Electric forklift energy recovery hydraulic system and electric forklift

Abstract

The application discloses an electric forklift energy recovery hydraulic system and an electric forklift. The system comprises a main pump and a secondary pump which are respectively in transmission connection with a main motor and a secondary motor, wherein the secondary pump is a two-quadrant pump; an outlet of the main pump is connected with an inlet one of an electric control main valve, and an outlet of the secondary pump is connected with an inlet two of the electric control main valve; a working port of the electric control main valve is respectively connected with a lifting oil cylinder, an inclination oil cylinder and a side shift oil cylinder; a pressure sensor is arranged for collecting pressure of a large cavity of the lifting oil cylinder; a controller is electrically connected with the main motor, the secondary motor and the electric control main valve, and is used for driving the electric forklift to act and recovering energy according to a pressure signal collected by the pressure sensor and a control signal input by an electric control handle. The application realizes double-pump confluence oil supply during lifting, independent control of each actuating mechanism during descending and efficient recovery of potential energy, and improves energy utilization efficiency of the system and controllability of the whole machine; meanwhile, hydraulic impact and goods shaking caused by sudden change of speed during lifting can be inhibited.

Description

Technical Field

[0001] This invention belongs to the field of electric forklift technology, specifically relating to an energy recovery hydraulic system for electric forklifts and an electric forklift. Background Technology

[0002] Forklifts are widely used material handling vehicles in the industrial sector. During their work cycle, the forks frequently perform lifting and lowering operations. Currently, existing forklift hydraulic systems still have the following three core problems: First, most systems use a single pump or a simple dual pump for oil supply. Lifting and lowering actions share the same oil circuit as auxiliary actions such as steering, tilting, and lateral movement. During combined actions, the flow distribution is affected by load pressure, resulting in large system energy loss, delayed action response, and poor stability. Second, during the lowering of the forks under load, the gravitational potential energy of the load is converted into the heat energy of the hydraulic oil through the hydraulic valve throttling. This not only causes huge energy waste but also leads to an increase in hydraulic system oil temperature, accelerating the aging of seals and the deterioration of hydraulic oil, affecting the reliability and lifespan of the system. Third, the lifting speed of the forks is easily affected by load changes. Sudden speed changes during start-up and stopping can easily cause hydraulic shock and cargo shaking, posing operational safety hazards. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides an energy recovery hydraulic system for electric forklifts and an electric forklift, which enables dual-pump combined oil supply during lifting and independent control of each actuator during lowering, while efficiently recovering potential energy, thereby improving the system's energy utilization efficiency and overall machine operability; at the same time, it can suppress hydraulic shock and cargo shaking caused by sudden speed changes during lifting.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, an energy recovery hydraulic system for an electric forklift is provided, comprising: a main pump and an auxiliary pump respectively connected to a main motor and an auxiliary motor, wherein the auxiliary pump is a two-quadrant pump; the outlet of the main pump is connected to the inlet one of an electrically controlled main valve, and the outlet of the auxiliary pump is connected to the inlet two of the electrically controlled main valve; the working port of the electrically controlled main valve is respectively connected to a lifting cylinder, a tilting cylinder, and a side-shifting cylinder; a pressure sensor for collecting the pressure in the large chamber of the lifting cylinder; and a controller electrically connected to the main motor, the auxiliary motor, and the electrically controlled main valve for driving the electric forklift to move and performing energy recovery based on the pressure signal collected by the pressure sensor and the control signal input by the electric control handle.

[0005] Furthermore, the first inlet of the electrically controlled main valve is connected to the inlet of the main pump shut-off valve, the inlet of the tilt directional valve, the inlet of the side-shift directional valve, and the inlet of the main pump bypass valve, respectively; the second inlet of the electrically controlled main valve is connected to the inlet of the auxiliary pump shut-off valve; the outlet of the main pump shut-off valve is connected to the inlet of the lifting directional valve, the inlet of the auxiliary pump bypass valve, and the outlet of the auxiliary pump shut-off valve, respectively; the working port of the lifting directional valve is connected to the lifting cylinder through the working port of the electrically controlled main valve; the working port of the tilt directional valve is connected to the tilt cylinder through the working port of the electrically controlled main valve; the working port of the side-shift directional valve is connected to the side-shift cylinder through the working port of the electrically controlled main valve; the return ports of the tilt directional valve, the side-shift directional valve, the main pump bypass valve, and the auxiliary pump bypass valve are connected to the oil tank through the return port of the electrically controlled main valve, respectively.

[0006] Furthermore, the control terminals of the lifting directional valve, the tilting directional valve, the side shift directional valve, the main pump shut-off valve, the auxiliary pump shut-off valve, the main pump bypass valve, and the auxiliary pump bypass valve are electrically connected to the controller.

[0007] Furthermore, when the electric control handle issues a lifting command, the controller controls the lifting directional valve to switch to the rising position, and at the same time outputs speed control signals for the main motor and auxiliary motor, controlling both the main pump bypass valve and the auxiliary pump bypass valve to switch to the cut-off position. At this time, the main pump shut-off valve is in the one-way open position, and the auxiliary pump shut-off valve is in the open position. The hydraulic oil output by the main pump and the hydraulic oil output by the auxiliary pump merge and enter the large chamber of the lifting cylinder through the lifting directional valve to realize the single lifting action.

[0008] Furthermore, when the electric control handle issues a descent command and is in micro-throttling mode, the controller controls the main pump shut-off valve, auxiliary pump shut-off valve, and main pump bypass valve to switch to the cut-off position, while the auxiliary pump bypass valve is in the open position. The controller calculates the valve opening of the lifting directional valve based on the target descent speed set by the electric control handle and the pressure signal collected by the pressure sensor, and outputs the corresponding control current. The hydraulic oil in the large chamber of the lifting cylinder flows into the oil tank through the lifting directional valve and the auxiliary pump bypass valve; this is used to ensure the speed control accuracy during the micro-operation of descent through throttling speed regulation.

[0009] Furthermore, when the electric control handle issues a descent command and is in rapid descent mode, the controller controls the main pump shut-off valve, main pump bypass valve, and auxiliary pump bypass valve to switch to the cut-off position, and the auxiliary pump shut-off valve to switch to the open position. The controller calculates the auxiliary motor speed control signal based on the target descent speed set by the electric control handle and the displacement of the auxiliary pump. The hydraulic oil in the large chamber of the lifting cylinder enters the auxiliary pump through the lifting reversing valve and the auxiliary pump shut-off valve, and the auxiliary pump drives the auxiliary motor to generate electricity. This is used to achieve efficient, stable, and controllable energy recovery during rapid descent through volumetric speed regulation.

[0010] Furthermore, when the electric control handle issues a lifting command, and simultaneously issues a tilting command and / or a lateral movement command, the controller controls the lifting directional valve to switch to the lifting position, and at the same time outputs speed control signals for the main motor and auxiliary motor, controlling both the main pump bypass valve and the auxiliary pump bypass valve to switch to the cut-off position. At this time, the main pump shut-off valve is in the one-way open position, and the auxiliary pump shut-off valve is in the open position. A portion of the hydraulic oil output from the main pump and the hydraulic oil output from the auxiliary pump merge and enter the large chamber of the lifting cylinder through the lifting directional valve; another portion of the hydraulic oil output from the main pump enters the tilting directional valve and / or the lateral movement directional valve to realize the combination of lifting action and tilting action and / or lateral movement action.

[0011] Furthermore, when the electric control handle issues a descent command and is in micro-throttling mode, and simultaneously issues a tilt command and / or lateral movement command, the controller controls the main pump shut-off valve, auxiliary pump shut-off valve, and main pump bypass valve to switch to the cut-off position, while the auxiliary pump bypass valve is in the open position. The controller calculates the valve opening of the lifting directional valve based on the target descent speed set by the electric control handle and the pressure signal collected by the pressure sensor, and outputs the corresponding control current. The hydraulic oil in the large chamber of the lifting cylinder flows into the oil tank through the lifting directional valve and the auxiliary pump bypass valve. At the same time, the hydraulic oil output by the main pump enters the tilt directional valve and / or lateral movement directional valve to realize the combination of descent micro-motion and tilting and / or lateral movement.

[0012] Furthermore, when the electric control handle issues a descent command and is in rapid descent mode, and simultaneously issues a tilt command and / or a lateral movement command, the controller controls the main pump shut-off valve, main pump bypass valve, and auxiliary pump bypass valve to switch to the cut-off position, and the auxiliary pump shut-off valve to switch to the open position. The controller calculates the speed control signal of the auxiliary motor based on the target descent speed set by the electric control handle and the displacement of the auxiliary pump. The hydraulic oil in the large chamber of the lifting cylinder enters the auxiliary pump through the lifting reversing valve and the auxiliary pump shut-off valve, and the auxiliary pump drives the auxiliary motor to generate electricity. At the same time, the hydraulic oil output by the main pump enters the tilt reversing valve and / or the lateral movement reversing valve to realize the combination of rapid descent action and tilt action and / or lateral movement action.

[0013] In a second aspect, an electric forklift is provided, the electric forklift being equipped with the electric forklift energy recovery hydraulic system described in the first aspect.

[0014] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: (1) The present invention uses a main pump and an auxiliary pump that are respectively connected to the main motor and the auxiliary motor. The outlet of the main pump is connected to the inlet one of the electrically controlled main valve, and the outlet of the auxiliary pump is connected to the inlet two of the electrically controlled main valve. The working port of the electrically controlled main valve is respectively connected to the lifting cylinder, the tilting cylinder and the side-moving cylinder. A pressure sensor is used to collect the pressure of the large chamber of the lifting cylinder. The controller is electrically connected to the main motor, the auxiliary motor and the electrically controlled main valve respectively, and is used to drive the electric forklift to move and perform energy recovery based on the pressure signal collected by the pressure sensor and the control signal input by the electric control handle. It realizes the dual pumps to supply oil during lifting, and the independent control of each actuator during lowering and can efficiently recover potential energy, thereby improving the system's energy utilization efficiency and overall machine operability. At the same time, the lowering speed control mode can be distinguished according to the handle signal, so as to realize precise speed control during the micro-operation of lowering, efficient and stable energy recovery during rapid lowering, and can automatically adjust the speed ramp control parameters according to the load weight, which can effectively suppress the hydraulic shock and cargo shaking caused by sudden speed changes during lifting. (2) The present invention can be based on the existing forklift hydraulic system, and replaces the large displacement single pump commonly used in the existing system with two small displacement motor pumps. The main and auxiliary pump shut-off valves are added to the electronically controlled main valve. Through simple technical upgrades, the present invention can achieve a dual improvement in energy efficiency and operation performance with a small modification cost, and has a very broad prospect for industrial application. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the principle of an energy recovery hydraulic system for an electric forklift provided in an embodiment of the present invention; In the diagram: 1. Oil tank; 2. Main motor; 3. Main pump; 4. Auxiliary motor; 5. Auxiliary pump; 6. Controller; 7. Electric control handle; 8. Electric control main valve; 9. Lifting directional valve; 10. Tilting directional valve; 11. Side shift directional valve; 12. Lifting cylinder; 13. Tilting cylinder; 14. Side shift cylinder; 15. Pressure sensor; 16. Main pump shut-off valve; 17. Auxiliary pump shut-off valve; 18. Main pump bypass valve; 19. Auxiliary pump bypass valve. Detailed Implementation

[0016] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0017] Example 1 like Figure 1As shown, an energy recovery hydraulic system for an electric forklift includes: a main pump 3 and an auxiliary pump 5, which are respectively connected to a main motor 2 and an auxiliary motor 4 for transmission; the auxiliary pump 5 is a two-quadrant pump; the outlet of the main pump 3 is connected to the inlet one of an electrically controlled main valve 8, and the outlet of the auxiliary pump 5 is connected to the inlet two of the electrically controlled main valve 8; the working port of the electrically controlled main valve 8 is respectively connected to a lifting cylinder 12, a tilting cylinder 13, and a side-shifting cylinder 14; a pressure sensor 15 for collecting the pressure of the large chamber of the lifting cylinder 12; and a controller 6, which is electrically connected to the main motor 2, the auxiliary motor 4, and the electrically controlled main valve 8 for driving the electric forklift to move and for energy recovery based on the pressure signal collected by the pressure sensor 15 and the control signal input by the electric control handle 7; and also includes: an oil tank 1, a lifting reversing valve 9, a tilting reversing valve 10, a side-shifting reversing valve 11, a main pump shut-off valve 16, an auxiliary pump shut-off valve 17, a main pump bypass valve 18, an auxiliary pump bypass valve 19, a main pump overflow valve, and an auxiliary pump overflow valve, etc.

[0018] The main pump 3 is connected to the lifting cylinder 12, tilting cylinder 13, and side-shifting cylinder 14 respectively via the lifting directional valve 9, tilting directional valve 10, and side-shifting directional valve 11 of the electrically controlled main valve 8. The auxiliary pump 5 is connected to the lifting cylinder 12 via the lifting directional valve 9 of the electrically controlled main valve 8. The controller 6 receives signals from the electric control handle 7 and the pressure sensor 15, and outputs control signals for the speeds of the main and auxiliary motors and the current of each electro-proportional control valve. The lifting directional valve 9, tilting directional valve 10, and side-shifting directional valve 11 are all electro-proportional directional valves.

[0019] When the forks are raised, the auxiliary pump 5 operates in pump mode to supply oil to the lifting cylinder 12. When the forks are lowered, the auxiliary pump 5 operates in motor mode to drive the auxiliary motor 4 to rotate and generate electricity. The generated electrical energy is stored in the battery of the electric forklift, thus completing energy recovery.

[0020] In addition to the lifting directional valve 9, tilting directional valve 10, and side shifting directional valve 11, the main pump shut-off valve 16, auxiliary pump shut-off valve 17, main pump bypass valve 18, and auxiliary pump bypass valve 19 are also integrated. The lifting directional valve 9 controls the movement of the lifting cylinder 12, the tilting directional valve 10 controls the movement of the tilting cylinder 13, and the side shifting directional valve 11 controls the movement of the side shifting cylinder 14. The main pump shut-off valve 16 has a one-way shut-off function and controls the opening and closing of the oil circuit between the main pump 3 and the lifting cylinder 12. The auxiliary pump shut-off valve 17 controls the opening and closing of the oil circuit between the auxiliary pump 5 and the lifting cylinder 12.

[0021] The inlet of the electrically controlled main valve 8 is connected to the inlet of the main pump shut-off valve 16, the inlet of the tilt directional valve 10, the inlet of the side-shift directional valve 11, and the inlet of the main pump bypass valve 18. The second inlet of the electrically controlled main valve 8 is connected to the inlet of the auxiliary pump shut-off valve 17. The outlet of the main pump shut-off valve 16 is connected to the inlet of the lifting directional valve 9, the inlet of the auxiliary pump bypass valve 19, and the outlet of the auxiliary pump shut-off valve 17. The working port of the lifting directional valve 9 is connected to the lifting cylinder 12 through the working port of the electrically controlled main valve 8; the working port of the tilt directional valve 10 is connected to the tilt cylinder 13 through the working port of the electrically controlled main valve 8; and the working port of the side-shift directional valve 11 is connected to the side-shift cylinder 14 through the working port of the electrically controlled main valve 8. The return ports of the tilt directional valve 10, the side-shift directional valve 11, the main pump bypass valve 18, and the auxiliary pump bypass valve 19 are connected to the oil tank 1 through the return port of the electrically controlled main valve 8. The control terminals of the lifting directional valve 9, the tilting directional valve 10, the side shift directional valve 11, the main pump shut-off valve 16, the auxiliary pump shut-off valve 17, the main pump bypass valve 18, and the auxiliary pump bypass valve 19 are electrically connected to the controller 6.

[0022] The controller 6 receives signals from the electric control handle 7. When the forks descend, the controller sets the target descent speed based on the handle opening signal of the electric control handle 7, and divides the descent speed control mode into micro-control throttling mode and rapid descent mode. When the handle opening is in the range of 0~30%, the descent speed control mode is micro-control throttling mode. The controller 6 calculates the valve opening of the lifting reversing valve 9 based on the target descent speed and the signal from the pressure sensor 15 and outputs the corresponding current (the specific calculation process is prior art and will not be described in this application). The speed control accuracy during the micro-operation of descent is ensured through throttling speed regulation. When the handle opening is in the range of 30~100%, the descent speed control mode is rapid descent mode. The controller 6 calculates the speed control signal of the auxiliary motor 4 based on the target descent speed and the displacement of the auxiliary pump 5 (the specific calculation process is prior art and will not be described in this application). The efficient, stable and controllable energy recovery during rapid descent is achieved through volumetric speed regulation.

[0023] When the lifting and reversing valve 9 is in the neutral position, the controller 6 calculates the load weight based on the signal from the pressure sensor 15 (the specific calculation process is prior art and will not be described in detail here). Based on the different load weights, different speed ramp functions are used when switching between lifting and lowering modes of the forks to smooth the target speed command and avoid hydraulic shock and cargo shaking caused by sudden speed changes.

[0024] Single lifting action: When the electric control handle 7 issues a lifting command, the controller 6 controls the lifting reversing valve 9 to switch to the rising position, and at the same time outputs speed control signals for the main motor 2 and the auxiliary motor 4, controlling the main pump bypass valve 18 and the auxiliary pump bypass valve 19 to switch to the cut-off position. At this time, the main pump shut-off valve 16 is in the one-way connected position, and the auxiliary pump shut-off valve 17 is in the connected position. The hydraulic oil output by the main pump 3 and the hydraulic oil output by the auxiliary pump merge and enter the large chamber of the lifting cylinder 12 through the lifting reversing valve 9 to realize the single lifting action. At this time, the two pumps merge to supply oil, improving the working efficiency.

[0025] Single-action descent: When the electric control handle 7 issues a descent command, the controller 6 determines the descent speed control mode based on the handle opening signal of the electric control handle 7. When the handle opening is within the range of 0~30%, the descent speed control mode is the micro-control throttling mode. At this time, the controller 6 controls the main pump shut-off valve 16, the auxiliary pump shut-off valve 17, and the main pump bypass valve 18 to switch to the cut-off position, while the auxiliary pump bypass valve 19 is in the connected position. The controller 6 calculates the valve opening of the lifting directional valve 9 based on the target descent speed set by the electric control handle 7 and the pressure signal collected by the pressure sensor 15, and outputs the corresponding control current. The hydraulic oil in the large chamber of the lifting cylinder 12 flows into the oil tank 1 through the lifting directional valve 9 and the auxiliary pump bypass valve 19; this is used to ensure the speed control accuracy during the micro-operation of descent through throttling speed regulation. When the handle opening is within the range of 30~100%, the descent speed control mode is the rapid descent mode. At this time, the controller 6 controls the main pump shut-off valve 16, the main pump bypass valve 18, and the auxiliary pump bypass valve 19 to switch to the cut-off position, and the auxiliary pump shut-off valve 17 to switch to the open position. The controller 6 calculates the speed control signal of the auxiliary motor 4 based on the target descent speed set by the electric control handle 7 and the displacement of the auxiliary pump 5. The hydraulic oil in the large chamber of the lifting cylinder 12 enters the auxiliary pump 5 through the lifting reversing valve 9 and the auxiliary pump shut-off valve 17. The auxiliary pump 5 drives the auxiliary motor 4 to generate electricity. This is used to achieve efficient, stable, and controllable energy recovery during rapid descent through volumetric speed regulation.

[0026] Lifting combined with other actions: When lifting is combined with other actions, the controller 6 controls the corresponding electro-proportional directional valves of each action to switch, controls the main pump 3 to output the flow rate requested for lifting and other actions, controls the auxiliary pump 5 to output the flow rate requested for lifting, keeps the main pump shut-off valve 16 and the auxiliary pump shut-off valve 17 open, closes the main pump bypass valve 18 and the auxiliary pump bypass valve 19, at this time the lifting cylinder 12 is supplied with oil by the dual pumps combined, and other actions combined with lifting are supplied with oil by the main pump 3.

[0027] When the electric control handle 7 issues a lifting command, and simultaneously issues a tilting command and / or a lateral movement command, the controller 6 controls the lifting directional valve 9 to switch to the lifting position, and at the same time outputs speed control signals for the main motor 2 and the auxiliary motor 4, controlling the main pump bypass valve 18 and the auxiliary pump bypass valve 19 to switch to the cut-off position. At this time, the main pump shut-off valve 16 is in the one-way open position, and the auxiliary pump shut-off valve 17 is in the open position. A portion of the hydraulic oil output by the main pump 3 and the hydraulic oil output by the auxiliary pump merge and enter the large chamber of the lifting cylinder 12 through the lifting directional valve 9; another portion of the hydraulic oil output by the main pump 3 enters the tilting directional valve 10 and / or the lateral movement directional valve 11 to realize the combination of lifting action and tilting action and / or lateral movement action.

[0028] Combining descent with other actions: When descent is combined with other actions, controller 6 controls the switching valves corresponding to each action and determines the descent speed control mode based on the handle signal. When in micro-control throttling mode, the main pump shut-off valve 16, auxiliary pump shut-off valve 17, and main pump bypass valve 18 are closed, and the auxiliary pump bypass valve 19 is opened. Controller 6 calculates the valve opening of lifting and lowering directional valve 9 based on the target descent speed set by the electric control handle 7 and the signal from pressure sensor 15, and outputs the corresponding current. At this time, the main pump 3 supplies oil to other actions. The pressure oil in the large chamber of the lifting cylinder 12 flows into the oil tank 1 through the lifting reversing valve 9 and the auxiliary pump bypass valve 19. When in rapid descent mode, the main pump shut-off valve 16, the main pump bypass valve 18 and the auxiliary pump bypass valve 19 are closed, and the auxiliary pump shut-off valve 17 is opened. The controller 6 calculates the speed control signal of the auxiliary motor 4 based on the target descent speed and the displacement of the auxiliary pump 5. At this time, the main pump 3 supplies oil for other actions and outputs the requested flow rate. The pressure oil in the large chamber of the lifting cylinder 12 drives the auxiliary pump 5 to rotate the auxiliary motor 4, thereby realizing the recovery of descent potential energy.

[0029] (1) When the electric control handle 7 issues a descent command and the electric control handle 7 is in micro-control throttling mode, at the same time, the electric control handle 7 issues a tilt command and / or a lateral movement command; the controller 6 controls the main pump shut-off valve 16, the auxiliary pump shut-off valve 17 and the main pump bypass valve 18 to switch to the cut-off position, and the auxiliary pump bypass valve 19 is in the connected position. The controller 6 calculates the valve opening of the lifting reversing valve 9 according to the target descent speed set by the electric control handle 7 and the pressure signal collected by the pressure sensor 15 and outputs the corresponding control current. The hydraulic oil in the large chamber of the lifting cylinder 12 flows into the oil tank 1 through the lifting reversing valve 9 and the auxiliary pump bypass valve 19. At the same time, the hydraulic oil output by the main pump 3 enters the tilt reversing valve 10 and / or the lateral movement reversing valve 11 to realize the combination of descent micro-motion and tilting motion and / or lateral movement motion.

[0030] (2) When the electric control handle 7 issues a descent command and the electric control handle 7 is in rapid descent mode, at the same time, the electric control handle 7 issues a tilt command and / or a lateral movement command; the controller 6 controls the main pump shut-off valve 16, the main pump bypass valve 18 and the auxiliary pump bypass valve 19 to switch to the cut-off position, and the auxiliary pump shut-off valve 17 to switch to the open position. The controller 6 calculates the speed control signal of the auxiliary motor 4 according to the target descent speed set by the electric control handle 7 and the displacement of the auxiliary pump 5. The hydraulic oil in the large chamber of the lifting cylinder 12 enters the auxiliary pump 5 through the lifting reversing valve 9 and the auxiliary pump shut-off valve 17. The auxiliary pump 5 drives the auxiliary motor 4 to generate electricity. At the same time, the hydraulic oil output by the main pump 3 enters the tilt reversing valve 10 and / or the lateral movement reversing valve 11 to realize the combination of rapid descent action and tilt action and / or lateral movement action.

[0031] This invention features a dual-pump combined oil supply during lifting, improving operational efficiency. During descent, each actuator can be independently controlled and potential energy can be recovered, significantly enhancing system energy efficiency and overall machine operability. This invention can differentiate descent speed control modes based on handle signals, achieving precise speed control during micro-operations and efficient and stable energy recovery during rapid descent. It can also automatically adjust speed ramp control parameters according to load weight, effectively suppressing hydraulic shocks and cargo vibration caused by sudden speed changes during lifting. Based on the existing forklift hydraulic system, this invention uses two small-displacement motor pumps instead of the commonly used large-displacement single pump, and adds main and auxiliary pump shut-off valves to the electronically controlled main valve. Through simple technical upgrades, this invention can achieve a dual improvement in energy efficiency and operational performance with minimal modification cost, showing great promise for industrial application.

[0032] Example 2 Based on the electric forklift energy recovery hydraulic system described in Embodiment 1, this embodiment provides an electric forklift equipped with the electric forklift energy recovery hydraulic system described in Embodiment 1.

[0033] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An energy recovery hydraulic system for an electric forklift, characterized in that, include: The main pump (3) and auxiliary pump (5) are respectively connected to the main motor (2) and auxiliary motor (4). The auxiliary pump (5) is a two-quadrant pump. The outlet of the main pump (3) is connected to the inlet one of the electrically controlled main valve (8), and the outlet of the auxiliary pump (5) is connected to the inlet two of the electrically controlled main valve (8). The working port of the electrically controlled main valve (8) is respectively connected to the lifting cylinder (12), the tilting cylinder (13) and the side-shifting cylinder (14). Pressure sensor (15) used to collect pressure in the large cavity of lifting cylinder (12); The controller (6) is electrically connected to the main motor (2), the auxiliary motor (4) and the electric control main valve (8) respectively, and is used to drive the electric forklift to move and perform energy recovery based on the pressure signal collected by the pressure sensor (15) and the control signal input by the electric control handle (7). The inlet of the electrically controlled main valve (8) is connected to the inlet of the main pump shut-off valve (16), the inlet of the tilt reversing valve (10), the inlet of the side shift reversing valve (11), and the inlet of the main pump bypass valve (18), respectively. The inlet of the electrically controlled main valve (8) is connected to the inlet of the auxiliary pump shut-off valve (17); The outlet of the main pump shut-off valve (16) is connected to the inlet of the lifting reversing valve (9), the inlet of the auxiliary pump bypass valve (19), and the outlet of the auxiliary pump shut-off valve (17), respectively. The working port of the lifting reversing valve (9) is connected to the lifting cylinder (12) through the working port of the electric main valve (8); the working port of the tilting reversing valve (10) is connected to the tilting cylinder (13) through the working port of the electric main valve (8); the working port of the side shifting reversing valve (11) is connected to the side shifting cylinder (14) through the working port of the electric main valve (8). The return port of the tilt directional valve (10), the return port of the side shift directional valve (11), the outlet of the main pump bypass valve (18), and the outlet of the auxiliary pump bypass valve (19) are connected to the oil tank (1) through the return port of the electrically controlled main valve (8).

2. The electric forklift energy recovery hydraulic system according to claim 1, characterized in that, The control terminals of the lifting directional valve (9), the tilt directional valve (10), the side shift directional valve (11), the main pump shut-off valve (16), the auxiliary pump shut-off valve (17), the main pump bypass valve (18), and the auxiliary pump bypass valve (19) are electrically connected to the controller (6).

3. The electric forklift energy recovery hydraulic system according to claim 2, characterized in that, When the electric control handle (7) issues a lifting command, the controller (6) controls the lifting reversing valve (9) to switch to the rising position, and at the same time outputs the speed control signals of the main motor (2) and the auxiliary motor (4), and controls the main pump bypass valve (18) and the auxiliary pump bypass valve (19) to switch to the cut-off position. At this time, the main pump shut-off valve (16) is in the one-way connection position, and the auxiliary pump shut-off valve (17) is in the connection position. The hydraulic oil output by the main pump (3) and the hydraulic oil output by the auxiliary pump merge and enter the large chamber of the lifting cylinder (12) through the lifting reversing valve (9) to realize the single lifting action.

4. The energy recovery hydraulic system for electric forklifts according to claim 2, characterized in that, When the electric control handle (7) issues a descent command and the electric control handle (7) is in micro-control throttling mode, the controller (6) controls the main pump shut-off valve (16), the auxiliary pump shut-off valve (17) and the main pump bypass valve (18) to switch to the cut-off position, and the auxiliary pump bypass valve (19) is in the connected position. The controller (6) calculates the valve opening of the lifting reversing valve (9) according to the target descent speed set by the electric control handle (7) and the pressure signal collected by the pressure sensor (15) and outputs the corresponding control current. The hydraulic oil in the large chamber of the lifting cylinder (12) flows into the oil tank (1) through the lifting reversing valve (9) and the auxiliary pump bypass valve (19); it is used to ensure the speed control accuracy during the descent micro-operation by means of throttling speed regulation.

5. The electric forklift energy recovery hydraulic system according to claim 2, characterized in that, When the electric control handle (7) issues a descent command and the electric control handle (7) is in the rapid descent mode, the controller (6) controls the main pump shut-off valve (16), the main pump bypass valve (18) and the auxiliary pump bypass valve (19) to switch to the cut-off position, and the auxiliary pump shut-off valve (17) to switch to the connected position. The controller (6) calculates the speed control signal of the auxiliary motor (4) according to the target descent speed set by the electric control handle (7) and the displacement of the auxiliary pump (5). The hydraulic oil in the large chamber of the lifting cylinder (12) enters the auxiliary pump (5) through the lifting reversing valve (9) and the auxiliary pump shut-off valve (17). The auxiliary pump (5) drives the auxiliary motor (4) to generate electricity. This is used to achieve efficient, stable and controllable energy recovery during rapid descent through volumetric speed regulation.

6. The electric forklift energy recovery hydraulic system according to claim 2, characterized in that, When the electric control handle (7) issues a lifting command, and at the same time issues a tilting command and / or a lateral movement command, the controller (6) controls the lifting reversing valve (9) to switch to the lifting position, and at the same time outputs the speed control signals of the main motor (2) and the auxiliary motor (4), and controls the main pump bypass valve (18) and the auxiliary pump bypass valve (19) to switch to the cut-off position. At this time, the main pump shut-off valve (16) is in the one-way connection position, and the auxiliary pump shut-off valve (17) is in the connection position. A part of the hydraulic oil output by the main pump (3) and the hydraulic oil output by the auxiliary pump merge and enter the large chamber of the lifting cylinder (12) through the lifting reversing valve (9); another part of the hydraulic oil output by the main pump (3) enters the tilting reversing valve (10) and / or the lateral movement reversing valve (11) to realize the combination of lifting action and tilting action and / or lateral movement action.

7. The energy recovery hydraulic system for electric forklifts according to claim 2, characterized in that, When the electric control handle (7) issues a descent command and the electric control handle (7) is in micro-control throttling mode, at the same time, the electric control handle (7) issues a tilt command and / or a lateral movement command; the controller (6) controls the main pump shut-off valve (16), the auxiliary pump shut-off valve (17) and the main pump bypass valve (18) to switch to the cut-off position, and the auxiliary pump bypass valve (19) is in the connected position. The controller (6) calculates the valve opening of the lifting reversing valve (9) according to the target descent speed set by the electric control handle (7) and the pressure signal collected by the pressure sensor (15) and outputs the corresponding control current. The hydraulic oil in the large chamber of the lifting cylinder (12) flows into the oil tank (1) through the lifting reversing valve (9) and the auxiliary pump bypass valve (19); at the same time, the hydraulic oil output by the main pump (3) enters the tilt reversing valve (10) and / or the lateral movement reversing valve (11) to realize the combination of descent micro-motion and tilting motion and / or lateral movement motion.

8. The energy recovery hydraulic system for electric forklifts according to claim 2, characterized in that, When the electric control handle (7) issues a descent command and the electric control handle (7) is in rapid descent mode, at the same time, the electric control handle (7) issues a tilt command and / or a lateral movement command; the controller (6) controls the main pump shut-off valve (16), the main pump bypass valve (18) and the auxiliary pump bypass valve (19) to switch to the cut-off position, and the auxiliary pump shut-off valve (17) to switch to the connected position. The controller (6) calculates the speed control signal of the auxiliary motor (4) according to the target descent speed set by the electric control handle (7) and the displacement of the auxiliary pump (5). The hydraulic oil in the large chamber of the lifting cylinder (12) enters the auxiliary pump (5) through the lifting reversing valve (9) and the auxiliary pump shut-off valve (17). The auxiliary pump (5) drives the auxiliary motor (4) to generate electricity. At the same time, the hydraulic oil output by the main pump (3) enters the tilt reversing valve (10) and / or the lateral movement reversing valve (11) to realize the combination of rapid descent action and tilt action and / or lateral movement action.

9. An electric forklift, characterized in that, The electric forklift is equipped with the electric forklift energy recovery hydraulic system as described in any one of claims 1 to 8.

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