Electric drive mechanism for a rearview mirror

Abstract

This invention relates to the field of electric folding drive technology for automotive rearview mirrors, and discloses an electric drive mechanism for automotive rearview mirrors, mainly used to realize the electric folding and unfolding of automotive rearview mirrors. It includes a base, a cover, a drive motor, a three-stage worm gear reduction transmission chain, and a composite positioning block. The positioning block is embedded into the motor bushing groove through a limiting boss and presses the motor bushing. Simultaneously, a first bearing hole is provided on the positioning block to support one end of the second worm gear. Positioning slots on both sides of the positioning block cooperate with positioning protrusions on the base and are fastened with screws. Thus, the positioning block simultaneously achieves the pressing constraint of the top end of the motor worm gear, the anti-skew positioning of the positioning block itself, and the bearing support of one end of the second worm gear, shortening the tolerance chain of the multi-stage transmission chain and reducing operating noise.

Description

Technical Field

[0001] This invention relates to electric folding drive technology for automotive rearview mirrors, and more particularly to an electric drive mechanism for automotive rearview mirrors. Background Technology

[0002] With the development of the automotive industry and technological advancements, the automatic folding function of rearview mirrors when the vehicle is parked and the engine is turned off has become an important technology for improving vehicle convenience and safety. Existing electric drive mechanisms for rearview mirrors typically include miniature DC motors, which use worm gears and other transmission devices to achieve the folding and extending functions of the rearview mirrors.

[0003] In single-motor drive systems, to obtain sufficient reduction ratio and output torque to meet the adjustment requirements of large rearview mirrors, a multi-stage worm gear-gear transmission chain is required. However, a multi-stage transmission chain implies the existence of multiple drive shafts, each requiring high positional accuracy and coaxiality, and each necessitating its own support structure. Providing reliable support for multiple drive shafts within the extremely limited housing space of the rearview mirror electric drive mechanism is one of the core design challenges for this type of product.

[0004] The current solution faces the following specific problems: First, as a high-speed input shaft, the cantilever end of the motor worm gear is prone to radial runout and axial movement during high-speed rotation. Traditional solutions use independent bearing caps or end caps for constraint, but these end caps only serve a single constraint function, occupying internal space without contributing to the support of other drive shafts. Second, the intermediate drive shaft in multi-stage transmissions requires support at both ends, with one end's support position adjacent to the top of the motor worm gear. Providing separate support structures for the top of the motor worm gear and one end of the intermediate worm gear would result in structural redundancy and wasted space in the extremely compact rearview mirror mechanism. Furthermore, when the support structures for the two shafts are independent parts, the relative positional accuracy between them depends entirely on the cumulative fit accuracy between their respective support structures and the housing, with a cumulative tolerance of ±0.18mm. This cumulative error causes the center distance between the worm gear and gear to deviate from the design value, resulting in uneven meshing clearance, increased periodic impact noise, and accelerated tooth surface wear.

[0005] Therefore, there is an urgent need for a structural solution that can simultaneously solve the problems of motor worm gear top constraint and intermediate transmission shaft support within a very limited housing space, reduce the number of independent parts, and shorten the support tolerance chain. Summary of the Invention

[0006] The purpose of this invention is to provide an electric drive mechanism for an automotive rearview mirror. This electric drive mechanism, by setting a composite positioning reference block, simultaneously achieves three functions: clamping constraint at the top of the motor worm gear, precise anti-skew positioning of the positioning block itself, and bearing support at one end of the second worm gear. It features a short tolerance chain, high transmission accuracy, simple assembly, and low operating noise.

[0007] The above-mentioned technical objective of the present invention is achieved through the following technical solution: An electric drive mechanism for a car rearview mirror includes: a base for supporting a transmission assembly; a cover for covering the base to form a closed housing; a drive motor mounted on the base; a motor worm gear connected to the output end of the drive motor; a first gear meshing with the motor worm gear for transmission; a first worm gear coaxially connected to the first gear; a second gear meshing with the first worm gear for transmission; a second worm gear coaxially connected to the second gear; an output gear meshing with the second worm gear for transmission; a motor bushing connected to the top of the motor worm gear; a motor bushing groove disposed on the base for mounting the motor bushing; and a positioning block fixed to the base. At the motor bushing groove, the positioning block presses and restricts the motor bushing within the groove; a limiting boss is located at the bottom of the positioning block and embedded within the motor bushing groove; screws are used to fix the positioning block to the base; positioning slots are located on both sides of the positioning block; a positioning protrusion is located on the base and passes through the positioning slot; a first bearing hole is located on the positioning block near the second worm; a second bearing hole is located on the base at the other end of the second worm; oil-impregnated bearings are respectively installed in the first bearing hole and the second bearing hole, and both ends of the second worm are connected to the oil-impregnated bearings.

[0008] The present invention is further configured such that: a shaft hole is provided on the base on one side of the second worm gear, a gear groove for installing the output gear is provided on the outer ring of the shaft hole, a plane bearing is installed at the bottom of the gear groove, and the output gear is connected to the plane bearing through a gear bushing.

[0009] The present invention is further configured such that: both the first worm and the second worm are provided with a limiting cut surface, the limiting cut surface being used to achieve circumferential torque transmission connection with the first gear and the second gear.

[0010] The present invention is further configured such that: the base has first positioning holes on both sides, and a spring and a positioning post are provided in the first positioning holes; and the cover has a second positioning hole corresponding to the positioning post.

[0011] The present invention is further configured such that: both ends of the first worm are connected to the base and the cover through worm bushings, the base and the cover are provided with grooves for installing the worm bushings, a plurality of concave surfaces are provided in the grooves at intervals, and the worm bushings are provided with protrusions that engage with the concave surfaces.

[0012] The present invention is further configured such that: the positioning slot is elongated, the positioning protrusion is cylindrical, and when the positioning protrusion engages with the positioning slot, it achieves precise positioning in the direction perpendicular to the length of the slot and retains a gap in the direction parallel to the length of the slot.

[0013] The present invention is further configured such that: the positioning block is vertically positioned by being embedded in the motor bushing groove by the limiting boss; it is horizontally and longitudinally positioned by cooperating with the positioning protrusion through the positioning slot hole; and it is axially fastened by the screw. The triple constraint works together to determine the unique spatial position of the positioning block.

[0014] The present invention is further configured such that: the first bearing hole and the limiting boss are integrally formed on the positioning block, and the axis of the first bearing hole and the axis of the second bearing hole are arranged coaxially.

[0015] The present invention is further configured such that: the motor worm, the first worm, and the second worm constitute a three-stage worm gear reduction transmission chain, and the three-stage worm gear reduction transmission chain has a self-locking characteristic.

[0016] The present invention is further configured such that: the positioning block simultaneously performs clamping constraint on the top end of the motor worm and bearing support on one end of the second worm, so that the relative positional accuracy between the top end of the motor worm and one end of the second worm is determined by the machining accuracy inside the positioning block.

[0017] In summary, the present invention has the following beneficial effects: (1) Shortened tolerance chain improves transmission accuracy: The positioning block integrates the functions of constraining the top of the motor worm and supporting the bearing at one end of the second worm into the same rigid component, so that the relative positional accuracy of the two shaft ends is determined by the relative machining accuracy of the limiting boss inside the positioning block and the first bearing hole. As the dimensional relationship between the internal features of a single part, this accuracy can be guaranteed by one mold forming or one clamping process, and the accuracy can reach ±0.05mm. Compared with the cumulative tolerance of ±0.18mm of the traditional split support scheme, the accuracy is improved by about 3.6 times. The shortened tolerance chain directly improves the meshing accuracy of the second worm and the output gear. The reduced center distance deviation reduces the backlash fluctuation, reduces the impact during reversing, and significantly improves the repeatability of the rearview mirror folding action.

[0018] (2) Vibration suppression and noise reduction of the motor worm: The positioning block presses the motor bushing into the slot of the motor bushing through the limiting boss, so that the motor bushing is clamped between the bottom surface of the slot and the bottom surface of the positioning block, forming a rigid clamping constraint on the top of the motor worm. This constraint transforms the motor worm from a cantilever beam model to a beam model with constraints at both ends, significantly increasing its first natural frequency, making the operating speed much lower than the critical speed, suppressing resonance, and reducing operating noise. At the same time, the positioning block, as a rigid body, directly connects the top of the motor worm and one end of the second worm, changing the vibration transmission path. The vibration energy is attenuated due to damping at the screw connection interface between the positioning block and the base, reducing the interference of high-frequency motor vibration on the meshing stability of the second worm.

[0019] (3) Triple constraint positioning ensures assembly consistency: The positioning block achieves vertical positioning by embedding the limiting boss into the motor shaft sleeve groove, achieves lateral and longitudinal positioning by cooperating with the positioning slot and positioning protrusion, and achieves axial fastening by screws. The synergistic effect of the triple constraints ensures the uniqueness and repeatability of the positioning block's installation position. The positioning protrusion passing through the positioning slot allows the positioning block to obtain precise pre-positioning before the screw is tightened, eliminating rotational deviation caused by the screw tightening torque, ensuring that the actual position of the first bearing hole is consistent with the design position, and improving the consistency of batch assembly.

[0020] (4) Compact layout achieves three-stage reduction: The positioning block utilizes the spatial proximity between the top of the motor worm and one end of the second worm within the housing to integrate the two support points into the same component, reducing the number of independent parts and freeing up layout space within the compact housing, thus enabling the three-stage worm gear reduction transmission chain to be realized within a limited space. The three-stage worm gear reduction transmission chain provides sufficient reduction ratio and output torque, while also possessing self-locking characteristics, allowing the rearview mirror to maintain its position against vibration without the need for an additional locking mechanism after folding into place.

[0021] (5) Long-term reliability assurance: The positioning block adopts a triple constraint design, which maintains positional stability under long-term vibration and temperature cycling environment. Even if a single constraint is slightly relaxed, the remaining constraints can still maintain the position of the positioning block. The oil-impregnated bearing relies on internally stored lubricating oil to achieve self-lubrication, without the need for external oil supply maintenance, and is suitable for long-term service in a closed housing. The worm gear bushing and the groove's protrusion and concave surface engagement structure achieve circumferential anti-rotation and axial limiting, preventing the bushing from shifting during operation. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the present invention.

[0023] Figure 2 This is a schematic diagram of the internal structure of the present invention.

[0024] Figure 3 This is an exploded view of the present invention.

[0025] Figure 4 This is a schematic diagram of a worm gear.

[0026] Figure 5 This is a schematic diagram of the positioning block.

[0027] Figure 6 This is a schematic diagram of the base.

[0028] Figure 7 This is a schematic diagram of the cross-section of the drive motor.

[0029] Figure 8 This is a schematic diagram of the base from another perspective.

[0030] Figure 9 This is a schematic diagram of the worm gear bushing.

[0031] In the diagram: 1. Base; 2. Cover; 3. Drive motor; 4. Motor worm gear; 5. First gear; 6. First worm gear; 7. Second gear; 8. Second worm gear; 9. Output gear; 10. Motor bushing; 11. Motor bushing groove; 12. Positioning block; 13. Limiting boss; 14. Screw; 15. Positioning slot; 16. Positioning protrusion; 17. First bearing hole; 18. Second bearing hole; 19. Oil-impregnated bearing; 20. Shaft hole; 21. Gear groove; 22. Surface bearing; 23. Gear bushing; 24. Limiting cut surface; 25. First positioning hole; 26. Spring; 27. Positioning pin; 28. Second positioning hole; 29. ​​Worm gear bushing; 30. Groove; 31. Concave surface; 32. Protrusion. Detailed Implementation

[0032] The present invention will now be described in further detail with reference to the accompanying drawings.

[0033] like Figures 1 to 3 As shown, the present invention discloses an electric drive mechanism for a car rearview mirror. Figure 1 This shows the overall enclosed shell structure consisting of the base 1 and the cover 2. Figure 2 The arrangement of the transmission components inside base 1 is shown. Figure 3 The exploded assembly relationship between the various transmission components, support components, and cover 2 is shown. The electric drive mechanism is formed by the base 1 and cover 2 to form a closed shell, and integrates a three-stage worm gear reduction transmission chain and a composite positioning reference block 12 to realize the electric folding and extension functions of the rearview mirror.

[0034] like Figure 1 , Figure 2 , Figure 6 , Figure 8As shown, the housing assembly includes a base 1 and a cover 2. The base 1, serving as the main load-bearing structure, is manufactured using injection molding and integrates multiple functional features such as a motor bushing groove 11, a second bearing hole 18, a shaft hole 20, a gear groove 21, a positioning protrusion 16, a first positioning hole 25, and a groove 30. The cover 2 covers the base 1 to form a closed housing, protecting the internal transmission components from dust and moisture intrusion. The base 1 has first positioning holes 25 on both sides, each containing a spring 26 and a positioning post 27. The cover 2 has second positioning holes 28 corresponding to the positioning posts 27. During assembly, the positioning posts 27 are inserted into the second positioning holes 28 to achieve precise alignment between the base 1 and the cover 2, and the springs 26 provide preload to ensure a tight fit between the cover 2 and the base 1.

[0035] like Figure 2 , Figure 3 , Figure 4 As shown, the transmission chain assembly achieves three-stage reduction. The drive motor 3, mounted on the base 1, is a micro DC motor with a typical operating speed of 3000 to 10000 rpm. The motor worm 4 is connected to the output end of the drive motor 3, serving as the high-speed input end of the transmission chain. The first gear 5 meshes with the motor worm 4, achieving the first stage of reduction. The first worm 6 is coaxially connected to the first gear 5, and has a limiting surface 24. The limiting surface 24 engages with the inner hole of the first gear 5 to achieve circumferential torque transmission, transferring the rotational motion of the first gear 5 to the first worm 6. The second gear 7 meshes with the first worm 6, achieving the second stage of reduction. The second worm 8 is coaxially connected to the second gear 7, and also has a limiting surface 24. The limiting surface 24 engages with the inner hole of the second gear 7 to achieve circumferential torque transmission. The output gear 9 meshes with the second worm 8, achieving the third stage of reduction, ultimately outputting a low-speed, high-torque rotational motion to drive the rearview mirror folding. The motor worm 4, the first worm 6, and the second worm 8 constitute a three-stage worm gear reduction transmission chain. This transmission chain has a self-locking characteristic, which allows the rearview mirror to maintain its position without an additional locking mechanism after it is folded into place.

[0036] like Figure 7As shown, the support structure of the motor worm gear 4 is as follows: one end of the motor worm gear 4 is connected to the output end of the drive motor 3 for support, and the other end, i.e., the top end, is connected to the motor bushing 10. A motor bushing groove 11 is provided on the base 1, and the motor bushing 10 is installed in the motor bushing groove 11. The positioning block 12 is fixed at the motor bushing groove 11, and the limiting boss 13 provided at the bottom of the positioning block 12 is embedded in the motor bushing groove 11, pressing and restricting the motor bushing 10 within the motor bushing groove 11, so that the motor bushing 10 is clamped between the bottom surface of the motor bushing groove 11 and the bottom surface of the positioning block 12. This pressing constraint transforms the motor worm gear 4 from a cantilever beam model with one end fixed and the other free into a beam model with both ends constrained, significantly increasing its first natural frequency and suppressing radial runout and axial movement during high-speed rotation.

[0037] like Figure 8 , Figure 9 As shown, the support structure of the first worm 6 is as follows: Both ends of the first worm 6 are connected to the base 1 and the cover 2 via worm bushings 29. The base 1 and the cover 2 are provided with grooves 30 for installing the worm bushings 29. Several concave surfaces 31 are spaced apart within the grooves 30. The worm bushings 29 are provided with protrusions 32 that engage with the concave surfaces 31. During assembly, the protrusions 32 of the worm bushings 29 are embedded in the concave surfaces 31 of the grooves 30, achieving circumferential anti-rotation and axial limiting, preventing the worm bushings 29 from rotating or moving axially during operation.

[0038] like Figure 3 , Figure 5 , Figure 8 As shown, the support structure of the second worm 8 is as follows: Both ends of the second worm 8 are supported by oil-impregnated bearings 19 located in the first bearing hole 17 and the second bearing hole 18, respectively. The first bearing hole 17 is located on the positioning block 12 near the second worm 8, and the second bearing hole 18 is located on the base 1 at the other end of the second worm 8. The oil-impregnated bearings 19 are respectively installed in the first bearing hole 17 and the second bearing hole 18, and both ends of the second worm 8 are connected to the oil-impregnated bearings 19. The first bearing hole 17 and the limiting boss 13 are integrally formed on the positioning block 12, and the axis of the first bearing hole 17 is coaxial with the axis of the second bearing hole 18 to ensure the smooth rotation of the second worm 8. The oil-impregnated bearings 19 achieve self-lubrication by storing lubricating oil internally, requiring no external oil supply maintenance, and are suitable for long-term service within a sealed housing.

[0039] like Figure 5 , Figure 7 As shown, the positioning block 12, as the core component of the present invention, is located in the spatial intersection area between the top of the motor worm 4 and one end of the second worm 8, and simultaneously performs three functions.

[0040] (1) Pressing constraint at the top of the motor worm 4: The positioning block 12 is embedded into the motor bushing groove 11 through the limiting boss 13 at its bottom, and presses and restricts the motor bushing 10 in the motor bushing groove 11, thereby indirectly achieving rigid constraint on the cantilever end of the motor worm 4 when it rotates at high speed.

[0041] (2) Precise positioning of the positioning block 12 itself: The positioning block 12 is provided with positioning slots 15 on both sides, and the positioning slots 15 are long slots; the base 1 is provided with positioning protrusions 16, which are cylindrical and pass through the positioning slots 15. When the positioning protrusions 16 and the positioning slots 15 are engaged, precise positioning is achieved in the direction perpendicular to the length of the slot, and a gap is maintained in the direction parallel to the length of the slot to compensate for manufacturing errors.

[0042] The positioning block 12 achieves vertical positioning by embedding the limiting boss 13 into the motor shaft sleeve groove 11, achieves horizontal and longitudinal positioning by cooperating with the positioning protrusion 16 through the positioning slot 15, and achieves axial fastening by the screw 14. The triple constraint works together to determine the unique spatial position of the positioning block 12.

[0043] (3) Bearing support at one end of the second worm 8: The positioning block 12 is integrally provided with a first bearing hole 17, which contains an oil-impregnated bearing 19, directly providing rotational support for one end of the second worm 8.

[0044] The three functions of the positioning block 12 create a coupling effect, resulting in a shortened tolerance chain. Since the top constraint of the motor worm 4 and the bearing support at one end of the second worm 8 are integrated into the same rigid component, the relative positional relationship between the top position of the motor worm 4 and the center of the bearing at one end of the second worm 8 depends only on the relative machining accuracy between the internal limiting boss 13 of the positioning block 12 and the first bearing hole 17.

[0045] This concerns the dimensional accuracy between features within a single part, which can be directly guaranteed through a single mold forming or single clamping process, achieving an accuracy of ±0.05mm. In contrast, if two independent supports are used to constrain the top of the motor worm 4 and support one end of the second worm 8 respectively, their relative positions depend on a series of three factors: the fit tolerance between independent part A and the housing, the form and position tolerances between the two mounting areas of the housing itself, and the fit tolerance between independent part B and the housing, resulting in a cumulative tolerance of approximately ±0.18mm. This invention shortens the tolerance chain from three series links to a single link, improving accuracy by approximately 3.6 times.

[0046] like Figure 2 , Figure 3 , Figure 6As shown, the support structure of the output gear 9 is as follows: A shaft hole 20 is provided on the base 1 on one side of the second worm gear 8. A gear groove 21 for mounting the output gear 9 is provided on the outer circumference of the shaft hole 20. A plane bearing 22 is mounted at the bottom of the gear groove 21. The output gear 9 is connected to the plane bearing 22 via a gear bushing 23. The plane bearing 22 bears the axial load of the output gear 9, and the gear bushing 23 facilitates the connection and transition between the output gear 9 and the plane bearing 22.

[0047] In practical use, this invention is applied to the electric folding control of automotive rearview mirrors. When the rearview mirror needs to be folded, a control signal drives the drive motor 3 to rotate forward. The drive motor 3 drives the motor worm gear 4 to rotate at high speed. The motor worm gear 4 drives the first gear 5 to achieve the first stage of reduction. The first gear 5 drives the coaxial first worm gear 6 to rotate. The first worm gear 6 drives the second gear 7 to achieve the second stage of reduction. The second gear 7 drives the coaxial second worm gear 8 to rotate. The second worm gear 8 drives the output gear 9 to achieve the third stage of reduction. The output gear 9 outputs a low-speed, high-torque rotational motion to fold the rearview mirror. When the rearview mirror needs to be unfolded, the control signal drives the drive motor 3 to rotate in the reverse direction. The transmission chain moves in the reverse direction, unfolding the rearview mirror to the working position. The self-locking characteristic of the three-stage worm gear reduction transmission chain allows the rearview mirror to automatically maintain its position after folding or unfolding, eliminating the need for an additional locking mechanism.

[0048] To verify the above technical solution, the present invention tests the technical effect of the composite positioning structure of the positioning block.

[0049] 1. Verification Method: A comparative experiment was conducted, preparing 20 sets of samples each of the proposed solution (integrated support with positioning blocks) and the traditional solution (separate independent support). Performance was compared under the same testing conditions. Accuracy testing used a coordinate measuring machine to detect the relative positional deviation of the key shaft ends; noise testing measured operating noise using a sound level meter in a semi-anechoic chamber; assembly testing statistically analyzed the standard deviation of positional deviations in batch assemblies; reliability testing involved detecting performance degradation after 10,000 folding cycles.

[0050] 2. Comparison of Technical Effects Shaft end relative position tolerance ±0.18mm (cumulative value of three-stage series connection) ±0.05mm (internal accuracy of a single part) Accuracy improved by 3.6 times The tolerance chain is shortened from three links to a single link, guaranteed by the machining accuracy inside the positioning block. Operating noise level 48dB(A) (significant vibration at the cantilever end) 42dB(A) (Vibration suppression due to end-constraints) Reduced by 6 dB(A) The motor worm gear is changed from a cantilever beam to a beam with constraints at both ends, which increases the natural frequency and suppresses resonance. Batch assembly position standard deviation σ = 0.06 mm (operator-dependent calibration) σ=0.02mm (triple constraint self-positioning) Consistency improved by 3 times The positioning protrusion inserts into the positioning slot to achieve pre-positioning and eliminate screw tightening misalignment. Gap change after 10,000 cycles 0.08mm (Loose fit of multiple parts) 0.02mm (triple constraint coordinated maintenance) Stability improved by 4 times Triple constraint redundancy design, where the remaining constraints maintain their positions when a single constraint relaxes. Number of supporting parts 2 pieces (independent end caps + independent bearing housings) 1 piece (positioning block integration) Reduce by 50% Functional integration saves housing space and facilitates a compact layout of the three-stage drivetrain. 3. Verification Conclusion Test results show that shortening the tolerance chain improves the relative position accuracy of the shaft end by 3.6 times, directly improving the worm gear meshing accuracy and reducing backlash fluctuations and commutation impacts. The rigid clamping constraint at the top of the motor worm reduces operating noise by 6 dB(A), meeting the vehicle's quiet operation requirements. The triple-constraint self-positioning mechanism improves batch assembly consistency by 3 times and eliminates human adjustment errors. Ten thousand cycles of durability testing verified the long-term stability of the triple-constraint redundant design, with clearance variation only 25% of that of the traditional solution. Comprehensive verification results demonstrate that the technical solution of this invention effectively solves the contradiction between multi-axis support accuracy and spatial compactness in the rearview mirror electric drive mechanism.

Claims

1. An electric drive mechanism for a car rearview mirror, characterized in that, include: A base (1) is used to support the transmission components; a cover (2) is fitted onto the base (1) to form a closed shell; A drive motor (3) is mounted on the base (1); a motor worm (4) is connected to the output end of the drive motor (3); a first gear (5) is meshed with the motor worm (4); a first worm (6) is coaxially connected to the first gear (5); a second gear (7) is meshed with the first worm (6); a second worm (8) is coaxially connected to the second gear (7); an output gear (9) is meshed with the second worm (8); a motor bushing (10) is connected to the top of the motor worm (4); a motor bushing groove (11) is provided on the base (1) for installing the motor bushing (10); a positioning block (12) is fixed at the motor bushing groove (11), and the positioning block (12) presses and restricts the motor bushing (10) on the base (1). The motor shaft sleeve groove (11) is located inside the positioning block (12); a limiting boss (13) is located at the bottom of the positioning block (12) and embedded in the motor shaft sleeve groove (11); a screw (14) is used to fix the positioning block (12) to the base (1); a positioning slot (15) is located on both sides of the positioning block (12); a positioning protrusion (16) is located on the base (1) and passes through the positioning slot (15); a first bearing hole (17) is located on the positioning block (12) on the side close to the second worm (8); a second bearing hole (18) is located on the base (1) at the other end of the second worm (8); an oil-impregnated bearing (19) is installed in the first bearing hole (17) and the second bearing hole (18) respectively, and the two ends of the second worm (8) are connected to the oil-impregnated bearing (19).

2. The electric drive mechanism for a car rearview mirror according to claim 1, characterized in that, The base (1) has a shaft hole (20) on one side of the second worm (8). The outer ring of the shaft hole (20) has a gear groove (21) for installing the output gear (9). A plane bearing (22) is installed at the bottom of the gear groove (21). The output gear (9) is connected to the plane bearing (22) through a gear bushing (23).

3. The electric drive mechanism for a car rearview mirror according to claim 1, characterized in that, Both the first worm (6) and the second worm (8) are provided with a limiting cut surface (24), which is used to achieve circumferential torque transmission connection with the first gear (5) and the second gear (7).

4. The electric drive mechanism for a car rearview mirror according to claim 1, characterized in that, The base (1) has first positioning holes (25) on both sides, and a spring (26) and a positioning post (27) are provided in the first positioning holes (25). The cover (2) has a second positioning hole (28) corresponding to the positioning post (27).

5. The electric drive mechanism for a car rearview mirror according to claim 1, characterized in that, The first worm (6) is connected to the base (1) and the cover (2) at both ends through worm bushings (29). The base (1) and the cover (2) are provided with grooves (30) for installing the worm bushings (29). A plurality of concave surfaces (31) are provided in the grooves (30) at intervals. The worm bushings (29) are provided with protrusions (32) that engage with the concave surfaces (31).

6. The electric drive mechanism for a car rearview mirror according to claim 1, characterized in that, The positioning slot (15) is long and the positioning protrusion (16) is cylindrical. When the positioning protrusion (16) cooperates with the positioning slot (15), it achieves precise positioning in the direction perpendicular to the length of the slot and retains a gap in the direction parallel to the length of the slot.

7. The electric drive mechanism for a car rearview mirror according to claim 1, characterized in that, The positioning block (12) is vertically positioned by embedding the limiting boss (13) into the motor bushing groove (11), and is horizontally and longitudinally positioned by cooperating with the positioning protrusion (16) through the positioning slot (15). It is axially fastened by the screw (14). The triple constraint works together to determine the unique spatial position of the positioning block (12).

8. The electric drive mechanism for a car rearview mirror according to claim 1, characterized in that, The first bearing hole (17) and the limiting boss (13) are integrally formed on the positioning block (12), and the axis of the first bearing hole (17) is coaxial with the axis of the second bearing hole (18).

9. The electric drive mechanism for a car rearview mirror according to claim 1, characterized in that, The motor worm (4), the first worm (6) and the second worm (8) constitute a three-stage worm gear reduction transmission chain, which has a self-locking characteristic.

10. The electric drive mechanism for a car rearview mirror according to claim 1, characterized in that, The positioning block (12) simultaneously clamps and constrains the top end of the motor worm (4) and supports the bearing at one end of the second worm (8), so that the relative positional accuracy between the top end of the motor worm (4) and one end of the second worm (8) is determined by the machining accuracy inside the positioning block (12).

Images