CN202808201U - Hydraulic control system and crane with same - Google Patents
Hydraulic control system and crane with same Download PDFInfo
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- CN202808201U CN202808201U CN 201220528864 CN201220528864U CN202808201U CN 202808201 U CN202808201 U CN 202808201U CN 201220528864 CN201220528864 CN 201220528864 CN 201220528864 U CN201220528864 U CN 201220528864U CN 202808201 U CN202808201 U CN 202808201U
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Abstract
The utility model discloses a hydraulic control system, this hydraulic control system includes main pump unit (1), main valve unit (2), actuating mechanism (3), act on stopper (4) of this actuating mechanism and control valve (5) of controlling this stopper, the main pump unit has load feedback and pressure differential regulatory function, pressure hydraulic fluid port (1P) of main pump unit is connected with pressure hydraulic fluid port (2P) of main valve unit, two work hydraulic fluid ports (2A) of main valve unit, 2B) connect respectively in two work oil circuit (3A of actuating mechanism, 3B), work hydraulic fluid port (5A) and the control mouth of stopper of control valve are connected, this hydraulic control system still includes auxiliary pump (6), the oil-out of this auxiliary pump communicates with pressure hydraulic fluid port (5P) of control valve (5). A crane is also provided, comprising a hydraulic control system as above. The hydraulic control system has the advantages of good micromotion performance and good stability.
Description
Technical field
The utility model relates to Hydraulic Field, particularly, relates to a kind of hydraulic control system.
Background technology
Be illustrated in figure 1 as the hydraulic control system of existing a kind of hoisting crane, this hydraulic control system main pump unit 1, main valve unit 2, actuating unit 3(is the hoist motor of hoisting crane for example), act on the control cock 5 of drg 4 and this drg 4 of control of this actuating unit 3, main pump unit 1 is with load feedback and pressure reduction regulatory function, the pressure hydraulic fluid port 1P of main pump unit 1 is connected with the pressure hydraulic fluid port 2P of main valve unit 2, two actuator port 2A of main valve unit 2,2B is connected to two working oil path 3A of actuating unit 3,3B, the actuator port 5A of control cock 5 is connected with the control mouth of drg 4.
The pressure of the pressure hydraulic fluid port 1P of main pump unit 1 is P, and the load pressure of actuating unit 3 is PLS, and this load pressure PLS feeds back to the feedback port 1LS of main pump unit 1.The flow Q of the pressure hydraulic fluid port 1P output of main pump unit 1 introduces actuating unit 3 by the restriction of the proportional reversing valve 21 of main valve unit 2.Simultaneously, be incorporated into control cock 5 after the fixed pressure reducing valve decompression of the pressure oil of the pressure hydraulic fluid port 1P of main pump unit 1 output by main valve unit 2.The pressure differential deltap p=P-PLS at the restriction two ends of the proportional reversing valve 21 of main valve unit 2.P acts on the right-hand member of the spool of load feedback valve 12 by the second control mouthful 12B, P is through the proportional pressure-reducing valve 13 post-decompression pressure P of main pump unit 1 ' control the right-hand member that mouthful 12C acts on the spool of load feedback valve 12 by the 3rd, PLS acts on the left end of the spool of load feedback valve 12, the default spring force Pk(definite value of load feedback valve 12 by the first control mouthful 12A) act on the left end of the spool of load feedback valve 12.When LS spool stress balance, Pk+PLS=P+P', so Δ p=P-PLS=Pk-P ', the master variable pump 11 of main pump unit 1 is kept a stable discharge capacity.If the load pressure PLS of actuating unit 3 changes, then dynamic Δ p will be greater than or less than Pk-P', be to recover the spool of load feedback valve 12 to the force balance state this moment, the pressure oil of the actuator port 12P output of load feedback valve 12 acts on the displacement control mouth of master variable pump 11, automatically adjust the discharge capacity of master variable pump 11, then change master variable pump 11 delivery rate Q, again make Δ p=Pk-P'=definite value, realize thus the load feedback function of main pump unit 1.
Can correspondingly change the running velocity of actuating unit 3 to the flow Q of actuating unit 3 outputs by control.According to formula
(in the formula, C is coefficient of flow, and A is the valve port flow area of the proportional reversing valve 21 of main valve unit 2, and ρ is fluid density) can by the size of control Δ p and the size of control valve port flow area A, control to the flow Q of actuating unit 3 outputs.If Δ p value is less, the variation delta A of the valve port flow area A that then the variation delta Q of identical flow Q is corresponding is larger, and the variation delta A of valve port flow area A is then corresponding with the operational stroke of the spool of the proportional reversing valve 21 of main valve unit 2.Thereby if Δ p value is less, then the operational stroke of the spool of the proportional reversing valve 21 of the corresponding main valve of the variation delta Q unit 2 of identical flow Q is larger, that is to say that the performance accuracy of main valve unit 2 is higher, and the fretting performance of hydraulic control system is better.Thereby, can regulate P ' by the proportional pressure-reducing valve 13 of regulating main pump unit 1 as required, and then regulate Δ p, with the fretting performance of this regulator solution pressure control system.
In existing above-mentioned hydraulic control system, as indicated above, the control presssure oil sources of drg 4 is taken from main valve unit 2, and the pressure oil of main valve unit 2 is from main pump unit 1.Therefore, the minimum value of Δ p need to reach the response pressure of drg 4, otherwise can cause drg 4 to work.Therefore, existing hydraulic control system can't improve by further reducing Δ p the fretting performance of hydraulic efficiency pressure system, thereby causes the fretting performance of this hydraulic efficiency pressure system not ideal enough.In addition, because the control oil sources of whole hydraulic efficiency pressure system is all from the master variable pump 11 of main pump unit 1, when there are a plurality of actuating units 3 in hydraulic efficiency pressure system, and a plurality of actuating units 3 and drg 4 thereof are when all needing a large amount of hydraulic oil, the inadequate situation of moment control fluid amount may appear, so that drg 4 can't work, thereby affect the normal operation of actuating unit 3, cause the less stable of hydraulic control system.
The utility model content
The purpose of this utility model provide a kind of fretting performance better, stability hydraulic control system preferably.
To achieve these goals, on the one hand, the utility model provides a kind of hydraulic control system, this hydraulic control system comprises main pump unit, the main valve unit, actuating unit, act on the control cock of drg and this drg of control of this actuating unit, described main pump unit is with load feedback and pressure reduction regulatory function, the pressure hydraulic fluid port of described main pump unit is connected with the pressure hydraulic fluid port of described main valve unit, two actuator ports of described main valve unit, be connected to two working oil path of described actuating unit, the actuator port of described control cock is connected with the control mouth of described drg, wherein, this hydraulic control system also comprises complementary pump, and the oil outlet of this complementary pump is communicated with the pressure hydraulic fluid port of described control cock.
Preferably, this hydraulic control system also comprises the three-way flowrate valve, this three-way flowrate valve has entrance, constant flow outlet and overflow outlet, the entrance of described three-way flowrate valve is connected with the oil outlet of described complementary pump, and the constant flow outlet of described three-way flowrate valve is connected with the pressure hydraulic fluid port of described control cock.
Preferably, the overflow of described three-way flowrate valve outlet is connected to the repairing oil circuit of described hydraulic control system.
Preferably, be serially connected with the repairing check valve on any working oil path of described actuating unit, the overflow of described three-way flowrate valve outlet is connected to being connected on the oil circuit between the actuator port of described repairing check valve and described main valve unit.
Preferably, this hydraulic control system also comprises the by pass valve on the oil circuit of being connected between the pressure hydraulic fluid port of the other constant flow outlet that is connected on described three-way flowrate valve and described control cock.
Preferably, described main pump unit comprises master variable pump, load feedback valve and proportional pressure-reducing valve, and has described pressure hydraulic fluid port and feedback port; Described master variable delivery side of pump is communicated with described pressure hydraulic fluid port, described load feedback valve have an actuator port that is communicated with described master variable capacity of pump control mouth, the first control that is communicated with described feedback port mouthful, be communicated with the pressure hydraulic fluid port of described main pump unit second control mouth and be communicated with the outlet of described proportional pressure-reducing valve the 3rd control mouth; The entrance of described proportional pressure-reducing valve is communicated with the pressure hydraulic fluid port of described main pump unit.
Preferably, described complementary pump and described master variable pump are by identical engine drive.
Preferably, described complementary pump is integrated in the described main pump unit.
On the other hand, the utility model also provides a kind of hoisting crane, and this hoisting crane comprises hydraulic control system as indicated above.
Preferably, described actuating unit is the hoist motor of hoisting crane.
Pass through technique scheme, because hydraulic control system also comprises complementary pump, the oil outlet of this complementary pump is communicated with the pressure hydraulic fluid port of described control cock, therefore the control oil of drg is from complementary pump, rather than from main pump unit, thereby the pressure differential deltap p at the restriction two ends of the proportional reversing valve of main valve unit is not subjected to the restriction of the response pressure of drg, can improve as required the fretting performance of hydraulic efficiency pressure system by further reduction Δ p.In addition, because the control oil of drg is from complementary pump, thereby also reduce requirement to the hydraulic oil supply of main pump unit, be not prone to the inadequate situation of control fluid amount, therefore improved the stability of hydraulic control system.
Other feature and advantage of the present utility model will partly be described in detail in the specific embodiment subsequently.
Description of drawings
Accompanying drawing is to be used to provide further understanding of the present utility model, and consists of the part of specification sheets, is used from explanation the utility model with the following specific embodiment one, but does not consist of restriction of the present utility model.In the accompanying drawings:
Fig. 1 is the principle schematic of existing hydraulic control system;
Fig. 2 is the principle schematic according to the hydraulic control system of a kind of preferred implementation of the present utility model.
Description of reference numerals
1 main pump unit; 2 main valve unit;
3 actuating units; 4 drgs;
5 control cock; 6 complementary pumps;
7 three-way flowrate valves; 8 repairing check valves;
9 by pass valves; 11 master variable pumps;
12 load feedback valves; 13 proportional pressure-reducing valves;
21 proportional reversing valves; 14 balance cocks;
15 return oil pressure valves.
The specific embodiment
Below in conjunction with accompanying drawing the specific embodiment of the present utility model is elaborated.Should be understood that the specific embodiment described herein only is used for description and interpretation the utility model, is not limited to the utility model.
As shown in Figure 2, provide a kind of hydraulic control system according to a kind of embodiment of the present utility model, this hydraulic control system comprises main pump unit 1, main valve unit 2, actuating unit 3, this drg 4 of drg 4(that acts on this actuating unit 3 for example can be brake cylinder) and control this drg 4 this control cock 5 of control cock 5(for example can be the two-bit triplet solenoid directional control valve), described main pump unit 1 is with load feedback and pressure reduction regulatory function, the pressure hydraulic fluid port 1P of described main pump unit 1 is connected with the pressure hydraulic fluid port 2P of described main valve unit 2, two actuator port 2A of described main valve unit 2,2B is connected to two working oil path 3A of described actuating unit 3,3B, the actuator port 5A of described control cock 5 is connected with the control mouth of described drg 4, wherein, this hydraulic control system also comprises complementary pump 6, and the oil outlet of this complementary pump 6 is communicated with the pressure hydraulic fluid port 5P of described control cock 5.
Above-mentioned main pump unit 1 with load feedback and pressure reduction regulatory function can adopt various suitable forms.As a kind of concrete embodiment, as shown in Figure 1, described main pump unit 1 comprises master variable pump 11, load feedback valve 12 and proportional pressure-reducing valve 13, and has described pressure hydraulic fluid port 1P and feedback port 1LS; The outlet of described master variable pump 11 is communicated with described pressure hydraulic fluid port 1P, the 3rd control mouthful 12C that described load feedback valve 12 has the actuator port 12P that is communicated with the displacement control mouth of described master variable pump 11, the first control mouthful 12A that is communicated with described feedback port 1LS, the second control mouthful 12B that is communicated with the pressure hydraulic fluid port 1P of described main pump unit 1 and is communicated with the outlet of described proportional pressure-reducing valve 13; The entrance of described proportional pressure-reducing valve 13 is communicated with the pressure hydraulic fluid port 1P of described main pump unit 1.
The pressure of the pressure hydraulic fluid port 1P of main pump unit 1 is P, and the load pressure of actuating unit 3 is PLS, and this load pressure PLS feeds back to the feedback port 1LS of main pump unit 1.The flow Q of the pressure hydraulic fluid port 1P output of main pump unit 1 introduces actuating unit 3 by the restriction of the proportional reversing valve 21 of main valve unit 2.The pressure differential deltap p=P-PLS at the restriction two ends of the proportional reversing valve 21 of main valve unit 2.P acts on the right-hand member of the spool of load feedback valve 12 by the second control mouthful 12B, P is through the proportional pressure-reducing valve 13 post-decompression pressure P of main pump unit 1 ' control the right-hand member that mouthful 12C acts on the spool of load feedback valve 12 by the 3rd, PLS acts on the left end of the spool of load feedback valve 12, the default spring force Pk(definite value of load feedback valve 12 by the first control mouthful 12A) act on the left end of the spool of load feedback valve 12.When LS spool stress balance, Pk+PLS=P+P ', so Δ p=P-PLS=Pk-P ', the master variable pump 11 of main pump unit 1 is kept a stable discharge capacity.If the load pressure PLS of actuating unit 3 changes, then dynamic Δ p will be greater than or less than Pk-P', this moment is for to make the spool of load feedback valve 12 return to the force balance state, the pressure oil of the actuator port 12P output of load feedback valve 12 acts on the displacement control mouth of master variable pump 11, automatically adjust the discharge capacity of master variable pump 11, then change master variable pump 11 delivery rate Q, again make Δ p=Pk-P'=definite value, realize thus the load feedback function of main pump unit 1.
Can correspondingly change the running velocity of actuating unit 3 to the flow Q of actuating unit 3 outputs by control.According to formula
(in the formula, C is coefficient of flow, and A is the valve port flow area of the proportional reversing valve 21 of main valve unit 2, and ρ is fluid density) can by the size of control Δ p and the size of control valve port flow area A, control to the flow Q of actuating unit 3 outputs.If Δ p value is less, the variation delta A of the valve port flow area A that then the variation delta Q of identical flow Q is corresponding is larger, and the variation delta A of valve port flow area A is then corresponding with the operational stroke of the spool of the proportional reversing valve 21 of main valve unit 2.Thereby if Δ p value is less, then the operational stroke of the spool of the proportional reversing valve 21 of the corresponding main valve of the variation delta Q unit 2 of identical flow Q is larger, that is to say that the performance accuracy of main valve unit 2 is higher, and the fretting performance of hydraulic control system is better.Thereby, can be as required, regulate P ' (when for example this proportional pressure-reducing valve 13 is for electric proportional pressure-reducing valve by the proportional pressure-reducing valve 13 of regulating main pump unit 1, regulate P ' by regulating the electric current that applies to this electricity proportional pressure-reducing valve), and then regulate Δ p, with the fretting performance of this regulator solution pressure control system.
By technique scheme of the present utility model, because hydraulic control system also comprises complementary pump 6, the oil outlet of this complementary pump 6 is communicated with the pressure hydraulic fluid port 5P of described control cock 5, therefore the control oil of drg 4 is from complementary pump 6, rather than from main pump unit 1, thereby the pressure differential deltap p at the restriction two ends of the proportional reversing valve of main valve unit 2 is not subjected to the restriction of the response pressure of drg 4, can improve as required the fretting performance of hydraulic efficiency pressure system by further reduction Δ p.In addition, because the control oil of drg 4 is from complementary pump 6, thereby also reduce requirement to the hydraulic oil supply of main pump unit 1, be not prone to the inadequate situation of control fluid amount, therefore improved the stability of hydraulic control system.
Preferably, this hydraulic control system also comprises three-way flowrate valve 7, this three-way flowrate valve 7 has entrance 7P, constant flow outlet 7A and overflow outlet 7R, the entrance 7P of described three-way flowrate valve 7 is connected with the oil outlet of described complementary pump 6, and the constant flow outlet 7A of described three-way flowrate valve 7 is connected with the pressure hydraulic fluid port 5P of described control cock 5.Thereby, even the too much flow of complementary pump 6 outputs, the flow that constant flow outlet 7A by this three-way flowrate valve 7 is delivered to the pressure hydraulic fluid port 5P of control cock 5 also keeps fixing, thereby can namely be drg 4 for control cock 5() stable control oil flow is provided.
More preferably, this hydraulic control system also comprises the by pass valve 9 on the oil circuit of being connected between the pressure hydraulic fluid port 5P of the other constant flow outlet 7A that is connected on described three-way flowrate valve 7 and described control cock 5.Thereby prevent the hypertonia of the control oil that provides for control cock 5.Three-way flowrate valve 7 and by pass valve 9 can integrate.
The overflow outlet 7R of three-way flowrate valve 7 can be connected to the fuel tank of hydraulic control system, preferably be connected to the repairing oil circuit of hydraulic control system, thereby the repairing oil circuit that directly is hydraulic efficiency pressure system replenishes fluid, prevents from affecting normal operation because of the moment low on fuel of hydraulic control system.For example as shown in Figure 2, be serially connected with repairing check valve 8 on any working oil path 3A of described actuating unit 3.The effect of repairing check valve 8 is to be actuating unit 3 repairings, to prevent for example hoist motor of hoisting crane of actuating unit 3() fluid provides quantity not sufficient and causes the hook accident of slipping during too fast transferring.The overflow of described three-way flowrate valve 7 outlet 7R is connected to being connected on the oil circuit between the actuator port 2A of described repairing check valve 8 and described main valve unit 2, thereby is connected to the repairing oil circuit.
As shown in Figure 2, the hydraulic oil that provides of complementary pump 6 can also provide hydraulic oil for other hydraulic part 20 in the hydraulic control system.
For example as indicated above, when the rotating speed of driving engine improved, the flow of complementary pump 6 outputs increased, and flows into the also corresponding increase of flow of three-way flowrate valve 7 by entrance 7P.But three-way flowrate valve 7 remains a fixed value by the flow that constant flow outlet 7A outputs to by pass valve 9, and the flow that increases part all flows to the system oil return road to system's repairing from the overflow outlet 7R of three-way flowrate valve 7.The flow that flows into like this by pass valve 7 is always a fixing numerical value, thereby guaranteed no matter the rotating speed of driving engine is for how high, system can keep a highly stable control oil pressure to be used for opening drg 4 or supplying with the hydraulic part that other need to stablize control fluid by three-way flowrate valve 7 and by pass valve 9 all the time, makes it not be subjected to the impact of engine speed.
On the other hand, the utility model also provides a kind of hoisting crane, and this hoisting crane comprises hydraulic control system as indicated above.Actuating unit in this hydraulic control system for example can be the hoist motor of hoisting crane.In Fig. 1 and Fig. 2, the parts of Reference numeral 14 representatives are balance cock, and its effect is to control when hoist motor is done down maneuver to avoid out of control.The parts of Reference numeral 15 representative are back pressure valve, and its effect is that the oil return line for hydraulic control system provides back pressure pressure, the repairing when more being conducive to simultaneously the elevator action.
Below describe by reference to the accompanying drawings preferred implementation of the present utility model in detail; but; the utility model is not limited to the detail in the above-mentioned embodiment; in technical conceive scope of the present utility model; can carry out multiple simple variant to the technical solution of the utility model, these simple variant all belong to protection domain of the present utility model.
Need to prove that in addition each the concrete technical characterictic described in the above-mentioned specific embodiment in reconcilable situation, can make up by any suitable mode.For fear of unnecessary repetition, the utility model is to the no longer separately explanation of various possible array modes.
In addition, also can carry out combination in any between the various embodiment of the present utility model, as long as it is without prejudice to thought of the present utility model, it should be considered as content disclosed in the utility model equally.
Claims (10)
1. hydraulic control system, this hydraulic control system comprises main pump unit (1), main valve unit (2), actuating unit (3), act on the control cock (5) of drg (4) and this drg of control (4) of this actuating unit (3), described main pump unit (1) is with load feedback and pressure reduction regulatory function, the pressure hydraulic fluid port (1P) of described main pump unit (1) is connected with the pressure hydraulic fluid port (2P) of described main valve unit (2), two actuator port (2A of described main valve unit (2), 2B) be connected to two working oil path (3A of described actuating unit (3), 3B), the actuator port (5A) of described control cock (5) is connected with the control mouth of described drg (4), it is characterized in that, this hydraulic control system also comprises complementary pump (6), and the oil outlet of this complementary pump (6) is communicated with the pressure hydraulic fluid port (5P) of described control cock (5).
2. hydraulic control system according to claim 1, it is characterized in that, this hydraulic control system also comprises three-way flowrate valve (7), this three-way flowrate valve (7) has entrance (7P), constant flow outlet (7A) and overflow outlet (7R), the entrance (7P) of described three-way flowrate valve (7) is connected with the oil outlet of described complementary pump (6), and the constant flow outlet (7A) of described three-way flowrate valve (7) is connected with the pressure hydraulic fluid port (5P) of described control cock (5).
3. hydraulic control system according to claim 2 is characterized in that, the overflow outlet (7R) of described three-way flowrate valve (7) is connected to the repairing oil circuit of described hydraulic control system.
4. hydraulic control system according to claim 3, it is characterized in that, be serially connected with repairing check valve (8) on any working oil path (3A) of described actuating unit (3), the overflow of described three-way flowrate valve (7) outlet (7R) is connected to being connected on the oil circuit between the actuator port (2A) of described repairing check valve (8) and described main valve unit (2).
5. hydraulic control system according to claim 2, it is characterized in that this hydraulic control system also comprises the by pass valve (9) on the oil circuit of being connected between the pressure hydraulic fluid port (5P) of the other constant flow outlet (7A) that is connected on described three-way flowrate valve (7) and described control cock (5).
6. the described hydraulic control system of any one in 5 according to claim 1, it is characterized in that, described main pump unit (1) comprises master variable pump (11), load feedback valve (12) and proportional pressure-reducing valve (13), and has described pressure hydraulic fluid port (1P) and feedback port (1LS); The outlet of described master variable pump (11) is communicated with described pressure hydraulic fluid port (1P), the 3rd control mouthful (12C) that described load feedback valve (12) has the actuator port (12P) that is communicated with the displacement control mouth of described master variable pump (11), the first control mouthful (12A) that is communicated with described feedback port (1LS), the second control mouthful (12B) that is communicated with the pressure hydraulic fluid port (1P) of described main pump unit (1) and is communicated with the outlet of described proportional pressure-reducing valve (13); The entrance of described proportional pressure-reducing valve (13) is communicated with the pressure hydraulic fluid port (1P) of described main pump unit (1).
7. hydraulic control system according to claim 6 is characterized in that, described complementary pump (6) and described master variable pump (11) are by identical engine drive.
8. hydraulic control system according to claim 6 is characterized in that, described complementary pump (6) is integrated in the described main pump unit (1).
9. a hoisting crane is characterized in that, this hoisting crane comprises according to claim 1 the described hydraulic control system of any one in 8.
10. hoisting crane according to claim 9 is characterized in that, described actuating unit (3) is the hoist motor of hoisting crane.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201220528864 CN202808201U (en) | 2012-10-16 | 2012-10-16 | Hydraulic control system and crane with same |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201220528864 CN202808201U (en) | 2012-10-16 | 2012-10-16 | Hydraulic control system and crane with same |
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| CN202808201U true CN202808201U (en) | 2013-03-20 |
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| CN 201220528864 Expired - Fee Related CN202808201U (en) | 2012-10-16 | 2012-10-16 | Hydraulic control system and crane with same |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103727082A (en) * | 2013-12-27 | 2014-04-16 | 三一汽车起重机械有限公司 | Hydraulic system and engineering machine |
| CN104006019A (en) * | 2014-05-15 | 2014-08-27 | 安徽博一流体传动股份有限公司 | Load-sensitive control valve capable of remotely adjusting pressure difference |
| CN108916138A (en) * | 2018-09-21 | 2018-11-30 | 徐州重型机械有限公司 | Hydraulic system and its control method, engineering machinery |
| CN108980130A (en) * | 2018-08-06 | 2018-12-11 | 中联重科股份有限公司 | Differential pressure regulating valve unit, hydraulic control system and engineering machinery |
-
2012
- 2012-10-16 CN CN 201220528864 patent/CN202808201U/en not_active Expired - Fee Related
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103727082A (en) * | 2013-12-27 | 2014-04-16 | 三一汽车起重机械有限公司 | Hydraulic system and engineering machine |
| CN103727082B (en) * | 2013-12-27 | 2016-08-31 | 三一汽车起重机械有限公司 | Hydraulic system and engineering machinery |
| CN104006019A (en) * | 2014-05-15 | 2014-08-27 | 安徽博一流体传动股份有限公司 | Load-sensitive control valve capable of remotely adjusting pressure difference |
| CN108980130A (en) * | 2018-08-06 | 2018-12-11 | 中联重科股份有限公司 | Differential pressure regulating valve unit, hydraulic control system and engineering machinery |
| CN108916138A (en) * | 2018-09-21 | 2018-11-30 | 徐州重型机械有限公司 | Hydraulic system and its control method, engineering machinery |
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