CN114776672A - An electric forklift energy recovery system - Google Patents

Abstract

The invention provides an energy recovery system for an electric forklift, including a hydraulic drive module, a control module and an energy recovery module; the hydraulic drive module includes a lift cylinder group, a hydraulic power unit and a three-position six-way electromagnetic reversing valve. The hydraulic power unit is communicated with the lifting cylinder group; 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; a rotating mechanism is installed on the slider, Through the movement of the slider, the rotating mechanism is rotated, and the rotating mechanism is connected with the generator through the electromagnetic clutch. The control module selectively controls the three-position six-way electromagnetic reversing valve, the two-position two-way electromagnetic reversing valve, the two The engagement of the three-way electromagnetic reversing valve and the electromagnetic clutch makes the outlet of the lifting cylinder group communicate with the inlet of the recovery cylinder group, which is used to recover the energy of the load or the sliding block descending process. The invention can effectively improve the utilization efficiency of energy and relieve the anxiety of the electric forklift.

Description

An electric forklift energy recovery system

technical field

The invention relates to the field of electric forklifts or the field of energy conversion of lifting equipment, in particular to an electric forklift energy recovery system.

Background technique

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

The traditional forklift hydraulic system uses the hydraulic valve to directly release the pressure oil to the fuel tank to achieve load reduction. This method has a huge energy loss due to the heavy load of the forklift and the working characteristics of frequent lifting. At present, traditional electric forklifts that are not environmentally friendly and energy-saving are common, and the energy utilization efficiency is low. Therefore, it is necessary to carry out a new energy-saving design for the lifting system of the electric forklift, reasonably recycle its lifting potential energy, and realize the energy-saving transformation of the electric forklift.

At present, the existing electric forklift energy recovery system usually uses hydraulic accumulator and hydraulic motor to drive the motor to generate electricity to save energy. However, the technology is not yet mature, the energy recovery efficiency is difficult to guarantee, and the control is complicated. The requirements are high and the accumulator equipment is huge, which affects the internal space layout of the electric forklift and the operation mobility of the whole vehicle. It is extremely unsuitable for the installation and use of small electric forklifts.

SUMMARY OF THE INVENTION

In view of the deficiencies in the prior art, the present invention provides an electric forklift energy recovery system, which can effectively improve the energy utilization efficiency, relieve the anxiety of the electric forklift's battery life, and reduce the use cost of the electric forklift.

The present invention achieves the above technical purpose through the following technical means.

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

The hydraulic drive module includes a lift cylinder group, a hydraulic power unit and a three-position six-way electromagnetic reversing valve. The lift cylinder group is used to lift and lower loads, and the hydraulic power unit is connected with the three-position six-way electromagnetic reversing valve. The lift cylinder group is connected to make the lift cylinder group go up and down synchronously;

The energy recovery module includes a recovery oil 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 oil cylinder group is used for lifting the slider; the recovery oil cylinder group inlet The two-position three-way electromagnetic reversing valve is communicated with the inlet of the three-position six-way electromagnetic reversing valve; the inlet of the recovery oil 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. , the rotating mechanism is rotated by the movement of the slider, the rotating mechanism is connected with the generator through the electromagnetic clutch, and the battery is used to store the electric energy generated by the motor;

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 and recovery of the lift cylinder group are connected. The cylinder bank inlet is connected to recover the energy of the load and/or slide down process.

Further, the hydraulic power unit includes a motor, a variable displacement hydraulic pump, a hydraulic oil tank and a second relief valve, the motor is used to drive the variable displacement hydraulic pump, and the variable displacement hydraulic pump inlet is communicated with the hydraulic oil tank, A second overflow valve is installed at the outlet of the variable displacement hydraulic pump; the battery is connected to the motor.

Further, the interfaces of the three-position six-way electromagnetic reversing valve include P port, T port, D port, A port, B port and C port, the P port and D port are respectively connected with the hydraulic power unit, the T port The port is communicated with the two-position three-way electromagnetic reversing valve, the A port and the C port are respectively communicated with the hydraulic oil tank, and the B port is communicated with the lift cylinder group.

Further, a first check valve is installed between the inlet of the recovery oil cylinder group and the two-position three-way electromagnetic reversing valve to prevent hydraulic oil from flowing from the recovery oil cylinder group to the two-position three-way electromagnetic reversing valve; the recovery oil cylinder group The first overflow valve is installed at the inlet.

Further, the hydraulic control module includes a first pressure sensor, a second pressure sensor and a console; the first pressure sensor is used to detect the working pressure of the lift cylinder group, and the second pressure sensor is used to detect the work of the recovery cylinder group pressure; the console obtains the SOC value of the battery; the console selectively controls the three-position six-way electromagnetic reversing valve, two-position The engagement of the two-way electromagnetic reversing valve, the two-position three-way electromagnetic reversing valve and the electromagnetic clutch.

Further, the rotating mechanism includes a screw and a transmission, the screw is installed on the slider, the screw is rotated by the movement of the slider, one end of the screw is connected to the generator through the transmission, and an electromagnetic field is installed between the transmission and the generator. clutch.

Further, when the forklift transports the load from a high place to a low place or the forklift is unloaded, if p _r < p _m and p _{l >} p _r , the console controls the SB2 solenoid of the three-position six-way solenoid reversing valve. The coil is energized, so that the A port and the P port and the B port and the T port are respectively connected. Convert the potential energy released during the no-load descent of the load or the forklift into the kinetic energy of the slider; where _pr is the detection value of the second pressure sensor; pm is the set pressure of the first relief valve, and _{p l} is the first pressure The detection value of the sensor;

When p _r = p _m or p _l ≤ p _r , the console controls the SB2 electromagnetic coil of the three-position six-way electromagnetic directional valve to be energized, so that the A port and the P port and the B port and the T port are respectively connected, so The console controls the reset of the two-position three-way solenoid valve to make the T port of the three-position six-way solenoid reversing valve communicate with the hydraulic oil tank, which is used to lower the load or the forklift to the target height with no load.

Further, when SOC<SOC _m and p _r >0, the console controls the electromagnetic clutch to engage, and the rotary mechanism is rotated through the movement of the slider to drive the generator to charge the battery; SOC is the SOC value of the battery obtained by the console , SOC _m is the SOC value when the battery is overcharged; the console controls the two-position two-way electromagnetic reversing valve to make the inlet of the recovery cylinder group communicate with the hydraulic oil tank;

When SOC≥SOC _m or p _r =0, the console controls the two-position two-way solenoid valve to block the connection between the inlet of the recovery cylinder group and the hydraulic oil tank, and the console controls the two-position three-way solenoid valve to make the three-position six-way The T port of the electromagnetic reversing valve is communicated with the hydraulic oil tank, and the console controls the electromagnetic clutch to be disconnected.

The beneficial effects of the present invention are:

1. The electric forklift energy recovery system of the present invention can recover the potential energy of the goods through the movable slider during the process of the electric forklift transporting the goods from a high place to a low place, and the recovered potential energy is driven by a screw drive generator to generate electricity. It is converted into electrical energy and stored in the battery, which improves the utilization efficiency of energy.

2. The electric forklift energy recovery system of the present invention can alleviate the problems of electric forklift cruising range anxiety and high use cost, the recovered energy is converted into electric energy to charge the battery, and the charging time and use cost of the forklift are reduced.

3. The electric forklift energy recovery system of the present invention recovers the potential energy during the load drop process through the slider, reduces the throttling loss of the hydraulic valve compared with the traditional valve control system, and avoids the excessive temperature of the hydraulic system components due to throttling. The service life of the hydraulic valve is improved, the leakage loss of the hydraulic system is reduced, and the energy recovery efficiency is further improved.

4. In the electric forklift energy recovery system of the present invention, the process of charging the battery by releasing the potential in the slider is an independent recovery process, which is less affected by the working conditions of the electric forklift, and the slider can be adjusted according to the generator model. Decrease the speed and improve the charging efficiency of the generator.

5. The electric forklift energy recovery system of the present invention can use sliders with different weights to match electric forklifts with different rated load capacities, and the product coverage is wide.

Description of drawings

In order to illustrate the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. The drawings in the following description are of the present invention. In some embodiments, it is obvious to those of ordinary skill in the art that other drawings can be obtained according to these drawings without any creative effort.

FIG. 1 is a schematic diagram of an electric forklift energy recovery system according to the present invention.

FIG. 2 is a schematic diagram of the load drop energy recovery according to the present invention.

FIG. 3 is a schematic diagram of the load drop according to the present invention.

FIG. 4 is a schematic diagram of the auxiliary charging principle of the slider descending according to the present invention.

FIG. 5 is a schematic diagram of the load rising according to the present invention.

In the picture:

1-motor; 2-speed sensor; 3-ECU; 4-variable displacement hydraulic pump; 5-second one-way valve; 6-hydraulic oil tank; 7-second relief valve; 8-three-position six-way electromagnetic switch Directional valve; 11-first pressure sensor; 12-first lift cylinder; 13-second lift cylinder; 14-load; 16-console; 17-slider; 18-screw; 19-first recovery cylinder ; 20- The second recovery cylinder; 22- The first relief valve; 23- The second pressure sensor; 24- Transmission; 25- Generator; 26- Inverter; Direction valve; 30-two-position two-way electromagnetic reversing valve; 32-electromagnetic clutch; 33-first one-way valve.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

The following describes in detail the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary, and are intended to explain the present invention and should not be construed as limiting the present invention.

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "axial", The orientation or positional relationship indicated by "radial", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description , rather than indicating or implying that the indicated device or element must have a particular orientation, be constructed and operate in a particular orientation, and therefore should not be construed as limiting the invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and should not be construed as indicating or implying relative importance or implying the number of indicated technical features. Thus, a feature defined as "first" or "second" may expressly or implicitly include one or more of that feature. In the description of the present invention, "plurality" means two or more, unless otherwise expressly and specifically defined.

In the present invention, unless otherwise expressly specified and limited, the terms "installed", "connected", "connected", "fixed" and other terms should be understood in a broad sense, for example, it may be a fixed connection or a detachable connection , or integrally connected; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or the internal communication between the two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

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

The hydraulic drive module includes a first lift cylinder 12, a second lift cylinder 13, a hydraulic power unit and a three-position six-way electromagnetic reversing valve 8. The first lift cylinder 12 and the second lift 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, and the variable displacement hydraulic pump 4. The inlet of the displacement hydraulic pump 4 is communicated with the hydraulic oil tank 6, a second check valve 5 is installed between the inlet of the variable displacement hydraulic pump 4 and the hydraulic oil tank 6, and the outlet of the variable displacement hydraulic pump 4 is installed with a second relief valve 7; the battery 27 is connected to the motor 1 . A rotational speed sensor 2 is installed on the input shaft of the variable displacement hydraulic pump 4 for detecting the rotational speed of the variable displacement hydraulic pump 4 . The interfaces of the three-position six-way electromagnetic reversing valve 8 include P port, T port, D port, A port, B port and C port, the P port and D port are respectively connected with the hydraulic power unit, and the T port is It is communicated with the two-position three-way electromagnetic reversing valve 30 , the A port and the C port are respectively communicated with the hydraulic oil tank 6 , and the B port is respectively communicated with the first lift cylinder 12 and the second lift cylinder 13 . The first lift cylinder 12 and the second lift cylinder 13 can be regarded as being connected in parallel between port B and the load 14 . The hydraulic power unit communicates with the first lift cylinder 12 and the second lift cylinder 13 through the three-position six-way electromagnetic reversing valve 5, so as to make the first lift cylinder 12 and the second lift cylinder 13 ascend and descend synchronously;

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 The oil cylinder 19 and the second recovery oil cylinder 20 are used to lift the slider 17 synchronously; the inlets of the first recovery oil cylinder 19 and the second recovery oil cylinder 20 pass through the two-position three-way electromagnetic reversing valve 30 and the three-position six-way electromagnetic reversing valve 8 The inlet of the first recovery cylinder 19 and the second recovery cylinder 20 are communicated with the hydraulic oil tank 6 through the two-position two-way electromagnetic reversing valve 28; The rotating mechanism is rotated, and the rotating mechanism is connected with the generator 25 through the electromagnetic clutch 32, and the generator 25 is connected with the battery 27 through the inverter 26 for storing the electric energy generated by the motor 25; the first recovery cylinder 19 A first check valve 33 is installed between the inlet of the second recovery cylinder 20 and the two-position three-way electromagnetic reversing valve 30 to prevent hydraulic oil from flowing from the first recovery cylinder 19 and the second recovery cylinder 20 to the two-position three-way solenoid The reversing valve 30; the first relief valve 22 is installed at the inlet of the first recovery oil cylinder 19 and the second recovery oil cylinder 20.

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

The control module includes a first pressure sensor 11, a second pressure sensor 23 and a console 16; the first pressure sensor 11 is used to detect the working pressure of the first lift cylinder 12 and the second lift cylinder 13, and the first Two pressure sensors 23 are used to detect the working pressure of the first recovery cylinder 19 and the second recovery cylinder 20; the console 16 obtains the SOC value of the battery 27; The detected value of the battery 27 and the SOC value of the battery 27 are selected to selectively control 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, The outlets of the first lift cylinder 12 and the second lift cylinder 13 are communicated with the inlets of the first recovery cylinder 19 and the second recovery cylinder 20 for recovering the energy of the load 10 and/or the sliding block 17 during the descending process.

The following is a detailed description of the operation mode of the electric forklift potential energy recovery system from the analysis of five typical operating conditions of the electric forklift load drop, no-load drop, load rise, no-load rise, and transportation conditions as examples, and the examples are used for the present invention. Further description should not be construed as limiting the protection scope of the present invention, and some non-essential improvements and adjustments made by those skilled in the art according to the content of the present invention also belong to the protection scope of the present invention.

As shown in FIG. 2 , when the forklift transports the load from a high place to a low place or the forklift is unloaded, if p _r < p _m and p _{l >} p _r , the console 16 controls the three-position six-way electromagnetic switch. The SB2 solenoid coil of the valve 8 is energized, so that the A port and the P port and the B port and the T port are respectively connected. The port is communicated with the first recovery cylinder 19 and the second recovery cylinder 20. The console 16 controls the reset of the two-position two-way electromagnetic reversing valve 28 to block the inlet of the first recovery cylinder 19 and the second recovery cylinder 20 and the hydraulic oil tank. 6 is connected to convert the potential energy released during the load 14 or the forklift’s no-load descent into the kinetic energy of the slider 17; wherein _pr is the detection value of the second pressure sensor 23; _pm is the adjustment of the first relief valve 22 constant pressure, p _l is the detection value of the first pressure sensor 11;

When p _r = p _m or p _l ≤ p _r , the 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 and the P port and the B port and the T port are respectively connected , the console 16 controls the reset of the two-position three-way solenoid valve 30 to make the T port of the three-position six-way solenoid reversing valve 8 communicate with the hydraulic oil tank 6, so as to lower the load 14 or the forklift to the target height without load, as shown in the figure 3 shown.

As shown in FIG. 4 , when SOC<SOC _m and _pr >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 make the first recovery cylinder 19 and the inlet of the second recovery oil cylinder 20 are communicated with the hydraulic oil tank 6, and the rotation mechanism is rotated by the movement of the slider 17 to drive the generator 25 to charge the battery 27; SOC is the SOC value of the battery 27 obtained by the console 16, and SOC _m is the battery 27 SOC value when overcharging; when SOC≥SOC _m or p _r =0, the 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 and the hydraulic oil tank 6 is connected, the console 16 controls the two-position three-way solenoid valve 30 to make the T port of the three-position six-way electromagnetic reversing valve 8 communicate with the hydraulic oil tank 6, and the console 16 controls the electromagnetic clutch 32 to disconnect, as shown in Figure 5 shown.

It should be understood that although this specification is described according to various embodiments, not each embodiment only includes an independent technical solution, and this description in the specification is only for the sake of clarity, and those skilled in the art should take the specification as a whole , the technical solutions in each embodiment can also be appropriately combined to form other implementations that can be understood by those skilled in the art.

The series of detailed descriptions listed above are only specific descriptions for the feasible embodiments of the present invention, and they are not intended to limit the protection scope of the present invention. Changes should all be included within the protection scope of the present invention.

Claims (8)

1. An electric forklift energy recovery system, characterized in that, comprising a hydraulic drive module, a control module and an energy recovery module; The hydraulic drive module includes a lift cylinder group (12, 13), a hydraulic power unit and a three-position six-way electromagnetic reversing valve (8), and the lift cylinder group (12, 13) is used for lifting a load (14) , the hydraulic power unit is communicated with the lift cylinder group (12, 13) through a three-position six-way electromagnetic reversing valve (8), so as to make the lift cylinder group (12, 13) synchronously lift; The energy recovery module includes a recovery oil 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 oil cylinder group (19, 20) is used to lift the sliding block (17); the inlet of the recovery oil cylinder group (19, 20) passes through a two-position three-way electromagnetic reversing valve (30) and a three-position six-way electromagnetic reversing valve The inlet of the valve (8) is communicated; the inlet of the recovery oil cylinder group (19, 20) is communicated with the hydraulic oil tank (6) through a two-position two-way electromagnetic reversing valve (28); a rotating mechanism is installed on the slider (17) , the rotation mechanism is rotated by the movement of the slider (17), the rotation mechanism is connected with the generator (25) through the electromagnetic clutch (32), and the battery (27) is used to store the electrical energy generated by the motor (25); The control module selectively controls 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) The engagement of the lift cylinders (12, 13) makes the outlet of the lift cylinder group (12, 13) communicate with the inlet of the recovery cylinder group (19, 20) for recovering the energy in the descending process of the load (10) and/or the slider (17). 2. The electric forklift energy recovery system according to claim 1, wherein the hydraulic power unit comprises 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 communicated with the hydraulic oil tank (6), the variable displacement hydraulic pump (4) ) A second overflow valve (7) is installed at the outlet; 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 P port, T port, D port, A port, B port and C port, the P port and the D port are respectively connected with the hydraulic power unit, the T port is connected with the two-position three-way electromagnetic reversing valve (30), the A port and the C port are respectively connected with the hydraulic oil tank (6) , the B port is communicated with the lift cylinder group (12, 13). 4. The electric forklift energy recovery system according to claim 1, wherein a first check valve is installed between the inlet of the recovery cylinder group (19, 20) and the two-position three-way electromagnetic reversing valve (30). (33), for preventing hydraulic oil from flowing from the recovery cylinder group (19, 20) to the two-position three-way electromagnetic reversing valve (30); a first relief 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, wherein the control module comprises a first pressure sensor (11), a second pressure sensor (23) and a console (16); the first pressure sensor (11) The pressure sensor (11) is used to detect the working pressure of the lift 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 console (16) Acquiring the SOC value of the battery (27); the console (16) selectively controls three bits according to the detected values of the first pressure sensor (11), the second pressure sensor (16) and the SOC value of the battery (27) Engagement of the 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). 6. The electric forklift energy recovery system according to claim 1, wherein the rotating mechanism comprises a screw (18) and a transmission (24), the screw (18) is mounted on the slider (17), The movement of the slider (17) causes the screw (18) to rotate, and one end of the screw (18) is connected to the generator (25) through the transmission (24), and an electromagnetic field is installed between the transmission (24) and the generator (25). clutch (32). 7 . The electric forklift energy recovery system according to claim 5 , wherein when the forklift transports the load from a high place to a low place or the forklift is no-loaded, if p _r < p _m and p _{l >} p _r , the console (16) controls the SB2 solenoid coil of the three-position six-way electromagnetic reversing valve (8) to be energized, so that the A port and the P port and the B port and the T port are respectively connected, and the console (16) controls The two-position three-way solenoid valve (30) communicates the T port of the three-position six-way electromagnetic reversing valve (8) with the recovery cylinder group (19, 20), so as to release the load (14) or the forklift during the no-load lowering process. The potential energy is converted into the kinetic energy of the slider (17); wherein, p _r is the detection value of the second pressure sensor (23); p _m is the set pressure of the first relief valve (22), and p _l is the first pressure sensor (11) detection value; When p _r = p _m or p _l ≤ p _r , the console (16) controls the SB2 solenoid coil of the three-position, six-way solenoid reversing valve (8) to be energized, so that the A port and the P port and the B port are connected to each other. The T ports are respectively connected, and the console (16) controls the reset of the two-position three-way solenoid valve (30) so that the T port of the three-position six-way solenoid reversing valve (8) is communicated with the hydraulic oil tank (6), so as to connect the load to the hydraulic oil tank (6). (14) or the forklift descends to the target height with no load. 8. The electric forklift energy recovery system according to claim 7, characterized in that, when SOC< _SOCm , and _pr >0, the console (16) controls the electromagnetic clutch (32) to engage, and the sliding block The movement of (17) makes the rotating mechanism rotate to drive the generator (25) to charge the battery (27); SOC is the SOC value of the battery (27) obtained by the console (16), and SOC _m is the SOC when the battery (27) is overcharged value; When SOC≥SOC _m or p _r =0, the console (16) controls the two-position two-way solenoid valve (28) to block the communication between the inlet of the recovery cylinder group (19, 20) and the hydraulic oil tank (6). The console (16) controls the two-position three-way solenoid valve (30) to make the T port of the three-position six-way electromagnetic reversing valve (8) communicate with the hydraulic oil tank (6), and the console (16) controls the two-position two-way The electromagnetic reversing valve (28) communicates the inlet of the recovery oil cylinder group (19, 20) with the hydraulic oil tank (6), and the console (16) controls the electromagnetic clutch (32) to be disconnected.

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