JP3822003B2 - Electric power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric actuator type power steering device (electric power steering device) in which a power assist portion in a rack and pinion type steering device is formed by an electric motor, and in particular, an electric actuator is formed. The present invention relates to an electric power steering apparatus that enhances a function of blocking vibration and noise around a ball screw mechanism.
[0002]
[Prior art]
In a conventional electric power steering device, for example, as disclosed in JP-A-10-24852, a shaft screw connected to a rack bar, a nut screw that forms a ball screw mechanism together with the shaft screw, and the nut screw at one end thereof An electric actuator including an armature having a stator and a stator that rotationally drives the armature is provided. And the rack bar which receives power assistance from the electric actuator which consists of these structures meshes | engages with a pinion gear. Further, the pinion gear is connected to a steering shaft, and both end portions of the rack bar are connected to wheels through tie rods or the like.
[0003]
[Problems to be solved by the invention]
In the conventional apparatus having such a configuration, when the vehicle travels on an uneven road or the like, an external force is transmitted to the rack bar connected to the wheels. In contrast to the input of such an external force, in the prior art, for example, as shown in FIG. 5, an external force is applied to the shaft screw 10 connected to the rack bar, and this external force is applied to the ball screw mechanism. It is propagated to the nut screw 20 to be formed, and further to the cylindrical rotor 30. The external force input to the rotor 30 is propagated to the housing 50 via the bearings 40 and the like, and finally propagates to a steering wheel (handle) that forms the steering device. In addition, when the external force is input, the portion of the shaft screw that engages with the ball is bent and deformed. As a result, the rolling noise of the ball in the ball screw mechanism portion becomes abnormally large, and these abnormal sounds are generated. It will be transmitted to the passenger compartment. In order to solve such a problem, a power steering device having an electric actuator in which an elastic member or the like that allows a minute displacement of the nut screw is provided between the nut screw and a rotor containing the nut screw ( An object (problem) of the present invention is to provide an electric power steering device.
[0004]
[Means for Solving the Problems]
In order to solve the above problems, the following measures are taken in the present invention. That is, in the first aspect of the present invention, the shaft screw connected to the rack bar forming the rack-and-pinion type steering mechanism and the threaded portion of the shaft screw are engaged via a ball, and the shaft screw A nut screw that forms a ball screw mechanism between the nut screw and the one end side of the nut screw having a diameter larger than that of the intermediate portion, and the nut screw is connected to the one end side having the increased diameter. A rotor having a hollow shape, a lock nut screwed to the one end of the rotor to prevent the nut screw from being removed , an electric motor including the rotor and rotating the rotor, and the electric motor Cylindrical housing that holds the motor and contains the above parts In the electric power steering apparatus having a Ranaru electric actuator, and the outer peripheral portion of the nut screw to form the electric actuator, between the inner wall portion of the rotor opposed to the outer peripheral portion, in the radial direction of the nut screw A configuration is adopted in which an elastic member that absorbs relative displacement is provided.
[0005]
By adopting such a configuration, the radial displacement between the shaft screw and the nut screw forming the ball screw mechanism becomes possible. For example, an external force is applied from the wheel side to the shaft screw via the rack bar. However, the nut screw will act to absorb or release these external forces. Therefore, no abnormality occurs in the meshing engagement in the ball screw mechanism. As a result, it is possible to suppress the occurrence of abnormal noise.
[0006]
Next, the invention described in claim 2 will be described. The basic point of this is the same as that of the first aspect. The feature is that the nut screw is held via an elastic member so that the axial displacement of the nut screw is possible. That is, according to the present invention, in the electric power steering apparatus according to claim 1, between the nut screw and the rotor and between the nut screw and the lock nut, both axial directions of the nut screw may be provided. An elastic member that absorbs the relative displacement of the nut screw in the axial direction is provided at the terminal portion . By adopting such a configuration, in those of the present invention, with respect to the rack bar and vibration in the axial direction of input shaft screw them, so that it can be absorbed by deformation of the elastic member Thus, the meshing engagement in the ball screw mechanism can be always maintained smoothly. As a result, it is possible to suppress the generation of abnormal noise and the like, and it is possible to prevent vibration and noise from propagating to the steering mechanism, particularly the steering handle.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the configuration according to the present embodiment is formed on the basis of a rack and pinion type steering mechanism 9, and a rack bar that forms the rack and pinion type steering mechanism 9. A shaft screw 1 provided integrally with 91 and a threaded portion (screw portion) 11 of the shaft screw 1 are engaged via a ball 2, and a ball screw mechanism is formed together with the threaded portion 11 and the ball 2. The nut screw 3 and one end thereof are expanded in diameter than the intermediate portion (portion included in the stator 7 described later), and the entire axial direction of the nut screw 3 is included in the expanded one end side. Te, a hollow rotor 6 relative rotational movement is coupled to impossible in between the nut screw 3, the Forming a lock nut 65, a motor armature be those provided outside together with the rotor 6 of the rotor 6 which is screwed on the one end side of the chromatography data 6 serves to cause retaining the nut screw 3 Magnets 66, a stator 7 that is provided outside these armatures and has a plurality of coils 77, and holds (fixes) the stator 7, and a rotor 6 that forms the armatures via a bearing 81. It is basically composed of a housing 8 to be supported, and an electric motor is formed by adding a rotor 6, a magnet 66, and a stator 7 to these. And what consists of such a structure WHEREIN: Between the said nut screw 2 and the place of the one end part side of the rotor 6 which includes the said nut screw 2, the elastic member 5 is provided. is there.
[0008]
Next, a specific configuration of the ball screw mechanism that forms the electric actuator having such a configuration will be described with reference to FIGS. First, as for the first embodiment, as shown in FIG. 2, a rubber-like elastic member 5 is provided on the outer diameter side of the nut screw 3. By adopting such a configuration, the nut screw 3 is held such that it can be displaced in the radial direction in accordance with the elastic deformation of the elastic member 5. Therefore, even if the threaded portion 11 of the shaft screw 1 connected to the rack bar 91 is bent and deformed, the nut screw 3 is slightly displaced in the radial direction so as to correspond to this. The minute displacement (escape) of the nut screw 3 in the radial direction causes no inconvenience in the meshing engagement between the ball 2 and the nut screw 3 and the meshing engagement between the ball 2 and the threaded portion 11 of the shaft screw 1. It becomes like this. As a result, the rotational motion is smoothly transmitted between the shaft screw 1 and the nut screw 3 in the ball screw mechanism portion via the ball 2. In addition, in what consists of such a structure, between the said rotor 6 and the nut screw 3, the lock pin 36 is provided so that rotational motion may be transmitted between both smoothly. By adopting such a configuration, the power assist force (rotational force) from the electric motor side is transmitted from the rotor 6 to the nut screw 3 and further to the shaft screw 1 via the ball screw mechanism, and the shaft The screw 1 and the rack bar 91 (see FIG. 1) connected thereto are driven in the axial direction.
[0009]
Further, in these series of operations, even if vibration or the like is transmitted from the wheel side to the rack bar 91 and further to the shaft screw 1, the nut screw 3 is supported by the rubber-like elastic member 5, The vibration or the like is absorbed and blocked at the rubber-like elastic member 5. Accordingly, these vibrations and the like are not propagated to the steering mechanism 9 via the housing 8 or the like. Further, the rolling sound of the ball 2 in the ball screw mechanism is also blocked at the rubber-like elastic member 5. Therefore, these noises and the like are not transmitted to the vehicle interior via the steering mechanism 9 or the like.
[0010]
Next, a second embodiment will be described based on FIG. The basic configuration of this is the same as that described in the first embodiment. The characteristic feature is that a tolerance ring 51 that allows displacement of the nut screw 3 in the radial direction is provided between the nut screw 3 and the rotor 6 containing the nut screw 3. is there. The tolerance ring 51 is made of a metal ring-shaped member, and its cross-sectional shape is in contact with the convex portion 516 that contacts the inner wall of the rotor 6 and the outer peripheral portion of the nut screw 3 as shown in FIG. The concave portion 513 is a continuous body, and the spring reaction force in the radial direction is exhibited by such elastic deformation of the concave and convex portions. Therefore, by providing a tolerance ring (wave spring) 51 exhibiting such a function on the outer peripheral portion of the nut screw 3, the nut screw 3 can move in the radial direction with respect to vibration input from the shaft screw 1 side. A small displacement is caused on the rotor 6 side. The vibration input is absorbed by the minute displacement in the radial direction, and the occurrence of hitting sound (abnormal noise) with the ball 2 is suppressed. Further, the meshing engagement in the ball screw mechanism is smoothly maintained, and the rolling motion and the like of the ball 2 are normally maintained. Therefore, the rolling sound of the ball 2 does not become abnormally loud.
[0011]
Next, a third embodiment will be described based on FIG. As shown in FIG. 4, in addition to the first embodiment, both ends of the nut screw 3 are arranged so that the nut screw 3 can be displaced in the axial direction. The elastic member 55 is provided at the portion. Specifically, as shown in FIG. 4, between the outer peripheral portion of the nut screw 3 and the inner wall portion of the rotor 6 facing the outer peripheral portion, the same rubber-like elasticity as described in the first embodiment is provided. The member 5 is provided, and is elastic between the nut screw 3 and the rotor 6 and between the nut screw 3 and the lock nut 65 at both end portions in the axial direction of the nut screw 3. A member (spring) 55 is provided. By providing such an elastic member (spring) 55, the nut screw 3 can be displaced slightly in the axial direction against the external force transmitted in the axial direction transmitted to the rack bar 91 and the shaft screw 1. It will be possible to deal with. That is, among the disturbance inputs from the wheel side, the input to the axial direction of the shaft screw 1 can be absorbed or interrupted, and the rolling motion of the ball 2 can be maintained smoothly. Will be able to.
[0012]
【The invention's effect】
According to the present invention, a shaft screw connected to a rack bar forming a rack-and-pinion type steering device and a ball screw between the shaft screw and a threaded portion of the shaft screw are engaged with the shaft screw. A nut screw that forms a mechanism, and one end side of which is larger than the middle portion, and the nut screw is connected to the enlarged one end side, and includes a hollow shape that includes the entire axial direction of the nut screw. A rotor having the above configuration, a lock nut that is screwed onto the one end of the rotor to prevent the nut screw from coming off , an electric motor that includes the rotor, and that rotates the rotor, and that holds the electric motor An electric actuator comprising a cylindrical housing or the like containing the above-mentioned parts Regard the electric power steering apparatus having the absorption and the outer peripheral portion of the nut screw to form the electric actuator, between the inner wall portion of the rotor opposed to the outer peripheral portion, the relative displacement in the radial direction of the nut screw Therefore, relative displacement is possible between the shaft screw and the nut screw forming the ball screw mechanism, and an inappropriate external force is transmitted from the wheel side to the shaft screw. Even now, the nut screw can absorb or block these external forces. As a result, it has become possible to prevent any abnormality from occurring in the meshing engagement in the ball screw mechanism, and to suppress the generation of abnormal noise. Moreover, on the premise of a simple configuration (see FIG. 5) in which both are connected so that a nut screw is included in one end of the rotor, only an elastic member is added to this. The fact that the above-described effects are achieved is also a great advantage of the present invention.
[0013]
Further, in the case where the nut screw is held via an elastic member, particularly a rubber-like elastic member, the nut screw is appropriately displaced in the radial direction by the intervention of the elastic member. In addition, external forces such as vibrations transmitted to the shaft screw can be absorbed or cut off. Therefore, the meshing engagement in the ball screw mechanism is always kept in a normal state, and the generation of abnormal noise can be suppressed. Further, since the nut screw is included at one end of the rotor as described above, the radial displacement of the nut screw is naturally restricted by the inner wall portion of the rotor while the elastic member allows the radial displacement of the nut screw. The effect of preventing excessive displacement of the screw has also been obtained. In addition, even if the elastic member breaks or the like, there is no possibility that the nut screw will fall off the rotor.
[0014]
Further, by holding the nut screw so that it can be displaced also in the axial direction, disturbance input from the wheel side transmitted to the rack bar and further to the shaft screw, particularly the rack bar and the shaft screw. The nut screw can absorb or attenuate the vibration input or the like by displacing the nut screw in the axial direction with respect to the vibration input or the like driven in the axial direction. As a result, the meshing engagement in the ball screw mechanism can be maintained in a normal state, and the generation of abnormal noise can be suppressed. Further, the meshing engagement in the ball screw mechanism portion can be always maintained smoothly. As a result, the generation of abnormal noise can be suppressed, and vibration and noise can be reduced. , It can be prevented from propagating to the steering wheel.
[Brief description of the drawings]
FIG. 1 is a partially broken sectional view showing an overall configuration of the present invention.
FIG. 2 is a cross-sectional view showing the contents of the first embodiment around the ball screw mechanism that forms the main part of the present invention.
FIG. 3 is a cross-sectional view showing the contents of the second embodiment around the ball screw mechanism.
FIG. 4 is a cross-sectional view showing the contents of the third embodiment around the ball screw mechanism.
FIG. 5 is a cross-sectional view showing a configuration around a ball screw mechanism portion in a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Shaft screw 11 Thread part 2 Ball 3 Nut screw 36 Lock pin 5 Elastic member 51 Tolerance ring (wave spring)
513 Concave portion 516 Convex portion 55 Elastic member (spring)
6 Rotor 66 Magnet 7 Stator 77 Coil 8 Housing 81 Bearing 9 Steering mechanism (rack and pinion type steering mechanism)
91 rack bar

Claims (2)

A shaft screw connected to a rack bar that forms a rack and pinion type steering mechanism, and a nut screw that engages with a threaded portion of the shaft screw via a ball and forms a ball screw mechanism with the shaft screw And a rotor having a hollow shape in which one end side is enlarged in diameter than the intermediate portion, and the nut screw is connected to the enlarged one end side, and includes the entire axial direction of the nut screw. A lock nut that is screwed to the one end of the rotor to prevent the nut screw from coming off; an electric motor that includes the rotor and rotates the rotor; and the electric motor that holds the electric motor, and the components described above. An electric actuator having an electric actuator comprising a cylindrical housing including In Lower steering device, and the outer peripheral portion of the nut screw to form the electric actuator, between the inner wall portion of the rotor opposed to the outer peripheral portion, an elastic member for absorbing the relative displacement in the radial direction of the nut screw An electric power steering apparatus characterized by comprising a configuration provided. The electric power steering apparatus according to claim 1, wherein the nut screw and the rotor, and the nut screw and the lock nut are located at both end portions in the axial direction of the nut screw. An electric power steering apparatus comprising an elastic member for absorbing relative displacement in the axial direction of a nut screw.

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