A potential energy recovery system for forklifts

Abstract

The present invention provides a forklift potential energy recovery system, which belongs to the field of energy recycling technology. The system includes a main mast lifting cylinder, a sub-mast lifting cylinder, a sub-mast rotating motor and a sub-mast rotating cylinder. The system is characterized in that it also includes an energy recovery and release system. The energy recovery and release system includes a hydraulic pump motor, an electric generator and a battery. The hydraulic pump motor is respectively connected to the oil tank, the main mast lifting cylinder, the sub-mast lifting cylinder, the sub-mast side shift motor and the sub-mast rotating cylinder. The hydraulic pump motor, the electric generator and the battery are connected in sequence. The advantage is that the energy recovery and release system can recover the energy of the pressure oil flowing back to the oil tank when the main mast falls back, the sub-mast falls back and the sub-mast rotates, thereby avoiding energy loss caused by the circulation of pressure oil.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy recycling, and in particular relates to a forklift potential energy recovery system. Background Art

[0002] A forklift refers to a variety of wheeled transport vehicles used for loading and unloading, stacking and short-distance transportation of palletized goods. It is a commonly used lifting tool and is usually driven by an electric generator or motor. Its working principle is that the engine or motor drives the hydraulic pump to generate hydraulic energy, and the lifting cylinder converts the hydraulic energy into the gravitational potential energy of the goods.

[0003] Electric forklifts use batteries as their energy source, replacing engines with electric motors to drive the hydraulic system, completing tasks such as lifting, lowering, transferring, and unloading cargo. Because forklifts generate significant potential energy while lowering a load, conventional forklifts dissipate this energy in the throttle valve. This results in significant energy loss and increases oil temperature, affecting the life of hydraulic components and the oil, and potentially causing leaks and unstable operation. Current research on forklift potential energy uses hydraulic accumulators to store the pressurized oil in the lift cylinder during the lowering process. However, as the accumulator pressure gradually increases with the amount of recovered oil, this can cause changes in maneuverability during the lowering process. Other research uses electrical energy recovery, employing a separate hydraulic motor-motor generator connected to the rodless chamber of the lift cylinder. When the lift cylinder lowers the load, hydraulic oil in the rodless chamber flows into the hydraulic motor, driving the motor generator to generate electricity, which is then stored in the battery. This stored energy is then released during lifting or other operations. In this working method, the energy recovery system and release system are two different systems, involving multiple energy conversions, making the system complex and inefficient. Summary of the Invention

[0004] The purpose of the present invention is to address the above-mentioned problems in the existing technology and to propose a potential energy recovery system with high recovery rate.

[0005] The objectives of the present invention can be achieved through the following technical solutions: a forklift potential energy recovery system, including a main mast lifting cylinder, a sub-mast lifting cylinder, a sub-mast rotating motor and a sub-mast rotating cylinder, and also including an energy recovery and release system, the energy recovery and release system includes a hydraulic pump motor, an electric generator and a battery, the hydraulic pump motor is respectively connected to the oil tank, the main mast lifting cylinder, the sub-mast lifting cylinder, the sub-mast rotating motor and the sub-mast rotating cylinder, the hydraulic pump motor, the electric generator and the battery are connected in sequence.

[0006] In the above-mentioned forklift potential energy recovery system, the main mast lifting cylinder and the oil tank are connected via at least one first reversing valve.

[0007] In the above-mentioned forklift potential energy recovery system, three one-way valves are arranged between the first reversing valve connected to the hydraulic pump motor and the hydraulic pump motor. The three one-way valves include a first one-way valve, a second one-way valve and a third one-way valve. The first reversing valve is respectively connected to the outlet of the first one-way valve and the inlet of the second one-way valve, the outlet of the second one-way valve is connected to the oil tank, the inlet of the first one-way valve is connected to the outlet of the third one-way valve, and the inlet of the third one-way valve is connected to the hydraulic pump motor.

[0008] In the above-mentioned forklift potential energy recovery system, a first overload protection valve is provided between the first reversing valve connected to the main mast lifting cylinder and the main mast lifting cylinder.

[0009] In the above-mentioned forklift potential energy recovery system, two second reversing valves in different directions are arranged between the sub-gantry lifting cylinder and the hydraulic pump motor. The hydraulic pump motor draws pressure oil from the oil tank and flows through one of the second reversing valves to the sub-gantry lifting cylinder, and the sub-gantry lifting cylinder performs lifting; when the sub-gantry lifting cylinder starts to fall back, the pressure oil flows through the other second reversing valve to the hydraulic pump motor.

[0010] In the above-mentioned forklift potential energy recovery system, a second overload protection valve is provided between the auxiliary mast lifting cylinder and the two second reversing valves, and the auxiliary mast lifting cylinder is connected to the two second reversing valves respectively through the second overload protection valve.

[0011] In the above-mentioned forklift potential energy recovery system, the sub-mast rotation motor and the hydraulic pump motor are connected via a third reversing valve, and the sub-mast rotation cylinder and the hydraulic pump motor are connected via a fourth reversing valve.

[0012] In the above-mentioned forklift potential energy recovery system, an overload valve is connected between the two oil inlets of the sub-gantry rotation motor and the third reversing valve, and a balancing valve is connected between the two oil inlets of the sub-gantry rotation cylinder and the fourth reversing valve.

[0013] In the above-mentioned forklift potential energy recovery system, a pressure regulating unit is further provided between the hydraulic pump motor and the auxiliary mast lifting cylinder.

[0014] In the above-mentioned forklift potential energy recovery system, the pressure regulating unit includes a seventh electromagnetic reversing valve and a first relief valve, and the seventh electromagnetic reversing valve is connected to the first relief valve and the hydraulic pump motor respectively.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] (1) A forklift potential energy recovery system, which is equipped with an energy recovery and release system to recover the energy of the pressure oil flowing back to the oil tank when the main mast falls back, the auxiliary mast falls back, and the auxiliary mast rotates, thereby avoiding energy loss caused by the circulation of pressure oil;

[0017] (2) The energy recovery and release system includes a hydraulic pump motor, an electric generator and a battery. The hydraulic pump motor is connected to the oil tank, the main gantry lifting cylinder, the auxiliary gantry lifting cylinder, the auxiliary gantry rotation motor and the auxiliary gantry rotation cylinder respectively. The hydraulic pump motor, the electric generator and the battery are connected in sequence. By setting up a set of energy recovery and release systems, energy can be recovered and released from the main gantry oil circuit and the auxiliary gantry oil circuit at the same time, which simplifies the recovery and release system, reduces the energy conversion process and improves the energy conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the system structure of the present invention. DETAILED DESCRIPTION

[0019] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0020] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0021] like Figure 1 As shown, a forklift potential energy recovery system includes a main mast lifting cylinder, a sub-mast lifting cylinder 20.3, a sub-mast rotation motor 28 and a sub-mast rotation cylinder 26, and also includes an energy recovery and release system. The energy recovery and release system includes a hydraulic pump motor 30, an electric generator 13 and a battery 32. The hydraulic pump motor 30 is respectively connected to the oil tank, the main mast lifting cylinder, the sub-mast lifting cylinder 20.3, the sub-mast rotation motor 28 and the sub-mast rotation cylinder 26, and the hydraulic pump motor 30, the electric generator 13 and the battery 32 are connected in sequence.

[0022] It is worth mentioning that when the main gantry and the auxiliary gantry start to fall back, the hydraulic pump motor 30 acts as a hydraulic motor and the electric generator 13 acts as a generator. The pressure oil in the main gantry lifting cylinder and the auxiliary gantry lifting cylinder 20.3 flows to the hydraulic pump motor 30, driving the electric generator 13 to reverse and generate electricity, and the electricity is stored in the battery 32; when the main gantry and the auxiliary gantry start to lift or the auxiliary gantry rotates or moves sideways, the battery 32 generates electricity. At this time, the hydraulic pump motor 30 acts as a hydraulic pump and the electric generator 13 acts as an electric motor. The hydraulic pump motor 30 draws pressure oil from the oil tank and flows it in the direction of the main gantry lifting cylinder and the auxiliary gantry lifting cylinder 20.3.

[0023] Specifically, the hydraulic pump motor 30 is coaxially arranged with the electric generator 13 to reduce friction and improve efficiency.

[0024] In this embodiment, by providing an energy recovery and release system, energy can be recovered from the pressure oil flowing back to the oil tank when the main gantry and the auxiliary gantry are lowered, and when the auxiliary gantry is rotated, thereby avoiding energy loss caused by the circulation of pressure oil; and the energy recovery and release system includes a hydraulic pump motor 30, an electric generator 13 and a battery 32, and the hydraulic pump motor 30 is respectively connected to the oil tank, the main gantry lifting cylinder, the auxiliary gantry lifting cylinder 20.3, the auxiliary gantry rotation motor 28 and the auxiliary gantry rotation cylinder 26, and the hydraulic pump motor 30, the electric generator 13 and the battery 32 are connected in sequence. By providing a set of energy recovery and release systems, energy can be recovered and released from the main gantry oil circuit and the auxiliary gantry oil circuit at the same time, which simplifies the recovery and release system, reduces the energy conversion process, and improves the energy conversion efficiency.

[0025] It is worth mentioning that a motor controller 31 is also provided between the electric generator 13 and the battery 32 to adjust and control the operating speeds of the main mast lifting cylinder, the auxiliary mast lifting cylinder 20.3, the auxiliary mast rotation motor 28 and the auxiliary mast rotation cylinder 26.

[0026] Specifically, the main mast lifting cylinder includes a first lifting cylinder 20.1, a second lifting cylinder 20.2, a third lifting cylinder 20.3 and a fourth lifting cylinder 20.4. The first lifting cylinder 20.1, the second lifting cylinder 20.2, the third lifting cylinder 20.3 and the fourth lifting cylinder 20.4 are respectively connected to the hydraulic pump motor 30, and the first lifting cylinder 20.1 is connected to the second lifting cylinder 20.2, and the third lifting cylinder 20.3 is connected to the fourth lifting cylinder 20.4. When the working pressure of the pressure oil in one of the lifting cylinders between the first lifting cylinder 20.1 and the second lifting cylinder 20.2 or between the third lifting cylinder 20.3 and the fourth lifting cylinder 20.4 is lower than the required working pressure, the pressure oil in the other lifting cylinder can directly flow into one of the lifting cylinders, pushing the lifting cylinder to complete the relevant lifting operation. Because the pressure oil is directly used between the pressure oils, there is no energy conversion, and thus the energy utilization rate is higher.

[0027] Preferably, the main mast lifting cylinder and the oil tank are connected via at least one first reversing valve.

[0028] Specifically, the first reversing valve includes a first solenoid reversing valve 1, a second solenoid reversing valve oil 2 and a third solenoid reversing valve 3. The hydraulic pump motor 30, the first solenoid reversing valve 1, the third solenoid reversing valve 3 and the second solenoid reversing valve oil 2 are connected in sequence. The second solenoid reversing valve 2 and the third solenoid reversing valve 3 are set in the same direction, and the first solenoid reversing valve 1 and the second solenoid reversing valve 2 are in different directions. When the main mast is lifted, the first solenoid reversing valve 1 is energized, and the pressure oil passes through the first solenoid reversing valve 1, the third solenoid reversing valve 3 and the second solenoid reversing valve 2 toward the main mast. The oil cylinder is circulated. At this time, the second solenoid reversing valve 2 and the third solenoid reversing valve 3 are in the power-off state to prevent the pressure oil from flowing back. When the main gantry falls back, the first solenoid reversing valve 1 is powered off, and the second solenoid reversing valve 2 and the third solenoid reversing valve 3 are powered on. The pressure oil flows along the second solenoid reversing valve 2, the third solenoid reversing valve 3 and the first solenoid reversing valve 1 to the hydraulic pump motor 30. The hydraulic pump motor 30 acts as a hydraulic motor at this time. The hydraulic pump motor 30 drives the electric generator 13 to reverse, and the electric generator 13 generates electricity, and the electricity is stored in the battery 32.

[0029] Further preferably, three one-way valves are arranged between the first reversing valve connected to the hydraulic pump motor 30 and the hydraulic pump motor 30. The three one-way valves include a first one-way valve 12.1, a second one-way valve 12.2 and a third one-way valve 12.3. The first reversing valve is connected to the outlet of the first one-way valve 12.1 and the inlet of the second one-way valve 12.2 respectively, the outlet of the second one-way valve 12.2 is connected to the oil tank, the inlet of the first one-way valve 12.1 is connected to the outlet of the third one-way valve 12.3, and the inlet of the third one-way valve 12.3 is connected to the hydraulic pump motor 30.

[0030] In this embodiment, when the main mast lifting cylinder is lifting, the hydraulic pump motor 30 acts as a hydraulic pump, flowing the pressure oil from the oil tank toward the first solenoid reversing valve 1. The pressure oil flows to the first solenoid reversing valve 1 through the third one-way valve 12.3 and the first one-way valve 12.1. When the main mast lifting cylinder is lowering, the pressure oil flows back to the oil tank through the second one-way valve 12.2.

[0031] Further preferably, a first overload protection valve is provided between the first reversing valve connected to the main mast lifting cylinder and the main mast lifting cylinder.

[0032] In this embodiment, the first throttle valve 19.1, the second throttle valve 19.2, the third throttle valve 25.1 and the fourth throttle valve 25.2 are respectively connected between the first lifting cylinder 20.1, the second lifting cylinder 20.2, the third lifting cylinder 20.3 and the fourth lifting cylinder 20.4 and the second solenoid reversing valve 2. By providing multiple throttle valves, the main mast lifting cylinder can be protected from overload.

[0033] It is worth mentioning that a gate valve 21 is connected between the second solenoid reversing valve 2 and the oil tank, a fourth overflow valve 11 is connected between the first solenoid reversing valve 1 and the oil tank, and the gate valve 21 and the fourth overflow valve 11 are connected to the third one-way valve through a ninth one-way valve 12.9.

[0034] Further preferably, two second reversing valves in different directions are provided between the sub-gantry lifting cylinder 20.3 and the hydraulic pump motor 30. The hydraulic pump motor 30 draws pressure oil from the oil tank and flows through one of the second reversing valves to the sub-gantry lifting cylinder 20.3, and the sub-gantry lifting cylinder 20.3 is lifted; when the sub-gantry lifting cylinder 20.3 starts to fall back, the pressure oil flows through the other second reversing valve to the hydraulic pump motor 30.

[0035] It is worth mentioning that a fourth electromagnetic reversing valve 4 is also provided between the auxiliary mast lifting cylinder 20 . 3 and the hydraulic pump motor 30 .

[0036] In this embodiment, two second reversing valves are provided between the sub-gantry lifting cylinder 20.3 and the hydraulic pump motor 30. The two second reversing valves include a fifth solenoid reversing valve 5 and a sixth solenoid reversing valve 6. The hydraulic pump motor 30 draws pressure oil from the oil tank and flows the pressure oil through the fourth solenoid reversing valve 4 and the fifth solenoid reversing valve 5 to the sub-gantry lifting cylinder 20.3, so that the sub-gantry lifting cylinder 20.3 is lifted; when the sub-gantry lifting cylinder 20.3 falls back, the pressure oil flows to the hydraulic pump motor 30 through the sixth solenoid reversing valve 6. By providing two second reversing valves in different directions, it is prevented that the pressure oil in the sub-gantry lifting cylinder 20.3 may flow back when the sub-gantry lifting cylinder 20.3 is working, causing the sub-gantry to fall back and posing a safety hazard.

[0037] Preferably, a second overload protection valve is provided between the auxiliary mast lifting cylinder 20.3 and the two second reversing valves, and the auxiliary mast lifting cylinder 20.3 is connected to the two second reversing valves respectively through the second overload protection valve.

[0038] Specifically, the second overload protection valve includes a fifth throttle valve 19.3, which is connected to the auxiliary mast lifting cylinder 20.3, the fifth electromagnetic reversing valve 5 and the sixth electromagnetic reversing valve 6 respectively.

[0039] In this embodiment, a second overload protection valve is provided between the auxiliary mast lifting cylinder 20.3 and the two second reversing valves. The auxiliary mast lifting cylinder 20.3 is connected to the two second reversing valves respectively through the second overload protection valve, which can provide overload protection for the auxiliary mast lifting cylinder 20.3 to prevent the oil pressure of the auxiliary mast lifting cylinder 20.3 from being too high and causing the cylinder to explode.

[0040] It is worth mentioning that a fourth one-way valve 12.4 is also provided between the fifth solenoid reversing valve 5 and the fifth throttle valve 19.3, and a rotary valve 22 is also provided between the fifth throttle valve 19.3 and the oil tank. When the oil pressure in the auxiliary mast lifting cylinder 20.3 is too high, the pressure oil in the auxiliary mast lifting cylinder 20.3 can be manually released by rotating the valve 22.

[0041] Further preferably, the sub-gantry rotation motor 28 and the hydraulic pump motor 30 are connected via a third reversing valve, and the sub-gantry rotation cylinder 26 and the hydraulic pump motor 30 are connected via a fourth reversing valve.

[0042] In this embodiment, the third reversing valve includes a first, third, four-way solenoid reversing valve, and the fourth reversing valve includes a second, third, four-way solenoid reversing valve. When the sub-gantry moves to the left, the left electromagnet 8 of the first, third, four-way solenoid reversing valve is energized, and the pressure oil enters the sub-gantry rotation motor 28 through the left oil circuit; when the sub-gantry moves to the right, the right electromagnet 7 of the first, third, four-way solenoid reversing valve is energized, and the pressure oil enters the sub-gantry rotation motor 28 through the right oil circuit; and when the sub-gantry rotates to the left, the left electromagnet 10 of the second, third, four-way solenoid reversing valve is energized, and the pressure oil enters the sub-gantry rotation cylinder 26 through the left oil circuit; when the sub-gantry rotates to the right, the right electromagnet 9 of the second, third, four-way solenoid reversing valve is energized, and the pressure oil enters the sub-gantry rotation cylinder 26 through the right oil circuit.

[0043] It is worth mentioning that a fifth one-way valve 12.5 and a sixth one-way valve 12.6 are arranged between the two oil inlets of the auxiliary gantry rotating cylinder 26 and the first three-position four-way solenoid reversing valve. The outlets of the two one-way valves are respectively connected to the two oil inlets of the auxiliary gantry rotating cylinder 26, and the inlets of the two one-way valves are respectively connected to the first three-position four-way solenoid reversing valve.

[0044] It is worth mentioning that the seventh one-way valve 12.7 and the eighth one-way valve 12.8 are arranged between the two oil inlets of the sub-gantry rotation motor 28 and the second, third, four-way solenoid reversing valve. The inlets of the two one-way valves are respectively connected to the two oil inlets of the sub-gantry rotation motor 28, and the outlets of the two one-way valves are respectively connected to the second, third, four-way solenoid reversing valve.

[0045] Further preferably, an overload valve is connected between the two oil inlets of the auxiliary mast rotation motor 28 and the third reversing valve, and a balance valve is connected between the two oil inlets of the auxiliary mast rotation cylinder 26 and the fourth reversing valve.

[0046] In this embodiment, an overload valve is also connected between the sub-gantry rotation motor 28 and the third reversing valve, and the overload valve includes a first overload valve 18.1 and a second overload valve 18.2. The first overload valve 18.1 and the second overload valve 18.2 are respectively connected to the two sub-gantry rotation motors 28 and the second three-position four-way solenoid reversing valve; a balancing valve is also connected between the sub-gantry rotation cylinder 26 and the fourth reversing valve, and the balancing valve includes a first balancing valve 17.1 and a second balancing valve 17.2. The first balancing valve 17.1 and the second balancing valve 17.2 are respectively connected to the two oil inlets of the sub-gantry rotation cylinder 26, to provide overload protection for the sub-gantry rotation motor 28 and the sub-gantry rotation cylinder 26.

[0047] It is worth mentioning that the outlets of the first balancing valve 17 . 1 and the second balancing valve 17 . 2 are both connected to the first three-position four-way electromagnetic reversing valve via the second gate valve 23 .

[0048] Preferably, a pressure regulating unit is further provided between the hydraulic pump motor 30 and the auxiliary mast lifting cylinder 20.3.

[0049] Further preferably, the pressure regulating unit includes a seventh electromagnetic reversing valve 14 and a relief valve 15 , and the seventh electromagnetic reversing valve 14 is connected to the first relief valve 15 and the hydraulic pump motor 30 respectively.

[0050] In this embodiment, a pressure regulating unit is further provided between the hydraulic pump motor 30 and the auxiliary mast lifting cylinder 20.3. The pressure regulating unit includes a seventh solenoid reversing valve 14 and a relief valve 15. The seventh solenoid reversing valve 14 is connected to the first relief valve 15 and the hydraulic pump motor 30, respectively. By providing the pressure regulating unit, the oil pressure of the auxiliary mast lifting cylinder 20.3 is regulated to prevent damage to the auxiliary mast lifting cylinder 20.3 due to excessive oil pressure.

[0051] Specifically, a second relief valve 27.1 is provided between the first three-position electromagnetic reversing valve and the hydraulic pump motor 30, and a third relief valve 27.2 is provided between the second three-position four-way electromagnetic reversing valve and the hydraulic pump motor 30.

[0052] It is worth mentioning that an overload protection unit is also provided between the auxiliary gantry lifting cylinder 20.3, the auxiliary gantry rotation motor 28 and the auxiliary gantry rotation cylinder 26. The overload protection unit includes a first one-way protection valve 29.1, a second one-way protection valve 29.2, a third one-way protection valve 29.3 and a one-way stop valve 16. The first one-way protection valve 29.1 is connected to the one-way stop valve 16, the auxiliary gantry lifting cylinder 20.3 and the second one-way protection valve 29.2 respectively; the second one-way protection valve 29.2 is connected to the first three-position four-way solenoid reversing valve, the second overflow valve 27.1 and the third one-way protection valve 29.3; the third one-way protection valve 29.3 is connected to the second three-position four-way solenoid reversing valve and the third overflow valve 27.2.

[0053] It should be noted that, in the present invention, descriptions such as "first", "second", "one", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly defined. The terms "connected", "fixed", etc. should be understood in a broad sense. For example, "fixed" can be a fixed connection, a detachable connection, or an integral whole; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0054] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in this field can implement it. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0055] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Persons skilled in the art may make various modifications, additions, or substitutions to the described specific embodiments without departing from the spirit of the present invention or exceeding the scope of the appended claims.

Claims

1. A forklift potential energy recovery system, comprising a main mast lifting cylinder, a sub-mast lifting cylinder, a sub-mast rotation motor and a sub-mast rotation cylinder, characterized in that: It also includes an energy recovery and release system, which includes a hydraulic pump motor, an electric generator and a battery. The hydraulic pump motor is respectively connected to the oil tank, the main gantry lifting cylinder, the auxiliary gantry lifting cylinder, the auxiliary gantry rotation motor and the auxiliary gantry rotation cylinder. The hydraulic pump motor, the electric generator and the battery are connected in sequence; the main gantry lifting cylinder and the oil tank are connected through at least one first reversing valve, the first reversing valve includes a first solenoid reversing valve, a second solenoid reversing valve and a third solenoid reversing valve, the hydraulic pump motor, the first solenoid reversing valve, the third solenoid reversing valve and the second solenoid reversing valve They are connected in sequence, with the second solenoid reversing valve and the third solenoid reversing valve being set in the same direction, and the first solenoid reversing valve and the second solenoid reversing valve being set in different directions. When the main mast is lifted, the first solenoid reversing valve is energized, and the pressure oil flows toward the main mast lifting cylinder through the first solenoid reversing valve, the third solenoid reversing valve and the second solenoid reversing valve. At this time, the second solenoid reversing valve and the third solenoid reversing valve are in a power-off state to prevent the pressure oil from flowing back. When the main mast is lowered, the first solenoid reversing valve is de-energized, and the second and third solenoid reversing valves are energized. The pressure oil flows to the hydraulic pump motor along the second solenoid reversing valve, the third solenoid reversing valve and the first solenoid reversing valve. A motor controller is also provided between the electric generator and the battery to adjust and control the operating speed of the main mast lifting cylinder, the auxiliary mast lifting cylinder, the auxiliary mast rotation motor and the auxiliary mast rotation cylinder.

2. A forklift potential energy recovery system according to claim 1, characterized in that: Three one-way valves are arranged between the first reversing valve connected to the hydraulic pump motor and the hydraulic pump motor. The three one-way valves include a first one-way valve, a second one-way valve and a third one-way valve. The first reversing valve is connected to the outlet of the first one-way valve and the inlet of the second one-way valve respectively. The outlet of the second one-way valve is connected to the oil tank, the inlet of the first one-way valve is connected to the outlet of the third one-way valve, and the inlet of the third one-way valve is connected to the hydraulic pump motor.

3. A forklift potential energy recovery system according to claim 1 or 2, characterized in that: A first overload protection valve is provided between the first reversing valve connected to the main mast lifting cylinder and the main mast lifting cylinder.

4. A forklift potential energy recovery system according to claim 1, characterized in that: Two second reversing valves in different directions are arranged between the sub-gantry lifting cylinder and the hydraulic pump motor. The hydraulic pump motor draws pressure oil from the oil tank and flows through one of the second reversing valves to the sub-gantry lifting cylinder, and the sub-gantry lifting cylinder is lifted; when the sub-gantry lifting cylinder starts to fall back, the pressure oil flows through the other second reversing valve to the hydraulic pump motor.

5. A forklift potential energy recovery system according to claim 4, characterized in that: A second overload protection valve is provided between the auxiliary mast lifting cylinder and the two second reversing valves, and the auxiliary mast lifting cylinder is connected to the two second reversing valves respectively through the second overload protection valve.

6. A forklift potential energy recovery system according to claim 1, characterized in that: The auxiliary mast rotation motor is connected to the hydraulic pump motor via a third reversing valve, and the auxiliary mast rotation oil cylinder is connected to the hydraulic pump motor via a fourth reversing valve.

7. A forklift potential energy recovery system according to claim 6, characterized in that: An overload valve is further connected between the two oil inlets of the auxiliary gantry rotating motor and the third reversing valve, and a balance valve is further connected between the two oil inlets of the auxiliary gantry rotating cylinder and the fourth reversing valve.

8. A forklift potential energy recovery system according to claim 1, characterized in that: A pressure regulating unit is further provided between the hydraulic pump motor and the auxiliary mast lifting cylinder.

9. A forklift potential energy recovery system according to claim 8, characterized in that: The pressure regulating unit includes a seventh electromagnetic reversing valve and a first relief valve. The seventh electromagnetic reversing valve is connected to the first relief valve and the hydraulic pump motor respectively.

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