A method for designing asymmetric tooth profile based on multi-stage worm gear transmission structure

Abstract

The present invention discloses an asymmetric tooth profile design method based on a multi-stage worm gear transmission structure. When designing the transmission structure, the limit torque of each stage of the transmission structure under extreme low temperature is first calculated according to the original multi-stage worm gear transmission structure. By comparing the limit torque with the preset safety value, the worm gear transmission structure that is easily damaged in extreme low temperature can be identified, that is, the structure to be corrected that needs to be adjusted is identified. The influence of extreme low temperature on the extreme load is considered to ensure that the scheme meets the load requirements. Then, the pressure surface of the worm in the structure to be corrected is calibrated and adjusted. Specifically, according to the preload temperature and the extreme load, the first pressure angle of the pressure surface is adjusted so that the first pressure angle is greater than the second pressure angle of the non-pressurized surface, so that the corresponding load-bearing capacity of the structure to be corrected is increased, so that the hidden car door handle can work normally under low temperature and high load conditions without occupying additional space.

Description

Technical Field

[0001] The invention relates to the technical field of reversing gear structure design, and in particular to an asymmetric tooth profile design method based on a multi-stage worm gear transmission structure. Background Art

[0002] In the new energy vehicle industry, as competition becomes increasingly fierce, in-depth research on various parts of new energy vehicles has become more and more in-depth to solve the various pain points of new energy vehicles. In many cases, the improvement of new energy vehicles involves the improvement of the transmission structure. For example, the power transmission structure of hybrid new energy vehicles needs to achieve power transmission through a gearbox, and the hidden door handle needs to achieve the movement of the door handle relative to the door body through the transmission structure to embed the door handle into the door body or push the door handle out of the door body.

[0003] Under the premise that new energy vehicles have demands for increasing passenger space, it is a technical problem that needs to be urgently solved by those skilled in the art to enable the above-mentioned transmission structure to meet the load requirements while occupying less space. Summary of the invention

[0004] The purpose of the present invention is to provide an asymmetric tooth profile design method based on a multi-stage worm gear transmission structure to solve the technical problem that the transmission structure of current new energy vehicles needs to meet the requirements of small space occupation and high load capacity at the same time.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] A method for designing an asymmetric tooth profile based on a multi-stage worm gear transmission structure, comprising:

[0007] According to the torque output by the power unit, the transmission ratio of each transmission structure and the limit load of the action unit, the limit torque of each transmission structure is calculated; wherein the limit load of the action unit is negatively correlated with the preset limit low temperature;

[0008] The transmission structure whose limit torque exceeds the preset safety value is defined as a structure to be corrected; the structure to be corrected includes a worm and a gear, and the worm is driven by the upper transmission structure or power unit to drive the gear to rotate through meshing;

[0009] The tooth profile parameters of the worm are set. The tooth profile parameters include the pressurized surface and the non-pressurized surface. According to the preload temperature and the limit load, the first pressure angle of the pressurized surface is adjusted so that the first pressure angle is greater than the second pressure angle of the non-pressurized surface.

[0010] The worm is modeled according to the tooth profile parameters of the worm, and an asymmetric tooth profile tool is manufactured based on the modeled worm.

[0011] Optionally, the tooth profile parameters of the worm include a pitch circle diameter;

[0012] The process of adjusting the first pressure angle of the pressurizing surface includes:

[0013] Calculate the limit meshing force F based on the limit torque and pitch circle diameter t ;

[0014] According to the contact stress formula, the limit meshing force F t , elastic modulus of the worm and tooth profile parameters of the worm to calculate the limiting contact stress σ H ;

[0015] Determine the limit contact stress σ H Is it greater than the preset safety stress?

[0016] If yes, then increase the first pressure angle according to the preset first interval value, obtain new tooth profile parameters, and return to execute the contact stress formula, the limit meshing force F t , elastic modulus of the worm and tooth profile parameters of the worm to calculate the limiting contact stress σ H ;

[0017] If not, the tooth profile parameters after limit adjustment are obtained.

[0018] Optionally, it also includes:

[0019] A temperature feedback relationship between a preset temperature difference and a pressure angle, wherein the temperature feedback relationship is a negative correlation relationship;

[0020] After obtaining the tooth profile parameters after the limit adjustment, the method further includes:

[0021] According to the relationship between the limit temperature and the temperature feedback, the temperature feedback is performed on the first pressure angle to obtain the temperature feedback pressure angle after the temperature feedback;

[0022] According to the contact stress formula, the limit meshing force Ft, the elastic modulus of the worm and the tooth profile parameters including the warm feed pressure angle, the warm feed contact stress σT is calculated;

[0023] Determine whether the absolute value between the temperature feedback contact stress σT and the safety stress is less than the preset safety margin;

[0024] If not, the first pressure angle is reduced according to the preset second interval value, and a new tooth profile parameter is obtained, and the process returns to execute the relationship between the limit temperature and the temperature feedback, and the temperature feedback pressure angle after the temperature feedback is obtained;

[0025] If yes, the tooth profile parameters after temperature feed adjustment are obtained.

[0026] Optionally, the temperature feedback relationship is:

[0027] ;

[0028] Where α is the first pressure angle after temperature feedback, α is the first pressure angle at room temperature, r is the radius of the worm at room temperature, and α m is the thermal contraction coefficient of the worm material, It is the difference between normal temperature and extreme temperature.

[0029] Optionally, the contact stress formula is:

[0030] ;

[0031] In the formula, is the contact stress, Ft is the limit meshing force, E is the Young's modulus, is Poisson's ratio, d w is the pitch circle diameter, b is the tooth width, and T is the limit torque.

[0032] A transmission structure includes a worm and a gear, wherein the worm and the gear adopt the asymmetric tooth profile design method based on the multi-stage worm gear transmission structure as described above.

[0033] A hidden door handle for an automobile comprises a power unit, an action unit and a multi-stage transmission structure, wherein the power unit drives the action unit to extend and retract through the multi-stage transmission structure, and the end of the action unit is connected to the door handle;

[0034] At least one level of the transmission structure includes a worm and a gear, the worm includes a pressurized surface and a non-pressurized surface, and a first pressure angle of the pressurized surface is greater than a second pressure angle of the non-pressurized surface.

[0035] Optionally, the power unit includes a motor, the action unit includes a push rod; the transmission structure includes a first worm, a first gear, a second worm, a second gear and a screw connected between the motor and the push rod;

[0036] The first worm is fixedly connected to the motor shaft of the motor, the first gear is meshed with the first worm; the second worm rotates synchronously with the first gear; the second gear is meshed with the second worm;

[0037] The second gear is provided with an internal threaded hole, the screw rod is threadedly connected to the internal threaded hole, and the end of the screw rod is connected to the push rod.

[0038] Optionally, the axis of the first worm is arranged in parallel with the axis of the second gear, and the axis of the first gear is arranged to coincide with the axis of the second worm.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] The asymmetric tooth profile design method based on the multi-stage worm gear transmission structure provided by the present invention, when designing the transmission structure, firstly calculates the limit torque of each stage of the transmission structure under extreme low temperature according to the original multi-stage worm gear transmission structure, and compares the limit torque with the preset safety value, so as to identify the worm gear transmission structure that is easily damaged in extreme low temperature, that is, to identify the structure to be corrected that needs to be adjusted, which takes into account the influence of extreme low temperature on the limit load to ensure that the scheme meets the load requirements. Then, the pressure surface of the worm in the structure to be corrected is calibrated and adjusted, specifically, the first pressure angle of the pressure surface is adjusted according to the preload temperature and the limit load, so that the first pressure angle is greater than the second pressure angle of the non-pressurized surface, so that the corresponding load-bearing capacity of the structure to be corrected is increased, and the first pressure angle of the worm pressure surface is increased, so that the sliding rate of the tooth surface is reduced, and the wear of the pressure surface is significantly reduced, and the correction method does not require additional space. Therefore, the asymmetric tooth profile design method based on the multi-stage worm gear transmission structure can improve the load capacity without taking up additional space. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0042] The structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with this technology. They are not used to limit the conditions under which the present invention can be implemented, and therefore have no substantive technical significance. Any structural modification, change in proportion or adjustment of size, without affecting the effects and purposes that can be achieved by the present invention, should still fall within the scope of the technical contents disclosed by the present invention.

[0043] Figure 1 A schematic diagram of a first process flow of an asymmetric tooth profile design method based on a multi-stage worm gear transmission structure provided by an embodiment of the present invention;

[0044] Figure 2 A second flow chart of the asymmetric tooth profile design method based on a multi-stage worm gear transmission structure provided by an embodiment of the present invention;

[0045] Figure 3 A third flow chart of the asymmetric tooth profile design method based on a multi-stage worm gear transmission structure provided by an embodiment of the present invention;

[0046] Figure 4A schematic diagram of the overall structure of a transmission structure provided by an embodiment of the present invention;

[0047] Figure 5 A schematic diagram of a partial structure of a transmission structure provided by an embodiment of the present invention;

[0048] Figure 6 Schematic diagram of tooth shape optimization of the worm in an embodiment of the present invention;

[0049] Figure 7 Schematic diagram of tooth shape optimization of gears in an embodiment of the present invention.

[0050] Illustrations: 100, power unit; 200, transmission structure; 210, first worm; 220, first gear; 230, second worm; 240, second gear; 250, screw; 201, pressurized surface; 202, non-pressurized surface; 300, action unit. DETAILED DESCRIPTION

[0051] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] In the description of the present invention, it should be understood that the terms "upper", "lower", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. It should be noted that when a component is considered to be "connected" to another component, it may be directly connected to the other component or there may be a centrally arranged component at the same time.

[0053] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0054] like Figures 1 to 7 As shown, Figure 1 A first flow chart of an asymmetric tooth profile design method based on a multi-stage worm gear transmission structure provided by an embodiment of the present invention, Figure 2 A second flow chart of the asymmetric tooth profile design method based on a multi-stage worm gear transmission structure provided by an embodiment of the present invention, Figure 3A third flow chart of an asymmetric tooth profile design method based on a multi-stage worm gear transmission structure provided by an embodiment of the present invention, Figure 4 The overall structural diagram of the transmission structure provided by the embodiment of the present invention is as follows: Figure 5 A schematic diagram of a partial structure of a transmission structure provided by an embodiment of the present invention, Figure 6 is a schematic diagram of the tooth shape optimization of the worm in an embodiment of the present invention, Figure 7 Schematic diagram of tooth shape optimization of gears in an embodiment of the present invention.

[0055] Embodiment 1:

[0056] In this embodiment, a transmission structure is disclosed. The transmission structure is applicable to new energy vehicles, and is applicable to structures driven by motors such as automobile gearboxes and automobile hidden door handles. It should be noted that the above transmission structure has different forward loads and reverse loads. Taking the automobile hidden door handle as an example, there is a large load when the door handle is pushed out of the door body, and a relatively small load when the door handle is retracted into the door body. In this regard, in this embodiment, the transmission structure and its tooth profile design method are improved so that the volume occupied by the transmission structure is smaller under the same load, which satisfies the requirements of occupying less space and meeting higher load requirements.

[0057] In this embodiment, the transmission structure includes a worm and a gear. The tooth profile of the worm and the tooth profile of the gear can adopt the following asymmetric tooth profile design method based on a multi-stage worm gear transmission structure. Through this asymmetric tooth profile design method, the adjusted worm or gear occupies a smaller volume under the same load, thereby meeting the requirements of occupying less space while meeting higher load requirements.

[0058] like Figures 1 to 3 As shown, taking the hidden door handle of a car as an example, the asymmetric tooth profile design method based on the multi-stage worm gear transmission structure is introduced in detail; to facilitate the understanding of technical personnel in this field, the process of extending the hidden door handle of the car into the door body is defined as forward rotation, and the process of retracting the hidden door handle of the car into the door body is defined as reverse rotation, and the load of the forward rotation is usually greater than the load of the reverse rotation.

[0059] The asymmetric tooth profile design method based on the multi-stage worm gear transmission structure in this embodiment includes:

[0060] S100, calculating the respective limit torques of each transmission structure 200 according to the torque output by the power unit 100, the transmission ratio of each transmission structure 200 and the limit load of the action unit 300; wherein the limit load of the action unit 300 is negatively correlated with the preset limit low temperature;

[0061] It should be understood that, under normal temperature conditions, the power unit 100 rotates forward, and drives the action unit 300 through the multi-stage transmission structure 200, so that the hidden door handle of the car extends out of the door body; the power unit 100 rotates reversely, and drives the action unit 300 through the multi-stage transmission structure 200, so that the hidden door handle of the car retracts into the door body; in the case of winter in the north, the surface of the hidden door handle of the car is easy to freeze, and this is the worst working state of the transmission structure 200 of the hidden door handle of the car, which is defined as the limit state. At this time, the load of the action unit 300 is defined as the limit load, and the action unit 300 needs to break the ice layer on the surface to extend from the door body. In this embodiment, the limit load can be set to 550N. It can be understood that as the extreme low temperature of the environment further decreases, the thicker the ice layer, the corresponding limit load needs to be increased accordingly;

[0062] S200, defining the transmission structure 200 whose limit torque exceeds the preset safety value as a structure to be corrected; the structure to be corrected includes a worm and a gear, and the worm is driven by the upper transmission structure 200 or the power unit 100 to drive the gear to rotate through meshing;

[0063] S300, setting the tooth profile parameters of the worm, the tooth profile parameters including the pressurized surface 201 and the non-pressurized surface 202, adjusting the first pressure angle of the pressurized surface 201 according to the preload temperature and the limit load, so that the first pressure angle is greater than the second pressure angle of the non-pressurized surface 202;

[0064] The pressurized surface 201 refers to the side where the worm and the gear form contact in each stage of the transmission structure 200 when the power unit 100 rotates forward to drive the hidden door handle of the automobile to extend out of the door body. This side plays the role of transmitting the torque of the power unit 100, so it is called the pressurized surface 201; while the non-pressurized surface 202 refers to the side where the worm and the gear form contact in each stage of the transmission structure 200 when the power unit 100 rotates reversely to drive the hidden door handle of the automobile to retract the door body. The load is relatively small when the hidden door handle of the automobile is retracted into the door body, and the contact side at this time is called the non-pressurized surface 202;

[0065] S400, modeling the worm according to the tooth profile parameters of the worm, and manufacturing an asymmetric tooth profile tool according to the modeled worm. Then, the worm and the gear can be manufactured correspondingly by the asymmetric tooth profile tool, which is the same as the manufacturing process of ordinary plastic gears and will not be described in detail in this embodiment.

[0066] Specifically, in the asymmetric tooth profile design method based on the multi-stage worm gear transmission structure in this embodiment, when designing the transmission structure 200, the limit torque of each stage of the transmission structure 200 under extreme low temperature is calculated according to the original multi-stage worm gear transmission structure 200. By comparing the limit torque with the preset safety value, the worm gear transmission structure that is easily damaged in extreme low temperature can be identified, that is, the structure to be corrected that needs to be adjusted is identified, which takes into account the influence of extreme low temperature on the limit load to ensure that the scheme meets the load requirements. Then, the pressure surface 201 of the worm in the structure to be corrected is calibrated and adjusted, specifically, according to the preload temperature and the limit load, the first pressure angle of the pressure surface 201 is adjusted, so that the first pressure angle is greater than the second pressure angle of the non-pressurized surface 202, so that the corresponding load-bearing capacity of the structure to be corrected is increased, and the first pressure angle 201 of the worm pressure surface is increased, so that the sliding rate of the tooth surface is reduced, and the wear of the pressure surface is significantly reduced. The correction method does not require additional space. Therefore, the asymmetric tooth profile design method based on the multi-stage worm gear transmission structure can improve the load capacity without occupying additional space.

[0067] In addition, for the hidden door handles of the car, the asymmetric tooth profile design method based on the multi-stage worm gear transmission structure in this embodiment has a greater load-bearing capacity under the limit state under the same modulus, and the transmission structure 200 has a smaller volume under the same load condition. Moreover, due to the increase in the pressure angle, the sliding rate of the tooth surface is reduced, which significantly reduces the wear of the tooth surface.

[0068] Furthermore, the tooth profile parameters of the worm include parameters such as pitch circle diameter, module, number of teeth, tooth width, etc.;

[0069] In step S300, the process of adjusting the first pressure angle of the pressurizing surface 201 includes:

[0070] S311. Calculate the limit meshing force F based on the limit torque and pitch circle diameter t ; Among them, the limit meshing force F t Obtained by dividing the pitch circle radius by the limiting torque;

[0071] S312, according to the contact stress formula, the limit meshing force F t , elastic modulus of the worm and tooth profile parameters of the worm to calculate the limiting contact stress σ H ;

[0072] S313. Determine the limit contact stress σ H Is it greater than the preset safety stress?

[0073] S314: If yes, increase the first pressure angle according to the preset first interval value, obtain new tooth profile parameters, and return to execute the method according to the contact stress formula, the limit meshing force F t , elastic modulus of the worm and tooth profile parameters of the worm to calculate the limiting contact stress σ H ;

[0074] S315: If not, obtain the tooth profile parameters after limit adjustment.

[0075] Specifically, the contact stress formula is: ;

[0076] In the formula, is the contact stress, Ft is the limit meshing force, E is the Young's modulus, is Poisson's ratio, d w is the pitch circle diameter, b is the tooth width, and T is the limit torque. The contact stress formula can use a variation of the above Hertz formula to describe and calculate the stress distribution of the two elastic bodies in the contact area. In this embodiment, the contact stress formula is used to estimate the contact stress between the worm and the gear at different pressure angles to ensure that the first pressure angle after the limit parameter adjustment can make the parameters of the worm and the gear in the structure to be corrected meet the load requirements under the limit condition.

[0077] As other optional implementations, the contact stress formula can also be measured by other methods such as table lookup method, for example, *Ft, K1 is the pressure angle influence coefficient and is greater than 0, indicating that as the pressure angle increases, the contact stress decreases, thereby estimating the contact stress and providing a reference for subsequent design.

[0078] Furthermore, the asymmetric tooth profile design method based on the multi-stage worm gear transmission structure 200 also includes:

[0079] S001, a temperature feedback relationship between a preset temperature difference and a pressure angle, wherein the temperature feedback relationship is a negative correlation relationship;

[0080] After obtaining the tooth profile parameters after the limit adjustment, the method further includes:

[0081] S321, performing temperature feedback on the first pressure angle according to a relationship between the limit temperature and the temperature feedback, to obtain a temperature-feedback pressure angle after temperature feedback;

[0082] S322, calculating the warm feed contact stress σT according to the contact stress formula, the limit meshing force Ft, the elastic modulus of the worm and the tooth profile parameters including the warm feed pressure angle;

[0083] S323, judging whether the absolute value between the temperature feedback contact stress σT and the safety stress is less than a preset safety margin;

[0084] S324, if not, then reduce the first pressure angle according to the preset second interval value, obtain new tooth profile parameters, and return to execute the temperature feedback of the first pressure angle according to the relationship between the limit temperature and the temperature feedback to obtain the temperature-fed pressure angle after the temperature feedback;

[0085] S325. If yes, the tooth profile parameters after temperature feed adjustment are obtained.

[0086] Specifically, the temperature feedback relationship is:

[0087] ;

[0088] Where α is the first pressure angle after temperature feedback, α is the first pressure angle at room temperature, r is the radius of the worm at room temperature, and α m is the thermal contraction coefficient of the worm material, is the absolute value of the difference between normal temperature and the limit temperature. It should be noted that the above temperature feedback relationship characterizes the contraction of the worm under low temperature conditions; when the tooth profile contracts equally, it usually means that the pressure angle will change, and the pressure angle is negatively correlated with the temperature, that is, as the temperature of the worm decreases, its pressure angle tends to increase; therefore, in step S321, it is possible to estimate the change in the pressure angle of the worm under low temperature, obtain the temperature-feed pressure angle, and recalculate the temperature-feed contact stress σT of the limit state based on the temperature-feed pressure angle, and the temperature-feed contact stress σT is lower than the limit contact stress σ H , and determine the difference between the temperature-fed contact stress σT and the safety stress through step S323. Since the pressure angle tends to increase under the limit state, the corresponding temperature-fed contact stress σT will also decrease. Then, it can be known that the absolute value between the temperature-fed contact stress σT and the safety stress increases; if the absolute value is too high, it indicates that the first pressure angle is too large, which is more likely to cause the transmission structure 200 to have greater noise. Therefore, step S324 can be executed to appropriately reduce the first pressure angle. Under the first pressure angle, it can ensure that the temperature-fed contact stress σT under the limit condition is lower than the safety stress, thereby ensuring the normal use of the worm; at room temperature, the load is lower than the limit condition. At this time, the transmission structure 200 can still operate normally and with low noise under the first pressure angle.

[0089] As another optional implementation, the temperature feedback relationship can be α(T)=α+K2* , K2 is the temperature influence coefficient and is greater than 0. It can be obtained through empirical formulas such as testing and table lookup to estimate the pressure angle when the temperature decreases ( The increase after the increase provides a reference for subsequent design.

[0090] On the basis of the above implementation, the second interval value is smaller than the first interval value. It is understandable that, through steps S311 to S315, the tooth profile parameters with the first pressure angle improved can be obtained, and the normal use of the worm under the limit torque can be guaranteed at this time; then, through steps S321 to S325, the first pressure angle is fine-tuned for the second time, so that the worm can be used normally under the limit state (low temperature) and the limit torque, and the noise of the worm under normal temperature can be reduced.

[0091] On the basis of the above implementation, after determining the first pressure angle, the complete tooth profile parameters (including the number of teeth, module, pressure angle, tooth width, etc.) are obtained, and then the complete tooth profile can be drawn by the tooth profile parameters, such as Figure 6 and Figure 7 As shown (the left side is the tooth profile before optimization, and the right side is the tooth profile after optimization).

[0092] Step S400 models the worm according to the tooth profile parameters of the worm, and manufactures an asymmetric tooth profile tool according to the modeled worm, specifically including:

[0093] Using the tooth profile parameters, a specific model of the worm and gear is established. Specifically, KISSsoft and the tooth profile parameters are used to establish an end face tooth profile (asymmetric) of a gear tooth, which is then imported into SolidWorks. The scanning command is used to establish a specific model based on the gear helix angle. Then, an asymmetric tooth profile tool is made based on the modeled worm.

[0094] Subsequently, the asymmetric tooth profile tool can be used to process the tooth profile of the plastic raw material to obtain a plastic worm and a plastic gear. Then, the obtained transmission structure 200 can be subjected to other tests to verify the performance of the transmission structure 200 under different conditions. The performance test includes but is not limited to a noise test, a fatigue test, a high temperature test, etc. For example, the transmission structure 200 can be subjected to a large load test under an environment of 80°C to verify whether the performance of the worm or gear in the transmission structure 200 is qualified when softened by high temperature. The specific performance test is set by the actual production requirements and is not specifically expanded in this embodiment.

[0095] Embodiment 2:

[0096] like Figure 4 and Figure 5As shown, this embodiment specifically discloses a hidden door handle for automobile, including a power unit 100, an action unit 300 and a multi-stage transmission structure 200, wherein the power unit 100 drives the action unit 300 to extend and retract through the multi-stage transmission structure 200, and the end of the action unit 300 is connected to the door handle; at least one stage of the transmission structure 200 includes a worm and a gear, and the worm includes a pressurized surface 201 and a non-pressurized surface 202, and the first pressure angle of the pressurized surface 201 is greater than the second pressure angle of the non-pressurized surface 202. The power unit 100 can be a stepper motor or a servo motor.

[0097] Specifically, the first pressure angle is 30°, and the first pressure angle is adjusted by the above-mentioned asymmetric tooth profile design method based on the multi-stage worm gear transmission structure; the second pressure angle is 20°, which is a conventional choice.

[0098] Exemplarily, the power unit 100 includes a motor, and the action unit 300 includes a push rod; the transmission structure 200 includes a first worm 210, a first gear 220, a second worm 230, a second gear 240 and a screw 250 connected between the motor and the push rod; the first worm 210 is fixedly connected to the motor shaft of the motor, and the first gear 220 is meshed with the first worm 210; the second worm 230 rotates synchronously with the first gear 220; the second gear 240 is meshed with the second worm 230; the second gear 240 is provided with an internal threaded hole, the screw 250 is threadedly connected to the internal threaded hole, and the end of the screw 250 is connected to the push rod.

[0099] Specifically, the axis of the first worm 210 is arranged in parallel with the axis of the second gear 240, and the axis of the first gear 220 is arranged to coincide with the axis of the second worm 230, so that the overall structure of the hidden door handle of the automobile is more compact.

[0100] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for designing an asymmetric tooth profile based on a multi-stage worm gear transmission structure, characterized in that: include: According to the torque output by the power unit, the transmission ratio of each transmission structure and the limit load of the action unit, the limit torque of each transmission structure is calculated; wherein the limit load of the action unit is negatively correlated with the preset limit low temperature; The transmission structure whose limit torque exceeds the preset safety value is defined as a structure to be corrected; the structure to be corrected includes a worm and a gear, and the worm is driven by the upper transmission structure or power unit to drive the gear to rotate through meshing; The tooth profile parameters of the worm are set. The tooth profile parameters include the pressurized surface and the non-pressurized surface. According to the preload temperature and the limit load, the first pressure angle of the pressurized surface is adjusted so that the first pressure angle is greater than the second pressure angle of the non-pressurized surface. The worm is modeled according to the tooth profile parameters of the worm, and an asymmetric tooth profile tool is manufactured based on the modeled worm.

2. The asymmetric tooth profile design method based on a multi-stage worm gear transmission structure according to claim 1, characterized in that: The tooth profile parameters of the worm include the pitch circle diameter; The process of adjusting the first pressure angle of the pressurizing surface includes: Calculate the limit meshing force F based on the limit torque and pitch circle diameter t ; According to the contact stress formula, the limit meshing force F t , elastic modulus of the worm and tooth profile parameters of the worm to calculate the limiting contact stress σ H ; Determine the limit contact stress σ H Is it greater than the preset safety stress? If yes, then increase the first pressure angle according to the preset first interval value, and obtain new tooth profile parameters, and return to execute the contact stress formula, the limit meshing force F t , elastic modulus of the worm and tooth profile parameters of the worm to calculate the limiting contact stress σ H ; If not, the tooth profile parameters after limit adjustment are obtained.

3. The asymmetric tooth profile design method based on a multi-stage worm gear transmission structure according to claim 2, characterized in that: Also includes: A temperature feedback relationship between a preset temperature difference and a pressure angle, wherein the temperature feedback relationship is a negative correlation relationship; After obtaining the tooth profile parameters after the limit parameter adjustment, the method further includes: According to the relationship between the limit temperature and the temperature feedback, the temperature feedback is performed on the first pressure angle to obtain the temperature feedback pressure angle after the temperature feedback; According to the contact stress formula, the limit meshing force Ft, the elastic modulus of the worm and the tooth profile parameters including the warm feed pressure angle, the warm feed contact stress σT is calculated; Determine whether the absolute value between the temperature feedback contact stress σT and the safety stress is less than the preset safety margin; If not, the first pressure angle is reduced according to the preset second interval value, and a new tooth profile parameter is obtained, and the process returns to execute the relationship between the limit temperature and the temperature feedback, and the temperature feedback pressure angle after the temperature feedback is obtained; If yes, the tooth profile parameters after temperature feed adjustment are obtained.

4. The asymmetric tooth profile design method based on a multi-stage worm gear transmission structure according to claim 3 is characterized in that: The temperature feedback relationship is: ； Where α is the first pressure angle after temperature feedback, α is the first pressure angle at room temperature, r is the radius of the worm at room temperature, and α m is the thermal contraction coefficient of the worm material, It is the difference between normal temperature and extreme temperature.

5. The asymmetric tooth profile design method based on a multi-stage worm gear transmission structure according to claim 3, characterized in that: The contact stress formula is: ； In the formula, is the contact stress, Ft is the limit meshing force, E is the Young's modulus, is Poisson's ratio, d w is the pitch circle diameter, b is the tooth width, and T is the limit torque.

6. The asymmetric tooth profile design method based on a multi-stage worm gear transmission structure according to claim 3, characterized in that: The second interval value is smaller than the first interval value.

7. A transmission structure, characterized in that: It comprises a worm and a gear, wherein the worm and the gear adopt an asymmetric tooth profile design method based on a multi-stage worm gear transmission structure as described in any one of claims 1 to 6.

8. A hidden door handle for a car, characterized in that: It includes a power unit, an action unit and a multi-stage transmission structure, wherein the power unit drives the action unit to extend and retract through the multi-stage transmission structure, and the end of the action unit is connected to a door handle; At least one level of the transmission structure includes a worm and a gear, the worm includes a pressurized surface and a non-pressurized surface, the first pressure angle of the pressurized surface is greater than the second pressure angle of the non-pressurized surface, and the worm and the gear adopt the asymmetric tooth profile design method based on the multi-stage worm gear transmission structure as described in any one of claims 1-6.

9. The automobile hidden door handle according to claim 8, characterized in that: The power unit includes a motor, and the action unit includes a push rod; the transmission structure includes a first worm, a first gear, a second worm, a second gear and a screw connected between the motor and the push rod; The first worm is fixedly connected to the motor shaft of the motor, the first gear is meshed with the first worm; the second worm rotates synchronously with the first gear; the second gear is meshed with the second worm; The second gear is provided with an internal threaded hole, the screw rod is threadedly connected to the internal threaded hole, and the end of the screw rod is connected to the push rod.

10. The automobile hidden door handle according to claim 9, characterized in that: The axis of the first worm is arranged in parallel with the axis of the second gear, and the axis of the first gear is arranged to coincide with the axis of the second worm.

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