Hydraulic system and method of hydraulic control

Abstract

The application provides a hydraulic system and a hydraulic control method, comprising: a first variable plunger pump and a second variable plunger pump, the first variable plunger pump is driven by a first driving part, and the second variable plunger pump is driven by a second driving part; a driving motor is used for driving a centrifugal pump, the first variable plunger pump and the second variable plunger pump are connected with the driving motor, and output oil of the first variable plunger pump and / or output oil of the second variable plunger pump is used for driving the driving motor to operate; wherein the hydraulic system has different displacement operation states, and the working conditions of the first variable plunger pump and the working conditions of the second variable plunger pump are controlled according to the displacement operation state of the hydraulic system. Through the technical scheme provided by the application, the technical problem of high fuel consumption of the hydraulic system in the prior art during small displacement operation can be solved.

Description

Hydraulic systems and hydraulic control methods Technical Field

[0001] This invention relates to the field of sand pump drive technology, and more specifically, to a hydraulic system and a hydraulic control method. Background Technology

[0002] Currently, fracturing fluid mixing trucks utilize automated control technology to automatically track the fracturing process, achieving automatic control of parameters such as fluid level, additives, density, and sand pump discharge pressure. Their function is to mix, stir, and transport fracturing media. The mixing truck is powered by a platform engine and an undercarriage engine, which control the operation of the water centrifugal pump, mixing tanks, auger motor, various additive pumps, hydraulic system cooling, and sand pump, all hydraulically driven. During on-site operations, one mixing truck is paired with multiple fracturing trucks, with the mixing truck acting as the heart of the entire process. Fracturing fluid mixing trucks are vehicle-mounted continuous mixing systems for on-site fracturing fluid operations, meeting the requirements of on-site mixing and pressurization. Their function is to achieve accurate, continuous, and uniform feeding and high-quality continuous fluid preparation. The fracturing fluid mixing truck is also powered by a platform engine and an undercarriage engine, which control the operation of the water centrifugal pump, various mixing tanks, various additive pumps, hydraulic system cooling, and fracturing fluid discharge pump, all hydraulically driven. During on-site operations, fracturing fluid mixing trucks can be connected to sand mixing trucks for on-site mixing and pressurization. Currently, both types of equipment are matched using either a chassis engine-driven hydraulic single-pump system to drive the sand pump, or a combination of a hydraulic pump driven by an engine on a platform to drive the sand pump.

[0003] However, when performing small-displacement operations on-site, the rotational speed of the sand pump or fracturing fluid discharge pump must be kept relatively constant to coordinate with the fracturing truck's operation. This means that even with small-displacement operations, both the platform engine and the off-platform engine must run simultaneously, resulting in high fuel consumption on-site. Furthermore, the excessively low load on the platform engine leads to severe oil burning. Summary of the Invention

[0004] The main objective of this invention is to provide a hydraulic system and a hydraulic control method to solve the technical problem of high fuel consumption in existing hydraulic systems during small-displacement operations.

[0005] To achieve the above objectives, according to one aspect of the present invention, a hydraulic system is provided, comprising: a first variable displacement piston pump and a second variable displacement piston pump, wherein the first variable displacement piston pump is driven by a first drive unit, and the second variable displacement piston pump is driven by a second drive unit; a drive motor for driving a centrifugal pump, wherein both the first and second variable displacement piston pumps are connected to the drive motor, and the output oil of the first variable displacement piston pump and / or the output oil of the second variable displacement piston pump is used to drive the drive motor to operate; wherein the hydraulic system has different displacement operating states, and the operating conditions of the first and second variable displacement piston pumps are controlled according to the displacement operating state of the hydraulic system.

[0006] Furthermore, the hydraulic system has a first displacement operating state and a second displacement operating state, where the displacement of the first displacement operating state is greater than that of the second displacement operating state. When the hydraulic system is in the first displacement operating state, both the first variable piston pump and the second variable piston pump are in working state, and the working displacement of the drive motor is kept at the maximum displacement. When the hydraulic system is in the second displacement operating state, the first variable piston pump is in a non-working state, the second variable piston pump is in a working state, and the working displacement of the drive motor is reduced to the preset displacement.

[0007] Furthermore, the drive motor is a variable displacement motor; when the hydraulic system is in the first displacement operating state, the swashplate angle of the drive motor is kept at the maximum displacement; when the hydraulic system is in the second displacement operating state, the swashplate angle of the drive motor is adjusted to adjust the working displacement of the drive motor to the preset displacement.

[0008] Furthermore, the drive motor is an electric motor; when the hydraulic system is in the first displacement operation state, the electric motor is de-energized; when the hydraulic system is in the second displacement operation state, the electric motor is energized, so that the electric motor can adjust the swashplate tilt angle of the drive motor through electronic control.

[0009] Furthermore, the drive motor is a hydraulically controlled motor, the first variable displacement piston pump is driven by the power take-off of the chassis, and the hydraulic system also includes:

[0010] The first directional valve is connected to the drive motor; when the hydraulic system is in the first displacement operation state, the first directional valve is in the first reversing position; when the hydraulic system is in the second displacement operation state, the first directional valve is in the first initial position.

[0011] Furthermore, the hydraulic system also includes a pressure reducing valve connected to the first directional valve; and / or,

[0012] The first directional valve is a pneumatic directional valve, a solenoid directional valve, or a manual directional valve.

[0013] Furthermore, the drive motor includes a first fixed displacement motor and a second fixed displacement motor; when the hydraulic system is in the first displacement operation state, the first fixed displacement motor and the second fixed displacement motor are connected in parallel, and both the first fixed displacement motor and the second fixed displacement motor are in the working state;

[0014] Specifically, when the hydraulic system is in the second displacement operating state, the second variable displacement piston pump is at zero displacement, and the first variable displacement piston pump is in the working state; or...

[0015] When the hydraulic system is in the second displacement operation state, the second variable piston pump is connected in series with the first variable piston pump.

[0016] Furthermore, the first variable displacement piston pump is driven by the power take-off (PTO) of the chassis vehicle, and the hydraulic system also includes:

[0017] The second directional valve is connected to the second variable displacement piston pump;

[0018] The third directional valve, the second directional valve and the second fixed displacement motor are all connected to the third directional valve;

[0019] Specifically, when the hydraulic system is in the first displacement operation state, the second directional valve is in the second reversing position; when the hydraulic system is in the second displacement operation state, the second directional valve is in the second initial position, and the third directional valve is in the third reversing position, so that the oil inlet of the second fixed displacement motor is connected to the oil outlet of the second fixed displacement motor.

[0020] Furthermore, the second directional valve is a pneumatically controlled directional valve, or a solenoid-operated directional valve, or a manually operated directional valve; and / or,

[0021] The third directional valve is a hydraulically controlled directional valve.

[0022] Furthermore, the first variable displacement piston pump is driven by the power take-off (PTO) of the chassis vehicle, and the hydraulic system also includes:

[0023] The fourth directional valve is connected to the second variable displacement piston pump;

[0024] The fifth directional valve, the fourth directional valve, the first metering motor, and the second metering motor are all connected to the fifth directional valve;

[0025] Specifically, when the hydraulic system is in the first displacement operation state, the fourth directional valve is in the fourth directional position; when the hydraulic system is in the second displacement operation state, the fourth directional valve is in the fourth initial position and the fifth directional valve is in the fifth initial position, so that the first fixed displacement motor and the second fixed displacement motor can be connected in series by adjusting the fifth directional valve.

[0026] Furthermore, the hydraulic system also includes:

[0027] Hydraulic oil tank;

[0028] The first replenishing pump, the hydraulic oil tank and the first variable piston pump are all connected to the first replenishing pump. The operation of the first replenishing pump generates suction to draw the hydraulic oil in the hydraulic oil tank into the oil inlet of the first variable piston pump for replenishment.

[0029] The second replenishing pump is connected to both the hydraulic oil tank and the second variable piston pump. The operation of the second replenishing pump generates suction to draw the hydraulic oil in the hydraulic oil tank into the suction port of the second variable piston pump for replenishment.

[0030] Furthermore, a first relief valve is provided inside the first variable displacement piston pump to allow the oil entering the first variable displacement piston pump to overflow into the housing of the first variable displacement piston pump via the first relief valve; and / or,

[0031] The second variable displacement piston pump is equipped with a second overflow valve so that the oil entering the second variable displacement piston pump overflows into the housing of the second variable displacement piston pump through the second overflow valve.

[0032] According to another aspect of the present invention, a hydraulic control method is provided, which employs the hydraulic system provided above; the hydraulic control method includes: driving a first variable displacement piston pump to operate using a first drive unit, and driving a second variable displacement piston pump to operate using a second drive unit; driving a drive motor through the first variable displacement piston pump and / or the second variable displacement piston pump, and driving a centrifugal pump using the drive motor; and controlling the operation of the first variable displacement piston pump and the second variable displacement piston pump according to the displacement operation state of the hydraulic system.

[0033] By applying the technical solution of this invention, the operation of the first variable displacement piston pump and the second variable displacement piston pump are controlled according to the displacement operation state of the hydraulic system. Specifically, adjusting the first drive unit facilitates the control of the operation of the first variable displacement piston pump, and adjusting the second drive unit facilitates the control of the operation of the second variable displacement piston pump. This allows for reasonable control of the driving of the first and second drive units, enabling the selection of either the first or second drive unit for driving during small displacement operations. This effectively reduces the amount of engine oil burned for driving, thereby reducing energy consumption and achieving energy saving, emission reduction, and low carbon emissions. Attached Figure Description

[0034] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0035] Figure 1 shows a schematic diagram of a hydraulic system provided according to Embodiment 1 of the present invention;

[0036] Figure 2 shows a schematic diagram of a hydraulic system provided according to Embodiment 2 of the present invention;

[0037] Figure 3 shows a schematic diagram of a hydraulic system provided according to Embodiment 3 of the present invention;

[0038] Figure 4 shows a schematic diagram of a hydraulic system provided according to Embodiment 4 of the present invention.

[0039] The above figures include the following reference numerals:

[0040] 10. First variable displacement piston pump;

[0041] 20. Second variable displacement piston pump;

[0042] 30. Drive motor; 31. First quantitative motor; 32. Second quantitative motor;

[0043] 41. First directional control valve; 42. Second directional control valve; 43. Third directional control valve; 44. Fourth directional control valve; 45. Fifth directional control valve;

[0044] 50. Hydraulic oil tank;

[0045] 60. Pressure gauge. Detailed Implementation

[0046] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0047] As shown in Figures 1 to 4, the present invention provides a hydraulic system comprising: a first variable displacement piston pump 10 and a second variable displacement piston pump 20, wherein the first variable displacement piston pump 10 is driven by a first drive unit and the second variable displacement piston pump 20 is driven by a second drive unit; and a drive motor 30 for driving a centrifugal pump. Both the first variable displacement piston pump 10 and the second variable displacement piston pump 20 are connected to the drive motor 30, and the output oil of the first variable displacement piston pump 10 and / or the output oil of the second variable displacement piston pump 20 is used to drive the drive motor 30. The hydraulic system has different displacement operating states, and the operating states of the first and second variable displacement piston pumps are controlled according to the displacement operating states of the hydraulic system.

[0048] The hydraulic system provided by this invention controls the operation of the first and second variable displacement piston pumps based on the displacement operation status of the hydraulic system. Specifically, adjusting the first drive unit facilitates control of the operation of the first variable displacement piston pump, and adjusting the second drive unit facilitates control of the operation of the second variable displacement piston pump. This allows for reasonable control of the driving of the first and second drive units, enabling the selection of either the first or second drive unit for driving during low-displacement operations. This effectively reduces the amount of engine oil burned for driving, thereby reducing energy consumption and achieving energy saving, emission reduction, and low carbon emissions.

[0049] Specifically, the first drive unit is the chassis vehicle, and the second drive unit is the engine on the platform.

[0050] In this embodiment, the hydraulic system has a first displacement operating state and a second displacement operating state, where the displacement of the first displacement operating state is greater than that of the second displacement operating state. When the hydraulic system is in the first displacement operating state, both the first variable piston pump 10 and the second variable piston pump 20 are in working state, and the working displacement of the drive motor 30 is kept at the maximum displacement. When the hydraulic system is in the second displacement operating state, the first variable piston pump 10 is in a non-working state, the second variable piston pump 20 is in a working state, and the working displacement of the drive motor 30 is reduced to a preset displacement.

[0051] The technical solution provided by the embodiments of the present invention allows the hydraulic system to operate in a first displacement state during high-displacement operations. During low-displacement operations, the hydraulic system can operate in a second displacement state, in which case the first variable displacement piston pump 10 is in a non-working state. Correspondingly, the chassis does not need to be started, while the centrifugal pump speed is maintained. Thus, during low-displacement operations, only the platform engine needs to operate, eliminating the need to start the chassis, thereby reducing fuel consumption. Furthermore, because the platform engine drives the centrifugal pump, the load rate of the platform engine is effectively increased, reducing oil consumption and achieving energy saving, emission reduction, and low carbon emissions. Therefore, the hydraulic system provided by the present invention can solve the technical problem of high fuel consumption in existing hydraulic systems during low-displacement operations.

[0052] Specifically, the centrifugal pump in this embodiment can be a sand pump or a fracturing fluid pump.

[0053] In Embodiment 1 of the present invention, the drive motor 30 is a variable displacement motor. When the hydraulic system is in the first displacement operating state, the swashplate angle of the drive motor 30 is maintained at the maximum displacement. When the hydraulic system is in the second displacement operating state, the swashplate angle of the drive motor 30 is adjusted to adjust the working displacement of the drive motor 30 to the preset displacement. This configuration facilitates the adjustment of the working displacement of the drive motor 30 by adjusting its variable displacement.

[0054] Specifically, in this embodiment, the drive motor 30 is an electronically controlled motor, which can be understood as an electronically controlled variable displacement motor. When the hydraulic system is in the first displacement operating state, the electronically controlled motor is de-energized; when the hydraulic system is in the second displacement operating state, the electronically controlled motor is energized, so that the electronically controlled motor can adjust the swashplate angle of the drive motor 30 through electronic control. This facilitates control and adjustment.

[0055] As shown in Figure 1, this embodiment employs a dual-pump confluence system—a chassis hydraulic pump and a platform hydraulic pump—to drive an electronically controlled variable displacement motor for the sand pump. The chassis drives a first variable displacement piston pump 10, and the platform engine drives a second variable displacement piston pump 20. The first variable displacement piston pump 10 has a first replenishing pump (located inside or outside the first variable displacement piston pump 10), and the second variable displacement piston pump 20 has a second replenishing pump (located inside or outside the second variable displacement piston pump 20). The first and second replenishing pumps generate oil during operation. The hydraulic oil in the hydraulic tank 50 is drawn in by suction, reaching the suction ports of the first variable piston pump 10 and the second variable piston pump 20 to replenish the pipeline of the closed system. Then, it overflows into the housing of the first variable piston pump 10 through the first relief valve built into the first variable piston pump 10, and overflows into the housing of the second variable piston pump 20 through the second relief valve built into the second variable piston pump 20, so as to cool the rotating parts in the housing of the first variable piston pump 10 and the housing of the second variable piston pump 20, respectively. Then, it flows back into the hydraulic tank 50.

[0056] When the control units of the first variable piston pump 10 and the second variable piston pump 20 receive the signal, the hydraulic oil in the servo cylinder of the first variable piston pump 10 will drive the swashplate to move, and the hydraulic oil in the servo cylinder of the second variable piston pump 20 will drive the swashplate to move. As the tilt angle of the swashplate changes, the first variable piston pump 10 and the second variable piston pump 20 will have flow output, thereby driving the sand pump drive motor 30 to operate.

[0057] When a large displacement is required for on-site operations, the chassis and the engine on the platform work simultaneously, that is, the first variable displacement piston pump 10 and the second variable displacement piston pump 20 work simultaneously. The drive motor 30 is an electronically controlled variable displacement motor, and the drive motor 30 is not energized, so that the swashplate tilt angle of the drive motor 30 is kept at the maximum displacement. At this time, the drive motor 30 can drive the sand pump to operate at maximum power.

[0058] When a small displacement is required for on-site operations, the chassis vehicle is not in operation; only the second variable displacement piston pump 20, driven by the engine on the platform, is working. At this time, the drive motor 30 is energized, causing its swashplate angle to change and adjust to the preset small displacement. Since the sand pump uses a centrifugal pump, the discharge volume is small, so the input power of the sand pump is also low. Using a small displacement motor keeps the sand pump within a reasonable speed range. This reduces the use of the chassis vehicle's engine, meeting the requirements for emission reduction and fuel economy on-site.

[0059] The functions and roles of each hydraulic component in this system are as follows: The hydraulic oil tank 50 provides the working medium for transmitting power to the entire hydraulic system; the drive motor 30 is the actuator, which is an electrically controlled variable motor that converts pressure energy into mechanical energy; the first variable piston pump 10 is the power element in the hydraulic system, which converts mechanical energy into pressure energy and transitions the working medium from a low-pressure state to a high-pressure state; the pressure gauge 60 displays the driving oil pressure during operation; the second variable piston pump 20 is the power element in the hydraulic system, which converts mechanical energy into pressure energy and transitions the working medium from a low-pressure state to a high-pressure state.

[0060] In Embodiment 2 of the present invention, the drive motor 30 is a hydraulically controlled motor, and the first variable displacement piston pump 10 is driven by the power take-off of the chassis vehicle. The hydraulic system also includes a first directional valve 41, which is connected to the drive motor 30. When the hydraulic system is in a first displacement operating state, the first directional valve 41 is in a first directional position; when the hydraulic system is in a second displacement operating state, the first directional valve 41 is in a first initial position. With this configuration, the displacement can be easily adjusted adaptively by controlling the directional switching of the first directional valve 41. In this embodiment, when the first directional valve 41 is in the first initial position, the first directional valve 41 does not switch; when the first directional valve 41 is in the first directional position, the first directional valve 41 switches.

[0061] Specifically, the hydraulic system also includes a pressure reducing valve, which is connected to the first directional valve 41. With this configuration, when the hydraulic system is in the second displacement operation state, the pressure is reduced through the pressure reducing valve.

[0062] Specifically, the first directional valve 41 is a pneumatic directional valve, a solenoid directional valve, or a manual directional valve.

[0063] As shown in Figure 2, the scheme of using a chassis hydraulic pump and a platform hydraulic pump to drive a sand pump hydraulic variable motor in Embodiment 2 is as follows: the chassis drives a first variable piston pump 10 and the platform engine drives a second variable piston pump 20. The first variable piston pump 10 contains a first replenishing pump and the second variable piston pump 20 contains a second replenishing pump. The first and second replenishing pumps generate suction during operation, and the hydraulic oil in the hydraulic oil tank 50 reaches the suction port of the first variable piston pump 10 and the suction port of the second variable piston pump 20 to replenish the pipeline of the closed system. Then, the oil overflows into the housing of the first variable piston pump 10 through the first overflow valve built into the first variable piston pump 10 and into the housing of the second variable piston pump 20 through the second overflow valve built into the second variable piston pump 20. This cools the rotating parts in the housings of the first and second variable piston pumps and then flows back into the hydraulic oil tank 50.

[0064] When the control units of the first variable piston pump 10 and the second variable piston pump 20 receive a signal, the hydraulic oil in the servo cylinder of the first variable piston pump 10 will drive the swashplate to move, and the hydraulic oil in the servo cylinder of the second variable piston pump 20 will drive the swashplate to move. As the tilt angle of the swashplate changes, the first variable piston pump 10 and the second variable piston pump will have flow output, thereby driving the sand pump drive motor 30 to operate.

[0065] Since the hydraulic pump driven by the chassis vehicle uses the full-power PTO of the chassis vehicle, the full-power PTO is engaged using pneumatic control. At this time, the first reversing valve 41 can be a pneumatic reversing valve (or a solenoid reversing valve or a manual reversing valve), which can work simultaneously with the pneumatic control valve of the chassis vehicle's PTO. That is, when the chassis vehicle is working, the first reversing valve 41 will reverse at the same time as the full-power PTO is engaged.

[0066] When a large displacement is required for on-site operations, the chassis vehicle and the engine on the platform work simultaneously, that is, the first variable displacement piston pump 10 and the second variable displacement piston pump 20 work simultaneously, the first reversing valve 41 reverses the direction, the sand pump drive motor 30 adopts a hydraulically controlled variable displacement motor, and the swashplate tilt angle of the sand pump drive motor 30 is kept at the maximum displacement. At this time, the sand pump drive motor 30 can drive the sand pump to operate at maximum power.

[0067] When a small displacement motor is required for on-site operations, the chassis vehicle is not in operation, and the first reversing valve 41 is in the non-reversing position. This causes the swashplate angle of the sand pump drive motor 30 to change, resulting in a pre-set small displacement state (a pressure reducing valve can also be added before the first reversing valve 41 to proportionally adjust the displacement of the sand pump drive motor 30). In this case, only the second variable displacement piston pump 20, driven by the platform engine, is operational. Since the sand pump is a centrifugal pump, the discharge volume is small, so the input power of the sand pump is also low. Using a small displacement motor keeps the sand pump within a reasonable speed range. This reduces the use of the chassis vehicle engine, meeting the requirements for emission reduction and fuel economy on-site.

[0068] The functions and roles of each hydraulic component in this system are as follows: The hydraulic oil tank 50 provides the working medium for transmitting power to the entire hydraulic system;

[0069] The sand pump drive motor 30 is an actuator, which is a hydraulically controlled variable motor that converts pressure energy into mechanical energy. The first variable piston pump 10 is a power element in the hydraulic system that converts mechanical energy into pressure energy and transitions the working medium from a low-pressure state to a high-pressure state. The pressure gauge 60 displays the driving oil pressure during operation. The second variable piston pump 20 is a power element in the hydraulic system that converts mechanical energy into pressure energy and transitions the working medium from a low-pressure state to a high-pressure state. The first reversing valve 41 switches and adjusts the sand pump drive motor 30 between large-displacement and small-displacement operation by reversing the direction.

[0070] In Embodiment 3 of the present invention, the drive motor 30 includes a first fixed displacement motor 31 and a second fixed displacement motor 32. When the hydraulic system is in the first displacement operating state, the first fixed displacement motor 31 and the second fixed displacement motor 32 are connected in parallel, and both the first fixed displacement motor 31 and the second fixed displacement motor 32 are in working state. When the hydraulic system is in the second displacement operating state, the second variable displacement piston pump 20 is at zero displacement, and the first variable displacement piston pump 10 is in working state, thereby facilitating effective adjustment of the displacement.

[0071] Specifically, the first variable displacement piston pump 10 is driven by the power take-off (PTO) of the chassis vehicle. The hydraulic system also includes a second directional valve 42 and a third directional valve 43. The second directional valve 42 is connected to the second variable displacement piston pump 20. Both the second directional valve 42 and the second fixed displacement motor 32 are connected to the third directional valve 43. When the hydraulic system is in the first displacement operating state, the second directional valve 42 is in the second reversing position; when the hydraulic system is in the second displacement operating state, the second directional valve 42 is in the second initial position, and the third directional valve 43 is in the third reversing position, so that the oil inlet and outlet of the second fixed displacement motor 32 are connected. This configuration simplifies adjustment and facilitates effective regulation.

[0072] In this embodiment, the second directional valve 42 is a pneumatic directional valve, a solenoid directional valve, or a manual directional valve.

[0073] Specifically, in this embodiment, the third directional valve 43 is a hydraulically controlled directional valve.

[0074] As shown in Figure 3, in Embodiment 3, a scheme using a chassis hydraulic pump and a platform hydraulic pump to drive two fixed displacement motors (first fixed displacement motor 31 and second fixed displacement motor 32) is employed. The chassis drives the first variable displacement piston pump 10, and the platform engine drives the second variable displacement piston pump 20. The first variable displacement piston pump 10 contains a first replenishing pump, and the second variable displacement piston pump 20 contains a second replenishing pump. Due to the operation of the first and second replenishing pumps, suction is generated, and the hydraulic oil in the hydraulic oil tank 50 reaches the suction ports of the first and second variable displacement piston pumps 10 and 20, respectively, replenishing the pipeline of the closed system. Then, the oil overflows into the housing of the first variable displacement piston pump 10 through the first overflow valve built into the first variable displacement piston pump 10, and overflows into the housing of the second variable displacement piston pump 20 through the second overflow valve built into the second variable displacement piston pump 20. This cools the rotating parts within the housing of the first variable displacement piston pump 10 and then flows back into the hydraulic oil tank 50.

[0075] When the control units of the first variable piston pump 10 and the second variable piston pump 20 receive signals, the hydraulic oil in the servo cylinder of the first variable piston pump 10 will drive the swashplate to move, and the hydraulic oil in the servo cylinder of the second variable piston pump 20 will drive the swashplate to move. As the tilt angle of the swashplate changes, the first variable piston pump 10 and the second variable piston pump 20 will have flow output, thereby driving the sand pump drive motor 30 to operate (the first fixed displacement motor 31 and the second fixed displacement motor 32 are mechanically connected to maintain synchronization).

[0076] Since the hydraulic pump driven by the chassis vehicle uses the full-power PTO of the chassis vehicle, the full-power PTO is engaged using pneumatic control. At this time, the reversing valve can be a pneumatic reversing valve (or a solenoid reversing valve or a manual reversing valve), which can work simultaneously with the pneumatic control valve of the chassis vehicle's PTO. That is, when the chassis vehicle is working, the reversing valve will reverse at the same time the full-power PTO is engaged.

[0077] When a large displacement is required for on-site operations, the chassis vehicle and the engine on the platform work simultaneously, that is, the first variable piston pump 10 and the second variable piston pump 20 work simultaneously, the second reversing valve 42 reverses the direction, the first fixed displacement motor 31 and the second fixed displacement motor 32 are connected in parallel and both are kept at the maximum displacement. At this time, the first fixed displacement motor 31 and the second fixed displacement motor 32 can drive the sand pump to operate at maximum power.

[0078] When low displacement is required for on-site operations, and the chassis is not in operation, the second directional valve 42 is in the non-reversing position. At this time, the third directional valve 43 will reverse, connecting the inlet and outlet ports of the second fixed displacement motor 32, achieving zero displacement operation. Only the first fixed displacement motor 31 drives the sand pump, meaning only the second variable displacement plunger pump 20 driven by the platform engine is operational. Since the sand pump is a centrifugal pump, the discharge volume is small, so the input power is also low. Using a small displacement motor keeps the sand pump within a reasonable speed range. This reduces the use of the chassis engine, meeting the requirements for emission reduction and fuel economy on-site.

[0079] The functions and roles of each hydraulic component in this system are as follows: The hydraulic oil tank 50 provides the working medium for transmitting power to the entire hydraulic system; the first fixed displacement motor 31 is the actuator, converting pressure energy into mechanical energy; the first variable displacement piston pump 10 is the power element in the hydraulic system, converting mechanical energy into pressure energy and transitioning the working medium from a low-pressure state to a high-pressure state; the pressure gauge 60 displays the driving oil pressure during operation; the second variable displacement piston pump 20 is the power element in the hydraulic system, converting mechanical energy into pressure energy and transitioning the working medium from a low-pressure state to a high-pressure state; the second directional valve 42 controls the hydraulic directional valve to switch directions through switching. The third directional valve 43 determines whether the second fixed displacement motor 32 participates in driving the system through switching, thus enabling the equipment to operate at a large displacement or a small displacement; the second fixed displacement motor 32 is the actuator, converting pressure energy into mechanical energy.

[0080] In Embodiment 4 of the present invention, the drive motor 30 includes a first fixed displacement motor 31 and a second fixed displacement motor 32. When the hydraulic system is in the first displacement operation state, the first fixed displacement motor 31 and the second fixed displacement motor 32 are connected in parallel, and both the first fixed displacement motor 31 and the second fixed displacement motor 32 are in operation. When the hydraulic system is in the second displacement operation state, the second variable displacement piston pump 20 is connected in series with the first variable displacement piston pump 10, thereby facilitating effective adjustment of the displacement.

[0081] Specifically, the first variable displacement piston pump 10 is driven by the power take-off (PTO) of the chassis vehicle. The hydraulic system also includes a fourth directional valve 44 and a fifth directional valve 45. The fourth directional valve 44 is connected to the second variable displacement piston pump 20, and the fourth directional valve 44, the first fixed displacement motor 31, and the second fixed displacement motor 32 are all connected to the fifth directional valve 45. When the hydraulic system is in the first displacement operating state, the fourth directional valve 44 is in the fourth directional position; when the hydraulic system is in the second displacement operating state, the fourth directional valve 44 is in the fourth initial position, and the fifth directional valve 45 is in the fifth initial position, so that the first fixed displacement motor 31 and the second fixed displacement motor 32 are connected in series through the adjustment of the fifth directional valve 45. This configuration simplifies the adjustment process and facilitates effective regulation.

[0082] As shown in Figure 4, in Embodiment 4, a scheme using a chassis hydraulic pump and a platform hydraulic pump to drive two fixed displacement motors (first fixed displacement motor 31 and second fixed displacement motor 32) is employed. The chassis drives the first variable displacement piston pump 10, and the platform engine drives the second variable displacement piston pump 20. The first variable displacement piston pump 10 contains a first replenishing pump, and the second variable displacement piston pump 20 contains a second replenishing pump. Due to the operation of the first and second replenishing pumps, suction is generated, and the hydraulic oil in the hydraulic oil tank 50 reaches the suction ports of the first variable displacement piston pump 10 and the second variable displacement piston pump 20, replenishing the pipeline of the closed system. Then, the oil overflows through the replenishing overflow valve built into the first variable displacement piston pump 10 and the second variable displacement piston pump 20, respectively, to cool the rotating parts inside the housing of the first variable displacement piston pump 10. Finally, the oil flows back into the hydraulic oil tank 50.

[0083] When the control units of the first variable piston pump 10 and the second variable piston pump 20 receive signals, the hydraulic oil in the servo cylinder of the first variable piston pump 10 will drive the swashplate to move, and the hydraulic oil in the servo cylinder of the second variable piston pump 20 will drive the swashplate to move. As the tilt angle of the swashplate changes, the first variable piston pump 10 and the second variable piston pump 20 will have flow output, so that the first fixed displacement motor 31 and the second fixed displacement motor 32 will operate synchronously (either a double fixed displacement motor or two identical fixed displacement motors connected mechanically to maintain synchronization).

[0084] Since the hydraulic pump driven by the chassis vehicle uses the full-power PTO of the chassis vehicle, the full-power PTO is engaged using pneumatic control. At this time, the reversing valve can be a pneumatic reversing valve (or a solenoid reversing valve or a manual reversing valve), which works simultaneously with the pneumatic control valve of the chassis vehicle's PTO. That is, when the chassis vehicle is working, the reversing valve will reverse at the same time the full-power PTO is engaged.

[0085] When a large displacement is required for on-site operations, the chassis vehicle and the engine on the platform work simultaneously, that is, the first variable piston pump 10 and the second variable piston pump 20 work simultaneously, the reversing valve reverses, and the dual fixed displacement motor or two fixed displacement motors are connected in parallel to maintain the maximum displacement. At this time, the fixed displacement motor can drive the sand pump to operate at maximum power.

[0086] When a small displacement motor is required for on-site operations, and the chassis is not in operation, the fourth directional valve 44 is in the non-reversing position. At this time, the fifth directional valve 45 will not reverse, keeping the dual fixed displacement motor or the two fixed displacement motors connected in series at the minimum displacement to drive the sand pump. That is, only the second plunger pump driven by the engine on the platform is working. Since the sand pump is a centrifugal pump, the discharge volume is small, so the input power of the sand pump is also small. Using a small displacement motor keeps the sand pump within a reasonable speed range. This reduces the use of the chassis engine, meeting the requirements for emission reduction and fuel economy on-site.

[0087] The functions and roles of each hydraulic component in this system are as follows: The hydraulic oil tank 50 provides the working medium for transmitting power to the entire hydraulic system; the first fixed displacement motor 31 is the actuator, using one double fixed displacement motor or two identical fixed displacement motors, which converts pressure energy into mechanical energy; the first variable displacement piston pump 10 is the power element in the hydraulic system, converting mechanical energy into pressure energy and transitioning the working medium from a low-pressure state to a high-pressure state; the pressure gauge 60 displays the driving oil pressure during operation; the second variable displacement piston pump 20 is the power element in the hydraulic system, converting mechanical energy into pressure energy and transitioning the working medium from a low-pressure state to a high-pressure state; the fourth directional valve 44 achieves the switching of the hydraulically controlled directional valve through switching; the fifth directional valve 45 determines whether the double fixed displacement motor or two fixed displacement motors are connected in series or parallel to participate in the drive, so as to maintain whether the equipment operates at a large displacement or a small displacement.

[0088] In all the above embodiments, the hydraulic system further includes a hydraulic oil tank 50, a first replenishing pump, and a second replenishing pump. Both the hydraulic oil tank 50 and the first variable displacement piston pump 10 are connected to the first replenishing pump. The first replenishing pump generates suction to draw hydraulic oil from the hydraulic oil tank 50 into the suction port of the first variable displacement piston pump 10 for replenishment. Both the hydraulic oil tank 50 and the second variable displacement piston pump 20 are connected to the second replenishing pump. The second replenishing pump generates suction to draw hydraulic oil from the hydraulic oil tank 50 into the suction port of the second variable displacement piston pump 20 for replenishment.

[0089] Specifically, in all the above embodiments, a first overflow valve is provided inside the first variable displacement piston pump 10 so that the oil entering the first variable displacement piston pump 10 overflows into the housing of the first variable displacement piston pump 10 through the first overflow valve. A second overflow valve is provided inside the second variable displacement piston pump 20 so that the oil entering the second variable displacement piston pump 20 overflows into the housing of the second variable displacement piston pump 20 through the second overflow valve.

[0090] In another embodiment of the present invention, a hydraulic control method is provided, which employs the hydraulic system provided in all the above embodiments. The hydraulic control method includes: driving a first variable displacement piston pump using a first drive unit, and driving a second variable displacement piston pump using a second drive unit; driving a drive motor via the first and / or second variable displacement piston pumps, and driving a centrifugal pump using the drive motor; and controlling the operation of the first and second variable displacement piston pumps according to the displacement operation state of the hydraulic system.

[0091] As can be seen from the above description, the above embodiments of the present invention achieve the following technical effects: by using a combination of dual hydraulic pumps or multiple hydraulic pumps, and by using a variable displacement motor or a combination of two or more motors in series or parallel, the sand pump of the sand mixing truck or the fracturing fluid discharge pump of the mixing truck can be driven separately, which can stop the chassis vehicle from working during small-displacement construction operations on site, thereby achieving the effect of energy saving and emission reduction.

[0092] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0093] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this application. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0094] In the description of this application, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is usually based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this application; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0095] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0096] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be construed as limiting the scope of protection of this application.

[0097] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A hydraulic system, characterized in that, include: A first variable displacement piston pump (10) and a second variable displacement piston pump (20) are provided. The first variable displacement piston pump (10) is driven by a first drive unit, and the second variable displacement piston pump (20) is driven by a second drive unit. A drive motor (30) is provided to drive the centrifugal pump. Both the first variable displacement piston pump (10) and the second variable displacement piston pump (20) are connected to the drive motor (30). The output oil of the first variable displacement piston pump (10) and / or the output oil of the second variable displacement piston pump (20) are used to drive the drive motor (30) to operate. The hydraulic system has different displacement operating states. The operation of the first variable displacement piston pump and the operation of the second variable displacement piston pump are controlled according to the displacement operating state of the hydraulic system. The hydraulic system has a first displacement operating state and a second displacement operating state. The displacement of the first displacement operating state is greater than that of the second displacement operating state. Displacement in the first displacement operation state; when the hydraulic system is in the first displacement operation state, both the first variable piston pump (10) and the second variable piston pump (20) are in working state, and the working displacement of the drive motor (30) is kept at the maximum displacement; when the hydraulic system is in the second displacement operation state, the first variable piston pump (10) is in non-working state, the second variable piston pump (20) is in working state, and the working displacement of the drive motor (30) is reduced to a preset displacement; the drive motor (30) is a single variable motor; when the hydraulic system is in the first displacement operation state, the swashplate angle of the drive motor (30) is kept at the angle corresponding to the maximum working displacement of the drive motor; when the hydraulic system is in the second displacement operation state, the swashplate angle of the drive motor (30) is adjusted to adjust the working displacement of the drive motor (30) to the preset displacement.

2. The hydraulic system according to claim 1, characterized in that, The drive motor (30) is an electric motor; when the hydraulic system is in the first displacement operation state, the electric motor is in the de-energized state; when the hydraulic system is in the second displacement operation state, the electric motor is in the energized state, so that the electric motor can adjust the swashplate tilt angle of the drive motor (30).

3. The hydraulic system according to claim 1, characterized in that, The drive motor (30) is a hydraulically controlled motor. The first variable displacement piston pump (10) is driven by the power take-off of the chassis vehicle. The hydraulic system also includes a first directional valve (41) connected to the drive motor (30). When the hydraulic system is in the first displacement operation state, the first directional valve (41) is in the first directional position. When the hydraulic system is in the second displacement operation state, the first directional valve (41) is in the first initial position. The displacement of the drive motor is adjusted by controlling the directional control of the first directional valve (41).

4. The hydraulic system according to claim 3, characterized in that, The hydraulic system further includes a pressure reducing valve connected to the first directional valve (41); and / or, the first directional valve (41) is a pneumatic directional valve, a solenoid directional valve, or a manual directional valve.

5. The hydraulic system according to any one of claims 1 to 4, characterized in that, The hydraulic system further includes: a hydraulic oil tank (50); a first replenishing pump, wherein the hydraulic oil tank (50) and the first variable piston pump (10) are both connected to the first replenishing pump, and the first replenishing pump generates suction to draw the hydraulic oil in the hydraulic oil tank (50) into the suction port of the first variable piston pump (10) for replenishment; and a second replenishing pump, wherein the hydraulic oil tank (50) and the second variable piston pump (20) are both connected to the second replenishing pump, and the second replenishing pump generates suction to draw the hydraulic oil in the hydraulic oil tank (50) into the suction port of the second variable piston pump (20) for replenishment.

6. The hydraulic system according to claim 5, characterized in that, The first variable piston pump (10) is provided with a first overflow valve so that the oil entering the first variable piston pump (10) overflows into the housing of the first variable piston pump (10) through the first overflow valve; and / or, the second variable piston pump (20) is provided with a second overflow valve so that the oil entering the second variable piston pump (20) overflows into the housing of the second variable piston pump (20) through the second overflow valve.

7. A hydraulic control method, characterized in that, The hydraulic control method employs the hydraulic system described in any one of claims 1 to 6; the hydraulic control method includes: driving a first variable displacement piston pump using a first drive unit, and driving a second variable displacement piston pump using a second drive unit; driving a drive motor via the first variable displacement piston pump and / or the second variable displacement piston pump, and driving a centrifugal pump using the drive motor; and controlling the operation of the first variable displacement piston pump and the second variable displacement piston pump according to the displacement operation state of the hydraulic system.

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