A transmission mechanism, assembly process, and starter

Abstract

The application provides a transmission mechanism, an assembly process and a starter. The transmission mechanism comprises an integrated transmission shaft and a one-way clutch. A ring-shaped clamping groove is integrally formed on a journal section of the shaft by a first shaft ring and a second shaft ring. A full-tooth section and a half-tooth section helical spline are arranged on a tail section of the shaft. The full-tooth section tooth groove unit is twice as much as the half-tooth section. Each tooth groove unit of the half-tooth section helical spline is partially aligned with two corresponding adjacent tooth groove units of the full-tooth section helical spline in the circumferential direction. The inner spline shaft of the one-way clutch can move between a pulling-out station and a pressing-in station. The slip ring and the transmission shaft are designed as an integrated structure, and the shaft retaining ring and the mounting groove are omitted. The characteristics of the inner spline shaft being capable of being pulled out and pressed in relative to the slide are utilized to design an assembly mode in which the transmission shaft axial limiting is realized without an opening retaining ring after assembly, and the opening retaining ring groove on the transmission shaft is cancelled. The assembly process only needs three steps of insertion, rotation and pressing-in, and is simple to operate, saves assembly time and improves production efficiency.

Description

Technical Field

[0001] This invention relates to the field of starter technology, specifically to a transmission mechanism for a starter, an assembly process for the transmission mechanism, and a starter employing the transmission mechanism. Background Technology

[0002] Currently, starters widely used in commercial vehicles are mainly divided into two types based on their mechanical structure design: starters with front support and starters without front support. Among them, starters without front support are increasingly widely used due to their high sealing performance, strong environmental adaptability, and easier physical matching with the engine.

[0003] Reference Appendix Figure 1-2 As shown, most current mainstream front-supportless starters employ a one-way clutch structure that rotates but does not disengage. In this structure, power transmission and disconnection rely on the axial movement of the drive shaft 100', thus requiring a slip ring 102' for the shift fork 101' to be mounted on the drive shaft. In traditional designs, this slip ring typically consists of two stamped left and right slip rings. During assembly, two washers 103' are first installed on the step of the drive shaft, then the two slip rings are fitted on, and finally, a shaft retaining ring 104' is used to limit the slip rings at the step of the drive shaft. Simultaneously, the drive shaft 100' is screwed to the internal splined shaft 201' of the one-way clutch 200'. To prevent the drive shaft from disengaging from the one-way clutch, an open retaining ring 105' is installed at the rear end of the drive shaft for limiting its movement. The above-mentioned traditional structure has the following weaknesses in practical use:

[0004] 1. The two split slip rings 102′ are mostly made of cold-rolled steel plates for stamping to facilitate deep drawing. The wear resistance and impact resistance of the material itself are relatively poor. After a certain number of uses, the risk of slip ring breakage increases significantly.

[0005] 2. The shaft retaining ring 104' used to fix the slip ring 102' may come loose during operation. Once it comes loose, the axial positioning of the drive shaft 100' will fail.

[0006] 3. The open retaining ring 105′ used to prevent the drive shaft from coming off also has the risk of falling off. Once the open retaining ring falls off, the drive shaft will eventually come off from the front end when it moves backward, and the starter will completely fail.

[0007] 4. The annular groove 106′ on the drive shaft, which is used to install the open retaining ring and the shaft retaining ring, are stress concentration points. Under severe working conditions such as engine overload, there is a risk of shaft breakage at these locations.

[0008] Therefore, how to further improve the reliability of the transmission mechanism of the front-supportless starter and eliminate the above-mentioned weak links has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0009] The purpose of this invention is to provide a transmission mechanism for starters, particularly suitable for front-supportless starters with a one-way clutch structure that rotates but does not extend. This transmission mechanism, through improvements to the structure of the drive shaft and one-way clutch, fundamentally eliminates the failure risks associated with conventional solutions, such as the detachment of open retaining rings and shaft retaining rings, as well as slip ring breakage and shaft breakage, significantly improving the overall reliability of the machine. To achieve the above objectives, the transmission mechanism of this invention replaces the originally separately assembled slip ring structure on the drive shaft with an integrally formed part of the drive shaft, thereby eliminating the need for shaft retaining rings and their mounting grooves. Simultaneously, utilizing the characteristic that the splined shaft within the one-way clutch can be pulled out and pressed in relative to its slide, an assembly method is designed that achieves axial positioning of the drive shaft without the need for open retaining rings after assembly, thus eliminating the need for open retaining ring grooves on the drive shaft.

[0010] This invention is achieved through the following technical solution: a transmission mechanism, including a transmission shaft and a one-way clutch; the transmission shaft is an integral shaft having a head section, a journal section, a tail section, and an extension section sequentially along the axial direction; the outer circumference of the journal section is integrally formed with an annular groove for cooperating with a shift fork; the outer circumferential surface of the tail section is provided with a helical spline, the helical spline including a full-tooth helical spline and a half-tooth helical spline arranged along the axial direction, the half-tooth helical spline being located near the extension section; the number of toothed units of the full-tooth helical spline is twice that of the half-tooth helical spline, and each toothed unit of the half-tooth helical spline is partially aligned circumferentially with two corresponding adjacent toothed units of the full-tooth helical spline, so that when After the full-tooth helical spline rotates one tooth pitch relative to the internal half-tooth helical spline, the half-tooth helical spline can form an axial lock with the internal half-tooth helical spline; the one-way clutch includes a slide and an internal spline shaft; the internal spline shaft can move relative to the slide between a pull-out position and a press-in position, and the inner wall of the internal spline shaft is formed with an internal half-tooth helical spline; at the pull-out position, the drive shaft can be inserted from the front end of the internal spline shaft until the front end face of the full-tooth helical spline passes over the rear end face of the internal half-tooth helical spline; at the press-in position, the extended section of the drive shaft abuts against the bottom of the slide to prevent the drive shaft from moving away from the shaft head section, so that the front end face of the full-tooth helical spline no longer passes over the rear end face of the internal half-tooth helical spline.

[0011] Furthermore, the annular groove is formed by a first collar and a second collar integrally formed on the outer wall of the journal section, spaced apart.

[0012] Furthermore, the half-tooth segment helical spline includes N tooth groove units, and the full-tooth segment helical spline includes 2N tooth groove units; wherein, in the circumferential direction, the arc length occupied by one tooth groove unit of the half-tooth segment helical spline is the same as and corresponds to the arc length occupied by any two adjacent tooth groove units of the full-tooth segment helical spline.

[0013] Furthermore, the toothed unit includes a helical tooth and a helical groove; the arc length occupied by the helical groove of the half-tooth segment helical spline is the same as and corresponds to the arc length occupied by the helical groove of the full-tooth segment helical spline; the arc length occupied by the helical tooth of the half-tooth segment helical spline is the same as and corresponds to the sum of the arc lengths occupied by an adjacent helical tooth, a helical groove, and a helical tooth in the full-tooth segment helical spline.

[0014] Furthermore, N is selected from any one of 5, 6, 7, and 8.

[0015] Furthermore, the outer circumference of the shaft end section is provided with a straight spline for connecting the drive gear, and a snap ring groove for assembling a snap ring is provided at the front end of the straight spline.

[0016] On the other hand, an assembly process for the transmission mechanism includes the following steps: Step 1: Before assembly, the internal spline shaft of the one-way clutch is pulled out by about 2.6-5mm; the internal spline shaft is positioned in the pulled-out position; Step 2: The rear end of the transmission shaft is inserted into the internal spline shaft, so that the extended section of the transmission shaft abuts against the bottom of the slide, and the front end face of the full-tooth helical spline passes over the rear end face of the internal half-tooth helical spline; Step 3: The transmission shaft is rotated so that the full-tooth helical spline rotates by one tooth pitch, so that the half-tooth helical spline and the internal half-tooth helical spline form an axial lock; Step 4: The internal spline shaft is pressed into the pressing position, and the extended section is kept abutting against the bottom of the slide during the pressing process.

[0017] On the other hand, a starter includes a motor, a shift fork, and the transmission mechanism, wherein the transmission shaft engages with the shift fork via an annular groove; the starter also includes a middle cover and an armature shaft driven by the motor, wherein a bearing is provided on the middle cover; the front end of the internal spline shaft abuts against the bearing, and the rear end of the slide abuts against the end face of the armature shaft, thereby restricting the internal spline shaft to a press-in position, and such that the internal spline shaft can only be pulled out with an axial clearance less than a preset value relative to the slide, the preset value being less than the distance required for the front end face of the full-tooth helical spline to pass over the rear end face of the internal half-tooth helical spline.

[0018] Furthermore, the axial clearance is 0.2mm-0.8mm.

[0019] Furthermore, the starter is a front-supportless starter with a one-way valve that rotates but does not engage in operation for an internal combustion engine.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The slip ring and drive shaft are designed as a single unit, made of alloy carburized steel with carburizing and quenching treatment, resulting in high surface hardness and wear resistance, and high strength and toughness in the core. This completely solves the problem of traditional stamped slip rings being prone to breakage after long-term use. In addition, the one-piece slip ring structure eliminates the need for a shaft retaining ring and its mounting groove, fundamentally eliminating the dual risks of shaft breakage caused by the retaining ring coming off and stress concentration at that location.

[0022] 2. By utilizing the characteristics of the internal spline shaft for pull-out assembly and press-in limiting, and in conjunction with the rear stop surface of the drive shaft, axial limiting is achieved, completely eliminating the need for the open retaining ring and preventing serious failure modes such as drive shaft disengagement and starter failure caused by the open retaining ring falling off.

[0023] 3. In the assembly process of the transmission mechanism, only three steps are required: insertion, rotation, and pressing. The operation is simple, saving assembly time and improving production efficiency. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of a starter motor using existing technology.

[0025] Figure 2 This is an exploded view of a drive shaft and a one-way clutch in the prior art.

[0026] Figure 3 This is a perspective view of the transmission mechanism in this invention and a cross-sectional view of the transmission mechanism along its axis.

[0027] Figure 4 This is a perspective view of the drive shaft in this invention.

[0028] Figure 5 This is a side view of the transmission shaft in this invention and a cross-sectional view along AA and BB.

[0029] Figure 6 This is a cross-sectional view of the three helical splines when the drive shaft is inserted into the internal spline shaft and has not rotated in this invention.

[0030] Figure 7 This is a cross-sectional view of the three helical splines after the transmission shaft has rotated through one full tooth segment in this invention.

[0031] Figure 8 This is a cross-sectional view of the one-way clutch in the pull-out position in this invention.

[0032] Figure 9 This is a cross-sectional view of the one-way clutch in the pressing position in this invention.

[0033] Figure 10 This is a perspective view of the internal spline shaft and a cross-sectional view along the axis of the present invention.

[0034] Figure 11This is a flowchart illustrating the assembly process of the transmission mechanism in this invention.

[0035] Figure 12 This is a perspective view of the starter motor in this invention and a cross-sectional view along its axis.

[0036] Figures 1-2 Reference numerals in existing Chinese drawings: drive shaft 100′, shift fork 101′, slip ring 102′, washer 103′, shaft retaining ring 104′, open retaining ring 105′, annular groove 106′, one-way clutch 200′, internal spline shaft 201′.

[0037] Figures 3-12 Reference numerals in the accompanying drawings of this invention: transmission shaft 100, shaft head section 1, straight spline 11, snap ring groove 12, journal section 2, first collar 21, second collar 22, annular clamping groove 23, shaft tail section 3, extended section 4, stop surface 41, spiral spline 5, full-tooth spiral spline 51, half-tooth spiral spline 52, tooth groove unit 53, spiral tooth 531, spiral groove 532.

[0038] One-way clutch 200, slide 6, internal spline shaft 7, internal half-tooth helical spline 8.

[0039] Shift fork 300, motor 400, middle cover 500, armature shaft 600, bearing 700, drive gear 800. Detailed Implementation

[0040] The technical solutions in 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.

[0041] See appendix Figure 3-12 As shown, the present invention provides a transmission mechanism for a starter motor, including a drive shaft 100 and a one-way clutch 200.

[0042] As attached Figure 4 As shown, the drive shaft 100 is an integral stepped shaft formed along the axial direction. From the front end to the rear end (with the power output direction as the front), it has a shaft head section 1, a shaft journal section 2, a shaft tail section 3, and an extended section 4 in sequence. The end face of the extended section 4 forms an axial stop surface 41. In this invention, the shaft head section 1 is defined as the front end of the drive shaft 100, and the extended section 4 is defined as the rear end of the drive shaft 100. If there are subsequent descriptions of the front and rear orientations, these shall prevail.

[0043] The drive shaft 100 is preferably made of alloy carburizing steel such as 20CrMnTi. After carburizing and quenching treatment, its surface has high hardness and high wear resistance, while the core maintains high strength and sufficient toughness. Thus, when subjected to impact and torque, it completely eliminates the risk of breakage of traditional stamped slip rings due to poor wear resistance and impact resistance.

[0044] The outer circumference of the shaft head section 1 is provided with a straight spline 11 for connecting the drive gear 800 to transmit torque, and a snap ring groove 12 is provided at the front end of the straight spline 11 for assembling the snap ring 12 to axially limit the drive gear 800.

[0045] The outer circumference of the journal section 2 is integrally formed with an annular groove 23 for cooperating with the shift fork 300; the annular groove 23 is formed by a first collar 21 and a second collar 22 integrally formed on the outer wall of the journal section 2 by means of cold extrusion or the like; this integral slip ring structure completely replaces the traditional split stamped slip ring and shaft retaining ring, which not only eliminates the risk of the shaft retaining ring coming off at the source, but also eliminates the stress concentration point at the shaft because there is no need to open the shaft retaining ring groove, thus greatly reducing the risk of shaft breakage.

[0046] As attached Figure 4-7 As shown, a helical spline 5 is provided on the outer circumferential surface of the shaft tail section 3. The helical spline 5 is divided into two sections along the axial direction, including a full-tooth helical spline 51 and a half-tooth helical spline 52. The half-tooth helical spline 52 is located on the side close to the extended section 4. The tooth groove unit 53 of the full-tooth helical spline 51 is twice the tooth groove unit 53 of the half-tooth helical spline 52.

[0047] As attached Figure 5 As shown, the toothed unit 53 refers to a basic unit consisting of a helical tooth 531 and an adjacent helical groove 532. Preferably, the half-tooth segment has 6 teeth and 6 grooves, and the full-tooth segment has 12 teeth and 12 grooves. Each toothed unit 53 of the half-tooth segment helical spline 52 is partially aligned circumferentially with two corresponding adjacent toothed units 53 of the full-tooth segment helical spline 51, so that when the full-tooth segment helical spline 51 rotates one tooth pitch relative to the inner half-tooth helical spline 8, the half-tooth segment helical spline 52 can form an axial lock with the inner half-tooth helical spline 8.

[0048] Appendix Figure 6 This is a cross-sectional view of the three helical splines when the drive shaft 100 is inserted into the internal spline shaft 7 and is not rotated: the red line represents the tooth groove profile of the internal half-tooth helical spline 8, the black line represents the tooth groove profile of the half-tooth segment helical spline 52, and the blue line represents the tooth groove profile of the full-tooth segment helical spline 51. In this state, the front end face 51a of the full-tooth segment helical spline 51 completely extends beyond the rear end face 8a of the internal half-tooth helical spline 8.

[0049] Appendix Figure 7After rotating the full-tooth helical spline 51 by one tooth pitch, the cross-sectional view of the three helical splines is as follows: From an axial perspective, it can be seen that the half-tooth helical spline 52 (black line) and the inner half-tooth helical spline 8 (red line) have partially crossed, which means that the two have formed axial jamming; it can also be seen that the full-tooth helical spline 51 (blue line) and the inner half-tooth helical spline 8 (red line) have not crossed, which means that the two have not formed axial jamming. Therefore, after the inner spline shaft 7 is pressed into the pressing position, a part of the front end of the full-tooth helical spline 51 will be engaged in the inner half-tooth helical spline 8.

[0050] In this invention, as shown in the appendix Figure 8-11 As shown, the one-way clutch 200 includes a slide 6 and an internal splined shaft 7; the internal splined shaft 7 is capable of being positioned relative to the slide 6 in a pull-out position (see attached diagram). Figure 8 Between the pressing station and the pressing station (attached) Figure 9 The inner spline shaft 7 has an inner half-tooth helical spline 8 (also an N-tooth N-groove) formed on its inner wall, the tooth profile of which is matched with the half-tooth segment helical spline 52 on the drive shaft 100. (See attached...) Figure 11 As shown, when pulling out the station, the inner spline shaft 7 is first pulled back about 2.6-5mm. At this time, the drive shaft 100 can be smoothly inserted from the front end of the inner spline shaft 7, and the stop surface 41 of the extended section 4 can be pushed all the way to the bottom of the slide block 6. In this state, the front end face 51a of the full-tooth spiral spline 51 passes over the rear end face 8a of the inner half-tooth spiral spline 8. Then, the drive shaft 100 is rotated by a full tooth pitch (e.g., 30°), and the half-tooth spiral spline 52 forms an axial lock with the inner half-tooth spiral spline 8. Finally, the internal spline shaft 7 is pressed into the pressing position, and the stop surface 41 is kept against the bottom of the slide block 6 throughout the process. When pressing into the position, the extended section 4 of the drive shaft 100 abuts against the bottom of the slide block 6 to prevent the drive shaft 100 from moving away from the shaft head section 1, so that the front end face 51a of the full-tooth helical spline 51 no longer passes over the rear end face 8a of the internal half-tooth helical spline 8. The drive shaft 100 is thus reliably axially limited, and there is no need to use an open retaining ring, eliminating the risk of the open retaining ring falling off.

[0051] In this invention, as shown in the appendix Figure 5-6As shown, the half-tooth segment helical spline 52 includes N tooth groove units 53, and the full-tooth segment helical spline 51 includes 2N tooth groove units 53; N is selected from any one of 5, 6, 7, and 8. In terms of circumferential correspondence, the arc length occupied by one tooth groove unit 53 of the half-tooth segment helical spline 52 is the same as and corresponds to the arc length occupied by any two adjacent tooth groove units 53 of the full-tooth segment helical spline 51. The arc length occupied by one helical groove 532 of the half-tooth segment helical spline 52 is the same as and corresponds to the arc length occupied by one helical groove 532 of the full-tooth segment helical spline 51; the arc length occupied by one helical tooth 531 of the half-tooth segment helical spline 52 is the same as and corresponds to the sum of the arc lengths occupied by an adjacent helical tooth 531, a helical groove 532, and a helical tooth 531 in the full-tooth segment helical spline 51. It should be noted that the arc length occupied by each spiral groove 532 refers to the arc length occupied by its groove opening, and the arc length occupied by each spiral tooth 531 refers to the arc length occupied by its outer surface. Furthermore, the bottom of the spiral groove 532 and the outer surface of the spiral tooth 531 are connected by a ramp transition.

[0052] Taking a half-tooth spiral spline 52 with 6 teeth and 6 grooves, and a full-tooth spiral spline 51 with 12 teeth and 12 grooves as an example: a spiral groove 532a (with an arc length of 24° at the groove opening) on ​​the half-tooth spiral spline 52 coincides with a spiral groove 532b (with an arc length of 24° at the groove opening) on ​​the full-tooth spiral spline 51 in the circumferential direction and has the same size; while a spiral tooth 531a (with an arc length of 36° at the outer surface) on the half-tooth spiral spline 52 corresponds to and is the same as the total arc length (36°) occupied by the first spiral tooth 531b (with an arc length of 6° at the outer surface), the second spiral groove 532b (with an arc length of 24° at the groove opening), and the second spiral tooth 531b (with an arc length of 6° at the outer surface) arranged consecutively on the full-tooth spiral spline 51. With this specific circumferential layout, during assembly, simply inserting the drive shaft 100 and rotating it by one full tooth pitch (i.e., 30°) will ensure that the tooth end face of the half-tooth helical spline 52 reliably engages with the rear end face 8a of the inner half-tooth helical spline 8 of the inner spline shaft 7. It should be noted that, to more clearly explain the tooth groove correspondence between the full-tooth helical spline 51 and the half-tooth helical spline 52, the specific arc length values ​​(6°, 24°, 36°) given above are only one feasible example; other specific values ​​are also acceptable as long as the conditions are met.

[0053] In this invention, as shown in the appendix Figure 4 As shown, the root of the shoulder between all shaft segments on the drive shaft 100, such as the journal segment 2 and the tail segment 3, adopts a rounded corner for smooth transition. This completely eliminates the sharp stress concentration points in the open retaining ring groove and shaft retaining ring groove in the traditional structure, and significantly enhances the fatigue resistance and overload fracture resistance of the drive shaft 100.

[0054] With the above structure, this transmission mechanism achieves reliable assembly of the transmission shaft 100 and the one-way clutch 200 without retaining rings. It has fewer parts, better structural rigidity, and completely solves the problems of breakage and failure caused by retaining ring detachment and stress concentration grooves on the shaft in traditional solutions.

[0055] As attached Figure 11 As shown, an assembly process for the transmission mechanism includes the following steps:

[0056] Step 1: Before assembly, pull the inner splined shaft 7 of the one-way clutch 200 outward by about 2.6-5mm relative to the slide 6; so that the inner splined shaft 7 is in the pulled-out position;

[0057] Step 2: Insert the rear end of the drive shaft 100 (one end of the extended section 4) into the inner spline shaft 7 until the stop surface 41 of the extended section 4 of the drive shaft 100 abuts against the bottom of the slide block 6. At this time, the front end face 51a of the full-tooth spiral spline 51 has completely passed the rear end face 8a of the inner half-tooth spiral spline 8.

[0058] Step 3: Rotate the drive shaft 100 so that the full-tooth helical spline 51 rotates by one tooth pitch (e.g., 30° for N=6). After rotation, the front end face of the half-tooth helical spline 52 will form an axial jam with the rear end face 8a of the inner half-tooth helical spline 8, and the drive shaft 100 will no longer be able to disengage forward.

[0059] Step 4: Press the internal spline shaft 7 back into the slide block 6, returning it to the pressing position. During the pressing process, keep the extended section 4 against the bottom of the slide block 6. After pressing into place, a portion of the front end of the full-tooth helical spline 51 is engaged in the internal half-tooth helical spline 8, while the extended section 4 has reached the bottom of the slide block 6 and cannot move further. The front end face 51a of the full-tooth helical spline 51 can no longer pass the rear end face 8a of the internal half-tooth helical spline 8, and the full-tooth helical spline 51 can no longer rotate relative to the internal spline shaft 7. The drive shaft 100 is then completely locked in the one-way clutch 200.

[0060] The assembly process of the transmission mechanism described in this invention utilizes the pull-out characteristic of the internal spline shaft 7, requiring only three actions: insertion, rotation, and pressing to complete the assembly. This process is simple, efficient, and eliminates the need for additional open retaining rings after assembly.

[0061] As attached Figure 12 As shown, a starter of the present invention is a front-supportless starter with a one-way valve that rotates but does not engage in operation for an internal combustion engine. The starter includes a motor 400, a shift fork 300, and the aforementioned transmission mechanism. The transmission shaft 100 engages with the shift fork 300 via an annular groove 23, so that the transmission shaft 100 is pushed forward under the action of an electromagnetic switch.

[0062] The starter also includes a middle cover 500 and an armature shaft 600 driven by a motor 400. The middle cover 500 is provided with a bearing 700. After the starter is fully assembled, the front end of the inner spline shaft 7 abuts against the end face of the bearing 700, while the rear end of the slide 6 abuts against the end face of the armature shaft 600. This front-to-back abutting structure firmly restricts the inner spline shaft 7 in the axial direction to the press-in position.

[0063] The internal spline shaft 7 can only be pulled out with an axial clearance smaller than a preset value relative to the slide 6. This preset value is less than the distance required for the front end face of the full-tooth helical spline 51 to pass over the rear end face of the internal half-tooth helical spline 8. Due to machining and assembly tolerances, the internal spline shaft 7 can still be pulled out with a small axial clearance relative to the slide 6, which is controlled within the range of 0.2mm-0.8mm. This axial clearance value is much smaller than the minimum pull-out distance of 2.6mm corresponding to the drive shaft 100 needing to rotate one tooth pitch during assembly. Therefore, throughout the entire service life of the starter, the actual pull-out amount of the internal spline shaft 7 is never sufficient for the front end face 51a of the full-tooth helical spline 51 to pass over the rear end face 8a of the internal half-tooth helical spline 8. This ensures that the axial jamming relationship between the half-tooth helical spline 52 and the internal half-tooth helical spline 8 can never be released, and the drive shaft 100 cannot disengage from the one-way clutch 200, fundamentally ensuring the long-term reliable operation of the starter.

[0064] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A transmission mechanism, characterized in that: Includes drive shaft and one-way clutch; The drive shaft is an integral shaft consisting of a head section, a journal section, a tail section, and an extension section along the axial direction. The outer circumference of the journal section is integrally formed with an annular groove for engaging with the shift fork. The outer circumference of the tail section is provided with a helical spline, which includes a full-tooth helical spline and a half-tooth helical spline arranged along the axial direction. The half-tooth helical spline is located on the side closer to the extension section. The number of tooth groove units of the full-tooth helical spline is twice that of the half-tooth helical spline. Each tooth groove unit of the half-tooth helical spline is partially aligned with the corresponding two adjacent tooth groove units of the full-tooth helical spline in the circumferential direction, so that when the full-tooth helical spline rotates one tooth pitch relative to the inner half-tooth helical spline, the half-tooth helical spline can form an axial lock with the inner half-tooth helical spline. The one-way clutch includes a slide and an internal spline shaft; the internal spline shaft can move relative to the slide between a pull-out position and a press-in position, and the inner wall of the internal spline shaft is formed with an internal half-tooth helical spline; in the pull-out position, the drive shaft can be inserted from the front end of the internal spline shaft until the front end face of the full-tooth helical spline passes over the rear end face of the internal half-tooth helical spline; in the press-in position, the extended section of the drive shaft abuts against the bottom of the slide to prevent the drive shaft from moving away from the shaft head section, so that the front end face of the full-tooth helical spline no longer passes over the rear end face of the internal half-tooth helical spline.

2. The transmission mechanism according to claim 1, characterized in that: The annular groove is formed by a first collar and a second collar integrally formed on the outer wall of the journal section, spaced apart.

3. The transmission mechanism according to claim 2, characterized in that: The half-tooth segment helical spline includes N tooth groove units, and the full-tooth segment helical spline includes 2N tooth groove units; wherein, in the circumferential direction, the arc length occupied by one tooth groove unit of the half-tooth segment helical spline is the same as and corresponds to the arc length occupied by any two adjacent tooth groove units of the full-tooth segment helical spline.

4. The transmission mechanism according to claim 3, characterized in that: The toothed unit includes a helical tooth and a helical groove; the arc length occupied by the helical groove of the half-tooth segment helical spline is the same as and corresponds to the arc length occupied by the helical groove of the full-tooth segment helical spline; the arc length occupied by the helical tooth of the half-tooth segment helical spline is the same as and corresponds to the sum of the arc lengths occupied by an adjacent helical tooth, a helical groove, and a helical tooth in the full-tooth segment helical spline.

5. The transmission mechanism according to claim 4, characterized in that: The N is selected from any one of 5, 6, 7, and 8.

6. The transmission mechanism according to claim 1, characterized in that: The outer circumference of the shaft head section is provided with a straight spline for connecting the drive gear, and a snap ring groove is provided at the front end of the straight spline.

7. An assembly process for the transmission mechanism as described in any one of claims 1 to 6, characterized in that: Includes the following steps: Step 1: Before assembly, pull out the internal spline shaft of the one-way clutch by about 2.6-5mm; so that the internal spline shaft is in the pulled-out position; Step 2: Insert the rear end of the drive shaft into the internal spline shaft, so that the extended section of the drive shaft abuts against the bottom of the slide, and the front end face of the full-tooth helical spline passes over the rear end face of the internal half-tooth helical spline. Step 3: Rotate the drive shaft to make the full-tooth helical spline rotate one tooth pitch, so that the half-tooth helical spline and the inner half-tooth helical spline form an axial lock; Step 4: Press the internal spline shaft into the pressing station, and keep the extended section against the bottom of the slide during the pressing process.

8. A starter motor, characterized in that: Includes a motor, a shift fork, and a transmission mechanism as described in any one of claims 1 to 6, wherein the transmission shaft engages with the shift fork via an annular groove; The starter also includes a middle cover and an armature shaft driven by a motor. The middle cover is provided with a bearing. The front end of the internal spline shaft abuts against the bearing, and the rear end of the slide abuts against the end face of the armature shaft to restrict the internal spline shaft to the press-in position, and to make the internal spline shaft only able to pull out an axial clearance of less than a preset value relative to the slide. The preset value is less than the distance required for the front end face of the full-tooth helical spline to pass over the rear end face of the internal half-tooth helical spline.

9. The starter motor according to claim 8, characterized in that: The axial clearance is 0.2mm-0.8mm.

10. The starter motor according to claim 9, characterized in that: The starter is a front-supportless starter with a one-way valve that rotates but does not engage, designed for internal combustion engines.

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