阅读说明：本技术 一种液压系统、工程机械及其控制方法 (Hydraulic system, engineering machinery and control method thereof ) 是由 王术冬 贺电 于 2021-08-31 设计创作，主要内容包括：本发明实施例提供了一种液压系统、工程机械及其控制方法,包括：液压油箱、电比例泵、多路阀组件、主供油管路、旁路溢流管路、检测装置和控制器；检测装置其用于检测三通流量阀溢出的单位流量或者位于三通流量阀之后的旁路溢流管路上压力；控制器分别与电比例泵、多路工作联和检测装置电连,控制器根据检测装置的检测结果控制电比例泵。本发明提供的液压系统,三通流量阀引入反馈机制,实时检测流经旁路溢流管路的油液状态,根据检测结果控制电比例泵的流量,以满足系统需求值并有少量的富余,以最少发热量将流量与系统的需求匹配。并且这种控制方式,液压系统中各机构随时处于有压力待命状态,有效提高液压系统的响应速度。(The embodiment of the invention provides a hydraulic system, engineering machinery and a control method thereof, wherein the control method comprises the following steps: the system comprises a hydraulic oil tank, an electric proportional pump, a multi-way valve assembly, a main oil supply pipeline, a bypass overflow pipeline, a detection device and a controller; the detection device is used for detecting unit flow overflowed by the three-way flow valve or pressure on a bypass overflow pipeline behind the three-way flow valve; the controller is respectively electrically connected with the electric proportional pump, the multi-path working link and the detection device, and the controller controls the electric proportional pump according to the detection result of the detection device. According to the hydraulic system provided by the invention, the three-way flow valve introduces a feedback mechanism, the state of oil flowing through the bypass overflow pipeline is detected in real time, and the flow of the electric proportional pump is controlled according to the detection result, so that the requirement value of the system is met and a small amount of surplus is provided, and the flow is matched with the requirement of the system with the least heating value. In addition, by the control mode, all mechanisms in the hydraulic system are in a pressure standby state at any time, and the response speed of the hydraulic system is effectively improved.)

1. A hydraulic system, comprising:

a hydraulic oil tank;

an oil inlet of the electric proportional pump is communicated with the hydraulic oil tank;

oil inlets of the main oil supply pipeline and the bypass overflow pipeline are respectively connected with an oil outlet of the electric proportional pump, and an oil outlet of the bypass overflow pipeline is connected with the hydraulic oil tank;

the multi-way valve assembly comprises a multi-way working link and a three-way flow valve, the multi-way working link is respectively communicated with the main oil supply pipeline, and the three-way flow valve is connected in series with a bypass overflow pipeline;

the detection device is used for detecting the unit flow overflowed by the three-way flow valve or the pressure on the bypass overflow pipeline behind the three-way flow valve;

and the controller is electrically connected with the electric proportional pump, the multi-path working unit and the detection device respectively, and controls the electric proportional pump according to a detection result of the detection device.

2. The hydraulic system of claim 1, wherein a damping orifice is disposed on the bypass overflow line after the three-way flow valve, and the sensing device is a pressure sensing device for sensing pressure on the line between the damping orifice and the three-way flow valve.

3. The hydraulic system of claim 1, wherein the sensing device is a flow sensing device configured to sense a unit flow of the three-way flow valve.

4. The hydraulic system as claimed in claim 1, wherein a damping hole is provided on the bypass overflow pipeline after the three-way flow valve, and a bypass overflow valve is connected in parallel to both ends of the damping hole.

5. The hydraulic system as claimed in claim 1, wherein a bypass solenoid valve is provided in the bypass overflow line, and a spring chamber of the three-way flow valve is communicated with an oil return spring chamber of the multi-way working link through the bypass solenoid valve to communicate with the hydraulic oil tank.

6. The hydraulic system of claim 1, further comprising: the main overflow valve, the pilot filter and the pilot reducing valve;

an oil inlet of the main overflow valve is communicated with an oil outlet of the electric proportional pump, and an oil outlet of the main overflow valve is communicated with the hydraulic oil tank; the oil inlet of the pilot reducing valve is connected to a pipeline between the oil inlet of the main overflow valve and the oil outlet of the electric proportional pump through the pilot filter, the oil outlet of the pilot reducing valve is communicated with the oil inlet spring cavity of the multi-way working connector, and the oil return port of the pilot reducing valve is communicated with the hydraulic oil tank.

7. The hydraulic system of claim 1, further comprising: an oil absorption filter and a high pressure filter; an oil inlet of the electric proportional pump is connected with the hydraulic oil tank through the oil suction filter; and the oil outlet of the electric proportional pump is connected with the high-pressure filter.

8. A work machine, comprising: the hydraulic system of any one of claims 1-7.

9. A method of controlling a hydraulic system according to any one of claims 1-7, comprising the steps of:

predicting total flow demands required by all the working units according to the current of each working unit, and controlling the opening of the electric proportional pump according to the total flow demands;

detecting unit flow overflowed by a three-way flow valve of the bypass overflow pipeline or a pressure value on the bypass overflow pipeline behind the three-way flow valve;

and adjusting the opening degree of the electric proportional pump according to the unit flow or the pressure value.

10. The method for controlling a hydraulic system according to claim 9, wherein the step of adjusting the opening degree of the electro-proportional pump according to the unit flow rate or the pressure value comprises:

judging whether the unit flow or the pressure value is within a preset range;

if the unit flow or the pressure value is judged and obtained to reach the upper limit of the threshold value, controlling to reduce the opening degree of the electric proportional pump; and if the unit flow or the pressure value is judged and obtained to reach the lower threshold, controlling to increase the opening of the electric proportional pump.

Technical Field

The invention relates to the field of hydraulic pressure, in particular to a hydraulic system, engineering machinery and a control method thereof.

Background

At present, the concrete pump truck cantilever crane multi-way valve has two types of PSL and PSV. The PSV multi-way valve is matched with a load-sensitive variable pump and is generally used for a long-arm pump truck. The PSL multiport valves are generally matched with fixed displacement pumps for short arm pump trucks. Because the flow regulation response characteristic of the PSV multi-way valve and the load-sensitive variable pump has no quick response of the electric proportional pump, the PSL multi-way valve configuration is already popularized on a long-arm pump truck.

The electric proportional pump is matched with the PSL multi-way valve, the discharge capacity of the electric proportional pump needs to be adjusted, and the requirement of the arm support multi-way valve is met at any time. If the oil supply of the oil pump is too little, the folding and unfolding speed of the arm support is slow, and if the oil supply of the oil pump is too much, the system overflows and generates heat.

The existing adjusting method mainly converts the current value (given by a remote controller) of each coupling proportional valve of the boom multi-way valve into the flow demand of each coupling valve core. And feeding back the flow demand of each unit to the controller, and summing to obtain the total flow required by the boom multi-way valve. And outputting proper current to the electric proportional oil pump by the controller according to the corresponding relation between the control current value and the discharge capacity of the electric proportional oil pump, so that the oil pump supplies proper flow to the arm frame multi-way valve. However, the consistency of the current value of the boom multi-way valve and the opening degree of the valve core is poor, and the current value and the flow cannot correspond to each other one by one. The actual required flow and the calculated flow of the boom multi-way valve have larger errors. The current value of the electric proportional oil pump and the discharge capacity of the oil pump are not completely in a linear relation, and the flow error output by the oil pump is large by setting the current value of the oil pump, so that the system is heated due to overlarge flow of the oil pump, or the arm support is slow in action due to undersize flow of the oil pump.

Disclosure of Invention

The embodiment of the invention provides a hydraulic system, engineering machinery and a control method thereof, which are used for solving the problems that the actual required flow, calculated flow and output flow errors of a multi-way valve of an existing hydraulic system arm frame are large, so that the system is heated due to overlarge oil pump flow, or the arm frame is slow in action due to undersized oil pump flow.

An embodiment of the present invention provides a hydraulic system, including:

a hydraulic oil tank;

an oil inlet of the electric proportional pump is communicated with the hydraulic oil tank;

oil inlets of the main oil supply pipeline and the bypass overflow pipeline are respectively connected with an oil outlet of the electric proportional pump, and an oil outlet of the bypass overflow pipeline is connected with the hydraulic oil tank;

the multi-way valve assembly comprises a multi-way working link and a three-way flow valve, the multi-way working link is respectively communicated with the main oil supply pipeline, and the three-way flow valve is connected in series with a bypass overflow pipeline;

the detection device is used for detecting the unit flow overflowed by the three-way flow valve or the pressure on the bypass overflow pipeline behind the three-way flow valve;

and the controller is electrically connected with the electric proportional pump, the multi-path working unit and the detection device respectively, and controls the electric proportional pump according to a detection result of the detection device.

According to the hydraulic system provided by the embodiment of the invention, a damping hole is arranged on the bypass overflow pipeline behind the three-way flow valve, the detection device is a pressure detection device, and the pressure detection device is used for detecting the pressure on the pipeline between the damping hole and the three-way flow valve.

According to the hydraulic system provided by the embodiment of the invention, the detection device is a flow detection device, and the flow detection device is used for detecting the unit flow of the three-way flow valve.

According to the hydraulic system provided by the embodiment of the invention, a damping hole is arranged on the bypass overflow pipeline behind the three-way flow valve, and two ends of the damping hole are connected with the bypass overflow valve in parallel.

According to the hydraulic system provided by the embodiment of the invention, a bypass electromagnetic valve is arranged in the bypass overflow pipeline, and a spring cavity of the three-way flow valve is communicated with the return oil spring cavities of the working links through the bypass electromagnetic valve so as to be communicated with the hydraulic oil tank.

According to an embodiment of the invention, the hydraulic system further comprises: the main overflow valve, the pilot filter and the pilot reducing valve;

an oil inlet of the main overflow valve is communicated with an oil outlet of the electric proportional pump, and an oil outlet of the main overflow valve is communicated with the hydraulic oil tank; the oil inlet of the pilot reducing valve is connected to a pipeline between the oil inlet of the main overflow valve and the oil outlet of the electric proportional pump through the pilot filter, the oil outlet of the pilot reducing valve is communicated with the oil inlet spring cavity of the multi-way working connector, and the oil return port of the pilot reducing valve is communicated with the hydraulic oil tank.

According to an embodiment of the invention, the hydraulic system further comprises: an oil absorption filter and a high pressure filter; an oil inlet of the electric proportional pump is connected with the hydraulic oil tank through the oil suction filter; and the oil outlet of the electric proportional pump is connected with the high-pressure filter.

The embodiment of the invention also provides a control method of the hydraulic system, which comprises the following steps:

predicting total flow demands required by all the working units according to the current of each working unit, and controlling the opening of the electric proportional pump according to the total flow demands;

detecting unit flow overflowed by a three-way flow valve of the bypass overflow pipeline or a pressure value on the bypass overflow pipeline behind the three-way flow valve;

and adjusting the opening of the electric proportional pump according to the unit flow or the pressure value.

According to the control method of the hydraulic system of one embodiment of the present invention, the step of adjusting the opening degree of the electric proportional pump according to the unit flow rate or the pressure value includes:

judging whether the unit flow or the pressure value is within a preset range;

if the unit flow or the pressure value is judged and obtained to reach the upper limit of the threshold value, controlling to reduce the opening degree of the electric proportional pump; and if the unit flow or the pressure value is judged and obtained to reach the lower limit of the threshold value, controlling to increase the opening degree of the electric proportional pump.

The hydraulic system, the engineering machinery and the control method thereof provided by the embodiment of the invention are provided with a hydraulic oil tank, an electric proportional pump, a multi-way valve assembly, a main oil supply pipeline, a bypass overflow pipeline, a detection device and a controller, a feedback mechanism is introduced by utilizing a three-way flow valve, the state of oil flowing through the bypass overflow pipeline is detected in real time, the flow of the electric proportional pump is controlled according to the detection result, the requirement value of the system is met, a small amount of surplus exists, and the flow is matched with the requirement of the system with the minimum heating value. In addition, by the control mode, all mechanisms in the hydraulic system are in a pressure standby state at any time, and the response speed of the hydraulic system can be effectively improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a schematic diagram of a hydraulic system according to an embodiment of the present invention;

FIG. 2 is a flow chart of a method of controlling a hydraulic system provided by one embodiment of the present invention;

reference numerals:

1. a hydraulic oil tank; 11. A high pressure filter; 12. An electric proportional pump;

13. an oil absorption filter; 2. A main oil supply line; 21. A main overflow valve;

22. a pilot filter; 23. A pilot pressure reducing valve; 3. A bypass overflow line;

31. a three-way flow valve; 32. A pressure detection device; 33. A damping hole;

34. a bypass overflow valve; 35. A bypass solenoid valve; 4. A first working unit;

5. a second working unit; 6. A back pressure valve.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, 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 of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

An embodiment of the present invention provides a hydraulic system, as shown in fig. 1, the hydraulic system includes: the system comprises a hydraulic oil tank 1, an electric proportional pump 12, a main oil supply pipeline 2, a bypass overflow pipeline 3, a multi-way valve assembly, a detection device and a controller.

The hydraulic oil tank 1 is used for supplying oil to a hydraulic system and is provided with an oil outlet and an oil return port. An oil inlet of the electric proportional pump 12 is communicated with the hydraulic oil tank 1; oil inlets of the main oil supply pipeline 2 and the bypass overflow pipeline 3 are respectively connected with an oil outlet of the electric proportional pump 12, and an oil outlet of the bypass overflow pipeline 3 is connected with the hydraulic oil tank 1; the multi-way valve assembly comprises a multi-way working link and a three-way flow valve 31, the multi-way working link is respectively communicated with the main oil supply pipeline 2, and the three-way flow valve 31 is connected in series with the bypass overflow pipeline 3; the detection device is used for detecting the unit flow overflowed by the three-way flow valve 31 or the pressure on the bypass overflow pipeline 3 behind the three-way flow valve 31. The three-way flow valve 31 is used for guiding redundant oil back to the hydraulic oil tank 1 when the flow in the oil way exceeds the actual required flow of the multi-way working union. The controller is respectively electrically connected with the electric proportional pump 12 and the multi-path working unit and the detection device, and the controller controls the electric proportional pump 12 according to the detection result of the detection device.

In this embodiment, as shown in fig. 1, when the hydraulic system is in operation, the controller predicts a total flow demand required by all the working units according to the current of each working unit, controls the electric proportional pump 12 according to the total flow demand, and gives a preliminary current value to the electric proportional pump 12, so that the flow provided by the electric proportional pump 12 can be quickly matched to a value near the demand value of the hydraulic system. Then the oil flowing through the bypass overflow pipeline 3 is detected, and the electric proportional pump 12 is finely adjusted according to the detected unit flow or pressure value.

For example, if the detection device detects that the backpressure value is 0 or less than the lower limit of the preset range, it is determined that no surplus flow of the electric proportional pump 12 overflows from the three-way flow valve 31, and at this time, the controller increases the current of the electric proportional pump 12 to increase the output of the oil until the three-way flow valve 31 has a certain surplus flow (determined by detecting the backpressure value generated by the overflow flow of the three-way flow valve). If the back pressure value generated by the surplus flow of the three-way flow valve 31 is detected to be too high and exceeds the upper limit of the preset range, the flow supplied by the electric proportional pump 12 is considered to be too much and exceeds the system requirement, and at the moment, the controller adjusts the current of the electric proportional pump 12 to be small, so that the flow output of the electric proportional pump 12 is reduced. The flow of the electric proportional pump 12 is controlled to meet the demand value of the system and have little margin, and the electric proportional pump 12 is matched with the demand value of the system with the least heating value. In addition, in this control mode, the electric proportional pump 12 is in a pressure standby state at any time, and the response speed of the hydraulic system can be effectively improved.

The hydraulic system provided by the embodiment of the invention is provided with a hydraulic oil tank, an electric proportional pump, a multi-way valve assembly, a main oil supply pipeline, a bypass overflow pipeline, a detection device and a controller, a feedback mechanism is introduced by utilizing a three-way flow valve, the state of oil flowing through the bypass overflow pipeline 3 is detected in real time, the flow of the electric proportional pump 12 is controlled according to a detection result, the requirement value of the system is met, a small amount of surplus exists, and the flow is matched with the requirement of the system with the minimum heating value. In addition, by the control mode, all mechanisms in the hydraulic system are in a pressure standby state at any time, and the response speed of the hydraulic system can be effectively improved.

As shown in fig. 1, a damping hole 33 is provided on the bypass overflow line 3 after the three-way flow valve 31, the detection device is a pressure detection device 32, and the pressure detection device 32 is used for detecting the pressure on the line between the damping hole 33 and the three-way flow valve 31.

At this time, the pressure detection device 32 monitors the front end pressure of the damping orifice in real time, and if the pressure detection device 32 detects that the backpressure value is 0 or less than the lower limit of the preset range, it is determined that no redundant flow of the electric proportional pump 12 overflows from the three-way flow valve 31, and at this time, the current of the electric proportional pump 12 is increased, and the output of the oil is increased until the three-way flow valve 31 has a certain redundant flow (determined by detecting the backpressure value generated by the overflow flow of the three-way flow valve). If the back pressure value generated by the surplus flow of the three-way flow valve 31 is detected to be too high and exceeds the upper limit of the preset range, the flow supplied by the electric proportional pump 12 is considered to be too much and exceeds the system requirement, and at the moment, the current of the electric proportional pump 12 is adjusted to be reduced, so that the flow output of the electric proportional pump 12 is reduced. The flow of the electric proportional pump 12 is controlled to meet the demand value of the system and have little margin, and the electric proportional pump 12 is matched with the demand value of the system with the least heating value.

Alternatively, in other embodiments of the present application, the detecting device is a flow rate detecting device, and the flow rate detecting device is used for detecting the unit flow rate of the three-way flow valve 31. The change of the unit flow rate is used for controlling the work of the hydraulic system.

Meanwhile, the two ends of the damping hole 33 can be connected with bypass overflow valves 34 in parallel. The use of the bypass spill valve 34 to define the highest pressure at the front of the orifice 33 ensures that the three-way flow valve 31 is also normally unloaded in the event of a failure of the sensing device or system.

For convenient installation, the detection device and the damping hole 33 can be embedded into the three-way flow valve 31 during actual installation.

As shown in fig. 1, a bypass electromagnetic valve 35 is disposed in the bypass overflow pipeline 3, and a spring cavity of the three-way flow valve 31 is communicated with an oil return spring cavity of each working joint through the bypass electromagnetic valve 35, and further communicated with the hydraulic oil tank 1.

For example, in the present embodiment, a first working pair 4 and a second working pair 5 are provided. The first working unit 4 and the second working unit 5 are both used for controlling the arm support to act. The spring cavity of the three-way flow valve 31 is communicated with the oil return spring cavity of the first working connector 4 and the oil return spring cavity of the second working connector 5 through the bypass electromagnetic valve 35, and further communicated with the hydraulic oil tank 1.

When the first working unit 4 and the second working unit 5 are operated, the electric proportion and the flow characteristic of each unit are firstly obtained, the total flow required by the working units is roughly estimated, then a preliminary current value is given to the electric proportional pump 12 according to the electric proportion flow characteristic of the electric proportional pump 12, the flow provided by the electric proportional pump 12 can be quickly matched to the vicinity of the required value of the system, the current of the electric proportional pump 12 is finely adjusted according to the pressure value of the front end of the damping hole 33 on the three-way flow valve oil return circuit, the flow of the electric proportional pump 12 is corrected, and the situation that the electric proportional pump 12 has excessive surplus flow to cause the heating of the system or the situation that the flow provided by the oil pump is too little to cause the slow motion of the arm support is avoided. The oil liquid flowing through the first working connection 4 and the second working connection 5 finally flows back to the hydraulic oil tank 1 through the oil return ends of the working connections and the backpressure valve 6.

In this embodiment, the hydraulic system further includes: a main relief valve 21, a pilot filter 22, and a pilot relief valve 23.

The oil inlet of the main overflow valve 21 is communicated with the oil outlet of the electric proportional pump 11, the oil outlet of the main overflow valve 21 is communicated with the hydraulic oil tank 1, and the main overflow valve 21 is used for guiding the oil back to the hydraulic oil tank 1 when the pressure in the oil path exceeds a preset value, for example, the pressure exceeds 37 MPA. An oil inlet of a pilot reducing valve 23 is connected to a pipeline between an oil inlet of the main overflow valve 21 and an oil outlet of the electric proportional pump 11 through a pilot filter 22, an oil outlet of the pilot reducing valve 23 is communicated with an oil inlet spring cavity of the multi-way working connector, and an oil return port of the pilot reducing valve 23 is communicated with the hydraulic oil tank 1. The pilot filter 22 is used for filtering oil, and the pilot reducing valve 23 is used for adjusting the pressure of the filtered oil, so that the overhigh pressure in the control oil circuit is avoided.

In the working process, the electric proportional pump 12 guides oil in the hydraulic oil tank 1 into the oil inlet spring cavity of the multi-way working connection through the pilot filter 22 and the pilot reducing valve 23, so that the opening degree of the valve cores of all the working connections is adjusted, the oil entering the multi-way working connection can enter the arm support oil cylinder, and the action of the arm support is adjusted.

As shown in fig. 1, the filter is provided with two, an oil suction filter 13 and a high pressure filter 11. An oil inlet of the electric proportional pump 12 is connected with the hydraulic oil tank 1 through an oil absorption filter 13; the oil outlet of the electric proportional pump 12 is connected with the high-pressure filter 11.

The oil suction filter 13 is used for protecting the electric proportional pump 12 and other hydraulic components so as to avoid sucking in polluted impurities and effectively control the cleanliness of the hydraulic system. The high pressure filter 11 is used to filter impurities in a high pressure environment.

In the working process, the electric proportional pump 12 guides oil in the hydraulic oil tank 1 into the oil suction filter 13 through an oil outlet and then enters the oil pump, and the oil boosted by the oil pump is filtered through the high-pressure filter and enters the system.

The invention also provides engineering machinery, such as an engineering vehicle like a pump truck or a crane. As shown in fig. 1, the working machine comprises the above-mentioned hydraulic system. The specific structure can be referred to the description related to fig. 1, and is not described herein again.

When the engineering machinery works, the controller predicts the total flow demand required by all the working units according to the current of each working unit, controls the electric proportional pump 12 according to the total flow demand, and gives a preliminary current value to the electric proportional pump 12, so that the flow provided by the electric proportional pump 12 can be quickly matched to be close to the demand value of the hydraulic system. Then the oil flowing through the bypass overflow pipeline 3 is detected, and the electric proportional pump 12 is finely adjusted according to the detected unit flow or pressure value. If the detection device detects that the backpressure value is 0 or less than the lower limit of the preset range, the electric proportional pump 12 is determined to have no redundant flow to overflow from the three-way flow valve 31, at the moment, the current of the electric proportional pump 12 is adjusted to be large, the output of oil liquid is increased, and the three-way flow valve 31 has a certain surplus flow (the backpressure value generated by the overflow flow of the three-way flow valve is detected for judgment). If the back pressure value generated by the surplus flow of the three-way flow valve 31 is detected to be too high and exceeds the upper limit of the preset range, the flow supplied by the electric proportional pump 12 is considered to be too much and exceeds the system requirement, and at the moment, the current of the electric proportional pump 12 is adjusted to be reduced, so that the flow output of the electric proportional pump 12 is reduced. The flow of the electric proportional pump 12 is controlled to meet the demand value of the system and have little margin, and the electric proportional pump 12 is matched with the demand value of the system with the least heating value. In addition, in this control mode, the electric proportional pump 12 is in a pressure standby state at any time, and the response speed of the hydraulic system can be effectively improved.

The engineering machinery provided by the embodiment of the invention is provided with the hydraulic system, a feedback mechanism is introduced by utilizing a three-way flow valve, the state of the oil flowing through the bypass overflow pipeline 3 is detected in real time, the flow of the electric proportional pump 12 is controlled according to the detection result, the requirement value of the system is met, a small amount of surplus exists, and the flow is matched with the requirement of the system with the least heating value. In addition, by the control mode, all mechanisms in the hydraulic system are in a pressure standby state at any time, and the response speed of the hydraulic system can be effectively improved.

The invention also provides a control method of the hydraulic system, which is used for controlling the hydraulic system.

As shown in fig. 2, the control method of the hydraulic system includes the steps of:

step S201: predicting total flow demands required by all the working links according to the current of each working link, and controlling the opening of the electric proportional pump according to the total flow demands;

step S202: detecting unit flow overflowed by a three-way flow valve of a bypass overflow pipeline or a pressure value on the bypass overflow pipeline behind the three-way flow valve;

step S203: and adjusting the opening of the electric proportional pump according to the unit flow or the pressure value.

When the hydraulic system works, the controller firstly predicts the total flow demand required by all the working units according to the current of each working unit, controls the electric proportional pump 12 according to the total flow demand, and gives a preliminary current value to the electric proportional pump 12, so that the flow provided by the electric proportional pump 12 can be quickly matched to be close to the demand value of the hydraulic system. Then the oil flowing through the bypass overflow pipeline 3 is detected, and the electric proportional pump 12 is finely adjusted according to the detected unit flow or pressure value.

In the control process, the controller judges whether the unit flow or the pressure value is within a preset range; if the unit flow or the pressure value is judged to reach the upper limit of the threshold value, the opening degree of the electric proportional pump 12 is controlled to be reduced; and if the unit flow rate or the pressure value is judged to reach the lower threshold, controlling to increase the opening of the electric proportional pump 12.

For example, if the detection device detects that the backpressure value is 0 or less than the lower limit of the preset range, it is determined that no surplus flow of the electric proportional pump 12 overflows from the three-way flow valve 31, and at this time, the controller increases the current of the electric proportional pump 12 to increase the output of the oil until the three-way flow valve 31 has a certain surplus flow (determined by detecting the backpressure value generated by the overflow flow of the three-way flow valve). If the back pressure value generated by the surplus flow of the three-way flow valve 31 is detected to be too high and exceeds the upper limit of the preset range, the flow supplied by the electric proportional pump 12 is considered to be too much and exceeds the system requirement, and at the moment, the controller adjusts the current of the electric proportional pump 12 to be small, so that the flow output of the electric proportional pump 12 is reduced. The flow of the electric proportional pump 12 is controlled to meet the demand value of the system and have little margin, and the electric proportional pump 12 is matched with the demand value of the system with the least heating value. In addition, in this control mode, the electric proportional pump 12 is in a pressure standby state at any time, and the response speed of the hydraulic system can be effectively improved.

According to the control method of the hydraulic system, provided by the embodiment of the invention, a feedback mechanism is introduced by using the three-way flow valve 31, the state of the oil flowing through the bypass overflow pipeline 3 is detected in real time, and the flow of the electric proportional pump 12 is controlled according to the detection result, so that the requirement value of the system is met, a small amount of surplus exists, and the flow is matched with the requirement of the system with the least heating value. In addition, by the control mode, all mechanisms in the hydraulic system are in a pressure standby state at any time, and the response speed of the hydraulic system can be effectively improved.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.