Pile driving machine and pressure control method

Abstract

To provide a pile press-in machine capable of accurately detecting hydraulic pressure in a gripping mechanism and stably operating the gripping mechanism while reducing a size and weight of a device.SOLUTION: A pile press-in machine for pressing-in piles into a ground comprising a gripping mechanism having a plurality of cylinders includes: a pressure control circuit that supplies hydraulic pressure to the gripping mechanism; a pressure detection mechanism that detects hydraulic pressure in the pressure control circuit; and a plurality of branch circuits that branch from the pressure control circuit and supply hydraulic pressure to the plurality of cylinders. Some of the plurality of branch circuits maintain pressure. Remaining branch circuits use the gripping mechanism as a pressure accumulation mechanism that accumulates pressure accompanied by supply of hydraulic pressure to the cylinder by elastic deformation of the gripping mechanism, and circulate a part of the hydraulic pressure supplied to the cylinder to the pressure control circuit.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a pile driving machine for driving a pile into ground and a pressure control method. [Background technology]

[0002] A known construction technique for driving and burying various types of steel pipe piles, structural steel piles, and other piles into the ground involves gripping the top end of an existing pile that has already been buried in the ground with a clamp to generate a reaction force, and then raising and lowering the chuck holding the pile, thereby successively pressing in new piles adjacent to the existing pile.

[0003] The pile driving machine used for such construction has a saddle that is fixed to the existing pile via multiple clamps, and a slide frame that can move back and forth relative to the saddle. A chuck is attached to the slide frame via a leader mast and a chuck frame. The chuck is equipped with a chuck mechanism that grips the pile to be driven. The pile to be driven is gripped by the chuck mechanism, the chuck is positioned at a predetermined position relative to the saddle, and the chuck frame and chuck are raised and lowered together along the leader mast to drive the pile into the ground.

[0004] Incidentally, gripping mechanisms such as clamps that grip existing piles and chucks that grip piles generate gripping force using hydraulic pressure, and there is a demand for safe hydraulic control that eliminates the risk of tipping over, etc. For example, Patent Document 1 discloses a clamping mechanism for pile-mounting work equipment, and describes a configuration in which a fluid pressure cylinder (hydraulic cylinder) is built into the gripping claws of the clamping mechanism, and the cylinder is operated by hydraulic pressure from a fluid pressure circuit (hydraulic circuit) to generate gripping force.

[0005] Furthermore, for example, Patent Document 2 discloses a technology in which an accumulator is connected to a hydraulic circuit, and side rollers follow changes in pile width to grip the pile even when a pile-mounting moving device is moved over an existing pile. Furthermore, for example, Patent Document 3 discloses a technology in which a counterweight is placed in a hydraulic oil circuit that supplies hydraulic oil to an actuator for driving a work device in a work machine such as a mobile crane, thereby eliminating the need for an accumulator to drive other actuators. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Publication No. 6-19639 [Patent Document 2] Japanese Patent Application Publication No. 6-306863 [Patent Document 3] Japanese Patent Application Laid-Open No. 2017-77966 Summary of the Invention [Problem to be solved by the invention]

[0007] For example, as disclosed in Patent Document 1, a gripping mechanism having a cylinder, such as a clamp or chuck of a pile driving machine, generates hydraulic pressure in the cylinder via a hydraulic circuit using oil supplied from a hydraulic output unit, and maintains that pressure to maintain the gripping force. The pressure in the hydraulic circuit is usually detected by a pressure sensor located in the circuit, and when a pressure drop is detected, a notification to that effect is displayed on a display device.

[0008] However, in a gripping mechanism that operates hydraulically, pressure loss due to the passage of time and temperature changes is unavoidable. In particular, when a pile driving machine is used in cold regions, the volume of oil (hydraulic oil) in the hydraulic circuit contracts, raising concerns about a drop in pressure. Therefore, for example, Patent Document 2 uses an accumulator, and Patent Document 3 uses a counterweight to efficiently control the pressure in the hydraulic circuit.

[0009] However, devices such as accumulators and counterweights are generally large and heavy, hindering efforts to make pile driving machines smaller and lighter. In other words, there is a demand for technology in the gripping mechanism of pile driving machines that can efficiently maintain pressure by suppressing pressure drops in the hydraulic circuit while also making the device smaller and lighter.

[0010] Furthermore, when a pressure sensor is installed in the hydraulic circuit, there is no sensor for each cylinder of the gripping mechanism, so the pressure sensor may not accurately detect the pressure in the cylinder, and the accurate pressure in the gripping mechanism may not be detected. For example, in cold regions, the hoses that make up the hydraulic circuit have a large surface area and are easily affected by ambient temperature, making it easy for the pressure sensor to detect a pressure drop rate due to volumetric contraction of the oil. On the other hand, the cylinders of the gripping mechanism have a small surface area, so the oil temperature drop due to ambient temperature is small, and even in the same environment, the pressure drop rate in the gripping mechanism may be small. This reduction in detection accuracy, such as a discrepancy between the pressure drop rate detected by the pressure sensor and the actual pressure drop rate in the gripping mechanism, becomes a problem.

[0011] In view of the above circumstances, the object of the present invention is to provide a pile driving machine and a pressure control method that can accurately detect the hydraulic pressure in the gripping mechanism while reducing the size and weight of the device, and enable the gripping mechanism to operate stably. [Means for solving the problem]

[0012] In order to achieve the above object, according to the present invention, there is provided a pile driving machine for driving piles into the ground, comprising a gripping mechanism having a plurality of cylinders, a pressure control circuit for supplying hydraulic pressure to the gripping mechanism, a pressure detection mechanism for detecting the pressure of the hydraulic pressure in the pressure control circuit, and a plurality of branch circuits branching from the pressure control circuit for supplying hydraulic pressure to the plurality of cylinders, The cross-sectional area of ​​the hose constituting the pressure control circuit is configured to be smaller than the cross-sectional area of ​​the cylinder, and in the plurality of branch circuits, pressure is maintained by a pressure maintenance valve in some of them, and pressure maintenance is not performed in the remaining branch circuits by not providing or operating a pressure maintenance valve, and in the branch circuit in which pressure maintenance is not performed, a pressure accumulation mechanism is configured to include a cylinder located on the distal end side of the gripping mechanism, and the pressure accumulation mechanism is configured to accumulate pressure by elastically deforming as a structure by the thrust of the cylinder when the gripping mechanism is closed at a predetermined pressure, There is provided a pile driving machine characterized in that it is configured to return a part of the hydraulic pressure supplied to the cylinder to the pressure control circuit.

[0016] The gripping mechanism is a plurality of clamps that grip the existing piles, and at least one of the branch circuits connected to the plurality of clamps may not be provided with the pressure retention valve.

[0017] The multiple clamps are a first clamp, a second clamp, a third clamp, and a fourth clamp, which are arranged in that order from the front of the pile driving machine, and at least a portion of the branch circuit connected to the cylinder of the third clamp and / or the fourth clamp may not be provided with the pressure maintaining valve.

[0018] Each of the plurality of clamps may have two cylinders, and the branch circuit may be connected to the two cylinders together.

[0019] Each of the plurality of clamps may have two cylinders, and the branch circuits may be connected to the two cylinders, respectively.

[0020] According to another aspect of the present invention, there is provided a pressure control method in a pressure control circuit that supplies hydraulic pressure to a gripping mechanism having a plurality of cylinders, the pressure control circuit having a plurality of branch circuits that branch off from the pressure control circuit and supply hydraulic pressure to the plurality of cylinders, The cross-sectional area of ​​the hose constituting the pressure control circuit is configured to be smaller than the cross-sectional area of ​​the cylinder, and in some of the plurality of branch circuits, pressure is maintained by a pressure maintenance valve, while in the remaining branch circuits, pressure is not maintained because a pressure maintenance valve is not provided or is not operated, and in the branch circuit where pressure is not maintained, a pressure accumulating mechanism is configured to include a cylinder located on the distal end side of the gripping mechanism, and when the gripping mechanism is closed at a predetermined pressure, the pressure accumulating mechanism accumulates pressure by elastically deforming as a structure due to the thrust of the cylinder, and a portion of the hydraulic pressure supplied to the cylinder is returned to the pressure control circuit. A pressure control method is provided. [Effects of the Invention]

[0021] According to the present invention, a pile driving machine and a pressure control method are provided that are capable of accurately detecting hydraulic pressure in the gripping mechanism and stably operating the gripping mechanism, while also achieving a compact and lightweight device. Specifically, the hydraulic pressure can be detected accurately by utilizing the pressure accumulation effect generated by the elastic deformation of the gripping mechanism and suppressing the pressure drop rate of the pressure control circuit. [Brief explanation of the drawings]

[0022] [Figure 1]1A is a schematic explanatory diagram of a pile driving machine according to an embodiment of the present invention, in which (a) is a side view, (b) is a rear view, (c) is a plan view seen from above, and (d) is a plan view showing the relationship between the clamp and the chuck and the pile. [Figure 2] FIG. 10 is a schematic diagram showing an example of hydraulic piping related to a clamp of the pile driving machine. [Figure 3] FIG. 10 is a schematic explanatory diagram of a hydraulic circuit in a conventional clamp. [Figure 4] 1 is a schematic explanatory diagram of a hydraulic circuit according to an embodiment of the present invention; [Figure 5] 10A and 10B are schematic explanatory diagrams illustrating elastic deformation of a clamp. [Figure 6] FIG. 10 is a schematic explanatory diagram of a hydraulic circuit according to another embodiment of the present invention. [Figure 7] 10 is a graph showing pressure changes according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals, and redundant description will be omitted. While possible piles to be pressed into include steel pipe piles, steel sheet piles (U-shaped, hat-shaped, etc.), concrete piles, and various types of shaped steel, the present embodiment will be described assuming that the pile is a steel sheet pile.

[0024] <Configuration of the pile driving machine> Figure 1 is a schematic explanatory diagram of a pile driving machine 1 according to an embodiment of the present invention, where (a) is a side view, (b) is a rear view, (c) is a plan view seen from above, and (d) is a plan view showing the relationship between the clamp and chuck and the pile. As shown in Figure 1, the pile driving machine 1 is composed of a reaction block 2, a platform 3, and a driving block 4.

[0025] The reaction block 2 includes multiple clamps 11 and a saddle 12 to which these clamps 11 are attached. In this embodiment, four clamps 11 are attached to the saddle 12 in the front-to-rear direction. Here, the clamps 11 are designated, in order from the front, as a first clamp 11a, a second clamp 11b, a third clamp 11c, and a fourth clamp 11d, and these may be collectively referred to as the clamps 11. The clamps 11 have the function of hydraulically gripping the upper end of an existing pile 9 previously embedded in the ground to fix the saddle 12 and absorb the reaction force of the press-in. The clamps 11 are equipped with multiple hydraulic cylinders 16, some or all of which are supplied with hydraulic oil (hereinafter simply referred to as oil) via hydraulic hoses or the like that constitute a hydraulic circuit described below, to control their operation. The hydraulic cylinders 16 include, for example, a cylinder 16a for opening and closing the clamp and a cylinder 16b for moving the clamp left and right. Note that the clamps 11 may grip objects other than the existing pile 9, such as a reaction support frame for absorbing the reaction force.

[0026] In this embodiment, of the multiple clamps 11, the first clamp 11a, which is closest to the press-fit block 4, is provided eccentrically so as to protrude toward the press-fit block 4 beyond the saddle 12, and the other clamps 11b to 11d are shaped in a straight line in the vertical direction to achieve a better balance of strength and lighter weight than curved clamps. The positional relationship between the clamps 11 is such that they can move left and right on the underside of the saddle 12. Note that the shapes and arrangement of the multiple clamps 11 shown in FIG. 1 are merely examples, and the clamps 11 of the present invention are not limited to the illustrated form.

[0027] In this specification, the term "forward" refers to the direction in which the pile driving machine 1 advances in driving work, and in Figures 1(a), (c), and (d), the right side of the page is the forward side, and the left side of the page is the rear. The left-right direction is determined by looking at the driving work direction from above, and in Figures 1(c) and (d), the lower side of the page is the right side, and the upper side of the page is the left side.

[0028] A groove-shaped slide guide 13, for example, extending from the front end toward the rear, is provided on the upper left and right sides of the saddle 12. In addition, a bracket 14 is provided on the rear end of the saddle 12 in the center of the width direction, as a fixing part to which one end of a front / rear cylinder 23, the other end of which is fixed to the platform 3 (described later), is fixed.

[0029] The platform 3 has a slide frame 21 attached to the upper surface of the saddle 12, and a leader mast 22. The slide frame 21 is installed on the upper surface of the saddle 12 and slides along the slide guide 13. One end of a front and rear cylinder 23 is fixed to the slide frame 21. The reaction block 2 and the platform 3 are connected via the front and rear cylinder 23 by fastening a pin, tube, or the like in a hole 25 formed in the other end of the front and rear cylinder 23.

[0030] A groove-shaped slide guide 26 is provided on the front side of the leader mast 22, into which the sliding portion 36 of the press-fit block 4 is fitted, and brackets 27 for attaching the press-fit block 4 are provided on both the left and right sides of the front lower part of the leader mast 22.

[0031] The press-fitting block 4 has a chuck 31 that grips the pile 10 to be newly driven (or pulled out), a chuck frame 32 that supports the chuck 31, and an elevation cylinder 33 that raises and lowers the chuck frame 32 relative to the platform 3. The chuck 31 is provided with an opening 34 through which the pile 10 is inserted in the vertical direction, and a chuck mechanism 35 that grips the pile 10 that has passed through this opening 34. In the embodiment shown in Fig. 1(c), the chuck mechanism 35 is composed of a pair of claws that clamp the pile 10.

[0032] The rear side of the chuck frame 32 has a sliding portion 36 that is fitted into the slide guide 26 of the platform 3 and slides along the slide guide 26, and also has a pair of lifting cylinders 33 whose tips 28 are fixed to the bracket 27 of the platform 3.

[0033] <An example of hydraulic piping for a pile driving machine> In the pile driving machine 1 configured as described with reference to Fig. 1, the operation of the clamp 11 is controlled by hydraulic pressure. Fig. 2 is a schematic diagram showing an example of hydraulic piping related to the clamp of the pile driving machine 1.

[0034] As shown in Figure 2, an oil supply pipe 41 and an oil return pipe 42 connected to a hydraulic unit 5 provided outside the pile driving machine 1 are connected to a control manifold 43 installed inside the leader mast 22. Oil sent from the hydraulic unit 5 is then sent to the clamp 11 side by a switching valve 44, and controls, for example, the opening and closing of the clamp 11.

[0035] 2, hydraulic hoses 45, 46, and 47 for opening and closing the clamps, for moving them left and right, and for moving them back and forth are each connected to a control manifold 43, and are connected via hydraulic hoses from branch manifolds 48 and 49 to hydraulic cylinders 16 that position the operation of each of the four clamps 11a to 11d. For example, hydraulic hose 45 is connected to hydraulic cylinder 16a that controls the opening and closing of clamp 11, and hydraulic hose 46 is connected to hydraulic cylinder 16b that controls the left and right movement of clamp 11. A connecting jig such as a coupler may be used for the connections.

[0036] 2 shows an example of piping for a steel sheet pile, and since there is no need to adjust the clamp 11 forward or backward, the tip of the hydraulic hose 47 for forward or backward movement is closed. In this embodiment, the clamp 11 does not move forward or backward, but in cases where adjustment of the position in the forward or backward direction is required, such as for steel pipe piles, it is connected in a similar manner. Also, in FIG. 2, there are two hydraulic hoses for positioning the opening and closing and the left and right movement of the clamp 11, but they are shown as one. Note that the platform 3 shown in FIG. 2 is provided with hydraulic hoses 45, 46, and 47 for opening and closing, left and right movement, and forward and backward movement of the clamp 11, but if the platform is used exclusively for piles and no forward or backward movement of the clamp 11 is required, the hydraulic hose 47 for forward and backward movement may be omitted.

[0037] <Conventional hydraulic circuit for clamping> The inventors have noticed that, among the hydraulic piping described above with reference to Fig. 2, the conventional circuit configuration has a problem in stably maintaining a gripping force, particularly with regard to the hydraulic circuit that opens and closes the multiple clamps 11 (first clamp 11a to fourth clamp 11d). Below, this problem will be explained with reference to a hydraulic circuit diagram. Note that, although the multiple cylinders of the multiple clamps 11 are collectively illustrated as "hydraulic cylinders 16 (16a, 16b)" in Figs. 1 and 2, in the following explanation, the opening and closing cylinders of each of the clamps 11a to 11d may be assigned different reference numerals.

[0038] Figure 3 is a schematic diagram of a hydraulic circuit S1 in a conventional clamp, with arrows in the figure indicating the flow of oil. As shown in Figure 3, an oil supply pipe 41 connected to a hydraulic unit 5 is connected to a control manifold 43 (not shown in Figure 3) and a switching valve 44. A pressure control circuit 60 is provided on the clamp 11 side, which supplies oil pressure to the clamp 11 by supplying oil and controls the pressure related to opening and closing. A pressure sensor C1 is provided in the pressure control circuit 60 as a pressure detection mechanism that detects the pressure of the oil pressure in the pressure control circuit 60.

[0039] Each of the multiple clamps 11 (first clamp 11a to fourth clamp 11d) has two opening and closing cylinders (hereinafter simply referred to as cylinders). As shown in the figure, first clamp 11a has cylinders 70a and 70b, second clamp 11b has cylinders 72a and 72b, third clamp 11c has cylinders 74a and 74b, and fourth clamp 11d has cylinders 76a and 76b.

[0040] The pressure control circuit 60 is provided with a plurality of branch circuits that branch off on the downstream side (clamp side) of the pressure control circuit 60 and supply hydraulic pressure to the plurality of cylinders of each of the clamps 11a to 11d. The number of branch circuits is arbitrary, and for example, in the configuration of Fig. 3, four branch circuits 80a to 80d are provided that collectively supply hydraulic pressure to the cylinders of the first clamp 11a to the fourth clamp 11d, respectively.

[0041] A pressure maintenance valve V1 and a pressure sensor C1 are provided upstream of the pressure control circuit 60 (for example, near the switching valve 44 in the leader mast 22). The branch circuits 80a to 80d are each provided with pressure maintenance valves V2a, V2b, V2c, and V2d that are different from the pressure maintenance valve V1.

[0042] The hydraulic circuit S1 is provided with a return circuit 90 for causing return oil from the plurality of cylinders of each of the clamps 11a to 11d to flow upstream and return it to the hydraulic unit 5 via a return oil pipe .

[0043] In the hydraulic circuit S1 shown in FIG. 3, hydraulic pressure is supplied to the multiple cylinders of each clamp 11a-11d by the pressure control circuit 60 and branch circuits 80a-80d, resulting in clamp closure. Even if hydraulic pressure is supplied up to a predetermined pressure based on the pressure sensor C1 while the clamp is closed and then the hydraulic pressure supply is stopped, the function (hydraulic pressure retention function) of the pressure retention valves V1 and V2a-V2d maintains the supplied hydraulic pressure, thereby maintaining the clamp closure state. This configuration maintains the gripping force of the clamp 11 as a gripping mechanism. The pressure sensor C1 provided in the pressure control circuit 60 measures the pressure within the pressure control circuit 60 and detects multiple states, such as a state in which the gripping force is maintained or a state in which the pressure is decreasing. The pressure sensor C1 also detects fluctuations in the pressure within the pressure control circuit 60, such as the rate of pressure decrease.

[0044] In addition, by switching the switching valve 44 and supplying hydraulic pressure from the return circuit 90 to the pressure retention valve V1 and pressure retention valves V2a to V2d, the pressure retention function is released, and the return oil is returned to the hydraulic unit 5 via the pressure control circuit 60, thereby releasing the clamp.

[0045] In the hydraulic circuit S1 configured as described above, the gripping force of the clamp 11 is maintained by maintaining hydraulic pressure with the pressure maintenance valve V1 and pressure maintenance valves V2a to V2d. However, when the ambient temperature drops suddenly, for example in cold regions, the hoses that make up the pressure control circuit 60 have a large surface area relative to the amount of oil, and a drop in oil temperature in the hoses causes the oil volume to shrink, which is likely to cause the pressure sensor C1 to detect the rate of pressure drop. On the other hand, the cylinders of the clamp 11 and their peripheral circuits (for example, parts of the branch circuits 80a to 80d) have a small surface area relative to the amount of oil, and the internal oil temperature is less susceptible to the ambient temperature, so the pressure drop is limited.

[0046] In other words, in hydraulic circuit S1, when the ambient temperature drops suddenly in cold regions or the like, as long as hydraulic pressure is maintained between cylinders 70a, 70b, 72a, 72b, 74a, 74b, and 76a, 76b of each clamp and pressure maintenance valves V2a-V2d, no pressure drop occurs in the cylinders of clamp 11, and sufficient gripping force is maintained. Nevertheless, there is a problem in that due to volumetric contraction of the oil in the hoses that make up pressure control circuit 60, pressure sensor C1 may detect a significant rate of pressure drop even if pressure maintenance valve V1 is functioning normally.

[0047] <Hydraulic circuit according to an embodiment of the present invention> In view of the problems with the conventional hydraulic circuit S1 described above, the present inventors have discovered that the above problems can be solved by a hydraulic circuit S2 having the configuration described below. The hydraulic circuit S2 according to an embodiment of the present invention will be described below with reference to Figure 4. Note that components having the same functional configuration as those in the conventional hydraulic circuit S1 will be given the same reference numerals, and their description may be omitted.

[0048] FIG. 4 is a schematic diagram of a hydraulic circuit S2 according to an embodiment of the present invention, with arrows in the diagram indicating the flow of oil. In the hydraulic circuit S2 according to this embodiment, some of the multiple branch circuits branching off downstream (on the clamp side) of the pressure control circuit 60 are provided with pressure retention valves, while the remaining branch circuits are not provided with pressure retention valves. As an example, as shown in FIG. 4, branch circuits 80a, 80b, and 80d are provided with pressure retention valves V2a, V2b, and V2d, respectively, while branch circuit 80c is not provided with a pressure retention valve. Note that the number and number of branch circuits that do not have pressure retention valves are optional, but it is necessary that at least some of the branch circuits be provided with pressure retention valves.

[0049] Furthermore, the configuration of hydraulic circuit S2 is configured with a rigidity that allows the clamps 11 serving as gripping mechanisms to be elastically deformed appropriately as a structure by the thrust of the cylinders of each clamp when they are closed with a predetermined pressure. That is, clamps 11 of hydraulic circuit S2 are designed to function as a pressure accumulation mechanism that accumulates excess elastic deformation so that a portion of the hydraulic pressure in hydraulic circuit S2 can be returned to pressure control circuit 60 by intentionally causing elastic deformation as described below.

[0050] In the hydraulic circuit S2 configured as shown in Figure 4, hydraulic pressure is maintained by pressure retention valve V1 and pressure retention valves V2a, V2b, and V2d, thereby maintaining the gripping force of clamp 11. The inventors discovered that by using a steel material that can elastically deform appropriately for clamp 11, clamp 11 elastically deforms in a direction spreading from its crotch (crotch O, described below with reference to Figure 5), and that particularly components around the cylinder located on the distal end of clamp 11 (components that absorb the expansion and contraction of the cylinder) undergo significant elastic deformation, allowing more hydraulic pressure to accumulate in the cylinder located on the distal end of clamp 11 than in cylinders at other locations. By utilizing this, when the ambient temperature suddenly drops, for example in cold regions, the pressure accumulation effect caused by elastically deforming clamp 11 allows oil to return to pressure control circuit 60 from branch circuit 80c, which does not have a pressure retention valve, thereby suppressing pressure drop in pressure control circuit 60 and keeping the rate of pressure drop low. This is because the cross-sectional area of ​​the hose that makes up the pressure control circuit 60 is significantly different from the cross-sectional area of ​​the cylinder (here, cylinders 74a and 74b of the third clamp 11c), and because the clamp 11 is elastically deformed by hydraulic pressure, giving it a pressure accumulation effect.

[0051] FIG. 5 is a schematic diagram illustrating the elastic deformation of the clamp, with (a) being an enlarged view and (b) being an AA cross section. Also, FIG. 5(c) is an AA cross section of a conventional clamp. As an example, FIG. 5 illustrates the cylinders 74a and 74b when the third clamp 11c grips the existing pile 9. As shown in FIG. 5(a), the third clamp 11c is a structure made of, for example, elastically deformable steel. When oil is supplied to the cylinders 74a and 74b and the existing pile 9 is gripped by hydraulic pressure (i.e., the clamp is closed), an elastic deformation amount e1 occurs in the entire structure. As shown in the figure, the elastic deformation amount differs depending on the position of each cylinder, e.g., e2 or e3.

[0052] Here, the inner diameter φd of the hoses that make up the hydraulic circuit S2 and the inner diameter φD of the cylinders 74a and 74b are significantly different, and naturally, their cross-sectional areas are also significantly different. For example, the inner cross-sectional area AD of the cylinders 74a and 74b is approximately 30 to 400 times the inner cross-sectional area Ad of the hoses that make up the hydraulic circuit S2.

[0053] In this way, if the ambient temperature suddenly drops in a cold climate or the like while clamp 11 is elastically deformed as a structure, the volume of oil in the hose that constitutes pressure control circuit 60 will contract. Then, in branch circuit 80c, which is not provided with a pressure maintenance valve, the elastic deformation returns, and the pressure accumulation effect is released, causing oil to return from branch circuit 80c to pressure control circuit 60, suppressing the pressure drop in pressure control circuit 60 and keeping the rate of pressure drop low. In the example shown in Figure 5, for example, the amount of returned oil is "inner diameter cross-sectional area AD of cylinders 74a, 74b × (e2 + e3)," which is sufficient to suppress the pressure drop in the hose that constitutes pressure control circuit 60, which has a small inner diameter cross-sectional area.

[0054] In addition, in the clamp cross-sectional configuration shown in FIG. 5(b), the vertical length of the upper cross section of the crotch portion O of the clamp 11 is defined as h, the widthwise length as b, and the dimensions of the present invention configuration in FIG. 5(b) are defined as h2 × b2, while the dimensions of the conventional configuration in FIG. 5(c) are defined as h1 × b1. It is known that the second moment of area Ix, which relates to the rigidity of the clamp 11 in the expansion direction, is proportional to the cube of the distance in the length direction h. Therefore, reducing the length in the h direction and reducing the cross-sectional area of ​​the crotch portion O of the clamp 11 can increase flexibility. In other words, it is preferable to design the dimension h2 of the present invention shown in FIG. 5(b) to be smaller than the conventional dimension h1 shown in FIG. 5(c) to increase flexibility. The same applies to the B-B cross section shown in FIG. 5(a).

[0055] Furthermore, the amount of elastic deformation tends to increase in proportion to the cylinder thrust P of cylinders 74a and 74b (see arrows in FIG. 5) and the distance L (L1, L2 in FIG. 5) from crotch portion O to each cylinder. Therefore, in designing clamp 11 and cylinders 74a and 74b, it is preferable to appropriately determine the thrust P and distance L so as to achieve the desired amount of elastic deformation.

[0056] As explained above, it is preferable to design the clamp 11 and the cylinders 74a, 74b so that the vertical length h of the crotch portion O of the clamp 11, the cylinder thrust P of the cylinders 74a, 74b, and the distance L from the crotch portion O to each cylinder achieve the desired amount of elastic deformation. In doing so, it is necessary to design the clamp 11 and the cylinders 74a, 74b within a range that will not cause them to break due to excessive mechanical deflection.

[0057] <Action and effect> 4 and 5, the following advantageous effects can be achieved. Even if the volume of oil in the hoses constituting the pressure control circuit 60 contracts and a pressure drop is a concern when the hydraulic pressure is maintained by the pressure retention valve V1 and the pressure retention valves V2a, V2b, and V2d and the existing pile 9 is gripped (clamp closed state), oil flows back to the pressure control circuit 60 from the branch circuit 80c in which the cylinders 74a and 74b are arranged, suppressing the pressure drop and keeping the rate of pressure drop low. In other words, the hydraulic pressure in the clamp 11 can be detected with high accuracy.

[0058] In particular, when pressure sensor C1 is provided upstream of the hydraulic circuit (i.e., upstream of pressure control circuit 60) as in this embodiment, it is possible to avoid a situation in which pressure sensor C1 detects an increase in the rate of pressure decrease even when hydraulic pressure is maintained by pressure retention valve V1 and pressure retention valves V2a, V2b, and V2d, no pressure drop occurs in clamps 11a-11d, and sufficient gripping force is maintained. This makes it possible to stably operate clamp 11 based on the detection by pressure sensor C1. Note that it is possible to install pressure sensors near the cylinders of each clamp to reliably detect the pressure of each clamp 11a-11d and ensure stable operation, but this could result in an increase in the size and cost of the entire device.

[0059] Furthermore, as can be seen by comparing the conventional hydraulic circuit S1 (see FIG. 3) with the hydraulic circuit S2 according to this embodiment (see FIG. 4), the configuration according to this embodiment is a configuration in which the pressure retention valve V2c is not provided in some of the branch circuits (branch circuit 80c in this case) in the conventional hydraulic circuit S1. This eliminates the need for additional equipment or additional controls, and contributes to reducing the weight and size of the pile driving machine 1. In addition, this improves the accuracy of hydraulic pressure detection in the clamp 11, enabling stable operation of the clamp 11. In addition, the reduction in equipment from the conventional configuration contributes to cost reduction.

[0060] While one embodiment of the present invention has been described above, the present invention is not limited to the illustrated embodiment. It is clear that a person skilled in the art can conceive of various modifications and alterations within the scope of the ideas set forth in the claims, and it is understood that these modifications and alterations also fall within the technical scope of the present invention.

[0061] In the hydraulic circuit S2 according to the above embodiment, the branch circuits 80a, 80b, and 80d are provided with pressure retention valves V2a, V2b, and V2d, respectively, while the branch circuit 80c is not provided with a pressure retention valve. However, the number and arrangement of pressure retention valves are not limited to this. That is, a pressure retention valve must be provided in at least one of the branch circuits, and at least one other branch circuit is not provided with a pressure retention valve, as long as the pressure accumulation effect generated by the elastic deformation of the clamp can be utilized. Here, the pressure retention valve is preferably provided in the branch circuit connected to the cylinder of the clamp that grips the existing pile 9. This is because providing pressure retention valves in both the pressure control circuit 60 and the branch circuits is desirable to double-retain the clamp's gripping force even when the pile driving machine 1 is stopped.

[0062] For example, in the hydraulic circuit S2 according to the above embodiment, the case where only branch circuit 80c is not provided with a pressure retention valve is illustrated, but it is also possible that only branch circuit 80b is not provided with a pressure retention valve, or that both branch circuits 80b and 80c are not provided with pressure retention valves. It is also possible that branch circuits 80a and 80d are not provided with pressure retention valves. In a pile driving machine 1 equipped with multiple clamps, some of the clamps at the rear end (e.g., clamps 11c and / or 11d) may not grip the existing pile 9. Therefore, from the viewpoint of stable clamp operation, it is also possible to configure the pile driving machine 1 so that one or both of branch circuits 80a and 80b are not provided with pressure retention valves.

[0063] In the above embodiment, the case where four clamps 11 (11a to 11d) are attached to the saddle 12 of the pile driving machine 1 is illustrated and described, but the number of clamps 11 is not limited to this. For example, depending on the type of pile driving machine, three clamps may be attached, and the present invention can be easily applied to the first to third clamps.

[0064] Furthermore, in the hydraulic circuit S2 according to the above embodiment, a configuration has been illustrated and described in which a pressure retention valve is not provided at a predetermined location, for example, in the branch circuit 80c, but a means may also be used in which the hydraulic pressure is not maintained by a pressure retention valve at a predetermined location.

[0065] Furthermore, while the above embodiment illustrates and describes the scope of application of the present invention to a hydraulic circuit that opens and closes multiple clamps 11 (first clamp 11a to fourth clamp 11d), the present invention can be applied to various mechanisms and devices that operate with hydraulic pressure supplied from a hydraulic circuit. For example, the present invention can be applied to various gripping mechanisms such as a chuck for a pile driving machine, a casing chuck, and a casing lock, which are devices that function as so-called pressure accumulation mechanisms that deform elastically as a structure.

[0066] <Another embodiment of the present invention> In the hydraulic circuit S2 according to the above embodiment, four branch circuits 80a to 80d are provided to collectively supply hydraulic pressure to the cylinders of the first to fourth clamps 11a to 11d, respectively. However, the configuration of the hydraulic circuit according to the present invention is not limited to this. Below, a hydraulic circuit S3 according to another embodiment of the present invention will be described with reference to Fig. 6. Note that, in the following, components having the same functional configuration as those of the hydraulic circuits S1 and S2 described above will be assigned the same reference numerals, and their description may be omitted.

[0067] FIG. 6 is a schematic diagram of a hydraulic circuit S3 according to another embodiment of the present invention, with arrows indicating the flow of oil. As shown in FIG. 6, in the hydraulic circuit S3 according to this embodiment, each of the branch circuits 80a-80d is connected to two cylinders of the first clamp 11a-fourth clamp 11d. In other words, each of the branch circuits 80a-80d has a first circuit connected to one cylinder and a second circuit connected to the other cylinder. For example, the branch circuit 80a has a first circuit 82a connected to one cylinder 70a and a second circuit 82b connected to the other cylinder 70b. Similarly, branch circuit 80b has a first circuit 84a connected to one cylinder 72a and a second circuit 84b connected to the other cylinder 72b, branch circuit 80c has a first circuit 86a connected to one cylinder 74a and a second circuit 86b connected to the other cylinder 74b, and branch circuit 80d has a first circuit 88a connected to one cylinder 76a and a second circuit 88b connected to the other cylinder 76b.

[0068] In each of the branch circuits 80a to 80d, the first circuits 82a, 84a, 86a, and 88a are provided with pressure maintenance valves V2a to V2d, while the second circuits 82b, 84b, 86b, and 88b are not provided with pressure maintenance valves.

[0069] In the hydraulic circuit S3 configured as shown in Fig. 6, hydraulic pressure is maintained by pressure retention valve V1 and pressure retention valves V2a-V2d, thereby maintaining the pressure in at least one cylinder of each of clamps 11a-11d and maintaining the gripping force. In this state, if the ambient temperature suddenly drops, for example in a cold region, oil returns from second circuits 82b, 84b, 86b, and 88b, which do not have pressure retention valves, to the upstream pressure control circuit 60, suppressing the pressure drop in the pressure control circuit 60 and keeping the rate of pressure drop low. This is due to the large difference in cross-sectional area between the hoses constituting the pressure control circuit 60 and the cylinders (cylinders 70b-76b in this case), as described in the above embodiment, and also because the clamps 11 are elastically deformed by hydraulic pressure, providing a pressure accumulation effect.

[0070] 6 illustrates a configuration in which all of the branch circuits 80a to 80d have a first circuit and a second circuit, but such a circuit configuration does not have to be applied to all of the branch circuits 80a to 80d. That is, it is sufficient if at least one of the branch circuits 80a to 80d is configured to have a first circuit and a second circuit. In that case, a branch circuit that does not have a first circuit and a second circuit may be configured to supply hydraulic pressure collectively to the cylinders of the clamps, similar to the conventional hydraulic circuit S1.

[0071] The branch circuits and the number of branch circuits configured with a first circuit and a second circuit are optional, but it is necessary that at least some of the branch circuits have this configuration. In a pile driving machine 1 equipped with multiple clamps, some of the clamps at the rear end (e.g., clamps 11c and / or 11d) may not grip the existing pile 9, so from the perspective of stable clamp operation, it is desirable to configure one or both of the branch circuits 80a and 80b with a first circuit and a second circuit.

[0072] <Example> As an example of the present invention, to confirm the effect of suppressing pressure drop in the hydraulic circuit S2 described in the above embodiment, we verified the pressure change in the pressure control circuit when the oil temperature drops. Specifically, we measured the pressure change in the circuit when the oil temperature drops over time in a pressure control circuit where a pressure maintenance valve is provided in the branch circuit and a pressure control circuit where no pressure maintenance valve is provided. Figure 7 is a graph showing the pressure change in an example of the present invention.

[0073] As shown in Figure 7, when the oil temperature in the circuit dropped from 32°C to 21°C over a 10-minute period, the pressure in the pressure control circuit with the pressure retention valve dropped from 34 MPa to 20 MPa in just 6 minutes. On the other hand, without the pressure retention valve, the pressure in the pressure control circuit only dropped from 34 MPa to 27 MPa over 10 minutes. The results shown in Figure 7 indicate that even if the ambient temperature of the pile driving machine drops suddenly in cold regions, resulting in a corresponding drop in the oil temperature in the pressure control circuit, the rate of pressure drop detected by the pressure sensor C1 can be kept low by adopting a circuit configuration that does not include a pressure retention valve in the branch circuit. The results of this example confirmed that by omitting a pressure retention valve in the branch circuit and utilizing the elastic deformation of the clamp structure and the resulting pressure accumulation effect, accurate hydraulic pressure detection in the clamp can be achieved when a pressure sensor is installed in the pressure control circuit. [Industrial Applicability]

[0074] The present invention can be applied to a pile driving machine that drives piles into the ground. [Explanation of symbols]

[0075] 1...Pile press machine 2...Reaction block 3. Platform 4...Press-fit block 5...Hydraulic unit 9...Existing pile 10...Pile 11...Clamp 11a...First clamp 11b...Second clamp 11c…Third clamp 11d…Fourth clamp 12...Saddle 13...Slide guide 14...Bracket 16...Hydraulic cylinder 21...Slide frame 22...Leader mast 23...Front and rear cylinders 26...Slide guide 27…Bracket 31...Chuck 32...Chuck frame 33...Lifting cylinder 35...Chuck mechanism 41...Oil supply pipe 42...Return oil piping 43...Control manifold 44...Switching valve 45, 46, 47...Hydraulic hoses 60...Pressure control circuit 70a, 70b...(first clamp) cylinder 72a, 72b...(Second clamp) cylinder 74a, 74b...(third clamp) cylinder 76a, 76b...(fourth clamp) cylinder 80a~80d...Branch circuits 90...Return circuit C1...Pressure sensor S1...(conventional) hydraulic circuit S2...Hydraulic circuit (according to an embodiment of the present invention) S3...Hydraulic circuit (according to another embodiment of the present invention) V1: Pressure maintaining valve V2a~V2d...Pressure maintaining valves

Claims

1. A pile driving machine for driving piles into the ground, a gripping mechanism having a plurality of cylinders; a pressure control circuit for supplying hydraulic pressure to the gripping mechanism; a pressure detection mechanism that detects the pressure of the hydraulic pressure in the pressure control circuit; a plurality of branch circuits branching from the pressure control circuit to supply hydraulic pressure to the plurality of cylinders; The cross-sectional area of ​​the hose constituting the pressure control circuit is configured to be smaller than the cross-sectional area of ​​the cylinder, In the plurality of branch circuits, pressure is maintained by a pressure maintenance valve in some of the branch circuits, and pressure maintenance is not performed in the remaining branch circuits because a pressure maintenance valve is not provided or is not activated, In the branch circuit where pressure is not maintained, a pressure accumulation mechanism is configured to include a cylinder located at the end side of the gripping mechanism, and the pressure accumulation mechanism is configured to accumulate pressure by elastically deforming as a structure due to the thrust of the cylinder when the gripping mechanism is closed at a predetermined pressure, and is configured to return a portion of the hydraulic pressure supplied to the cylinder to the pressure control circuit.

2. The gripping mechanism is a plurality of clamps that grip the existing piles, The pile driving machine according to claim 1, wherein at least one of the branch circuits connected to the plurality of clamps is not provided with the pressure retention valve.

3. The plurality of clamps are a first clamp, a second clamp, a third clamp, and a fourth clamp, which are arranged in this order from the front of the pile driving machine, 3. The pile driving machine according to claim 2, wherein the pressure retention valve is not provided in at least a part of the branch circuit connected to the cylinder of the third clamp and / or the fourth clamp.

4. Each of the plurality of clamps has two cylinders, 4. The pile driving machine according to claim 2, wherein the branch circuit is connected to two of the cylinders together.

5. Each of the plurality of clamps has two cylinders, 4. The pile driving machine according to claim 2, wherein the branch circuits are connected to two of the cylinders, respectively.

6. A pressure control method in a pressure control circuit that supplies hydraulic pressure to a gripping mechanism having a plurality of cylinders, comprising: the pressure control circuit has a plurality of branch circuits branching from the pressure control circuit to supply hydraulic pressure to the plurality of cylinders, The cross-sectional area of ​​the hose constituting the pressure control circuit is configured to be smaller than the cross-sectional area of ​​the cylinder, In the plurality of branch circuits, pressure is maintained by a pressure maintenance valve in some of the branch circuits, and pressure is not maintained in the remaining branch circuits because a pressure maintenance valve is not provided or is not activated, In the branch circuit where pressure is not maintained, a pressure accumulator mechanism is configured to include a cylinder located on the distal end side of the gripping mechanism, and when the gripping mechanism is closed at a predetermined pressure, the pressure accumulator mechanism accumulates pressure by elastically deforming as a structure due to the thrust of the cylinder, and returns a portion of the hydraulic pressure supplied to the cylinder to the pressure control circuit.

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