JP2011020645A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a general structure which is applicable to various models and simplified by removing a bearing housing for pressing a first bearing and reducing the number of parts and press-in man-hours in a pressure imparting mechanism of an electric power steering device in which a worm gear and a worm wheel are engaged with each other and the first bearing supporting one end of a worm shaft is movable relative to a gear housing, and is spring-biased in a direction to tighten the engagement. <P>SOLUTION: A spring hook shaft 30 is provided at an end of a worm gear 10 supported by a first bearing 20. The spring hook shaft axially projects from the first bearing 20 and projects toward the outside from a long hole 32 of a gear housing 8. A bearing 34 for a spring hook is provided around the spring hook shaft, and an extension spring 36 is extended between the bearing 34 for the spring hook and the gear housing 8. The worm gear 10 is biased in a direction to tighten the engagement with a worm wheel 12. Accordingly, a bearing housing which has been conventionally essential can be omitted. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to an electric power steering apparatus using a motor as a generation source of a steering assist force, and more particularly to a preload applying mechanism for applying a preload to a gear meshing portion to reduce backlash.

As this type of electric power steering apparatus, as shown in FIG. 9, a steering assisting electric motor 101, a worm gear 103 linked to an output shaft 101a of the electric motor 101 via a shaft coupling 102, and 2. Description of the Related Art An apparatus is known that includes a worm wheel 104 that meshes, and that transmits the rotational output of an electric motor 101 to a steering means that decelerates from the worm wheel 104 and connects to a wheel (see, for example, Patent Document 1).

The worm gear 103 constituting the reduction gear mechanism is provided on the worm shaft 105, and the non-motor side end portion 106 and the motor side end portion 107 which are both ends of the worm shaft 105 are respectively a first bearing 108 and a second bearing which are ball bearings. While being supported by the bearing 109, the first bearing 108 is press-fitted into the bearing housing 110, the bearing housing 110 is held movably toward the worm wheel 104 with respect to the gear housing 111, and the second bearing 109 is attached to the gear housing 111. On the other hand, the outer ring is fixed and held.

The bearing housing 110 is provided with a spring-hanging projection 112 at the center and protrudes outward from a long hole 114 provided in the side wall 113 of the gear housing 111. A tension spring 116 made of a coil spring is stretched between the projections 115, and the spring hooking projection 112 is elastically biased toward the locking projection 115.

For this reason, the bearing housing 110 pulled by the tension spring 116 tries to move to the worm wheel 104 side together with the integrated first bearing 108, and the worm shaft 105 has a portion supported by the second bearing 109 of the motor side end 107. As a fulcrum, the counter motor side end portion 106 side where the bearing housing 110 and the first bearing 108 are integrated is oscillated and biased so as to approach the worm wheel 104 side, and the worm gear 103 is the distance between the rotation centers of the worm wheel 104. The worm gear 103 is constantly pressed to a meshing portion of the worm wheel 104 to reduce the backlash and automatically adjust the backlash amount.

JP 2005-231486 A

In the electric power steering apparatus disclosed in Patent Document 1, the first bearing 108 must be moved and urged by the tension spring 116 in order to apply pressure to the meshing portion of the worm gear 103 and the worm wheel 104. However, the amount of movement of the first bearing 108 for applying pressure is small, and only a slight gap is provided between the gear housing 111 and the first bearing 108. It cannot be pulled directly by the tension spring 116, and needs to be pulled by the tension spring 116 through the bearing housing 110.

For this reason, in the conventional electric power steering apparatus, the bearing housing 110 is an essential component. However, the presence of the bearing housing 110 leads to an increase in the number of parts, and the number of dedicated processes also increases because the outer ring of the first bearing 108 must be press-fitted. In addition, when the size of the first bearing 108 is changed by changing the model, the bearing housing 110 must be manufactured each time. However, since the bearing housing 110 is originally a component that requires high-precision processing, the cost increases. Will be invited.

Therefore, the present invention simplifies the structure by omitting the bearing housing 110 in the preload applying mechanism, and at the same time omits the press-fitting process of the first bearing 108 during assembly, thereby reducing the number of parts and the number of assembly steps. The purpose is to reduce the cost by simplifying the system and to have versatility that is compatible with many models.

According to the first aspect of the electric power steering apparatus of the present invention, a worm gear provided on one end of a worm shaft driven by an electric motor and a worm wheel meshing with the worm gear are arranged in the gear housing. A first bearing that supports both ends of the shaft to the gear housing via bearings and supports the opposite end of the worm shaft on the side opposite to the electric motor side across the worm gear. The worm gear can be moved by fixing the second bearing, which is movable with respect to the gear housing, supporting the motor side end on the electric motor side, to the gear housing, and biasing the first bearing side toward the worm wheel. The worm shaft is swung around the second bearing side as a fulcrum so as to maintain a mesh with the worm wheel by applying a predetermined pressure. The electric power steering system-energized,
A spring-hanging projection is provided at the end of the worm shaft on the side opposite to the motor so as to be integrally rotatable or relatively rotatable, and protrudes through the first bearing,
A tension spring is applied between the spring hooking projection and the gear housing, and the tension spring directly oscillates the worm shaft in a direction in which the engagement between the worm gear and the worm wheel becomes stronger.

According to a second aspect of the present invention, in the first aspect, the spring hooking protrusion is provided so as to rotate integrally with the worm shaft, and a separate interposed member is provided on the spring hooking protrusion, and the tension spring is provided on the intermediate member. It is characterized by multiplying.

According to a third aspect of the present invention, in the first or second aspect, the spring hooking protrusion protrudes outward of the gear housing and is movable toward the worm wheel with respect to the gear housing.
The tension spring is also disposed outside the gear housing.

According to a fourth aspect of the present invention, in the above second or third aspect, the spring hooking protrusion is provided so as to rotate integrally with the worm shaft, and the interposition member is a spring hooking bearing.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the tension spring comprises an endless elastic belt wound between the spring hooking projection and the gear housing. Features.

According to the first aspect of the present invention, since the spring-hanging protrusion protrudes in the axial direction from the first bearing and the tension spring is stretched between the gear housing, the first spring is directly pulled to pull the first spring. Since the bearing can be moved, the bearing housing, which was essential in the conventional structure, can be omitted. As a result, the number of parts and the number of press-fitting steps can be reduced. This simplifies the structure and facilitates assembly, and even if the bearing size changes due to model changes, the spring-hanging projection can be used in common regardless of the bearing size. There is no need to produce bearing housings that require processing, and a general-purpose structure that can be used for many models can be obtained.

According to the second aspect of the present invention, since the spring hooking protrusion is provided so as to rotate integrally with the worm shaft, and the spring hooking protrusion is provided with a separate interposition member, the spring hooking protrusion and the tension spring are provided by the interposition member. Since it is not made to contact directly, the friction between a spring hooking protrusion and a tension spring can be avoided, and durability can be improved. In addition, if the interposed member is a rotation transmission blocking means that does not transmit the rotation of the worm shaft to the tension spring, even if the spring hooking projection rotates together with the worm shaft, this rotation is not transmitted to the tension spring, so adjustment of pressure is applied. Can be performed with high accuracy.

According to the third aspect of the present invention, since the spring hooking protrusion and the tension spring are arranged outside the gear housing, the degree of freedom in arranging the tension spring can be increased.

According to the fourth aspect of the present invention, even if the spring hooking protrusion rotates integrally with the worm shaft, the spring hooking bearing becomes the rotation transmission blocking means by using the interposed member as the spring hooking bearing, and the spring hooking Because the rotation of the worm shaft is not transmitted to the tension spring hung on the bearing for the bearing, it is possible to adjust the pressure with high precision and to improve the durability by avoiding friction between the spring projection and the tension spring. Can do. .

According to the fifth aspect of the present invention, since the tension spring is constituted by the endless elastic belt, the elastic hook is wound between the spring hooking protrusion and a part of the gear housing, so that the spring hooking protrusion is the worm. Even if the shaft rotates integrally with the shaft, the worm shaft can be oscillated and biased while the elastic belt rotates.

Sectional drawing which shows the whole electric power steering apparatus which concerns on 1st Embodiment of this invention. 2-2 sectional view of FIG. The figure which expands and shows the preload provision mechanism part of FIG. The figure which shows notionally the preload provision mechanism part of FIG. 3 from the axial direction of a worm shaft The figure which expands and shows the cushion ring part of FIG. FIG. 4 is a diagram corresponding to FIG. 4 according to the second embodiment. The figure which corresponds to FIG. 3 according to the third embodiment The figure which shows the structure of the support hole and spring-hanging shaft which concern on 4th Example. Sectional view showing the entire conventional electric power steering device

The first embodiment will be described below with reference to FIGS. In FIG. 1, an electric power steering apparatus 1 includes a steering shaft 2 whose one end is connected to a steering wheel (not shown) for steering, a torsion bar 3 inserted into a cylindrical portion of the steering shaft 2, and the torsion bar 3. A pinion shaft 4 coaxially connected to the lower end of the steering shaft 2 in the illustrated state, and a power assisting means 5 for transmitting auxiliary power to the pinion shaft 4 are provided. A pinion 6 is provided on the pinion shaft 4 and meshes with a rack 7 connected to a steering mechanism connected to wheels. The pinion shaft 4 is supported by a ball bearing 9 with respect to the gear housing 8.

The power assisting means 5 includes a worm gear 10 and a worm wheel 12 that mesh with each other, and an electric motor 14 that transmits a rotational output to the worm gear 10. The electric motor 14 is a torque sensor (not shown) that detects the steering torque applied to the handle by the relative rotational displacement of the steering shaft 2 and the pinion shaft 4 according to the twist of the torsion bar 3 that is twisted by the action of the steering torque applied to the handle. ) And the steering assist power is transmitted to the pinion shaft 4 via the speed reduction mechanism 15 to assist the steering force by the steering wheel.

The speed reduction mechanism 15 includes a worm shaft 11 that is rotationally driven by the electric motor 14, a worm gear 10 that is formed concentrically around an axially intermediate portion thereof, and a worm wheel 12 that is fitted and fixed in the middle of the pinion shaft 4. The rotation of the electric motor 14 is decelerated and transmitted to the pinion shaft 4 by the engagement of the worm gear 10 and the worm wheel 12.

In FIG. 2, the gear housing 8 is made of a light alloy such as an aluminum alloy formed by casting or the like, and includes a first housing portion 8a for housing the worm gear 10 and a second housing portion 8b for housing the worm wheel 12. And a side wall 8c that covers the side portion of the first housing portion 8a, and the wall portions of the first housing portion 8a and the second housing portion 8b are continuous via the side wall 8c.

A first bearing hole 16 is formed in the vicinity of the side wall 8c of the first housing portion 8a. The first bearing hole 16 supports a non-motor side end 18 which is one end of the worm shaft 11. The first bearing 20 is inserted. A second bearing hole 22 is provided on the electric motor 14 side of the first housing portion 8a, and a second end 24 for inserting and supporting the motor side end 24 of the worm shaft 11 is inserted into the second bearing hole 22. A bearing 25 is mounted. Although the 1st and 2nd bearings 20 and 25 in this form are ball bearings, it is not limited to this. The second bearing hole 22 faces the motor chamber 14a. An electric motor 14 for rotating the worm shaft is accommodated in the motor chamber 14a.

Next, the speed reduction mechanism 15 will be described in more detail. Both end portions of the worm shaft 11 in the axial direction form an anti-motor side end 18 and a motor side end 24. A serration portion 28 is provided at the tip of the motor side end portion 24 so as to be connected to the output shaft 26 of the electric motor 14 so as to be integrally rotatable. The worm shaft 11 is arranged such that its axis C2 is parallel to the axis C1 (FIG. 1) of the pinion shaft 4 with a difference of 90 °.

A spring hook shaft 30 serving as a spring hook projection is attached to the end 18 of the worm shaft 11 opposite to the motor so as to rotate integrally with the worm shaft 11. The spring hook shaft 30 is coaxial with the worm shaft 11 and protrudes outward of the gear housing 8 in the direction of the axis C2 of the worm shaft 11, and the axis C2 of the worm shaft 11 on the side wall 8c of the gear housing 8 intersects. A spring-loaded bearing 34, which is a bearing made of a ball bearing and is an example of an interposition member in the present invention, is mounted at the tip of the spring-hanging shaft 30. Has been.

A tension spring 36 made of an appropriate spring such as a coil spring is stretched between the spring-carrying bearing 34 and a spring locking piece 35 provided on the gear housing 8, and the non-motor side end 18 is connected to the spring locking piece. The preload applying mechanism is configured by urging to the 35 side. The spring locking piece 35 has a line L passing through the center of the worm wheel 12 parallel to the axial line C2 of the worm shaft 11 in the vicinity of the side wall 8c in the outer wall of the second storage portion 8b in which the worm wheel 12 is stored. It protrudes outward from the vicinity of the intersecting part.

In the worm shaft 11, the first bearing 20 that supports the non-motor side end 18 is movable with respect to the first bearing hole 16, and the spring hook shaft 30 is movable along the long hole 32. Therefore, the center C of the second bearing 25 at the motor-side end 24 is supported as a fulcrum and can swing within a plane including the center C and the length direction of the long hole 32, and the anti-motor is driven by the tension of the tension spring 36. The side end 18 is oscillated and biased so as to approach the worm wheel 12.

For this reason, by repressing the worm gear 10 in the direction in which the distance H between the rotation centers with the worm wheel 12 is shortened and urging the meshing portion in the radial direction, pressure is applied to the meshing portion to reduce backlash, The change in the backlash amount is reduced by reducing the change in the pressure applied to the meshing portion. The distance H between the rotation centers is also the distance between the center of the worm gear 10 and the line L on the axis C2 of the worm shaft 11.

A cushion ring 44 is interposed between the first bearing 20 and a stepped portion formed by the large-diameter portion 11a formed on the outer peripheral portion of the worm shaft 11 in the vicinity thereof. A preload is applied in the axial direction to restrain the movement of the worm gear 10 in the axial direction, and the first bearing 20 is also elastically pressed in the direction of the side wall 8c with a predetermined set load. The backlash of the bearing 20 is prevented.

The second bearing 25 that supports the motor-side end 24 is fitted and held with one end of the outer ring 25a in contact with a stepped portion 22a provided in the second bearing hole 22, The other end side of the outer ring 25a is pressed and held by a stopper screw 40 screwed into a screw hole 38 formed in the gear housing 8 in the vicinity of the second bearing hole 22. Further, a cushion ring 45 described later is provided between the second bearing 25 and a stepped portion formed by the large diameter portion 11b formed in the outer peripheral portion of the worm shaft 11 in the vicinity thereof and on the side opposite to the motor side end portion 18 side. Axial preload is applied.

The motor side end portion 24 is held through the inner ring 25c of the second bearing 25, and the bearing surface of the motor side end portion 24 shaft and the second bearing with the center C of the second bearing 25 as a fulcrum. The swing of a minute angle required for backlash adjustment is possible within a clearance formed by the inner diameter of the 25 inner rings 25c.

Next, the first bearing 20 will be described in detail. As shown in detail in FIG. 3, the first bearing 20 includes an outer ring 20 a, a ball 20 b, and an inner ring 20 c, and the outer ring 20 a is fitted in the first bearing hole 16 and the inner wall surface of the first bearing hole 16. Is elastically held on the inner periphery of the first O-ring 50 provided between the worm wheel 11 and the worm wheel 11 as it approaches the worm wheel 12 by the amount of elastic deformation of the first O-ring 50. A small amount of movement is possible in the direction of The first bearing hole 16 has a shape that allows such movement of the first bearing 20.
The first O-ring 50 is retained by one end of a cylindrical collar 46 press-fitted into a large-diameter stepped hole 48 that expands the first bearing hole 16.

An annular recess 51 corresponding to a state where the diameter of the end of the first bearing hole 16 is reduced is formed in the side wall 8c in which the elongated hole 32 is formed. 32 is formed, and the second O-ring 52 is accommodated in the recess 51. The second O-ring 52 gives resistance when the first bearing 20 moves outward in the axial direction of the worm shaft 11 as the worm shaft 11 swings. The washer 54 and the side wall 8c are fixed. The washer 54 is interposed between the step 16a formed at the end of the first bearing hole 16 and a portion that changes to the recess 51 and the outer ring 20a, and a slight clearance is provided between the step 16a. ing.

The first O-ring 50 and the second O-ring 52 form a radial spring and a thrust spring, and a floating that elastically supports the non-motor side end portion 18 of the worm shaft 11 via the first bearing 20. Support structure. For this reason, the worm shaft 11 can swing within a small range corresponding to the crushing allowance of the first O-ring 50. As a result, the worm gear 10 also moves slightly to adjust the meshing with the worm wheel 12 and backlash. Is supposed to take. At this time, since the outer ring 20a of the first bearing 20 is elastically in contact with the parallel plane of the washer 54, the second O-ring 52 is elastically deformed as a whole, so that the worm shaft 11 is swung. Reduce backlash in the thrust direction.

Next, the preload applying mechanism by the tension spring 36 will be described in detail. As shown in FIG. 3, the spring hooking bearing 34 includes an outer ring 34b and an inner ring 34c in which a locking groove 34a is formed, and a ball 34d is interposed between the outer ring 34b and the inner ring 34c. The outer ring 34b and the inner ring 34c are made of resin, and the locking groove 34a is formed as an annular groove on the outer periphery of the outer ring 34b. The locking groove 34a is for hooking one end of the tension spring 36, and can be easily formed by making the outer ring 34b made of resin.

The inner ring 34c of the spring-loaded bearing 34 passes through the shaft portion of the spring-loaded shaft 30 having a head portion 30a at one end and the other end is in contact with one side of the inner ring 34c, and the other end side is a spring-loaded shaft. By tightening with a nut 30b fastened to a male screw formed around 30, the spring hanging shaft 30 is connected and fixed so as to be integrally rotatable. In addition, it can replace with this nut 30b and fixing means, such as press fitting, are possible suitably. The lower end of the spring hook shaft 30 in the illustrated state is press-fitted into the shaft hole 11c formed from the shaft end of the non-motor side end 18 into the shaft center portion of the worm shaft 11, and is integrated with the worm shaft 11, The spring hanging shaft 30 rotates integrally. The connection between the worm shaft 11 and the spring hook shaft 30 can be performed by any appropriate means other than press fitting.

As shown in FIG. 4, both ends of the tension spring 36 are arc-shaped hooks 36a, and one hook 36a has a curvature slightly smaller than the inner diameter of the locking groove 34a formed on the outer periphery of the outer ring 34b. A small circle is drawn, and it is wound around the outer periphery of the outer ring 34b while being elastically deformed and then closely fitted into the locking groove 34a. The other hook 36a is locked in the locking hole 35a. The tension spring 36 is not limited to a coil spring, and various types such as a leaf spring and a rubber spring can be applied.

Next, the cushion ring 45 will be described in detail with reference to FIG. FIG. 5 shows a cushion ring 45 provided at the motor side end 24 of the worm shaft 11. The cushion ring 44 provided at the non-motor side end 18 has the same structure. The cushion ring 45 has a doughnut-shaped rubber ring 45b sandwiched between a pair of metal ring plates 45a, the motor side end portion 24 is penetrated to the center side, a step portion formed by the large diameter portion 11b of the worm shaft 11 and a second portion. The worm shaft 10 is sandwiched between inner rings 25c of the bearing 25, and the worm shaft 10 is urged toward the first bearing 20 by the repulsive elasticity of the rubber ring 45b compressed by the pair of ring plates 45a. The movement to the bearing 25 side is suppressed. Each outer peripheral portion of the pair of ring plates 45a bends to the opposite side to form an escape portion when swinging. In the figure, reference numeral 25a denotes an outer ring of the second bearing 25, and 25b denotes the same ball.

Next, an assembly procedure of the electric power steering apparatus 1 will be described. When the worm gear 10 is assembled in the gear housing 8, the first bearing 20 is inserted into the first bearing hole 16 in advance, and the spring hook shaft 30 is attached to the shaft end of the non-motor side end 18. The worm shaft 11 is inserted into the first housing portion 8a from the second bearing hole 22, the worm gear 10 and the worm wheel 12 are engaged, and then the second bearing 25 is set in the second bearing hole 22 and the worm The motor-side end 24 of the shaft 11 is supported, and a stopper screw 40 is screwed into the screw hole 38 of the gear housing 8.

The axial force generated by fastening the stopper screw 40 is transmitted to the worm shaft 11 via the outer ring 25a, the ball 25b, and the inner ring 25c of the second bearing 25. Thereby, the clearance in the axial direction of the second bearing 25 is eliminated, and the worm shaft 11 is moved toward the first bearing 20. Further, the axial force generated by fastening the stopper screw 40 is transmitted from the worm shaft 11 to the gear housing 8 through the inner ring 20a, the ball 20b, and the outer ring 20c of the first bearing 20. Thereby, the clearance in the axial direction of the first bearing 20 is eliminated, and the worm shaft 11 can be elastically fixed in the axial direction to prevent the worm gear 10 from rattling in the axial direction.

Subsequently, the spring that passes through the center of the first bearing 20 that supports the non-motor side end 18 of the worm shaft 11 and further protrudes to the outside through the long hole 32 provided in the side wall 8c of the gear housing. A spring hanging bearing 34 is attached and fixed to the hanging shaft 30, and a tension spring 36 is stretched between the spring hanging bearing 34 and a spring locking piece 35 provided on the gear housing 8.
As a result, the worm shaft 11 is swung so that the counter-motor side end 18 approaches the worm wheel 12 side by the elasticity of the tension spring 36. As a result, the distance H between the rotation center of the worm gear 10 and the worm wheel 12 is increased. By repressing in the shortening direction, the meshing part is urged in the radial direction, pressure is applied to the meshing part to reduce backlash, and the change in the pressure of the meshing part is reduced to reduce the change in the backlash amount. Less.

As described above, according to the present embodiment, the tension spring 36 is applied to the spring hook shaft 30 to pull it, and therefore, the first bearing 20 can be moved together with the non-motor side end portion 18 of the worm shaft 11. As a result, the first bearing 20 can be moved without providing a bearing housing that has been conventionally required to move the first bearing 20. As a result, the bearing housing and the number of parts related thereto can be reduced. In addition, when the conventional bearing housing is used, it is necessary to press-fit the bearing into the bearing housing, which increases the number of work steps, but such press-fitting work is also unnecessary.

In particular, the bearing housing is a member that requires relatively high-precision machining for its production, and if the bearing size changes due to the model change, it is a dedicated part that needs to be re-produced accordingly. If the spring hanging shaft 30 is used as in the present embodiment, the spring hanging shaft 30 can be used in common even when changing to a bearing of a different size, so there is no need to produce each bearing of a different size, and the versatility is high. Will be. For this reason, the number of parts can be reduced, the structure and assembly work can be simplified, the cost can be reduced, and a general-purpose structure that can be used for many models can be obtained.

Further, since the spring hooking shaft 34 is mounted on the spring hooking shaft 30 projecting from one end of the worm gear 10, the rotation of the worm shaft 11 is prevented from being transmitted to the tension spring 36, and the spring hooking bearing 34 is cut off from rotation transmission. Therefore, even if the shaft end of the worm shaft 11 is pulled by the tension spring 36, the rotation of the worm shaft 11 is not hindered and accurate power assist driving is possible. In addition, it is possible to avoid wear of the spring hanging shaft 30 and the tension spring 26 and improve durability.

In the first embodiment described above, the example in which the spring-loaded bearing 34 is attached to the tension spring locking portion at the tip of the spring-loaded shaft 30 has been described. A cylindrical sliding bearing (not shown) may be rotatably mounted, and the hook 36a of the tension spring 36 may be locked on the outer periphery of the sliding bearing. At this time, if necessary, a concave groove for locking the hook may be provided on the outer peripheral surface of the sliding bearing.

Although the second bearing 25 is used on the other end side of the worm gear 10, a spherical self-aligning bearing that can swing with the center of the inner ring as a fulcrum can be used instead of the second bearing 25. . Thereby, the one end side of worm gear 10 can also be supported so that rocking is possible. Further, the speed reduction mechanism 15 composed of the worm gear 10 and the worm wheel 12 may be constituted by a bevel gear depending on the gear ratio.

Next, a second embodiment will be described with reference to FIG. FIG. 6 shows a modified example of a pressurizing mechanism that applies tension to the worm shaft 11 in order to preload the meshing portion of the worm gear 10 and the worm wheel 12 so as to oscillate and bias the worm shaft 11 in a direction to maintain the preload. FIG. 5 is a conceptual diagram corresponding to FIG. 4. The pressurizing mechanism of the present embodiment uses an endless elastic belt instead of the tension spring 36 made of the coil spring described in the first embodiment as a tension spring.
In addition, since it is the same structure as 1st Embodiment except a pressurization provision mechanism, the same code | symbol is used and the figure of 1st Embodiment shall be referred as needed about parts other than a pressurization provision mechanism. .

In FIG. 6, the pressurizing mechanism is configured such that a belt 64 is wound between a first pulley 60 provided on the spring hanging shaft 30 and a second pulley 62 provided on the pulley shaft 61, and an appropriate tension pulley 66 is wound around the belt 64. It is structured to give tension. One pulley 60 is an example of an interposition member in the present invention.
As in the previous embodiment, the spring hanging shaft 30 is provided at one end of the worm shaft 11 so as to be integrally rotatable, and is inserted through a long hole 32 provided in the side wall 8c of the gear housing and protrudes outside (FIG. 3). A grooved first pulley 60 is attached to the tip of 30 so as to be integrally rotatable. On the other hand, on the outer wall of the gear housing 8 close to the first pulley 60, a pulley shaft 61 parallel to the spring hook shaft 30 is provided in place of the spring locking piece 35 in FIG. A grooved second pulley 62 is also rotatably mounted on 61.

The belt 64 is an elastic endless belt made of rubber, for example, and is wound around a pair of first pulley 60 and second pulley 62 that are spaced apart from each other. It is pressed to obtain. However, the tension pre 66 is not necessarily required, and a tensioner that is urged by a spring and is slidably pressed against the belt may be used. In the case where such a tension adjusting member is provided, the belt 64 may be a low-elasticity connecting member that does not expand and contract so much, such as a chain, a string, or a wire.
Further, if the belt 64 is made of an elastic body and the tension of the belt 64 is adjusted in advance so that a predetermined tension is generated between the first pulley 60 and the second pulley 62, the tension pulley 64 and the tensioner are omitted. You can also

According to the electric power steering apparatus according to the second embodiment configured as described above, an elastic belt 64 capable of adjusting tension is used instead of the tension spring 36 of the first embodiment, and this is used as the first pulley 60 and Since the tension pulley 66 adjusts the tension around the second pulley 62, the worm shaft 11 is always pulled toward the pulley shaft 61 with a predetermined force. The applied preload can be adjusted to maintain a constant strength.

In addition, when the worm shaft 11 rotates, the first pulley 60 rotates as a unit and further rotates the belt 64, but the rotation of the belt 64 is transmitted to the second pulley 62, and only rotates idly to rotate to the pulley shaft 61. Is not transmitted, the second pulley 62 serves as a rotation transmission blocking means. In this way, even if the worm shaft 11 rotates, tension can be applied by the belt 64 without hindering this rotation.

Note that the first pulley 60 can also be rotatably attached to the spring hook shaft 30. In this case, the first pulley 60 functions as a rotation transmission blocking means, so that it is not necessary to rotate the belt 64. Therefore, instead of the belt 64, the first pulley 60 and the second pulley 62 may be pulled by a coil spring or the like. Further, instead of the pulley, an interposed member made of a material that can slide with low friction such as a metal bearing may be provided on the spring hook shaft 30 as a rotation transmission blocking means, and one end of the tension adjusting member may be locked thereon.
Further, the spring-loaded bearing 34 of the first embodiment can be used instead of the pulley.

Next, a third embodiment will be described with reference to FIG. FIG. 7 is a sectional view showing a part corresponding to FIG. 3 according to the preload applying mechanism according to the third embodiment.
In the present embodiment, the rotation transmission blocking means described in the first embodiment is configured as a spring hanging shaft 80 that is rotatably supported on one end side of the worm shaft 11.

That is, in FIG. 7, a support hole 70 is formed at one end of the worm shaft 11, and a cylindrical metal bearing 72 is press-fitted into the support hole 70.
A male screw 73 is screwed around one end of the worm shaft 11, and a cylindrical portion 75 of a bottomed cylindrical cap 74 is screwed to the male screw 73. A female screw (reference numeral omitted) that is screwed with the male screw 73 is screwed on the inner periphery of the cylindrical portion 75 on the opening side. A through hole 77 is formed in the center of the circular bottom 76 of the cap 74.

A leg portion 82 of a spring hanging shaft 80 is rotatably supported on the metal bearing 72. The spring hook shaft 80 is a member corresponding to the spring hook shaft 30 of the first embodiment, but in this example, the leg portion 82 is rotatable relative to the worm shaft 11 through the metal bearing 72. To do.

The spring hook shaft 80 is formed with a flange 84 that protrudes perpendicular to the axis at an axially intermediate portion, and a locking portion 86 having a small diameter is formed above the flange 84. The low friction material washers 88 are disposed above and below the flange 84, the leg portion 82 is inserted into the metal bearing 72, and the cap 74 is inserted into the through hole 77 in the state where the cap 74 is inserted into the shaft of the worm shaft 11. When screwed into the end portion, the spring hook shaft 80 is fixed to the shaft end portion of the worm shaft 11 so as to be relatively rotatable. The through hole 77 has a larger hole size than the outer diameter of the locking portion 86.

Therefore, when the hook portion 36a of the tension spring 36 is hooked on the locking portion 86 protruding upward from the cap 74, the worm shaft 11 is engaged with the worm gear 10 and the worm wheel 12 by the tension spring 36 via the spring hook shaft 80. The preload applied to (see FIG. 2) is oscillated and biased so as to maintain a constant strength.
Note that. The tension spring 36 is the same as that shown in FIG. 2, but the hook portion 36 a is reduced in accordance with the outer diameter of the locking portion 86. The locking structure with the gear housing on the other end side of the tension spring 36 is the same as in FIG.

When the worm shaft 11 rotates with the spring hook shaft 80 pulled by the tension spring 36 in this way, the rotation is not transmitted to the leg portion 82 supported by the metal bearing 72, and this portion becomes the rotation transmission blocking means. The spring hook shaft 80 is not rotated integrally with the worm shaft 11. For this reason, since friction due to rotation does not occur between the locking portion 86 and the hook portion 36a, the hook portion 36a of the tension spring 36 can be directly hooked on the locking portion 86, and the spring-loaded bearing of the first embodiment. Interposition members such as 34 and the pulley of the second embodiment can be omitted. However, it is possible to arbitrarily provide any intervening member on the locking portion 86.

The above-described structure in this embodiment is an example, and specific individual structures such as the spring hanging shaft 80 and the cap 74 can be variously modified. The point is that the rotation transmission blocking means is provided on the worm shaft 11 side so that the spring hook shaft 80 does not rotate integrally with the worm shaft 11 and only the tension for swinging and energizing the worm shaft 11 is applied to the worm shaft 11. Good. Further, the belt 64 of the second embodiment can be wound around the spring hook shaft 80. In this case, a pulley may be provided.
Furthermore, the thickness of the spring hanging shaft can be arbitrarily changed.

FIG. 8 relates to a fourth embodiment in which a worm shaft 11 having compatibility is configured so that it can be attached to a common worm shaft 11 even if the thickness of the spring hook shaft is changed as described above. 7 shows the axial end of the worm shaft 11 from the axial direction, and B shows the longitudinal section (axial section). In this example, a rib 90 projecting in the center direction in the support hole 70 is formed in a substantially cross shape when A is viewed in the axial direction. The central portion of each rib 90 does not intersect and surrounds a narrow hole 92 formed by the respective inner end. The inner diameter of the support hole 70 is D1, and the inner diameter of the narrow hole 92 is D2.

As shown in B, the height h <b> 1 extending in the axial direction of each rib 90 is about half of the depth H of the support hole 70. In the illustrated state, the rib 90 is not formed between the upper end surface 91 of the rib 90 and the opening of the support hole 70, so that the original wide hole is formed. The height h2 of the wide hole portion is H-h1. The remaining half of the depth H of the support hole 70 is about half.
Other configurations of the worm shaft 11 are the same as those in FIG. By configuring the worm shaft 11 in this manner, the worm shaft 11 can be shared with a thick spring hanging shaft and a thin spring hanging shaft.

C in the figure shows a state in which a thick spring hanging shaft 94 is attached as in FIG. 7, and D shows a state in which a thin spring hanging shaft 94A is attached. The thick spring hanging shaft 94 and the thin spring hanging shaft 94A differ only in the thickness of the leg portion fitted into the support hole 70, and the outer diameter of the leg portion 94 in the thick spring hanging shaft 94 is larger than the inner diameter D1 of the support hole 70. It is slightly small d1, and the length L1 is about the depth h1 of the wide hole in which the rib 90 in the support hole 70 is not formed.
The leg portion 94A of the thin spring hanging shaft 94A has the inner diameter of the narrow hole 92 d2 slightly smaller than D2, and the length L2 is substantially equal to the depth H of the support hole 70.

As shown in FIG. 3C, when the leg portion 96 of the thick spring hanging shaft 94 is inserted into the support hole 70, the bottom portion of the leg portion 96 rides on the upper end surface 91 of the rib 90 and is rotatably supported.
Therefore, when the cap 74 is screwed onto the shaft end of the worm shaft 11 with the low friction material washers 88 interposed above and below the flange 84, the spring hook shaft 94 is fixed to the shaft end of the worm shaft 11 so as to be relatively rotatable. The If the upper end surface 91 of the rib 90 is provided with an annular rib or a plurality of independent hemispherical small protrusions, the washer 88 can be omitted. In this case, the annular rib or the like causes sliding friction with the flange 84. Can be reduced. Reference numeral 95 denotes an annular groove for spring application.

In order to replace the thick hanging shaft 94 with the thin spring hanging shaft 94A, when the leg portion 96A of the thin spring hanging shaft 94A is put into the support hole 70 as shown in FIG. The narrow hole 92 is inserted and supported by the rib 90 so as to be rotatable. Thereafter, the cap 74 is attached to the top and bottom of the flange 84 with the low friction material washers 88 interposed therebetween, as in C.

E in the figure is an example using the spring hanging shaft 30 of FIG. 3 as a thin spring hanging shaft. In this example, the outer diameter d3 of the leg portion 30c of the spring hook shaft 30 is slightly larger than the inner diameter D2 of the narrow hole 92. When the lower end side of the leg portion 30c is press-fitted into the narrow hole 92, the narrow hole 92 The inner end of the rib 90 surrounding 92 is press-fitted while being deformed, and is integrated with the worm shaft 11. Therefore, it is possible to attach a press-fitting type thin spring hanging shaft. If the outer diameter of the leg is slightly larger than the inner diameter D1 of the support hole 70, a thick hanging shaft can be press-fitted.

In this way, the thick suspending shaft 94 and the thin spring suspending shaft 94A can be used for the common worm shaft 11, and the press-fit spring suspending shaft 30 can be attached. As a result, a spring hanging shaft having a thickness that can withstand this pressure can be freely selected according to the required pressure, so that versatility is increased and the pressure adjustment is facilitated.

The present invention is not limited to the above-described embodiments, and various modifications and applications can be made within the principle of the invention. For example, the hook portion 36a may be directly hooked on the spring hook shaft 30 of the first embodiment without using an interposition member such as the spring hook bearing 34 or the like. In this case, even if the spring hook shaft 30 is rotated, slip occurs between the hook portion 36a, and the slip at the hook portion 36a becomes a rotation transmission blocking means. Therefore, the high-precision pressure adjustment is not required. It is fully applicable in some cases. Further, depending on the shape of the gear housing 8, the tension spring 36 and the belt 64 can be provided in the gear housing 8.

Further, since it is sufficient if the spring hooking projection is integrated with the worm shaft 11 so as to be integrally rotatable or relatively rotatable, for example, the non-motor side end portion 18 of the worm shaft 11 is reduced in diameter from the bearing portion. The extended portion itself may be used as a spring hanging shaft.
Furthermore, even when the spring-hanging projection is provided separately from the worm shaft 11, it is not always necessary to have a shaft shape like the spring-hanging shaft 30 or 80, and it is sufficient to have a spring-engaging projection portion. A non-motor side end portion 18 may protrude from the first bearing 20 and may be a C or E clip fitted to the outer peripheral portion of the protruding end portion.

DESCRIPTION OF SYMBOLS 1 ... Electric power steering apparatus, 8 ... Gear housing, 10 ... Worm gear, 11 ... Worm shaft, 12 ... Worm wheel, 18 ... Non-motor side edge part, 20 ... 1st bearing, 22 ... Motor side edge part, 25 ... 2nd bearing, 30 ... Spring hanging shaft (spring hanging projection), 34 ... Bearing for spring hanging, 36 ... Tension spring, 64 ... Belt, 80 ... Spring hanging shaft

Claims (5)

A worm gear provided on one end of a worm shaft driven by an electric motor and a worm wheel meshing with the worm gear are arranged in the gear housing, and both ends of the worm shaft are supported by the gear housing via bearings. The first bearing that supports the opposite end of the motor on the opposite side of the electric motor across the worm gear is movable with respect to the gear housing, and the end of the motor on the side of the electric motor is The second bearing to be supported is fixed to the gear housing, and the first bearing side is spring-biased to the worm wheel side, so that the worm gear is applied with a predetermined pressure with the worm wheel so as to maintain meshing. In the electric power steering apparatus in which the shaft is oscillated and biased about the second bearing side as a fulcrum,
A spring-hanging projection is provided at the end of the worm shaft on the side opposite to the motor so as to be integrally rotatable or relatively rotatable, and protrudes through the first bearing,
An electric power characterized in that a tension spring is stretched between the spring-hanging projection and the gear housing, and the worm shaft is directly oscillated and biased in the direction in which the engagement between the worm gear and the worm wheel is strengthened by the tension spring. Steering device. 2. The electric motor according to claim 1, wherein the spring hooking protrusion is provided so as to rotate integrally with the worm shaft, a separate interposed member is provided on the spring hanging protrusion, and the tension spring is hung on the interposed member. Power steering device. The spring-hanging protrusion protrudes outward of the gear housing and is movable to the worm wheel side with respect to the gear housing.
3. The electric power steering apparatus according to claim 1, wherein the tension spring is also disposed outside the gear housing. 4. The electric power steering apparatus according to claim 2, wherein the spring hooking protrusion is provided so as to rotate integrally with the worm shaft, and the interposed member is a spring hooking bearing. The electric power steering apparatus according to any one of claims 1 to 4, wherein the tension spring is configured by an endless elastic belt wound between the spring hooking protrusion and a gear housing.

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