WO2002055793A1

WO2002055793A1 - Hydraulic control circuit of boom cylinder of working machine

Info

Publication number: WO2002055793A1
Application number: PCT/JP2001/011004
Authority: WO
Inventors: Tetsuya Yoshino; Yoshiyuki Shimada
Original assignee: Shin Caterpillar Mitsubishi Ltd.
Priority date: 2001-01-15
Filing date: 2001-12-14
Publication date: 2002-07-18
Also published as: JP3849970B2; JP2002212979A

Abstract

A hydraulic control circuit, comprising a boom cylinder for vertically moving a boom, a control valve for controlling the supply and discharge of pressure oil to and from the boom cylinder, and a regenerative circuit for supplying a part of the discharged oil from the head side oil chamber of the boom cylinder to the rod side oil chamber, wherein, based on the selection of a mode selector switch (22), a first boom section control valve (14) is held at a neutral position (N) while the boom is being lowered, and the discharged oil in the head side oil chamber (8a) of the boom cylinder (8) is fed to an oil tank (13) through a second boom section control valve (15), whereby the boom can be lowered by its own weight and a boom lowering speed can be varied according to the type of a work and the skill of an operator.

Description

Description Hydraulic control circuit for boom cylinder in work machine

The present invention belongs to the technical field of a hydraulic control circuit for a boom cylinder in a working machine such as a hydraulic shovel used for various types of construction work and civil engineering work. Background art

Generally, in a work machine such as a hydraulic excavator, a front attachment mounted on the body of the machine is a boom whose base end is supported by the body of the machine so as to be able to swing up and down, and the front end of the boom can be moved back and forth. And a work attachment such as a packet breaker or a clamshell attached to the tip of the stick. In this apparatus, the above-mentioned bob moves up and down by the expansion and contraction operation of the boom cylinder. As a hydraulic control circuit of the boom cylinder, a conventional hydraulic control circuit as shown in FIG. 3 is known. ing.

That is, in FIG. 3, 8 is a cylinder cylinder, 11 and 12 are first and second hydraulic pumps, 13 is an oil tank, and 14 is a hydraulic cylinder with the first hydraulic pump 11 as a hydraulic oil supply source. —Control valve for the first boom that controls the supply and discharge of pressurized oil to the boom cylinder 8, and 15 is the control for the second boom that controls the supply of pressurized oil to the boom cylinder 8 using the second hydraulic pump 12 as the supply source of pressurized oil. Valves, 16 are control valves for other hydraulic actuators such as bucket cylinders installed on hydraulic excavators, and 17 is a pilot line E on the ascending and descending sides based on the operation of the operating lever 18 for the boom. This is a pilot valve that outputs the pilot pressure to F. A is a head line connecting the first boom control valve 14 and the second boom control valve 15 with the head oil chamber 8a of the boom cylinder 8, and B is a first boom. A rod-side line connecting the control valve 14 to the head-side oil chamber 8b of the cylinder cylinder 8, and D is a regeneration line that connects the head-side line A and the rod-side line B. Ah, the reproduction line! Is provided with a regeneration valve 19 and a check valve 21. In this case, when the operation lever 18 for the boom is operated to the lower side, the control valve 14 for the first boom and the valve 19 for regeneration are switched by the pilot pressure output from the pilot valve 17 to the lower pilot line F. You. As a result, the pressure oil from the first hydraulic pump 11 is supplied to the boom cylinder 8 via the first boom control valve 14 to the mouth-side oil chamber 8 b of the boom cylinder 8. The oil discharged from the oil chamber 8a is discharged to the oil tank 13 via the first boom control valve 14 and the load side oil chamber 8b via the regeneration valve 19 and the check valve 21. It is being supplied to In other words, when the pressure in the head-side oil chamber 8a is higher than the pressure in the rod-side oil chamber 8b when the boom is lowered, the oil discharged from the head-side oil chamber 8a is used as reclaimed oil. The rod-side oil chamber 8b can be supplied to the rod-side oil chamber 8b in addition to the pressure oil of the first hydraulic pump 11 supplied from the first boom control valve 14. As a result, the operation speed of the boom cylinder 8 can be increased without the pressure side oil chamber 8b being in a reduced pressure state. In addition, during a combined operation of another hydraulic actuator (eg, a bucket cylinder) using the first hydraulic pump 11 as a hydraulic oil supply source and a boom lowering operation, the excess pump flow obtained by the regenerated oil is used for another hydraulic pump. Since the supply can be performed overnight, it is possible to suppress a decrease in the operating speed of the other hydraulic actuators during the combined operation, thereby contributing to the improvement of the working efficiency. By the way, in the prior art, in order to improve the working efficiency as much as possible, the amount of the regenerated oil from the cylinder side oil chamber to the cylinder side oil chamber is increased so that the cylinder speed is increased. However, with this setting, there is a problem that the speed is too fast to operate when performing a work requiring fine operation or when the operator is a beginner. On the other hand, if the amount of regenerated oil is set to be small so that it can be easily operated by a fine operation or a beginner, there is a problem that the effect of providing the regenerating circuit is reduced and the working efficiency is reduced. There is a problem to be solved by the present invention. Further, in a working machine equipped with a front attachment including the boom, stick, work attachment, and the like, for example, in a case where a packet is moved back and forth along the ground to remove rocks that roll on a flat ground. There is a bucket Since it is necessary to draw a substantially horizontal trajectory at the tip of the boat, the boom must be operated in addition to the stick operation. In addition, when performing crushed stone work using a breaker, it is necessary to operate the boom down and press the breaker against the rock so that the breaker always receives appropriate thrust. In addition, when scooping up an object using the clamshell, it is necessary to recognize that the clamshell has come into contact with the object and stop the operation of lowering the boom. However, there is a problem in that the boom operation always requires careful attention, the operation is complicated, and the fatigue level of the operation increases. Further, there is another problem to be solved in that the pressurized oil is supplied to the boom cylinder during the boom operation, so that the fuel consumption increases and the fuel efficiency is poor. Disclosure of the invention

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and has been created with the object of solving these problems, and a boom cylinder that expands and contracts to move the boom up and down, and a boom based on operation of an operating tool. An operating position for controlling the supply and discharge of hydraulic oil to and from the oil chambers on the head side rod side of the cylinder, a control valve that can be switched to a neutral position where no supply and discharge of hydraulic oil is performed, and In a hydraulic control circuit for a boom cylinder having a regeneration circuit for supplying oil discharged from the oil chamber on the weight holding side for holding the weight of the boom to the other oil chamber, the hydraulic control circuit includes: Neutral holding means capable of holding the control valve in the neutral position regardless of the position of the control valve; a discharge oil passage for flowing the discharged oil from the oil chamber on the weight holding side to the oil tank without passing through the control valve; It is provided with a and valve means for opening and closing control of the road.

By doing so, it is possible to lower the boom by its own weight or to change the descent speed of the boom in accordance with the work content and the skills of the operator. Is improved.

Further, the present invention provides a boom cylinder which expands and contracts to move the boom up and down, a first hydraulic pump as a pressure oil supply source, and controls the oil chambers on the head side rod side of the boom cylinder based on operation of an operating tool. The first control valve, which can be switched to an operating position for controlling hydraulic oil supply / discharge and a neutral position not performing hydraulic oil supply / discharge, and a second hydraulic pump for supplying hydraulic oil The second control pulp is used as a supply source to control the supply of pressurized oil to the oil chamber on the weight holding side that holds the weight of the boom, and the oil discharged from the oil chamber on the weight holding side is the other. In a hydraulic control circuit of a boom cylinder having a regeneration circuit for supplying the oil to the oil chamber, the hydraulic control circuit being capable of holding the first control valve in a neutral position regardless of operation of the operating tool. Means is provided, and the second control valve is further provided with discharge control means for flowing the discharged oil from the oil chamber on the weight holding side to the oil tank.

In this way, the second control valve can be used to lower the boom's own weight or change the boom's descent speed in accordance with the work content and the skill of the work overnight. In addition, workability and operability are improved, and parts can be shared. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective view of a hydraulic excavator.

FIG. 2 is a hydraulic control circuit diagram showing an embodiment of the present invention.

FIG. 3 is a hydraulic control circuit diagram showing a conventional example. BEST MODE FOR CARRYING OUT THE INVENTION

Next, embodiments of the present invention will be described with reference to the drawings. In the drawings, reference numeral 1 denotes a hydraulic excavator. The hydraulic excavator 1 includes a crawler-type lower traveling body 2, an upper revolving body 3 rotatably supported by the lower traveling body 2, and a front of the upper revolving body 3. The front attachment 4 includes a boom 5 that is supported by the upper revolving unit 3 so as to be able to swing up and down, and a front and rear end of the boom 5. A stick 6 swingably supported, a bucket 7 swingably supported at the front end of the stick 6, a boom cylinder 8 for swinging the boom 5, the stick 6, and the bucket 7. The basic configuration such as the configuration of the member devices such as the stick cylinder 9 and the bucket cylinder 10 is the same as the conventional one.

Note that the tip of the stick 6 is Instead of the packet 7, various work equipment such as a breaker and a clamshell (both not shown) are attached.

Now, FIG. 2 shows a hydraulic control circuit of the boom cylinder 8. In FIG. 2, 11 and 12 are first and second hydraulic pumps, 13 is an oil tank, 14 and Reference numeral 15 denotes a control valve for the first and second booms to be described later. Reference numeral 16 denotes a packet control valve, and the bucket control pulp 16 is provided in parallel with the first boom control valve 14. The control valves provided in parallel with the first and second boom control valves 14 and 15 are, in addition to the bucket control valve 16, various hydraulic actuators provided on the hydraulic excavator 1. However, they are omitted in FIG. Further, in FIG. 2, A is a head side line connecting the first boom control valve 14 and the second boom control valve 15 to the head side oil chamber 8 a of the boom cylinder 8, B is a port side line connecting the first boom control valve 14 and the load side oil chamber 8b of the boom cylinder 8, and D is a regeneration line connecting the head side line A and the rod side line B. Line.

The boom cylinder 8 is extended by the supply of pressurized oil to the head-side oil chamber 8a and the oil discharge from the head-side oil chamber 8b to raise the boom 5; The boom 5 is lowered by supplying compressed oil to the side and discharging oil from the head-side oil chamber 8a. In this case, the head-side oil chamber 8a is Holding the weight of the cement 4 corresponds to the weight holding side oil chamber of the present invention. Further, the first boom control valve 14 includes ascending and descending pilot ports 14a and 14b, and a pilot port input to these pilot ports 14a and 14b. It is composed of a spool valve whose opening degree of the supply and discharge valve paths 14 c to 14 f described later is adjusted by pressure. In other words, the control valve 14 for the first boom is located at the neutral position N when the pilot pressure is not input to both the pilot ports 14a and 14b, and the pressure oil supply and discharge to the boom cylinder 8 is performed. However, when the pilot pressure is input to the rising pilot port 14a, it is displaced to the rising position X and the hydraulic oil from the first hydraulic pump 11 passes through the head side line A. The supply valve path 14c for supplying to the head-side oil chamber 8a of the boom cylinder 8 is opened, and the oil discharged from the rod-side oil chamber 8b is supplied to the oil via the rod-side line B. Tank 1 The discharge valve channel 1 4 d for flowing to 3 is opened. Further, the control valve 14 for the first boom is displaced to the lower position Y by the input of the pie port pressure to the lower pilot port 14 b, and the pressure from the first hydraulic pump 11 is changed. Open the supply valve line 14e for supplying oil to the load side oil chamber 8b via the load side line B, and open the head side oil chamber 8a to the head side line. It is configured to open a discharge valve path 14 f for flowing the oil discharged to A to the oil tank 13 through a restrictor 14 g. Here, the oil from the head side oil chamber 8a of the first boom control valve 14 at the descending side position Y to the oil tank 13 is discharged from the throttle provided in the discharge valve path 14f. This is performed in a state where the flow rate is adjusted by 14 g, but the oil discharge flow rate of the discharge valve path 14 f is set to a flow rate necessary to obtain a slow boom lowering speed suitable for performing a fine operation. ing.

On the other hand, the second boom control valve 15 has ascending and descending pilot ports 15a and 15b, and a pilot port input to these pilot ports 15a and 15b. It is composed of a spool valve whose opening degree of supply and discharge valve paths 15c and 15d described later is adjusted by pressure. In other words, the control valve 15 for the second boom is located at the neutral position N when the pilot pressure is not input to both the pilot ports 15a and 15b, and the hydraulic oil for the boom cylinder 8 is No supply / discharge is performed, but when the pilot pressure is input to the rising pilot port 15a, it is displaced to the rising position X to open the supply valve passage 15c. The hydraulic oil from the second hydraulic pump 12 is supplied to the head side oil chamber 8a of the boom cylinder 8 via the head side line A. Further, the control pulp 15 for the second boom is displaced to the descending position Y by opening the pilot port 15b when the pilot pressure is input to the descending ^! Pilot port 15b, so that the discharge valve path 15d is opened. As a result, the oil discharged from the head-side oil chamber 8a passes through the head-side line A to the oil tank 13 through the throttle 15e provided in the discharge valve path 15d. It is configured to flow. Further, in FIG. 3 shown in FIG. 3, reference numeral 17 denotes a boom pilot valve, which is composed of an ascending-side pilot port valve 17 A and a descending-side pilot port valve 17 B. However, these ascending and descending pilot valves 17 A and 17 B are operated by operating the boom operation lever 18 to the boom ascending and descending sides. The pilot pressure corresponding to the manipulated variable is output. The pilot pressure output from the ascending pilot valve 17 A passes through the ascending pilot line E, and the ascending pilot port 14 a of the first and second boom control pulp 14, 15, Entered in 15 a. The pilot pressure output from the descending pilot valve 17B is input to a pilot port 19a of a regeneration valve 19 to be described later via a descending pilot line F, and a mode switching valve is provided. Supplied to 20.

The regeneration valve 19 is disposed on the regeneration line D, and is constituted by a spool valve having a pilot port 19a. When the pilot pressure is not input to the pilot port 19a, the regeneration valve 19 is located at the closed position X for closing the regeneration line D, but the pilot pressure is applied to the pilot port 19a. Is input, the reproduction line D is switched to the open position Y that opens through the aperture 19b. Further, reference numeral 21 denotes a check valve provided on the regeneration line D. The check valve 21 operates when the pressure of the head side line A is higher than that of the mouth side line B. The oil flow from the head side line A to the mouth side line B is allowed, but the flow in the opposite direction is prevented. Thus, when the regeneration valve 19 is located at the open position Y and the pressure of the head side line A is higher than the load side line; B, the oil of the head side line A is regenerated. It flows to the root line B via the service line D.

Further, the mode switching valve 20 is an electromagnetic three-position switching valve having first and second solenoids 20a and 20b, and both solenoids 20a and 20b are energized. If not, the pressure of the descending pilot line F is input to the descending pilot port 14 b of the control valve 14 for the first boom, and the descending pilot port 15 b of the control pulp 15 for the second boom. Is placed in the neutral position N, which conducts the oil to the oil tank 13, but when the first solenoid 20 a is energized, the pressure of the descending pilot line F increases to the descending side of the first boom control valve 14. Switch to the first position X for input to the pilot port 14b and the descending pilot port 15b of the control valve 15 for the second boom. Also, when the second solenoid 2 Ob is energized, the pressure of the descending pilot line F is reduced to the descending pilot port 15 of the second boom control valve 15. b, and is switched to a second position Y where the descending pilot port 14 b of the first boom control valve 14 is connected to the oil tank 13.

On the other hand, 22 is a mode selection switch provided on the driver's seat, and the mode selection switch 22 is a first and second solenoids 20a, 20b of the mode switching valve 20. Is electrically connected to the The mode selection switch 22 can be arbitrarily selected from “boom lowering speed L 0W”, “boom lowering speed HIGH”, and “boom own weight lowering”. When the boom lowering speed L OW is set, both solenoids 20a and 2Ob of the mode switching valve 20 are not energized, and the boom lowering speed HIGH is set. In this case, the first solenoid 20a is energized, and when "boom self-weight descent" is set, the second solenoid 2Ob is energized.

In FIG. 2, reference numeral 23 denotes a line relief valve provided in a relief oil passage extending from the rod side line B to the oil tank 13.

In the configuration described above, when raising the pump 5 and operating the boom operation lever 18 to the rising side, the pie port pressure output from the rising side pilot valve 17 A will be reduced. , First and second boom control valves 14 and 15 ascending side pipe port Input to ports 14a and 15a, first and second boom control valves 14 and 15 Switch to ascending position X. As a result, the pressure oil of both the first and second hydraulic pumps 11 and 12 passes through the first and second boom control valves 14 and 15 to the head side oil of the boom cylinder 8. As a result of being supplied to the chamber 8a, the raising operation of the boom 5 against the weight of the front attachment 4 can be performed strongly.

On the other hand, when lowering the boom 5, when performing a fine operation or when the operator is a beginner, the mode selection switch 22 is set to “boom lowering speed L OW”. When the mode selection switch 22 is set to the “boom lowering speed L OW”, the solenoids 20 a and 20 b of the mode switching valve 20 are not energized as described above. The valve 20 is located at the neutral position N, and the pressure of the descending pilot line F is input to the descending pilot port 14 b of the control valve 14 for the first boom and the control valve 1 for the second boom. 5 descending side The pilot port 15 b communicates with the oil tank 13. In this state, operating the boom operation lever 18 to the descending side will cause the pilot port pressure output from the descending pilot valve 17 B to decrease the pilot port 1 4 b of the first boom control valve 14. And input to the pilot port 19 a of the regeneration valve 19 to switch the first boom control valve 14 to the lower position Y and to switch the regeneration valve 19 to the open position Y. On the other hand, the second bloom control valve 15 is held at the neutral position N. As a result, the pressure oil from the first hydraulic pump 11 is supplied to the load side oil chamber 8 b of the boom cylinder 8 via the first boom control valve 14, and the head side line A When the pressure of the oil is higher than that of the inlet side line B, part of the oil discharged from the head side oil chamber 8a is transferred to the load side oil via the regeneration valve 19 and the check valve 21. Room 8b is supplied as reclaimed oil. The remaining oil discharged from the head side oil chamber 8a is discharged to the oil tank 13 via the first boom control valve 14.

In other words, when set to the “boom lowering speed L OW”, the oil discharge from the head side oil chamber 8 a of the boom cylinder 8 to the oil tank 13 is performed by the first boom control valve 1. 4 is performed only via the discharge valve path 14f, but the oil discharge flow rate of the discharge valve path 14f is set to a flow rate at which a slow boom lowering speed is obtained. As a result, the boom 5 descends slowly, improving operability when performing a fine operation or when the operator is a beginner.

On the other hand, when lowering the boom 5, if it is desired to improve the work efficiency or perform a work requiring a fast boom descent such as an excavation loading operation, set the mode selection switch 22 to the “boom”. Lowering speed HI GH ”. As a result, the first solenoid 20 a of the mode switching valve 20 is energized, and the mode switching valve 20 increases the pressure of the descending pilot line F by the first and second boom control valves 14, 14. Switch to the first position X to be input to 15 descending pilot ports 14 b and 15 b of 15. In this state, when the boom operation lever 18 is operated to the lower side, the pilot pressure output from the lower / lower side pilot valve 17 B is changed to the lower side of the first and second boom control valves 14 and 15. Input to the pilot ports 14b, 15b and the pilot port 19a of the regenerating norb 19, switch the first and second boom control valves 14, 15 to the down position Y and play Valve 1 9 open position Switch to Y. Thereby, the pressure oil from the first hydraulic pump 11 is supplied to the rod-side oil chamber 8 b of the boom cylinder 8 via the first boom control valve 14, and at the same time, J, While the pressure in the head side line A is higher than the pressure in the head side line B, a part of the oil discharged from the head side oil chamber 8a passes through the regeneration valve 19 and the check valve 21. It is supplied as regenerated oil to the port side oil chamber 8b. The remaining oil discharged from the head side oil chamber 8a is discharged to the oil tank 13 via the first boom control valve 14 and the second boom control valve 15.

In other words, when the boom lowering speed is set to HIGH, the oil discharge from the head side oil chamber 8a of the boom cylinder 8 to the oil tank 13 is controlled by both the first and second booms. This is done via the exhaust valve passages 14f, 15d of the valves 14 and 15, so that the second boom can be used as compared with the case where only the first boom control valve 14 described above is used. The amount of oil discharge increases by the amount of the control valve 15 and the oil is quickly discharged from the head-side oil chamber 8a, so that the boom 5 is lowered at a high speed. be able to.

In addition, when the bucket 7 is moved back and forth along the ground to remove rocks that fall on flat ground, when performing crushing work with a breaker, or when scooping up objects with a clamshell Set the mode select switch 2 2 to “Boom self-weight descent”. As a result, the second solenoid 2 Ob of the mode switching valve 20 is energized, and the mode switching valve 20 changes the pressure of the descending pilot line F to the descending pilot port of the second boom control valve 15. Input to 15b, and switch to the second position Y that connects the lower pilot port 14b of the first boom control valve 14 to the oil tank 13. In this state, when the boom operation lever 18 is operated in the descending direction, the pilot port pressure output from the descending pilot valve 17 B is applied to the descending pilot port 15 of the second boom control valve 15. b and the pilot port 19 a of the regeneration valve 19 are input to the second boom control valve 15 to the lower position Y and the regeneration valve 19 to the open position Y. On the other hand, the first boom control valve 14 is held at the neutral position N. In this state, there is no supply of hydraulic oil from the hydraulic pumps 11 and 12 to the port-side oil chamber 8b of the cylinder cylinder 8, but the rod-side oil chamber 8b has the head-side oil chamber 8b. one of the oil discharged from a The part is supplied as regeneration oil to the port side oil chamber 8b via the regeneration valve 19 and the check valve 21. The remaining oil discharged from the head side oil chamber 8a flows into the oil tank 13 via the second boom control valve 15.

In other words, if the boom is lowered while it is set to “Boom self-weight descent”, there is no pressure oil supply from the hydraulic pumps 11 and 12 to the boom cylinder 8, but the load side oil chamber 8b, the oil discharged from the oil chamber 8a is supplied as reclaimed oil, and the remaining oil discharged from the oil chamber 8a is supplied to the control valve 1 for the second boom. Through 5, it will flow to the oil tank 13. In this state, the boom 5 descends by its own weight due to the weight of the front attachment 4 until the work attachments such as the bucket 5, the breaker 23, and the clamshell come into contact with the ground, rocks, etc. and are restricted. Become. Thus, when the bucket 7 is moved back and forth along the ground to remove rocks that fall on a flat ground, the bucket 5 can drop by its own weight without paying careful attention to the boom operation. 7 can be kept grounded. Further, when performing the breaker work, the breaker is pressed down by the weight of the front attachment 4 so that thrust necessary for the crushing work can be obtained. Further, when performing the work of picking up an object with the clamshell, the boom 5 will descend by its own weight until the clamshell comes into contact with the object, and will automatically stop when it comes into contact. As described above, in the present embodiment, when lowering the boom 5, if the mode selection switch 22 is set to the “boom lowering speed HIGH”, the head-side oil chamber 8 a of the pump cylinder 8 is set. If the oil discharge flow from the tank to the oil tank 13 increases, the descent speed of the boom 5 increases, and if the mode selection switch 22 is set to the “boom descent speed L OW”, the oil chamber on the head side The oil discharge flow from 8a to the oil tank 13 decreases, and the lowering speed of the boom 5 decreases. Further, if the mode selection switch 22 is set to “boom self-weight lowering” and operated to the boom lowering side, the boom 5 will lower its own weight due to the weight of the front unit 4.

As a result, the lowering speed of the boom 5 can be arbitrarily selected according to the work content and the skill of the operator. Also, the removal work of the rock on the flat ground by the packet 7, the crushing work by the breaker 23, or the clamshell In such a case, the boom 5 can be lowered by its own weight, and the operability and workability are improved. improves. Further, when the boom 5 is lowered by its own weight, there is no supply of pressurized oil from the hydraulic pumps 11 and 12 to the boom cylinder 8, so that it is possible to contribute to the reduction of fuel consumption, as well as the boom descent and other hydraulic actuators. During the combined operation with the evening, the pump flow rate is not blocked by the boom cylinder 8, so that it is possible to avoid a reduction in the operating speed of the other hydraulic actuator during the combined operation.

Moreover, in this case, the oil discharge flow from the head J oil chamber 8a to the oil tank 13 increases, and the oil flows from the head side oil chamber 8a to the oil tank 13 when the boom own weight falls. The discharge is performed by using the second boom control valve 15. The second boom control valve 15 discharges the hydraulic oil of the second hydraulic pump 12 when the boom 5 is raised. Since the valve operates to supply the oil to the head-side oil chamber 8a, a single valve has a plurality of functions, so that the members can be shared and contribute to cost reduction. Further, since the control pulp 15 for the second boom is a spool valve whose opening is adjusted by the input pilot pressure, good operability corresponding to the operation amount of the operation lever 18 for the boom is obtained. be able to. Industrial applicability

The hydraulic control circuit for a cylinder cylinder according to the present invention comprises: a control pulp that can be switched between an operating position for controlling hydraulic oil supply and discharge to a cylinder cylinder based on operation of an operating tool, and a neutral position for not performing hydraulic oil supply and discharge; Neutral holding means that is equipped with a regeneration circuit that supplies oil discharged from the oil chamber on the weight holding side of one cylinder to the other oil chamber, and that can hold the control valve at the neutral position regardless of the operation of operating tools. And a discharge oil passage for flowing oil discharged from the weight holding side oil chamber to the oil tank without passing through the control pulp, and pulp means for controlling opening and closing of the discharge oil passage. As a result, it is possible to lower the boom by its own weight or to change the descent speed of the boom in accordance with the skill level of the work content, and the workability and operability are improved.

The hydraulic control circuit for a boom cylinder according to the present invention includes: an operating position for controlling a hydraulic oil supply and discharge to the boom cylinder based on an operation of an operating tool by using a first hydraulic pump as a hydraulic oil supply source; A first control valve that can be switched to a neutral position that does not perform discharge, and a second hydraulic pump that uses a hydraulic oil supply as a source for the boom cylinder weight holding oil chamber. A second control valve that controls the supply of pressurized oil, a regeneration circuit that supplies the oil discharged from the weight holding side oil chamber to the other oil chamber, and the first control valve regardless of the operation of the operating tool Neutral holding means capable of holding the oil in the neutral position is provided, and the second control valve is provided with a discharge control means for flowing the oil discharged from the weight holding side oil chamber to the oil tank. Have been. As a result, the second control pulp can be used to lower the boom's own weight or change the boom's descent speed in accordance with the work content, the skill of the operator, etc. The property can be improved and the members can be shared.

Claims

The scope of the claims

1. A boom cylinder that expands and contracts to move the boom up and down, and an operation position and a hydraulic oil supply and discharge that control hydraulic oil supply and discharge to each oil chamber on the head side rod side of the boom cylinder based on operation of the operating tool The control oil can be switched to a neutral position in which the oil is not supplied, and the oil discharged from the oil chamber on the weight holding side that holds the weight of the boom is supplied to the other oil chamber. A hydraulic pressure control circuit for a beam cylinder having a regeneration circuit, the hydraulic pressure control circuit comprising: a neutral holding means capable of holding a control valve at a neutral position regardless of operation of an operating tool; A boom cylinder for a working machine, comprising: a discharge oil passage for flowing oil discharged from an oil chamber into an oil tank without passing through a control valve; and valve means for controlling opening and closing of the discharge oil passage. Oil of Control circuit.

2. The boom cylinder that expands and contracts to move the boom up and down, and the first hydraulic pump is used as a hydraulic oil supply source, and each oil chamber on the head side rod side of the boom cylinder is operated based on the operation of the operating tool. A first control valve that can be switched to an operating position for controlling hydraulic oil supply and discharge, a neutral position that does not perform hydraulic oil supply and discharge, and a second hydraulic pump as a hydraulic oil supply source. The second control norb controls the supply of pressurized oil to the oil chamber on the weight holding side that holds the weight of the boom, and the regeneration circuit that supplies oil discharged from the oil chamber on the weight holding side to the other oil chamber. A hydraulic control circuit for the pump cylinder provided with a neutral holding means capable of holding the first control valve at a neutral position regardless of operation of the operating tool; If the valve has a weight holding side oil chamber Hydraulic control circuit of the boom cylinder in a work machine that was provided discharge control means and feature for flowing discharge oil to the oil evening link of.