JPH0725589A - Hydraulic drive device for revolution of crane - Google Patents

Abstract

PURPOSE:To prevent an overturning accident of a revolving superstructure at the time of revolving operation without depending on an operator for his/her skill and experience. CONSTITUTION:In a hydraulic drive device to revolve a crane having a hydraulic motor 6 for revolution to drive a revolving superstructure with a boom set on it and a directional control valve 7 for revolution to control rotational speed and rotational direction of the hydraulic motor 6 for revolution, hydraulic pressure at the front and the rear of a ristrictor 31 provided on a main conduit run 5 is led to a directional control valve 33 by pilot conduit runs 34, 35, and by its differential pressure, control force in the opening direction is given. In the meantime, by a computer 37, in accordance with length of the boom, a boom angle, a load of a hoisted cargo and others, a safety critical flow rate is set, in accordance with its set value, control force in the closing direction is generated in a proportional solenoid 33b of the directional control valve 33, and when a flow rate of pressure oil flowing in the main conduit run 5 exceeds the safety critical flow rate, the directional control valve 33 is actuated to open, the pressure oil of the main conduit run 5 is released from a bleed conduit run 32 to a tank 10, and speed of the hydraulic motor 6 for revolution is restrained down to limitting speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic drive device for a swing of a crane for driving a swing structure on which a boom is installed, and the safety of the crane has been improved by improving the hydraulic circuit. It is intended to be further improved.

[0002]

2. Description of the Related Art A crane is equipped with a boom, and a revolving structure is mounted on the tip of the boom so that a suspended load can be transferred while revolving. The present invention is
This is an improvement of the swing hydraulic drive device for driving the swing structure so that the operator can operate the swing structure more safely than the conventional one. Therefore, the technical contents of a general crane that has been conventionally used for this crane will be described with reference to FIGS. 3 to 4.
FIG. 3 is a side view showing an overall image of a conventional general crane, and FIG. 4 is a hydraulic circuit diagram relating to a conventional hydraulic drive device for turning a general crane.

First, referring to FIG. 3, the basic structure of the crane will be outlined. In FIG. 3, 20 is a traveling body such as a crawler, and 21 is mounted on the traveling body 20 so as to be capable of turning. A revolving structure, 22 is a boom installed on the front part of the revolving structure 21 so as to be capable of undulating, and 23 is a suspended load 2 hung around a pulley provided at the top of the boom 22.
It is a hoisting rope for hanging 4. The revolving structure 21 is configured to be driven in a desired direction in forward and reverse directions at a desired speed by a hydraulic motor for revolving, and the suspended load 24 can be transferred while revolving. The boom 22 is erected and supported at an appropriate angle, for example, by winding a hoisting rope 25 connected to the top of the boom 22 with a winch 26. Further, the boom 22 can be changed in length to any of several kinds by assembling by connecting an appropriate number of connecting booms as unit boom pieces, as needed. it can. The hoisting rope 23 can transport the suspended load 24 at its tip up and down by driving a winch 27 that winds up and rewinds the hoisting rope 23. In addition to such a structure, a crane, which is required to have a thorough safety, is equipped with an overload prevention device as an indispensable structure in order to prevent an excessive load from being suspended during work. Reference numeral 28 is an angle detector of an overload prevention device for detecting a boom angle Φ which is the inclination angle of the boom 22, and 29 is a hoisting rope 25 when a hoisting load 24 is hung from the hoisting rope 23 and a hoisting load is applied. It is a tension detector of the overload prevention device for detecting the applied tension. The tension applied to the undulating rope 25 detected by the tension detector 29 serves as a basis for calculating the suspension load during crane work, and thus, the overload prevention device determines whether or not the suspended load 24 is excessive. Can be determined by. This overload prevention device will be described in detail later.

Next, referring to FIG. 4, a hydraulic drive device for driving such a crane, particularly a hydraulic drive device for a turning hydraulic motor will be mainly described.
Reference numeral 1 is a prime mover, 2 is a gear group for transmitting rotational power of the prime mover 1, 3 is rotational power of the prime mover 1 is transmitted by the gear group 2, and pressure oil for mainly driving a turning hydraulic motor 6 is generated. The turning hydraulic pumps 4 and 4 are variable displacement hydraulic pumps that generate pressure oil for driving an actuator (not shown) of a hydraulic system different from the turning hydraulic motor 6 described later. Both of these hydraulic pumps 3 and 4 have a gear group 2
It can be simultaneously driven by one prime mover 1 via. Reference numeral 5 is a main pipe which is connected to the discharge port of the turning hydraulic pump 3 and guides pressure oil from the pump 3 to a turning direction switching valve 7 and an auxiliary direction switching valve 8 described later, and 6 is the swivel body 21.
A turning hydraulic motor 7 for driving the turning hydraulic motor 6 is connected to the main pipe line 5 and is operated by an operating lever to adjust or switch the flow rate and direction of the pressure oil supplied to the turning hydraulic motor 6. This is a directional valve for turning that controls the rotation speed and rotation direction of the. This turning direction switching valve 7 is
The opening amount can be adjusted by the operation amount of the operation lever to control the supply flow rate to the turning hydraulic motor 6, that is, its rotation speed, and the pair of turning hydraulic motor pipes described later can be changed depending on the operation direction of the operation lever. Pressure oil can be supplied and discharged through the passages 12 and 13, and the rotation direction of the turning hydraulic motor 6 can be controlled to be switched between forward and reverse desired directions. Reference numeral 8 denotes an attached directional switching valve that is attached to the main pipe line 5 and is used to control a sub-actuator (not shown) driven by the turning hydraulic pump 3 and has the same function as the turning directional switching valve 7. . A typical example of this sub-actuator is an outrigger cylinder. The attached directional control valve 8 is of a center bypass type, and when it is not operated, that is, in the neutral position, the pressure oil of the hydraulic pump 3 for swirling passes through the center bypass passage at the center, and the directional control valve for swivel. I am led to 7. Further, the attached directional control valve 8 is used only when the turning directional control valve 7 is not operated, and the pressure oil is supplied and discharged through a pair of pipe lines 14 and 15 which will be described later by the operation thereof, and is not shown. Drive the sub-actuator. Reference numeral 9 is a return pipe for returning the pressure oil of the turning hydraulic motor 3 to the tank 10. Reference numeral 11 is a primary side of the turning directional switching valve 7 and the attached directional switching valve 8 at the primary side to the main conduit 5. It is a relief valve which is connected and whose secondary side is connected to the return line 9. The relief valve 11 has a function of keeping the hydraulic pressure on the primary side of the turning direction switching valve 7 or the attached direction switching valve 8 below a set pressure.
Alternatively, it functions to allow the excess flow rate generated in the process of adjusting the flow rate supplied to the sub-actuator by these directional control valves 7 and 8 to the tank 10 through the return line 9. 12,
Reference numeral 13 supplies the pressure oil on the secondary side to the turning hydraulic motor 6 through one by switching the turning direction switching valve 7.
A pair of turning hydraulic motor pipes for discharging the pressure oil of the motor 6 from the tank port of the turning direction switching valve 7 to the return pipe 9 through the other, and 14 and 15 by a switching operation of the attached direction switching valve 8. It is a pair of sub-actuator conduits that perform the same function as the turning hydraulic motor conduits 12 and 13 that supply and discharge pressure oil to and from the sub-actuator.

A conventional hydraulic drive system for turning a crane is
Since such a hydraulic circuit is provided, the boom 22 having a predetermined length is installed at a predetermined boom angle Φ, and the hoisting rope 23
After the suspended load 24 is hung on the vehicle, the directional control valve 7 for swiveling is operated by the operating lever in order to swivel and transfer the suspended load 24.
The pressure oil generated in the turning hydraulic pump 3 passes through the center bypass passage of the attached direction switching valve 8 through the main pipe line 5 and is then guided to the turning direction switching valve 7. The turning direction switching valve 7 supplies the pressure oil to the turning hydraulic motor 6 through one of the turning hydraulic motor pipelines 12 and 13 according to the operating direction of the operating lever, and supplies the pressure oil of the motor 6 through the other. It is discharged to the return pipe line 9 and the turning hydraulic motor 6 is rotated in the forward and reverse predetermined directions. At the same time, the opening amount is adjusted according to the operation amount of the operation lever, and the turning hydraulic motor 6
The supply flow rate to the device is adjusted to rotate it at a predetermined speed. In that case, when the operating lever of the turning direction switching valve 7 is operated with a full stroke, the entire flow rate of the pressure oil generated by the turning hydraulic pump 3 is supplied to the turning hydraulic motor 6, and the motor 6 rotates at the maximum speed. It will be driven at speed. In this way, in the process of adjusting the supply flow rate of the pressure oil to the turning hydraulic motor 6, if the flow rate of the pressure oil in the main pipeline 5 is excessive, the hydraulic pressure in the main pipeline 5 rises. Since the set pressure of the relief valve 11 is exceeded, the valve 11 is activated to supply the excess amount of pressure oil to the tank 1 through the return pipe 9.
Escape to 0.

[0006] In the crane, when the load 24 hung on the tip of the hoisting rope 23 exerts a moment to incline the machine about the traveling body 20 as a fulcrum, that is, a falling moment, and an excessively large load 24 is hung. There is a risk of falling. Therefore, as a safety device for preventing such a fall, an overload prevention device is provided, and when the load of the suspended load 24 exceeds the rated load which is the limit value of the suspended load that can be applied to the crane, Safety devices such as an alarm device and a crane deactivation mechanism are activated. The overturning moment that defines this rated load changes if the working radius R (horizontal distance between the center of the revolving structure and the hanging load shown in FIG. 3) changes, even if the load of the suspended load is constant. The larger it is, the more it increases. The working radius R is determined by the length of the boom 22 and the boom angle Φ that is the inclination angle of the boom 22, and increases as the length of the boom 22 increases and the boom angle Φ decreases. Therefore, in the crane overload prevention device, the data regarding the rated load is set for each length of the boom 22 in correspondence with the boom angle Φ and stored in the storage device. When the boom angle Φ and the tension applied to the undulating rope 25 are detected by the angle detector 28 and the tension detector 29, the boom angle Φ detected by the angle detector 28 is stored in the storage device. The rated load data is called, and the hanging load of the hanging load 24 is calculated based on the tension detected by the tension detector 29.
Both values are compared. As a result, if the calculated value of the suspension load exceeds the value of the called rated load, the safety device is activated, which can prevent the crane from tipping over.

[0007]

As described above, such an overload preventing device provided in a conventional crane is effective in preventing the crane from falling over. As a result of examining preventive measures, it was found that there is still room for improvement. With respect to this point, when the revolving structure 21 is revolved by operating the operation lever of the reversing direction switching valve 7 during the work of transferring the suspended load 24 by the crane, as shown in FIG. The suspended load 24 swayed by the centrifugal force swings outward by the horizontal distance ΔR, so that the apparent working radius R ′ increases correspondingly and the tipping moment of the crane also increases. Further, when the turning of the revolving unit 21 is suddenly stopped during braking, the horizontal dynamic load increases, and similarly, the overturning moment of the crane increases. The fall of the crane due to such an increase in the fall moment can be prevented by carefully monitoring the state of the suspended load 24 and operating the operation lever appropriately according to the state of the suspended load 24. Such operation of the revolving structure 21 is a work that requires skill and experience. The angular velocity of the revolving unit 21 is the same if the operation amount of the operation lever of the direction switching valve 7 is the same, but the load 24
Even if the operation amount is the same, the peripheral speed of fluctuates greatly due to changes in the working radius R and the like. That is, when the boom 22 is long, the boom angle Φ is small, and further, when the rope length from the tip of the boom 22 to the suspended load 24 is long, even if the operation amount of the operation lever is the same,
The peripheral speed of the suspended load 24 relatively increases. As a result, the apparent work radius R'is further increased in such a case, and when the operation amount of the operation lever is increased, particularly when it is maximized, the apparent work due to the centrifugal force during the turning operation is performed. Due to the increase of the radius R'and the increase of the horizontal load at the time of braking, the overturning moment increases to a non-negligible condition depending on the conditions, which causes a problem in safety. In a crane in which safety is infinitely required, it is not desirable to leave the operation of the revolving structure 21 only to the skill and experience of the operator in recent years, especially when the number of skilled operators is drastically reduced.

The present invention has been made in view of the above problems in the prior art, and aims to improve the problems.
An object of the present invention is to provide a hydraulic drive device for a swing of a crane, which can surely prevent a fall accident that may occur when a swing structure is turned, without depending on the skill and experience of an operator.

[0009]

The object of the present invention is to provide a "slewing hydraulic motor for driving a swinging body on which a boom is installed, and a swivel for generating pressure oil for driving the swinging hydraulic motor. Hydraulic pump and a directional control valve for controlling the rotational speed and direction of the hydraulic motor for turning by adjusting or switching the flow rate and direction of the pressure oil supplied from the hydraulic pump for turning to the hydraulic motor for turning. And a flow rate detecting means for detecting the flow rate of the pressure oil guided from the turning hydraulic pump to the turning direction switching valve, and a turning direction switching valve from the turning hydraulic pump. Regarding the flow rate of pressure oil to be leaked, the fall prevention condition setting means for setting the fall prevention condition of the crane based on the parameter of the crane's fall moment, and the detection detected by the flow rate detection means. When the result does not satisfy the above-described fall prevention condition set by the fall prevention condition setting means, a switching valve that opens to allow the pressure oil on the primary side of the flow rate detection means to escape to the tank is provided to operate the revolving structure. A crane hydraulic drive for turning a crane according to claim 1 characterized in that "the crane is prevented from tipping over at times", "for turning to drive a swinging body having a boom installed" A hydraulic motor, a turning hydraulic pump that generates pressure oil for driving the turning hydraulic motor, and a turning hydraulic pump that are connected to the turning hydraulic pump by a main pipe and supply the turning hydraulic pump to the turning hydraulic motor. A turning direction switching valve that controls the rotation speed and rotation direction of the turning hydraulic motor by adjusting and switching the flow rate and direction of pressure oil, and is attached to the main pipeline and driven by the turning hydraulic pump. In a turning hydraulic drive device for a crane having a center bypass type directional control valve for controlling the actuator, a throttle provided in the center bypass passage of the directional control valve is used, The flow rate detecting means for detecting the flow rate of the pressure oil guided to the direction switching valve and the flow rate of the pressure oil guided from the swing hydraulic pump to the swing direction switching valve are determined based on the crane overturning moment parameter. The fall prevention condition setting means for setting the prevention condition and the flow rate detecting means which is opened when the detection result detected by the flow rate detecting means does not satisfy the fall prevention condition set by the fall prevention condition setting means. A switching valve that releases the pressure oil on the primary side to the tank was installed to prevent the crane from tipping over when operating the revolving structure. " It is achieved by each device of the hydraulic drive system for turning of a crane according to claim 3 of the present invention.

[0010]

Since the hydraulic drive device for turning a crane according to claims 1 and 3 of the claims adopts such a structure, a boom having a predetermined length is fixed at a predetermined boom angle. After hanging up the suspended load, and operating the turning direction switching valve to rotate and transfer this suspended load,
The pressure oil generated by the turning hydraulic pump is guided to the turning direction switching valve, and the turning hydraulic motor rotates in the forward and reverse predetermined directions at a predetermined rotation speed. The flow rate of the pressure oil guided from the turning hydraulic pump to the turning direction switching valve is detected, while the fall prevention condition setting means determines the flow rate of the pressure oil based on the crane overturning moment parameter. Conditions are set. When the flow rate of the pressure oil detected by the flow rate detecting means does not satisfy the fall prevention condition set for this flow rate, the switching valve for releasing the pressure oil on the primary side of the flow rate detecting means to the tank is opened. , The pressure oil guided from the turning hydraulic pump to the turning direction switching valve is released to the tank, and the rotation speed of the turning hydraulic motor is suppressed to the speed limit. The same applies to the hydraulic swing drive device for a crane according to the second aspect of the present invention, which is dependent on the first aspect of the present invention.

[0011]

Embodiments of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a hydraulic circuit diagram relating to a hydraulic drive device for turning of a crane according to a first embodiment of the present invention, and FIG. 2 is a hydraulic circuit diagram relating to a hydraulic drive device for turning of a crane according to a second embodiment of the present invention. is there. In FIGS. 1 and 2, the parts to which the same reference numerals as those in FIG. 4 already described are given represent the same parts as those in the same figure, and therefore will not be described in detail to avoid duplication of description.

First, the first embodiment will be described with reference to FIG. 1. The crane hydraulic drive system for a crane according to the first embodiment has a boom 22 as in the conventional hydraulic drive device described in FIG. A turning hydraulic motor 6 that drives the turning body 21, a turning hydraulic pump 3 that generates pressure oil for driving the turning hydraulic motor 6, and a turning lever that is operated by an operating lever. A turning direction switching valve 7 for controlling the rotation speed and the turning direction of the turning hydraulic motor 6 by adjusting or switching the flow rate and direction of the pressure oil supplied to the working hydraulic motor 6 is provided. There is no difference in the base configuration compared to. The hydraulic circuit shown in FIG. 1 is similar to the variable displacement hydraulic pump 4 shown in FIG. 4, the gear group 2 provided with the hydraulic pump 4, and the attached directional control valve 8 used for controlling the sub-actuator. However, the basic hydraulic circuit itself is made simpler than that of FIG. 4, and the common parts with FIG. 4 are also shown in a simplified manner.

Therefore, the first point regarding the improvement in the present invention is as follows.
The configuration of the embodiment will be described. In FIG. 1, reference numeral 31 is a diaphragm provided in the main conduit 5 as a differential pressure detector. This throttle 31 generates a differential pressure before and after it due to the fluid resistance when the pressure oil passes, and the flow rate of the pressure oil flowing through the main pipeline 5 can be obtained by this differential pressure. It functions as a flow rate detecting means for detecting the flow rate of the pressure oil guided from the hydraulic pump 3 to the turning direction switching valve 7.
32 is a bleed conduit that branches from the main conduit 5 on the primary side of the throttle 31 and communicates with the tank 10. 33 is provided in this bleed conduit 32 and is operated by a control signal to open and close the bleed conduit 32. It is a switching valve as an off valve. Although the switching valve 33 is preset to the closed state, it is switched by a control signal to open and the pressure oil on the primary side of the throttle 31 is released to the tank 10 through the bleed pipe 32. Reference numeral 33a is a spring for biasing the switching valve 33 in the closing direction to preset it in the closed state, and 33b is a proportional solenoid for exciting the switching valve 33 by the control signal to operate to give the switching valve 33 a controlling force in the closing direction. A predetermined value is set through the control signal according to a command from a fall prevention condition setting mechanism described later. 34 is a bleed line 32
Of the throttle valve 31, that is, the upstream pressure of the throttle 31 as a control signal, is guided to the signal receiving portion of the switching valve 33 to apply a control force in the opening direction to the switching valve 33. In the pilot pipe which is branched from the control valve and connected to the signal receiving portion of the switching valve 33, the downstream pressure of the throttle 31 is guided to the signal receiving portion of the switching valve 33 as a control signal, and the switching valve 3
3 is a pilot conduit for applying control force in the closing direction, similar to the proportional solenoid. The switching valve 33 includes the proportional solenoid 33a, the pilot conduit 34, and the pilot conduit 3
Since the opening / closing control is performed by the control force of No. 5, if the slight preset force of the spring 33a is ignored, the opening operation is performed when the control force by the differential pressure across the throttle 31 becomes larger than the control force by the proportional solenoid 33b, and the turning force The pressure oil guided from the hydraulic pump 3 to the turning direction switching valve 7 escapes to the tank 10 through the bleed conduit 32, and is otherwise closed.

The structure of the fall prevention condition setting mechanism for setting the control force by the proportional solenoid 33b is as follows.
A controller 36 generates a control signal for exciting the proportional solenoid 33b in response to the calculation result of the calculator 37 described later, and 37 calculates and sets the fall prevention condition of the crane based on the parameter of the fall moment of the crane. It is an arithmetic unit as a fall prevention condition setting means. This calculator 3
In 7, based on the parameter of the tipping moment,
The speed limit of the hydraulic motor 6 for turning for preventing the crane from tipping over, and further, the flow rate of the main pipeline 5 commensurate with the speed limit are calculated and set. That is, with respect to the flow rate of the main oil line 5 which is the flow rate of the pressure oil sent to the turning direction switching valve 7, the safety is a limit value of the flow rate for keeping the turning hydraulic motor 6 at the speed limit to ensure safety. The limit flow rate is set. In the controller 36, the data regarding the set safe limit flow rate is converted into a control signal for exciting the proportional solenoid 33b, and a signal for causing the proportional solenoid 33b to generate a control force commensurate with the set safe limit flow rate is generated. Be done. In this embodiment, such a safety limit flow rate is directly calculated and set by the calculator 37. However, since the speed of the hydraulic motor and the flow rate supplied to the motor are front and back integrated, the calculation is performed. In the process of setting a speed limit by the device 37 and producing a control signal by the controller 36, the velocity may be converted into a flow rate to produce the control signal as described above. The point is to prevent the crane from falling over. When setting the condition, whether it is direct or indirect, the condition may be set for the factor that defines the flow rate of the pressure oil guided from the turning hydraulic pump 3 to the turning direction switching valve 7. 38 is a command signal path for guiding the control signal generated by the controller 36 to the proportional solenoid 33b, and 39a, 39
Symbols b, 39c, ... Are signal paths for inputting information signals and detection signals relating to the parameters of the crane's overturning moment to the calculator 37. The information signal is, for example, the length of the boom 22 assembled by connecting the connecting booms, and the detection signal is, for example, the boom angle Φ detected by an overload prevention device or the like, the suspension load, the suspension from the tip of the boom 22. The length of the rope up to the load 24 can be mentioned.
The signals input from 39b, 39c, ...
It is shown in FIG. Signals relating to these parameters are sent to the arithmetic unit 37 through these signal paths 39a, 39b, 39c.
Since it is input through ..., the safety limit flow rate set there, in other words, the speed limit of the turning hydraulic motor 6 is different if the length of the boom 22, the boom angle Φ, the suspension load, etc. are different.
Naturally, the set values will be different. Further, the turning hydraulic drive device is also provided with a limit release switch for preventing the switching valve 33 as a bleed valve from operating as necessary, and when the limit release switch is operated, its operation signal is calculated. The switching valve 33 can be normally closed by being input to the device 37.

Since the device of the first embodiment of the present invention has such a structure, the boom 22 having a predetermined length is installed at a predetermined boom angle Φ, and the hoisting rope 23 is provided with a load 24.
In order to rotate the directional control valve 7 after it is hung, the directional control valve 7 is operated by the operating lever, and the pressure oil generated in the hydraulic pump 3 for control is transferred to the directional control valve 7 for the control path through the main pipe line 5. As is the case with the conventional device, the turning hydraulic motor 6 is rotated at a predetermined rotation speed in the forward and reverse predetermined directions in accordance with the operation amount and the operation direction of the operation lever. At this time, a differential pressure is generated before and after the throttle 31 due to the fluid resistance when the pressure oil passes, and the differential pressure acts on the switching valve 33 as a control force in the opening direction. That is, the hydraulic pressures before and after the throttle 31 are guided to the signal receiving portion of the switching valve 33 through the pilot pipes 34 and 35, respectively, to give the switching valve 33 control force in the opening direction and the closing direction, respectively. Since the hydraulic pressure in the passage 34 is higher than the hydraulic pressure in the pilot conduit 35, the differential pressure eventually acts as a control force in the opening direction. On the other hand, in the arithmetic unit, based on the data about the length of the boom 22 as an information signal that is input in advance, the boom angle Φ as a detection signal that is detected and input during work, and the data such as the suspension load of the suspended load 24. The safety limit flow rate, which is the condition for preventing the crane from tipping over, is set, and the data is sent to the controller 36. The data is converted in the controller 36 into a control signal for causing the proportional solenoid 33b to generate a control force commensurate with the set safety limit flow rate, and the control signal is
It is output to the proportional solenoid 33b through the command signal path 38. As a result, the proportional solenoid 33b is excited by this control signal to generate a control force equivalent to the differential pressure across the throttle 31 generated by the throttle 31 due to the safety limit flow rate, and the control force closes the switching valve 33. It is given as a direction control force. Then, in the switching valve 33, the differential pressure before and after the throttle 31 for detecting the flow rate of the pressure oil flowing through the main pipeline 5 acts as a control force in the opening direction, while the throttle generated by the throttle 31 due to the safety limit flow rate. Since the control force equivalent to the front-back differential pressure acts as the control force in the closing direction, the flow rate of the pressure oil flowing through the main pipeline 5 is calculated by the calculator 37 when the suspended load 24 is swung and transferred. When the safety limit flow rate, which is the set condition for preventing the crane from falling, is exceeded, in other words, when the rotation speed of the turning hydraulic motor 6 exceeds the speed limit, the switching valve 33 as a bleed-off valve is opened. The pressure oil guided from the turning hydraulic pump 3 to the turning direction switching valve 7 escapes to the tank 10 through the bleed pipe 32, and the speed of the turning hydraulic motor 6 is suppressed to the speed limit. Therefore, according to the apparatus of the present embodiment, it is possible to reliably prevent a fall accident that may occur when the swing structure is turned, without depending on the skill and experience of the operator. Therefore, the device of this embodiment is
It is also possible to apply to a remotely operated crane.
Further, in the device of the first embodiment, as described above, the limit release switch is provided so that the operation signal thereof can be input to the computing unit 37. Therefore, the speed of the swing motor 6 as described above can be increased. The restricting mechanism can be adapted so that a skilled operator does not operate it by operating the restricting release switch as necessary, and the skill and experience can be utilized to perform the turning operation.

Next, a second embodiment will be described with reference to FIG. 2. The crane hydraulic drive for turning of the second embodiment is different from the first embodiment in controlling the sub-actuator. The auxiliary directional control valve 8 to be used is provided, and the same hydraulic circuit as the basic hydraulic circuit shown in FIG. 4 which has already been described in the section "Prior Art" is used. The apparatus of this embodiment embodies the technical idea described in the first embodiment in such a hydraulic circuit. That is, a main bypass 5 for guiding the pressure oil from the turning hydraulic pump 3 to the turning direction switching valve 7 is provided with a center bypass type directional switching valve 8 for controlling a sub-actuator driven by the pump 3. In the center bypass passage of the attached directional control valve 8, a throttle 31a having exactly the same function as the throttle 33 described in the first embodiment is integrally provided as a flow rate detecting means. And this diaphragm 3
As in the device of the first embodiment, 1a is provided with a bleed conduit 32 that branches from the main conduit 5 to the tank 10 on the primary side, and the hydraulic pressure before and after that is provided as a bleed-off valve as a switching valve. Pilot lines 34, 35 leading to the signal receiving portion 33 are provided, so that the switching valve 33 is provided with control forces in the opening direction and the closing direction, respectively. Therefore, the device of the second embodiment is the same as the device of the first embodiment except that the device corresponding to the throttle 31 is provided in the center bypass passage of the center bypass type directional control valve 8. There is essentially no difference compared to the example device. According to the apparatus of the second embodiment, as described above, the throttle as the flow rate detecting means can be integrally provided in the center bypass passage of the directional control valve, so that the number of parts and the assembly process of parts can be reduced. Therefore, productivity can be improved.

[0017]

As is apparent from the above description, the present invention according to claim 1 of the appended claims and claim 2 which is dependent on this aspect of the invention has the structure described in claim 1 thereof, in particular, The fall prevention condition setting means for setting the fall prevention condition of the crane based on the moment parameter and the detection result detected by the flow rate detection means do not satisfy the fall prevention condition set by the fall prevention condition setting means. A switching valve that sometimes opens to allow the pressure oil on the primary side of the flow rate detecting means to escape to the tank is provided ", which may occur when the revolving structure is revolved. It is possible to provide a hydraulic drive device for a crane that can reliably prevent a fall accident without depending on the skill and experience of an operator. Further, the present invention according to claim 3 of the claims has such an effect,
Since the flow rate adjusting means is configured by using the throttle provided in the center bypass passage of the attached directional control valve, when manufacturing such a turning hydraulic drive device, "the number of parts and the assembly process of parts can be reduced, We can improve productivity. "
That effect can also be played together.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram relating to a hydraulic drive device for turning a crane according to a first embodiment of the present invention.

FIG. 2 is a hydraulic circuit diagram of a turning hydraulic drive system for a crane according to a second embodiment of the present invention.

FIG. 3 is a side view showing an overall image of a conventional general crane.

FIG. 4 is a hydraulic circuit diagram relating to a conventional hydraulic drive device for turning a general crane.

[Explanation of symbols]

 1 Motor 3 Swing hydraulic pump 5 Main line 6 Swing hydraulic motor 7 Swing direction switching valve 8 Attached direction switching valve 10 Tank 21 Swiveling body 22 Boom 24 Suspended load 28 Angle detector 29 Tension detector 31 Throttling 32 Bleed pipeline 33 Bleed-off valve 33a Spring 33b Proportional solenoid 34, 35 Pilot line 36 Controller 37 Operator 38 Command signal line 39a to 39e Signal line

Claims (3)

[Claims] 1. A swing hydraulic motor for driving a swing structure having a boom, a swing hydraulic pump for generating pressure oil for driving the swing hydraulic motor, and a swing hydraulic pump from the swing hydraulic pump. A turning hydraulic drive for a crane that has a turning direction switching valve that controls the rotation speed and rotation direction of the turning hydraulic motor by adjusting or switching the flow rate and direction of the pressure oil supplied to the motor. Regarding the flow rate detecting means for detecting the flow rate of the pressure oil guided from the hydraulic pump to the turning direction switching valve, and the flow rate of the pressure oil guided from the turning hydraulic pump to the turning direction switching valve, as a parameter of the tipping moment of the crane. The fall prevention condition setting means for setting the fall prevention condition of the crane based on this, and the detection result detected by the flow rate detection means are set by this fall prevention condition setting means. When the above-mentioned fall prevention conditions are not satisfied, a switching valve that opens to open the pressure oil on the primary side of the flow rate detecting means to the tank is provided to prevent the crane from falling when the swing structure is operated. A hydraulic drive system for turning a crane, which is characterized in that 2. A fall prevention condition setting means for setting a fall prevention condition of a crane based on a parameter of a fall moment of a crane, wherein the parameters are a boom length, a boom inclination angle, and a load of a suspended load. The hydraulic drive system for a swing of a crane according to claim 1. 3. A revolving hydraulic motor for driving a revolving structure provided with a boom, a revolving hydraulic pump for generating pressure oil for driving the revolving hydraulic motor, and a revolving hydraulic pump and a main pipeline. A turning direction switching valve that is connected and controls the rotation speed and rotation direction of the turning hydraulic motor by adjusting or switching the flow rate and direction of the pressure oil supplied from the turning hydraulic pump to the turning hydraulic motor, In a turning hydraulic drive device for a crane, which has a center bypass type directional control valve attached to the main pipeline and controls a sub-actuator driven by a turning hydraulic pump, the crane is provided in the center bypass passage of the directional control valve. A flow rate detecting means configured by using a throttle for detecting the flow rate of the pressure oil guided from the turning hydraulic pump to the turning direction switching valve, and a turning direction pump from the turning hydraulic pump. Regarding the flow rate of the pressure oil guided to the directional control valve, the fall prevention condition setting means for setting the fall prevention condition of the crane based on the parameter of the crane's fall moment, and the detection result detected by the flow rate detection means are the fall prevention conditions. Provided with a switching valve that opens when the fall prevention conditions set by the setting means are not satisfied and releases the pressure oil on the primary side of the flow rate detection means to the tank, preventing the crane from falling when operating the revolving structure. A hydraulic drive device for a swing of a crane, which is characterized in that