KR102364133B1 - Hydraulic control valve and hydraulic control circuit - Google Patents

Abstract

Provides a hydraulic control valve and hydraulic control circuit that can reduce the pressure loss of the return oil when the hydraulic cylinder is contracted and reduce costs and improve fuel efficiency without installing a quick return circuit externally do. The hydraulic control valve of one embodiment has a valve body which controls supply/discharge of hydraulic oil to a hydraulic cylinder. The valve body has a main tank passage and a sub tank passage. The main tank passage is connected to the tank via a back pressure maintaining means. The sub tank passage is directly connected to the tank without passing through the back pressure maintaining means. And in the state in which the hydraulic cylinder is switched to the retracting position, the head side supply/discharge passage through which the return oil from the head side oil chamber of the hydraulic cylinder flows is in communication with both the main tank passage and the sub tank passage. .

Description

Hydraulic control valve and hydraulic control circuit

An embodiment of the present invention relates to a hydraulic control valve and a hydraulic control circuit.

A hydraulic excavator, which is a type of construction machine, is an attachment for work, and includes a boom, an arm, and a bucket operated by a hydraulic cylinder. The hydraulic control circuit (hydraulic cylinder circuit) that drives each hydraulic cylinder controls the hydraulic pump and tank, and both oil chambers (head side oil chamber and rod side oil chamber) on the expansion and contraction side of the hydraulic cylinder and the control valve (hydraulic control). valve) connected through the And the control valve controls supply/discharge of the hydraulic oil to the hydraulic cylinder, ie, the expansion/contraction operation of the cylinder.

By the way, in the hydraulic cylinder, the pressure-receiving area of the piston to the head-side oil chamber is larger than the pressure-receiving area to the rod-side oil chamber by the cross-sectional area of the piston rod. Therefore, due to the difference in the water pressure area between the oil chamber on the head side and the oil chamber on the rod side, during the cylinder contraction operation (in the operation of supplying hydraulic oil to the rod side oil chamber and discharging the pressure oil from the head side oil chamber), the oil chamber on the head side There was a possibility that the flow rate of the return oil of . In this case, the pressure loss of the return oil becomes large, the operating speed of the hydraulic cylinder is lowered, and further, improvement of the fuel efficiency of the hydraulic excavator is sometimes obstructed.

As a countermeasure against this point, a quick return circuit communicating with the tank is branched to the head side conduit of the hydraulic cylinder, and part of the return oil from the head side oil chamber of the hydraulic cylinder is directly returned to the tank during the cylinder retraction operation. Reducing the pressure loss of return oil is performed (refer patent document 1). However, when a quick return circuit is installed, it is necessary to newly install a hydraulic pipe or a quick return valve, and there exists a possibility of cost increase.

Japanese Patent Laid-Open No. 2013-137062

The problem to be solved by the present invention is that it is possible to reduce the pressure loss of the return oil during the contracting operation of the hydraulic cylinder without installing the quick return circuit externally, thereby reducing the cost and improving the fuel efficiency. An object of the present invention is to provide a hydraulic control valve capable of being able to operate and a hydraulic control circuit having the hydraulic control valve.

The hydraulic control valve of the embodiment has a valve body that is connected between a hydraulic cylinder, a hydraulic pump, and a tank and controls supply/discharge of hydraulic oil to the hydraulic cylinder by switching operation. The valve body has a main tank passage and a sub tank passage. The main tank passage is connected to the head side supply/discharge passage connected to the oil chamber on the head side of the hydraulic cylinder, and the tank via the back pressure holding means. The sub tank passage is directly connected to the tank without passing through the back pressure maintaining means. And in the state in which the hydraulic cylinder is switched to the retracting position, the head side supply/discharge passage through which the return oil from the head side oil chamber of the hydraulic cylinder flows is in communication with both the main tank passage and the sub tank passage. .

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing of the hydraulic control valve of 1st Embodiment.
Fig. 2 is a configuration diagram of a hydraulic control circuit according to the first embodiment.
It is sectional drawing of the hydraulic control valve of 2nd Embodiment.
Fig. 4 is a configuration diagram of a hydraulic control circuit according to the second embodiment.
5 is a schematic configuration diagram of a hydraulic excavator according to an embodiment.

Hereinafter, a hydraulic control valve according to an embodiment and a hydraulic control circuit including the hydraulic control valve will be described with reference to the drawings.

The hydraulic control valve and hydraulic control circuit of the embodiment described below are mainly used for construction machines. Then, first, an example of an applied construction machine will be described first. Fig. 5 shows a schematic configuration of a hydraulic excavator representative as a construction machine.

As shown in Fig. 5, in the hydraulic excavator 300, the body body 305 and the upper turning body 305 and the upper turning mechanism 302 having a turning motor on the lower traveling body 301 driven by the hydraulic motor The sieve 303 is mounted so as to be able to turn. A cap 304 is installed on the upper revolving body 303 , and an attachment for work is attached to the front of the cap 304 .

As an attachment for work, the boom 311 is provided in the front center part of the cap 304. As shown in FIG. Moreover, the arm 312 is provided in the front-end|tip of the boom 311 so that an up-down rotation is possible. Further, at the tip of the arm 312 , a bucket 313 is provided so as to be able to rotate up and down. Here, reference numeral 314 denotes a hydraulic cylinder for raising and lowering the boom 311 . Reference numeral 315 denotes a hydraulic cylinder for pushing and pulling of the arm 312 (movements in a direction away from and close to the upper revolving body 303 ). Reference numeral 316 denotes a hydraulic cylinder for excavation and dumping (earth removal) of the bucket 313 .

(First embodiment)

Fig. 1 is a cross-sectional view of a hydraulic control valve according to a first embodiment, and Fig. 2 is a configuration diagram of a hydraulic control circuit. In the first embodiment, the hydraulic control circuit of the hydraulic cylinder 316 for the bucket 313 shown in FIG. 5 will be described as an example.

This hydraulic control circuit includes a hydraulic cylinder 1 (hydraulic cylinder 316) for moving a load (bucket 313), a hydraulic control valve 10, a hydraulic pump 3, and a tank T. have

The hydraulic cylinder 1 is provided with two working oil chambers: a rod-side oil chamber 1A partitioned by a piston 1P, and a head-side oil chamber (rod-opposite oil chamber) 1B. A rod connected to the piston 1P passes through the rod-side oil chamber 1A. Accordingly, the pressure-receiving area of the piston 1P with respect to the rod-side oil chamber 1A is smaller than the pressure-receiving area of the piston 1P with respect to the head-side oil chamber 1B by the cross-sectional area of the rod. In this hydraulic cylinder 1, when pressure oil is supplied to the rod-side oil chamber 1A, return oil from the head-side oil chamber 1B is generated and the entire length is contracted. On the other hand, when pressure oil is supplied to the head side oil chamber 1B, return oil from the rod side oil chamber 1A is generated, and the hydraulic cylinder 1 is elongated in its entire length.

Therefore, due to the above-described pressure-receiving area difference, when the hydraulic cylinder 1 is contracted, the discharge amount of the return oil from the head-side oil chamber 1B is higher than the supply amount of the pressure oil to the rod-side oil chamber 1A. becomes more The configuration used as a countermeasure is included in the hydraulic control valve 10 .

The hydraulic control valve 10 controls supply/discharge of hydraulic oil to the hydraulic cylinder 1 . The hydraulic control valve 10 is configured to be positioned in three positions: the neutral position N, the A position (first position), and the B position (the second position). As shown in FIG. 1 , the hydraulic control valve 10 is a spool type in which a spool 50 is slidably inserted in the axial direction into a sleeve hole 40 formed through a sleeve hole 40 in the axial direction of the valve body 11 . It is a directional valve. The hydraulic control valve 10 is driven by pilot pressures PA and PB.

The valve body 11 of the hydraulic control valve 10 is provided with a rod-side supply/discharge port 12A and a head-side supply/discharge port 12B disposed on both sides with an axial center therebetween. Here, in Fig. 1, each flow path on the rod side is formed on the left side from the center in the axial direction, and each flow path on the head side is formed on the right side from the center in the axial direction. The rod side supply/discharge port 12A is connected to the rod side oil chamber 1A of the hydraulic cylinder 1 via the rod side supply/discharge line 2A, and the head side supply/discharge port 12B is connected to the head side supply/discharge line 2B ) is connected to the oil chamber 1B on the head side of the hydraulic cylinder 1 .

A pump passage 13 is provided around the sleeve hole 40 of the valve body 11 , which is arranged centrally in the axial direction. The pump passage 13 is connected to a discharge port of the hydraulic pump 3 . First tank passages 14A and 14B are provided on both sides of the pump passage 13 . A rod-side bridge passage 15A and a head-side bridge passage 15B are provided on both outer sides of the first tank passages 14A and 14B. On both sides of the rod-side bridge passage 15A and the head-side bridge passage 15B, a rod-side supply-discharge passage 16A connected to the rod-side supply-discharge port 12A, and a head connected to the head-side supply-discharge port 12B A side supply/discharge passage 16B is provided.

Moreover, when the rod side of the left side of FIG. 1 is demonstrated, the main tank passage 17A as a 2nd tank passage is provided outside the rod side supply/discharge passage 16A. The rod-side bridge passage 15A is connected to the pump passage 13 through the load check valve 20 . Further, the main tank passage 17A and the first tank passage 14A are connected to the tank T via a back pressure check valve 5 .

Next, referring to the head side on the right side of FIG. 1 , a sub tank passage 19 as a third tank passage is provided outside the head side supply/discharge passage 16B. On the outside of the sub tank passage 19, a branch supply/discharge passage 18 branchingly connected to the head side supply/discharge passage 16B is provided. A main tank passage 17B as a second tank passage is provided outside the branch supply/discharge passage 18 . The head-side bridge passage 15B is connected to the pump passage 13 through the load check valve 20 . Further, the main tank passage 17B and the first tank passage 14B are connected to the tank T via a back pressure check valve (back pressure maintaining means) 5 . On the other hand, the sub tank passage 19 is directly connected to the tank T without passing through the back pressure check valve.

Further, the rod-side supply/discharge passage 16A and the head-side supply/discharge passage 16B are connected to the main tank passages 17A, 17B via relief valves 21A, 21B for discharging excessive high pressure.

The spool 50 has, on both end surfaces in the axial direction, a pilot pressure receiving surface 50A for the A position for switching the position of the spool 50 from the neutral position N to the A position, and the position of the spool 50 . It has a pilot pressure receiving surface 50B for the B position for switching from the neutral position N to the B position. The spool 50 has a central land portion 51 at a central position in the axial direction. First annular recesses 52A and 52B are formed on both outer sides of the central land portion 51 . Further, first land portions 53A, 53B are provided on both outer sides of the first annular recessed portions 52A, 52B. Further, second annular recesses 54A and 54B are formed on both outer sides of the first land portions 53A and 53B. Further, second land portions 57A, 57B are provided on both outer sides of the second annular recessed portions 54A and 54B.

Moreover, especially on the head side, the spool 50 has the 3rd land part 55B and the annular recessed part 56B between the 2nd annular recessed part 54B and the 2nd land part 57B. . These land portions and annular recesses are formed alternately arranged in the axial direction.

Moreover, the 1st notch 61 is formed in the outer periphery of the center side edge in the 2nd land parts 57A, 57B located at the outermost side. Moreover, in the 3rd land part 55B on the head side, the 2nd notch 62 is formed in the outer periphery of a center side edge. Moreover, the 3rd notch 63 is formed in the 1st land parts 53A, 53B in the outer periphery of the edge opposite to a center. Moreover, the 4th notches 64 are formed in the outer periphery of both edges of the center land part 51. As shown in FIG.

The hydraulic control valve 10 is provided with pilot ports Pa and Pb so as to face both ends of the spool 50 . Among the two pilot ports Pa and Pb, one pilot port Pa is a port for inputting the pilot pressure PA for switching the spool 50 to the A position. The pilot port Pa is disposed at the end of the positioning mechanism 70 provided in the valve body 11 . In addition, the other pilot port Pb is a port for inputting the pilot pressure PB for switching operation of the spool 50 to B position. The pilot port Pb is disposed on the side where the positioning mechanism 70 is not provided. The operation mechanism (direction switching mechanism) of the spool 50 is comprised by two pilot ports Pa and Pb and the positioning mechanism 70 .

The positioning mechanism 70 is disposed on one side of the valve body 11 and has a cap-shaped casing 71 having an open one end. This casing 71 is provided and fixed to one side surface of the valve body 11 so as to close one end of the sleeve hole 40 of the valve body 11 . A spring accommodating chamber 71a in which the coil spring 77 is accommodated is provided in the casing 71 . A small-diameter hole 71b is provided at the end of the spring accommodating chamber 71a through a stopper wall 71c, and a pilot port Pa is opened in the end wall 71d of the small-diameter hole 71b. has been

A rod 72 is integrally fixed to the end of the spool 50 on the positioning mechanism 70 side. The rod 72 is inserted in the casing 71, and the head part 73 which has an outer peripheral flange faces the pilot port Pa. A first spring bearing sleeve 74 and a second spring bearing sleeve 75 are provided on the outer periphery of the rod 72 so as to be slidable in the axial direction. As for the 1st spring bearing sleeve 74 and the 2nd spring bearing sleeve 75, the mutually opposing ends are comprised as the collision ends 74b, 75b. In addition, at the opposite ends of the first spring bearing sleeve 74 and the second spring bearing sleeve 75, flange portions 74a and 75a for receiving a spring force are provided.

The coil spring 77 for pressing the spool 50 toward the neutral position is attached to the outer periphery of the first spring bearing sleeve 74 and the second spring bearing sleeve 75 . Both ends of the coil spring 77 are accommodated in both flange portions 74a and 75a of the first spring bearing sleeve 74 and the second spring bearing sleeve 75 in a compressed state.

The positioning mechanism 70 positions and holds the spool 50 at the neutral position N when the pilot pressures PA and PB are not introduced into the pilot ports Pa and Pb. That is, by the force of the coil spring 77 , the first spring bearing sleeve 74 is pressed to the left in FIG. 1 , and the second spring bearing sleeve 75 is pressed to the right in FIG. 1 . Thereby, the impact ends 74b, 75b of the 1st spring bearing sleeve 74 and the 2nd spring bearing sleeve 75 are spaced apart from each other (in FIG. 1, it is not shown). And the flange portion 74a of the first spring bearing sleeve 74 abuts against the stopper wall 71c inside the casing 71 , and the flange portion 75a of the second spring bearing sleeve 75 is connected to the valve body 11 ) abuts against the stopper wall 45 provided on the periphery of the opening of the sleeve hole 40 . Thereby, the spool 50 fixed to the rod 72 is held in the neutral position N.

Further, the positioning mechanism 70 holds the spool 50 at the A position when the pilot pressure PA is introduced into the pilot port Pa. That is, in the state of the neutral position, when the pilot pressure PA is introduced into the pilot port Pa, the pilot pressure PA is applied to the end surface of the rod 72 or the pilot pressure receiving surface 50A for the A position of the spool 50. Acting, the spool 50 is pressed and moved to the right in the drawing. At that time, the coil spring 77 is contracted, and the first spring bearing sleeve 74 moves to the right. Then, the impact end 74b of the first spring bearing sleeve 74 collides with the impact end 75b of the second spring bearing sleeve 75 and is fixed in position. Thereby, the spool 50 fixed to the rod 72 is held in the A position.

Further, the positioning mechanism 70 holds the spool 50 at the B position when the pilot pressure PB is introduced into the pilot port Pb. That is, in the state of the neutral position, when the pilot pressure PB is introduced into the pilot port Pb, the pilot pressure PB acts on the pilot pressure receiving surface 50B for the B position of the spool 50, and the spool 50 It is pressed and moved to the left in the drawing. At that time, the coil spring 77 is contracted, and the second spring bearing sleeve 75 moves to the left. Then, the impact end 75b of the second spring bearing sleeve 75 collides with the impact end 74b of the first spring bearing sleeve 74 and is fixed in position. Thereby, the spool 50 fixed to the rod 72 is held in the B position.

Next, the action of the hydraulic control valve 10 and the hydraulic control circuit will be described with reference to FIGS. 1 and 2 .

First, the case when the spool 50 is in the neutral position N will be described. In this case, the pump passage 13 communicates with the first tank passages 14A, 14B via the fourth notch 64 and the first annular recesses 52A, 52B. At this time, the rod-side bridge passage 15A, the head-side bridge passage 15B, the rod-side supply/discharge passage 16A, and the head-side supply/discharge passage 16B are maintained in a closed state.

Next, the case when the spool 50 is in the A position will be described. In this case, communication between the pump passage 13 and the first tank passages 14A and 14B is blocked. Further, on the rod side (the pressure oil supply side in the left side of Fig. 1), the rod-side bridge passage 15A and the rod-side supply/discharge passage 16A communicate through the third notch 63 and the second annular recess 54A. do. As a result, the pressure oil flowing into the rod-side bridge passage 15A through the load check valve 20 passes through the third notch 63 and the second annular recess 54A to the rod-side supply/discharge passage 16A. is brought in Then, the pressure oil is introduced into the rod-side oil chamber 1A of the hydraulic cylinder 1 through the rod-side supply/discharge port 12A and the rod-side supply/discharge line 2A.

On the other hand, on the head side (the discharge side of the return oil on the right side in Fig. 1), the head side bridge passage 15B is closed. And the head side supply/discharge passage 16B and the sub tank passage 19 communicate through the second notch 62 and the second annular recess 54B. Further, the branch supply/discharge passage 18 connected to the head-side supply/discharge passage 16B communicates with the main tank passage 17B via the first notch 61 and the annular recessed portion 56B. Thereby, the return oil from the head side oil chamber 1B of the hydraulic cylinder 1 is discharged to the tank T through both the main tank passage 17B and the sub tank passage 19 .

That is, the return oil passing through the main tank passage 17B is discharged to the tank T through the back pressure check valve 5 . On the other hand, the return oil passing through the sub tank passage 19 is discharged directly to the tank T without passing through the back pressure check valve. Here, in general, the back pressure check valve 5 is set so that the pressure (back pressure) of the hydraulic oil in the main tank passages 17A and 17B becomes a pressure of about 0.3 to 0.5 MPa.

The hydraulic control valve 10 is switched to the A position when the hydraulic cylinder 1 for buckets is contracted. When the hydraulic cylinder 1 for buckets is contracted, the bucket 313 performs an extrusion operation (also referred to as a dump or opening operation).

Next, the case when the spool 50 is in the B position will be described. In this case, communication between the pump passage 13 and the first tank passages 14A and 14B is blocked. In addition, on the head side (the pressure oil supply side in the right side of FIG. 1), the head side bridge passage 15B and the head side supply/discharge passage 16B communicate through the third notch 63 and the second annular recess 54B. do. Thereby, the pressure oil flowing into the head-side bridge passage 15B through the load check valve 20 passes through the third notch 63 and the second annular recess 54B to the head-side supply/discharge passage 16B. is brought in And the pressure oil is introduced into the head side oil chamber 1B of the hydraulic cylinder 1 through the head side supply/discharge port 12B and the head side supply/discharge line 2B.

On the other hand, on the rod side (the discharge side of the return oil on the left side of Fig. 1), the rod-side bridge passage 15A is closed. And the rod side supply/discharge passage 16A and the main tank passage 17A communicate through the first notch 61 and the second annular recess 54A. Thereby, the return oil from the rod-side oil chamber 1A of the hydraulic cylinder 1 is discharged to the tank T through the main tank passage 17A. That is, the return oil passing through the main tank passage 17A is discharged to the tank T through the back pressure check valve 5 .

This hydraulic control valve 10 is switched to the B position when the hydraulic cylinder 1 for buckets is extended. When the hydraulic cylinder 1 for buckets is extended and operated, the bucket 313 performs excavation (also referred to as a closing operation).

In this way, in the hydraulic control valve 10 , a sub tank passage 19 as a third tank passage is provided outside the head side supply/discharge passage 16B provided in the valve body 11 . Further, on the outside of the sub tank passage 19, a branch supply/discharge passage 18 branchingly connected to the head side supply/discharge passage 16B is provided. Further, on the outside of the branch supply/discharge passage 18, a main tank passage 17B as a second tank passage is provided. Further, the head-side bridge passage 15B is connected to the pump passage 13 through the load check valve 20 . Further, the main tank passage 17B and the first tank passage 14B are connected to the tank T via a back pressure check valve (back pressure maintaining means) 5 . On the other hand, the sub tank passage 19 is directly connected to the tank T without passing through the back pressure check valve.

For this reason, when the hydraulic cylinder 1 is contracted, the return oil from the head side oil chamber 1B is discharged to the tank T through both the main tank passage 17B and the sub tank passage 19 . can do. Accordingly, compared to the case where the return oil is discharged to the tank T only through the main tank passage 17B, the pressure loss of the return oil can be reduced. In particular, the sub tank passage 19 returns the return oil from the head side oil chamber 1B directly to the tank T without passing through the back pressure check valve 5, so that the pressure loss can be significantly reduced.

In addition, the return oil from the head side oil chamber 1B is branched into both the main tank passage 17B and the sub tank passage 19 inside the valve body 11 to flow. For this reason, compared with the case where a quick return circuit for quickly returning the return oil from the head side oil chamber 1B to the tank T is separately provided outside the hydraulic control valve 10, the circuit configuration can be simplified. can That is, in the valve body 11 itself of the hydraulic control valve 10, there is a sub tank passage 19 that discharges the return oil directly to the tank T without passing through the back pressure check valve separately from the main tank passage 17B. installed. Therefore, it is not necessary to provide the quick return circuit separately from the hydraulic control valve 10, and the circuit configuration can be simplified.

In addition, only by switching the position of the spool 50 to the A position for retracting operation of the hydraulic cylinder 1, the return oil from the head side oil chamber 1B of the hydraulic cylinder 1 is transferred to the main tank passage ( In addition to returning to tank T via 17B), it is possible to return to tank T via sub tank passage 19 . That is, the two tank passages (the main tank passage 17B and the sub tank passage 19) can be opened and closed by switching operation of one spool 50 . In this case, since the means for switching the opening/closing of the sub tank passage 19 is provided on the spool 50 integrally, an operation means separate from the spool 50 is unnecessary, and at the same time, opening/closing control of the flow path is not required. it gets easier That is, there is no need to provide a quick return valve for opening and closing the quick return circuit as in the prior art, and the configuration can be simplified.

Moreover, the head side supply/discharge passage 16B (branch supply/discharge passage 18) is made to communicate with the main tank passage 17B via the first notch 61 by the switching operation of the spool 50 . In addition to this, the head side supply/discharge passage 16B is communicated with the sub tank passage through the second notch 62 . Thereby, the return oil from the head side oil chamber 1B of the hydraulic cylinder 1 is discharged to the tank T through the main tank passage 17B and the sub tank passage 19 . In this case, the first notch 61 and the second notch 62 maintain a relative position determined by machining. Therefore, the timing at which the head-side supply/discharge passage 16B (branch supply/discharge passage 18) communicates with the main tank passage 17B and the timing that the head-side supply/discharge passage 16B communicates with the sub-tank passage 19 deviate from each other. no work

(Second embodiment)

Next, based on FIG. 3 and FIG. 4, 2nd Embodiment is demonstrated. 3 is a cross-sectional view of the hydraulic control valve 100 according to the second embodiment, and FIG. 4 is a configuration diagram of a hydraulic control circuit. In this 2nd embodiment, the hydraulic control circuit of the hydraulic cylinder 315 for arm 312 shown in FIG. 5 is taken as an example and demonstrated.

This hydraulic control circuit includes a hydraulic cylinder 1 (hydraulic cylinder 315) for moving a load (arm 312), a hydraulic control valve 100, two hydraulic pumps 103 and 203, and a tank. (T). As shown in FIG. 3 and FIG. 4, it is common to make the hydraulic cylinder 1 for arms (hydraulic cylinder 315) move with two hydraulic pumps 103 and 203. As shown in FIG.

Here, the configuration of the hydraulic cylinder 1 is the same as that of the first embodiment, but the configuration of the hydraulic control valve 100 is different from the first embodiment because two hydraulic pumps 103 and 203 are used. That is, as shown in FIG. 3 , two spools 150 and 250 are used for the hydraulic control valve 100 , and the two spools 150 and 250 are used to control supply/discharge of hydraulic oil to the hydraulic cylinder 1 . ) by

More specifically, the hydraulic control valve 100 controls the supply/discharge of the pressure oil to the hydraulic cylinder 1 . The two spools 150 and 250 in the hydraulic control valve 100 are each configured to be positioned in three positions: the neutral position N, the A position (first position), and the B position (the second position). has been

Further, as shown in FIG. 3 , the hydraulic control valve 100 has a spool 150 in the two sleeve holes 140 and 240 that are formed to pass through in parallel to each other along the axial direction in the valve body 111 , respectively. , 250) is axially slidably inserted, and is a spool type directional selector valve. Each of the spools 150 and 250 is driven by the pilot pressures PA and PB. In addition, the structure of each spool 150,250 and each flow path switched by each spool 150,250 is basically the same as that of 1st Embodiment, and the same structural part as 1st Embodiment has a 1st The code|symbol of the 100th group which added 100 and the code|symbol of the 200th group which added 200 to the code|symbol shown by the 2 digits in embodiment are attached|subjected, and it is made to correspond with the structural part of 1st Embodiment.

The valve body 111 of the hydraulic control valve 100 is provided with a rod-side supply/discharge port 112A and a head-side supply/discharge port 112B disposed on both sides with an axial center therebetween. Here, in Fig. 1, each flow path on the rod side is formed on the left side from the center in the axial direction, and each flow path on the head side is formed on the right side from the center in the axial direction. The rod-side supply/discharge port 112A is connected to the rod-side oil chamber 1A of the hydraulic cylinder 1 via a rod-side supply/discharge line 2A. The head-side supply/discharge port 112B is connected to the head-side oil chamber 1B of the hydraulic cylinder 1 via a head-side supply/discharge line 2B.

Pump passages 113 and 213 arranged at the center in the axial direction are provided around the sleeve holes 140 and 240 of the valve body 111 . The pump passages 113 and 213 are connected to the discharge ports of the hydraulic pumps 103 and 203, respectively. First tank passages 114A, 114B, 214A, and 214B are provided on both outer sides of the pump passages 113 and 213 . Rod-side bridge passages 115A, 215A and head-side bridge passages 115B, 215B are provided on both sides of the first tank passages 114A, 114B, 214A, 214B. On both sides of the rod-side bridge passages 115A, 215A and the head-side bridge passages 115B, 215B, the rod-side supply and discharge passages 116A and 216A communicate with both the rod-side supply and discharge ports 112A, and the head-side supply and discharge ports. Head-side supply/discharge passages 116B and 216B communicating with 112B are provided.

Moreover, when the rod side on the left side of FIG. 3 is demonstrated, main tank passages 117A, 217A as 2nd tank passages are provided outside the rod-side supply/discharge passages 116A and 216A. The rod-side bridge passages 115A and 215A are respectively connected to the pump passages 113 and 213 via the load check valves 120 and 220 . Further, the main tank passages 117A and 217A and the first tank passages 114A and 214A are connected to the tank T via a back pressure check valve (back pressure holding means) 5 .

Next, referring to the head side on the right side of FIG. 3 , sub tank passages 119 and 219 as third tank passages are provided outside the head side supply and discharge passages 116B and 216B. On the outside of the sub tank passages 119 and 219, branch supply and discharge passages 118 and 218 communicating with each other are provided. These branch supply and discharge passages 118 and 218 are connected to the head side supply and discharge passages 116B and 216B via a pilot check valve 280, which will be described later.

In addition, main tank passages 117B and 217B as second tank passages are provided outside the branch supply/discharge passages 118 and 218 . The head-side bridge passages 115B and 215B are connected to the pump passages 113 and 213 via the load check valves 120 and 220 . Further, the main tank passages 117B and 217B and the first tank passages 114B and 214B are connected to the tank T via a back pressure check valve (back pressure holding means) 5 . On the other hand, the sub tank passages 119 and 219 are directly connected to the tank T without passing through the back pressure check valve.

Further, the rod-side supply/discharge passage 116A and the head-side supply/discharge passage 116B are connected to the main tank passages 117A, 117B via relief valves 121A, 121B for discharging excessive high pressure.

The spools 150 and 250 are, on both end surfaces in the axial direction, pilot pressure receiving surfaces 150A and 250A for the A position for switching the positions of the spools 150 and 250 to the A position, and the spools 150 and 250 It has pilot pressure receiving surfaces 150B and 250B for the B position for switching the position to the B position.

The configuration on the outer periphery of the spools 150 and 250 is the same as that of the first embodiment, as indicated by the corresponding reference numerals in the first embodiment (refer to FIG. 1 ). That is, the spools 150 and 250 have a center land portion 51 at a central position in the axial direction, and have first annular recesses 52A and 52B on both outer sides of the center land portion 51 . Further, first land portions 53A and 53B are provided on both outer sides of the first annular concave portions 52A and 52B, and second annular concave portions ( 54A, 54B) are formed. Further, second land portions 57A, 57B are provided on both outer sides of the second annular recessed portions 54A, 54B. Further, on the head side, the spools 150 and 250 have a third land portion 55B and an annular recessed portion 56B between the second annular concave portion 54B and the second land portion 57B. . These land portions and annular recesses are formed alternately arranged in the axial direction.

Moreover, the 1st notch 61 is formed in the outer periphery of the center side edge of the 2nd land part 57A, 57B located at the outermost side. A second notch 62 is formed on the outer periphery of the center-side edge of the third land portion 55B on the head side. A third notch 63 is formed on the outer periphery of the edge opposite to the center of the first land portions 53A and 53B. And the 4th notches 64 are formed in the outer periphery of both edges of the center land part 51. As shown in FIG.

Moreover, in the hydraulic control valve 100, the pilot ports Pa and Pb are respectively provided so that both ends of each spool 150, 250 may face. One pilot port Pa among the two pilot ports Pa and Pb is a port for inputting the pilot pressure PA for switching the spools 150 and 250 to the A position. The pilot port Pa is disposed at an end of the positioning mechanism 70 provided in the valve body 111 .

In addition, the other pilot port Pb is a port for inputting the pilot pressure PB for switching operation of the spools 150 and 250 to a B position. The pilot port Pb is disposed on the side where no positioning mechanism is provided. The operation mechanism (direction switching mechanism) of the spools 150 and 250 is constituted by two pilot ports Pa and Pb and a positioning mechanism 70 . About the positioning mechanism 70, it has the same structure as 1st Embodiment, and a detailed description is abbreviate|omitted.

Next, the pilot check valve 280 and a regeneration passage for introducing a part of the return oil to the pressure oil supply side will be described.

Between the head side supply/discharge passage 216B and the branch supply/discharge passage 218, a pilot check valve 280 is provided as described above. This pilot check valve 280 cuts off communication between the head side supply/discharge passage 216B and the branch supply/discharge passage 218 when no pilot signal is input. The pilot check valve 280 performs a check function to prevent the pressure oil flowing into the head-side supply/discharge passageway 216B from flowing to the branch supply-discharge passageway 218 side downstream of the head-side supply-discharge passageway 216B. The pilot check valve 280 permits communication between the head-side supply/discharge passage 216B and the branch supply/discharge passage 218 when a pilot signal is input.

In addition, the pilot check valve 280 controls the operation of the poppet-shaped main valve body 281 that opens and closes the flow path between the head side supply/discharge passage 216B and the branch supply/discharge passage 218 , and the main valve body 281 . It has a pilot mechanism part 285 to control. The main valve body 281 is slidably inserted in the valve body accommodating hole formed in the valve body 111 in the valve opening/closing direction. A back pressure chamber 281a is provided inside the main valve body 281 . The back pressure chamber 281a communicates with the head side supply/discharge passage 216B on the upstream side through the pores 281b.

The pilot mechanism part 285 has the casing 285a attached so that the valve body accommodation hole of the main valve body 281 might be covered. A slide hole 285b is formed inside the casing 285a. A sub-valve body 286 is slidably inserted into this slide hole 285b. The sub-valve body 286 is connected to the piston 287 , and when a pilot pressure is applied to the piston 287 , the sub-valve body 286 moves to the open side. Small-diameter flow paths 288a, 288b, 288c, and 288d are provided in the casing 285a and the portion of the valve body 111 in which the casing 285a is provided.

Under this configuration, when the pilot pressure acts on the pressure receiving surface of the piston 287 , the piston 287 moves, and the sub-valve body 286 connected to the piston 287 moves. Then, the pressure oil flowing into the back pressure chamber 281a of the main valve body 281 flows to the downstream side of the main valve body 281 through the small-diameter flow paths 288a, 288b, 288c, 288d. Then, as the pressure difference between the back pressure chamber 281a and the main valve body 281 is eliminated, the main valve body 281 moves to the open position. As a result, the return oil flows from the upstream head side supply/discharge passage 216B to the downstream branch supply/discharge passage 218 .

When the return oil flows into the branch supply/discharge passage 218 , the return oil also flows into the branch supply/discharge passage 118 that communicates with the branch supply/discharge passage 218 . When the two spools 150 and 250 are in the A position, both the branch supply and discharge passages 118 and 218 communicate with the main tank passages 117B and 217B through the first notch 61 . For this reason, the return oil that has flowed into the branch supply/discharge passages 118 and 218 flows into the main tank passages 117B and 217B through the first notch 61 and is discharged to the tank T through the back pressure check valve 5 . do.

A part of the return oil flowing into the branch supply/discharge passages 118 and 218 is introduced into the hydraulic oil supply path to the rod-side oil chamber 1A of the hydraulic cylinder 1 depending on the pressure level. This passage is called the regeneration passage. The regeneration passage includes a head-side radial hole 254 formed in a peripheral wall at a position on the head side of one spool 250 , an axial passage 255 formed inside the spool 250 , and the spool 250 . It is comprised by the rod side radial direction hole 256 formed in the peripheral wall of the position on the rod side, and the check valve 260 inserted in the predetermined location of the axial direction passage 255. As shown in FIG.

The head-side radial hole 254 is disposed at a position communicating with the branch supply/discharge passage 218 when the spool 250 is positioned at the A position. Further, the rod-side radial hole 256 is disposed at a position that communicates with the rod-side supply/discharge passage 216A when the spool 250 is positioned at the A position. The check valve 260 is disposed at a position to open and close the head side radial hole 254, and is set to open when the pressure of the head side supply/discharge passage 216B is higher than the pressure of the rod side supply/discharge passage 216A. there is.

Next, the action of the hydraulic control valve 100 and the hydraulic control circuit will be described with reference to Figs. 3 and 4 .

First, when the spools 150 and 250 are in the neutral position (N) will be described. In this case, the pump passages 113 and 213 communicate with the first tank passages 114A, 114B, 214A, and 214B via the fourth notch 64 and the first annular recesses 52A and 52B. At this time, the rod-side bridge passages 115A, 215A, the head-side bridge passages 115B, 215B, the rod-side supply/discharge passages 116A, 216A, and the head-side supply/discharge passages 116B, 216B are maintained in a closed state.

The switching operation of the two spools 150 and 250 is performed synchronously. That is, the pilot pressure PA or the pilot pressure PB is simultaneously introduced to the two spools 150 and 250 . Moreover, the pilot pressure PA for moving the spools 150 and 250 to A position is introduce|transduced into the pilot port of the pilot check valve 280 as a pilot pressure.

Next, a description will be given of the case where the spools 150 and 25 are in the A position. In this case, communication between the pump passages 113 and 213 and the first tank passages 114A, 114B, 214A, and 214B is blocked. In addition, on the rod side (the pressure oil supply side in the left side of Fig. 3), the rod-side bridge passages 115A and 215A and the rod-side supply and discharge passages 116A and 216A are connected to the third notch 63 and the second annular recess 54A. ) is communicated through Thereby, each of the hydraulic oil from the hydraulic pumps 103 and 203 flowing into the rod-side bridge passages 115A and 215A through the load check valves 120 and 220, the third notch 63 and the second annular It flows into the rod-side supply/discharge passages 116A and 216A through the concave portion 54A. Then, the pressure oil is introduced into the rod-side oil chamber 1A of the hydraulic cylinder 1 through the rod-side supply/discharge port 112A and the rod-side supply/discharge line 2A.

On the other hand, on the head side (the discharge side of the return oil on the right side in Fig. 3), the head side bridge passages 115B and 215B are closed. And the head side supply/discharge passages 116B and 216A and the sub tank passages 119 and 219 communicate with each other through the second notch 62 and the second annular recess 54B. Further, by operating the pilot check valve 280 to be disposed in the open position, the return oil flowing into the head side supply and discharge passages 116B and 216B is introduced into the branch supply and discharge passages 118 and 218 . At this time, since the spools 150 and 250 are at the A position, the branch supply/discharge passages 118 and 218 and the main tank passages 117B and 217B communicate with each other through the first notch 61 .

Thereby, the return oil from the head side oil chamber 1B of the hydraulic cylinder 1 is discharged to the tank T through both the main tank passages 117B and 217B and the sub tank passages 119 and 219. . That is, the return oil passing through the main tank passages 117B and 217B is discharged to the tank T through the back pressure check valve 5 . The return oil passing through the sub tank passages 119 and 219 is discharged directly to the tank T without passing through the back pressure check valve. Here, the back pressure check valve 5 is generally set so that the pressure (back pressure) of the hydraulic oil in the main tank passages 117A, 117B, 217A, 217B becomes a pressure of about 0.3 to 0.5 MPa.

The hydraulic control valve 100 is switched to the A position when the arm hydraulic cylinder 1 (hydraulic cylinder 315) is contracted. When the hydraulic cylinder 1 for arms (hydraulic cylinder 315) is contracted, the arm 312 will perform an extrusion operation.

Next, a description will be given of a case in which the spools 150 and 250 are in the B position. In this case, communication between the pump passages 113 and 213 and the first tank passages 114A, 114B, 214A, and 214B is blocked. In addition, on the head side (the pressure oil supply side in the right side of FIG. 3), the head side bridge passages 115B, 215B and the head side supply/discharge passages 116B, 216B are connected to the third notch 63 and the second annular recess 54B. ) is communicated through Thereby, the pressure oil flowing into the head-side bridge passages 115B and 215B through the load check valves 120 and 220 passes through the third notch 63 and the second annular recessed portion 54B through the head-side supply/discharge passage. (116B, 216B). And the pressure oil is introduced into the head side oil chamber 1B of the hydraulic cylinder 1 through the head side supply/discharge port 112B and the head side supply/discharge line 2B.

On the other hand, on the rod side (the discharge side of the return oil on the left side in Fig. 3), the rod-side bridge passages 115A and 215A are closed. And the rod side supply/discharge passages 116A and 216A and the main tank passages 117A and 217A communicate with each other through the first notch 61 and the second annular recess 54A. Thereby, the return oil from the rod-side oil chamber 1A of the hydraulic cylinder 1 is discharged to the tank T through the main tank passages 117A and 217A. That is, the return oil passing through the main tank passages 117A and 217A is discharged to the tank T through the back pressure check valve 5 .

This hydraulic control valve 10 is switched to the B position when the arm hydraulic cylinder 1 (hydraulic cylinder 315) is extended. When the hydraulic cylinder 1 for arms (hydraulic cylinder 315) is extended, the arm 312 is pulled.

For example, as shown in FIG. 5, when extruding from the state which folded the arm 315, the hydraulic cylinder 315 for arms is contracted and operated. At this time, due to the weight of the arm 312 or the bucket 313 , a large inertial force toward the contracting side acts on the hydraulic cylinder 1 . In doing so, the supply of the hydraulic oil to the rod-side oil chamber 1A of the hydraulic cylinder 1 cannot keep up, and there is a risk of cavitation.

At such a time, the regeneration passage functions. That is, since the pressure of the return oil from the head side oil chamber 1B is high at that time, the return introduced from the head side supply and discharge passages 116B and 216B through the pilot check valve 280 into the branch supply and discharge passage 218 is high. The oil opens the check valve 260 of the regeneration passage and joins the pressure oil in the rod-side supply/discharge passages 116A and 216A. Thereby, a sufficient amount of oil can be supplied to the rod-side oil chamber 1A of the hydraulic cylinder 1 while preventing cavitation.

In this way, in the hydraulic control valve 100 and the hydraulic control circuit, the return oil from the head side oil chamber 1B is transferred to the main tank passages 117B and 217B and the sub-tank during the contracting operation of the hydraulic cylinder 1 . It can be discharged to the tank (T) through the passages on both sides of the passages (119, 219). Accordingly, compared to the case of discharging the return oil to the tank T through only the main tank passages 117B and 217B, the pressure loss of the return oil can be reduced. In particular, the sub tank passages 119 and 219 return oil returned from the head side oil chamber 1B directly to the tank T without passing through the back pressure check valve 5, so that the pressure loss can be significantly reduced. .

Further, inside the valve body 111, the return oil from the head-side oil chamber 1B is branched into both the main tank passages 117B and 217B and the sub-tank passages 119 and 219 to flow. For this reason, compared to the case where a quick return circuit for quickly returning the return oil from the head side oil chamber 1B to the tank T is separately provided outside the hydraulic control valve 100, the circuit configuration can be simplified. there is. That is, in the valve body 111 of the hydraulic control valve 100 itself, the sub tank passage 119 for discharging the return oil directly to the tank T without passing through the back pressure check valve separately from the main tank passages 117B and 217B. , 219) are being installed. Therefore, it is not necessary to provide the quick return circuit separately from the hydraulic control valve 100, and the circuit configuration can be simplified.

In addition, only by switching the positions of the two spools 150 and 250 to the A position for contracting operation of the hydraulic cylinder 1, the return oil from the head side oil chamber 1B of the hydraulic cylinder 1 is transferred to the main In addition to returning to the tank T through the tank passages 117B and 217B, it is possible to return to the tank T through the sub tank passages 119 and 219. That is, by switching operation of the spools 150 and 250, two sets of two tank passages (the main tank passages 117B and 217B and the sub tank passages 119 and 219) can be opened and closed. In this case, since the means for switching the opening/closing of the sub tank passages 119 and 219 is provided on the spools 150 and 250 integrally, an operation means separate from the spools 150 and 250 is unnecessary, and the flow path opening/closing control becomes easy. That is, as in the prior art, there is no need to provide a quick return valve for opening and closing the quick return circuit, so that the configuration can be simplified.

In addition, the branch supply/discharge passages 118 and 218 are made to communicate with the main tank passages 117B and 217B via the first notch 61 by the switching operation of the spools 150 and 250 . In addition to this, the head side supply/discharge passages 116B and 216B are communicated with the sub tank passages 119 and 219 via the second notch 62 . Thereby, the return oil from the head side oil chamber 1B of the hydraulic cylinder 1 is discharged to the tank T through the main tank passages 117B and 217B and the sub tank passages 119 and 219. In this case, the first notch 61 and the second notch 62 maintain a relative position determined by machining. Accordingly, the timing at which the branch supply/discharge passages 118 and 218 communicate with the main tank passages 117B and 217B and the timing at which the head side supply and discharge passages 116B and 216B communicate with the sub tank passages 119 and 219 deviate from each other. there is no

Also, only when a pilot signal is input to the pilot check valve 280 , the return oil flowing into the head side supply/discharge passages 116B and 216B passes through the first notch 61 and the second notch 62 through the main tank passage. (117B, 217B) and the sub-tank passages (119, 219). That is, in the state where the pilot signal is not input to the pilot check valve 280, the flow of the pressure oil discharged to the tank T through the first notch 61 and the main tank passages 117B and 217B is restricted. can Thereby, the support force of the hydraulic cylinder 1 with respect to an external force can be maintained.

For example, as in the second embodiment, if the two spools 150 and 250 have a total of four notches 61 , 61 , 62 , 62 , the tank T passed through the spools 150 and 250 . The leakage amount of the hydraulic oil to the furnace increases, and there is a fear that the supporting force of the hydraulic cylinder 1 with respect to an external force may decrease. Therefore, when the pilot check valve 280 is closed, the return oil does not flow into the main tank passages 117B and 217B. Thereby, increase in the leakage amount of the hydraulic oil which has passed through the 1st notch 61 can be suppressed, and it becomes possible to fully support the external force which acts on the hydraulic cylinder 1 .

Further, a part of the return oil from the head side oil chamber 1B of the hydraulic cylinder 1 can be supplied to the rod side oil chamber 1A through the regeneration passage, so that the pressure oil to the rod side oil chamber 1A is reduced. Cavitation can be prevented while being able to make up for a supply shortage.

In addition, this invention is not limited to embodiment mentioned above, It is the range which does not deviate from the meaning of this invention WHEREIN: What added various changes to embodiment mentioned above is included. For example, even in the case of a hydraulic control valve using one spool of the first embodiment, a check valve can be inserted into the spool to form a regeneration passage as in the second embodiment.

In addition, although the above-mentioned embodiment demonstrated the case where the back pressure check valve 5 was used as a back pressure holding means, other back pressure holding means can also be used.

Further, in the above-described embodiment, communication switching means for communicating and blocking the head-side supply/discharge passages 16B, 116B, and 216B to and from the sub-tank passages 19, 119, 219 is provided in the spools 50, 150, and 250 itself. Although the case where it was installed was shown, you may provide communication switching means separately from the spools 50, 150, 250 for direction switching. In that case, when the supply/discharge control of the pressure oil to the hydraulic cylinder 1 is performed by the switching operation of the spools 50, 150, 250, the sub-tank passage 19, 119 and 219) are interlocked with communication switching means for opening and closing. By doing so, it is possible to easily return the return oil from the head side oil chamber 1B to the tank T with a small pressure loss during the contracting operation of the hydraulic cylinder 1 .

According to at least one embodiment described above, the return oil from the head side oil chamber 1B is discharged from the main tank passages 17B, 117B, 217B and the sub tank passages 19, when the hydraulic cylinder 1 is contracted. It can be discharged to the tank (T) through the passages on both sides of 119 and 219. Therefore, compared to the case where the return oil is discharged to the tank T only through the main tank passages 17B, 117B, and 217B, the pressure loss of the return oil can be reduced. In particular, the sub tank passages 19 , 119 , and 219 return oil returned from the head side oil chamber 1B directly to the tank T without passing through the back pressure check valve 5 , so that the pressure loss is greatly reduced. can do.

Further, inside the valve body 11, the return oil from the head side oil chamber 1B is branched into both the main tank passages 17B, 117B, 217B and the sub tank passages 19, 119, 219. making it flow For this reason, compared with the case where a quick return circuit for quickly returning the return oil from the head side oil chamber 1B to the tank T is separately provided outside the hydraulic control valves 10 and 100, the circuit configuration is reduced can be simplified. That is, the sub for discharging the return oil directly to the tank T without passing through the back pressure check valve separately from the main tank passages 17B, 117B and 217B to the valve bodies 11 and 111 of the hydraulic control valve 10 itself. Tank passages 19, 119 and 219 are provided. Therefore, it is not necessary to provide the quick return circuit separately from the hydraulic control valves 10 and 100, and the circuit configuration can be simplified.

Although several embodiments of the present invention have been described, these embodiments are presented as examples and limiting the scope of the invention is not intended. These embodiments can be implemented in other various forms, and various abbreviations, substitutions, and changes can be made in the range which does not deviate from the summary of invention. These embodiments and modifications thereof are also included in the scope of the invention described in the claims and their equivalents as long as they are included in the scope and gist of the invention.

1: hydraulic cylinder
1A: Rod side oil seal
1B: Head side oil seal
1P: piston
3: hydraulic pump
5: Back pressure check valve (back pressure maintaining means)
10: hydraulic control valve
11: valve body
12A: Load side supply/discharge port
12B: head side supply/discharge port
13: pump passage
14A, 14B: first tank passage
15A: rod side bridge passage
15B: head side bridge passage
16A: rod side supply/discharge passage
16B: head side supply/discharge passage
17A, 17B: main tank passage
18: branch supply and distribution passage
19: sub tank passage
20: load check valve
40: sleeve hole
50 : spool
61: first notch
62: second notch
70: positioning mechanism
100: hydraulic control valve
111: valve body
112A: Load side supply/discharge port
112B: head side supply/discharge port
113: pump passage
114A, 114B: first tank passage
115A: rod side bridge passage
115B: head side bridge passage
116A: rod side supply/discharge passage
116B: head side supply/discharge passage
117A, 117B : main tank passage
118: branch supply and distribution passage
119: sub tank passage
120: load check valve
140: sleeve hole
150: spool
213: pump passage
214A, 214B: first tank passage
215A: rod side bridge passage
215B: head side bridge passage
216A: rod side supply and discharge passage
216B: head side supply/discharge passage
217A, 217B : main tank passage
218: branch supply and distribution passage
219: sub tank passage
220: load check valve
240: sleeve hole
250 : spool
260: check valve
280: pilot check valve
Pa : Pilot port for switching A position
Pb : Pilot port for B position switching
PA, PB : Pilot pressure

Claims (7)

A hydraulic control valve having a valve body that is installed between a hydraulic cylinder and a hydraulic pump, is installed between a hydraulic cylinder and a tank, and is switched to control supply/discharge of hydraulic oil to the hydraulic cylinder,
The valve body is
a head side supply/discharge passage connected to the head side oil chamber of the hydraulic cylinder;
a main tank passage connected to the tank through a back pressure maintaining means;
and a sub-tank passage directly connected to the tank without passing through a back pressure maintaining means;
In a state in which the hydraulic cylinder is switched to a position in which the hydraulic cylinder is operated to the contracting side, the head-side supply/discharge passage through which the return oil from the head-side oil chamber of the hydraulic cylinder flows is provided to both the main tank passage and the sub-tank passage. Connected, hydraulic control valve. According to claim 1,
inside the valve body,
A spool for communicating the supply/discharge passage on the head side with the main tank passage in a state in which the hydraulic cylinder is switched to a position for operating the hydraulic cylinder to the contracting side is provided slidably;
and communication switching means for communicating the head side supply/discharge passage with the sub tank passage in a state in which the spool is switched to a position for operating the hydraulic cylinder to the retracting side. 3. The method of claim 2,
The hydraulic control valve in which the communication switching means is provided on the spool. 4. The method of claim 3,
a first notch on the outer periphery of the flow path closing land portion on the spool for communicating the head side supply/discharge passage with the main tank passage while the spool is switched to a position for operating the hydraulic cylinder to the contracting side; and a second notch for communicating a head-side supply/discharge passage to the sub-tank passage. 5. The method of claim 4,
A pilot check is performed on either one of a flow path in front of the first notch that communicates the head-side supply/discharge passage to the main tank passage and a flow path in front of the second notch that communicates the head-side supply/discharge passage to the sub tank passage. A hydraulic control valve with a valve installed. 6. The method according to claim 4 or 5,
A rod side supply/discharge passage connected to the rod side oil chamber of the hydraulic cylinder is provided in the valve body,
In the inside of the valve body or the inside of the spool, in a state in which the spool is switched to a position for operating the hydraulic cylinder to the contracting side, a portion of the return oil flowing into the head side supply/discharge passage is transferred through the check valve. A hydraulic control valve provided with a regeneration passage leading to a rod-side supply/discharge passage. A hydraulic cylinder, a hydraulic pump, a tank, and a hydraulic control valve installed between the hydraulic cylinder and the hydraulic pump and installed between the hydraulic cylinder and the tank and operated to control supply/discharge of hydraulic oil to the hydraulic cylinder In a hydraulic control circuit,
The hydraulic control valve is the hydraulic control valve according to any one of claims 1 to 5,
and the main tank passage of the hydraulic control valve is connected to the tank via a back pressure check valve as the back pressure maintaining means for maintaining a constant pressure in the main tank passage.

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