Three-stage transmission electronic throttle valve of diesel engine

Abstract

A three-stage transmission electronic throttle valve of a diesel engine comprises a valve shell, a valve shaft assembly, a driving assembly and an intermediate transmission mechanism. The valve shaft assembly comprises a valve shaft and a sector gear, and the sector gear is connected with the top end of the valve shaft. The driving assembly comprises a motor and a driving gear, the driving gear is connected with the output end of the motor, and the driving gear is in transmission connection with the sector gear through an intermediate transmission mechanism; wherein the intermediate transmission mechanism comprises a first intermediate gear and a second intermediate gear, the first intermediate gear and the second intermediate gear are duplicate gears, the first intermediate gear comprises a first input large gear and a first output small gear, and the second intermediate gear comprises a second input large gear and a second output small gear; the first input large gear is in meshed connection with the driving gear, the first output small gear is in meshed connection with the second input large gear, and the second output small gear is in meshed connection with the sector gear. The valve plate is large in torque transmission ratio and high in precision and stability, and the valve plate is not prone to shaking under large pressure difference.

Description

Technical Field

[0001] This utility model relates to an electronic throttle valve in the intake system of an automobile engine. Background Technology

[0002] The electronic throttle valve is a core actuator in the intake system of a modern diesel engine management system. Connected to the air filter above and the engine block below, it primarily controls the engine's air-fuel ratio, adjusts the intake and exhaust pressure difference, optimizes exhaust temperature, effectively activates the catalyst in the aftertreatment system, and reduces exhaust pollutant emissions. Currently, the working principle of a diesel engine's electronic throttle valve is based on the current operating status and exhaust emissions. The electronic control unit (ECU) uses pulse width modulation (PWM) signals to control a DC motor, which drives a transmission gear to rotate. This gear then rotates the valve plate within a certain angle range, thereby adjusting the throttle opening angle and controlling the intake air volume to ensure the engine operates at its optimal state.

[0003] In existing diesel engine electronic throttle technology, two-stage gear transmission is commonly used. However, diesel vehicles often face heavy loads or require high torque output. In such cases, the engine requires more intake air volume and pressure, which leads to a greater pressure difference on both sides of the valve plate. Although two-stage gear transmission can provide a faster transmission response, its transmission ratio is limited, and its torque transmission capacity is also limited. When the throttle is under a large air flow pressure difference, it is prone to instability, often causing the valve plate to vibrate, generating vibration and noise, which further affects the control accuracy of the equipment and reduces its service life. Summary of the Invention

[0004] The technical problem to be solved by this utility model is to provide an electronic throttle valve with a large torque transmission ratio, high precision and stability, and less valve plate vibration under large pressure difference.

[0005] Another technical problem to be solved by this utility model is to provide an electronic throttle valve with high mechanical strength in the mounting cavity of the valve body.

[0006] Another technical problem to be solved by this utility model is to provide an electronic throttle valve with a simple and reliable installation of a sector gear assembly.

[0007] This utility model provides a three-stage transmission electronic throttle valve for a diesel engine, including a valve housing, a valve shaft assembly, a drive assembly, and an intermediate transmission mechanism. The valve shaft assembly includes a valve shaft and a sector gear assembly, the sector gear assembly including a sector gear connected to the top end of the valve shaft. The drive assembly includes a motor and a drive gear, the drive gear being connected to the output end of the motor and connected to the sector gear via the intermediate transmission mechanism. The intermediate transmission mechanism includes a first intermediate gear and a second intermediate gear, both of which are double gears. The first intermediate gear includes a first input large gear and a first output small gear, and the second intermediate gear includes a second input large gear and a second output small gear. The first input large gear meshes with the drive gear, the first output small gear meshes with the second input large gear, and the second output small gear meshes with the sector gear. The number of teeth on the drive gear is less than the number of teeth on the first input large gear, the number of teeth on the first output small gear is less than the number of teeth on the second input large gear, and the number of teeth on the second output small gear is less than the number of teeth on the sector gear.

[0008] Preferably, the valve housing includes a valve body and a cover plate. The valve body has an installation cavity, and the cover plate covers the opening of the installation cavity and is connected to the valve body. The drive assembly, intermediate transmission mechanism and sector gear assembly are respectively disposed in the installation cavity.

[0009] Preferably, the outer wall of the mounting cavity of the valve body is integrally provided with outwardly protruding reinforcing ribs.

[0010] Preferably, the sector gear assembly includes a return torsion spring; the sector gear includes a sector gear body and an annular guide post; the sector gear body has a through hole for the valve shaft to pass through, one end of the annular guide post is connected to the side of the sector gear body facing the valve shaft and surrounds the through hole; the valve shaft passes through the annular guide post, and the top end of the valve shaft extends into the through hole of the sector gear body and is connected to the sector gear body; the return torsion spring is sleeved on the annular guide post.

[0011] Preferably, the side of the annular guide post is provided with a torsion spring push-stop portion, the torsion spring push-stop portion having a first push-stop portion side elevation and a second push-stop portion side elevation facing each other; the two ends of the return torsion spring are respectively provided with a first stop leg and a second stop leg; when the sector gear assembly has not yet been installed on the valve body, the first stop leg and the second stop leg of the return torsion spring sleeved on the annular guide post abut against the first push-stop portion side elevation and the second push-stop portion side elevation respectively, so that the return torsion spring has a preload torque.

[0012] Preferably, the bottom surface of the mounting cavity is provided with an upwardly protruding return column, and the two opposite sides of the return column are respectively provided with a first return column side surface and a second return column side surface; when the sector gear assembly and the valve housing are in the installed state, the first stop leg and the second stop leg of the return torsion spring abut against the first return column side surface and the second return column side surface, respectively; when the sector gear rotates away from the predetermined initial position, the first stop leg is stuck on the first return column side surface, and the torsion spring push part pushes the second stop leg away from the second return column side surface to twist the return torsion spring.

[0013] This utility model has at least the following advantages and features:

[0014] 1. The three-stage transmission electronic throttle valve for diesel engines in this embodiment of the present invention achieves three-stage speed change by changing the structure of the intermediate gear and sector gear assembly and introducing a force transmission method of four transmission gears. The transmission ratio between the drive gear and the first input large gear is 5.3, the transmission ratio between the first output small gear and the second input large gear is 2.3, and the transmission ratio between the second output small gear and the sector gear is set to 5.7. Compared with the existing electronic throttle valve, it can achieve higher transmission torque and greatly improve the stability of the valve plate under large air flow pressure difference, avoiding flow fluctuations caused by valve plate position angle vibration that could lead to system over-tolerance alarms.

[0015] 2. The diesel engine three-stage transmission electronic throttle valve of this utility model uses three-stage gear transmission to make torque transmission more precise. After the motor output end rotates a lot, the valve shaft only rotates a small angle, so as to more accurately control the rotation angle of the valve plate, improve the flow control accuracy at each position, and better adapt to the application in high torque output environment.

[0016] 3. The three-stage transmission electronic throttle valve of the diesel engine in this embodiment of the present invention can significantly improve the mechanical strength of the valve body mounting cavity by setting outwardly protruding reinforcing ribs on the outer wall of the valve body mounting cavity, thus solving the problem of insufficient mechanical strength of the valve body mounting cavity in the prior art.

[0017] 4. In this embodiment of the utility model, only a single-direction spring is needed to make the return torsion spring, which can be fixed to the sector gear and have a preload torque after the return torsion spring is installed on the sector gear. This not only greatly simplifies the installation process of the return torsion spring, but also ensures that the sector gear assembly is reliably installed on the valve body. Attached Figure Description

[0018] Figure 1 A schematic diagram of the external structure of a three-stage transmission electronic throttle valve for a diesel engine according to an embodiment of the present invention is shown.

[0019] Figure 2This invention provides a schematic diagram of the internal structure of a three-stage transmission electronic throttle valve for a diesel engine according to an embodiment of the present invention.

[0020] Figure 3 A schematic diagram of the structure of the three-stage transmission electronic throttle valve body of the diesel engine according to an embodiment of the present invention is shown;

[0021] Figure 4 A schematic diagram of the structure of the DC motor drive gear according to an embodiment of the present invention is shown;

[0022] Figure 5 A three-dimensional structural schematic diagram of the first intermediate gear according to an embodiment of the present invention is shown;

[0023] Figure 6 A three-dimensional structural schematic diagram of the second intermediate gear according to an embodiment of the present invention is shown;

[0024] Figure 7 A three-dimensional installation schematic diagram of the sector gear assembly according to an embodiment of the present invention is shown;

[0025] Figure 8 This diagram shows a three-dimensional structural schematic of the valve body of this utility model without the sector gear assembly installed.

[0026] Figure 9 This diagram shows a three-dimensional structural schematic of the valve body after the installation of the three-stage gear transmission mechanism according to an embodiment of the present invention.

[0027] The components include: valve housing-1, valve body-10, cover plate-12, mounting cavity-110, perforation-1101, air intake channel-120, valve shaft-30, valve plate-32, angle sensor-40, positioning magnet-42, reinforcing rib-130, first fixed-axis mounting post-140, second fixed-axis mounting post-150, return post-160, first return post side facade-161, second return post side facade-162, first fixed shaft-170, second fixed shaft-180, DC motor-50, and drive gear-51. First intermediate gear - 72, second intermediate gear - 73, sector gear assembly - 34, first input large gear - 720, first output small gear - 721, second input large gear - 730, second output small gear - 731, sector gear - 340, return torsion spring - 350, sector gear body - 341, annular guide post - 342, torsion spring push-stop part - 343, through hole - 3411, first stop leg - 351, second stop leg - 352, side profile of first push-stop part - 3431, side profile of second push-stop part - 3432. Detailed Implementation

[0028] To enable those skilled in the art to better understand the technical solution of this utility model, the present utility model will be further described in detail below with reference to the accompanying drawings.

[0029] Please see Figures 1 to 3 According to an embodiment of the present invention, a three-stage transmission electronic throttle valve for a diesel engine includes a valve housing, a valve shaft assembly, a detection assembly, a drive assembly, and an intermediate transmission mechanism.

[0030] The valve housing 1 includes a valve body 10 and a cover plate 12. The valve body 10 is provided with an installation cavity 110 and an air inlet passage 120. The cover plate 12 covers the opening of the installation cavity 110 and is connected to the valve body 10. The bottom surface of the installation cavity 110 is provided with a through hole 1101 for the valve shaft 30 (described below) to pass through, a first fixed-axis mounting post 140, and a second fixed-axis mounting post 150. The bottom surface of the installation cavity 110 is provided with an upwardly protruding return post 160. The two opposite sides of the return post 160 are respectively provided with a first return post side surface 161 and a second return post side surface 162. Both the first return post side surface 161 and the second return post side surface 162 are machined surfaces. In this embodiment, the height of the first return column side facade 161 is greater than the height of the second return column side facade 162, so as to match the height of the two stop legs of the return torsion spring 350 described below (the heights of the two stop legs of the return torsion spring 350 are also different, one higher and one lower), and a guide surface is provided above the second return column side facade 162. Mounting holes are provided on the top surfaces of the first fixed-axis mounting column 140 and the second fixed-axis mounting column 150.

[0031] The outer wall of the mounting cavity 110 of the valve body 10 is integrally provided with outwardly protruding reinforcing ribs 130. By providing reinforcing ribs 130, the mechanical strength of the valve body mounting cavity in this embodiment is significantly improved.

[0032] The valve shaft assembly includes a valve shaft 30, a valve plate 32, and a sector gear assembly 34. The valve plate 32 is connected to the valve shaft 30 within the intake passage 120 and its shape is adapted to the intake passage 120.

[0033] The detection assembly includes an angle sensor 40 and a positioning magnet 42. The angle sensor 40 is used to sense changes in the magnetic field of the positioning magnet 42 and output a detection signal. The angle sensor 40 is located at one end of the cover plate 12 near the valve shaft 30, and the positioning magnet 42 is located at one end of the sector gear assembly 34 near the cover plate 12.

[0034] The drive assembly includes a DC motor 50 and a drive gear 51. The drive gear 51 is connected to the output end of the DC motor 50 and is connected to the sector gear 340 through an intermediate transmission mechanism.

[0035] Please see Figures 4 to 7The intermediate transmission mechanism includes a first intermediate gear 72 and a second intermediate gear 73, both of which are double gears. The first intermediate gear 72 includes a first input large gear 720 and a first output small gear 721 arranged coaxially. The second intermediate gear 73 includes a second input large gear 730 and a second output small gear 731 arranged coaxially. The first input large gear 720 meshes with the drive gear 51, the first output small gear 721 meshes with the second input large gear 730, and the second output small gear 731 meshes with the sector gear 340. The number of teeth on the drive gear 51 is less than the number of teeth on the first input large gear 720, the number of teeth on the first output small gear 721 is less than the number of teeth on the second input large gear 730, and the number of teeth on the second output small gear 731 is less than the number of teeth on the sector gear 340. In this embodiment, the transmission ratio between the drive gear 51 and the first input large gear 720 is 5.3; the transmission ratio between the first output small gear 721 and the second input large gear 730 is 2.3; and the transmission ratio between the second output small gear 731 and the sector gear 340 is 5.7.

[0036] The drive assembly, intermediate transmission mechanism, and sector gear assembly are respectively disposed in the mounting cavity 110. The drive assembly and sector gear assembly 34 are respectively disposed at both ends of the mounting cavity 110. The DC motor 50 is preferably fixed in the mounting cavity by fixing bolts, and the two intermediate gears are disposed between the drive gear 51 and the sector gear assembly 34.

[0037] In this embodiment, the drive gear 51 is a 10-tooth gear. Preferably, the center distance between the drive gear 51 and the first input gear 720 is 25.46 mm. The pressure angle of the drive gear 51 is 20 degrees, the module is 0.8, the addendum coefficient is 1.3, the backlash coefficient is 0.61, and the displacement coefficient is 0.3.

[0038] In this embodiment, the first input large gear 720 of the first intermediate gear 72 has 53 teeth, and the first output small gear 721 has 10 teeth. Preferably, the center distance between the first input large gear 720 and the drive gear 51 is 25.46 mm, the pressure angle of the first input large gear 720 is 20 degrees, the module is 0.8, the addendum coefficient is 0.85, the backlash coefficient is 0.61, and the displacement coefficient is -0.15. The center distance between the first output small gear 721 and the second input large gear 730 is 15.6 mm, the pressure angle of the first output small gear 721 is 20 degrees, the module is 0.9, the addendum coefficient is 1.45, the backlash coefficient is 0.73, and the displacement coefficient is 0.45.

[0039] In this embodiment, the second input large gear 730 of the second intermediate gear 73 has 23 teeth, and the second output small gear 731 has 10 teeth. Preferably, the center distance between the second input large gear 730 and the first output small gear 721 is 15.6 mm, the pressure angle of the second input large gear 730 is 20 degrees, the module is 0.9, the addendum coefficient is 1.45, the backlash coefficient is 0.37, and the displacement coefficient is 0.45. The center distance between the second output small gear 731 and the sector gear 340 described below is 30.6 mm, the pressure angle of the second output small gear 731 is 20 degrees, the module is 0.9, the addendum coefficient is 1.45, the backlash coefficient is 0.73, and the displacement coefficient is 0.45.

[0040] In this embodiment, the sector gear assembly 34 includes a sector gear 340 and a return torsion spring 350. The sector gear 340 is connected to the top end of the valve shaft 30. Specifically, the sector gear 340 includes a sector gear body 341 and an annular guide post 342; the sector gear body 341 is provided with a through hole 3411 for the valve shaft 30 to pass through, and the sector gear 340 is press-fitted to one end of the valve shaft 30 adjacent to the mounting cavity 110 (i.e., the top end of the valve shaft 30) through the through hole 3411, and is fixedly connected by laser welding. One end of the annular guide post 342 is connected to the side of the sector gear body 341 facing the valve shaft 30 and surrounds the through hole 3411, and the side of the annular guide post 342 is provided with a torsion spring push-stop part 343. A return torsion spring 350 is sleeved on the outside of the annular guide post 342. The two ends of the return torsion spring 350 are respectively provided with a first stop leg 351 and a second stop leg 352, and the first stop leg 351 and the second stop leg 352 have a curved shape. The torsion spring push part 343 has a first push part side surface 3431 and a second push part side surface 3432 that are opposite to each other.

[0041] The sector gear 340 is a 57-tooth gear. Preferably, the center distance between the sector gear 340 and the second output pinion 731 is 30.6 mm. The pressure angle of the sector gear 340 is 20 degrees, the module is 0.9, the addendum coefficient is 1, the backlash coefficient is 0.39, and the displacement coefficient is -0.05.

[0042] The installation steps and working principle of a three-stage transmission electronic throttle valve for a diesel engine according to an embodiment of this utility model are as follows.

[0043] The first installation step involves assembling the return torsion spring 350 onto the sector gear 340. One specific method is as follows: First, press the first stop leg 351 of the return torsion spring 350 tightly against the side surface 3431 of the first push part of the torsion spring push part 343. Second, rotate the second stop leg 352 counterclockwise one turn, engaging it against the side surface 3432 of the second push part of the torsion spring push part 343. Both stops are now firmly against the sides of the torsion spring push part 343. At this point, the return torsion spring 350, once installed onto the sector gear 340, has preload torque, forming a single integrated component. This structure requires only a single helical spring to securely bind the return torsion spring 350 to the sector gear 340, greatly simplifying the installation process. The result after the return torsion spring is installed onto the sector gear is as follows. Figure 7 As shown.

[0044] Installation step two involves assembling the sector gear assembly 34 into the valve body 10 of the electronic throttle. One specific method is as follows: First, slide the second stop leg 352 of the return torsion spring 350 into the guide surface above the side face 162 of the second return column. Second, continue pushing the sector gear assembly 34 in, sliding the second stop leg 352 into the side face 162 of the second return column, and sliding the first stop leg 351 into the side face 161 of the first return column. Due to the preload torque of the return torsion spring 350 after installation on the sector gear 340, the sector gear 340 can be reliably fixed in the return column position on the valve body 10, achieving flow control at the default position of the electronic throttle. This also significantly reduces the time required to install the sector gear onto the electronic throttle valve body, reducing assembly time and costs. The situation after the sector gear assembly is installed on the throttle valve body is as follows. Figure 8 As shown.

[0045] Installation step three involves assembling the first intermediate gear 72 and the second intermediate gear 73 into the valve body 10 of the electronic throttle. One specific implementation method is as follows: First, the center of the second intermediate gear 73 is inserted into the second fixed shaft 180, and the second output pinion 731 meshes with the sector gear 340. Second, the center of the first intermediate gear 72 is inserted into the first fixed shaft 170, and the first input large gear 720 meshes with the drive gear 51. The first output pinion 721 meshes with the second input large gear 730. The first fixed shaft 170 and the second fixed shaft 180 are respectively inserted into the first fixed shaft mounting post 140 and the second fixed shaft mounting post 150 within the mounting cavity of the electronic throttle. The drive gear 51, the first intermediate gear 72, the second intermediate gear 73, and the sector gear 340 together constitute a three-stage gear transmission mechanism. The position of the installed three-stage gear transmission mechanism on the valve body is as follows: Figure 9 As shown.

[0046] In use, the DC motor 50 drives the drive gear 51 to rotate, which in turn drives the first intermediate gear 72 and the second intermediate gear 73 to rotate, thereby causing the sector gear 340 to rotate and deviate from its predetermined initial position. During this process, the sector torsion spring pusher 343 pushes the second stop leg 352 of the return torsion spring 350 away from the side surface 162 of the second return column. The return torsion spring 350 is then twisted clockwise, and the first stop leg 351 of the return torsion spring remains stuck on the side surface 161 of the first return column. At this time, the return torsion spring 350 compresses to generate a return torque. When the drive torque of the DC motor is removed, the return torsion spring 350, under the action of torque, drives the sector gear 340 through the second stop leg 352. The sector gear 340 returns to its default position under the action of the return torque, thereby causing the valve plate 32 to return quickly.

[0047] This utility model embodiment improves the design of the aforementioned valve body, intermediate gear, and sector gear assembly structure by introducing a force transmission method using four transmission gears to achieve three-stage speed change. The transmission ratio between the drive gear and the first input large gear is 5.3, the transmission ratio between the first output small gear and the second input large gear is 2.3, and the transmission ratio between the second output small gear and the sector gear is set to 5.7. This solves the technical problems of insufficient torque transmission, inadequate accuracy and stability caused by the gear transmission ratio of the existing throttle body, as well as the easy vibration of the valve plate under large pressure differentials. Compared with the existing diesel engine electronic throttle body, the three-stage transmission electronic throttle body of this utility model embodiment can effectively improve the output torque under the same conditions, and the torque transmission is more accurate. At the same time, it reduces the stress load on each gear, achieves smooth and stable operation, reduces the vibration and noise of the valve plate under large pressure differentials, and improves the stability, reliability, and durability of the system.

[0048] Obviously, those skilled in the art can make various modifications and variations to this utility model without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this utility model and their equivalents, this utility model also intends to include these modifications and variations.

Claims

1. A three-stage transmission electronic throttle valve for a diesel engine, comprising a valve housing, a valve shaft assembly, a drive assembly, and an intermediate transmission mechanism; the valve shaft assembly includes a valve shaft and a sector gear assembly, the sector gear assembly including a sector gear connected to the top end of the valve shaft; the drive assembly includes a motor and a drive gear, the drive gear being connected to the output end of the motor, and the drive gear being connected to the sector gear via the intermediate transmission mechanism; characterized in that, The intermediate transmission mechanism includes a first intermediate gear and a second intermediate gear, both of which are double gears. The first intermediate gear includes a first input large gear and a first output small gear, and the second intermediate gear includes a second input large gear and a second output small gear. The first input large gear is meshed with the drive gear, the first output small gear is meshed with the second input large gear, and the second output small gear is meshed with the sector gear. The number of teeth on the drive gear is less than the number of teeth on the first input large gear, the number of teeth on the first output small gear is less than the number of teeth on the second input large gear, and the number of teeth on the second output small gear is less than the number of teeth on the sector gear.

2. The three-stage transmission electronic throttle valve for a diesel engine according to claim 1, characterized in that, The valve housing includes a valve body and a cover plate. The valve body has an installation cavity. The cover plate covers the opening of the installation cavity and is connected to the valve body. The drive assembly, the intermediate transmission mechanism, and the sector gear assembly are respectively disposed in the installation cavity.

3. The three-stage transmission electronic throttle valve for a diesel engine according to claim 2, characterized in that, The outer wall of the mounting cavity of the valve body is integrally provided with outwardly protruding reinforcing ribs.

4. A three-stage transmission electronic throttle valve for a diesel engine according to claim 1, characterized in that, The transmission ratio between the drive gear and the first input large gear is 5.3; the transmission ratio between the first output small gear and the second input large gear is 2.3; and the transmission ratio between the second output small gear and the sector gear is 5.

7.

5. A three-stage transmission electronic throttle valve for a diesel engine according to claim 4, characterized in that, The drive gear is a 10-tooth gear; the first input large gear is a 53-tooth gear, and the first output small gear is a 10-tooth gear; the second input large gear is a 23-tooth gear, and the second output small gear is a 10-tooth gear; the sector gear is a 57-tooth gear.

6. A three-stage transmission electronic throttle valve for a diesel engine according to claim 1, characterized in that, The sector gear assembly includes a return torsion spring; the sector gear includes a sector gear body and an annular guide post; the sector gear body is provided with a through hole for the valve shaft to pass through, and one end of the annular guide post is connected to the side of the sector gear body facing the valve shaft and surrounds the through hole; The valve shaft passes through the annular guide post, and the top end of the valve shaft extends into the through hole of the sector gear body and is connected to the sector gear body; the return torsion spring is sleeved on the outside of the annular guide post.

7. A three-stage transmission electronic throttle valve for a diesel engine according to claim 6, characterized in that, The annular guide post is provided with a torsion spring push-block part on its side, and the torsion spring push-block part has a first push-block part side elevation and a second push-block part side elevation that are opposite to each other. The return torsion spring is provided with a first stop leg and a second stop leg at its two ends respectively; when the sector gear assembly is not yet installed on the valve body, the first stop leg and the second stop leg of the return torsion spring sleeved on the annular guide post abut against the side surface of the first push part and the side surface of the second push part respectively, so that the return torsion spring has a preload torque.

8. A three-stage transmission electronic throttle valve for a diesel engine according to claim 7, characterized in that, The valve housing includes a valve body, the valve body is provided with an installation cavity, the bottom surface of the installation cavity is provided with an upwardly protruding return column, and the two opposite sides of the return column are respectively provided with a first return column side elevation and a second return column side elevation. When the sector gear assembly and valve housing are in the installed state, the first stop leg and the second stop leg of the return torsion spring abut against the side surface of the first return column and the side surface of the second return column, respectively. When the sector gear rotates away from the predetermined initial position, the first stop leg is stuck on the side surface of the first return column, and the torsion spring push part pushes the second stop leg away from the side surface of the second return column to twist the return torsion spring.

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