Transmission mechanism for steering control

Abstract

The utility model provides a transmission mechanism for steering control. The transmission mechanism comprises a worm, a sector-ring-shaped worm gear, a steering output shaft, a shell, a guide flat key, a gap adjusting screw and a worm gear fastening screw. The worm is axially fixed in the shell through a thrust angular contact ball bearing, and the sector-ring-shaped worm gear and the shell form a radial sliding pair through a guide flat key and is adjustably fixed to the end of the steering output shaft through a worm gear fastening screw. The worm gear is of a sector-ring-shaped structure (preferably 120 degrees), a key groove matched with the guide flat key is formed in the inner surface, and conical surface counter bores are formed in the two ends and are in sliding fit with the conical head of the gap adjusting screw. The clearance adjusting screw is screwed in to push the worm gear to move in the radial direction, and precise adjustment of the meshing clearance of the worm gear and the worm is achieved in combination with the limiting effect of the guide flat key. The clearance control device has the advantages of being compact in structure, convenient and fast to adjust, low in cost and the like, and has the performance characteristic of completely meeting the steering performance requirement of an automobile steering system on clearance control in the aspect of steering control transmission.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of vehicle steering system especially relates to a transmission mechanism for steering control. BACKGROUND

[0002] The development trend of steering technology is the electric power steering system of pure electric power.

[0003] At present, the electric power steering system (EPS) has been gradually popularized in the field of passenger cars, but it has not been widely used in the field of commercial vehicles. This is because the traditional commercial vehicle steering gear generally adopts a circulating ball screw nut + rack and pinion type steering gear deceleration and torque increasing power transmission mechanism. The circulating ball screw nut transmission pair has a steering force output limit and cannot meet the demand of commercial vehicles for large steering force. The output torque of the circulating ball type commercial vehicle pure electric steering gear today is between 1500Nm and 1800Nm, which can only be used on light trucks and micro commercial vehicles. It cannot meet the demand of medium and heavy commercial vehicles for large steering force. In order to solve this problem, a large torque electric power steering system suitable for commercial vehicles, i.e. commercial vehicle electric power steering system (CV-EPS), must be developed.

[0004] The planetary gear type electric steering in the prior art discards the structure of the existing traditional circulating ball steering gear and innovatively realizes large torque output of pure electric steering with a planetary gear deceleration mechanism with high bearing capacity. Its characteristics are: a planetary gear type transmission mechanism is used to realize large torque steering assistance, a worm and worm gear transmission mechanism is used to realize steering control. Steering control and steering assistance are independent of each other. The driving force of the assistance motor does not pass through the worm and worm gear transmission mechanism, so that the worm and worm gear transmission mechanism is subjected to small force and has small wear during use, thereby being able to maintain precise steering control performance for a long time.

[0005] To maintain the precise steering control performance of the worm and worm gear transmission mechanism, the premise is that the worm and worm gear transmission mechanism for steering control originally has the characteristics of small meshing clearance (tending to zero clearance), small idle stroke and good control precision follow-up after the product assembly is completed.

[0006] However, the machining and manufacturing errors of parts are unavoidable, and the meshing clearance also inevitably exists. The clearance will have an idle stroke of control transmission, which will inevitably affect the precise control of the steering gear. UTILITY MODEL CONTENTS

[0007] The utility model aims at providing a transmission mechanism for steering control, specifically a worm and worm gear transmission mechanism with adjustable center distance. The mechanism can compensate for the meshing clearance caused by the machining error of parts, ensure that the transmission mechanism maintains small clearance and high precision for a long time, realize precise control, and meet the steering performance requirements of medium and heavy commercial vehicles.

[0008] The utility model discloses a transmission mechanism for steering control, it is characterized by including worm, worm wheel, casing, guide flat key, clearance adjustment screw and worm wheel fastening screw, the worm is axially fixed in the casing through a pair of thrust angular contact ball bearing, the worm wheel forms radial slidable connection with steering output shaft through guide flat key, the worm wheel fastening screw realizes adjustable fixing of worm wheel and output shaft through the radial clearance hole that sets up on the worm wheel, clearance adjustment screw realizes meshing clearance adjustment through the conical surface cooperation structure drive worm wheel.

[0009] Further, the worm wheel is a fan ring structure.

[0010] Further, the central angle of the worm wheel is preferably 120°.

[0011] Further, a plurality of radial clearance holes are provided on the worm wheel, and the radial clearance hole is a circular hole with a diameter greater than the outer diameter of the worm wheel fastening screw.

[0012] Further, the radial clearance hole is a waist-shaped slot hole in the same direction as the guide flat key.

[0013] Further, a semicircular hole is provided at the left and right ends of the worm wheel, and the semicircular hole is a conical counterbore.

[0014] Further, the clearance adjustment screw is an internal hexagon countersunk screw, and the conical surface on the side of the head of the internal hexagon countersunk screw is matched with the conical surface of the semicircular hole, and the internal hexagon countersunk screw is rotated to push the worm wheel radially.

[0015] The transmission mechanism for steering control has the following beneficial effects:

[0016] The sliding pair structure of the guide flat key and the worm wheel key groove, combined with the conical surface pushing effect of the clearance adjustment screw, realizes the radial position fine adjustment of the worm wheel relative to the worm, can effectively eliminate the problem of too large meshing clearance caused by machining error, and improves the transmission precision. The radial clearance design between the worm wheel fastening screw and the worm wheel fixing hole, and the waist-shaped hole optional structure allow the worm wheel to freely slide during adjustment, simplify the assembly process and ensure reliable locking after adjustment. The clearance adjustment screw adopts the cooperation of the internal hexagon countersunk screw and the worm wheel conical counterbore, through the linear control of the screw rotation depth, ensures that the both ends of the worm wheel are offset synchronously and equidistantly, and avoids the problem of uneven meshing caused by unilateral deflection. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description, and the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained from the structures shown in these drawings without creative labor.

[0018] Figure 1 The structural schematic diagram of the steering control transmission mechanism of the present application is shown in the figure.

[0019] Figure 2 The worm gear and guide key mounting structure schematic diagram of the present application is shown in the figure.

[0020] Figure 3 The gap adjustment screw structure schematic diagram of the worm gear of the present application is shown in the figure.

[0021] Figure 4 The Figure 3 The K-K cross-sectional view schematic diagram is shown in the figure.

[0022] Figure 5 The worm gear fastening screw mounting hole structure schematic diagram of the present application is shown in the figure.

[0023] In the figure, 1 is a steering output shaft, 2 is a gap adjustment screw, 3 is a worm gear, 4 is a guide key, 5 is a worm gear fastening screw, 6 is a housing, 7 is a thrust angular contact ball bearing, 8 is a worm, and 9 is a guide key fixing screw. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all the embodiments. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0025] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0026] As Figures 1-5 shown, a transmission mechanism for steering control includes a worm 8, a worm gear 3, a steering output shaft 1, a guide key 4, a gap adjustment screw 2, a worm gear fastening screw 5, a housing 6 and other parts.

[0027] The housing 6 provides support and protection for the internal moving mechanism parts, a pair of thrust angular contact ball bearings 7 are arranged at both ends of the worm 8 and are placed inside the housing 6; the housing 6 is internally provided with bearings for fixing and positioning the steering output shaft 1. The worm 8 and the steering output shaft 1 are both axially fixed and can only rotate around the axis. The steering hand torque of the steering control can be transmitted from the worm input to the worm gear 3 engaged with the worm; the worm gear 3 is fixedly connected with the output shaft 1 as a whole, and the torque transmitted to the worm gear 3 is transmitted to the output shaft 1 through the worm gear fastening screw 5 between the worm gear 3 and the output shaft 1.

[0028] The output shaft 1 is a special-shaped shaft part, one end of which is provided with a tapered external spline for connecting with a steering drop arm, and the other end has a frame-type planet carrier structure; the frame-type planet carrier on the output shaft 1 is a structural component of the last-stage planetary gear transmission mechanism. The large steering assist torque transmitted by the steering assist motor is transmitted to the output shaft 1 through the last-stage planetary gear transmission mechanism and the frame-type planet carrier structure after being reduced and increased in torque.

[0029] The worm gear 3 is fixed on the frame-type planet carrier structure end face of the output shaft 1 through the worm gear fastening screw 5. The worm gear 3 part is not a complete circular ring shape, but a sector ring structure, because of the characteristics of the commercial vehicle steering gear: the rotation angle of the steering gear output shaft is about ±45°, and the preferred embodiment adopts a sector ring worm gear structure with a central angle of 120°, which effectively reduces the volume and weight of the part, and one blank can process three sector ring worm gears, thereby reducing the product manufacturing cost.

[0030] The frame-type planet carrier structure at the end of the steering output shaft 1 in the embodiment has four upright columns and two side plates, the lower side plate extends downward to form a torque output end, and the upper side plate is provided with corresponding screw holes for screwing the worm gear fastening screw 5 and the clearance adjusting screw 2. A key groove is formed on the matching surface between the worm gear 3 and the upper side plate of the frame-type planet carrier, a guide flat key 4 is arranged in the key groove between the worm gear 3 and the upper side plate, and a guide flat key fixing screw 9 is used to fix the guide flat key 4 on the upper side plate of the frame-type planet carrier. The worm gear 3 can slide radially relative to the steering output shaft 1 along the direction of the guide flat key 4, so as to facilitate the adjustment of the meshing clearance between the worm gear 3 and the worm 8.

[0031] Four fixing holes for pressing the worm gear are formed on the worm gear 3 in the embodiment, and the fixing holes are used for screwing the worm gear fastening screw 5. There needs to be a suitable radial gap between the fixing holes on the worm gear 3 and the worm gear fastening screw, so as to ensure that the worm gear 3 has enough sliding distance when adjusting the meshing clearance with the worm 8. The fixing holes for pressing the worm gear on the worm gear 3 can be formed into circular holes with enough radial clearance, or can be formed into waist-shaped strip holes, as long as there is enough adjustment gap in the sliding direction.

[0032] The left and right ends of the worm wheel 3 are respectively provided with a semicircular hole, which is a tapered counterbore. The semicircular hole is used to cooperate with the gap adjusting screw 2 and adjust the gap between the left and right ends of the worm wheel 3. The worm wheel fastening screw 5 is an internal hexagonal flat round head screw; the gap adjusting screw 2 is an internal hexagonal countersunk head screw. The side surface of the head of the internal hexagonal countersunk head screw is a tapered surface, which is in contact with the tapered counterbore of the semicircular hole at the left and right ends of the worm wheel 3.

[0033] When the gap adjusting screw 2 is screwed downward, the tapered surface of the side surface of the gap adjusting screw 2 pushes and extrudes the tapered counterbore of the semicircular hole at the left and right ends of the worm wheel 3. The left and right ends of the worm wheel 3 are also pushed and extruded outward. The circular ring-shaped worm wheel 3 is like a lever with the middle position contact point O as a fulcrum. By adjusting the screwing depth of the gap adjusting screw 2, the distance between the left and right ends of the worm wheel 3 and the axis of the worm 8 is ensured to be equal. The worm wheel 3 is completely positioned. Finally, the worm wheel fastening screw 5 is compressed to complete the center distance adjustment assembly of the worm and worm wheel transmission mechanism.

[0034] In the assembly of the steering control transmission mechanism, the worm 8 and the steering output shaft 1 are assembled in place to ensure that the shaft does not move axially and can rotate flexibly. The guide flat key 4 is embedded in the key groove on the upper side plate and fixed by the guide flat key fixing screw 9. Then the key groove of the worm wheel 3 is aligned with the guide flat key 4, and the worm wheel 3 is buckled on the upper side plate of the frame type planetary carrier of the steering output shaft 1. The worm wheel fastening screw 5 is screwed in to preliminarily fix the worm wheel 3 without compression. When adjusting the meshing gap between the worm wheel 3 and the worm 8, the worm wheel 3 is pushed radially outward along the direction of the guide flat key 4. When the pitch circle of the worm wheel 3 is in contact with and tangent to the cylindrical pitch surface of the worm 8, it is exactly zero gap cooperation. The center distance formed by the zero gap cooperation between the worm wheel 3 and the worm 8 is equal to the center distance formed between the bearing holes of the housing. By adjusting the center distance between the worm wheel 3 and the worm 8 in the radial sliding manner, the inevitable cooperation gap caused by the machining errors of the worm wheel 3, the worm 8 and the housing 6 can be eliminated.

[0035] In the above embodiments, the basic principles and main features of the utility model and the advantages of the utility model are described. It should be understood by those skilled in the art that the utility model is not limited by the above embodiments, and the above embodiments and descriptions in the specification are only to illustrate the principles of the utility model. Without departing from the spirit and scope of the utility model, the changes and modifications made by those skilled in the art do not deviate from the spirit and scope of the utility model, and should be within the protection scope of the claims of the utility model.

Claims

1. A transmission mechanism for a steering maneuver, characterized in that The invention discloses a worm gear steering mechanism, which comprises a worm (8), a worm wheel (3), a housing (6), a steering output shaft (1), a guide flat key (4), a gap adjusting screw (2) and a worm wheel fastening screw (5).

2. A transmission mechanism for steering manoeuvres according to claim 1, characterised in that The worm wheel (3) is a fan ring structure.

3. A transmission mechanism for steering manoeuvres according to claim 1, characterised in that The central angle of the worm wheel (3) is 120°.

4. A transmission mechanism for steering manoeuvres according to claim 1, characterised in that The worm wheel (3) is provided with a plurality of radial gap holes, which are circular holes with a diameter larger than the outer diameter of the worm wheel fastening screw (5).

5. A transmission mechanism for steering manoeuvres according to claim 1, characterised in that The radial gap holes are waist-shaped strip holes with the same direction as the guide flat key (4).

6. A transmission mechanism for steering manoeuvres according to claim 1, characterised in that The left and right ends of the worm wheel (3) are provided with a semicircular hole, which is a tapered counterbore.

7. A transmission mechanism for steering manoeuvres according to claim 6, characterised in that The gap adjusting screw (2) is an internal hexagon countersunk screw, which is matched with the tapered surface of the semicircular hole through the tapered surface of the side of the internal hexagon countersunk screw head, and the internal hexagon countersunk screw is rotated to push the worm wheel (3) to move radially.

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