A closed pump capable of controlling output displacement under pressure cut-off and a control method thereof

Abstract

A closed pump and control method capable of controlling output displacement under pressure cut-off. The invention solves the problem that the existing closed pump is difficult to get out of the mud when being driven, and the system has high energy consumption. It includes a main pump, an oil replenishing pump, a variable mechanism, a variable control valve, a first overflow valve, a drive motor and a pressure cut-off valve; a first throttle valve divides the oil circuit into a first oil circuit and a second oil circuit, so that a pressure difference is formed between the first oil circuit and the second oil circuit for controlling the variable mechanism. The beneficial effect of the present invention is that a pressure cut-off valve and a first throttle valve are provided, a pressure difference is generated at both ends of the first throttle valve, and the pressure oil of the variable mechanism needs to return to the oil tank through the first throttle valve, so that the main pump can still maintain a certain displacement output under the pressure cut-off state, so that the travel system can still provide a certain driving force when the vehicle slips, and at the same time, the system generates little heat and has low energy consumption.

Description

Technical Field

[0001] The present invention relates to a closed pump control system, in particular to a closed pump capable of controlling output displacement under pressure cut-off and a control method thereof. Background Art

[0002] The closed hydraulic system drive form commonly used in agricultural machinery travel systems (such as harvesters) is as follows: Figure 1 The diagram shows the principle of a closed hydraulic system for propulsion. The engine drives the main pump, which delivers pressurized oil to the motor. The motor then connects to the wheel ends, rotating the wheels to propel the vehicle. Propulsion requires a balance between adhesion, driving force, and resistance. Adhesion must be greater than or equal to the driving force, and the driving force must be greater than the resistance. Both conditions must be met for the vehicle to propel. If adhesion is less than the driving force, the wheels will slip. If the driving force is less than the resistance, the vehicle will stop.

[0003] Harvesters often encounter muddy conditions when operating in the fields. In muddy fields, the low adhesion between the wheels and the ground often causes the vehicle to slip and become immobile. When the vehicle slips, the closed hydraulic system that drives it operates as follows: the main pump continues to pump pressurized oil to the motor. Because the vehicle is slipping, it cannot move. The system pressure gradually rises to the set pressure of the high-pressure relief valve. Some of this high-pressure oil is returned through the high-pressure relief valve (a safety relief valve, typically set to the maximum system pressure), while some of the oil drives the motor. When the vehicle's adhesion is less than the driving force, the vehicle comes to a standstill. The main pump continues to operate, and the system pressure rapidly rises to the set pressure of the high-pressure relief valve, causing the wheels to slip. If external force is applied to tow the vehicle, despite the slippage, the vehicle still has some driving force. The combination of external force and the vehicle's own driving force allows the vehicle to escape easily. However, this operating condition generates significant heat in the hydraulic system, resulting in high energy consumption. Moreover, since the system overflows under high pressure, the system oil temperature will rise rapidly and the energy loss will be large. Summary of the Invention

[0004] In order to solve the problems in the background art that the existing closed pump is difficult to get out of the mud when driven and the system energy consumption is high, the present invention provides a closed pump and a control method that can control the output displacement under pressure cut-off.

[0005] The technical solution of the present invention is: a closed pump capable of controlling output displacement under pressure cut-off, comprising a main pump,

[0006] Oil charge pump, to add oil to the closed circuit;

[0007] The variable mechanism is connected to the main pump to change the output displacement of the main pump;

[0008] The variable control valve is connected to the variable mechanism to control the variable mechanism and realize the control of the output displacement of the main pump;

[0009] The first relief valve is provided on the closed circuit to limit the maximum pressure of the system;

[0010] A driving motor, which is driven by the main pump to output mechanical energy;

[0011] The pressure cut-off valve is installed between the variable control valve and the oil tank. The pressure oil in the closed circuit is selected as the control oil of the pressure cut-off valve, and interacts with the set pressure of the pressure cut-off valve to control the on and off of the pressure cut-off valve;

[0012] The first throttle valve is arranged between the variable control valve and the oil tank, dividing the oil circuit into the first oil circuit and the second oil circuit, so that a pressure difference is formed between the first oil circuit and the second oil circuit. When the system pressure reaches the set pressure of the pressure cut-off valve, the variable mechanism is maintained in action by the pressure oil in the first oil circuit, so that the main pump can still maintain a certain displacement output in the pressure cut-off state.

[0013] As a further improvement of the present invention, the first throttle valve is arranged between the variable control valve and the pressure cut-off valve.

[0014] As a further improvement of the present invention, the first throttle valve is arranged between the pressure cut-off valve and the oil tank.

[0015] As a further improvement of the present invention, the first throttle valve is implemented in the form of a fixed throttle hole.

[0016] As a further improvement of the present invention, the first throttle valve is implemented in an adjustable manner.

[0017] As a further improvement of the present invention, the oil charge pump is connected to the variable control valve via a second throttle valve, and the first throttle valve and the second throttle valve are arranged in parallel to form a damping bridge circuit.

[0018] As a further improvement of the present invention, a second overflow valve for limiting the pressure of the oil charge pump is also included.

[0019] As a further improvement of the present invention, the opening pressure of the first overflow valve is greater than the set pressure of the pressure cut-off valve.

[0020] As a further improvement of the present invention, the variable control valve is an electromagnetic variable control valve, a manual variable control valve, a hydraulic variable control valve or an electric proportional variable control valve.

[0021] A control method includes an engine, a wheel, and the above-mentioned closed pump capable of controlling output displacement under pressure cutoff, wherein the engine is connected to the main pump, and the drive motor is connected to the wheel, wherein the control steps are as follows:

[0022] The engine drives the main pump to output pressure oil to the drive motor, and the drive motor drives the drive wheels to drive the vehicle. The oil supply pump replenishes oil to the system and also provides control oil to the variable control valve and variable mechanism;

[0023] When a vehicle is traveling on a muddy road and the adhesion between the vehicle and the ground is less than the driving force, the wheels will slip. Under this condition, the system pressure will quickly rise to the set pressure of the pressure cut-off valve, which will open and unload the pressure oil in the variable control valve and the variable mechanism; causing the main pump to operate at a small displacement and unable to provide the system with the pressure oil required for operation. As a result, the vehicle will have no driving force output and will be stationary.

[0024] At this time, the pressure oil in the first oil circuit needs to pass through the first throttle valve to unload and return the oil. The first throttle valve and the second throttle valve form a parallel damping bridge circuit. When the vehicle slips and the system pressure rises to the set pressure of the pressure cut-off valve, when the flowing pressure oil passes through the first throttle valve, a certain pressure difference will be generated before and after the throttle port of the first throttle valve, that is, the pressure in the first oil circuit is greater than the pressure in the second oil circuit. By adjusting the size of the first throttle valve, the size of the pressure difference between the first oil circuit and the second oil circuit can be changed. When the system pressure reaches the set pressure of the pressure cut-off valve, the first throttle valve can be adjusted to generate a certain pressure in the first oil circuit to maintain the operation of the variable mechanism, so that the main pump can still maintain a certain displacement output in the pressure cut-off state. The size of the output displacement of the main pump in the pressure cut-off state can be controlled by changing the size of the first throttle valve. In this way, when the vehicle slips, the travel system can still provide a certain driving force, reduce the difficulty of the vehicle to get out of the way, and at the same time, no excess flow will overflow from the first overflow valve.

[0025] The beneficial effect of the present invention is that a pressure cut-off valve is provided, through which the load can be unloaded when the wheels slip, and energy consumption is low. At the same time, a first throttle valve is provided, so that a pressure difference is generated at both ends of the first throttle valve. The pressure oil of the variable mechanism needs to return to the oil tank through the first throttle valve, so that the main pump can still maintain a certain displacement output when the pressure is cut off. In this way, when the vehicle slips, the walking system can still provide a certain driving force, reducing the difficulty of the vehicle getting out of the way. At the same time, no excess flow will overflow from the high-pressure overflow valve, and the system generates little heat and has low energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Attachment Figure 1 It is a structural diagram of an existing vehicle traveling system.

[0027] Attachment Figure 2Schematic diagram of the structure of an embodiment of the present invention.

[0028] In the figure, 1. Main pump; 2. Make-up oil pump; 3. Variable mechanism; 4. Variable control valve; 5. First overflow valve; 6. Drive motor; 7. Pressure cut-off valve; 8. First throttle valve; 9. First oil circuit; 10. Second oil circuit; 11. Second throttle valve; 12. Second overflow valve; 13. Fuel tank; 14. Engine; 15. Wheels. DETAILED DESCRIPTION

[0029] The embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0030] Depend on Figure 2 As shown, a closed pump capable of controlling output displacement under pressure cut-off comprises a main pump 1,

[0031] Oil replenishment pump 2, replenishing oil to the closed circuit;

[0032] Variable mechanism 3, connected to the main pump, changes the output displacement of the main pump;

[0033] The variable control valve 4 is connected to the variable mechanism to control the variable mechanism and realize the control of the output displacement of the main pump;

[0034] The first relief valve 5 is provided on the closed circuit to limit the maximum pressure of the system;

[0035] A drive motor 6 is driven by the main pump to output mechanical energy;

[0036] The pressure cut-off valve 7 is arranged between the variable control valve and the oil tank 13. The pressure oil in the closed circuit is selected as the control oil of the pressure cut-off valve, and interacts with the set pressure of the pressure cut-off valve to control the on and off of the pressure cut-off valve; the oil replenishing pump replenishes the oil in the external oil tank into the closed system. The oil in the closed pump itself is an internal circulation. Due to leakage and working reasons, an oil replenishing pump needs to be set to replenish the external oil. Here, the oil tank 13 refers to the oil storage place in the closed pump casing, which is the internal space of the closed pump, the same below.

[0037] The first throttle valve 8 is provided between the variable control valve and the oil tank 13, dividing the oil circuit therein into a first oil circuit 9 and a second oil circuit 10, so that a pressure difference is formed between the first oil circuit and the second oil circuit. When the system pressure reaches the set pressure of the pressure cut-off valve, the pressure oil in the first oil circuit maintains the action of the variable mechanism, so that the main pump can still maintain a certain displacement output in the pressure cut-off state. The beneficial effect of the present invention is that the pressure cut-off valve is provided, and the pressure cut-off valve can be used to unload the load when the wheel slips, thereby reducing energy consumption. At the same time, the first throttle valve is provided to generate a pressure difference between the two ends of the first throttle valve. The pressure oil of the variable mechanism needs to return to the oil tank through the first throttle valve, so that the main pump can still maintain a certain displacement output in the pressure cut-off state. In this way, the travel system can still provide a certain driving force when the vehicle slips, reducing the difficulty of the vehicle to get out of the way. At the same time, no excess flow will overflow from the high-pressure relief valve, resulting in low system heat generation and low energy consumption.

[0038] A pressure shutoff valve is added to the closed-loop pump to limit the system's maximum operating pressure. When the system operating pressure reaches the set pressure of the pressure shutoff valve, the valve opens, unloading the control oil circuit of the variable control valve. At this point, the variable mechanism loses its control oil function, and the main pump operates at a very low displacement. The pressure oil output is only used to maintain system leakage. At this point, the main pump's output pressure remains at the set pressure of the pressure shutoff valve. In other words, when the system pressure reaches the pressure of the pressure shutoff valve, the pump switches to high-pressure, low-displacement operation. Because the output flow is very small and insufficient to drive the motor, the system performs almost no work under this condition, consuming very little energy. However, the pressure oil in the control oil circuit of the variable mechanism is unloaded and cannot provide sufficient pressure to drive the variable mechanism. As a result, the main pump operates at a low displacement, unable to supply the pressure oil required for operation. This results in a loss of driving force and a vehicle immobilization. In the present invention, a first throttle valve is provided. At this time, the first throttle valve and the second throttle valve form a parallel damping bridge circuit. When the vehicle slips and the system pressure rises to the set pressure of the pressure cut-off valve, the pressure oil in the first oil circuit (control oil circuit) needs to pass through the first throttle valve to unload and return the oil. When the flowing pressure oil passes through the first throttle valve, a certain pressure difference will be generated before and after the throttle port. The pressure in the first oil circuit is greater than the pressure in the second oil circuit. The pressure difference between the first oil circuit and the second oil circuit can be changed by adjusting the size of the first throttle valve. When the system pressure reaches the set pressure of the pressure cut-off valve, the first throttle valve can be adjusted to generate a certain pressure in the first oil circuit to maintain the operation of the variable mechanism, so that the main pump can still maintain a certain displacement output in the pressure cut-off state. The size of the output displacement of the main pump in the pressure cut-off state can be controlled by changing the size of the first throttle valve. In this way, when the vehicle slips, the traveling system can still provide a certain driving force, reducing the difficulty of the vehicle to get out of the way. At the same time, no excess flow will overflow from the high-pressure relief valve, and the system generates little heat and consumes low energy.

[0039] The first throttle valve is located between the variable control valve and the pressure cutoff valve. Specifically, it is located between the pressure cutoff valve and the fuel tank. The first throttle valve can be located before or after the valve (pressure cutoff valve) for ease of maintenance, assembly, and use.

[0040] The first throttle valve is implemented as a fixed orifice. Specifically, it is adjustable. The variable orifice allows the pressure in the first oil circuit to be adjusted via the first throttle valve. This allows the main pump displacement to be controlled via the variable mechanism even when the pressure cutoff valve is operating. In practical applications, this reduces overall system energy consumption while providing a certain displacement and power, facilitating towing, even when the wheels are stuck in mud.

[0041] The oil charge pump is connected to the variable control valve via the second throttle valve 11, and the first throttle valve and the second throttle valve are arranged in parallel to form a damping bridge circuit. Such a structure can provide a certain flow rate for the variable mechanism, making it easier to control.

[0042] The present invention also includes a second relief valve 12 for limiting the pressure of the oil charge pump. This structure makes the product safer. The second relief valve is mainly used to ensure the safety of the oil charge pump.

[0043] The opening pressure of the first relief valve is greater than the set pressure of the pressure cut-off valve. This structure makes the product safer, reduces system pressure shock, and protects various system components.

[0044] The variable control valve is a solenoid variable control valve, a manual variable control valve, a hydraulic variable control valve or an electric proportional variable control valve. Such a structure is convenient for product control.

[0045] A control method includes an engine 13, wheels 14 and a closed pump capable of controlling output displacement under pressure cut-off, wherein the engine is connected to a main pump, and the drive motor is connected to the wheels, and the control steps are as follows: the engine drives the main pump to output pressure oil to the drive motor, and the drive wheels drive the vehicle to move through the drive motor, and the oil supply pump supplies oil to the system while also providing control oil to the variable control valve and the variable mechanism; when the vehicle is traveling on a muddy road and the adhesion between the vehicle and the ground is less than the driving force, the wheels will slip, and under this working condition, the system pressure will quickly rise to the set pressure of the pressure cut-off valve, the pressure cut-off valve will open and unload the pressure oil in the variable control valve and the variable mechanism; causing the main pump to operate at a small displacement and unable to provide the system with the pressure oil required for work; the vehicle will have no driving force output and will be stationary; at this time, the pressure oil in the first oil circuit needs to be unloaded and returned through the first throttle valve, The first throttle valve and the second throttle valve form a parallel damping bridge circuit. When the vehicle slips and the system pressure rises to the set pressure of the pressure cut-off valve, when the flowing pressure oil passes through the first throttle valve, a certain pressure difference will be generated before and after the throttle port of the first throttle valve, that is, the pressure in the first oil circuit is greater than the pressure in the second oil circuit. The pressure difference between the first oil circuit and the second oil circuit can be changed by adjusting the size of the first throttle valve. When the system pressure reaches the set pressure of the pressure cut-off valve, a certain pressure can be generated in the first oil circuit by adjusting the first throttle valve to maintain the operation of the variable mechanism, so that the main pump can still maintain a certain displacement output in the pressure cut-off state. The size of the output displacement of the main pump in the pressure cut-off state can be controlled by changing the size of the first throttle valve. In this way, when the vehicle slips, the walking system can still provide a certain driving force to reduce the difficulty of the vehicle to get out of the way, and at the same time, no excess flow will overflow from the first overflow valve.

[0046] In the description of the present invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inside," and "outside" and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0047] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium, or they can refer to internal connections between two components. A person of ordinary skill in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances. In addition, in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0048] Technical personnel should note: Although the present invention has been described according to the above specific implementation methods, the inventive concept of the present invention is not limited to this invention. Any modification using the inventive concept will be included in the scope of protection of this patent.

Claims

1. A closed pump capable of controlling output displacement under pressure cut-off, comprising a main pump, Oil charge pump, to add oil to the closed circuit; The variable mechanism is connected to the main pump to change the output displacement of the main pump; The variable control valve is connected to the variable mechanism to control the variable mechanism and realize the control of the output displacement of the main pump; The first relief valve is provided on the closed circuit to limit the maximum pressure of the system; A driving motor, which is controlled and driven by the main pump to output mechanical energy; It is characterized by : It includes a pressure cut-off valve, which is located between the variable control valve and the oil tank. The pressure oil in the closed circuit is selected as the control oil of the pressure cut-off valve, and interacts with the set pressure of the pressure cut-off valve to control the on and off of the pressure cut-off valve; The first throttle valve is located between the variable control valve and the oil tank, dividing the oil circuit into a first oil circuit and a second oil circuit, so that a pressure difference is formed between the first oil circuit and the second oil circuit. When the system pressure reaches the set pressure of the pressure cut-off valve, the pressure oil in the first oil circuit maintains the operation of the variable mechanism, so that the main pump can still maintain a certain displacement output in the pressure cut-off state; The oil charge pump is connected to the variable control valve through the second throttle valve, and the first throttle valve and the second throttle valve are arranged in parallel to form a damping bridge circuit; and a second overflow valve is also included for limiting the pressure of the oil charge pump.

2. A closed pump capable of controlling output displacement under pressure cut-off according to claim 1, characterized in that The first throttle valve is arranged between the variable control valve and the pressure cut-off valve.

3. A closed pump capable of controlling output displacement under pressure cut-off according to claim 1, characterized in that The first throttle valve is arranged between the pressure cut-off valve and the oil tank.

4. A closed pump capable of controlling output displacement under pressure cut-off according to claim 1, 2 or 3, characterized in that The first throttle valve is implemented in the form of a fixed throttle hole.

5. A closed pump capable of controlling output displacement under pressure cut-off according to claim 1, 2 or 3, characterized in that The first throttle valve is implemented in an adjustable manner.

6. A closed pump capable of controlling output displacement under pressure cut-off according to claim 1, characterized in that The opening pressure of the first relief valve is greater than the set pressure of the pressure cut-off valve.

7. A closed pump capable of controlling output displacement under pressure cut-off according to claim 1, characterized in that The variable control valve is an electromagnetic variable control valve, a manual variable control valve, a hydraulic variable control valve or an electric proportional variable control valve.

8. A control method, characterized in that: The invention comprises an engine, wheels and a closed pump capable of controlling output displacement under pressure cut-off according to any one of claims 1 to 7, wherein the engine is connected to the main pump, and the drive motor is connected to the wheels, wherein the control steps are: The engine drives the main pump to output pressure oil to the drive motor, and the drive motor drives the drive wheels to drive the vehicle. The oil supply pump replenishes oil to the system and also provides control oil to the variable control valve and variable mechanism; When a vehicle is traveling on a muddy road and the adhesion between the vehicle and the ground is less than the driving force, the wheels will slip. Under this condition, the system pressure will quickly rise to the set pressure of the pressure cut-off valve, which will open and unload the pressure oil in the variable control valve and the variable mechanism; causing the main pump to operate at a small displacement and unable to provide the system with the pressure oil required for operation. As a result, the vehicle will have no driving force output and will be stationary. At this time, the pressure oil in the first oil circuit needs to pass through the first throttle valve to unload and return the oil. The first throttle valve and the second throttle valve form a parallel damping bridge circuit. When the vehicle slips and the system pressure rises to the set pressure of the pressure cut-off valve, when the flowing pressure oil passes through the first throttle valve, a certain pressure difference will be generated before and after the throttle port of the first throttle valve, that is, the pressure in the first oil circuit is greater than the pressure in the second oil circuit. By adjusting the size of the first throttle valve, the size of the pressure difference between the first oil circuit and the second oil circuit can be changed. When the system pressure reaches the set pressure of the pressure cut-off valve, the first throttle valve can be adjusted to generate a certain pressure in the first oil circuit to maintain the operation of the variable mechanism, so that the main pump can still maintain a certain displacement output in the pressure cut-off state. The size of the output displacement of the main pump in the pressure cut-off state can be controlled by changing the size of the first throttle valve. In this way, when the vehicle slips, the travel system can still provide a certain driving force, reduce the difficulty of the vehicle to get out of the way, and at the same time, no excess flow will overflow from the first overflow valve.

Images