CN213451075U

CN213451075U - Double-loop hydraulic system

Info

Publication number: CN213451075U
Application number: CN202022115607.8U
Authority: CN
Inventors: 姜伟; 姜洪; 王震山; 王清送; 张夕航; 史浙安; 陈钊汶; 郑志雨; 张赛
Original assignee: Shanghai Shengbang Hydraulic Co ltd; Xuzhou Shengbang Machinery Co Ltd; Zhejiang Sunbun Technology Co Ltd; Sunbun Group Co Ltd
Current assignee: Shanghai Shengbang Hydraulic Co ltd; Xuzhou Shengbang Machinery Co Ltd; Zhejiang Sunbun Technology Co Ltd; Sunbun Group Co Ltd
Priority date: 2020-09-24
Filing date: 2020-09-24
Publication date: 2021-06-15
Anticipated expiration: 2030-09-24

Abstract

A dual circuit hydraulic system. The problems of complex structure and difficult confluence of the existing double-pump or multi-pump hydraulic system are solved. The hydraulic oil supply device comprises a first main oil inlet, a second main oil inlet, a first working oil port, a first main reversing valve, a first auxiliary reversing valve, a second working oil port, a second main reversing valve and a second auxiliary reversing valve, wherein the first main oil inlet is connected with the oil inlet of the first main reversing valve, the oil outlet of the first main reversing valve is connected with the oil inlet of a first compensator, the second main oil inlet is connected with the oil inlet of the first auxiliary reversing valve, and pressure oil at the oil outlet of the first compensator and pressure oil at the oil outlet of the first auxiliary reversing valve are connected with the first working oil port after passing through the first main reversing valve. The utility model discloses realize hydraulic system's rational distribution, to compound action promote to some extent simultaneously look after the energy consumption and generate heat promptly. The utility model discloses simple structure still has, convenient assembling, and the action is reliable, advantages such as long service life.

Description

Double-loop hydraulic system

Technical Field

The utility model relates to a hydraulic system, concretely relates to two return circuit hydraulic system.

Background

The hydraulic system is generally divided into a single pump system and a multi-pump system, the single pump system realizes all actions by only one working oil pump, and the multi-pump system realizes all actions by two or more oil pumps. The single-pump system has the advantages of low cost, simple and reliable system, but is difficult to realize simultaneous work of a plurality of actions, and even the plurality of actions can be realized by the forced throttling of the low-pressure side, the single-pump system has the defects of high pressure loss and large heat productivity; the double-pump or multi-pump system has the advantages of being capable of well realizing multi-action simultaneous movement and relatively low in energy consumption, but has the problems of complex system and high cost.

The common single pump system comprises a series/parallel loop of an open center system, a compensation system before a valve of a closed center, a compensation system after the valve and the like; the double-pump and multi-pump systems are commonly used for excavating machinery and are provided with a double-loop hydraulic system with complex logic relation and the like. The confluence of the existing double-pump and multi-pump hydraulic systems is usually realized through a confluence valve, the control logic on the whole is complex, the pipeline arrangement is complex and huge, and the confluence is unreliable, and the action of low pressure needs to be forced to be boosted to be combined with high pressure by compensation during the combined action to realize the combined action, so that extra additional pressure loss and heat generation are brought in the compensation link, and the energy consumption is high.

SUMMERY OF THE UTILITY MODEL

For solving the current double pump or the multiple pump hydraulic system structure complicacy among the background art, the problem of confluence difficulty, the utility model provides a two return circuit hydraulic system.

The technical scheme of the utility model is that: a double-loop hydraulic system comprises a first main oil inlet, a second main oil inlet, a first working group and a second working group, the first working group comprises at least one first working connection, the first working connection comprises a first working oil port, a first main reversing valve and a first auxiliary reversing valve, the second working group comprises at least one second working connection, the second working connection comprises a second working oil port, a second main reversing valve and a second auxiliary reversing valve, the first main oil inlet is connected with the oil inlet of the first main reversing valve, the oil outlet of the first main reversing valve is connected with the oil inlet of the first compensator, and the pressure oil at the oil outlet of the first compensator and the pressure oil at the oil outlet of the first auxiliary reversing valve are connected with the first working oil port after passing through the first main reversing valve.

As an improvement of the utility model, the main oil inlet of second link to each other with the oil inlet of the main reversing valve of second, the oil-out of the main reversing valve of second link to each other with the oil inlet of second compensator, the oil inlet of the supplementary reversing valve of first main oil inlet and second link to each other, the pressure oil of the second compensator oil outlet department links to each other with the second working fluid port after the pressure oil of the supplementary reversing valve oil outlet department of second all passes through the main reversing valve of second.

As a further improvement, the first compensator include first control chamber and first spring chamber, the pressure oil of first compensator oil-out links to each other with first feedback oil circuit, the opening of the pressure oil of first compensator of pressure oil and the elasticity in first spring chamber, first feedback oil circuit of first compensator oil inlet department was chosen to first control chamber mutually supported control.

As a further improvement, the first main throttle orifice is provided between the oil inlet of the first main directional control valve and the oil outlet of the first main directional control valve, the pressure oil of the oil outlet of the first compensator is connected with the first feedback oil path through the first check valve, and the first feedback oil path is connected with the first spring cavity of the first compensator in different first work links.

As a further improvement of the present invention, the pilot oil circuit is further provided with a pilot oil circuit for driving the first main directional control valve and the second main directional control valve to operate, the pilot oil circuit is connected to the control chamber of the first main directional control valve through the first pilot control valve, the pilot oil circuit is connected to the control chamber of the second main directional control valve through the second pilot control valve, the first pilot control valve and the second pilot control valve respectively have the first position when being installed and the second position for opening the pilot oil to operate through the first main directional control valve and the second main directional control valve respectively.

As a further improvement, the first auxiliary reversing valve has a first position when installing and a second position for opening the pressure oil of the main oil inlet of the second to pass through, and the first auxiliary reversing valve is an electric control reversing valve.

As the utility model discloses a further improvement still includes the first guide's oil circuit that is used for driving first main directional control valve action, first main directional control valve on be equipped with first guide's break-make return circuit, second main directional control valve on be equipped with second guide's break-make return circuit, first guide's oil circuit pass through second guide's break-make return circuit on the second main directional control valve and should ally oneself with first supplementary switching-over valve control chamber on link to each other.

As a further improvement, the system further comprises a second pilot oil path for driving the second main directional control valve to act, the second pilot oil path is connected with a second auxiliary directional control valve control cavity on the first main directional control valve through a first pilot on-off loop, and the first pilot oil path and the second pilot oil path are both provided with shuttle valves.

As the utility model discloses a further improvement, first guide's break-make return circuit and second guide's break-make return circuit are realized first guide's oil circuit, second guide's oil circuit break-make function by the valve rod of the first main change valve of its place antithetical couplet, the valve rod drive switching-over of second main change valve respectively.

As a further improvement, the pilot operated directional control valve of first supplementary switching-over valve for having the on-off formula or for the valve rod is the pilot operated proportional control valve of proportional formula, first supplementary switching-over valve for the pilot operated directional control valve and by this first guide's oil circuit drive of antithetical couplet its action.

The beneficial effects of the utility model are that, through the mode in two return circuits, realize hydraulic system's rational distribution, to compound action promoting to some extent promptly and look after the energy consumption simultaneously and generate heat. The utility model discloses simple structure still has, convenient assembling, and the action is reliable, advantages such as long service life.

Drawings

Fig. 1 is a hydraulic principle schematic diagram of a first embodiment of the present invention.

Fig. 2 is a schematic view of a hydraulic principle of the second embodiment of the present invention.

Fig. 3 is an enlarged schematic view of the first main directional control valve 32 of fig. 1.

Fig. 4 is an enlarged schematic view at I of fig. 2.

Fig. 5 is a schematic view of the first auxiliary direction valve 33 of fig. 2.

In the figure, 1, a first working group; 2. a second workgroup; 3. a first working unit; 31. a first working oil port; 32. a first main directional control valve; 33. a first auxiliary directional control valve; 331. an auxiliary choke; 332. a load check valve; 333. a one-way valve; 34. a first primary orifice; 35. a first pilot on-off loop; 36. a second pilot on-off loop; 4. a second working unit; 41. a second working oil port; 42. a second main directional control valve; 43. a second auxiliary directional control valve; 5. a first compensator; 6. a first check valve; 7. a pilot oil path; 71. a first pilot control valve; 72. a second pilot control valve; 73. a first pilot oil passage; 74. a second pilot oil passage; 8. a shuttle valve; 9. a second compensator; p1, a first main oil inlet; p2, a second main oil inlet; LS1, first feedback oil path.

Detailed Description

The embodiments of the present invention will be further explained with reference to the accompanying drawings:

referring to fig. 1 and fig. 2-5, a dual-circuit hydraulic system includes a first main oil inlet P1, a second main oil inlet P2, a first working group 1 and a second working group 2, where the first working group includes at least one first working link 3, the first working link includes a first working oil port 31, a first main directional control valve 32 and a first auxiliary directional control valve 33, the second working group includes at least one second working link 4, the second working link includes a second working oil port 41, a second main directional control valve 42 and a second auxiliary directional control valve 43, the first main oil inlet is connected to an oil inlet of the first main directional control valve, an oil outlet of the first main directional control valve is connected to an oil inlet of a first compensator 5, the second main oil inlet is connected to an oil inlet of the first auxiliary directional control valve, and pressure oil at an oil outlet of the first compensator and pressure oil at an oil outlet of the first auxiliary directional control valve are connected to the first working oil port through the first main directional control valve And (4) connecting. Specifically, the second main oil inlet is connected with an oil inlet of a second main reversing valve, an oil outlet of the second main reversing valve is connected with an oil inlet of a second compensator 9, the first main oil inlet is connected with an oil inlet of a second auxiliary reversing valve, and pressure oil at an oil outlet of the second compensator and pressure oil at an oil outlet of the second auxiliary reversing valve are connected with a second working oil port after passing through the second main reversing valve. The beneficial effects of the utility model are that, through the mode in two return circuits, realize hydraulic system's rational distribution, to compound action promoting to some extent promptly and look after the energy consumption simultaneously and generate heat. The utility model discloses simple structure still has, convenient assembling, and the action is reliable, advantages such as long service life. In particular, the second working pair and the first working pair may be similar or identical. More specifically speaking, the utility model discloses a P1 is first workgroup fuel feeding, and P2 realizes the two return circuits fuel feeding of double pump for the fuel feeding of second workgroup. When the composite action is carried out, the auxiliary reversing valve is adjusted, so that the second main oil inlet can supply oil for the first working oil port, the first main oil inlet can supply oil for the second working oil port, the reliable confluence is realized, and the control of the composite action is reliable. Through the setting of first main switching-over valve, second main switching-over valve, first supplementary switching-over valve and second supplementary switching-over valve, realize quick reliable confluence, and the energy consumption is low. During specific composite action, the flow is converged behind the main throttling port, so that the energy consumption is low and the environment is protected. Meanwhile, a first compensator 5 and a second compensator 9 are respectively added to the first working connection and the second working connection, the compensators are arranged behind the main reversing valve to realize post-valve compensation, the function of the post-valve compensator is mainly to improve the composite action harmony of the oil supply state of the left double-connection or the right double-connection single pump, and at the moment, the composite action can also keep better action harmony even if the output flow of the oil pump is less than the flow required by the two actions.

The first working group comprises two, three or four first working couples. Specifically, the second working group comprises one, two, three or four second working groups. The structure enables the system to supply oil to two to eight working devices (the working devices are execution elements, and working oil ports such as A1A2A3A4 … … and the like in a schematic diagram), and the working devices can realize oil supply to the working devices by one pump or two pumps, and the hydraulic system is usually a double-pump system and can be extended to three-pump and four-pump oil supply. This patent describes a typical four-operation device (i.e., A1A2A3a4 four working ports for output, which are used to drive four actuators, such as cylinders and motors). When one of the pumps supplies oil to the pump, the oil supply can be realized only by the action of the main reversing valve; when the other pump supplies oil to the other pump, the other pump needs to be supplied with oil through the auxiliary reversing valve. Two of the four-linkage working mechanism are arranged on the same side, the P1 supplies oil to the A1B1/A2B2 working device through the first main reversing valve of the A1B1/A2B2 linkage, and supplies oil to the A3B3/A4B4 through the second auxiliary reversing valve, at the moment, the valve rod of the first main reversing valve is provided with a first main throttling port 34, and the second auxiliary reversing valve is provided with an auxiliary throttling port 331 serving as an auxiliary throttling port. The P2 oil supply is a duplicate of the P1 oil supply. A1B1/A2B2 is arranged on one side, and A3B3/A4B4 is arranged on the other side, which is for the sake of simplicity of principle, and of course, the A1B1/A2B2/A3B3/A4B4 may be arranged crosswise. The utility model discloses in, when P1 and P2 compound action just for A1B1 fuel feeding, it sets up compensator (valve back compensation) at the oil-out of first main change valve, and be A1B1 fuel feeding after compensator P1 and P2 confluence behind first main change valve, the flow of supplementary choke just can not produce loss of pressure and generate heat at main choke, further reduce energy consumption and calorific capacity, and make two executor components all can go on according to the percentage of required flow when the product compound action, compound action is more reliable.

The first compensator 5 comprises a first control cavity and a first spring cavity, pressure oil at an oil outlet of the first compensator is connected with a first feedback oil way, and the pressure oil at an oil inlet of the first compensator, the elasticity of the first spring cavity and the pressure oil of the first feedback oil way are selected by the first control cavity to be matched with each other to control an opening of the first compensator. Specifically, a first main throttling port 34 is arranged between an oil inlet of the first main reversing valve and an oil outlet of the first main reversing valve, pressure oil at the oil outlet of the first compensator is connected with a first feedback oil path LS1 through a first one-way valve 6, and the first feedback oil path is communicated with first spring cavities of first compensators on different first working links on the first working group. The utility model discloses set up the compensator behind the first main choke of main reversing valve (variable choke behind the valve), through first compensator, the setting of second compensator, make the system have the variable throttling arrangement behind the valve, compensate its effect behind the valve and do not have what effect to work alone, he can't maintain the differential pressure around the main choke and keep unchangeable, but do beneficial to compound action (two actuating mechanisms work together), make two actuating mechanism members all can go on according to the percentage of required flow, for example A1 needs 200L, A2 needs 100L, but only can supply 150L, through pressure compensator behind the valve, can make A1 output 100L, A2 output 50L. The function of the check valve is to ensure that the highest pressure of each action pair can be picked up, for example, when A1 and A2 act simultaneously, the pressure of A1 is higher than that of A2, if the check valve is not arranged, the A1 sends oil to A2 through the LS oil way, the pressure of LS1 cannot reflect the highest pressure of the system, the establishment of the highest pressure of the system is influenced, and the action of A1 is further influenced. The function of the variable throttling device after the valve is added is mainly to improve the composite action coordination of the oil supply state of the left duplex or right duplex single pump, and at the moment, the composite action can keep better action coordination even if the output flow of the oil pump is less than the flow required by the two actions. The valve post-compensation device can realize better composite action coordination when two actions work together no matter how much flow is provided by the oil pump, and the phenomena of high-pressure action stop and low-pressure action acceleration do not occur, wherein the composite action of oil supply of one oil pump such as A1/B1 and A2/B2 or A3/B3 and A4/B4 is aimed at. The variable throttling opening behind the valve is arranged, and meanwhile, the oil outlet of the auxiliary variable throttling opening is arranged behind the variable throttling opening behind the valve, so that the pressure loss generated by the output flow of the auxiliary throttling opening on the main throttling opening and the variable throttling opening behind the valve is completely cancelled, the energy is saved, the heat is less, and the efficiency is higher.

The utility model discloses still including the pilot oil circuit 7 that is used for driving first main change valve, the action of second main change valve, pilot oil lu-tung link to each other through the control chamber of first pilot control valve 71 with first main change valve, pilot oil lu-tung link to each other through the control chamber of second pilot control valve 72 with the second main change valve, first pilot control valve, second pilot control valve first position when having the installation respectively with open the second position that is convenient for pilot oil through being used for driving first main change valve, the action of second main change valve respectively. Specifically speaking, first supplementary switching-over valve have the first position when installing and open the second position that is convenient for second main oil inlet pressure oil to pass through, first supplementary switching-over valve be automatically controlled switching-over valve. Specific theory, the utility model discloses can realize the switching-over of first main switching-over valve, second main switching-over valve, first supplementary switching-over valve and the supplementary switching-over valve of second through automatically controlled mode. For the electric control scheme, electric control is flexible, changeable and controllable, and can be controlled according to human thought, so that the electric control scheme is simple.

The utility model discloses still including the first guide's oil circuit 73 that is used for driving first main directional control valve action, first main directional control valve on be equipped with first guide break-make return circuit 35, second main directional control valve on be equipped with second guide break-make return circuit 36, first guide oil sweetgum fruit on through second main directional control valve on the second guide break-make return circuit and should ally oneself with first supplementary switching-over valve control chamber on link to each other. Specifically, the pilot oil circuit comprises a second pilot oil circuit 74 used for driving a second main reversing valve to act, the second pilot oil circuit is connected with a second auxiliary reversing valve control cavity on the second main reversing valve through a first pilot on-off circuit on the first main reversing valve, and the first pilot oil circuit and the second pilot oil circuit are both provided with shuttle valves 8. More specifically, the first pilot on-off loop and the second pilot on-off loop are driven by a valve rod of a first main reversing valve and a valve rod of a second main reversing valve of the first pilot on-off loop and the second pilot on-off loop respectively to be reversed so as to realize the on-off function of the first pilot oil path and the second pilot oil path. More specifically, the first auxiliary reversing valve is a hydraulic control reversing valve with an on-off type or a hydraulic control proportional regulating valve with a proportional type valve rod, and the first auxiliary reversing valve is a hydraulic control reversing valve and is driven to act by the first pilot oil path. More specifically, the first auxiliary reversing valve is provided with an auxiliary throttle 331 and/or a load check valve 332 and/or a check valve 333. The arrangement of the first check valve and the load check valve enables the system to pick up the highest pressure for feedback during compound action, and the situation that when one working device is high in pressure and one working device is low in pressure, the flow of the high-pressure side reversely enters the low-pressure side is avoided. The one-way valve 333 is provided to stop the pressure at the load and prevent pressure shock and pressure fluctuation caused by releasing the pressure from the high pressure side to the low pressure side if the pressure at the load is high during the composite action, so that the composite action of the product is more stable. The utility model discloses a set up first guide break-make return circuit, second guide break-make return circuit at the both ends of first main change valve, second main change valve, and realize its break-make by the main valve stem drive of this first main change valve, second main change valve that allies oneself with to when making the compound action, make an oil pump correspond an action, no longer produce the contact between another action, be independent mutually. When the connection does not act, the pilot oil of the first pilot oil path can pass through, and when the connection does any action, the pilot oil path can be cut off. For example, referring to fig. 2, 4 and 5, a motion is taken as an example, such as a1 and B1, pilot oil is led out through a shuttle valve, passes through a second pilot on-off oil path of the A3/B3 working link and then is connected in series through a second pilot on-off loop of the a4/B4 working link, and reaches a first auxiliary reversing valve control chamber of the a1/B1 working link.

When only A1/B1 works, the pilot oil of a1 and B1 controls the first main reversing valve to reverse, the oil of P1 can pass through, and the other part of the pilot oil of a1 and B1 passes through the shuttle valve and then reaches the first auxiliary reversing valve control cavity of the working connection of A1/B1 through the second pilot on-off circuit of the connection of A3/B3 and the connection of A4/B4, so that the oil of the P2 oil pump can supply oil to A1/B1.

When A1/B1 and A3/B3 or A4/B4 work together, at the moment, the second pilot oil on-off circuit is reversed along with the reversing of any one of A3/B3 and A4/B4, the oil circuit of the first auxiliary reversing valve, which controls A1/B1, of a1 and B1 is cut off, the valve rod of the first auxiliary reversing valve is reset under the action of a spring cavity spring, the circuit of the P2 oil pump supplying oil to A1/B1 is cut off, and the composite action independence under the hydraulic control is achieved. Namely, the P1 is the combined oil supply of A1/B1, and the P2 is the oil supply of A3/B3 or A4/B4.

The utility model discloses a pilot oil in each work antithetical couplet picks up the back through the shuttle valve in the liquid accuse scheme, and the pilot break-make oil return of the main oil supply work antithetical couplet of another oil pump again, if there is such pilot break-make return circuit of multichannel, then need establish ties to it, controls the auxiliary control choke of this work antithetical couplet, realizes logical: when one working unit works independently, the double pumps can be combined; when the main oil supply work of the two oil pumps or the oil pumps are connected to work together, the two oil pumps respectively supply oil for the corresponding working mechanism. The first auxiliary reversing valve and the second auxiliary reversing valve are on-off hydraulic control reversing valves or proportional hydraulic control proportional regulating valves with proportional valve rods. The first auxiliary reversing valve and the second auxiliary reversing valve can be made into a switch type or a proportional relation with the pilot oil. The proportional auxiliary reversing valve enables the product to be adjusted more accurately and saves more energy. The utility model provides a first main change valve, second main change valve realize for the tribit eight leads to the switching-over valve, and the proportional reversing valve that also can adopt the oil control of leading of course realizes, makes equipment have reciprocating work's function.

In the description of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for convenience of description and simplification of the description, but do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood in specific cases to those skilled in the art. In addition, in the description of the present invention, "a plurality" means two or more unless otherwise specified.

The skilled person should understand that: although the present invention has been described in accordance with the above embodiments, the inventive concept is not limited to this embodiment, and any modification of the inventive concept will be included in the scope of the patent claims.

Claims

1. A double-loop hydraulic system is characterized by comprising a first main oil inlet (P1), a second main oil inlet (P2), a first working group (1) and a second working group (2), wherein the first working group comprises at least one first working link (3), the first working link comprises a first working oil port (31), a first main reversing valve (32) and a first auxiliary reversing valve (33), the second working group comprises at least one second working link (4), the second working link comprises a second working oil port (41), a second main reversing valve (42) and a second auxiliary reversing valve (43), the first main oil inlet is connected with an oil inlet of the first main reversing valve, an oil outlet of the first main reversing valve is connected with an oil inlet of a first compensator (5), and the second main oil inlet is connected with an oil inlet of the first auxiliary reversing valve, and the pressure oil at the oil outlet of the first compensator and the pressure oil at the oil outlet of the first auxiliary reversing valve are connected with the first working oil port after passing through the first main reversing valve.

2. The dual-circuit hydraulic system of claim 1, wherein the second main oil inlet is connected to an oil inlet of a second main directional control valve, an oil outlet of the second main directional control valve is connected to an oil inlet of a second compensator (9), the first main oil inlet is connected to an oil inlet of a second auxiliary directional control valve, and pressure oil at an oil outlet of the second compensator and pressure oil at an oil outlet of the second auxiliary directional control valve both pass through the second main directional control valve and are connected to a second working oil port.

3. The dual-circuit hydraulic system as recited in claim 1, wherein the first compensator (5) includes a first control chamber and a first spring chamber, the pressure oil at the oil outlet of the first compensator is connected to the first feedback oil path, and the first control chamber selects the pressure oil at the oil inlet of the first compensator to cooperate with the elastic force of the first spring chamber and the pressure oil of the first feedback oil path to control the opening of the first compensator.

4. The dual-circuit hydraulic system as recited in claim 3, characterized in that a first main throttle (34) is provided between an oil inlet of the first main directional control valve and an oil outlet of the first main directional control valve, the pressure oil at the oil outlet of the first compensator is connected to a first feedback oil path (LS 1) through a first check valve (6), and the first feedback oil path is communicated with the first spring chamber of the first compensator in different first working couples in the first working group.

5. A dual circuit hydraulic system as claimed in claim 1, further comprising a pilot oil circuit (7) for actuating the first and second main directional control valves, said pilot oil circuit being connected to the control chamber of the first main directional control valve via a first pilot control valve (71), said pilot oil circuit being connected to the control chamber of the second main directional control valve via a second pilot control valve (72), said first and second pilot control valves having respective first positions when installed and second positions opened to facilitate passage of pilot oil for actuating the first and second main directional control valves, respectively.

6. The dual circuit hydraulic system of claim 5, wherein the first auxiliary direction valve has a first position when installed and a second position open to allow passage of pressurized oil from the second main inlet port, the first auxiliary direction valve being an electronically controlled direction valve.

7. The dual-circuit hydraulic system as recited in claim 1, further comprising a first pilot oil path (73) for driving the first main directional control valve to operate, wherein the first main directional control valve is provided with a first pilot on-off circuit (35), the second main directional control valve is provided with a second pilot on-off circuit (36), and the first pilot oil path is connected to the first auxiliary directional control chamber of the first main directional control valve through the second pilot on-off circuit of the second main directional control valve.

8. The dual-circuit hydraulic system as recited in claim 7 further comprising a second pilot oil circuit (74) for actuating a second main directional control valve, said second pilot oil circuit being connected to a second auxiliary directional control chamber of the first main directional control valve through a first pilot on-off circuit of the first main directional control valve, said first pilot oil circuit and said second pilot oil circuit each having a shuttle valve (8) disposed thereon.

9. The dual-circuit hydraulic system as claimed in claim 7, wherein the first pilot on-off circuit and the second pilot on-off circuit are driven by a valve rod of the first main directional control valve and a valve rod of the second main directional control valve respectively to realize on-off functions of the first pilot oil path and the second pilot oil path.

10. The dual-circuit hydraulic system of claim 7, wherein the first auxiliary directional control valve is an on-off type pilot-controlled directional control valve or a proportional type pilot-controlled proportional control valve having a proportional valve stem, and the first auxiliary directional control valve is a pilot-controlled directional control valve and is driven by the first pilot oil path.