JP5309670B2 - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To constitute a structure which prevents the occurrence of unpleasant noises like gearing noises or vibration and which gives an assistance force from an electric motor stably at low cost by reducing the number of part items. <P>SOLUTION: A sliding bearing 22 is used for a bearing which supports the tip part of a worm shaft 7. This sliding bearing 22 is structured by inserting a part dislocated from a part supporting a pressing piece 10 at the tip part of the worm shaft 7 into a through-hole 23 provided in a guide block 13a retained inside a housing 3a in a state that sliding contact is possible. Then, guide wall sections provided in the guide block 13a guide the worm shaft 7 via the pressing piece 10 in such a way as to cause the shaft to move away from and near to the worm wheel 4. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The electric power steering apparatus according to the present invention is used as a steering apparatus for an automobile, and uses an electric motor as auxiliary power to reduce the force required for the driver to operate the steering wheel. is there. The present invention can suppress the generation of an unpleasant noise called a rattling noise in the worm type reduction gear portion constituting such an electric power steering apparatus, and can improve the operational feeling of the steering wheel. The structure was invented with the intention of simplifying the structure with a small number of parts.

  A power steering device is widely used as a device to reduce the force required for the driver to operate the steering wheel when giving a steering angle to the steered wheels (usually the front wheels except for special vehicles such as forklifts) Has been. In addition, an electric power steering apparatus that uses an electric motor as an auxiliary power source in such a power steering apparatus has begun to spread in recent years. The electric power steering device can be made smaller and lighter than the hydraulic power steering device, has advantages such as easy control of the magnitude (torque) of auxiliary power and less power loss of the engine.

  Various structures of the electric power steering apparatus are known. In any structure, the electric motor is attached to the rotating shaft that is rotated by the operation of the steering wheel and gives a steering angle to the steered wheel as the wheel rotates. Auxiliary power is applied through a speed reducer. In general, a worm reducer is used as the reducer. In the case of an electric power steering device using a worm speed reducer, a worm that is rotationally driven by the electric motor and a worm wheel that rotates together with the rotating shaft are engaged with each other, and auxiliary power of the electric motor is applied to the rotating shaft. Communicate freely. However, in the case of a worm reducer, if no measures are taken, it is called a rattling sound when changing the rotation direction of the rotating shaft based on the backlash existing in the meshing portion of the worm and the worm wheel. Unpleasant noise may occur.

  Conventionally, as described in Patent Documents 1 and 2, it is considered that the worm is elastically pressed toward the worm wheel by an elastic member such as a spring as a structure capable of suppressing the generation of such rattling noise. ing. 15 to 20 show an example of the electric power steering device described in Patent Document 1 among them. A front end portion of a steering shaft 2 that is a rotating shaft that is rotated in a predetermined direction by the steering wheel 1 is rotatably supported inside the housing 3, and the worm wheel 4 is fixed to this portion. A worm 6 that meshes with the worm wheel 4 and is rotationally driven by an electric motor 5 is provided with worm teeth 8 at an intermediate portion in the axial direction of the worm shaft 7, and both ends of the worm shaft 7 are arranged in a single row. The housing 3 is rotatably supported by a pair of rolling bearings 9a, 9b such as deep groove ball bearings. Further, a biasing member 10 is externally fitted to a portion protruding from the rolling bearing 9 a at the tip of the worm shaft 7, and a coil spring 11 that is an elastic member is provided between the biasing member 10 and the housing 3. Is provided.

  Specifically, a holding recess 12 is provided in a portion of the housing 3 that faces the tip of the worm shaft 7, and the guide block 13 is held in the holding recess 12. Further, a portion near the tip of the worm shaft 7 is formed on the guide block 13 with an elastic ring 14 made of an elastic material such as rubber, and the rolling bearing 9a held on the outer diameter side of the elastic ring 14. By these, it supports so that rotation and the far-and-near movement with respect to the said worm wheel 4 are possible. The urging member 10 can freely rotate relative to the rolling bearing 9a at a portion protruding from the rolling bearing 9a at the tip of the worm shaft 7 (actually, the worm on the inner side of the urging member 10). The shaft 7 is externally fitted freely. The urging member 10 does not rotate, but is held on the axially outer side surface of the guide block 13 (the side surface on the back side of the holding recess 12) so as to be able to move to and away from the worm wheel 4.

Therefore, a pair of guide wall portions 15, 15 each divided into two on the axially outer side surface of the guide block 13 are separated in the axial direction of the worm wheel 4, and the main body of the guide block 13 It is provided in a state of protruding from the portion 16 on the opposite side to the worm tooth 8. A distance D 15 between the guide wall portions 15 and ₁₅ is slightly larger than a width W of the biasing member 10 (D ₁₅ > W). The worm wheel 4 is sandwiched between the worm wheels 4 so that the worm wheel 4 can be moved in a perspective direction and the axial displacement of the worm wheel 4 is suppressed.

  Furthermore, a pair of bent portions 18, 18 formed by bending the coil portion 17 inward in the radial direction at both ends of the wire constituting the coil spring 11 which is an elastic member and is externally fitted to the biasing member 10, The guide wall portions 15 and 15 are locked to locking recesses 19 and 19 formed in the both guide wall portions 15 and 15. In this state, the inner peripheral surface of the coil spring 11 is in elastic contact with the surface of the biasing member 10 on the side opposite to the worm wheel 4. Then, the coil spring 11 presses the worm teeth 8 against the worm wheel 4 via the biasing member 10 to suppress backlash between the worm teeth 8 and the worm wheel 4, and the teeth Suppressing the sound of hitting.

In the case of the conventional structure as described above, the worm shaft 7 is supported in such a manner that the worm shaft 7 is elastically pressed toward the worm wheel 4 so as to support the worm shaft 7 so as to be able to move to and away from the worm wheel 4. Is supported by an elastic ring 14, a rolling bearing 9 a, a guide block 13, a biasing member 10, and a coil spring 11. In the case of such a structure, the number of parts is large, and as a result, the assembling work becomes troublesome and the manufacturing cost may increase.
On the other hand, Patent Document 3 describes a structure in which the tip portion of the worm shaft is supported by a sliding bearing and the holding cylinder constituting the sliding bearing is supported by a guide block via an annular coil spring. . In Patent Document 4, the guide block is supported in the housing in a bent state (elastically deformed), and the worm is elastically directed toward the worm wheel by the elastic force of the guide block itself based on the bending. The structure to press is described.

  In the case of the structures described in these Patent Documents 3 and 4, since the sliding bearing is used instead of the rolling bearing, the number of parts can be reduced, and the cost can be reduced. However, in the case of the structures described in Patent Documents 3 and 4, since the elastic force is applied (elastically pressed) by the annular coil spring or the guide block itself, the setting of the elastic force becomes troublesome, There is a possibility that it is difficult to apply a desired elastic force to the worm shaft. For this reason, there is a possibility that unpleasant noises and vibrations such as rattling noises cannot be sufficiently prevented. In addition, in the case of the structures described in Patent Documents 3 and 4, since a mechanism for restricting the displacement of the worm shaft in a desired direction (guidance of the worm shaft) is not provided, In addition to the direction approaching the worm wheel, specifically, there is a possibility of displacement in the axial direction of the worm wheel. Such a displacement of the worm shaft causes a shift at the meshing portion of the worm wheel and the worm tooth, the auxiliary force applied from the electric motor becomes unstable (the auxiliary torque is likely to fluctuate), and the steering wheel. There is a possibility of giving a sense of incongruity to the operation.

  Patent Document 5 describes a structure that regulates the displacement direction of the worm shaft by guiding a rolling bearing that supports the tip of the worm shaft with a guide portion provided in the guide block. However, in the case of such a structure described in Patent Document 5, since the tip of the worm shaft is supported by the rolling bearing, the number of parts increases correspondingly, and the assembly work becomes troublesome and the manufacturing cost is increased. May increase.

JP 2004-306898 A JP 2007-321846 A JP 2001-233225 A JP 2001-270448 A JP 2002-67992 A

  In view of the circumstances as described above, the present invention is low cost by suppressing the number of parts, can prevent generation of unpleasant noise and vibration such as rattling noise, and is stable from an electric motor. Thus, the present invention has been invented to realize an electric power steering device capable of providing auxiliary force.

In any of the electric power steering devices of the present invention, the housing, the rotating shaft, the worm wheel, the worm, the electric motor, and the urging member are similar to the above-described conventionally known electric power steering devices. And an elastic member.
Of these, the housing is supported by a fixed part such as a vehicle body and does not rotate during steering.
The rotating shaft is rotatably provided with respect to the housing, and is rotated by an operation of a steering wheel, and gives a steering angle to the steered wheels in accordance with the rotation. As such a rotation shaft, for example, the steering shaft 2 or the intermediate shaft 20 having the structure shown in FIG. 15 described above, or the input shaft (pinion shaft) of the steering gear unit 21 can be employed.
Further, the worm wheel is concentric with a part of the rotating shaft inside the housing, concentric with the rotating shaft (a state in which relative rotation is prevented by an external fitting fixing by an interference fit, a key engagement, a spline engagement, etc. Supported) and rotate with this axis of rotation.
The worm is provided with worm teeth at an intermediate portion in the axial direction of the worm shaft. Then, in a state where the worm teeth are engaged with the worm wheel, both end portions in the axial direction of the worm shaft are rotatably supported with respect to the housing by bearings.
In the electric motor, the base end portion of the worm shaft and the tip end portion of the output shaft are engaged with each other so as to freely transmit a rotational force, so that the worm shaft can be driven to rotate in both directions.
The biasing member rotatably supports the tip of the worm shaft.
The elastic member (for example, a coil spring) presses the worm teeth toward the worm wheel via the biasing member.

In particular, in the electric power steering apparatus of the present invention, at least the bearing far from the electric motor among the bearings that respectively support both axial ends of the worm shaft is a sliding bearing.
In addition, the sliding bearing is inserted into a through hole provided in the guide block held in the housing in a state where the sliding portion can be slidably contacted with a portion separated from the portion supporting the biasing member at the tip of the worm shaft. It is composed by doing.
In the case of the electric power steering apparatus according to the first, sixth, and seventh aspects of the present invention, the guide block for restricting the displacement of the urging member is integrated with the guide block. The guide portion is used to guide the worm shaft through the biasing member such that the worm wheel can only move in the direction of the worm wheel (with the axial displacement of the worm wheel prevented). Furthermore, in the case of the invention described in claim 1, with at least a part of the guide block being elastically deformed (for example, radially inward) (by an interference fit), the guide block is placed in the housing. keeping. On the other hand, in the case of the invention described in claim 6, the guide block is held in the housing in a state where the second elastic member mounted on the guide block is elastically deformed. On the other hand, in the case of the invention described in claim 7, the guide block is held in the housing in a state where the concave and convex portions provided in the housing and the guide block are engaged with the concave and convex portions. ing.
On the other hand, in the case of the electric power steering device according to the third aspect of the present invention, the worm shaft can be directly moved by the inner peripheral surface of the through hole, and only the perspective movement with respect to the worm wheel can be performed (the shaft of the worm wheel). Guidance (with direction displacement blocked). To this end, specifically, a pair of flat surfaces parallel to each other are provided on the inner peripheral surface of the through hole. Then, by allowing the displacement of the worm shaft along the two flat surfaces between the two flat surfaces, the worm shaft is guided so as to allow only the perspective movement relative to the worm wheel.
If necessary, the worm shaft can be guided by the guide portion through the urging member and directly by the inner peripheral surface of the through hole .

In any case, the second elastic member (for example, a leaf spring) mounted on the guide block is preferably used as in the invention described in claim 2 when the invention described in claim 1 is implemented. ) Is elastically deformed, and this guide block is held in the housing.
Further, when the electric power steering apparatus of the present invention described in claim 3 as described above is implemented, the distance between the flat surfaces facing each other is preferably set to A as in the invention described in claim 4. When the outer diameter of the outer peripheral surface of the worm shaft that overlaps the through hole in the radial direction is B, A ≧ B.
Further, when the invention described in claims 1 to 4 as described above is carried out, preferably, as in the invention described in claim 5, a recess and a protrusion provided in the housing and the guide block are provided. The guide block is held in the housing in a state where the concave and convex portions are engaged.

Further, when carrying out the invention described in claim 5 or claim 7, such as described above, and the concave portion and the convex portion may be provided in any of the housing and the guide block. However, more preferably, as in the invention described in claim 8, the inner surface of the housing, the portion (a cylindrical holding recess) which fitted into a guide block having an outer peripheral surface of circular cross section, a concave as a recess A groove is provided over the entire circumference in a state of being recessed from the inner surface, and a convex portion provided on the outer peripheral surface of the guide block is engaged with the concave and convex portions in the concave groove.

According to the electric power steering apparatus of the present invention having the above-described configuration, it is possible to prevent generation of unpleasant noises and vibrations such as rattling noise, and to stably apply auxiliary force from the electric motor. The possible structure can be configured at low cost with a reduced number of parts.
That is, in the case of the electric power steering apparatus of the present invention, the bearing far from the electric motor is a sliding bearing, and this sliding bearing is inserted into the through hole provided in the guide block held in the housing, and the worm shaft. It is configured by inserting a portion that is disengaged from the portion that supports the urging member at the tip portion in a sliding contactable state. For this reason, compared with the case where the front-end | tip part of the said worm shaft is supported by a rolling bearing, a number of parts can be reduced and it can comprise simply and at low cost. In addition, the sliding bearing is constituted by the through hole provided in the guide block, and the sliding bearing is supported by the guide block via the elastic member in order to apply an elastic force to the worm shaft via the biasing member. Compared to the structure, the desired elastic force can be easily applied to the worm shaft (the desired elastic force can be accurately applied, and the elastic force can be easily set and adjusted). And based on such an elastic force, a worm tooth can be appropriately pressed toward a worm wheel, and it can fully prevent generation | occurrence | production of unpleasant noise and vibration like a rattling sound.

In the case of the electric power steering apparatus according to the first, sixth, and seventh aspects of the present invention, the biasing member is guided by the guide portion provided integrally with the guide block. Thus, the displacement of the worm shaft can be strictly regulated in a predetermined direction. For this reason, it is possible to reliably prevent the auxiliary force applied from the electric motor from becoming unstable (the auxiliary torque is likely to fluctuate) based on the worm shaft being displaced in a direction other than the predetermined direction.
Furthermore, in the case of the invention described in claims 1, 2 and 6, at least a part of the guide block (invention 1) or a second elastic member such as a leaf spring mounted on the guide block (invoice) Since the guide block is held in the housing in the state in which the items 2 and 6) are elastically deformed, the elastic force of the guide block itself or the elasticity of the second elastic member (plate spring or the like) Based on the force (when necessary, both the elastic force of the guide block itself and the elastic force of the second elastic member), the guide block rattles in the housing (for example, rotates with the worm shaft, (Displacement in the axial direction) can be prevented. In particular, the inner surface of the housing or the outer peripheral surface of the guide block in a direction in which a gap is formed between the inner surface of the housing and the outer peripheral surface of the guide block (based on a difference in thermal expansion coefficient or the like) due to a temperature change. Even when the is deformed (thermal expansion), it is possible to prevent the guide block from rattling in the housing, and to prevent vibration and noise accompanying the rattling.
In the case of the electric power steering apparatus according to the third aspect of the present invention, the worm shaft is directly guided by the inner peripheral surface of the through hole constituting the slide bearing provided in the guide block. Similar to the first, sixth, and seventh aspects , the displacement of the worm shaft can be strictly regulated in a predetermined direction. For this reason, it is possible to reliably prevent the auxiliary force applied from the electric motor from becoming unstable (the auxiliary torque is likely to fluctuate) based on the worm shaft being displaced in a direction other than the predetermined direction. In addition, when the invention described in claim 3 is adopted, the through hole constituting the sliding bearing guides the worm shaft, so that compared to the case where the invention described in claims 1, 6 and 7 is adopted. Since the guide portion is not required to be provided separately, the configuration can be simplified. Furthermore, in the case of the invention described in claim 3 (and claim 4), a pair of parallel flat surfaces are provided on the inner peripheral surface of the through hole so as to face each other. in order to guide the worm shaft, the displacement of the worm shaft, with a simple configuration, can be more strictly regulated.

Further, when the present invention is implemented, if an elastic member is provided between the guide block and the biasing member, the worm teeth are directed to the worm wheel as compared with the case where the elastic member is provided between the housing and the housing. The pressing force can be set more finely, and unpleasant noises and vibrations such as rattling noise can be more reliably prevented. Moreover, since the guide block, the urging member, and the elastic member can be handled as an assembly (subassembly), the members can be easily assembled to the housing and the worm shaft .

When the guide block is held in the housing with the concave and convex portions provided in the housing and the guide block being engaged with the concave and convex portions as in the inventions described in claims 5 and 7 , Based on this uneven engagement, the guide block can be prevented from rattling in the housing (for example, rotating with the worm shaft or being displaced in the axial direction).
Further, as in the invention described in claim 8 , when a concave groove serving as a concave portion is provided on the entire inner surface of the housing and the convex portion provided on the outer peripheral surface of the guide block is engaged with the concave and convex portions in this concave groove. Therefore, it is possible to more reliably prevent the guide block from being displaced in the axial direction.

[First example of embodiment]
FIGS. 1-5 has shown the 1st example of embodiment of this invention corresponding to Claim 1,5,7,8 . The feature of the electric power steering apparatus of this example is that it is possible to prevent unpleasant noises and vibrations such as rattling noises, and to provide stable auxiliary power from the electric motor 5 (FIGS. 15 and 16). In order to reduce the number of parts and to reduce the number of components, the structure that supports the tip of the worm shaft 7 (the right end of FIGS. 1 and 2) is devised. In addition, since the structure and operation of the entire electric power steering apparatus are the same as those of the conventional structure shown in FIGS. 15 to 20 described above, illustrations and explanations of equivalent parts are omitted or simplified. The description will focus on the features of the example.

  The worm 6 is formed by providing worm teeth 8 at an intermediate portion in the axial direction of the worm shaft 7. In the state where the worm teeth 8 are engaged with the worm wheel 4, the base end portion on the side closer to the electric motor 5 among the axial end portions of the worm shaft 7 is a single row deep groove type ball bearing. Similarly, the rolling bearing 9 supports the distal end portion on the side far from the electric motor 5 by the sliding bearing 22 so as to be rotatable with respect to the housing 3a. In the case of this example, the rolling bearing 9 supports the worm shaft 7 with respect to the housing 3a so as to be able to be slightly oscillated, similarly to the conventional structure described above. Since the angle of this oscillating displacement is small, it can be easily absorbed by the low moment rigidity of the single row deep groove ball bearing. This is the same as in the case of the conventional structure.

  On the other hand, the sliding bearing 22 has a portion (a tip-proximal portion) separated from a portion of the worm shaft 7 that supports the urging member 10 in a through hole 23 provided in the guide block 13a held in the housing 3a. ) Is inserted in a state where sliding contact is possible. For this reason, in the case of this example, a holding recess 12a is provided in a portion of the housing 3a facing the tip of the worm shaft 7, and the guide block 13a is held in the holding recess 12a. Of these, the holding recess 12a is a bottomed cylindrical recess that opens inside the housing 3a and does not change in the axial direction (the inner diameter is constant). The guide block 13a is made of a slippery (low sliding resistance) synthetic resin such as polyamide resin or polytetrafluoroethylene resin, or relatively self-lubricating instead of having a self-lubricating property such as copper or a copper alloy. It is made of soft metal and made as one piece. In place of such a single material structure of metal or synthetic resin, the portion in sliding contact with the outer peripheral surface of the worm shaft 7 has a multilayer structure of the above-described synthetic resin and metal, and such a synthetic resin. A sliding bearing 22 composed of a layer and a metal layer may be provided on the guide block 13a.

  Such a guide block 13a includes a main body portion 24, a cylindrical portion 25, and a pair of guide wall portions 15, 15 each serving as a guide portion. Of these, the main body 24 has an outer peripheral surface having a circular cross section, and the through hole 23 is formed in the center. The cylindrical portion 25 has an outer peripheral surface that is continuous with the outer peripheral surface of the main body portion 24 (having the same outer diameter), and is an outer side surface in the axial direction of the main body portion 24 (a side surface facing the inner surface of the holding recess 12a). ) To protrude outward in the axial direction, and is provided integrally with the main body 24. The guide wall portions 15 and 15 are provided integrally with the main body portion 24 on the inner diameter side of the cylindrical portion 25 so as to protrude outward from the axial outer surface of the main body portion 24 in the axial direction. Yes. In addition, the inner side surfaces of both the guide wall portions 15 and 15 are parallel planes, and the biasing member 10 that is externally fitted to the tip portion of the worm shaft 7 is sandwiched between the inner side surfaces. .

In the case of this example, as shown in detail in FIG. 5, at least a pair of convex portions 26 and 26 are provided on the outer peripheral surface of the main body portion 24 so as to protrude radially outward from the outer peripheral surface. ing. At the same time, of the inner surface of the holding recess 12a, the guide block 13a is fitted in the holding recess 12a and is aligned with the projections 26, 26, and radially outward from the inner surface. A concave groove 27 to be recessed is provided over the entire circumference. Then, with the guide block 13a held in the holding recess 12a, the projections 26 and 26 and the recess 27 are engaged with each other. In the case of this example, the guide block 13a is fitted in the holding recess 12a without looseness in an elastically deformed state (by an interference fit). Therefore, in the case of this example, the outer diameter of the main body 24 in the free state (for example, as shown in FIG. 5, the outer diameter of the main body is D ₂₄ and the height 26 of the convex portion 26 is of the outer diameter D = D ₂₄ + h also contains the height h protrusion 26), the inner diameter of the holding recess 12a (e.g., as shown in FIG. 2, the inner diameter of the holding recess 12a and d _12, concave When the depth of the groove 27 is f, the inner diameter d = d ₁₂ + f) including the depth f of the concave groove 27 is larger (D> d). At the same time, on the inner side surface in the axial direction of the main body 24 (the side surface opposite to the inner surface of the holding recess 12a), on the inner diameter side portion of each of the convex portions 26, 26, from the inner side surface in the axial direction outside. An elastic deformation allowing recess 28 to be recessed is provided.

  In a state where the guide block 13 a is held in the holding recess 12 a, a part of the guide block 13 a, that is, a peripheral portion of the elastic deformation allowing recess 28 is elastically deformed radially inward of the main body 24. Based on the elastic force of the guide block 13a itself based on the elastic deformation, the convex portions 26, 26 are pressed toward the bottom of the concave groove 27, and the guide block 13a is inserted into the holding concave portion 12a. It is held (internally fitted) without rattling. In the case of this example in which such an elastic deformation allowing recess 28 is provided, since the guide block 13a can be easily elastically deformed in a predetermined direction by the elastic deformation allowing recess 28, the guide block 13a is elastically deformed. Thus, it is possible to easily perform the work of assembling into the holding recess 12a (improvement of assembling workability). Further, the guide block 13a is prevented from being displaced in the axial direction based on the concave / convex engagement between the convex portions 26 and 26 and the concave groove 27. Instead of the pair of convex portions 26, 26, as shown in FIG. 3, a convex portion 26a can be provided over the entire circumference on the outer peripheral surface of the main body 24 of the guide block 13a.

Further, in the state where the guide block 13a is held (assembled) in the holding recess 12a as described above, the inner side surfaces (side surfaces facing each other) of the both guide wall portions 15 and 15 are respectively connected to the central axis of the worm wheel 4. It is arranged in a direction perpendicular to it. Then, the biasing member 10 that is externally fitted to the distal end portion of the worm shaft 7 is sandwiched between the inner side surfaces of the guide wall portions 15 and 15, and the biasing member 10 is connected to the both side surfaces. The guide walls 15 and 15 are supported in a state where displacement along the inner side surfaces of the guide wall portions 15 and 15 is possible and the displacement in the direction of the central axis of the worm wheel 4 is suppressed. Accordingly, the worm shaft 7 is guided by the guide wall portions 15 and 15 via the biasing member 10 so as to be able to move only in the distance direction relative to the worm wheel 4. Further, the bent portions 18 and 18 of the coil spring 11 which is an elastic member and is externally fitted to the biasing member 10 are locked to the locking recesses 19 and 19 formed in the both guide wall portions 15 and 15. . Then, the worm teeth 8 of the worm 6 are applied to the worm wheel 4 based on the elasticity of the coil spring 11 spanned (provided) between the biasing member 10 and the guide wall portions 15, 15 in this way. It is pushing toward.

  Also, a through hole constituting the slide bearing 22 is provided with a base end side portion of the distal end portion of the worm shaft 7 with respect to a portion where the urging member 10 is externally fitted to the main body portion 24 of the guide block 13a. 23 is inserted. In the case of this example, the inner diameter of the through-hole 23 is made larger than the outer diameter of the portion that overlaps the through-hole 23 in the radial direction at the tip of the worm shaft 7 (the portion that passes through the through-hole 23). The worm shaft 6 is allowed to displace (in the radial direction) within the through hole 23. More specifically, the cross-sectional shape of the through hole 23 is an oval oval shape, and the short diameter of the through hole 23 is the center of the worm wheel 4 in a state where the guide block 13a is held in the holding recess 12a. They are arranged in a direction parallel to the axis, and the long diameter of the through hole 23 faces in a direction perpendicular to the central axis of the worm wheel 4. Therefore, the tip of the worm shaft 7 has a larger displacement tolerance in the direction perpendicular to the central axis of the worm wheel 4 than the displacement tolerance in the direction parallel to the central axis of the worm wheel 4.

In the case of this example as described above, it is possible to prevent the generation of unpleasant noises and vibrations such as rattling noise, and to provide a stable auxiliary force from the electric motor 5 with a reduced number of parts. It can be configured with low cost and low cost.
That is, in this example, as described above, the bearing far from the electric motor 5 is the sliding bearing 22, and this sliding bearing 22 is provided in the guide block 13a held in the holding recess 12a of the housing 3a. A portion of the worm shaft 7 that is out of the portion supporting the urging member 10 at the tip end portion of the worm shaft 7 is inserted into the through hole 23 so as to be in sliding contact. For this reason, compared with the case where the tip of the worm shaft 7 is supported by a rolling bearing such as the conventional structure described above or the structure described in Patent Document 5, the number of parts is reduced, and Can be configured at low cost. In addition, the sliding bearing 22 is constituted by the through-hole 23 provided in the guide block 13a, and an elastic force is applied to the worm shaft 7 through the biasing member 10, so that it is described in the aforementioned Patent Document 3. Compared to the structure in which the sliding bearing is supported on the guide block via an elastic member, such as the above-described structure, it is possible to easily apply a desired elastic force to the worm shaft 7 (the desired elastic force can be accurately applied, and this The elastic force can be easily set and adjusted.) Based on such elastic force, the worm teeth 8 of the worm 6 can be appropriately pressed toward the worm wheel 4, and unpleasant noise and vibration such as rattling noise can be prevented.

  Further, in the case of this example, since the biasing member 10 is guided by the guide wall portions 15 and 15 provided integrally with the guide block 13a, the displacement of the worm shaft 7 is changed to a predetermined value via the biasing member 10. It can be strictly regulated in the direction. For this reason, it is possible to reliably prevent the auxiliary force applied from the electric motor 5 from becoming unstable (the auxiliary torque is likely to fluctuate) due to the worm shaft 7 being displaced in a direction other than the predetermined direction. Further, since the coil spring 11 is provided between the guide block 13a and the biasing member 10, an elastic member such as the structure described in Patent Documents 4 and 5 described above is interposed between the housing and the housing. Compared with the case where it provides, the force which presses the worm tooth 8 toward the worm wheel 4 can be set more finely, and unpleasant noises and vibrations such as rattling noise can be prevented more reliably. Moreover, since the guide block 13a, the urging member 10 and the coil spring 11 can be integrally handled as an assembly, the members 13a, 10 and 11 can be easily assembled to the housing 3a and the worm shaft 7. Yes.

In the case of this example, in the main body 24 of the guide block 13a, at least the radially outer portion of the guide block 13a is elastically deformed radially inward from the elastic deformation allowing recess 28, and the guide block 13a is moved. It is held in the holding recess 12a of the housing 3a. Therefore, based on the elastic force of the guide block 13a itself, more specifically, on the basis of the fact that the convex portions 26, 26 are pressed against the concave groove 27 based on the elastic force, the guide block 13a is It is possible to reliably prevent rattling (for example, rotation with the worm shaft 7 or displacement in the axial direction) in the holding recess 12a. In particular, as the temperature changes, the holding recess 12a and the holding recess 12a are formed in a direction in which a gap is formed between the inner peripheral surface of the holding recess 12a and the outer peripheral surface of the main body 24 (based on a difference in coefficient of thermal expansion). Even if the main body 24 is deformed (thermally expanded), the guide block 13a can be prevented from rattling in the holding recess 12a, and vibrations and noise caused by this rattling can be prevented.

[Second Example of Embodiment]
FIG. 6 shows a second example of an embodiment of the present invention corresponding to claims 1, 5 , 7, and 8 . In the case of this example, a pair of notches 29a and 29b are provided on the outer peripheral surface of the guide block 13b in the axial direction of the guide block 13b and recessed radially inward from the outer peripheral surface. Yes. Of these notches 29a and 29b, the side close to the convex portions 26 and 26 provided on the outer peripheral surface of the main body 24 of the guide block 13b {the side close to the worm wheel 4 (see FIG. 1) in the assembled state} One notch 29 a reaches the through hole 23 provided at the center of the main body 24 (communication with the through hole 23). On the other hand, the other notch 29b on the side far from each convex part 26, 26 {the side far from the worm wheel 4 in the assembled state} does not reach the through hole 23 (not communicated with the through hole 23). It has a bottomed shape. In the case of this example, the guide block 13b is elastically deformed (in the direction of reducing the diameter) in a state where the guide block 13b is held in the holding recess 12a (see FIGS. 1 and 2). More specifically, the inner surfaces facing each other of the one notch 29a are elastically deformed in a direction approaching each other, and the inner surfaces facing each other of the other notch 29b are elastically deformed in a direction away from each other. Then, based on the elastic force of the guide block 13b itself based on such elastic deformation, the convex portions 26, 26 are pressed toward the bottom of the concave groove 27 (see FIGS. 1 and 2), and the guide block 13b is held (internally fitted) in the holding recess 12a without rattling.
Other configurations and operations are the same as those in the first example described above, and thus redundant description is omitted.

[Third example of embodiment]
FIG. 7 shows a third example of an embodiment of the present invention corresponding to claims 1, 2, and 5-8 . In the case of this example, the guide block 13e is recessed from the inner side surface into the axially inner side surface {the side surface on the side farther from the inner surface of the holding recess 12a (see FIGS. 1 and 2) in the assembled state}. In this state, a pair of locking grooves 37, 37 are provided. Each of the locking grooves 37, 37 has a partial arc-shaped groove path that is symmetrical with respect to the other notch 29a with the axial inner surface of the guide block 13e viewed from the axial direction. Then, a leaf spring 38 as a second elastic member, which is curved in a partial arc shape, is engaged with the pair of locking grooves 37, 37 over the pair of locking grooves 37, 37. doing. The leaf spring 38 has a curvature radius in the free state of the peripheral surface on the convex curved surface side in a free state of the inner surface on the outer side with respect to the radial direction of the guide block 13e among the inner surfaces of the locking grooves 37, 37. The radius of curvature is approximately the same. In the case of this example, such a leaf spring 38 is attached to the guide block 13e by being engaged with the engagement grooves 37, 37.

With the guide block 13e fitted with the leaf spring 38 held in the holding recess 12a (internally fitted), the leaf spring 38 is reduced in diameter in the locking grooves 37, 37 (guide). It is elastically deformed radially inward of the block 13e. Based on the elastic force (elastic force in the direction toward the outside in the radial direction) based on the elastic deformation of the leaf spring 38 and the elastic deformation of the guide block 13e itself, the convex portions 26 and 26 are formed in the concave grooves 27 ( 1), the guide block 13e is held (internally fitted) in the holding recess 12a without rattling. In the case of this example, the necessary elastic force can be obtained from both the plate spring 38 and the guide block 13e itself. For example, the elastic force of the guide block cannot be obtained. In some cases, the guide block 13e can be prevented from rattling based only on the elastic force of the leaf spring 38.
Other configurations and operations are the same as those in the above-described second example, and thus redundant description is omitted.

[Fourth Example of Embodiment]
8 to 11 show a fourth example of an embodiment of the present invention corresponding to claims 3 and 4. In the case of the first example of the embodiment shown in FIGS. 1 to 5 described above, guide wall portions 15 and 15 for restricting the displacement of the urging member 10 are integrated with the guide block 13a. The worm shaft 7 is guided by the guide wall portions 15 and 15 via the biasing member 10 so as to be able to move only in the distance direction relative to the worm wheel 4 (see FIGS. 1 to 5). On the other hand, in the case of this example, the guide wall portions 15 and 15 guide the worm shaft 7 through the biasing member 10 as described above, and the inner peripheral surface of the through hole 23a provided in the guide block 13c. Also, the worm shaft 7 is directly guided. For this reason, in this example, a pair of parallel flat surfaces 30 and 30 are provided on the inner peripheral surface of the through hole 23a so as to face each other. In the case of this example, when the interval between the two flat surfaces 30 and 30 is A, and the outer diameter of the outer peripheral surface of the worm shaft 7 is B, the outer diameter of the portion overlapping the through hole 23a in the radial direction. In addition, A ≧ B (where “A−B” is a small value of 0.1 mm or less). Then, by allowing the displacement of the worm shaft 7 along the two flat surfaces 30, 30 between the two flat surfaces 30, 30, the worm shaft 7 can be moved only in the perspective direction relative to the worm wheel 4. Guided as possible.

  In this example, the guide wall portions 15 and 15 for guiding the urging member 10 are provided, but such guide wall portions 15 and 15 can be omitted. That is, the worm shaft 7 can be guided only by the inner peripheral surface of the through hole 23a provided in the guide block 13c. In such a case, the shape of the guide block 13c can be configured more simply because the guide wall portions 15 and 15 need not be provided. In any case, if the worm shaft 7 is guided directly by the inner peripheral surface of the through hole 23a constituting the slide bearing 22 provided in the guide block 13c, the displacement of the worm shaft 7 is changed in a predetermined direction. It can be strictly regulated. Moreover, if the worm shaft 7 is guided by both the guide wall portions 15 and 15 and the through hole 23a, the displacement of the worm shaft 7 can be more strictly regulated. For this reason, it is possible to reliably prevent the auxiliary force applied from the electric motor 5 from becoming unstable (the auxiliary torque is likely to fluctuate) based on the displacement of the worm shaft 7 in a direction other than the predetermined direction.

In the case of this example, the holding recess 12b is constituted by a large-diameter portion 31 that opens to the inside of the housing 3b and a small-diameter portion 32 that is concentric with the large-diameter portion 31 and has a smaller inner diameter than the large-diameter portion 31. doing. Then, the guide block 13c is held in the holding recess 12b by fitting the main body 24a of the guide block 13c into the large-diameter portion 31 without rattling. Accordingly, in the case of this example, the cylindrical portion 25 (see, for example, FIGS. 1 to 4) like the guide block 13a of the first example of the embodiment described above is not provided. Further, in order to prevent the guide block 13c from rattling in the holding recess 12b while the guide block 13c is held in the holding recess 12b, for example, the main body portion 24a is tightly fitted to the large diameter portion 31. Therefore, it is preferable to hold the main body 31 in a state of being elastically deformed.
Other configurations and operations are the same as those of the first to third examples described above, and thus a duplicate description is omitted.

[Fifth Example of Embodiment]
12 to 14 show a fifth example of the embodiment of the invention corresponding to claims 3 to 5 , 7 and 8 . In the case of this example, the convex part 33 is provided in the outer peripheral surface intermediate part of the main-body part 24b of the guide block 13d in the state which protrudes radially outward from this outer peripheral surface. At the same time, of the inner surface of the holding recess 12c of the housing 3b, the guide block 13d is recessed in the radially outward direction from the inner surface in a portion aligned with the protrusion 33 with the guide block 13d fitted inside the holding recess 12c. A recessed groove 34 is provided over the entire circumference. Then, in a state where the guide block 13d is held in the holding concave portion 12c (a state where the main body portion 24b is fitted inside the large diameter portion 31), the convex portion 33 and the concave groove 34 are engaged with each other. In the case of this example, the guide block 13d is prevented from rattling (displacement) in the axial direction on the basis of the concave-convex engagement between the convex portion 33 and the concave groove 34. ). Further, in the case of this example, the portion of the outer peripheral surface of the main body portion 24b that is off the axially outer side (the side opposite to the inner surface of the holding recess 12c) from the portion where the convex portion 33 is provided, and A convex portion 35 different from the convex portion 33 is provided on a portion opposite to the convex portion 33 in the radial direction so as to protrude radially outward from the outer peripheral surface. In the case of this example, the other convex portion 35 is provided with a concave and convex portion in the axially long concave groove 36 provided at a position aligned with the other convex portion 35 on the inner surface of the large-diameter portion 31 of the holding concave portion 12c. It is combined. The guide block 13d is prevented from rattling (rotating) in the circumferential direction based on the concave / convex engagement between the other convex portion 35 and the concave groove 36 (to prevent rotation), and the guide block Positioning in the circumferential direction of 13d is intended.
Other configurations and operations are the same as those in the above-described fourth example, and thus redundant description is omitted.

Sectional drawing similar to FIG. 17 which shows the 1st example of embodiment of this invention. The A section enlarged view of FIG. B arrow view of FIG. The perspective view shown in the state before taking out an urging member, a guide block, and a coil spring, and combining each. The figure which took out the guide block and was seen from the left side of FIG. The figure similar to FIG. 5 which shows the 2nd example of embodiment of this invention. Sectional drawing similar to FIG. 5 which shows the 3rd example. Sectional drawing similar to FIG. 1 showing the fourth example. The C section enlarged view of FIG. DD sectional drawing of FIG. The figure corresponded to the EE cross section of FIG. Sectional drawing similar to FIG. 9 which shows the 5th example of embodiment of this invention. FF sectional drawing of FIG. GG sectional drawing. The partially cut side view which shows an example of a conventional structure. FIG. 16 is an enlarged HH sectional view of FIG. 15. The expanded sectional view of the lower right part of FIG. II sectional drawing of FIG. The perspective view shown in the state which took out and combined the biasing member, the guide block, and the coil spring. Similarly disassembled perspective view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering shaft 3, 3a, 3b Housing 4 Worm wheel 5 Electric motor 6 Worm 7 Worm shaft 8 Worm tooth 9, 9a, 9b Rolling bearing 10 Energizing member 11 Coil spring 12, 12a, 12b, 12c Holding recessed part 13 , 13a, 13b, 13c, 13d, 13e Guide block 14 Elastic ring 15 Guide wall 16 Main body 17 Coil 18 Bent 19 Locking recess 20 Intermediate shaft 21 Steering gear unit 22 Slide bearing 23, 23a Through hole 24, 24a 24b Main body part 25 Cylindrical part 26, 26a Convex part 27 Concave groove 28 Elastic deformation allowable concave part 29a, 29b Notch 30 Flat surface 31 Large diameter part 32 Small diameter part 33 Convex part 34 Concave groove 35 Convex part 36 Concave groove 37 Locking Groove 38 leaf spring

Claims (8)

A housing that is supported by a fixed portion and does not rotate; a rotating shaft that is rotatably provided to the housing and is rotated by an operation of a steering wheel; A worm wheel that is supported concentrically with the rotary shaft inside the housing and rotates together with the rotary shaft, and a worm tooth is provided at an axially intermediate portion of the worm shaft. A worm in which both end portions in the axial direction of the worm shaft are rotatably supported with respect to the housing by bearings in a state where the worm teeth are engaged with the worm wheel, a base end portion of the worm shaft, and a distal end portion of the output shaft An electric motor that freely engages transmission of rotational force, an urging member that rotatably supports the tip of the worm shaft, and via the urging member The serial worm teeth at the electric power steering apparatus that includes a resilient member for pressing toward the worm wheel,
Of the bearings that respectively support both axial ends of the worm shaft, at least the bearing far from the electric motor is a sliding bearing.
By inserting the sliding bearing into a through hole provided in the guide block held in the housing in a state in which the tip portion of the worm shaft is separated from the portion supporting the biasing member in a sliding contactable state. Configured
A guide portion for restricting the displacement of the urging member is provided on the guide block integrally with the guide block, and the worm shaft is moved by the guide portion through the urging member, and only the perspective movement with respect to the worm wheel is performed. Is possible ,
Furthermore, the electric power steering apparatus , wherein the guide block is held in the housing in a state where at least a part of the guide block is elastically deformed . The electric power steering apparatus according to claim 1 , wherein the second elastic member mounted on the guide block is elastically deformed and the guide block is held in the housing. A housing that is supported by a fixed portion and does not rotate; a rotating shaft that is rotatably provided to the housing and is rotated by an operation of a steering wheel; A worm wheel that is supported concentrically with the rotary shaft inside the housing and rotates together with the rotary shaft, and a worm tooth is provided at an axially intermediate portion of the worm shaft. A worm in which both end portions in the axial direction of the worm shaft are rotatably supported with respect to the housing by bearings in a state where the worm teeth are engaged with the worm wheel, a base end portion of the worm shaft, and a distal end portion of the output shaft An electric motor that freely engages transmission of rotational force, an urging member that rotatably supports the tip of the worm shaft, and via the urging member The serial worm teeth at the electric power steering apparatus that includes a resilient member for pressing toward the worm wheel,
Of the bearings that respectively support both axial ends of the worm shaft, at least the bearing far from the electric motor is a sliding bearing.
By inserting the sliding bearing into a through hole provided in the guide block held in the housing in a state in which the tip portion of the worm shaft is separated from the portion supporting the biasing member in a sliding contactable state. Configured
By providing a pair of flat surfaces parallel to each other on the inner peripheral surface of the through hole and allowing the displacement of the worm shaft along the two flat surfaces between the two flat surfaces, An electric power steering device characterized in that the worm shaft is guided so as to allow only a perspective movement relative to the worm wheel .   The distance between the flat surfaces facing each other is A, and the outer diameter of the portion of the outer peripheral surface of the worm shaft that overlaps with the through hole in the radial direction is B, where A ≧ B. Electric power steering device. The electric type according to any one of claims 1 to 4 , wherein the guide block is held in the housing in a state in which the concave portion and the convex portion provided in the housing and the guide block are engaged with each other. Power steering device. A housing that is supported by a fixed portion and does not rotate; a rotating shaft that is rotatably provided to the housing and is rotated by an operation of a steering wheel; A worm wheel that is supported concentrically with the rotary shaft inside the housing and rotates together with the rotary shaft, and a worm tooth is provided at an axially intermediate portion of the worm shaft. A worm in which both end portions in the axial direction of the worm shaft are rotatably supported with respect to the housing by bearings in a state where the worm teeth are engaged with the worm wheel, a base end portion of the worm shaft, and a distal end portion of the output shaft An electric motor that freely engages transmission of rotational force, an urging member that rotatably supports the tip of the worm shaft, and via the urging member The serial worm teeth at the electric power steering apparatus that includes a resilient member for pressing toward the worm wheel,
Of the bearings that respectively support both axial ends of the worm shaft, at least the bearing far from the electric motor is a sliding bearing.
By inserting the sliding bearing into a through hole provided in the guide block held in the housing in a state in which the tip portion of the worm shaft is separated from the portion supporting the biasing member in a sliding contactable state. Configured
A guide portion for restricting the displacement of the urging member is provided on the guide block integrally with the guide block, and the worm shaft is moved by the guide portion through the urging member, and only the perspective movement with respect to the worm wheel is performed. Is possible ,
Furthermore, the electric power steering apparatus, wherein the second elastic member mounted on the guide block is elastically deformed and the guide block is held in the housing . A housing that is supported by a fixed portion and does not rotate; a rotating shaft that is rotatably provided to the housing and is rotated by an operation of a steering wheel; A worm wheel that is supported concentrically with the rotary shaft inside the housing and rotates together with the rotary shaft, and a worm tooth is provided at an axially intermediate portion of the worm shaft. A worm in which both end portions in the axial direction of the worm shaft are rotatably supported with respect to the housing by bearings in a state where the worm teeth are engaged with the worm wheel, a base end portion of the worm shaft, and a distal end portion of the output shaft An electric motor that freely engages transmission of rotational force, an urging member that rotatably supports the tip of the worm shaft, and via the urging member The serial worm teeth at the electric power steering apparatus that includes a resilient member for pressing toward the worm wheel,
Of the bearings that respectively support both axial ends of the worm shaft, at least the bearing far from the electric motor is a sliding bearing.
By inserting the sliding bearing into a through hole provided in the guide block held in the housing in a state in which the tip portion of the worm shaft is separated from the portion supporting the biasing member in a sliding contactable state. Configured
A guide portion for restricting the displacement of the urging member is provided on the guide block integrally with the guide block, and the worm shaft is moved by the guide portion through the urging member, and only the perspective movement with respect to the worm wheel is performed. Is possible ,
Further, the electric power steering apparatus is characterized in that the guide block is held in the housing in a state where the concave and convex portions provided in the housing and the guide block are engaged with each other . On the inner surface of the housing, a concave groove serving as a concave portion is provided over the entire circumference in a state of being recessed from the inner surface in a portion where the guide block having an outer peripheral surface having a circular cross section is fitted, and the guide block is provided in the concave groove. The electric power steering device according to claim 5 or 7 , wherein the convex portions provided on the outer peripheral surface of the motor are engaged with each other.

Images