JP2005313659A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simply install a worm and a worm wheel to a first storage hole and a second storage hole in such a constitution that a distance between rotation centers of the worm and a worm wheel made of metal is not adjusted. <P>SOLUTION: The electric power steering device is provided with the worm 3 interlocked/connected to an electric motor 1 for steering assistance; the worm wheel 4 engaged with the worm 3 and supported on a steering shaft 63 of a steering mechanism having the steering shaft 63; a housing 5 having a first storage hole 5a for storing the worm 3 and a second storage hole 5b for storing the worm wheel 4; and a first bearing 7 and a second bearing 8 for supporting both ends of the worm 3 on the first storage hole 5a. The worm 3 and the worm wheel 4 are made of metal and an outer diameter of the second bearing 8 opposite to the electric motor 1 is made smaller than the outer diameter of the first bearing 7. A non-distortion ring 12 is fitted between the outer peripheral surface of the second bearing 8 and the first storage hole 5a and the distance H between the rotation centers is made nonadjustable. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electric power steering apparatus using an electric motor as a generation source of a steering assist force.

  As an electric power steering device for a vehicle, for example, a steering torque applied to the input shaft is detected by a relative angular displacement amount of an input shaft connected to a steering wheel and an output shaft connected coaxially to the input shaft via a torsion bar, Based on the detected torque or the like, the steering assisting electric motor is driven, and the rotational force of the electric motor is transmitted to the steering mechanism via the worm and the worm wheel, so that the operation of the steering mechanism according to the rotation of the steering wheel is performed. Assisting by the rotation of the electric motor, it is configured to reduce the labor burden on the driver for steering.

  A housing having a first housing hole for housing the worm and a second housing hole for housing the worm wheel; a first bearing and a second bearing for supporting both end portions of the worm in the first housing hole; A rotating shaft that externally supports the worm wheel and a third bearing that supports the rotating shaft in the second receiving hole are provided, and a worm having a first bearing and a second bearing externally fitted to both ends is provided. After being inserted and supported in the first accommodation hole, the worm wheel fitted on the rotating shaft is inserted and supported in the second accommodation hole.

  By the way, in the electric power steering device, when the worm and the worm wheel are made of metal as in Patent Document 1, the rattling noise caused by the backlash generated in the meshing portion of the worm and the worm wheel is increased. It is necessary to reduce the amount of rush by dimensional tolerance. On the other hand, when one of the worm and the worm wheel is made of a synthetic resin, since one tooth portion has flexibility, the rattling noise caused by backlash can be reduced, and the worm is first accommodated. After being inserted and supported in the hole, the worm wheel fitted on the rotating shaft can be inserted and supported in the second accommodation hole.

However, when one of the worm and the worm wheel is made of a synthetic resin, there is a problem that both cannot transmit a large rotational torque as compared with a metal one. Therefore, in order to transmit a large rotational torque, the worm and worm wheel must be made of metal.
Japanese Patent No. 2830992

  However, when the worm and the worm wheel are made of metal, the tooth portion does not bend at all, so the worm is inserted and supported in the first accommodation hole, and then the worm wheel fitted on the rotating shaft is inserted in the second accommodation hole It cannot be supported, and after the worm wheel is inserted and supported in the second accommodation hole, the worm having the first bearing and the second bearing fitted on both ends cannot be inserted and supported in the first accommodation hole. . Therefore, when both are made of metal, for example, one of the worm and the worm wheel can be moved in a direction in which the distance between the rotation centers of the two becomes longer, and the backlash amount of the meshing portion after the worm and the worm wheel are assembled Must be configured to be adjustable.

  However, if it is possible to move in the direction in which the distance between the rotation centers becomes longer or shorter, the stability of the worm or worm wheel on the moving side is likely to deteriorate, and the backlash amount of the engagement portion is easily changed. It is preferable to reduce the amount of backlash by dimensional tolerance.

  The present invention has been made in view of such circumstances, and in the configuration in which the distance between the rotation centers of the metal worm and the worm wheel is not adjusted, the worm and the worm wheel are formed in the first accommodation hole and the second accommodation hole. An object of the present invention is to provide an electric power steering device that can be easily incorporated.

  An electric power steering device according to a first aspect of the present invention is a worm coupled to a steering assisting electric motor, a worm wheel meshed with the worm and supported on the rotating shaft of a steering mechanism having a rotating shaft, A housing having a first housing hole for housing a worm and a second housing hole for housing the worm wheel; and a first bearing and a second bearing for supporting both ends of the worm in the first housing hole, In the electric power steering apparatus configured to assist steering by the rotation of the electric motor, the worm and the worm wheel are made of metal, and the outer diameter of the second bearing opposite to the electric motor is the outer diameter of the first bearing. The first receiving hole is opened to the electric motor side, and the second opening is opened to the counter-electric motor side. The has, wherein the non flexures ring is fitted between the second bearing outer peripheral surface and the first housing hole of.

  In the first invention, the outer diameter of the second bearing opposite to the electric motor is formed to be smaller than the outer diameter of the first bearing, and the worm and the worm wheel are connected to the second bearing by the first accommodation hole. Since the worm with the first bearing and the second bearing fitted on both ends is inserted into the first receiving hole from the first opening port, the second can be made. The worm can be biased so that the distance between the rotation centers on the bearing side becomes long, and in this state, the worm wheel externally fitted to the rotation shaft can be inserted and supported in the second receiving hole. After insertion, the worm can be inserted into place. Thereafter, the non-flexible ring can be inserted into the first accommodation hole from the second opening, and the non-flexible ring can be fitted between the outer peripheral surface of the second bearing and the first accommodation hole, and the distance between the rotation centers Can be unadjusted.

  In the electric power steering apparatus according to the second aspect of the present invention, the distance between the rotation centers of the worm and the worm wheel becomes longer than the dimension of the second bearing in the first accommodation hole plus the end of the worm and worm wheel. The second bearing is formed in a size that can be biased in the direction.

  In the second invention, the position where the second bearing side does not interfere with the worm wheel in the middle of inserting the worm having the first bearing and the second bearing fitted on both ends into the first accommodation hole from the first opening. The worm wheel can be easily incorporated.

  According to the first and second inventions, a large torque can be generated by the metal worm and worm wheel, and the worm and worm wheel with the non-adjustment of the distance between the rotation centers are provided in the first accommodation hole and the second worm wheel. 2 can be easily incorporated into the receiving hole, and the backlash amount of the meshing portion can be maintained.

  Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof. FIG. 1 is an enlarged cross-sectional view of a main part showing the configuration of an electric power steering apparatus according to the present invention, FIG. 2 is an enlarged view of a meshing portion of a worm and a worm wheel, and FIG. 3 is a cross-sectional view showing the overall structure of the electric power steering apparatus It is.

  The electric power steering apparatus includes an electric motor 1 for assisting steering, a worm 3 coupled to an output shaft 1a of the electric motor 1 via a shaft coupling 2, a worm wheel 4 meshing with the worm 3, and a worm 3 A steering mechanism 6 having a housing 5 having a first housing hole 5a for housing the worm wheel 4 and a second housing hole 5b for housing the worm wheel 4 and a rotating shaft (described later) for supporting the worm wheel 4 and connected to the worm wheel 4. The electric motor 1 is attached to one end of the housing 5.

  The steering mechanism 6 has one end connected to a steering wheel A for steering and a first steering shaft 61 having a cylindrical part 61a at the other end, and is inserted into the cylindrical part 61a, and one end thereof is a first part. A torsion bar 62 connected to the cylindrical portion 61a of the steering shaft 61 and twisted by the action of the steering torque applied to the steering wheel A, and a rotating shaft connected to the other end of the torsion bar 62 and connected to the worm wheel 4 The second steering shaft 63 is connected to, for example, a rack and pinion type steering mechanism (not shown) via a universal joint and an intermediate shaft.

  The worm 3 includes a metal shaft member having a tooth portion 31 at the center and shaft portions 32 and 33 at both ends, and a first bearing 7 formed of a rolling bearing is fitted on one shaft portion 32. A second bearing 8 made of a rolling bearing is fitted on the other shaft portion 33.

  The second bearing 8 is formed with a smaller diameter than the first bearing 7. The second bearing 8 has a direction in which the distance H between the rotation centers of the worm 3 and the worm wheel 4 becomes longer than the dimension obtained by adding the hose h and h of the end of the worm 3 and the worm wheel 4 in the first accommodation hole 5a. The second bearing 8 is formed in a size capable of being biased.

  The worm wheel 4 is made of metal having teeth on the outer peripheral portion and a fitting hole 4 a in the central portion, and is fitted and fixed in the middle of the second steering shaft 63.

  On both sides of the worm wheel 4 of the second steering shaft 63, a third bearing 9 and a fourth bearing 10 made of rolling bearings are fitted.

  The first receiving hole 5 a of the housing 5 is elongated in the axial length direction of the worm 3, and a first fitting portion 51 that internally fits and supports the first bearing 7 at one end portion, and the first fitting portion 51. A first opening 52 opened to the outside, an annular groove 53 provided on one side of the first fitting portion 51, and a stepped portion 54 in the radial direction provided on the other side of the first fitting portion 51. The retaining ring 11 is fitted in the annular groove 53. Further, a second fitting portion 55 having a smaller diameter than the first fitting portion 5a and a second opening 56 opened to the outside from the second fitting portion 55 are provided at the other end of the first accommodation hole 5a. Is provided. A metal non-flexible ring 12 is fitted between the second fitting portion 55 and the outer peripheral surface of the second bearing 8, and the lid 13 is removably screwed to the second opening 56. Yes. The non-flexible ring 12 has a cylindrical shape and prevents the worm 3 from being biased by being fitted to the outer peripheral surfaces of the second fitting portion 55 and the second bearing 8. The non-flexible ring 12 is made of metal and may be configured not to be bent in a cylindrical state.

  In the second accommodation hole 5b, a third fitting portion 57 into which the third bearing 9 is fitted and a fourth fitting portion 58 into which the fourth bearing 10 is fitted are provided concentrically. The center-to-center distance between the center of the third fitting portion 57 and the fourth fitting portion 58 and the center of the first fitting portion 51 and the second fitting portion 55, in other words, the first fitting portion 51 and the second fitting. The worm 3 is supported by the joint portion 55 via the first bearing 7 and the second bearing 8, and is supported by the third fitting portion 57 and the fourth fitting portion 58 via the third bearing 9 and the fourth bearing 10. The distance H between the rotation centers of the worm wheel 4 and the worm wheel 4 is set so that the backlash amount at the meshing portion between the worm 3 and the worm wheel 4 is reduced.

  Further, the housing 5 has a third accommodation hole 5c connected to the second accommodation hole 5b, and a steering torque applied to the steering wheel A by the relative rotational displacement amount of the steering shafts 61 and 63 according to the torsion of the torsion bar 62. A torque sensor 14 to be detected is housed in the third housing hole 5c, and the electric motor 1 is driven and controlled based on the torque detected by the torque sensor 14 and the like.

FIG. 4 is an explanatory view showing a process of incorporating the electric power steering apparatus. In the electric power steering apparatus configured as described above, the worm 3 and the worm wheel 4 are assembled in the housing 5 in the following process, for example.
(1) The worm 3 having the first bearing 7 fitted on one shaft 32 and the second bearing 8 fitted on the other shaft 33 is connected to the first opening 52 from the other shaft 33 side. Then, it inserts in the 1st accommodation hole 5a, and stops the insertion operation in the middle of this insertion, and it is in an incomplete insertion state (refer to Drawing 4).
(2) The fourth bearing 10 is fitted into the fourth fitting portion 58.
(3) The worm wheel 4 and the second steering shaft 63 that are externally fitted and fixed in the middle of the second steering shaft 63 are inserted into the second accommodation hole 5b, and the other end side of the second steering shaft 63 is connected to the fourth side. While being fitted in the bearing 10, the worm 3 is biased by the worm wheel 4 in a direction in which the distance H between the rotation centers becomes longer, and the other end side of the second steering shaft 63 is brought into the non-interference state with the worm 3. The inner fit is supported. In this case, in the second bearing 8, the distance H between the rotation centers of the worm 3 and the worm wheel 4 becomes longer than the dimension obtained by adding the tooth end h and h of the worm 3 and the worm wheel 4 in the first accommodation hole 5 a. Since the second bearing 8 is formed in such a size that it can be biased in the direction, the worm 3 can be biased to a position where it does not interfere with the worm wheel 4, and the worm wheel 4 can be easily assembled.
(4) While the third bearing 9 is fitted on one end of the second steering shaft 63, the third bearing 3 is fitted in the third fitting portion 57, and the second steering shaft 63 is inserted into the second receiving hole 5b. To support.
(5) The worm 3 in the middle of insertion is completely inserted into a fixed position, the first bearing 7 is fitted into the first fitting portion 51, and the non-flexible ring 12 is inserted from the second opening 56 into the first receiving hole 5a. The non-flexible ring 12 is inserted into the second fitting portion 55 and the outer peripheral surface of the second bearing 8, and the worm 3 is supported in the first accommodation hole 5a.
(6) The retaining ring 11 is fitted in the annular groove 53 to prevent the first bearing 7 from moving in the axial direction, and the lid 13 is screwed into the second opening 56 to axially move the non-flexible ring 12. Stop moving to.

  As described above, the worm 3 is in an incomplete insertion state, the second bearing 8 side of the worm 3 can be biased in the direction in which the distance H between the rotation centers becomes longer, and the worm wheel 4 is incorporated into the second accommodation hole 5b. After that, the worm 3 is completely inserted into a fixed position and the non-flexible ring 12 is fitted, so that the worm 3 and the worm wheel 4 are made of metal, and the backlash amount of the meshing portion is small. Even when it is set, the worm 3 and the worm wheel 4 can be easily incorporated. The procedure for assembling the worm 3 and the worm wheel 4 is not limited to the above-described procedures (1) to (6). The worm 3 and the output shaft 1a of the electric motor 1 may be integrated.

FIG. 5 is an enlarged cross-sectional view showing another configuration of the main part of the electric power steering apparatus.
In this embodiment, first and second air supply holes 59a and 59b that are open to the outside from between the first bearing 7 and the second bearing 8 of the first accommodation hole 5a and communicate with the air supply source, An exhaust hole 59c that is open to the outside from between the second air supply holes 59a and 59b and exhausts the air in the first accommodation hole 5a to the outside is provided.

The first air supply hole 59 a is formed in the vicinity of the first bearing 7, and the second air supply hole 59 b is formed in the vicinity of the second bearing 8.
The air supply source is air that is taken into the front bumper from the front portion of the vehicle on which the electric power steering device is mounted and exhausted from the radiator. The second air supply holes 59a and 59b communicate with each other through an air supply pipe.

  In general, in the electric power steering apparatus, a lubricant having a relatively high viscosity such as grease is applied to the teeth of the worm 3 and the worm wheel 4, and the lubricant is rotated in one direction. Although it flows to the one end side and the other end side of the worm 3 along the tooth trace of the worm 3 by rotation in the other direction, the amount of lubricant in the meshing portion decreases with time, but in the present invention, Since air is supplied from the first and second air supply holes 59a and 59b to the first housing hole 5a, the lubricant flows from the meshing portion side to one end side and the other end side of the worm 3 due to the supply air pressure by the air supply. Moreover, since the lubricant on one end side and the other end side of the worm 3 can flow to the meshing portion side, the amount of lubricant in the meshing portion can be maintained for a long period of time. Note that the air supplied from the first and second supply holes 59a and 59b to the first accommodation hole 5a is exhausted to the outside through the exhaust hole 59c. In addition, when the supply air pressure supplied from the first and second supply holes 59a and 59b is insufficient, the supply path between the air supply source and the first and second supply holes 59a and 59b is in the middle. A turbocharger may be connected to the system so that the supply air pressure is increased by the turbocharger.

It is an expanded sectional view of the important section showing composition of an electric power steering device concerning the present invention. It is an enlarged view of the meshing part of the worm and the worm wheel of the electric power steering apparatus according to the present invention. It is sectional drawing which shows the whole structure of the electric power steering apparatus which concerns on this invention. It is explanatory drawing which shows the integration process of the electric power steering apparatus which concerns on this invention. It is an expanded sectional view showing other composition of the principal part of the electric power steering device concerning the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric motor 3 Worm 4 Worm wheel 5 Housing 5a 1st accommodating hole 5b 2nd accommodating hole 7 1st bearing 8 2nd bearing 52 1st opening 56 56 2nd opening 12 Non-flexible ring H Distance between rotation centers h Tooth end Notake

Claims (2)

  A worm coupled to a steering assisting electric motor, a worm wheel meshed with the worm and supported by the rotating shaft of a steering mechanism having a rotating shaft, a first receiving hole for receiving the worm, and the worm A housing having a second housing hole for housing a wheel; and a first bearing and a second bearing for supporting both ends of the worm in the first housing hole, and assisting steering by rotation of the electric motor. In the electric power steering apparatus, the worm and the worm wheel are made of metal, and the outer diameter of the second bearing opposite to the electric motor is formed smaller than the outer diameter of the first bearing. The one accommodation hole has a first opening opened to the electric motor side and a second opening opened to the counter-electric motor side, and the outer peripheral surface of the second bearing and the first opening are opened. An electric power steering apparatus characterized by non flexures ring is fitted between the housing hole.   The second bearing has a size that allows the second bearing to be displaced in a direction in which the distance between the rotation centers of the worm and the worm wheel becomes longer than the dimension obtained by adding the end of the worm and the worm wheel in the first accommodation hole. The electric power steering apparatus according to claim 1, wherein the electric power steering apparatus is formed.

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