CN111005899B - Load-sensitive hydraulic system with controllable oil pump limit displacement, control method and engineering machinery - Google Patents
Load-sensitive hydraulic system with controllable oil pump limit displacement, control method and engineering machinery Download PDFInfo
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- CN111005899B CN111005899B CN201911390987.1A CN201911390987A CN111005899B CN 111005899 B CN111005899 B CN 111005899B CN 201911390987 A CN201911390987 A CN 201911390987A CN 111005899 B CN111005899 B CN 111005899B
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- 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
- F15B11/02—Systems essentially incorporating special features for controlling the speed or actuating force of an output member
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
- F04B49/002—Hydraulic systems to change the pump delivery
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
- F04B49/005—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00 changing the phase relationship of two working pistons in one working chamber or the phase-relationship of a piston and a driven distribution member
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- 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
- F15B11/02—Systems essentially incorporating special features for controlling the speed or actuating force of an output member
- F15B11/028—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the actuating force
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- 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
- F15B11/02—Systems essentially incorporating special features for controlling the speed or actuating force of an output member
- F15B11/04—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed
- F15B11/042—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed by means in the feed line, i.e. "meter in"
- F15B11/0423—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed by means in the feed line, i.e. "meter in" by controlling pump output or bypass, other than to maintain constant speed
Abstract
The invention relates to a load-sensitive hydraulic system with controllable oil pump limit displacement, a control method and engineering machinery. Wherein, the controllable load sensitive hydraulic system of oil pump limit discharge volume includes: the load-sensitive variable pump comprises a variable mechanism and an oil pump, wherein the variable mechanism is connected with the oil pump; and the control mechanism is operably connected with the variable mechanism and is configured to operably control the variable mechanism according to working conditions so as to adjust the limit displacement of the oil pump through the variable mechanism. The invention can be realized in a load sensitive system, and the limit displacement of the oil pump can be adjusted at will in an adjustable range according to the requirements of working conditions.
Description
Technical Field
The invention relates to the field of engineering machinery, in particular to a load-sensitive hydraulic system with controllable oil pump limit displacement, a control method and engineering machinery.
Background
The crane hydraulic system is responsible for power transmission and speed control and adjustment of actions such as crane hoisting, amplitude variation, stretching and the like, a load sensitive technology is generally adopted on the existing medium and small tonnage cranes, and the crane hydraulic system has the advantages of being stable and reliable and good in control performance. With the rapid development of the hydraulic system technology of the wheel crane, especially under the background of increasing fuel cost, more and more attention is paid to a method for realizing energy conservation by optimizing the power matching of the hydraulic system of the wheel crane and an engine. The upgrading of a load sensitive system is an industry research direction to better realize the matching with the engine power on the basis of keeping the good performance of the original system.
The limit displacement control mode of the related oil pump is to control a load sensitive system through constant power or variable power, wherein the constant power control mode cannot perform matching adjustment on a hydraulic system according to the working condition of an engine; and the control mode of variable power is inflexible, and the limit displacement of the oil pump cannot be accurately matched with the rotating speed of the engine.
Disclosure of Invention
Some embodiments of the invention provide a load-sensitive hydraulic system with a controllable oil pump limit displacement, a control method and engineering machinery, which can adjust the oil pump limit displacement according to different working conditions.
Some embodiments of the present invention provide a load-sensitive hydraulic system in which the limit displacement of an oil pump is controllable, comprising:
the load-sensitive variable pump comprises a variable mechanism and an oil pump, wherein the variable mechanism is connected with the oil pump;
and
a control mechanism operatively connected to the variable mechanism, the control mechanism configured to operatively control the variable mechanism according to operating conditions to adjust a limit displacement of the oil pump by the variable mechanism.
In some embodiments, the variable displacement mechanism comprises a variable displacement cylinder, the variable displacement cylinder is connected with the oil pump, the control mechanism comprises an electro-proportional valve and a controller, the controller is connected with the electro-proportional valve, the controller is configured to control the current of the electro-proportional valve according to operating condition parameters, and the electro-proportional valve is connected with the variable displacement cylinder through an oil path to control the reciprocating motion of the variable displacement cylinder so as to adjust the limit displacement of the oil pump.
In some embodiments, the load-sensitive hydraulic system with controllable oil pump limit displacement includes a throttle valve, the throttle valve is disposed at an output end of the oil pump, the variable mechanism includes a differential pressure control valve, the differential pressure control valve is connected to the electro-proportional valve and the output end of the oil pump, a first control end of the differential pressure control valve is connected to the output end of the oil pump, a second control end of the differential pressure control valve is connected to the output end of the oil pump, and a connection position is located at a downstream of the throttle valve, the differential pressure control valve is controlled by the output end pressure and the load pressure of the oil pump, so that the output end pressure and the load of the oil pump always keep a constant value relationship, and then the displacement of the oil pump is changed between 0 and the limit displacement according to the opening degree of the throttle valve.
In some embodiments, the variable cylinder comprises a cylinder barrel, a cylinder rod and a piston, the piston is arranged in the cylinder barrel and divides the cylinder barrel into a first cavity and a second cavity, the first end of the cylinder rod penetrates through the first cavity and is connected with the oil pump in a driving mode, and the second end of the cylinder rod is connected with the piston.
In some embodiments, the load-sensitive hydraulic system with controllable limit displacement of the oil pump further comprises an oil tank, the electro-proportional valve connects the output end of the oil pump and the second chamber of the variable cylinder through an oil path, and the electro-proportional valve is configured to selectively introduce the oil output from the output end of the oil pump into the second chamber and control the amount of oil entering the second chamber or introduce the oil of the second chamber to the oil tank.
In some embodiments, the electro-proportional valve comprises a valve core, a first working position, a second working position, a first control end and a second control end, and the pressure difference between the acting force of the first control end and the acting force of the second control end drives the valve core to move so that the valve core is in a first limit position, the electro-proportional valve is in the first working position, or the valve core is in a second limit position, the electro-proportional valve is in the second working position, or the valve core is between the first limit position and the second limit position;
the electro proportional valve is configured to:
at a first station, introducing oil at the output end of the oil pump into the second chamber or introducing the oil in the second chamber to the oil tank;
at a second station, oil at the output of the oil pump is introduced into the second chamber.
In some embodiments, the first control end is provided with a proportional electromagnet.
In some embodiments, the first control end is further provided with a first spring.
In some embodiments, the second control end is provided with a second spring, and the second end of the cylinder rod penetrates through the second cavity to be connected with the second spring.
In some embodiments, the load-sensitive hydraulic system with controllable oil pump limit displacement further comprises an engine, a rotation speed sensor and a pressure sensor, wherein the engine is in driving connection with the oil pump, the rotation speed sensor is arranged on the engine, the pressure sensor is arranged at the output end of the oil pump, the rotation speed sensor and the pressure sensor are both electrically connected with the controller, and the controller is configured to adjust the current of the electro proportional valve according to engine rotation speed signals transmitted by the rotation speed sensor and the pressure sensor and a pressure signal at the output end of the oil pump.
In some embodiments, the load-sensitive hydraulic system with controllable oil pump limit displacement further comprises an oil tank, and the variable mechanism further comprises a differential pressure control valve, wherein the differential pressure control valve is connected with the output end of the oil pump, the electric proportional valve and the oil tank; the differential pressure control valve is configured to selectively direct oil output from the output of the oil pump therethrough to the electro proportional valve such that the oil is directed through the electro proportional valve into the second chamber or direct oil from the second chamber directed out of the electro proportional valve therethrough to the oil tank.
In some embodiments, the differential pressure control valve comprises a third station, a fourth station, a third control end and a fourth control end, the third control end is used for controlling the differential pressure control valve to be in the third station, and the fourth control end is used for controlling the differential pressure control valve to be in the fourth station;
the differential pressure control valve is configured to:
at a third station, guiding the oil of the second chamber led out from the electro proportional valve to the oil tank through the electro proportional valve;
in a fourth station, oil output by the output end of the oil pump is guided to the electro-proportional valve through the electro-proportional valve, so that the oil is guided into the second cavity through the electro-proportional valve.
In some embodiments, the third control end is provided with a third spring.
In some embodiments, the fourth control terminal is connected to the output terminal of the oil pump.
Some embodiments of the invention provide a working machine comprising a load-sensitive hydraulic system with a controllable limit displacement of an oil pump as described above.
Some embodiments of the present invention provide a control method of the above load-sensitive hydraulic system in which the limit displacement of the oil pump is controllable, including: controlling the constant power of the oil pump;
according to the power expression N ═ PxVRow board，
Wherein N is the power of the oil pump, P is the output end pressure of the oil pump, VRow boardIs the displacement of the oil pump;
due to the discharge V of the oil pumpRow boardThe current I of the electro proportional valve is positively or negatively correlated, so the power expression is transformed into N ═ P × I;
when the oil pump reaches a constant power value, if the pressure P increases, the control current I is reduced so as to keep the power of the oil pump at a constant value.
In some embodiments, wherein the load-sensitive hydraulic system in which the limit displacement of the oil pump is controllable further comprises an engine, the engine is in driving connection with the oil pump, and the control method comprises:
the variable power control of the oil pump is realized by acquiring a first power value N of the oil pump corresponding to a first rotating speed value of the engine according to an engine characteristic curve1And a second power value N of the oil pump corresponding to a second rotation speed value of the engine2；
When the rotational speed of the engine reaches a first rotational speed value, a first power value N1＝P1×I1If the pressure P is1Increasing, then controlling the current I1Decrease;
when the rotating speed of the engine reaches a second rotating speed value, a second power value N2＝P2×I2If the pressure P is2Increasing, then controlling the current I2And (4) reducing.
Some embodiments of the present invention provide a control method for the load-sensitive hydraulic system with a controllable oil pump limit displacement, wherein the load-sensitive hydraulic system with the controllable oil pump limit displacement further includes an engine, and the control method includes: the controller controls the flow of the electro proportional valve according to the load pressure and/or the engine speed so as to control the reciprocating motion of the variable cylinder and further adjust the limit displacement of the oil pump.
Some embodiments of the present invention provide a control method of the above load-sensitive hydraulic system in which the limit displacement of the oil pump is controllable, including: controlling the displacement and the limit displacement of the oil pump, wherein a second control end of the electro proportional valve is provided with a second spring, and a second end of the cylinder rod penetrates through a second cavity to be connected with the second spring; the variable mechanism further comprises a differential pressure control valve, and the differential pressure control valve is connected with the output end of the oil pump, the electro proportional valve and the oil tank;
when the proportional electromagnet is not electrified, a throttling valve arranged at the output end of the oil pump is fully opened, when a system has a load, the electro-proportional valve is positioned at a first station under the action of a first spring, the differential pressure control valve is positioned at a third station under the action of the load, oil in a second cavity of the variable cylinder flows to the oil tank through the electro-proportional valve and the differential pressure control valve, the oil pump is changed towards large displacement, the pressure of the output end of the oil pump is increased, the second end of the cylinder rod compresses a second spring, the second spring acts on a second control end of the electro-proportional valve, when the acting force of the second spring is greater than that of the first spring, the electro-proportional valve is switched to the second station, at the moment, the oil at the output end of the oil pump flows to a second cavity, and after the electro-proportional valve and the differential pressure control valve reach dynamic balance, the displacement of the oil pump is the initial limit displacement at the moment;
the load sensitive system changes the displacement of the oil pump between 0 and the initial limit displacement according to the opening degree of the throttle valve;
when the oil pump is electrified, a throttling valve arranged at the output end of the oil pump is fully opened, the system has a load, and when the current reaches the maximum value, the electric proportional valve is positioned at a first station under the combined action of the proportional electromagnet and a first spring, the pressure difference control valve is positioned at a third station under the action of the load, the oil in a second cavity of the variable cylinder flows to an oil tank through the electric proportional valve and the pressure difference control valve, the oil pump is changed to a large displacement, the second end of the cylinder rod compresses a second spring, the second spring acts on a second control end of the electric proportional valve, when the acting force of the second spring is greater than the sum of the acting forces of the proportional electromagnet and the first spring, the electric proportional valve is switched to the second station, at the moment, the oil at the output end of the oil pump flows to the second cavity, and after the electric proportional valve and the pressure difference control valve reach dynamic balance, the displacement of the oil pump is at the maximum displacement limit;
the load sensing system enables the displacement of the oil pump to be changed between 0 and the maximum limit displacement according to the opening degree of the throttle valve;
when the proportional electromagnet is electrified, a throttle valve arranged at the output end of the oil pump is fully opened, the system has a load, and the maximum current value is not reached, the electric proportional valve is positioned at a first station under the combined action of the proportional electromagnet and the first spring, the pressure difference control valve is positioned at a third station under the action of the load, oil in the second cavity of the variable cylinder flows to the oil tank through the electric proportional valve and the pressure difference control valve, the oil pump is changed to a large displacement, the second end of the cylinder rod compresses the second spring, the second spring acts on the second control end of the electric proportional valve, when the acting force of the second spring is larger than the sum of the acting forces of the proportional electromagnet and the first spring, the electric proportional valve is switched to the second station, at the moment, the oil at the output end of the oil pump flows to the second cavity, and the electric proportional valve and the pressure difference control valve reach dynamic balance, and the displacement of the oil pump is at the middle limit;
the load sensitive system changes the displacement of the oil pump between 0 and the middle limit displacement according to the opening degree of the throttle valve.
Based on the technical scheme, the invention at least has the following beneficial effects:
in some embodiments, the control mechanism is operatively connected with the variable mechanism, and the control mechanism is configured to operatively control the variable mechanism according to the working conditions so as to adjust the limit displacement of the oil pump through the variable mechanism for the purpose of controlling different limit displacements of the oil pump.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without limiting the invention. In the drawings:
FIG. 1 is a schematic diagram of a load sensitive hydraulic system with controllable oil pump limit displacement provided in accordance with some embodiments of the present invention;
FIG. 2 is a schematic diagram of a variable cylinder and electro-proportional valve provided in accordance with some embodiments of the present invention.
The reference numbers in the drawings illustrate the following:
1-an oil tank;
2-an oil pump;
3, an engine;
4-variable cylinder; 41-a cylinder barrel; 42-cylinder rod; 43-a piston; 44-a fourth spring; 45-a first cavity; 46-a second cavity;
5-an electro proportional valve; 51-a first spring; 52-a second spring; 53-proportional electromagnet;
6-differential pressure control valve; 61-a third spring;
7-a controller;
8-a rotation speed sensor;
9-a pressure sensor;
10-throttle valve.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments. It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without any inventive step, are within the scope of the present invention.
In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate orientations or positional relationships based on those shown in the drawings, and are used merely for convenience in describing the present invention and for simplifying the description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore, should not be taken as limiting the scope of the present invention.
Technical terms in the present disclosure are explained first.
Oil pump limit displacement: the maximum allowable displacement of the oil pump under a certain working condition, and the actual working displacement of the oil pump which is subjected to load sensitive control after the limit displacement is set is less than or equal to the limit displacement. For a common oil pump, the limit displacement of the oil pump is the nominal displacement.
As shown in fig. 1, some embodiments provide a load-sensitive hydraulic system with a controllable limit displacement of an oil pump, which includes a load-sensitive variable displacement pump and a control mechanism.
The load-sensitive variable pump comprises a variable mechanism and an oil pump 2, wherein the variable mechanism is connected with the oil pump 2.
The control mechanism is operatively connected with the variable mechanism, and the control mechanism is configured to operatively control the variable mechanism according to the working condition so as to adjust the limit displacement of the oil pump 2 through the variable mechanism.
In some embodiments, the variable displacement mechanism comprises a variable displacement cylinder 4, the variable displacement cylinder 4 is connected with the oil pump 2, the control mechanism comprises an electro-proportional valve 5 and a controller 7, the controller 7 is connected with the electro-proportional valve 5, the controller 7 is configured to control the current of the electro-proportional valve 5 according to the operating condition parameters, and the electro-proportional valve 5 is connected with the variable displacement cylinder 4 through an oil path to control the reciprocating motion of the variable displacement cylinder 4 so as to adjust the limit displacement of the oil pump 2.
In some embodiments, the load-sensitive hydraulic system with controllable oil pump limit displacement includes a throttle valve 10, the throttle valve 10 is disposed at an output end of the oil pump 2, the variable mechanism includes a differential pressure control valve 6, the differential pressure control valve 6 is connected to the electro-proportional valve 5 and the output end of the oil pump 2, a first control end of the differential pressure control valve 6 is connected to the output end of the oil pump 2, a second control end of the differential pressure control valve 6 is connected to the output end of the oil pump 2, and the connection position is located downstream of the throttle valve 10, the differential pressure control valve 6 is controlled by the output end pressure and the load pressure of the oil pump 2, so that the output end pressure and the load of the oil pump 2 always keep a constant value relationship, and further, according to the opening degree of the throttle valve 10, the displacement of the oil pump 2 is changed from 0 to the limit displacement.
In some embodiments, a load-sensitive hydraulic system with controllable oil pump limit displacement includes an oil tank 1, an oil pump 2, an engine 3, a variable cylinder 4, and an electro-proportional valve 5.
The input end of the oil pump 2 is connected with the oil tank 1. The engine 3 is in driving connection with the oil pump 2.
As shown in fig. 2, the variable cylinder 4 includes a cylinder tube 41, a cylinder rod 42, and a piston 43. The piston 43 is provided in the cylinder 41 to divide the interior of the cylinder 41 into a first chamber 45 and a second chamber 46. A first end of the cylinder rod 42 is drivingly connected to the oil pump 2 through the first chamber 45, and a second end of the cylinder rod 42 is connected to the piston 43.
As shown in fig. 1, the cylinder rod 42 projects toward the first end thereof, the displacement of the oil pump 2 decreases, the cylinder rod 42 projects toward the second end thereof, and the displacement of the oil pump 2 increases.
An electro proportional valve 5 connects the output of the oil pump 2 and the second chamber 46 of the variable cylinder 4, the electro proportional valve 5 being configured to selectively introduce oil output from the output of the oil pump 2 into the second chamber 46 and control the amount of oil entering the second chamber 46 or direct oil from the second chamber 46 to the oil tank 1.
In some embodiments, the electro-proportional valve 5 is configured to introduce oil output from the output end of the oil pump 2 into the second chamber 46 and control the amount of oil entering the second chamber 46 for the purpose of controlling different displacements of the oil pump 2, and can change the limit displacement of the oil pump according to the engine frequency, achieve any matching of the hydraulic system and the engine power, reduce the operating speed of the engine, and prevent the engine from stalling.
In some embodiments, the electro-proportional valve 5 includes a first station, a second station, a first control end for controlling the electro-proportional valve 5 in the first station, and a second control end for controlling the electro-proportional valve 5 in the second station.
The electro proportional valve 5 is configured to:
in the first station, the oil at the output end of the oil pump 2 is introduced into the second chamber 46 or the oil in the second chamber 46 is introduced into the oil tank 1;
in the second station, the oil at the output of the oil pump 2 is introduced into the second chamber 46.
In some embodiments, the first control end of the electro-proportional valve 5 is provided with a proportional electromagnet 53, and the purpose of variable limit displacement of the oil pump can be achieved by changing the control current led to the proportional electromagnet 53.
In some embodiments, the first control end of the electro proportional valve 5 is further provided with a first spring 51. The first spring 51 is an oil pump initial limit displacement setting spring, and the oil pump initial limit displacement value can be set by the first spring 51 under the condition that the proportional electromagnet 53 is not energized.
Of course, the initial limit displacement of the oil pump may not be obtained by providing the first spring 51, and the purpose of setting the initial limit displacement value of the oil pump may be achieved by, for example, setting the minimum current to the proportional electromagnet 53.
In some embodiments, the second control end of the electro-proportional valve 5 is provided with a second spring 52, and the second end of the cylinder rod 42 extends out of the second chamber 46 to be connected to the second spring 52. The second spring 52 is a displacement feedback spring, and can realize the accurate matching of the control current led into the proportional electromagnet 53 and the limit displacement of the oil pump.
The cylinder tube 41 includes a first end and a second end along the extension and contraction direction of the cylinder rod 42, and the first end of the cylinder rod 42 passes through the first chamber 45 and the first end to be connected to the oil pump 2. The second end of the cylinder rod 42 extends out of the second chamber 46 and the second end is connected to a second spring 52.
In some embodiments, as shown in fig. 1, the load-sensitive hydraulic system with controllable oil pump limit displacement further includes an engine 3, a rotation speed sensor 8 and a pressure sensor 9, the engine 3 is drivingly connected to the oil pump 2, the rotation speed sensor 8 is disposed on the engine 3, the pressure sensor 9 is disposed on an output end of the oil pump 2, both the rotation speed sensor 8 and the pressure sensor 9 are electrically connected to the controller 7, and the controller 7 is configured to adjust the current of the electro-proportional valve 5 according to engine rotation speed signals transmitted by the rotation speed sensor 8 and the pressure sensor 9 and a pressure signal at the output end of the oil pump 2.
The controller 7 obtains a rotating speed signal of the engine 3 detected by the rotating speed sensor 8 and a pressure signal of the output end of the oil pump 2 detected by the pressure sensor 9, and the controller 7 sends a current signal for controlling the electric proportional valve 5 to be led in according to the rotating speed signal and the pressure signal, so that the precise control of the limit displacement of the oil pump and the control current is realized.
In some embodiments, the load-sensitive hydraulic system with controllable oil pump limit displacement further comprises a differential pressure control valve 6, wherein the differential pressure control valve 6 is connected with the output end of the oil pump 2, the electro-proportional valve 5 and the oil tank 1; the differential pressure control valve 6 is configured to selectively direct the oil output from the output side of the oil pump 2 to the electro proportional valve 5 therethrough so that the oil is introduced into the second chamber 46 through the electro proportional valve 5, or direct the oil of the second chamber 46 from the electro proportional valve 5 therethrough to the oil tank 1.
In some embodiments, the differential pressure control valve 6 includes a third position, a fourth position, a third control end for controlling the differential pressure control valve 6 in the third position, and a fourth control end for controlling the differential pressure control valve 6 in the fourth position.
The differential pressure control valve 6 is configured to:
in the third station, the oil of the second chamber 46 led out of the electro proportional valve 5 is led to the oil tank 1 through the electro proportional valve;
in the fourth position, the oil output from the output of the oil pump 2 is directed through it to the electro proportional valve 5, so that the oil is introduced into the second chamber 46 through the electro proportional valve 5.
In some embodiments, the third control end is provided with a third spring 61.
In some embodiments, the fourth control terminal is connected to the output terminal of the oil pump 2.
The differential pressure control valve 6 is used for realizing load sensitive control of a hydraulic system and can realize that the oil inlet pressure of a main valve is higher than the highest load by a certain differential pressure. The differential pressure control valve 6 is used for setting the front-back differential pressure of the throttle opening of the main valve, the oil pump 2 can provide corresponding flow according to the system requirement, and the flow required by the system is not influenced by the load pressure.
In some embodiments, electro-proportional valve 5 includes a first port, a second port, and a third port. The first oil port of the electro-proportional valve 5 is connected with the second cavity 46 of the variable cylinder 4, the second oil port of the electro-proportional valve 5 is connected with the differential pressure control valve 6, and the third oil port of the electro-proportional valve 5 is connected with the output end of the oil pump 2.
When the electro-proportional valve 5 is in the first station, the first oil port and the second oil port of the electro-proportional valve 5 are communicated, and the third oil port of the electro-proportional valve 5 is cut off. When the electro-proportional valve 5 is in the second station, the first oil port and the third oil port of the electro-proportional valve 5 are communicated, and the second oil port of the electro-proportional valve 5 is cut off.
In some embodiments, the differential pressure control valve 6 includes a fourth port connected to the second port of the electro-proportional valve 5, a fifth port connected to the oil tank 1, and a sixth port connected to the output end of the oil pump 2.
When the differential pressure control valve 6 is at the first station, the fourth oil port and the fifth oil port of the differential pressure control valve 6 are communicated, and the sixth oil port of the differential pressure control valve 6 is cut off. When the differential pressure control valve 6 is at the second station, the fourth oil port and the sixth oil port of the differential pressure control valve 6 are communicated, and the fifth oil port of the differential pressure control valve 6 is cut off.
In some embodiments, the variable cylinder 4 comprises a fourth spring 44, the fourth spring 44 is disposed in a first chamber 45 of the variable cylinder 4, a first end of the fourth spring 44 abuts a first end of the cylinder tube 41, and a second end of the fourth spring 44 abuts the piston 43.
Some embodiments provide a work machine including a load-sensitive hydraulic system with controllable limit displacement of an oil pump as described above.
In some embodiments, the work machine comprises a crane, a hydraulic excavator, a rotary drilling rig, or the like.
Some embodiments provide a method of controlling a load-sensitive hydraulic system in which a limit displacement of an oil pump is controllable, comprising: the control of the oil pump 2 at constant power, wherein,
according to the power expression N ═ PxVRow board
Where N is the power of the oil pump 2, P is the output pressure of the oil pump 2, VRow boardIs the displacement of the oil pump 2.
Due to the discharge V of the oil pump 2Row boardThe power expression is therefore transformed into N × I, in positive correlation with the current I of the electro proportional valve 5.
When the motor 3 reaches a constant power value, the control current I is reduced if the pressure P is increased, and the control current I is increased if the pressure P is reduced, so that the power of the motor 3 is maintained at a constant value.
Since the limit displacement of the oil pump is controlled by the action force of the proportional electromagnet 53, and the action force of the proportional electromagnet 53 is controlled by the current, the limit displacement of the oil pump is positively correlated with the current I, and the controller 7 acquires the system pressure P detected by the pressure sensor 9 according to P × I ═ N (constant), and when the system pressure increases, the controller 7 reduces the current I to the proportional electromagnet 53, that is, the constant power control of the engine can be realized.
In some embodiments, a method of controlling a load-sensitive hydraulic system in which the oil pump limit displacement is controllable, comprises: control of variable power of the oil pump 2, wherein:
according to the characteristic curve of the engine 3, a first power value N of the oil pump 2 corresponding to a first rotating speed value of the engine 3 is obtained1And a second power value N of the oil pump 2 corresponding to a second rotation speed value of the engine 32。
When the rotation speed of the engine 3 reaches the first rotation speed value, the first power value N is used1＝P1×I1If the pressure P is1Increasing, then controlling the current I1And (4) reducing.
When the rotation speed of the engine 3 reaches the second rotation speed value, according to the second power value N2＝P2×I2If the pressure P is2Increasing, then controlling the current I2And (4) reducing.
Of course, according to the characteristic curve of the engine 3, not only the first power value corresponding to the first rotation speed value and the second power value corresponding to the second rotation speed value are obtained, but also the third power value corresponding to the third rotation speed value and the fourth power value corresponding to the fourth rotation speed value, and the like may be obtained.
Since the limit displacement of the oil pump is controlled by the force of the proportional electromagnet 53 and the force of the proportional electromagnet 53 is controlled by the current, the limit displacement of the oil pump is positively correlated with the current I, and according to P × I — N ═ f (N), when the power N is set to vary with the rotation speed N of the engine, the controller 7 acquires the system pressure P detected by the pressure sensor 9 when the power corresponding to the rotation speed is obtained, and when the system pressure increases, the controller 7 reduces the current I to the proportional electromagnet 53, thereby realizing the variable power control of the engine.
In some embodiments, the load-sensitive hydraulic system with the controllable oil pump limit displacement can not only realize the matching of the hydraulic system and the engine power (comprising constant power and variable power), but also realize the precise matching of the oil pump limit displacement and the engine speed.
In some embodiments, a load-sensitive hydraulic system control method with controllable oil pump limit displacement includes: the controller 7 controls the flow rate of the electro proportional valve 5 according to the load pressure and/or the engine speed to control the reciprocating motion of the variable cylinder 4, thereby adjusting the limit displacement of the oil pump 2.
In some embodiments, a method of controlling a load sensitive hydraulic system with a controllable limit displacement of an oil pump, comprising: controlling the displacement and the limit displacement of the oil pump 2, wherein a second control end of the electro-proportional valve 5 is provided with a second spring 52, and a second end of the cylinder rod 42 penetrates through the second cavity 46 to be connected with the second spring 52; the variable mechanism further comprises a differential pressure control valve 6, and the differential pressure control valve 6 is connected with the output end of the oil pump 2, the electro-proportional valve 5 and the oil tank 1;
when the proportional electromagnet 53 is not electrified, and the throttle valve 10 arranged at the output end of the oil pump 2 is fully opened, and the system has a load, the electro proportional valve 5 is in a first working position under the action of a first spring 51, the differential pressure control valve 6 is in a third working position under the action of a load, oil in the second cavity 46 of the variable cylinder 4 flows to the oil tank 1 through the electro proportional valve 5 and the differential pressure control valve 6, the oil pump 2 changes towards large displacement, the pressure at the output end of the oil pump 2 rises, the second end of the cylinder rod 42 compresses a second spring 52, the second spring 52 acts on a second control end of the electro proportional valve 5, when the acting force of the second spring 52 is greater than that of the first spring 51, the electro-proportional valve 5 is switched to the second station, at this time, the oil at the output end of the oil pump 2 flows to the second chamber 46, and after the electro-proportional valve 5 and the differential pressure control valve 6 reach dynamic balance, the displacement of the oil pump 2 at this time is the initial (minimum) limit displacement;
the load-sensitive system then varies the oil pump displacement between 0 and the initial limit displacement depending on the opening degree of the throttle valve 10.
The proportional electromagnet 53 is electrified, the throttle valve 10 arranged at the output end of the oil pump 2 is fully opened, the system has a load, when the current reaches the maximum value, the electro proportional valve 5 is in the first working position under the combined action of the proportional electromagnet 53 and the first spring 51, the differential pressure control valve 6 is in the third working position under the action of load, the oil in the second cavity 46 of the variable cylinder 4 flows to the oil tank 1 through the electro proportional valve 5 and the differential pressure control valve 6, the oil pump 2 changes towards large discharge, the second end of the cylinder rod 42 compresses the second spring 52, the second spring 52 acts on the second control end of the electro proportional valve 5, when the force of the second spring 52 is greater than the sum of the forces of the proportional electromagnet 53 and the first spring 51, the electro-proportional valve 5 is switched to a second station, at this time, oil at the output end of the oil pump 2 flows to the second cavity 46, and after the electro-proportional valve 5 and the differential pressure control valve 6 reach dynamic balance, the displacement of the oil pump 2 is the maximum limit displacement at this time;
the load-sensitive system then varies the oil pump displacement between 0 and the maximum limit displacement, depending on the size of the opening of the throttle valve 10.
When the proportional electromagnet 53 is electrified, the throttle valve 10 arranged at the output end of the oil pump 2 is fully opened, the system has a load and does not reach the maximum current value, the electro-proportional valve 5 is in a first working position under the combined action of the proportional electromagnet 53 and the first spring 51, the differential pressure control valve 6 is in a third working position under the action of the load, the oil in the second chamber 46 of the variable cylinder 4 flows to the oil tank 1 through the electro-proportional valve 5 and the differential pressure control valve 6, the oil pump 2 is changed towards large discharge, the second end of the cylinder rod 42 compresses the second spring 52, the second spring 52 acts on the second control end of the electro-proportional valve 5, when the acting force of the second spring 52 is larger than the sum of the acting forces of the proportional electromagnet 53 and the first spring 51, the electro-proportional valve 5 is switched to the second working position, at the moment, the oil at the output end of the oil pump 2 flows to the second chamber 46, and the electro-proportional valve 5 and the differential pressure control valve 6 reach dynamic balance, at this time, the displacement of the oil pump 2 is the middle limit displacement;
the load sensitive system changes the displacement of the oil pump between 0 and the middle limit displacement according to the opening degree of the throttle valve.
In some specific embodiments, the load-sensitive hydraulic system with controllable oil pump limit displacement is used for realizing the controllability of the oil pump limit displacement, and the specific control process is as follows:
when the engine 3 is shut off, the differential pressure control valve 6 is in the third position under the spring force of the third spring 61, the electro-proportional valve 5 is in the first position under the action of the first spring 51, the second chamber 46 of the variable cylinder 4 is in an unloading state at this time, the piston 43 is at the rightmost end (second end) of the cylinder tube 41 under the action of the fourth spring 44, the cylinder rod 42 compresses the second spring 52, the second spring 52 is at the compression maximum, and the swing angle of the oil pump 2 is at the maximum displacement.
When the engine 3 is ignited, because the pressure at the output end of the oil pump 2 is rapidly increased, at this time, the differential pressure control valve 6 is in the fourth station under the action of the pressure at the output end of the oil pump 2, the electro-proportional valve 5 is still in the first station, the oil is fed into the second chamber 46 of the variable cylinder 4, the piston 43 of the variable cylinder 4 is pushed to move towards the left end (first end part) of the cylinder barrel 41, and the oil pump 2 changes towards small displacement until the oil pump 2 reaches very small displacement.
When the handle is operated, the differential pressure control valve 6 is in a third working position under the action of load, at the moment, the second cavity 46 of the variable cylinder 4 starts to unload, the piston 43 of the variable cylinder 4 moves towards the second end of the cylinder barrel 41, the oil pump 2 changes towards large displacement, the cylinder rod 42 of the variable cylinder 4 compresses the second spring 52, the second spring 52 acts on the second control end of the electric proportional valve 5, when the spring force of the second spring 52 is greater than the acting force of the first spring 51, the electric proportional valve 5 is in the first working position, at the moment, the second cavity 46 of the variable cylinder 4 is communicated with the output end of the oil pump 2, the second cavity 46 of the variable cylinder 4 stops unloading, finally, a dynamic balance is achieved, and at the moment, the displacement of the oil pump 2 is an initial limit displacement.
When the oil pump reaches the initial limit displacement, if the proportional electromagnet 53 is electrified, the electro-proportional valve 5 is in the first station under the action of electromagnetic force, at this time, the second chamber 46 of the variable cylinder 4 is in an unloading state, the piston 43 of the variable cylinder 4 continues to move rightwards, the oil pump 2 changes towards large displacement, the cylinder rod 42 of the variable cylinder 4 continues to compress the second spring 52, when the spring acting force of the second spring 52 is greater than the sum of the acting forces of the first spring 51 and the proportional electromagnet 43, the electro-proportional valve 5 is switched to the second station, at this time, the second chamber 46 of the variable cylinder 4 is communicated with the output end of the oil pump 2, the second chamber 46 of the variable cylinder 4 stops unloading, and finally, a dynamic balance is achieved, at this time, the displacement of the oil pump 2 is in the middle limit displacement.
When the current that energizes the proportional solenoid 53 reaches the maximum, the displacement of the oil pump 2 at which the electro-proportional valve 5 reaches dynamic balance is the maximum limit displacement.
In some specific embodiments, the load-sensitive hydraulic system with controllable oil pump limit displacement is used for realizing constant power control of the oil pump, and the specific control process is as follows:
according to the power expression N ═ PxVRow boardDue to the maximum displacement V of the pumpRow boardThe power expression is then converted to N ═ P × I, which is positively correlated to the current I to the proportional electromagnet 53. The constant power control is that when the system reaches a power control point, along with the increase of the system pressure P, the controller 7 controls the current I led to the proportional electromagnet 53 to decrease, the maximum displacement of the oil pump 2 decreases, and the power N is always ensured to be constant, that is, the constant power control. The constant power control can ensure that the system can still normally run under the condition that the torque of a transmission shaft or the power of an oil pump and the like are limited.
In some specific embodiments, the load-sensitive hydraulic system with controllable oil pump limit displacement is used for realizing variable power control of an oil pump, and the specific control process is as follows:
since the output of the engine 3 and the number of revolutions of the engine 3 have a certain relationship, if the number of revolutions of the engine 3 is high, the output is high (depending on the engine 3 characteristic curve), and in order to fully develop the performance of the engine 3, the system can perform variable power control, that is, set the relational expression N between the power and the number of revolutions of the engine to be f (N), and set different power control points N depending on the number of revolutions of the engine.
Assuming that the rotation speed of the engine 3 is 800, the power N at the rotation speed is f (800), and the power control process at 800 revolutions is the constant power control process at 800 revolutions.
As the rotation speed of the engine 3 increases, when the rotation speed is 1200 revolutions, the power at the rotation speed may be determined to be N ═ f (1200), and the power control process at 1200 revolutions is the constant power control process at 1200 revolutions.
In the system, the corresponding current introduced into the proportional electromagnet 53 at different rotating speeds of the engine 3 can be set according to the requirement, so that the power at different rotating speeds of the engine 3 is different, and the variable power control is realized.
The power of the oil pump is limited by the power of the engine.
In some specific embodiments, the load-sensitive hydraulic system with the controllable oil pump limit displacement is used for realizing the accurate matching control of the oil pump limit displacement and the rotating speed of the engine 3, and the specific control process is as follows:
the control point set generally for constant power or variable power control is higher, the control is started only when the power is higher for heavy load or system demand, and the control is automatic adjustment, and the displacement of the oil pump cannot be controlled under the working condition that the power control point is not reached.
The present embodiment is also used to achieve the adjustment of the displacement of the oil pump 2 by adjusting the current to the proportional electromagnet 53 when the system does not reach the power control point. Under the light load or medium load working condition, a user can set the limit displacement of the oil pump corresponding to the rotating speed of a certain engine 3 according to the requirement of the working condition. If a user can set a small current under the idle working condition of the engine 3 under the working condition that the required speed is slow, the limit displacement of the oil pump is small, and the requirement of slow speed can be met even if the user handle is fully opened.
In some specific embodiments, the load-sensitive hydraulic system with the controllable oil pump limit displacement is used for realizing the variable limit displacement of the load-sensitive system, and the specific control process is as follows:
the load sensitive system varies the displacement of the oil pump between 0 and a maximum displacement as the load varies. The embodiment of the disclosure can be realized in a load-sensitive system, the maximum displacement of the oil pump can be adjusted, that is, along with the change of the load, the oil pump can realize the displacement change between 0 and the set limit displacement. When the flow demand difference of multiple actuators sharing one pump is large, the flow demand difference can be met by setting different limit displacements of different actuators.
Based on the above embodiments, the present disclosure has at least the following advantages:
1) the oil pump limit displacement of the load sensitive system is accurately controlled by the current led into the proportional electromagnet, and the oil pump limit displacement is positively correlated with the current led into the proportional electromagnet and is irrelevant to the working pressure of the system.
2) And under the condition that the proportional electromagnet is not electrified, the proportional electromagnet has certain initial limit displacement. The actual displacement of the load sensitive system oil pump can operate in the range of 0 to the initial limit displacement.
3) By establishing the relation between the current led into the proportional electromagnet and the engine rotating speed n, the accurate matching of the oil pump limit displacement and the engine rotating speed can be realized.
4) By establishing the relation between the current led into the proportional electromagnet and the system pressure P, the arbitrary matching of the oil pump limit displacement and the engine power can be realized.
In the description of the present invention, it should be understood that the terms "first", "second", "third", etc. are used to define the components, and are used only for the convenience of distinguishing the components, and if not otherwise stated, the terms have no special meaning, and thus, should not be construed as limiting the scope of the present invention.
Furthermore, the technical features of one embodiment may be combined with one or more other embodiments advantageously without explicit negatives.
Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present invention and not to limit the same; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art will understand that: modifications to the specific embodiments of the invention or equivalent substitutions for parts of the technical features may be made; without departing from the spirit of the present invention, it is intended to cover all aspects of the invention as defined by the appended claims.
Claims (12)
1. A load sensitive hydraulic system with controllable oil pump limit displacement, comprising:
the load-sensitive variable pump comprises a variable mechanism and an oil pump (2), wherein the variable mechanism is connected with the oil pump (2), the variable mechanism comprises a variable cylinder (4), and the variable cylinder (4) is connected with the oil pump (2); and
a control mechanism operatively connected to the variable mechanism, the control mechanism being configured to operatively control the variable mechanism in accordance with operating conditions to adjust a limit displacement of the oil pump (2) by the variable mechanism, the control mechanism comprising an electro-proportional valve (5) and a controller (7);
the throttle valve (10), the throttle valve (10) is arranged at the output end of the oil pump (2), the variable mechanism comprises a differential pressure control valve (6), the differential pressure control valve (6) is connected with the electro proportional valve (5) and the output end of the oil pump (2), the first control end of the differential pressure control valve (6) is connected with the output end of the oil pump (2), the second control end of the differential pressure control valve (6) is connected with the output end of the oil pump (2), the connecting position is positioned at the downstream of the throttle valve (10), the differential pressure control valve (6) is controlled by the output end pressure and the load pressure of the oil pump (2) to ensure that the output end pressure and the load of the oil pump (2) always keep a constant value relationship, the displacement of the oil pump (2) is changed from 0 to the limit displacement according to the opening degree of the throttle valve (10);
the controller (7) is connected with the electro-proportional valve (5), the controller (7) is configured to control the current of the electro-proportional valve (5) according to working condition parameters, the electro-proportional valve (5) is connected with the variable cylinder (4) through an oil way to control the reciprocating motion of the variable cylinder (4) so as to adjust the limit displacement of the oil pump (2);
the variable cylinder (4) comprises a cylinder barrel (41), a cylinder rod (42) and a piston (43), the piston (43) is arranged in the cylinder barrel (41) and divides the interior of the cylinder barrel (41) into a first cavity (45) and a second cavity (46), the first end of the cylinder rod (42) penetrates through the first cavity (45) and is connected with the oil pump (2) in a driving mode, and the second end of the cylinder rod (42) is connected with the piston (43);
the load-sensitive hydraulic system further comprises an oil tank (1), the electro-proportional valve (5) is connected with the output end of the oil pump (2) and a second cavity (46) of the variable cylinder (4) through an oil path, and the electro-proportional valve (5) is configured to selectively introduce the oil output from the output end of the oil pump (2) into the second cavity (46) and control the oil amount entering the second cavity (46) or introduce the oil of the second cavity (46) into the oil tank (1);
the electro-proportional valve (5) comprises a valve core, a first station, a second station, a first control end and a second control end, wherein the valve core is driven to move by the pressure difference between the acting force of the first control end and the acting force of the second control end, so that the valve core is located at a first limit position, the electro-proportional valve (5) is located at the first station, or the valve core is located at a second limit position, the electro-proportional valve (5) is located at the second station, or the valve core is located between the first limit position and the second limit position;
the electro proportional valve (5) is configured to:
in a first station, introducing oil at the output end of the oil pump (2) into the second chamber (46) or introducing oil in the second chamber (46) to the oil tank (1);
-in a second station, introducing the oil at the output of the oil pump (2) into the second chamber (46);
the first control end is provided with a proportional electromagnet (53);
the first control end is also provided with a first spring (51).
2. The load sensitive hydraulic system with controllable oil pump limit displacement of claim 1, characterized in that the second control end is provided with a second spring (52), and the second end of the cylinder rod (42) passes out of the second chamber (46) to be connected with the second spring (52).
3. The load-sensitive hydraulic system with the controllable limit displacement of the oil pump as recited in claim 1, characterized by further comprising an engine (3), a rotation speed sensor (8) and a pressure sensor (9), wherein the engine (3) is in driving connection with the oil pump (2), the rotation speed sensor (8) is arranged on the engine (3), the pressure sensor (9) is arranged at the output end of the oil pump (2), the rotation speed sensor (8) and the pressure sensor (9) are both electrically connected with the controller (7), and the controller (7) is configured to adjust the current of the electro-proportional valve (5) according to engine rotation speed signals transmitted by the rotation speed sensor (8) and the pressure sensor (9) and a pressure signal at the output end of the oil pump (2).
4. The load-sensitive hydraulic system with controllable oil pump limit displacement according to claim 1, characterized by further comprising an oil tank (1), wherein the variable mechanism further comprises a differential pressure control valve (6), and the differential pressure control valve (6) is connected with the output end of the oil pump (2), the electro-proportional valve (5) and the oil tank (1); the differential pressure control valve (6) is configured to selectively direct oil output by the output of the oil pump (2) therethrough towards the electro-proportional valve (5) so that oil is introduced into the second chamber (46) through the electro-proportional valve (5), or direct oil of the second chamber (46) which is introduced out of the electro-proportional valve (5) therethrough towards the oil tank (1).
5. The load-sensitive hydraulic system with the controllable limit displacement of the oil pump as recited in claim 4, characterized in that the differential pressure control valve (6) comprises a third position, a fourth position, a third control end and a fourth control end, wherein the third control end is used for controlling the differential pressure control valve (6) to be in the third position, and the fourth control end is used for controlling the differential pressure control valve (6) to be in the fourth position;
the differential pressure control valve (6) is configured to:
in a third position, oil of the second chamber (46) from which the electro proportional valve (5) leads out is led to the oil tank (1) through the electro proportional valve;
in a fourth position, the oil output by the output of the oil pump (2) is directed through it to the electro proportional valve (5) so that it is introduced into the second chamber (46) through the electro proportional valve (5).
6. The load-sensitive hydraulic system with the controllable limit displacement of the oil pump as recited in claim 5, characterized in that the third control end is provided with a third spring (61).
7. The load-sensitive hydraulic system with controllable oil pump limit displacement according to claim 5, characterized in that the fourth control terminal is connected to the output of the oil pump (2).
8. A working machine, characterized by comprising a load-sensitive hydraulic system with controllable limit displacement of an oil pump according to any one of claims 1 to 7.
9. A control method of the load sensitive hydraulic system with controllable limit displacement of the oil pump as claimed in claim 1, comprising: controlling the constant power of the oil pump (2);
according to the power expression N ═ PxVRow board，
Wherein N is the power of the oil pump (2), P is the output end pressure of the oil pump (2), and VRow boardThe displacement of the oil pump (2);
due to the discharge V of the oil pump (2)Row boardIs positively or negatively correlated with the current I of the electro proportional valve (5), so the power expression is transformed into N ═ P × I;
when the oil pump (2) reaches a constant power value, if the pressure P increases, the control current I is reduced so as to keep the power of the oil pump (2) at a constant value.
10. The control method of the load-sensitive hydraulic system with the controllable oil pump limit displacement according to claim 9, wherein the load-sensitive hydraulic system with the controllable oil pump limit displacement further comprises an engine (3), and the engine (3) is in driving connection with the oil pump (2), and the control method comprises the following steps:
the variable power control of the oil pump (2), wherein a first power value N of the oil pump (2) corresponding to a first rotating speed value of the engine (3) is obtained according to a characteristic curve of the engine (3)1And a second power value N of the oil pump (2) corresponding to a second rotational speed value of the engine (3)2；
When the rotational speed of the engine (3) reaches a first rotational speed value, a first power value N1＝P1×I1If the pressure P is1Increasing, then controlling the current I1Reduction;
when the rotational speed of the engine (3) reaches a second rotational speed value, a second power value N2＝P2×I2If the pressure P is2Increasing, then controlling the current I2And (4) reducing.
11. A control method of the load-sensitive hydraulic system in which the limit displacement of the oil pump is controlled, as recited in claim 1, wherein the load-sensitive hydraulic system in which the limit displacement of the oil pump is controlled further includes an engine (3), the control method comprising: the controller (7) controls the flow of the electro proportional valve (5) according to the load pressure and/or the engine speed so as to control the reciprocating motion of the variable cylinder (4) and further adjust the limit displacement of the oil pump (2).
12. A control method of the load sensitive hydraulic system with controllable limit displacement of the oil pump as claimed in claim 1, comprising: controlling the displacement and the limit displacement of the oil pump (2), wherein a second spring (52) is arranged at a second control end of the electro-proportional valve (5), and a second end of the cylinder rod (42) penetrates through a second cavity (46) to be connected with the second spring (52); the variable mechanism further comprises a differential pressure control valve (6), and the differential pressure control valve (6) is connected with the output end of the oil pump (2), the electro-proportional valve (5) and the oil tank (1);
when the proportional electromagnet (53) is not electrified, the throttle valve (10) arranged at the output end of the oil pump (2) is fully opened, when the system is loaded, the electro-proportional valve (5) is in a first working position under the action of a first spring (51), the differential pressure control valve (6) is in a third working position under the action of the load, oil in the second cavity (46) of the variable cylinder (4) flows to the oil tank (1) through the electro-proportional valve (5) and the differential pressure control valve (6), the oil pump (2) is changed to a large discharge quantity, the pressure of the output end of the oil pump (2) is increased, the second end of the cylinder rod (42) compresses a second spring (52), the second spring (52) acts on a second control end of the electro-proportional valve (5), when the acting force of the second spring (52) is larger than the acting force of the first spring (51), the electro-proportional valve (5) is switched to the second working position, and at the oil at the output end of the oil pump (2) flows to the second cavity (46), after the electro-proportional valve (5) and the differential pressure control valve (6) reach dynamic balance, the displacement of the oil pump (2) is the initial limit displacement at the moment;
the load-sensitive hydraulic system changes the displacement of the oil pump between 0 and the initial limit displacement according to the opening degree of the throttle valve (10);
when the proportional electromagnet (53) is electrified, the throttle valve (10) arranged at the output end of the oil pump (2) is fully opened, the system has a load, when the current reaches the maximum value, the electric proportional valve (5) is positioned at a first station under the combined action of the proportional electromagnet (53) and the first spring (51), the differential pressure control valve (6) is positioned at a third station under the action of the load, oil in the second cavity (46) of the variable cylinder (4) flows to the oil tank (1) through the electric proportional valve (5) and the differential pressure control valve (6), the oil pump (2) is changed to a large discharge quantity, the second end of the cylinder rod (42) compresses the second spring (52), the second spring (52) acts on the second control end of the electric proportional valve (5), and when the acting force of the second spring (52) is greater than the sum of the acting forces of the proportional electromagnet (53) and the first spring (51), the electric proportional valve (5) is switched to the second station, at the moment, oil at the output end of the oil pump (2) flows to the second cavity (46), and after the electro-proportional valve (5) and the differential pressure control valve (6) reach dynamic balance, the displacement of the oil pump (2) is the maximum limit displacement at the moment;
the load sensitive system changes the displacement of the oil pump between 0 and the maximum limit displacement according to the opening degree of the throttle valve (10);
when the proportional electromagnet (53) is electrified, the throttle valve (10) arranged at the output end of the oil pump (2) is fully opened, the system has a load, and the maximum current value is not reached, the electric proportional valve (5) is positioned at a first station under the combined action of the proportional electromagnet (53) and the first spring (51), the differential pressure control valve (6) is positioned at a third station under the action of the load, oil in the second cavity (46) of the variable cylinder (4) flows to the oil tank (1) through the electric proportional valve (5) and the differential pressure control valve (6), the oil pump (2) is changed to a large discharge quantity, the second end of the cylinder rod (42) compresses the second spring (52), the second spring (52) acts on the second control end of the electric proportional valve (5), and when the acting force of the second spring (52) is greater than the sum of the acting forces of the proportional electromagnet (53) and the first spring (51), the electric proportional valve (5) is switched to the second station, at the moment, oil at the output end of the oil pump (2) flows to the second cavity (46), and after the electro-proportional valve (5) and the differential pressure control valve (6) reach dynamic balance, the displacement of the oil pump (2) is the middle limit displacement;
the load-sensitive system changes the displacement of the oil pump between 0 and the middle limit displacement according to the opening degree of the throttle valve (10).
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