KR20080039596A - Compensational apparatus of free apartness of worm shaft for electric power steering system - Google Patents

Abstract

A clearance compensating apparatus of a worm shaft of an electric power steering device is provided to prevent vibration and noise of the apparatus caused from radial clearance by placing clearance compensating units such as damper bushes at the outside of a first bearing of an electric motor. A plurality of damper bushes(50), arranged at two sides of one of two bearings(34,36) rotating two supporting ends extended to two sides of a worm shaft(32) of a reduction gear, are placed between extension parts(32a) of the worm shaft and fixed rings(80) inserted at first grooves(33a) recessed at a distance from the extension parts. The damper bushes are placed between plate rings(51) with rubber rings(53) whose section is square. An elastic strip(60) is bent to press a support end of one of the worm shafts.

Description

Compensational Apparatus of Free Apartness of Worm Shaft for Electric Power Steering System}

1 is a perspective view showing a conventional column type electric steering apparatus,

2 is a cross-sectional structural view showing a rotational force transmission structure between the motor and the shaft according to FIG.

3 is a cross-sectional view showing main parts including a worm shaft and a worm wheel of the electric steering apparatus according to one embodiment of the present invention;

4 is an enlarged cross-sectional view of a worm shaft portion of the steering apparatus;

5 is an exploded perspective view illustrating an exploded part of the worm shaft clearance compensation device of FIG. 4;

Figure 6 is a sectional perspective view for illustrating the overall structure of the worm shaft gap compensation device of the present invention.

<Code Description of Major Parts of Drawing>

   3: electric motor 4: housing

  32: worm shaft 42: worm wheel

  34: first bearing 36: second bearing

  50: damper bush 60: elastic strip

         70: elastic cap

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus mounted on a vehicle such as an automobile and assisting a steering operation of a driver by assisting a steering force of the vehicle by driving an electric motor. By providing a, to compensate for the play caused by the wear of the worm shaft, and relates to the play compensation device of the electric power steering device to reduce the noise.

For example, an electric power steering device mounted on an automobile includes an electric motor connected to a steering mechanism from a steering member to a steering wheel, and the motor power is steered through a worm football. The mechanism is adapted to assist the steering operation by the driver in the steering member. Moreover, in such a steering apparatus, the tooth hitting sound which generate | occur | produced in the engagement part of the tooth | tip part contained in the said worm football may be transmitted to a driver as rattle noise (rattle noise), and this may give an unpleasant feeling, There is a demand for reduction.

Thus, in the conventional apparatus, as described in, for example, Japanese Patent Laid-Open No. 2000-43739, a worm wheel mounted on the steering mechanism has a worm shaft connected to an output shaft side of the electric motor in the worm shaft. By biasing on the side), the backlash at the tooth engaging portion between the worm wheel and the worm shaft is absorbed to suppress the rattle sound.

In addition, in the conventional apparatus, as described in, for example, Japanese Patent Laid-Open No. 2003-63424, a permanent magnet is provided near the tooth engagement portion, and magnetically attracted by this magnet. By using a lubricating oil made of a fluid, the lubricating oil is always interposed in the tooth engaging portion, so as to buffer the rattle sound with the lubricating oil.

However, in the conventional apparatus as described above, the vibration system including the worm football and the electric motor has not been sufficiently considered, and due to the natural vibration of the vibration system, rattle sound may occur or steering peeling may decrease. In detail, the vibrometer is connected to the steering mechanism via the gear engaging portion of the worm football, which is the inertia element, and the steering mechanism and the motor are the reference end side and the free end side, respectively. For example, when the disturbance from the steering wheel side is reversely input, especially in an assist dead zone in which the electric motor is not driven, the vibration system tends to vibrate (resonance), thereby causing rattle sounds. This may be large or may cause a drastic reduction in steering peeling.

It is an object of the present invention to provide an electric power steering apparatus capable of suppressing generation of rattle sounds and reduction of steering peeling caused by a vibrometer including a worm football and an electric motor, in view of the above conventional problems.

In general, the power steering system is applied to the vehicle as a crisis means to reduce the steering force of the steering wheel (handle) to ensure the stability of the steering state. Such a power steering device is a conventional hydraulic power steering device (HPS) using hydraulic pressure. Hydraulic Power Steering System has been widely used in vehicles.However, unlike the conventional method of using hydraulic power, the electric power steering system (EPS; Electrical) makes it easier for the driver to steer by using the rotational power of the electric motor. Power steering systems are commonly installed in vehicles.

The electric power steering device (EPS) drives the electric motor in the ECU according to the driving conditions of the vehicle detected by the vehicle speed sensor and the steering torque sensor, thereby providing a light and comfortable steering feeling at low speeds and heavy steering at high speeds. In addition to providing a sense of direction and good directional stability, and in emergency situations, the steering is made to provide optimum steering conditions to the driver.

These electric power steering devices are classified according to the installation position of the electric motor providing the auxiliary power, among which column assist type electric power steering system (hereinafter, abbreviated as "C-EPS") The electric motor is installed on the outside of the steering column disposed between the steering wheel and the gearbox so as to transmit the rotational force of the driver's steering wheel to the lower side and assists the steering shaft rotation inside the steering wheel. Lightens the momentum

1 is a view showing a schematic configuration of the conventional C-EPS as described above, the conventional C-EPS is based on a general steering device.

First, the steering shaft 2 is provided inside the steering column 1 provided in a hollow so that both ends of the steering shaft 2 are rotatably supported by a bearing (not shown), and one end of the steering shaft 2 is provided in the driver's seat. It is coupled to a steering wheel (not shown), and the other end is connected to a universal joint (not shown) installed on the gearbox side.

In addition, an outer side of the steering column 2 is provided with an electric motor 3 for steering assistance in a direction orthogonal to this, and the steering shaft in the rotary shaft end of the electric motor 3 and the steering column 1 are installed. In the center portion of the shaft 2, a reduction gear composed of a pair of drive gears and driven gears is provided to reduce the electric motor output to an appropriate level and assist the rotational steering force of the steering shaft 2 by the driver's operation.

At this time, the worm shaft used in the C-EPS is usually used as a pair of worm shaft and worm wheel gear because the power transmission must be made in the state that the two shafts are staggered.

That is, as shown in Figure 2 enlarged the main portion of Figure 1, the worm shaft 32 is splined to the output shaft 30 end of the electric motor is made so that the rotational force of the electric motor can be transmitted to the shock gear (32). The worm wheel 42 is configured to engage with the worm gear 32 in a state of being pressed into the outer circumference of the steering shaft 2 inserted into the steering column 1, so that the rotational force from the electric motor 3 is a pair of rotational force. It is configured to assist the rotational force of the steering shaft (2) via the worm shaft and the worm wheel.

Here, both ends of the worm shaft 32 is supported by a pair of bearings 34 in the housing 4 so as to be rotatable.

Therefore, the conventional C-EPS having the above-described configuration drives the electric motor in the ECU according to the driving conditions of the vehicle detected by the vehicle speed sensor and the steering torque sensor, and the driving force of the electric motor rotates through the above-described reduction gear. The speed is transmitted to the steering shaft at a reduced speed to assist the driver in steering wheel steering.

However, since a separate clearance compensation device is not provided on the worm shaft side of the conventional column type electric steering device, wear caused by frequent friction between the worm shaft and the worm wheel is directly led to the play of the reduction gear, and such play is the vibration of the device. There was a problem that the noise caused to lower the performance and reliability of the product.

Accordingly, the present invention has been made to improve the problems of the prior art as described above, and provides a clearance compensation means such as an O-ring on the outer diameter edge side of the bearing for supporting the worm shaft shaft end of the bearing for supporting the worm shaft of the C-EPS By absorbing or compensating the radial play caused by the axial swing of the worm shaft and the wear of the gear teeth by the axial clearance of the bearing, the worm shaft play absorber of the electric power steering device prevents vibration and noise of the device caused by the play. The purpose is to provide.

Accordingly, the present invention has been made to improve the problems of the prior art as described above, the outer side of the electric motor side first bearing 34 to rotatably support the worm shaft shaft end of the bearing for supporting the worm shaft of the C-EPS By providing clearance compensation means such as damper bushes in the shaft, the radial clearance caused by the axial oscillation of the worm shaft due to the axial clearance of the bearing and the wear of gear teeth is absorbed or compensated, and vibration and noise of the device caused by the clearance are prevented. It is an object of the present invention to provide a worm shaft play-back absorber of an electric power steering device that prevents.

In order to achieve the above object, the worm shaft play-absorbing device of the electric power steering apparatus according to the present invention includes a steering angle sensor for detecting a steering angle of a steering wheel, a torsion bar installed in a steering column, and a torsion bar during steering. Torque sensor for detecting the torsion, Vehicle speed sensor for detecting the traveling speed of the vehicle, Drive electric motor that is installed to assist the steering force on the axis of the steering column, Worm shaft for transmitting the driving force of the electric motor to the steering shaft And a deceleration gear comprising a worm wheel, and an ECU configured to calculate a signal input from the steering angle sensor, the vehicle speed sensor, and the torque sensor to control a driving force of an output shaft of a driving electric motor. Both support ends extending to both sides of the worm shaft 32 of the gear are rotatably supported. Among the bearings 34 and 36, a plurality of damper bushes arranged in contact with both sides of the output shaft side first bearing of the electric motor are coaxial with one of the supporting ends of the worm shaft 32, and the enlarged portion of the worm shaft 32 It is characterized in that it is disposed between the enlarged portion and the fixing ring inserted into the first groove concave formed at the set distance spaced position.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

3 is a cross-sectional view showing a main part including a worm shaft and a worm wheel of the electric steering apparatus according to an embodiment of the present invention, FIG. 4 is an enlarged cross-sectional view of a worm shaft portion of the steering apparatus, and FIG. 5 is a worm shaft of FIG. 4. 6 is an exploded perspective view showing an exploded part of the play compensation device, and FIG. 6 is a cross-sectional perspective view illustrating the whole structure of the worm shaft play compensation device of the present invention.

Referring to the configuration of a column type electric power steering apparatus (hereinafter referred to as C-EPS) with reference to Figure 3, a steering angle sensor (not shown) for detecting the steering angle of the steering wheel is a steering column ( 1) is installed at one end of the steering column (1) inside the torsion bar and the torque sensor for detecting the torsion of the torsion bar is installed, the vehicle speed sensor for detecting the traveling speed of the vehicle is provided, the steering angle sensor, vehicle speed It includes an ECU that calculates the signal input from the sensor and torque sensor.

At this time, the electric motor (3) operated on the basis of the signal calculated from the ECU to assist the steering force is installed on the axis of the steering shaft (2) to be orthogonal to this direction, and the drive motor (3) side Worm shaft 32 and the worm shaft wheel 42 is provided with a worm shaft is configured to reduce the rotational output speed from the electric motor to be transmitted to the shaft (2).

As shown in FIG. 3, when the wear occurs due to frequent friction between the internal components of the reduction gear including the worm shaft 32 and the worm wheel 42, the present invention absorbs the play between the gears caused by such wear. The first bearing 34 to rotatably support the worm shaft 32 of the reduction gear so that it can be configured to include a housing (4) including the second bearing 36 to surround the reduction gear have.

Between the enlarged portion 32a of the worm shaft 32 and the fixing ring 45 inserted into the enlarged portion 32a and the first groove 33a recessed at a set distance spaced apart, the worm shaft of the reduction gear ( A plurality of damper bushes 50 in contact arrangement on both sides of the first bearing side of the output shaft 30 of the electric motor among the two bearings 34 and 36 which rotatably support both of the supporting ends extending to both sides of 32), Coaxially with one support end of the worm shaft 32, a fixed portion inserted into the enlarged portion 32a of the worm shaft 32 and the first groove 33a concavely formed at a position spaced apart from the enlarged portion 32a. It is arranged between the rings 45.

In addition, the damper bush 50 includes a rubber ring 53 having a rectangular cross section between the plate rings 51 on both sides, and at least one inner circumference of the plate rings 51 on both sides is different. A bend forming portion 51a is formed that is bent at a set distance from the inner surface of one plate-shaped ring 51.

Further, by applying a preload to the second bearing 36 of the shaft supporting the other shaft of the electric motor output shaft 30, one end is coupled to the housing and the other end is connected to the second bearing 36. An elastic strip 60 that is bent to preload the other supporting end of the worm shaft 32 which is rotatably supported is configured such that the worm shaft and the worm wheel are always in contact with each other.

In addition, an elastic cap 70 connected to the housing so as to surround the other supporting end portion so as to be disposed between the other bearing end side second bearing 36 of the worm shaft 32 and the elastic strip 60. ), The lower portion of the elastic cap 70 is provided with a cutout portion (70a) is formed as a whole, the elastic strip 60 is configured to be inserted and passed through.

In addition, the second groove 33b formed on the outer circumference of the support end in contact with the inner diameter of the one bearing end side first bearing 34 of the worm shaft 32 compensates for the play caused by wear of the first bearing 34. An elastic ring 80 is applied to apply an elastic force so as to be inserted therein.

In addition, as can be seen through Figure 4, the elastic ring 80 is in contact with both sides of the bearing 34 for supporting the shaft end of the worm shaft 32 to absorb the axial and radial play of the worm shaft 32 Or to compensate.

Therefore, according to the present invention having the above configuration, the electric motor driving command is calculated by the ECU according to the driving conditions of the vehicle detected by the vehicle speed sensor and the steering torque sensor to drive the electric motor at an appropriate rotational speed. The rotational force is transmitted to the steering shaft while being decelerated at an appropriate rotational speed through a reduction gear composed of a worm shaft and a worm wheel, to assist the steering wheel steering force of the driver.

At this time, in the present invention, by providing a damper bush fixed to the outside of the first bearing for supporting the worm shaft 32, which is a reduction gear, when the reduction gear is worn out due to frequent friction, by controlling the play is generated by the maximum force, thereby It is possible to reduce the noise due to irregular contact between the teeth.

In addition, the worm shaft and the worm wheel are always provided by applying a preload to the second bearing 36 of the shaft supporting the other shaft of the electric motor output shaft 30 due to the addition of the elastic strip 60. By coming into contact with each other, the play of this part is severely regulated.

Moreover, the said elastic cap 70 is arrange | positioned between the 2nd bearing 36 of the other support end side of the said worm shaft 32, and the said elastic strip 60, surrounding the said other support end part. Since the support end of the other side of the worm shaft 32 is spaced apart from the worm wheel 42, it is essentially blocked.

In addition, the first bearing 34 is provided by an elastic ring 80 inserted into a second groove 33b formed on an outer circumference of the support end portion in contact with the inner diameter of the first bearing 34 on one support end side of the worm shaft 32. The play caused by abrasion of) is elastically applied and pressurized to always compensate.

As a result, the various elastic means described above are interposed between the housing 4 together with the first and second bearings 36, thereby simultaneously absorbing or compensating the axial and radial play of the worm shaft 32. will be.

As described above, according to the worm shaft clearance absorption structure of the column type electric power steering apparatus of the present invention, the clearance compensation device for applying elastic force is provided on the outer side of the bearing supporting the worm shaft to rotate, thereby absorbing the clearance of the worm shaft due to wear between gear teeth. Thus, the vibration and noise of the device can be prevented in advance, and thus, the performance and reliability of the product can be further increased.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom.

Claims (7)

A steering angle sensor that detects the steering angle of the steering wheel, a torsion bar installed in the steering column to which torsion occurs when steering, a torque sensor that detects torsion of the torsion bar, a vehicle speed sensor that detects the speed of the vehicle, and a steering column A drive electric motor installed to assist steering on the shaft, a reduction gear consisting of a worm shaft and a worm wheel so as to transmit the driving force of the electric motor to the steering shaft, and a signal input from the steering angle sensor, vehicle speed sensor, and torque sensor In the column type electric power steering apparatus comprising an ECU for controlling the driving force of the output shaft of the drive electric motor by calculating Contact arrangement is arranged on both sides of the first bearing on the output shaft 30 side of the electric motor 3 of both bearings 34 and 36 for rotatably supporting both support ends extending to both sides of the worm shaft 32 of the reduction gear. A plurality of damper bushes 50 are formed coaxially with one of the supporting ends of the worm shaft 32, the recessed portion 32a of the worm shaft 32 and a position spaced apart from the enlarged portion 32a and a set distance apart. The worm shaft clearance compensation device of the electric power steering device, characterized in that disposed between the fixing ring 80 inserted into the groove (33a). The method of claim 1, The damper bush (50) is a worm shaft gap compensation device of the electric power steering device, characterized in that the rubber ring (53) having a rectangular cross section is interposed between the plate-shaped rings (51) on both sides. The method of claim 2, At least one inner circumferential portion of the plate-shaped rings 51 on both sides includes a bent forming portion 51a that is bent at a set distance from the inner surface of the other plate-shaped ring 51. Worm shaft playoff device. The method of claim 2 or 3, By applying a preload to the second bearing 36 of the shaft supporting the other shaft of the electric motor output shaft 30, one end is coupled to the housing 4 and the other end rotates to the bearing 36. The worm shaft of the electric power steering apparatus, comprising an elastic strip 60 that is bent to preload the other end of the worm shaft 32, which is possibly supported, so that the worm shaft and the worm wheel are always in contact with each other. Gap Compensation Device. The method of claim 3, wherein An elastic cap connected to the housing 4 so as to surround the other support end portion so as to be disposed between the support bearing side side second bearing 36 of the worm shaft 32 and the elastic strip 60; 70. A worm shaft playoff device for an electric power steering device, comprising: 70). The method of claim 5, wherein The lower portion of the elastic cap (70) is a worm shaft clearance compensation device of the electric power steering device, characterized in that it has a notched portion (70a) is formed as a whole. The method of claim 1, Elastic force to compensate for play caused by wear of the first bearing 34 in the second groove 33b formed on the outer circumference of the support end in contact with the inner diameter of the one bearing end side of the first bearing 34 of the worm shaft 32. Worm shaft clearance compensation device of the electric power steering device, characterized in that the elastic ring 80 is applied.

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