Triple Hydraulic Control System for Forklift Trucks Enabling Dual-Mode Driving

Abstract

The present invention discloses a triple hydraulic control system for a forklift capable of realizing dual-mode driving, belonging to the technical field of the hydraulic system of an electric forklift. The oil outlet of the pump is connected to a multi-way valve, and the multi-way valve is respectively connected to a lifting cylinder, a tilting cylinder and a third oil cylinder; the oil return port of the multi-way valve is connected to a selection valve; the selection valve is connected to a first solenoid valve, a second solenoid valve and a third solenoid valve; the first solenoid valve is connected to the oil inlet of the lifting cylinder; the second solenoid valve is connected to the tilting cylinder; the third solenoid valve is connected to the third oil cylinder. The balance valve of the present invention ensures the smooth operation of the forklift when the forklift performs a forward tilting action; the retarder valve performs speed throttling control when the forklift forks descend, and the descent is smooth; when a failure occurs in the hydraulic system in the automatic driving mode, it automatically switches to the hydraulic system in the manual driving mode.

Description

Technical Field

[0001] The present invention relates to a hydraulic system for an electric forklift, and specifically to a triple hydraulic control system for a forklift that can achieve dual-mode driving. Background Art

[0002] It is a trend for electric counterbalance forklifts to achieve unmanned automatic driving, which can improve productivity. The existing hydraulic system for the manual driving mode is a traditional mechanical valve and cannot perform proportional control using the electrical signals of the controller. Considering a full switch to solenoid valves, the cost increases too much. At the same time, in case of a failure in the hydraulic system, the entire vehicle in the automatic driving mode cannot move, which will reduce production efficiency. Therefore, on the basis of the automatic driving mode, it is necessary to retain the existing manual driving mode.

[0003] A Chinese patent discloses a triple hydraulic control system for a forklift that can achieve automatic driving and manual driving. The first oil circuit of the selection valve is connected to the multi-way valve, and the second oil circuit of the selection valve is connected to the priority valve; the oil outlet A of the priority valve is respectively connected to the first solenoid valve, the second solenoid valve, and the third solenoid valve; the first solenoid valve is connected to the lifting cylinder, the second solenoid valve is connected to the tilt cylinder, and the third solenoid valve is connected to the third oil cylinder; the PF port of the priority valve is connected to the PF port of the multi-way valve through a check valve; the LS port of the priority valve is connected to the LS port of the multi-way valve; the multi-way valve is controllably connected to the lifting cylinder, the tilt cylinder, and the third oil cylinder; the controller is electrically connected to the pump, the selection valve, the first solenoid valve, the second solenoid valve, and the third solenoid valve. The hydraulic system of this invention can achieve automatic driving control and manual driving control, and at the same time can have an energy-saving mode for automatic driving. The deficiencies of the above technology are: two priority valves are needed to achieve priority steering, the oil circuit is complex, and the control is inconvenient. Summary of the Invention

[0004] Based on the above technical problems, the present invention provides a triple hydraulic control system for a forklift that can achieve dual-mode driving.

[0005] The present invention is achieved through the following technical solutions: A triple hydraulic control system for a forklift that can achieve dual-mode driving, the oil outlet of the pump is connected to a multi-way valve, and the multi-way valve is respectively connected to a lifting cylinder, a tilt cylinder, and a third oil cylinder;

[0006] The oil return port of the multi-way valve is connected to a selection valve;

[0007] The selection valve is connected to a first solenoid valve, a second solenoid valve, and a third solenoid valve;

[0008] The first solenoid valve is connected to the oil inlet of the lifting cylinder;

[0009] The second solenoid valve is connected to the tilt cylinder;

[0010] The third solenoid valve is connected to the third oil cylinder.

[0011] Furthermore, the A1 port of the multi-way valve is connected to the large chamber of the lifting cylinder, and the B1 port is blocked with an oil plug; the A2 port of the multi-way valve is connected to the large chamber of the tilt cylinder, and the B2 port is connected to the small chamber of the tilt cylinder; the A5 port of the multi-way valve is connected to the large chamber of the third oil cylinder, and the B5 port is connected to the small chamber of the third oil cylinder; the PF port of the multi-way valve is connected to the oil inlet of the steering system, and the LS port is connected to the control oil port of the steering system.

[0012] The 2 port of the selector valve is respectively connected to the P3 port of the first solenoid valve, the P4 port of the second solenoid valve, and the P6 port of the third solenoid valve, and the 1 port of the selector valve is connected to the fuel tank;

[0013] The A3 port of the first solenoid valve is connected to the oil inlet of the lifting cylinder, and the B3 port is blocked with an oil plug; the A4 port of the second solenoid valve is connected to the large chamber oil inlet of the tilt cylinder, and the B4 port is connected to the small chamber oil inlet of the tilt cylinder; the A6 port of the third solenoid valve is connected to the large chamber oil inlet of the third oil cylinder, and the B6 port is connected to the small chamber oil inlet of the third oil cylinder.

[0014] The B4 port of the second solenoid valve is connected with a balance valve, and the other oil port of the balance valve is connected to the small chamber oil inlet of the tilt cylinder.

[0015] The large chamber of the lifting cylinder is connected with a speed reducing valve, and the oil inlet of the speed reducing valve is respectively connected to the A3 port of the first solenoid valve and the A1 port of the multi-way valve.

[0016] The pump and the motor are connected by a spline.

[0017] The controller is connected to the pump motor, the first solenoid valve, the second solenoid valve, the third solenoid valve and the selector valve through a circuit.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. The selector valve is connected to the oil return port of the multi-way valve, without affecting the original mechanical control; the automatic driving system uses the priority valve integrated in the original multi-way valve to achieve priority steering, simplifies the system structure, and is easier to achieve priority control of the oil circuit;

[0020] 2. The balance valve ensures the smooth operation of the forklift when the forklift performs a forward tilt action; the speed reducing valve performs speed throttling control when the forklift forks descend, and the descent is smooth;

[0021] 3. When a failure occurs in the hydraulic system of the automatic driving mode, the selector valve can achieve automatic power-off and automatically switch to the hydraulic system of manual driving. The driver can still operate the forklift normally to work, or drive to the maintenance point for fixed-point maintenance, improving the maintenance efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is the working principle diagram of the present invention;

[0023] In the figure: 1. Pump; 2. Selective valve; 3. Balance valve; 4. First solenoid valve; 5. Second solenoid valve; 6. Lifting cylinder; 7. Tipping cylinder; 8. Multi-way valve; 9. Retarding valve; 10. Pump motor; 11. Controller; 12. Third oil cylinder; 13. Third solenoid valve. Detailed implementation mode

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0025] Combined with Figure 1 As shown, a triple hydraulic control system for a forklift that can achieve dual-mode driving. The pump 1 is connected to the motor 10 through a spline. The pump 1 sucks oil from the fuel tank, and the oil outlet of the pump 1 is connected to the P port of the multi-way valve 8;

[0026] The A1 port of the multi-way valve 8 is connected to the inlet port of the retarding valve 9. The outlet port of the retarding valve 9 is connected to the large chamber of the lifting cylinder 6. The B1 port of the multi-way valve 8 is blocked with an oil plug. The A2 port of the multi-way valve 8 is connected to the large chamber of the tipping cylinder 7. The B2 port of the multi-way valve 8 is connected to the small chamber of the tipping cylinder 7. The A5 port of the multi-way valve 8 is connected to the large chamber of the third oil cylinder 12. The B5 port of the multi-way valve 8 is connected to the small chamber of the third oil cylinder 12. The PF port of the multi-way valve 8 is connected to the inlet port of the steering system, and the LS port is connected to the control oil port of the steering system.

[0027] The selective valve 2 switches between the automatic driving and manual driving modes. The inlet port of the selective valve 2 is connected to the return port T of the multi-way valve 8. The port 1 of the selective valve is connected to the fuel tank. The port 2 of the selective valve 2 is respectively connected to the P3 port of the first solenoid valve 4, the P4 port of the second solenoid valve 5, and the P6 port of the third solenoid valve 13;

[0028] The A3 port of the first solenoid valve 4 is connected to the inlet port of the retarding valve 9. The B3 port is blocked with an oil plug; the T3 port is connected to the fuel tank for oil return. The retarding valve smoothly controls the descending speed of the forklift forks. When the forklift forks are descending, speed throttling control is performed;

[0029] The A4 port of the second solenoid valve 5 is connected to the inlet port of the large chamber of the tipping cylinder 7. The B4 port is connected to the inlet port of the balance valve 3. The outlet port of the balance valve 3 is connected to the inlet port of the small chamber of the tipping cylinder 7; the T4 port is connected to the fuel tank for oil return. The balance valve mainly controls the whole vehicle to ensure a certain back pressure for the oil return of the small chamber during the forward tipping action, ensuring the smooth operation of the forward tipping action;

[0030] The A6 port of the third solenoid valve 13 is connected to the inlet port of the large chamber of the third oil cylinder 12. The B6 port is connected to the inlet port of the small chamber of the third oil cylinder 12; the T6 port is connected to the fuel tank for oil return.

[0031] Furthermore: The third solenoid valve 13 and the third oil cylinder 12 in this embodiment can be removed, and in this case, it is applicable to the forklift two-stage hydraulic control system.

[0032] The controller 11 is electrically connected to the pump motor 10, the first solenoid valve 4, the second solenoid valve 5, the third solenoid valve 13, and the selector valve 2. The first solenoid valve, the second solenoid valve, and the third solenoid valve respectively control the lift cylinder, the tilt cylinder, and the third oil cylinder, so as to realize the integration of two hydraulic control modes of the electric forklift. When a fault occurs in the hydraulic system of the automatic driving mode, the selector valve can cut off the power automatically and switch to the hydraulic system of the manual driving mode automatically. The driver can still operate the forklift normally to work and drive it to the maintenance point for fixed-point maintenance, improving the maintenance efficiency.

[0033] Working principle:

[0034] The pump outlet passes through the multi-way valve, and the return oil port of the multi-way valve is connected to the selector valve to perform the selection and switching between the automatic driving and the manual driving modes, and the circuit signal for the selection and switching is controlled by the controller;

[0035] The first solenoid valve adopts the O-type function to control the lift cylinder of the electric forklift. When the forklift is lifted, the controller outputs control signals to the pump motor, the selector valve, and the first solenoid valve respectively. The pump motor drives the pump to operate, the selector valve switches to the automatic driving mode, and after the solenoid valve is energized, the spool moves to the right, and the oil circuit for the lifting action is connected, and the whole vehicle performs the lifting action;

[0036] When the forklift fork needs to be lowered, the controller outputs control signals to the pump motor, the selector valve, and the first solenoid valve respectively. The pump motor drives the pump to operate, the selector valve switches to the manual driving mode, and after the solenoid valve is de-energized, the spool moves to the left, and the lower chamber of the lift cylinder is connected to the return oil circuit, and it descends under the action of gravity, while the oil inlet is blocked. At this time, the controller controls the pump motor to operate at a low speed, and at the same time, the selector valve is de-energized, and the main oil circuit returns oil through the multi-way valve; that is, when the fork is lowered, the pump unloads through the multi-way valve.

[0037] The second solenoid valve controls the tilting cylinder to tilt forward or backward. When tilting forward is required, the controller outputs control signals to the pump motor, the selection valve, and the second solenoid valve respectively. The pump motor drives the pump to operate. The selection valve switches to the automatic driving mode. The second solenoid valve is energized, and the spool moves to the right. The hydraulic oil flows through the pump, the selection valve, the second solenoid valve to the tilting cylinder to perform the forward tilting action. When the large chamber of the tilting cylinder is filled with oil and the small chamber returns oil, it needs to pass through the balance valve for oil return to ensure the smooth operation of the forward tilting action. When tilting backward is required, the controller outputs control signals to the pump motor, the selection valve, and the second solenoid valve respectively. The pump motor drives the pump to operate. The selection valve switches to the automatic driving mode. The second solenoid valve is energized, and the spool moves to the left. The hydraulic oil flows through the pump, the selection valve, the second solenoid valve to the tilting cylinder to perform the backward tilting action. The small chamber of the tilting cylinder is filled with oil and the large chamber returns oil.

[0038] The third solenoid valve controls the extension and retraction of the third oil cylinder. When extension is required, the controller outputs control signals to the pump motor, the selection valve, and the third solenoid valve respectively. The pump motor drives the pump to operate. The selection valve switches to the automatic driving mode. The third solenoid valve is energized, and the spool moves to the right. The hydraulic oil flows through the pump, the multi-way valve, the selection valve, the third solenoid valve to the third oil cylinder to perform the extension action. The large chamber of the tilting cylinder is filled with oil and the small chamber returns oil. When retraction is required, the controller outputs control signals to the pump motor, the selection valve, and the third solenoid valve respectively. The pump motor drives the pump to operate. The selection valve switches to the automatic driving mode. The third solenoid valve is energized, and the spool moves to the left. The hydraulic oil flows through the pump, the multi-way valve, the selection valve, the third solenoid valve to the third oil cylinder to perform the retraction action. The small chamber of the tilting cylinder is filled with oil and the large chamber returns oil. Since the action requirements of the third oil cylinder are smooth, the control current given by the controller to the pump motor is small. Generally, the pump motor only needs to maintain a relatively low rotational speed, about 600 r / min. Therefore, the variable displacement speed regulation function is achieved through the rotational speed of the pump.

[0039] When the automatic driving mode is started and there are neither lifting, lowering actions, nor forward, backward tilting actions, nor steering actions, then the controller will output control signals to the selection valve and the pump motor. The selection valve automatically switches to the manual driving mode. The pump motor drives the pump to operate at a low speed. The pump unloads through the multi-way valve to reduce the heat generation of the hydraulic system, that is, the energy-saving mode.

[0040] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A triple hydraulic control system for a forklift that can achieve dual-mode driving. The oil outlet of the pump (1) is connected to a multi-way valve (8), and the multi-way valve (8) is respectively connected to a lifting cylinder (6), a tilt cylinder (7), and a third cylinder (12); characterized in that: The oil return port of the multi-way valve (8) is connected to a selection valve (2); The selection valve (2) is connected to a first solenoid valve (4), a second solenoid valve (5), and a third solenoid valve (13); The first solenoid valve (4) is connected to the oil inlet of the lifting cylinder (6); The second solenoid valve (5) is connected to the tilt cylinder (7); The third solenoid valve (13) is connected to the third cylinder (12); The A1 port of the multi-way valve (8) is connected to the large chamber of the lifting cylinder (6), and the B1 port is blocked with an oil plug; the A2 port of the multi-way valve (8) is connected to the large chamber of the tilt cylinder (7), and the B2 port is connected to the small chamber of the tilt cylinder (7); the A5 port of the multi-way valve (8) is connected to the large chamber of the third cylinder (12), and the B5 port is connected to the small chamber of the third cylinder (12); the PF port of the multi-way valve (8) is connected to the oil inlet of the steering system, and the LS port is connected to the control oil port of the steering system; The port 2 of the selection valve (2) is respectively connected to the P3 port of the first solenoid valve (4), the P4 port of the second solenoid valve (5), and the P6 port of the third solenoid valve (13), and the port 1 of the selection valve is connected to the fuel tank; The A3 port of the first solenoid valve (4) is connected to the oil inlet of the lifting cylinder (6), and the B3 port is blocked with an oil plug; the A4 port of the second solenoid valve (5) is connected to the oil inlet of the large chamber of the tilt cylinder (7), and the B4 port is connected to the oil inlet of the small chamber of the tilt cylinder (7); the A6 port of the third solenoid valve (13) is connected to the oil inlet of the large chamber of the third cylinder (12), and the B6 port is connected to the oil inlet of the small chamber of the third cylinder (12).

2. The triple hydraulic control system for a forklift capable of dual-mode driving according to claim 1, characterized in that: The B4 port of the second solenoid valve (5) is connected to a balance valve (3), and the other oil port of the balance valve (3) is connected to the oil inlet of the small chamber of the tilt cylinder (7).

3. The triple hydraulic control system for a forklift capable of realizing dual-mode driving according to claim 1, wherein: The large chamber of the lifting cylinder (6) is connected to a speed reduction valve (9), and the oil inlet of the speed reduction valve (9) is respectively connected to the A3 port of the first solenoid valve (4) and the A1 port of the multi-way valve (8).

4. The triple hydraulic control system for a forklift capable of dual-mode driving according to claim 1, characterized in that: The pump (1) is connected to the motor (10) through a spline.

5. The triple hydraulic control system for a forklift capable of achieving dual-mode driving according to claim 4, characterized in that: The controller (11) is connected to the pump motor (10), the first solenoid valve (4), the second solenoid valve (5), the third solenoid valve (13), and the selection valve (2) through an electric circuit.

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