Shift structure and shift method for an eight-speed transmission

Abstract

The application discloses a gear shifting structure and gear shifting method of an eight-gear transmission, which comprises a first gear shifting fork shaft, a second gear shifting fork shaft, a high-low gear shifting fork shaft and a shifting head. The first gear shifting fork shaft is provided with a first gear guide block and a second gear guide block, and the second gear shifting fork shaft is provided with a third gear guide block and a fourth gear guide block. The high gear guide block on the high-low gear shifting fork shaft is arranged close to the middle, and the high-low gear shifting fork shaft is provided with a connecting rod. The end of the connecting rod is connected with a low gear guide block, the low gear guide block passes through the rear end of the second gear guide block and the fourth gear guide block from the direction, is led to the side of the first gear shifting fork shaft away from the second gear shifting fork shaft, and the low gear guide block corresponds to the position of the second gear guide block. The shifting head is located in the same plane with all the guide blocks and between the guide blocks. The shifting head is respectively connected with a gear selecting motor and a gear shifting motor in the transverse direction and the axial direction of the shifting fork shaft. Under the premise of ensuring the gear shifting capacity, one gear shifting motor is reduced, and the cost and the size of the eight-gear transmission are reduced.

Description

Technical Field

[0001] This invention belongs to the field of eight-speed transmissions, and relates to a shifting structure and shifting method for an eight-speed transmission. Background Technology

[0002] Currently, commercial vehicle eight-speed AMTs mainly adopt a main and auxiliary gearbox structure, and most use a 4x2 transmission route. Due to the different shift strokes of the main and auxiliary gearboxes (e.g., the main gearbox stroke is 10mm, and the auxiliary gearbox stroke is 20mm), existing AMT actuators require two different units to perform the shifting of the main gearbox and the auxiliary gearbox.

[0003] like Figure 1 As shown, in the prior art, an execution unit is set in the main gearbox and the auxiliary gearbox respectively. Generally, a shift motor is used. The two shift motors control the shifting of the main gearbox and the auxiliary gearbox respectively. One is used to select the high and low gears, and the other is used to select the specific gear.

[0004] However, having two execution units inevitably leads to increased space occupation, higher costs, and greater structural complexity, thus increasing the manufacturing cost of commercial vehicles. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a shifting structure and shifting method for an eight-speed transmission. While ensuring shifting capability, it reduces one shifting motor, thereby reducing the cost and size of the eight-speed transmission.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A shifting structure for an eight-speed transmission includes a first gear shift fork shaft, a second gear shift fork shaft, a high / low gear shift fork shaft, and a shift head.

[0008] The middle part of the first gear shift fork shaft is provided with two axially spaced first gear guide blocks and second gear guide blocks. The first gear guide block is close to the front end of the first gear shift fork shaft, and the second gear guide block is close to the rear end of the first gear shift fork shaft. The middle part of the second gear shift fork shaft is provided with two axially spaced third gear guide blocks and fourth gear guide blocks. The third gear guide block is close to the front end of the second gear shift fork shaft, and the fourth gear guide block is close to the rear end of the second gear shift fork shaft.

[0009] The high and low gear shift fork shaft is equipped with a high gear guide block and a low gear guide block. The high gear guide block is located near the middle and corresponds to the position of the third gear guide block. The high and low gear shift fork shaft is equipped with a connecting rod. The end of the connecting rod is connected to the low gear guide block. The low gear guide block passes through the rear end of the second and fourth gear guide blocks via the connecting rod and goes around to the side of the first gear shift fork shaft away from the second gear shift fork shaft. The low gear guide block corresponds to the position of the second gear guide block.

[0010] The shift head and all the aforementioned guide blocks are located on the same plane and between the guide blocks. The shift head is connected to a gear selection motor and a gear shifting motor in the lateral and axial directions along the shift fork shaft, respectively. The gear selection motor is used for lateral movement, and the gear shifting motor is used for axial movement along the shift fork shaft.

[0011] Preferably, the spacing between the guide blocks of adjacent shift fork shafts is 1-2 mm.

[0012] Preferably, the relative distance between the high-grade guide block and the low-grade guide block in the axial direction is greater than the distance between the first-grade guide block and the second-grade guide block.

[0013] Preferably, the spacing between the first-level guide block and the second-level guide block is the same as the spacing between the third-level guide block and the fourth-level guide block.

[0014] Preferably, a reverse gear shift fork shaft is provided on the side of the first gear shift fork shaft away from the second gear shift fork shaft, a low gear guide block is located between the reverse gear shift fork shaft and the first gear shift fork shaft, and a reverse gear guide block is provided on the middle part of the reverse gear shift fork shaft.

[0015] Preferably, the spacing between the first-level guide block and the second-level guide block is the same as the spacing between the third-level guide block and the fourth-level guide block.

[0016] Preferably, the height of the connecting rod is lower than the height of all the guide blocks.

[0017] A shifting method based on the shifting structure of the eight-speed transmission includes the following steps:

[0018] When shifting gears at the same high or low gear, the gear selector motor moves between the two guide blocks of the corresponding shift fork shaft, and then the shift motor drives it to move axially, which in turn moves the corresponding gear guide block to engage the gear.

[0019] When shifting from fourth to fifth gear, move the shifter horizontally by half a shifter position, while simultaneously returning the fourth gear guide block and the high gear guide block to neutral. Then, engage the high gear guide block and move the shifter to the first gear guide block position to engage fifth gear.

[0020] When you need to downshift from fifth to fourth gear, simultaneously shift the second gear guide block and the low gear guide block back to neutral, then shift the low gear guide block to engage the gear, and then move the shifter to the fourth gear guide block position to engage fourth gear.

[0021] The preferred process for shifting from fourth to fifth gear is as follows:

[0022] First, the gear selector motor moves the shift head half a shift head's distance towards the high / low gear shift fork shaft;

[0023] Then, through the action of the shift motor, the fourth gear guide block and the high gear guide block are simultaneously shifted to the neutral position.

[0024] The gear selection motor continues to move half a guide block position towards the high / low gear shift fork shaft, separately engaging the high gear guide block of the auxiliary gearbox. The shift motor continues to move to engage the high gear of the auxiliary gearbox, realizing the high / low gear switching of the auxiliary gearbox.

[0025] After shifting to a higher gear, turn the steering wheel back to the corresponding neutral position;

[0026] Select the first gear guide block, which is currently in fifth gear, and engage fifth gear.

[0027] The preferred process for downgrading from fifth gear to fourth gear is as follows:

[0028] First, the gear selector motor moves the dial head half a dial head's distance towards the lower gear guide block;

[0029] By actuating the shift motor, both the first gear guide block and the low gear guide block can be simultaneously shifted to the neutral position.

[0030] The main gear selector motor continues to move half a guide block position towards the low gear guide block until the low gear guide block of the auxiliary gearbox is engaged alone. The shift motor continues to move so that the auxiliary gearbox can be engaged in low gear, thus realizing the switching between high and low gear.

[0031] After shifting to low gear, turn the steering wheel back to the corresponding neutral position on the main gearbox;

[0032] Select the fourth gear guide on the dial and engage fourth gear.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] This invention uses a connecting rod to guide the low-gear guide block from the rear end of the second and fourth gear guide blocks, around to the side of the first gear shift fork shaft away from the second gear shift fork shaft, and aligns it with the position of the second gear guide block. This allows the shift head to simultaneously return both the fourth and high gear guide blocks to neutral when shifting from fourth to fifth gear, and then engage the high gear guide block again. Similarly, when shifting from fifth to fourth gear, the shift head can simultaneously return both the second and low gear guide blocks to neutral, and then engage the low gear guide block again. This allows the main and auxiliary gearboxes to use a single shift motor to complete the shifting process, reducing the number of shift motors while maintaining shifting capability, thus lowering the cost and size of the eight-speed transmission.

[0035] Furthermore, the low-gear guide block is located between the reverse gear shift fork shaft and the first gear shift fork shaft, so that the shift motor can also perform the reverse gear engagement action when in neutral.

[0036] Furthermore, the height of the connecting rod is lower than the height of the guide block, so it will not interfere with the movement of the gear selection motor. Attached Figure Description

[0037] Figure 1 The schematic diagram of the main and auxiliary gearboxes of an existing eight-speed transmission;

[0038] Figure 2This is a schematic diagram of the shifting structure of the eight-speed transmission of the present invention;

[0039] Figure 3 This is a schematic diagram of the four-gear structure of the present invention;

[0040] Figure 4 This is a schematic diagram of the principle of shifting from fourth gear to neutral in this invention;

[0041] Figure 5 This is a schematic diagram of the five-speed gear structure of the present invention;

[0042] Figure 6 This is a schematic diagram of the principle of shifting from fifth gear to neutral in this invention;

[0043] Figure 7 This is a flowchart illustrating the principle of shifting from fourth to fifth gear in this invention.

[0044] Figure 8 This is a flowchart illustrating the principle of reducing five gears to four gears in this invention.

[0045] Wherein: 1-First gear shift fork shaft; 2-Second gear shift fork shaft; 3-High and low gear shift fork shaft; 4-Reverse gear shift fork shaft; 5-First gear guide block; 6-Second gear guide block; 7-Third gear guide block; 8-Fourth gear guide block; 9-High gear guide block; 10-Low gear guide block; 11-Connecting rod; 12-Reverse gear guide block; 13-Shift head. Detailed Implementation

[0046] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0047] It should be noted that the terms “front,” “back,” “left,” “right,” “up,” and “down” used in the following description refer to the directions shown in the attached diagram, while the terms “inside” and “outside” refer to the directions toward or away from the geometric center of a specific component, respectively.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0049] like Figure 2As shown, the shifting structure of the eight-speed transmission of the present invention includes a first gear shift fork shaft 1, a second gear shift fork shaft 2, a high / low gear shift fork shaft 3, and a shift head 13.

[0050] The first gear shift fork shaft 1, the second gear shift fork shaft 2, and the high / low gear shift fork shaft 3 are arranged in parallel in sequence. The first gear shift fork shaft 1 and the second gear shift fork shaft 2 are the main gearbox, and the high / low gear shift fork shaft 3 is the auxiliary gearbox.

[0051] The middle part of the first gear shift fork shaft 1 is provided with two axially spaced first gear guide blocks 5 and second gear guide blocks 6. The first gear guide block 5 is close to the front end of the first gear shift fork shaft 1, and the second gear guide block 6 is close to the rear end of the first gear shift fork shaft 1. The middle part of the second gear shift fork shaft 2 is provided with two axially spaced third gear guide blocks 7 and fourth gear guide blocks 8. The third gear guide block 7 is close to the front end of the second gear shift fork shaft 2, and the fourth gear guide block 8 is close to the rear end of the second gear shift fork shaft 2. The distance between the first gear guide block 5 and the second gear guide block 6 is the same as the distance between the third gear guide block 7 and the fourth gear guide block 8.

[0052] The high / low gear shift fork shaft 3 has its front end in the high gear position and its rear end in the low gear position. When the high / low gear shift fork shaft 3 is in the low gear position, the front end of the first gear shift fork shaft 1 is in first gear and the rear end is in second gear, and the front end of the second gear shift fork shaft 2 is in third gear and the rear end is in fourth gear. When the high / low gear shift fork shaft 3 is in the high gear position, the front end of the first gear shift fork shaft 1 is in fifth gear and the rear end is in sixth gear, and the front end of the second gear shift fork shaft 2 is in seventh gear and the rear end is in eighth gear.

[0053] The high and low gear shift fork shaft 3 is provided with a high gear guide block 9 and a low gear guide block 10. The high gear guide block 9 is located near the middle and corresponds to the position of the third gear guide block 7. The high and low gear shift fork shaft 3 is provided with a connecting rod 11. The end of the connecting rod 11 is connected to the low gear guide block 10. The low gear guide block 10 passes through the rear end direction of the second gear guide block 6 and the fourth gear guide block 8 via the connecting rod 11, and goes around to the side of the first gear shift fork shaft 1 away from the second gear shift fork shaft 2. The low gear guide block 10 corresponds to the position of the second gear guide block 6.

[0054] According to design requirements, the relative axial distance between the high-grade guide block 9 and the low-grade guide block 10 can be the same as or greater than the distance between the first-grade guide block 5 and the second-grade guide block 6.

[0055] The spacing between the guide blocks of adjacent shift fork shafts is 1-2mm.

[0056] The first gear guide block 5, the second gear guide block 6, the third gear guide block 7, the fourth gear guide block 8, the second guide block, the high gear guide block 9, the low gear guide block 10, and the dial head 13 are all located on the same plane. The dial head 13 is located between the guide blocks. The dial head 13 is connected to a gear selection motor and a gear shifting motor along the transverse and axial directions of the shift fork shaft, respectively, to drive the guide blocks to move. The gear selection motor moves back and forth between the guide blocks along the transverse direction. The gear selection motor is connected to the gear shifting motor. The gear shifting motor, along with the gear selection motor and the dial head 13, moves along the axial direction to select the gear and engage the gear.

[0057] The height of the connecting rod 11 is lower than the height of the guide block, so it will not interfere with the movement of the gear selection motor. Furthermore, when the first gear shift fork shaft 1 and the second gear shift fork shaft 2 move to the rear end, the corresponding guide block and the connecting rod 11 still have a gap, so that the connecting rod 11 will not interfere with the first gear shift fork shaft 1 and the second gear shift fork shaft 2 when engaging gears.

[0058] A reverse gear shift fork shaft 4 is provided on the side of the first gear shift fork shaft 1 away from the second gear shift fork shaft 2. The reverse gear shift fork shaft 4 is located in the main gearbox. The low gear guide block 10 is located between the reverse gear shift fork shaft 4 and the first gear shift fork shaft 1. A reverse gear guide block 12 is provided on the middle part of the reverse gear shift fork shaft 4.

[0059] like Figure 3 As shown, this is a structure where the auxiliary gearbox of an eight-speed transmission engages low gear and the main gearbox engages fourth gear. The gear selector motor moves horizontally by half a position of shift knob 13, as shown... Figure 4 As shown, the main gearbox can be simultaneously shifted back to neutral by the shift motor, and the auxiliary gearbox can be moved to neutral by the low gear. This allows a single actuator to simultaneously shift back two shift fork shafts, thus achieving upshifting.

[0060] In such Figure 5 and Figure 6 In the five gear configuration shown, when downshifting, the auxiliary gearbox is disengaged from a high gear by simultaneously shifting the second gear guide block 6 and the high gear guide block 9 back to neutral, and then the low gear guide block 10 is engaged again, thus achieving the operation of downshifting from a high gear to a low gear.

[0061] The shifting process of the above eight-speed transmission is as follows:

[0062] When shifting gears at the same high or low gear, the gear selector motor moves between the two guide blocks of the corresponding shift fork shaft, and then the shift motor drives it to move axially, which in turn moves the corresponding gear guide block to engage the gear.

[0063] like Figure 7 The image shows the process of shifting from fourth to fifth gear. Initially, the main gearbox is in fourth gear and the auxiliary gearbox is in a low gear.

[0064] First, the gear selector motor moves the dial 13 half the distance of the dial 13 towards the high / low gear shift fork shaft 3, so that one dial 13 can block two guide blocks at the same time.

[0065] Then, the shift motor actuates, simultaneously moving the fourth-gear guide block 8 of the main gearbox and the high-gear guide block 9 of the auxiliary gearbox towards the neutral position. When the fourth-gear guide block 8 of the main gearbox moves to the neutral position, if the shift travel of the auxiliary gearbox is greater than that of the main gearbox, the high-gear guide block 9 of the auxiliary gearbox needs to continue moving.

[0066] In order for the high-gear guide block 9 of the auxiliary gearbox to continue to return to neutral, the main gearbox selection motor continues to move half a guide block position to the high / low gear shift fork shaft 3, and the high-gear guide block 9 of the auxiliary gearbox is engaged separately. The shift motor continues to operate, so that the auxiliary gearbox returns to neutral.

[0067] The shift motor continues to move, which can engage the auxiliary gearbox in a higher gear, thus enabling the switching between high and low gears in the auxiliary gearbox.

[0068] After engaging high gear, dial 13 can return to the corresponding neutral position on the main gearbox.

[0069] When the auxiliary gearbox is engaged in a high gear, dial 13 returns to the neutral position of the main gearbox. Dial 13 can then smoothly select the first gear guide block 5, which is currently in fifth gear, and engage fifth gear. This achieves the shift from fourth to fifth gear.

[0070] like Figure 8 The image above shows the process of shifting from fifth gear to fourth gear. Initially, the main compartment is in fifth gear and the auxiliary compartment is in a higher gear.

[0071] First, the gear selector motor moves the dial 13 half a dial 13 distance toward the low gear guide block 10, so that one dial 13 can block two guide blocks at the same time.

[0072] By actuating the shift motor, both the first gear guide block 5 of the main gearbox and the low gear guide block 10 of the auxiliary gearbox can be simultaneously shifted to the neutral position. When the first gear guide block 5 of the main gearbox moves to the neutral position, if the shift travel of the auxiliary gearbox is greater than that of the main gearbox, the low gear guide block 10 of the auxiliary gearbox needs to continue moving.

[0073] In order for the low-gear guide block 10 of the auxiliary gearbox to continue returning to neutral, the main gearbox selection motor continues to move half a guide block position towards the low-gear guide block 10 until the low-gear guide block 10 of the auxiliary gearbox is engaged alone. The engagement motor then continues to operate, thus returning the auxiliary gearbox to neutral.

[0074] The shift motor continues to move, which allows the auxiliary gearbox to engage a lower gear, thus enabling the switching between high and low gears.

[0075] After shifting to low gear, dial 13 can return to the corresponding neutral position on the main gearbox.

[0076] When the auxiliary gearbox is engaged in low gear and the dial 13 returns to the neutral position of the main gearbox, the dial 13 can then select the fourth gear guide block 8 and engage fourth gear, thereby reducing the gear from fifth to fourth.

[0077] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0078] It should be understood that the above description is for illustrative purposes and not for limitation. Many embodiments and applications beyond the provided examples will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of this teaching should not be determined by reference to the above description, but rather by reference to the foregoing claims and the full scope of their equivalents. For purposes of completeness, all articles and references, including patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the foregoing claims is not intended as a waiver of that subject matter, nor should it be construed as an indication that the applicant has not considered that subject matter as part of the disclosed inventive subject matter.

Claims

1. A shifting structure for an eight-speed transmission, characterized in that, It includes a first gear shift fork shaft (1), a second gear shift fork shaft (2), a high and low gear shift fork shaft (3), and a shift head (13); The middle part of the first gear shift fork shaft (1) is provided with two axially spaced first gear guide blocks (5) and second gear guide blocks (6). The first gear guide block (5) is close to the front end of the first gear shift fork shaft (1), and the second gear guide block (6) is close to the rear end of the first gear shift fork shaft (1). The middle part of the second gear shift fork shaft (2) is provided with two axially spaced third gear guide blocks (7) and fourth gear guide blocks (8). The third gear guide block (7) is close to the front end of the second gear shift fork shaft (2), and the fourth gear guide block (8) is close to the rear end of the second gear shift fork shaft (2). The high and low gear shift fork shaft (3) is provided with a high gear guide block (9) and a low gear guide block (10). The high gear guide block (9) is located near the middle and corresponds to the position of the third gear guide block (7). The high and low gear shift fork shaft (3) is provided with a connecting rod (11). The end of the connecting rod (11) is connected to the low gear guide block (10). The low gear guide block (10) passes through the rear end direction of the second gear guide block (6) and the fourth gear guide block (8) through the connecting rod (11) and goes around to the side of the first gear shift fork shaft (1) away from the second gear shift fork shaft (2). The low gear guide block (10) corresponds to the position of the second gear guide block (6). The dial head (13) is located on the same plane as all the guide blocks and between the guide blocks. The dial head (13) is connected to a gear selection motor and a gear shifting motor in the transverse and axial directions of the shift fork shaft, respectively. The gear selection motor is used for transverse movement, and the gear shifting motor is used for axial movement along the shift fork shaft.

2. The shifting structure of the eight-speed transmission according to claim 1, characterized in that, The spacing between the guide blocks of adjacent shift fork shafts is 1-2mm.

3. The shifting structure of the eight-speed transmission according to claim 1, characterized in that, The relative distance between the high-grade guide block (9) and the low-grade guide block (10) in the axial direction is greater than the distance between the first-grade guide block (5) and the second-grade guide block (6).

4. The shifting structure of the eight-speed transmission according to claim 1, characterized in that, The spacing between the first guide block (5) and the second guide block (6) is the same as the spacing between the third guide block (7) and the fourth guide block (8).

5. The shifting structure of the eight-speed transmission according to claim 1, characterized in that, A reverse gear shift fork shaft (4) is provided on the side of the first gear shift fork shaft (1) away from the second gear shift fork shaft (2). The low gear guide block (10) is located between the reverse gear shift fork shaft (4) and the first gear shift fork shaft (1). A reverse gear guide block (12) is provided on the middle part of the reverse gear shift fork shaft (4).

6. The shifting structure of the eight-speed transmission according to claim 1, characterized in that, The height of the connecting rod (11) is lower than the height of all the guide blocks.

7. A shifting method based on the shifting structure of the eight-speed transmission according to any one of claims 1-6, characterized in that, Includes the following processes: When shifting gears at the same high or low gear, the gear selector motor moves between the two guide blocks of the corresponding shift fork shaft, and then the shift motor drives it to move axially, which in turn moves the corresponding gear guide block to engage the gear. When shifting from fourth to fifth gear, move the shifter (13) horizontally by half a shifter (13) position, and simultaneously return the fourth gear guide block (8) and the high gear guide block (9) to neutral. Then, continue to engage the high gear guide block (9), and then move the shifter (13) to the first gear guide block (5) position to engage fifth gear. When it is necessary to downshift from fifth to fourth gear, simultaneously shift the second gear guide block (6) and the low gear guide block (10) back to neutral, then shift the low gear guide block (10) back to the gear position, and then move the shifter (13) to the fourth gear guide block (8) position to engage fourth gear.

8. The shifting method of the eight-speed transmission according to claim 7, characterized in that, The specific process of shifting from fourth to fifth gear is as follows: First, the gear selector motor moves the dial (13) half the distance of the dial (13) towards the high / low gear shift fork shaft (3); Then, by operating the shift motor, the fourth gear guide block (8) and the high gear guide block (9) are simultaneously shifted to the neutral position; The gear selection motor continues to move half a guide block position towards the high and low gear shift fork shaft (3), and separately engages the high gear guide block (9) of the auxiliary gearbox. The gear shift motor continues to move to engage the high gear of the auxiliary gearbox, thereby realizing the high and low gear switching of the auxiliary gearbox. After shifting to a higher gear, turn the dial (13) back to the corresponding neutral position; Select the first gear guide block (5) which is currently in fifth gear using the dial (13), and engage fifth gear.

9. The shifting method of the eight-speed transmission according to claim 7, characterized in that, The specific process of downshifting from fifth gear to fourth gear is as follows: First, the gear selector motor moves the dial (13) half the distance of the dial (13) towards the low gear guide block (10); By operating the shift motor, the first gear guide block (5) and the low gear guide block (10) can be simultaneously shifted to the neutral position. The main gear selector motor continues to move half a guide block position towards the low gear guide block (10) until the low gear guide block (10) of the auxiliary gearbox is engaged alone. The shift motor continues to move so that the auxiliary gearbox can be engaged in low gear, thus realizing the switching between high gear and low gear. After engaging low gear, turn the dial (13) back to the corresponding neutral position on the main gearbox; Select the fourth gear guide block (8) with the dial (13) and engage the fourth gear.

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