JPH0438258B2 - - 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 supply of pressure oil from the main pump 2 is cut off, and the oil passages 6 and 7 leading to the oil inflow and outflow ports of the swing motor 5 are both hydraulically operated. Although it is closed by the spool of the switching valve 4, the rotating motor 5 is forced to rotate due to the rotational inertia of the upper rotating body, so oil is sucked in from one port and discharged at high pressure from the other port. Ru. 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 being rotated, hydraulic braking torque is automatically generated in the hydraulic motor 5, reducing the swinging speed of the upper rotating body and shortening the rotation speed of the upper rotating body. 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, the oil passage 6
and 7, the main return circuit 1 from the swing motor and other actuators via check valves 9, 9'.
0 oil is constantly replenished through the oil path 11, and on the other hand, when the hydraulic switching valve 4 is in the neutral position C, this is to prevent abnormally high pressure from being trapped in the oil paths 6 and 7 for some reason. Relief valves 12, 12' are provided.

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 operation lever to neutral, making it easy to stop 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 Figure 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 operating 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 and carefully so that no pendulum movement occurs in the suspended load 39. A high degree of skill is required to make the suspended load 39 follow the swinging motion in accordance with the pendulum motion and stop the swinging, otherwise it would not only reduce the cycle time but also be dangerous.

In addition, even in the same cargo handling work, as shown in FIG.
In cargo handling machines that are directly attached, pendulum movement is unlikely to occur even if a swing brake force is applied; rather, it may be better to forcibly stop the swing to some extent to improve cycle time and make it easier to position the load.

Problems to be Solved by the Invention As mentioned above, when the front attachment of a hydraulic excavator is replaced and used for various purposes, depending on the work involved, when the swing operation lever is set to neutral, the swing braking 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, an electromagnetic switching valve is provided which normally shuts off a pair of operating circuits that supply pressure oil to a hydraulic motor for swing driving, but connects them to each other based on a hydraulic signal. Then, the electric signal from the limit switch is linked to the operating lever of the manually operated lever-type hydraulic switching valve that switches and supplies pressure oil to the operating circuit of the hydraulic motor, and closes the electrical circuit only when the operating lever is in a position other than neutral. The electrical circuit for operating the electromagnetic switching valve is cut off, a normally closed relay is provided, and an electrical circuit is provided so that power is supplied to the limit switch and the relay by a switch that can be freely opened and closed.

Action Close the switch and connect the power circuit to the limit switch and relay.

In this state, when the operating lever of the hydraulic switching valve for operating the swing hydraulic motor is neutral, that is, when no swinging operation is being performed, the internal electric circuit of the limit switch that is linked to the operating lever is open. Since no excitation current is sent to the relay, the power supply circuit passes through the internal electrical circuit of the relay to the excitation coil of the electromagnetic switching valve. As a result, the pair of operating circuits that supply pressure oil to the hydraulic motor are in communication, and the hydraulic motor is in a state where it can be easily rotated by an external force. Next, when a turning operation is started using the operating lever of the hydraulic switching valve for operating the hydraulic motor, a limit switch that is linked to the movement of the operating lever is activated, and the power supply circuit is closed.
Since the relay is energized, the internal electrical circuit of the relay is opened, and the electrical signal sent from the power supply to the excitation coil of the electromagnetic switching valve is cut off. As a result, 1
Communication between the pair of hydraulic motor operating hydraulic circuits is broken, and each circuit becomes independent, so that normal startup and acceleration can be performed during turning operations.

Note that when the swing operation lever is returned to the neutral position after starting the swing, the electromagnetic switching valve is again operated by the excitation current from the relay as described above, and the hydraulic motor enters the free swing state.

Next, when the switch is opened, the solenoid switching valve will
Regardless of the position of the operating lever, since it is not excited, the swing system returns to the same circuit configuration as 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 a relief valve 17 and communicates with a manually operated lever type hydraulic switching valve 4 for operating the swing motor 5, and when the operating lever 16 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 16 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 relief valve is designed to open from direction 7 to direction 6, and when the hydraulic switching valve 4 is suddenly set to the C position after the hydraulic excavator upper rotating body with large inertia is turned by the hydraulic motor 5, the To prevent passages 6 and 7 from being closed and generating high pressure,
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'.

The oil discharged from the pilot pump 3 serves as an auxiliary hydraulic pressure source for operation when a swing brake device 23, which will be described later, is also used, and has a relief valve 18 to keep the circuit pressure at a constant value. It is led to predetermined equipment through a filter 20 and an oil path 25.

Further, a two-position electromagnetic switching valve 13 is provided between the oil passages 6 and 7, which blocks both oil passages when not energized, and forms an oil passage that communicates with each other when energized. The excitation coil of the valve 13 is connected to the electric wire 2
8, connected to a power source 32 via a relay 14, an electric wire 27, and a switch 22. In addition, the relay 14
The internal electric circuit is closed when not energized, and is opened when energized, and the excitation coil is activated by the movement of the operating lever 16 of the hydraulic switching valve 4 for operating the hydraulic motor 5. Interlockingly, the internal electrical circuit is connected to the power source 32 via the switch 22, the limit switch 15, and the electric wire 26 due to the action of the limit switch 15, which closes the internal electric circuit when the operation lever 16 is in a position other than the neutral position.

The switch 22 is installed in a position that is easy to operate in the driver's cab, and is a known switch for opening and closing the circuit of the power source 23, and is operated by the driver's free will. When the circuit is closed, the pressure switch 1
5. Supply voltage to the main circuit of the relay 14 at the same time.

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

First, when the switch 22 is open and the pressure switch 15 and relay 14 are not energized,
Since the electromagnetic switching valve 13 is not excited, the spool position of the electromagnetic switching valve 13 is always at the D position, that is,
The oil passages 6 and 7 are not allowed to communicate with each other. Therefore, in this state, by operating the swing operation lever, the hydraulic switching valve 4 becomes the A, B, or C position, and the hydraulic motor 5 is rotated forward or reverse, or is rotated against the inertial force of the upper rotating body. When the hydraulic excavator is decelerated 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, a description will be given of when the switch 22 is operated and the limit switch 15 and the continuator 14 are energized.

When the turning operation is not performed, that is, when the operation lever is in the neutral position, the limit switch 15 is not operated, and the internal electric circuit of the limit switch 15 is therefore open, so the coil of the relay 14 is not excited, and its internal electric circuit is is a closed circuit.
Therefore, the electricity from the power source 32 passes through the switch 22, the electric wire 27, the internal circuit of the relay 14, and the electric wire 28, and reaches the excitation coil of the electromagnetic switching valve 13, and as a result, the spool of the electromagnetic switching valve 13 is switched to the E position. The oil passages 6 and 7 are brought into communication.

In order to rotate the hydraulic motor 5 from this state, when the rotation operation lever is operated and the internal electric circuit of the limit switch 15 is closed, the power supply 32
Excite the coil of the relay 14 through the switch 22, the internal electric circuit of the limit switch 15, and the electric wire 26 to open the internal electric circuit of the relay 14,
Since the power supply circuit that was energizing the electromagnetic switching valve 13 is cut off, the spool of the electromagnetic switching valve 13 is switched from the E position to the D position, the oil passages 6 and 7 are cut off, and the oil pressure similar to that shown in FIG. 5 is maintained. The circuit state is restored, and the hydraulic motor 5 starts to be activated by the pressure oil sent via the hydraulic switching valve 4. As the hydraulic motor 5 rotates, the upper revolving body with large inertia rotates, and then, in order to stop at a predetermined position, when the swing operation lever is returned to the neutral position, the limit switch 15 is activated and its internal electrical circuit is opened. As a result, the excitation of the relay 14 is interrupted, so that the internal electrical circuit of the relay 14 is closed again, and the electromagnetic switching valve 13 is closed.
is excited, and its spool position changes from D position to E
Since the oil passages 6 and 7 continue to rotate freely due to the position passage and no brake torque is generated, even when the attachment is hanging down as shown in Fig. 3, load swing at the tip does not occur. . In addition, when slowly stopping the rotating upper structure with inertia, operate the swing operation lever gradually or intermittently in the direction of reverse rotation, or use the method shown in the hydraulic/electrical circuit diagram in Figure 1. In addition, a swing brake device 2 such as a hydraulic release type installed on the five axes of the swing motor
3 may be prepared and operated.

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, and Fig. 3 is a diagram of a hydraulic excavator when a front attachment is equipped with a crane device. FIG. 4 is a side view of the front attachment of the hydraulic excavator when the gripping tool is attached, and FIG. 5 is a hydraulic circuit diagram of the swing system of a conventional hydraulic excavator. 4...Hydraulic switching valve, 8,8'...Relief valve,
9, 9'...Check valve, 13...Solenoid switching valve,
14...Relay, 15...Limit switch, 1
6...operation lever, 22...switch.

Claims (1)

[Claims] 1 In a swing drive system in which a hydraulic switching valve is operated by operating a manual operation lever to rotate a hydraulic motor forward, reverse, or stop, and the rotating upper body is rotated by the rotational force of the hydraulic motor, pressure oil inflow to the hydraulic motor is An electromagnetic switching valve that communicates a pair of oil passages leading to the outflow port with an electric signal, and an operating lever of the manually operated lever-type hydraulic switching valve for operating the hydraulic motor, when the operating lever is in a position other than the neutral position. and a relay which is opened by an electric signal from a limit switch that closes the electric circuit and is normally closed, and an electric circuit is provided between the switch near the driver's seat and the electromagnetic switching valve via the relay. , a free rotation system for a hydraulic excavator, characterized by having an electric circuit that excites a relay via the limit switch.