CN108953262B

CN108953262B - Hydraulic valve capable of being controlled by micro motion, hydraulic control system and engineering machinery

Info

Publication number: CN108953262B
Application number: CN201810772519.XA
Authority: CN
Inventors: 潘文华; 林伟; 苏洪昌
Original assignee: CHANGDE ZHONGLIAN ZHONGKE HYDRAULIC Co Ltd
Current assignee: CHANGDE ZHONGLIAN ZHONGKE HYDRAULIC Co Ltd
Priority date: 2018-07-13
Filing date: 2018-07-13
Publication date: 2020-01-31
Anticipated expiration: 2038-07-13
Also published as: CN108953262A

Abstract

The invention relates to the field of hydraulic control, and discloses micro-controllable hydraulic valves, a hydraulic control system and engineering machinery, wherein each hydraulic valve comprises a valve body (1) and a valve rod (2) with a valve rod inner cavity, a one-way valve core (3a, 3b) is installed in each valve rod inner cavity, each one-way valve core divides each valve rod inner cavity into a forward oil cavity (211) capable of being communicated with oil ports of the valve body and a reverse oil cavity (212) provided with a return spring (4), each valve rod (2) at least has a micro-control position and a quick-control position, and in each micro-control position, at least forward oil cavities corresponding to the one-way valve cores are communicated to the other oil ports of the valve body through the reverse oil cavity in a throttling mode when each one-way valve core is located at the opening position.

Description

Hydraulic valve capable of being controlled by micro motion, hydraulic control system and engineering machinery

Technical Field

The invention relates to the field of hydraulic control, in particular to hydraulic valves capable of being controlled finely, and further relates to hydraulic control systems with the hydraulic valves and engineering machinery with the hydraulic control systems.

Background

The smoothness of the operation action (e.g. rotation) of a construction machine such as a truck crane is an important factor in consideration of the handling performance thereof. At present, an integrated rotary control valve used by a medium-and-small-tonnage truck crane usually adopts a bypass throttling design, and the flow of hydraulic oil entering a motor changes along with the change of load when micro-motion operation is executed, so that the motion speed is unstable when actions such as rotation and the like are executed.

Disclosure of Invention

The invention aims to overcome the technical problem of unstable movement speed when a hydraulic control system executes inching operation in the prior art, and provides inching-controllable hydraulic valves which can control a hydraulic actuating element to stably execute inching operation and have the advantages of compact structure, wide application range of and the like.

In order to achieve the above purpose, the invention provides inching-controllable hydraulic valve in , comprising a valve body with a plurality of oil ports and a valve rod arranged in the valve body in a sliding manner, wherein a valve rod inner cavity is arranged in the valve rod, a one-way valve seat is formed in the valve rod inner cavity and is provided with a one-way valve core, the one-way valve core divides the valve rod inner cavity into a forward oil cavity capable of being communicated with oil ports of the valve body and a reverse oil cavity provided with a return spring, the return spring tends to keep the one-way valve core at a closed position engaged with the one-way valve seat, and the one-way valve core can move from the closed position to an open position under the action of oil pressure in the forward oil cavity.

Preferably, an th orifice for throttling communication between the forward oil chamber and the reverse oil chamber is formed on the check valve core, an oil inlet hole and an oil outlet hole are formed on the valve rod, the oil inlet hole extends from the forward oil chamber and communicates the forward oil chamber to the oil ports of the valve body at the inching control position and the inching control position, and the oil outlet hole communicates to the forward oil chamber when the check valve core is at the open position and selectively communicates to the oil ports of the valve body or is closed along with sliding of the valve rod.

Preferably, the valve rod is formed with a plurality of oil inlet holes radially distributed to enable the positive pressure oil chamber to communicate with the oil ports of the valve body at different sliding positions.

Preferably, a second orifice is formed in the check valve core for throttling communication between the reverse oil chamber and another oil ports of the valve body.

Preferably, the valve rod is formed with an oil return hole extending from the reverse oil chamber, the oil return hole having a flare at an end near the check valve spool to be able to remain opposite to the second orifice at different movement positions of the check valve spool.

Preferably, the plurality of oil ports of the valve body include an oil inlet, an oil return port, a th working oil port and a second working oil port, the valve rod inner cavity includes a left valve rod inner cavity and a right valve rod inner cavity which are symmetrically arranged in the valve rod and respectively and correspondingly provided with a left check valve core and a right check valve core, and the valve rod has a middle position, a left micro-motion control position, a right micro-motion control position, a left quick-motion control position and a right quick-motion control position.

Preferably, at the left inching control position or the right inching control position, the oil inlet is communicated to the forward oil cavity of the left valve rod inner cavity and directly communicated to the th working oil port when the left check valve core is at the open position, and the second working oil port is communicated to the forward oil cavity of the right valve rod inner cavity and is communicated to the oil return port through the reverse oil cavity in the right valve rod inner cavity in a throttling manner when the right check valve core is at the open position.

Preferably, two ends of the valve rod are respectively provided with a plug which is detachably connected with the left valve rod inner cavity or the right valve rod inner cavity in a sealing mode, the end of the return spring abuts against the plug to bias the one-way valve core to the closed position at the other end end, and/or at least end of the valve rod is provided with a pilot control oil cavity for driving the valve rod to slide.

A second aspect of the invention provides a hydraulic control system including a micro-controllably hydraulic valve as described above.

A third aspect of the invention provides work machines comprising the hydraulic control system.

In addition, because the unidirectional valve core is integrated in the valve rod, the flow of the hydraulic oil is stable by utilizing the damping effect formed by the unidirectional valve core, the overlarge volume of the hydraulic valve is avoided, and the hydraulic valve has the advantages of compact structure, wide application range and the like.

Drawings

FIG. 1 is a schematic diagram of preferred embodiments of a hydraulic control system according to the invention;

FIG. 2 is a schematic cross-sectional illustration of a micro-controllable hydraulic valve used in the hydraulic control system of FIG. 1;

FIG. 3 is a schematic cross-sectional view of the micro-controllable hydraulic valve of FIG. 2 in a left micro-motion control position;

FIG. 4 is a schematic cross-sectional view of the micro-controllable hydraulic valve of FIG. 2 in a left quick control position.

Description of the reference numerals

The hydraulic control valve comprises a valve body 1, a valve rod 2, a valve rod 21a, a left valve rod inner cavity 21b, a right valve rod inner cavity 211, a forward oil cavity 212, a reverse oil cavity 22, a one-way valve seat 22, an oil inlet hole 23, an oil return hole 24, an oil outlet hole 25, a 241-flaring hole, a left one-way valve core 3a, a right one-way valve core 3b, an th damping hole 31, a second damping hole 32, a return spring 4, a plug 5, a left pilot control oil cavity 6a, a right pilot control oil cavity 6b, a left end cover 7a, a right end cover 7b, a sealing ring 8, a middle position spring 9, a th spring support 11a, a second spring support 11b and a motor 12.

Detailed Description

The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

In the present invention, the terms "upper, lower, left, right" used in an orientation word such as "upper, lower, left, right" generally refer to upper, lower, left, right with reference to the drawings, and "inner, outer" refer to inner, outer with respect to the profile of each part itself, in the present invention, the terms "", "second", etc. are used only to distinguish the different parts or structures in parallel, which do not represent the difference in the structural form thereof, for example, the " working fluid port", "second working fluid port" described later are used in the embodiment to correspond to the two fluid ports connected to the motor, respectively, and along with the directional control of the hydraulic valve of the present invention, they may be selectively communicated with the fluid inlet path or the fluid return path of the hydraulic control system (through the fluid inlet and fluid return ports on the valve body), thereby achieving the forward and reverse rotation of the motor, the " working fluid port", "second working fluid port" may be identical in the structural form, and also, the left and right check spools 3a may be symmetrically disposed in the valve stem, and the structures thereof may be identical.

For the purpose of clearly understanding the technical solution of the present invention, the basic principle and the preferred structure of the inching-controllable hydraulic valve of the present invention will be described below by taking kinds of directional control valves applied in a hydraulic control system as an example, on the basis of which the key technical concept of the present invention can be relatively easily understood, and further steps can be taken to obtain other embodiments covered in the scope of the appended claims.

Referring first to fig. 1, hydraulic control system applicable to a swing mechanism of an automobile crane, including a motor 12 for driving a turntable to swing, two working oil chambers of the motor 12 being connected in a hydraulic circuit to enable rotation by pumping and returning of hydraulic oil, in which a shuttle valve is a part for performing a shuttle operation thereof, having an oil inlet P, an oil return T, a working oil port a, and a second working oil port b. it is understood that although reference numerals of the respective oil ports are placed on their connecting oil paths in fig. 1 for ease of understanding, the positions of the reference numerals are essentially identical to those of the corresponding oil ports in fig. 2 to 4 described later.

The oil inlet P of the reversing valve can be connected with an oil inlet passage provided with an oil pump (not shown), the oil return port T can be connected to an oil tank, the th working oil port A and the second working oil port B are respectively connected to two working oil cavities of the motor 12, therefore, the motor 12 can be controlled to rotate forwards, reversely or stop by the reversing operation of the reversing valve, and the reversing operation of the reversing valve can be realized by the pressure change in the left pilot control oil port a and the right pilot control oil port B of which the pressure is controlled by the operating handle.

According to the hydraulic control system shown in fig. 1, in order to control the motor 12 to stably perform the inching operation, unlike the three-position directional control valve used in the conventional art, the present invention employs a five-position directional control valve having two inching control positions, i.e., in the case of the left inching control position I in fig. 1, the motor 12 can be stably rotated in rotational directions, which effectively prevents the change of the operating speed according to the load, and in the case of the left quick control position II, the motor 12 is rapidly rotated in the rotational direction, it can be understood in conjunction with the following description that, although the schematic diagram shown in fig. 1 divides the direction change position of the directional control valve into five positions, for example, the direction change position of the left inching control position I may not be limited to a certain fixed position at the time of the valve stem operation of the hydraulic valve, but may be a certain region, in the range of the valve stem movement during the switching from the middle position to the left quick control position II, the output flow of the motor 12 is substantially constant due to be not changed according to the valve stem movement and the change of the load, when the valve stem 2 reaches the control position, the one-way control valve stem 2, the hydraulic oil flows through the valve stem 12, and the one-way flow rate of the one-way flow of the one-way directional control valve stem is increased, and the hydraulic oil flows through the valve port of the.

The structure of the switching valve used in the hydraulic control system is described below, which is preferred type inching controllable hydraulic valve, can realize inching control in both rotation directions of the motor 12, has compact structure and wide application range , wherein, because the inching control part of the switching valve has symmetrical structure and completely same operating principle, when the control motor 12 inching in different directions, the sliding displacement of the valve rod and the action mechanism of the one-way valve core are the same, therefore, the switching valve is only described in the rotation control mode towards side.

Referring to fig. 2 to 4, the reversing valve includes a valve body 1, a valve stem 2, pairs of check valve cores (a left check valve core 3a and a right check valve core 3b), a plug 5, a left end cap 7a, a right end cap 7b, etc. the valve stem 2 is slidably disposed in the valve body 1 and has a left valve stem inner cavity 21a and a right valve stem inner cavity 21b in which check valve seats 22 are formed to be engaged with the left check valve core 3a and the right check valve core 3b, respectively, whereby the left valve stem inner cavity 21a and the right valve stem inner cavity 21b are partitioned into a forward oil chamber 211 and a reverse oil chamber 212, respectively.

In the sliding process of the valve rod 2, the forward oil cavity 211 can be communicated to oil ports on the valve body 1. in the left inching control position shown in fig. 3, the forward oil cavity 211 of the left valve rod inner cavity 21a is communicated to the oil inlet P, the forward oil cavity 211 of the right valve rod inner cavity 21b is communicated to the second working oil port b, a return spring 4 is arranged in the reverse oil cavity 212, and the return spring 4 acts on the corresponding left one-way valve core 3a and the right one-way valve core 3b to keep the closed positions engaged with the one-way valve seat 22, when oil ports on the valve body 1 introduce pressure oil to the communicated forward oil cavity 211, the left one-way valve core 3a and the right one-way valve core 3b can be moved from the closed positions to the open positions by overcoming the elastic force of the return spring 4.

As shown in fig. 2, the valve stem 2 of the reversing valve is held in the neutral position, at which time the oil inlet P is connected to the oil return T and is blocked from the th working port a and the second working port B, the hydraulic actuator remains stationary because no pressurized oil is delivered to the hydraulic actuator (e.g., the motor 12 in fig. 1).

The left pilot control oil port a in fig. 1 is connected with a pressure oil source by operating the handle, so that pressure is built in the left pilot control oil cavity 6a of the reversing valve, and the drive valve rod 2 slides rightwards to the left inching control position shown in fig. 3. Naturally, the movement of the valve rod 2 may be driven in other ways, such as electrically controlled reversing, manually reversing, etc.

As shown in fig. 3, when the valve stem 2 of the reversing valve moves to the left inching control position, the oil inlet P communicates with the forward oil chamber 211 of the left valve stem cavity 21a through the oil inlet hole 23 on the valve stem 2, and the oil pressure formed in the forward oil chamber 211 opens the left check valve body 3a, thereby communicating with the working port a through the oil outlet hole 25 and , so that the pressure oil delivered by the oil inlet path is pumped to oil chambers of the motor 12.

Meanwhile, the second working oil port B is communicated to the forward oil cavity 211 of the right valve rod inner cavity 21B through another oil inlet holes 23 on the valve rod 2, hydraulic oil discharged from the motor 12 is pressurized in the forward oil cavity 211 to open the right one-way valve core 3B, however, the oil outlet hole 25 on the side is sealed at the moment and is not communicated with any oil port, the hydraulic oil can only enter the reverse oil cavity 212 provided with the reset spring 4 through the damping hole 31 on the right one-way valve core 3B, and then enters the oil return port T through the second damping hole 32 and the oil return hole 24 on the valve rod 2. due to the throttling action of the damping hole 31 and the second damping hole 32, the hydraulic oil of the motor 12 can stably flow back, the shaking phenomenon caused by load change is effectively avoided, and the stable micro-motion control is realized.

In this process, the rotation speed ω of the motor 12 is determined by the flow rate Qt from the second working port B to the return port T, and can be expressed as:

ω ═ f (qt) … … … … … … … … formula [1]

In the inching control position, the right one-way valve core 3b is stressed in balance, and under the condition of neglecting hydraulic force and friction force, the stress balance relationship is as follows:

PB S1-Pt S2 ═ K (X0+ X) … … … formula [2]

Where PB is the oil pressure of the second hydraulic port B and the forward oil chamber 211 communicated therewith, Pt is the oil pressure of the reverse oil chamber 212 provided with the return spring 4, and S1 and S2 are the effective acting areas of the two oil pressures, respectively. K and X0 are the stiffness and precompression amount of the return spring 4, and X is the displacement of the right check spool 3 b. The effective acting area of the right check valve body 3b is denoted as S, and in the open state, S1 is S2 is S; note that the oil pressure difference between the forward oil chamber 211 and the reverse oil chamber 212 is Δ P — PB, and can be obtained by equation [2 ]:

Δ P ═ K (X0+ X)/S … … … … … formula [3]

Since the stiffness of the return spring 4 is small and the precompression amount is large, the displacement of the right check valve element 3b at the time of opening is relatively small, and thus Δ P is approximately constant. According to the basic hydraulic principle, the flow rate Qt from the second working port B to the return port T can be expressed as:

qm (Δ P, S3) … … … … … … formula [4]

S3 is the flow area of the damper hole 31, Qt is also approximately constant, i.e., the flow rate Qt from the second port B to the return port T remains substantially constant, and its magnitude is only related to the flow area of the damper hole 31. in conjunction with equations [1] to [4], the rotational speed ω of the motor 12 is substantially constant and is not affected by other changing factors (e.g., load changes), thereby achieving smooth inching.

The micro-motion control principle of the micro-motion controllable hydraulic valve in the preferred embodiment of the invention is analyzed by a qualitative and quantitative analysis method, so that the hydraulic actuating element of the motor 12 can stably execute micro-motion operation by utilizing the hydraulic valve in the invention, and the change of the action speed caused by load change is reduced or avoided.

Referring to fig. 4, when the valve stem 2 of the reversing valve slides from the left inching control position to the left quick control position, the oil inlet P is still communicated to the forward oil chamber 211 of the left valve stem cavity 21a through the oil inlet hole 23 on the valve stem 2, and the oil pressure formed in the forward oil chamber 211 opens the left check valve core 3a, and is communicated to the th working oil port a through the oil outlet hole 25 to supply oil to the working oil chamber of the motor 12.

At this time, the oil outlet hole 25 on the right side of the valve rod 2 is communicated with the oil return port T, therefore, the hydraulic oil discharged from the motor 12 enters the forward oil chamber 211 of the right valve rod inner chamber 21B through the second working oil port B and another oil inlet holes 23 on the valve rod 2 to open the right check valve core 3B, and the hydraulic oil in the forward oil chamber 211 of the right valve rod inner chamber 21B directly enters the oil return port T through the oil outlet hole 25 to realize oil return, meanwhile, the hydraulic oil in the reverse oil chamber 212 of the right check valve core 3B can enter the oil return port T through the damping hole 31 or the second damping hole 32 to realize pressure relief, so that the right check valve core 3B reaches the maximum opening, and the motor 12 can realize quick action with the maximum oil return flow.

For example, when only micro-motions are required, the reversing valve may be provided with a one-way spool only on the side and achieve direct communication and throttling communication between the oil ports by switching between the micro-motion control position and the quick-motion control position, thereby performing the micro-motions, while in the other motion directions, the existing structure may be maintained to perform the motions with a constant flow area.

With continued reference to fig. 2 to 4, in the fine control position and the fast control position, as the valve rod 2 slides, the oil inlet P and the second control oil port B are both communicated to the corresponding positive pressure oil chamber 211 through the oil inlet hole 23. to this end, in preferred embodiments, a plurality of oil inlet holes 23 distributed along the radial direction may be formed on the valve rod 2, so that the forward oil chamber 211 corresponding to the one-way valve element is communicated with the same oil ports on the valve body 1 at different sliding positions of the valve rod 2, so that external hydraulic oil can enter the corresponding forward oil chamber 211 at both the fine control position and the fast control position.

Since the check spool needs to move in the valve rod 2 and the second orifice 32 is kept in communication with the corresponding oil return hole 24 of the valve rod 2 in the area corresponding to the fine control position without being affected by the opening degree of the check spool, a flared opening 241 may be formed at end of the oil return hole 24 close to the corresponding check spool to be able to keep opposite to the second orifice 32 at different moving positions of the check spool.

For example, for convenience of maintenance or assembly, a detachably connected plug 5 may be respectively provided at both ends of the valve stem 2, the plug 5 may be, for example, screwed to the rear ends of the corresponding left and right check valve spools 3a and 3b and support ends of the return spring 4, wherein a sealing ring 8 may be provided between the plug 5 and the corresponding check valve spool to prevent leakage of hydraulic oil.

Further, as described above, the operation of the valve stem 2 can be pilot-controlled by oil pressure, and for this purpose, a left pilot-controlled oil chamber 6a and a right pilot-controlled oil chamber 6b can be formed. In the illustrated embodiment, both ends of the valve body 1 are bolted with a left end cap 7a and a right end cap 7b, and a left pilot-controlled oil chamber 6a and a right pilot-controlled oil chamber 6b are respectively located therein to be able to apply oil pressure to the corresponding plugs 5, thereby driving the valve rod 2 to slide.

In particular, as shown in FIG. 2, a th spring bracket 11a and a second spring bracket 11b are arranged in the right end cover 7b and support the neutral spring 9 therebetween, ends of the th spring bracket 11a and the second spring bracket 11b, which are far away from each other, abut against the valve body 1 and the right end cover 7b, respectively, whereby, when no pilot pressure oil acts, the neutral spring 9 presses the th spring bracket 11a and the second spring bracket 11b in a direction away from each other to hold the valve stem 2 in the neutral position shown in FIG. 2.

When the left pilot control oil chamber 6a is filled with pressure oil, the valve rod 2 is driven to slide to the right, as shown in fig. 3, the th spring bracket 11a is driven to move to the right by the valve rod 2 and compresses the middle spring 9 until the valve rod 2 slides to the required micro-motion control position.

The oil pressure in the left pilot control oil cavity 6a is increased, the valve rod 2 slides to the right in steps, so that the spring support 11a continuously slides to the right until contacting with the second spring support 11b and reaching the limit movement position, as shown in fig. 4, at this time, the valve rod 2 slides to the right to the limit position, the opening degree of the valve port is maximum, and the quick action of the hydraulic actuator is realized.

The hydraulic valve which can be controlled in a micro mode and is provided by the invention can be applied to a hydraulic control system to realize the micro control of a hydraulic actuating element and improve the micro stability of the hydraulic actuating element. The hydraulic control system can be applied to various engineering machines such as automobile cranes, excavators and the like, and can effectively improve the control performance of the hydraulic control system.

The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, numerous simple modifications can be made to the technical solution of the invention, including combinations of the individual specific technical features in any suitable way. The invention is not described in detail in order to avoid unnecessary repetition. Such simple modifications and combinations should be considered within the scope of the present disclosure as well.

Claims

A micro-controllable hydraulic valve, comprising a valve body (1) with a plurality of oil ports and a valve rod (2) arranged in the valve body (1) in a sliding way, characterized in that a valve rod inner cavity (21a, 21b) is arranged in the valve rod (2), a check valve seat (22) is formed in the valve rod inner cavity (21a, 21b) and a check valve core (3a, 3b) is arranged, the check valve core (3a, 3b) divides the valve rod inner cavity (21a, 21b) into a forward oil cavity (211) which can be communicated with oil ports of the valve body (1) and a reverse oil cavity (212) which is provided with a return spring (4), the return spring (4) tends to keep the check valve core (3a, 3b) at a closed position which is jointed with the check valve seat (22), the check valve core (3a, 3b) can move from the closed position to an open position under the action of oil pressure in the forward oil cavity (211),

the valve rod (2) is at least provided with a micro-motion control position and a quick-motion control position, wherein in the quick-motion control position, the forward oil cavity (211) is directly communicated to another oil ports of the valve body (1) when the one-way valve cores (3a, 3b) are in the opening position, and in the micro-motion control position, the forward oil cavity (211) corresponding to at least one-way valve cores (3a, 3b) is communicated to another oil ports of the valve body (1) through the reverse oil cavity (212) in a throttling mode when the one-way valve cores (3a, 3b) are in the opening position.
2. The inching-controllable hydraulic valve according to claim 1, wherein the check spool (3a, 3b) is formed with a damping hole (31) for throttling communication between the forward oil chamber (211) and the reverse oil chamber (212), the valve stem (2) is formed with an oil inlet hole (23) and an oil outlet hole (25), the oil inlet hole (23) extends from the forward oil chamber (211) and communicates the forward oil chamber (211) to the oil ports of the valve body (1) at the inching control position and the snap control position, and the oil outlet hole (25) communicates to the forward oil chamber (211) when the check spool (3a, 3b) is at the open position and selectively communicates to the oil ports of the valve body (1) or is closed as the valve stem (2) slides.
3. A micro-controllable hydraulic valve according to claim 2, characterized in that the valve stem (2) has formed thereon a plurality of oil inlet holes (23) distributed radially to enable the forward oil chamber (211) to communicate with oil ports of the valve body (1) at different sliding positions.
4. The inching-controllable hydraulic valve according to claim 1, characterized in that the check valve spool (3a, 3b) is formed with a second orifice (32) for throttling communication between the reverse oil chamber (212) and the other oil ports of the valve body (1).
5. The micro-controllable hydraulic valve according to claim 4, characterized in that the valve rod (2) is formed with an oil return hole (24) extending from the reverse oil chamber (212), the oil return hole (24) having a flared opening (241) at an end near the check valve spool (3a, 3b) to be able to remain opposite to the second orifice (32) at different movement positions of the check valve spool (3a, 3 b).
6. The micro-controllable hydraulic valve according to any of claims 1-5, wherein the plurality of oil ports of the valve body (1) include an oil inlet (P), an oil return port (T), a working oil port (A) and a second working oil port (B), the valve rod cavities (21a, 21B) include a left valve rod cavity (21a) and a right valve rod cavity (21B) which are symmetrically disposed in the valve rod (2) and respectively and correspondingly installed with a left check valve core (3a) and a right check valve core (3B), and the valve rod (2) has a middle position, a left micro-motion control position, a right micro-motion control position, a left quick-motion control position and a right quick-motion control position.
7. The micro-controllable hydraulic valve according to claim 6, wherein in the left micro-motion control position or the right micro-motion control position, the oil inlet (P) is connected to the forward oil chamber (211) of the left valve stem cavity (21a) and directly to the th working oil port (A) when the left check valve spool (3a) is in the open position, and the second working oil port (B) is connected to the forward oil chamber (211) of the right valve stem cavity (21B) and throttled to the oil return port (T) through the reverse oil chamber (212) in the right valve stem cavity (21B) when the right check valve spool (3B) is in the open position.
8. A micro-controllable hydraulic valve according to claim 6, characterized in that both ends of the valve stem (2) are provided with plugs (5) detachably and sealingly connected with the left or right stem cavities (21a, 21b), respectively, the end of the return spring (4) abuts against the plugs (5) to bias the one-way valve element (3a, 3b) to the closed position at the other end, and/or at least end of the valve stem (2) is provided with a pilot control oil cavity (6a, 6b) for driving the valve stem (2) to slide.
A hydraulic control system of the kind 9, , comprising a micro-controllable hydraulic valve according to any of claims 1 to 8 through .
10, a working machine, characterized in that the working machine comprises a hydraulic control system according to claim 9.