Control method of electronic control hydraulic system

Abstract

The invention discloses a control method of an electric control hydraulic system, the electric control hydraulic system comprises a motor, a hydraulic pump connected with the motor, a control valve and an oil tank, an oil inlet of the hydraulic pump is communicated with the oil tank, an oil outlet of the hydraulic pump is communicated with an oil inlet of the control valve, and a working oil port of the control valve is connected with an actuator; comprising the following steps: starting a motor and a control valve; collecting pressure data P1 of the upstream side of the control valve and pressure data P2 of the downstream side of the control valve in real time; calculating a difference value P between the currently collected pressure data P1 and the pressure data P2; the difference value P is compared with a preset value, if the difference value P is equal to the preset value, the motor is kept at the current rotating speed, if the difference value P is smaller than the preset value, the rotating speed of the motor is increased, and if the difference value P is larger than the preset value, the rotating speed of the motor is reduced. The rotating speed of the motor can be controlled in a self-adaptive mode, on-demand supply of flow is achieved, energy loss caused by redundant flow bypass is avoided, and energy consumption of the system is greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of hydraulic technology, and in particular to a control method for an electro-hydraulic system. Background Technology

[0002] Currently used load-sensitive systems primarily employ three-way pressure compensators (load-sensitive valves) to achieve precise and stable speed regardless of load changes, mainly in fixed-displacement pump hydraulic systems. When the fixed-displacement pump operates at a fixed speed or outputs more hydraulic oil than the actuator requires, the pump outputs more oil than needed. Some of this excess oil enters the actuator, while the excess returns to the hydraulic tank via the bypass of the load-sensitive valve. Because the excess oil must overcome the spring force of the load-sensitive valve to return to the tank, the hydraulic system generates unnecessary energy consumption and heats the hydraulic fluid. For electric counterbalance forklifts, this increased energy consumption translates to reduced range, increased charging frequency, and negatively impacts usability. Summary of the Invention

[0003] This invention addresses the technical problems existing in the prior art by providing a control method for an electro-hydraulic system that enables on-demand oil supply without the need for a load-sensitive valve, effectively avoiding energy loss caused by excess flow passing through the load-sensitive valve.

[0004] The technical solution adopted by this invention to solve its technical problem is: a control method for an electro-hydraulic system, the electro-hydraulic system including an electric motor, a hydraulic pump connected to the electric motor, a control valve, and an oil tank, the oil inlet of the hydraulic pump being connected to the oil tank, the oil outlet of the hydraulic pump being connected to the oil inlet of the control valve, and the working oil port of the control valve being connected to an actuator; including the following steps:

[0005] Start the motor and control valve;

[0006] Real-time acquisition of pressure data P1 on the upstream side of the control valve and pressure data P2 on the downstream side of the control valve;

[0007] Calculate the difference ΔP between the currently collected pressure data P1 and pressure data P2;

[0008] The difference ΔP is compared with a preset value. If the difference ΔP is equal to the preset value, the motor is kept at its current speed. If the difference ΔP is less than the preset value, the speed of the motor is increased. If the difference ΔP is greater than the preset value, the speed of the motor is decreased.

[0009] Furthermore, the pressure data P1 is obtained by detecting the first pressure sensor, and the pressure data P2 is obtained by detecting the second pressure sensor.

[0010] Furthermore, the control valve is a multi-way valve, which includes multiple directional valves arranged in parallel. The pressure data P1 is obtained by detecting the pressure of the hydraulic oil output from the outlet of the hydraulic pump using the first pressure sensor. The pressure data P2 is the maximum value of the pressure feedback from the pressure feedback ports of the multiple directional valves.

[0011] Furthermore, a plurality of second pressure sensors corresponding one-to-one with the plurality of directional valves are provided. The plurality of second pressure sensors are used to collect the pressure feedback oil port of the corresponding directional valve, and the pressure values ​​collected by each second pressure sensor are compared, and the maximum value among them is taken as the pressure data P2.

[0012] Furthermore, a second pressure sensor is provided, and the pressure feedback ports of the plurality of directional valves are connected to the pressure detection port of the second pressure sensor through one or more shuttle valves. The pressure value detected by the second pressure sensor constitutes the pressure data P2.

[0013] Furthermore, among the plurality of directional valves, one of the directional valves is a lifting directional valve, and the actuator connected to the working port of the lifting directional valve is a lifting cylinder for controlling the lifting and lowering of the forks of the forklift; another of the directional valves is a tilting directional valve, and the actuator connected to the working port of the tilting directional valve is a tilting cylinder for controlling the forward and backward tilting of the mast of the forklift.

[0014] Furthermore, the multi-way valve is a load-sensitive multi-way valve.

[0015] Furthermore, the preset value ranges from 1.5 to 2.0 MPa.

[0016] Furthermore, the pressure data P1 and pressure data P2 are processed by an ECU controller, which controls the speed of the electric motor.

[0017] Furthermore, the hydraulic pump is a gear pump.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. This invention can collect pressure data P1 from the upstream side of the control valve and pressure data P2 from the downstream side of the control valve in real time, and calculate the difference ΔP between the currently collected pressure data P1 and pressure data P2. The difference ΔP is compared with a preset value. If the difference ΔP is equal to the preset value, the motor is kept at the current speed. If the difference ΔP is less than the preset value, the speed of the motor is increased. If the difference ΔP is greater than the preset value, the speed of the motor is decreased. Therefore, this invention can adaptively control the speed of the motor, so that the output flow of the hydraulic pump achieves an effect similar to that of a variable pump, thereby eliminating the energy loss caused by excess flow bypass. It truly realizes on-demand flow supply, greatly reduces the energy consumption of the system, and improves the endurance of the electric counterbalance forklift.

[0020] 2. The flow output of the hydraulic pump of the present invention is only related to the size of the valve core opening of the control valve and has nothing to do with the load. That is, the flow is output according to the actuator requirements and has nothing to do with the load. Therefore, it has the advantages of high control precision, low system energy consumption and energy saving.

[0021] 3. This invention replaces the flow compensation valve structure of the traditional load-sensitive valve with a first and a second pressure sensor, simplifying the control valve structure. Furthermore, the use of a high-sensitivity pressure sensor improves the system's responsiveness and error performance compared to the traditional load-sensitive valve structure. The controller in this invention allows for easy setting of the difference ΔP between pressure data P1 and pressure data P2, making it significantly easier to set compared to traditional structures.

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments; however, the control method of the electro-hydraulic system of the present invention is not limited to the embodiments. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the electro-hydraulic system of the present invention;

[0024] Figure 2 This is a simplified flowchart of the control method of the present invention;

[0025] In the diagram, 1 is the electric motor, 2 is the gear pump, 3 is the control valve, 4 is the actuator, 5 is the first pressure sensor, 6 is the second pressure sensor, and 7 is the ECU controller. Detailed Implementation

[0026] In this invention, the terms "first," "second," etc., are used only to distinguish similar objects, not to describe a specific order or sequence, nor should they be construed as indicating or implying relative importance. Furthermore, in the description of this invention, unless otherwise specified, "a plurality of" refers to two or more. In the description of this invention, unless otherwise explicitly stated and limited, the term "connection" should be interpreted broadly; it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0027] Please see Figure 1 , Figure 2 As shown, the present invention provides a control method for an electro-hydraulic system, such as... Figure 1 As shown, this electro-hydraulic system is applied to forklifts, specifically electric counterbalance forklifts, but not limited to them. It includes an electric motor 1, a hydraulic pump connected to the motor 1, a control valve 3, and an oil tank. The hydraulic pump is specifically a gear pump 2, with its inlet connected to the oil tank and its outlet connected to the inlet of the control valve 3. The working port of the control valve 3 is connected to an actuator 4. The electro-hydraulic system also includes a controller, a first pressure sensor 5, and a second pressure sensor 6. The first pressure sensor 5 detects pressure data P1 upstream of the control valve 3, and the second pressure sensor 6 detects pressure data P2 downstream of the control valve 3. The controller is preferably an ECU controller 7, which controls the speed of the electric motor 1 by outputting logical signals based on the input signals from the first pressure sensor 5 and the second pressure sensor 6.

[0028] like Figure 2 As shown, the above control method includes the following steps:

[0029] Start motor 1 and control valve 3;

[0030] Real-time acquisition of pressure data P1 on the upstream side of control valve 3 and pressure data P2 on the downstream side of control valve 3;

[0031] Calculate the difference ΔP between the currently collected pressure data P1 and pressure data P2;

[0032] The difference ΔP is compared with a preset value (the preset value ranges from 1.5 to 2.0 MPa). If the difference ΔP is equal to the preset value, the motor 1 is kept at the current speed. If the difference ΔP is less than the preset value, the speed of the motor 1 is increased. If the difference ΔP is greater than the preset value, the speed of the motor 1 is decreased.

[0033] In this embodiment, the control valve 3 is a multi-way valve, specifically a load-sensitive multi-way valve, which includes multiple directional valves arranged in parallel. The inlet of each directional valve is connected to the outlet of the hydraulic pump (i.e., gear pump 2), the working port of each directional valve is connected to the corresponding actuator 4, and the return port of each directional valve is connected to the oil tank. The pressure data P1 is obtained by detecting the pressure of the hydraulic oil output from the outlet of the gear pump 2 using the first pressure sensor 5. The pressure data P2 is the maximum value among the pressure feedback ports of the multiple directional valves.

[0034] In this embodiment, a plurality of second pressure sensors 6 are provided, each corresponding to one of the plurality of directional valves. The plurality of second pressure sensors 6 are used to collect the pressure feedback from the pressure feedback port of the corresponding directional valve, and the pressure values ​​collected by each second pressure sensor 6 are compared, and the maximum value is taken as the pressure data P2. In other embodiments, a second pressure sensor 6 is provided, and the pressure feedback ports of the plurality of directional valves are connected to the pressure detection port of the second pressure sensor 6 through one or more shuttle valves. The pressure value detected by the second pressure sensor 6 constitutes the pressure data P2. Specifically, when there are two directional valves, only one shuttle valve is used. One inlet of the shuttle valve is connected to the pressure feedback port of one of the directional valves, and the other inlet of the shuttle valve is connected to the pressure feedback port of the other directional valve. The outlet of the shuttle valve is connected to the pressure detection port of the second pressure sensor 6. When there are more than two directional valves, multiple shuttle valves are used, and at least two of the multiple shuttle valves are connected in series. For example, when there are three directional valves, two shuttle valves can be used. These two shuttle valves are named the first shuttle valve and the second shuttle valve, respectively. The two inlets of the first shuttle valve are connected to the pressure detection ports of two of the directional valves, and the outlet of the first shuttle valve and the pressure detection ports of the remaining directional valves are connected to the two inlets of the second shuttle valve, respectively. The outlet of the second shuttle valve is connected to the pressure detection port of the second pressure sensor 6.

[0035] Of the plurality of directional valves, one is a lifting directional valve, the actuator 4 connected to the working port of which is a lifting cylinder for controlling the lifting and lowering of the forklift's forks; another is a tilting directional valve, the actuator 4 connected to the working port of which is a tilting cylinder for controlling the forward and backward tilting of the forklift's mast. The number of directional valves is specifically two, but not limited to this.

[0036] In a control method for an electro-hydraulic system according to the present invention, when the lifting directional valve and the tilting directional valve are in the neutral position, the second pressure sensor 6 outputs no pressure signal to the ECU controller 7. If the motor 1 drives the gear pump 2 to rotate and output flow at this time, since the second pressure sensor 6 has no pressure signal, the ECU controller 7 controls the motor 1 to gradually stop rotating, so that the gear pump 2 does not output flow.

[0037] When the lifting or tilting directional valve is operated, the load pressure is fed back to the second pressure sensor 6 through the internal pressure feedback channel of the lifting or tilting directional valve. The signal from the second pressure sensor 6 is then output to the ECU controller 7. The ECU controller 7 automatically adjusts the speed of the motor 1 by comparing the pressure signal from the first pressure sensor 5, causing the gear pump 2 to output a corresponding flow rate. When the pressure difference ΔP between the upstream (pump end) and downstream (load end) pressures of the control valve 3 reaches a set value, the speed of the motor 1 stops increasing. As the valve stem opening of each directional valve changes, the ECU controller 7 controls the speed of the motor 1 by comparing the pressure signals from the first pressure sensor 5 and the second pressure sensor 6, and always maintains a constant pressure difference between the upstream (pump end) and downstream (load end) pressures of the control valve 3. Therefore, the flow rate output by each directional valve is only related to the valve core opening and area, and is not affected by the load, resulting in high control accuracy.

[0038] Therefore, this invention collects the pressure at the pump end and the pressure at the load end, and compares the pressure signals to enable the ECU controller 7 to adaptively control the speed of the motor 1. As a result, the speed of the motor 1 changes with the pressure difference, and the output flow of the gear pump 2 is output on demand according to the speed of the actuator 4. This makes the output flow of the gear pump 2 achieve the effect of a variable pump, without the energy loss caused by excess flow bypass. It truly realizes on-demand flow supply, greatly reduces the energy consumption of the system, and improves the endurance of the electric counterbalance forklift.

[0039] The control method of the electro-hydraulic system of the present invention, the parts not covered herein are the same as or can be implemented by using existing technology.

[0040] The above embodiments are only used to further illustrate a control method for an electro-hydraulic system of the present invention. However, the present invention is not limited to the embodiments. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A control method for an electro-hydraulic system, the electro-hydraulic system comprising an electric motor, a hydraulic pump connected to the electric motor, a control valve, and an oil tank, wherein the oil inlet of the hydraulic pump is connected to the oil tank, the oil outlet of the hydraulic pump is connected to the oil inlet of the control valve, and the working port of the control valve is connected to an actuator; characterized in that: Includes the following steps: Start the motor and control valve; Real-time acquisition of pressure data P1 on the upstream side of the control valve and pressure data P2 on the downstream side of the control valve; Calculate the difference ΔP between the currently collected pressure data P1 and pressure data P2; The difference ΔP is compared with a preset value. If the difference ΔP is equal to the preset value, the motor is kept at its current speed. If the difference ΔP is less than the preset value, the speed of the motor is increased. If the difference ΔP is greater than the preset value, the speed of the motor is decreased.

2. The control method for the electro-hydraulic system according to claim 1, characterized in that: The pressure data P1 is obtained by detecting the first pressure sensor, and the pressure data P2 is obtained by detecting the second pressure sensor.

3. The control method for the electro-hydraulic system according to claim 2, characterized in that: The control valve is a multi-way valve, which includes multiple directional valves arranged in parallel. The pressure data P1 is obtained by detecting the pressure of the hydraulic oil output from the outlet of the hydraulic pump using the first pressure sensor. The pressure data P2 is the maximum value of the pressure feedback from the pressure feedback ports of the multiple directional valves.

4. The control method for the electro-hydraulic system according to claim 3, characterized in that: A plurality of second pressure sensors are provided, each corresponding to one of the plurality of directional valves. The pressures fed back from the pressure feedback ports of the corresponding directional valves are collected by the plurality of second pressure sensors respectively, and the pressure values ​​collected by each second pressure sensor are compared, and the maximum value among them is taken as the pressure data P2.

5. The control method for the electro-hydraulic system according to claim 3, characterized in that: A second pressure sensor is provided, and the pressure feedback ports of the plurality of directional valves are connected to the pressure detection port of the second pressure sensor through one or more shuttle valves. The pressure value detected by the second pressure sensor constitutes the pressure data P2.

6. The control method for the electro-hydraulic system according to any one of claims 3-5, characterized in that: Among the plurality of directional valves, one of the directional valves is a lifting directional valve, the actuator connected to the working port of which is a lifting cylinder for controlling the lifting and lowering of the forks of the forklift; and one of the directional valves is a tilting directional valve, the actuator connected to the working port of which is a tilting cylinder for controlling the forward and backward tilting of the mast of the forklift.

7. The control method for the electro-hydraulic system according to claim 3, characterized in that: The multi-way valve is a load-sensitive multi-way valve.

8. The control method for the electro-hydraulic system according to claim 1, characterized in that: The preset value ranges from 1.5 to 2.0 MPa.

9. The control method for the electro-hydraulic system according to claim 1, characterized in that: The pressure data P1 and pressure data P2 are processed by an ECU controller, which also controls the speed of the electric motor.

10. The control method for the electro-hydraulic system according to claim 1, characterized in that: The hydraulic pump is a gear pump.

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