CN108266413B - Asymmetric electro-hydrostatic actuator based on pressure selection valve - Google Patents
Asymmetric electro-hydrostatic actuator based on pressure selection valve Download PDFInfo
- Publication number
- CN108266413B CN108266413B CN201711348907.7A CN201711348907A CN108266413B CN 108266413 B CN108266413 B CN 108266413B CN 201711348907 A CN201711348907 A CN 201711348907A CN 108266413 B CN108266413 B CN 108266413B
- Authority
- CN
- China
- Prior art keywords
- valve core
- oil
- valve
- electro
- asymmetric
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
- F15B11/08—Servomotor systems without provision for follow-up action; Circuits therefor with only one servomotor
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B13/00—Details of servomotor systems ; Valves for servomotor systems
- F15B13/02—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors
- F15B13/04—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor
- F15B13/0401—Valve members; Fluid interconnections therefor
- F15B13/0402—Valve members; Fluid interconnections therefor for linearly sliding valves, e.g. spool valves
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B15/00—Fluid-actuated devices for displacing a member from one position to another; Gearing associated therewith
- F15B15/08—Characterised by the construction of the motor unit
- F15B15/14—Characterised by the construction of the motor unit of the straight-cylinder type
- F15B15/1423—Component parts; Constructional details
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Fluid-Pressure Circuits (AREA)
Abstract
The invention relates to an asymmetric electro-hydrostatic actuator based on a pressure selection valve, which comprises a servo motor, a bidirectional hydraulic pump, the pressure selection valve, two oil supplementing valves, an energy accumulator and an asymmetric structure actuating cylinder. The structural size of the electro-hydrostatic actuator can be reduced by adopting the asymmetric structural actuating cylinder, so that the electro-hydrostatic actuator can meet the more severe installation size limitation; by using the pressure selection valve, the common bidirectional hydraulic pump can be used for driving and controlling the actuating cylinder with the asymmetric structure, and the control effect close to that of the actuating cylinder with the symmetric structure is obtained. The invention can improve the integration level of the electro-hydrostatic actuator and reduce the quality of the electro-hydrostatic actuator on the basis of not increasing the design, manufacture and control difficulty of the hydraulic pump. The electro-hydrostatic actuator is suitable for occasions with larger working stroke and higher requirements on the size and the weight of the electro-hydrostatic actuator.
Description
Technical Field
The invention belongs to the hydraulic transmission and control technology, and relates to an asymmetric electro-hydrostatic actuator based on a pressure selection valve.
Background
The electro-hydrostatic actuator is an important flight control device in a multi-electric airplane, and compared with a hydraulic servo actuator of a traditional airplane, the electro-hydrostatic actuator directly uses electric energy as an input energy source, so that an intricate and complex hydraulic pipeline in the traditional airplane can be omitted, the maintainability of the airplane is improved, and the failure risk is reduced. However, since the electro-hydrostatic actuator integrates a plurality of components such as a servo motor, a hydraulic pump, a valve block, an actuating cylinder and the like, the volume and weight of the electro-hydrostatic actuator are obviously less than those of the traditional hydraulic servo actuator, and the application range of the electro-hydrostatic actuator is limited.
At present, most electro-hydrostatic actuators all use the actuating cylinder of symmetric structure, and this is mainly because two-way hydraulic pump is mostly symmetric structure, and the actuating cylinder of using symmetric structure can avoid because the positive and negative suction of hydraulic pump, the flow that flows out and the inconsistent suction and the pressure build-up problem that arouse of the positive and negative direction operation demand flow of actuating cylinder. However, the use of the symmetric actuator cylinder makes the overall size of the electro-hydrostatic actuator larger, because the symmetric actuator cylinder needs to adopt a double-rod form, the minimum axial dimension required by the double-rod actuator cylinder is twice of the full operating stroke, and the minimum axial dimension required by the asymmetric actuator cylinder is twice of the full operating stroke, which differs by one time of the full operating stroke.
At present, a few electro-hydrostatic actuators adopt actuating cylinders with asymmetric structures for improving system integration and reducing system size, in order to match the characteristic that input and output flows of two cavities of the actuating cylinders are unequal due to asymmetric actuating cylinders, the electro-hydrostatic actuators with the structures need to be matched with specially designed asymmetric three-port hydraulic pumps, the three-port hydraulic pumps have larger difference compared with hydraulic pump structures generally used in industry, and the design means and the verification method are not mature, so that the electro-hydrostatic actuators with the structures are generally high in price and easy to break down, and the application range of the electro-hydrostatic actuators is limited.
Disclosure of Invention
In order to overcome the above-mentioned disadvantages of the prior art, such as the large size of the actuator cylinder with a symmetric structure, the use of the actuator cylinder with an asymmetric structure, and the need of an immature three-port pump design, the present invention provides an asymmetric electro-hydrostatic actuator based on a pressure selection valve, which not only uses the actuator cylinder with an asymmetric structure to reduce the structural size of the electro-hydrostatic actuator, but also uses the pressure selection valve to control the driving of the actuator cylinder with an asymmetric structure by using a common bidirectional hydraulic pump.
In order to achieve the purpose of the invention, the technical scheme adopted by the invention is as follows: the utility model provides an asymmetric electro-hydrostatic actuator based on pressure selection valve, including servo motor 1, two-way hydraulic pump 2, pressure selection valve 3, the oil supplementing valve, energy storage ware 5, asymmetric structure pressurized strut 6, servo motor 1 and two-way hydraulic pump 2 rigid connection, the port links to each other with the left and right chamber of asymmetric structure pressurized strut 6 respectively about two-way hydraulic pump 2, and simultaneously, pressure selection valve 3 has four hydraulic fluid ports, first hydraulic fluid port A, second hydraulic fluid port B connects the left and right chamber of asymmetric structure pressurized strut 6 respectively, third hydraulic fluid port C, fourth hydraulic fluid port D links to each other with energy storage ware 5, and energy storage ware 5 links to each other with the right chamber and the left chamber of asymmetric structure pressurized strut 6 respectively through two oil supplementing valves simultaneously.
The pressure selection valve 3 comprises a valve sleeve 31, a mandril 32, a right valve core 33, a right valve core spring 34, a left valve core spring 35 and a left valve core 36; the left valve core 36 and the right valve core 33 are connected through the mandril 32, the left valve core 36 and the right valve core 33 are respectively installed in the valve sleeve 31 through the left valve core spring 35 and the right valve core spring 34, under the action of only the spring force, the oil ports on the left valve core 36 and the right valve core 33 are respectively communicated with the third oil port C and the fourth oil port D on the valve sleeve 31, and the communication quantity is 1/3 with all openings.
The right spool spring 34 and the left spool spring 35 are both straight springs.
Compared with the prior art, the invention has the beneficial effects that:
1) by using the actuating cylinder with the asymmetric structure, the size of the electro-hydrostatic actuator can be effectively reduced, and theoretically, the axial size of the actuating cylinder with the asymmetric structure is only half of that of the actuating cylinder with the symmetric structure.
2) After the pressure selection valve is used, the pressure selection valve automatically switches oil ways according to the pressure change of the system to realize oil supplement of the actuating cylinder or discharge redundant oil back to the energy accumulator so as to coordinate the relation between the input and output flow of the actuating cylinder with the asymmetric structure and the input and output flow of the hydraulic pump, so that the actuating cylinder with the asymmetric structure can be driven and controlled by the bidirectional hydraulic pump which is mature in industry, the equipment cost is reduced, and the reliability is improved.
3) The pressure selection valve has certain oil supplementing capacity, so that an oil supplementing valve with small capacity can be selected during system design, the integration level of the electro-hydrostatic actuator can be further improved, and the volume can be reduced.
The invention is suitable for occasions with larger working stroke and higher requirements on the size and the weight of the electro-hydrostatic actuator.
Drawings
FIG. 1 is a system schematic of the present invention;
FIG. 2 is a block diagram of a pressure selection valve according to the present invention;
wherein: 1. the hydraulic control system comprises a servo motor, 2, a bidirectional hydraulic pump, 3, a pressure selection valve, 41, a first oil supplementing valve, 42, a second oil supplementing valve, 5, an energy accumulator, 6, an asymmetric structure actuating cylinder, 31, a valve sleeve, 32, a push rod, 33, a right valve core, 34, a right valve core spring, 35, a left valve core spring, 36 and a left valve core.
Detailed Description
The invention is further described below with reference to the accompanying drawings and examples.
As shown in fig. 1, the hydraulic control system comprises a servo motor 1, a bidirectional hydraulic pump 2, a pressure selection valve 3, two oil replenishing valves, an energy accumulator 5 and an asymmetric structure actuator cylinder 6 oil replenishing valve, wherein the two oil replenishing valves are a first oil replenishing valve 41 and a second oil replenishing valve 42; the servo motor 1 is rigidly connected with the bidirectional hydraulic pump 2, the left and right ports of the bidirectional hydraulic pump 2 are respectively connected with the left and right cavities of the asymmetric structure actuator cylinder 6, meanwhile, the pressure selection valve 3 is provided with four oil ports, a first oil port A and a second oil port B are respectively connected with the left and right cavities of the asymmetric structure actuator cylinder 6, a third oil port C and a fourth oil port D are connected with the energy accumulator 5, and meanwhile, the energy accumulator 5 is respectively connected with the right cavity and the left cavity of the asymmetric structure actuator cylinder 6 through two oil supplementing valves.
Fig. 2 shows the structure of the pressure selection valve, and the pressure selection valve 3 comprises a valve sleeve 31, a ram 32, a right valve core 33, a right valve core spring 34, a left valve core spring 35 and a left valve core 36; the left valve core 36 and the right valve core 33 are connected through the mandril 32, the left valve core 36 and the right valve core 33 are respectively installed in the valve sleeve 31 through the left valve core spring 35 and the right valve core spring 34, under the action of only the spring force, the oil ports on the left valve core 36 and the right valve core 33 are respectively communicated with the third oil port C and the fourth oil port D on the valve sleeve 31, and the communication quantity is 1/3 with all openings.
The right spool spring 34 and the left spool spring 35 are both straight springs, so that the spool can move more uniformly.
The principle of the invention is explained by respectively dividing four conditions of positive direction movement load, negative direction movement load and negative direction movement load, assuming that the extension direction of the actuator cylinder is the positive direction of the actuator cylinder movement, and the load direction of the actuator cylinder retraction is the positive direction of the load;
1) positive direction load of positive direction motion: because the load is in the positive direction, the left cavity of the actuating cylinder 6 with the asymmetric structure is high-pressure, and the right cavity of the actuating cylinder is low-pressure; under the high pressure action of the left cavity of the actuating cylinder 6, the left valve core 36 of the pressure selection valve pushes the right valve core 33 to move rightwards by overcoming the spring force of the right valve core spring 34 through the mandril 32, so that the oil path between the left valve core 36 and the third oil port C on the valve sleeve 31 is cut off, and the oil path between the right valve core 33 and the fourth oil port D on the valve sleeve 31 is opened; because the motion is in the positive direction, the left cavity of the asymmetric structure actuator cylinder 6 is an oil suction cavity, the right cavity of the asymmetric structure actuator cylinder is an oil discharge cavity, the left end of the bidirectional hydraulic pump 2 is an oil discharge end, and the right end of the bidirectional hydraulic pump is an oil suction end; because the oil path between the left valve core 36 of the pressure selection valve and the third oil port C of the valve sleeve 31 is cut off, all the oil discharged from the left end of the bidirectional hydraulic pump 2 enters the left cavity of the asymmetric-structure actuator cylinder 6, meanwhile, the oil path between the right valve core 33 of the pressure selection valve and the fourth oil port D of the valve sleeve 31 is opened, the oil in the energy accumulator 5 passes through the oil path and enters the right end of the bidirectional hydraulic pump 2 together with the oil flowing out from the right cavity of the asymmetric-structure actuator cylinder 6, and the difference of the oil absorption flow rate required by the right end of the bidirectional hydraulic pump 2 is compensated for the oil flowing out from the right cavity of the asymmetric-structure actuator cylinder.
2) Negative direction motion positive direction load: because the load is in the positive direction, the left cavity of the actuating cylinder 6 with the asymmetric structure is high-pressure, and the right cavity of the actuating cylinder is low-pressure; under the high pressure action of the left cavity of the actuating cylinder 6, the left valve core 36 of the pressure selection valve pushes the right valve core 33 to move rightwards by overcoming the spring force of the right valve core spring 34 through the mandril 32, so that the oil path between the left valve core 36 and the third oil port C on the valve sleeve 31 is cut off, and the oil path between the right valve core 33 and the fourth oil port D on the valve sleeve 31 is opened; because the motion is in a negative direction, the right cavity of the asymmetric structure actuator cylinder 6 is an oil suction cavity, the left cavity of the asymmetric structure actuator cylinder is an oil discharge cavity, the right end of the bidirectional hydraulic pump 2 is an oil discharge end, and the left end of the bidirectional hydraulic pump is an oil suction end; because the oil path between the left valve core 36 of the pressure selection valve and the third oil port C of the valve sleeve 31 is cut off, all the oil discharged from the left cavity of the asymmetric structure actuator cylinder 6 enters the left end of the bidirectional hydraulic pump 2, meanwhile, the oil path between the right valve core 33 of the pressure selection valve and the fourth oil port D of the valve sleeve 31 is opened, one part of the oil discharged from the right end of the bidirectional hydraulic pump 2 flows into the energy accumulator 5 through the oil path, the other part of the oil flows into the right cavity of the asymmetric structure actuator cylinder 6, and the difference of the oil flow rate discharged from the right end of the bidirectional hydraulic pump 2 by the oil flowing into the right cavity of the asymmetric structure actuator cylinder 6 at the moment.
3) Positive direction motion negative direction load: because the load is in a negative direction, the right cavity of the actuating cylinder 6 with the asymmetric structure is high-pressure, and the left cavity of the actuating cylinder is low-pressure; under the high pressure action of the right cavity of the actuating cylinder 6, the right valve core 33 of the pressure selection valve pushes the left valve core 36 to move leftwards by overcoming the spring force of the left valve core spring 35 through the mandril 32, so that the oil path between the left valve core 36 and the third oil port C on the valve sleeve 31 is opened, and the oil path between the right valve core 33 and the fourth oil port D on the valve sleeve 31 is cut off; because the motion is in the positive direction, the left cavity of the asymmetric structure actuator cylinder 6 is an oil suction cavity, the right cavity of the asymmetric structure actuator cylinder is an oil discharge cavity, the left end of the bidirectional hydraulic pump 2 is an oil discharge end, and the right end of the bidirectional hydraulic pump is an oil suction end; because the oil path between the right valve core 33 of the pressure selection valve and the fourth oil port D of the valve sleeve 31 is cut off, all the oil discharged from the right cavity of the asymmetric structure actuator cylinder 6 enters the right end of the bidirectional hydraulic pump 2, meanwhile, the oil path between the left valve core 36 of the pressure selection valve and the third oil port C of the valve sleeve 31 is opened, the oil in the energy accumulator 5 joins the oil discharged from the left end of the bidirectional hydraulic pump 2 through the oil path and then enters the left cavity of the asymmetric structure actuator cylinder 6 together, and the difference of the oil absorption flow rate required by the left cavity of the asymmetric structure actuator cylinder 6 when the oil discharged from the left end of the bidirectional hydraulic pump 2 is compensated.
4) Negative direction motion negative direction load: because the load is in a negative direction, the right cavity of the actuating cylinder 6 with the asymmetric structure is high-pressure, and the left cavity of the actuating cylinder is low-pressure; under the high pressure action of the right cavity of the actuating cylinder 6, the right valve core 33 of the pressure selection valve pushes the left valve core 36 to move leftwards by overcoming the spring force of the left valve core spring 35 through the mandril 32, so that the oil path between the left valve core 36 and the third oil port C on the valve sleeve 31 is opened, and the oil path between the right valve core 33 and the fourth oil port D on the valve sleeve 31 is cut off; because the motion is in a negative direction, the right cavity of the asymmetric structure actuator cylinder 6 is an oil suction cavity, the left cavity of the asymmetric structure actuator cylinder is an oil discharge cavity, the right end of the bidirectional hydraulic pump 2 is an oil discharge end, and the left end of the bidirectional hydraulic pump is an oil suction end; because the oil path between the right spool 33 of the pressure selection valve and the fourth port D of the valve housing 31 is cut off, all the oil discharged from the right end of the two-way hydraulic pump 2 enters the right cavity of the asymmetric-structure actuator cylinder 6, meanwhile, the oil path between the left spool 36 of the pressure selection valve and the third port C of the valve housing 31 is opened, a part of the oil discharged from the left cavity of the asymmetric-structure actuator cylinder 6 flows into the energy accumulator 5 through the oil path, and the other part of the oil flows into the left end of the two-way hydraulic pump 2, so as to compensate the difference that the oil flowing into the left end of the two-way hydraulic pump 2 at the moment is smaller than the flow rate of the oil discharged from the.
The foregoing detailed description is intended to illustrate and not limit the invention, which is intended to be within the spirit and scope of the appended claims, and any changes and modifications that fall within the true spirit and scope of the invention are intended to be covered by the following claims.
Claims (4)
1. An asymmetric electro-hydrostatic actuator based on a pressure selection valve, which is characterized in that: the servo motor (1) is rigidly connected with the bidirectional hydraulic pump (2), left and right ports of the bidirectional hydraulic pump (2) are respectively connected with left and right cavities of the asymmetric-structure actuating cylinder (6), meanwhile, the pressure selection valve (3) is provided with four oil ports, a first oil port A and a second oil port B are respectively connected with the left and right cavities of the asymmetric-structure actuating cylinder (6), a third oil port C and a fourth oil port D are connected with the energy accumulator (5), and meanwhile, the energy accumulator (5) is respectively connected with the right cavity and the left cavity of the asymmetric-structure actuating cylinder (6) through the two oil replenishing valves;
the oil discharge or oil absorption of the energy accumulator (5) and the asymmetrical structure actuating cylinder (6) is controlled by adjusting the pressure of the left cavity and the right cavity of the asymmetrical structure actuating cylinder (6) and adjusting the pressure selection valve (3).
2. The asymmetric electro-hydrostatic pressure-selective valve-based actuator of claim 1, wherein: the pressure selection valve (3) comprises a valve sleeve (31), a mandril (32), a right valve core (33), a right valve core spring (34), a left valve core spring (35) and a left valve core (36); the left valve core (36) is connected with the right valve core (33) through a mandril (32), and the left valve core (36) and the right valve core (33) are respectively installed in the valve sleeve (31) through a left valve core spring (35) and a right valve core spring (34).
3. The asymmetric electro-hydrostatic pressure-selective valve-based actuator of claim 2, wherein: under the action of only a spring force, oil ports on the left valve core (36) and the right valve core (33) are communicated with a third oil port C and a fourth oil port D on the valve sleeve (31) respectively, and the communication quantity is 1/3 with all openings.
4. The asymmetric electro-hydrostatic pressure-selective valve-based actuator of claim 2, wherein: the right valve core spring (34) and the left valve core spring (35) are both straight springs.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201711348907.7A CN108266413B (en) | 2017-12-15 | 2017-12-15 | Asymmetric electro-hydrostatic actuator based on pressure selection valve |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201711348907.7A CN108266413B (en) | 2017-12-15 | 2017-12-15 | Asymmetric electro-hydrostatic actuator based on pressure selection valve |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN108266413A CN108266413A (en) | 2018-07-10 |
| CN108266413B true CN108266413B (en) | 2021-02-12 |
Family
ID=62772020
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201711348907.7A Active CN108266413B (en) | 2017-12-15 | 2017-12-15 | Asymmetric electro-hydrostatic actuator based on pressure selection valve |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN108266413B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102019131980A1 (en) * | 2019-11-26 | 2021-05-27 | Moog Gmbh | Electrohydrostatic system with pressure sensor |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5575150A (en) * | 1995-04-12 | 1996-11-19 | Northrop Grumman Corporation | Stiffness enhanced electrohydrostatic actuator |
| JP3563365B2 (en) * | 2001-04-26 | 2004-09-08 | ティーエスコーポレーション株式会社 | Actuator device for controlling the control surface of aircraft |
| CN102588382B (en) * | 2012-03-19 | 2014-11-26 | 北京航空航天大学 | Direct-drive electro-hydraulic actuator |
| CN103032403A (en) * | 2012-12-27 | 2013-04-10 | 中国航空工业集团公司金城南京机电液压工程研究中心 | Airplane frame position control actuator |
| CN104728193B (en) * | 2015-03-18 | 2017-03-08 | 北京航空航天大学 | The Electrical hydrostatic actuator of load-sensitive |
| CN106939910A (en) * | 2017-04-22 | 2017-07-11 | 新乡市新倍增自动化设备有限公司 | A kind of Electrical hydrostatic actuator single rod symmetrical hydraulic cylinder at a high speed |
-
2017
- 2017-12-15 CN CN201711348907.7A patent/CN108266413B/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| CN108266413A (en) | 2018-07-10 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN102226453B (en) | Dual-redundancy electro hydraulic servo actuator | |
| CN204512079U (en) | A kind of two remaining Electrical hydrostatic actuator | |
| CN102230484B (en) | Integrated continuous gas-driving hydraulic force booster | |
| CN104806588B (en) | Dual-pump flow-converging hydraulic control system | |
| CN105889159A (en) | Hydraulic system with ultra-high pressure outputting capacity | |
| CN110005664B (en) | Bidirectional speed regulation hydraulic control system based on negative load oil return cavity of hydraulic cylinder | |
| CN105782147A (en) | Double-acting hydraulic control system of supercharging device | |
| CN103085865A (en) | Load sensitive turning hydraulic system of loading machine | |
| CN105090141A (en) | Hydraulic variable control system and vehicle | |
| CN104029721B (en) | Loader hydraulic transfer | |
| CN105065361B (en) | Proportional flow unit under compound control of electromagnetic switch valves and proportional throttle valve in parallel | |
| CN104989690A (en) | Overload relief valve | |
| CN110594214B (en) | Hydraulic control system of metal packing hydraulic press | |
| CN108266413B (en) | Asymmetric electro-hydrostatic actuator based on pressure selection valve | |
| CN104132023A (en) | Controllable variable-section hydraulic cylinder and hydraulic control system and method therefor | |
| CN105134538A (en) | Variable control piston of variable hydraulic pump and motor and application thereof | |
| CN110630582B (en) | Cylinder energy storage type hydraulic cylinder | |
| CN204200727U (en) | Axial plunger variable motor hydraulic speed regulation loop system | |
| CN109501339B (en) | Hydraulic control system for pressurized oil cylinder of double-layer tire vulcanizer | |
| CN202031822U (en) | Integral-type concrete pump high-low-pressure switching device | |
| CN102304931B (en) | Hydraulic energy-saving control system and method for loader movable arm | |
| CN204704187U (en) | Overload unloading valve | |
| CN204851560U (en) | Positive flow control electric proportional pump | |
| JP7200385B2 (en) | Variable displacement hydraulic pump set and excavator | |
| CN202326059U (en) | Double-acting pressurizing gas-liquid composite pump |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |