JP4493543B2 - Fluid pressure circuit - Google Patents

Description

  The present invention relates to a fluid pressure circuit including a fluid pressure cylinder that is operated by a working fluid that passes through a control valve.

  2. Description of the Related Art Conventionally, there is a hydraulic excavator A shown in FIG. 2, for example, as a working machine capable of working in a narrow area such as between structures.

  The hydraulic excavator A includes a lower traveling body 1, an upper revolving body 3 provided on the lower traveling body 1 via a swivel bearing portion 2, and a cab 4 mounted on the upper revolving body 3. The working device 5 is provided on the body 3 so as to be operable on the side of the cab 4. The working device 5 is provided with a boom 6 provided on the upper swing body 3 so as to be movable up and down. A telescopic arm 7 (hereinafter referred to as a telescoreme 7) as a multistage telescopic arm that can be provided and has a multistage telescopic function, and a clamshell bucket 8 as an attachment operatively provided at the tip of the telescoreme 7 Has been.

  The telescore 7 of the hydraulic excavator A is expanded and contracted by the hydraulic circuit shown in FIG. This hydraulic circuit is mounted on the upper swing body 3 shown in FIG. 2, and the engine 11 is supplied with a constant pump horsepower from the engine 11 to discharge the hydraulic oil stored in the tank 12 under constant horsepower control. A variable displacement main pump 13 and a control valve for controlling hydraulic oil discharged to a center bypass line 14 connected to the discharge line of the main pump 13 and a parallel line 15 branched from the center bypass line 14 Has 16.

  In addition, a load hold check valve 17 that holds the load pressure of the control valve 16 is provided in the parallel line 15, and is connected to a tank line 18 that returns to the tank 12 and releases oil. A main relief valve 20 is provided.

  Further, a telescopic cylinder 21 (hereinafter referred to as a telescopic cylinder 21) as a single rod type fluid pressure cylinder for expanding and contracting the telescore 7 shown in FIG. 2 has a single rod type piston having a rod 22a only on one side. 22 forms a bottom chamber 21a and a rod chamber 21b, a bottom line 23 is connected between the bottom chamber 21a and the spool 16a of the control valve 16, and a rod line 24 is connected between the rod chamber 21b and the spool 16a. In the rod line 24, a slow return valve 25 is provided as a meter-out flow control valve. This slow return valve 25 has a check valve 25a that passes hydraulic oil supplied to the rod chamber 21b through the control valve 16 and stops the return oil from the rod chamber 21b, and a return flow rate of the return oil from the rod chamber 21b. It is formed by connecting a variable aperture 25b to be controlled in parallel.

  In this hydraulic circuit, when the spool 16a of the control valve 16 is in a neutral state, the hydraulic oil discharged from the main pump 13 circulates in the tank 12, and when the spool 16a is switched to the expansion side shown in FIG. The hydraulic oil discharged from the pump 13 is supplied to the bottom chamber 21a side of the telescopic cylinder 21 via the bottom line 23, and the return oil from the rod chamber 21b side passes through the slow return valve 25 and the spool 16a of the rod line 24. Then, by returning from the tank line 18 to the tank 12, the rod 22a of the telescopic cylinder 21 extends and the telescore 7 extends.

  When the spool 16a is switched to the contraction side shown in FIG. 3, the hydraulic oil discharged from the main pump 13 is supplied to the rod chamber 21b of the telescopic cylinder 21 via the rod line 24, and at the bottom chamber 21a side. Is returned to the tank 12 from the tank line 18 through the bottom line 23 and the spool 16a, the rod 22a of the telescopic cylinder 21 is contracted, and the telescore 7 is contracted.

  Such a hydraulic excavator A extends and contracts the telescore 7 perpendicularly to the ground and excavates the pit H with the clamshell bucket 8, so the construction work of the structure in urban areas is possible because of its good work efficiency. Although it is often used for subway construction, etc., especially when working in an urban area, it is important to shorten the construction period, and therefore it is desired to improve the work amount.

  However, in the hydraulic circuit as described above, if the extension speed of the telescopic cylinder 21 is increased, the supply of pressure oil to the bottom chamber 21a of the telescopic cylinder 21 cannot catch up, and the telescopic cylinder 21 may become negative pressure, When such a negative pressure occurs, the seal of the telescopic cylinder 21 is damaged or a response delay occurs. Further, when the contraction speed of the telescopic cylinder 21 is increased, there is a problem that it is not easy to increase the telescopic speed of the telescore 7 because the pressure loss of the piping due to the return oil increases.

  If the telescopic cylinder 21 is extended while the telescore 7 is extended and the clamshell bucket 8 is landed, the bottom chamber pressure may rise to the set pressure of the main relief valve 20 and the telescopic cylinder 21 may be buckled. There is also the problem of being.

Therefore, when the telescopic cylinder is extended, a regenerative circuit that regenerates the entire amount of return oil from the rod chamber while maintaining a constant pressure is provided in the bottom chamber to increase the telescore, and the telescopic cylinder shrinks. At this time, there is known a hydraulic circuit for providing a drain circuit that allows the return oil from the bottom chamber side to directly escape to the tank and reduce the back pressure to increase the shrinkage of the telescore. Further, in this hydraulic circuit, a high back pressure is applied to the rod chamber side to prevent the telescopic cylinder from buckling (see, for example, Patent Document 1).
JP-A-8-246490 (page 3-5, FIG. 1)

  However, in the fluid pressure circuit described in Patent Document 1 described above, when the telescopic cylinder is extended, the return oil is regenerated while maintaining a constant pressure. Since the main pump pressure becomes high, there is a problem that energy loss due to fluid friction in the pipe increases.

  In addition, since the entire amount of return oil is regenerated to the bottom chamber side, the speed increase of the telescopic cylinder due to regeneration becomes on / off, and there is a problem that speed adjustment and fine operation cannot be performed when the telescopic cylinder is extended.

  Furthermore, for example, when the telescopic cylinder does not extend due to the clamshell bucket hitting a rock or the like, the back pressure on the rod chamber side for buckling prevention does not stand, but only the high pressure on the bottom chamber side acts, and the telescopic cylinder is seated. There is a risk of bending.

  The present invention has been made in view of these points, and an object of the present invention is to provide a fluid pressure circuit that suppresses energy loss. The present invention also provides a fluid pressure circuit capable of easily adjusting the extension speed of the fluid pressure cylinder. Furthermore, it aims at providing the fluid pressure circuit which prevented buckling of the fluid pressure cylinder.

According to the first aspect of the present invention, there is provided a control valve for controlling the working fluid, a single rod type piston actuated by the working fluid passing through the control valve, a rod chamber formed on the rod side by the piston and the rod via the piston. A fluid pressure cylinder having a bottom chamber formed on the opposite side of the chamber, a flow rate control valve for controlling the return flow rate from the rod chamber, and a branch flow upstream from the flow rate control valve for the return fluid from the rod chamber, A regeneration valve that operates using the fluid pressure of the working fluid supplied to the bottom chamber as a pilot pressure and regenerates a partial flow rate of the fluid controlled by the flow control valve according to the pilot pressure to the bottom chamber, and the regeneration valve and a check valve provided between the bottom chamber, communicates with the bottom chamber of the fluid pressure cylinder, open in response to a decrease in the rod chamber pressure generated in the rod chamber of the hydraulic cylinder The buckling prevention check valve that enables operation and the bottom chamber pressure generated in the bottom chamber of the fluid pressure cylinder by operating the opening operation of the buckling prevention check valve prevents the fluid pressure cylinder from buckling. It is a fluid pressure circuit provided with a relief valve that suppresses to a predetermined pressure .

請 Motomeko 2 the described invention, the hydraulic circuit according to claim 1, and a passage connected directly to the tank from between the bottom chamber and the control valve, provided in the passageway, the fluid pressure through the control valve A logic valve that opens and operates with the fluid pressure of the working fluid supplied to the rod chamber of the cylinder as a pilot pressure, and a bypass sequence valve that sets the pilot pressure supplied to the logic valve to a predetermined pressure are provided.

According to a third aspect of the present invention, the fluid pressure circuit according to the first or second aspect is used for expansion and contraction of a multistage telescopic arm of a work device operably provided in a work machine.

According to the first aspect of the present invention, the regeneration valve is operated using the fluid pressure of the working fluid supplied to the bottom chamber of the fluid pressure cylinder as a pilot pressure, and the rod is controlled by the flow rate control valve corresponding to the pilot pressure. By regenerating only a partial flow rate of the return fluid from the chamber to the bottom chamber, for example, energy loss can be suppressed as compared with a case where a constant back pressure is applied to the fluid pressure of the regenerated fluid by a relief valve or the like. In addition, compared with the case where the entire amount of return fluid is regenerated, the flow rate control valve can easily adjust the extension speed of the fluid pressure cylinder, and it can prevent buckling in response to a decrease in the rod chamber pressure of the fluid pressure cylinder. The check valve opens and the relief valve that is activated by this opening reduces the bottom chamber pressure of the fluid pressure cylinder to a predetermined pressure that can prevent buckling of the fluid pressure cylinder. It is possible to prevent the buckling of the fluid pressure cylinder with the relief valve by providing a check valve for buckling prevention that will be closed until the rod chamber pressure drops. The circuit can be manufactured inexpensively and easily with a simple configuration using a flow control valve, a regeneration valve , a check valve , a buckling prevention check valve and a relief valve .

According to the invention 請 Motomeko 2, opening a passage in connected directly to the tank from between the bottom chamber and the control valve, the fluid pressure of the hydraulic fluid supplied to the rod chamber through the control valve as a pilot pressure operation By providing a logic valve that returns to the tank, a part of the return fluid that returns to the tank is released directly from the upstream side of the control valve to the tank by the bypass circuit to make a plurality of return flow paths, and the return fluid at the time of the contraction operation of the hydraulic cylinder The pressure loss of the control valve alone can be reduced, the contraction speed of the fluid pressure cylinder can be secured, the operating pressure of the logic valve can be kept constant by the bypass sequence valve, and the operation stability of the bypass circuit can be improved, and The circuit can be manufactured inexpensively and easily with a simple configuration using these bypass sequence valves, logic valves, and passages.

According to the invention of claim 3 , by using the fluid pressure circuit for the multistage telescopic arm of the working device of the work machine, it is possible to reliably prevent buckling of the multistage telescopic arm extending in a long shape.

  Hereinafter, the present invention will be described in detail with reference to the embodiment shown in FIG. In addition, about the same component as the prior art shown in FIG. 3, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted. In describing this embodiment, FIG. 2 used in the background art will be referred to as appropriate.

  FIG. 1 shows a hydraulic circuit as a fluid pressure circuit, and this hydraulic circuit is mounted on the upper swing body 3 shown in FIG.

  In the bottom line 23, a low pressure relief valve 31 and a check valve 32 for flowing only return oil are connected in parallel between the bottom chamber 21 a of the telescopic cylinder 21 via the control valve 16.

  Furthermore, on the bottom chamber 21a side of the bottom line 23, a bypass circuit 34 for allowing the return oil from the bottom chamber 21a to escape directly to the tank 12 and a buckling prevention circuit 35 for preventing buckling of the telescopic cylinder 21 are provided. Yes.

  Further, a drop prevention circuit 36 for preventing the rod 22a of the piston 22 from dropping is directly attached to the telescopic cylinder 21 on the rod chamber 21b side.

  Further, on the downstream side of the slow return valve 25 of the rod line 24, a regeneration line 37 is branched as a regeneration passage connected between the low pressure relief valve 31 of the bottom line 23 and the bypass circuit 34. Between the regeneration line 37 and the bottom line 23, a regeneration valve 38 that regenerates return oil from the rod chamber 21b to the bottom chamber 21a side and a check valve that stops the return oil from the bottom line 23 are checked. A valve 39 is sequentially provided from the rod line 24 to the bottom line 23. The regeneration valve 38, the check valve 39, and the slow return valve 25 allow the flow rate of most of the return oil from the rod chamber 21b to flow through the regeneration line 37. Thus, a regeneration circuit 40 that regenerates from the bottom line 23 to the bottom chamber 21a is configured.

  Further, the bypass circuit 34 is branched between the bottom chamber 21a of the bottom line 23 and the control valve 16, and a drain passage 41 directly connected to the tank 12 via the center bypass line 14, and this passage A pilot operated logic valve 42 provided in 41 and a bypass sequence valve 44 provided in a bypass pilot pressure line 43 led to the logic valve 42 from the upstream side of the slow return valve 25 of the rod line 24. ing.

  A return spring 45 is brought into contact with the logic valve 42 at one end side, and the hydraulic pressure of the hydraulic oil supplied to the rod chamber 21b, specifically, the inlet pressure of the slow return valve 25 is passed through the bypass pilot pressure line 43. To the other end.

  The logic valve 42 can be opened by a pilot pressure introduced via a bypass pilot pressure line 43, and can be closed by a return spring 45 due to a decrease in the pilot pressure. .

  The bypass sequence valve 44 sets the pilot pressure guided to the logic valve 42 via the bypass pilot pressure line 43 to a predetermined pressure.

  Further, an orifice 46 for releasing the residual pressure of the bypass pilot pressure line 43 is provided between the bypass pilot pressure line 43 and the passage 41.

  The buckling prevention circuit 35 is branched from the bottom chamber 21a of the bottom line 23 and the bypass circuit 34, and is provided in the connection line 51 connected between the logic valve 42 and the orifice 46 of the passage 41, From the bottom line 23 toward the passage 41, a pilot check valve 53 and a relief valve 54, which are pilot operated check valves as a check valve for buckling prevention, are sequentially provided.

  The rod pressure generated in the rod chamber 21b of the telescopic cylinder 21 is guided to the pilot check valve 53 as a pilot pressure via the pilot pressure line 56 branched from the rod line 24. That is, the opening operation can be performed only when the supply of hydraulic oil to the bottom chamber 21a is stopped.

  The relief valve 54 is a low pressure relief valve that is operated by opening the pilot check valve 53, and suppresses the bottom chamber pressure generated in the bottom chamber 21a of the telescopic cylinder 21 to a predetermined pressure. The predetermined pressure is set to a pressure that prevents the telescopic cylinder 21 from buckling.

  Further, the fall prevention circuit 36 includes a check valve 61 as a fall prevention check valve provided in the rod line 24, a fall prevention logic valve 62 provided in parallel to the check valve 61, and the rod line 24. And an overload relief valve 64 provided in a connection line 63 branched and connected to the passage 41.

  The check valve 61 stops return oil from the rod chamber 21b.

  Further, a return spring 66 is brought into contact with one end side of the fall prevention logic valve 62, and a pilot pressure line 67 branched from the bottom line 23 is guided to the other end side. The pilot pressure line 67 guides the hydraulic pressure of the hydraulic oil supplied to the bottom chamber 21a, specifically, the inlet pressure of the low pressure relief valve 31 to the drop prevention logic valve 62 as a pilot pressure.

  The fall prevention logic valve 62 can be opened by the pilot pressure introduced through the pilot pressure line 67 and can be closed by the return spring 66 due to the decrease in the pilot pressure. Yes.

  Further, the overload relief valve 64 sets the load pressure of the rod chamber 21b.

  Further, a return spring 71 is brought into contact with one end side of the regeneration valve 38, and a branched pilot pressure line 72 branched from the bottom line 23 is guided to the other end side. The branch pilot pressure line 72 guides the hydraulic pressure of the hydraulic oil supplied to the bottom chamber 21a, specifically, the inlet pressure of the low pressure relief valve 31 to the regeneration valve 38 as a pilot pressure.

  The regenerative valve 38 can be opened by the pilot pressure introduced through the branch pilot pressure line 72 and can be closed by the return spring 71 due to the decrease in the pilot pressure. Therefore, the regeneration valve 38 has a function of adjusting the regeneration flow rate toward the bottom chamber 21a, that is, a metering function.

  Next, the operation of the above embodiment will be described.

(Telescopic cylinder 21 extension operation)
When the telescopic cylinder 21, that is, the telescore 7 of the hydraulic excavator A is extended, when the operator operates an operation lever (not shown), the spool 16a of the control valve 16 is switched to the expansion side.

  As a result, the hydraulic oil discharged from the main pump 13 is supplied from the parallel line 15 to the bottom line 23 via the load hold check valve 17, and the inlet pressure of the low pressure relief valve 31 is set to the flow rate supplied from the main pump 13. The pressure oil that is approximately proportional and has flowed out of the low pressure relief valve 31 is supplied to the bottom chamber 21a of the telescopic cylinder 21, and pushes the piston 22 of the telescopic cylinder 21 toward the rod chamber 21b.

  At the same time, the inlet pressure of the low pressure relief valve 31 is guided to the drop prevention logic valve 62 through the pilot pressure line 67, and the drop prevention logic valve 62 is opened to return the hydraulic oil in the rod chamber 21b of the telescopic cylinder 21 to return oil. Flows to the slow return valve 25 side and the regeneration valve 38 side.

  This return oil is controlled in flow rate by the regeneration valve 38, and a part of the flow rate is returned from the slow return valve 25 to the tank 12 through the control valve 16 to the tank line 18, so that the telescopic cylinder 21, that is, telescoreum 7 grows. Most of the flow rate of the return oil flows from the bottom line 23 to the bottom chamber 21a side through the check valve 39 at the regeneration valve 38 opened by the inlet pressure of the low pressure relief valve 31 guided through the branch pilot pressure line 72. As a result of the reproduction, the elongation of the telescopic cylinder 21, that is, the telescore 7 is increased.

  Therefore, the regeneration flow rate to the bottom chamber 21a is adjusted by the slow return valve 25 and the regeneration valve 38 to adjust the increase in the extension speed of the telescopic cylinder 21, and is controlled from the slow return valve 25 during fine operation. Since the flow rate flowing out to the valve 16 is controlled by the control valve 16, the telescopic cylinder 21, that is, the telescore 7 can be finely operated.

  When the telescore 7 expands and the clamshell bucket 8 lands and the telescore 7 stops extending, the rod chamber pressure in the rod chamber 21b of the telescopic cylinder 21 decreases, and the rod chamber pressure decreases to prevent buckling. The pilot check valve 53 of the circuit 35 is opened and the relief valve 54 is actuated, and the bottom chamber pressure is pulled down to the tank 12 via the passage 41, and the telescopic cylinder 21 is prevented from buckling.

(Telescopic cylinder 21 contraction)
When the telescopic cylinder 21, that is, the telescome 7 of the hydraulic excavator A is contracted, when the operator operates an operation lever (not shown), the spool 16a of the control valve 16 is switched to the contracting side.

  As a result, the hydraulic oil discharged from the main pump 13 is supplied from the parallel line 15 to the rod line 24 via the load hold check valve 17, and the rod chamber of the telescopic cylinder 21 via the slow return valve 25 and the check valve 61. Guided by 21b, the piston 22 of the telescopic cylinder 21 is pushed toward the bottom chamber 21a.

  At the same time, the bypass sequence valve 44 is opened by the rise of the inlet pressure of the slow return valve 25, and the logic valve 42 is opened by the pilot pressure introduced through the bypass pilot pressure line 43.

  Therefore, the return oil from the bottom chamber 21a of the telescopic cylinder 21 is returned from the tank line 18 to the tank 12 via the check valve 32 and the control valve 16, and a part of the return oil is returned from the opened logic valve 42. It is directly relieved to the tank 12 by a separate circuit via the passage 41, the pressure loss only by the control valve 16 is reduced, and the main pump pressure is lowered.

  At this time, since the discharge flow rate of the main pump 13 under constant horsepower control increases as the pressure decreases, the contraction speed of the telescopic cylinder 21, that is, the telescore 7 is increased.

  Further, when the supply of hydraulic oil to the bottom chamber 21a of the telescopic cylinder 21 is stopped, the inlet pressure of the low pressure relief valve 31 is lowered, and the drop prevention logic valve 62, which is led as the pilot pressure, closes the rod. The chamber pressure is maintained and the piston 22 of the telescopic cylinder 21 is prevented from dropping.

  Next, effects of the above-described embodiment will be listed.

  By operating the regeneration valve 38 using the hydraulic pressure of the hydraulic oil supplied to the bottom chamber 21a of the telescopic cylinder 21 as a pilot pressure, and regenerating a partial flow rate of the return oil corresponding to the pilot pressure to the bottom chamber 21a side, For example, the main pump pressure can be prevented from increasing more than necessary and energy loss can be suppressed as compared with the conventional case in which a constant back pressure is applied to the hydraulic pressure by a relief valve or the like.

  In addition, the regeneration circuit 40 regenerates most of the flow rate of the return oil to the bottom chamber 21a, and releases a part of the flow rate from the slow return valve 25 to the tank 12 via the control valve 16, thereby reducing the pressure to the bottom chamber 21a. It is possible to prevent the occurrence of negative pressure due to the oil supply not catching up, and it is possible to reliably prevent damage to the seal of the telescopic cylinder 21 and response delay due to the occurrence of such negative pressure, and to regenerate the entire amount of return oil The speed increase of the telescopic cylinder 21 does not turn on and off as in the conventional case, and the regeneration flow rate of the regeneration valve 38 can be finely adjusted according to the pilot pressure. The extension speed of the cylinder 21 can be easily adjusted.

  Further, the regeneration circuit 40 includes the slow return valve 25, the regeneration valve 38, and the check valve 39, so that the regeneration circuit 40 can be manufactured inexpensively and easily.

  Further, when the clamshell bucket 8 provided at the tip of the telescore 7 has landed or when the clamshell bucket 8 abuts against a rock or the like and the extension of the telescopic cylinder 21 stops, the rod chamber of the telescopic cylinder 21 When the pressure drops, the pilot check valve 53 opens in response to this drop, and the relief valve 54 that is activated by this opening action can prevent the telescopic cylinder 21 from buckling and the telescopic cylinder 21 from buckling. By reducing the pressure to a predetermined pressure, buckling of the telescopic cylinder 21 can be reliably prevented.

  Furthermore, by providing a logic valve 42 in the passage 41 that opens with the hydraulic pressure of the hydraulic oil supplied to the rod chamber 21b of the telescopic cylinder 21 through the control valve 16 in the passage 41, control is performed from the bottom chamber 21a of the telescopic cylinder 21. A part of the return oil that returns to the tank 12 through the valve 16 is released directly from the upstream side of the control valve 16 to the tank 12 by the bypass circuit 34 to make a plurality of return flow paths, and the return oil when the telescopic cylinder 21 is contracted. The pressure loss of only the control valve 16 can be reduced, and the flow rate of the main pump 13 under constant horsepower control can be increased to ensure the contraction speed of the telescopic cylinder 21.

  At the same time, by setting the hydraulic oil supplied to the bottom chamber 21a of the telescopic cylinder 21 to a predetermined pressure by the low pressure relief valve 31, the operational stability of the telescopic cylinder 21 can be improved and the telescopic cylinder 21 can be stably extended. Can be controlled to be easy for the operator to use.

  Therefore, the expansion / contraction speed of the telescopic cylinder 21 can be secured.

  The bypass circuit 34 can improve the stability of the operation by keeping the operating pressure of the logic valve 42 constant by the bypass sequence valve 44, and can be simplified by the bypass sequence valve 44, the logic valve 42 and the passage 41. With a simple structure, it can be manufactured inexpensively and easily.

  The buckling prevention circuit 35 can be manufactured inexpensively and easily with a simple configuration of the pilot check valve 53 and the relief valve 54, and the pilot check that remains closed until the rod chamber pressure of the telescopic cylinder 21 decreases. By providing the valve 53, the relief valve 54 can be set to a low pressure that can reliably prevent the telescopic cylinder 21 from buckling.

  Furthermore, by directly attaching the fall prevention circuit 36 to the rod chamber 21b side, there is no piping between the rod chamber 21b side and the fall prevention circuit 36, and the fall prevention circuit 36 malfunctions due to piping damage, etc. When the supply of hydraulic oil to the bottom chamber 21a of the telescopic cylinder 21 is stopped, the fall prevention circuit 36 can reliably prevent the rod 22a of the piston 22 from dropping.

  The fall prevention circuit 36 can be manufactured inexpensively and easily with a simple configuration including the check valve 61, the fall prevention logic valve 62, and the overload relief valve 64.

  In addition, since the drop prevention logic valve 62 of the drop prevention circuit 36, the regeneration valve 38, the logic valve 42 of the bypass circuit 34, and the like are switched using the drive system hydraulic pressure as a pilot pressure, for example, a pilot pressure line from a pilot pump or an electric There is no need to use a signal line, the piping and wiring structure can be simplified, and a response delay due to the pilot pressure line is less likely to occur.

  Then, by using such a hydraulic circuit for the telescore 7 of the working device 5 of the excavator A, the extension speed of the telescore 7 can be easily adjusted, and the telescore 7 can be finely operated. In addition to improving the operability of the telescope, it is possible to reliably prevent buckling of the telescore 7 that extends in a long shape, improve the reliability of the hydraulic excavator A, and improve the amount of work by the telescore 7 to shorten the work period This also makes it possible to reduce work costs.

  In particular, when working with the telescore 7, it is necessary to adjust the extension speed rather than the contraction speed. Therefore, by adjusting the extension speed of the telescopic cylinder 21 and the telescore 7 as described above, workability can be improved. Improvement can be achieved.

  In addition, the fluid pressure circuit of the present invention can be used for other devices including a fluid pressure cylinder.

It is a circuit diagram showing one embodiment of a fluid pressure circuit concerning the present invention. It is a description side view which shows the working machine provided with the fluid pressure circuit same as the above. It is a circuit diagram which shows the fluid pressure circuit of a prior art example.

5 Working device 7 Telescopic arm as multi-stage telescopic arm
12 tanks
16 Control valve
21 Telescopic cylinder as fluid pressure cylinder
21a Bottom chamber
21b Rod chamber
22 Piston
22a rod
25 Slow return valve as flow control valve
38 Regeneration valve
39 Check valve as check valve
41 passage
42 Logic valve
44 Sequence valve for bypass
53 Pilot check valve as a check valve for buckling prevention
54 Relief valve

Claims (3)

A control valve for controlling the working fluid;
A one-rod type piston actuated by a working fluid that has passed through a control valve, a fluid pressure cylinder having a rod chamber formed on the rod side by the piston and a bottom chamber formed on the opposite side of the rod chamber via the piston;
A flow rate control valve for controlling the return flow rate from the rod chamber;
The return fluid from the rod chamber is branched upstream of the flow control valve for the return fluid, and the fluid pressure of the working fluid supplied to the bottom chamber operates as a pilot pressure, and is controlled by a flow control valve corresponding to this pilot pressure. A regeneration valve for regenerating a partial flow rate of the fluid to the bottom chamber;
A check valve provided between the regeneration valve and the bottom chamber ;
A check valve for buckling prevention that communicates with the bottom chamber of the fluid pressure cylinder and that enables an opening operation in response to a decrease in the rod chamber pressure generated in the rod chamber of the fluid pressure cylinder;
A relief valve that operates by opening the check valve for buckling prevention and suppresses the bottom chamber pressure generated in the bottom chamber of the fluid pressure cylinder to a predetermined pressure that prevents buckling of the fluid pressure cylinder. Characteristic fluid pressure circuit. A passage directly connected to the tank from between the bottom chamber and the control valve;
A logic valve that is provided in the passage and that opens and operates with the fluid pressure of the working fluid supplied to the rod chamber of the fluid pressure cylinder through the control valve as a pilot pressure;
Fluid pressure circuit according to claim 1, characterized by including a bypass sequence valve for setting a pilot pressure supplied to the logic valve to a predetermined pressure. 3. The fluid pressure circuit according to claim 1, wherein the fluid pressure circuit is used for expansion and contraction of a multistage telescopic arm of a work device operably provided in the work machine.

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