Hydraulic action mechanism control method for electric forward-moving fork truck

Abstract

The application discloses a control method of a hydraulic action mechanism of an electric forward-moving forklift, and the main design concept of the application is that a plurality of response time parameters of forklift action switches are stored in a pump controller in advance, including pump motor start-stop time and electromagnetic valve port action time corresponding to each forklift action switch, and the valve port action time and the pump motor start-stop time are provided with a time difference; when it is detected that the forklift action switch is triggered, the pump controller respectively issues instruction signals to the pump motor and the electromagnetic valve port corresponding to the current forklift action switch according to the response time parameters, so that the pump motor start-stop control and the electromagnetic valve opening and closing control with time sequence are realized. Without increasing the cost of the forklift, the application can effectively reduce the abnormal sound and the body shaking of the forklift caused by the action execution mechanism working, optimizes the electrical control of the pump motor and the hydraulic electromagnetic valve, can be flexibly adjusted according to actual needs, and is positioned from the user's use angle, and the comfort of the forklift operation is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of electric forklift control, and more particularly to a control method for the hydraulic actuation mechanism of an electric reach truck. Background Technology

[0002] Reach trucks offer advantages such as small operating space, high lifting height, and low risk of overload at high positions, making them the most widely used product in Category II industrial vehicles. Designed primarily for operation in confined spaces and narrow aisles, these trucks feature a compact structure and high mobility and flexibility, helping users maximize storage space utilization. They are mainly responsible for stacking and moving pallets within warehouses and have a wide range of applications in distribution centers and warehousing environments.

[0003] Currently, most reach trucks experience instantaneous impacts, noise, and shaking during the operation of their actuators, which has become a technological bottleneck in the development of reach truck products.

[0004] For example, during the lifting and switching process (the same situation may also occur during forward and backward movement, tilting, lateral movement, etc., which will not be elaborated here), when the valve port is suddenly closed, the oil pressure between the lifting cylinder and the multi-way reversing valve will suddenly drop due to inertia. The kinetic energy of the liquid flow is converted into pressure energy, which causes high pressure to be generated at the solenoid valve port and brings impact vibration. In addition, the pump motor is often blocked, which causes the pressure in the pipeline to rise sharply and produce abnormal noises such as whistling.

[0005] To address the noise and vibration issues caused by the instantaneous change in motion state, a common solution is to add an accumulator and a one-way throttle valve to the hydraulic circuit. This replenishes or releases the pressure inside the hydraulic lines during the reversal, forming a buffer circuit. However, this approach has two drawbacks: firstly, it increases costs, and secondly, the buffering effect is not significant according to actual tests. Summary of the Invention

[0006] In view of the above, the present invention aims to provide a control method for the hydraulic action mechanism of an electric reach truck to solve the aforementioned technical problems.

[0007] The technical solution adopted in this invention is as follows:

[0008] This invention provides a control method for the hydraulic actuator of an electric reach truck, comprising:

[0009] The pump controller stores the response time parameters of several forklift action switches in advance. The response time parameters include the pump motor start-up and stop time and the valve port actuation time of the solenoid valve corresponding to each forklift action switch. The valve port actuation time and the pump motor start-up and stop time have a preset time difference.

[0010] When the forklift action switch is detected to be triggered, the pump controller issues command signals to the pump motor and the solenoid valve port corresponding to the currently triggered forklift action switch according to the response time parameter. The command signals include: start and stop signals for the pump motor, and open and close signals for the solenoid valve port.

[0011] In at least one of the possible implementations, the pump controller also stores a preset variable rate of the pump motor associated with the response time parameter, the variable rate including an acceleration rate and a deceleration rate;

[0012] When the forklift action switch is triggered, the pump controller adjusts the pump motor speed according to the variable rate.

[0013] In at least one possible implementation, the response time parameter is characterized by a pre-calibrated electrical characteristic curve that includes the pump motor response time and the corresponding solenoid valve orifice response time.

[0014] In at least one of the possible implementations, the triggering includes switching the action direction, starting from static, or switching from running to stopping.

[0015] In at least one of the possible implementations, the forklift action switch includes any one of the following: a lifting switch, a forward / backward movement switch, a tilting switch, or a side movement switch.

[0016] In at least one of the possible implementations, the valve opening signal sent by the pump controller to the solenoid valve also includes a valve opening degree control command based on the current magnitude.

[0017] In at least one possible implementation, the control method further includes:

[0018] After the forklift action switch triggers the forklift mast to perform a lowering action, it is detected and determined whether the operation has entered the stage of switching from the end of the stroke of the rear lifting cylinder to the stroke stage of the front lifting cylinder.

[0019] If so, a trigger signal is input to the pump controller, forcing the pump controller to output a preset larger current to the solenoid valve.

[0020] Compared with existing technologies, the main design concept of this invention lies in pre-storing response time parameters of several forklift action switches in the pump controller, including the pump motor start-up and stop times and the valve port actuation times of the corresponding solenoid valves for each forklift action switch, with a time difference between the valve port actuation time and the pump motor start-up and stop times. When a forklift action switch is detected to be triggered, the pump controller sends command signals to the pump motor and the solenoid valve port corresponding to the current forklift action switch according to the response time parameters, thereby realizing time-sequential pump motor start-up and stop and solenoid valve opening and closing control. This invention, without increasing forklift costs, can effectively reduce abnormal noise and vehicle body shaking caused by the forklift's actuators, optimize the electrical control of the pump motor and hydraulic solenoid valves, and can be flexibly adjusted according to actual needs, thus significantly improving the comfort of forklift operation from the user's perspective.

[0021] Furthermore, after triggering the forklift mast to perform the lowering action, when it is detected and determined that the stroke of the rear lifting cylinder has ended and the stroke of the front lifting cylinder has switched, a trigger signal is input to the pump controller, forcing the pump controller to output a preset larger current to the solenoid valve to increase the corresponding oil flow. This improves the high mast operation efficiency of the forklift safely, effectively and cost-efficiently. In particular, when the forklift mast is lowering, the operation efficiency of switching from the rear cylinder stroke to the front cylinder is greatly improved, further enhancing the forklift's operating performance and maximizing the satisfaction of driving operation requirements. Attached Figure Description

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described below with reference to the accompanying drawings, wherein:

[0023] Figure 1 A flowchart illustrating the control method for the hydraulic actuation mechanism of an electric reach truck provided in an embodiment of the present invention;

[0024] Figure 2 This is a schematic diagram of the electrical characteristic curves of the response time parameters provided in an embodiment of the present invention. Detailed Implementation

[0025] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0026] This invention proposes an embodiment of a control method for the hydraulic actuator of an electric reach truck, specifically, as follows: Figure 1 As shown, it includes:

[0027] Step S1: The response time parameters of several forklift action switches are stored in the pump controller in advance;

[0028] The forklift operation switches mentioned here include: lifting switches, forward / backward switches, tilt switches, side-shift switches, etc.; and the response time parameter specifically refers to: the pump motor start-up and closing time and the valve port actuation time of the solenoid valve corresponding to each of the forklift operation switches, and the valve port actuation time and the pump motor start-up and closing time have a preset time difference. In actual operation, it can be pre-calibrated as follows: Figure 2 The schematic diagram shows the electrical characteristic curves of the pump motor response time and the corresponding solenoid valve orifice response time. Taking a lifting switch as an example, the opening time of the solenoid valve orifice corresponding to the lifting or lowering action triggered by the lifting switch is earlier than the pump motor start time, while the pump motor stop time is earlier than the closing time of the solenoid valve orifice corresponding to the lifting or lowering action. It should be noted that in some preferred embodiments of the present invention, the closing time of the solenoid valve orifice needs to be designed within a predetermined time length threshold. This is because if the closing timeout is extended, the forklift action may not be able to reliably stop or switch.

[0029] Step S2: When the forklift action switch is detected to be triggered (the triggering here is not limited to the switching of action direction, but can also include the change from static start-up and from running to stopping, that is, the state of a certain action actuator changes relative to the previous moment), the pump controller sends command signals to the pump motor and the solenoid valve port corresponding to the currently triggered forklift action switch according to the response time parameter.

[0030] From the above, it can be understood that the time difference achieves the following effect:

[0031] When the actuator starts, stops, or changes direction, during the oil supply phase, a certain flow rate is allowed to pass through the corresponding solenoid valve port to prevent the pump motor speed from reaching the preset value before the valve port is opened. When the oil supply is stopped, the closing time of the corresponding valve port is extended to avoid the impact caused by the sudden closure of the valve port.

[0032] The command signals mentioned herein include:

[0033] (1) For the start and stop signals of the pump motor;

[0034] In addition, in some other embodiments, the pump controller also stores a preset variable speed of the pump motor, which includes an acceleration rate and a deceleration rate. When the forklift action switch is triggered, the pump controller adjusts the speed of the pump motor according to the variable speed.

[0035] Taking the lifting switch as another example, while adjusting the motor opening and closing time according to the above response time parameter, the pump motor speed can be adjusted for acceleration and deceleration according to this variable rate. Those skilled in the art will understand that the setting of the variable rate and the setting of the response time parameter need to be calibrated together.

[0036] (2) For the valve opening and closing signals of the solenoid valve;

[0037] In addition, the valve opening signal sent by the pump controller to the solenoid valve also includes a valve opening degree control command based on the magnitude of the current supplied to the solenoid valve coil.

[0038] To elaborate further, modern warehousing systems have abandoned the traditional horizontal expansion model of warehouses, shifting towards vertical expansion. Using high racking not only improves land utilization and inventory capacity but also reduces land costs for businesses. Therefore, reach trucks have a small operating space and a high lifting height, generally optimal at 6-8 meters, with the highest operating height for seated reach trucks currently on the market reaching 12.5 meters. However, the higher the forklift mast lifting height, the longer the operator's lifting operation takes, resulting in lower operational efficiency. Taking a three-stage reach truck mast as an example, its descent can be divided into two stages: the first stage is the descent of the inner mast, i.e., the stroke stage of the rear lifting cylinder; the second stage is the descent of the fork carriage, i.e., the stroke stage of the front lifting cylinder. The speed reduction caused by switching from the rear cylinder to the front cylinder after the rear cylinder's stroke is very significant.

[0039] In this situation, the conventional solution is to simply adjust the mast lifting speed by changing the pump motor speed. However, increasing the forklift mast lifting speed in this way will also cause the instantaneous impact and shaking during lifting and lowering, as mentioned earlier. This is especially true for high masts, and may even increase the risk of rollover accidents. Therefore, this invention proposes that the mast lowering speed be determined based on factors such as the weight of the mast and the cargo, the cylinder diameter, the rolling resistance of the mast, and the valve opening size of the solenoid valve. The weight of the mast and the cargo, as well as the rolling resistance of the mast, can be determined beforehand. For the cylinder diameter, a preferred configuration is a 1:1 ratio between the diameters of the front and rear lifting cylinders, which minimizes the reduction in speed of the front cylinder. Therefore, from the perspective of the electrical control of this invention, specific implementation details can be designed for adjusting the valve opening of the solenoid valve.

[0040] Based on the aforementioned concept that the output current of the pump controller can control the opening degree of the solenoid valve, this invention provides an embodiment of a hydraulic actuation mechanism control method for the lowering action of a forklift mast, including:

[0041] After the forklift action switch triggers the forklift mast to perform a lowering action, it is detected and determined whether it has entered the stage of: the end of the stroke of the rear lifting cylinder and the switch to the stroke stage of the front lifting cylinder (corresponding to the second lowering stage mentioned above);

[0042] If so, a preset trigger signal is input to the pump controller, forcing the pump controller to output a preset larger current to the solenoid valve (which can be increased by 2 times, 3 times, etc., based on the solenoid valve control current during normal lifting and lowering of the forklift), so that the opening of the solenoid valve corresponding to this action stage increases, thereby increasing the hydraulic oil flow through the valve port instantaneously to improve the lowering efficiency.

[0043] Finally, based on the above embodiments, it can be further explained that, for the implementation of inputting a preset trigger signal to the pump controller, two photoelectric elements staggered by 1 / 4 pitch can be preferably configured and placed on the outer side of the forklift's mast to sense the sides of the forks. The electrical signals output by the two photoelectric elements should be 90° out of phase with each other (if one is used as a reference signal, the other signal leads or lags the reference signal by 90°, thereby determining the direction of movement). In this way, when the forklift mast is triggered to descend, the photoelectric elements can accurately sense the fork carriage and determine the current direction of movement (avoiding misjudging it as an upward phase). At this time, a valid level signal can be output to the pump controller, allowing the pump controller to provide a larger current to the corresponding solenoid valve port according to a predetermined program.

[0044] In summary, the main design concept of this invention lies in pre-storing response time parameters of several forklift action switches within the pump controller. These parameters include the pump motor start-up and closing times and the corresponding solenoid valve actuation times for each forklift action switch, with a time difference between the valve actuation time and the pump motor start-up and closing times. When a forklift action switch is detected to be triggered, the pump controller sends command signals to the pump motor and the solenoid valve corresponding to the current forklift action switch based on the response time parameters, thereby achieving time-sequential pump motor start-up and shutdown and solenoid valve opening and closing control. This invention effectively reduces abnormal noise and vehicle body shaking caused by the forklift's actuators without increasing forklift costs, optimizes the electrical control of the pump motor and hydraulic solenoid valves, and allows for flexible adjustment according to actual needs. Ultimately, from the user's perspective, this significantly improves the comfort of forklift operation.

[0045] Furthermore, after triggering the forklift mast to perform the lowering action, when it is detected and determined that the stroke of the rear lifting cylinder has ended and the stroke of the front lifting cylinder has switched, a trigger signal is input to the pump controller, forcing the pump controller to output a preset larger current to the solenoid valve to increase the corresponding oil flow. This improves the high mast operation efficiency of the forklift safely, effectively and cost-efficiently. In particular, when the forklift mast is lowering, the operation efficiency of switching from the rear cylinder stroke to the front cylinder is greatly improved, further enhancing the forklift's operating performance and maximizing the satisfaction of driving operation requirements.

[0046] In this embodiment of the invention, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent the existence of A alone, A and B simultaneously, or B alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship. "At least one of the following" and similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, at least one of a, b, and c can represent: a, b, c, a and b, a and c, b and c, or a and b and c, where a, b, and c can be single or multiple.

[0047] The above description of the structure, features, and effects of the present invention is based on the embodiments shown in the figures. However, the above are only preferred embodiments of the present invention. It should be noted that the technical features involved in the above embodiments and their preferred methods can be reasonably combined and matched by those skilled in the art to form a variety of equivalent solutions without departing from or changing the design concept and technical effects of the present invention. Therefore, the present invention is not limited to the scope of implementation shown in the figures. Any changes made in accordance with the concept of the present invention, or modifications to equivalent embodiments, that do not exceed the spirit covered by the specification and figures, should be within the protection scope of the present invention.

Claims

1. A control method for the hydraulic actuator of an electric reach truck, characterized in that, include: The pump controller stores the response time parameters of several forklift action switches in advance. These response time parameters include the pump motor start-up and stop times and the valve port actuation time of the solenoid valve corresponding to each forklift action switch. The valve port actuation time and the pump motor start-up and stop times have a preset time difference. This time difference means that the opening time of the solenoid valve corresponding to the lifting action is earlier than the pump motor start time, and the pump motor stop time is earlier than the closing time of the solenoid valve corresponding to the lifting action. This is used to ensure that during the start-up, stop-up, or direction-switching of the actuator, a certain flow rate passes through the corresponding solenoid valve during the oil supply phase, preventing the pump motor speed from reaching the preset value before the valve port is open. Furthermore, for stopping oil supply, the closing time of the corresponding valve port is extended to avoid sudden valve closure causing impact. When the forklift action switch is detected to be triggered, the pump controller issues command signals to the pump motor and the valve port of the solenoid valve corresponding to the currently triggered forklift action switch according to the response time parameter. The command signals include: start and stop signals for the pump motor, and open and close signals for the solenoid valve.

2. The control method for the hydraulic actuation mechanism of an electric reach truck according to claim 1, characterized in that, The pump controller also stores a preset variable rate of the pump motor associated with the response time parameter, the variable rate including acceleration rate and deceleration rate; When the forklift action switch is triggered, the pump controller adjusts the pump motor speed according to the variable rate.

3. The control method for the hydraulic actuation mechanism of an electric reach truck according to claim 1, characterized in that, The response time parameter is characterized by a pre-calibrated electrical characteristic curve that includes the pump motor response time and the corresponding solenoid valve orifice response time.

4. The control method for the hydraulic actuation mechanism of an electric reach truck according to claim 1, characterized in that, The triggering includes switching the action direction, starting from static or switching from running to stopping.

5. The control method for the hydraulic actuation mechanism of an electric reach truck according to claim 1, characterized in that, The forklift action switch includes any one of the following: lifting switch, forward / backward movement switch, tilting switch, and side movement switch.

6. The control method for the hydraulic actuation mechanism of an electric reach truck according to any one of claims 1 to 5, characterized in that, The valve opening signal sent by the pump controller to the solenoid valve also includes valve opening degree control commands based on the current magnitude.

7. The control method for the hydraulic actuation mechanism of an electric reach truck according to claim 6, characterized in that, The control method further includes: After the forklift action switch triggers the forklift mast to perform a lowering action, it is detected and determined whether the operation has entered the stage of switching from the end of the stroke of the rear lifting cylinder to the stroke stage of the front lifting cylinder. If so, a trigger signal is input to the pump controller, forcing the pump controller to output a preset larger current to the solenoid valve.

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