Hydraulic system, control method and wheeled excavator

Abstract

The present invention relates to a hydraulic system, and in order to solve the problem that it is difficult to be compatible with large flow control and small flow refined control in the existing hydraulic system, a hydraulic system, a control method and a wheeled excavator are provided, wherein the oil inlet and the first working oil port of the electric proportional valve in the hydraulic system are connected to the first oil port of the pressure oil source and the hydraulic actuator correspondingly; the oil inlet and the oil outlet of the opening and closing solenoid are connected to the oil inlet and the first working oil port of the electric proportional valve correspondingly, and the controller outputs the electric proportional valve control current for controlling the valve opening from the oil inlet of the electric proportional valve to the first working oil port according to the operating signal of the operating device; when the operating signal is less than or equal to the minimum signal value of the valve port fully open, the controller controls the opening and closing solenoid valve to be in a cut-off state, otherwise the opening and closing solenoid valve is controlled to be in a conducting state. The present invention can be well compatible with the refined operation control of small flow and the high-speed action operation control of large flow.

Description

Technical Field

[0001] The present invention relates to a hydraulic system, and more particularly to a hydraulic system, a control method and a wheeled excavator. Background Art

[0002] In the field of engineering machinery, hydraulic actuators such as cylinders and motors are used to drive related components to achieve the movement of related components of engineering machinery. The hydraulic system that drives and controls the hydraulic actuators includes the hydraulic actuators, control valves for controlling the hydraulic actuators, and a pressure oil source that provides pressure oil for the hydraulic actuators. The control valve is connected between the hydraulic actuator and the pressure oil source. The control valve is electrically or hydraulically controlled, and its valve core usually moves axially to open or close the valve port to achieve control of the hydraulic actuator.

[0003] When the pressure oil source provides sufficient pressure oil, the speed of the hydraulic actuator's action is related to the valve opening. The larger the valve opening, the larger the flow through the control valve, and the hydraulic actuator moves quickly. On the contrary, the hydraulic actuator moves slowly. For the control of hydraulic actuators that require large flow, control valves with large-diameter valve cores are often used. However, when controlling the flow, the valve opening of the control valve with a large-diameter valve core changes rapidly, and it is not suitable for fine operation. In construction machinery, some hydraulic actuators have different requirements under different working conditions. For example, the travel motor of a wheeled excavator needs to rotate at high speed when driving on the road in order to obtain a faster driving speed; but when performing excavation operations, the travel motor needs to run at low speed in order to perform fine operation control. Therefore, there is often a contradiction between large-flow fast action control and small-flow fine operation control in the hydraulic system of construction machinery. Summary of the invention

[0004] The technical problem to be solved by the present invention is to address the problem that it is difficult to reconcile large flow control and small flow fine control in existing hydraulic systems, and to provide a hydraulic system, a control method and a wheeled excavator that take into account the needs of large flow rapid action control and small flow fine control in the hydraulic system.

[0005] The technical solution of the present invention to achieve its purpose is as follows: a hydraulic system is provided.

[0006] It includes a hydraulic actuator, a pressure oil source, an electric proportional valve, a controller for controlling the electric proportional valve, and a control device connected to the controller for operating the hydraulic actuator; the oil inlet and the first working oil port of the electric proportional valve are correspondingly connected to the pressure oil source and the first oil port of the hydraulic actuator;

[0007] The controller outputs an electric proportional valve control current for controlling the valve opening between the oil inlet of the electric proportional valve and the first working oil port according to the operating signal of the operating device; it is characterized in that it also includes an opening and closing solenoid valve, the oil inlet and oil outlet of the opening and closing solenoid valve are connected to the oil inlet and the first working oil port of the electric proportional valve correspondingly, and the control end of the opening and closing solenoid valve that controls its opening and closing is connected to the controller; when the operating signal is less than or equal to the minimum signal value of the valve port fully open, the controller controls the opening and closing solenoid valve to be in a cut-off state, and when the operating signal is greater than the minimum signal value of the valve port fully open, the controller controls the opening and closing solenoid valve to be in a conducting state.

[0008] In the present invention, when the operating range of the operating device is small, the opening and closing solenoid valve is in a closed state, and the oil flowing to the hydraulic actuator is controlled by the electric proportional valve, which is more suitable for fine operation control; when the operating range of the operating device is large, and the output operation signal (current or voltage) value is greater than the minimum signal value of the valve port fully open, the opening and closing solenoid valve is in a conducting state, and the oil can flow to the hydraulic actuator through the opening and closing solenoid valve and the electric proportional valve, and the maximum flow to the hydraulic actuator is greatly increased, making the hydraulic actuator suitable for large flow and fast action. Therefore, the present invention can be well compatible with small flow fine operation control and large flow and high-speed action operation control.

[0009] When the operating device is operated, the operating amplitude is effectively increased, the operating signal gradually increases from zero, the control current of the electric proportional valve output by the controller according to the operating signal of the operating device gradually increases, and the valve opening between the oil inlet of the electric proportional valve and the first working oil port also gradually increases; when the operating signal increases to a certain value, the valve opening between the oil inlet of the electric proportional valve and the first working oil port increases to the maximum, that is, it reaches full opening, and the value of the operating signal at this time is the minimum signal value of the valve opening fully open.

[0010] In the above hydraulic system, when the manipulation signal is greater than the minimum signal value of the valve port fully open, the controller always outputs the control current of the electric proportional valve to fully open the valve port of the electric proportional valve. At this time, the valve port opening of the electric proportional valve and the opening and closing solenoid valve reaches the maximum value, and the pressure oil flowing to the hydraulic actuator changes with the pressure oil flow provided by the pressure oil source. The speed of the hydraulic actuator can be controlled by controlling the flow of the pressure oil source. Furthermore, the pressure oil source includes a hydraulic pump and a power drive device that drives the hydraulic pump to suck oil from the hydraulic oil tank. The pump port of the hydraulic pump is connected to the oil inlet of the electric proportional valve, and the controller is connected to the control unit of the power drive device. When the manipulation signal is greater than the minimum signal value of the valve port fully open, the controller sends a speed signal to the control unit of the power drive device according to the size of the manipulation signal so that the speed of the power drive device changes in a positive correlation with the size of the manipulation signal. The speed of the power drive device is controlled according to the manipulation signal, that is, the speed of the hydraulic pump is controlled, thereby realizing the control of the flow of the hydraulic pump.

[0011] In the above hydraulic system, when the manipulation signal is greater than the minimum signal value for full valve opening, the electric proportional valve control current output by the controller changes positively with the magnitude of the manipulation signal within the range between Iint and Imax, wherein Imax is the electric proportional valve control current for fully opening the electric proportional valve, and Iint is the electric proportional valve control current for opening the electric proportional valve to a predetermined opening; the sum of the valve port flow area of ​​the predetermined opening of the electric proportional valve and the valve port flow area when the opening and closing solenoid valve is turned on is equal to the valve port flow area when the electric proportional valve is fully open. When the manipulation signal increases and reaches the minimum signal value of the valve port fully open, the electric proportional valve is fully open, and the control current of the electric proportional valve is Imax, which is the maximum value; if the manipulation signal continues to increase slightly, the controller controls the opening and closing solenoid valve to open, and at the same time reduces the control current of the electric proportional valve to Iint. When the control current of the electric proportional valve is Iint, the valve port opening of the electric proportional valve can only reach a certain predetermined value. At this time, the sum of the valve port flow area of ​​the electric proportional valve and the valve port flow area of ​​the opening and closing solenoid valve is equal to the flow area when the valve port of the electric proportional valve is fully open. That is, in the hydraulic system, when the manipulation signal changes from equal to the minimum signal value of the valve port fully open to slightly greater than the minimum signal value of the valve port fully open, the total flow area of ​​the electric proportional valve and the opening and closing solenoid valve is equal to or close to each other, and no sudden change will occur, thereby avoiding sudden changes in the flow area and causing violent hydraulic shocks. Similarly, when the control signal changes from greater than the minimum signal value for full valve opening to equal to the minimum signal value for full valve opening, the control current of the electric proportional valve also changes from Iint to Imax, that is, the opening of the electric proportional valve increases from the preset value to full opening, and at the same time, the opening and closing solenoid valve also changes from opening to closing, avoiding sudden changes in the flow area and causing violent hydraulic shocks.

[0012] In the above hydraulic system, when the manipulation signal is less than or equal to the minimum signal value of the fully open valve port, the controller outputs the electric proportional valve control current which changes positively correlated with the magnitude of the manipulation signal within the range between zero and Imax.

[0013] The technical solution of the present invention to achieve its purpose is as follows: a control method for a hydraulic system is provided, characterized in that the hydraulic system includes an electric proportional valve whose oil inlet and first working oil port are connected to a pressure oil source and a first oil port of a hydraulic actuator, an on-off solenoid valve whose oil inlet and oil outlet are connected to the oil inlet and first working oil port of the electric proportional valve, a controller for controlling the electric proportional valve and the on-off solenoid valve, and a control device connected to the controller for controlling the hydraulic actuator; the control method is as follows:

[0014] The controller outputs an electric proportional valve control current for controlling the valve opening of the electric proportional valve according to the control signal of the control device;

[0015] When the manipulation signal is less than or equal to the minimum signal value for full valve opening, the controller controls the opening and closing solenoid valve to be in the cut-off state; otherwise, the controller controls the opening and closing solenoid valve to be in the on state, that is, when the manipulation signal is greater than the minimum signal value for full valve opening, the controller controls the opening and closing solenoid valve to be in the on state.

[0016] In the control method of the hydraulic system, the pressure oil source includes a hydraulic pump and a power drive device for driving the hydraulic pump to suck oil from the hydraulic oil tank, the pump port of the hydraulic pump is connected to the oil inlet of the electric proportional valve, and the controller is connected to the control unit of the power drive device;

[0017] When the control signal is greater than the minimum signal value for full valve opening, the controller always outputs the electric proportional valve control current to fully open the electric proportional valve and sends a speed signal to the control unit of the power drive device according to the size of the control signal so that the speed of the power drive device changes in a positive correlation with the size of the control signal.

[0018] In the control method of the hydraulic system, when the manipulation signal is greater than the minimum signal value of the fully open valve port, the controller outputs the electric proportional valve control current that changes positively with the magnitude of the manipulation signal within the range between Iint and Imax.

[0019] In the control method of the above hydraulic system, when the manipulation signal is less than or equal to the minimum signal value for full valve opening, the controller outputs the electric proportional valve control current, which changes positively correlated with the magnitude of the manipulation signal within the range between zero and the electric proportional valve control current value that fully opens the electric proportional valve.

[0020] The technical solution of the present invention to achieve its purpose is as follows: a wheeled excavator is provided, characterized in that it has the hydraulic system described above, wherein the first oil port of the hydraulic actuator is the forward oil inlet port of the travel motor.

[0021] Compared with the prior art, the present invention is well compatible with the refined operation control of small flow and the high-speed operation control of large flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a hydraulic principle diagram of the hydraulic system of the present invention.

[0023] Figure 2 It is a control circuit block diagram of the hydraulic system of the present invention.

[0024] Figure 3 It is a partial hydraulic principle diagram of the hydraulic system of the wheel excavator of the present invention.

[0025] Parts names and serial numbers in the figure:

[0026] Hydraulic oil tank 10, dual pump oil supply assembly 20, hydraulic pump 21, second hydraulic pump 22, power drive device 23, main control valve assembly 30, hydraulic control main valve 31, rotary main valve 32, dipper arm main valve 33, bulldozer main valve 34, bucket main valve 35, boom main valve 36, hydraulic actuator 40, electric proportional pilot valve 50, electric proportional pressure reducing valve 51, first solenoid valve 52, second solenoid valve 53, opening and closing solenoid valve 60, cartridge valve 61, two-position three-way solenoid valve 62, controller 7, operating device 8. DETAILED DESCRIPTION

[0027] The specific implementation scheme is described below with reference to the accompanying drawings.

[0028] Embodiment 1.

[0029] like Figure 1 Figure 2 As shown, the hydraulic system in this embodiment includes a hydraulic actuator 40, a pressure oil source, an electric proportional valve, a controller 7 for controlling the electric proportional valve, an operating device 8 connected to the controller 7 for operating the hydraulic actuator, an opening and closing solenoid valve 60, etc.

[0030] The pressure oil source is composed of a hydraulic oil tank 10, a hydraulic pump 21 whose oil suction port is connected to the hydraulic oil tank, and a power drive device 23 for driving the hydraulic pump 21 to rotate. The power drive device 23 is an electric motor or a fuel engine. The speed of the hydraulic pump 21 can be controlled by controlling the speed of the power drive device 23, thereby adjusting the flow of the hydraulic pump 21 within a certain range.

[0031] The electric proportional valve 3 is composed of a hydraulically controlled main valve 31 and an electric proportional pilot valve 50. The electric proportional pilot valve 50 includes an electric proportional pressure reducing valve 51, a first solenoid valve 52, and a second solenoid valve 53. The oil inlet of the electric proportional pressure reducing valve 51 is connected to the pilot oil source, and the oil outlet is connected to the oil inlet of the first solenoid valve 52 and the second solenoid valve 53 at the same time; the first solenoid valve 52 and the second solenoid valve 53 are both two-position three-way solenoid valves. The oil outlets of the first solenoid valve 52 and the second solenoid valve 53 are connected to the left and right hydraulically controlled ends of the hydraulically controlled main valve 31, and the oil return ends are connected to the hydraulic oil tank 10. The first solenoid valve 52 and the second solenoid valve 53 connect the oil outlet of the electric proportional pressure reducing valve 51 with the corresponding hydraulically controlled end of the hydraulically controlled main valve 31 or connect the hydraulically controlled end of the hydraulically controlled main valve with the hydraulic oil tank. The electric proportional pressure reducing valve 51 outputs the pilot pressure oil of the corresponding pressure according to the electric proportional valve control current applied thereto, and acts on the left end of the hydraulically controlled main valve 31 through the first solenoid valve 52 or acts on the right end of the hydraulically controlled main valve 31 through the second solenoid valve 53, so that the hydraulically controlled main valve 31 opens the corresponding valve opening in the left position or the right position. The pressure of the pilot pressure oil output by the electric proportional pressure reducing valve 51, the electric proportional valve control current, and the valve opening of the hydraulically controlled main valve are positively correlated, that is, the greater the electric proportional valve control current, the greater the pressure of the pilot pressure oil output, and the greater the valve opening of the hydraulically controlled main valve corresponding to the functional position.

[0032] In this embodiment, the electric proportional pilot valve 50 may also be composed of two electric proportional pressure reducing valves, and one electric proportional pressure reducing valve is connected between the two hydraulic control ends of the hydraulic control main valve 31 and the pilot pressure oil source.

[0033] The hydraulically controlled main valve 31 is a three-position valve, the oil inlet end of which is connected to the pump port of the hydraulic pump 21, the oil return port is connected to the hydraulic oil tank 10, and the first working oil port (A1 port) and the second working oil port (B1 port) are connected to the first oil port (A port) and the second oil port (B port) of the hydraulic actuator. The hydraulic actuator is a hydraulic motor. When the electric proportional pressure reducing valve 51 and the first solenoid valve 52 are energized and the hydraulically controlled main valve 31 is in the left position, the oil inlet of the hydraulically controlled main valve 31 is connected to the first working oil port (A1 port), and the pressure oil output by the hydraulic pump 21 enters the first oil port of the hydraulic motor through the hydraulically controlled main valve 31, and the hydraulic motor rotates forward; when the electric proportional pressure reducing valve 51 and the second solenoid valve 53 are energized and the hydraulically controlled main valve 31 is in the right position, the oil inlet of the hydraulically controlled main valve 31 is connected to the second working oil port (B1 port), and the pressure oil output by the hydraulic pump 21 enters the second oil port of the hydraulic motor through the hydraulically controlled main valve 31, and the hydraulic motor rotates reversely. The structural type of the hydraulically controlled main valve 31 changes accordingly according to the different functions of the hydraulic actuator 40 to which it is connected. For example, when the hydraulic actuator is a unidirectional rotating hydraulic motor, the hydraulically controlled main valve 31 can be simplified into a two-position valve, and its only one working oil port is connected to the first oil port of the hydraulic motor, and the second oil port of the hydraulic motor can be directly connected to the oil tank. In this case, the electric proportional pilot valve 50 also changes accordingly.

[0034] The on-off solenoid valve 60 is composed of a cartridge valve 61 and a two-position three-way solenoid valve 62. The cartridge valve 61 is a two-position two-way valve, and its state is a closed state or a fully open state. The oil inlet of the cartridge valve 61 is connected to the oil inlet of the hydraulic control main valve 31, that is, it is connected to the pump port of the hydraulic pump 21. The oil outlet of the cartridge valve 61 is connected to the first working oil port (A1 port) of the hydraulic control main valve 31, that is, it is connected to the first oil port of the hydraulic actuator 40. The first oil port of the two-position three-way solenoid valve 62 is connected to the control end of the cartridge valve 61, the second oil port is connected to the oil inlet of the cartridge valve 61, and the third oil port is connected to the hydraulic oil tank 10. The first oil port is selectively connected to the second oil port or the third oil port. When the two-position three-way solenoid valve 62 is energized, the first oil port is connected to the third oil port, and the cartridge valve is opened; when the two-position three-way solenoid valve 62 is de-energized, the first oil port is connected to the second oil port, and the cartridge valve 61 is closed.

[0035] like Figure 2 As shown, the operating device 8, the electric proportional pilot valve 50 in the electric proportional valve and the two-position three-way solenoid valve in the opening and closing solenoid valve 60 are all connected to the controller 7.

[0036] The operating device 8 is used to operate and control the hydraulic actuator 40. The operating device 8 can be an electric control handle. The operator performs the operation swing. When the electric control handle swings, the corresponding operating signal is transmitted to the controller 7. The operating signal can be a voltage signal or a current signal. The controller 7 controls the electric proportional pilot valve 50, the opening and closing solenoid valve 60 and other devices according to the operating signal. For example, when the electric control handle swings forward, the controller makes the first solenoid valve 52 electrically conductive according to the operating signal output by the electric control handle forward swing, and outputs the corresponding electric proportional valve control current to the electric proportional pressure reducing valve 51 according to the size of the operating signal. The hydraulically controlled main valve 31 is in the left position under the action of the pilot pressure oil, and the valve port is opened to the corresponding opening. The pressure oil output by the hydraulic pump 21 enters the first oil port of the hydraulic motor through the hydraulically controlled main valve 31, so that the hydraulic motor rotates forward. When the electric control handle swings backward, the controller 7 makes the second solenoid valve 53 electrically conductive according to the control signal output by the electric control handle, and at the same time outputs the corresponding electric proportional valve control current to the electric proportional pressure reducing valve 51 according to the size of the control signal. The hydraulically controlled main valve 31 is in the right position under the action of the pilot pressure oil, and the valve port is opened to the corresponding opening. The pressure oil output by the hydraulic pump 21 enters the second oil port of the hydraulic motor through the hydraulically controlled main valve 31, causing the hydraulic motor to reverse.

[0037] The controller 7 is connected to the power drive device 23 and can send a rotation speed instruction to the power drive device 23 to make the power drive device 23 work at a corresponding rotation speed.

[0038] In this embodiment, when the manipulation performed by the operating device 8 is to make the hydraulically controlled main valve 31 work in the right position, the controller 7 controls the electric proportional valve control current of the electric proportional pressure reducing valve 51 according to the manipulation signal output, and the electric proportional valve control current output by the controller and the valve port opening of the hydraulically controlled main valve are positively correlated with the size of the manipulation signal, that is, the larger the manipulation signal is, the larger the electric proportional valve control current and the valve port opening of the hydraulically controlled main valve are, until the electric proportional valve control current reaches the maximum value and the valve port of the hydraulically controlled main valve is fully opened. During this process, the opening and closing solenoid valve is in a closed state.

[0039] When the manipulation performed by the manipulation device 8 is to make the hydraulically controlled main valve 31 work in the left position, the control method of the hydraulic system is as follows:

[0040] The controller 7 energizes the first solenoid valve 52 in the electric proportional pilot valve according to the manipulation signal, and connects the oil outlet end of the electric proportional pressure reducing valve 51 with the hydraulically controlled left end of the hydraulically controlled main valve 31 .

[0041] When the control signal is less than or equal to the minimum signal value of the fully open valve port, the controller 7 outputs the electric proportional valve control current in the range of zero value and Imax and changes positively with the magnitude of the control signal. Imax is the electric proportional valve control current value of the fully open valve port of the hydraulic control main valve. When the control signal is less than or equal to the minimum signal value of the fully open valve port, the controller 7 controls the on-off solenoid valve 60 to be in a closed state, and the pressure oil output by the hydraulic pump 21 can only flow to the hydraulic actuator through the hydraulic control main valve 31.

[0042] The control signal gradually increases from zero value, the control current of the electric proportional valve output by the controller 7 gradually increases according to the size of the control signal of the control device 8, and the valve opening of the hydraulically controlled main valve also gradually increases; when the control signal increases to a certain value, the valve opening of the hydraulically controlled main valve increases to the maximum, that is, it reaches full opening, and the value of the control signal at this time is the minimum signal value of the valve fully open.

[0043] When the manipulation signal is greater than the minimum signal value of the valve port fully open, the controller 7 controls the on-off solenoid valve 60 to be in a conducting state, and the pressure oil output by the hydraulic pump 21 can flow to the hydraulic actuator through the hydraulically controlled main valve 31 and the on-off solenoid valve 60 .

[0044] When the manipulation signal is greater than the minimum signal value of the valve port fully open, there are two control modes for the electric proportional valve. The first control mode is that the controller always outputs the electric proportional valve control current that makes the valve port of the hydraulic main valve fully open, the valve port opening of the hydraulic main valve and the opening and closing solenoid valve reaches the maximum value, and the pressure oil flowing to the hydraulic actuator changes with the pressure oil flow rate provided by the hydraulic pump. The speed of the hydraulic actuator 40 can be controlled by controlling the flow rate of the hydraulic pump 21. At this time, the controller 7 can send a speed signal to the control unit of the power drive device 23 according to the size of the manipulation signal so that the speed of the power drive device 23 changes in a positive correlation with the size of the manipulation signal. The larger the manipulation signal value output by the manipulation device 8, the higher the speed of the power drive device 23, the greater the pressure oil flow output by the hydraulic pump 21, and the faster the action of the hydraulic actuator 40. If the hydraulic actuator is a hydraulic motor, its speed is faster.

[0045] When the control signal is greater than the minimum signal value of the valve port fully open, the second control mode of the electric proportional valve is: when the control signal increases from the minimum signal value of the valve port fully open to slightly greater than the minimum signal value of the valve port fully open, the controller 7 controls the opening and closing electromagnetic valve 60 to open and conduct, and at the same time controls the electric proportional valve control current of the electric proportional pressure reducing valve 51 to decrease from Imax to Iint. Under the action of the electric proportional valve control current Iint, the electric proportional pressure reducing valve 51 outputs the corresponding pilot pressure oil to open the valve port of the hydraulic control main valve 31 to the predetermined valve port opening; the sum of the valve port flow area of ​​the predetermined valve port opening of the hydraulic control main valve 31 and the valve port flow area when the opening and closing electromagnetic valve 60 is turned on is equal to the valve port flow area of ​​the hydraulic control main valve 31 when the valve port is fully open. When the manipulation signal increases and reaches the minimum signal value of the valve port fully open, the hydraulically controlled main valve is fully opened, and the control current of the electric proportional valve is Imax, which is the maximum value; if the manipulation signal continues to increase slightly, the controller controls the opening and closing solenoid valve 60 to open, and at the same time reduces the control current of the electric proportional valve to Iint. When the control current of the electric proportional valve is Iint, the valve port opening of the hydraulically controlled main valve can only reach a certain predetermined value. At this time, the sum of the valve port flow area of ​​the hydraulically controlled main valve and the valve port flow area of ​​the opening and closing solenoid valve 60 is equal to the flow area of ​​the hydraulically controlled main valve 31 when the valve port is fully open. That is, in the hydraulic system, when the manipulation signal changes from being equal to the minimum signal value of the valve port fully open to being slightly greater than the minimum signal value of the valve port fully open, the total flow area of ​​the hydraulically controlled main valve 31 and the opening and closing solenoid 60 is equal to or close to each other, and no sudden change will occur, thereby avoiding sudden changes in the flow area and causing violent hydraulic shocks. Similarly, when the control signal changes from slightly greater than the minimum signal value for full valve opening to equal to the minimum signal value for full valve opening, the control current of the electric proportional valve also changes from Iint to Imax, that is, the opening of the hydraulically controlled main valve increases from the preset value to full opening, and at the same time, the opening and closing solenoid valve 60 also changes from opening to closing, avoiding sudden changes in the flow area and causing violent hydraulic shocks.

[0046] In the second control mode, when the manipulation signal is greater than the minimum signal value for full valve opening, the controller 7 outputs the electric proportional valve control current in the range of Iint and Imax and changes in a positive correlation with the magnitude of the manipulation signal, that is, the valve opening of the hydraulically controlled main valve changes in a positive correlation with the magnitude of the manipulation signal within the range of the predetermined valve opening and full opening. The larger the manipulation signal, the larger the valve opening of the hydraulically controlled main valve.

[0047] In this embodiment, when the manipulation signal is less than or equal to the minimum signal value of the valve port fully open, the pressure oil output by the hydraulic pump 21 can only flow to the hydraulic actuator through the hydraulically controlled main valve 31, and at this stage it can be used to perform fine operation control on the hydraulic actuator 40; when the manipulation signal is greater than the minimum signal value of the valve port fully open, the pressure oil output by the hydraulic pump can flow to the hydraulic actuator through the hydraulically controlled main valve and the opening and closing solenoid valve, and the maximum flow rate is increased, so that the hydraulic actuator works in a high-speed action state with a large flow rate, thereby realizing that the hydraulic system of the present invention is well compatible with fine operation control of small flow rates and high-speed operation control of large flow rates, thereby meeting corresponding needs.

[0048] Embodiment 2.

[0049] Figure 3 The invention shows a partial oil circuit in the hydraulic system of a wheeled excavator. The hydraulic system of the traveling part of the wheeled excavator is the hydraulic system in the first embodiment, that is, the hydraulic actuator 40 in the first embodiment is the travel motor of the excavator, the hydraulic pump 21 and the second hydraulic pump 22 constitute the dual pump oil supply assembly 20, the hydraulic control main valve 31 is the travel wheel main valve, and it and the rotary main valve 32, the arm main valve 33, the boom main valve 36, the bucket main valve 35, and the bulldozer main valve 34 constitute the main control valve assembly 30, wherein the hydraulic control main valve 31 and the rotary main valve 32 and the arm main valve 33 are supplied with oil by the hydraulic pump 21; the boom main valve 36, the bucket main valve 35, and the bulldozer main valve 34 are supplied with oil by the second hydraulic pump.

[0050] In the hydraulic system, the first oil port of the hydraulic motor is the forward oil inlet, that is, when the first oil port of the hydraulic motor is filled with pressurized oil, the hydraulic motor rotates forward and the wheeled excavator moves forward; when the second oil port of the hydraulic motor is filled with pressurized oil, the hydraulic motor rotates reversely and the wheeled excavator moves backward.

[0051] In a wheeled excavator, when it is controlled to move, if the operating amplitude of the operating device 8 is small (when the signal value in the slot output by it is less than the minimum signal value of the valve fully open), the pressure oil flow to the travel motor is small, which is suitable for fine operation control. However, if the operating amplitude of the operating device is large (when the signal value in the slot output by it is greater than the minimum signal value of the valve fully open), the pressure oil flow to the travel motor is large, which is suitable for making the wheeled excavator travel at a faster speed, such as driving on a road, to meet the road speed requirements.

[0052] On a wheeled excavator, the control device can be in various forms, such as using an electric control handle for driving, controlling the working position of the hydraulic control main valve according to the swing direction of the electric control handle, and controlling the opening of the hydraulic control main valve and the opening and closing of the on-off solenoid valve according to the swing amplitude of the electric control handle. The control device can also be composed of a foot accelerator pedal and a gear handle, controlling the working position of the hydraulic control main valve according to the gear position of the gear handle, controlling the opening of the hydraulic control main valve and the opening and closing of the on-off solenoid valve according to the amplitude of the foot accelerator pedal, and controlling the speed of the travel motor.

Claims

1. A hydraulic system, comprising a hydraulic actuator, a pressure oil source, an electric proportional valve, a controller for controlling the electric proportional valve, and a control device connected to the controller for operating the hydraulic actuator; the oil inlet and the first working oil port of the electric proportional valve are connected to the pressure oil source and the first oil port of the hydraulic actuator respectively; The controller outputs an electric proportional valve control current for controlling the valve opening between the electric proportional valve oil inlet and the first working oil port according to the control signal of the control device; Features It also includes an opening and closing solenoid valve, the oil inlet and oil outlet of which are connected to the oil inlet and the first working oil port of the electric proportional valve, and the control end of the opening and closing solenoid valve that controls its opening and closing is connected to a controller; when the manipulation signal is less than or equal to the minimum signal value of the valve port fully open, the controller controls the opening and closing solenoid valve to be in a cut-off state, and when the manipulation signal is greater than the minimum signal value of the valve port fully open, the controller controls the opening and closing solenoid valve to be in a conducting state; the pressure oil source includes a hydraulic pump and a power drive device that drives the hydraulic pump to suck oil from a hydraulic oil tank, the pump port of the hydraulic pump is connected to the oil inlet of the electric proportional valve, and the controller is connected to a control unit of the power drive device; When the control signal is greater than the minimum signal value of the valve port fully open, the controller always outputs the electric proportional valve control current to fully open the valve port of the electric proportional valve and sends a speed signal to the control unit of the power drive device according to the size of the control signal so that the speed of the power drive device changes in a positive correlation with the size of the control signal; The electric proportional valve is composed of a hydraulically controlled main valve and an electric proportional pilot valve. The electric proportional pilot valve includes an electric proportional pressure reducing valve, a first solenoid valve and a second solenoid valve. The oil inlet end of the electric proportional pressure reducing valve is connected to the pilot oil source, and the oil outlet end of the electric proportional pressure reducing valve is connected to the oil inlet ends of the first solenoid valve and the second solenoid valve at the same time; the oil outlet ends of the first solenoid valve and the second solenoid valve are correspondingly connected to the left hydraulic control end and the right hydraulic control end of the hydraulically controlled main valve, and the oil return ends of the first solenoid valve and the second solenoid valve are both connected to the hydraulic oil tank.

2. The hydraulic system according to claim 1, characterized in that When the manipulation signal is less than or equal to the minimum signal value for full valve opening, the controller outputs an electric proportional valve control current that varies positively with the magnitude of the manipulation signal in the range between zero and Imax, wherein Imax is the electric proportional valve control current that fully opens the electric proportional valve.

3. A hydraulic system, comprising a hydraulic actuator, a pressure oil source, an electric proportional valve, a controller for controlling the electric proportional valve, and a control device connected to the controller for operating the hydraulic actuator; the oil inlet and the first working oil port of the electric proportional valve are connected to the pressure oil source and the first oil port of the hydraulic actuator accordingly; The controller outputs an electric proportional valve control current for controlling the valve opening between the electric proportional valve oil inlet and the first working oil port according to the control signal of the control device; Features It also includes an opening and closing solenoid valve, the oil inlet and oil outlet of which are connected to the oil inlet and the first working oil port of the electric proportional valve correspondingly, and the control end of the opening and closing solenoid valve that controls its opening and closing is connected to the controller; when the manipulation signal is less than or equal to the minimum signal value of the valve port fully open, the controller controls the opening and closing solenoid valve to be in a cut-off state, and when the manipulation signal is greater than the minimum signal value of the valve port fully open, the controller controls the opening and closing solenoid valve to be in a conducting state, and the electric proportional valve control current output by the controller changes positively with the magnitude of the manipulation signal within the range between Iint and Imax, wherein Imax is the electric proportional valve control current that makes the valve port of the electric proportional valve fully open, and Iint is the electric proportional valve control current that makes the valve port of the electric proportional valve open to a predetermined opening; the sum of the valve port flow area of ​​the predetermined opening of the electric proportional valve and the valve port flow area when the opening and closing solenoid valve is turned on is equal to the valve port flow area when the valve port of the electric proportional valve is fully open; The electric proportional valve is composed of a hydraulically controlled main valve and an electric proportional pilot valve. The electric proportional pilot valve includes an electric proportional pressure reducing valve, a first solenoid valve and a second solenoid valve. The oil inlet end of the electric proportional pressure reducing valve is connected to the pilot oil source, and the oil outlet end of the electric proportional pressure reducing valve is connected to the oil inlet ends of the first solenoid valve and the second solenoid valve at the same time; the oil outlet ends of the first solenoid valve and the second solenoid valve are correspondingly connected to the left hydraulic control end and the right hydraulic control end of the hydraulically controlled main valve, and the oil return ends of the first solenoid valve and the second solenoid valve are both connected to the hydraulic oil tank.

4. The hydraulic system according to claim 3, characterized in that When the manipulation signal is less than or equal to the minimum signal value of the valve port fully open, the controller outputs the electric proportional valve control current in a range between zero and Imax and changes in positive correlation with the magnitude of the manipulation signal.

5. A method for controlling a hydraulic system, characterized in that The hydraulic system includes an electric proportional valve whose oil inlet and first working oil port are connected to the pressure oil source and the first oil port of the hydraulic actuator, an on-off solenoid valve whose oil inlet and oil outlet are connected to the oil inlet and the first working oil port of the electric proportional valve, a controller for controlling the electric proportional valve and the on-off solenoid valve, and a control device connected to the controller for controlling the hydraulic actuator; The pressure oil source includes a hydraulic pump and a power drive device that drives the hydraulic pump to suck oil from the hydraulic oil tank. The pump port of the hydraulic pump is connected to the oil inlet of the electric proportional valve, and the controller is connected to the control unit of the power drive device. The control method is as follows: The controller outputs an electric proportional valve control current for controlling the valve opening of the electric proportional valve according to the control signal of the control device; When the control signal is less than or equal to the minimum signal value of the valve port fully open, the controller controls the on-off solenoid valve to be in a cut-off state; when the control signal is greater than the minimum signal value of the valve port fully open, the controller controls the on-off solenoid valve to be in a conducting state and always outputs the electric proportional valve control current that makes the valve port of the electric proportional valve fully open, and sends a speed signal to the control unit of the power drive device according to the size of the control signal so that the speed of the power drive device changes in a positive correlation with the size of the control signal; The electric proportional valve is composed of a hydraulically controlled main valve and an electric proportional pilot valve. The electric proportional pilot valve includes an electric proportional pressure reducing valve, a first solenoid valve and a second solenoid valve. The oil inlet end of the electric proportional pressure reducing valve is connected to the pilot oil source, and the oil outlet end of the electric proportional pressure reducing valve is connected to the oil inlet ends of the first solenoid valve and the second solenoid valve at the same time; the oil outlet ends of the first solenoid valve and the second solenoid valve are correspondingly connected to the left hydraulic control end and the right hydraulic control end of the hydraulically controlled main valve, and the oil return ends of the first solenoid valve and the second solenoid valve are both connected to the hydraulic oil tank.

6. The control method of the hydraulic system according to claim 5, characterized in that When the manipulation signal is less than or equal to the minimum signal value of the valve port fully open, the controller outputs the electric proportional valve control current in a range between zero and Imax and changes in positive correlation with the magnitude of the manipulation signal.

7. A method for controlling a hydraulic system, characterized in that The hydraulic system includes an electric proportional valve whose oil inlet and first working oil port are connected to the pressure oil source and the first oil port of the hydraulic actuator, an on-off solenoid valve whose oil inlet and oil outlet are connected to the oil inlet and the first working oil port of the electric proportional valve, a controller for controlling the electric proportional valve and the on-off solenoid valve, and a control device connected to the controller for controlling the hydraulic actuator; The electric proportional valve is composed of a hydraulically controlled main valve and an electric proportional pilot valve. The electric proportional pilot valve includes an electric proportional pressure reducing valve, a first solenoid valve, and a second solenoid valve. The oil inlet end of the electric proportional pressure reducing valve is connected to the pilot oil source, and the oil outlet end of the electric proportional pressure reducing valve is connected to the oil inlet ends of the first solenoid valve and the second solenoid valve at the same time; the oil outlet ends of the first solenoid valve and the second solenoid valve are connected to the left and right hydraulic control ends of the hydraulically controlled main valve respectively, and the oil return ends of the first solenoid valve and the second solenoid valve are both connected to the hydraulic oil tank; The control method is as follows: The controller outputs an electric proportional valve control current for controlling the valve opening of the electric proportional valve according to the control signal of the control device; When the manipulation signal is less than or equal to the minimum signal value for full valve opening, the controller controls the on-off solenoid valve to be in the cut-off state; when the manipulation signal is greater than the minimum signal value for full valve opening, the controller controls the on-off solenoid valve to be in the on state and the controller outputs the electric proportional valve control current which changes in a positive correlation with the magnitude of the manipulation signal within the range between Iint and Imax, wherein Imax is the electric proportional valve control current for fully opening the valve port of the electric proportional valve, and Iint is the electric proportional valve control current for opening the valve port of the electric proportional valve to a predetermined opening; the sum of the valve port flow area of ​​the predetermined opening of the electric proportional valve and the valve port flow area when the on-off solenoid valve is on is equal to the valve port flow area when the valve port of the electric proportional valve is fully open.

8. The control method of the hydraulic system according to claim 7, characterized in that When the manipulation signal is less than or equal to the minimum signal value of the valve port fully open, the controller outputs the electric proportional valve control current in a range between zero and Imax and changes in positive correlation with the magnitude of the manipulation signal.

9. A wheeled excavator, characterized in that A hydraulic system according to any one of claims 1 to 4, wherein the first oil port of the hydraulic actuator is a forward oil inlet port of the travel motor.

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