JPH11230375A - Directional control valve having restoration circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a directional control valve of a spool type in which a flow rate control notch is opened to a load port, which can exhibits a regenerating function with no counter-flow of pressure oil during operation in one direction and which can prevent pressure oil from counter flowing even in the opposite direction. SOLUTION: A valve element 60 in a check valve 60 is composed of two parts, that is, a seat valve part 60a and a piston part 60b, and the piston part 60b is formed therein with a baby piston part 61 adapted to be slidably fitted in the seat valve part while a back pressure chamber is formed in the rear surface side of the piston part. Oil passages 67, 68 for introducing an inlet pressure of a check valve into the back pressure chamber are formed in the seat valve part and the baby piston part, and a second oil passage 69 for introducing an outlet pressure of the check valve between the rear surface part 63 of the seat valve part and an end surface part 62 of the piston part is formed in the outer peripheral part of the seat valve part which slides together with a spool, and the spool is formed therein with a third oil passage 57 communicating the back pressure chamber with a tank port Tr in response to an operation in one direction, but cutting off the communication in response to an operation in a direction opposite to the former direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a directional control valve having a regenerative circuit, and more particularly to a directional control valve having a regenerative circuit used for a construction machine such as a hydraulic shovel performing a work in which a negative load is applied by its own weight.

[0002]

2. Description of the Related Art An example of an operation in which a negative load due to its own weight acts on a hydraulic excavator is a surface compaction operation. In this rolling work, as shown in FIG. 4, the boom 100 is lowered and the bucket 10 provided at the tip of the arm 101 is moved.
2. Put your back on the ground. In this rolling work, bucket 1
02, the boom 100, the arm 101, and the bucket 1 at the beginning of the lowering operation of the boom 100 before the back of the boom 100 hits the ground surface.
02 acts on the boom cylinder 10 as a negative load.
The rod 10a is forcibly pushed down by this negative load and tends to descend. At this time, if the amount of oil sent from the hydraulic pump to the rod side of the boom cylinder 10 is larger than the oil amount corresponding to the descending speed of the rod 10a, the rod 1
At the same time, the cylinder tube 10b receives an upward force as indicated by a broken-line arrow A, while the cylinder tube 10b receives a downward force as indicated by a solid-line arrow A. Here, the cylinder tube 10
Since b is pin-connected to the shovel body, when an upward force acts on the cylinder tube 10b, this force causes the front part of the shovel body to rise as indicated by the solid line arrow C, resulting in deterioration of operability.

To eliminate this problem, the boom cylinder 10
It is not necessary to send pressure oil from the hydraulic pump to the rod side of the boom 100.
After 2 hits the ground, it is necessary to compress the boom cylinder 10 with pressure oil from a hydraulic pump and press the bucket 102 against the surface of the ground.

In order to solve such a problem, at the beginning of the boom lowering, a part of the oil returned from the bottom side of the boom cylinder 10 to the tank is returned to the rod side of the boom cylinder 10 so that the boom lowering speed becomes constant. A directional control valve having a regeneration circuit for sending pressure oil from a hydraulic pump to the rod side of the boom cylinder 10 has also been proposed.

FIG. 5 shows a conventional example of a closed center type load sensing valve. This directional control valve is disclosed in Japanese Utility Model Laid-Open No. 5-81509.

In FIG. 5, when the spool 211 of the directional control valve 201 is moved to the right in the drawing, the pressure oil on the bottom side 11 of the boom cylinder 10 is initially supplied to the directional control valve 1 when the boom is lowered.
At the same time, the fluid flows from the load port 206 to the tank port 208, flows from the regeneration port 216 to the load port 207 from the recycled oil passage 217 via the check valve 218, and fills the rod side 12 of the boom cylinder 10. The direction control valve 201 has two pump ports 202,
When the spool 211 is moved rightward in the figure, the pump port 203 and the feeder port 205 communicate with each other. Therefore, the load port 206 and the regeneration port 216
By adjusting the relationship between the flow control notch between the pump port 203 and the flow control notch between the pump port 203 and the feeder port 205, the supply of pressure oil from the hydraulic pump is delayed, and when the boom lowering speed becomes constant, the hydraulic pump Pressure oil to the rod side of the boom cylinder 10.

When the bucket 102 comes into contact with the ground surface and rolls, the movement of the boom cylinder 10 stops, and the bottom side 11
The pressure on the rod side 12 increases on the contrary, but the pressure oil does not flow backward due to the action of the check valve 218.

When raising the boom by moving the spool 211 to the left, the pressure oil of the hydraulic pump flows from the pump port 202 to the feeder port 204 and is supplied to the bottom side 11 of the boom cylinder 10 and the rod side 12 of the boom cylinder 10 Is returned from the load port 207 of the directional control valve 201 to the tank port 209. At this time, since the connection between the load port 206 and the reproduction port 216 is cut off, no malfunction occurs.

Next, a center bypass oil passage is provided.
A conventional example of a so-called open center type directional control valve will be described with reference to FIG. This is an example of application to an actual machine.

In FIG. 6, oil discharged from a hydraulic pump 20 is supplied to a pump port P, and a downstream side of the pump port P is provided in a directional control valve 21A in a center bypass port Pb.
And a parallel port Pp. The center bypass port Pb further includes right and left bypass ports Pbr and Pb.
1 and the parallel port Pp further branches to the right and left feeder passages Fr and Fl, and the port Pp and the passages Ppr and Pl.
A hold check valve 23 is disposed between the pl.

Around the spool hole in which the spool 22A of the valve body 21a slides, the lands 1,
Next to it, the right tank port Tr, land 2, next to the right load port Aa, land 3, next to the right feeder port Ppr, and the center center bypass ports Pb, Pb.
r, left side feeder port Ppl across Pbl,
A land 4, a left load port Ba and a land 5, and a left tank port T1 and a land 6 are formed next to the land 4 and the land 5, respectively.

The spool 22A has right and left load ports Aa,
Ba has a large diameter portion 7, and lands 3 and 4 have meter-in flow control notches 22 a and 22 b formed in lands 3 and 4, and lands 2 and 5 have meter-out flow control notches 22 c and 22 c. A small diameter portion 8 is formed at the right and left feeder ports Ppr and Ppl and the tank ports Tr and Tl. Notch 2 for lands 3 and 4
2a, 22b and notches 22c at the lands 2, 5;
22d is a feeder port Ppr, Ppl and a tank port Tr, a small diameter portion 8 of the spool 22A.
Open to Tl.

When lowering the boom cylinder 10 when the spool 22A is moved to the left from the illustrated position,
Connect the load port Aa to the bottom side 11 of the boom cylinder 10
And the load port Ba is connected to the rod side 1 of the boom cylinder 10.
Connect to 2. When the spool 22A is moved to the left, the notch 22c of the land 2 portion connects the port Aa and the port Tr, and the notch 22b of the land 4 portion connects the port Ppl and the port Ba.

The bottom side 11 of the boom cylinder 10
The non-return valve 16 provided in the pipe is an anti-drift valve for drop prevention which operates by a hydraulic signal of the remote control valve 15.

The direction control valve 21A is provided with a regeneration circuit as follows.

An axial oil passage 32 is provided in the spool 22A, a radial oil passage 30 perpendicular to the oil passage 32 is provided in the land 2 portion, and a similar oil passage 31 is provided in the land 1 portion. The check valve 24. Further, a radial oil passage 33 is provided in the land 4 portion, and the oil passage 32
And a check valve 25 is arranged between 33 and 33.

When the spool 22A is moved leftward in the figure,
The pressure oil from the bottom side 11 of the boom cylinder 10 returns to the load port Aa, and the notch 22c of the land 2 portion
Through the oil passage 3
Part of the pressure oil guided from 0 to the oil passage 32 is returned to the tank port Tr via the check valve 24 and the oil passage 31,
The rest is via the check valve 25 and the oil passage 33 through the load port Ba.
To regenerate to the rod side 12 of the boom cylinder 10. Even if the rod side 12 of the boom cylinder 10 becomes high pressure in this state, the discharge oil of the hydraulic pump 20 flowing into the port Ba does not flow backward to the port Aa by the function of the check valve 25.

When the operation spool 22A is operated rightward in the drawing by raising the boom, the oil passage 33 is connected to the feeder port Ppl and the oil passage 30 is connected to the tank port Tr. Feeder port Ppl
Pressure oil (discharge oil of the hydraulic pump 20) flows into the tank port Tr
There is no backflow to.

There are two types of directional control valves of the open center type in a spool that slides in the valve body.
One is the type shown in FIG. 6 described above, and the other is the type shown in FIG.
It is a type shown in FIG.

The spool 22A shown in FIG. 6 has the large diameter portion 7 at the right and left load ports Aa and Ba as described above, and the notches 22a and 22b at the lands 3 and 4 and the lands 2 and 5 The notches 22c and 22d of the feeder port P are formed at the small diameter portion 8 of the spool 22A.
Opened to pr, Ppl and tank ports Tr, Tl. On the other hand, the spool 22B in FIG.
a and Ba are small-diameter portions 8B.
The notches 22a and 22b of the portion 4 and the notches 22c and 22d of the lands 2 and 5 are both open to the load port Aa or Ba at the small diameter portion 8B.

FIG. 7 shows that, when the spool 22B is moved to the left from the position shown in the drawing, when the boom cylinder 10 is lowered, the load port B is connected to the boom cylinder 10 in a manner opposite to that shown in FIG. , The load port A is connected to the rod side 12 of the boom cylinder 10. When the spool 22B is moved to the left, the notch 22a of the land 3 connects the port Ppr to the port Aa, and the notch 22d of the land 5 connects the port Ba and the port Tl.

[0022]

As described above, both the closed center type directional control valve and the open center type directional control valve having a regeneration function are known.

However, in the case of the closed center type directional control valve shown in FIG. 5, the center portion in the spool 11 is already used for load pressure detection by providing a load pressure detection passage (not shown). The spool 1 for playback
The central part within 1 cannot be used. For this reason,
As shown in the figure, the oil passage 17 for regeneration must be provided in the valve body, and there is a problem in simplification of equipment.

In the case of an open center type directional control valve,
There are no such restrictions. For this reason, as shown in FIG. 6, the central portion in the spool can be used as the oil passage 32 for regeneration, and the equipment can be simplified as compared with the closed center type.

However, as described above, the open center type directional control valve is divided into two types depending on the design of the spool, and is of the type shown in FIG.
a, 22b, 22c, 22d are load ports Aa or Ba
Directional control valve 21 having a spool type that opens to the side
If an attempt is made to provide a regeneration circuit similar to the direction control valve 21A of FIG.

FIG. 7 shows a case where a regeneration circuit similar to that of the direction control valve 21A of FIG. 6 is provided, and the state is indicated by a two-dot chain line. An axial oil passage 32 is provided in the spool 22B, a radial oil passage 30 perpendicular to the oil passage 32 is provided in the land 4, and a similar oil passage 31 is provided in the land 5 in the reverse direction. The stop valve 24 is arranged. A radial oil passage 33 perpendicular to the oil passage 32 is provided at the land 2, and the check valve 25 is disposed between the oil passage 32 and the oil passage 33.

The operation of lowering the boom by moving the spool 22B to the left in the drawing is the same as in FIG. 6, and there is no particular problem. That is, the return oil from the bottom side 11 of the boom cylinder 10 is regenerated to the rod side 12 of the boom cylinder 10, and no backflow of the pressure oil occurs even when the rod side 12 becomes high pressure. However, with the operation of raising the boom to move the spool 22B rightward in the figure, the oil passage 30 is moved to the feeder port Ppl.
Is connected to the tank port Tr, the oil discharged from the hydraulic pump 20 supplied to the feeder port Ppl escapes from the tank port Tr to the tank through the oil passages 30, 32, and 33. I will. For this reason, pressure oil cannot be supplied to the bottom side of the boom cylinder 10, and the boom cannot be raised.

If the boom directional control valve is of the type shown in FIG. 6, such a problem does not occur. But,
2. Description of the Related Art In construction machines such as hydraulic excavators, directional control valves of a plurality of non-driving members such as a boom, an arm, and a bucket are arranged in the form of a multiple valve. In this case, using the multiple direction valve of the type shown in FIG. 7 as the direction control valve of FIG. 7 and using only the direction control valve of the boom type shown in FIG. 6 makes it possible to lower the boom by operating the spool to the left in the drawing. Therefore, it is necessary to reverse the two pipes connecting the boom cylinder and the valve. That is, in the directional control valve of the type shown in FIG. 7, the rod-side pipe of the boom cylinder 10 is connected to the load port A and the bottom pipe is connected to the load port B of the directional control valve of the type shown in FIG. Connect the rod side piping of cylinder 10 to load port B
, And the bottom pipe must be connected to the load port A. When the pipes connected to the load ports A and B are reversed as described above, the connection work of the pipes is complicated and error-prone. Also, a directional control valve other than the boom in the multiple valve (FIG. 7)
When the spool 22B is operated leftward in the figure, the pressure oil flows out of the load port A, but only the boom directional control valve (type in FIG. 6) flows out of the load port B. , Service, and inspection may cause confusion.

In the type shown in FIG. 7, if the land 2 is sufficiently long, there is no possibility that the oil passage 33 is connected to the tank port Tr. However, the notch 22c in the portion of the land 2 becomes long, and not only the spool shape of the portion of the land 2 needs to be reexamined, but also the position of the tank port Tr differs only in the direction control valve for the boom in the multiple valve. Also, the connection of the tank port Tr needs to be reconsidered.

An object of the present invention is a directional control valve having a spool type in which a notch for controlling a flow rate is opened to a load port, and a one-way operation of the spool can perform a regeneration function without causing a backflow of pressure oil. It is an object of the present invention to provide a directional control valve having a regeneration circuit that does not cause a backflow of pressure oil even when the spool is operated in the opposite direction.

[0031]

In order to achieve the above object, the present invention has a check valve which opens and closes a regeneration oil passage in a spool, and returns oil from the actuator when the spool is unidirectionally operated. (A) a valve element of the check valve is provided with a seat valve portion slidable in a spool, and a valve member located on the back side of the seat valve portion and similarly in the spool. Is composed of two parts of a slidable piston part, a piston part having a smaller diameter than the seat diameter of the seat valve part is provided on the piston part, and this baby piston part is slidably fitted to the seat valve part. (B) a back pressure chamber is formed on the back side of the piston in the spool, with the end face of the piston located radially outside the baby piston facing the back of the seat valve;
A first oil passage for guiding the inlet pressure of the check valve to the back pressure chamber is provided in the seat valve portion and the baby piston portion, and (c) the seat facing the outer periphery of the seat valve portion that slides with the spool. A second oil passage for guiding the outlet pressure of the check valve is provided between the back surface of the valve portion and the end surface portion of the piston portion, and (d) a back pressure chamber is provided in the spool by a one-way operation of the spool. And a third oil passage for communicating with the spool in a reverse operation of the spool.

As described above, the valve body of the check valve is constituted by the two portions of the seat valve portion and the piston portion, and the check valve is provided between the rear portion of the seat valve portion and the end surface portion of the piston portion via the second passage. By inducing the outlet pressure of the valve and providing a first oil passage and a third oil passage in relation to the back pressure chamber, the pressure in the back pressure chamber is adjusted according to the operation direction of the spool, so that the reverse pressure is only generated when necessary. Open the stop valve and perform an appropriate regeneration function without backflow.

That is, when the spool is operated in the above one direction, the back pressure chamber communicates with the tank port through the third oil passage, so that the back oil is throttled by the first oil passage provided in the baby piston. The pressure in the pressure chamber becomes the pressure in the tank port.
At this time, if the inlet pressure P1 of the check valve ≧ the outlet pressure P2 of the check valve, the inlet pressure of the check valve acting on the seat diameter portion of the seat valve portion and the reverse pressure guided to the back portion of the seat valve portion. The hydraulic pressure generated by the outlet pressure of the stop valve becomes a force in the valve opening direction, and is generated by the outlet pressure of the check valve guided to the end face portion of the piston portion and the pressure of the back pressure chamber acting on the back portion of the piston portion. The hydraulic pressure also becomes a force in the valve opening direction, and the return oil from the actuator is regenerated through the check valve. When the inlet pressure P1 of the check valve <the outlet pressure P2 of the check valve, the inlet pressure of the check valve acting on the seat diameter portion of the seat valve portion and the outlet of the check valve guided to the rear portion of the seat valve portion. The oil pressure generated by the pressure becomes a force in the valve closing direction, the check valve closes, and no backflow of the pressure oil occurs.

When the spool is operated in the reverse direction, even if the outlet of the check valve is connected to the tank port, the communication between the back pressure chamber and the tank port by the third oil passage is interrupted, and the pressure in the back pressure chamber is reduced. Since the pressure becomes equal to the inlet pressure of the check valve, the hydraulic pressure acting on the entire check valve becomes a force in the valve closing direction, and no backflow of the pressure oil occurs.

In order to obtain the above hydraulic pressure relationship, a predetermined area relationship is required, and the seat diameter of the seat valve portion of the valve body is d1, and the diameter of the baby piston portion of the piston portion is d.
2. If the diameter of the outer peripheral portion of the seat valve portion is d3, d
It is sufficient to set 1 <d3 and d2 <d1.

[0036]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 21 denotes a directional control valve having a regeneration function according to the present embodiment.
Has a valve body 21a formed with a pump port P to which the discharge oil from the hydraulic pump 20 is supplied, and load ports A and B for supplying and discharging the pressure oil to and from the boom cylinder 10; Is branched into a center bypass port Pb and a parallel port Pp in the valve body 21a, and the center bypass port Pb is further branched into right and left bypass ports Pbr and Pbl connected to the tank T, and the parallel port P
p further branches into right and left feeder passages Fr and Fl, and a hold check valve 23 is disposed between the parallel port Pp and the feeder passages Fr and Fl.

The valve body 21a has a spool hole 21b.
Is formed, and the spool 22 is inserted into the spool hole 21b. The bypass ports Pb, Pbr, and Pbl are formed around the spool hole 21b. The right and left sides of the bypass port Pb, Pbr and Pbl are connected to the land 1, the right tank port Tr connected to the tank T, the land 2, and the load. A right load port Aa connected to the port A, a land 3, and a right feeder port Ppr connected to the feeder passage Fr are formed, and bypass ports Pb and Pbr, P
A left feeder port Ppl connected to the feeder passage Fl, a land 4, a left load port Ba connected to the load port B, a land 5, a left tank port Tl connected to the tank T, and a land 6 are sequentially formed on the left side of the drawing bl. .

The spool 22 has right and left tank ports Tr,
T1 has a large-diameter portion 7 and right and left load ports Aa,
The portions of Ba and feeder ports Ppr, Ppl are small-diameter portions 8B, 8, and notches 22a, 22b for controlling the flow rate of meter-in are provided on lands 3, 4 of spool 22.
Are formed at the lands 2 and 5 of the spool 22, and notches 22 c and 22 d for meter-out flow control are formed at the lands 2 and 5, and the notches 22 a and 22 b at the lands 3 and 4 and the notches 22 c at the lands 2 and 5 are formed. , 22d open to the load ports Aa, Ba at the small diameter portions 8B, 8B, respectively.

The load port A is connected to the rod side 12 of the boom cylinder 10, and the load port B is connected to the boom cylinder 1
0 is connected to the bottom side 11. When the spool 22 is moved to the left from the illustrated position, the notch 22a of the land 3 connects the feeder port Ppr to the load port Aa, and the notch 22d of the land 5 connects to the load port Ba.
And the tank port Tl, the pressure oil is supplied and discharged in the contracting direction of the boom cylinder 10, and the boom is lowered. Conversely, when the spool 22 is moved to the right in the figure, the notch 22b of the land 4 is moved to the feeder port Ppl and the load port B.
a, the notch 22c of the land 2 connects the load port Aa and the tank port Tr, and the boom cylinder 1
Pressure oil is supplied / discharged in the direction of 0 extension, and the boom is raised.

Reference numeral 15 denotes a remote control valve. When the remote control valve 15 is operated to generate a hydraulic signal Pa, the spool 22 moves to the left in the figure, and when operated to generate a hydraulic signal Pb, the spool 22 moves to the right in the figure. Move towards Bottom side 11 of boom cylinder 10
The hydraulic signal P of the remote control valve 15
A check valve 16 is provided as an anti-drift valve for preventing a fall which operates in a.

The direction control valve 21 incorporates a regeneration circuit 50. The reproduction circuit 50
And a radial oil passage 52 provided in the land 4 at a right angle to the oil passage 51.
And a radial oil passage 53 similarly provided at a right angle to the oil passage 51 in the land 5 portion, and provided between the oil passages 51 and 52 and the oil passage 53. 5
A check valve 54 for preventing the flow of the pressure oil toward the oil passage 2, a radial oil passage 55 provided in the land 2 at a right angle to the oil passage 51, and provided between the oil passage 51 and the oil passage 55. The check valve 56 provided on the land 1 and the check valve 56
And a radial oil passage 57 that opens into a back pressure chamber 66 (described later).

The check valve 56 sets the pressure in the oil passage 51 (the inlet pressure of the check valve 56) to P1 and the pressure in the oil passage 55 (the check valve 56).
When the spool 22 is moved to the left in the figure, the valve opens when P1 ≧ P2, and when P1 <P2, the valve closes. When the spool 22 is moved to the right in the figure, The valve is not opened even if P1 ≧ P2. Hereinafter, details of the check valve 56 will be described with reference to FIG.

In FIG. 2, the check valve 56 has a valve element 60 which has a seat diameter of d1 and a sliding diameter d3 (> d1) which is slidable in the spool 22. And a diameter d which is located on the back side of the seat valve portion 60a and is also slidable in the spool 22.
It is composed of two parts, a piston part 60b having three sliding parts. A baby piston part 6 having a diameter d2 smaller than the seat diameter d1 of the seat valve part 60a is provided in the piston part 60b.
1, the baby piston portion 61 is slidably fitted to the seat valve portion 60a, and an end surface portion 62 of the piston portion 60b radially outside the baby piston portion 61 is attached to the back surface portion 63 of the seat valve portion 60a. A pressure receiving chamber 64 is formed between the baby piston portion 61 of the piston portion 60b and the seat valve portion 60a so as to face each other so as to be in contact with each other. A back pressure chamber 66 is provided on the back side of the piston portion 60b in the spool 22.
A check valve 56 is provided at the center of the seat valve portion 60a.
An oil passage 67 for guiding the inlet pressure of the piston to the pressure receiving chamber 64 is formed, and the pressure of the pressure receiving chamber 64 (the inlet pressure of the check valve 56) is guided to the back pressure chamber 66 at the center of the baby piston portion 61 of the piston portion 60b. An axial throttle passage 68 is formed.

Further, the sliding portion of the seat valve portion 60a which slides on the spool 22 has an end face portion 6 of the piston portion 60b.
Check valve 56 between the valve seat 2 and the rear portion 63 of the seat valve portion 60a.
A groove-shaped oil passage 69 is formed to guide the outlet pressure of the oil passage, and the pressure from the oil passage 69 is reliably applied to the end face portion 62 of the piston portion 60b between the end face portion 62 and the back face portion 63 of the seat valve portion 60a. A radiation groove 62a for guiding is formed. Reference numeral 70 denotes a weak spring that holds the valve body 60 at the closed position when not operated.

The oil passage 57 is formed in the land 1 of the spool 22. The oil passage 57 connects the back pressure chamber 66 to the tank port Tr when the spool 22 is moved leftward in the figure, and is blocked by the land 1 when the spool 22 is moved rightward in the figure.

The operation of the check valve 56 will be described in detail.

The area of the portion of the seat diameter d1 of the seat valve portion 60a is A1, the area of the diameter d2 of the baby piston portion 61 is A2, and the area of the end surface of the piston portion 60b on the side of the back pressure chamber 28 having the diameter d3 is A3. The pressure in the oil passage 51 and the pressure in the load port A are P1 and P2 as described above, and the pressure in the back pressure chamber 66 is P3.

The hydraulic pressure Fa acting on the seat valve portion 60a
Since the pressure in the pressure receiving chamber 64 is the same P1 as the pressure in the oil passage 51, Fa = (A1-A2) (P1-P2) (1) is calculated, and the oil pressure Fb acting on the piston portion 60b is , Fb = (A3-A2) (P2-P3) + A2 (P1-P3) (2)

When the spool 22 is moved to the left in the figure,
As described above, the feeder port Ppr is connected to the load port Aa via the notch 22a, and the oil passage 55
Is connected to the load port Aa, and the back pressure chamber 66 is connected to the tank port Tr via the oil passage 57. At this time, if it is assumed that P1 ≧ P2 at the beginning of the boom lowering operation, the hydraulic pressure Fa acting on the seat valve portion 60a in the above equation (1) =
(A1-A2) (P1-P2) is the rightward force in the figure,
Acts on the seat valve portion 60a in the valve opening direction. At this time, the pressure P3 of the back pressure chamber 66 becomes the pressure Pt of the tank port Tr (substantially 0) due to the throttle effect of the throttle passage 68 provided in the baby piston portion 61, and the pressure P3 during the boom lowering operation.
2 = Pt, the hydraulic pressure Fb acting on the piston portion 60b in the above equation (2) is Fb = A2 (P1-P
t), and moves the piston portion 60b rightward in the figure. Therefore, the seat valve portion 60a is opened by the oil pressure Fa in the valve opening direction, and a part of the pressure oil guided from the bottom side 11 of the boom cylinder 10 to the oil passage 32 passes through the check valve 54 and the oil passage 53. Through the check port 56 and the oil passage 55 to the load port Aa.
Regenerate to the rod side 12 of the boom cylinder 10.

On the other hand, when the bucket 102 comes into contact with the ground surface in this state and P2> P1, the hydraulic pressure Fa acting on the seat valve portion 60a in the above equation (1) = F (A1-A2) (P1-
P2) is a force in the valve closing direction on the left side in the figure, and the seat valve portion 6
0a is closed. At this time, the pressure P1 of the oil passage 51 becomes
Since it can be considered that P1 = Pt, the hydraulic pressure Fb of the above formula (2) acting on the piston portion 60b is as follows: Fb = (A3-A2) (P2-Pt), and still faces the right. Therefore, even if the bucket reaches the ground surface by the operation of lowering the boom and P2> P1, the seat valve portion 60a is closed, and there is no danger of backflow.

Next, when the spool 22 is moved rightward in the figure to raise the boom, the load port Aa is connected to the tank port Tr via the notch 22c as described above, and the oil passage 55 is also closed. It is connected to the tank port Tr, and P2 = Pt. On the other hand, at this time, the oil passage 57 is closed by the land 1, and P3 = P1. Therefore, the hydraulic pressure Fa acting on the seat valve portion 60a in the above formula (1) becomes a right force in the drawing of Fa = (A1-A2) (P1-Pt), and the seat valve portion 60a is moved in the valve opening direction. Works. However, the oil pressure Fb acting on the piston portion 60b in the above equation (2) becomes a force in the valve closing direction on the left side in the drawing, Fb = (A3-A2) (Pt-P1), and the total oil pressure ( The hydraulic pressure F acting on the entire check valve 25 is as follows: F = Fa + Fb =-(A3-A1) (P1-Pt) At this time, P1 is the discharge pressure of the hydraulic pump 20, and the hydraulic pressure F is the force on the left side in the figure to close the check valve 56, and the discharge pressure of the hydraulic pump 20 does not return to the tank.

FIG. 3 shows, as a comparative example, a basic valve structure relating to the check valve of the present invention. Check valve 80A of FIG.
The oil passage 68a is provided in the valve body 81a, and the back pressure chamber 82 is connected to the oil passage 55 (the outlet side of the check valve) via the oil passage 68a. When the spool 22 is moved to the left in the figure, the pressure P3 of the back pressure chamber 82 becomes the pressure P2 of the oil passage 55. Therefore, if P1 ≧ P2, the valve body 81a opens and the pressure oil in the oil passage 51 becomes It flows to the load port Aa via the oil passage 55, and when the pressure on the load port Aa side increases and P2> P1, the valve body 81a closes. However, when the spool 22 is moved rightward in the figure, the oil passage 55 and the tank port Tr
Is connected, the pressure P3 of the back pressure chamber 82 is also changed to the tank port T.
The pressure Pt becomes r, the valve element 81a opens, and the discharge oil of the hydraulic pump flows to the tank.

The check valve 80B shown in FIG.
Check valve 80A connects the back pressure chamber 82 to the outlet side of the check valve via the oil passage 68a, whereas the oil passage 51, which is the inlet side of the check valve, and the back pressure chamber via the oil passage 68b. 82 are connected. In the case of this structure, P1 ≧ P2 and the back pressure chamber 8
If the second pressure P3 is always equal to the pressure P1 of the oil passage 51, the valve body 81b remains in the closed state. Therefore, the oil passage 57 is provided in the land 1 of the spool 22 for opening and closing the valve body 81b. . When the spool 22 is moved to the left in the figure, the pressure P3 of the back pressure chamber 82 becomes the pressure Pt of the tank port Tr. Therefore, the valve body 81b is opened, and when the spool 22 is moved to the right in the figure, the back pressure is increased. Since the pressure P3 in the chamber 82 becomes the pressure P1 in the oil passage 51, the valve body 81b closes. However, when the spool 22 is moved to the left in the figure, even if the pressure at the load port Aa increases and P2> P1, the pressure P3 of the back pressure chamber 82 remains at the pressure Pt of the tank port Tr, so the valve body 81b Also remain open.

In this embodiment, the check valve 80 shown in FIG.
A is basically closed, and its opening and closing is performed by using an oil passage 57 for detecting the operation direction of the spool 22, and the outlet pressure (pressure of the oil passage 55) P2 of the check valve 80B in FIG. The valve body of the check valve is divided into a seat portion 60a and a piston portion 60b in order to act on the valve member. This allows
As described above, the outlet pressure of the check valve (the pressure of the oil passage 55) P2
Even if the pressure becomes higher than the pressure P1 of the oil passage 51 on the inlet side, the seat valve portion 60a is closed, so that there is no possibility of a malfunction in a series of operations. Even when the valve body is divided into two parts, the seat valve portion 60a has a structure in which the sliding portion 69 is provided on the outer periphery, so that the coaxiality between the seat valve portion 60a and the oil passage 51 is secured, and the seat valve portion 60a is Good sheet properties can be maintained.

[0056]

According to the present invention, the valve body of the check valve is composed of two parts, the seat valve part and the piston part, and the second passage is provided between the back part of the seat valve part and the end face part of the piston part. To the outlet pressure of the check valve via the
An oil passage and a third oil passage are provided to adjust the pressure of the back pressure chamber in accordance with the operating direction of the spool. However, in the one-way operation of the spool, the regeneration function can be performed without the backflow of the pressure oil, and the backflow of the pressure oil does not occur even in the opposite operation of the spool.
Therefore, in the boom direction control valve of the hydraulic excavator, the regeneration function of the boom lowering operation can be achieved without fear of backflow, and the boom raising operation can also be achieved without fear of backflow.

In a multiple valve having a spool type in which a notch for controlling the flow rate is opened to the load port, the size of the land is changed only for the directional control valve for providing the regeneration function.
There is no need to change the spool type, and the regeneration function can be easily added, and the piping connection work becomes complicated,
There is no risk of confusion in service and inspection.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing a main part of a directional control valve having a climax period according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a detailed structure of a check valve shown in FIG.

FIG. 3 is a diagram showing a comparative example.

FIG. 4 is a diagram illustrating the appearance of a hydraulic excavator and a surface compaction operation as an example of an operation in which a negative load is applied.

FIG. 5 is a sectional view of a conventional closed center type directional control valve having a regeneration function.

FIG. 6 is a cross-sectional view of a conventional open center type directional control valve having a regeneration function.

FIG. 7 is a sectional view of another conventional open center type directional control valve.

[Explanation of symbols]

P Pump port Pb Center bypass port (Pbr: right, Pbl:
Left) Pp parallel port Ppr, Ppl right, left feeder port A, Aa right load port B, Ba left load port Tr, Tl right, left tank port 1, 2, 3, 4, 5, 6 land 7 spool large diameter part 8, 8B Spool small diameter portion 10 Boom cylinder 11 Bottom side 12 Rod side 15 Remote control valve 16 Anti-drift valve 20 Hydraulic pump 21 Directional control valve 22 Spool 22a, 22b, 22c, 22d Notch 23 Hold check valve 50 Regeneration circuit 51, 52 , 53 oil passage 54 check valve 55 oil passage 56 check valve 57 oil passage (third oil passage) 60 valve element 60 a seat valve part 60 b piston part 61 baby piston part 62 end face part 63 back part 64 pressure receiving chamber 66 back pressure Chamber 67 Oil passage (first oil passage) 68 Throttle passage (first oil passage) 9 oil passage (second oil passage) 70 spring

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kinya Takahashi 650 Kandamachi, Tsuchiura-shi, Ibaraki Pref. Within Hitachi Construction Machinery Engineering Co., Ltd.

Claims (2)

[Claims] A directional control valve having a built-in check valve for opening and closing a regeneration oil passage in a spool, and a regeneration circuit for returning oil returned from an actuator to the actuator when the spool is operated in one direction; The valve body of the check valve is composed of a seat valve portion slidable in the spool and a piston portion located on the back side of the seat valve portion and also slidable in the spool. A baby piston part having a smaller diameter than the seat diameter of the seat valve part is provided, the baby piston part is slidably fitted to the seat valve part, and the end face part of the piston part radially outside the baby piston part is seated. (B) A back pressure chamber is formed on the back side of the piston in the spool, and the inlet pressure of the check valve is applied to the seat valve and the baby piston to the back pressure chamber. Guidance (C) an outlet pressure of a check valve is provided between an outer peripheral portion of the seat valve portion that slides with the spool and a rear portion of the seat valve portion facing the end portion of the piston portion. (D) a third oil passage is provided in the spool to allow the back pressure chamber to communicate with the tank port by one-way operation of the spool and to shut off the communication by operating the spool in the reverse direction. Directional control valve having a regeneration circuit. 2. A directional control valve having a regeneration circuit according to claim 1, wherein a seat diameter of a seat valve portion of said valve body is d1,
When the diameter of the baby piston portion of the piston portion is d2 and the diameter of the outer peripheral portion of the seat valve portion is d3, d1 <d
3. A directional control valve having a regeneration circuit, wherein d2 <d1.