JP2011236592A - Hydraulic circuit for attaching and detaching counterweight of work machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic circuit which avoids accidental movement of a counterweight lifting cylinder without depending on an operator's manual operation, thereby improving reliability.SOLUTION: A direction control valve 18 is provided on the way of a center bypass duct 14 between a hydraulic pump 9 or a tank 10 and a counterweight lifting cylinder 11. At the neutral position (A) of the direction control valve 18, feeding of pressure oil via a pair of main pipelines 19A and 19B to the cylinder 11 is stopped, while one main pipeline 19B connected to a bottom side oil chamber B of the cylinder 11 is made to communicate with the tank via a low pressure pipeline 17 through a return passage 18C provided in the direction control valve 18. On the way of the center bypass pipeline 14, a switching valve 26 switchable between interruption position (a) and communication position (b) according to operation signals from a pilot operation valve 23 is provided between the hydraulic pump 9 and the direction control valve 18.

Description

  The present invention relates to a hydraulic circuit for attaching / detaching a counterweight of a work machine that is preferably used for attaching or removing a counterweight to / from a work machine such as a hydraulic excavator or a hydraulic crane.

  In general, a working machine such as a hydraulic excavator is configured such that a working device such as a boom and an arm is provided on the front side of the vehicle body, and a counterweight is provided on the rear side of the vehicle body to balance the weight of the entire vehicle body. Since such a counterweight is heavy, for example, when a hydraulic excavator is transported to a work site using a trailer or the like, the counterweight is removed from the rear end side of the vehicle body, and the counterweight is transported separately from the vehicle body side. There are things to do.

  There are also various work devices with different weights, such as for light excavation, for medium excavation, for heavy excavation, etc., depending on the type and content of excavation work. May change work equipment. When the work device is replaced, it is necessary to replace the counterweight with a different weight corresponding to each work device.

  For this reason, the body frame is provided with a counterweight attachment / detachment device such as a lifting / lowering hydraulic cylinder (weight raising / lowering cylinder) on the rear side thereof, and this counterweight attachment / detachment device allows the counterweight to be moved to the rear end side of the frame. There is known a structure that can be attached and detached with (see, for example, Patent Documents 1 and 2).

  This type of prior art counterweight attachment / detachment device supplies and discharges pressure oil from a hydraulic source to a front weight lifting cylinder via a direction control valve, thereby extending and lowering the weight of the counterweight by expanding and contracting the rod of the weight lifting cylinder. Perform the action. When the attachment and removal of the counterweight are completed, the directional control valve is returned to the neutral position to stop the supply and discharge of pressure oil.

Japanese Utility Model Publication No. 6-25288 JP 2008-255611 A

  By the way, the above-described counterweight attaching / detaching device according to the related art holds the weight lifting cylinder in a stopped state when the excavator is operated to perform excavation work by the working device, and the movement of the weight lifting cylinder is completely stopped. It is necessary to keep. For this reason, for example, a manual gate valve is provided between the bottom oil chamber of the weight lifting cylinder and the direction control valve.

  This gate valve is composed of, for example, a manual on-off valve, and is manually closed to ensure operational safety when the weight elevating cylinder is not used for a long time. In this way, the gate valve prevents a part of the pressure oil flowing from the hydraulic pump to the directional control valve from leaking to the bottom oil chamber of the weight lifting cylinder and moving the weight lifting cylinder by a manual operation. It is.

  However, since the gate valve used in the prior art is manually operated, it may be forgotten to tighten. In this case, a part of the pressure oil flowing from the hydraulic pump to the directional control valve is part of the weight lifting cylinder. If it leaks to the bottom side oil chamber, the weight raising / lowering cylinder is erroneously moved. For this reason, it is desired to stop inadvertent movement of the weight lifting cylinder without relying on manual operation.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a counterweight for a work machine that can stop inadvertent movement of the weight lifting cylinder without relying on manual operation. The object is to provide a detachable hydraulic circuit.

  In order to solve the above-described problems, the present invention provides a hydraulic pump configured with a hydraulic source of a work machine together with a tank, and the counter weight is moved up and down when the counter weight is detachably attached to the frame of the work machine. A weight lifting cylinder driven by pressure oil from the hydraulic pump to move up and down, and provided between the weight lifting cylinder and the hydraulic power source, is always in a neutral position to shut off the supply and discharge of the pressure oil and neutral A directional control valve for supplying and discharging pressure oil from the hydraulic source to the weight lifting cylinder when switched from a position, and an operating means for switching the directional control valve by outputting an operation signal to the directional control valve And is applied to a hydraulic circuit for attaching and detaching a counterweight of a working machine.

  A feature of the configuration adopted by the invention of claim 1 is that the direction control valve is connected to the weight elevating cylinder by being arranged in the neutral position until an operation signal is output from the operation means. A predetermined one of the pair of main pipelines is configured to communicate with the tank, and until an operation signal is output from the operation means between the hydraulic pump and the direction control valve. When the operation signal is output, the hydraulic oil from the hydraulic pump to the weight lifting cylinder is switched from the blocking position to the communication position when the operation signal is output. In other words, a configuration is provided in which one switching valve that allows the circulation of the gas is provided.

  According to a second aspect of the present invention, the directional control valve is disposed in the middle of a center bypass pipe connecting the hydraulic pump to the tank, and communicates and blocks the center bypass pipe with respect to the tank. A pair of main pipelines are controlled to be switched, and the one switching valve is provided in the middle of the center bypass pipeline between the hydraulic pump and the direction control valve.

  Further, according to the invention of claim 3, the actuator comprises a plurality of actuator control valves for supplying the hydraulic oil discharged from the hydraulic pump to a plurality of hydraulic actuators, and the actuator control valves are connected in a predetermined arrangement. A control valve group, and on the downstream side of the control valve group, until the operation signal is output from the operation means, the control valve group is in a communicating position to allow pressure oil from the hydraulic pump to flow to the tank side. When the operation signal is output, another switching valve is provided that switches from the communication position to the shut-off position and shuts off the flow of the pressure oil.

  As described above, according to the first aspect of the present invention, the direction control valve provided between the hydraulic pressure source and the weight raising / lowering cylinder is disposed at the neutral position until the operation signal is output from the operation means. In the position, the supply and discharge of the pressure oil to and from the pair of main pipelines connected to the weight raising / lowering cylinder is shut off, and for example, one main pipeline connected to the bottom side oil chamber of the weight raising / lowering cylinder communicates with the tank side Keep on. For this reason, even if a part of the pressure oil flowing from the hydraulic pump to the directional control valve leaks to one main pipe side, this pressure oil is only discharged to the tank side, and the bottom side oil chamber of the weight lifting cylinder Will not be supplied.

  In addition, one switching valve provided between the hydraulic pump and the direction control valve is in a blocking position until an operation signal is output from the operation means, and is directed from the hydraulic pump to the weight lifting cylinder. Since the flow of the pressure oil is cut off, the pressure oil from the hydraulic pump does not flow to the weight lifting cylinder side through the direction control valve until the operator operates the operation means. The occurrence of pressure oil leakage can be prevented on the upstream side. For this reason, it is possible to doubly prevent the weight lifting cylinder from being erroneously moved by leakage oil or the like from the direction control valve.

  On the other hand, when the operator operates the operation means and outputs an operation signal, that is, when the lifting / lowering operation of the counterweight is performed using the weight lifting cylinder, the one switching valve is switched from the shut-off position to the communication position. Therefore, the pressure oil from the hydraulic pump flows toward the direction control valve. At this time, since the directional control valve is switched from the neutral position in accordance with the operation signal, the pressure oil from the hydraulic source can be supplied to and discharged from the weight lifting cylinder, thereby driving the weight lifting cylinder to the rod Can be expanded and contracted, and the work of attaching and detaching the counterweight can be executed.

  Therefore, as long as the operator does not operate the operating means, it is possible to prevent the hydraulic oil from leaking on the directional control valve side and the weight lifting cylinder from malfunctioning due to this leaking oil etc. more double on the safe side. it can. Thereby, for example, the careless movement of the weight raising / lowering cylinder can be stopped without relying on manual operation by a gate valve used in the prior art, and the safety and reliability of the apparatus can be improved.

  According to the invention of claim 2, a directional control valve is arranged in the middle of a center bypass pipe connecting the hydraulic pump to the tank, and the center bypass pipe is located between the directional control valve and the hydraulic pump. One switching valve is provided on the way. As a result, when the one switching valve is in the shut-off position, the pressure oil from the hydraulic pump can be shut off from flowing toward the direction control valve through the center bypass pipe, and the pressure oil leaks in the direction control valve. Can be prevented. Then, when the one switching valve is switched from the shut-off position to the communication position by the operation signal from the operation means, the pressure oil from the hydraulic pump is circulated to the direction control valve through the center bypass pipe, and the neutral position according to the operation signal. The directional control valve that has been switched to allows the pressure oil to be supplied to and discharged from the weight lifting cylinder, and can be driven to extend and contract the weight lifting cylinder.

  Furthermore, since the invention according to claim 3 is configured such that another switching valve is provided on the downstream side of the control valve group including a plurality of actuator control valves, the other switching valve is not operated until an operation signal is output from the operating means. , The pressure oil from the hydraulic pump is circulated so as to be discharged to the tank side, and the pressure oil from the hydraulic pump is circulated toward the directional control valve together with one switching valve. Can be blocked. On the other hand, when the operation signal is output, by switching the other switching valve from the communication position to the blocking position, the pressure oil from the hydraulic pump can be blocked from being discharged to the tank side. High pressure oil can be circulated toward the direction control valve.

1 is a front view showing a hydraulic excavator to which a counterweight attaching / detaching hydraulic circuit according to a first embodiment of the present invention is applied. It is a circuit diagram which shows the hydraulic circuit for counterweight attachment / detachment by 1st Embodiment. It is a circuit diagram which shows the hydraulic circuit for counterweight attachment / detachment by 2nd Embodiment.

  Hereinafter, a case where a counterweight attaching / detaching hydraulic circuit of a working machine according to an embodiment of the present invention is applied to a hydraulic excavator will be described as an example and described in detail with reference to the accompanying drawings.

  Here, FIG. 1 and FIG. 2 show a first embodiment of the present invention. In the figure, reference numeral 1 denotes a hydraulic excavator as a working machine. The hydraulic excavator 1 is mounted on a self-propelled lower traveling body 2 and is rotatable on the lower traveling body 2. The upper revolving body 3 constituting the vehicle body and a work device 7 described later are roughly constituted.

  Reference numeral 4 denotes a revolving frame that constitutes a base frame of the upper revolving structure 3, and the revolving frame 4 is configured as a sturdy support structure formed by welding a plurality of steel plates or the like. On the revolving frame 4, a cab 5 that defines a cab is provided on the front side thereof, and on the rear side of the cab 5, for example, an engine (not shown), a hydraulic pump 9 described later, and the like are provided. The building cover 6 etc. accommodated in the inside are provided.

  7 is a working device provided on the front side of the swing frame 4, and the work device 7 is attached, for example, such that the base end side of the boom 7 </ b> A can be moved up and down on the front portion of the swing frame 4. A bucket 7C as a work tool is rotatably provided via the arm 7B. The work device 7 performs excavation work such as earth and sand using the bucket 7C on the front end side.

  A counterweight 8 is detachably provided on the rear end side of the swing frame 4, and the counterweight 8 balances the weight of the entire upper swing body 3 with respect to the work device 7 on the front side. Here, the counterweight 8 is lifted to the rear end side of the revolving frame 4 or hung from the rear end side by using a counterweight lifting device (not shown) including a weight lifting cylinder 11 and the like which will be described later. To do. Thus, the counterweight 8 is detachably attached to and removed from the revolving frame 4.

  Reference numeral 9 denotes a main hydraulic pump that constitutes a hydraulic power source together with the tank 10, and the hydraulic pump 9 is rotationally driven by, for example, the engine provided in the building cover 6 of the upper swing body 3. As a result, the hydraulic pump 9 discharges hydraulic oil sucked from the tank 10 as high-pressure oil, and supplies the oil to a weight elevating cylinder 11 and the like described later.

  Reference numeral 11 denotes a weight elevating cylinder composed of a hydraulic cylinder that constitutes a part of the counterweight elevating device. As shown in FIG. 2, the weight elevating cylinder 11 is slidably fitted into a tube 11A and is inserted into the tube 11A so that two oil chambers, that is, a rod-side oil chamber A and a bottom-side oil chamber B. And a rod 11C whose proximal end is fixed to the piston 11B and whose distal end protrudes outside the tube 11A. The rod side oil chamber A in the tube 11A is located on the rod 11C side of the weight lifting cylinder 11, and the bottom side oil chamber B is located on the bottom side of the tube 11A.

  Here, the weight lifting cylinder 11 extends and contracts the rod 11 </ b> C from the tube 11 </ b> A by supplying and discharging pressure oil from the hydraulic pump 9 to the rod-side oil chamber A and the bottom-side oil chamber B. When the rod 11C of the weight raising / lowering cylinder 11 is extended, the counterweight 8 is lifted upward while being lifted to the rear end side of the turning frame 4 (see FIG. 1) by the counterweight raising / lowering device. When the rod 11C of the weight raising / lowering cylinder 11 is contracted, the counterweight 8 is lowered while being suspended downward from the rear end side of the turning frame 4 by the counterweight raising / lowering device.

  Reference numeral 12 denotes a discharge pipe connected to the discharge side of the main hydraulic pump 9, and the discharge pipe 12 has a first center bypass pipe 13 and a second center bypass pipe 14, which will be described later, on the tip side. It is connected to the. Then, the pressure oil discharged from the hydraulic pump 9 is supplied from the discharge pipe 12 toward the first and second center bypass pipes 13 and 14. A plurality of actuator control valves (all not shown) for supplying and discharging pressure oil to and from the plurality of hydraulic actuators are provided in the middle of the first center bypass conduit 13.

  Reference numeral 14 denotes a second center bypass pipe connected to the distal end side of the discharge pipe 12, and the center bypass pipe 14 is communicated with and cut off from the tank 10 by a directional control valve 18 described later. In the middle of the center bypass pipe 14, a control valve device 15 and a switching valve 26 described later are provided in series.

  Reference numeral 15 denotes a control valve device 15 for attaching / detaching a counterweight disposed in the middle of the center bypass conduit 14. Here, the control valve device 15 includes a pressure oil supply line 16 branched from the center bypass line 14 at a position upstream of a direction control valve 18 described later, a low pressure line 17 described later, and a direction control. And a valve 18.

  Reference numeral 17 denotes a low-pressure pipe which is always connected to the tank 10, and one end side of the low-pressure pipe 17 is connected to and cut off from a main pipe 19A, 19B, which will be described later, via a directional control valve 18, and the other end is connected to the center. The bypass pipe 14 is always connected to a position downstream of the directional control valve 18.

  Reference numeral 18 denotes a directional control valve for attaching / detaching a counterweight provided in the middle of the center bypass conduit 14, and the directional control valve 18 is, for example, a 6 port 3 position having hydraulic pilot portions 18A, 18B on both the left and right sides. It consists of a hydraulic pilot type directional control valve, and is always placed in the neutral position (A). The direction control valve 18 is switched from the neutral position (A) to the left and right switching positions (B) and (C) according to the pilot pressure supplied to the hydraulic pilot parts 18A and 18B from a pilot operation valve 23 described later. Here, the direction control valve 18 has a return passage portion 18C at a position where it is in the neutral position (A), and this return passage portion 18C is a main pipe which will be described later by the direction control valve 18 in the neutral position (A). 19B is communicated with the low pressure line 17.

  Reference numerals 19A and 19B denote a pair of main pipes that connect the weight elevating cylinder 11 to the hydraulic pump 9 and the tank 10, and the main pipes 19A and 19B are disposed between the direction control valve 18 and the weight elevating cylinder 11. . One of the main pipelines 19A and 19B is connected to the bottom side oil chamber B of the weight lifting cylinder 11, and the other main pipeline 19A is connected to the rod side oil chamber A of the weight lifting cylinder 11. .

  When the directional control valve 18 is switched from the neutral position (A) to the switching position (B), the main line 19A is connected to the hydraulic pump 9 via the supply line 16, and the main line 19B is connected via the low-pressure line 17. Connected to the tank 10. Thereby, the pressure oil from the hydraulic pump is supplied to the rod side oil chamber A of the weight raising / lowering cylinder 11 via the main pipeline 19A, and the oil in the bottom side oil chamber B is directed to the tank 10 from the main pipeline 19B side. Discharged. As a result, the rod 11C of the weight raising / lowering cylinder 11 is displaced so as to shrink toward the inside of the tube 11A.

  When the directional control valve 18 is switched from the neutral position (A) to the switching position (C), the main line 19A is connected to the tank 10 via the low pressure line 17, and the main line 19B is hydraulically connected via the supply line 16. Connected to pump 9. Thereby, the pressure oil from the hydraulic pump 9 is supplied to the bottom side oil chamber B of the weight raising / lowering cylinder 11 via the main pipe line 19B, and the oil in the rod side oil chamber A is sent to the tank 10 from the main pipe line 19A side. It is discharged towards. As a result, the rod 11C of the weight raising / lowering cylinder 11 extends so as to protrude from the tube 11A.

  Reference numeral 20 denotes a pilot-operated check valve provided in the middle of the main pipeline 19B. The check valve 20 keeps the valve closed while the directional control valve 18 is in the neutral position (A), for example, and the weight elevating cylinder 11 The oil liquid is prevented from leaking from the bottom side oil chamber B through the main pipeline 19B. Thereby, the check valve 20 prevents the rod 11C of the weight raising / lowering cylinder 11 from being displaced in the reduction direction by the load (self-weight) from the counterweight 8.

  On the other hand, when the directional control valve 18 is switched from the neutral position (A) to the switching position (B), for example, pressure oil supplied to the main line 19A side is supplied to the check valve 20 as a pilot pressure. As a result, the check valve 20 is forcibly opened to allow the oil liquid to be discharged from the bottom side oil chamber B of the weight elevating cylinder 11 through the main pipeline 19B. Further, when the direction control valve 18 is switched to the switching position (c), the check valve 20 is configured to supply the pressure oil from the hydraulic pump 9 into the bottom side oil chamber B of the weight lifting cylinder 11 via the main pipeline 19B. Is to be opened.

  21 is a slow return valve provided in the middle of the main pipeline 19B. The slow return valve 21 is located between the weight elevating cylinder 11 and the check valve 20 and is a check valve provided in the middle of the main pipeline 19B. 21A and a throttle valve 21B connected in parallel to the check valve 21A. The slow return valve 21 smoothes the flow of pressure oil by opening the check valve 21A when pressure oil is supplied into the bottom side oil chamber B of the weight lifting cylinder 11 from the main line 19B side.

  However, when the oil liquid is discharged from the bottom side oil chamber B of the weight raising / lowering cylinder 11 through the main line 19B, the check valve 21A of the slow return valve 21 is closed, and the oil liquid at this time passes through the throttle valve 21B to the tank 10. Discharged to the side. For this reason, the oil liquid flowing through the throttle valve 21B is given a throttling action, and the operation of the rod 11C of the weight elevating cylinder 11 contracting into the tube 11A is suppressed to a slower speed by the throttle valve 21B.

  Reference numeral 22 denotes a pilot pump as an auxiliary pump. The pilot pump 22 is rotationally driven together with the hydraulic pump 9 by the engine, and constitutes a pilot hydraulic source for the pilot operation valve 23 described later together with the tank 10.

  Reference numeral 23 denotes a pilot operation valve composed of a pressure reducing valve type pilot valve. The pilot operation valve 23 constitutes an operation means and has an operation lever 23A disposed in, for example, the cab 5 (see FIG. 1). . The pilot operation valve 23 supplies pilot pressure to the hydraulic pilot portions 18A and 18B of the direction control valve 18 when the operator manually tilts the operation lever 23A.

  Reference numerals 24A and 24B denote a pair of pilot lines. The pilot lines 24A and 24B connect the output side of the pilot operation valve 23 to the hydraulic pilot parts 18A and 18B of the directional control valve 18, and these hydraulic pilot parts 18A and 18B Supply pilot pressure to 18B. That is, when the operator tilts the operation lever 23A in the direction of arrow C in FIG. 2, the directional control valve 18 is supplied with the pilot pressure from the pilot line 24A to the hydraulic pilot portion 18A, and from the neutral position (A). Switch to the switching position (b). As a result, the weight raising / lowering cylinder 11 is driven in the reduction direction, and the counterweight 8 is operated to be suspended downward by the weight raising / lowering cylinder 11.

  On the other hand, when the operator tilts the operation lever 23A in the direction indicated by the arrow D in FIG. 2, the directional control valve 18 is supplied with the pilot pressure from the pilot line 24B to the hydraulic pilot portion 18B, and from the neutral position (A). Switch to the switching position (c). As a result, the weight lifting cylinder 11 is driven in the extending direction, and the counterweight 8 is lifted upward.

  Reference numeral 25 denotes a high pressure selection valve (hereinafter referred to as a shuttle valve 25) as an operation signal output means. The shuttle valve 25 is disposed between a pair of pilot lines 24A and 24B. When any one of 24B becomes higher pressure than the other, the pressure at this time is taken out as an operation signal and supplied to an output line 27 described later. That is, in the pair of pilot pipes 24A and 24B, when the operator tilts the operation lever 23A of the pilot operation valve 23 in the directions indicated by arrows C and D, a pilot pressure corresponding to the operation amount is generated. Then, the pilot pressure at this time is taken out as an operation signal by the shuttle valve 25 and is supplied to a switching valve 26 described later via an output line 27.

  Reference numeral 26 denotes a switching valve provided in the middle of the center bypass conduit 14 between the hydraulic pump 9 and the direction control valve 18. The switching valve 26 is constituted by, for example, a 2-port 2-position hydraulic pilot type switching valve. Has been. The switching valve 26 is normally disposed at the cutoff position (a), and when the pilot pressure as the operation signal is supplied from the output pipe 27, the switching valve 26 is switched from the cutoff position (a) to the communication position (b). The switching valve 26 shuts off the center bypass conduit 14 at an intermediate position while being arranged at the shut-off position (a), and allows the flow of pressure oil from the hydraulic pump 9 toward the direction control valve 18 and the weight lifting cylinder 11 side. Stop.

  However, when the operator tilts the operation lever 23A of the pilot operation valve 23 in either of the directions indicated by arrows C and D, a pilot pressure corresponding to the operation amount is generated. The operation signal is taken out from either one of 24A and 24B by the shuttle valve 25. The switching valve 26 switches from the shut-off position (a) to the communication position (b) when the pilot pressure is supplied as an operation signal from the output line 27 side. As a result, the pressure oil from the hydraulic pump 9 flows to the direction control valve 18 through the center bypass pipe 14.

  Reference numeral 28 denotes a relief valve, which sets the maximum discharge pressure of the pressure oil by the main hydraulic pump 9. When the pressure in the discharge pipe 12 exceeds the relief set pressure, the relief valve 28 is opened to relieve the excess pressure to the tank 10 side.

  The hydraulic circuit for attaching and detaching the counterweight of the hydraulic excavator 1 according to the present embodiment has the above-described configuration, and the operation thereof will be described next.

  First, when lifting the counterweight 8 to the rear end side of the swing frame 4 using a counterweight lifting / lowering device (not shown), the operator tilts the operation lever 23A of the pilot operation valve 23 in the direction indicated by the arrow D. To do. Thereby, a pilot pressure is generated in the pilot pipe line 24B, and this pilot pressure is taken out as an operation signal by the shuttle valve 25.

  For this reason, the switching valve 26 is switched from the cutoff position (a) to the communication position (b) when the pilot pressure is supplied as an operation signal from the output line 27 side. Thereby, the pressure oil from the hydraulic pump 9 can be circulated to the direction control valve 18 side through the center bypass conduit 14. At this time, the directional control valve 18 is supplied with the pilot pressure from the pilot operation valve 23 to the hydraulic pilot section 18B via the pilot line 24B, and is switched from the neutral position (A) to the switching position (C).

  As a result, the pressure oil from the hydraulic pump 9 is supplied to the bottom side oil chamber B of the weight lifting cylinder 11 through the supply pipe 16 and the main pipe 19B, and the weight lifting cylinder 11 is connected to the rod 11C from the tube 11A. By extending the counterweight, the counterweight lifting device can be operated. For example, the counterweight 8 can be lifted up to the rear end side of the swing frame 4.

  In this case, the operator performs a tilting operation (hereinafter referred to as a fine operation) so as to slowly finely adjust the operation lever 23A of the pilot operation valve 23 in the direction of arrow D, whereby the direction control valve 18 is in the neutral position (A). It is possible to finely adjust the stroke amount when switching from the switch position to the switch position (b). The extension speed of the weight raising / lowering cylinder 11 can be variably controlled so as to become slower or faster according to the stroke amount.

  On the other hand, when the counterweight 8 is suspended from the rear end side of the turning frame 4 toward the ground, the operator tilts the operation lever 23A of the pilot operation valve 23 in the direction of arrow C. As a result, a pilot pressure is generated in the pilot line 24A, and this pilot pressure is supplied to the output line 27 via the shuttle valve 25, so that the switching valve 26 is connected from the shut-off position (a) to the communication position. The state is switched to (b).

  At this time, the directional control valve 18 is switched from the neutral position (A) to the switching position (B) by the pilot pressure from the pilot operation valve 23 via the pilot line 24A. Therefore, the pressure oil from the hydraulic pump 9 is supplied from the supply line 16 side to the rod side oil chamber A of the weight lifting cylinder 11 via the main line 19A, and from the bottom side oil chamber B to the slow return valve 21, The oil is discharged through the main line 19B. Thereby, the rod 11C of the weight lifting cylinder 11 is reduced into the tube 11A, and the counterweight 8 can be suspended to the ground side by the counterweight lifting device.

  Even in this case, the operator can finely adjust the stroke amount when the directional control valve 18 is switched from the neutral position (A) to the switching position (B) by finely operating the operation lever 23A of the pilot operation valve 23. The reduction speed of the weight raising / lowering cylinder 11 can be variably controlled so as to be reduced or increased according to the stroke amount.

  By the way, after such a work of attaching and detaching the counterweight 8 is completed, it is required to keep the weight lifting cylinder 11 in a stopped state without operating for a long time. That is, in such a case, it is necessary to prohibit inadvertent movement of the weight lifting cylinder 11 in order to ensure operational safety.

  Therefore, according to the first embodiment, the directional control valve 18 is provided in the middle of the center bypass conduit 14 between the hydraulic pump 9, the tank 10 and the weight elevating cylinder 11, and the neutral position of the directional control valve 18 is set. In (A), the supply of pressure oil to the weight lifting cylinder 11 via the pair of main pipelines 19A and 19B is shut off, and one main pipeline 19B connected to the bottom side oil chamber B of the weight lifting cylinder 11 is The return passage portion 18 </ b> C provided in the direction control valve 18 is configured to communicate with the tank 10 via the low pressure pipe 17.

  Thus, until the pilot pressure as the operation signal is supplied from the pilot operation valve 23, the directional control valve 18 is held at the neutral position (A) and connected to the bottom side oil chamber B of the weight raising / lowering cylinder 11. The main pipeline 19B can be kept in communication with the tank 10 by the return passage portion 18C of the direction control valve 18.

  For this reason, even if a part of the pressure oil flowing through the center bypass pipe 14 from the hydraulic pump 9 toward the direction control valve 18 leaks to the main pipe 19B side, this leaked oil is discharged to the direction control valve 18. It can be discharged to the tank 10 side by the return passage portion 18C, prevents pressure from being accumulated in the main pipe line 19B between the direction control valve 18 and the check valve 20, and the bottom side oil chamber B of the weight lifting cylinder 11 The pressure oil can be prevented from being supplied accidentally.

  Moreover, in the present embodiment, one switching valve 26 is provided in the middle of the center bypass conduit 14 between the hydraulic pump 9 and the direction control valve 18, and the switching valve 26 is a pilot operation valve 23. Until the operation signal is output from the hydraulic pump 9, the hydraulic oil 9 is blocked from flowing through the center bypass pipe 14 from the hydraulic pump 9 toward the direction control valve 18, and the operation signal is output. When it is done, it switches from the shut-off position (a) to the communication position (b) to allow the flow of pressure oil.

  Thus, until the operator tilts the pilot operation valve 23, the switching valve 26 is held at the shut-off position (a), and the pressure oil from the hydraulic pump 9 moves to the direction control valve 18 side through the center bypass line 14. It is possible to prevent the oil from flowing, and it is possible to prevent pressure oil from leaking in the direction control valve 18. For this reason, it can prevent double that the weight raising / lowering cylinder 11 is moved accidentally by the leak oil etc. from the direction control valve 18. FIG.

  Therefore, according to the first embodiment, unless the operator operates the pilot operation valve 23, pressure oil leaks on the directional control valve 18 side, or the weight elevating cylinder 11 malfunctions due to this leaked oil or the like. Doing so can be doubled on the safer side. As a result, for example, as described in the prior art, inadvertent movement of the weight lifting cylinder 11 can be stopped without relying on manual operation by a gate valve, and the safety and reliability of the apparatus can be improved. .

  Next, FIG. 3 shows a second embodiment of the present invention. The feature of this embodiment is a control including a plurality of control valves for actuators for supplying pressure oil from a hydraulic pump to a plurality of hydraulic actuators. A valve group is provided, and another switching valve is provided downstream of the control valve group. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the figure, reference numeral 31 denotes a first center bypass pipe employed in the second embodiment, and the first center bypass pipe 31 is the first center bypass pipe described in the first embodiment. 13 was used instead. Then, the pressure oil discharged from the hydraulic pump 9 is supplied from the discharge pipe 12 toward the first center bypass pipe 31 and the second center bypass pipe 14. The downstream side of the first center bypass conduit 31 is connected to the tank 10 via a return conduit 31A.

  Reference numeral 32 denotes a control valve group provided in the middle of the first center bypass conduit 31. The control valve group 32 is, for example, an actuator control valve 33, 34, 35, 36, consisting of five directional control valves. 37. These actuator control valves 33, 34, 35, 36, and 37 are, for example, pressure oils for hydraulic actuators (not shown) such as a traveling hydraulic motor, a turning hydraulic motor, a boom cylinder, an arm cylinder, and a bucket cylinder. It controls the supply and discharge of the.

  Reference numeral 38 denotes a pressure oil supply line branched from the first center bypass line 31, and the supply line 38 is supplied from the hydraulic pump 9 via the first center bypass line 31. A so-called parallel circuit is configured in which the actuator control valves 33, 34, 35, 36, and 37 are connected in parallel to each other so as to have a parallel relationship with the pressure oil.

  Reference numeral 39 denotes another switching valve provided on the most downstream side of the center bypass pipe 31 in the control valve group 32. The other switching valve 39 is constituted by, for example, a 2-port 2-position hydraulic pilot type switching valve. Yes. The other switching valve 39 is normally arranged at the communication position (c), and when a pilot pressure as an operation signal is supplied from a pilot pipe 40 described later, the switching valve 39 is switched from the communication position (c) to the cutoff position (d). .

  The switching valve 39 switched to the blocking position (d) blocks the first center bypass pipe 31 from the tank 10 on the downstream side. As a result, in the first center bypass pipe 31, the portion upstream of the other switching valve 39 is maintained in a relatively high pressure state by the pressure oil from the hydraulic pump 9.

  Reference numeral 40 denotes a pilot pipe for supplying pilot pressure to another switching valve 39. One end of the pilot pipe 40 is connected to a position in the middle of the output pipe 27, and the other end is a hydraulic pilot section of the other switching valve 39 ( (Not shown). In the pilot pipe 40, like the output pipe line 27, when the operator tilts the operation lever 23 </ b> A of the pilot operation valve 23 in either the arrow C or D direction, the pilot pressure corresponding to the operation amount is obtained. Is supplied.

  For this reason, the other switching valve 39 is connected to the pilot pipe when the one switching valve 26 is switched from the shut-off position (a) to the communication position (b) by the pilot pressure (operation signal) from the output pipe 27 side. The communication position (c) is switched to the shut-off position (d) by the pilot pressure supplied via 40. When one switching valve 26 switches so as to return from the communication position (b) to the shut-off position (a), the other switch valve 39 is linked to the communication position (c) from the shut-off position (d). Switch to return to.

  Thus, in the present embodiment configured as described above, as in the first embodiment, until the operator tilts the pilot operation valve 23, the one switching valve 26 is set to the cutoff position (a). It is possible to prevent the pressure oil from the hydraulic pump 9 from flowing to the direction control valve 18 side through the center bypass pipe 14 and to prevent the weight lifting cylinder 11 from being erroneously moved. it can.

  In particular, in the second embodiment, another switching valve 39 is provided on the downstream side of the control valve group 32 including the plurality of actuator control valves 33 to 37. Therefore, until the operation signal is output from the pilot operation valve 23, the pressure oil flowing from the hydraulic pump 9 through the first center bypass pipe 31 is returned by setting the other switching valve 39 to the communication position (c). It can distribute | circulate so that it may discharge | emit to the pipe line 31A (tank 10) side.

  As a result, when all of the actuator control valves 33 to 37 are disposed at the neutral position, the pressure in the first center bypass conduit 31 is reduced to a pressure equivalent to that on the tank 10 side as shown in FIG. . When the pressure in the first center bypass pipe 31 is reduced to the tank pressure level, the pressure in the second center bypass pipe 14 is similarly kept at a low pressure.

  Therefore, in the other switching valve 39, the pressure oil from the hydraulic pump 9 is used for attaching / detaching the counterweight until the pilot operation valve 23 is operated and the operation signal is output in order to perform the attaching / detaching operation of the counterweight 8. The flow toward the control valve device 15 (direction control valve 18) can be prevented double and triple together with the one switching valve 26, and the inadvertent movement of the weight lifting cylinder 11 is stopped, and the safety of the device is stopped. And reliability can be improved.

  On the other hand, when an operation signal is output from the pilot operation valve 23 in order to attach / detach the counterweight 8, the other switching valve 39 is switched from the communication position (c) to the shut-off position (d), so that the hydraulic pump It is possible to block the pressure oil from 9 from being discharged to the tank 10 side through the first center bypass pipe 31. As a result, the pressure in the first center bypass conduit 31 rises, and the pressure in the second center bypass conduit 14 can be increased to an equally high pressure, which is switched to the communication position (b). High pressure oil can be circulated toward the direction control valve 18 via the switching valve 26.

  In the first embodiment, the case where the direction control valve 18 constituting the control valve device 15 for attaching / detaching the counterweight is provided in the middle of the center bypass pipe 14 has been described as an example. However, the present invention is not limited to this. For example, the directional control valve is configured to be a 4-port 3-position directional control valve without using the center bypass pipe, and the hydraulic pump 9, the tank 10, and the weight lifting cylinder 11 It is good also as a structure which is connected and interrupted | blocked via a pair of main pipelines.

  In each of the above embodiments, the case where the counterweight 8 of the excavator 1 is attached and removed from the rear end side of the revolving frame 4 has been described as an example. However, the present invention is not limited to this. For example, a counter of various working machines of a type in which a counterweight is detachably mounted on the rear end side of the vehicle body, such as a hydraulic crane, a wheel loader, a bulldozer, or various working machines. The present invention can also be applied to a weight attaching / detaching hydraulic circuit.

1 Hydraulic excavator (work machine)
3 Upper swing body (car body)
4 Turning frame 5 Cab 7 Working device 8 Counterweight 9 Hydraulic pump (hydraulic power source)
10 Tank (hydraulic power source)
DESCRIPTION OF SYMBOLS 11 Weight raising / lowering cylinder 14,31 Center bypass line 15 Control valve apparatus for attachment / detachment of counterweight 17 Low pressure line 18 Directional control valve 18C Return passage part 19A, 19B Main line 21 Slow return valve 23 Pilot operation valve (operation means)
23A Operation lever 25 Shuttle valve (operation signal output means)
26 One switching valve 27 Output line 32 Control valve group 33 to 37 Actuator control valve 39 Other switching valve 40 Pilot piping A Rod side oil chamber B Bottom side oil chamber

Claims (3)

A hydraulic pump that constitutes a hydraulic power source of the work machine together with a tank, and is driven by pressure oil from the hydraulic pump to move the counter weight up and down when the counter weight is detachably attached to the frame of the work machine. A weight raising / lowering cylinder, and between the weight raising / lowering cylinder and the hydraulic power source, the pressure from the hydraulic power source is switched to the neutral position when the pressure oil is switched from the neutral position. Counterweight attaching / detaching hydraulic pressure for a working machine comprising: a directional control valve for supplying and discharging oil to and from the weight raising and lowering cylinder; and an operating means for outputting an operation signal to the directional control valve and switching the directional control valve. In the circuit
The directional control valve is arranged at the neutral position until an operation signal is output from the operation means, so that one of the predetermined main lines connected to the weight lifting cylinder is predetermined. Is configured to communicate with the tank,
Between the hydraulic pump and the directional control valve, the flow of pressure oil from the hydraulic pump toward the weight lifting cylinder is shut off until an operation signal is output from the operation means, A counter weight of a work machine is provided with a switching valve that switches from the shut-off position to the communication position when the operation signal is output to allow the flow of pressure oil to the weight lifting cylinder. Hydraulic circuit for   The directional control valve is arranged in the middle of a center bypass line connecting the hydraulic pump to the tank, and is configured to communicate and block the center bypass line with respect to the tank and to switch and control the pair of main lines. 2. The hydraulic circuit for attaching and detaching a counterweight of the work machine according to claim 1, wherein the one switching valve is provided in the middle of the center bypass pipe line between the hydraulic pump and the direction control valve.   A control valve group comprising a plurality of actuator control valves for supplying pressure oil discharged from the hydraulic pump to a plurality of hydraulic actuators, the actuator control valves being connected in a predetermined arrangement; On the downstream side of the group, until the operation signal is output from the operation means, it becomes a communication position to allow the pressure oil from the hydraulic pump to flow to the tank side, and when the operation signal is output, 3. The hydraulic circuit for attaching / detaching a counterweight of a work machine according to claim 1 or 2, wherein another switching valve for switching from a communication position to a blocking position to block the flow of the pressure oil is provided.

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