Load sensing hydraulic system, warming-up control method and working machine

Abstract

The present application relates to a hydraulic system, in order to solve the problem of existing load sensitive hydraulic system warm-up, the present application constructs a kind of load sensitive hydraulic system, warm-up control method and engineering machinery, wherein the hydraulic system includes for closed median control valve, variable pump, the electromagnetic valve for the inlet and outlet oil port respectively with the inlet oil path of control valve and the load feedback port of variable pump connection, low temperature heating valve group containing unloading valve and electric proportional valve, temperature detector for detecting hydraulic oil temperature, controller for controlling electric proportional valve and electromagnetic valve;Unloading valve inlet and outlet oil port correspond with control valve inlet oil path and hydraulic oil tank communication.This application, in the process of warm-up, gradually increase pump displacement and unloading pressure with the improvement of oil viscosity, avoid high pressure or large flow unloading under the condition of large oil viscosity, leading to pump damage.

Description

Technical Field

[0001] This invention relates to a hydraulic system, and more specifically, to a load-sensitive hydraulic system, a warm-up control method, and engineering machinery. Background Technology

[0002] When construction machinery is in operation, its hydraulic system needs to be maintained at a suitable temperature so that the hydraulic fluid has a viscosity suitable for flow in the pipeline. When the construction machinery is first started, the hydraulic fluid in its system is close to the ambient temperature, requiring a warm-up operation for a corresponding period of time based on the hydraulic fluid temperature, so that the hydraulic fluid temperature reaches the requirements for normal operation of the hydraulic system.

[0003] Current methods for warming up construction machinery typically include: 1. installing heating rods in the hydraulic oil tank; 2. utilizing the cooling system of the construction machinery's power system; and 3. using the self-heating of the hydraulic system oil to raise the oil temperature. In the aforementioned warm-up methods, using heating rods to heat the hydraulic oil can easily lead to localized high temperatures near the heating rods, causing oil deterioration. While using a cooling system to raise the oil temperature is feasible in lower-temperature areas, the power system itself requires a considerable amount of time to reach its full temperature. For some high-efficiency machines, such as electric machinery, the heat generated during non-operational states is minimal. Utilizing the self-heating of the hydraulic system oil to raise its temperature occurs after the machine is started but before any operation is performed. The hydraulic pump outputs oil that flows back to the hydraulic tank through pipelines within the hydraulic system. The amount of heat generated by the hydraulic system oil depends on the power absorbed by the hydraulic pump from the power supply device (engine or electric motor). For load-sensitive hydraulic systems, the hydraulic pump is a piston pump, which absorbs power from the power device according to the load. When no hydraulic actuators are being operated, the variable displacement pump is at its minimum displacement, supplementing the hydraulic system with flow. At this time, the heat generated by the hydraulic oil is very small. Warming up using this method takes a long time, especially in low-temperature (-25℃ to 0℃) and ultra-low-temperature (-50℃ to -25℃) regions. Summary of the Invention

[0004] The technical problem to be solved by the present invention is the warm-up problem of existing load-sensitive hydraulic systems, and provides a load-sensitive hydraulic system, a warm-up control method and engineering machinery, so as to achieve rapid increase of hydraulic system oil temperature.

[0005] The technical solution of this invention to achieve its objective is as follows: A load-sensitive hydraulic system is constructed, including a closed-position control valve for controlling hydraulic actuators, a variable pump whose pump port is connected to the oil inlet of the control valve, wherein the load feedback port of the control valve is connected to the load feedback port of the variable pump via a load feedback oil circuit, and further comprising:

[0006] The solenoid valve has its inlet and outlet ports connected to the oil inlet circuit of the control valve and the load feedback port of the variable pump, respectively, and is used to connect or disconnect the oil circuit between the oil inlet circuit of the control valve and the load feedback port of the variable pump.

[0007] The low-temperature heating valve assembly includes an unloading valve and an electro-proportional valve for controlling the opening degree of the unloading valve; the inlet and outlet ports of the unloading valve are connected to the oil inlet circuit of the control valve and the hydraulic oil tank; the inlet port of the electro-proportional valve is connected to the pilot oil source.

[0008] Temperature detector, used to detect hydraulic oil temperature;

[0009] The controller is used to control the output pressure of the electro-proportional valve and the on / off state of the solenoid valve.

[0010] In this invention, the controller controls the solenoid valve and the electro-proportional valve, so that the hydraulic system sequentially goes through the states of low-pressure unloading at the maximum displacement of the variable pump, low-pressure unloading at the maximum displacement of the constant pressure pump, and high-pressure unloading of the constant pressure pump. This allows the pump displacement and unloading pressure to gradually increase as the hydraulic oil temperature rises during warm-up, with the improvement of oil viscosity. This avoids pump damage caused by high-pressure or high-flow unloading when the oil viscosity is high.

[0011] In the load-sensitive hydraulic system of the present invention, the hydraulic system further includes a hydraulic steering control device. The variable pump includes a first variable pump connected to the inlet of the control valve and a second variable pump connected to the inlet of the hydraulic steering control device. The EF port of the hydraulic steering control device is connected to the confluence inlet of the control valve, and the inlet of the unloading valve is connected to the EF port. The load feedback port of the hydraulic steering control device and the load feedback port of the control valve are connected to the load feedback port of the second variable pump via a shuttle valve, and the load feedback port of the control valve is connected to the load feedback port of the first variable pump. The inlet and outlet ports of the solenoid valve are connected to the inlet of the hydraulic steering control device and the load feedback port of the second variable pump, respectively.

[0012] In a preferred embodiment of the present invention, the hydraulic steering control device includes a flow amplification valve, a steering gear connected to the flow amplification valve, and a steering cylinder connected to the steering working port of the flow amplification valve. Under the control of the steering gear, the flow amplification valve outputs steering pressure oil to the steering cylinder.

[0013] The technical solution of this invention to achieve its objective is as follows: A warm-up control method is constructed and applied to the aforementioned load-sensitive hydraulic system, comprising the following steps:

[0014] S1: The controller de-energizes the solenoid valve to put it in the off state, outputs the maximum current to the electro-proportional valve to make the valve opening of the unloading valve reach the maximum, and executes step S2 after a period of time.

[0015] S2: The controller energizes the solenoid valve to put it in the conducting state, outputs the maximum current to the electro-proportional valve to make the valve opening of the unloading valve reach the maximum, and executes step S3 after a period of time.

[0016] S3: The controller energizes the solenoid valve to put it in the conducting state, outputs a predetermined current to the electro-proportional valve to reduce the valve opening of the unloading valve, until the hydraulic oil temperature reaches the predetermined value, at which point the controller de-energizes the solenoid valve and the electro-proportional valve.

[0017] In the warm-up control method of the present invention, in step S1, step S2 is executed after the solenoid valve is de-energized and the maximum current of the electro-proportional valve continues for a first predetermined time, or after the solenoid valve is de-energized and the maximum current of the electro-proportional valve continues until the hydraulic oil reaches a first predetermined temperature.

[0018] In the warm-up control method of the present invention, in step S2, after the solenoid valve is energized and the maximum current of the electro-proportional valve continues for a second predetermined time, or after the solenoid valve is energized and the maximum current of the electro-proportional valve continues until the hydraulic oil reaches a second predetermined temperature, step S3 is executed.

[0019] In the warm-up control method of the present invention, in step S3, the control current output by the controller to the electro-proportional valve gradually decreases from the maximum current to a predetermined current according to the time gradient or temperature gradient.

[0020] The technical solution of the present invention to achieve its purpose is as follows: to construct an engineering machine having the aforementioned load-sensitive hydraulic system.

[0021] Compared with the prior art, in this invention, as the oil viscosity improves during the warm-up process, the pump displacement and unloading pressure are gradually increased, avoiding pump damage caused by high pressure or high flow rate unloading when the oil viscosity is high. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the load-sensitive hydraulic system of the present invention.

[0023] Figure 2 This is a flowchart of the warm-up control method of the present invention.

[0024] Component names and serial numbers in the diagram:

[0025] Hydraulic oil tank 1, first variable pump 2, second variable pump 3, pilot oil source valve 4, solenoid valve 5, shuttle valve 6, steering gear 7, flow amplification valve 8, steering cylinder 9, control valve 10, first hydraulic actuator 11, second hydraulic actuator 12, temperature detector 13, low temperature heating valve group 14, unloading valve 141, electro-proportional valve 142. Detailed Implementation

[0026] The specific implementation plan is described below with reference to the attached diagram.

[0027] Example 1.

[0028] In this embodiment, the load-sensitive hydraulic system includes a closed-position control valve 10 for controlling hydraulic actuators, a variable pump whose pump port is connected to the oil inlet of the control valve, the load feedback port of the control valve 10 being connected to the load feedback port of the variable pump via a load feedback oil circuit, and also includes a solenoid valve 5, a cryogenic heating valve group 14, a temperature detector 13, and a controller (not shown in the figure).

[0029] The inlet and outlet ports of the solenoid valve 5 are connected to the oil inlet of the control valve 10 and the load feedback port of the variable pump, respectively, to connect or disconnect the oil passage between the oil inlet of the control valve 10 and the load feedback port of the variable pump.

[0030] The low-temperature heating valve assembly 14 includes an unloading valve 141 and an electro-proportional valve 142 for controlling the opening degree of the unloading valve port; the inlet and outlet ports of the unloading valve 141 are connected to the oil inlet circuit of the control valve 10 and the hydraulic oil tank; the oil inlet port of the electro-proportional valve is connected to the pilot oil source.

[0031] Temperature detector 13 is used to detect the temperature of hydraulic oil.

[0032] The controller is used to control the output pressure of the electro-proportional valve 142 and the on / off state of the solenoid valve 5.

[0033] Optionally, such as Figure 1 As shown, the hydraulic system also includes a hydraulic steering control device. The variable pumps include a first variable pump 2 connected to the inlet of the control valve 10 and a second variable pump 3 connected to the inlet of the hydraulic steering control device. The EF port of the hydraulic steering control device is connected to the confluence inlet of the control valve 10, and the inlet of the unloading valve 141 is connected to the EF port. The load feedback port of the hydraulic steering control device and the load feedback port of the control valve 10 are connected to the load feedback port of the second variable pump 3 via the shuttle valve 6, and the load feedback port of the control valve 10 is connected to the load feedback port of the first variable pump 2. The inlet and outlet ports of the solenoid valve 5 are connected to the inlet of the hydraulic steering control device and the load feedback port of the second variable pump, respectively.

[0034] Optionally, the hydraulic steering control device includes a flow amplification valve 8 and a steering gear 7 connected to the flow amplification valve 8, and a steering cylinder 9 connected to the steering working port of the flow amplification valve 8. Under the control of the steering gear 7, the flow amplification valve 8 outputs steering pressure oil to the steering cylinder 9 to achieve steering.

[0035] The pump port of the second variable pump 3 is unidirectionally connected to the oil inlet of the flow amplification valve 8. The EF port of the flow amplification valve 8 is connected to the confluence port of the control valve 10 (i.e., the distribution valve). The working port of the control valve 10 is connected to the first hydraulic actuator 11 and the second hydraulic actuator 12. The pressure oil provided by the second variable pump 3 prioritizes meeting the flow requirements of the hydraulic steering control device. The excess flow is then combined through the EF port of the flow amplification valve 8 to the confluence port of the control valve 10, where it merges with the pressure oil supplied by the first variable pump 2 and is supplied to the control valve 10.

[0036] The control valve 10 is a closed-position valve core. When the first hydraulic actuator 11 or the second hydraulic actuator 12 is not operated, the pressure oil supplied by the EF port and the first variable pump cannot be unloaded and flow back to the hydraulic oil tank through the control valve.

[0037] When the load-sensitive hydraulic system is applied to a loader, the first hydraulic actuator 11 and the second hydraulic actuator 12 are the boom cylinder and the bucket cylinder, respectively. When the load-sensitive hydraulic system is applied to other construction machinery, the first hydraulic actuator 11 and the second hydraulic actuator 12 can be other corresponding hydraulic actuators, such as hydraulic motors, cylinders, etc.

[0038] The load feedback port (LS1 port) of the flow amplification valve 8 is connected to one inlet end of the shuttle valve 6, and the load feedback port (LS port) of the control valve 10 is connected to the other inlet end of the shuttle valve 6. The outlet end of the shuttle valve 6 is connected to the load feedback port (X1 port) of the second variable pump 3 via a one-way damping valve. The load feedback port (LS port) of the control valve 10 is also connected to the load feedback port (X1 port) of the first variable pump 2. The solenoid valve 5 is a switching valve, with its inlet end connected to the inlet port of the flow amplification valve 8 and its outlet end connected to the load feedback port (X1 port) of the second variable pump 3.

[0039] In the cryogenic heating valve assembly 14, the inlet of the unloading valve 141 is connected to the EF port of the flow amplification valve 8, and the outlet is connected to the hydraulic oil tank 1. The inlet of the electro-proportional valve 142 is connected to the outlet of the pilot oil source valve 4, and the outlet is connected to the hydraulic control end of the unloading valve 141. The inlet of the pilot oil source valve 4 is connected to the pump port of the second variable pump 3, reducing the high-pressure working pressure oil of the second variable pump 3 to low-pressure pilot control oil for control.

[0040] Temperature detector 13 is used to detect the temperature of the hydraulic oil tank. The controller is connected to solenoid valve 5, electro-proportional valve 142 and temperature detector 13. The controller controls the opening and closing of solenoid valve 5 and is also used to output control current to electro-proportional valve 142, so that electro-proportional valve 142 outputs corresponding pilot control pressure oil to unloading valve 141, so that the valve opening of unloading valve 41 is at the corresponding value.

[0041] In this embodiment, when construction machinery such as loaders using the load-sensitive hydraulic system of this embodiment is operating in a cold environment, the hydraulic oil temperature is too low when the machinery is first started, making it unsuitable for operation. At this time, the load-sensitive hydraulic system can perform a warm-up operation, raising the oil temperature while the hydraulic actuators are not in operation. The process is as follows:

[0042] After the machine is started, the electro-proportional valve 142 and the solenoid valve 5 remain de-energized. At this time, the second variable pump 3 replenishes the hydraulic system with flow at a standby pressure of 2.5 MPa and minimum displacement.

[0043] After entering the warm-up process, the controller energizes the proportional valve 142 and outputs maximum current, at which point the unloading valve 141 is in a large-flow state. The second variable pump 3 begins to increase its displacement from its minimum displacement until the pressure drop generated by the flow reaches the standby pressure of the second variable pump 3. In this state, the second variable pump 3 absorbs power from the drive unit, such as an electric motor or engine, and converts it into heat through the unloading valve 141, raising the oil temperature. The oil heating power in this state is greater than the heating power of the hydraulic system during machine startup, and the oil viscosity begins to gradually improve.

[0044] After the solenoid valve 5 is de-energized and the electro-proportional valve 142 operates at maximum current for a first predetermined time (e.g., 1-2 minutes), or when the hydraulic oil temperature reaches a first predetermined value (2 degrees Celsius), the controller energizes the electro-proportional valve 142 and maintains maximum current, while also energizing the solenoid valve 5. At this time, the second variable pump 3 changes from a load-sensitive pump to a constant-pressure pump, outputting flow at maximum displacement. Simultaneously, the pump inlet pressure of the second variable pump 3 also increases. The heating power of the hydraulic system for the hydraulic fluid is further increased.

[0045] After the solenoid valve 5 is energized and the electro-proportional valve 142 is in maximum current state for a second predetermined time (e.g., 1-2 minutes), or when the hydraulic oil temperature reaches a second predetermined value (e.g., the hydraulic oil temperature reaches 5 degrees Celsius), the controller keeps the solenoid valve 5 energized while reducing the control current of the electro-proportional valve 142, reducing the valve opening of the unloading valve, and increasing the pump port pressure of the second variable pump 3 to heat the system in an overflow state, so that the heating power of the hydraulic oil reaches its peak. When the controller detects through the temperature detector 13 that the oil temperature has been heated to the predetermined temperature (e.g., reaching 5-10°C), it de-energizes the solenoid valve 5 and the electro-proportional valve 142, ending the warm-up operation.

[0046] In this embodiment, the solenoid valve 5 and the electro-proportional valve 142 can be controlled by the controller. During the warm-up process, the hydraulic system is operated in sequence in states such as low-pressure unloading at the maximum displacement of the variable pump, low-pressure unloading at the maximum displacement of the constant pressure pump, and high-pressure unloading of the constant pressure pump. This allows the pump displacement and unloading pressure to gradually increase as the oil viscosity improves during the warm-up process, thereby gradually increasing the power for heating the oil. This avoids rapid warm-up in cases where high pressure or high flow unloading could damage the pump due to high oil viscosity.

[0047] Example 2.

[0048] like Figure 1 Figure 2 As shown, this embodiment discloses a warm-up control method, which is applied to the load-sensitive hydraulic system in Embodiment 1. The warm-up control steps are as follows:

[0049] Step S1: The controller de-energizes solenoid valve 5, putting it in the off state, and outputs maximum current to electro-proportional valve 142. Electro-proportional valve 142 outputs pressurized oil, causing the valve opening of unloading valve 141 to reach its maximum. This state continues for a first predetermined time (e.g., 1-2 minutes) or until the hydraulic oil reaches a first predetermined temperature (until the hydraulic oil temperature reaches 2 degrees Celsius), then step S2 is executed. During the execution of step S1, unloading valve 141 is in a large flow state. The displacement of the second variable pump 3 increases from the standby state until the pressure drop generated by the oil flow reaches the standby pressure of the second variable pump 3.

[0050] Step S2: The controller energizes solenoid valve 5, putting it in the conducting state. This outputs maximum current to the proportional valve 142, maximizing the opening of the unloading valve 141. This state continues for a second predetermined time (e.g., 1-2 minutes) or until the hydraulic oil reaches a second predetermined temperature (until the hydraulic oil temperature reaches 5 degrees Celsius), at which point step S3 is executed. At this time, the second variable pump 3 changes from a load-sensitive pump to a constant-pressure pump, outputting flow at maximum displacement, and the pump inlet pressure also increases. The heating power of the hydraulic system on the oil is further increased compared to the heating power in step S1.

[0051] Step S3: The controller energizes the solenoid valve to put it in the conducting state, outputting a predetermined current to the electro-proportional valve 142 to reduce the valve opening of the unloading valve 141 until the hydraulic oil temperature reaches the predetermined value. At this point, the controller de-energizes the solenoid valve 5 and the electro-proportional valve 142. In this step, reducing the control current of the electro-proportional valve 142 lowers the valve opening of the unloading valve 141, increasing the pump pressure at the inlet of the second variable pump 3, and heating the system in an overflow state. This allows the heating power of the hydraulic oil to reach its peak, enabling the oil temperature to quickly reach the desired value.

[0052] Optionally, in step S3, the control current output by the controller to the electro-proportional valve 142 gradually decreases from the maximum current to a predetermined current according to the time gradient or temperature gradient. That is, when executing step S3, the control current output by the controller to the electro-proportional valve 142 decreases as the duration increases or as the hydraulic oil temperature increases, decreasing from the maximum current value to the predetermined value, and the opening degree of the unloading valve 141 also decreases gradually accordingly.

[0053] Example 3.

[0054] This embodiment discloses an engineering machinery having a load-sensitive hydraulic system as described in Embodiment 1, such as... Figure 1 As shown. The construction machinery can be a wheel loader or other machinery, such as a grader.

Claims

1. A load-sensitive hydraulic system, comprising a closed-position control valve for controlling hydraulic actuators, a variable displacement pump whose pump port is connected to the inlet oil circuit of the control valve, wherein the load feedback port of the control valve is connected to the load feedback port of the variable displacement pump via a load feedback oil circuit, characterized in that... Also includes: The solenoid valve has its inlet and outlet ports connected to the oil inlet circuit of the control valve and the load feedback port of the variable pump, respectively, and is used to connect or disconnect the oil circuit between the oil inlet circuit of the control valve and the load feedback port of the variable pump. The low-temperature heating valve assembly includes an unloading valve and an electro-proportional valve for controlling the opening degree of the unloading valve; the inlet and outlet ports of the unloading valve are connected to the oil inlet circuit of the control valve and the hydraulic oil tank; the inlet port of the electro-proportional valve is connected to the pilot oil source. Temperature detector, used to detect hydraulic oil temperature; A controller is used to control the output pressure of the electro-proportional valve and the on / off state of the solenoid valve; The hydraulic system also includes a hydraulic steering control device. The variable pump includes a first variable pump connected to the inlet of the control valve and a second variable pump connected to the inlet of the hydraulic steering control device. The EF port of the hydraulic steering control device is connected to the confluence inlet of the control valve, and the inlet of the unloading valve is connected to the EF port. The load feedback port of the hydraulic steering control device and the load feedback port of the control valve are connected to the load feedback port of the second variable pump via a shuttle valve, and the load feedback port of the control valve is connected to the load feedback port of the first variable pump. The inlet and outlet ports of the solenoid valve are connected to the inlet port of the hydraulic steering control device and the load feedback port of the second variable pump.

2. The load-sensitive hydraulic system according to claim 1, characterized in that, The hydraulic steering control device includes a flow amplification valve, a steering gear connected to the flow amplification valve, and a steering cylinder connected to the steering working port of the flow amplification valve. Under the control of the steering gear, the flow amplification valve outputs steering pressure oil to the steering cylinder.

3. A warm-up control method, applied to the load-sensitive hydraulic system according to any one of claims 1-2, characterized in that... The steps are as follows: S1: The controller de-energizes the solenoid valve to put it in the off state, outputs the maximum current to the electro-proportional valve to make the valve opening of the unloading valve reach the maximum, and executes step S2 after a period of time. S2: The controller energizes the solenoid valve to put it in the conducting state, outputs the maximum current to the electro-proportional valve to make the valve opening of the unloading valve reach the maximum, and executes step S3 after a period of time. S3: The controller energizes the solenoid valve to put it in the conducting state, outputs a predetermined current to the electro-proportional valve to reduce the valve opening of the unloading valve, until the hydraulic oil temperature reaches the predetermined value, at which point the controller de-energizes the solenoid valve and the electro-proportional valve.

4. The warm-up control method according to claim 3, characterized in that, In step S1, step S2 is executed after the solenoid valve is de-energized and the maximum current of the electro-proportional valve continues for a first predetermined time, or after the solenoid valve is de-energized and the maximum current of the electro-proportional valve continues until the hydraulic oil reaches a first predetermined temperature.

5. The warm-up control method according to claim 4, characterized in that, In step S2, step S3 is executed after the solenoid valve is energized and the maximum current of the electro-proportional valve continues for a second predetermined time, or after the solenoid valve is energized and the maximum current of the electro-proportional valve continues until the hydraulic oil reaches a second predetermined temperature.

6. The warm-up control method according to any one of claims 3-5, characterized in that, In step S3, the control current output by the controller to the electro-proportional valve gradually decreases from the maximum current to the predetermined current according to the time gradient or temperature gradient.

7. An engineering machinery, characterized in that, A load-sensitive hydraulic system having any one of claims 1-2.

Images