction switching valves 3 and 7 are suddenly switched to the arm retracted position, the pump discharge amount on the first hydraulic circuit 1 side only increases sharply, and the boom undulation on the first hydraulic circuit side is raised. Since the direction switching valve 2 is throttled and most of the temporarily increased pump discharge amount is supplied to the arm cylinder side, there is no risk of boom boom phenomenon and smooth leveling work is performed. Can be done.

〔Example〕

1 to 3 show an embodiment of the present invention, which is shown in FIG.
1 is a swivel mounted on a crawler traveling device 12 so as to be rotatable by a swivel motor, 13 is a boom pivoted on the swivel base 11 so as to be hoistable by a boom cylinder 14, and 15 is rotatable by an arm cylinder 16. An arm pivotally mounted on the tip of the boom 13 and a bucket 17 pivotably mounted on the tip of the arm 15 by a bucket cylinder 18. The engine 19 with an all-speed governor on the swivel base 11 has an equivalent variable discharge type (axial piston type).
Simultaneously drive the pumps P1 and P2 of the
The hydraulic circuit 1 and the pump P2 supply pressure oil to the second hydraulic circuit 4, respectively.

As shown in FIG. 1, the first hydraulic circuit 1 includes a directional control valve 2 and 3 at the discharge port of the pump P1 and a directional control valve 2 for controlling the swing motor.
0 and a left traveling motor control directional switching valve 21 are connected in parallel, and a resistance valve 22 is connected between a bypass passage 6'which conducts at a neutral position of the omnidirectional switching valve and a tank T.
The primary pressure of the resistance valve 22 is transmitted to the discharge amount control device 24 of the pump P1 via the pilot oil passage 23.

In the second hydraulic circuit 4, a right travel motor control directional switching valve 25, a bucket cylinder control directional switching valve 26, and a directional switching valve 5 are connected in parallel to the discharge port of the pump P2, and the downstream side of the directional switching valve 5 is connected. A directional control valve 7 is connected in series via a bypass passage 6 to the side of the directional control valve. The path 37 is connected.

Only one boom cylinder 14 is shown as a representative in FIG.
Is connected in parallel to the output side ports of the boom raising / lowering direction switching valves 2 and 5 which are synchronously switched by the operating lever 28, and the arm cylinder 16 is arm-rotating direction switching which is synchronously switched by the operating lever 29. The output ports of valves 3 and 7 are connected in parallel. Therefore, if one of the operating levers is operated independently, the corresponding cylinder can be quickly expanded and contracted by the discharge pressure oil of both pumps P1 and P2.

Since the discharge amount control devices 8 and 24 of each pump have the same structure, only the pump P2 shown in FIG. 3 will be described below. The parent-child piston 30 operatively linked to the pump swash plate so that its tilt angle can be adjusted decreases the tilt angle or the pump discharge amount due to the discharge hydraulic pressure (load hydraulic pressure) of the pump P2 constantly supplied to the slave cylinder 31. Always pressed in the direction C,
The hydraulic pressure in the parent cylinder 32 provided on the opposite side is controlled by a servo valve 33 that is switched by a change in load and a servo valve 34 that is switched by the presence or absence of the primary pressure of the resistance valve 27.

The servo valve 33 is controlled by a servo cylinder 35 to which the pump discharge hydraulic pressure is constantly transmitted. When the load is increased, the communication port A to the parent cylinder 32 is connected to the tank T, and when the load is decreased, the servo valve 33 is connected. The communication port B to 34 is connected to the pump discharge port. Therefore, as will be described later, the parent-child piston 30 is displaced according to the increase or decrease of the load, and the displacement is fed back to the outer casing of the servo valve 33 via the lever 36.

Further, the servo valve 34 is connected to the resistance valve 2 via the pilot oil passage 37.
Controlled by a servo cylinder 9 connected to the primary side of 7,
When the bypass passage 6 is completely connected as shown in FIG. 1, or when the directional control valve 5 is in the half-open position intermediate between the neutral position and the boom raising position (right side position in FIG. 1), the resistance is reduced. The servo valve 34 is switched to the position shown in FIG. 3 by the primary pressure of the valve 27, and the parent cylinder 32 is communicated with the tank T to minimize the pump discharge amount, but the direction switching valve of the second hydraulic circuit 4 is used. When any one of the two is switched to the left or right position, the primary pressure of the resistance valve 27 disappears, so that the servo valve 34 moves to the third position.
The parent cylinder 32 is connected to the port B of the servo valve 33 by switching to the lower end position in the figure. 38 is the parent and child piston 3
This lever feeds the displacement of 0 to the outer casing of the servo valve 34.

Therefore, if pressure is not generated on the primary side of the resistance valve 27,
Since the port B of the servo valve 33 is connected to the parent cylinder 32 via the servo valve 34, the servo valve 33 returns to the neutral position in FIG. 3 when the discharge amount of the pump P2 reaches the discharge amount according to the load. .

When the boom raising / lowering direction switching valves 5 and 2 are set to a half-open position intermediate between the neutral position and the boom raising position, the device for releasing the operating pilot hydraulic pressure of the servo cylinder 9 to the tank T is the first hydraulic circuit side direction switching. An oil passage 40 that connects between the low pressure side oil passage (return oil passage) 39 and the servo cylinder 9 when the boom is raised on the output side of the valve 2 is provided, and the check valve 10 is inserted into the oil passage 40. I will do it. In the case shown in the figure, in order to quickly discharge the operating pilot hydraulic pressure of the servo cylinder 9, the throttle 41 is inserted into the pilot oil passage 37 and the oil passage 39 is inserted.
Although the check valve 42 is inserted between the connecting portion of the check valve 10 and the boom cylinder 14, it is not always necessary if the length of the oil passage 40 and the flow passage resistance can be reduced.

Therefore, the check valve 10 is controlled in conjunction with the direction switching valve 2 and is opened / closed depending on whether the oil passage 39 is on the low pressure side or 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 by the check valve 10 which is opened and closed by the internal pilot pressure in conjunction with the direction switching valve 2 has been described above. As shown in Fig. 4, the solenoid cylinder 43 is connected between the servo cylinder 9 and the tank T, and the boom hoisting direction switching valve 5 is provided between the neutral position and the boom raising position, and between the neutral position and the boom tilting position. It is also possible to provide a switch device 44 that emits a signal when it moves to any intermediate position so that the solenoid valve 43 opens when the switch issues a signal.

Therefore, the boom hoisting direction switching valves 5 and 2 are positioned in the middle between the neutral position and the boom tilting position (left position in FIG. 4) to give a slight tilting force to the boom 13, and at the same time, the arm turning direction switching valve. It is also possible to prevent the boom from jumping up when the back surface of the bucket 17 expands the ground while operating the arms 3 and 7 to rotate the arm 15 in the pulling direction. Incidentally, FIG. 4 omits the first hydraulic circuit.

〔The invention's effect〕

According to the present invention, when performing horizontal or sloping ground leveling work as shown in FIG. 2, the boom up / down direction switching valves 2 and 5 are set in a half-open state toward the boom upright side, and the boom 13 is moved to a certain extent. Since it is supported by the boom cylinder extension force, not only the ground contact force of the bucket 17 can be reduced, but also when the arm turning direction switching valves 3 and 7 are operated to turn the arm 15 for leveling. Since the boom bounce phenomenon as described above does not occur, the ground leveling work can be performed accurately and smoothly, and the boom 13 and the arm 15 can be operated independently.
Alternatively, they can be operated simultaneously, which is a great effect.

[Brief description 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, which also shows a hydraulic system diagram, and FIG. 3 is a pump discharge amount control device on the second hydraulic circuit side. FIG. 4 and FIG. 4 are hydraulic circuit diagrams of the essential parts of another embodiment. P1, P2 ... Variable discharge pump, 6, 6 '... Bypass passage, 13 ... Boom, 14 ... Boom cylinder,
15 ... arm, 16 ... arm cylinder, 17 ... bucket, 22,27 ... resistance valve, 23,37 ... pilot oil passage.

Claims (2)

[Claims] Claims: 1. Bypass passages are provided in the first and second hydraulic circuits, which are separately driven by variable discharge pumps, and are controlled to open and close in conjunction with the respective directional control valves. With the presence or absence of the primary side pressure of the resistance valve connected between the passage and the tank respectively, the pump discharge amount of the hydraulic circuit is reduced,
An increasing pump discharge amount control device attached to each of the pumps, and a device for switching the boom hoisting direction switching valves respectively connected in the first and second hydraulic circuits substantially in synchronization;
In a power shovel equipped with a device for switching the arm circuit directional switching valves respectively connected to the second hydraulic circuit in a substantially synchronous manner, a boom hoisting directional switching valve of the first hydraulic circuit (1) is provided.
(2) and the arm rotation direction switching valve (3) are connected in parallel to the pump discharge port thereof, and downstream of the boom hoisting direction switching valve (5) connected to the pump discharge port of the second hydraulic circuit (4). Side, the arm rotation direction switching valve (7) is connected in series through the bypass passage (6), and the servo cylinder (9) of the second hydraulic circuit side pump discharge amount control device (8) and the tank are connected. A valve that is opened / closed in conjunction with the boom up / down direction switching valve is connected between the two, and when the spool of the boom up / down direction switching valve moves to an intermediate position between the neutral position and the boom up position, A control device for a power shovel, characterized in that an operation pilot hydraulic pressure of a pump discharge amount control device is configured to be released to a tank. 2. A check valve (10), which is a check valve (10), which comprises a low pressure side oil passage and a servo cylinder at the time of boom raising at the output side of the boom hydraulic directional directional control valve (2). The control device for a power shovel according to claim (1), which is connected between (9).