An energy recovery system for electric forklifts

Abstract

The present invention provides an energy recovery system for an electric forklift, comprising a hydraulic drive module, a control module and an energy recovery module; the hydraulic drive module comprises a lifting cylinder group, a hydraulic power unit and a three-position six-way electromagnetic reversing valve, and the hydraulic power unit is connected to the lifting cylinder group; the energy recovery module comprises a recovery cylinder group, a two-position two-way electromagnetic reversing valve, a two-position three-way electromagnetic reversing valve, a generator and a battery; a rotating mechanism is installed on the slider, and the rotating mechanism is rotated by the movement of the slider, and the rotating mechanism is connected to the generator through an electromagnetic clutch, and the control module selectively controls the engagement of the three-position six-way electromagnetic reversing valve, the two-position two-way electromagnetic reversing valve, the two-position three-way electromagnetic reversing valve and the electromagnetic clutch, so that the outlet of the lifting cylinder group is connected to the inlet of the recovery cylinder group, which is used to recover the energy of the load or the slider descending process. The present invention can effectively improve the utilization efficiency of energy and alleviate the endurance anxiety of electric forklifts.

Description

Technical Field

[0001] The invention relates to the field of electric forklifts or the field of energy conversion of lifting equipment, and in particular to an energy recovery system for electric forklifts. Background Art

[0002] With the rapid development of social economy, modern industrial logistics system has become the infrastructure to promote social development and economic construction, and it is of great significance to the formation of national economic scale and the development of modern industry. The types, frequency and scale of logistics in modern industrial logistics system are increasing rapidly. Therefore, the importance of loading and unloading is more significant. Forklifts are widely used in various places in the industrial transportation industry with their efficient handling capacity and strong operation flexibility. On the other hand, the energy crisis and the pressure of energy conservation and emission reduction are severe. The cause of energy conservation and environmental protection has vigorously promoted the transformation and upgrading of forklifts, and also put forward higher standards and requirements for the energy consumption of forklift hydraulic systems.

[0003] Traditional forklift hydraulic systems use hydraulic valves to release pressurized oil directly into the oil tank to achieve load reduction. This method causes huge energy losses for forklifts with heavy loads and frequent lifting. At present, traditional electric forklifts that are not environmentally friendly and energy-saving are common and have low energy utilization efficiency. Therefore, it is necessary to make new energy-saving designs for the lifting systems of electric forklifts, reasonably recycle and reuse their lifting potential energy, and realize energy-saving transformation of electric forklifts.

[0004] The existing energy recovery systems for electric forklifts usually use hydraulic accumulators and hydraulic motors to drive motors to generate electricity to save energy, but the technology is not yet mature, the energy recovery efficiency is difficult to guarantee, and the control is complex. It has high requirements for motors and electric motors, and the accumulator equipment is large, which affects the internal space layout of the electric forklift and the operational maneuverability of the entire vehicle. It is extremely unsuitable for installation and use in small electric forklifts. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides an energy recovery system for an electric forklift, which can effectively improve the energy utilization efficiency, alleviate the range anxiety of the electric forklift, and reduce the use cost of the electric forklift.

[0006] The present invention achieves the above technical objectives through the following technical means.

[0007] An energy recovery system for an electric forklift, comprising a hydraulic drive module, a control module and an energy recovery module;

[0008] The hydraulic drive module includes a lifting cylinder group, a hydraulic power unit and a three-position six-way electromagnetic reversing valve. The lifting cylinder group is used to lift the load. The hydraulic power unit is connected to the lifting cylinder group through the three-position six-way electromagnetic reversing valve to make the lifting cylinder group rise and fall synchronously.

[0009] The energy recovery module includes a recovery cylinder group, a two-position two-way electromagnetic reversing valve, a two-position three-way electromagnetic reversing valve, a generator and a battery; the recovery cylinder group is used to lift the slider; the inlet of the recovery cylinder group is connected with the inlet of the three-position six-way electromagnetic reversing valve through the two-position three-way electromagnetic reversing valve; the inlet of the recovery cylinder group is connected with the hydraulic oil tank through the two-position two-way electromagnetic reversing valve; a rotating mechanism is installed on the slider, and the rotating mechanism is rotated by the movement of the slider, and the rotating mechanism is connected to the generator through an electromagnetic clutch, and the battery is used to store the electrical energy generated by the motor;

[0010] The control module selectively controls the engagement of the three-position six-way electromagnetic reversing valve, the two-position two-way electromagnetic reversing valve, the two-position three-way electromagnetic reversing valve and the electromagnetic clutch to connect the outlet of the lifting cylinder group with the inlet of the recovery cylinder group, so as to recover energy during the load and / or slider descent process.

[0011] Furthermore, the hydraulic power unit includes a motor, a variable displacement hydraulic pump, a hydraulic oil tank and a second overflow valve, the motor is used to drive the variable displacement hydraulic pump, the inlet of the variable displacement hydraulic pump is connected to the hydraulic oil tank, and the outlet of the variable displacement hydraulic pump is installed with a second overflow valve; the battery is connected to the motor.

[0012] Furthermore, the interfaces of the three-position six-way solenoid reversing valve include port P, port T, port D, port A, port B and port C. The port P and port D are respectively connected to the hydraulic power unit, the port T is connected to the two-position three-way solenoid reversing valve, the port A and port C are respectively connected to the hydraulic oil tank, and the port B is connected to the lifting cylinder group.

[0013] Furthermore, a first one-way valve is installed between the recovery cylinder group inlet and the two-position three-way electromagnetic reversing valve to prevent hydraulic oil from flowing from the recovery cylinder group to the two-position three-way electromagnetic reversing valve; and a first overflow valve is installed at the recovery cylinder group inlet.

[0014] Furthermore, the hydraulic control module includes a first pressure sensor, a second pressure sensor and a control console; the first pressure sensor is used to detect the working pressure of the lifting cylinder group, and the second pressure sensor is used to detect the working pressure of the recovery cylinder group; the control console obtains the SOC value of the battery; the control console selectively controls the engagement of the three-position six-way solenoid reversing valve, the two-position two-way solenoid reversing valve, the two-position three-way solenoid reversing valve and the electromagnetic clutch according to the detection values ​​of the first pressure sensor, the second pressure sensor and the SOC value of the battery.

[0015] Furthermore, the rotating mechanism includes a screw and a transmission. The screw is installed on a slider. The screw rotates by the movement of the slider. One end of the screw is connected to the generator through the transmission. An electromagnetic clutch is installed between the transmission and the generator.

[0016] Furthermore, when a forklift is moving a load from a high place to a low place or when the forklift is descending without a load, if p r <p m And p l＞ p r When the control console controls the SB2 electromagnetic coil of the three-position six-way electromagnetic reversing valve to be energized, so that the A port is connected to the P port and the B port is connected to the T port respectively, and the control console controls the two-position three-way electromagnetic valve to connect the T port of the three-position six-way electromagnetic reversing valve to the recovery cylinder group, which is used to convert the potential energy released during the load or forklift's unloaded descent into the kinetic energy of the slider; wherein, p r is the detection value of the second pressure sensor; p m The set pressure of the first relief valve, p l is the detection value of the first pressure sensor;

[0017] When p r =p m or l ≤p r When the control console controls the SB2 electromagnetic coil of the three-position six-way electromagnetic reversing valve to be energized, so that the A port is connected to the P port and the B port is connected to the T port respectively. The control console controls the two-position three-way electromagnetic valve to reset so that the T port of the three-position six-way electromagnetic reversing valve is connected to the hydraulic oil tank, which is used to lower the load or the empty forklift to the target height.

[0018] Furthermore, when SOC <SOC m , and p r >0, the console controls the electromagnetic clutch to engage, and the movement of the slider causes the rotating mechanism to rotate, thereby driving the generator to charge the battery; SOC is the SOC value of the battery obtained by the console, SOC m The SOC value when the battery is overcharged; the control console controls the two-position two-way electromagnetic reversing valve to connect the inlet of the recovery cylinder group with the hydraulic oil tank;

[0019] When SOC ≥ SOC m or p r =0, the console controls the two-position two-way solenoid valve to block the recovery cylinder group inlet from connecting with the hydraulic oil tank, the console controls the two-position three-way solenoid valve to connect the T port of the three-position six-way solenoid reversing valve with the hydraulic oil tank, and the console controls the electromagnetic clutch to disconnect.

[0020] The beneficial effects of the present invention are:

[0021] 1. The electric forklift energy recovery system of the present invention can recover the potential energy of the goods through the movable slider when the electric forklift moves the goods from a high place to a low place, and convert the recovered potential energy into electrical energy by driving the generator with a screw to store it in the battery, thereby improving the energy utilization efficiency.

[0022] 2. The electric forklift energy recovery system of the present invention can alleviate the problems of electric forklift range anxiety and high use cost. The recovered energy is converted into electrical energy to charge the battery, reducing the charging time and use cost of the forklift.

[0023] 3. The electric forklift energy recovery system described in the present invention recovers the potential energy during the load lowering process through the slider, which reduces the throttling loss of the hydraulic valve compared with the traditional valve control system, avoids the overheating of the hydraulic system components due to throttling, increases the life of the hydraulic valve, reduces the leakage loss of the hydraulic system, and further improves the energy recovery efficiency.

[0024] 4. The electric forklift energy recovery system described in the present invention is an independent recovery process in which the potential energy in the slider is released to charge the battery. This process is less affected by the working conditions of the electric forklift. At the same time, the slider descent speed can be adjusted according to the generator model to improve the charging efficiency of the generator.

[0025] 5. The electric forklift energy recovery system of the present invention can use sliders of different weights to match electric forklifts with different rated load capacities, and the product coverage is wide. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. The drawings described below are some embodiments of the present invention. For ordinary technicians in this field, it is obvious that other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 This is a schematic diagram of the energy recovery system for an electric forklift according to the present invention.

[0028] Figure 2 This is a schematic diagram of the load reduction energy recovery principle of the present invention.

[0029] Figure 3 This is a load reduction principle diagram of the present invention.

[0030] Figure 4 This is a schematic diagram of the slider descending auxiliary charging principle of the present invention.

[0031] Figure 5 This is a load increase principle diagram of the present invention.

[0032] In the figure:

[0033] 1-motor; 2-speed sensor; 3-ECU; 4-variable displacement hydraulic pump; 5-second one-way valve; 6-hydraulic oil tank; 7-second overflow valve; 8-three-position six-way electromagnetic reversing valve; 11-first pressure sensor; 12-first lifting cylinder; 13-second lifting cylinder; 14-load; 16-control console; 17-slider; 18-screw; 19-first recovery cylinder; 20-second recovery cylinder; 22-first overflow valve; 23-second pressure sensor; 24-transmission; 25-generator; 26-inverter; 27-battery; 28-two-position two-way electromagnetic reversing valve; 30-two-position two-way electromagnetic reversing valve; 32-electromagnetic clutch; 33-first one-way valve. DETAILED DESCRIPTION

[0034] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

[0035] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0036] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "axial", "radial", "vertical", "horizontal", "inner", "outer" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0037] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0038] like Figure 1 As shown, the electric forklift energy recovery system of the present invention includes a hydraulic drive module, a control module and an energy recovery module;

[0039] The hydraulic drive module includes a first lifting cylinder 12, a second lifting cylinder 13, a hydraulic power unit and a three-position six-way electromagnetic reversing valve 8. The first lifting cylinder 12 and the second lifting cylinder 13 are respectively installed at the bottom of the load 14. The hydraulic power unit includes a motor 1, a variable displacement hydraulic pump 4, a hydraulic oil tank 6 and a second relief valve 7. The motor 1 is used to drive the variable displacement hydraulic pump 4. The inlet of the variable displacement hydraulic pump 4 is connected to the hydraulic oil tank 6. A second one-way valve 5 is installed between the inlet of the variable displacement hydraulic pump 4 and the hydraulic oil tank 6. A second relief valve 7 is installed at the outlet of the variable displacement hydraulic pump 4. The battery 27 is connected to the motor 1. A speed sensor 2 is installed on the input shaft of the variable displacement hydraulic pump 4 to detect the speed of the variable displacement hydraulic pump 4. The interfaces of the three-position six-way electromagnetic reversing valve 8 include a P port, a T port, a D port, an A port, a B port and a C port. The P port and the D port are respectively connected to the hydraulic power unit, the T port is connected to the two-position three-way electromagnetic reversing valve 30, the A port and the C port are respectively connected to the hydraulic oil tank 6, and the B port is respectively connected to the first lifting cylinder 12 and the second lifting cylinder 13. The first lifting cylinder 12 and the second lifting cylinder 13 can be regarded as connected in parallel between the B port and the load 14. The hydraulic power unit is connected to the first lifting cylinder 12 and the second lifting cylinder 13 through the three-position six-way electromagnetic reversing valve 5, so as to make the first lifting cylinder 12 and the second lifting cylinder 13 rise and fall synchronously;

[0040] The energy recovery module includes a first recovery cylinder 19, a second recovery cylinder 20, a two-position two-way electromagnetic reversing valve 28, a two-position three-way electromagnetic reversing valve 30, a generator 25 and a battery 27; the first recovery cylinder 19 and the second recovery cylinder 20 are used to synchronously lift the slider 17; the inlets of the first recovery cylinder 19 and the second recovery cylinder 20 are connected to the inlet of the three-position six-way electromagnetic reversing valve 8 through the two-position three-way electromagnetic reversing valve 30; the inlets of the first recovery cylinder 19 and the second recovery cylinder 20 are connected to the hydraulic oil tank 6 through the two-position two-way electromagnetic reversing valve 28; the slider 17 is installed The rotating mechanism rotates by moving the slider 17. The rotating mechanism is connected to the generator 25 through an electromagnetic clutch 32. The generator 25 is connected to the battery 27 through an inverter 26 and is used to store the electric energy generated by the motor 25. A first check valve 33 is installed between the inlet of the first recovery cylinder 19 and the second recovery cylinder 20 and the two-position three-way electromagnetic reversing valve 30 to prevent the hydraulic oil from flowing from the first recovery cylinder 19 and the second recovery cylinder 20 to the two-position three-way electromagnetic reversing valve 30. A first overflow valve 22 is installed at the inlet of the first recovery cylinder 19 and the second recovery cylinder 20.

[0041] The rotating mechanism includes a screw 18 and a transmission 24. The screw 18 is installed on the slider 17. The screw 18 rotates by the movement of the slider 17. One end of the screw 18 is connected to the generator 25 through the transmission 24. An electromagnetic clutch 32 is installed between the transmission 24 and the generator 25.

[0042] The control module includes a first pressure sensor 11, a second pressure sensor 23 and a control console 16; the first pressure sensor 11 is used to detect the working pressure of the first lifting cylinder 12 and the second lifting cylinder 13, and the second pressure sensor 23 is used to detect the working pressure of the first recovery cylinder 19 and the second recovery cylinder 20; the control console 16 obtains the SOC value of the battery 27; the control console 16 selectively controls the engagement of the three-position six-way electromagnetic reversing valve 8, the two-position two-way electromagnetic reversing valve 28, the two-position three-way electromagnetic reversing valve 30 and the electromagnetic clutch 32 according to the detection values ​​of the first pressure sensor 11 and the second pressure sensor 16 and the SOC value of the battery 27, so that the outlets of the first lifting cylinder 12 and the second lifting cylinder 13 are connected to the inlets of the first recovery cylinder 19 and the second recovery cylinder 20, so as to recover the energy of the load 10 and / or the slider 17 during the descending process.

[0043] The following is a specific description of the operation mode of the potential energy recovery system of an electric forklift by analyzing five typical operating conditions, namely, load reduction, no-load reduction, load increase, no-load increase, and transportation conditions. The embodiments are used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by technicians in this field based on the above contents of the present invention also fall within the scope of protection of the present invention.

[0044] like Figure 2 As shown, when a forklift is moving a load from a high place to a low place or when the forklift is descending empty, if p r <p m And p l＞ p r When the control console 16 controls the SB2 electromagnetic coil of the three-position six-way electromagnetic reversing valve 8 to be energized, so that the A port is connected to the P port and the B port is connected to the T port respectively, and the control console 16 controls the two-position three-way electromagnetic valve 30 to connect the T port of the three-position six-way electromagnetic reversing valve 8 to the first recovery cylinder 19 and the second recovery cylinder 20, and the control console 16 controls the two-position two-way electromagnetic reversing valve 28 to reset to block the inlet of the first recovery cylinder 19 and the second recovery cylinder 20 from being connected to the hydraulic oil tank 6, so as to convert the potential energy released during the unloaded descent of the load 14 or the forklift into the kinetic energy of the slider 17; wherein, p r is the detection value of the second pressure sensor 23; p m The pressure of the first relief valve 22 is set, p l is the detection value of the first pressure sensor 11;

[0045] When p r =p m or l ≤p r When the control console 16 controls the SB2 electromagnetic coil of the three-position six-way electromagnetic reversing valve 8 to be energized, so that the A port is connected to the P port and the B port is connected to the T port respectively. The control console 16 controls the two-position three-way electromagnetic valve 30 to reset so that the T port of the three-position six-way electromagnetic reversing valve 8 is connected to the hydraulic oil tank 6, so as to lower the load 14 or the unloaded forklift to the target height. Figure 3 shown.

[0046] like Figure 4 As shown, when SOC <SOC m , and p r >0, the console 16 controls the electromagnetic clutch 32 to engage, and the console 16 controls the two-position two-way electromagnetic reversing valve 28 to connect the inlet of the first recovery cylinder 19 and the second recovery cylinder 20 to the hydraulic oil tank 6, and the movement of the slider 17 causes the rotating mechanism to rotate, thereby driving the generator 25 to charge the battery 27; SOC is the SOC value of the battery 27 obtained by the console 16, SOC m The SOC value when the battery 27 is overcharged; when SOC ≥ SOC m or p r =0, the control console 16 controls the two-position two-way solenoid valve 28 to reset and block the inlet of the first recovery cylinder 19 and the second recovery cylinder 20 from being connected to the hydraulic oil tank 6, the control console 16 controls the two-position three-way solenoid valve 30 to connect the T port of the three-position six-way solenoid reversing valve 8 to the hydraulic oil tank 6, and the control console 16 controls the electromagnetic clutch 32 to be disconnected. Figure 5 shown.

[0047] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0048] The series of detailed descriptions listed above are only specific descriptions of feasible embodiments of the present invention. They are not intended to limit the scope of protection of the present invention. All equivalent embodiments or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. An energy recovery system for an electric forklift, characterized in that: It includes a hydraulic drive module, a control module and an energy recovery module; The hydraulic drive module comprises a lifting cylinder group (12, 13), a hydraulic power unit and a three-position six-way electromagnetic reversing valve (8); the lifting cylinder group (12, 13) is used to lift a load (14); the hydraulic power unit is connected to the lifting cylinder group (12, 13) via the three-position six-way electromagnetic reversing valve (8) and is used to make the lifting cylinder group (12, 13) rise and fall synchronously; The energy recovery module comprises a recovery cylinder group (19, 20), a two-position two-way electromagnetic reversing valve (28), a two-position three-way electromagnetic reversing valve (30), a generator (25) and a battery (27); the recovery cylinder group (19, 20) is used to lift the slider (17); the inlet of the recovery cylinder group (19, 20) is connected to the inlet of the three-position six-way electromagnetic reversing valve (8) through the two-position three-way electromagnetic reversing valve (30); the inlet of the recovery cylinder group (19, 20) is connected to the hydraulic oil tank (6) through the two-position two-way electromagnetic reversing valve (28); a rotating mechanism is installed on the slider (17), and the rotating mechanism is rotated by the movement of the slider (17); the rotating mechanism is connected to the generator (25) through the electromagnetic clutch (32), and the battery (27) is used to store the electric energy generated by the motor (25); The control module selectively controls the engagement of a three-position six-way electromagnetic reversing valve (8), a two-position two-way electromagnetic reversing valve (28), a two-position three-way electromagnetic reversing valve (30) and an electromagnetic clutch (32), so that the outlet of the lifting cylinder group (12, 13) is connected to the inlet of the recovery cylinder group (19, 20), so as to recover energy during the descending process of the load (10) and / or the slider (17).

2. The electric forklift energy recovery system according to claim 1, characterized in that: The hydraulic power unit comprises a motor (1), a variable displacement hydraulic pump (4), a hydraulic oil tank (6) and a second overflow valve (7); the motor (1) is used to drive the variable displacement hydraulic pump (4); the inlet of the variable displacement hydraulic pump (4) is connected to the hydraulic oil tank (6); the outlet of the variable displacement hydraulic pump (4) is provided with a second overflow valve (7); the battery (27) is connected to the motor (1).

3. The electric forklift energy recovery system according to claim 1, characterized in that: The interfaces of the three-position six-way electromagnetic reversing valve (8) include a P port, a T port, a D port, an A port, a B port and a C port, wherein the P port and the D port are respectively connected to the hydraulic power unit, the T port is connected to the two-position three-way electromagnetic reversing valve (30), the A port and the C port are respectively connected to the hydraulic oil tank (6), and the B port is connected to the lifting cylinder group (12, 13).

4. The electric forklift energy recovery system according to claim 1, characterized in that: A first check valve (33) is installed between the inlet of the recovery cylinder group (19, 20) and the two-position three-way electromagnetic reversing valve (30) to prevent hydraulic oil from flowing from the recovery cylinder group (19, 20) to the two-position three-way electromagnetic reversing valve (30); a first overflow valve (22) is installed at the inlet of the recovery cylinder group (19, 20).

5. The electric forklift energy recovery system according to claim 3, characterized in that: The control module comprises a first pressure sensor (11), a second pressure sensor (23) and a control console (16); the first pressure sensor (11) is used to detect the working pressure of the lifting cylinder group (12, 13), and the second pressure sensor (23) is used to detect the working pressure of the recovery cylinder group (19, 20); the control console (16) obtains the SOC value of the battery (27); the control console (16) selectively controls the engagement of the three-position six-way electromagnetic reversing valve (8), the two-position two-way electromagnetic reversing valve (28), the two-position three-way electromagnetic reversing valve (30) and the electromagnetic clutch (32) according to the detection values ​​of the first pressure sensor (11), the second pressure sensor (23) and the SOC value of the battery (27).

6. The electric forklift energy recovery system according to claim 1, characterized in that: The rotating mechanism comprises a screw (18) and a transmission (24); the screw (18) is mounted on a slider (17); the screw (18) rotates through movement of the slider (17); one end of the screw (18) is connected to a generator (25) through the transmission (24); an electromagnetic clutch (32) is installed between the transmission (24) and the generator (25).

7. The electric forklift energy recovery system according to claim 5, characterized in that: When a forklift is moving a load from a high place to a low place or when the forklift is descending without a load, p r <p m and p l＞ p r When the control console (16) controls the SB2 electromagnetic coil of the three-position six-way electromagnetic reversing valve (8) to be energized, so that the A port is connected to the P port and the B port is connected to the T port respectively, and the control console (16) controls the two-position three-way electromagnetic reversing valve (30) to connect the T port of the three-position six-way electromagnetic reversing valve (8) to the recovery cylinder group (19, 20), so as to convert the potential energy released during the load (14) or the forklift's unloaded descent into the kinetic energy of the slider (17); wherein, p r is the detection value of the second pressure sensor (23); p m Set the pressure of the first relief valve (22), p l is the detection value of the first pressure sensor (11); when p r =p m or p l ≤ p r When the control console (16) controls the SB2 electromagnetic coil of the three-position six-way electromagnetic reversing valve (8) to be energized, so that the A port is connected to the P port and the B port is connected to the T port respectively. The control console (16) controls the two-position three-way electromagnetic reversing valve (30) to be reset so that the T port of the three-position six-way electromagnetic reversing valve (8) is connected to the hydraulic oil tank (6), so as to lower the load (14) or the unloaded forklift to the target height.

8. The electric forklift energy recovery system according to claim 7, characterized in that: when SOC< SOC m ,and p r > At 0, the control console (16) controls the electromagnetic clutch (32) to engage, and the movement of the slider (17) causes the rotating mechanism to rotate, thereby driving the generator (25) to charge the battery (27); SOC Get the SOC value of the battery (27) for the console (16), SOC m When overcharging the battery (27) SOC value; when SOC ≥ SOC m or p r =0, the control console (16) controls the two-position two-way electromagnetic reversing valve (28) to block the inlet of the recovery cylinder group (19, 20) from being connected to the hydraulic oil tank (6), the control console (16) controls the two-position three-way electromagnetic reversing valve (30) to connect the T port of the three-position six-way electromagnetic reversing valve (8) to the hydraulic oil tank (6), the control console (16) controls the two-position two-way electromagnetic reversing valve (28) to connect the inlet of the recovery cylinder group (19, 20) to the hydraulic oil tank (6), and the control console (16) controls the electromagnetic clutch (32) to be disconnected.

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