JP2005104625A - Overturn preventive control device of working vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an overturn preventive control device of a working vehicle capable of reliably preventing the overturn of a vehicle body caused by excessive load on a tip part of a working machine. <P>SOLUTION: The overturn preventive control device comprises a relief means (35) which is connected to a cylinder chamber (9b) under the holding pressure of a hydraulic cylinder (9) to vertically drive a working machine and relieves oil in the cylinder chamber (9b) at the pressure lower than the relief pressure during a regular work of the hydraulic cylinder (9) under the command from the outside, a vehicle body inclination angle detector (42) to detect the angle of inclination in the predetermined direction of a vehicle body, and a controller (42) to output the relief command to the relief means (35) when the detected angle of inclination of the vehicle body is not lower than a predetermined value. The relief means (35) comprises a relief valve (36) which is connected to the cylinder chamber (9b) and set to the pressure lower than the relief pressure during the regular work, and a solenoid valve (37) which is disposed between the relief valve (36) and a tank (40) and opened/closed under the relief command of the controller (42). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a work vehicle overturn prevention control device that can reliably prevent overturn due to an excessive load when an overload is applied to a work machine of the work vehicle such as a hydraulic excavator.

  2. Description of the Related Art Conventionally, as an overhead wire collector, one using a work vehicle such as a hydraulic excavator as described in Patent Document 1, for example, is known. FIG. 10 shows the configuration of the overhead wire collector described in Patent Document 1. In FIG. 10, the hydraulic excavator main body 71 is provided with an upper swinging body 73 rotatably on an upper part of a lower traveling body 72, and a work implement 74 is attached to the upper swinging body 73 so as to be swingable in a vertical plane. In the work machine 74, a boom 76, an arm 78, and a grapple 80 for gripping timber are sequentially connected. These work machines are respectively moved in a vertical direction by a boom cylinder 75 and in a front-rear direction by an arm cylinder 77. Further, the bucket cylinder 79 swings instead of the bucket.

Two winches 82HAL and 82HBL are mounted as a double winch on a winch mounting base 81 on the side surface of the upper swing body 73. Wire rope 88HAL as one striated body unwound from one winch 82HAL
Is pulled out via a lower pulley 89a attached to the tip of the arm 78 of the working machine 74. In addition, the wire rope 88HBL as the other cable body unwound from the other winch 82HBL
Is pulled out through an upper pulley 89 b attached to the tip of the arm 78.

  The wire rope 88HBL is wound around a pulley 93 tied by a wire rope 92 around a standing tree 91 as a stationary object located at a remote place, and a tip portion folded back through the pulley 93 is connected to a carriage 94. Yes.

  The carriage 94 has two pulleys 95 and 95 attached to the upper part and one pulley 96 attached to the lower part so as to be rotatable. The upper pulleys 95 and 95 are mounted on a wire rope 88HBL stretched on the upper side. It is movably engaged. Further, the lower wire rope 88HAL is wound around a pulley 96 below the carriage 94 and suspended downward, and a lumber 98 as a load is lifted by a hook 97 attached to the tip thereof. The hook 97 is hooked on the mounting wire 99 of the timber 98.

  In a state where the lumber 98 is suspended by the hook 97, one of the two winches 82HAL and 82HBL is driven in synchronism with the wire winding side and the other with the wire unwinding side, thereby driving the lumber 98 in a predetermined manner. Transport to position and gather.

  By the way, the gathering machine as described above is not only used on a flat ground, but is often used in a valley of a mountainous area as shown in FIG. 11, for example. (Kiguchi) is lifted and the other end is slid on the ground (usually called “hana”) so that the total weight of the timber is not hung on the wire ropes 88HAL and 88HBL. However, there is a case where the lower end side of the timber 98 slides down on a steep slope during transportation, and thus the wire ropes 88HAL and 88HBL may be overloaded suddenly. At this time, if the boom 76 and the arm 78 of the hydraulic excavator main body 71 are in a high upward position, the tension due to the excessive load applied to the wire ropes 88HAL and 88HBL generates a moment in a direction that causes the hydraulic excavator to fall to the valley side. In the unlikely event that the overturning moment due to the wire tension exceeds the stability moment in the direction in which the excavator main body 71 is stationary, the excavator will overturn.

  As a fall prevention device for preventing a fall of the hydraulic excavator when a work vehicle such as a hydraulic excavator works on a slope in a mountainous area as described above, for example, a fall alarm device for a construction machine described in Patent Document 2 is provided. Are known. This overturn warning device is provided with an inclination angle detection device for detecting an inclination angle in a predetermined direction of the lower traveling body on the lower traveling body of the excavator, and a detection angle detected by the inclination angle detection device and a predetermined setting are provided. An alarm device such as a buzzer is operated to warn an operator when it is determined that the detected angle is equal to or greater than the set angle by comparing with the angle.

  However, even if the above-mentioned fall prevention device is mounted on a work vehicle such as a hydraulic excavator used as a gathering machine as described above, the operation timing of the operator even if the alarm device issues an alarm when the vehicle body tilts more than a set angle There is a risk that the fall will not be reliably prevented. In addition, even if the operator lowers the work implement (boom, arm, etc.) via the hydraulic circuit by operating the lever after the alarm sounds, the work implement drive speed during normal lever operation is slow, There is a possibility that the fall cannot be prevented because the speed at which the stable moment for returning the vehicle body to the original stable posture increases is slower than the speed at which the fall moment decreases as the work machine is lowered.

Japanese Patent Laid-Open No. 2001-63967 (page 4, FIG. 2) JP-A-60-199130 (page 3-4, FIG. 6-10)

  The present invention has been made paying attention to the above-mentioned problems, and an object thereof is to provide a work vehicle overturn prevention control device that can reliably prevent the vehicle body from overturning due to an excessive load applied to the end of the work implement. Yes.

In order to achieve the above object, the first invention provides:
In a work vehicle in which a work machine that moves up and down by expansion and contraction of a hydraulic cylinder is provided at the upper part of the vehicle body, and a work is performed by applying a load to the tip of the work machine
The cylinder chamber is connected to a cylinder chamber that receives the holding pressure of the hydraulic cylinder for driving the work implement, and receives oil from the cylinder chamber with a relief pressure lower than the relief pressure during normal operation of the hydraulic cylinder in response to an external command. Relief means for relief,
A vehicle body tilt angle detector for detecting a tilt angle of the vehicle body in a predetermined direction;
A controller is provided that outputs a command to the relief means when the vehicle body inclination angle detected by the vehicle body inclination angle detector exceeds a predetermined value, thereby reducing the holding pressure of the hydraulic cylinder.

In this case, the second invention provides the relief means,
A relief valve that is connected to a cylinder chamber that receives the holding pressure of the hydraulic cylinder and is set to a relief pressure lower than a relief pressure during normal operation of the hydraulic cylinder;
It is preferable to provide an electromagnetic on-off valve that is provided between the relief valve and the tank and that opens and closes in response to a command from the controller.

In this case, the third invention provides the relief means,
Provided between the cylinder chamber that receives the holding pressure of the hydraulic cylinder and the tank, and a relief pressure that is lower and higher than the relief pressure during normal operation of the hydraulic cylinder is switched in response to an external command. A two-stage relief valve set to be possible,
In response to a command from the controller, the two-stage relief valve is preferably provided with a relief pressure switching means for outputting a command to switch to a low set relief pressure.

A fourth invention is the first, second or third invention, wherein the work vehicle is
Two winches are mounted on the vehicle body in the vicinity of the base of the work machine that can move up and down,
A plurality of pulleys are provided at the tip of the working machine,
Of the two wire ropes wound around each of the two winches, one wire rope is connected to any one of a plurality of pulleys at the tip of the work implement and a standing tree positioned far from the vehicle. Connect to the first jig via the pulley attached to the column,
A second wire rope is used to lift the timber to be transported via at least one other pulley of the plurality of pulleys at the tip of the work machine and the pulley connected to the first jig. Connected to the jig
The two winches are characterized by being a gathering machine that transports the timber by controlling the wire winding and unwinding speeds in synchronization with each other.

Further, the fifth aspect of the invention drives a working machine provided at the top of the vehicle body so as to freely move up and down by extending and contracting a hydraulic cylinder,
Work by applying a load to the tip of the work machine,
In the work vehicle overturn prevention method for preventing the vehicle body from overturning when an overload is applied,
Detect the tilt angle of the vehicle body in a predetermined direction,
When the detected inclination angle is equal to or greater than a predetermined value, the oil in the cylinder chamber that receives the holding pressure of the hydraulic cylinder is relieved to reduce the holding pressure,
The work machine is lowered by the load.

  According to the first or fifth invention, when an overload is applied to the work implement and it starts to overturn, the holding pressure of the hydraulic cylinder for driving the work implement is automatically forcedly relieved and lowered. As the work implement descends, the overturning moment decreases and the stability moment of the vehicle body increases. At this time, by increasing the oil flow rate at the time of relief of the work implement holding pressure and increasing the work implement descending speed, the stability moment becomes larger than the fall moment before reaching the vehicle body fall limit angle. , Can reliably prevent the fall. Further, since the work implement is automatically lowered without the operator's operation, there is no operation delay, the work implement lowering can be started at an early stage of the start of the fall, and the vehicle body can be reliably prevented from falling.

  According to the second or third invention, the holding pressure of the hydraulic cylinder can be reliably relieved by a simple hydraulic circuit configuration.

  In addition, according to the fourth invention, when applied to an overhead wire gathering machine, an increase in wire rope tension due to a sudden excessive load caused by sliding of timber in the gathering caused a tipping moment of the work vehicle. Even in this case, the vehicle body can be reliably prevented from falling.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an explanatory diagram of a material collector according to the first embodiment. In FIG. 1, the gathering machine includes two winches 13 and 14 and two pulleys 15 and 16 in a work vehicle 1 such as a hydraulic excavator. The work vehicle 1 includes a lower traveling body 2 (crawler type in the drawing) having a crawler traveling apparatus or a wheeled traveling apparatus with an outrigger, and an upper turn mounted on the upper portion of the lower traveling body 2 so as to freely pivot. And a cab 4 on the left and right sides (left side in the figure) of the front part, and in a vertical plane on the side of the cab 4 (right side in the figure). A work machine 5 is provided so as to freely swing. In the work machine 5, the boom 6, the arm 7, and the bucket 8 are connected in such a manner as to be swingable in the vertical direction and the front-rear direction, and are driven by expansion and contraction of the boom cylinder 9, the arm cylinder 10, and the bucket cylinder 11, respectively.

  The first winch 13 is provided on the lower side and the second winch 14 is provided on the upper side on the left and right other sides (the right side of the boom 6 in the figure) of the front part of the upper swing body 3. It is to be driven by. Although not shown, an operation lever for operating the cylinders 9, 10, 11 and the winches 13, 14 is provided inside the cab 4.

  The two pulleys 15 and 16 are attached to the lower end of the tip of the arm 7, and the two wire ropes 17a and 17b respectively unwound from the first and second winches 13 and 14 are respectively It is connected to the outside via pulleys 15 and 16.

  Further, a pulley 20 is connected via a slinger 19 to a column 18 made of a standing tree (referred to as a front pole) or the like located far from the work vehicle 1. The wire rope 17 b unwound from the second winch 14 is connected to the shackle 21 to which the pulley 24 is connected via the pulley 16 and the pulley 20. The shackle 21 is connected to a pulley 22 that is rotatably provided on a wire rope 17 b between the pulley 16 and the pulley 20. The wire rope 17a unwound from the first winch 13 is connected to a shackle 26 to which a latch 27 is attached via the pulley 15 and the pulley 24. A ring-shaped stopper 25 is inserted in the wire rope 17a between the pulley 24 and the shackle 26. A wire tied around the lumber 28 is suspended from the latch 27.

  When transporting the timber 28 from the timber cutting site such as a valley to the accumulation site where the collector 1 is located, the first winch 13 slightly wraps the wire rope 17a, lifts only one side of the timber 28, and The other side is brought into contact with the ground, and while maintaining this state, the winding speed of the wire rope 17a by the first winch 13 and the unwinding speed of the wire rope 17b by the second winch 14 are synchronized with each other. The rotational speeds of the first and second winches 13 and 14 are controlled so as to be driven. Alternatively, when transporting in a valley, the winding amount and the unwinding amount of each of the wire ropes 17a and 17b are adjusted, and the timber 28 is suspended in a state of floating in the air. The winding speed of the wire rope 17a by the winch 13 and the unwinding speed of the wire rope 17b by the second winch 14 may be driven in synchronization with each other. As a result, the pulley 22 is rolled onto the wire rope 17b while the tension of the wire rope 17b is adjusted to a predetermined level so as not to be excessively tensioned, and the pulley 24 is suspended from the lumber 28 while the work vehicle 1 is suspended. Be drawn towards.

  FIG. 2 is a circuit diagram of the control device of the first embodiment. In FIG. 2, the pressure oil discharged from the hydraulic pump 30 is supplied to the boom cylinder 9 via the switching valve 31 and the pipe lines 38 and 39. When the switching valve 31 is switched to the A position (boom raising side), the pressure oil flows into the bottom chamber 9b of the boom cylinder 9 via the pipe line 38, and the oil flowing out of the head chamber 9a flows into the pipe line 39 and the switching valve. Drain to the tank 40 via 31. When the switching valve 31 is switched to the B position (boom lowering side), the pressure oil flows into the head chamber 9a of the boom cylinder 9 via the conduit 39, and the oil that flows out of the bottom chamber 9b flows into the conduit 38 and Drain to the tank 40 via the switching valve 31.

  A pipe line connecting the hydraulic pump 30 and the switching valve 31 is connected to the tank 40 via a relief valve 32. Note that a check valve 41 capable of inflow of oil from the tank 40 to the head chamber 9a side is connected to the pipe line 39. Since the speed of surrounding by the dead weight of the boom 6 is high when the boom is lowered, the check valve 41 The oil is made to flow in an auxiliary manner into the head chamber 9a.

  The pipe line 38 connected to the bottom chamber 9b is connected to the tank 40 via a parallel circuit of a relief valve 33 and a check valve 34 set to a predetermined pressure. The pipe line 38 is connected to the tank 40 via a relief means 35 comprising a series circuit of a relief valve 36 and an electromagnetic on-off valve 37. The first relief valve 33 is set to a relief pressure for protecting these hydraulic devices when an excessive load is applied to the boom cylinder 9 and an excessive pressure is generated in the bottom chamber 9b. The second relief valve 36 is set to a relief pressure lower than the relief pressure during normal operation in the boom cylinder 9 (<relief pressure of the first relief valve 33).

  The work vehicle 1 is also provided with a vehicle body inclination angle detector 42 that detects an inclination angle in a predetermined direction (usually the vehicle longitudinal direction, which is the swinging direction of the work machine 5 when performing the gathering work). . In the present embodiment, the vehicle body inclination angle detector 42 is constituted by an inclination switch that turns on an output contact signal when the inclination angle is equal to or larger than a preset setting angle. An operation current is supplied to the solenoid portion 37 a of the electromagnetic on-off valve 37 through the output contact of the vehicle body inclination angle detector 42.

  The vehicle body inclination angle detector 42 is not limited to the inclination switch. That is, a vehicle body tilt angle detector 42 that measures the vehicle body tilt angle is used, and a controller (not shown) compares the measured vehicle body tilt angle with a predetermined set angle, and the electromagnetic on-off valve 37 is based on the comparison result. An operation current command may be output to the solenoid unit 37a. That is, in this embodiment, the tilt switch itself of the vehicle body tilt angle detector 42 also has a function as a controller.

Next, the operation of the above configuration will be described with reference to FIG. FIG. 3 is an explanatory diagram of the operation of the present invention.
When collecting work by the gathering machine, first, the boom cylinder 9 is extended and the arm cylinder 10 and bucket cylinder 11 are reduced in order to raise the boom 6, the arm 7 and the bucket 8 to the vicinity of the rising end. Next, with the timber 28 suspended, the first winch 13 and the second winch 14 are driven by a predetermined amount, and the hanging angle α of the wire ropes 17a, 17b is set to a predetermined value (in the example shown in FIG. α1.) Adjustment is performed to adjust the tension of the wire ropes 17a and 17b to a predetermined value or less. In addition, the said drooping angle refers to the angle which the line which connects between the pulleys 15 and 16 on the work vehicle side, and the pulley 20 on the standing tree 18 side, and the wire ropes 17a and 17b, as shown in FIG.

  Next, the timber 28 is transported to the work vehicle 1 side by controlling the rotation speed of the first winch 13 and the second winch 14 in synchronization. At this time, the tension of the wire ropes 17a and 17b is kept below a predetermined value.

  However, as described above, when an excessive load is applied to the wire ropes 17a and 17b due to the sliding of the timber 28, an excessive tension exceeding a predetermined allowable value is suddenly generated in the wire ropes 17a and 17b. A moment due to this excessive tension acts on the overturning side of the work vehicle 1. At this time, since the distance L1 from the overturning fulcrum is large when the boom is initially at a higher position than the balance with the stability moment of the vehicle body, the allowable load for overturning (hereinafter referred to as the overturning allowable load) is small. That is, when the overturning moment due to the excessive tension is larger than the vehicle body stability moment (moment for returning work vehicle 1 to a stable posture), work vehicle 1 starts to tilt. When the vehicle body inclination angle exceeds a predetermined value, the output contact of the vehicle body inclination angle detector 42 is turned on, and an operation current is supplied to the solenoid portion 37a of the electromagnetic on-off valve 37. Switches to the open position (position A in the figure).

  At this time, since the holding pressure of the bottom chamber 9b of the boom cylinder 9 is larger than the set relief pressure of the relief valve 36, the oil in the bottom chamber 9b is tanked via the relief valve 36 of the relief means 35 and the electromagnetic on-off valve 37. Relief to 40. Then, as shown in FIG. 3, since the boom 6 is pulled by excessive tension and is lowered downward at a predetermined speed, the hanging angle α2 of the wire ropes 17a, 17b at this time gradually increases, and accordingly, the tension P2 Becomes smaller. Further, when the boom 6 is lowered, the distance L2 from the overturning fulcrum becomes small, so the overturning allowable load becomes large. As a result, the allowable fall load is greater than the wire tension (load). That is, the stability moment of the work vehicle 1 becomes larger than the fall moment due to the wire tension, and the work vehicle 1 stops tilting and returns to the original stable posture (installation position), so that the fall is prevented.

  FIG. 4 shows the movement of the work machine 5 when the relief valve 36 is relieved. According to the applicant's confirmation test, when the relief valve 36 was relieved at the rising end of the boom 6, the work implement 5 was lowered to the horizontal level position after about 1 second. At this time, it was confirmed that the tension of the wire ropes 17a and 17b at the boom rising end was reduced to about 50 KN (5 tons) after one second.

For comparison, FIG. 5 shows the motion of the working machine when the vehicle falls over in the conventional case (when there is no forced relief of the bottom chamber pressure of the boom cylinder 9). According to FIG. 5, when a fall moment due to excessive tension is generated at a position where the boom 6 is at the ascending end as a result of testing on a vehicle of the same class as the work vehicle of the confirmation test shown in FIG. It was found that the car body tilted to about 35 degrees, the limit of car body fall, after 2 seconds. The tension applied to the wire ropes 17a and 17b was about 78 KN (7.8 tons) at the start of the inclination, but about 64 KN (6.4 tons) after 1 second and about 42 KN (4.2 tons) after 2 seconds. After about 27KN (2.7 tons)
) And decreases as the boom 6 descends. However, the vehicle body holding force to return the vehicle body to the original horizontal posture (stable posture) is about 34.5 KN (3.45 tonnes) at the start of inclination in terms of wire rope tension.
What was present was about 33.5 KN (3.35 tons) after 1 second, and about 28.9 KN (2.89 tons) after 2 seconds, and about 15.2 KN (1.52 tons) after 3 seconds. . As can be seen from this result, in the conventional case, when the vehicle body begins to tilt, the wire tension decreases, but since it is always greater than the vehicle body holding force, it can be understood that the vehicle eventually falls.

  Comparing the data in FIG. 4 and FIG. 5, even if the overturning moment increases due to the sudden excessive tension generated by the timber sliding down, the speed at which the body tilts for the first 3 seconds is Although it is slow (it takes about 3.2 seconds until the overturn limit angle), when the hydraulic pressure in the bottom chamber 9b of the boom cylinder 9 according to the present invention is relieved via the relief valve 36, the boom 6 is lowered by the wire tension. It can be seen that the speed is faster than the vehicle body tilt speed. Therefore, if the action of lowering the boom 6 is taken at the initial stage of the body tilt, for example, within about 2 seconds after the start of the tilt and / or when the tilt angle is about 10 degrees or less, the tilt can be sufficiently followed. I understood. At this time, the hanging angle of the wire ropes 17a and 17b is increased by lowering the boom, the wire tension is reduced, and the overturning moment is reduced. Furthermore, since the distance L1 from the fall fulcrum is large when the boom is initially at a higher position than the balance with the stability moment of the vehicle body, the stability moment becomes larger than the fall moment before reaching the fall limit angle. The boom lowering speed, that is, the flow rate of draining via the relief valve 36 may be set.

  FIG. 6 is a graph showing this state. The horizontal axis in FIG. 6 represents the boom angle in the downward direction when the boom rising end angle is 0 degree, and the vertical axis represents the wire tension. The solid curve represents the wire tension that contributes to the overturning moment, the alternate long and short dash line curve represents the vehicle body stability moment according to the present invention converted to the wire tension, and the dashed curve represents the conventional vehicle body. This shows the moment converted to wire tension. According to FIG. 6, when the boom 6 is lowered by relieving the hydraulic pressure in the bottom chamber 9 b of the boom cylinder 9, the boom angle increases, and the vehicle body stability moment is the wire tension at an angle smaller than the vehicle body fall limit angle. Because it exceeds the falling moment due to, it can be returned to its original stable posture before the vehicle falls.

  Next, based on FIG. 7, the circuit of the control apparatus of 2nd Embodiment is demonstrated. In addition, the same code | symbol is attached | subjected to the structure which has a function substantially the same as the structure in FIG. 2 of above-mentioned 1st Embodiment, and the following description is abbreviate | omitted. In this embodiment, instead of the relief valve 36 and the electromagnetic on-off valve 37, a pipe 38 connected to the bottom chamber 9 b of the boom cylinder 9 is connected to the tank 40 via a pilot-type two-stage relief valve 44. The pilot oil discharged from the pilot hydraulic pump 46 is supplied to the pilot operating portion 44 a of the two-stage relief valve 44 via the electromagnetic switching valve 45. Here, the relief means 35 is constituted by the two-stage relief valve 44, the electromagnetic switching valve 45 and the pilot hydraulic pump 46. An operation current is input to the solenoid operation portion 45 a of the electromagnetic switching valve 45 via the output contact of the vehicle body inclination angle detector 42.

  The two-stage relief valve 44 is set so that the relief pressure is slightly higher than the circuit pressure when the pilot pressure is not applied to the pilot operating portion 44a, and when the pilot pressure is applied to the pilot operating portion 44a, the relief pressure is The relief pressure is set lower than the holding pressure at which the normal working machine 5 is held by the cylinder 9.

The operation according to the configuration of the second embodiment will be described. In addition, the operation | movement by a structure different from 1st Embodiment is demonstrated here.
As described above, when the timber 28 slides down and the like, the wire ropes 17a and 17b suddenly generate excessive tension exceeding a predetermined allowable value, and when the overturning moment due to the excessive tension is larger than the stable moment of the work vehicle 1, The vehicle 1 begins to tilt. When the inclination angle becomes equal to or greater than a predetermined value, the output contact of the vehicle body inclination angle detector 42 is turned on, and an operation current is supplied to the solenoid operation portion 45a of the electromagnetic switching valve 45. Is switched to the A position shown in the drawing, whereby the pilot oil from the pilot hydraulic pump 46 is supplied to the pilot operating portion 44 a of the two-stage relief valve 44.

  Then, since the two-stage relief valve 44 is set to a relief pressure lower than the normal holding pressure of the boom cylinder 9, the oil in the bottom chamber 9 b of the boom cylinder 9 passes through the two-stage relief valve 44 and the tank 40. To drain the pressure in the bottom chamber 9b. For this reason, the working machine 5 is pulled down by the tension of the wire ropes 17a and 17b, and starts to descend at a predetermined speed. As a result, as in the first embodiment, the tension of the wire ropes 17a and 17b is reduced, the falling moment is reduced, and the vehicle body stability moment is increased, so that the vehicle body is prevented from falling.

  Next, the circuit of the control device of the third embodiment will be described with reference to FIG. In the present embodiment, a single two-stage relief valve 48 is provided by using both the relief valve 33 and the two-stage relief valve 44 of FIG. Here, the relief means 35 is constituted by the two-stage relief valve 48, the electromagnetic switching valve 45 and the pilot hydraulic pump 46. A check valve 34 is provided in parallel with the two-stage relief valve 48. When the pilot pressure from the electromagnetic switching valve 45 is not applied to the pilot operating portion 48a, the two-stage relief valve 48 is a relief for protecting the hydraulic equipment from an excessive pressure in the same manner as the relief valve 33. When the pilot pressure is applied to the pilot operating portion 48a, the relief pressure is set to a relief pressure lower than the holding pressure at which the normal working machine 5 is held by the boom cylinder 9.

  Since the operation according to the configuration of the present embodiment is substantially the same as that of the second embodiment by replacing the two-stage relief valve 44 in the second embodiment with the two-stage relief valve 48, description thereof is omitted here.

  In the above embodiment, a gathering machine is given as an example of a work vehicle, and a gathering machine of a type in which timber is suspended via a latch 27 attached to the tip of the first wire rope 17a as shown in FIG. However, the application range of the present invention is not limited to this method. For example, as shown in FIG. 9, both ends of the first wire rope 52a are endlessly connected to the shackle 26 provided with the latch 27, and the first wire rope 52a is endlessly attached to the first winch 51 mounted on the work vehicle. Of course, the present invention can also be applied to a wound product.

  9 will be described in detail. A first winch 51 having an endless drum on the lower side, a second winch on the upper side, and a second winch on the upper side of the upper swing body 3 of the work vehicle 1 such as a hydraulic excavator. A winch 14 is mounted, and pulleys 15 a, 15 b and 16 are attached to the lower end of the arm 7 of the work machine 5. The wire rope 52b unwound from the second winch 14 is connected to the shackle 21 to which the pulley 55 is connected via the pulley 16 and the pulley 20 on the standing tree 18 side. A weight 56 is suspended from the pulley 55 so that the endless wire rope 52a wound around the pulley 55 is not twisted. The wire rope 52a wound endlessly around the first winch 51 has one end 53 connected to one side of the shackle 26 to which the latch 27 is attached via the pulley 15a. An end portion 54 is connected to the other side of the shackle 26 via the pulley 15 b and the pulley 55. The shackle 26 is connected to a pulley 57 that rolls on a wire rope 52b between the pulley 16 and the pulley 20, and a pulley 58 that rolls on a wire rope 52a between the pulley 15b and the pulley 55. Has been.

  When transporting timber with the timber having this structure, the tension of the wire rope 52b is adjusted by the second winch 14, and the wire rope 52a is driven endlessly by the first winch 51 to determine the transport direction and speed of the timber. I have control.

  The present invention can also be applied to a work vehicle (so-called arm crane) that can also be used for a load lifting work, in which a lifting hook is provided at the tip of a working machine of a hydraulic excavator. In this case, in general, in an arm crane using a small hydraulic excavator, the difference value between the allowable load of the suspended load and the falling limit load for preventing the vehicle body from falling, that is, the margin to the falling is small. When the fall prevention control device according to the present invention is applied, the margin can be increased, and fall prevention can be surely performed.

It is explanatory drawing of the material collector of 1st Embodiment which concerns on this invention. It is a circuit diagram of the control device of the first embodiment. It is explanatory drawing of the action | operation of this invention. It is explanatory drawing of a motion of a working machine when the relief valve of this invention is relieved. It is explanatory drawing of a motion of the working machine in the conventional case (when there is no forced relief of the bottom chamber pressure of a boom cylinder). It is a graph explaining the effect of this invention. It is a circuit diagram of the control apparatus of 2nd Embodiment. It is a circuit diagram of the control apparatus of 3rd Embodiment. It is a figure which shows the other structural example of the gathering machine to which this invention is applied. It is a figure which shows the structure of the conventional gathering machine. It is explanatory drawing of the fall of the conventional gathering machine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Work vehicle, 2 ... Lower traveling body, 3 ... Upper turning body, 5 ... Working machine, 6 ... Boom, 7 ... Arm, 9 ... Boom cylinder, 9a ... Head chamber, 9b ... Bottom chamber, 10 ... Arm cylinder, 13, 14 ... winch, 15, 15a, 15b, 16 ... pulley, 17a, 17b ... wire rope, 18 ... standing tree (post), 20 ... pulley, 21 ... shackle, 22, 24 ... pulley, 26 ... shackle, 27 ... Latch, 28 ... Lumber, 30 ... Hydraulic pump, 31 ... Switching valve, 33 ... Relief valve, 35 ... Relief means, 36 ... Relief valve, 37 ... Electromagnetic on-off valve, 38, 39 ... Pipe line, 40 ... Tank, 42 DESCRIPTION OF SYMBOLS ... Vehicle body inclination angle detector, 44 ... Two-stage relief valve, 45 ... Electromagnetic switching valve, 46 ... Pilot hydraulic pump, 48 ... Two-stage relief valve, 51 ... Winch, 52a, 52b ... Wire rope, 71 ... Hydraulic pressure Shovel body, 72 ... Lower traveling body, 73 ... Upper turning body, 74 ... Working machine, 75 ... Boom cylinder, 76 ... Boom, 82HAL, 82HBL ... Winch, 88HAL, 88HBL ... Wire rope, 89a, 89b ... Pulley, 91 ... Tachiki, 92 ... wire rope, 97 ... hook, 98 ... timber.

Claims (5)

In the work vehicle that is provided with a work machine (5) that moves up and down by the expansion and contraction of the hydraulic cylinder (9) on the upper part of the vehicle body and works by applying a load to the tip of the work machine (5)
Connected to the cylinder chamber (9b) that receives the holding pressure of the hydraulic cylinder (9) for driving the work machine, receives a command from the outside, and is lower than the relief pressure during normal operation of the hydraulic cylinder (9) Relief means (35) for relieving the oil in the cylinder chamber (9b) with a relief pressure;
A vehicle body tilt angle detector (42) for detecting a tilt angle of the vehicle body in a predetermined direction;
Control for reducing the holding pressure of the hydraulic cylinder (9) by outputting a command to the relief means (35) when the vehicle body inclination angle detected by the vehicle body inclination angle detector (42) becomes a predetermined value or more. A work vehicle overturn prevention control device comprising: a container (42). The relief means (35)
A relief valve (36) connected to a cylinder chamber (9b) that receives the holding pressure of the hydraulic cylinder (9) and set to a relief pressure lower than the relief pressure during normal operation of the hydraulic cylinder (9). When,
The electromagnetic on-off valve (37) provided between the relief valve (36) and the tank (40) and opened and closed in response to a command from the controller (42). The work vehicle overturn prevention control device according to claim 1. The relief means (35)
A relief pressure lower than a relief pressure during normal operation of the hydraulic cylinder (9) provided between a cylinder chamber (9b) that receives the holding pressure of the hydraulic cylinder (9) and a tank (40); A two-stage relief valve (44) in which a high relief pressure is set to be switchable in response to an external command;
Relief pressure switching means (45) for receiving a command from the controller (42) and outputting a command for switching to a low set relief pressure to the two-stage relief valve (44). Item 2. A work vehicle overturn prevention control device according to Item 1. The work vehicle overturn prevention control device according to claim 1, 2, or 3, wherein the work vehicle (1) is:
Two winches (13, 14) are mounted on the vehicle body near the base of the work machine (5) that can move up and down,
Provided with a plurality of pulleys (15, 16) at the tip of the work machine (5),
Of the two wire ropes (17a, 17b) wound around the two winches (13, 14), one wire rope (17b) is connected to one of a plurality of pulleys at the tip of the work implement. Connected to the first jig (21) via one (16) and a pulley (20) attached to a post such as a standing tree (18) located far from the vehicle,
The other wire rope (17a) is routed through at least one other pulley (15) of the plurality of pulleys at the tip of the work machine and the pulley (24) connected to the first jig (21). Then connect the lumber (28) to be transported to the second jig (26) that lifts,
The work is characterized by being a gathering machine for carrying the lumber (28) by controlling the wire winding and unwinding speeds of the two winches (13, 14) in synchronization with each other. Vehicle fall prevention control device. A work machine (5) provided at the top of the vehicle body that can move up and down is driven up and down by expansion and contraction of the hydraulic cylinder (9)
Work by applying a load to the tip of the work machine (5)
In the work vehicle overturn prevention method for preventing the vehicle body from overturning when an overload is applied,
Detect the tilt angle of the vehicle body in a predetermined direction,
When the detected inclination angle is equal to or greater than a predetermined value, the oil in the cylinder chamber (9b) that receives the holding pressure of the hydraulic cylinder (9) is relieved to reduce the holding pressure,
A work vehicle fall prevention method, wherein the work machine (5) is lowered by the load.