A hydraulic control system and its control method

Abstract

The present invention discloses a hydraulic control system and its control method. The hydraulic control system includes an oil tank, a hydraulic pump with an inlet end communicating with the oil tank, a supply oil pipeline with one end communicating with the outlet end of the hydraulic pump, a hydraulic motor with an inlet port communicating with the other end of the supply oil pipeline, an outlet port of the hydraulic motor communicating with the oil tank through a return oil pipeline, a variable-frequency motor connected to the hydraulic pump to drive its operation, an overflow valve and a hydraulic directional control valve arranged on the supply oil pipeline, and the overflow valve is connected to the oil tank through an overflow pipeline. It is convenient to adjust and can greatly reduce energy consumption and losses.

Description

Technical Field

[0001] The present invention relates to a hydraulic control system and a control method thereof. Background Art

[0002] As Figure 1 shown, in the prior art, a hydraulic control system includes an oil tank, a hydraulic pump with an inlet end communicating with the oil tank, an oil supply pipeline with one end communicating with the outlet end of the hydraulic pump, a hydraulic motor with an inlet port communicating with the other end of the oil supply pipeline, and an outlet port of the hydraulic motor communicating with the oil tank through a return oil pipeline. An overflow valve, a hydraulic directional control valve and a flow regulating valve are arranged on the oil supply pipeline, and the overflow valve is connected with the oil tank through an overflow pipeline.

[0003] When the prior art hydraulic control system works, first, a corresponding power system needs to be established. For example, if the maximum oil pressure for driving a load is set to 100 kg / cm 2 , so the oil pressure in the oil supply pipeline of the whole hydraulic system is 100 kg / cm 2 , so the oil supply pressure of the hydraulic pump must be greater than 100 kg / cm 2 , so the excess oil is returned to the oil tank through the overflow valve. When adjusting the rotational speed of the hydraulic motor, the flow regulating valve is used for adjustment, and the hydraulic directional control valve controls the forward or reverse rotation of the hydraulic motor. However, in actual use, the oil pressure required to drive the load is less than 100 kg / cm 2 , and the whole hydraulic control system still supplies oil at full load, which greatly wastes energy, and the oil temperature rises and heat loss occurs. In addition, when the oil pressure for driving the load is greater than the preset value, the whole hydraulic system cannot be used and needs to be reset. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects existing in the prior art, and provide a hydraulic control system and a control method thereof, which are convenient to adjust, energy-saving and greatly reduce losses.

[0005] To achieve the above technical effects, the technical solution of the present invention is: a hydraulic control system includes an oil tank, a hydraulic pump with an inlet end communicating with the oil tank, an oil supply pipeline with one end communicating with the outlet end of the hydraulic pump, a hydraulic motor with an inlet port communicating with the other end of the oil supply pipeline, and an outlet port of the hydraulic motor communicating with the oil tank through a return oil pipeline. A variable frequency motor for driving the hydraulic pump to operate is connected to the hydraulic pump. An overflow valve and a hydraulic directional control valve are arranged on the oil supply pipeline, and the overflow valve is connected with the oil tank through an overflow pipeline.

[0006] Further improved, the hydraulic pump is a piston pump.

[0007] Further improved, a detection unit for detecting the rotational speed is provided at the output end of the hydraulic motor. The detection unit is electrically connected to the frequency converter of the variable-frequency motor, or the detection unit is electrically connected to the controller of the hydraulic control system, and the controller is electrically connected to the variable-frequency motor.

[0008] Further improved, the detection unit is an encoder.

[0009] Further improved, the plunger pump is a plunger pump with a built-in pressure-limiting function.

[0010] To achieve the above technical effects, another technical solution of the present invention is: a control method for a hydraulic control system, characterized in that when the load is unchanged, according to the oil pressure required for the hydraulic motor to drive the load, the rotational speed of the variable-frequency motor is adjusted so that the hydraulic pump maintains a constant oil supply pressure and is the same as the oil pressure required for the hydraulic motor to drive the load, ensuring that the hydraulic motor maintains a constant rotational speed, and the hydraulic motor is adjusted to rotate forward or backward by adjusting the hydraulic directional valve; when the load becomes smaller, the rotational speed of the load is detected by the encoder at the output end of the hydraulic motor and converted into an electrical signal and sent to the frequency converter or the controller. At this time, the load rotational speed is greater than the set rotational speed, and the controller or the frequency converter controls the variable-frequency motor to reduce the rotational speed, and the hydraulic pump reduces the oil supply pressure; when the load becomes larger, the rotational speed of the load is detected by the encoder at the output end of the hydraulic motor and converted into an electrical signal and sent to the frequency converter or the controller. At this time, the load rotational speed is less than the set rotational speed, and the controller or the frequency converter controls the variable-frequency motor to increase the rotational speed, and the hydraulic pump increases the oil supply pressure. When the oil pressure in the oil supply pipeline exceeds the set pressure of the relief valve, the relief valve opens for pressure relief.

[0011] The advantages and beneficial effects of the present invention are as follows: directly controlling the plunger pump by the variable-frequency motor to provide the oil pressure required for the hydraulic motor to drive the load, the entire hydraulic system does not need to operate at full load, which not only saves energy consumption but also reduces the loss caused by oil heating. In addition, when adjusting the rotational speed of the hydraulic motor, it is only necessary to directly control the variable-frequency motor, which is convenient to adjust. Brief Description of the Drawings

[0012] Figure 1 is a schematic diagram of the prior art;

[0013] Figure 2 is a schematic diagram of the present invention.

[0014] In the figure: 1, oil tank; 2, hydraulic pump; 3, hydraulic motor; 4, variable-frequency motor; 5, relief valve; 6, hydraulic directional valve; 7, detection unit. Detailed Embodiments

[0015] The following will further describe the specific embodiments of the present invention in conjunction with the accompanying drawings and embodiments. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention, and cannot be used to limit the protection scope of the present invention.

[0016] As Figure 2 shown, the hydraulic control system of the embodiment includes an oil tank 1, a hydraulic pump 2 with an oil inlet end communicating with the oil tank 1, an oil supply pipeline with one end communicating with the oil outlet end of the hydraulic pump 2, a hydraulic motor 3 with an oil inlet communicating with the other end of the oil supply pipeline, an oil outlet of the hydraulic motor 3 communicating with the oil tank 1 through an oil return pipeline, a variable-frequency motor 4 connected to the hydraulic pump 2 to drive its operation, an overflow valve 5 and a hydraulic directional valve 6 provided on the oil supply pipeline, and the overflow valve 5 communicating with the oil tank 1 through an overflow pipeline.

[0017] In the preferred embodiment of the present embodiment, the hydraulic pump 2 is a piston pump. Since the piston pump has a high rated pressure, high speed, large driving power of the pump; high efficiency, with a volumetric efficiency of about 95% and a total efficiency of about 90%; long service life; convenient variable displacement, with various forms; light weight per unit power; and the main parts of the piston pump are all under compressive stress, the material strength performance can be fully utilized.

[0018] In order to achieve automatic control, in the preferred embodiment of the present embodiment, a detection unit 7 for detecting its rotational speed is provided at the output end of the hydraulic motor 3. The detection unit 7 is electrically connected to the frequency converter of the variable-frequency motor 4, or the detection unit 7 is electrically connected to the controller of the hydraulic control system, and the controller is electrically connected to the variable-frequency motor 4. Preferably, the detection unit 7 is an encoder.

[0019] In order to further protect the entire hydraulic system, the piston pump is a piston pump with a built-in pressure limiting function, which cooperates with the overflow valve 5 to form a double protection, making the entire hydraulic system operate stably.

[0020] A control method for a hydraulic control system. Specifically, the oil pressure required to drive the load is 80 kg / cm 2 , and according to the oil pressure required by the hydraulic motor 3 to drive the load, the rotational speed of the variable-frequency motor 4 is adjusted so that the hydraulic pump 2 maintains a constant oil supply pressure of 80 kg / cm 2 . The maximum oil supply pressure of the entire hydraulic control system is set by setting the overflow valve 5, such as setting it to 100 kg / cm 2 . At this time, the overflow valve 5 will not generate oil return, and the variable-frequency motor 4 does not need to work at full load, and it can reduce oil heating and reduce losses. The hydraulic motor 3 is adjusted to rotate forward or backward by adjusting the hydraulic directional valve 6; when the oil pressure for driving the load becomes small, such as when it needs 60 kg / cm 2, the encoder at the output end of the hydraulic motor 3 detects the rotational speed of the load and converts it into an electrical signal to be sent to the frequency converter or the controller. At this time, the rotational speed of the load is greater than the set rotational speed, and the controller or the frequency converter controls the frequency conversion motor 4 to reduce the rotational speed until the oil supply pressure of the hydraulic pump 2 is 60 kg / cm 2 , thus facilitating adjustment; when the load increases, the encoder at the output end of the hydraulic motor 3 detects the rotational speed of the load and converts it into an electrical signal to be sent to the frequency converter or the controller. At this time, the rotational speed of the load is less than the set rotational speed, and the controller or the frequency converter controls the frequency conversion motor 4 to increase the rotational speed. Additionally, when the oil pressure required by the load exceeds the load of the entire hydraulic control system and the oil pressure in the oil supply pipeline exceeds the set pressure of the relief valve 5, the relief valve 5 opens to relieve pressure, thereby ensuring the stable operation of the entire hydraulic control system.

[0021] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art of this technology, without departing from the technical principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A control method for a hydraulic control system, characterized in that, The hydraulic control system includes an oil tank, a hydraulic pump with an inlet end communicating with the oil tank, an oil supply pipeline with one end communicating with the outlet end of the hydraulic pump, a hydraulic motor with an inlet port communicating with the other end of the oil supply pipeline, an outlet port of the hydraulic motor communicating with the oil tank through a return oil pipeline, a variable frequency motor connected to the hydraulic pump to drive its operation, an overflow valve and a hydraulic directional control valve arranged on the oil supply pipeline, the overflow valve communicating with the oil tank through an overflow pipeline, the hydraulic pump being a piston pump, a detection unit for detecting the rotational speed of the hydraulic motor arranged at the output end of the hydraulic motor, the detection unit being electrically connected to the frequency converter of the variable frequency motor, or the detection unit being electrically connected to the controller of the hydraulic control system, and the controller being electrically connected to the variable frequency motor; When the load remains unchanged, according to the oil pressure required for the hydraulic motor to drive the load, the rotational speed of the variable frequency motor is adjusted so that the hydraulic pump maintains a constant oil supply pressure and is the same as the oil pressure required for the hydraulic motor to drive the load, ensuring that the hydraulic motor maintains a constant rotational speed, and the hydraulic motor is adjusted to rotate forward or backward by adjusting the hydraulic directional control valve; when the load becomes smaller, the rotational speed of the load is detected by the encoder at the output end of the hydraulic motor and converted into an electrical signal and sent to the frequency converter or the controller. At this time, the load rotational speed is greater than the set rotational speed, and the controller or the frequency converter controls the variable frequency motor to reduce the rotational speed, and the hydraulic pump reduces the oil supply pressure; when the load becomes larger, the rotational speed of the load is detected by the encoder at the output end of the hydraulic motor and converted into an electrical signal and sent to the frequency converter or the controller. At this time, the load rotational speed is less than the set rotational speed, and the controller or the frequency converter controls the variable frequency motor to increase the rotational speed, and the hydraulic pump increases the oil supply pressure. When the oil pressure in the oil supply pipeline exceeds the set pressure of the overflow valve, the overflow valve opens for pressure relief.

2. The control method of the hydraulic control system according to claim 1, characterized in that, The detection unit is an encoder.

3. The control method of the hydraulic control system according to claim 1, wherein The piston pump is a piston pump with a built-in pressure limiting function.

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