A double stack forklift master hydraulic control method

Abstract

This invention discloses a main hydraulic control method for a dual-stabilized forklift, comprising: during lifting operations, opening the primary or secondary lifting oil circuit to drive the lifting operation; collecting the current working oil pressure V1 of the lifting oil circuit; when V1>V0, reducing the motor speed to a preset high-speed speed n1; when the forklift is lifted to 15-20mm from the top, further reducing the motor speed; after lifting to the top, opening the unloading oil circuit in the lifting oil circuit; opening the primary or secondary return oil circuit to drive the lowering operation; collecting the working oil pressure V2 of the primary or secondary return oil circuit in real time; when V2>V0, reducing the lowering speed; when the lowering position of the lifting cylinder assembly is 15-20mm from the bottom, reducing the lowering speed. This invention avoids the swaying of the entire vehicle caused by excessively fast lifting speed or improper control during heavy-load lifting or high-position lifting, or the impact or jerking sensation during lowering, thereby improving the stacking stability and safety of the forklift.

Description

Technical Field

[0001] This invention belongs to the field of forklift technology, specifically relating to a main hydraulic control method for a dual-stabilized forklift. Background Technology

[0002] In a double stacker forklift, two-stage masts or two independent lifting mechanisms are typically used to achieve the lifting function. The lifting action driven by the first-stage lifting cylinder group to drive the first-stage mast (or main lifting mechanism) is usually referred to as "first-stage lifting," while the lifting action driven by the second-stage lifting cylinder group to drive the second-stage mast (or auxiliary lifting mechanism) is usually referred to as "second-stage lifting." In other words, a double stacker forklift has dual lifting capabilities.

[0003] Traditional double-stacking forklifts typically have hydraulic systems with only basic dual-lifting capabilities, controlling the lifting and lowering actions of the primary and secondary lifting mechanisms via simple hydraulic circuits. However, during the lifting or lowering process, the hydraulically controlled lifting cylinders cannot adjust the lifting or lowering speed in real time according to changes in load weight (heavy or light) and lifting height (low or high position). This results in the lifting speed of the primary and secondary lifting mechanisms failing to adaptively adjust to working conditions. Especially during heavy-load or high-position lifting, excessive speed or improper control can easily cause the entire vehicle to sway, severely affecting the stability and safety of stacking. Similarly, during lowering, the descent speed is difficult to control smoothly, easily producing impacts or jerks, further exacerbating the dynamic instability of the entire vehicle.

[0004] Furthermore, rigid impacts occur at the end of the stroke when the lifting cylinder reaches the top or the bottom, which not only reduces the stability of the stacking but also increases the risk of fatigue damage to structural components.

[0005] In summary, the hydraulic control method of the dual stacker forklift needs to be adjusted so that the lifting speed of the lifting mechanism can be adaptively adjusted according to the load and lifting height, thereby improving the active stability of the dual stacker forklift during lifting and lowering. Summary of the Invention

[0006] The purpose of this invention is to provide a main hydraulic control method for a dual stacker forklift, which not only achieves dual lifting functions, but also has the function of adjusting stability according to load weight (heavy load and light load) and lifting position.

[0007] The specific technical solution of the present invention is as follows: A hydraulic control method for a dual-stabilized forklift includes lifting and lowering operations of a primary lifting cylinder group and a secondary lifting cylinder group, comprising the following steps: S1. Set the safety oil pressure V0 of the hydraulic working oil circuit, the safety lifting height H1 of the first-stage lifting cylinder group, and the limit lifting height H. 高and the safe descent height H2; S2. During lifting operations, open the first-level lifting oil circuit of the first-level lifting cylinder group or the second-level lifting oil circuit of the second-level lifting cylinder group to drive the first-level lifting cylinder group or the second-level lifting cylinder group to lift. S3. Collect the working oil pressure V1 of the current hoisting oil circuit. When V1>V0, reduce the speed of the motor driving the gear pump to the preset high speed n1, thereby reducing the hoisting speed. S4. Collect the lifting position of the current working first-stage or second-stage lifting cylinder group. When it is lifted to 15-20mm from the top, continue to reduce the motor speed and reduce the lifting speed uniformly. Once the hoisting reaches the top, open the unloading oil circuit in the hoisting oil circuit to allow the oil in the hoisting oil circuit to return to the hydraulic oil tank; S5. During the lowering operation, open the first-level return oil circuit of the first-level lifting cylinder group or the second-level return oil circuit of the second-level lifting cylinder group to drive the first-level lifting cylinder group or the second-level lifting cylinder group to lower. S6. Real-time acquisition of the working oil pressure V2 of the primary or secondary return oil circuit. When V2>V0, reduce the descent speed. S7. Collect the current descent position of the first-stage or second-stage lifting cylinder group. When the descent position of the lifting cylinder group is 15-20mm from the bottom, reduce the oil volume in the return oil circuit to uniformly reduce the descent speed of the lifting cylinder group.

[0008] In a further step, step S3 also includes collecting the lifting height H11 of the currently operating first-stage lifting cylinder assembly; When H11>H1 and V1>V0, reduce the lifting speed and open the booster oil circuit in the first-stage lifting oil circuit to allow the oil in the first-stage lifting oil circuit to enter the booster oil cylinder for boosting. When H11>H 高 When the motor speed is reduced to the preset low speed n2, the speed is reduced.

[0009] In a further step, in step S3, when V1>V0 in the secondary lifting oil circuit, while reducing the lifting speed, the booster oil circuit in the secondary lifting oil circuit is also opened, so that the oil in the lifting oil circuit enters the booster cylinder for boosting.

[0010] In a further embodiment, the working oil pressure V1 of the currently operating lifting oil circuit is detected by a pressure sensor installed on the primary or secondary lifting oil circuit.

[0011] In a further embodiment, the lifting or lowering position of the primary or secondary lifting cylinder group is detected by a lifting photoelectric switch installed on the primary or secondary lifting cylinder group.

[0012] In a further solution, in step S7, it further includes collecting the lowering height H12 of the first-stage lifting cylinder group in the current operation. When H12 < H2 and V2 > V0, the pressure relief oil circuit in the first-stage oil return oil circuit is opened, so that the oil in the booster cylinder returns to the hydraulic oil tank for pressure relief.

[0013] In a further solution, in step S7, when the second-stage lifting cylinder group has lowered to the bottom and V2 < V0 in the second-stage oil return oil circuit, the pressure relief oil circuit in the second-stage oil return oil circuit is opened, so that the oil in the booster cylinder returns to the hydraulic oil tank for pressure relief.

[0014] The control method of the present invention respectively controls the rotation speed of the motor and the opening and closing of the booster oil circuit, the pressure relief oil circuit and the load relief oil circuit according to the oil pressure and the lifting position in the lifting or oil return oil circuit during the first-stage lifting operation or the second-stage lifting operation, so that the forklift can adjust the lifting or lowering speed in real time according to the changes in the load weight (heavy load or light load) and the lifting height (low position or high position) of the first-stage lifting cylinder group. Thus, it avoids the excessive lifting speed or improper control that is likely to cause the whole vehicle to shake during heavy load lifting or high position lifting, or the impact or jerks during lowering, and ultimately greatly improves the stacking stability and safety of the forklift.

[0015] Moreover, the present invention can reduce the lifting or lowering speed at the end of the stroke when the lifting cylinder reaches the top or lowers to the bottom, and at the same time strengthen the buffering performance of the hydraulic oil circuit through load relief, which not only reduces the stacking stability but also increases the risk of fatigue damage to the structural components. Specific Embodiment

[0016] The following will describe the present application in detail with reference to the embodiments. It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0017] In the present application, unless otherwise clearly defined and limited, the terms "installation", "connection", "connection", "fixation", "fixed setting" and other terms should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection, an electrical connection, or a communication connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the internal communication of two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0018] For the convenience of description, the present application defines the lifting action of the first gantry in the double-stacking forklift as "first-stage lifting", and the lifting action of the second gantry as "second-stage lifting". Correspondingly, the switch for controlling the above actions, because it is usually a finger pressure contact switch arranged on the control handle, is collectively called "finger tip switch" in the present application.

[0019] In this application, the "active stability control function" is referred to as the "main stability function," and correspondingly, the integrated hydraulic valve assembly used to implement this function is called the main stability integrated valve block.

[0020] A hydraulic control method for the main stability of a dual-stabilized forklift includes lifting and lowering operations of a primary lifting cylinder group and a secondary lifting cylinder group, comprising the following steps: S1. Set the safety oil pressure V0 of the hydraulic working oil circuit, the safety lifting height H1 of the first-stage lifting cylinder group, and the limit lifting height H. 高 ; S2. During lifting operations, open the first-level lifting oil circuit of the first-level lifting cylinder group or the second-level lifting oil circuit of the second-level lifting cylinder group to drive the first-level lifting cylinder group or the second-level lifting cylinder group to lift. S3. Collect the working oil pressure V1 of the current hoisting oil circuit. When V1>V0, reduce the speed of the motor driving the gear pump to the preset high speed n1, thereby reducing the hoisting speed. S4. Collect the lifting position of the current working first-stage or second-stage lifting cylinder group. When it is lifted to 15-20mm from the top, continue to reduce the motor speed and reduce the lifting speed uniformly. Once the hoisting reaches the top, open the unloading oil circuit in the hoisting oil circuit to allow the oil in the hoisting oil circuit to return to the hydraulic oil tank; S5. During the lowering operation, open the first-level return oil circuit of the first-level lifting cylinder group or the second-level return oil circuit of the second-level lifting cylinder group to drive the first-level lifting cylinder group or the second-level lifting cylinder group to lower. S6. Real-time acquisition of the working oil pressure V2 of the primary or secondary return oil circuit. When V2>V0, reduce the descent speed. S7. Collect the current descent position of the first-stage or second-stage lifting cylinder group. When the descent position of the lifting cylinder group is 15-20mm from the bottom, reduce the oil volume in the return oil circuit to uniformly reduce the descent speed of the lifting cylinder group.

[0021] In another embodiment, step S3 further includes collecting the lifting height H11 of the currently operating first-stage lifting cylinder assembly; When H11>H1 and V1>V0, reduce the lifting speed and open the booster oil circuit in the first-stage lifting oil circuit to allow the oil in the first-stage lifting oil circuit to enter the booster oil cylinder for boosting. When H11>H 高 When the motor speed is reduced to the preset low speed n2, the speed is reduced.

[0022] In step S3, when V1 > V0 in the secondary lifting oil circuit, while reducing the lifting speed, the boost oil circuit in the secondary lifting oil circuit is also opened, causing the oil in the lifting oil circuit to enter the boost cylinder for boosting.

[0023] In this embodiment, the working oil pressure V1 of the currently working lifting oil circuit is detected by a pressure sensor installed on the primary lifting oil circuit or the secondary lifting oil circuit.

[0024] The lifting height H11 of the primary lifting cylinder group can be detected by a wire rope displacement sensor installed on the primary lifting cylinder group. Specifically, the wire rope displacement sensor is installed on the left primary lifting cylinder. When the left primary lifting cylinder moves up and down, the wire rope expands and contracts with the piston rod, and then outputs an electrical signal proportional to the displacement to the forklift controller ECU, thereby controlling the opening of the boost oil circuit or reducing the motor speed.

[0025] The lifting position or lowering position of the primary lifting cylinder group or the secondary lifting cylinder group is detected by a lifting photoelectric switch installed on the primary lifting cylinder group or the secondary lifting cylinder group. That is, it is determined whether the primary lifting cylinder group or the secondary lifting cylinder group has risen to the top or lowered to the bottom.

[0026] That is, the lifting photoelectric switch is used to detect the positions of the primary lifting cylinder group and the secondary lifting cylinder group to achieve buffer control when lifting to the top and lowering to the bottom.

[0027] In another embodiment, in step S7, it further includes collecting the lowering height H12 of the currently working primary lifting cylinder group. When H12 < H2 and V2 > V0, the pressure relief oil circuit in the primary oil return circuit is opened, causing the oil in the boost cylinder to return to the hydraulic oil tank for pressure relief.

[0028] In step S7, when the secondary lifting cylinder group has lowered to the bottom and V2 < V0 in the secondary oil return circuit, the pressure relief oil circuit in the secondary oil return circuit is opened, causing the oil in the boost cylinder to return to the hydraulic oil tank for pressure relief.

[0029] In this embodiment, the primary lifting oil circuit refers to the hydraulic oil circuit composed of the primary lifting cylinder group, the gear pump, and the hydraulic oil tank. The gear pump is driven by a motor to supply oil, guiding the oil in the hydraulic oil tank into the rodless cavities of each lifting cylinder in the primary lifting cylinder group to drive its lifting. Similarly, the primary oil return circuit returns the oil in the rodless cavities of each lifting cylinder in the primary lifting cylinder group to the hydraulic oil tank.

[0030] Similarly, the secondary lifting oil circuit and the secondary oil return circuit refer to the hydraulic oil circuits composed of the secondary lifting cylinder group, the gear pump, and the hydraulic oil tank.

[0031] The booster oil circuit includes a second bidirectional shut-off solenoid valve. The input end of the second bidirectional shut-off solenoid valve is connected to the lifting oil circuits of the primary lifting cylinder group and the secondary lifting cylinder group, respectively, and its output end is connected to the booster cylinder. This allows the oil in the lifting oil circuit to be introduced into the booster cylinder to boost the pressure of the lifting oil circuit.

[0032] The pressure relief oil circuit includes a first bidirectional shut-off solenoid valve connected in series in the primary or secondary return oil circuit, which allows the oil in the booster cylinder to enter the hydraulic oil tank for pressure relief.

[0033] The unloading oil circuit includes a safety relief valve and a two-position two-way electromagnetic proportional valve, both of which are connected to the oil outlet of the gear pump. The safety relief valve and the two-position two-way electromagnetic proportional valve are both connected to the hydraulic oil tank.

[0034] To better illustrate this, the first-stage lifting and second-stage lifting will be explained separately below: In this embodiment, for a double-stacking forklift, the safe oil pressure V0 of the hydraulic working circuit is set to ≤9MPa, the safe lifting height H1 of the first-stage lifting cylinder group is 1.7-1.8m, and the limited lifting height H... 高 It is 2m; The speed of the motor driving the gear pump is set to a preset high speed n1 of 1800-2000 rpm and a low speed n2 of 1000-1200 rpm.

[0035] The hoisting actions for a single-stage hoisting operation: S11. Operate the first-stage lifting fingertip switch, the motor drives the gear pump to deliver oil, and opens the first-stage lifting oil circuit to drive the first-stage lifting cylinder group to lift; S12. Real-time acquisition of the current working oil pressure V11 of the first-stage lifting oil circuit, the lifting height H11 of the first-stage lifting cylinder group, and the lifting position; When V11>V0, reduce the speed of motor 19 to the preset high speed n1 (e.g., 1800rpm), thereby reducing the first-level lifting speed. The first-level lifting speed can be controlled according to heavy or light load, improving its applicability. When V11>V0 and H11>H1, the motor speed is reduced to the preset high-speed speed n1, and the booster oil circuit is opened. The oil in the first-stage lifting oil circuit enters the booster cylinder, so that the first-stage lifting oil circuit is automatically boosted; thus realizing the automatic boosting of the hydraulic system of the whole vehicle and improving the stability of the lifting cylinder group at the high position. When H11>H 高 At this time, the motor speed is reduced to a preset low speed n2 (e.g., 1000 rpm), thereby further reducing the first-level lifting speed and improving lifting stability. S13. Collect the lifting position of the first-stage lifting oil cylinder group. When the lifting position is 15 mm from the topmost end, further and uniformly reduce the motor speed, such as 1000 rpm, 900, 800, 700, 600 rpm, ……, to reduce the flow rate ramp of the oil discharged by the gear pump and uniformly reduce the first-stage lifting speed; thus, when the first-stage lifting oil cylinder group is approaching the top during lifting, buffering can be achieved to avoid rigid impact, improve the stacking stability, and reduce the risk of fatigue damage to the structural members.

[0036] After lifting to the top, open the safety overflow valve on the first pressure relief oil path; meanwhile, open the two-position two-way electromagnetic proportional valve on the pressure relief oil path to allow the oil to return to the hydraulic oil tank through the first pressure relief oil path and the second pressure relief oil path respectively.

[0037] Lowering action of the first-stage lifting operation: S21. When operating the first-stage lowering fingertip switch, the motor stops working and the gear pump stops working. Open the first-stage oil return path, that is, the piston rod in the first-stage lifting left oil cylinder group pushes the oil into the first-stage oil return path under the action of gravity to drive the first-stage lifting oil cylinder group to lower; S22. Collect the current working oil pressure V21 of the first-stage oil return path and the lowering position of the first-stage lifting oil cylinder group; When V21 > V0, control the current magnitude of the first two-position two-way electromagnetic proportional valve set in the first-stage oil return path to reduce the opening size of the first two-position two-way electromagnetic proportional valve, thereby reducing the lowering speed; When the lowering position is 15 - 20 mm from the bottommost end, control the current of the first two-position two-way electromagnetic proportional valve set in the first-stage oil return path to decrease in a ramp, making its opening decrease linearly and the lowering speed decrease uniformly; When the lowering position is 15 - 20 mm from the bottommost end and V21 < V0, open the pressure relief oil path to allow the oil in the booster oil cylinder to enter the hydraulic oil tank for pressure relief; thus, the automatic pressure relief function of the whole vehicle is completed.

[0038] Lifting action of the second-stage lifting operation: S31. When operating the second-stage lifting fingertip switch, the motor drives the gear pump to deliver oil, and at the same time open the second-stage lifting oil path to drive the second-stage lifting oil cylinder group to lift; S32. Real-time collect the current working oil pressure V12 of the second-stage lifting oil path, When V12 > V0, reduce the motor speed to the preset speed n1 (such as 2000 rpm), thereby reducing the second-stage lifting speed; At the same time, open the booster oil path, and the oil in the second-stage lifting oil path enters the booster oil cylinder through the booster oil path to automatically boost the second-stage lifting oil path; S33. Collect the lifting position of the secondary lifting oil cylinder group. When the lifting position is 15 - 20 mm away from the topmost end, reduce the motor speed to decrease the flow rate slope of the oil discharged by the gear pump, and uniformly reduce the secondary lifting speed, thus realizing the automatic buffering function when the secondary lifting oil cylinder group is almost at the top. After lifting to the top, open the safety overflow valve on the first pressure relief oil circuit. Meanwhile, open the two-position two-way electromagnetic proportional valve on the pressure relief oil circuit to allow the oil to return to the hydraulic oil tank through the first pressure relief oil circuit and the second pressure relief oil circuit respectively.

[0039] The lowering action of the secondary lifting operation: S41. Operate the secondary lowering fingertip switch, stop the motor, and simultaneously open the secondary oil return circuit (while closing the primary oil return circuit) to drive the secondary lifting oil cylinder group to lower. S42. Collect the current working oil pressure V22 of the secondary oil return circuit and the lowering position of the secondary lifting oil cylinder group. When the lowering position is 15 - 20 mm away from the bottommost end, control the current slope of the second two-position two-way electromagnetic proportional valve installed on the secondary oil return circuit to decrease, linearly reduce its opening, and uniformly reduce the lowering speed. When lowering to the bottom and V22 < V0, open the pressure relief oil circuit to allow the oil in the booster oil cylinder to enter the hydraulic oil tank for pressure relief.

[0040] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application are within the scope of protection of the claims of the present application.

Claims

1. A hydraulic control method for the main stability of a dual-stabilized forklift, comprising lifting and lowering operations of a primary lifting cylinder group and a secondary lifting cylinder group, characterized in that: It includes the following steps: S1. Set the safety oil pressure V0 of the hydraulic working oil circuit, the safety lifting height H1 of the first-stage lifting cylinder group, and the limit lifting height H. 高 ; S2. When hoisting, open the first-stage hoisting oil circuit of the first-stage hoisting oil cylinder group or the second-stage hoisting oil circuit of the second-stage hoisting oil cylinder group, so as to drive the first-stage hoisting oil cylinder group or the second-stage hoisting oil cylinder group to hoist; S3. Collect the working oil pressure V1 of the hoisting oil circuit in current work. When V1 > V0, reduce the rotational speed of the motor driving the gear pump to the preset high rotational speed n1, thereby reducing the hoisting speed; S4. Collect the hoisting position of the first-stage hoisting oil cylinder group or the second-stage hoisting oil cylinder group in current work. When it hoists to 15 - 20 mm away from the topmost end, continue to reduce the rotational speed of the motor and uniformly reduce the hoisting speed; When hoisting reaches the top, open the unloading oil circuit in the hoisting oil circuit to make the oil in the hoisting oil circuit return to the hydraulic oil tank; S5. When lowering, open the first-stage oil return oil circuit of the first-stage hoisting oil cylinder group or the second-stage oil return oil circuit of the second-stage hoisting oil cylinder group to drive the first-stage hoisting oil cylinder group or the second-stage hoisting oil cylinder group to lower; S6. Real-time collect the working oil pressure V2 of the first-stage or second-stage oil return oil circuit. When V2 > V0, reduce the lowering speed; S7. Collect the lowering position of the first-stage hoisting oil cylinder group or the second-stage hoisting oil cylinder group in current work. When the lowering position of the hoisting oil cylinder group is 15 - 20 mm away from the bottommost end, reduce the oil volume in the oil return oil circuit to uniformly reduce the lowering speed of the hoisting oil cylinder group.

2. The main hydraulic control method for a dual-stabilized forklift according to claim 1, characterized in that: In step S3, it also includes collecting the hoisting height H11 of the first-stage hoisting oil cylinder group in current work; When H11 > H1 and V1 > V0, reduce the hoisting speed and open the pressurizing oil circuit in the first-stage hoisting oil circuit to make the oil in the first-stage hoisting oil circuit enter the pressurizing oil cylinder for pressurization; When H11>H 高 When the motor speed is reduced to the preset low speed n2, the speed is reduced.

3. The main hydraulic control method for a dual-stabilized forklift according to claim 1, characterized in that: In step S3, when V1 > V0 in the second-stage hoisting oil circuit, while reducing the hoisting speed, also open the pressurizing oil circuit in the second-stage hoisting oil circuit to make the oil in the hoisting oil circuit enter the pressurizing oil cylinder for pressurization.

4. A main hydraulic control method for a dual-stabilized forklift according to claim 2 or 3, characterized in that: The collection of the working oil pressure V1 of the hoisting oil circuit in current work is detected by a pressure sensor installed on the first-stage hoisting oil circuit or the second-stage hoisting oil circuit.

5. The main hydraulic control method for a dual-stabilized forklift according to claim 1, characterized in that: The hoisting position or lowering position of the first-stage hoisting oil cylinder group or the second-stage hoisting oil cylinder group is detected by a hoisting photoelectric switch installed on the first-stage hoisting oil cylinder group or the second-stage hoisting oil cylinder group.

6. The main hydraulic control method for a dual-stabilized forklift according to claim 1, characterized in that: In step S7, when the first-stage hoisting oil cylinder group descends to 15 - 20 mm away from the bottommost end and V2 < V0, open the pressure relief oil circuit in the first-stage oil return oil circuit to make the oil in the pressurizing oil cylinder return to the hydraulic oil tank for pressure relief.

7. The main hydraulic control method for a dual-stabilized forklift according to claim 1, characterized in that: In step S7, when the second-stage hoisting oil cylinder group has descended to the bottom and V2 < V0 in the second-stage oil return oil circuit, open the pressure relief oil circuit in the second-stage oil return oil circuit to make the oil in the pressurizing oil cylinder return to the hydraulic oil tank for pressure relief.