Design method of asymmetric efficiency transmission system

Abstract

The invention provides an asymmetric efficiency transmission system design method, which is applied to the technical field of transmission control, and comprises the following steps: S1, constructing a main transmission path model with a first driving side shaft part and a first load side shaft part, S2, constructing a shunt transmission path model with a second driving side shaft part and a second load side shaft part, and S3, constructing a shunt transmission path model with a second driving side shaft part and a second load side shaft part. S3, a parallel node model of the main and shunt transmission paths is constructed, a first load side shaft part and a second load side shaft part are connected through a worm and gear transmission structure, and a second load side shaft with the axial constraint rigidity being # imgabs0 # serves as a worm shaft; according to the design method, the total positive transmission efficiency and the total reverse transmission efficiency of the system and the relational expression between the parameters are obtained, model selection design is conducted on the actual rigidity characteristics and the transmission characteristics of all the models according to the relational expression, the transmission system can have the high positive transmission efficiency and the low reverse transmission efficiency through the design method, and the reverse transmission efficiency is flexible and adjustable.

Description

Technical Field

[0001] The present application relates to the technical field of asymmetric efficiency transmission, and in particular to a design method for an asymmetric efficiency transmission system. Background Art

[0002] Asymmetric efficiency transmission mechanism is widely used. Typically, in the gear rack type (P-EPS) and double gear rack type (DP-EPS) electric power steering with lower power, the motor drives a small gear to rotate through a pair of worm gears. The small gear meshes with the steering gear rack to convert the rotational motion of the gear into the lateral movement of the rack, driving the steering rod to move and thus realize the steering of the steering wheel. In the parallel axis type (R-EPS), the motor drives the ball screw mechanism through the synchronous belt. The ball screw converts the circular motion of the pulley into the lateral movement of the screw, driving the steering rod to move and thus realize the steering of the steering wheel.

[0003] The above-mentioned asymmetric efficiency transmission mechanisms have major defects when applied to the wire-controlled steering system of electric vehicles. First of all, due to the limitation of the worm gear material (generally PA66 nylon), the maximum rack force that can be driven by the rack and pinion steering machine is generally only about 12kN. The wire-controlled steering system is generally aimed at electric vehicles, which are relatively heavy, and the rack force requirement generally needs to reach 15kN. Secondly, since the power is transmitted through the worm gear mechanism, the mechanical efficiency is low, which is unacceptable for electric vehicles that are very sensitive to energy consumption. In addition, low mechanical efficiency also means that there are a large number of friction pairs in the transmission system, which leads to large resistance fluctuations during starting and reversing, which is not conducive to precise servo control. In addition to the rack and pinion configuration, planetary roller screw and trapezoidal screw configuration steering machines also have such problems, so they are generally only used in rear-wheel steering with relatively low efficiency and response requirements.

[0004] Although the parallel axis steering gear can meet the requirements of large rack force output of more than 15kN, and the mechanical efficiency of the synchronous belt and ball screw mechanism is very high, there is another problem, that is, the reverse efficiency of the transmission system is too high, and the load on the steering wheel of the whole vehicle is almost entirely applied to the motor through the steering gear. This is very unfavorable to the self-stability of the steering system. Balancing the road load completely through the motor output is not only demanding on the control software and hardware, and it is difficult to achieve the ideal performance level, but also greatly deteriorates the working condition of the motor and greatly reduces the life of the motor.

[0005] Based on this, there is an urgent need to improve and develop the above-mentioned asymmetric efficiency transmission mechanisms in terms of transmission form and transmission principle, so as to improve their forward transmission efficiency from the drive side to the load side on the one hand, thereby increasing the rack force or screw thrust or other forms of steering execution power that can be obtained by the steering actuator, and on the other hand reduce their reverse transmission efficiency from the load side to the drive side, reduce road disturbances and harmful excitations entering the drive side, and thereby improve the self-stabilization performance of the steering system. Summary of the invention

[0006] In view of this, an embodiment of the present specification provides a design method for an asymmetric efficiency transmission system. By using this design method, the transmission system can have both high forward transmission efficiency and low reverse transmission efficiency, and the reverse transmission efficiency is flexibly adjustable.

[0007] The embodiments of this specification provide the following technical solutions:

[0008] A method for designing an asymmetric efficiency transmission system comprises the following steps: S1, constructing a main transmission path model having a first drive side shaft component and a first load side shaft component, wherein the torsional stiffness of the first drive side shaft component is k1; S2, constructing a shunt transmission path model having a second drive side shaft component and a second load side shaft component, wherein the torsional stiffness of the second drive side shaft component is k2, k2>k1; S3, constructing a parallel node model of the main and shunt transmission paths, wherein the first and second drive side shaft components are connected by a node transmission structure, and the first and second load side shaft components are connected by a worm gear transmission structure and are constrained by an axial stiffness of k s The second load-side shaft is used as the worm shaft; S4. The deformation coordination equation is established by combining the stiffness parameters and transmission parameters of each model to obtain the relationship between the total forward and reverse transmission efficiency of the system and the above parameters, and the actual stiffness characteristics and transmission characteristics of each model are selected and designed based on this until the target value of the system transmission efficiency is obtained.

[0009] In order to optimize the technical solution, the following technical measures are also taken:

[0010] As a preferred embodiment, the second load-side shaft component includes a second load-side shaft and a second intermediate transmission structure assembled on the second load-side shaft, and the second intermediate transmission structure is located between the node transmission structure and the worm gear transmission structure along the transmission path.

[0011] As a preferred embodiment, the forward transmission efficiency of the worm gear transmission structure does not exceed 50% and the reverse transmission efficiency does not exceed 10%.

[0012] As a preferred embodiment, the following step is added between S3 and S4, and the equivalent torsional stiffness k' generated by the axial constraint stiffness of the worm shaft on the corresponding worm wheel shaft is calculated using the following formula:s ;

[0013] k' s =R 2 k s ;

[0014] Where R is the pitch circle diameter of the worm gear.

[0015] As a preferred implementation, in S4, the relationship between the total forward and reverse transmission efficiency of the system and the model stiffness parameters and transmission parameters obtained according to the deformation coordination equation is as follows:

[0016]

[0017] Wherein, η is the total forward transmission efficiency of the system, η' is the total reverse transmission efficiency of the system, i1 represents the transmission ratio of the main transmission path, i2 represents the transmission ratio of the node transmission structure, η1 and η'1 are the forward and reverse transmission efficiencies of the main transmission path, η2 and η'2 are the forward and reverse transmission efficiencies of the node transmission structure, η3 and η'3 are the forward and reverse transmission efficiencies of the second intermediate transmission structure, η4 and η'4 are the forward and reverse transmission efficiencies of the worm gear structure,

[0018] As a preferred embodiment, the second drive side shaft component includes a second drive side shaft and a second coupling installed at the output end of the second drive side shaft, the second drive side shaft is coupled to the second load side shaft component through the second coupling, and the torsional stiffness of the second drive side shaft component is adjusted by selecting the torsional stiffness parameters of the second coupling.

[0019] As a preferred embodiment, the first drive side shaft component includes a first drive side shaft and a first coupling installed at the output end of the first drive side shaft, the first drive side shaft is coupled to the first load side shaft component through the first coupling, and the torsional stiffness of the second drive side shaft component is adjusted by selecting the torsional stiffness parameters of the first coupling.

[0020] As a preferred implementation, in S4, under the condition that the transmission ratios i1, i2 and the torsional stiffness k1 are determined, only the torsional stiffness k2 is adjusted until an ideal total forward transmission efficiency of the system is obtained.

[0021] As a preferred embodiment, in S4, under the condition that the transmission ratios i1, i2 and the torsional stiffness k1 are determined, only the axial constraint stiffness k s Adjust until the desired total system forward transmission efficiency is obtained.

[0022] As a preferred embodiment, in S3, the axial constraint stiffness of the worm shaft is greater than the torsional stiffness of the worm wheel shaft.

[0023] As a preferred embodiment, in S3, the first load-side shaft component includes a first load-side shaft and a first intermediate transmission structure assembled on the first load-side shaft, and the first intermediate transmission structure is located between the node transmission structure and the worm gear transmission structure along the transmission path.

[0024] Compared with the prior art, the at least one technical solution adopted in the embodiments of this specification can achieve the following beneficial effects:

[0025] First, during forward transmission, the torque power output from the driving side will be diverted when passing through the node transmission structure. Since the torsional stiffness of the first driving side shaft component is greater than that of the second driving side shaft component, according to the constraint of deformation coordination, most of the power will enter the main transmission path from the first driving side shaft component and only a small part of the power will enter the diverted transmission path. Conversely, since the axial constraint stiffness of the worm shaft is greater than that of the worm gear shaft, which is also a general design principle, according to the constraint of deformation coordination, during reverse transmission, most of the power will be distributed to the worm shaft and transmitted from the diverted transmission path when passing through the worm gear transmission structure. On the basis of realizing the forward and reverse power diversion, the main transmission path can have a high forward transmission efficiency and the diversion transmission path can have a low reverse transmission efficiency by utilizing the selection design of the stiffness parameters and the transmission parameters of the transmission path according to the established deformation coordination equation. In this way, most of the power is transmitted from the high-efficiency main transmission path during forward transmission, and the energy loss on the diversion path is limited, so that the system can still obtain a relatively high forward transmission efficiency. Similarly, most of the power is consumed on the inefficient diversion transmission path during reverse transmission, so that the system can still obtain a relatively low reverse transmission efficiency.

[0026] Furthermore, since the forward and reverse transmission efficiencies of the system can be individually optimized by adjusting the stiffness characteristics and transmission characteristics of the shaft components on each transmission path, structural decoupling of the forward transmission efficiency and the reverse transmission efficiency can be achieved, thereby enhancing the flexibility in transmission system design.

[0027] Furthermore, in this embodiment, the different distribution ratios of torque power in forward and reverse transmission are determined by the mechanical characteristics of the structure and are completely adaptive, without the need for active intervention. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 It is a flowchart of the first implementation of this application;

[0030] Figure 2 It is a schematic diagram of the transmission structure of the first embodiment of the present application;

[0031] Figure 3 It is a schematic diagram of the transmission structure on the main transmission path in the first embodiment of the present application;

[0032] Figure 4 It is a schematic diagram of the transmission structure on the split transmission path in the first embodiment of the present application;

[0033] Figure 5 is a structural schematic diagram of the motor assembly in the second embodiment of the present application;

[0034] Figure 6 is a schematic diagram of the structure of the wire-controlled steering system in the third embodiment of the present application;

[0035] Figure 7 It is a structural schematic diagram of the asymmetric efficiency transmission system in Example 3 of the present application. DETAILED DESCRIPTION

[0036] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0037] The following describes the implementation methods of the present application through specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the following embodiments and the features in the embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present application.

[0038] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present application, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspect described herein can be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this device and / or practice this method.

[0039] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present application. The drawings only show components related to the present application rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0040] The embodiments of this specification propose a design method for an asymmetric efficiency transmission system, which aims to solve the problem in the prior art that the asymmetric efficiency transmission system cannot have both high forward transmission efficiency and low reverse transmission efficiency. It not only enables the transmission system to have the advantages of high forward transmission efficiency and low reverse transmission efficiency, but also makes the reverse transmission efficiency flexibly adjustable.

[0041] The inventive concepts contained in this specification will be further disclosed below in conjunction with the technical contents shown in the accompanying drawings and specific embodiments.

[0042] Embodiment 1

[0043] like Figures 1 to 4 As shown, Figure 3 The middle arrow S1 shows the transmission direction of the positive torque power from the drive end 1 to the load end 2 on the main transmission path 3. Figure 4The middle arrow S2 shows the transmission direction of the positive torque power from the drive end 1 to the load end 2 on the shunt transmission path 4, and each transmission shaft is supported by a bearing 12 that meets its specific characteristic requirements. The asymmetric efficiency transmission system design method includes the following steps: S1, constructing a main transmission path 3 model with a first drive side shaft component and a first load side shaft component, wherein the torsional stiffness of the first drive side shaft component is k1; S2, constructing a shunt transmission path model with a second drive side shaft component and a second load side shaft component, wherein the torsional stiffness of the second drive side shaft 41 component is k2, k2>k1; S3, constructing a parallel node model of the main and shunt transmission paths, wherein the first and second drive side shaft components are connected by a node transmission structure 5, and the first and second load side shaft components are connected by a worm gear transmission structure 6 and are constrained by an axial stiffness of k s The second load-side shaft 43 is used as the worm shaft and the first load-side shaft 33 is used as the worm wheel shaft; S4. The deformation coordination equation is established in combination with the stiffness parameters and transmission parameters of each model to obtain the relationship between the total forward and reverse transmission efficiency of the system and the above parameters, and the actual stiffness characteristics and transmission characteristics of each model are selected and designed based on this until the target value of the system transmission efficiency is obtained.

[0044] Here, if Figure 1 As shown, the angular displacement of the output end of the first drive side shaft component relative to its input end during forward transmission under the state of loading the rated transmission load is recorded as the first equivalent torsional deformation Q1, which is used to measure the torsional stiffness k1 of the first drive side shaft component. Under the same state, the angular displacement of the output end of the second drive side shaft component relative to its input end during forward transmission is recorded as the second equivalent torsional deformation Q2, which is used to measure the torsional stiffness k2 of the first drive side shaft component. Then k1>k2. By using this stiffness characteristic, according to the constraint of deformation coordination, the torque power at the node transmission structure can be adaptively distributed according to the set ratio during forward transmission. Preferably, the node transmission structure adopts a bevel gear transmission structure composed of a bevel gear driving wheel 51 and a bevel gear driven wheel 52, and its transmission ratio can be flexibly configured according to the working conditions.

[0045] Similarly, the first and second load-side shaft components are connected by the worm gear transmission structure 6, and the second load-side shaft 43 is used as the worm shaft and the first load-side shaft 33 is used as the worm shaft. Figure 3As shown, the worm 61 is mounted on the second load-side shaft 43, and the worm wheel 62 is mounted on the first load-side shaft 33. Having low reverse transmission efficiency or self-locking characteristics is an important known characteristic of the worm gear transmission structure. When the worm gear is engaged, the worm shaft will be subjected to a large axial force. In order to prevent the worm from axial displacement or deformation, the axial constraint stiffness of the worm shaft must meet the target design value, while the torsional stiffness of the worm wheel shaft does not need to exceed this design value. Therefore, in the worm gear transmission structure, the axial constraint stiffness of the worm shaft should be greater than the torsional stiffness of the worm wheel shaft. Specifically, as shown in the figure, the axial displacement of the worm shaft under the rated transmission load is recorded as the equivalent axial displacement L1, and the displacement of the equivalent axial displacement L1 is used to measure the axial constraint stiffness k of the second load-side shaft, i.e., the worm shaft. s , then k s The torsional stiffness of the worm gear shaft is greater than that of the worm gear shaft. By utilizing this stiffness characteristic and according to the constraint of deformation coordination, the torque power at the worm gear transmission structure can be adaptively distributed according to a set ratio during reverse transmission.

[0046] On the basis of realizing the forward and reverse power diversion, the main transmission path 3 can have a high forward transmission efficiency and the diversion transmission path 4 can have a low reverse transmission efficiency by utilizing the stiffness parameters and transmission parameter selection design of the transmission path model according to the established deformation coordination equation. In this way, most of the power is transmitted from the high-efficiency main transmission path 3 during forward transmission, and the energy loss on the diversion path is limited, so that the system can still obtain a relatively high forward transmission efficiency. Similarly, most of the power is consumed on the inefficient diversion transmission path 4 during reverse transmission, so that the system can still obtain a relatively low reverse transmission efficiency.

[0047] In this embodiment, the main function of the shunt transmission path 4 in forward transmission or reverse transmission is to consume energy, especially the energy transmitted from the load end to the drive end during reverse transmission. Therefore, the shunt transmission path 4 is preferably configured in the form of a multi-stage transmission. Specifically, the second load-side shaft component includes a second load-side shaft 43 and a second intermediate transmission structure 42 assembled on the second load-side shaft 43. The second intermediate transmission structure 42 is located between the node transmission structure 5 and the worm gear transmission structure 6 along the transmission path. The input end of the second intermediate transmission structure 42 is suitable for connecting to the second drive side shaft 41 through a coupling. The second intermediate transmission structure 42 described here is preferably a cylindrical gear set, a synchronous belt transmission set, or a combined transmission structure including a worm gear, etc., which are not listed one by one here.

[0048] In this embodiment, the forward transmission efficiency of the worm gear transmission structure 6 does not exceed 50% and the reverse transmission efficiency does not exceed 10%. In particular, the worm gear transmission structure 6 is a self-locking worm gear transmission structure, that is, the reverse transmission efficiency is almost zero.

[0049] In this embodiment, the following step is added between S3 and S4, and the equivalent torsional stiffness k' generated by the axial constraint stiffness of the worm shaft on the corresponding worm wheel shaft is calculated using the following formula: s ;

[0050] k' s =R 2 k s ;

[0051] Where R is the pitch circle diameter of the worm gear.

[0052] Furthermore, in S4, the relationship between the total forward and reverse transmission efficiency of the system and the model stiffness parameters and transmission parameters obtained according to the deformation coordination equation is as follows:

[0053]

[0054] Wherein, η is the total forward transmission efficiency of the system, η' is the total reverse transmission efficiency of the system, i1 represents the transmission ratio of the main transmission path 3, i2 represents the transmission ratio of the node transmission structure 5, η1 and η'1 are the forward and reverse transmission efficiencies of the main transmission path 3, η2 and η'2 are the forward and reverse transmission efficiencies of the node transmission structure 5, η3 and η'3 are the forward and reverse transmission efficiencies of the second intermediate transmission structure 42, η4 and η'4 are the forward and reverse transmission efficiencies of the worm gear structure,

[0055]

[0056] It can be seen from the mathematical expression that when the system is transmitting in the forward direction, the overall efficiency of the system will be slightly lower than the efficiency of the main transmission path 3 due to the diversion of the less efficient diversion transmission path 4. 12 , k 1s The effect of the transmission ratios i1 and i2 on the overall efficiency is much greater than the effect of the lower η4 on the overall efficiency. The physical mechanism is that the torsional stiffness of the main transmission path 3 on the driving side is greater than that of the shunt transmission path 4, that is, the torsional stiffness of the first driving side shaft component is greater than that of the second driving side shaft component. Due to the constraint of deformation coordination, the path with greater stiffness also transmits greater power. Therefore, most of the power is transmitted through the more efficient main transmission path 3, and the overall energy loss caused by the inefficient shunt transmission path 4 is very small, so the system still has a very high total forward transmission efficiency.

[0057] When the system is reversely transmitted, due to the self-locking effect of the worm gear, η'4 is close to or equal to 0, and since the axial constraint stiffness of the worm shaft is generally much greater than the torsional stiffness of the transmission system, most or even all of the power is transmitted by the shunt transmission path 4. At this time, the overall efficiency basically depends on the self-locking performance of the worm gear. When the axial constraint of the worm shaft is reliable and the self-locking of the worm gear is reliable, the system as a whole can achieve self-locking, that is, it has a very low reverse transmission efficiency.

[0058] In addition, in this embodiment, when the transmission ratio i1 is determined, the transmission ratio i2 can be flexibly defined in the design, k1, k2, k s Precise control can be achieved through structural design, material selection, and setting couplings with target stiffness characteristics in the path. The system efficiency can be precisely designed by adjusting the parameters. In addition, under the condition that i2 and k1 are determined, changing k2 can adjust the total forward transmission efficiency of the mechanism without basically affecting the total reverse transmission efficiency. Conversely, changing k s The total reverse transmission efficiency of the system can be adjusted without substantially affecting the total forward transmission efficiency, thereby achieving structural decoupling of the forward and reverse transmission efficiencies. The effect of adjusting the system transmission ratio on the system transmission efficiency can be offset by adjusting the stiffness characteristics of the first drive side shaft component or the second drive side shaft component, thereby achieving structural decoupling between the system transmission ratio and the transmission efficiency, further enhancing the flexibility and adaptability of the transmission system during application. Furthermore, in this embodiment, the different distribution ratios of torque power in the forward and reverse transmissions are determined by the structural mechanical characteristics, which are fully adaptive and do not require active intervention.

[0059] Specifically, the second drive side shaft component includes a second drive side shaft 41 and a second coupling installed at the output end of the second drive side shaft 41, the second drive side shaft 41 is coupled to the second load side shaft component through the second coupling, and the torsional stiffness of the second drive side shaft component is adjusted by selecting the torsional stiffness parameter of the second coupling. Similarly, the first drive side shaft 31 component includes a first drive side shaft 31 and a first coupling installed at the output end of the first drive side shaft 31, the first drive side shaft 31 is coupled to the first load side shaft component through the first coupling, and the torsional stiffness of the second drive side shaft component is adjusted by selecting the torsional stiffness parameter of the first coupling. Here, it needs to be further explained that the "coupling" here should be understood in a broad sense, that is, all components that can realize the coupling function of the two transmission shafts should be included. For example, elastic rubber blocks or springs that realize the coupling of the two transmission shafts should also be included in the category of the "coupling", as long as they can provide a certain torsional deformation and, under the premise of meeting the transmission requirements, make the stiffness characteristics of the first drive side shaft 31 and the second drive side shaft 41 meet the set gap value.

[0060] In this embodiment, in S3, the first load-side shaft 33 component includes a first load-side shaft 33 and a first intermediate transmission structure 32 assembled on the first load-side shaft 33, and the first intermediate transmission structure 32 is located between the node transmission structure 5 and the worm gear transmission structure 6 along the transmission path. Here, the main purpose of setting the first intermediate transmission structure 32 is to adjust the transmission ratio of the transmission system, so the specific transmission form can be flexibly configured. Preferably, the first intermediate transmission structure 32 is set to a high transmission efficiency gear transmission structure such as a cylindrical gear transmission structure or a bevel gear transmission structure.

[0061] Embodiment 2

[0062] like Figure 5 As shown, this embodiment provides a motor assembly, including a drive motor 100 and the asymmetric efficiency transmission system described in the first embodiment, wherein the first drive-side shaft component is suitable for obtaining power from the motor shaft of the drive motor 100 .

[0063] Specifically, the asymmetric efficiency transmission system is placed as a whole in a casing, and the casing is connected to the outer shell of the drive motor 100 through a fastener 7. The first drive side shaft component includes a first drive side shaft 311 and a rigid coupling 321. The first drive side shaft 311 is integrally connected to the motor shaft of the drive motor 100. The first intermediate transmission mechanism is not set on the first load side shaft 331. The first drive side shaft 311 is rigidly connected to the first load side shaft 331 through the rigid coupling 321, that is, i1=1, η1=η'1=100%, and the drive side node structure 51 includes a bevel gear pair and a planetary gear set 511 meshed with the driving wheel of the bevel gear pair. The driven wheel of the bevel gear pair is installed on the second drive side shaft 311. In forward transmission, the power is transmitted from the bevel gear to the first load side shaft 331. The forward and reverse transmission efficiencies of the node structure 51 on the driving side can reach more than 90%. The second load-side shaft component includes a second load-side shaft and a second intermediate transmission mechanism 4211 installed on the second load-side shaft. The second intermediate transmission mechanism 4211 is a cylindrical gear transmission structure, one end of which has an input transmission shaft, which is coupled to the second drive-side shaft through an elastic coupling. The forward and reverse transmission efficiency of the second intermediate transmission mechanism 4211 is η3=η'3, η3 is 95% to 99%. The worm gear structure 61 has a lower efficiency due to the need for reliable self-locking performance. Its forward transmission efficiency η4 does not exceed 50%, and its reverse transmission efficiency η'4 does not exceed 10%. If a self-locking worm gear is used, η'4=0. When the transmission ratio i2≥1, k 12 Take 2 to 3, k 1s Taking 0.3 to 0.5 and substituting it into the above formula, it is calculated that the total forward transmission efficiency of the system is above 80%, and the total reverse transmission efficiency does not exceed 25%.

[0064] In this embodiment, the motor assembly is configured with the above-mentioned asymmetric efficiency transmission system. Since the reverse transmission efficiency is low, it can effectively shield most of the disturbances and excitations from the load side. At the same time, due to the high forward transmission efficiency, the power output from the drive motor 100 to the load side is sufficient and stable.

[0065] Embodiment 3

[0066] like Figure 6 to Figure 7 As shown, this embodiment provides a wire-controlled steering system and a vehicle using the wire-controlled steering system, wherein the wire-controlled steering system includes the above-mentioned motor assembly, specifically, the steering system includes a motor assembly and a steering actuator, the motor assembly includes a steering motor 200 and an asymmetric efficiency transmission system 301 connected between the steering motor 200 and the steering actuator, the steering motor 200 is controlled by a steering motor controller 201 for speed and torque, the motor shaft of the steering motor 200 is coupled to a first driving side shaft 312 of the asymmetric efficiency transmission system 301, preferably, the motor shaft of the steering motor 200 The machine shaft is integrally connected to the first drive side shaft 312, and the steering actuator specifically includes a synchronous belt transmission component 401, a ball screw assembly and a steering shaft 601, wherein the driving wheel of the synchronous belt transmission component 401 is coupled to the first load side shaft 332 of the asymmetric efficiency transmission system 301, and the ball screw assembly includes a screw nut 501 rigidly connected to the driven wheel of the synchronous belt transmission component 401 and a ball screw 502 matched with the screw nut 501, one end of the ball screw 502 is rigidly connected to the steering shaft 601, and one end of the steering shaft 601 is connected to the steering wheel through a ball pin and a steering knuckle. During the steering process, the controller controls the steering motor 200 to output the target torque according to the needs of the whole vehicle. The torque power is transmitted from the asymmetric efficiency transmission system 301 to the synchronous belt transmission component 401, driving the driven wheel of the synchronous belt transmission component 401 to rotate, so that the screw nut 501 follows the rotation, driving the ball screw 502 and the steering shaft 601 to move laterally along the shell, thereby controlling the deflection of the steering wheel of the whole vehicle.

[0067] refer to Figure 6As shown, in the asymmetric efficiency transmission system 301 in this embodiment, the first intermediate transmission mechanism is not arranged on the first load side shaft 332, and the first drive side shaft 312 is coupled with the first load side shaft 332 through the first coupling 322. At this time, the transmission ratio of the first transmission path 3 is 1, and the forward and reverse transmission efficiencies are close to 100%. The second drive side shaft 412 is coupled with the second load side shaft 432 through the second coupling 442, and the second intermediate transmission structure 422 is composed of a pair of cylindrical gears with a transmission ratio less than 1. The overall transmission ratio of the shunt transmission path 4 is also 1, but the forward and reverse transmission efficiencies are lower than those of the first transmission path 3. The drive side node structure 52 adopts a bevel gear transmission structure, and the load side node structure adopts a worm gear structure 62.

[0068] In this embodiment, i2 is designed to be 3, k 12 Take 2, k 1s Take 0.3, design the worm gear to be self-locking, design i1 to be 1, and the rest are the same as in Example 2. Substitute the deformation coordination equation to calculate that the total forward transmission efficiency of the mechanism is about 97%, and the reverse transmission efficiency is about 23%.

[0069] In addition, the transmission efficiency of the synchronous belt transmission component is about 98%, the forward and reverse transmission efficiencies of the ball screw are about 95% and 90% respectively, and the transmission efficiency of the steering shaft 601 is about 95%. The overall forward transmission efficiency of the steering system involved in this embodiment is about 85%, and the reverse transmission efficiency is about 20%, which meets the ideal design requirements of high forward transmission efficiency and low reverse transmission efficiency. In actual engineering, various parameters can be designed, adjusted and iterated through theoretical calculations and tests, and finally achieve characteristics suitable for the requirements of the vehicle, meeting the different requirements of different vehicles for the steering system.

[0070] In this specification, the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the embodiments described later, the description is relatively simple, and the relevant parts can be referred to the partial description of the previous embodiments.

[0071] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for designing an asymmetric efficiency transmission system, characterized in that: The steps include: S1, constructing a main transmission path model having a first drive-side shaft component and a first load-side shaft component, wherein the torsional stiffness of the first drive-side shaft component is k1; S2, constructing a split transmission path model having a second drive-side shaft component and a second load-side shaft component, wherein the torsional stiffness of the second drive-side shaft component is k2, k2>k1; S3. Construct a parallel node model of the main and branch transmission paths, wherein the first and second drive-side shaft components are connected by a node transmission structure, and the first and second load-side shaft components are connected by a worm gear transmission structure and an axial constraint stiffness of k s The second load-side shaft is used as a worm shaft; S4. The deformation coordination equation is established by combining the stiffness parameters and transmission parameters of each model to obtain the relationship between the total forward and reverse transmission efficiency of the system and the above parameters. Based on this, the actual stiffness characteristics and transmission characteristics of each model are selected and designed until the target value of the system transmission efficiency is obtained.

2. The asymmetric efficiency transmission system design method according to claim 1, characterized in that: The second load-side shaft component includes a second load-side shaft and a second intermediate transmission structure assembled on the second load-side shaft, wherein the second intermediate transmission structure is located between the node transmission structure and the worm gear transmission structure along the transmission path.

3. The asymmetric efficiency transmission system design method according to claim 1 or 2, characterized in that: The forward transmission efficiency of the worm gear transmission structure does not exceed 50% and the reverse transmission efficiency does not exceed 10%.

4. The asymmetric efficiency transmission system design method according to claim 2, characterized in that: Add the following steps between S3 and S4, and use the following formula to calculate the equivalent torsional stiffness k' generated by the axial constraint stiffness of the worm shaft on the corresponding worm wheel shaft s ; k' s =R 2 k s ; Where R is the pitch circle diameter of the worm gear.

5. The asymmetric efficiency transmission system design method according to claim 4, characterized in that: In S4, the relationship between the total forward and reverse transmission efficiency of the system and the model stiffness parameters and transmission parameters obtained according to the deformation coordination equation is as follows: Wherein, η is the total forward transmission efficiency of the system, η' is the total reverse transmission efficiency of the system, i1 represents the transmission ratio of the main transmission path, i2 represents the transmission ratio of the node transmission structure, η1 and η'1 are the forward and reverse transmission efficiencies of the main transmission path, η2 and η'2 are the forward and reverse transmission efficiencies of the node transmission structure, η3 and η'3 are the forward and reverse transmission efficiencies of the second intermediate transmission structure, η4 and η'4 are the forward and reverse transmission efficiencies of the worm gear structure, 6. The asymmetric efficiency transmission system design method according to claim 1, characterized in that: The second drive side shaft component includes a second drive side shaft and a second coupling installed at the output end of the second drive side shaft. The second drive side shaft is coupled to the second load side shaft component through the second coupling. The torsional stiffness of the second drive side shaft component is adjusted by selecting the torsional stiffness parameters of the second coupling.

7. The asymmetric efficiency transmission system design method according to claim 1 or 6, characterized in that: The first drive side shaft component includes a first drive side shaft and a first coupling installed at the output end of the first drive side shaft. The first drive side shaft is coupled to the first load side shaft component through the first coupling. The torsional stiffness of the second drive side shaft component is adjusted by selecting the torsional stiffness parameters of the first coupling.

8. The asymmetric efficiency transmission system design method according to claim 5, characterized in that: In S4, under the condition that the transmission ratios i1, i2 and the torsional stiffness k1 are determined, only the torsional stiffness k2 is adjusted until the ideal total forward transmission efficiency of the system is obtained.

9. The asymmetric efficiency transmission system design method according to claim 5, characterized in that: In S4, under the condition that the transmission ratios i1, i2 and torsional stiffness k1 are determined, only the axial constraint stiffness k s Adjustments are made until an ideal total forward transmission efficiency of the system is obtained; in S3, the axial constraint stiffness of the worm shaft is greater than the torsional stiffness of the worm wheel shaft.

10. The asymmetric efficiency transmission system design method according to claim 1, characterized in that: In S3, the first load-side shaft component includes a first load-side shaft and a first intermediate transmission structure assembled on the first load-side shaft, wherein the first intermediate transmission structure is located between the node transmission structure and the worm gear transmission structure along the transmission path.

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