Outrigger device

Abstract

To provide an outrigger device capable of preventing a cylinder rod of an outrigger cylinder from naturally descending and easily ensuring the stroke of the outrigger cylinder.SOLUTION: A flow passage connection member 51R is provided with an extension prevention valve P2R, which is a pilot check valve that opens and closes using the pressure of the extension side flow passage 45R as a pilot pressure and blocks the flow of hydraulic oil from a contraction side hydraulic oil chamber 44R toward a control valve C. Therefore, a contraction side flow passage 46R is closed when no particular operation is being performed. When an operator operates the control valve C to switch a right outrigger cylinder spool SR to an extension position PR2, high-pressure hydraulic oil flows into an extension side hydraulic oil chamber 43R, and the extension prevention valve P2R opens due to the application of pilot pressure. At this time, the contraction side flow passage 46R is opened, allowing hydraulic oil to flow out of the contraction side hydraulic oil chamber 44R.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to an outrigger device for a work machine. [Background technology]

[0002] Conventionally, a work machine having a work implement mounted on a truck or the like is equipped with an outrigger device to resist a tipping moment generated by the load of the work implement. In particular, an outrigger device mounted on a truck or the like is equipped with an outrigger cylinder, the cylinder rod of which is extendable in the vertical direction of the vehicle, at the tip of an outrigger box which is extendable in the vehicle width direction.

[0003] In this type of outrigger device, after the outrigger box is extended in the vehicle width direction, the outrigger cylinder is extended to transfer the load applied to the vehicle's traveling gear to the outrigger device. For this reason, the outrigger cylinder is equipped with a pilot check valve that blocks the flow of hydraulic oil when the operator is not performing the shortening operation, and prevents the outrigger cylinder from being shortened by the load caused by the overturning moment generated by the vehicle weight or the load of the work equipment.

[0004] The cylinder rod of an outrigger cylinder is constantly subjected to a force in the direction of extension due to its own weight and the weight of the structure attached to the end of the cylinder rod. Outrigger cylinders resist such forces by utilizing the sliding resistance of the packings provided on the cylinder tube and piston, and the effect of stopping the operation of the actuator by blocking the flow of the working fluid (hereinafter referred to as the "fluid lock effect"), so the amount of natural descent of the cylinder rod is kept low. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2008-309212 A [Patent Document 2] JP 2022-180148 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, if the packing is worn or there is a dimensional error that occurs during processing or assembly, the cylinder rod may naturally extend even when no extension action is being performed. In particular, the cylinder rod is likely to extend when vibrations are applied to the outrigger device as the vehicle travels.

[0007] If the sliding resistance of the packing is increased to prevent this natural descent of the cylinder rod, the resistance when operating the outrigger cylinder also increases, resulting in unnecessary energy loss.In addition, because the control valve has a structure that requires the spool to slide, it is difficult to completely eliminate leakage of working fluid even when the flow path is closed, and there is a limit to the ability of the control valve to exert a fluid locking effect to prevent the descent of the cylinder rod.

[0008] Therefore, the above-mentioned Patent Document 1 discloses an outrigger device equipped with a double check valve in which, in addition to a pilot check valve as a safety device to prevent the outrigger cylinder from retracting, a pilot check valve is also installed to prevent the outrigger cylinder from extending.

[0009] Regarding the arrangement of the double check valve, in the case of an outrigger device in which the outrigger cylinder operates along the vertical direction of the vehicle as disclosed in the above-mentioned Patent Document 2, the double check valve is directly fixed to the head end of the cylinder tube. The reason why the double check valve is arranged in such a position is because the pilot check valve on the side that prevents the outrigger cylinder from unintentionally shortening is a check valve that is required to be installed by the mobile crane structure standard. This check valve prevents the hydraulic oil in the outrigger cylinder from leaking out all at once if the pipe between the outrigger cylinder and the control valve breaks. In other words, the double check valve is fixed to the head end of the cylinder tube in order to connect the hydraulic oil chamber on the side from which the hydraulic oil flows out due to the load in the direction in which the outrigger cylinder shortens to the double check valve without using piping. Furthermore, since the double check valve is fixed to the head side end of the cylinder tube, good accessibility to the double check valve is maintained during manufacture and maintenance of the outrigger device.

[0010] However, because the outrigger cylinder is housed inside the cylinder box, the outrigger cylinder is shortened by the thickness of the double check valve, resulting in a reduction in the cylinder stroke. If the cylinder stroke of the outrigger cylinder is insufficient, it becomes difficult to transfer the load from the vehicle to the outrigger device, which causes a decrease in stability during work. Therefore, small work machines on which it is difficult to mount large outrigger devices may ensure the stroke by not mounting a pilot check valve to prevent the extension of the outrigger cylinder, making it difficult to prevent the cylinder rod from naturally descending when the packing, etc., wears.

[0011] The present invention has been made in response to such problems, and aims to provide an outrigger device that can prevent the cylinder rod from descending naturally and that easily ensures the stroke of the outrigger cylinder. [Means for solving the problem]

[0012] A first invention is an outrigger device that is mounted on a work machine and includes an outer box having an opening formed on the outside of the machine body, an inner box stored inside the outer box, and an outrigger cylinder that is fixed to an outer end of the inner box and is extendable and contractable along the up-down direction of the machine body, a control valve connected to the outrigger device is capable of switching a high-pressure side flow path connected to a pump and a low-pressure side flow path connected to a hydraulic fluid tank between an extension position that connects to the side that extends the outrigger cylinder, a retraction position that connects to the side that retracts the outrigger cylinder, and a stop position that does not connect to the outrigger cylinder, an extension-side flow passage connecting an extension-side working fluid chamber of the outrigger cylinder, into which a working fluid flows in to extend the outrigger cylinder, to the control valve, and a shortening-side flow passage connecting a shortening-side working fluid chamber of the outrigger cylinder, into which a working fluid flows in to shorten the outrigger cylinder, to the control valve, each of which comprises a first pipeline having one end connected to the control valve and piped to the outside of the outer box, a second pipeline having one end connected to the outrigger cylinder, piped inside the inner box, and bending in accordance with the protruding state of the inner box, and a flow passage connecting member connecting the other end of the first pipeline to the other end of the second pipeline, the outrigger cylinder is provided with a shortening prevention device at a connection portion with the second pipeline, the shortening prevention device includes a shortening prevention valve that opens the extension-side flow passage when the control valve is in a shortening position and closes the extension-side flow passage when the control valve is in a stop position, The flow passage connection member is fixed to the outer box and is characterized in that it is equipped with an extension prevention valve that opens the shortened side flow passage when the control valve is in the extended position and closes the shortened side flow passage when the control valve is in the stopped position.

[0013] A second invention is an outrigger device characterized in that the extension prevention valve described in the first invention is a pilot check valve that controls the opening and closing of the shortening side flow path using the pressure of the working fluid applied to the extension side flow path as a pilot pressure. Effect of the Invention

[0014] According to the present invention, it is possible to provide an outrigger device that can prevent the cylinder rod from descending naturally and that easily ensures the stroke of the outrigger cylinder. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a side view of a mobile crane, which is an example of a work machine equipped with an outrigger device. [Diagram 2] FIG. 2 is a diagram showing a structure of an outrigger device according to one embodiment of the present invention. [Diagram 3] 1A, 1B, and 1C are a front view, a right side view, and a top view, respectively, showing the structure of an inner box of an outrigger device according to one embodiment of the present invention. [Figure 4] 1 is a hydraulic circuit diagram of a mobile crane according to an embodiment of the present invention. FIG. [Diagram 5] FIG. 2 is an enlarged view of an outrigger device portion in a hydraulic circuit diagram of the mobile crane according to one embodiment of the present invention. [Figure 6] 1 is a diagram showing the shape of the piping inside the outrigger device of one embodiment of the present invention when deformed in accordance with the protruding state of the inner box. FIG. [Figure 7] 1A, 1B, 1C are a front view, a left side view, and a top view, showing the appearance of a flow path connecting member according to one embodiment of the present invention. [Figure 8] 7(a) is a cross-sectional view taken along line AA in FIG. 7(b), and FIG. 7(b) is a cross-sectional view taken along line BB and line CC in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings, taking a mobile crane having a crane device mounted on a truck as an example of a work machine. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals, and duplicated explanations are omitted. It should be noted that the drawings are schematic. Therefore, it should be noted that the relationship and ratio between the thickness and the planar dimensions are different from the actual ones, and the drawings include parts with different dimensional relationships and ratios. In addition, the embodiments shown below are examples of devices and methods for embodying the technical idea of ​​the present invention, and the technical idea of ​​the present invention does not specify the materials, shapes, structures, displays, etc. of the components to the embodiments described below.

[0017] <Mobile crane structure> In the following explanations and drawings relating to the configuration of the mobile crane, the direction in which the crane-mounted vehicle moves forward (the direction in which it travels with the shift selected in D range, etc.) may be described as "forward" or "front." Similarly, in the following explanations and drawings, the direction in which the crane-mounted vehicle moves backward (the direction in which it travels with the shift selected in R range) may be described as "rear" or "rear." Also, in the following explanations and drawings, the "left side" may be the left side from the perspective of the driver driving the crane-mounted vehicle, the "right side" may be the right side from the perspective of the driver driving the crane-mounted vehicle, the "lower side" may be the lower side from the perspective of the driver driving the crane-mounted vehicle, and the "upper side" may be the upper side from the perspective of the driver driving the crane-mounted vehicle. Also, unless otherwise specified, the crane apparatus will be described as rotating along the fore-and-aft direction of the vehicle so as to face toward the rear of the vehicle, and the boom is in a position where it is lowered to a horizontal angle.

[0018] First, the mobile crane will be described with reference to FIG. In the mobile crane 1, a crane apparatus 2 is mounted between the driver's seat CV and the loading platform LB of the vehicle V. The crane apparatus 2 is fixed to the chassis frame CF of the vehicle V by a base B, and a column 5 is supported on the base B via a swivel device (not shown) so as to be rotatable about an axis along the vertical direction. The base end of a boom 6 is supported by the column 5 so as to be swingable about an axis in the horizontal direction, and a hook HO is suspended from the tip of the boom 6.

[0019] The base B is equipped with an outrigger device OR that extends in the vehicle width direction. By extending the outrigger device OR and extending the outrigger cylinder to touch the ground, the load applied to the traveling gear of the vehicle V is transferred to the outrigger device OR, thereby ensuring the stability of the vehicle V when performing work using the crane device 2.

[0020] <Outrigger device structure> Next, the structure of the outrigger unit OR will be described with reference to Fig. 2. In Fig. 2, hydraulic piping is partially simplified. The outrigger device OR includes a right outer box 10R having a rectangular parallelepiped shape and hollow with the right side of the vehicle open, a left outer box 10L having a rectangular parallelepiped shape and hollow with the left side of the vehicle open, a right inner box 20R having a rectangular parallelepiped shape that is stored in the right outer box 10R and can be extended to the right side of the vehicle, and a left inner box 20L having a rectangular parallelepiped shape that is stored in the left outer box 10L and can be extended to the left side of the vehicle. The right outer box 10R and the left outer box 10L are arranged side by side in the front and rear of the vehicle in a direction parallel to their respective length directions. Therefore, the right outer box 10R and the left outer box 10L are formed to have the same length.

[0021] A roller 11R is provided on the underside of the right outer box 10R at the end on the right side of the vehicle, the roller 11R protruding partially into the right outer box 10R and contacting the underside of the right inner box 20R to support the right inner box 20R. The left outer box 10L is also provided with a roller 11R.

[0022] Next, the structure of the right inner box 20R will be described with reference to Fig. 3. Note that the left inner box 20L has a similar structure to the right inner box 20R, and therefore a description thereof will be omitted. A hollow right cylinder box 30R having a rectangular parallelepiped shape is fixed to the tip of the right inner box 20R, extending downward from the upper surface of the right inner box 20R. A right outrigger cylinder 40R is disposed inside the right cylinder box 30R, and a cylinder tube 42R is fixed in such a manner that a cylinder rod 41R extends downward. A shortening prevention device 70R, the details of which will be described later, is fixed to the head side end of the cylinder tube 42R.

[0023] An outrigger device fixing lever 31R is provided on the vehicle front surface of the right cylinder box 30R. The outrigger device fixing lever 31R is connected to a stopper pin 32R provided inside the right inner box 20R via a wire W. The stopper pin 32R is biased in the downward direction of the vehicle, and is moved upward by pushing in the outrigger device fixing lever 31R.

[0024] The right inner box 20R is provided with a roller 33 and a sliding plate 34 at the end of the side to which the right cylinder box 30R is not fixed. The roller 33 is supported on the upper part of the right inner box 20R so as to be rotatable about a rotation axis along the vehicle front-rear direction, and the sliding plate 34 is fixed to the lower surface of the right inner box 20R. Although not shown, the sliding plate 34 is also fixed to the vehicle front side surface and the vehicle rear side surface of the right inner box 20R, and contacts the inner surface of the right outer box 10R. The roller 33 and the sliding plate 34 contact the inner surface of the right outer box 10R to suppress rattling of the outrigger device OR and reduce resistance when it protrudes.

[0025] Although not shown, through holes are formed on the underside of the right outer box 10R at a position which overlaps vertically with the stopper pin 32R when the right inner box 20R is stored, and at positions which overlap vertically with the stopper pin 32R every time the right inner box 20R is extended by one-third of the possible extension length. When the right inner box 20R is in the stored position or in the extended position set for each third of the extendable length, the stopper pin 32R fits into the through hole, fixing the right inner box 20R. When the outrigger device fixing lever 31R is pulled, the stopper pin 32R connected by a wire contracts and comes out of the through hole of the right outer box 10R, allowing the right inner box 20R to operate.

[0026] <Hydraulic circuit structure> Next, the hydraulic circuit of the mobile crane 1 will be described with reference to Fig. 4. Note that the description will be simplified for the parts other than those related to the outrigger units OR. Hydraulic oil supplied from hydraulic oil tank T is sent to control valve C by hydraulic pump P. Control valve C has multiple spools, and is operated by an operator to control the open / closed states of boom hoisting circuit EC1, winch rotation circuit EC2, boom extension / retraction circuit EC3, column rotation circuit EC4, right outrigger cylinder circuit EC5, and left outrigger cylinder circuit EC6. When all circuits are closed, relief valve RV opens and hydraulic oil returns to hydraulic oil tank T via filter F.

[0027] Next, the right outrigger cylinder circuit EC5 and the left outrigger cylinder circuit EC6 will be described with reference to Fig. 5. Since the left outrigger cylinder circuit EC6 has the same structure as the right outrigger cylinder circuit EC5, a description of the left outrigger cylinder circuit EC6 will be omitted below.

[0028] The right outrigger cylinder circuit EC5 has, as flow paths for hydraulic oil, an extension side flow path 45R connected to a hydraulic oil chamber (hereinafter referred to as the "extension side hydraulic oil chamber 43R") on the side into which the cylinder rod 41R extends when hydraulic oil flows in, and a shortening side flow path 46R connected to a hydraulic oil chamber (hereinafter referred to as the "shortening side hydraulic oil chamber 44R") on the side into which the cylinder rod 41R shortens when hydraulic oil flows in. A flow passage connection member 51R and a shortening prevention device 70R are connected to the extension side flow passage 45R and the shortening side flow passage 46R.

[0029] The right outrigger cylinder circuit EC5 has a first pipe line on the control valve C side and a second pipe line on the right outrigger cylinder 40R side across the flow path connecting member 51R. Therefore, in the following, where necessary, the first pipeline in the extension-side flow path 45R will be referred to as the "first extension-side pipeline 47R," the second pipeline in the extension-side flow path 45R will be referred to as the "second extension-side pipeline 48R," the first pipeline in the shortening-side flow path 46R will be referred to as the "first shortening-side pipeline 49R," and the second pipeline in the shortening-side flow path 46R will be referred to as the "second shortening-side pipeline 50R."

[0030] The control valve C is provided with a right outrigger cylinder spool SR between a high-pressure side passage HP connected to a hydraulic pump P and a low-pressure side passage LP connected to a hydraulic oil tank T. The right outrigger cylinder spool SR has a shortened position PR1 in which the high-pressure side flow passage HP is connected to the shortened side flow passage 46R and the low-pressure side flow passage LP is connected to the extended side flow passage 45R, an extended position PR2 in which the high-pressure side flow passage HP is connected to the extended side flow passage 45R and the low-pressure side flow passage LP is connected to the shortened side flow passage 46R, and a stop position PR3 in which neither the high-pressure side flow passage HP nor the low-pressure side flow passage LP is connected to the extended side flow passage 45R and the shortened side flow passage 46R, and the right outrigger cylinder spool SR is allowed to pass.

[0031] A shortening prevention device 70R is provided between the extension side hydraulic oil chamber 43R and the second extension side pipe 48R and between the shortening side hydraulic oil chamber 44R and the second shortening side pipe 50R. The shortening prevention device 70R is fixed to the right outrigger cylinder 40R, and is directly connected to the extension side hydraulic oil chamber 43R and is connected to the shortening side hydraulic oil chamber 44R by a pipe fixed to the cylinder tube 42R.

[0032] The shortening prevention device 70R includes a shortening prevention valve P1R which is a pilot check valve that opens and closes using the pressure of the shortening side flow passage 46R as a pilot pressure and blocks the flow of hydraulic oil from the extension side hydraulic oil chamber 43R toward the control valve C. Therefore, the extension-side flow passage 45R is closed when no particular operation is being performed. When an operator operates the control valve C to switch the right outrigger cylinder spool SR to the retraction position PR1, high-pressure hydraulic oil flows into the retraction-side hydraulic oil chamber 44R, and pilot pressure is applied, opening the retraction prevention valve P1R. At this time, the extension-side flow passage 45R opens, allowing hydraulic oil to flow out of the extension-side hydraulic oil chamber 43R.

[0033] While the operator is not operating the control valve C, a force acts on the right outrigger cylinder 40R in a direction that tries to shorten the cylinder rod 41R due to the load of the vehicle V and the crane apparatus 2. However, in the right outrigger cylinder circuit EC5, the force that tries to shorten the cylinder rod 41R tries to cause hydraulic oil to flow out of the extension-side hydraulic oil chamber 43R, and the hydraulic oil pressure generated by such a force acts in a direction that closes the shortening prevention valve P1R. As a result, the flow path from the extension-side hydraulic oil chamber 43R to the control valve C remains closed, and the fluid locking action of the shortening prevention valve P1R prevents the right outrigger cylinder 40R from shortening.

[0034] The passage connection member 51R includes an extension prevention valve P2R which is a pilot check valve that opens and closes the pressure of the extension side passage 45R as a pilot pressure and blocks the flow of hydraulic oil from the contraction side hydraulic oil chamber 44R toward the control valve C. Therefore, the contraction side flow passage 46R is closed when no particular operation is being performed. When an operator operates the control valve C to switch the right outrigger cylinder spool SR to the extension position PR2, high-pressure hydraulic oil flows into the extension side hydraulic oil chamber 43R, and pilot pressure is applied, opening the extension prevention valve P2R. At this time, the contraction side flow passage 46R is opened, allowing hydraulic oil to flow out of the contraction side hydraulic oil chamber 44R.

[0035] While the operator is not operating the control valve C, a force acts on the right outrigger cylinder 40R in a direction that tries to extend the cylinder rod 41R due to the weight of the cylinder rod 41R. However, in the right outrigger cylinder circuit EC5, the force that tries to extend the cylinder rod 41R tries to cause hydraulic oil to flow out of the retraction side hydraulic oil chamber 44R, and the hydraulic oil pressure generated by this force acts in a direction that closes the extension prevention valve P2R. As a result, the flow path from the retraction side hydraulic oil chamber 44R to the control valve C remains closed, and the fluid lock action of the extension prevention valve P2R prevents the right outrigger cylinder 40R from extending.

[0036] <Outrigger device piping> Next, referring again to FIG. 2, the piping of the first pipeline will be described. As for the left outrigger cylinder circuit EC6, the position of the control valve C is shifted toward the right side of the vehicle, so that the extension side first pipe 47L and the contraction side first pipe 49L have a short structure, and therefore their structure is the same as the left outrigger cylinder circuit EC6, and therefore their explanation will be omitted.

[0037] The flow path connecting member 51R is fixed to the upper side of the inner surface of the right outer box 10R via a rib (not shown) so as not to come into contact with the inner surface of the right outer box 10R or the outer surface of the right inner box 20R.

[0038] The first extension-side pipe 47R and the first shortening-side pipe 49R are piped through the outside of the right outer box 10R such that one end is connected to the control valve C and the other end is located near the flow path connecting member 51R inside the right outer box 10R. Although not shown, a through hole of a size that allows the end portions of the first extension-side pipe 47R and the first shortening-side pipe 49R to pass through is formed at a position overlapping with the flow path connecting member 51R on the vehicle front surface of the right outer box 10R. The first extension-side pipe 47R is connected to the flow path connecting member 51R via this through hole.

[0039] Next, the piping of the second pipeline will be described with reference to FIG. The extension side second pipe 48R and the shortening side second pipe 50R connect from the flow path connection member 51R to the shortening prevention device 70R. Therefore, one end is connected to the flow path connection member 51R, passes between the inner surface of the right outer box 10R and the outer surface of the right inner box 20R, and is piped from the right side surface side to the left side surface side. Then, at the left side surface side end of the right inner box 20R, it is wound 180 degrees so as to draw an arc convex to the left, passes through the inside of the right inner box 20R, and the other end is connected to the shortening prevention device 70R through the inside of the right inner box 20R.

[0040] Since the extension-side second pipe 48R and the shortening-side second pipe 50R are fixed inside the right inner box 20R, as shown in (b), they bend so that the wound position moves according to the protruding state of the right inner box 20R. Therefore, deformable resin piping is used for the extension-side second pipe 48R and the shortening-side second pipe 50R.

[0041] <Structure of flow path connecting member> Next, the structure of the flow path connecting member 51R will be described with reference to FIGS. In the description of the flow path connecting member 51R, the direction along an imaginary straight line from the front to the back may be referred to as the front-rear direction, the direction along an imaginary straight line from the left side to the right side as the left-right direction, and the direction along an imaginary straight line from the bottom to the top as the up-down direction. Also, the flow path connecting member 51L provided in the left outrigger cylinder circuit EC6 has the same structure as the flow path connecting member 51R provided in the right outrigger cylinder circuit EC5, and therefore a description thereof will be omitted.

[0042] The flow passage connection member 51R is a joint block for hydraulic piping in which a flow passage for hydraulic oil is formed, and is formed in a rectangular parallelepiped shape with a width shorter than half the width of the right inner box 20R, a length about 1.5 to 1.7 times the width, and a thickness that can be accommodated between the inner surface of the right outer box 10R and the outer surface of the right inner box 20R. In addition, the corners between the front surface and the top surface and the corners between the front surface and the left side surface are chamfered, and a female screw part 52 for fixing the flow passage connection member 51R to the right outer box 10R is formed on the right side of the front surface.

[0043] The flow path connection member 51R has, as a connection portion with the piping shown in Figures 2 and 6, a first extension-side plug hole 53 for connecting the first extension-side pipeline 47R on the left side of the front face, a second extension-side plug hole 54 for connecting the second extension-side pipeline 48R on the upper front side of the left side, a first shortening-side plug hole 55 for connecting the first shortening-side pipeline 49R on the central part of the front face, and a second shortening-side plug hole 56 for connecting the second shortening-side pipeline 50R on the upper back side of the left side. That is, the extension-side first plug hole 53 and the shortening-side first plug hole 55 are formed adjacent to each other on the same surface of the flow path connecting member 51R. Also, the extension-side second plug hole 54 and the shortening-side second plug hole 56 are formed adjacent to each other on the same surface of the flow path connecting member 51R. Although each plug hole in FIG. 7 is shown with a plug attached, each plug hole 53 to 56 has a female thread portion formed therein, to which a piping joint can be fixed, and the first extension side pipe 47R, the second extension side pipe 48R, the first shortening side pipe 49R, and the second shortening side pipe 50R can be detachably attached.

[0044] As shown in Figure 8, the flow path connection member 51R has within it a lower layer extension side flow path 57A and an upper layer extension side flow path 57B which connect the extension side first plug hole 53 and the extension side second plug hole 54, and a lower layer shortening side flow path 58A and an upper layer shortening side flow path 58B which connect the shortening side first plug hole 55 and the shortening side second plug hole 56. The expansion-side first plug hole 53 is bored deeper than the range in which the female thread portion for fixing the joint is formed, and also functions as the expansion-side flow passage 57A on the lower layer side. The shortened side flow passage 58A on the lower layer side is formed by a first flow passage 581 formed along the front-to-rear direction from the shortened side first plug hole 55, a second flow passage 582 shifted from the first flow passage toward the right side side and formed along the front-to-rear direction, and a third flow passage 583 formed along the left-right direction so as to connect these flow passages at the center in the front-to-rear direction.

[0045] The lower extension-side flow passage 57A is connected to the upper extension-side flow passage 57B by an extension-side vertical flow passage 57C formed at a position shifted toward the center in the left-right direction from the center of the extension-side first plug hole 53. The upper extension-side flow passage 57B is formed horizontally from the axis of the extension-side second plug hole 54 toward the right side surface. The lower shortening-side flow passage 58A is connected to the upper shortening-side flow passage 58B formed horizontally from the shortening-side second plug hole 56 toward the right side surface by a shortening-side vertical flow passage 58C formed at the end of the back side of the second flow passage 582 on the right side surface side.

[0046] In the lower layer inside the flow path connection member 51R, holes having a larger diameter than the third flow path 583 are formed on the left and right sides of the third flow path 583 at a position concentric with the third flow path 583 formed along the left-right direction of the lower layer shortened side flow path 58A. A poppet 60 biased to the left side by a coil spring is enclosed in a right side portion 59 of this hole across the third flow passage 583, and the poppet 60 forms a check valve with the third flow passage 583 as a valve seat. Therefore, the poppet 60 blocks the hydraulic oil flowing from the shortened-side second plug hole 56 to the shortened-side first plug hole 55.

[0047] The left side portion 61 sandwiching the third flow passage 583 constitutes a part of the first flow passage 581, and is connected to the lower extension side flow passage 57A via a throttle 57R. The left side portion 61 also houses a cylindrical piston 62 formed so that the central portion in the length direction has a smaller diameter than the other portions. A seal material 63 is fitted into the small diameter portion of the piston 62, and divides the extension side flow passage 57A and the shortening side flow passage 58A. Of the axial ends of the piston 62, a push rod 64 extends from the side facing the shortening side flow passage 58A, and a stopper rod 65 extends from the side facing the extension side flow passage 57A.

[0048] When a pressure difference occurs between the extension side flow passage 57A and the contraction side flow passage 58A, the piston 62 moves left and right. When the pressure in the contraction-side flow passage 58A is higher than the pressure in the extension-side flow passage 57A, the piston 62 moves to the left side. At this time, the contraction-side flow passage 58A is closed by the poppet 60. The piston 62 stops at a certain position because the stopper rod 65 comes into contact with the plug 65P attached to the left side. When the pressure in the extension-side flow passage 57A is higher than the pressure in the shortening-side flow passage 58A, the piston 62 moves to the right side. At this time, the push rod 64 comes into contact with the poppet 60. When the pressure difference between the extension-side flow passage 57A and the shortening-side flow passage 58A exceeds the biasing force applied to the poppet 60, the poppet 60 moves to the right side, and the shortening-side flow passage 58A opens.

[0049] The hydraulic oil pressure applied by the weight of the cylinder rod 41R is directed from the third flow passage 583 to the first flow passage 581. Therefore, the extension prevention valve P2R can use this hydraulic oil pressure to strongly bring the poppet 60 into contact with the third flow passage 583, which serves as the valve seat.

[0050] Regarding the fluid locking effect, a check valve can exhibit a stronger fluid locking effect than a spool valve. This is because a check valve has a higher ability to prevent hydraulic oil leakage than a spool valve, and hydraulic oil leakage is less likely to occur even when a large load is applied. This is because a spool valve requires the spool to slide when switching flow paths, and is structured to require a gap that allows the spool to operate, whereas a check valve does not require the valve body and valve seat to slide, and the spool can be made to fit tightly against the valve seat by utilizing the hydraulic oil pressure acting in the direction of closing the flow path, and during manufacturing, the spool can be brought into contact with the valve body and then struck, making it easy to process it into a shape that allows the spool to fit tightly against the valve seat.

[0051] <Action and function of contraction prevention valve and extension prevention valve> Next, the operation of the shortening prevention valves P1R, P1L and the extension prevention valves P2R, P2L will be described. Note that in the following description, the structure of the outrigger unit OR on the right side of the vehicle described above with reference to the drawings will be used as an example, but the structure on the left side of the vehicle is similar.

[0052] When performing work using the mobile crane 1, first, the right inner box 20R of the outrigger device OR is extended in the vehicle width direction, and the right outrigger cylinder 40R is extended until the load of the vehicle V is transferred, thereby ensuring the stability of the mobile crane 1. At this time, a force in the shortening direction is constantly acting on the right outrigger cylinder 40R due to the mass of the vehicle V and the crane equipment 2. Therefore, with only the fluid locking action of the right outrigger cylinder spool SR, the right outrigger cylinder 40R may shorten until the load is transferred to the traveling gear of the vehicle V during work, which may cause the stability of the mobile crane 1 to be lost.

[0053] Therefore, the outrigger device OR has a shortening prevention valve P1R provided in the shortening prevention device 70R that blocks the hydraulic oil flowing from the extension side hydraulic oil chamber 43R, which is the hydraulic oil chamber from which hydraulic oil flows out when the right outrigger cylinder 40R shortens, toward the control valve C, thereby exerting a stronger fluid locking effect than the right outrigger cylinder spool SR, and preventing the right outrigger cylinder 40R from shortening during operation.

[0054] The shortening prevention device 70R is fixed directly to the right outrigger cylinder 40R because if a piping such as a hose is provided between the shortening prevention device 70R and the extension side hydraulic oil chamber 43R, and the piping is damaged and hydraulic oil leaks, the shortening prevention device 70R will not be effective and the right outrigger cylinder 40R will shorten. In other words, to eliminate the risk of piping damage and ensure safety during work, the shortening prevention device 70R is fixed directly to the right outrigger cylinder 40R.

[0055] When an operator performs an operation to retract the right outrigger cylinder 40R, the right outrigger cylinder spool SR takes the retraction position PR1, and hydraulic pressure is applied to the retraction-side flow passage 46R. This hydraulic pressure acts inside the retraction-side hydraulic oil chamber 44R and simultaneously acts on the retraction prevention valve P1R, which uses the hydraulic pressure of the retraction-side flow passage 46R as its pilot pressure, opening the retraction prevention valve P1R. As a result, the retraction-side flow passage 45R, which was closed by the retraction prevention valve P1R, opens, allowing hydraulic oil to flow out of the retraction-side hydraulic oil chamber 43R, and the right outrigger cylinder 40R retracts.

[0056] After work using the mobile crane 1 is completed, the crane apparatus 2 is put into a stored position, and with the right outrigger cylinder 40R fully retracted, the right inner box 20R is stored inside the right outer box 10R. Thereafter, the vehicle V is driven, and at this time, a force in the extension direction acts on the right outrigger cylinder 40R due to vibrations generated by the vehicle's driving that is stronger than the force acting due to the mass of the cylinder rod 41R, and the right outrigger cylinder 40R may extend little by little. In addition, if the sealing material inside the right outrigger cylinder 40R and the spool SR for the right outrigger cylinder are worn, they may not be able to resist the mass of the cylinder rod 41R even when the vehicle V is stopped, and the right outrigger cylinder 40R may extend naturally.

[0057] Therefore, the outrigger device OR prevents the right outrigger cylinder 40R from extending by having the extension prevention valve P2R block the hydraulic oil flowing from the shortening side hydraulic oil chamber 44R, through which hydraulic oil flows out when the right outrigger cylinder 40R extends, toward the control valve C, thereby exerting a stronger fluid locking effect than the right outrigger cylinder spool SR.

[0058] When an operator performs an operation to extend the right outrigger cylinder 40R, the right outrigger cylinder spool SR takes the extension position PR2, and hydraulic pressure is applied to the extension-side flow passage 45R. This hydraulic oil pressure acts inside the extension-side hydraulic oil chamber 43R and simultaneously acts on the extension prevention valve P2R, which uses the hydraulic pressure of the extension-side flow passage 45R as its pilot pressure, opening the extension prevention valve P2R. As a result, the contraction-side flow passage 46R, which was closed by the extension prevention valve P2R, opens, allowing hydraulic oil to flow out of the contraction-side hydraulic oil chamber 44R, and the right outrigger cylinder 40R extends.

[0059] In summary, while the operator is not performing any operation, the extension side flow path 45R is closed by the hydraulic oil pressure generated by a force acting in a direction to retract the right outrigger cylinder 40R, and is opened by the hydraulic oil pressure supplied from the hydraulic pump P via the control valve C only when the operator performs an operation to retract the right outrigger cylinder 40R. In other words, the right outrigger cylinder 40R does not retract when the operator is not performing any operation, and retracts only when the operator performs an operation.

[0060] Similarly, while the operator is not performing any operation, the shortening side flow path 46R is closed by the hydraulic oil pressure generated by a force acting in a direction to extend the right outrigger cylinder 40R, and is opened by the hydraulic oil pressure supplied from the hydraulic pump P via the control valve C only when the operator performs an operation to extend the right outrigger cylinder 40R. In other words, the right outrigger cylinder 40R does not extend when the operator is not performing any operation, and extends only when the operator performs an operation.

[0061] <Effects> The extension prevention valve P2R is provided inside the flow passage connection member 51R, but if it were a double check valve integrally formed with the shortening prevention device 70R, the stroke of the right outrigger cylinder 40R would be further shortened by the thickness required to seal the extension prevention valve P2R. In addition, if an extension prevention device equipped with the extension prevention valve P2R, which is separate from the shortening prevention device 70R, were fixed to the side peripheral surface of the right outrigger cylinder 40R, problems would arise such as poor maintainability of the extension prevention device, and the length of the right inner box 20R becoming shorter due to the increased width of the right cylinder box 30R, resulting in a decrease in stability when the outrigger device OR is extended. Furthermore, in order to ensure maintainability, openings must be formed in the right inner box 20R and the right cylinder box 30R, which reduces the strength of these members. Therefore, by incorporating the extension prevention valve P2R in the flow path connection member 51R fixed between the right outer box 10R and the right inner box 20R, it is possible to incorporate the extension prevention valve P2R into the right outrigger cylinder circuit EC5 without reducing the stroke of the right outrigger cylinder 40R and without reducing the strength of the right inner box 20R and the right cylinder box 30R.

[0062] In addition, in the case of a structure in which hydraulic oil piping is arranged on the outside and inside of the outer box, as in the outrigger device OR according to the present invention, the piping outside the outer box and the piping inside are connected by a flow path connecting member in which only a flow path is formed. Therefore, by incorporating the extension prevention valve P2R in such a flow path connecting member, it is possible to suppress the natural descent of the right outrigger cylinder 40R while keeping the structure of the outrigger device unchanged. Therefore, it is only necessary to change the equipment and procedures related to the manufacture of the flow path connecting member 51R of the outrigger device OR, and the equipment and procedures for manufacturing an outrigger device without the extension prevention valve P2R can be used without change, and further, it is easy to attach the flow path connecting member 51R equipped with an extension prevention valve to an outrigger device without the extension prevention valve P2R. Therefore, it is possible to manufacture an outrigger device OR equipped with an extension prevention valve P2R without a significant increase in cost.

[0063] The flow path connecting member 51R mounted on the outrigger unit OR according to the present invention can be made smaller than a double check valve. Similarly, the shortening prevention device 70R can also be made smaller than a double check valve. Therefore, it can be easily applied to a small outrigger unit OR in which it is difficult to design a wide space between the right outer box 10R and the right inner box 20R, and between the right cylinder box 30R and the right outrigger cylinder 40R.

[0064] <Modification> In the above embodiment, the flow path connection member 51R was arranged between the inner surface of the right outer box 10R and the outer surface of the right inner box 20R, but the location of the flow path connection member 51R is not necessarily limited to the above position, and for example, it may have a structure in which it is fixed to the outer surface of the outer box, or a structure in which it penetrates the outer box to connect the outer surface and the inner surface, and the effects of the present invention can be achieved with any such structure.

[0065] In the above embodiment, the flow path connection member 51R is fixed to the end of the right outer box 10R on the opening side, but it may be fixed to the opposite end. In the case of such a structure, the second pipe is accommodated inside the right outer box 10R and the right inner box 20R in a state of being wound up on a drum, and the length of the unwound range may be changed depending on the protruding state of the right inner box 20R, and even with such a structure, the effects of the present invention can be obtained.

[0066] In the above embodiment, the flow passage connection members 51R, 51L are provided with pilot check valves, but the flow passage connection members 51R, 51L do not necessarily have to be pilot check valves in which the piston 62 is operated by the hydraulic oil pressure applied to the extension-side flow passage 57A. For example, the flow passage connection members 51R, 51L may be check valves in which a push rod is moved by an input of an operation signal to press the poppet 60, thereby opening the contraction-side flow passage 58A. [Explanation of symbols]

[0067] 1...mobile crane, 10L...left outer box, 10R...right outer box, 20L...left inner box, 20R...right inner box, 30L...left cylinder box, 30R...right cylinder box, 40L...left outrigger cylinder, 40R...right outrigger cylinder, 47R...first extension side pipe line, 48R...second extension side pipe line, 49R...first shortening side pipe line, 50R...second shortening side pipe line, 51R...flow path connecting member, 60...poppet, 70R...shortening prevention device, P1R...shortening prevention valve, P2R...extension prevention valve

Claims

1. An outrigger device is mounted on a work machine and includes an outer box having an opening formed on the outside of the machine body, an inner box stored inside the outer box, and an outrigger cylinder fixed to an outer end of the inner box and extendable along the up-down direction of the machine body, a control valve connected to the outrigger device is capable of switching a high-pressure side flow path connected to a pump and a low-pressure side flow path connected to a hydraulic fluid tank between an extension position that connects to the side that extends the outrigger cylinder, a retraction position that connects to the side that retracts the outrigger cylinder, and a stop position that does not connect to the outrigger cylinder, an extension-side flow passage connecting an extension-side working fluid chamber of the outrigger cylinder, into which a working fluid flows in to extend the outrigger cylinder, to the control valve, and a shortening-side flow passage connecting a shortening-side working fluid chamber of the outrigger cylinder, into which a working fluid flows in to shorten the outrigger cylinder, to the control valve, each of which comprises a first pipeline having one end connected to the control valve and piped to the outside of the outer box, a second pipeline having one end connected to the outrigger cylinder, piped inside the inner box, and bending in accordance with the protruding state of the inner box, and a flow passage connecting member connecting the other end of the first pipeline to the other end of the second pipeline, the outrigger cylinder is provided with a shortening prevention device at a connection portion with the second pipeline, the shortening prevention device includes a shortening prevention valve that opens the extension-side flow passage when the control valve is in a shortening position and closes the extension-side flow passage when the control valve is in a stop position, The flow passage connection member is fixed to the outer box and is equipped with an extension prevention valve that opens the shortening side flow passage when the control valve is in the extension position and closes the shortening side flow passage when the control valve is in the stop position.

2. 2. The outrigger apparatus according to claim 1, wherein the extension prevention valve is a pilot check valve that controls opening and closing of the contraction side flow passage using a pressure of the working fluid applied to the extension side flow passage as a pilot pressure.

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