JP4807340B2 - Mobile crane - Google Patents

Description

  The present invention relates to a mobile crane provided with a mast backstop device functioning as a mast stop for a mast attached to an upper swing body so as to be freely raised and lowered.

  As a conventional mobile crane, a crawler-type lower traveling body, an upper revolving body that is pivotably mounted on the lower traveling body, and a swingable attachment to the upper revolving body, and a suspension tool is suspended from the tip. From the lowered first hoisting member (so-called lattice boom), the second hoisting member (so-called lattice mast) which is attached to the upper swing body so as to be hoisting freely and raises the first hoisting member, and the second hoisting member A balance weight that is suspended and is arranged at a position spaced apart from the rear end of the upper swing body by a predetermined distance, and a third hoisting member (so-called box mast or gantry) that hoists the second hoisting member. There is a counterbalance type crane equipped. The counter balance type crane is one of the modified forms of the standard crane in which the lattice boom is raised and lowered with a box mast or a gantry, and other modified forms include those in which the balance weight is simply removed.

  Lattice booms and lattice masts are long structures in which a large number of steel materials are assembled in a lattice pattern, and when they are raised from the upper revolving structure, they may swing under the influence of strong winds. For this reason, in the mobile crane provided with the lattice boom and / or the lattice mast, a backstop device is provided as a stop for these. There are backstop devices that can be expanded and contracted by the elastic force of the coil spring, and those that can be expanded and contracted by the internal pressure control of the hydraulic cylinder, both of which regulate the swinging motion of the lattice boom and lattice mast. It is configured to apply a biasing force from the rear to the front of the lattice boom or lattice mast.

  Since the lattice boom stands in a forward leaning posture so that the undulation angle does not exceed 90 degrees, the boom backstop device that applies the urging force from the rear of the lattice boom hardly receives the load of the lattice boom. For this reason, as a boom back stop device, a spring type such as a coil spring is more frequently used than a hydraulic type. On the other hand, the lattice mast stands upright in a tilted posture, and is balanced by being pulled forward via a boom guy line that connects the lattice boom and the tip portions of the lattice mast. Since the lattice mast load is applied to the mast backstop device depending on the tensile force of the lattice boom, it is preferable that the mastback stop device can adjust the biasing force in a wide range. From this point of view, the mast backstop device is preferably a hydraulic device.

  The hydraulic mast backstop device includes a hydraulic cylinder, a hydraulic pump that supplies hydraulic oil to the hydraulic cylinder, an electromagnetic switching valve that switches supply / shutoff of hydraulic oil from the hydraulic pump to the hydraulic cylinder, A cylinder pressure control valve that releases pressure oil when the internal pressure exceeds a predetermined set pressure is provided as a main component.

  By the way, in a mobile crane equipped with a hydraulic mast backstop device, if a large lateral load is applied to the lattice mast with a large compressive force acting on the lattice mast, the lattice mast is damaged. There is a fear. As a prior art in which a lateral load applied to a lattice mast by a mast backstop device is controlled in order to prevent damage to the lattice mast, there is a mast holding device disclosed in Patent Document 1. This mast holding device is provided with a mast support tension detector provided on a mast support pendant and a boom support pendant in a crane provided with a mast backstop device using a hydraulic cylinder as a means for generating thrust to push the mast forward. A boom support tension detector and a cylinder pressure detector for detecting the pressure of the hydraulic cylinder constituting the backstop device, and a calculation unit for inputting a detection value by these detectors and a crane style determination device, An expansion / contraction / stop signal is transmitted from the arithmetic unit to the direction switching valve for controlling expansion / contraction / stop of the hydraulic cylinder constituting the mast backstop device, and the direction switching valve is switched in response to the signal. Controlling the opening and closing of a pilot check valve provided in the extension side pipe line of the hydraulic cylinder constituting It is configured to hold the supporting force of the cylinder.

JP 2000-318982 A

  The mast holding device of Patent Document 1 determines whether or not a large compressive force is acting on the mast based on the tension detection results of the boom support tension detector and the mast support tension detector, and detects the cylinder pressure. The strength of the mast support force by the hydraulic cylinder is determined based on the detection results of the compressor, and the direction switching valve is switched from these determination results to prevent an excessive lateral load from acting on the mast. Specifically, when the moment around the front of the boom is large due to a suspended load work or the like, since the tension of the boom support pendant (boom guy line) is also large, the mast is pulled forward. At this time, it is not necessary to firmly support the mast with the mast backstop device. The mast is not raised or lowered in the crane operation, but the rearward tilt angle changes within a limited range due to changes in suspension load, SL weight (balance weight) load fluctuation, boom support pendant elongation, and the like. Therefore, it is necessary to cause the cylinder of the mast backstop device to follow a change in the angle of the mast, and the hydraulic cylinder of the backstop device is set to always extend at a low pressure in normal work. Conversely, if the boom is short and there is no suspended load and the boom angle is large, the tension of the boom support pendant will decrease and the mast will fall backwards, so the backstop device must support the mast firmly . The determination of the state in which the mast is about to fall backward is made by automatically determining the tension balance based on the tension detection results of the boom support tension detector and the mast support tension detector, etc., using a matrix determined in advance by an electric signal. Is output. When the cylinder support force of the mast backstop device is judged to be “strong” by the matrix, the directional control valve shuts off the hydraulic oil from the hydraulic pump to the hydraulic cylinder, the check valve closes instantly, and the hydraulic cylinder expands. Side oil is contained and the mast is supported only by its compression action.

In the apparatus of Patent Document 1, in order to set the hydraulic cylinder of the mast backstop device to always extend at a low pressure during normal work, the constant pressure relief valve of the pump circuit is set to a low pressure setting so as not to damage the mast. Pressure oil is supplied from the hydraulic pump to the extension side of the hydraulic cylinder by the switching valve.
However, if the constant pressure relief valve of the pump circuit is set to a low pressure so that the mast is not damaged, it is impossible to generate a thrust force for raising the mast in the hydraulic cylinder. In this case, if you want to change the position of the SL weight (balance weight) by changing the work posture to change the lifting capacity (on the side closer to the machine body), it is necessary to bother the boom to increase the moment around the front of the boom. It is cumbersome because you have to defeat it greatly before.
In order to solve this problem, the constant pressure relief valve of the pump circuit is set to a high pressure that can generate a thrust that can raise the mast, and the cylinder pressure detection is performed by switching the hydraulic cylinder support force between “strong” and “weak”. Although the method of switching the direction switching valve at the “elongation” and “stop” positions based on the detection result of the container is also conceivable, in this case, in a state where a large compressive force is acting on the lattice mast, A strong lateral load acts on the lattice mast due to the mast backstop device, and the possibility of causing damage (buckling) of the lattice mast remains unwieldy.
The raising operation of the lattice mast when lifting a heavy object becomes faster as an operation for lifting the heavy object from the ground, that is, a so-called ground-cutting operation, is performed with difficulty. If the lattice mast wakes up too quickly, the extension of the mast backstop device cannot catch up with the lattice mast, and the lattice mast and the mast backstop device are separated. When the raising operation of the lattice mast is stopped, the extended mast backstop device collides with the lattice mast, and a strong lateral load is applied.

The operation of the hydraulic cylinder at this time will be described in relation to the internal pressure. If the switching set pressure of the switching valve is P1, and the pressurized pressure compressed by the hydraulic cylinder under the load of the lattice mast is ΔP, the hydraulic pressure before lifting is set. The initial pressure of the cylinder is (P1 + ΔP). When the lattice mast is pulled forward when the heavy object is lifted and separated from the hydraulic cylinder, the hydraulic cylinder is extended by the internal pressure while the internal pressure is reduced from the initial pressure (P1 + ΔP) to the switching set pressure P1. When the internal pressure of the hydraulic cylinder reaches the switching set pressure P1, the switching valve is switched, pressure oil is supplied from the hydraulic pump to the hydraulic cylinder, and the hydraulic cylinder expands at an internal pressure that is less than the switching set pressure of the switching valve.
When the raising operation of the lattice mast is stopped and the hydraulic cylinder comes into contact with the lattice mast, the internal pressure of the hydraulic cylinder rises and reaches the switching set pressure P1. Then, the switching valve is switched, and the pressure oil is shut off from the hydraulic pump to the hydraulic cylinder. Since the hydraulic oil continues to be supplied from the hydraulic pump until the switching valve is switched after reaching the switching set pressure P1, the internal pressure when the switching valve is completely switched to Ps larger than the switching set pressure P1. It has become. Since the internal pressure when the hydraulic cylinder comes into contact with the lattice mast increases instantaneously, a lateral load is applied to the lattice mast with an internal pressure Ps larger than the switching set pressure P1.
In general, the switching set pressure P1 is preferably set based on the lateral load resistance of the lattice mast according to the compressive force acting on the lattice mast. However, since the internal pressure of the cylinder increases instantaneously as described above, the compressive force It is extremely difficult to control the increase in the cylinder internal pressure after calculating the above, and as a result, an excessive lateral load exceeding the lateral load resistance may be applied to the internal pressure Ps. That is, there is a risk that the lattice mast buckles when the internal pressure Ps exceeds the pressure that causes an excessive lateral load exceeding the lateral load resistance.

  The present invention was devised in view of such problems, and an object of the present invention is to provide a mobile crane capable of preventing a mast from being damaged by suppressing a lateral load by a mast backstop device against a lattice mast. It is in.

  The first feature of the mobile crane according to the present invention is that the lower traveling body, the upper swinging body that is pivotably mounted on the lower traveling body, and the upper swinging body are attached to be movable up and down. A boom, a mast that raises and lowers the boom, and a mast backstop device that functions as a curling stop for the mast, and the mastback stop device has one end attached to one of the upper swing body and the mast. A hydraulic cylinder having the other end capable of coming into contact with the upper revolving body or the other of the mast, a hydraulic pump for supplying pressure oil to the hydraulic cylinder, and disposed between the hydraulic pump and the hydraulic cylinder An electromagnetic switching valve for switching supply / cutoff of pressure oil from the hydraulic pump to the hydraulic cylinder, and communication between the electromagnetic switching valve and the hydraulic cylinder Based on the pressure detector for detecting the internal pressure of the cylinder side circuit and the detection result by the pressure detector, when the internal pressure of the cylinder side circuit is smaller than a predetermined switching set pressure, the hydraulic pump transfers to the cylinder side circuit. A controller that controls the electromagnetic switching valve to supply pressure oil to the cylinder side circuit when the internal pressure of the cylinder side circuit is larger than the switching set pressure while supplying pressure oil; and the cylinder In a mobile crane provided with a cylinder pressure control valve for releasing the pressure oil in the cylinder side circuit when the internal pressure of the side circuit exceeds a predetermined set pressure, the electromagnetic switching valve is disposed in the cylinder side circuit. The first accumulator is provided so that the internal pressure of the cylinder side circuit does not exceed the mast breakage pressure while switching from the supply of pressure oil to shut-off. That.

  According to this configuration, by carrying out heavy-duty ground cutting operations, the mast rises rapidly from the tilted position, stops the standing operation after separating from the hydraulic cylinder of the mast backstop device, and extends following the mast. Even if the hydraulic cylinder has collided, an increase in internal pressure in the cylinder side circuit communicating with the hydraulic cylinder is suppressed by the first accumulator, so that an excessive lateral load exceeding the lateral load resistance of the mast does not act. Specifically, when the hydraulic cylinder collides with the mast and the internal pressure of the cylinder side circuit rises to the switching setting pressure of the electromagnetic switching valve, the electromagnetic switching valve is switched to the cutoff state based on the detection result of the pressure detector. The internal pressure of the cylinder side circuit rises while reaching the switching set pressure and before the electromagnetic switching valve switches to the shut-off state, so that the pressure oil increases while accumulating in the first accumulator. Do not exceed pressure. Thereby, an excessive lateral load does not act on the mast, and the mast can be prevented from being damaged. The mast break pressure is the internal pressure of the cylinder side circuit corresponding to an excessive lateral load exceeding the lateral load resistance of the mast in a state where the compressive force is acting on the mast, and the compressive force acts on the mast. The pressure is smaller than the internal pressure of the cylinder side circuit corresponding to the lateral load resistance of the mast in the not-connected state.

  A second feature of the mobile crane according to the present invention is that the operating pressure is higher than that of the first accumulator, and the cylinder pressure control valve is released from the shutoff of pressure oil. The second accumulator is provided so that the internal pressure of the cylinder side circuit does not exceed the circuit breakage pressure during the switching to.

  Even if the electromagnetic switching valve is in the shut-off state, for example, when the suspended load is not lifted and blown by strong wind from the front of the machine, the mast backstop device has mast self-weight holding force + mast back tilting force due to strong wind. May be added. At this time, the internal pressure of the cylinder side circuit increases beyond the mast breakage pressure, and the pressure corresponding to the load tolerance limit of the mast that may cause damage to the hydraulic piping, the hydraulic cylinder, the mast itself, or the mast backstop itself ( Hereinafter, it is referred to as circuit break pressure). The set pressure of the cylinder pressure control valve is set lower than the circuit breakage pressure. However, when the load fluctuation due to strong wind is abrupt, the internal pressure of the cylinder side circuit is instantaneously caused by a delay in response of the cylinder pressure control valve. May exceed the set pressure of the cylinder pressure control valve. If the second accumulator is provided, even in this case, the pressure oil is effectively absorbed by the second accumulator, so that the pressure increasing speed is suppressed, the response delay of the cylinder pressure control valve is prevented, and the circuit breakage pressure is reduced. Can be prevented. Thereby, an excessive internal pressure does not act on the hydraulic circuit of the mast backstop device, and damage to the mastback stop device and the mast itself can be prevented. In addition, when the mast returns to the standing direction due to the reaction caused by the strong wind, the pressure oil accumulated in the second accumulator is released to the hydraulic cylinder in addition to the pump supply, so that the backstop follows. This will also ensure the sex.

  Note that the operating pressure of the first accumulator is less than the mast breakage pressure, and more preferably less than the switching set pressure of the electromagnetic switching valve. On the other hand, the operating pressure of the second accumulator is larger than the mast breakage pressure and less than the circuit breakage pressure, more preferably less than the set pressure of the cylinder pressure control valve. The capacity of each accumulator is set so that the pressure range in which the first accumulator easily accumulates pressure oil and the pressure range in which the second accumulator easily accumulates pressure oil do not overlap. When the capacity of each accumulator is set in this way, the predetermined pressure range that does not require delaying the internal pressure rise of the cylinder side circuit, that is, the pressure range involved in the mast breakage due to the lateral load, and the hydraulic circuit breakage due to the limit load By reducing the amount of pressure oil absorbed in a predetermined pressure range between the pressure ranges involved in the accumulator, the capacity of each accumulator can be reduced to save space.

  According to the present invention, even if heavy earthing operation is performed roughly, a strong lateral load is not applied to the mast by the mast backstop device, so that damage to the mast can be prevented.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is an overall view of a mobile counterbalance crane including a mast backstop device according to an embodiment of the present invention. The counterbalance type crane includes a crane body 1 and a weight carriage 2. The crane body 1 and the weight carriage 2 are connected by a connecting member 3. The crane body 1 includes a lower traveling body 4A having a crawler as traveling means, and an upper revolving body 4B that is rotatably mounted on the lower traveling body 4A.

  On the upper swing body 4B of the crane body 1, a boom 5 attached to the upper swing body 4B so as to be raised and lowered, and a mast 6 for raising and lowering the boom 5 are respectively provided with a boom foot pin 7 and a mast foot pin 8. The boom 5 and the top of the mast 6 are connected to each other by a boom guy line 9 and a boom hoisting rope 10, and the top of the mast 6 and the weight carriage 2 are connected by a carriage connecting cable 11. The boom 5 and the mast 6 are configured as long structures (so-called lattice boom and lattice mast) in which a large number of steel materials are assembled in a lattice shape. The upper swing body 4B also prevents the boom backstop device 12 that prevents the boom 5 from reversing, the mast support cable 13 provided between the mast 6 and the mast hoisting rope 14, and the mast 6 from reversing. A mast backstop device 15 is installed.

  The mast backstop device 15 is provided between the lower back surface of the mast 6 and the upper revolving body 4B, and supports the mast 6 from the rear to prevent its reversal, and functions as a curling stop for the mast 6. The hydraulic cylinder 17 has a rod portion 16 that can move forward and backward at one end.

  The hydraulic cylinder 17 is provided such that one end on the main body side is attached to the upper swing body 4B and the tip of the rod portion 16 at the other end can be brought into contact with the mast 6. The hydraulic cylinder 17 expands and contracts following the movement of the mast 6 and exerts a force against the reversal moment of the mast 6. Note that the tip of the rod portion 16 is not fixed to the mast 6, and can be brought into contact with the mast 6 to apply a biasing force, or can be separated from the mast 6.

  Next, a control circuit for the hydraulic cylinder 17 in the mast backstop device 15 will be described. FIG. 2 is a diagram showing a control circuit of the hydraulic cylinder 17 in the mast backstop device 15. The mast backstop device 15 shown in FIG. 1 is usually provided on both the left and right sides of the upper swing body 4B. However, for convenience of explanation, only one side is shown here, and only one hydraulic cylinder 17 is shown in FIG. Yes.

  As shown in FIG. 2, the control circuit of the hydraulic cylinder 17 includes the hydraulic pump 18, the electromagnetic switching valve 19, and the pressure oil pressure (cylinder side) in the cylinder-side circuit 20 between the electromagnetic switching valve 19 and the hydraulic cylinder 17. A pressure detector 21 that detects the internal pressure of the circuit 20, a controller 22 that switches and controls the electromagnetic switching valve 19 based on the detection result of the pressure detector 21, and two accumulators 23 and 24 installed in the cylinder side circuit 20. (First accumulator 23, second accumulator 24) and a cylinder pressure control valve 28 for regulating the upper limit of the internal pressure of the cylinder side circuit 20 are provided.

  The electromagnetic switching valve 19 is a two-position three-port switching valve and is disposed between the hydraulic pump 18 and the hydraulic cylinder 17. And the connection state A (state switched to the position shown by A in FIG. 2) which connected the pump side circuit 25 and the cylinder side circuit 20 to which pressure oil is supplied from the hydraulic pump 18, the pump side circuit 25 and the cylinder The connection with the side circuit 20 is cut off, and the state can be switched to the cutoff state B (the state switched to the position indicated by B in FIG. 2) in which the pump side circuit 25 is connected to the first relief circuit 26 connected to the tank 30. It is configured.

  The electromagnetic switching valve 19 is configured to be switched between the connection state A and the cutoff state B based on a signal from the controller 22 and to be in the cutoff state B in the non-energized state.

  A pump-side relief valve 29 is disposed between the pump-side circuit 25 and the first relief circuit 26. When the hydraulic pressure in the pump-side circuit 25 rises excessively, the pressure oil in the pump-side circuit 25 is discharged. It is configured so that it can be opened.

  The pressure detector 21 is installed in the cylinder side circuit 20 and is set to transmit a signal to the controller 22 when the internal pressure of the cylinder side circuit 20 becomes equal to or lower than a predetermined switching set pressure P1.

Here, when the hydraulic cylinder 17 is in contact with the mast 6, the internal pressure of the cylinder side circuit 20 communicating with the hydraulic cylinder 17 (that is, the internal pressure of the bottom chamber of the hydraulic cylinder 17) suddenly increases to a predetermined pressure. reached when, mast breakage pressure (mast lateral load resisting the predetermined pressure which will act on the mast 6 at contact portions of excessive lateral loads exceeding lateral load resisting property and the hydraulic cylinder 17 of the mast 6 Px ) . The switching set pressure P1 is set as a pressure smaller than the mast breakage pressure Px. In the present embodiment, the mast break pressure Px is about 5 MPa, and the switching set pressure P1 is set as about 4.3 MPa corresponding to a pressure of about 80% to 90% of the mast break pressure Px. The mast breakage pressure Px is a pressure smaller than the internal pressure of the cylinder side circuit 20 corresponding to the limit load of the mast 6.

  The controller 22 is set to switch the electromagnetic switching valve 19 to the connection state A when receiving a detection signal from the pressure detector 21 indicating that the internal pressure of the cylinder side circuit 20 is equal to or lower than a predetermined switching set pressure P1. ing. Further, when no signal is received from the pressure detector 21, that is, when the internal pressure of the cylinder side circuit 20 is larger than a predetermined switching set pressure P1, the electromagnetic switching valve 19 is set to be switched to the cutoff state B. . Thereby, it becomes possible to hold | maintain the internal pressure of the cylinder side circuit 20 more than switching setting pressure P1.

  When the internal pressure of the cylinder side circuit 20 becomes larger than a predetermined relief pressure P2 (set pressure) that is higher than the switching set pressure P1 that is the set pressure of the pressure detector 21, the cylinder pressure control valve 28 The relief valve opens the pressure oil in the circuit 20 to the second relief circuit 27 connected to the tank 30. The cylinder pressure control valve 28 can also be configured as an electromagnetic proportional relief valve that controls the pressure by a signal from the controller 22 based on the detection result by the pressure detector 21.

  The relief pressure P2 is increased when the mast 6 is blown by the wind from the front or tilted too much backward due to an erroneous operation, or when the carriage 2 is greatly lowered due to puncture of the tire of the weight carriage 2 or drop of the ground. When the cylinder 6 is moved largely rearward, the hydraulic cylinder 17 exhibits a large support force so that the mast 6 can be prevented from being reversed. The pressure is set to be smaller than the pressure at which the hydraulic cylinder 17 or the main body of the mast 6 may be damaged (hereinafter referred to as circuit damage pressure Py). In the present embodiment, the relief pressure P2 is set to about 12 MPa, for example.

  The first accumulator 23 is a gas load type that utilizes gas compressibility, and is configured such that the gas filling pressure P3 that is the lowest operating pressure is equal to or lower than the switching set pressure P1 that is the set pressure of the pressure detector 21. . In the present embodiment, the gas is sealed so that the gas filling pressure P3 is a pressure (about 1.3 MPa) that is about 3 MPa lower than the switching set pressure P1. Moreover, when the internal pressure of the cylinder side circuit 20 rises exceeding the switching set pressure P1, it is configured to accumulate at least pressure oil having a pressure equal to or higher than the switching set pressure P1. In addition, it is good not only as a gas load type accumulator but as a spring type accumulator using the elasticity of a spring.

  The second accumulator 24 is set such that the minimum operating pressure P4 is larger than the switching set pressure P1 of the electromagnetic switching valve 19 and smaller than the relief pressure P2 of the cylinder pressure control valve 28. Specifically, it is set as a pressure (about 10 MPa) smaller than the relief pressure P2 by about 2 MPa. Further, when the load of the mast 6 is applied to the hydraulic cylinder 17 and the internal pressure of the cylinder side circuit 20 tends to increase beyond the set pressure of the cylinder pressure control valve 28, the setting of the cylinder pressure control valve 28 is set. It is comprised so that the pressure oil of the pressure more than a pressure can be accumulate | stored at least.

  The first accumulator 23 is configured so that the pressure oil accumulation operation is not performed as simultaneously as possible with the pressure oil accumulation operation by the second accumulator 24. For example, the highest pressure (maximum operating pressure) in the pressure range in which the pressure oil in the first accumulator 23 can be effectively accumulated is set to be lower than the minimum operating pressure P4 of the second accumulator 24.

  Next, the operation of the mast backstop device 15 will be described. FIG. 3 is a diagram schematically showing a temporal change in the internal pressure of the cylinder side circuit 20 when the mast backstop device 15 is operated. In FIG. 3, the vertical axis represents the internal pressure P of the cylinder side circuit 20, the horizontal axis represents time t, and the hydraulic pressure change of the mast backstop device 15 according to the present embodiment is represented by the solid line X1, and a first accumulator as a comparative example is shown. A change in hydraulic pressure of the mast backstop device having the configuration without 23 is indicated by a broken line X2.

  When the mast 6 is erected, pressure oil is appropriately supplied from the hydraulic pump 18 to the hydraulic cylinder 17, and the hydraulic cylinder 17 is extended so as to follow the erection operation of the mast 6. The mast 6 in the normal working state is raised when the boom 5 is tilted forward in accordance with the lifting operation of the suspended load. However, an operation for lifting a heavy object from the ground, that is, a so-called ground cutting operation is performed in a rough manner. In the case of such a case, the standing operation of the mast 6 becomes faster. In this way, when the standing operation of the mast 6 is performed at a high speed, the extension of the hydraulic cylinder 17 cannot catch up, and the hydraulic cylinder 17 once extends away from the mast 6.

  As described above, when the mast 6 is erected, the hydraulic cylinder 17 is extended without receiving a load from the mast 6 (a load in a direction in which the hydraulic cylinder 17 is contracted). Therefore, the internal pressure of the cylinder side circuit 20 does not become higher than the switching set pressure P1 of the electromagnetic switching valve 19 (region up to time t1 in FIG. 3). In this case, a signal indicating that the internal pressure of the cylinder side circuit 20 is equal to or lower than the switching set pressure P1 is transmitted from the pressure detector 21 to the controller 22, and the controller 22 that receives the signal keeps the electromagnetic switching valve 19 in the connection state A. Accordingly, when the hydraulic oil is supplied from the hydraulic pump 18 to the hydraulic cylinder 17, the hydraulic cylinder 17 extends.

  The minimum operating pressure of the first accumulator 23 is set as a pressure larger than the internal pressure of the cylinder side circuit 20 when the hydraulic cylinder 17 extends following the standing operation of the mast 6. There is no pressure accumulation.

  When the standing motion of the mast 6 is stopped while the hydraulic cylinder 17 is extended (for example, when the ground cutting is completed), the tip of the rod portion 16 of the hydraulic cylinder 17 comes into contact with the mast 6 and the displacement of the rod portion 16 is changed. Is restrained. At this time, the internal pressure of the cylinder side circuit 20 is instantaneously increased by the pressure oil supplied from the hydraulic pump 18. In FIG. 3, the time when the tip of the rod portion 16 is in contact with the mast 6 is indicated by t1. Thereafter, when the internal pressure of the cylinder-side circuit 20 rises and reaches the gas charging pressure P3 of the first accumulator 23, pressure accumulation to the first accumulator 23 is started, and the hydraulic pressure rise speed decreases.

  When the internal pressure of the cylinder side circuit 20 increases at a low speed and reaches the switching set pressure P1, transmission of a signal from the pressure detector 21 to the controller 22 is stopped, and the electromagnetic switching valve 19 is shut off by the controller 22. Can be switched to. The following description will be made assuming that t2 time (see FIG. 3) is required until the switching of the electromagnetic switching valve 19 is completed.

  Here, the first accumulator 23 sets the mast breakage pressure Px between the start of the accumulation operation and the switching of the electromagnetic switching valve 19 to the shut-off state B based on the supply flow rate of the hydraulic oil from the hydraulic pump 18, for example. It is comprised so that it may have the capacity | capacitance which can accumulate | store the pressure oil of the pressure which does not exceed. As a result, the pressure is accumulated in the first accumulator 23 within the time t2 (see FIG. 3) from when the internal pressure of the cylinder side circuit 20 reaches the switching set pressure P1 until the switching of the electromagnetic switching valve 19 to the cutoff state B is completed. However, when the internal pressure of the cylinder side circuit 20 increases at a low speed and the switching to the cutoff state B is completed, the increase of the internal pressure of the cylinder side circuit 20 stops.

  Thus, while the electromagnetic switching valve 19 is switched from the connected state A to the shut-off state B, the pressure accumulation is performed by the first accumulator 23, so that the hydraulic pressure increase speed can be kept low, and the cylinder side circuit It can prevent that the internal pressure of 20 increases excessively. That is, as shown in FIG. 3, in this embodiment, when the mast 6 is erected, the internal pressure of the cylinder side circuit 20 does not exceed the mast breakage pressure Px, and the internal pressure is a pressure close to the switching set pressure P1. Is stopped. Thereby, it is possible to prevent a large lateral load from being applied to the mast 6 by the mast backstop device.

  On the other hand, as shown by the broken line X2 in FIG. 3, in the mast backstop device according to the comparative example having the configuration without the first accumulator 23, the standing operation of the mast 6 is stopped, and the rod in the hydraulic cylinder 17 is stopped at time t1. After the tip of the portion 16 comes into contact with the mast 6, the hydraulic pressure in the cylinder side circuit 20 and the hydraulic cylinder 17 is instantaneously increased to the switching set pressure P1 without decreasing the hydraulic pressure increase speed. After the internal pressure of the cylinder side circuit 20 reaches the switching set pressure P1, until the switching of the electromagnetic switching valve 19 to the cutoff state B is completed (during time t2), the cylinder side circuit 20 The internal pressure will rise. In this case, the urging force of the mast 6 by the mast backstop device may suddenly increase beyond the mast break pressure Px, and the mast 6 may be damaged.

  Next, in this embodiment, after the electromagnetic switching valve 19 is in the shut-off state B, the cylinder when a load (a load in a direction in which the hydraulic cylinder 17 contracts) is applied from the mast 6 to the mast backstop device 15. The internal pressure of the side circuit 20 will be described.

  When the load of the mast 6 is applied to the hydraulic cylinder 17 in the direction in which the hydraulic cylinder 17 contracts after the electromagnetic switching valve 19 enters the shut-off state B, the internal pressure of the cylinder side circuit 20 exceeds the mast breakage pressure Px. Will increase. In addition, when the compressive force is not acting on the mast 6, even if the internal pressure of the cylinder side circuit 20 exceeds the mast failure pressure Px, the mast 6 is not damaged.

  At this time, the internal pressure of the cylinder side circuit 20 first reaches the gas filling pressure P4 of the second accumulator 24, and then reaches the relief pressure P2 of the cylinder pressure control valve 28. Therefore, the hydraulic pressure increases while the pressure oil is accumulated in the second accumulator 24 from when the internal pressure of the cylinder side circuit 20 exceeds the relief pressure P2 until the cylinder pressure control valve 28 releases the pressure oil. The pressure increase rate is suppressed. That is, when the cylinder pressure control valve 28 shifts from the closed state to the open state, it is possible to reliably prevent the internal pressure of the cylinder side circuit 20 from exceeding the circuit breakage pressure Py. As a result, excessive internal pressure does not act on the hydraulic circuit of the mast backstop device, and damage to the mastback stop device can be prevented.

  As described above, the mast backstop device 15 for a mobile crane according to the present embodiment includes the hydraulic cylinder 17 having one end attached to the upper swing body 4B and the other end capable of contacting the mast 6, and the hydraulic pressure. A hydraulic pump 18 that supplies pressure oil to the cylinder 17, and an electromagnetic switching valve 19 that is disposed between the hydraulic pump 18 and the hydraulic cylinder 17 and switches supply / cutoff of pressure oil from the hydraulic pump 18 to the hydraulic cylinder 17. On the basis of the pressure detector 21 for detecting the internal pressure of the cylinder side circuit 20 and the detection result by the pressure detector 21, when the internal pressure of the cylinder side circuit 20 is smaller than the predetermined switching set pressure P1, the hydraulic pump 18 When pressure oil is supplied to the hydraulic cylinder 17 and the internal pressure of the cylinder side circuit 20 is larger than the switching set pressure P1, the hydraulic pump 18 supplies the hydraulic cylinder. 7 is disposed between the electromagnetic switching valve 19 and the hydraulic cylinder 17 to control the electromagnetic switching valve 19 so as to shut off the pressure oil, and when the internal pressure of the cylinder side circuit 20 exceeds a predetermined relief pressure P2, the pressure is increased. And a cylinder pressure control valve 28 for releasing oil.

  And it is arrange | positioned between the electromagnetic switching valve 19 and the hydraulic cylinder 17, and prevents the internal pressure of the cylinder side circuit 20 from exceeding the mast breakage pressure Px while the electromagnetic switching valve 19 switches from supply of pressure oil to cutoff. Between the first accumulator 23, the electromagnetic switching valve 19 and the hydraulic cylinder 17, the operating pressure is higher than that of the first accumulator 23, and the cylinder pressure control valve 28 is switched from shut-off of pressure oil to release. And a second accumulator 24 for preventing the internal pressure of the cylinder side circuit 20 from exceeding the circuit breakage pressure Py.

  According to this structure, by performing heavy earthing operations of heavy objects, the mast 6 rises rapidly from the backward tilted posture and stops the standing operation after being separated from the hydraulic cylinder 17 of the mast backstop device 15. Even if the hydraulic cylinder 17 that has extended following the collision collides, the increase in the internal pressure of the cylinder side circuit 20 is suppressed by the first accumulator 23, so that an excessive lateral load exceeding the lateral load resistance of the mast 6 is generated. Does not work.

  Specifically, when the hydraulic cylinder 17 collides with the mast 6 and the internal pressure of the cylinder side circuit 20 rises to the switching set pressure P1 of the electromagnetic switching valve 19, the electromagnetic switching valve 19 is shut off based on the detection result of the pressure detector 21. Switch to state. The internal pressure of the cylinder side circuit 20 rises while the hydraulic oil is accumulated in the first accumulator 23 until the electromagnetic switching valve 19 is switched to the shut-off state after reaching the switching set pressure P1, so the pressure increasing speed is suppressed. And does not exceed the mast break pressure Px. Thereby, an excessive lateral load does not act on the mast 6, and the mast 6 can be prevented from being damaged.

  On the other hand, when a load from the mast 6 side is applied to the hydraulic cylinder 17 after the electromagnetic switching valve 19 is cut off, the internal pressure of the cylinder side circuit 20 increases beyond the mast breakage pressure Px, and the cylinder side It approaches the circuit breakage pressure Py corresponding to the limit load of the mast 6 where the hydraulic piping such as the circuit 20 or the hydraulic cylinder 17 may be broken. Although the relief pressure P2 of the cylinder pressure control valve 28 is set lower than the circuit breakage pressure Py, the internal pressure of the cylinder side circuit 20 exceeds the relief pressure P2 of the cylinder pressure control valve 28, and the cylinder pressure control valve 28 Before the pressure oil is released, the pressure oil rises while being accumulated in the second accumulator 24, so the pressure increasing speed is suppressed and the circuit breakage pressure Py is not exceeded. Thereby, an excessive internal pressure does not act on the hydraulic circuit of the mast backstop device 15, and the mastback stop device 15 can be prevented from being damaged.

  Further, the volume of the first accumulator 23 is such that at least the pressure oil supplied from the hydraulic pump 18 is changed until the electromagnetic switching valve 19 is switched to the cutoff state B after the internal pressure of the cylinder side circuit 20 exceeds the minimum operating pressure. It is determined so that it can be accumulated. That is, the first accumulator 23 is configured such that the maximum operating pressure is greater than the switching set pressure P1. It should be noted that even when the internal pressure of the cylinder side circuit 20 rises larger than the switching set pressure P1, the maximum operating pressure is about 2 MPa or more larger than the switching set pressure P1 so that the pressure oil can be accumulated more reliably. Desirably configured.

  In addition, the cylinder pressure control valve 28 that controls the maximum pressure of the cylinder side circuit 20 can regulate the maximum pressure of the hydraulic cylinder 17 to a desired pressure, thereby making the force against the reversal moment of the mast 6 constant. It can be regulated.

  Further, a second accumulator 24 is provided in the cylinder side circuit 20 and has a minimum operating pressure set larger than the switching set pressure P1 and smaller than the relief pressure P2 of the cylinder pressure control valve 28. In the present embodiment, the minimum operating pressure of the second accumulator 24 is set as a pressure close to the relief pressure P2 of the cylinder pressure control valve 28 (about 80% of the relief pressure P2). It becomes possible to reduce the internal pressure fluctuation of the cylinder side circuit 20 due to the external force.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made as long as they are described in the claims.

(1) The minimum operating pressure of the first accumulator is not limited to the switching set pressure P1 or less of the electromagnetic switching valve. The minimum operating pressure is less than the switching set pressure P1 within a range smaller than the mast breakage pressure Px. You may set large. In this case, since the capacity of the first accumulator can be further reduced, space saving can be achieved.

(2) The relief pressure is not limited to the case where the minimum operating pressure P4 of the second accumulator is set to be equal to or lower than the relief pressure P2 of the cylinder pressure control valve 28, and the relief pressure is within a range smaller than the circuit breakage pressure Py. You may set larger than P2. In this case, since the capacity of the second accumulator can be further reduced, space saving can be achieved.

(3) One end of the hydraulic cylinder 17 may be fixed to the mast 6 and the other end may be provided so as to be in contact with the upper swing body 4B.

(4) The present invention is not limited to the counterbalance type crane in which the counterweight is suspended from the rear end of the upper swing body 4B with a predetermined distance rearward, but also to a standard crane in which the counterweight is mounted on the rear portion of the upper swing body 4B. The mast backstop device of can also be applied.

1 is an overall view of a counterbalance crane according to an embodiment of the present invention. It is a figure which shows the control circuit of the hydraulic cylinder in the mast backstop apparatus shown in FIG. It is a figure which shows typically the change of the hydraulic pressure of the cylinder side circuit at the time of the action | operation of a mast backstop apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Crane main body 4A Lower traveling body 4B Upper revolving body 5 Boom 6 Mast 15 Mast back stop device 16 Rod part 17 Hydraulic cylinder 18 Hydraulic pump 19 Electromagnetic switching valve 21 Pressure detector 22 Controller 23 1st accumulator 24 2nd accumulator 28 Cylinder pressure Control valve

Claims (1)

A lower traveling body, an upper revolving body that is pivotably mounted on the lower traveling body, a boom that is undulated with respect to the upper revolving body, a mast that raises and lowers the boom, It has a mast backstop device that functions as an anti-friction,
The mast backstop device is
A hydraulic cylinder having one end attached to one of the upper swing body or the mast and the other end provided so as to be in contact with the other of the upper swing body or the mast;
A hydraulic pump for supplying pressure oil to the hydraulic cylinder;
An electromagnetic switching valve that is disposed between the hydraulic pump and the hydraulic cylinder and switches supply / shutoff of pressure oil from the hydraulic pump to the hydraulic cylinder;
A pressure detector for detecting an internal pressure of a cylinder side circuit communicating between the electromagnetic switching valve and the hydraulic cylinder;
Based on the detection result by the pressure detector, when the internal pressure of the cylinder side circuit is smaller than a predetermined switching set pressure, pressure oil is supplied from the hydraulic pump to the cylinder side circuit, while the internal pressure of the cylinder side circuit A controller that controls the electromagnetic switching valve to shut off pressure oil from the hydraulic pump to the cylinder side circuit when the pressure is greater than the switching set pressure;
In the mobile crane provided with a cylinder pressure control valve that releases the pressure oil of the cylinder side circuit when the internal pressure of the cylinder side circuit exceeds a predetermined set pressure,
A first accumulator which is disposed in the cylinder side circuit and prevents the internal pressure of the cylinder side circuit from exceeding the mast lateral load resistance overpressure while the electromagnetic switching valve is switched from supply of pressure oil to cutoff ;
The cylinder side circuit is disposed in the cylinder side circuit, has a higher operating pressure than the first accumulator, and the internal pressure of the cylinder side circuit reduces the circuit breakage pressure while the cylinder pressure control valve is switched from shut-off of pressure oil to release. A mobile crane , comprising: a second accumulator that does not exceed the second accumulator .

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