JPH0438256B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a hydraulic system that can selectively freely rotate a hydraulically driven rotating body with a large inertial force.

Conventional Technology Hydraulic excavators have traditionally been used by replacing their front attachments, allowing them to be used not only as earthmoving machines such as backhoes and loading shovels, which are their original uses, but also as cargo handling machines with the characteristics of mobile cranes. Although often widely used, the functionality of the swing drive system of the upper revolving structure has given it performance suitable for the most commonly used earth-moving machines. In other words, when the swing operation lever is returned from the swing position to the neutral position, a hydraulic circuit system is adopted in which the inertia energy of the swing body is automatically absorbed by the hydraulic brake torque of the hydraulic motor, and the system is forcibly stopped and held. , which helps improve the safety and cycle time of earthwork operations. An embodiment of this type of hydraulic circuit is as shown in FIG. 5 rotates in the forward or reverse direction, and rotates the upper revolving body using a revolving pinion, gears, etc. When the hydraulic switching valve 4 is set to the neutral position, that is, the C position during swing operation, the pressure oil supply from the main pump 2 is cut off, and the swing motor 5
The oil passages 6 and 7 leading to the oil inflow and oil outflow ports are both closed by the spool of the hydraulic switching valve 4, but since the swing motor 5 is forcibly rotated due to the rotational inertia of the upper swing structure, one Oil is sucked in through a port and discharged under high pressure from the other port. The discharged high-pressure oil passes through the relief valve 8' or 8, is relieved to the oil passage 6 or 7 on the low-pressure side, and is sucked in again from the port on the opposite side of the hydraulic motor 5. This operation is repeated, and while the pressure oil passes through the relief valves 8 and 8' and becomes low pressure, the rotational inertia energy of the upper revolving body is consumed and the speed gradually decreases, until it finally stops and maintains its position. become. That is, when the hydraulic switching valve 4 is switched to the C position while the upper rotating body of the hydraulic excavator is rotating, a hydraulic control torque is automatically generated in the hydraulic motor 5 to reduce the swing speed of the upper rotating body and shorten the rotation speed. It has been given the ability to stop in time. In addition, in order for the hydraulic motor 5 to generate braking torque, the oil chamber of the operating part of the hydraulic motor 5 must be filled with oil, and oil may leak from the oil-tight part during braking, causing a lack of oil during rotation. In this case, braking torque cannot be exerted, so in order to prevent this, oil from the main return circuit 10 from the swing motor and other actuators is supplied to the oil passages 6 and 7 via the check valves 9 and 9' through the oil passage 11. After that, constant replenishment is carried out, and on the other hand, when the hydraulic switching valve 4 is in the neutral position C,
Relief valves 12 and 12' are provided to prevent abnormally high pressure from being trapped in the oil passages 6 and 7 for some reason.

The above-mentioned upper revolving body drive system with a hydraulic circuit configuration has advantages when used as an earth-moving machine or some cargo handling machines, but on the other hand, when changing the front attachment and using it for other purposes, it becomes difficult to operate. This often results in operational disadvantages. For example, in a general hydraulic backhoe equipped with a boom 34, an arm 35, and a backhoe bucket 36 shown in FIG. 2, the boom 34, arm 35, and backhoe bucket 36 are operated to scoop up earth and sand and rotate. When moving earth and sand to a transport vehicle or a predetermined location, the swing brake is automatically applied by simply setting the swing control lever to neutral, making it easy to stop the vehicle at a predetermined location. Even if the device is tilted to a certain degree, it is effective because it can maintain a fixed position for a short period of time without any operation. On the other hand, as shown in Fig. 3, arm 3
5, a winch box 37 is attached to the tip of the hook block 38 by a wire rope 40, and when handling a suspended load 39, the suspended load 39 is hoisted, the upper revolving structure is rotated to move it to a predetermined position, and the When the control lever is returned to neutral,
The winch box 37, which moves integrally with the upper rotating body, attempts to stop with a large deceleration due to the swing braking force, and the suspended load 39 causes a pendulum movement due to inertia, making it extremely difficult to position it at a predetermined position. Conventionally, a machine equipped with such an attachment has been operated by a skilled operator who carefully accelerates and decelerates the swing slowly to prevent pendulum movement from occurring in the suspended load 39. A high level of skill was required to make the suspended load 39 follow the pendulum movement and to stop the swinging, otherwise the cycle time would be reduced.

Also, in cargo handling work, as shown in Figure 4,
In a cargo handling machine in which a gripping tool 42 of wood or other material is directly attached to the tip of the arm 41, pendulum movement is unlikely to occur even when a swing brake force is applied, and it is better to forcibly stop the swing to a certain extent to improve cycle time. This makes positioning of luggage easier.

Problems to be Solved by the Invention As mentioned above, when the front attachment of a hydraulic excavator is reequipped and used for various purposes, depending on the work involved, when the swing operation lever is set to neutral, the swing brake force may vary. The effect may be an advantage or a disadvantage, so
The present invention aims to realize a hydraulic circuit system in which automatic braking performance when the swing operation lever is in the neutral state and free swing performance can be freely selected with a simple operation in one hydraulic excavator.

Means for Solving the Problem In order to provide the above functions, the present invention has the following hydraulic/electrical circuit configuration.

That is, a first pilot switching valve is provided that normally shuts off a pair of operating circuits that supply pressure oil to the hydraulic motor for swing drive, but communicates them based on a hydraulic signal, and switches and supplies pressure oil to the operating circuit of the hydraulic motor. a second switching valve that opens and closes a passage in response to an electrical signal from a limit switch that communicates with an operating lever of a manually operated lever-type hydraulic switching valve and closes an electric circuit only when the operating lever is in a state other than neutral; A third switching valve is provided that opens and closes the hydraulic circuit from the source using electric signals or other means by operating a switch, and the pressure oil from the pilot hydraulic pressure source is routed through the second and third switching valves to the first pilot. Provide an oil passage leading to the pilot oil chamber of the switching valve.

Operation When the third switching valve is operated by a switch or other means, the pressure oil of the pilot oil pressure source that has been shut off passes through the internal open passage of the third switching valve and reaches the inflow port of the second switching valve. At this time, when the operating lever of the manually operated lever-type hydraulic switching valve for operating the swing hydraulic motor is in the neutral position, that is, when no swing operation is being performed, the limit switch that is linked to the operating lever has an electrical circuit open. Since the second switching valve is not operated, the pressure oil that has reached the inlet port passes through the open passage of the second switching valve and flows into the pilot oil chamber of the first pilot switching valve. The hydraulic motor is actuated and communicates the pair of actuation circuits of the hydraulic motor, so that the hydraulic motor freely rotates due to an external force. Next, when the operating lever of the manually operated lever type hydraulic switching valve is operated, that is, the turning operation is started, the second switching valve shuts off the pressure oil sent through the third switching valve in response to an electric signal from the limit switch. Since the pilot oil chamber of the first pilot switching valve communicates with the tank via the second switching valve, the first pilot switching valve disconnects the pair of operating circuits of the hydraulic motor, making them independent, and starting the rotation. At this time, normal turning acceleration is performed. After starting the swing, when the swing operation lever is returned to neutral, the first pilot switching valve will be in the communicating position again as described above, and the machine will be in a free swing state. When the switch is released, the pressure oil from the pilot hydraulic pressure source will be transferred to the third switching valve. The first pilot switching valve is therefore cut off, and the swing system returns to the circuit configuration similar to a normal hydraulic excavator.

Embodiments Examples of the present invention will be described with reference to the drawings.

FIG. 1 is a hydraulic/electrical circuit diagram showing an embodiment of the present invention. Reference numeral 1 is an engine that drives a main pump 2 and a pilot pump 3, which sucks oil from a tank 21 through a suction strainer 19, and discharges oil. is regulated by the relief valve 17 and communicates with the manually operated lever type hydraulic switching valve 4 for operating the swing motor 5. When the operating lever 28 of the switching valve 4 is neutral, that is, in the C position, the pressure oil is in the C position open oil. It passes through the oil passage and oil passage 24 to reach another hydraulic switching valve (not shown), and further merges with the return oil passage of the other hydraulic switching valve group to form the main return circuit 10.
and flows into the tank 21. When the operating lever 28 of the hydraulic switching valve 4 is pushed or pulled, the spool of the hydraulic switching valve 4 moves and switches to the A or B position, and the pressure oil discharged from the main pump 2 is transferred to the oil path 6, the hydraulic motor 5, and the oil path. 7. To the tank 21 via the A position passage of the hydraulic switching valve 4, or to the tank 21 via the oil passage 7, the hydraulic motor 5, the oil passage 6, and the B position passage of the hydraulic switching valve 4.
The hydraulic motor 5 functions to rotate forward or reverse. 8 and 8' are respectively from oil passage 6 to 7,
This is a relief valve that opens from oil passages 7 to 6, and after the hydraulic excavator upper rotating body with large inertia is rotated by the hydraulic motor 5, the hydraulic switching valve 4 is suddenly set to the C position. When the oil passages 6 and 7 are closed, high pressure is prevented from being generated.
Furthermore, it is used to apply a constant braking torque to the hydraulic motor 5 during the relief operation. Also oil line 6,
7, the check valves 9 and 9' are provided in the direction in which oil is supplied from the main return circuit 10 through the oil passage 11, so that the oil passages 6 and 7 and the hydraulic motor 5
The internal hydraulic oil chamber is always filled with oil to prevent the hydraulic motor 5 from idling even when driven by an external force. Furthermore, the oil passages 6 and 7 are provided with relief valves 12 and 12', respectively, to prevent abnormal confinement pressure from occurring in the operating circuit when the hydraulic switching valve 4 is in the C position. The set pressure is generally higher than the set pressure of the relief valves 8, 8'.

On the other hand, the oil discharged from the pilot pump 3 serves as a pilot hydraulic pressure source, and has a relief valve 18 to keep the circuit pressure at a constant value, and a filter 2.
0, and communicates with the inlet port of the electromagnetic switching valve 15 through an oil passage 29. This electromagnetic switching valve 15 is connected to a switch 22 installed at an easy-to-operate position in the driver's cab.
The oil passage 30 leading to the output port communicates with either the tank 21 or the oil passage 29.

Between the oil passages 6 and 7, there is a pilot switching valve 13 in two positions, which blocks both oil passages when no pilot pressure is applied, and forms an oil passage that communicates with each other when pilot pressure is applied. The pilot oil chamber of the pilot switching valve 13 is
The outlet port of the two-position solenoid valve switching valve 14 and the oil passage 3
1 is connected. Then, the electromagnetic switching valve 14
is operated by a limit switch 32 that opens an electric circuit in conjunction with the operation of the operation lever 28, opens the circuit when in neutral, and closes it when the circuit is operated, and connects the oil passage 31 to the oil passage 30.
Alternatively, it is configured to selectively communicate with the tank 21.

Next, the operation of the hydraulic/electrical circuit having the above configuration will be described in detail.

First, when the switch 22 is open, the solenoid switching valve 1
5 is not energized. The spool of the electromagnetic switching valve 15 is in the H position, the oil passage 29 is blocked, and the oil passage 30 is open to the tank 21.
is closed, an electric signal acts on the electromagnetic switching valve 14, and the oil passage 31 is connected to the tank 21 regardless of whether the spool is in the F or G position, so the spool of the pilot switching valve 13 is always in the The D position is maintained, and the oil passages 6 and 7 are blocked from each other. In this state, the swing operation lever is operated, the hydraulic switching valve 4 is placed in the A, B, or C position, and the hydraulic motor 5 is rotated forward or reverse, or decelerated against the inertia of the upper rotating body. When the hydraulic excavator is stopped or held at a stop, the swing hydraulic circuit state is maintained similar to that of the conventional hydraulic excavator shown in FIG. 5 described above. Next, when the switch 22 is closed and the electromagnetic switching valve 15 is energized, the spool of the electromagnetic switching valve 15 is switched to the position, and the pressure oil from the pilot pump 3 is transferred to the oil path 29, the position passage of the electromagnetic switching valve 15, It reaches the inlet port of the electromagnetic switching valve 14 through the oil passage 30. At this time, if the operating lever is in the neutral state, that is, the limit switch 32 is in an open state and the electromagnetic switching valve 14 is not excited, the electromagnetic switching valve 14
is in the G position, so the pressure oil in the oil passage 30 is in the G position.
The position passage and oil passage 31 reach the pilot oil chamber of the pilot switching valve 13, and the pilot switching valve 13 reaches the pilot oil chamber of the pilot switching valve 13.
spool is switched to E position, oil passages 6 and 7
are communicated by the E position passage. From this state, when the operating lever 28 is operated to rotate the hydraulic motor 5, the hydraulic switching valve 4 changes from the C position to the A position or the B position, and at the same time the limit switch 32
The electric circuit is closed, energizing the electromagnetic switching valve 14, and switching the electromagnetic switching valve 14 to the F position. As a result, the pressure oil in the oil passage 30 is closed, the oil passage 31 passes to the tank 21, and the pilot oil chamber of the pilot switching valve 13 becomes tank pressure.
3 is in the D position, and the oil passages 6 and 7 are cut off, so that the hydraulic circuit state similar to that shown in FIG. Start booting. As the hydraulic motor 5 rotates, the upper rotating body with large inertia also rotates, and then, in order to stop it at a predetermined position, when the operating lever 28 is returned to the neutral position, the hydraulic switching valve 4 is moved to the C position.
position, the oil supply to and discharge from the hydraulic motor 5 is stopped, and the ports leading to the oil passages 6 and 7 are shut off. At the same time, however, the electric signal from the limit switch 32 that was energizing the electromagnetic switching valve 14 disappears. The electromagnetic switching valve 14 is in the G position, and the pressure oil in the oil passage 30 passes through the G position passage and the oil passage 31, flows into the pilot oil chamber of the pilot switching valve 13, and switches the pilot switching valve 13 to the E position, so that the oil The passages 6 and 7 are connected by the E position passage, and the hydraulic motor 5 continues to rotate freely due to the inertia of the upper rotating body and does not generate brake torque, so even when the attachment is hanging down as shown in Fig. 3, its suspension is maintained. No load swinging occurs. In addition, to slowly stop the upper revolving structure with inertia, the swing operation lever should be operated gradually or intermittently in the direction of reverse swing, or the hydraulic/electrical circuit shown in Fig. 1 should be Similarly, a method may be adopted in which a swing brake device 23 of a hydraulic release type or the like provided on the five axes of the swing motor is provided and operated. Note that the electromagnetic switching valve 15 for opening and closing the pilot oil pressure source oil passage in this embodiment does not necessarily have to be an electromagnetic type, and may be a hydraulic pilot type or manual type switching valve. It is preferable that it can be easily operated nearby.

Effects of the Invention If the swing hydraulic circuit according to the present invention is provided in the swing system of the upper rotating body of a hydraulic excavator, even if the front attachment is changed and the work content changes, the swing automatic brake can be maintained with the same machine. Both the free turning function and the free turning function can be freely selected by simply operating a switch near the driver's seat, making it easy for even inexperienced drivers to perform the safest and most efficient work according to various work conditions. be.

[Brief explanation of drawings]

Fig. 1 is a hydraulic/electrical circuit diagram showing an embodiment of the present invention, Fig. 2 is a side view of a hydraulic backhoe, Fig. 3 is a side view of a hydraulic excavator with a crane attached to its front attachment, and Fig. 2 is a side view of a hydraulic excavator. FIG. 4 is a side view of the front attachment of a hydraulic excavator equipped with a grip, and FIG. 5 is a hydraulic circuit diagram of a conventional hydraulic excavator swing system. 3...Pilot pump, 4...Hydraulic switching valve,
8, 8'... Relief valve, 9, 9'... Check valve, 12, 12'... Relief valve, 13... Pilot switching valve, 14... Solenoid switching valve, 15... Solenoid switching valve, 22... ...Switch, 28...Operation lever, 32...Limit switch.

Claims (1)

[Claims] 1 In a swing drive system in which the hydraulic motor is rotated forward, reversed, or stopped by operating a manual operating lever and switching the hydraulic switching valve, and the rotating upper body is rotated by the rotational force, the pressure oil inflow and the flow of pressure into the hydraulic motor are A first switching valve that shuts off and communicates a pair of oil passages leading to an outflow port using a hydraulic signal, and a manually operated lever-type hydraulic switching valve for operating the hydraulic motor, the operating lever being in a neutral position in conjunction with the operating lever. a second switching valve that opens and closes the oil passage in response to an electric signal from the limit switch that closes the electric circuit when the limit switch is in a position other than the position; and a third switching valve that opens and closes the oil passage from the pilot hydraulic pressure source in response to an electric signal, a hydraulic signal, or manually. The pilot oil chamber of the first switching valve communicates with the outlet port of the second switching valve, and the inlet port of the second switching valve communicates with the outlet port of the third switching valve through oil passages. Free rotation system for hydraulic excavators.