JP3553186B2 - Hydraulic circuit of telescopic cylinder - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a deep digging excavator equipped with a telescopic telescopic arm used for construction and civil engineering at the forefront, and specifically, in order to increase the telescopic speed of the working cylinder of the telescopic arm, The present invention relates to a hydraulic circuit for a telescopic cylinder including a speed increasing circuit and a drain circuit for reducing the back pressure of the working cylinder when shortened.
[0002]
[Prior art]
As a prior art of a conventional speed increasing circuit of a telescopic cylinder, for example, in Japanese Patent Application Laid-Open No. 5-321289, a boom that is pivotally supported above a deep digging excavator and that can swing up and down is provided. It comprises a telescopic arm that is attached and telescopically combines a plurality of arms to extend and contract in its length direction, and a clamshell bucket attached to the tip of the arm.
In this deep excavator, hydraulic cylinders operated by hydraulic pressure are configured in parallel in opposite directions to connect the pressure chambers of both hydraulic cylinders to each other, and supply hydraulic pressure to the pressure chamber of one hydraulic cylinder. The pressure oil discharged to the pressure chamber of the other cylinder is supplied, and the other hydraulic cylinder is also driven by supplying the pressure oil to one hydraulic cylinder. Therefore, a technique is described in which the pressure is supplied to one of the hydraulic cylinders so that the other hydraulic cylinder expands and contracts in synchronism, so that the expansion and contraction speed is increased.
[0003]
[Problems to be solved by the invention]
However, in the speed increasing circuit of the telescopic cylinder disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 5-321289, a hydraulic cylinder that hydraulically operates a telescopic telescopic arm that supports the clamshell bucket is arranged in parallel in the reverse direction, Since the pressure chambers of both hydraulic cylinders are connected to each other, the telescopic telescopic arm has a large diameter, and the working machine is large and heavy.
[0004]
Further, when the telescopic telescopic arm expands and contracts, by supplying pressure to one hydraulic cylinder, the other hydraulic cylinder is also driven, and by supplying pressure to one hydraulic cylinder, the other hydraulic cylinder synchronizes with the expansion and contraction speed. However, since the oil returning to the tank via the operation valve is throttled through the pilot check valve and the operation valve, a back pressure acts on the hydraulic cylinder.
In particular, the circuit resistance is large at high pressure, and this back pressure is further converted to the head side of the hydraulic cylinder, resulting in a large pressure loss in area ratio. The pressure loss affects the discharge pressure of the main pump.
[0005]
In the PQ curve of the variable displacement type main pump shown in FIG. 2, the pump discharge amount Q1 at the pump discharge pressure P1 rises to the pump discharge pressure P2 due to the above-mentioned pressure loss, and therefore decreases to the pump discharge amount Q2. I do. As a result, there is a problem that the shortening speed of the hydraulic cylinder is reduced, the shortening speed of the telescopic telescopic arm is reduced, and the working efficiency of the deep excavator is reduced.
[0006]
The present invention has been made in view of the above problems, and has a hydraulic circuit for a telescopic cylinder that improves the work efficiency of deep digging work by increasing the elevating speed of a clamshell bucket of a deep digging machine. The purpose is to provide.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a hydraulic circuit of a telescopic cylinder for a deep excavator according to the present invention uses a hydraulic pressure from a hydraulic pump 8 through an operating valve 11 and a counterbalance valve 16 to a single hydraulic pressure. The first pipeline 21a, 21b for supplying the pressure to the head side of the cylinder 5 and shortening the hydraulic cylinder 5 and the pressure oil from the hydraulic pump 8 are supplied to the bottom side of the hydraulic cylinder 5 via the operation valve 11. A hydraulic circuit of a telescopic cylinder having second pipelines 22a and 22b extending the hydraulic cylinder 5, wherein the relief valve 14 supplies oil discharged from the hydraulic cylinder 5 when the hydraulic cylinder 5 is extended. predetermined pressure is added, and, if said first conduit 21a, the oil discharged from the relief valve 14 which is opened at a pressure of from 21b to the pressure oil from the hydraulic pump 8 It is obtained by a structure in which a speed increasing circuit which flows into the hydraulic cylinder 5 by.
[0008]
The hydraulic circuit of the second telescopic cylinder supplies the pressure oil from the hydraulic pump 8 to the head side of the single hydraulic cylinder 5 via the operation valve 11 and the counterbalance valve 16 to shorten the hydraulic cylinder 5. The first pipelines 21a and 21b and the hydraulic oil from the hydraulic pump 8 are supplied to the bottom side of the hydraulic cylinder 5 via the operation valve 11, and the second pipelines 22a and 22b extending the hydraulic cylinder 5 are provided. A hydraulic circuit for a telescopic cylinder for a deep excavator having a relief valve 14 for applying a predetermined pressure to oil discharged from the hydraulic cylinder 5 when the hydraulic cylinder 5 is extended, Oil from the relief valve 14 released by the pressure from the pipes 21 a and 21 b is combined with the pressure oil from the hydraulic pump 8 and flows into the hydraulic cylinder 5. In which the provided.
[0009]
Further, a speed-up circuit that is shut off by a pilot check valve 15 that is closed by a shortening command oil pressure to the hydraulic cylinder 5, and oil that is discharged from the hydraulic cylinder 5 when the hydraulic cylinder 5 is shortened via the operation valve 11 to the tank 7. Drain pipe lines 30 and 31 are provided in parallel and return directly to the tank 7 via the pilot check valve 18 which is opened by the shortened command hydraulic pressure to the hydraulic cylinder 5 while being returned.
[0010]
[Action]
According to the above configuration, when the pressure oil from the hydraulic pump flows into the bottom side of the hydraulic cylinder, the hydraulic cylinder extends, the return oil from the head side of the hydraulic cylinder is shut off by the counterbalance valve, and is pressurized by the bottom side. The pressure on the head side merges with the pressure oil from the hydraulic pump via the relief valve and the speed increasing pilot check valve, and the pressure oil flows into the bottom side of the hydraulic cylinder to increase the speed of the hydraulic cylinder.
[0011]
When the hydraulic cylinder is extended, predetermined pressures are applied to the bottom side and the head side of the hydraulic cylinder, respectively. Therefore, even if the hydraulic cylinder is stopped halfway, it stops quickly and pulsation is reduced.
[0012]
Also, when pressure oil from the hydraulic pump flows into the head side of the hydraulic cylinder, the hydraulic cylinder shortens, and the return oil on the bottom side of the hydraulic cylinder returns to the tank via the operation valve and simultaneously issues a hydraulic command to shorten the hydraulic cylinder. Then, the return pilot check valve opens and returns directly to the tank without going through the operation valve, so that the resistance is reduced and the hydraulic cylinder increases in speed and shortens.
[0013]
When the load is suspended, the return side of the pressure oil is blocked by the counterbalance valve and the speed-increasing pilot check valve, so that the working machine does not drop due to leakage.
[0014]
【Example】
One embodiment of the present invention will be described with reference to FIGS.
First, the lower traveling body 1a of the hydraulic shovel 1 shown in FIG. 3 can travel freely by driving a traveling motor (not shown). An upper swing body 1b that can swing by driving a swing motor (not shown) is provided on the lower traveling body 1a. A boom 1c is attached to the upper swing body 1b by a bracket (not shown). The boom 1c is vertically swingable by driving a boom cylinder 1d. A base arm 2a having a hollow rectangular cross section for telescopic use is attached to the distal end of the boom 1c. The base arm 2a is vertically swingable by driving an arm cylinder 1f.
[0015]
A first telescopic arm 2b that slides in the base arm 2a is provided. The distal arm 2c is attached to the first telescopic arm 2b. A clamshell bucket 2d for grasping earth and sand is attached to the tip arm 2c.
[0016]
The hydraulic cylinder 5 is fixed to the first telescopic arm 2b shown in FIG. 1, and the base arm 2a fixes the piston 6 of the hydraulic cylinder 5.
The pulleys 3, 3 are attached to the distal end and the rear end of the first telescopic arm 2b, respectively, and the distal end of the proximal arm 2a, the rear end of the first telescopic arm 2b, and the rear end of the proximal arm 2a. And the movement of the steel cables 4 connecting the front end of the first telescoping arm 2b to the first telescopic arm 2b.
[0017]
Next, the hydraulic circuit of this embodiment shown in FIG. 1 will be described. A variable displacement hydraulic pump (hereinafter, referred to as a hydraulic pump) 8 is driven by a motor (not shown). The operation valve 11 is connected to the discharge line 20 of the hydraulic pump 8. The operation valve 11 is connected to pilot valves 10a and 10b by pilot pressure lines 41 and 42. The pilot valves 10a and 10b are mounted in conjunction with the pedal 10.
The operation valve 11 is switched by receiving a pilot pressure generated from pilot valves 10a and 10b when an operator operates the pedal 10.
[0018]
The control valve 11 is connected to the bottom chamber 5b of the hydraulic cylinder 5 via downstream pipes 22a and 22b.
The pipe 22a is connected to a branch pipe 29, and the pilot check valve 18 is interposed in the branch pipe 29. The pilot check valve 18 is connected to the tank 7 via return lines 30 and 31.
Thus, the return pipes 29, 30, 31 are provided in parallel with the pipes 22a, 22b.
[0019]
The pilot check valve 18 is connected to a pilot pipe 46 branched from the downstream pipe 21 a of the operation valve 11. Upon receiving the pilot pressure from the pilot line 46, the pilot check valve 18 opens.
[0020]
The downstream pipe 21 a of the operation valve 11 is connected to the counterbalance valve 16. The counter balance valve 16 is connected to the head chamber 5a of the hydraulic cylinder 5 via a pipe 21b.
The pipe 21b is connected to a branched pipe 24. The branch pipe 24 is connected to the relief valve 14, and the relief valve 14 is connected to the pilot check valve 15 via a pipe 25. The pilot check valve 15 is connected to a bottom pipe 22 b of the hydraulic cylinder 5 via a pipe 26.
[0021]
The pilot check valve 15 is connected to a pilot line 45 branched from the line 21b. The pilot check valve 13 is connected to a pilot line 43 branched from a line 22 a connected to the bottom chamber 5 b of the hydraulic cylinder 5. The pilot check valve 13 opens with the pressure supplied from the hydraulic pump 8.
The pilot check valve 13 is connected to the pilot check valve 15 via a pilot line 44.
[0022]
Further, the pilot check valve 13 is connected to the variable throttle 17 via a pilot line 45. The variable throttle 17 is connected to the head-side conduit 21b of the hydraulic cylinder 5.
When the pilot check valve 13 is opened by the pressure supplied from the hydraulic pump 8, the pilot pressure in the pilot lines 44 and 45 is transmitted from the pilot check valve 13 via the line 47 to the drain lines 30 and 31 from the tank 7. It is drained to.
[0023]
The pilot pipe 45 branches off from a pipe 21 b connected to the head side of the hydraulic cylinder 5. The pilot check valves 13 and 15 are pressed by the pressure supplied from the hydraulic pump 8 through the pilot line 45.
[0024]
The counter balance valve 16 includes a check valve 16a and a pressure regulating valve 16b. The set pressure of the pressure regulating valve 16b is such that when the clamshell bucket 2d rapidly falls down the underground hole and makes strong contact with the bottom of the hole, the oil on the head side of the hydraulic cylinder 5 is rapidly increased, and the pressure on the piston rod is strong. The set pressure is such that the high pressure in the pipeline 21b is released instantaneously so as not to buckle even if an impact is applied.
The set pressure of the pressure regulating valve 16b is set higher than the set pressure of the relief valve 14 interposed on the pipe 24. Thus, the pressure oil discharged from the head side of the hydraulic cylinder 5 cannot flow through the pressure regulating valve 16b and flows into the pipe 24.
[0025]
The variable throttle 17 is interposed on the pilot line 45. This variable throttle 17 is for adjusting the response of the pilot check valve 15. 12 is a relief valve.
[0026]
Next, the operation of the present embodiment will be described with reference to FIG.
The hydraulic circuit of FIG. 1 of this embodiment is performed by driving a hydraulic pump 8 by a motor (not shown) to suck oil from a tank and supply pressure oil to cylinders of various parts of the excavator.
[0027]
When the operation pedal 10 is depressed forward, the pilot pressure from the pilot pump 9 acts on the operation portion of the operation valve 11 from the line 40 via the pilot valve 10b via the pilot line 42, and the operation valve 11 is moved to the position c. Switch. Accordingly, the pressure oil discharged from the hydraulic pump 8 flows into the head chamber 5a of the hydraulic cylinder 5 from the line 21a through the check valve 16a of the counter balance valve 16 and the line 21b through the operation valve 11. At this time, the pressure oil acts on the pilot check valve 18 from the pipe 46 branched from the pipe 21a to perform an opening operation. As a result, the communication between the pipes 29 and 30 is established.
[0028]
The pressure oil flowing into the head chamber 5a of the hydraulic cylinder 5 shortens the hydraulic cylinder 5 and shortens the first telescopic arm 2b. The first telescoping arm 2b and the tip arm 2c are simultaneously shortened.
Drain oil discharged from the bottom chamber 5b of the hydraulic cylinder 5 is drained from the pipe 22b, the pipe 22a, and the operation valve 11 to the tank 7.
At the same time, the pressure oil flowing into the head chamber 5a of the hydraulic cylinder 5 acts on the pilot check valve 18 via the pilot line 46 branched from the line 21a to perform the opening operation. Thereby, the drain oil discharged from the bottom chamber 5b of the hydraulic cylinder 5 drains from the pipe 22b to the tank 7 through the pipe 29, the pilot check valve 18, the pipe 30, and the pipe 31 at the same time.
[0029]
With such a circuit, the pressure loss due to the back pressure is reduced, and the necessary pressing force on the head side of the hydraulic cylinder 5 is reduced.
As shown in the [discharge amount-discharge pressure] diagram of the variable displacement hydraulic pump shown in FIG. 2, the required pressure on the head side of the hydraulic cylinder 5 decreases from P1 to P2 and the discharge amount increases from Q1 to Q2. 5 shortening speed increases.
[0030]
Next, when the operating pedal 10 is depressed rearward, the pilot pressure from the pilot pump 9 acts on the operating portion of the operating valve 11 from the pipe 40 via the pilot valve 10a via the pilot pipe 41, and the operating valve 11 Switches to the b position. Thus, the pressure oil discharged from the hydraulic pump 8 flows through the operation valve 11 from the pipe 22a to the bottom chamber 5b of the hydraulic cylinder 5 via the pipe 22b.
At this time, the pressure oil discharged from the hydraulic pump 8 acts on the pilot check valve 13 from the pipe 22a through the pilot pipe 43 to open.
As a result, the pressure oil remaining in the pipes 44 and 45 is drained from the pilot check valve 13 to the tank 7 via the pipes 47, 30 and 31.
[0031]
On the other hand, the drain oil from the head chamber 5a of the hydraulic cylinder 5 tries to flow into the counterbalance valve 16 through the pipe 21b, but the set pressure of the pressure regulating valve 16b is reduced by the relief pressure provided between the branch pipe 24 and the pipe 25. Since it is higher than the set pressure of the valve 14, the pressure regulating valve 16b is not opened.
For this reason, the drain oil flows into the branch line 24 from the line 21b, and the pressure rises to a predetermined pressure higher than the bottom side, acts on the relief valve 14, opens the relief valve 14, and opens the pilot check valve from the line 25. It flows into the pipe line 26 through 15.
The pressure oil discharged from the relief valve 14 joins the pressure oil from the hydraulic pump 8 through the pipeline 22b and is supplied to the bottom side of the hydraulic cylinder 5 to increase the extension speed. The first telescopic arm 2b integrated with the hydraulic cylinder 5 extends. The first telescopic arm 2b and the distal end arm 2c are simultaneously extended by the steel cables 4, 4 guided to the pulleys 3, 3.
[0032]
【The invention's effect】
As described above, increasing the elevating speed of the clamshell bucket mounted on the tip of the telescopic arm of the hydraulic excavator is performed such that return oil on the head side of the hydraulic cylinder is shut off by the counterbalance valve, The pressure oil pressurized by the head side can be realized by a simple circuit configuration that joins the pressure oil discharged from the hydraulic pump via the relief valve and the pilot check valve.
[0033]
In addition, in response to a hydraulic command to shorten the hydraulic cylinder, the return pilot check valve opens and a line is provided to return the drain oil directly to the tank without passing through the operation valve. Can be shortened with increasing speed.
[Brief description of the drawings]
FIG. 1 is a view showing a telescopic hydraulic circuit according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a relationship between a discharge amount and a discharge pressure of a variable displacement hydraulic pump that is a main hydraulic pump.
FIG. 3 is an external view of a telescopic excavator according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Hydraulic excavator 2a ... Base arm 2b ... 1st telescopic arm 2c ... Tip arm 5 ... Cylinder 8 ... Variable displacement hydraulic pump 9 ... Pilot pump 10 ... Pedal 10a, 10b ... Pilot valve 11 ... Operating valves 13, 15, 18 ... Pilot check valve 14 ... Relief valve 16 ... Counter balance valve.

Claims (2)

Hydraulic oil from the hydraulic pump (8) is supplied to the head side of the single hydraulic cylinder (5) via the operation valve (11) and the counterbalance valve (16), and the hydraulic cylinder (5) is shortened. 1 pipe (21a, 21b)
Then, the hydraulic oil from the hydraulic pump (8) is supplied to the bottom side of the hydraulic cylinder (5) through the operating valve (11), and the second pipe (22a, 22b) having a hydraulic circuit of a telescopic cylinder for a deep excavator having the hydraulic cylinder (5) when the hydraulic cylinder (5) is extended.
The predetermined pressure is applied by the relief valve (14) to the oil to be discharged from, and the first conduit (21a, 21b) oil hydraulic pump discharged from the relief valve to be open at a pressure of from (14) (8) A hydraulic circuit for a telescopic cylinder, comprising a speed-increasing circuit for merging with the pressure oil from (8) and flowing into the hydraulic cylinder (5). Hydraulic oil from the hydraulic pump (8) is supplied to the head side of a single hydraulic cylinder (5) via the operation valve (11) and the counterbalance valve (16), and the hydraulic cylinder (5) is shortened . The hydraulic oil from the first pipeline (21a, 21b) and the hydraulic pump (8) is supplied to the bottom side of the hydraulic cylinder (5) via the operation valve (11), and the hydraulic cylinder (5) is extended. In the hydraulic circuit of a telescopic cylinder for a deep excavator having a second pipeline (22a, 22b), when the hydraulic cylinder (5) is extended, the hydraulic cylinder (5)
A predetermined pressure is applied to the oil discharged from the relief valve (14) by the relief valve (14), and the oil from the relief valve (14) released by the pressure from the first pipeline (21a, 21b) is supplied to the hydraulic pump (8). To increase the speed by flowing into the hydraulic cylinder (5) and to shut off by the pilot check valve (15), which is closed by the shortened command oil pressure to the hydraulic cylinder (5) When the circuit and the hydraulic cylinder (5) are shortened, oil discharged from the hydraulic cylinder (5) is returned to the tank (7) via the operation valve (11), and the hydraulic cylinder (5)
A drain pipe (30, 31) provided in parallel that directly recirculates to the tank (7) via the pilot check valve (18) that is opened by the shortened command hydraulic pressure to the telescopic cylinder Hydraulic circuit.

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