A forklift lifting hydraulic oil circuit with descending potential energy regeneration

Abstract

The present invention discloses a forklift lifting hydraulic oil circuit with descending potential energy regeneration, which includes a descending potential energy regeneration oil circuit, wherein the descending potential energy regeneration oil circuit includes a high-pressure energy storage oil circuit and a low-pressure energy storage oil circuit that work alternately. The lifting hydraulic oil circuit can recover most of the forklift's descending potential energy, thereby effectively reducing the forklift's energy consumption, solving the technical problems of high cost and high consumption caused by the large installed power of existing forklifts, improving the economy and service life of the entire forklift, and reducing environmental pollution.

Description

Technical Field

[0001] The invention belongs to the field of forklifts, and in particular relates to a forklift lifting hydraulic oil circuit with descending potential energy regeneration. Background Art

[0002] A forklift refers to a variety of wheeled handling vehicles used for loading and unloading, stacking and short-distance transportation of palletized goods. It is a commonly used lifting tool, usually driven by an engine 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] However, when the current forklifts are lowering with lifted cargo or when they are lowering empty, the mast, fork frame, shelf, cargo, etc. are at a high position, and the potential energy they possess is collectively referred to as gravitational potential energy. The mechanical energy generated by these gravitational potential energies when they are lowering is not recycled or reused, but is directly converted into thermal energy of the forklift hydraulic oil by the lifting cylinder, hydraulic valve, etc., and discharged into the surrounding environment. Therefore, the existing forklifts have the following problems: 1. High manufacturing cost: Due to a single lifting operation, the forklift needs to provide sufficient hydraulic energy, which is converted into the gravitational potential energy of the cargo through its lifting cylinder, and due to the requirement of operating efficiency, the required power is relatively large. For internal combustion forklifts, the installed power of the engine is relatively large, and the specifications of the engine's auxiliary facilities such as the cooling system, fuel system, intake and exhaust system, etc. also need to be increased accordingly, which increases the cost; and for electric forklifts, the power requirements of its motors and their controllers, batteries and other major components also need to be increased accordingly, resulting in high construction costs; ② Poor economic efficiency: As mentioned above, due to the increase in power, it is bound to lead to increased fuel consumption, or insufficient battery life and long downtime for charging, resulting in higher overall machine cost; ③ High thermal balance temperature of hydraulic oil: Existing forklifts have a high thermal conductivity, which is more expensive than conventional forklifts. Every time the vehicle descends, the potential energy of the cargo is completely converted into hydraulic energy. Since the hydraulic energy is not recycled and is directly converted into heat energy, the thermal equilibrium temperature of the hydraulic oil of the forklift is high; ④ Large impact on the ambient temperature: hydraulic energy is converted into heat energy and discharged into the surrounding environment, causing the ambient temperature to rise; ⑤ Reduced service life of the forklift: Since the installed power of the forklift is relatively high, the power it needs to transmit is relatively high, and the life of components with the same strength is bound to be affected; ⑥ Poor environmental protection: The increase in the installed capacity of the forklift will inevitably lead to higher energy consumption and a sharp increase in emissions. Summary of the invention

[0004] In view of this, it is necessary for the present invention to provide a forklift lifting hydraulic oil circuit with descending potential energy regeneration, which can recover most of the forklift's descending potential energy, thereby effectively reducing the forklift's energy consumption, solving the technical problems of high cost and high consumption caused by the large installed power of existing forklifts, improving the economy and service life of the forklift as a whole, and reducing environmental pollution.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention discloses a forklift lifting hydraulic oil circuit with descending potential energy regeneration, which includes a lifting oil circuit, a tilting oil circuit and a shutdown unloading oil circuit, and also includes:

[0007] The descending potential energy recovery oil circuit includes a high-pressure energy storage oil circuit that transports the hydraulic oil in the lifting cylinder to the high-pressure accumulator through a multi-way valve when the forklift is lowered under load, and a low-pressure energy storage oil circuit that transports the hydraulic oil in the lifting cylinder to the low-pressure accumulator through the multi-way valve when the forklift is lowered without load. The multi-way valve includes a lifting valve plate, and the lifting valve plate is connected to a valve-controlled switch. A descending speed limiting cut-off valve is also connected between the lifting valve plate and the lifting cylinder.

[0008] Furthermore, the lifting oil circuit is a hydraulic pump that delivers the hydraulic oil in the hydraulic oil tank to the lifting oil cylinder through the multi-way valve;

[0009] The tilt oil route is a hydraulic pump that delivers the hydraulic oil in the hydraulic tank to the tilt oil cylinder via the multi-way valve, and the tilt oil cylinder then returns the oil to the hydraulic oil tank;

[0010] The shutdown unloading oil circuit is a circuit in which the hydraulic pump transfers the hydraulic oil in the hydraulic oil tank back to the hydraulic oil tank through the multi-way valve.

[0011] Furthermore, the multi-way valve also includes a tilting valve plate, and the A and B oil ports of the tilting valve plate are respectively connected to the rod chamber and the rodless chamber of the tilting cylinder.

[0012] Furthermore, in the lifting oil circuit, a first one-way valve is connected to the inlet end of the hydraulic pump.

[0013] Furthermore, an oil suction filter is connected between the first one-way valve and the hydraulic oil tank.

[0014] Furthermore, a second one-way valve is provided between the multi-way valve and the descending potential energy recovery oil circuit for transporting the hydraulic oil in the lifting cylinder to the high-pressure accumulator or the low-pressure accumulator, and the A port of the second one-way valve is connected to the lifting valve plate.

[0015] Furthermore, the high-pressure energy storage oil circuit includes:

[0016] High-pressure accumulator;

[0017] A first electromagnetic ball valve, whose port A is connected to the high-pressure accumulator and the port B of the second one-way valve;

[0018] An adjustable flow valve, whose port A is connected to the port B of the first electromagnetic ball valve, and whose port B is connected to the inlet end of the hydraulic pump;

[0019] A high-pressure unloading valve, wherein the B port thereof is connected to the hydraulic oil tank, and the A port thereof is connected between the high-pressure accumulator and the first electromagnetic ball valve.

[0020] Furthermore, the low-pressure energy storage oil circuit includes:

[0021] Low pressure accumulator;

[0022] A second electromagnetic ball valve, whose B port is respectively connected to the high-pressure accumulator, the A port of the first electromagnetic ball valve, and the B port of the second one-way valve, and whose A port is connected to the low-pressure accumulator;

[0023] The low-pressure unloading valve has a B port connected to the hydraulic oil tank, and an A port connected to the A ports of the low-pressure accumulator and the second electromagnetic ball valve respectively.

[0024] Furthermore, the high-pressure accumulator and the low-pressure accumulator are both elastic accumulators.

[0025] Furthermore, an overflow valve is provided between the outlet end of the hydraulic pump and the hydraulic oil tank, one end of the overflow valve is connected between the tilting valve plate and the hydraulic oil tank, and the other end of the overflow valve is connected between the lifting valve plate and the hydraulic pump.

[0026] Compared with the prior art, the hydraulic oil circuit in the present invention has the following beneficial effects:

[0027] The forklift lifting hydraulic oil circuit in the present invention can recover most of the forklift's descending potential energy. Compared with conventional forklift hydraulic systems, it can effectively reduce the forklift's energy consumption, thereby further reducing the forklift's fuel consumption and use costs, and effectively reduce the installed capacity of the forklift as a whole, reduce the forklift's manufacturing cost, and because the installed capacity is reduced, the reduction in emissions can reduce environmental pollution, meeting environmental protection requirements; because most of the descending potential energy is recovered, the thermal equilibrium temperature of the forklift hydraulic system can be effectively reduced, thereby increasing the service life of the forklift as a whole. Furthermore, the forklift lifting hydraulic oil circuit in the present invention also has the advantages of easy maintenance and safety, which can effectively reduce the forklift's failure downtime rate and ensure smooth handling and stacking operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the hydraulic oil circuit for lifting a forklift in a preferred embodiment of the present invention;

[0029] Figure 2 When the forklift is lifted for the first time Figure 1 The hydraulic oil flow diagram of the lifting hydraulic oil circuit of the forklift;

[0030] Figure 3 The hydraulic oil flow diagram of the high-pressure accumulator 4 storing energy as the forklift load decreases;

[0031] Figure 4 The hydraulic oil flow diagram is when the high-pressure accumulator 4 has stored energy and the forklift is not lifting for the first time;

[0032] Figure 5 The hydraulic oil flow diagram of the forklift descending without load and the low-pressure accumulator 14 storing energy;

[0033] Figure 6 The low-pressure accumulator 14 has stored energy and the hydraulic oil flow diagram is when the forklift is not lifting for the first time;

[0034] Figure 7 It is the relationship curve between the internal pressure and the lifting and lowering of the forklift when the high-pressure accumulator 4 and the low-pressure accumulator 14 are working.

[0035] In the figure: 1-gravitational potential energy source, 2-lifting cylinder, 3-valve-controlled switch, 4-high-pressure accumulator, 5-first electromagnetic ball valve, 6-adjustable flow valve, 7-hydraulic oil tank, 8-oil suction filter, 9-first non-return valve, 10-hydraulic pump, 11-overflow valve, 12-second non-return valve, 13-second electromagnetic ball valve, 14-low-pressure accumulator, 15-multi-way valve, 16-tilting cylinder, 17-descending speed limit cut-off valve, 18-high-pressure unloading valve, 19-low-pressure unloading valve. DETAILED DESCRIPTION

[0036] For ease of understanding of the present invention, the present invention will be described more fully below in conjunction with specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly understood.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0038] like Figure 1 As shown in the figure, this embodiment discloses a forklift lifting hydraulic oil circuit with descending potential energy regeneration, which includes a lifting oil circuit, a tilting oil circuit, a shutdown unloading oil circuit and a descending potential energy regeneration oil circuit.

[0039] Among them, Figure 1As shown in , the lifting oil circuit includes a hydraulic oil tank 7, an oil suction filter 8, a first non-return valve 9, a hydraulic pump 10, a multi-way valve 15, a descending speed limit cut-off valve 17, and a lifting oil cylinder 2 connected in sequence, so that the hydraulic oil in the hydraulic oil tank 7 can be transported to the lifting oil cylinder 2 through the hydraulic pump 10 and the multi-way valve 15. It should be noted that the piston rod of the lifting oil cylinder 2 is connected with a gravity potential energy source 1, and the gravity potential energy source 1 here refers to the general term for objects with gravity potential energy, which mainly includes the inner mast, fork frame, shelf, fork, pallet, cargo, etc. of the forklift, which are the general term for objects with gravity potential energy when they are generally in a high position. It can be understood that the inner mast, fork frame, shelf, fork, etc. are inherent devices of the forklift. Each time they are operated, they move simultaneously with the operation, and their weight will not change, which is called fixed gravity potential energy; and each operation may change due to the different weights of the pallets and cargoes used, which is called variable gravity potential energy. It can be seen that the weight of the gravitational potential energy source 1 is the sum of the weight of the fixed gravitational potential energy source and the variable gravitational potential energy source. That is to say, when the forklift lifts the heavy object to a fixed height, the descending potential energy it possesses is different with the weight of the pallet and the cargo, and is a variable. Furthermore, the multi-way valve 15 includes a lifting valve plate 151 and a tilting valve plate 152. The multi-way valve 15 in the lifting oil circuit is mainly a lifting valve plate 151 connected between the descending speed limit cut-off valve 17 and the hydraulic pump 10. Furthermore, the lifting valve plate 151 is also connected to a valve-controlled switch 3. The valve-controlled switch 3 here has two pairs of normally open contacts. The lifting valve plate 151 is actuated to trigger the contacts to be connected, thereby causing the first electromagnetic ball valve 5 or the second electromagnetic ball valve 13 to be actuated. Specifically, the two pairs of contacts of the valve-controlled switch 3 are installed in the middle position of the valve core of the lifting valve plate 151, and the contacts are triggered to be connected or disconnected by the action of the valve core of the lifting valve plate 151.

[0040] Please continue reading Figure 1The tilt oil circuit includes a tilt oil cylinder 16, a multi-way valve 15, a relief valve 11, a hydraulic pump 10, a first non-return valve 9, an oil suction filter 8, and a hydraulic oil tank 7, which are connected in sequence. Specifically, the tilt oil cylinder 16 is connected to the tilt valve plate 152 in the multi-way valve 15. Specifically, the A and B oil ports of the tilt valve plate 152 are respectively connected to the rod chamber and the rodless chamber of the tilt oil cylinder 16. When the valve stem is pushed or pulled, the hydraulic oil flows from the hydraulic oil tank 7 through the oil suction filter 8, the first non-return valve 9, the hydraulic pump 10, the lifting valve plate 151, and the tilt valve plate 152 into the tilt oil cylinder 16 under the action of the hydraulic pump 10, and the return oil of the tilt oil cylinder 16 flows back to the hydraulic oil tank 7 through the T port of the tilt valve plate 152, thereby realizing the forward and backward tilting action of the forklift mast. Furthermore, the relief valve 11 is connected between the outlet end of the hydraulic pump 10 and the hydraulic oil tank 7, one end of the relief valve 11 is connected between the tilting valve plate 152 and the hydraulic oil tank 7, and the other end of the relief valve 11 is connected between the lifting valve plate 151 and the hydraulic pump 10. Mainly when the forklift is overloaded, it is used to limit the outlet pressure of the hydraulic pump 10 to not be higher than the maximum working pressure, avoid damage to the forklift and danger, and reduce the shutdown failure rate of the forklift and safety accidents caused by overload lifting.

[0041] Please continue reading Figure 1 The forklift lifting hydraulic oil circuit in this embodiment also includes a descending potential energy regeneration oil circuit. A second one-way valve 12 is provided between the multi-way valve 15 and the descending potential energy recovery oil circuit for transporting the hydraulic oil in the lifting cylinder 2 to the high-pressure accumulator 4 or the low-pressure accumulator 14. The A port of the second one-way valve 12 is connected to the lifting valve plate 151. The descending potential energy regeneration oil circuit mainly includes a high-pressure energy storage oil circuit and a low-pressure energy storage oil circuit that work alternately, wherein the high-pressure energy storage oil circuit includes a high-pressure accumulator 4, a first electromagnetic ball valve 5 and an adjustable flow valve 6 that are connected in sequence. Specifically, the high-pressure accumulator 4 is connected to the A port of the first electromagnetic ball valve 5, the B port of the first electromagnetic ball valve 5 is connected to the A port of the adjustable flow valve 6, the B port of the adjustable flow valve 6 is connected to the inlet end of the hydraulic pump 10, and the A port of the first electromagnetic ball valve 5 is also connected to the B port of the second one-way valve 12, so that when the load of the forklift decreases, the hydraulic oil in the lifting cylinder 2 is transported to the high-pressure accumulator 4 through the descending speed limit cut-off valve 17, the multi-way valve 15, and the second one-way valve 12, and when the high-pressure accumulator 4 has stored energy and the forklift is not lifted for the first time, the hydraulic oil in the high-pressure accumulator 4 is transported to the lifting cylinder 2 through the first electromagnetic ball valve 5, the adjustable flow valve 6, the hydraulic pump 10, and the multi-way valve 15. The high-pressure energy storage oil circuit also includes a high-pressure unloading valve 18 , the B port of the high-pressure unloading valve 18 is connected to the hydraulic oil tank 7 , and the A port thereof is connected between the high-pressure accumulator 4 and the second one-way valve 12 .

[0042] Further, the low-pressure energy storage oil circuit includes a low-pressure accumulator 14 and a second electromagnetic ball valve 13, the A port of the second electromagnetic ball valve 13 is connected to the low-pressure accumulator 14, and the B port thereof is connected to the B port of the second one-way valve 12, so that when the forklift is lowered without load, the hydraulic oil in the lifting cylinder 2 is delivered to the low-pressure accumulator 14 through the multi-way valve 15 and the second one-way valve 12, and when the low-pressure accumulator 14 has stored energy and the forklift is not lifted for the first time, the hydraulic oil in the low-pressure accumulator 14 is delivered to the lifting cylinder 2 through the second electromagnetic ball valve 13, the first electromagnetic ball valve 5, the adjustable flow valve 6, the hydraulic pump 10, and the multi-way valve 15. Further, the low-pressure energy storage oil circuit also includes a low-pressure unloading valve 19, the B port of the low-pressure unloading valve 19 is connected to the hydraulic oil tank 7, and the A port thereof is connected between the low-pressure accumulator 14 and the second electromagnetic ball valve 13. In addition, the high-pressure unloading valve 18 and the low-pressure unloading valve 19 in this embodiment are both manual unloading valves. When the forklift stops working, the high-pressure unloading valve 18 and the low-pressure unloading valve 19 are manually switched to release the hydraulic oil inside the high-pressure accumulator 4 and the low-pressure accumulator 14 to avoid shutdown in the energy storage state and generate danger; and when the first electromagnetic ball valve 5 fails and the forklift cannot be lowered or a temporary emergency operation is required, the high-pressure unloading valve 18 can be manually switched to the right position, the high-pressure unloading valve 18 is turned on, and the multi-way valve 15 lifts the valve plate The T port of 151 is connected to the hydraulic oil tank 7 through the second one-way valve 12 and the high-pressure unloading valve 18, and the high-pressure hydraulic oil inside the high-pressure accumulator 4 flows back to the hydraulic oil tank 7 through the high-pressure unloading valve 18, and the high-pressure accumulator 4 will no longer store energy, and then the lifting valve plate 151 is pushed forward to lift the valve stem to the final end, so that the second pair of contacts of the valve-controlled switch 3 is closed, the second electromagnetic ball valve 13 is turned on, and the hydraulic oil inside the low-pressure accumulator 14 flows back to the hydraulic oil tank 7 through the second electromagnetic ball valve 13 and the high-pressure unloading valve 18. In addition, after the high-pressure unloading valve 18 is manually switched to the right position, the T port of the lifting valve plate 151 is connected to the hydraulic oil tank 7 through the second one-way valve 12 and the high-pressure unloading valve 18, and the hydraulic oil circuit of the present invention will no longer have the energy storage and regeneration function, and is equivalent to the conventional forklift lifting hydraulic circuit function, and does not affect the continued use of the forklift.

[0043] Furthermore, regarding the selection of the high-pressure accumulator 4 and the low-pressure accumulator 14 in the descending potential energy regeneration oil circuit, the commonly used hydraulic accumulators are divided into elastic accumulators and gravity accumulators, among which the elastic accumulators can also be divided into gas bladder accumulators and spring accumulators according to the structure. Although the output hydraulic oil pressure of the gravity accumulator is a straight curve, and the working characteristic curve is more in line with the requirements of this patent, due to the complex structure and relatively large volume of the gravity accumulator, the installation space of the forklift is limited. Therefore, in this embodiment, it is preferred to use an elastic accumulator to store the hydraulic energy generated by the descent of the forklift. As the forklift mast descends, the gravity potential energy is released and converted into the hydraulic energy of the hydraulic oil. The pressure value inside the elastic accumulator will gradually increase until the forklift stops descending, and the pressure inside the accumulator will no longer increase. In this embodiment, two elastic accumulators are used to store hydraulic energy, namely the high-pressure accumulator 4 and the low-pressure accumulator 14. By switching the work, the no-load descending potential energy and the descending potential energy under the load working state are recovered respectively.

[0044] The technical solution of the present invention will be described more clearly and completely below in conjunction with the working state of the hydraulic oil circuit in this embodiment.

[0045] Those skilled in the art know that when a forklift is performing a lifting operation, the weight of the cargo it normally loads and unloads does not exceed the rated lifting capacity of the forklift, and more than 90% of the operating conditions are less than three-quarters of the rated lifting capacity, of which the no-load operating condition and the loaded operating condition each account for 50%. When performing a lifting operation, the hydraulic pump 10 is in a loaded working state and outputs high-pressure hydraulic oil; when descending or stationary, the hydraulic pump 10 is in an unloading working state, that is, during operation, regardless of whether the forklift is performing a lifting operation, the hydraulic pump remains in operation. The working states of the forklift mast lifting operation include loaded lifting, no-load descending, no-load lifting, loaded descending, loaded stationary, and no-load stationary. When the forklift is loading and unloading, the high-pressure unloading valve 18 and the low-pressure unloading valve 19 are manually switched so that the two are in a disconnected state, cutting off the oil flow back to the hydraulic oil tank 7, thereby preventing the pressure oil inside the lifting cylinder 2 from flowing back to the hydraulic oil tank 7 through the descending speed limiting cut-off valve 17, the lifting valve plate 151, and the high-pressure unloading valve 18 when the forklift mast descends, thereby preventing energy loss.

[0046] When the forklift is in a non-lifting working state, the high-pressure unloading valve 18 and the low-pressure unloading valve 19 are in a disconnected state, the lifting valve plate 151 of the multi-way valve 15 is in a neutral position, the two pairs of contacts of the valve-controlled switch 3 are both disconnected, the first electromagnetic ball valve 5 and the second electromagnetic ball valve 13 are both de-energized, and the hydraulic pump 10 draws hydraulic oil from the hydraulic oil tank 7. The hydraulic oil flows directly back to the hydraulic oil tank 7 after passing through the oil suction filter 8, the first check valve 9, the hydraulic pump 10, the lifting valve plate 151 of the multi-way valve 15, and the tilting valve plate 152. At this time, the hydraulic pump 10 is in a no-load unloading state.

[0047] When the forklift is lifted for the first time, when the lifting valve stem of the multi-way valve 15 is pulled backward, the lifting valve plate 151 of the multi-way valve 15 is switched to the right position, the hydraulic oil input of the tilting valve plate 152 is disconnected, and the hydraulic pump 10 extracts the hydraulic oil in the hydraulic oil tank 7 through the oil suction filter 8 and the first non-return valve 9 to reach the lifting valve plate 151 of the multi-way valve 15, and then passes through the descending speed limiting cut-off valve 17 to enter the lower chamber of the lifting cylinder 2, thereby lifting the gravity potential energy source 1 to achieve the first lifting of the forklift. For the specific oil flow direction, see Figure 2 .

[0048] When the forklift is loaded and descends, the lifting valve plate 151 of the multi-way valve 15 is pushed forward to lift the valve stem, and the descending speed limit cut-off valve 17 is connected to the second one-way valve 12 through the lifting valve plate 151. The hydraulic oil in the lower chamber of the lifting cylinder 2 flows into the high-pressure accumulator 4 through the descending speed limit cut-off valve 17, the lifting valve plate 151, and the second one-way valve 12. The high-pressure accumulator 4 is compressed, and after the valve stem of the lifting valve plate 151 returns to the middle position, the filling is stopped to achieve the purpose of energy storage. It should be noted that the second one-way valve 12 is provided to ensure that when the valve stem returns to the middle position, the hydraulic oil does not flow back to the lifting valve plate 151 and cause energy loss; and because the second solenoid ball valve 13 is in a power-off state, the high-pressure hydraulic oil that is cut off from returning flows into the low-pressure accumulator 14 and causes energy loss. In the specific hydraulic circuit, the flow direction of the hydraulic oil refers to Figure 3 .

[0049] The high-pressure accumulator 4 has been charged. When the forklift is not lifting for the first time, the hydraulic pump 10 works, pulling the lifting valve stem of the multi-way valve 15 backward, and the lifting valve plate 151 of the multi-way valve 15 is switched to the right position. The hydraulic oil input of the tilting valve plate 152 is disconnected, and the hydraulic oil at the outlet of the hydraulic pump 10 passes through the lifting valve plate 151 and the descending speed limit cut-off valve 17 in sequence, and enters the lower chamber of the lifting cylinder 2 to lift the heavy object. The valve core of the lifting valve plate 151 is pressed into the valve body, and the first contact of the valve control switch 3 is connected to send a signal, so that the first electromagnetic ball valve 5 is energized and switched to the left position, and the first electromagnetic ball valve 5 is connected with the high-pressure accumulator 4. At this time, the oil inside the high-pressure accumulator 4 passes through the first electromagnetic ball valve 5 and the adjustable throttle valve 6, and enters the suction port of the hydraulic pump 10, and a positive pressure is established at the suction port of the hydraulic pump 10. The hydraulic oil passes through the hydraulic pump 10, the lifting valve plate 151, and the descending speed limit cut-off valve 17 to enter the lifting cylinder 2, and lift the gravity potential energy source 1. The first non-return valve 9 prevents the hydraulic oil from flowing back from the high-pressure accumulator 4 to the suction port of the hydraulic pump 10 and flowing back to the hydraulic oil tank 7 to release pressure, which can effectively prevent the loss of hydraulic energy. The adjustable flow valve 6 can adjust the flow rate of the returning hydraulic oil to prevent excessive flow from causing damage to the hydraulic pump 10 due to excessive speed and instability of its power source load. As the pressure difference between the suction port of the hydraulic pump 10 and its outlet decreases, the load of the hydraulic pump 10 also decreases accordingly, and the power required for lifting is reduced accordingly, reducing energy consumption and achieving the purpose of energy regeneration. For the specific flow direction of the hydraulic oil in the hydraulic oil circuit, see Figure 4 .

[0050] When the forklift is lowered without load, and the fork frame does not move when lowering without load, it is necessary to continue to push the valve stem of the lifting valve plate 151 forward, and the valve core drives the second contact of the valve-controlled switch 3 to close, and the second electromagnetic ball valve 13 is energized and switched to the right position, and the second electromagnetic ball valve 13 is turned on and connected to the low-pressure accumulator 14. Under the action of the gravity potential energy source 1, the oil in the lower chamber of the lifting cylinder 2 flows into the low-pressure accumulator 14 through the descending speed limiting cut-off valve 17, the lifting valve plate 151, the second one-way valve 12, and the second electromagnetic ball valve 13. The low-pressure accumulator 14 is compressed, and after the valve stem returns to the center, the second contact of the valve-controlled switch 3 is disconnected, the second electromagnetic ball valve 13 loses power, and the filling stops, thereby achieving the purpose of energy storage. For specific hydraulic oil flow directions, please refer to Figure 5 However, the set starting pressure of the high-pressure accumulator 4 is equal to the switching pressure and cannot be effectively compressed. Therefore, the hydraulic oil cannot be filled into the high-pressure accumulator 4.

[0051] When the low-pressure accumulator 14 has stored energy and the forklift is not performing the first lifting operation, the hydraulic pump 10 works and continues to pull the lifting valve stem of the multi-way valve 15 backward. The lifting valve plate 151 of the multi-way valve 15 switches to the right position, and the pressure oil input of the tilting valve plate 152 is cut off. The hydraulic oil at the outlet of the hydraulic pump 10 passes through the lifting valve plate 151 and the descending speed limit cut-off valve 17 and enters the lower chamber of the lifting oil cylinder 2 to lift the heavy object. Under the action of the lifting valve stem of the lifting valve plate 151, the second contact of the valve-controlled switch 3 remains connected, and the first contact is connected to send a signal, that is, the two pairs of contacts of the valve-controlled switch 3 are connected, so that the second electromagnetic ball valve 13 is actuated and switched to the right position for conduction. At this time, the oil in the low-pressure accumulator 14 passes through the second electromagnetic ball valve 13, the first electromagnetic ball valve 5, and the adjustable throttle valve 6 in sequence, and enters the suction port of the hydraulic pump 10, and a positive pressure is established at the suction port of the hydraulic pump 10, and then passes through the lifting valve plate 151 and the descending speed limit cut-off valve 17, and enters the lower chamber of the lifting cylinder 2. For the specific flow direction of the hydraulic oil, see Figure 6 . And due to the function of the first non-return valve 9, it prevents the hydraulic oil from the low-pressure accumulator 14 from flowing back to the hydraulic oil tank 7 to release pressure, which can effectively prevent the loss of hydraulic energy. The adjustable flow valve 6 can adjust the flow rate of the returning hydraulic oil to prevent excessive flow from causing damage to the hydraulic pump 10 due to excessive speed and instability of its power source load. As the pressure difference of the hydraulic oil between the suction port and the outlet of the hydraulic pump 10 becomes smaller, the load of the hydraulic pump 10 also becomes smaller accordingly, and the power required for lifting is reduced accordingly, reducing energy consumption and achieving the purpose of energy regeneration.

[0052] It should be particularly noted that, regarding the determination of the working switching point pressure values ​​of the high-pressure accumulator 4 and the low-pressure accumulator 14, since the gravitational potential energy of the fixed gravitational potential energy is a fixed value within a certain relative working height range, in order to more effectively recover this part of the energy, it is preferred that the pressure value generated inside the low-pressure accumulator 14 when the forklift is unloaded and lowered from the highest position to the lowest point is determined as the working switching pressure value of the high-pressure accumulator 4 and the low-pressure accumulator 14.

[0053] The working pressure range of the high-pressure accumulator 4 is set accordingly according to the tonnage of the forklift, wherein the minimum starting working pressure setting value is equal to the working pressure switching value, and the maximum working pressure is set to the forklift half-loaded from the highest position to the end point, and the high-pressure accumulator 4 can be effectively compressed to fully store the high-pressure hydraulic oil returned by the lifting cylinder 2. At this time, the pressure value inside the high-pressure accumulator 4 is equal to the pressure value of the lower chamber of the lifting cylinder 2 when the lifting cylinder 2 is half-loaded and stationary in the middle position; the effective working energy storage volume of the high-pressure accumulator 4 is greater than the total volume of the hydraulic oil returned by the lifting cylinder 2 when the forklift lifting cylinder 2 drops from the highest position to the lowest position.

[0054] The working pressure range of the low-pressure accumulator 14 is also set accordingly according to the tonnage of the forklift. The highest working pressure is the pressure switching value; the lowest starting working pressure is adjusted so that the forklift can be lowered from the highest position to the end point without load, and the low-pressure accumulator 14 can be compressed to completely store the high-pressure hydraulic oil returned by the lifting cylinder 2, and the pressure value inside the low-pressure accumulator 14 at this time is equal to the pressure value of the lower chamber of the lifting cylinder 2 when the lifting cylinder 2 is in an unloaded state and stationary in the middle position. Adjust the starting pressure value of the low-pressure accumulator 14, and set its initial starting pressure value to the accumulator working pressure value when the lifting cylinder 2 initially moves from the highest position in this state, as the lowest starting pressure value; the effective working energy storage volume of the low-pressure accumulator 14 is greater than the total volume of the hydraulic oil returned by the lifting cylinder 2 when the forklift lifting cylinder 2 drops from the highest position to the lowest position.

[0055] The change of specific accumulator pressure can be combined with Figure 7 , Figure 7 In the figure, P is the pressure value inside the accumulator; P0 is the starting pressure of the low-pressure accumulator; P1 is the working switching pressure value of the high-pressure and low-pressure accumulators, and is also the maximum working pressure of the low-pressure accumulator and the starting pressure of the high-pressure accumulator; P2 is the maximum working pressure of the high-pressure accumulator; h is the height of the mast of the forklift; h0 is the height of the center of mass of the gravity potential energy source 1 when the forklift fork is lowered to the bottom; h1 is the height of the center of mass of the gravity potential energy source 1 when the forklift fork is lifted to the top. Among them, a is the energy storage curve of the high-pressure accumulator, b is the pressure release curve of the high-pressure accumulator, c is the energy storage curve of the low-pressure accumulator, and d is the pressure release curve of the low-pressure accumulator.

[0056] When the forklift load decreases and the load is greater than half load, the valve stem of the lifting valve plate 151 is pushed forward, the fork descends, and the center of mass position of the gravitational potential energy source 1 gradually decreases from h1 to h0. The pressure oil pressure P inside the lifting cylinder 2 is greater than the switching pressure value P1, and the high-pressure accumulator 4 starts to store energy and stores all the pressure oil returning from the lifting cylinder 2. At this time, the low-pressure accumulator 14 does not work. As the fork descends, the pressure inside the high-pressure accumulator 4 gradually increases. When it drops to the lowest point, the pressure value P inside the high-pressure accumulator 4 is less than the maximum working pressure value P2 of the high-pressure accumulator 4. When the forklift is fully loaded and drops from h1 to h0, the pressure inside the high-pressure accumulator reaches the maximum working pressure P2 of the high-pressure accumulator 4, thereby achieving the purpose of using the high-pressure accumulator 4 to store hydraulic energy.

[0057] When the forklift is unloaded, the valve stem of the lifting valve plate 151 is pushed forward, the fork descends, and the center of mass position of the gravitational potential energy source 1 gradually decreases from h1 to h0. The pressure oil pressure P inside the lifting cylinder 2 is greater than P0 and lower than the switching pressure P1. As the valve core of the multi-way valve 15 continues to be withdrawn, the second contact of the valve-controlled switch 3 is closed, the second electromagnetic ball valve 13 is turned on, and the low-pressure accumulator 14 begins to store energy, storing all the pressure oil returned from the lifting cylinder 2, and the high-pressure accumulator 4 does not work. When it drops to the lowest point, the pressure value inside the low-pressure accumulator 14 is less than the switching pressure value P1; when the forklift load is equal to half load and drops from h1 to h0, the pressure inside the low-pressure accumulator 14 is equal to the switching pressure P1, achieving the purpose of using the low-pressure accumulator 14 to store hydraulic energy.

[0058] When the forklift load is less than half load, the valve stem of the lifting valve plate 151 is pushed forward, the fork descends, and the center of mass position of the gravitational potential energy source 1 gradually decreases from h1 to between h0 and h1 and stops. The pressure oil pressure P inside the lifting cylinder 2 is greater than the switching pressure P1 and lower than P2. The high-pressure accumulator 4 stores energy and stops as the fork stops descending. As the valve core of the multi-way valve 15 continues to be withdrawn, the second contact of the valve-controlled switch 3 closes, the second electromagnetic ball valve 13 is turned on, and the low-pressure accumulator 14 starts to store energy, storing the residual pressure oil returned from the lifting cylinder 2. The pressure oil stored in the high-pressure accumulator 4 flows back to the low-pressure accumulator 14 at the same time. When it descends to the lowest point, the pressure value inside the low-pressure accumulator 14 is equal to the switching pressure value P1.

[0059] The high-pressure accumulator 4 has stored energy. When the forklift is lifted, the valve stem of the lifting valve plate 151 is pulled backwards, and the forks rise. At this time, the valve core is pressed in, and the first contact of the valve-controlled switch 3 is pressed down to close, and the first electromagnetic ball valve 5 is electrically connected. The pressure oil inside the high-pressure accumulator 4 reaches the oil suction port of the hydraulic pump 10 through the first electromagnetic ball valve 5 and the adjustable flow valve 6, and then is pressurized by the hydraulic pump 10 and sent to the lifting cylinder 2 through the multi-way valve 15 and the descending speed limit cut-off valve 17, lifting the gravity potential energy source 1, completing the reuse of the hydraulic energy inside the high-pressure accumulator 4.

[0060] The low-pressure accumulator 14 has stored energy. When the forklift is lifted, the valve stem of the lifting valve plate 151 is pulled backwards, and the fork rises. The valve core is pressed in, the first contact of the valve-controlled switch 3 is pressed down and closed, and the first electromagnetic ball valve 5 is electrically conductive. The valve stem of the lifting valve plate 151 is continuously pulled, and the valve core is continuously pressed in, the second contact of the valve-controlled switch 3 is pressed down and closed, and the second electromagnetic ball valve 13 is conductive. The pressure oil inside the low-pressure accumulator 14 reaches the oil suction port of the hydraulic pump 10 through the second electromagnetic ball valve 13, the first electromagnetic ball valve 5, and the adjustable flow valve 6, and then after being pressurized by the hydraulic pump 10, it is sent to the lifting cylinder 2 through the multi-way valve 15 and the descending speed limit cut-off valve 17, lifting the gravity potential energy source 1, and completing the reuse of the hydraulic energy inside the low-pressure accumulator 14.

[0061] When the forklift stops working, the high-pressure unloading valve 18 and the low-pressure unloading valve 19 are manually switched to release the internal pressure oil of the high-pressure accumulator 4 and the low-pressure accumulator 14 to avoid shutdown in the energy storage state and generate danger.

[0062] In addition, in the present invention, the pressure difference at both ends of the descending speed limit cut-off valve 17 is significantly reduced, so the compression degree of the working spring inside the descending speed limit cut-off valve 17 is significantly reduced when the forklift descends, which can effectively improve the working life of the descending speed limit cut-off valve 17. When the forklift is overloaded, the relief valve 11 works to adjust the pump outlet pressure to the maximum working pressure to avoid damage to the forklift and danger.

[0063] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0064] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A forklift lifting hydraulic oil circuit with descending potential energy regeneration, which includes a lifting oil circuit, a tilting oil circuit and a shutdown unloading oil circuit, characterized in that: Also includes: A descending potential energy recovery oil circuit, which includes a high-pressure energy storage oil circuit for conveying the hydraulic oil in the lifting oil cylinder to the high-pressure accumulator through a multi-way valve when the forklift is lowered under load, and a low-pressure energy storage oil circuit for conveying the hydraulic oil in the lifting oil cylinder to the low-pressure accumulator through the multi-way valve when the forklift is lowered without load, wherein the multi-way valve includes a lifting valve plate, the lifting valve plate is connected to a valve-controlled switch, and a descending speed limiting cut-off valve is also connected between the lifting valve plate and the lifting oil cylinder; A second one-way valve is further provided between the multi-way valve and the descending potential energy recovery oil circuit for conveying the hydraulic oil in the lifting oil cylinder to the high-pressure accumulator or the low-pressure accumulator, and the port A of the second one-way valve is connected to the lifting valve plate; The high-pressure energy storage oil circuit comprises: High-pressure accumulator; A first electromagnetic ball valve, whose port A is connected to the high-pressure accumulator and the port B of the second one-way valve; An adjustable flow valve, whose port A is connected to the port B of the first electromagnetic ball valve, and whose port B is connected to the inlet end of the hydraulic pump; A high-pressure unloading valve, whose B port is connected to the hydraulic oil tank, and whose A port is connected between the high-pressure accumulator and the first electromagnetic ball valve; The low-pressure energy storage oil circuit comprises: Low pressure accumulator; A second electromagnetic ball valve, whose B port is respectively connected to the high-pressure accumulator, the A port of the first electromagnetic ball valve, and the B port of the second one-way valve, and whose A port is connected to the low-pressure accumulator; The low-pressure unloading valve has a B port connected to the hydraulic oil tank, and an A port connected to the A ports of the low-pressure accumulator and the second electromagnetic ball valve respectively.

2. The forklift lifting hydraulic oil circuit according to claim 1, characterized in that: The lifting oil circuit is a hydraulic pump that delivers the hydraulic oil in the hydraulic oil tank to the lifting oil cylinder through the multi-way valve; The tilt oil route is characterized in that the hydraulic pump delivers the hydraulic oil in the hydraulic oil tank to the tilt oil cylinder via the multi-way valve, and the tilt oil cylinder then returns the oil to the hydraulic oil tank; The shutdown unloading oil circuit is a circuit in which the hydraulic pump transfers the hydraulic oil in the hydraulic oil tank back to the hydraulic oil tank through the multi-way valve.

3. The forklift lifting hydraulic oil circuit according to claim 2, characterized in that: The multi-way valve further comprises a tilting valve plate, and the A and B oil ports of the tilting valve plate are respectively connected to the rod chamber and the rodless chamber of the tilting oil cylinder.

4. The forklift lifting hydraulic oil circuit according to claim 3, characterized in that: An overflow valve is provided between the outlet end of the hydraulic pump and the hydraulic oil tank, one end of the overflow valve is connected between the tilting valve plate and the hydraulic oil tank, and the other end of the overflow valve is connected between the lifting valve plate and the hydraulic pump.

5. The forklift lifting hydraulic oil circuit according to claim 1, characterized in that: In the lifting oil circuit, a first one-way valve is connected to the inlet end of the hydraulic pump.

6. The forklift lifting hydraulic oil circuit according to claim 5, characterized in that: An oil suction filter is also connected between the first one-way valve and the hydraulic oil tank.

7. The forklift lifting hydraulic oil circuit according to claim 1, characterized in that: The high-pressure accumulator and the low-pressure accumulator are both elastic accumulators.

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