Single-rotation-direction series pump potential energy recovery hydraulic control system for industrial vehicles

Abstract

The present invention discloses a single-rotation tandem pump potential energy recovery hydraulic control system for an industrial vehicle, wherein the single-rotation tandem pump driven by a single motor is used as a power source for hydraulic operation, and then an external potential energy recovery valve block and a check valve are used to constitute a comprehensive and efficient potential energy recovery scheme. By detecting the cylinder bottom pressure and the position of the lift valve, the opening and closing of the valves related to the oil path are controlled, so as to smoothly switch the normal working mode, the light loads lowering mode and the heavy-load lowering potential energy recovery mode. In addition, there is no need to switch the direction of rotation in the process of lifting and lowering potential energy recovery, and the response lag problem is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of hydraulic systems for industrial vehicles, and more particularly to a single-rotation tandem pump potential energy recovery hydraulic control system for an industrial vehicle.Background Art

[0002] The potential energy recovery of existing industrial vehicles, such as forklifts, is mainly achieved by converting the gravitational potential energy into hydraulic pressure energy during the weight drop of the cargo on the forks, so that the hydraulic motor is driven by the pressure of the oil cylinder, and the hydraulic motor in turn drives the generator to convert the hydraulic pressure energy into electric energy for feedback and storage in the battery.

[0003] After testing, verifying and analyzing many related technical solutions in the art, it has been found that there are at least the following problems in the potential energy recovery hydraulic system currently used in the art. (1) When two sets of motors are used, the utilization of at least one of the motors is not high, resulting in a large power margin, high cost and large volume of the overall system. (2) In the process of potential energy recovery, the pressure oil needs to pass through an internal oil channel of a multi-way valve, which will cause a large pressure loss and affect an efficiency of energy recovery. (3) Pressure oil cannot participate in the whole process of energy recovery, there are flow loss and low recovery efficiency problems. When the potential energy is small and not enough to generate electricity, it still needs to consume electrical energy, and it is difficult to achieve energy-saving requirements of the system. (4) In some solutions using accumulators, the problem of pressure shock cannot be avoided when re-use is required due to the fact that it is difficult to store the pressure energy in the accumulator. Summary of the Invention

[0004] In view of the above problems, the present invention aims to provide a single-rotation tandem pump potential energy recovery hydraulic control system for an industrial vehicle, which solves the aforementioned technical problems.

[0005] The technical solution adopted by the present invention is as follows: The present invention provides a single-rotation tandem pump potential energy recovery hydraulic control system for an industrial vehicle, including an oil tank, a multi-way valve, a tilt oil cylinder and a lift oil cylinder connected to an oil path of the multi-way valve, and further including: a motor, a single-rotation tandem pump drivingly connected to the motor, an external potential energy recovery valve block, a pressure sensor and a displacement sensor; wherein the single-rotation tandem pump has an oil inlet which are in communication with each other and an independent oil outlet, each oil inlet of the single-rotation tandem pump is respectively in communication with the oil tank via a potential energy recovery check valve, and each independent oil outlet of the single-rotation tandem pump is respectively correspondingly connected to each independent oil inlet of the multi-way valve; one end of the external potential energy recovery valve block is connected to the lift oil cylinder, and the other end of the external potential energy recovery valve block is connected to the oil inlet of the single-rotation tandem pump; the pressure sensor is connected to the lift oil cylinder for detecting a cylinder bottom pressure of the lift oil cylinder; the displacement sensor is connected to a lift valve in the multi-way valve for detecting a position of the lift valve.

[0006] In at least one of the possible implementations, the single-rotation tandem pump is constructed in a manner including: the internal asymmetric structure of a first gear pump and a second gear pump being changed to a completely symmetric structure, the one-way seal being changed to a two-way seal, and the first gear pump and the second gear pump being connected in series, so as to form a dual-side pressure bearing single-rotation duplex pump driven by only one the motor.

[0007] In at least one of the possible implementations, when a cylinder bottom pressure of a lift oil cylinder fed back by a pressure sensor is less than a preset first pressure threshold value, a displacement sensor feedback signal is used to judge whether a lift valve in the multi-way valve is in a lowering position; if it is in a lowering position, controlling the oil liquid of the lift oil cylinder to flow back to the oil tank via the multi-way valve, and executing a lowering action; if it is not in the lowering position, controlling the external potential energy recovery valve block to be closed, and controlling channels between the independent oil inlets of the multi-way valve and the oil tank to be disconnected.

[0008] In at least one of the possible implementations, when a cylinder bottom pressure fed back by a pressure sensor is between the first pressure threshold value and a preset second pressure threshold value, it is judged whether a lift valve in the multi-way valve is in a lowering position by a displacement sensor feedback signal; if in a lowering position, controlling the external potential energy recovery valve block to open, and closing a channel through which the oil liquid of the lift oil cylinder flows from the multi-way valve back to the oil tank, so that the oil liquid flows into the single-rotation tandem pump for potential energy recovery; if it is not in the lowering position, controlling the external potential energy recovery valve block to be closed, and controlling channels between the independent oil inlets of the multi-way valve and the oil tank to be disconnected.

[0009] In at least one of the possible implementations, an overload protection valve group is provided in the multi-way valve, and the overload protection valve group is in communication with an independent oil inlet of the multi-way valve and the oil tank, respectively, at least for establishing a straight-through oil path between the output oil liquid of the single-rotation tandem pump and the oil tank when the valve group is powered off.

[0010] In at least one of the possible implementations, when the cylinder bottom pressure fed back by the pressure sensor is greater than the second pressure threshold value, the overload protection valve group is controlled to be powered off so that the oil liquid output from the independent oil outlet of the single-rotation tandem pump is directly returned to the oil tank.

[0011] In at least one of the possible implementations, the multi-way valve specifically includes: the lift valve connected to each independent oil inlet of the multi-way valve, the light loads lowering check valve group and the tilt valve; the lift valve is connected to the light load lowering check valve group, and connected together to the lift oil cylinder; the inlet of the tilt valve is connected to an independent oil inlet of the multi-way valve, and the outlet of the tilt valve is connected to the tilt oil cylinder.

[0012] In at least one of the possible implementations, the lift valve and the light load lowering check valve group are connected together with one end of a speed limiting valve externally disposed to the multi-way valve, and the other end of the speed limiting valve is connected to the lift oil cylinder.

[0013] In at least one of the possible implementations, a shut-off valve for manual operation is further provided inside the light load lowering check valve group.

[0014] In at least one of the possible implementations, the external potential energy recovery valve block is a proportional solenoid valve.

[0015] In contrast to the prior art, the main design concept of the present invention is to use a single-motor-driven, single-rotation tandem pump as the hydraulic oil pump acting during lifting and tilting, followed by an external potential energy recovery valve block and a check valve to prevent pressure energy from being unloaded. When heavy-duty lowering is performed, a single-rotation tandem pump is used as the generator motor to achieve overall high-efficiency potential energy recovery. More specifically, the opening and closing of the external potential energy recovery valve block and each valve in the multi-way valve is controlled by the cylinder bottom pressure feedback and the position of the lift valve in the multi-way valve, so as to smoothly switch between the normal lifting and / or tilting operation mode, or the light load lowering non-power generation mode, or the heavy-load lowering potential energy recovery mode. In addition, there is no need to switch the rotation direction in the process of lifting and lowering potential energy recovery, avoiding the problem of obvious response lag caused by rapid switching of lifting and lowering. The present invention ensures that the hydraulic system of an industrial vehicle can be designed with better power requirements for each working condition, without waste of power, and with reasonable use of the tandem pump displacement, not only is the operating mode switched freely, but also has significant advantages of low cost, small size, easy spatial arrangement, etc.Brief Description of the Drawings

[0016] In order that the objects, aspects and advantages of the present invention will become apparent, a more particular description of the present invention will be rendered by reference to the appended drawings, in which: Fig. 1 is a schematic configuration diagram of a single-rotation tandem pump potential energy recovery hydraulic control system for an industrial vehicle according to an embodiment of the present invention.Detailed Description of the Invention

[0017] Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein same or similar reference numerals refer to same or similar elements throughout or elements having the same or similar function. The embodiments described below with reference to the figures are exemplary only and are not to be construed as limiting the present invention.

[0018] The present invention proposes an embodiment of a single-rotation tandem pump potential energy recovery hydraulic control system for an industrial vehicle (for example, a forklift), as shown in Fig. 1, including: an oil tank 1 (mainly serving to store hydraulic oil, and being able to dissipate heat for a hydraulic system), a multi-way valve 9 (mainly serving to control a forklift to perform actions such as lifting and tilting), and a tilt oil cylinder 11 and a lift oil cylinder 12 connected to an oil path of the multi-way valve 9. The system also includes: a motor 5, a single-rotation tandem pump 7 drivingly connected to the motor 5 (the main function is to provide an oil source for the forklift action, and to serve as a motor to drive the motor to generate electricity when potential energy is recovered), and an external potential energy recovery valve block 14 (the external refers to the setting outside the multi-way valve, preferably using a proportional solenoid valve, which can provide good micro control performance of the system during lowering. Its main function is to guide the cylinder bottom pressure oil of the lift oil cylinder to the oil inlet of the tandem pump).

[0019] The single-rotation tandem pump 7 has an oil inlet in communication with each other, and an independent oil outlet. It will be appreciated that the oil inlets and the independent oil outlets of the tandem pumps correspond to the number of pumps in series. Each of the oil inlets of the single-rotation tandem pump 7 is connected to the oil tank 1 via a potential energy recovery check valve (the main function is to prevent the high-pressure oil liquid at the inlet of the single-rotation tandem pump from being directly returned to the oil tank during potential energy recovery, resulting in an inability to recover energy normally). And each independent oil outlet of the single-rotation tandem pump 7 is respectively connected to each independent oil inlet of the multi-way valve 9.

[0020] And one end of the external potential energy recovery valve block 14 is connected to the lift oil cylinder 12, and the other end of the external potential energy recovery valve block 14 is connected to the oil inlet of the single-rotation tandem pump 7.

[0021] The pressure sensor 13 is connected to the lift oil cylinder 12 for detecting a cylinder bottom pressure of the lift oil cylinder 12. The displacement sensor 8 is connected to a lift valve 91 in the multi-way valve 9 for detecting the position of the lift valve 91. It is to be understood that the displacement sensor 8, the pressure sensor 13, the motor 5, the above-mentioned electrically controlled valves, etc. are all connected to the original machine control unit of the forklift through electrical signals, and the present invention is not described or limited in detail.

[0022] In some preferred embodiments, the construction of the single-rotation tandem pump 7 can be referred to as follows: the internal asymmetric structure of the first gear pump C1 and the second gear pump C2 is changed to a completely symmetric structure, the one-way seal is changed to a two-way seal, and the first gear pump C1 and the second gear pump C2 are connected in series, thereby obtaining a dual-side pressure bearing single-rotation duplex pump which can be driven by only one motor 5. Taking the duplex pump as an example, in the pump mode operation (the normal operation working condition of the forklift), the motor 5 and the duplex pump use the same rotation direction to operate, while in the motor mode operation (the potential energy recovery working condition), the high-pressure oil still flows into the duplex pump from the oil inlet of the two gear pumps to generate electricity, and the duplex pump and the generator (the motor 5) still keep the original rotation direction to continue to operate, which greatly simplifies the difficulty of motor control.

[0023] An overload protection valve group 94 is provided in the multi-way valve 9, and the overload protection valve group 94 is connected to at least one independent oil inlet of the multi-way valve 9. The function of the overload protection valve group 94 is to prevent the lift oil cylinder 12 from continuing to lift after the cargo is overloaded, resulting in a safety accident of the vehicle. In the present invention, when the cargo is in the normal load range, the solenoid valve of the overload protection valve group 94 is energized, thereby disconnecting the channel of the single-rotation tandem pump 7 from the oil tank 1, so that the hydraulic system can be normally lifted and tilted.

[0024] When the load exceeds the rated load, conventional vehicles typically rely on a single main relief valve 95 as shown to limit the pressure to achieve overload protection. The main safety valve 95 has an opening characteristic, and the lifting of the cargo can be stopped only after an overload of 30% or more, so that the accurate overload protection cannot be achieved. Accordingly, the present invention proposes to monitor the cylinder bottom pressure of the lift oil cylinder 12 using the pressure sensor 13, and to set the cylinder bottom pressure (P2) at the rated load. After monitoring that the cylinder bottom pressure exceeds P2, the overload protection valve group 94 can be controlled to be immediately powered off, and at this time, the oil liquid output from the tandem pump flows directly into the oil tank 1 via each of the independent oil inlets of the multi-way valve 9 and the overload protection valve group 94. Due to the insufficient pressure, the lift oil cylinder 12 at this time cannot perform the lifting operation and cannot drive the tilt oil cylinder 11 to perform the tilting operation, so that accurate overload protection is achieved.

[0025] The multi-way valve 9 may specifically include: a lift valve 91 (the main function is to perform the action of the lift oil cylinder 12), a light load lowering check valve group 92 (the main function is to power up the electromagnetic valve when the cargo load is light and the potential energy recovery is insufficient, so as to achieve the lift oil cylinder lowering), and a tilt valve 93 (the main function is to perform the action of the tilt oil cylinder 11).

[0026] The inlet of the lift valve 91 is connected to a first independent oil inlet O1 and a second independent oil inlet O2 of the multi-way valve 9. The outlet of the lift valve 91 is connected to the light load down check valve group 92, and preferably to one end of the speed limiting valve 10, which is external to the multi-way valve 9. The other end of the speed limiting valve 10 is connected to a lift oil cylinder 12. The primary function of the speed limiting valve 10 as referred to herein is to prevent a vehicle safety accident from occurring when the light-duty lowering check valve assembly 92 is energized at an excessive rate of lowering.

[0027] An inlet port of the tilt valve 93 is connected to an independent oil inlet of the multi-way valve 9, and an outlet port of the tilt valve 93 is connected to the tilt oil cylinder 11.

[0028] The working mechanism of the present invention is schematically illustrated in connection with the above-described embodiment of the duplex pump: in normal operation, the duplex pump is operated as a pump mode in which only one motor 5 drives the pump in rotation. The first oil inlet a and the second oil inlet b of each of the two pumps of the duplex pump suck the oil from the oil tank 1 through the first potential energy recovery check valve 4 and the second potential energy recovery check valve 6, and the first oil suction filter 2 and the second oil suction filter 3 (the function thereof is to filter the impurities in the oil tank and protect the duplex pump from being worn by the large particles), respectively. The high-pressure oil flows from the first independent oil outlet c and the second independent oil outlet d to the two independent oil inlets of the multi-way valve 9. In particular, the displacement of the duplex pump can be freely combined according to the requirements of the system, when lifting and tilting are performed, as two independent oil pumps in series, to achieve confluence and diversion according to different working conditions. For the lifting working condition, the system needs a large flow, the duplex pump merges through the internal oil channel of the multi-way valve, and the two pumps of the duplex pump output the full flow. With regard to the inclined working condition, the system flow demand is relatively small; one pump of the duplex pump participates in the work, and the other pump directly communicates with the oil tank via the internal oil channel of the multi-way valve for oil return (in practical operation, it is preferable to flow through the oil return filter 15 back to the oil tank 1, so that the hydraulic oil can be circulated and filtered to ensure the cleanliness of the oil liquid), and at this time, the system flow is halved, the power is also halved, and the energy loss is small.

[0029] More specifically, when the lifting action is performed, the two-way output oil liquid of the duplex pump enters two independent oil inlets, and after the oil liquid flows together in the lift valve 91 of the multi-way valve 9, the oil flows to the lift oil cylinder 12 via the outlet of the multi-way valve 9 to achieve system lifting, and at this time, the system outputs full power.

[0030] When the tilting action is performed, the oil liquid output from the gear pump of one of the duplex pumps (for example, C2) flows directly from the return port of the multi-way valve 9 back to the oil tank via the lift valve 91, when the pump is operating at near zero power. The oil liquid enters the tilt valve 93 only through an independent oil inlet corresponding to the other gear pump (for example, C1) of the duplex pump and flows to the tilt oil cylinder 11 to achieve the tilting action, at which time the pump is operating at full power. The two gear pumps in the single-rotation duplex pump in the above-mentioned working conditions work independently and do not interfere with each other, the system power is reduced by half, and the energy consumption is greatly reduced.

[0031] However, when the heavy-load potential energy recovery is performed, the duplex pump works as a motor mode and cooperates with the external potential energy recovery valve block 14 to form a potential energy recovery loop, and at this time, the single-rotation duplex pump is equivalent to a motor with a relatively large displacement, and the oil liquid pressure is all used for potential energy recovery so as to drive the motor 5 to generate electricity.

[0032] More specifically, when the heavy-load lowering potential energy is recovered, the duplex pump acts as a motor to drive the motor to generate electric power, and at this time, the light load lowering check valve group 92 is powered off, and the channel of the high-pressure oil at the cylinder bottom of the lift oil cylinder 12 from the multi-way valve 9 back to the oil tank is closed. And the external potential energy recovery valve block 14 is powered, and the high-pressure oil at the cylinder bottom is led to the two oil inlets of the duplex pump via the external potential energy recovery valve block 14. Since the two oil inlets are in communication, the oil liquid enters the duplex pump freely under the action of pressure. At this time, the two gear pumps connected in series can be used as a large displacement motor to drive the motor to generate electricity. There is almost no pressure loss in the whole channel.

[0033] The cylinder bottom pressure can be used to generate electricity entirely, thereby greatly improving the efficiency of power generation. At the same time, during the potential energy recovery process, the hydraulic system can also achieve the combined operation of lowering and tilting. This is mainly due to: firstly, the rotation direction of the motor and the duplex pump is invariable under all working conditions, so that the switching response of the cylinder action is faster; secondly, the independent oil outlet of the duplex pump is connected to the independent oil inlet of the multi-way valve 9, and when potential energy is recovered, the normal tilting operation can still be realized through the multi-way valve and the oil path of the tilt oil cylinder.

[0034] It should also be noted that when the light load falls, the cylinder bottom pressure of the lift oil cylinder is low, which is insufficient to drive the generator to generate electricity, and at this time, the potential energy recovery operation is not performed, and the external potential energy recovery valve block can be controlled to be powered off, and the potential energy recovery function is shut down by the system. And a light load lowering oil return channel is still reserved in the multi-way valve 9, for example, controlling the light load lowering check valve group to be powered, the oil liquid at the cylinder bottom of the lift oil cylinder passes through the speed limiting valve, and then returns to the oil tank through the lift valve and the oil return filter, and the motor 5 will not work when the light load lowers, so as to avoid unnecessary energy recovery causing energy consumption.

[0035] Thus, in accordance with the various embodiments and the description of the principles set forth above, the present invention also provides a specific example of the electric control process of the hydraulic control system described above, mainly in the following three states: The first state: when the cylinder bottom pressure of the lift oil cylinder 12 fed back by the pressure sensor 13 is less than a first pressure threshold value P1 (the cylinder bottom pressure can be used to represent the load weight of the forklift, and P1 is a preset minimum pressure for the single-rotation tandem pump 7 to drive and generate electricity, that is to say, one of the quantitative parameters for judging whether to perform potential energy recovery), a signal fed back by the displacement sensor 8 is used to judge whether the lift valve 91 in the multi-way valve 9 is in a lowering position.

[0036] If in a lowering position, entering a light load lowering mode, the motor 5 not being powered (the single-rotation tandem pump 7 is in a non-power generation mode), controlling the power of the light load lowering check valve group 92 and controlling the power-off of the external potential energy recovery valve block 14, so that the oil liquid of the lift oil cylinder flows back to the oil tank 1 via the above-mentioned channels, such as the speed limiting valve 10, the lift valve 91 and the oil return filter 15, so as to achieve the lowering of lighter weight cargo.

[0037] If not in the lowering position, the single-rotation tandem pump 7 is in a pump working mode, and at this time, the light load lowering check valve 92 and the external potential energy recovery valve block 14 are controlled to be powered off, the overload protection valve group 94 is powered on, the channel between the independent oil inlet of the multi-way valve 9 and the oil tank 1 is disconnected, and the hydraulic system can perform a normal lifting and / or tilting operation.

[0038] The second state: when the cylinder bottom pressure fed back by the pressure sensor 13 is between a first pressure threshold value P1 and a second pressure threshold value P2 (P2 is an upper limit of the cylinder bottom pressure of the lift oil cylinder under a preset rated load, namely, an overload limit value), a signal fed back by the displacement sensor 8 is used to judge whether the lift valve 91 in the multi-way valve 9 is in a lowering position.

[0039] In the lowering position, the heavy-duty lowering potential energy recovery mode is entered, that is, the single-rotation tandem pump 7 is operated as a large displacement motor. At this time, the light load lowering check valve group 92 is controlled to be powered off, thereby closing the channel of the high-pressure oil at the bottom of the cylinder from the multi-way valve 9 back to the oil tank 1, and controlling the external potential energy recovery valve block 14 to be powered on. The high-pressure oil at the bottom of the cylinder is led to the oil inlet of the single-rotation tandem pump 7 through the external potential energy recovery valve block 14, and the oil inlet is unidirectionally blocked from the oil tank 1 by the potential energy recovery check valve. The high-pressure oil flowing back from the external potential energy recovery valve block 14 does not flow to the oil tank, and the oil liquid is free to enter the single-rotation tandem pump 7 under pressure for efficient power generation. If the tilt valve 93 is operated at the same time of potential energy recovery (the valve is powered by the operating rod of the forklift), the pressurized oil can enter the tilt valve 93 in the multi-way valve 9 through an independent oil inlet and flow into the tilt oil cylinder 11, so as to realize the combined action of potential energy recovery and tilting operation for heavy-load lowering.

[0040] By pre-setting the above-mentioned parameters and control logic by the forklift control unit, the natural switching between the recovery of potential energy for heavy-load reduction and the normal light load reduction can be effectively accomplished, and of course, the overload protection function of the system mentioned below is also included.

[0041] If not in the lowering position, the single-rotation tandem pump 7 is in a pump working mode, and at this time, the light load lowering check valve 92 and the external potential energy recovery valve block 14 are controlled to be powered off, the overload protection valve group 94 is powered on, the channel between the independent oil inlet of the multi-way valve 9 and the oil tank 1 is disconnected, and the hydraulic system can perform a normal lifting and / or tilting operation.

[0042] The third state: when the cylinder bottom pressure fed back by the pressure sensor 13 is greater than P2, the control overload protection valve group 94 is immediately powered off, and at this time, the oil liquid output from the single-rotation tandem pump 7 to the independent oil outlet is directly returned to the oil tank 1 via the overload protection valve group 94 and via the above-mentioned oil return filter 15, etc. At this time, the direct connection between each independent oil outlet of the tandem pump and the oil tank is established, and the hydraulic system of the forklift cannot perform the lifting and tilting actions, thus playing a reliable and safe protection role.

[0043] Finally, it may be supplemented that a shut-off valve 921 for manual operation is also provided inside the light load lowering check valve group 92. In this way, when either the external potential energy recovery valve block 14 or the light load lowering check valve group 92 fails, the channel of the return oil tank can be manually opened through the shut-off valve 921 to ensure that the lowering function of the lift oil cylinder can still be achieved. Of course, it will be understood that the potential energy recovery function is temporarily stopped when the vehicle is in the heavy-load reduction working condition.

[0044] In view of the above, the main design concept of the present invention is to use a single-motor-driven, single-rotation tandem pump as the hydraulic oil pump acting during lifting and tilting, followed by an external potential energy recovery valve block and a check valve to prevent pressure energy from being unloaded. When heavy-duty lowering is performed, a single-rotation tandem pump is used as the generator motor to achieve overall high-efficiency potential energy recovery. More specifically, the opening and closing of the external potential energy recovery valve block and each valve in the multi-way valve is controlled by the cylinder bottom pressure feedback and the position of the lift valve in the multi-way valve, so as to smoothly switch between the normal lifting and / or tilting operation mode, or the light load lowering non-power generation mode, or the heavy-load lowering potential energy recovery mode. In addition, there is no need to switch the rotation direction in the process of lifting and lowering potential energy recovery, avoiding the problem of obvious response lag caused by rapid switching of lifting and lowering. The present invention ensures that the hydraulic system of an industrial vehicle can be designed with better power requirements for each working condition, without waste of power, and with reasonable use of the tandem pump displacement, not only is the operating mode switched freely, but also has significant advantages of low cost, small size, easy spatial arrangement, etc.

[0045] The above embodiments, based on the schematic diagram, provide a detailed explanation of the construction, features, and effects of the present invention. However, the above are only the preferred embodiments of the present invention. It should be noted that the technical features involved in the above embodiments and their preferred modes can be reasonably combined and matched into multiple equivalent solutions by those skilled in the art without departing from or changing the design ideas and technical effects of the present invention; Therefore, the present invention is not limited by the scope of implementation as shown in the drawings. Any changes made in accordance with the concept of the present invention, or equivalent embodiments modified to equivalent changes, shall be within the scope of protection of the present invention as long as they do not exceed the spirit covered by the specification and drawings.

Claims

1. A single-rotation tandem pump potential energy recovery hydraulic control system for an industrial vehicle, comprising an oil tank, a multi-way valve, a tilt oil cylinder and a lift oil cylinder connected to an oil path of the multi-way valve, characterized by further comprising: a motor, a single-rotation tandem pump drivingly connected to the motor, an external potential energy recovery valve block, a pressure sensor and a displacement sensor; wherein the single-rotation tandem pump has an oil inlet which are in communication with each other and an independent oil outlet, each oil inlet of the single-rotation tandem pump is respectively in communication with the oil tank via a potential energy recovery check valve, and each independent oil outlet of the single-rotation tandem pump is respectively correspondingly connected to each independent oil inlet of the multi-way valve; one end of the external potential energy recovery valve block is connected to the lift oil cylinder, and the other end of the external potential energy recovery valve block is connected to the oil inlet of the single-rotation tandem pump; the pressure sensor is connected to the lift oil cylinder for detecting a cylinder bottom pressure of the lift oil cylinder; the displacement sensor is connected to a lift valve in the multi-way valve for detecting a position of the lift valve.

2. The single-rotation tandem pump potential energy recovery hydraulic control system for an industrial vehicle according to claim 1, characterized in that the single-rotation tandem pump is constructed in a manner comprising: the internal asymmetric structure of a first gear pump and a second gear pump being changed to a completely symmetric structure, the one-way seal being changed to a two-way seal, and the first gear pump and the second gear pump being connected in series, so as to form a dual-side pressure bearing single-rotation duplex pump driven by only one the motor.

3. The single-rotation tandem pump potential energy recovery hydraulic control system for an industrial vehicle according to claim 1, characterized in that when a cylinder bottom pressure of a lift oil cylinder fed back by a pressure sensor is less than a preset first pressure threshold value, a displacement sensor feedback signal is used to judge whether a lift valve in the multi-way valve is in a lowering position; if it is in a lowering position, controlling the oil liquid of the lift oil cylinder to flow back to the oil tank via the multi-way valve, and executing a lowering action; if it is not in the lowering position, controlling the external potential energy recovery valve block to be closed, and controlling channels between the independent oil inlets of the multi-way valve and the oil tank to be disconnected.

4. The single-rotation tandem pump potential energy recovery hydraulic control system for an industrial vehicle according to claim 3, characterized in that when a cylinder bottom pressure fed back by a pressure sensor is between the first pressure threshold value and a preset second pressure threshold value, it is judged whether a lift valve in the multi-way valve is in a lowering position by a displacement sensor feedback signal; if in a lowering position, controlling the external potential energy recovery valve block to open, and closing a channel through which the oil liquid of the lift oil cylinder flows from the multi-way valve back to the oil tank, so that the oil liquid flows into the single-rotation tandem pump for potential energy recovery; if it is not in the lowering position, controlling the external potential energy recovery valve block to be closed, and controlling channels between the independent oil inlets of the multi-way valve and the oil tank to be disconnected.

5. The single-rotation tandem pump potential energy recovery hydraulic control system for an industrial vehicle according to claim 4, characterized in that an overload protection valve group is provided in the multi-way valve, and the overload protection valve group is in communication with an independent oil inlet of the multi-way valve and the oil tank, respectively, at least for establishing a straight-through oil path between the output oil liquid of the single-rotation tandem pump and the oil tank when the valve group is powered off.

6. The single-rotation tandem pump potential energy recovery hydraulic control system for an industrial vehicle according to claim 5, characterized in that when the cylinder bottom pressure fed back by the pressure sensor is greater than the second pressure threshold value, the overload protection valve group is controlled to be powered off so that the oil liquid output from the independent oil outlet of the single-rotation tandem pump is directly returned to the oil tank.

7. The single-rotation tandem pump potential energy recovery hydraulic control system for an industrial vehicle according to claim 1, characterized in that the multi-way valve specifically comprises: the lift valve connected to each independent oil inlet of the multi-way valve, the light load lowering check valve group and the tilt valve; the lift valve is connected to the light load lowering check valve group, and connected together to the lift oil cylinder; the inlet of the tilt valve is connected to an independent oil inlet of the multi-way valve, and the outlet of the tilt valve is connected to the tilt oil cylinder.

8. The single-rotation tandem pump potential energy recovery hydraulic control system for an industrial vehicle according to claim 7, characterized in that the lift valve and the light load lowering check valve group are connected together with one end of a speed limiting valve externally disposed to the multi-way valve, and the other end of the speed limiting valve is connected to the lift oil cylinder.

9. The single-rotation tandem pump potential energy recovery hydraulic control system for an industrial vehicle according to claim 7, characterized in that a shut-off valve for manual operation is further provided inside the light load lowering check valve group.

10. The single-rotation tandem pump potential energy recovery hydraulic control system for an industrial vehicle according to claims 1 to 9, characterized in that the external potential energy recovery valve block is a proportional solenoid valve.

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