Worm gear and electric power steering device

Abstract

The present application relates to the transmission technical field, provide a worm gear drive mechanism and electric power steering device. Worm gear drive mechanism includes meshing transmission worm and transmission worm, transmission worm and transmission worm are contained in the shell filled with lubricating grease, worm gear drive mechanism further includes: lubricating grease return mechanism, mesh in transmission worm, follow transmission worm's rotation and rotate, transmission worm and lubricating grease return mechanism contact tooth surface part is different from transmission worm and transmission worm contact tooth surface part. The present application adds lubricating grease return mechanism through transmission worm side, realizes in the worm gear engagement movement process, lubricating grease return mechanism follows transmission worm rotation, will be extruded between transmission worm and transmission worm because of engagement movement lubricating grease take back transmission worm's tooth surface, effectively improves the lubricating performance of worm gear drive mechanism.

Description

Technical Field

[0001] This invention relates to the field of transmission technology, and more specifically, to a worm gear transmission mechanism and an electric power steering device. Background Technology

[0002] Worm gear transmission mechanisms transmit motion between two shafts through the meshing of a worm wheel and a worm. Under high-load transmission conditions, the grease between the worm wheel and the worm, especially the grease on the worm wheel tooth surface, is easily squeezed out due to the meshing motion, leading to increased friction between the worm wheel and the worm, causing damage to parts and generating noise.

[0003] Taking the application of worm gear transmission mechanism in EPS (Electric Power Steering) as an example, EPS uses worm gear transmission mechanism for steering assistance. The meshing between the worm wheel and worm is under high load. As the meshing proceeds, the grease on the worm wheel tooth surface is squeezed out due to the high load transmission, causing the meshing motion to jam. In particular, under low temperature conditions, the adhesion of the grease is reduced, making it easier to be squeezed out and detached from the worm wheel tooth surface as the meshing proceeds. This leads to damage to parts and noise due to lack of lubrication between the worm wheel and worm, affecting the user experience.

[0004] Currently, there is no effective way to improve the lubrication performance of worm gear transmission mechanisms.

[0005] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of the present invention, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] In view of this, the present invention provides a worm gear transmission mechanism and an electric power steering device, which can bring the grease squeezed out between the worm gear and the worm due to the meshing motion back to the tooth surface of the worm gear through a grease return mechanism added to the side of the worm gear, so as to effectively improve the lubrication performance of the worm gear transmission mechanism.

[0007] According to one aspect of the present invention, a worm gear transmission mechanism is provided, comprising a meshing worm wheel and a worm, wherein the worm wheel and the worm are housed in a housing filled with grease, and the worm gear transmission mechanism further comprises: a grease return mechanism, meshing with the worm wheel and rotating following the rotation of the worm wheel; the tooth surface portion of the worm wheel that contacts the grease return mechanism is different from the tooth surface portion of the worm wheel that contacts the worm.

[0008] The aforementioned worm gear transmission mechanism, by adding a grease return mechanism meshing with the transmission worm wheel, and the tooth surface of the transmission worm wheel that contacts the grease return mechanism being different from the tooth surface of the transmission worm, achieves the following effect during the meshing motion of the worm gear: the grease return mechanism rotates with the transmission worm wheel, bringing the grease squeezed out between the transmission worm wheel and the transmission worm back to the tooth surface of the transmission worm wheel due to the meshing motion, thereby realizing the return adjustment of the grease on the tooth surface of the transmission worm wheel and effectively improving the lubrication performance of the worm gear transmission mechanism;

[0009] The aforementioned worm gear transmission mechanism does not rely on improvements in the low-temperature performance of grease. By adding a grease return mechanism to the transmission worm wheel side, the lubrication performance of the worm gear transmission mechanism can be improved, especially under high load and low temperature conditions. This effectively avoids damage to parts and friction noise caused by jamming of the worm gear meshing motion, thus enhancing the user experience.

[0010] In some embodiments, the centerline of the grease return mechanism is offset from the axis of the transmission worm gear in the axial direction of the transmission worm wheel; wherein the centerline passes through the center of the grease return mechanism and extends radially along the transmission worm wheel.

[0011] In the aforementioned worm gear transmission mechanism, the centerline of the grease return mechanism is offset from the axis of the transmission worm in the axial direction of the transmission worm wheel. This offsets the tooth surfaces of the transmission worm wheel that contact the grease return mechanism and the tooth surfaces of the transmission worm wheel that contact the transmission worm in the axial direction of the transmission worm wheel. As the grease return mechanism rotates with the transmission worm wheel, it can bring the grease squeezed out between the transmission worm wheel and the transmission worm due to the meshing motion back to the tooth surface of the transmission worm wheel.

[0012] In some embodiments, the centerline is spaced 2mm-3mm from the axis of the transmission worm.

[0013] In the aforementioned worm gear transmission mechanism, the centerline of the grease return mechanism is spaced 2mm-3mm from the axis of the transmission worm. This ensures that the tooth surfaces of the transmission worm wheel that contact the grease return mechanism are offset from the tooth surfaces of the transmission worm wheel that contact the transmission worm, while simultaneously ensuring that the grease return mechanism meshes with the transmission worm wheel, thus achieving a stable fit between the grease return mechanism and the transmission worm wheel.

[0014] In some embodiments, along the axial direction of the drive worm gear, the width of the grease return mechanism is smaller than the tooth width of the drive worm gear.

[0015] The aforementioned worm gear transmission mechanism, by having a grease return mechanism with a width smaller than the tooth width of the transmission worm wheel, and by having the centerline of the grease return mechanism offset from the axis of the transmission worm along the axial direction of the transmission worm wheel, allows the grease return mechanism to occupy less space, avoids interference with other components, and makes the overall structure of the worm gear transmission mechanism compact, without significantly increasing the volume due to the addition of the grease return mechanism.

[0016] In some embodiments, the axis of the transmission worm and the axis of the transmission worm wheel, as well as the center line of the grease return mechanism and the axis of the transmission worm wheel, are perpendicularly intersected.

[0017] The aforementioned worm gear transmission mechanism, by having the axis of the transmission worm and the axis of the transmission worm wheel perpendicularly intersecting, forms a worm gear transmission mechanism suitable for transmission conditions where the intersection angle of the two shafts is 90°. By having the axis of the grease return mechanism perpendicularly intersecting the axis of the transmission worm wheel, the grease return mechanism is adapted to the transmission worm wheel. Thus, even when the centerline of the grease return mechanism is offset from the axis of the transmission worm along the axial direction of the transmission worm wheel, the grease returned to the tooth surface of the transmission worm wheel can be smoothly carried back by the grease return mechanism rotating with the transmission worm wheel, due to the meshing motion between the transmission worm wheel and the transmission worm.

[0018] In some embodiments, the grease return mechanism is an additional worm gear; the centerline is the axis of the additional worm gear.

[0019] In the aforementioned worm gear transmission mechanism, the grease return mechanism is formed as an additional worm, which occupies less space and makes the overall structure of the worm gear transmission mechanism compact. Furthermore, the axis of the additional worm is offset from the axis of the transmission worm in the axial direction of the transmission worm wheel. Thus, by rotating with the transmission worm wheel, the additional worm carries the grease squeezed out between the transmission worm wheel and the transmission worm due to the meshing motion back to the tooth surface of the transmission worm wheel.

[0020] In some embodiments, the additional worm is a single-start worm.

[0021] The aforementioned worm gear transmission mechanism, through a single-headed auxiliary worm, enables the transmission worm wheel to rotate one tooth per revolution of the auxiliary worm. This facilitates lubrication of each tooth surface of the transmission worm wheel as the auxiliary worm rotates with the transmission worm wheel. Furthermore, the single-headed auxiliary worm is easy to manufacture and has a small size.

[0022] In some embodiments, the grease return mechanism is an additional worm gear; the centerline is perpendicular to the axis of the additional worm gear.

[0023] In the aforementioned worm gear transmission mechanism, the grease return mechanism is formed as an additional worm wheel. The center line of the additional worm wheel, which passes through its center and is perpendicular to its axis, is offset from the axis of the transmission worm in the axial direction of the transmission worm wheel. Similarly, the additional worm wheel can rotate with the transmission worm wheel to bring the grease squeezed out between the transmission worm wheel and the transmission worm due to the meshing motion back to the tooth surface of the transmission worm wheel.

[0024] In some embodiments, the number of teeth of the additional worm gear is less than the number of teeth of the transmission worm gear.

[0025] The aforementioned worm gear transmission mechanism, by having an additional worm wheel with fewer teeth than the transmission worm wheel, allows the additional worm wheel to have a smaller volume, thereby avoiding interference with other components and preventing an increase in the overall volume of the worm gear transmission mechanism.

[0026] In some embodiments, the grease return mechanism is unloaded.

[0027] The aforementioned worm gear transmission mechanism, through a no-load grease return mechanism, can completely follow the rotation of the transmission worm gear and rotate in both directions. This ensures that the teeth of the grease return mechanism are in good contact with the corresponding tooth surfaces of the transmission worm gear, and prevents the grease return mechanism from carrying the grease back to the tooth surfaces of the transmission worm gear due to high load.

[0028] In some embodiments, the grease return mechanism is made of plastic.

[0029] The aforementioned worm gear transmission mechanism, through a grease return mechanism made of plastic, has a lighter weight, which facilitates its rotation with the transmission worm gear and brings the grease back to the tooth surface of the transmission worm gear; and the grease return mechanism made of plastic has a better grease adhesion effect, thereby improving the grease return adjustment effect.

[0030] According to another aspect of the present invention, an electric power steering device is provided, comprising a power steering motor and a transmission mechanism, wherein the transmission mechanism employs a worm gear transmission mechanism as described in any of the above embodiments, wherein the transmission worm of the worm gear transmission mechanism is coaxially connected to the output shaft of the power steering motor, and the transmission worm wheel of the worm gear transmission mechanism is coaxially connected to the steering column.

[0031] The aforementioned electric power steering system employs a worm gear transmission mechanism. Through a grease return mechanism added to the worm gear side, the grease squeezed out between the worm gear and the worm due to the meshing motion is brought back to the tooth surface of the worm gear. This achieves the return adjustment of the grease on the tooth surface of the worm gear, effectively improving the lubrication performance of the worm gear transmission mechanism and thus improving the overall performance of the electric power steering system.

[0032] The beneficial effects of this invention compared to the prior art include at least the following:

[0033] The worm gear transmission mechanism of this invention, by adding a grease return mechanism meshing with the transmission worm wheel, and wherein the tooth surface of the transmission worm wheel that contacts the grease return mechanism is different from the tooth surface of the transmission worm, achieves the following during the meshing motion of the worm gear: the grease return mechanism rotates with the transmission worm wheel, bringing back the grease squeezed out between the transmission worm wheel and the transmission worm due to the meshing motion to the tooth surface of the transmission worm wheel, thereby achieving the return adjustment of the grease on the tooth surface of the transmission worm wheel, and effectively improving the lubrication performance of the worm gear transmission mechanism. The worm gear transmission mechanism of this invention is suitable for transmission conditions such as electric power steering devices, without relying on the improvement of the low-temperature performance of the grease. The grease return mechanism added to the transmission worm wheel side can achieve the improvement of the lubrication performance of the worm gear transmission mechanism, especially the lubrication performance under high load and low temperature conditions, effectively avoiding the damage to parts and friction noise caused by the jamming of the worm gear meshing motion, and improving the user experience.

[0034] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Attached Figure Description

[0035] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0036] Figure 1 This diagram shows a structural schematic of the worm gear transmission mechanism in an embodiment of the present invention.

[0037] Figure 2 This diagram illustrates the positional relationship between the centerline of the grease return mechanism and the axis of the transmission worm in an embodiment of the present invention.

[0038] Figure 3 This diagram illustrates the structure of the additional worm gear in an embodiment of the present invention.

[0039] Figure 4 A schematic diagram of the electric power steering device in an embodiment of the present invention is shown. Detailed Implementation

[0040] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to fully and completely convey the concept of the exemplary embodiments to those skilled in the art.

[0041] The accompanying drawings are merely illustrative of the invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0042] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features in different embodiments can be combined with each other.

[0043] Figure 1 The structure of the worm gear transmission mechanism in the embodiment is shown, with reference to Figure 1 As shown, the worm gear transmission mechanism provided in this embodiment of the invention includes a meshing worm wheel 10 and a worm 20. The worm wheel 10 and the worm 20 are housed in a housing filled with grease (the grease and the housing are not specifically shown in the accompanying drawings of this invention). The worm gear transmission mechanism further includes:

[0044] The grease return mechanism 30 is engaged with the transmission worm gear 10 and rotates in accordance with the rotation of the transmission worm gear 10;

[0045] The tooth surface of the transmission worm gear 10 that contacts the grease return mechanism 30 is different from the tooth surface of the transmission worm gear 10 that contacts the transmission worm 20.

[0046] The location of the grease return mechanism 30 is not limited to... Figure 1 As shown, it is sufficient that the tooth surface of the transmission worm 10 is spaced apart from the transmission worm 20 on the circumference and that the tooth surface of the transmission worm 10 that contacts the grease return mechanism 30 is different from the tooth surface of the transmission worm 20.

[0047] The tooth surface of the worm gear 10 that contacts the worm 20 typically comprises all the tooth surfaces of the worm gear 10. Conversely, the tooth surface of the worm gear 10 that contacts the grease return mechanism 30 is only a portion of the tooth surface, such as the portion near a certain end face of the worm gear 10. Therefore, during the meshing motion of the worm gear, the grease return mechanism 30 rotates with the worm gear 10, carrying the grease squeezed out between the worm gear 10 and the worm 20 back to the tooth surface of the worm gear 10. This achieves the return and adjustment of the grease on the tooth surface of the worm gear 10, effectively improving the lubrication performance of the worm gear transmission mechanism.

[0048] The aforementioned worm gear transmission mechanism does not rely on improvements in the low-temperature performance of grease. The grease return mechanism 30 added to the transmission worm wheel 10 side can improve the lubrication performance of the worm gear transmission mechanism, especially under high load and low temperature conditions. This effectively avoids damage to parts and friction noise caused by jamming of the worm gear meshing motion, thus improving the user experience.

[0049] In one embodiment, the worm gear transmission mechanism can be a speed reducer, in which case the housing is the speed reducer housing; the worm gear transmission mechanism can also be other transmission mechanisms, all of which can effectively improve the lubrication performance of the worm gear transmission mechanism through the grease return mechanism 30 added to the side of the transmission worm wheel 10.

[0050] Figure 2 The diagram illustrates the positional relationship between the centerline of the grease return mechanism and the axis of the transmission worm gear in this embodiment. Figure 2 Specifically Figure 1 The left-side view. It should be noted that... Figure 1 and Figure 2 The grease return mechanism 30 is illustrated using a worm gear structure, but is not limited to this. The grease return mechanism 30 can be formed as any gear structure that can mesh with the transmission worm wheel 10. The grease return mechanism 30 of the gear structure rotates with the transmission worm wheel 10 and brings the grease squeezed out between the transmission worm wheel 10 and the transmission worm 20 due to the meshing motion back to the tooth surface of the transmission worm wheel 10.

[0051] Combination Figure 1 and Figure 2 As shown, in one embodiment, the center line 30' of the grease return mechanism 30 and the axis 20' of the transmission worm 20 are offset in the axial direction "z" of the transmission worm wheel 10; wherein, the center line of the grease return mechanism 30 passes through the center of the grease return mechanism 30 and extends radially along the transmission worm wheel 10.

[0052] Thus, by offsetting the centerline 30' of the grease return mechanism 30 from the axis 20' of the transmission worm 20 in the axial direction of the transmission worm wheel 10, the tooth surfaces of the transmission worm wheel 10 that contact the grease return mechanism 30 and the tooth surfaces of the transmission worm wheel 10 that contact the transmission worm 20 are offset in the axial direction of the transmission worm wheel 10. This allows the grease that is squeezed out between the transmission worm wheel 10 and the transmission worm 20 due to the meshing motion to be brought back to the tooth surfaces of the transmission worm wheel 10 by the grease return mechanism 30 as it rotates with the transmission worm wheel 10.

[0053] In one embodiment, continue to combine Figure 1 and Figure 2 As shown, the center line 30' of the grease return mechanism 30 is 2mm-3mm away from the axis 20' of the transmission worm gear 20.

[0054] The specific distance between the centerline 30' of the grease return mechanism 30 and the axis 20' of the transmission worm 20 can be set as needed, for example, 2mm, 2.2mm, 3mm, etc. By maintaining a distance of 2mm-3mm between the centerline 30' of the grease return mechanism 30 and the axis 20' of the transmission worm 20, the tooth surfaces of the transmission worm wheel 10 that contact the grease return mechanism 30 are offset from those of the transmission worm wheel 10 that contact the transmission worm 20 in the axial direction of the transmission worm wheel 10. This ensures that the grease return mechanism 30 meshes with the transmission worm wheel 10, resulting in a stable fit between the grease return mechanism 30 and the transmission worm wheel 10.

[0055] In one embodiment, continue to combine Figure 1 and Figure 2 As shown, along the axial direction "z" of the transmission worm gear 10, the width t1 of the grease return mechanism 30 is smaller than the tooth width t2 of the transmission worm gear 10.

[0056] When the grease return mechanism 30 is configured as an additional worm, the width t1 mentioned is the diameter of the additional worm; when the grease return mechanism 30 is configured as an additional worm wheel, the width t1 mentioned is the tooth width of the additional worm wheel.

[0057] By ensuring that the width t1 of the grease return mechanism 30 is smaller than the tooth width t2 of the transmission worm gear 10, and that the center line 30' of the grease return mechanism 30 is offset from the axis 20' of the transmission worm gear 20 along the axial direction "z" of the transmission worm gear 10, the grease return mechanism 30 occupies less space, avoids interference with other components, and makes the overall structure of the worm gear transmission mechanism compact, without significantly increasing the volume due to the addition of the grease return mechanism 30.

[0058] In one embodiment, combined Figure 1 and Figure 2 As shown, the axis 20' of the transmission worm 20 and the axis of the transmission worm wheel 10, as well as the center line 30' of the grease return mechanism 30 and the axis of the transmission worm wheel 10, are perpendicularly intersecting. At this time, the axis 20' of the transmission worm 20 is located within the intermediate plane 200 of the worm gear transmission mechanism.

[0059] By perpendicularly intersecting the axis 20' of the transmission worm 20 with the axis of the transmission worm wheel 10, the worm gear transmission mechanism is suitable for transmission conditions where the two shafts intersect at a 90° angle, such as in the transmission conditions of electric power steering devices. By perpendicularly intersecting the axis 30' of the grease return mechanism 30 with the axis of the transmission worm wheel 10, the grease return mechanism 30 is adapted to the transmission worm wheel 10. Thus, even when the centerline 30' of the grease return mechanism 30 and the axis 20' of the transmission worm 20 are offset along the axial direction "z" of the transmission worm wheel 10, the grease return mechanism 30 can rotate with the transmission worm wheel 10, smoothly bringing the grease squeezed out between the transmission worm wheel 10 and the transmission worm 20 due to the meshing motion back to the tooth surface of the transmission worm wheel 10.

[0060] Figure 3 The structure of the additional worm gear in the embodiment is shown, combined with Figures 1 to 3 As shown, in one embodiment, the grease return mechanism 30 is formed as an additional worm; in this case, the center line 30' of the grease return mechanism 30 is the axis 300 of the additional worm.

[0061] The auxiliary worm has the advantages of being small in size and easy to install; and the axis 300 of the auxiliary worm and the axis 20' of the transmission worm 20 are offset in the axial "z" direction of the transmission worm wheel 10, so that the grease squeezed out between the transmission worm wheel 10 and the transmission worm 20 due to the meshing motion can be brought back to the tooth surface of the transmission worm wheel 10 by the auxiliary worm rotating with the transmission worm wheel 10.

[0062] Furthermore, in one embodiment, the additional worm is a single-start worm. With a single-start additional worm, the transmission worm wheel 10 rotates one tooth per revolution of the additional worm, facilitating lubrication of each tooth surface of the transmission worm wheel 10 as the additional worm rotates with it; moreover, the single-start additional worm is easy to manufacture and has a small size.

[0063] That is, when the grease return mechanism 30 is an additional worm, the additional worm is formed as a small worm structure relative to the transmission worm 20.

[0064] In a specific worm gear transmission mechanism, taking the grease return mechanism as an additional worm as an example, the transmission worm wheel, transmission worm, and additional worm have the dimensions shown in the table below:

[0065]

[0066] Of course, the dimensions of the transmission worm gear, transmission worm, and auxiliary worm shown in the table above are only examples. In different embodiments, the specific dimensions of the transmission worm gear, transmission worm, and grease return mechanism can be flexibly adjusted according to the design requirements of different worm gear transmission mechanisms.

[0067] Continue to refer to Figure 1 and Figure 2 As shown, in one embodiment, the grease return mechanism 30 is formed as an additional worm gear; in this case, the centerline 30' of the grease return mechanism 30 passes through the center of the additional worm gear and is perpendicular to the axis of the additional worm gear.

[0068] In this embodiment, the grease return mechanism 30 is formed as an additional worm wheel, and the center line of the additional worm wheel passing through its center and perpendicular to its axis is offset from the axis 20' of the transmission worm 20 in the axial "z" direction of the transmission worm wheel 10. This also enables the additional worm wheel to follow the rotation of the transmission worm wheel 10 and bring the grease squeezed out between the transmission worm wheel 10 and the transmission worm 20 due to the meshing motion back to the tooth surface of the transmission worm wheel 10.

[0069] Furthermore, in one embodiment, the number of teeth on the additional worm gear is less than the number of teeth on the transmission worm gear 10. By making the number of teeth on the additional worm gear less than the number of teeth on the transmission worm gear 10, the additional worm gear has a smaller volume, thereby avoiding interference with other components and avoiding increasing the overall volume of the worm gear transmission mechanism.

[0070] That is, when the grease return mechanism 30 is an additional worm gear, the additional worm gear forms a small worm gear structure relative to the transmission worm gear 10.

[0071] In the above embodiments, the grease return mechanism 30 is unloaded. The unloaded grease return mechanism 30 can completely follow the rotation of the transmission worm gear 10, rotating forward or backward, ensuring that the teeth of the grease return mechanism 30 are in good contact with the corresponding tooth surfaces of the transmission worm gear 10, and preventing the grease return mechanism 30 from carrying grease back to the tooth surfaces of the transmission worm gear 10 due to high load.

[0072] Furthermore, in the above embodiments, the grease return mechanism 30 is made of plastic. The plastic grease return mechanism 30 has a lighter weight, making it easier to rotate with the drive worm gear 10 and bring the grease back to the tooth surface of the drive worm gear 10; and the plastic grease return mechanism 30 has better grease adhesion, which can improve the grease return adjustment effect.

[0073] In other embodiments, the grease return mechanism 30 may also be made of other materials, such as rubber, resin, or even metal, depending on the design requirements of the worm gear transmission mechanism.

[0074] Figure 4 The structure of the electric power steering device in the embodiment is shown; combined with Figures 1 to 4As shown, this embodiment of the invention also provides an electric power steering device, including a power steering motor 40 and a transmission mechanism. The transmission mechanism adopts the worm gear transmission mechanism described in any of the above embodiments. The transmission worm 20 of the worm gear transmission mechanism is coaxially connected to the output shaft 41 of the power steering motor 40, and the transmission worm wheel 10 of the worm gear transmission mechanism is coaxially connected to the steering column 50.

[0075] The electric power steering device described in this embodiment can specifically be a CEPS (Column-assist type Electric Power Steering) device. The transmission worm gear 10 can be made of plastic, the transmission worm 20 can be made of metal, and the grease return mechanism 30 can be formed as an additional worm made of plastic. When providing steering assistance, based on the torque signal on the steering wheel and the vehicle's speed signal, the vehicle's electronic control device controls the power assist motor 40 to generate auxiliary power of corresponding magnitude and direction, which is transmitted to the steering column 50 via the worm gear transmission mechanism to assist the driver in steering operations.

[0076] The aforementioned electric power steering device employs a worm gear transmission mechanism. Through a grease return mechanism 30 added to the side of the transmission worm gear 10, the grease squeezed out between the transmission worm gear 10 and the transmission worm 20 due to the meshing motion is brought back to the tooth surface of the transmission worm gear 10. This achieves the return adjustment of the grease on the tooth surface of the transmission worm gear 10, effectively improving the lubrication performance of the worm gear transmission mechanism, and thus improving the overall performance of the electric power steering device.

[0077] In summary, the worm gear transmission mechanism of the present invention, by adding a grease return mechanism 30 meshing with the transmission worm wheel 10, and wherein the tooth surface of the transmission worm wheel 10 in contact with the grease return mechanism 30 is different from the tooth surface of the transmission worm 20, achieves the following: during the meshing motion of the worm gear, the grease return mechanism 30 rotates with the transmission worm wheel 10, bringing back the grease squeezed out between the transmission worm wheel 10 and the transmission worm 20 due to the meshing motion back to the tooth surface of the transmission worm wheel 10, thereby achieving lubrication of the tooth surface of the transmission worm wheel 10. The grease return mechanism 30, added to the transmission worm gear 10 side, effectively improves the lubrication performance of the worm gear transmission mechanism. This invention's worm gear transmission mechanism is suitable for transmission conditions such as electric power steering devices. It does not rely on improving the low-temperature performance of the grease; the lubrication performance of the worm gear transmission mechanism, especially under high load and low temperature conditions, is improved through the grease return mechanism 30 added to the transmission worm gear 10 side. This effectively avoids damage to parts and friction noise caused by jamming in the worm gear meshing motion, enhancing the user experience.

[0078] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A worm and gear drive mechanism comprising a drive worm and a drive worm wheel in meshing engagement, characterised in that, The transmission worm gear and the transmission worm are housed in a housing filled with lubricating grease, and the worm gear transmission mechanism further includes: The grease return mechanism meshes with the transmission worm gear and rotates in accordance with the rotation of the transmission worm gear; The tooth surface of the transmission worm gear that contacts the grease return mechanism is different from the tooth surface of the transmission worm gear that contacts the transmission worm. The centerline of the grease return mechanism and the axis of the transmission worm are offset in the axial direction of the transmission worm wheel; wherein the centerline passes through the center of the grease return mechanism and extends radially along the transmission worm wheel.

2. The worm and gear transmission mechanism according to claim 1, wherein, The center line is spaced 2mm-3mm from the axis of the transmission worm.

3. The worm and gear drive mechanism as set forth in claim 1, wherein Along the axial direction of the transmission worm gear, the width of the grease return mechanism is smaller than the tooth width of the transmission worm gear.

4. The worm gear transmission mechanism as described in claim 1, characterized in that, The axis of the transmission worm and the axis of the transmission worm wheel, as well as the center line of the grease return mechanism and the axis of the transmission worm wheel, are all perpendicularly intersecting.

5. The worm gear transmission mechanism as described in any one of claims 1 to 4, characterized in that, The grease return mechanism is an additional worm gear; The centerline is the axis of the additional worm gear.

6. The worm gear transmission mechanism as described in claim 5, characterized in that, The additional worm gear is a single-start worm gear.

7. The worm gear transmission mechanism as described in any one of claims 1 to 4, characterized in that, The grease return mechanism is an additional worm gear.

8. The worm gear transmission mechanism as described in claim 7, characterized in that, The number of teeth on the additional worm gear is less than the number of teeth on the transmission worm gear.

9. The worm gear transmission mechanism as described in claim 1, characterized in that, The grease return mechanism is unloaded.

10. The worm gear transmission mechanism as described in claim 1, characterized in that, The grease return mechanism is made of plastic.

11. An electric power steering device, comprising a power steering motor and a transmission mechanism, characterized in that: The transmission mechanism adopts the worm gear transmission mechanism as described in any one of claims 1 to 10, wherein the transmission worm of the worm gear transmission mechanism is coaxially connected to the output shaft of the power assist motor, and the transmission worm wheel of the worm gear transmission mechanism is coaxially connected to the steering column.

Images