Electric steering system for an electric fork lift truck

Abstract

This invention relates to the field of forklift steering technology and discloses an electric steering system for an electric forklift, including a steering axle assembly, a steering wheel assembly, a left drive axle, a right drive axle, and a controller assembly. The steering wheel assembly is equipped with a torque sensor that detects the rotation angle of the steering wheel and outputs steering damping. When the torque sensor detects a steering wheel rotation angle of α, the controller assembly controls the rotation angle β of the steering wheel of the steering axle assembly to be α = α / A, the angular velocity ω1 of the left drive wheel of the left drive axle to be β(cotβ-L / 2) / 2πrt, and the angular velocity ω2 of the right drive wheel of the right drive axle to be β(cotβ+L / 2) / 2πrt; where A is the amplification factor of the steering wheel angle, B is the forklift wheelbase, L is the drive wheel track, r is the drive wheel radius, and t is the steering time. Therefore, it has the advantages of light operating force, good following and sensitivity, low noise, energy saving and environmental protection, simple structure, and easy interior layout.

Description

Technical Field

[0001] This invention relates to the field of forklift steering technology, and more specifically, to an electric steering system for an electric forklift. Background Technology

[0002] Currently, most three-point forklifts use hydraulic steering or electric power steering. Hydraulic steering systems are reliable and safe, but they have drawbacks such as high noise, high energy consumption, poor tracking and sensitivity, and susceptibility to pollution. Electric power steering systems offer good tracking and sensitivity, but require the installation of a mechanical transmission mechanism. Since forklifts are rear-wheel steering vehicles with compact interior space, it is difficult to install such a mechanical transmission mechanism.

[0003] In summary, how to provide a steering system that offers good responsiveness and sensitivity while being easy to deploy is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide an electric steering system for an electric forklift, which has light operating force, good following and sensitivity, low noise, energy saving and environmental protection, and simple structure, small size and easy interior layout.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] An electric steering system for an electric forklift, comprising a steering axle assembly, a steering wheel assembly, a left drive axle, a right drive axle, and a controller assembly, wherein the left drive axle and the right drive axle are symmetrically arranged about the axis of the forklift, and the steering axle assembly, the steering wheel assembly, the left drive axle, and the right drive axle are all signal connected to the controller assembly;

[0007] The steering wheel assembly is equipped with a torque sensor for detecting the rotation angle of the steering wheel and outputting steering damping.

[0008] When the torque sensor detects that the steering wheel rotation angle is α, the controller assembly controls the rotation angle β=α / A of the steering wheel of the steering axle assembly, the angular velocity ω1=β(cotβ-L / 2) / 2πrt of the left drive wheel of the left drive axle, and the angular velocity ω2=β (cotβ+L / 2) / 2πrt of the right drive wheel of the right drive axle.

[0009] Where A is the amplification factor of the steering wheel angle, B is the forklift wheelbase, L is the drive wheel track, r is the drive wheel radius, and t is the steering time.

[0010] Preferably, the steering axle assembly includes the steering wheel, the steering motor, and the reduction gearbox, wherein the input end of the reduction gearbox is connected to the output shaft of the steering motor, and the output end of the reduction gearbox is connected to the steering shaft of the steering wheel;

[0011] The steering motor is equipped with a speed sensor for detecting the rotational speed of the steering motor, and the output end or the steering shaft is equipped with an angle sensor for detecting the rotational angle of the steering wheel. The steering motor, the angle sensor and the speed sensor are all connected to the controller assembly via signal connection.

[0012] Preferably, when the speed sensor detects that the rotational speed n of the steering motor exceeds a first preset speed n1, the controller assembly controls the torque sensor to output high steering damping.

[0013] When the speed n of the steering motor detected by the speed sensor is lower than the second preset speed n2, the controller assembly controls the torque sensor to output low steering damping.

[0014] Preferably, the controller assembly includes a left drive controller, a right drive controller, and a steering motor controller. The left drive controller is signal-connected to the left drive axle to control the rotational speed of the left drive wheel, the right drive controller is signal-connected to the right drive axle to control the rotational speed of the right drive wheel, and the steering motor controller is signal-connected to the steering motor to control the rotational speed of the steering motor.

[0015] Preferably, the torque sensor, the speed sensor, and the angle sensor are all non-contact sensors.

[0016] The electric steering system of the electric forklift provided by this invention allows the driver to turn the steering wheel during steering. The torque sensor detects the steering wheel rotation angle α and transmits it to the controller assembly. The controller assembly controls the steering wheel rotation angle β = α / A based on the steering wheel rotation angle α measured by the torque sensor, where A is the amplification factor of the steering wheel angle. At the same time, it controls the angular velocity ω1 = β (cotβ-L / 2) / 2πrt of the left drive wheel and the angular velocity ω2 = β (cotβ+L / 2) / 2πrt of the right drive wheel, thereby realizing differential speed control of the left and right drive wheels and improving driving safety.

[0017] The electric steering system for electric forklifts provided by this invention eliminates the hydraulic valves, hydraulic pipes, hydraulic pumps, and hydraulic cylinders of traditional hydraulic steering systems, as well as the mechanical transmission parts in electric power steering systems. This makes the steering system simple in structure, easy to arrange, and less noisy, more energy-efficient and environmentally friendly. By using a controller assembly to control the differential rotation of the left and right drive axles, the operating force is light, and the following and sensitivity are better. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0019] Figure 1 A schematic diagram of a specific embodiment of the electric steering system for the electric forklift provided by the present invention;

[0020] Figure 2 A schematic diagram illustrating the principle of differential rotation of the left and right drive axles in an electric steering system;

[0021] Figure 3 This is a structural schematic diagram of the steering axle assembly;

[0022] Figure 4 This is a structural diagram of the steering wheel assembly;

[0023] Figure 5 This is a schematic diagram of the controller assembly.

[0024] Figures 1-5 middle:

[0025] 1 is the steering axle assembly, 11 is the speed sensor, 12 is the steering motor, 13 is the angle sensor, 14 is the reduction gearbox, 15 is the steering wheel, 2 is the controller assembly, 21 is the left drive controller, 22 is the right drive controller, 23 is the steering motor controller, 24 is the oil pump motor controller, 3 is the left drive axle, 4 is the steering wheel assembly, 41 is the steering wheel, 42 is the torque sensor, 5 is the right drive axle, 6 is the oil pump motor, β is the rotation angle of the steering wheel. O is the forklift's steering angle, B is the forklift's steering center, L is the forklift's wheelbase, r is the drive wheel track, R1 is the steering radius of the left drive wheel, and R2 is the steering radius of the right drive wheel. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] The core of this invention is to provide an electric steering system for electric forklifts, which is easy to operate, has good following and sensitivity, low noise, energy saving and environmental protection, and has a simple structure, small size and easy interior layout.

[0028] Please refer to Figures 1-5 , Figure 1 A schematic diagram of a specific embodiment of the electric steering system for the electric forklift provided by the present invention; Figure 2 A schematic diagram illustrating the principle of differential rotation of the left and right drive axles in an electric steering system; Figure 3 This is a structural schematic diagram of the steering axle assembly; Figure 4 This is a structural diagram of the steering wheel assembly; Figure 5 This is a schematic diagram of the controller assembly.

[0029] The electric steering system for electric forklifts provided by the present invention is used in electric forklifts such as three-point forklifts. It includes a steering axle assembly 1, a steering wheel assembly 4, a left drive axle 3, a right drive axle 5, and a controller assembly 2. The left drive axle 3 and the right drive axle 5 are symmetrically arranged about the axis of the forklift. The steering axle assembly 1, the steering wheel assembly 4, the left drive axle 3, and the right drive axle 5 are all signal connected to the controller assembly 2.

[0030] The steering wheel assembly 4 is equipped with a torque sensor 42 for detecting the rotation angle of the steering wheel 41 and outputting steering damping;

[0031] When the torque sensor 42 detects that the rotation angle of the steering wheel 41 is α, the controller assembly 2 controls the rotation angle β=α / A of the steering wheel 15 of the steering axle assembly 1, the angular velocity ω1=β(cotβ-L / 2) / 2πrt of the left drive wheel of the left drive axle 3, and the angular velocity ω2=β(cotβ+L / 2) / 2πrt of the right drive wheel of the right drive axle 5.

[0032] Where A is the amplification factor of the steering wheel angle, B is the forklift wheelbase, L is the front track, r is the drive wheel radius, and t is the steering time.

[0033] Please refer to Figure 1 The left drive axle 3 and the right drive axle 5 are symmetrically arranged about the axis of the forklift so as to perform differential control on the left and right drive wheels when turning, thereby improving steering safety. The specific structure, shape and size of the left drive axle 3 and the right drive axle 5 are determined according to the actual size of the forklift in production, and will not be described in detail here.

[0034] The steering axle assembly 1 is located at the rear of the forklift and mainly includes a steering wheel 15 and a steering motor 12 for driving the steering wheel 15. The center plane of the steering wheel 15 is located within the plane of symmetry of the forklift. The specific structure, shape and size of the steering axle assembly 1 are determined according to the actual production needs and will not be described in detail here.

[0035] Please refer to Figure 4 The steering wheel assembly 4 includes a steering wheel 41 and a torque sensor 42. The torque sensor 42 is used to detect the rotation angle α of the steering wheel 41 and output steering damping to the steering wheel 41 to adjust the torque required for the driver to rotate the steering wheel 41 and improve driving safety.

[0036] When the forklift turns, the driver rotates the steering wheel 41, and the torque sensor 42 outputs the rotation angle α of the steering wheel 41 to the controller assembly 2. It should be noted that the rotation angle α of the steering wheel 41 includes the rotation direction information. When the driver turns the steering wheel 41 to the left, the rotation angle α of the steering wheel 41 is a positive value; conversely, when the driver turns the steering wheel 41 to the right, the rotation angle α of the steering wheel 41 is a negative value.

[0037] Taking a forklift turning left as an example, after receiving the steering wheel rotation angle α, the controller assembly 2 can calculate the steering wheel 15 rotation angle β = α / A based on the steering wheel angle amplification factor A. Here, the steering wheel angle amplification factor A is a constant for a specific forklift model, typically set to 4-5. Then, the controller assembly 2 outputs the corresponding rotation angle information to the steering axle assembly 1, causing the steering wheel 15 to rotate by β. Figure 2 As shown.

[0038] According to trigonometric relationships,

[0039] The turning radius of the left drive wheel, R1 = Btan(π / 2 - β) - L / 2 = Bcotβ - L / 2,

[0040] The steering radius of the right drive wheel, R2 = Btan(π / 2 - β) + L / 2 = Bcotβ + L / 2,

[0041] Where B is the forklift wheelbase, which is the distance from the center of the steering wheel 15 to the axis of the drive wheel; L is the drive wheel track, which is the distance from the center plane of the left drive wheel to the center plane of the right drive wheel.

[0042] Depend on Figure 2 The forklift's steering angle can be determined. It is equal to the rotation angle β of the steering wheel 15, therefore,

[0043] Travel distance of the left drive wheel

[0044] Travel distance of the right drive wheel

[0045] Furthermore, according to the definition of angular velocity,

[0046] The angular velocity of the left drive wheel is ω1 = X1 / 2πrt = β(cotβ-L / 2) / 2πrt.

[0047] The angular velocity of the right drive wheel is ω2=X2 / 2πrt=β(cotβ+L / 2) / 2πrt,

[0048] Where r is the radius of the drive wheel and t is the turning time.

[0049] Therefore, the controller assembly 2 can calculate the angular velocity ω1 of the left drive wheel and the angular velocity ω2 of the right drive wheel according to the above formula, and output the above angular velocity information to the left drive axle 3 and the right drive axle 5, thereby realizing differential steering of the left and right drive wheels.

[0050] For example, when the forklift's steering center O is outside the drive wheel track L, the left and right drive wheels rotate in the same direction; when the forklift's steering center O is at the end of the drive wheel track L, the drive wheel at that end is stationary; when the forklift's steering center O is within the drive wheel track L, the left and right drive wheels rotate in opposite directions.

[0051] In this embodiment, the electric steering system eliminates the hydraulic valves, hydraulic pipes, hydraulic pumps and hydraulic cylinders of the traditional hydraulic steering system, as well as the mechanical transmission part in the electric power steering system, making the steering system simple in structure, easy to arrange, and with low noise and greater energy efficiency and environmental friendliness; the controller assembly 2 controls the differential rotation of the left and right drive axles, resulting in lighter operating force, better following and sensitivity.

[0052] In addition, the use of electric power steering system allows for a reduction in the size of the steering wheel 41, thereby increasing the driver's operating space and improving the driver's driving comfort.

[0053] To simplify the forklift's control system and improve its interior space utilization, preferably, the oil pump motor controller 24, which controls the speed of the oil pump motor 6, can be integrated into the controller assembly 2. Since the oil pump motor 6 drives the movement of the forks, the controller assembly 2 can adjust the fork movement in conjunction with the forklift's steering.

[0054] Based on the above embodiments, the structure of the steering axle assembly 1 is further defined; please refer to [reference needed]. Figure 3 The steering axle assembly 1 may include a steering wheel 15, a steering motor 12 and a reduction gearbox 14, with the input end of the reduction gearbox 14 connected to the output shaft of the steering motor 12.

[0055] The steering motor 12 is equipped with a speed sensor 11 for detecting the rotational speed of the steering motor 12, and an angle sensor 13 for detecting the rotational angle of the steering wheel 15 is provided at the output end or the steering shaft. The steering motor 12, the angle sensor 13 and the speed sensor 11 are all connected to the controller assembly 2 via signal.

[0056] The output shaft direction of the steering motor 12 can be parallel to or perpendicular to the steering shaft direction of the steering wheel 15. When the output shaft direction of the steering motor 12 is perpendicular to the steering shaft direction, the direction of the output torque can be changed through the reduction gearbox 14.

[0057] The types, models, and connection methods of the steering motor 12, gearbox 14, and steering wheel 15 are determined based on factors such as the size of the forklift in actual production, with reference to existing technologies, and will not be elaborated here.

[0058] Angle sensor 13 is installed at the output end of gearbox 14 or on the steering shaft of steering wheel 15 to detect the actual rotation angle of steering wheel 15, so as to prevent the error between the actual rotation angle of steering wheel 15 and the rotation angle β of steering wheel 15 from being too large.

[0059] Speed ​​sensor 11 is used to detect the rotational speed n of steering motor 12. The rotational speed n of steering motor 12 can reflect the current speed of forklift, which is beneficial for controller assembly 2 to control the steering damping output of torque sensor 42.

[0060] The higher the rotation speed of the steering motor 12, the higher the forklift speed, and the greater the steering damping output by the torque sensor 42, so as to reduce the steering speed and differential speed and avoid problems such as loss of control and rollover of the forklift when steering.

[0061] Preferably, when the speed n of the steering motor 12 detected by the speed sensor 11 exceeds the first preset speed n1, the controller assembly 2 controls the torque sensor 42 to output high steering damping.

[0062] When the speed n of the steering motor 12 detected by the speed sensor 11 is lower than the second preset speed n2, the controller assembly 2 controls the torque sensor 42 to output low steering damping.

[0063] It should be noted that the first preset speed n1 ≥ the second preset speed n2, and the specific values ​​of the two are determined according to the forklift model and working conditions; the high steering damping and low steering damping can be either fixed values ​​C or can change with the speed n of the steering motor 12, that is, the steering damping ζ = f(n).

[0064] Preferably, the torque sensor 42, speed sensor 11 and angle sensor 13 can all be non-contact sensors. The sensors do not need to contact the structure to be detected, which not only makes installation convenient, but also avoids the sensors affecting the normal operation of the steering wheel 41 and other structures.

[0065] Based on the above embodiments, the structure of the controller assembly 2 is further defined. The controller assembly 2 may include a left drive controller 21, a right drive controller 22, and a steering motor controller 23. The left drive controller 21 is connected to the left drive axle 3 to control the speed of the left drive wheel. The right drive controller 22 is connected to the right drive axle 5 to control the speed of the right drive wheel. The steering motor controller 23 is connected to the steering motor 12 to control the speed of the steering motor 12.

[0066] Please refer to Figure 5 The left drive controller 21, right drive controller 22 and steering motor controller 23 are all installed at the rear of the forklift. The specific structure, size and installation method of the three are determined according to the actual production needs, and will not be described in detail here.

[0067] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0068] The electric steering system for electric forklifts provided by this invention has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this invention.

Claims

1. An electric steering system for an electric forklift, characterized in that, The system includes a steering axle assembly (1), a steering wheel assembly (4), a left drive axle (3), a right drive axle (5), and a controller assembly (2). The left drive axle (3) and the right drive axle (5) are symmetrically arranged about the axis of the forklift. The steering axle assembly (1), the steering wheel assembly (4), the left drive axle (3), and the right drive axle (5) are all connected to the controller assembly (2) via signals. The steering wheel assembly (4) is equipped with a torque sensor (42) for detecting the rotation angle of the steering wheel (41) and outputting steering damping. When the torque sensor (42) detects that the rotation angle of the steering wheel (41) is α, the controller assembly (2) controls the rotation angle β=α / A of the steering wheel (15) of the steering axle assembly (1), the angular velocity ω1 of the left drive wheel of the left drive axle (3) is β(cotβ-L / 2) / 2πrt, and the angular velocity ω2 of the right drive wheel of the right drive axle (5) is β(cotβ+L / 2) / 2πrt; Where A is the magnification factor of the steering wheel (41) angle, B is the forklift wheelbase, L is the drive wheel track, r is the drive wheel radius, and t is the turning time; The controller assembly (2) also includes an oil pump motor controller (24) for controlling the rotational speed of the oil pump motor (6), the oil pump motor (6) for controlling the movement of the forks, so that the controller assembly (2) can adjust the movement of the forks in coordination with the steering of the forklift; The steering axle assembly (1) includes the steering wheel (15), the steering motor (12) and the reduction gearbox (14). The input end of the reduction gearbox (14) is connected to the output shaft of the steering motor (12), and the output end of the reduction gearbox (14) is connected to the steering shaft of the steering wheel (15). The steering motor (12) is equipped with a speed sensor (11) for detecting the rotational speed of the steering motor (12), and the output end or the steering shaft is equipped with an angle sensor (13) for detecting the rotational angle of the steering wheel (15). The steering motor (12), the angle sensor (13) and the speed sensor (11) are all connected to the controller assembly (2) via signals. The torque sensor (42), the speed sensor (11), and the angle sensor (13) are all non-contact sensors; When the speed sensor (11) detects that the rotational speed n of the steering motor (12) exceeds the first preset speed n1, the controller assembly (2) controls the torque sensor (42) to output high steering damping. When the speed n of the steering motor (12) detected by the speed sensor (11) is lower than the second preset speed n2, the controller assembly (2) controls the torque sensor (42) to output low steering damping; The controller assembly (2) includes a left drive controller (21), a right drive controller (22), and a steering motor controller (23). The left drive controller (21) is connected to the left drive axle (3) to control the rotational speed of the left drive wheel. The right drive controller (22) is connected to the right drive axle (5) to control the rotational speed of the right drive wheel. The steering motor controller (23) is connected to the steering motor (12) to control the rotational speed of the steering motor (12).

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