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(11) | EP 4 372 235 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
| published in accordance with Art. 153(4) EPC |
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| (54) | HYDRAULIC SYSTEM WITH ELECTRO-PROPORTIONAL CONTROL MULTI-WORKING-POSITION VALVE, AND CONTROL METHOD THEREOF |
| (57) Disclosed are a hydraulic system with electrical proportional control multi-position
valves, and a control method thereof. The hydraulic system comprises: a first main
pump, a second main pump, a pilot hydraulic control handle group, an arm cylinder,
a main controller, electrical proportional valves, and valve spools having multiple
working positions therein. A signal output end of the main controller communicates
with and controls a retreat pilot electrical proportional valve, and pilot ports in
two ends of the exterior of each valve are connected to the pilot hydraulic control
handle group and the retreat pilot electrical proportional valve respectively to adjust
the working positions of the valve spools. The main controller of the hydraulic system
can determine the working condition of an actuator, and can then be operated and controlled
under a heavy-load condition or a light-load condition; and the return oil flow of
an arm rod cavity can be controlled through an electrical proportional valve, area
proportions of return check valves and recycling check valves can be adjusted to adapt
to different working conditions, the backpressure proportion of the actuator can be
finely adjusted, and backpressure control of the actuator under different loads is
realized eventually. |
BACKGROUND OF THE INVENTION
1. Technical Field
[0001] The invention belongs to the field of hydraulic techniques, and particularly relates to a hydraulic system with electrical proportional control multi-position valves, and a control method thereof.
2. Description of Related Art
[0002] In engineering machines, when the direction of a load is opposite to the thrust direction of the hydraulic cylinder (in most cases), the load is called a drag load. In some conditions, due to changes of the working position or attitude of some actuators, the direction of a load applied to the hydraulic cylinder is the same as the thrust direction of the hydraulic cylinder under the influence of gravity, and the load in this case is called a tensile load. Under the condition of a tensile load, a vacuum is quite likely to be generated in the hydraulic elements due to insufficient flow in a cavity on the oil supply side of an oil cylinder. So, under the condition of a tensile load, the return backpressure is generally set to be high (the return backpressure should be set to ensure that a vacuum will not be generated in the hydraulic actuating elements in case of a minimum flow under a low engine speed) to protect the hydraulic actuating elements against damage caused by long-term cavitation. A high return backpressure of an actuator will lead to single actions of the actuator; or, if the return backpressure is high in case of a high engine speed, an energy loss may be caused; and particularly when an actuator is under the condition of a drag load, a high return backpressure will lead to high energy consumption of a machine and low working efficiency. Thus, how to avoid cavitation in case of a tensile load and avoid extra energy consumption caused by a high backpressure in case of a drag load is a problem to be urgently solved by engineering technicians.
BRIEF SUMMARY OF THE INVENTION
[0003] Objective of the invention: To overcome the defects in the prior art, the invention provides a hydraulic system with electrical proportional control multi-position valves, and a control method thereof. The hydraulic system can determine the working condition of an actuator, and then be operated and controlled under a heavy-load condition or a light-load condition to control the backpressure of the actuator in case of different loads, and to recycle return oil in an oil inlet cavity of the actuator through recycling check valves connected in parallel particularly under the condition of a tensile load to increase the oil inlet flow of the system, thus preventing a vacuum from being generated in the actuator and improving working efficiency; and when the actuator is under the condition of a drag load, a control valve can be automatically adjusted to a heavy-load position according to the load pressure to enlarge the oil return area of the actuator to decrease the return backpressure, thus reducing energy consumption of a machine.
[0004] Technical solution: The invention provides a hydraulic system with electrical proportional control multi-position valves, wherein when an arm retreats, the hydraulic system comprises:
A main pump unit, comprising a first main pump, a second main pump and a pilot oil pump, the first main pump, the second main pump and the pilot oil pump being connected to a power output end of an engine;
Outlets of the first main pump and the second main pump being connected to a main throttling valve group and an oil tank sequentially through corresponding by-pass pipes;
The pilot oil pump being connected to a retreat pilot electrical proportional valve and a pilot hydraulic control handle group, and the pilot hydraulic control handle group comprising a swing-out pilot hydraulic control handle and a retreat pilot hydraulic control handle;
An arm cylinder, the arm cylinder being divided into an arm rod cavity and an arm rodless cavity according to the change of an oil supply part when the arm cylinder swings outwards or retreats;
A main controller, a signal input end of the main controller communicating with and controlling a first pressure sensor for detecting the internal pressure of the arm rod cavity and a second pressure sensor for detecting the pressure of an outlet in the retreat pilot hydraulic control handle, and a signal output end of the main controller communicating with and controlling the retreat pilot electrical proportional valve; and
Valve spools each having multiple working positions, pilot ports being formed in two ends of an exterior of each of the valve spools, and communicating with and controlling the pilot hydraulic control handle group and the retreat pilot electrical proportional valve respectively;
Wherein, the valve spools comprise a first valve spool and a second valve spool, oil inlets connected to the main pump unit through pipes and oil return ports connected to the arm rod cavity through multiple connected pipes are formed in the first valve spool and the second valve spool respectively, and a pipe from the oil return port of the first valve spool to the oil inlet of the second valve spool is disposed at the oil return port in the first valve spool;
The oil inlet of the first valve spool is connected to the outlet of the first main pump through a by-pass pipe and is then communicated with the arm rodless cavity through the multiple connected pipes to form a first oil supply line, and the oil inlet of the second valve spool is connected to the outlet of the second main pump through a by-pass pipe and is then communicated with the arm rodless cavity through the multiple connected pipes to form a second oil supply line;
The arm rod cavity is connected to the first valve spool and the second valve spool sequentially through the multiple connected pipes to form a first oil return line, and the arm rod cavity is connected to the second valve spool and the oil tank sequentially through the multiple connected pipes to form a second oil return line.
[0005] In a further embodiment, the working positions of the first valve spool comprise a retreat position, an idling position and a swing-out position;
The working positions of the second valve spool comprise an idling position, a swing-out position, a light-load position and a heavy-load position.
[0006] In a further embodiment, return check valves and recycling check valves are disposed at the light-load position and the heavy-load position of the second valve spool respectively.
[0007] In a further embodiment, when the arm retreats under the condition of a drag load, the first valve spool is adjusted to the retreat position, the second valve spool is adjusted to the heavy-load position, and the pressure of the arm rodless cavity and the oil supply lines communicated with the arm rodless cavity is higher than the pressure of the oil return lines; the return check valve allows the first valve spool and the second valve spool to be communicated with the oil tank through pipes, such that the first oil return line and the second oil return line are connected in parallel; the first oil return line connected in parallel to the second valve spool is connected to the second oil supply line through the recycling check valve, but due to the fact that the pressure in the first oil return line is lower than the pressure in the second oil supply line, the recycling check valve at the heavy-load position is closed; and finally, oil in the first oil return line flows into the second oil return line through the return check valve and eventually reaches the oil tank;
When the arm retreats under the condition of a tensile load, the first valve spool is adjusted to the retreat position, the second valve spool is adjusted to the light-load position, the pressure of the arm rodless cavity and the oil supply lines communicated with the arm rodless cavity is lower than or equal to the pressure of the oil return lines, oil in the arm rod cavity is stopped when reaching the second valve spool through the second oil return line, and is converged with oil reaching the second valve spool through the first oil return line, and the converged oil is connected in parallel and communicated with the return check valve and the recycling check valve at the light-load position; part of the oil is supplied to the arm rodless cavity through the recycling check valve and the second oil supply line to be recycled, and the other part of oil returns into the oil tank through the return check valve;
When an arm actuator is not operated, the first valve spool and the second valve spool are located at the idling positions, the main pump unit does not supply oil to the arm cylinder through the return check valves and the recycling check valves of the second valve spool;
When the arm swings outwards without a drag load or tensile load, the first valve spool and the second valve spool are adjusted to the swing-out positions; due to the fact that no return check valve or recycling check valve is disposed at the swing-out positions, oil entering the valve spools from the main pump unit is supplied to the arm cylinder through the swing-out positions, and return oil of the arm cylinder returns into the oil tank through the swing-out positions.
[0008] In a further embodiment, the main controller determines a working condition of the arm cylinder according to pressure data acquired by the first pressure sensor and the second pressure sensor, and controls the retreat pilot electrical proportional valve to select and control the working position of the second valve spool according to the working condition.
[0009] In a further embodiment, when a load pressure detected by the first pressure sensor is lower than a preset value, the arm cylinder is determined as being under the condition of a tensile load; and when the load pressure detected by the first pressure sensor is greater than the preset value, the arm cylinder is determined as being under the condition of a drag load.
[0010] In a further embodiment, the pilot ports comprise a first swing-out pilot port formed in one end of the first valve spool, a first retreat pilot port formed in the other end of the first valve spool, a second swing-out pilot port formed in one end of the second valve spool, and a second retreat pilot port formed in the other end of the second valve spool; the second retreat pilot port is connected to the retreat pilot electrical proportional valve, the first retreat pilot port is connected to the retreat pilot hydraulic control handle, and the first swing-out pilot port and the second swing-out pilot port are both connected to the swing-out pilot hydraulic control handle, such that the working positions of the first valve spool and the second valve spool can be adjusted by operating the two pilot hydraulic control handles and by controlling the retreat pilot electrical proportional valve through the main controller according to the working condition, and the main controller can control the retreat pilot electrical proportional valve to adjust area proportions of the return check valves and the recycling check valves, so as to switch the first valve spool and the second valve spool to different working positions to adapt to different working conditions.
[0011] In a further embodiment, the signal input end of the main controller also communicates with and controls a first pilot electrical control handle and a second pilot electrical control handle, and the first pilot electrical control handle and the second pilot electrical control handle communicate with and control a first retreat pilot proportional valve which is connected to the first retreat pilot port, a first swing-out pilot proportional valve which communicates with and controls the first swing-out pilot port, a second swing-out pilot proportional valve which communicates with and controls the second swing-out pilot port, and a second retreat pilot proportional valve which communicates with and controls the second retreat pilot port, through the signal output end of the main controller.
[0012] In a further embodiment, when the arm actuator is not operated, the valve spools are located at the idling positions, the main pump unit does not supply oil to the arm cylinder through the valve spools, and overflow oil flows into the oil tank through corresponding main throttling valves.
[0013] In a further embodiment, when the arm retreats, the hydraulic system works by the following steps:
Detecting, by the main controller, pressure data of the first pressure sensor and the second pressure sensor in real time to determine the working condition;
When users operate the pilot hydraulic control handle group, sending, by the main controller, a control instruction to the retreat pilot electrical proportional valve according to working condition data;
Under the condition of a tensile load, adjusting the first valve spool to the retreat position and the second valve spool to the light-load position; when the arm retreats,
Allowing oil supplied by the first main pump and the second main pump to enter the arm rodless cavity through the first oil supply line and the second oil supply line respectively to push the arm to retreat;
Wherein, under this condition, part of return oil of the arm rod cavity enters the second valve spool through the return check valve in the first oil return line and is then supplied to the arm rodless cavity through the recycling check valve, and the other part of the return oil of the arm rod cavity enters the oil tank through the second oil return line;
Under the condition of a drag load, adjusting the second valve spool to the heavy-load position; and
When the arm retreats, allowing oil supplied by the first main pump and the second main pump to enter the arm rodless cavity sequentially through the first oil supply line and the second oil supply line to push the arm to retreat;
Wherein, due to the fact that the oil pressure in the second oil supply line at the position where the arm rodless cavity is communicated with the recycling check valve is higher than the oil pressure in the first oil return line under this condition, the recycling check valve cannot receive return oil from the first oil return line, and the first oil return line is connected in parallel to the second oil return line and is communicated with the second oil return line through the return check valve, such that return oil entering the first oil return line from the arm rod cavity flows into the oil tank through the return check valve and a second valve spool and oil tank connecting pipe, and finally, return oil in the second oil return line directly enters the oil tank through the second valve spool.
[0014] Compared with the prior art, the invention has the following beneficial effects:
- (1) In practical work, the main controller can determine the working condition of an actuator, and then be operated and controlled under a heavy-load condition or a light-load condition to recycle return oil in an oil inlet cavity of the actuator through recycling check valves connected in parallel particularly under the condition of a tensile load to increase the oil inlet flow of the system, thus preventing a vacuum from being generated in the actuator and improving working efficiency;
- (2) When an actuator is under the condition of a drag load, a control valve can be automatically adjusted to a heavy-load position according to the load pressure to enlarge the oil return area of the actuator to decrease the return backpressure, thus reducing energy consumption of a machine;
- (3) The valve spools can be adjusted and controlled through the retreat pilot electrical proportional valve to control the return oil flow of the arm rod cavity, and area proportions of the return check valves and the recycling check valves can be adjusted to adapt to different working conditions, the backpressure proportion of the actuator can be finely adjusted, and backpressure control of the actuator under different loads is realized eventually.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0015]
FIG. 1 is a working principle diagram of a multi-position valve according to the invention;
FIG. 2 is a schematic diagram of a hydraulic system with electrical proportional control multi-position valves in a state where an arm idles according to the invention;
FIG. 3 is an implementation diagram of the hydraulic system with electrical proportional control multi-position valves at a light-load position in a state where the arm retreats according to the invention;
FIG. 4 is an implementation diagram of the hydraulic system with electrical proportional control multi-position valves at a heavy-load position in the state where the arm retreats according to the invention;
FIG. 5 is a schematic diagram of the hydraulic system with electrical proportional control multi-position valves in an embodiment where pilot electrical control handles are adopted;
[0016] Reference signs: 1, engine; 2, first main pump; 3, second main pump; 4, pilot oil pump; 5, swing-out pilot hydraulic control handle; 6, retreat pilot hydraulic control handle; 7, retreat pilot electrical proportional valve; 8, second pressure sensor; 9, second retreat pilot port; 10, second swing-out pilot port; 11, oil inlet of the second valve spool; 12, second valve spool and oil tank connecting pipe; 13, return check valve; 14, recycling check valve; 15, second valve spool by-pass pipe; 16, pipe from the oil return port of the first valve spool to the oil inlet of the second valve spool; 17, first swing-out pilot port; 18, first retreat pilot port; 19, first valve spool by-pass pipe; 10, oil inlet of the first valve spool; 21, first valve spool and oil tank connecting pipe; 22, first valve spool and arm rod cavity connecting pipe; 23, second valve spool and arm rod cavity connecting pipe; 24, first valve spool and arm rodless cavity connecting pipe; 25, second valve spool and arm rodless cavity connecting pipe; 26, arm rodless cavity pipe; 27, arm rod cavity pipe; 28, first main throttling valve; 29, second main throttling valve; 30, oil tank; 32, arm cylinder; 33, first valve spool; 34, first pressure sensor; 35, first retreat pilot proportional valve; 36, first swing-out pilot proportional valve; 37, second swing-out pilot proportional valve; 38, second retreat pilot proportional valve; 39, first pilot electrical control handle; 40, second pilot electrical control handle; 41, second valve spool; 42, main controller.
DETAILED DESCRIPTION OF THE INVENTION
[0017] To gain a better understanding of the technical solution of the invention, the technical solution of the invention will be further described below in conjunction with the accompanying drawings, but the invention is not limited to the following description.
[0018] In engineering machines, when the direction of a load is opposite to the thrust direction of the hydraulic cylinder (in most cases), the load is called a drag load. In some conditions, due to changes of the working position or attitude of some actuators, the direction of a load applied to the hydraulic cylinder is the same as the thrust direction of the hydraulic cylinder under the influence of gravity, and the load in this case is called a tensile load. Under the condition of a tensile load, a vacuum is quite likely to be generated in the hydraulic elements due to insufficient flow in a cavity on the oil supply side of an oil cylinder. So, under the condition of a tensile load, the return backpressure is generally manually set to be high to protect elements against damage caused by cavitation. If the return backpressure is high when the hydraulic cylinder is under the condition of a common drag load, extra energy consumption will be caused, working efficiency will be reduced, and an undesired backpressure loss will be caused. Thus, how to avoid cavitation in case of a tensile load and avoid extra energy consumption caused by a high backpressure in case of a drag load is a problem to be urgently solved by engineering technicians.
[0019] The technical solution of the invention is further described in conjunction with FIG. 1 to FIG. 4. A hydraulic system with electrical proportional control multi-position valves comprises: an engine 1, a first main pump 2, a second main pump 3, a pilot oil pump 4, a swing-out pilot hydraulic control handle 5, a retreat pilot hydraulic control handle 6, a retreat pilot electrical proportional valve 7, a second pressure sensor 8, a first valve spool 33, a first pressure sensor 34, a second valve spool 41, a first main throttling valve 28, a second main throttling valve 29, an oil tank 30, an arm cylinder 32, and a main controller 42.
[0020] Wherein, the first main pump 2 and the second main pump 3 are both connected to a power output end of the engine 1; power output by the engine 1 drives the first main pump 2 and the second main pump 3 to operate; outlets of the first main pump 2 and the second main pump 3 are connected to a main throttling valve group and the oil tank 30 sequentially through corresponding by-pass pipes; the main throttling valve group comprises the first main throttling valve 28 connected to the oil tank 30 and the second main throttling valve 29 communicated with the oil tank 30;
The pilot oil pump 4, the first main pump 2 and the second main pump 3 are driven by the engine 1; the pilot oil pump 4 is connected to the retreat pilot electrical proportional valve 7 and a pilot hydraulic control handle group; the pilot hydraulic control handle group comprises the swing-out pilot hydraulic control handle 5 and the retreat pilot hydraulic control handle 6;
The arm cylinder 32 is divided into an arm rod cavity and an arm rodless cavity according to the change of an oil supply part when the arm cylinder swings outwards or retreats; when oil enters the arm cylinder 32 from an end without a piston rod, oil is supplied into the arm rodless cavity and returns through an end with the piston rod (the arm rod cavity), and the pressure in the arm rodless cavity is higher than the pressure in the arm rod cavity, so the piston rod in the arm rod cavity stretches out of the arm cylinder 32 and drives an arm to move; when oil enters the arm cylinder 32 from the end with the piston rod, oil is supplied into the arm rod cavity and returns through the end without the piston rod (the arm rodless cavity), the pressure in the arm rodless cavity is lower than the pressure in the arm rod cavity, so the piston rod retreats into the arm rodless cavity and finally drives the arm to move in an opposite direction.
[0021] A signal input end of the main controller 42 communicates with and controls the first pressure sensor 34 for detecting the pressure in the arm rodless cavity and the second pressure sensor 8 for detecting the pressure in the vicinity of the retreat pilot hydraulic control handle 6, and a signal output end of the main controller 42 communicates with and controls the retreat pilot electrical proportional valve 7, so the load condition of the arm cylinder 32 and an applicable operating position can be determined according to a load pressure signal of the arm cylinder 32 acquired by the first pressure sensor 34 and a pressure signal of the retreat pilot hydraulic control handle acquired by the second pressure sensor 8, and a control instruction is output to the retreat pilot electrical proportional valve 7 to perform proportional control on the valve spools.
[0022] Each of the valve spools has multiple working positions, and pilot ports are formed in two ends of the exterior of each of the valve spools, and communicate with and control the pilot hydraulic control handle group and the retreat pilot electrical proportional valve 7 respectively;
Wherein, in the invention, when the arm retreats, the valve spools comprise the first valve spool 33 and the second valve spool 41, and oil inlet and oil return ports are formed in the first valve spool 33 and the second valve spool 41 respectively; a first valve spool and oil tank connecting pipe 21 and a second valve spool and oil tank connecting pipe 12 are disposed at the oil return ports respectively, and the arm rod cavity is connected to the first valve spool 33 and the second valve spool 41 sequentially through pipes to form a first oil return line;
The oil inlet 20 of the first valve spool is connected to the outlet of the first main pump 2 through a by-pass pipe and is then communicated with the arm rodless cavity through multiple connected pipes to form a first oil supply line, and the oil inlet of the second valve spool 41 is connected to the outlet of the second main pump 3 through a by-pass pipe and is then communicated with the arm rodless cavity through the multiple connected pipes to form a second oil supply line; the by-pass pipes comprise a first valve spool by-pass pipe 19 and a second valve spool by-pass pipe 15.
[0023] The arm rod cavity is connected to the first valve spool 33 and the second valve spool 41 sequentially through pipes to form the first oil return line, and the arm rod cavity is connected to the second valve spool and oil tank connecting pipe 12 and the oil tank 30 sequentially through pipes to form a second oil return line.
[0024] As shown in FIG. 1 to FIG. 4, the oil inlets and the oil return ports comprise: an oil inlet 20 of the first valve spool, an oil return port of the first valve spool, an oil inlet 11 of the second valve spool, and an oil return port of the second valve spool 41;
The multiple connecting pipes on the oil supply lines and the oil return lines specifically comprise: a pipe 16 from the oil return port of the first valve spool to the oil inlet of the second valve spool, a first valve spool and oil tank connecting pipe 21, a first valve spool and arm rod cavity connecting pipe 22, a second valve spool and arm rod cavity connecting pipe 23, a first valve spool and arm rodless cavity connecting pipe 24, a second valve spool and arm rodless cavity connecting pipe 25, a second valve spool and oil tank connecting pipe, an arm rodless cavity pipe 26, and an arm rod cavity pipe 27;
Further, the flow direction of oil in the first oil supply line is specifically as follows: after the first main pump 2 inputs oil into the first valve spool 33, the oil enters the first valve spool and arm rodless cavity connecting pipe 24 through the oil inlet 20 of the first valve spool and is then supplied to the arm cylinder 32 through the arm rodless cavity pipe 26;
Further, the flow direction of oil in the second oil supply line is specifically as follows: oil output by the second main pump 3 enters the second valve spool and arm rodless cavity connecting pipe 25 through the oil inlet 11 of the second valve spool and is then supplied to the arm cylinder 32 through the arm rodless cavity pipe 26;
Further, the flow direction of oil in the first oil return line is specifically as follows: part of return oil in the arm cylinder 32 enters the first valve spool and arm rod cavity connecting pipe 22 through the arm rod cavity pipe 27 to flow into the first valve spool 33, then enters the second valve spool 41 through the pipe 16 from the oil return port of the first valve spool to the oil inlet of the second valve spool, and finally flows into the oil tank 30 through the second valve spool and oil tank connecting pipe 12.
[0025] Further, the flow direction of oil in the second oil return line is specifically as follows: part of return oil in the arm cylinder 32 enters the second valve spool and arm rod cavity connecting pipe 23 through the arm rod cavity pipe 27 to flow into the second valve spool 41, and finally flows into the oil tank 30 through the second valve spool and oil tank connecting pipe 12 communicated with the oil tank 30 to return into the oil tank 30.
[0026] Working positions of the first valve spool 33 comprise a retreat position, an idling position and a swing-out position; when the arm retreats, the first valve spool 33 is adjusted by the retreat pilot electrical proportional valve 7 to the retreat position.
[0027] Working positions of the second valve spool comprise an idling position, a swing-out position, a light-load position, and a heavy-load position.
[0028] Return check valves 13 and recycling check valves 14 are disposed at the light-load position and the heavy-load position of the second valve spool 41 respectively; when the arm is retreated under the condition of a drag load, the first valve spool 33 is adjusted to the retreat position, the second valve spool 41 is adjusted to the heavy-load position, and the pressure of the rodless cavity and the oil supply lines communicated with the rodless cavity is higher than the pressure of the oil return lines; the pipe 16 from the oil return port of the first valve spool to the oil inlet of the second valve spool is connected to the second valve spool 41 through the return check valve 13, such that the first oil return line is connected in parallel to the oil inlet of the second valve spool 41 to be communicated with the second oil return line, and the first oil return line connected in parallel to the second valve spool is connected to the second oil supply line through the recycling check valve, and due to the fact that the pressure in the first oil return line is lower than the pressure in the second oil supply line, the recycling check valve 14 at the heavy-load position is closed; and finally, oil in the first oil return line flows into the second oil return line through the return check valve 13 and finally reaches the oil tank 30;
When the arm is retreated under the condition of a tensile load, the first valve spool 33 is adjusted to the retreat position, the second valve spool 41 is adjusted to the light-load position, the pressure of the arm rodless cavity and the oil supply lines communicated with the arm rodless cavity is lower than or equal to the pressure of the oil return lines, oil in the arm rod cavity is stopped when reaching the second valve spool 41 through the second oil return line, and is converged with oil reaching the second valve spool 41 through the first oil return line, and the converged oil is connected in parallel and communicated with the return check valve 13 and the recycling check valve 14 at the light-load position; part of the oil is supplied to the arm cylinder 32 through the recycling check valve 14, the second oil supply line and the second valve spool and arm rodless cavity connecting pipe 25 to be recycled, and the other part of the oil returns into the oil tank 30 through the return check valve 13.
[0029] When an arm actuator is not operated, the first valve spool 33 and the second valve spool 41 are located at the idling positions, the main pump unit does not supply oil to the arm cylinder 32 through the return check valves 13 and the recycling check valves 14;
When the arm swings out without a drag load or tensile load, the first valve spool 33 and the second valve spool 41 are adjusted to the swing-out positions; due to the fact that no return check valve 13 or recycling check valve 14 is disposed at the swing-out positions, oil entering the valve spools from the main pump is supplied to the arm cylinder 32 through the swing-out positions, and return oil of the arm cylinder 32 returns to the oil tank 30 through the swing-out positions.
[0030] Further, when the arm swings outwards, the flow direction of oil in the first oil supply line is as follows: oil from the first main pump 2 is supplied to the arm cylinder 32 through the oil inlet 20 of the first valve spool, the first valve spool and arm rodless cavity connecting pipe 24, and the arm rodless cavity pipe 26;
The flow direction of oil in the second oil supply line is as follows: oil from the second main pump 3 is supplied to the arm cylinder 32 through the oil inlet 11 of the second valve spool, the second valve spool and arm rodless cavity connecting pipe 25, and the arm rodless cavity pipe 26;
The flow direction of oil the first oil return line is as follows: return oil from the arm cylinder 32 enters the oil tank 30 the arm rod cavity pipe 27, the first valve spool and arm rod cavity connecting pipe 22 and the first valve spool and oil tank connecting pipe 21, such that oil return of the first oil return line is realized;
The flow direction of oil in the second oil return line is as follows: return oil from the arm cylinder 32 enters the oil tank 30 through the arm rod cavity pipe 27, the second valve spool and arm rod cavity connecting pipe 23, and the second valve spool and oil tank connecting pipe 12, such that oil return of the second oil return line is realized;
Moreover, the first oil return line connected in parallel to the second valve spool 41 is connected to the second oil supply line through the recycling valves 14, such that return oil in the arm rod cavity returns through the first valve spool 33 and the second valve spool 41 on the first oil return line, and part of the return oil enters the second valve spool 41 through the recycling valve to be recycled.
[0031] The main controller 42 determines the working condition according to pressure data acquired by the first pressure sensor and the second pressure sensor, When a load pressure signal acquired by the first pressure sensor is less than a preset value, the main controller 42 determines that the arm cylinder 32 is under the condition of a tensile load; when the load pressure signal acquired by the first pressure sensor is greater than the preset value, the main controller 42 determines that the arm cylinder 32 is under the condition of a drag load.
[0032] The pilot ports comprise: a first swing-out pilot port 17 formed in one end of the first valve spool 33, a first retreat pilot port 18 formed in the other end of the first valve spool 33, a second swing-out pilot port 10 formed in one end of the second valve spool 41, and a second retreat pilot port 9 formed in the other end of the second valve spool 41; the second retreat pilot port 9 is connected to the retreat pilot electrical proportional valve 7, the first retreat pilot port 18 is connected to the retreat pilot hydraulic control handle 6, and the first swing-out pilot port 17 and the second swing-out pilot port 10 are connected to the swing-out pilot hydraulic control handle 5, such that the working positions of the first valve spool 33 and the second valve spool 41 can be adjusted by operating the two pilot hydraulic control handles and by controlling the retreat pilot electrical proportional valve 7 through the main controller according to the working condition, and the main controller 42 can control the retreat pilot electrical proportional valve 7 to adjust area proportions of the return check valves 13 and the recycling check valves 14 so as to switch the first valve spool 33 and the second valve spool 41 to different working positions to adapt to different working conditions.
[0033] Further, in conjunction with FIG. 5 which illustrates an embodiment where pilot electrical control handles rather than the pilot hydraulic control handles are used, the hydraulic system in this embodiment specifically comprises: a first retreat pilot proportional valve 35, a first swing-out pilot proportional valve 36, a second swing-out pilot proportional valve 37, a second retreat pilot proportional valve 38, a first pilot electrical control handle 39, and a second pilot electrical control handle 40.
[0034] Wherein, the signal input end of the main controller 42 communicates with and controls the first pilot electrical control handle 39 and the second pilot electrical control handle 40, and the first pilot electrical control handle 39 and the second pilot electrical control handle 40 communicate with and control the first retreat pilot proportional valve 35 which is connected to the first retreat pilot port 18, the first swing-out pilot proportional valve 36 which communicates with and controls the first swing-out pilot port 17, the second swing-out pilot proportional valve 37 which communicates with and controls the second swing-out pilot port 10, and the second retreat pilot proportional valve 38 which communicates with and controls the second retreat pilot port 9;
When users operate the electrical control handles, the electrical control handles send control signals to the main controller 42, the first pressure sensor 34 acquires the output pressure of the arm rodless cavity and inputs the output pressure to the main controller 42, and the main controller calculates a control signal according to the signals from the electrical control handles and the load pressure of the arm; when the arm retreats, the main controller sends the control signal to the first retreat pilot proportional valve 35 and the second retreat pilot proportional valve 38, the first retreat pilot proportional valve 35 outputs a control pressure to the first retreat pilot port 18 of the first valve spool 33 to control the first valve spool 33 of the arm to work at the retreat position, the second retreat pilot proportional valve 38 outputs a control pressure to the second retreat pilot port 9 of the second valve spool 41 to control the second valve spool 41 of the arm to work at the light-load position or the heavy-load position; when the arm swings out, the main controller sends the control signal to the first swing-out pilot proportional valve 36 and the second swing-out pilot proportional valve 37, the first swing-out pilot proportional valve 36 outputs a control pressure to the first swing-out pilot port 17 of the first valve spool 33 to control the first valve spool 33 of the arm to work at the swing-out position, and the second swing-out pilot proportional valve 37 outputs a control pressure to the second swing-out pilot port 10 of the second valve spool 41 to control the second valve spool 41 of the arm to work at the swing-out position.
[0035] When the arm retreats, the operating principle of the hydraulic system is as follows:
The main controller 42 detects pressure data of the first pressure sensor 34 and the second pressure sensor 8 in real time to determine the working condition;
When users operate the pilot hydraulic control handle group, the main controller sends a control instruction to the retreat pilot electrical proportional valve according to working condition data;
Under the condition of a tensile load, the first valve spool 33 is adjusted to the retreat position and the second valve spool 41 is adjusted to the light-load position; when the arm retreats,
Oil supplied by the first main pump 2 and the second main pump 3 enters the arm rodless cavity of the arm cylinder 32 through the first oil supply line and the second oil supply line respectively to push the arm to retreat;
Under this condition, part of return oil of the arm rod cavity of the arm cylinder 32 enters the second valve spool 41 through the return check valve 13 in the first oil return line and is then supplied to the arm rodless cavity through the recycling check valve 14, and the other part of the return oil of the arm rod cavity enters the oil tank 30 through the second oil return line;
Under the condition of a drag load, the second valve spool is adjusted to the heavy-load position;
When the arm retreats, oil supplied by the first main pump 2 and the second main pump 3 enters the arm rodless cavity of the arm cylinder 32 sequentially through the first oil supply line and the second oil supply line to push the arm to retreat;
Due to the fact that the oil pressure in the second oil supply line at the position where the arm rodless cavity is communicated with the recycling check valve 14 is higher than the oil pressure in the first oil return line under this condition, the recycling check valve 14 cannot receive return oil from the first oil return line, and the first oil return line is connected in parallel to the second oil return line and is communicated with the second oil return line through the return check valve 13, such that return oil entering the first oil return line from the arm rod cavity flows into the oil tank through the return check valve 13 and the second valve spool and oil tank connecting pipe 12, and finally, return oil in the second oil return line directly enters the oil tank through the second valve spool 41 and the second valve spool and oil tank connecting pipe.
[0036] The main controller 42 in the invention can determine different working conditions of an actuator when the arm retreats, and then be operated and controlled under a heavy-load condition or a light-load condition to recycle return oil in an oil inlet cavity of the actuator through the recycling check valves 14 connected in parallel under the condition of a tensile load to increase the oil inlet flow of the system, thus preventing a vacuum from being generated in the actuator and improving working efficiency;
When an actuator is under the condition of a drag load, a control valve can be automatically adjusted to a heavy-load position according to the load pressure to enlarge the oil return area of the actuator to decrease the return backpressure, thus reducing energy consumption of a machine.
[0037] The retreat pilot electrical proportional valve 7 can be operated to adjust the valve spools by means of an instruction sent by the main controller 42 according to the working condition, to control the return oil flow of the arm rod cavity, and area proportions of the return check valves 13 and the recycling check valves 14 can be adjusted to adapt to different working conditions, the backpressure proportion of the actuator can be finely adjusted, and backpressure control of the actuator under different loads is realized eventually.
[0038] Although the invention is described above with reference to accompanying drawings, those skilled in the art would appreciate that the disclosure is not limited to the embodiments described above, and various changes, modifications, and substitutions can be made without deviating from the scope of the invention.
a main pump unit, comprising a first main pump, a second main pump and a pilot oil pump, the first main pump, the second main pump and the pilot oil pump being connected to a power output end of an engine;
outlets of the first main pump and the second main pump being connected to a main throttling valve group and an oil tank sequentially through corresponding by-pass pipes;
the pilot oil pump being connected to a retreat pilot electrical proportional valve and a pilot hydraulic control handle group, and the pilot hydraulic control handle group comprising a swing-out pilot hydraulic control handle and a retreat pilot hydraulic control handle;
an arm cylinder, the arm cylinder being divided into an arm rod cavity and an arm rodless cavity according to the change of an oil supply part when the arm cylinder swings outwards or retreats;
a main controller, a signal input end of the main controller communicating with and controlling a first pressure sensor for detecting an internal pressure of the arm rod cavity and a second pressure sensor for detecting a pressure of an outlet in the retreat pilot hydraulic control handle, and a signal output end of the main controller communicating with and controlling the retreat pilot electrical proportional valve; and
valve spools each having multiple working positions, pilot ports being formed in two ends of an exterior of each of the valve spools, and communicating with and controlling the pilot hydraulic control handle group and the retreat pilot electrical proportional valve respectively;
wherein, the valve spools comprise a first valve spool and a second valve spool, oil inlets connected to the main pump unit through pipes and oil return ports connected to the arm rod cavity through multiple connected pipes are formed in the first valve spool and the second valve spool respectively, and a pipe from the oil return port of the first valve spool to the oil inlet of the second valve spool is disposed at the oil return port in the first valve spool;
the oil inlet of the first valve spool is connected to the outlet of the first main pump through a by-pass pipe and is then communicated with the arm rodless cavity through the multiple connected pipes to form a first oil supply line, and the oil inlet of the second valve spool is connected to the outlet of the second main pump through a by-pass pipe and is then communicated with the arm rodless cavity through the multiple connected pipes to form a second oil supply line;
the arm rod cavity is connected to the first valve spool and the second valve spool sequentially through the multiple connected pipes to form a first oil return line, and the arm rod cavity is connected to the second valve spool and the oil tank sequentially through the multiple connected pipes to form a second oil return line.
the working positions of the second valve spool comprise an idling position, a swing-out position, a light-load position and a heavy-load position.
when the arm retreats under the condition of a drag load, the first valve spool is adjusted to the retreat position, the second valve spool is adjusted to the heavy-load position, and a pressure of the arm rodless cavity and the oil supply lines communicated with the arm rodless cavity is higher than a pressure of the oil return lines; the return check valve allows the first valve spool and the second valve spool to be communicated with the oil tank through pipes, such that the first oil return line and the second oil return line are connected in parallel; the first oil return line connected in parallel to the second valve spool is connected to the second oil supply line through the recycling check valve, and finally, oil in the first oil return line flows into the second oil return line through the return check valve and eventually reaches the oil tank;
when the arm retreats under the condition of a tensile load, the first valve spool is adjusted to the retreat position, the second valve spool is adjusted to the light-load position, the pressure of the arm rodless cavity and the oil supply lines communicated with the arm rodless cavity is lower than or equal to the pressure of the oil return lines, oil in the arm rod cavity is stopped when reaching the second valve spool through the second oil return line, and is converged with oil reaching the second valve spool through the first oil return line, and the converged oil is connected in parallel and communicated with the return check valve and the recycling check valve at the light-load position; part of the oil is supplied to the arm rodless cavity through the recycling check valve and the second oil supply line to be recycled, and the other part of oil returns into the oil tank through the return check valve;
when an arm actuator is not operated, the first valve spool and the second valve spool are located at the idling positions, the main pump unit does not supply oil to the arm cylinder through the return check valves and the recycling check valves of the second valve spool;
when the arm swings outwards without a drag load or tensile load, the first valve spool and the second valve spool are adjusted to the swing-out positions; due to the fact that no return check valve or recycling check valve is disposed at the swing-out positions, oil entering the valve spools from the main pump unit is supplied to the arm cylinder through the swing-out positions, and return oil of the arm cylinder returns into the oil tank through the swing-out positions.
detecting, by a main controller, pressure data of a first pressure sensor and a second pressure sensor in real time to determine a working condition;
when users operate a pilot hydraulic control handle group, sending, by the main controller, a control instruction to a retreat pilot electrical proportional valve according to working condition data;
under the condition of a tensile load, adjusting a first valve spool to a retreat position and a second valve spool to a light-load position; when the arm retreats,
allowing oil supplied by a first main pump and a second main pump to enter an arm rodless cavity through a first oil supply line and a second oil supply line respectively to push the arm to retreat;
wherein, under this condition, part of return oil of an arm rod cavity enters the second valve spool through a return check valve in a first oil return line and is then supplied to the arm rodless cavity through a recycling check valve, and the other part of the return oil of the arm rod cavity enters an oil tank through a second oil return line;
under the condition of a drag load, adjusting the second valve spool to a heavy-load position; and
when the arm retreats, allowing oil supplied by the first main pump and the second main pump to enter the arm rodless cavity sequentially through the first oil supply line and the second oil supply line to push the arm to retreat;
wherein, due to the fact that an oil pressure in the second oil supply line at the position where the arm rodless cavity is communicated with the recycling check valve is higher than an oil pressure in the first oil return line under this condition, the recycling check valve cannot receive return oil from the first oil return line, and the first oil return line is connected in parallel to the second oil return line and is communicated with the second oil return line through the return check valve, such that return oil entering the first oil return line from the arm rod cavity flows into the oil tank through the return check valve and a second valve spool and oil tank connecting pipe, and finally, return oil in the second oil return line directly enters the oil tank through the second valve spool.