Steering system for rotating a steerable wheel

Abstract

A steering system for rotating a steerable wheel includes a gear located in a housing and rotatable relative to the housing by an electric motor. A planetary gear stage is located in the housing and has a sun gear, a planetary gear engaged with the sun gear, and a carrier connected to the planetary gear. Rotation of the gear causes rotation of the sun gear about an axis. Rotation of the sun gear causes planetary gears to rotate relative to the housing and revolve about the sun gear. The carrier is urged to rotate about the axis in response to the planetary gear rotating relative to the housing and rotating about the sun gear. The first bearing has a first ring on the gear and a second ring on the bracket. The gear and the support are rotatably supported in the shell through the first bearing.

Description

Technical Field

[0001] The invention relates to a steering system for turning a steerable wheel. Background Art

[0002] A known vehicle steering system includes a gearbox and a motor. The gearbox includes an output shaft that is rotatable to cause rotational movement of a steerable wheel. A pinion gear is operably connected to the output shaft such that rotation of the pinion gear about an axis of rotation causes the output shaft to rotate. The pinion gear is rotatably supported in the gearbox on two ball bearings that are aligned along the axis of rotation of the pinion gear. A steering column connects the pinion gear to a vehicle steering wheel.

[0003] In addition, the motor can be operated to cause the rotation of the output shaft to provide steering assistance. The motor is operably connected to the output shaft through one or more planetary gear stages installed in the gearbox. The output shaft of the motor, the output shaft and each planetary gear stage are aligned along a single axis in the gearbox. A steering system with this general structure is disclosed in U.S. Patent No. 11,498,616. Summary of the invention

[0004] According to one aspect of the present invention, alone or in combination with any other aspect, a steering system for turning a steerable wheel includes a housing and an electric motor. The gear is located in the housing and can be rotated relative to the housing by the electric motor. A planetary gear stage is located in the housing. The planetary gear stage has a sun gear, a planetary gear meshing with the sun gear, and a bracket connected to the planetary gear. The rotation of the gear causes the sun gear to rotate about an axis. The rotation of the sun gear causes the planetary gear to rotate relative to the housing and revolve around the sun gear. The bracket is caused to rotate about the axis in response to the planetary gear rotating relative to the housing and revolving around the sun gear. The first bearing has a first ring on the gear and a second ring on the bracket. The gear and the bracket are rotatably supported by each other in the housing through the first bearing. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The above and other features and advantages of the present invention will become apparent to those skilled in the art after reading the following description with reference to the accompanying drawings, in which:

[0006] Figure 1 is a schematic rear view of an example steering system for turning a steerable wheel;

[0007] Figure 2 yes Figure 1 Rear view of the EPS unit of the steering system;

[0008] Figure 3 is along Figure 2 A cross-sectional view taken along line 3-3 of ;

[0009] Figure 4 yes Figure 3 an enlarged view of a portion 4;

[0010] Figure 5 yes Figure 3 an enlarged view of a portion 5;

[0011] Figure 6 yes Figure 2 A cross-sectional view of a portion of an EPS unit;

[0012] Figure 7 yes Figure 2 An exploded view of a portion of an EPS unit;

[0013] Figure 8 yes Figure 2 A front perspective view of components of an EPS unit;

[0014] Fig. 9 yes Figure 6 an enlarged view of portion 9 of ; and

[0015] Fig.10 is along Figure 2 A cross-sectional view taken along line 10-10. DETAILED DESCRIPTION

[0016] The invention relates to a steering system for turning a steerable wheel. Figure 1 An example steering system 10 for turning a steerable wheel 12 is schematically shown. The steering system 10 may be used, for example, in a commercial vehicle. The steering system 10 includes an input shaft 14 and an electric power steering unit (“EPS unit”) 16 for providing steering assistance. The input shaft 14 extends from a first end 18 to a second end 20 ( Figure 3 ). The steering wheel 22 is connected to the first end 18. For example, the steering wheel 22 can be connected to the first end 18 via a steering column, one or more shafts, one or more joints (e.g., a universal joint), or any combination thereof. The pinion 24 ( Figure 3 ) is connected to the second end 20 or is disposed on the second end 20. The rotation of the steering wheel 22 transmits the torque to the pinion 24 through the input shaft 14. In other words, the pinion 24 is forced to rotate under the influence of the torque transmitted through the input shaft 14.

[0017] The steering linkage 26 is connected to the steerable wheels 12. As shown, the steering linkage 26 includes a first steering member 28, a second steering member 30, and a third steering member 32. The first steering member 28 is connected to an output shaft 34 of the EPS unit 16. The first steering member 28 may be, for example, a steering drop arm. The second steering member 30 is connected to the first steering member 28 and may be, for example, a tie rod. The third steering member 32 is connected to the second steering member 30 and one of the steerable wheels 12. The third steering member 32 may be, for example, a steering arm.

[0018] The EPS unit 16 provides steering assistance by causing movement of the steering linkage 26 (and therefore the steerable wheels 12) in response to rotation of the steering wheel 22. Figure 2 , the EPS unit 16 includes an electric motor 36 (eg, a reversible electric motor) and a gearbox 38 connected to the motor.

[0019] like Figure 3 As shown, the gearbox 38 has a housing 40 in which the pinion 24 is rotatably supported. The housing 40 can be formed as a single integral piece or assembled from separate sub-components. A cover 42 is connected to the housing 40 and receives the input shaft 14 in a manner that allows relative rotation therebetween. Thus, the first end 18 of the input shaft 14 can be located outside the housing 40, while the second end 20 can be located inside the housing 40. The torsion bar 44 and the output shaft 46 help to transfer the rotation of the second end 20 of the input shaft 14 to the pinion 24. The input shaft 14, the torsion bar 44, and the output shaft 46 can be coaxial with each other.

[0020] The torsion bar 44 extends inside the input shaft 14 and the output shaft 46. A first end 48 of the torsion bar 44 is fixed for rotation with the input shaft 14, and a second end 50 of the torsion bar is fixed for rotation with the output shaft 46. When the input shaft 14 is rotated by the steering wheel 22, the torsion bar 44 allows a specified amount of relative rotation between the input shaft and the output shaft 46, and the input shaft and the output shaft then rotate together.

[0021] The output shaft 46 has a first end 52 that extends into the second end 20 of the input shaft 14. The second end 54 of the output shaft 46 extends into a recess 56 of the pinion gear 24. The second end 54 can be engaged with the pinion gear 24 (e.g., by a spline) so that rotation of the output shaft 46 is transmitted to the pinion gear. Therefore, rotation of the output shaft 46 correspondingly causes or prompts the pinion gear 24 to rotate relative to the housing 40 about the pinion gear's axis of rotation A1 (also referred to herein as the "first axis of rotation") .

[0022] The first end 58 and the second end 60 of the pinion 24 are rotatably supported in the housing 40 by bearings 62, 64, respectively. Each bearing 62, 64 is a tapered roller bearing having an inner race or cone 66 that circumferentially engages the pinion 24, an outer race or cup 68 that circumferentially engages the inner surface of the housing 40 or the inner surface in the housing 40, and a plurality of tapered rollers 70 radially interposed between the cone and the cup. The cone 66 is rotatably fixed to the pinion 24, and the cup 68 is rotatably fixed to their respective inner surfaces. Therefore, when the pinion 24 rotates relative to the housing 40, the cone 66 can rotate relative to the cup 68. Each bearing 62, 64 may also include a cage 72 for its corresponding tapered roller 70. Although each bearing 62 , 64 is shown as a tapered roller bearing, at least one of the bearings 62 , 64 may be any other desired bearing such as, for example, a ball bearing, an angular contact ball bearing, a spherical roller bearing, a cylindrical roller bearing, and a needle bearing.

[0023] The preload of each bearing 62, 64 can be adjusted by a bearing adjuster 74. Figure 3 to Figure 4 As shown, the bearing adjuster includes external threads 76 for threaded engagement with internal threads 78 of the housing 40. The bearing adjuster 74 can be substantially cylindrical such that at least one of the first end 58 of the pinion 24 and the second end 54 of the output shaft 46 can extend into and / or through the bearing adjuster 74.

[0024] The bearing adjuster 74 may contact or come into contact with the cup 68 of the bearing 62. When in contact with the cup 68, screwing in / tightening the bearing adjuster 74 (i.e., driving the bearing adjuster toward the bearing 64) causes the cup 68 of the bearing 62 to move toward the other bearing 64 relative to the cone 66 of the bearing 62. This relative movement reduces one or more clearances between the elements of the bearing 62 and, therefore, increases the preload of the bearing 62. Conversely, screwing out / loosening the bearing adjuster 74 (i.e., driving the bearing adjuster away from the bearing 64) increases the clearance and reduces the preload of the bearing 62.

[0025] Threading in / tightening the bearing adjuster 74 also causes the pinion 24 to move along the first rotational axis A1 toward the bearing 64 through the bearing 62. This movement causes the cone 66 of the bearing 64 to move away from the bearing 62 relative to the cup 68 of the bearing 64, which reduces one or more clearances between the elements of the bearing 64 and increases the preload of the bearing 64. Conversely, threading out / loosening the bearing adjuster 74 increases the clearance and reduces the preload of the bearing 64.

[0026] The amount of torque required to rotate the pinion 24 about its axis of rotation A1 corresponds, at least in part, to the level of preload in the bearings 62, 64. In particular, increasing the preload increases the amount of torque required to rotate the pinion 24. This is because as the preload in the bearings increases, the friction between the elements of the bearings 62, 64 also increases.

[0027] Thus, the bearing preload and the "rotational torque" of the pinion can be set or adjusted as desired by screwing in / tightening or unscrewing / loosening the bearing adjuster 74. In certain gearbox 38 configurations, it may be beneficial for the pinion 24 to have a relatively high rotational torque value. This is at least in part because having a high rotational torque value and preload reduces the amount of noise, vibration, and / or harshness ("NVH") in the gearbox 38. For example, when the bearings 62, 64 have a high preload, the pinion 24 can be substantially prevented from being undesirably pushed axially (e.g., along its rotational axis A1) in response to a change in the rotational direction of the pinion and / or in response to an impact force. The pinion 24 that is pushed axially has the potential to cause or increase NVH in the gearbox.

[0028] However, in other gearbox configurations, such as the gearbox 38 configuration shown in the figures, relatively low rotational torque values ​​are desirable. The gearbox 38, as a low rotational torque system, may include features for reducing NVH. For example, Figure 3 to Figure 4 As shown, the gearbox 38 may include a resilient element 80 located in the recess 56 of the pinion 24. The resilient element 80 extends between the bottom 82 of the recess 56 and the second end 54 of the output shaft 46. Although the resilient element 80 directly contacts each of the pinion 24 (e.g., at the bottom 82 of the recess 56) and the output shaft 14, some gearbox 38 configurations may include one or more intermediate elements between the resilient element and at least one of the pinion and the output shaft. The resilient element 80 may be a wave spring, a coil spring, or any other suitable spring.

[0029] The resilient element 80 may be at least partially compressed between the pinion 24 and the output shaft 46 such that the resilient element applies a predetermined axial force to the pinion in a direction away from the output shaft. The axial loading of the pinion 24 reduces / damps any axial movement of the pinion. Damping the axial movement of the pinion 24 eliminates NVH in the gearbox 38 or at least reduces it to an acceptable level without increasing the preload of the bearings and / or the rotational torque value of the pinion 24.

[0030] like Figure 3As shown, the pinion 24 can be in the form of or include a worm shaft that is meshed to a worm gear 84 such that rotation of the pinion correspondingly rotates or causes the worm gear to rotate relative to the housing 40. The worm gear 84 can be operatively connected to the output shaft 34. Thus, rotation of the steering wheel 22 transmits torque to the output shaft 34 through the input shaft 14, the pinion 24, and the worm gear 84. Thus, the output shaft 34 can rotate or be forced to rotate under the influence of the torque originating from the steering wheel 22.

[0031] The pinion 24 can be pressed toward the worm gear 84 by the pressurizing device 86 of the gear box 38. Figure 3 and Figure 5 As shown, the pressurizing device 86 includes a reaction plate 88, an elastic element 90, and a plunger 92 inserted into a recess 94 of the housing 40. One side of the reaction plate 88 abuts against a first shoulder 96 of the housing 40, and the other side abuts against a cover 98 that closes the recess 94. The reaction plate 88 may include an external thread for threadedly engaging an internal thread of the housing 40. Therefore, undesired movement of the reaction plate 88 relative to the housing 40 is substantially prevented.

[0032] The resilient element 90 extends between the reaction plate 88 and the plunger 92. Although the resilient element 90 directly contacts each of the reaction plate 88 and the plunger 92, some pressurizing device 86 configurations may include one or more intermediate elements between the resilient element and at least one of the reaction plate and the plunger. The resilient element 90 may be a wave spring, a coil spring, or any other suitable spring.

[0033] The plunger 92 is movable in the recess 94 relative to the housing 40. For example, the plunger 92 can move along the recess 94 toward and away from the worm gear 84 in a direction transverse to the first rotational axis A1. However, the geometry of the recess 94 / housing 40 and the plunger 92 can be configured to substantially limit the movement of the plunger in a direction transverse to the first rotational axis A1. In addition, these movements of the plunger 92 can be constrained on one end by the reaction plate 88 and on the other end by the second shoulder 100 of the housing 40.

[0034] The plunger 92 includes a first recess 102 that faces substantially in a direction transverse to the first rotation axis A1. The resilient element 90 is located in the first recess 102 (e.g., completely within the first recess 102). At least one of the reaction plate 88 and the cover 98 may also extend into the first recess 102. The resilient element 90 is at least partially compressed between the reaction plate 88 and the plunger 92, so that the resilient element provides a pressure (generated by the internal bias of the resilient element) to the plunger, which urges the plunger away from the reaction plate.

[0035] The plunger 92 also includes a second recess 104 that faces substantially in the direction of the first axis of rotation A1. The cup 68 of the bearing 64 circumferentially engages the inner surface of the plunger 92 in the second recess 104 so that the bearing 64 moves with the plunger toward and away from the worm gear 84. Thus, the bearing 64 takes the form of a "floating bearing" that can move toward and away from the worm gear 84 in a direction transverse to the first axis of rotation A1. On the other hand, the bearing 62 is a "fixed bearing" because it is mounted in the housing 40 so that it is substantially prevented from moving relative to the housing 40 toward and away from the worm gear 84.

[0036] The pressure of the elastic element 90 urges the plunger 92 and the bearing 64 to move away from the reaction plate 88 and toward the worm gear 84. The second end 60 of the pinion 24 supported by the bearing 64 is pushed toward the worm gear 84 by the bearing 64. When the second end 60 is pushed toward the worm gear 84, the second end 60 pivots toward the worm gear about the pivot axis 106 defined by the bearing 62 until the pinion 24 is in close mesh with the worm gear. Therefore, the pressure generated by the elastic element 90 causes or urges the second end 60 of the pinion 24 to pivot about the pivot axis 106 until the pinion is in close mesh with the worm gear 84.

[0037] Because bearing 64 moves relative to housing 40 under pressure, bearings 62, 64 are intentionally misaligned (i.e., not coaxial) by at least a small amount when pinion 24 and worm gear 84 are tightly meshed. For example, cup axis 108 of cup 68 of bearing 64 may be offset relative to cup axis 110 of bearing 62 ( Figure 4 ) is offset in a direction transverse to the first rotation axis A1. In addition, due to its pivoting movement, the rotation axis A1 of the pinion 24 is at a non-zero angle relative to the cup axis 110 of the bearing 62.

[0038] The mounting arrangement of the bearings 62, 64 may be selected based on their intended misalignment. In other words, it may be beneficial to arrange the bearings 62, 64 in a manner that is relatively insensitive to bearing misalignment. An example of such a mounting arrangement is a direct mounting arrangement. Figures 3 to 5 As shown, the bearings 62, 64 can therefore be arranged in a direct mounting arrangement. Thus, each bearing 62, 64 is arranged so that the small end 112 of its tapered roller 70 points "outwardly" or away from the other bearing 62, 64.

[0039] The torque transmitted from the steering wheel 22 to the pinion 24 can generate a separation force between the pinion 24 and the worm wheel 84, which causes the pinion to pivot away from the worm wheel. The pressure of the elastic element 90 is configured to overcome the low separation force (i.e., a separation force equal to or lower than the predetermined separation force) and keep the pinion 24 tightly engaged to the worm wheel 84. Steering wheel torque equal to or lower than the predetermined torque can generate a low separation force. Therefore, when the steering wheel torque is equal to or lower than the predetermined torque, the pinion 24 and the worm wheel 84 remain tightly engaged. While the steering wheel torque is kept low, the internal stress of the bearings 62, 64 is within an acceptable range due to their misalignment.

[0040] However, the internal stress of the misaligned bearings 62, 64 may increase as the steering wheel torque exceeds the predetermined torque threshold. In order to counteract this potential increase in internal stress, the pressurizing device 86 can be configured so that the pressure of the elastic element 90 is overcome by a high separation force (i.e., a separation force higher than the predetermined separation force). A steering wheel torque higher than the predetermined torque can generate a high separation force. Therefore, these high separation forces cause the pinion 24 (e.g., its second end 60) to pivot at least partially away from the worm gear 84 to a position where the bearings 62, 64 are aligned with each other. In other words, the high separation force causes the second end 60 of the pinion 24 to pivot to a position where the cup-shaped member axes 108, 110 are coaxial. Aligning the bearings 62, 64 at least partially reduces the internal stress of the bearings, and thus helps to keep the internal stress of the bearings within an acceptable range under high steering wheel torque. Due to being pivoted by the high separation force, the rotation axis A1 of the pinion 24 can also be coaxial with the cup-shaped member axes 108, 110, the input shaft 14, the torsion bar 44 and the output shaft 46.

[0041] The gearbox 38 can be configured such that the second end 60 of the pinion gear 24 can only be pivoted away from the worm gear 84 by a disengagement force until the plunger 92 abuts the reaction plate 88. Thus, the maximum distance that the second end 60 of the pinion gear 24 can be pivoted away from the worm gear 84 can be limited by the maximum distance that the plunger 92 can travel toward the reaction plate 88. In addition, the gearbox 38 can be configured such that the cup axes 108, 110 are coaxial when the plunger 92 contacts the reaction plate 88.

[0042] Once the steering wheel torque returns to or below the predetermined torque threshold, the pressure of the resilient element 90 overcomes the separation force and causes the pinion 24 to pivot back into tight mesh with the worm wheel 84. In addition, the pressure can also compensate for wear of the teeth of the pinion 24 and / or the worm wheel 84 by causing the pinion to pivot further toward the worm wheel as the teeth of the pinion and / or the worm wheel wear. Thus, the pressure can maintain tight mesh between the pinion 24 and the worm wheel 84 even if the teeth of the pinion and / or the worm wheel wear.

[0043] The maximum distance that the second end 60 of the pinion 24 can be pivoted toward the worm gear 84 (e.g., to compensate for wear) can be limited by the maximum distance that the plunger 92 can travel toward the worm gear. Thus, the pinion 24 can be pivoted toward the worm gear 84 until the pinion is tightly meshed with the worm gear and / or until the plunger 92 contacts the second shoulder 100.

[0044] although Figures 3 to 5 The gearbox 38 is shown to have both the elastic element 80 and the pressurizing device 86 , but the gearbox 38 may be configured to include only one of the elastic element 80 and the pressurizing device 86 or neither of the elastic element 80 and the pressurizing device 86 .

[0045] like Figures 2 to 3 As shown, the steering system 10 also includes a controller 114 and one or more vehicle condition sensors 116 that cooperate to control the EPS unit 16 based on sensed vehicle conditions. In one example, the vehicle condition sensor 116 may include a torque sensor and / or a position sensor electrically connected to the controller 114. The torque sensor (when provided) senses the torque applied to the steering wheel 22 and generates a signal indicative of the torque. The position sensor (when provided) senses the rotational position of the steering wheel 22 and generates a signal indicative of the steering wheel position. It should be understood that the vehicle condition sensor 116 can be located inside the housing 40 (such as Figure 3 as shown) or outside the housing.

[0046] The signal from the vehicle condition sensor 116 is sent to the controller 114. The controller 114 analyzes the output of the vehicle condition sensor 116 and causes the operation of the motor 36 of the EPS unit 16 based on the output of the sensor. It is also contemplated that only torque measurement or only steering wheel position measurement may be used to cause the operation of the motor 16. The controller 114 may also have inputs that vary based on the sensed lateral acceleration of the vehicle or other vehicle operating conditions. In any case, the signal received by the controller 114 determines the speed and / or torque of the motor 36 and, therefore, determines the output shaft 118 ( Figure 6 ) is transmitted to the gearbox 38 to assist the speed and torque of the steerable wheels 12 in rotating.

[0047] like Figure 6 to Figure 7As shown, the output shaft 118 extends into the gearbox 38 along the second axis of rotation A2 and extends toward the first planetary gear stage 120. The first planetary gear stage 120 includes a sun gear 122 fixed to the output shaft 118 and rotatable therewith. The sun gear 122 is integrally formed with the output shaft 118 as a single unitary piece, but the sun gear can also be formed separately from the output shaft and then attached to the output shaft. The planet gears 124 mesh with the sun gear 122 and mesh with a ring gear 126 that is rotatably fixed in the housing 40. Rotation of the output shaft 118 and the fixed sun gear 122 about the second axis of rotation A2 causes the planet gears 124 to rotate accordingly or causes the planet gears 124 to rotate and orbit around the sun gear (and then around the second axis of rotation) while maintaining the meshing of the planet gears with the ring gear 126. Although three planet gears 124 are shown, the first planetary gear stage 120 can include any number of planet gears.

[0048] The planet gears 124 are rotatably supported on a carrier 128, which rotates about the second rotation axis A2 as the planet gears rotate and orbit around the sun gear 122. The carrier 128 is radially spaced from the housing 40 and is radially positioned between the sun gear 122 and the ring gear 126. The first planetary gear stage 120 can have a gear reduction ratio from the sun gear 122 to the carrier 128, for example, about 3:1 to about 10:1, but the second planetary gear stage can have any desired gear reduction ratio.

[0049] The first planetary gear stage 120 is operably connected to the second planetary gear stage 142 within the housing 40. However, unlike a typical gearbox arrangement, the first planetary gear stage 120 and the second planetary gear stage 142 are not directly connected to each other, nor are they aligned along a single axis. Instead, the first planetary gear stage 120 is operably connected in series with the second planetary gear stage 142 through one or more intermediate gears. Thus, the intermediate gears transfer torque from the first planetary gear stage 120 to the second planetary gear stage 142. In other words, the one or more intermediate gears serve as an intermediary for transferring the rotation of the first planetary gear stage 120 to the second planetary gear stage 142.

[0050] like Figure 6 to Figure 7 As shown, the one or more intermediate gears may include a first intermediate gear 130 fixed to rotate with the bracket 128. Therefore, the first intermediate gear 130 may rotate about the second rotation axis A2 together with the bracket 128. One end of the first intermediate gear 130 opposite to the bracket 128 may be rotatably supported in the housing 40 by a bearing 132 (e.g., a ball bearing).

[0051] The second intermediate gear 134 is rotatably mounted in the housing 40 and meshes with the first intermediate gear 130. Therefore, the rotation of the first intermediate gear 130 correspondingly causes the second intermediate gear 134 to rotate about the third rotation axis A3.

[0052] The third intermediate gear 136 is rotatably supported in the housing 40 by bearings 138, 140. The third intermediate gear 136 is also meshed with the second intermediate gear 134. The rotation of the second intermediate gear 134 correspondingly causes the third intermediate gear 136 to rotate about the fourth rotation axis A4. Although only one intermediate gear 134 is shown between the first intermediate gear 130 and the third intermediate gear 136, the gearbox 38 may include any number of intermediate gears between the first intermediate gear and the third intermediate gear.

[0053] The second planetary gear stage 142 includes a sun gear 144 that is rotatably fixed to the third intermediate gear 136. In particular, the sun gear 144 may include a first end 146 that extends into an opening 148 of the third intermediate gear 136, wherein the first end is engaged with the third intermediate gear in a rotationally fixed manner. Therefore, the sun gear 144 can rotate with the third intermediate gear 136 around the fourth rotation axis A4. The planetary gear 150 is meshed with the sun gear 144 and the teeth 152. The teeth 152 are located on the housing 40 adjacent to the second planetary gear stage 142 and extend circumferentially around the fourth rotation axis A4. Therefore, the teeth 152 are integrally formed with the housing 40 as a single, unitary piece. However, the teeth 152 may be provided on a component (e.g., a ring gear) that is separate from the housing 40 and attached to the housing 40.

[0054] Rotating the sun gear 144 about the fourth axis of rotation A4 correspondingly rotates or causes the planet gears 150 to rotate and orbit about the sun gear (and thus about the fourth axis of rotation) while maintaining meshing with the teeth 152. Although three planet gears 150 are shown, the second planetary gear stage 142 may include any number of planet gears.

[0055] The planet gears 150 are rotatably supported on a bracket 154, which rotates about the fourth rotation axis A4 when the planet gears rotate and revolve around the sun gear 144. The bracket 154 is radially spaced from the housing 40 and is radially positioned between the sun gear 144 and the teeth 152. The second planet gear stage 142 can have a gear reduction ratio from the sun gear 144 to the bracket 154, for example, about 3:1 to about 10:1, but the second planet gear stage can have any desired gear reduction ratio. It should be understood that the gearbox 38 can include additional planet gear stages (not shown) to achieve a desired gear reduction ratio through the gearbox.

[0056] The output shaft 34 is connected to the bracket 154 so that the bracket and the output shaft rotate together about the fourth rotation axis A4 relative to the housing 40. The output shaft 34 can be rotatably supported in the housing 40 by at least one bearing 156. The output shaft 34 extends from the housing 40 and includes a spline 158 external to the housing for connecting to the steering link 26.

[0057] The worm gear 84 is fixed to the bracket 154 of the second planetary gear stage 142 and can rotate therewith about the fourth rotation axis A4. Therefore, the rotation of the steering wheel 22 is transmitted to the output shaft 34 through the pinion 24, the worm gear 84 and the bracket 154. Although the worm gear 84 and its teeth are shown as extending completely around the fourth rotation axis A4 in the circumferential direction, the worm gear can be configured so that the worm gear and / or the teeth of the worm gear extend only partially around the fourth rotation axis in the circumferential direction. For example, the worm gear 84 and / or its teeth can extend about 150 degrees to about 180 degrees around the fourth rotation axis A4 in the circumferential direction, but the worm gear 84 and / or its teeth can be configured to extend any desired degree around the fourth rotation axis.

[0058] like Figures 6 to 8 As shown, the output shaft 34, the worm gear 84 and the bracket 154 are integrally formed into a single, unitary piece to define a one-piece output unit 160 of the gearbox 38. Forming the output shaft 34, the worm gear 84 and the bracket 154 into a single piece helps reduce angular play in the gearbox 38 and eliminates any potential alignment issues between these components that might otherwise occur if they were separate from one another. The bracket 154 (i.e., the bracket portion of the output unit) has a recess 162 into which the sun gear 144 extends. In particular, the sun gear 144 extends through a first portion 162a of the recess 162 along the fourth rotation axis A4 and extends into a second portion 162b of the recess, which may have a smaller diameter than the first portion. The second end 164 of the sun gear 144 may be rotatably supported in the second portion 162b of the recess 162 by a bearing 166 (e.g., a needle bearing) so that the sun gear and the bracket 154 can rotate relative to each other about the fourth rotation axis A4.

[0059] The bracket 154 also includes windows 168 that extend radially through the bracket at intervals in the circumferential direction. The number of windows 168 can be equal to the number of planet gears 150, because each planet gear can be located in a corresponding window, but at least one of the windows can be configured to receive multiple planet gears therein. Therefore, the planet gears 150 extend through the windows 168 so that they mesh with the sun gear 144 in the first portion 162a of the recess 162 and mesh with the teeth 152 that surround the bracket 154 in the circumferential direction. The planet gears 150 are connected to the bracket 154 and are retained in the windows by a shaft 170 that extends through the window 168 in the direction of the fourth rotation axis A4. The shaft 170 can be supported in an opening 172 on the bracket 154.

[0060] The bracket 154 also includes an axial end face 174, which faces the direction away from the third intermediate gear 136 of the fourth rotation axis A4. The output shaft 34 (i.e., the output shaft portion of the output unit 160) extends from the axial end face 174 along the fourth rotation axis A4. Therefore, one end of the output shaft 34 is connected to the bracket 154 (and connected to the worm gear 84 through the bracket), and the other end of the output shaft is located outside the housing. The worm gear 84 (i.e., the worm gear portion of the output unit 160) also extends from the axial end face 174 along the fourth rotation axis A4, so that it at least partially surrounds a portion of the output shaft 34 in the circumferential direction. The worm gear 84, which integrally forms a part of the output unit 160, defines external teeth on the output unit that mesh with the pinion gear. Therefore, in response to the torque from each of the steering wheel 22 and the motor 36, the output unit 160 is caused to rotate around the fourth rotation axis A4.

[0061] refer to Figure 6 and Fig. 9 , the output unit 160 is rotatably supported at one end (e.g., at or near the output shaft 34) by a bearing 156, and rotatably supported at the other end (e.g., at or near the bracket 154) by a bearing 140. In particular, the bearing 156 is a tapered roller bearing having an inner race or cone 66 that circumferentially engages the output shaft 34, an outer race or cup 68 that circumferentially engages the inner surface 176 of the housing 40, and a plurality of tapered rollers 70 radially interposed between the cone and the cup. The cone 66 is rotatably fixed to the output shaft 34, and the cup 68 is rotatably fixed to the inner surface 176. Therefore, when the output shaft 34 rotates relative to the housing 40, the cone 66 can rotate relative to the cup 68. The bearing 156 may also include a cage 72 for its corresponding tapered roller 70. At least a portion of the bearing 156 is located radially between the output shaft 34 and the worm gear 84 , but the bearing may be disposed at any other desired location on the outer shaft.

[0062] The bearing 140 is also a tapered roller bearing having an inner race or cone 66 that circumferentially engages the third intermediate gear 136 (e.g., an outer shoulder 178 of the third intermediate gear), an outer race or cup 68 that circumferentially engages the inner surface 180 of the bracket 154, and a plurality of tapered rollers 70 radially interposed between the cone and the cup. The bearing 140 may also include a retainer 72 for its respective tapered rollers 70. The inner surface 180 of the bracket 154 may define a third portion 162c of the recess 162 that may have a larger diameter than the first portion 162a of the recess. A portion of the third intermediate gear 136 extends into the recess 162 of the bracket 154 so that the inner surface 178 circumferentially surrounds the outer shoulder 180 of the third intermediate gear 136. Thus, the bearing 140 is radially located between the bracket 154 and the third intermediate gear 136. Cone 66 is rotatably fixed to outer shoulder 180 of third intermediate gear 136, and cup 68 can be rotatably fixed to inner surface 180 of bracket 154. In this case, when bracket 154 and third intermediate gear 136 rotate relative to each other, cone 66 and cup 68 rotate relative to each other.

[0063] Thus, the support 154 (and thus the output unit 160) and the third intermediate gear 136 are rotatably supported by each other via the bearing 140. The third intermediate gear 136 is also rotatably supported in the housing 40 via a bearing 138. The bearing 138 is a tapered roller bearing having an inner race or cone 66 that circumferentially engages a support surface 182 in the housing 40, an outer race or cup 68 that circumferentially engages an inner surface 184 of the third intermediate gear 136, and a plurality of tapered rollers 70 radially interposed between the cone and the cup. The bearing 138 may also include a cage 72 for its respective tapered rollers 70. The inner surface 184 of the third intermediate gear 136 may define a portion of the opening 148 of the third intermediate gear. The support surface 182 may be located on a support plate 186 that is inserted into and rotatably fixed in the housing 40. The support plate 186 may be at least partially retained within the housing 40 by a cover 190 and / or by a threaded interface between the support plate and the housing. A portion of the support surface 182 extends into the opening 148 so that the inner surface 184 of the third intermediate gear 136 circumferentially surrounds the support surface. Therefore, the bearing 138 is radially located between the support plate 186 and the third intermediate gear 136. The cone 66 is rotatably fixed to the support surface 182, and the cup 68 is rotatably fixed to the inner surface 184 of the third intermediate gear 136. In this case, when the third intermediate gear 136 rotates relative to the support plate 186, the cup 68 rotates relative to the cone 66.

[0064] In view of the above, it can be understood that the output unit 160 is rotatably supported on the housing 40 via the bearing 156, the third intermediate gear 136 is rotatably supported on the support plate 186 via the bearing 138, and the output unit and the third intermediate gear are rotatably supported by each other via the bearing 140. Therefore, the output unit 160 and the third intermediate gear 136 are mainly supported in the housing 40 via the bearings 138, 140, 156. Although the bearing 166 is radially positioned between the bracket 154 and the sun gear 144, the bearing is not used to support the output unit 160. In fact, in some configurations of the gearbox 38, the bearing 166 can be omitted. In such a configuration, the sun gear 144 can terminate outside the second portion 162b of the recess 162 (for example, the second end 164 of the sun gear can be located in the first portion 162a of the recess), and the second portion of the recess can be completely omitted.

[0065] However, in Figure 6 and Fig. 9 In the illustrated configuration of the gearbox 38, the first end 146 of the sun gear 144 is rotationally fixed to the third intermediate gear 136, and the second end 164 of the sun gear extends into the bracket 154, where it is rotatably supported by a bearing 166, so that the sun gear and the output unit 160 can rotate relative to each other. Extending the sun gear 144 into the bracket helps to keep the output unit 160 and the third intermediate gear 136 aligned on the fourth rotation axis A4. The output unit 160 (e.g., the bracket 154) and / or the third intermediate gear 136 out of alignment may increase the stress on the bearings 138, 140, 156. Therefore, the connection of the sun gear 144 to the bracket 154 via the bearing 166 helps to reduce the stress on the bearings 138, 140, 156 by at least partially keeping the output unit 160 and the third intermediate gear 136 properly aligned. Therefore, the bearing 166 is not used for support purposes like the bearings 138, 140, 156, but is used for alignment and stress purposes.

[0066] It should be understood that although any of the bearings 138, 140, 156 can be a different type of bearing (e.g., a ball bearing, an angular contact ball bearing, a spherical roller bearing, a cylindrical roller bearing, or a needle bearing), there are certain advantages to setting the bearing as a tapered roller bearing. For example, a ball bearing has point contact between its balls and each of the inner and outer rings, while a tapered roller bearing has line contact between the tapered rollers and each of the cone and cup. Line contact provides better stress distribution in the bearing than point contact because the load / stress in the bearing is dispersed over a relatively large area rather than being applied to a single point. In addition, tapered roller bearings are designed to support relatively high axial and radial loads. If the bearings 138, 140, 156 are ball bearings or angular contact ball bearings, they must be much larger than they are currently in order to provide the same axial / radial load support as they provide in the form of tapered roller bearings.

[0067] Typically, the EPS unit 16, or at least its gearbox 38, is mounted to a support structure (e.g., a frame) of the vehicle, between the support structure and one of the steerable wheels 12, such that an axial width 188 of the EPS unit 16 extends between the frame and the steerable wheel. The axial space between the frame and the steerable wheel may be very limited. Therefore, in order to reduce the axial width 188 of the EPS unit 16, the EPS unit splits the motor 36, the output shaft 118, and the first planetary gear stage 120 onto a different axis of rotation than the second planetary gear stage 142 and the output unit 160 via intermediate gears 130, 134, 136. Arranging the motor 36, the output shaft 118, the first planetary gear stage 120, the second planetary gear stage 142, and the output unit 160 on a single axis of rotation will greatly increase the axial width 188 of the EPS unit 16. Therefore, the specific arrangement of the features of the EPS unit 16 results in an axial width 188 that is less than would otherwise be possible.

[0068] In addition, if Figure 7 and Fig.10 As shown, each of the rotational axes A2, A3, A4 may intersect a single alignment axis A5 that extends transversely (e.g., perpendicularly) to each of the rotational axes A2, A3, A4. Due to this alignment, other dimensions of the gearbox 38 (e.g., a depth dimension of the gearbox that is substantially perpendicular to the axial width 188 of the gearbox) may remain relatively small without increasing the axial width. Although the first rotational axis A2, the second rotational axis A3, and the third rotational axis A4 are shown as being parallel to each other, at least one of the rotational axes A2, A3, A4 may be at an angle relative to at least one other of the rotational axes A2, A3, A4 and / or may be offset from the alignment axis A5.

[0069] During operation, the operator rotates the steering wheel 22, thereby causing the pinion 24 to rotate about the first rotation axis A1. This in turn causes the worm gear 84 (and thus the output unit 160) to rotate about the fourth rotation axis A4. At the same time, the controller 114, in response to the signal received from the vehicle condition sensor 116, activates the motor 36 to rotate the output shaft 118 about the second rotation axis A2, which causes the bracket 128 to rotate about the second rotation axis through the sun gear 122 and the planetary gears 124. As a result, the first intermediate gear 130 fixed to the bracket 128 is also caused to rotate about the second rotation axis A2.

[0070] The rotating first intermediate gear 130 causes the second intermediate gear 134 to rotate about the third rotation axis A3, which in turn causes the third intermediate gear 136 to rotate about the fourth rotation axis A4. The sun gear 144, which is rotatably fixed to the third intermediate gear 136, rotates about the fourth rotation axis A4 together with the third intermediate gear 136. The sun gear 144 causes the bracket 154 (and thus the attached output shaft 34) to rotate about the fourth rotation axis A4 through the planetary gears 150. Therefore, the force from the motor 36 is transmitted to the output shaft 34 through various features. The total gear reduction ratio from the output shaft 118 of the motor 36 to the output shaft 34 can be, for example, about 75:1 to about 600:1, but the gearbox 38 can be configured to have any desired total gear reduction ratio.

[0071] like Figure 1 As shown, when the output shaft 34 rotates about the fourth rotation axis A4, the first steering member 28 fixed to the output shaft is also caused to rotate about the fourth rotation axis A4. The first steering member 28 moves the second steering member 30 in a manner L, which causes the third steering member 32 to pivot in a manner R to steer (e.g., turn) the wheel 12.

[0072] In addition to providing steering assistance, the EPS unit 16 may also be configured by coupling the motor 36 with the steering wheel 22 to provide feedback or steering feel to the operator.

[0073] The above description is an example of the present invention. Of course, it is not possible to describe all conceivable combinations of components or methods for describing the present invention, but those skilled in the art will recognize that the present invention can be made into many further combinations and arrangements. Therefore, the present invention is intended to cover all such changes, modifications and variations that fall within the spirit and scope of the appended claims.

Claims

1. A steering system for rotating a steerable wheel, the steering system comprising: case; Electric motor; a gear located in the housing and rotatable relative to the housing by the electric motor; a planetary gear stage, the planetary gear stage being located in the housing, the planetary gear stage having a sun gear, planetary gears meshing with the sun gear, and a bracket connected to the planetary gears, the rotation of the gears causing the sun gear to rotate about an axis, the rotation of the sun gear causing the planetary gears to rotate relative to the housing and revolve around the sun gear, the bracket being caused to rotate about the axis in response to the planetary gears rotating relative to the housing and revolving around the sun gear; as well as A first bearing has a first ring on the gear and a second ring on the bracket, and the gear and the bracket are rotatably supported by each other in the housing through the first bearing. 2 . The steering system of claim 1 , further comprising a second bearing that rotatably supports the gear on a support surface in the housing. 3 .

3. The steering system according to claim 2, wherein: An outer race of the second bearing is located on the gear and an inner race of the second bearing is located on the support surface.

4. The steering system according to claim 3, wherein: The support surface is located on a support plate in the housing, the outer ring is located on an inner surface of the gear, and the inner surface circumferentially surrounds the support surface.

5. The steering system of claim 1 further comprising an output shaft rotatable relative to the housing via the bracket, the output shaft coupled to a steerable wheel such that rotation of the output shaft causes steering of the steerable wheel. 6 . The steering system of claim 5 , further comprising a second bearing that rotatably supports the output shaft on an inner surface of the housing.

7. The steering system according to claim 6, wherein: An outer ring of the second bearing is located on the housing, and an inner ring of the second bearing is located on the output shaft.

8. The steering system according to claim 6, wherein: The output shaft and the bracket are integrally formed as a single unitary piece, and the single-piece output shaft and bracket are rotatably supported in the housing through both the first bearing and the second bearing.

9. The steering system according to claim 6, wherein: The steering system also includes a third bearing that rotatably supports the gear on a support surface in the housing.

10. The steering system according to claim 9, wherein: The first bearing, the second bearing and the third bearing are tapered roller bearings.

11. The steering system according to claim 9, wherein: The gear, the carrier, and the output shaft are rotatably supported in the housing only by the first bearing, the second bearing, and the third bearing.

12. The steering system according to claim 9, wherein: The first end of the sun gear is rotatably fixed to the gear in the opening of the gear, and the second end of the sun gear is rotatably supported in the recess of the bracket by a fourth bearing, so that the sun gear and the bracket can rotate relative to each other.

13. The steering system according to claim 1, wherein: The bracket is coupled to a steerable wheel such that rotation of the bracket causes steering of the steerable wheel.

14. The steering system according to claim 1, wherein: The sun gear is rotatably fixed to the gear and is rotatably supported in a recess of the carrier by a second bearing such that the sun gear and the carrier are rotatable relative to each other.

15. The steering system of claim 1, wherein: The first bearing is a tapered roller bearing having tapered rollers between the first race and the second race.

16. The steering system of claim 1, wherein: The first ring is located on an outer shoulder of the gear and the second ring is located on an inner surface of the bracket.

17. The steering system of claim 1, wherein: The housing includes a tooth portion meshing with the planetary gears.

18. The steering system according to claim 1 further comprises a second planetary gear stage, the second planetary gear stage being located in the housing, the second planetary gear stage having a second sun gear, a second planetary gear meshing with the second sun gear, and a second bracket connected to the second planetary gear, the second bracket being operably connected to the gear so that the motor causes the gear to rotate through the second planetary gear stage.

19. The steering system of claim 18, further comprising: a second gear disposed in the housing and fixed for rotation with the second bracket; as well as A third gear is located in the housing and meshes with the gear and the second gear.

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