KR20080061529A - Compensational apparatus of free apartness of worm shaft for electric power steering system - Google Patents

Abstract

A clearance compensation apparatus for a worm shaft of an electric power steering system is provided to reduce vibration and noise by absorbing or compensating for radial clearance that is caused by axial shaking of the worm shaft and abrasion of gear teeth. A clearance compensation apparatus for a worm shaft of an electric power steering system comprises as follows. A steering angle sensor senses a steering angle of a steering wheel. A torsion bar is installed inside a steering column. A torque sensor senses torsion of a torsion bar. A vehicle speed sensor senses speed of a vehicle. A driving electric motor(3) is installed to support steering force. A speed-reducing sensor includes a worm shaft(32) and a worm wheel(42). A housing(4) is equipped with the driving electric motor and speed-reducing sensor and an ECU controls driving force of an output shaft of the motor. The apparatus further comprises an elastic cover(50) surrounding an outer portion of a first bearing(34) and an elastic cap(70) surrounding an outer portion of a second bearing(36).

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.

Figure 3 is a perspective view showing the appearance of the electric steering apparatus in an embodiment of the present invention,

4 is a side structural view showing one side of the electric steering apparatus of FIG. 3;

5 is a longitudinal sectional view of the worm shaft and peripheral elements according to line A-A of FIG.

6 is a cross-sectional view showing a main part including a worm shaft and a worm wheel according to the line B-B of FIG. 4, and

 FIG. 7 is an exploded perspective view illustrating disassembled parts of the worm shaft clearance compensation device of FIG. 4.

<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: elastic cover 60: compression ring

         70: elastic cap 71: receiving port

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. There is a case where the backlash is absorbed at the tooth engaging portion between the worm wheel and the worm shaft by suppressing 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 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 using hydraulic pressure ( HPS (Hydraulic Power Steering System) has been widely used in vehicles, but recently, unlike conventional methods that use hydraulic pressure, the driver's steering power is made easier by using the rotational power of the electric motor, and an environmentally friendly electric power steering device (EPS) is used. Electrical 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 1 is provided with an electric motor 3 for steering assistance in a direction orthogonal to the steering column 1, 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 is the rotational speed through the above-described reduction gear. Is transmitted to the steering shaft in a decelerated state 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 the elastic cover surrounding the outer portion of the bearing for supporting the worm shaft shaft end of the bearing for supporting the worm shaft of the C-EPS, and the elastic cover facing the By providing a gap compensation means consisting of a hollow elastic cap arranged to surround the outer portion of the second bearing for supporting the other end of the worm shaft, the radius due to the axial swing of the worm shaft due to the axial clearance of the bearing and the wear of the gear teeth It is an object of the present invention to provide a worm shaft clearance absorber of an electric power steering device that absorbs or compensates directional clearance, thereby preventing vibration and noise of the device caused by the clearance.

Accordingly, the present invention has been made to improve the problems of the prior art as described above, among the bearings supporting the worm shaft of the C-EPS, the electric motor side first bearing and the opposite second bearing rotatably supporting the worm shaft shaft end; By providing a gap compensation means such as an elastic cover, an elastic cap, and a compression ring on the outer side, the radial gap caused by the axial oscillation of the worm shaft and the wear of the gear teeth due to the axial clearance of the bearing is absorbed or compensated, resulting from the gap. An object of the present invention is to provide a worm shaft play absorber of an electric power steering device that prevents vibration and noise of a device.

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 an ECU for controlling the driving force of the output shaft of the driving motor by calculating a reduction gear including a worm wheel, a housing including the driving motor and the reduction gear, and a signal input from the steering angle sensor, the vehicle speed sensor, and the torque sensor. In the column type electric power steering apparatus including, the worm shaft 32 of the reduction gear Resilient cover arranged to surround the outer and end portions of the first bearing 34 of the output shaft side of the electric motor of both bearings (34, 36) rotatably supporting both supporting ends extending to both sides ( 50 and a hollow elastic cap 70 arranged to surround an outer portion of the second bearing 36 supporting the other end of the worm shaft 32 facing the elastic cover 50. .

The first bearing 34 is coaxial with one of the supporting ends of the worm shaft 32, and is concave at an enlarged portion 32a of the worm shaft 32 and a position spaced apart from the enlarged portion 32a. It is preferable that the configuration is disposed between the fixing ring inserted into the formed fastener and the snap ring connected to the fixing groove formed in the housing to support one side of the elastic cover.

In addition, the hollow portion of the elastic cap is preferably made of an elliptical cross-sectional shape.

In addition, it is preferable that the outer port of the elastic cap is provided with a receiving port connected to the compression ring in the concentric position where the second bearing is located inside.

In addition, the receiving port is preferably formed with a plurality of through holes penetrating to the hollow of the elastic cap.

In addition, it is preferable that the washer 90 and the urethane damper ring 91 are stacked and arranged between one side of the elastic cover and the snap ring.

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

Figure 3 is a perspective view showing the appearance of the electric steering apparatus in an embodiment of the present invention, Figure 4 is a side structural view showing one side of the electric steering apparatus of Figure 3, Figure 5 is a line AA of Figure 4 Figure 6 is a longitudinal cross-sectional view of the worm shaft and peripheral elements, Figure 6 is a cross-sectional view showing the main part including the worm shaft and the worm wheel according to the line BB of Figure 4, Figure 7 is an exploded view showing the components forming the worm shaft clearance compensation device of Disassembled perspective view.

Referring to the configuration of the column type electric power steering apparatus (hereinafter referred to as C-EPS) with reference to Figure 3, the 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 comprises an ECU that calculates a signal input from the sensor and the 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 A worm shaft composed of a worm shaft 32 and a worm wheel 42 is provided to reduce the rotational output speed from the electric motor and transmit the deceleration to the steering shaft 2.

5 and 6, the present invention is a gear caused by such wear when the wear occurs due to frequent friction between the internal gears of the reduction gear consisting of the worm shaft 32 and the worm wheel 42 as shown in FIG. Among the reduction gears, the first bearing 34 rotatably supporting the worm shaft 32 and the second bearing 36 include a housing 4 provided to surround the reduction gear. It is comprised to include.

The worm shaft 32 of the reduction gear is between the enlarged portion 32a of the worm shaft 32 and the fixing ring 45 inserted into the fixture 33a concave formed at a set distance from the enlarged portion 32a. Elastic cover (50) arranged to surround the outer and end portions of the first bearing (34) on the output shaft side of the electric motor among both bearings (34, 36) rotatably supporting both supporting ends extending to both sides of the motor (50). ) Is arranged, and on the opposite side of the resilient cover 50, the hollow arranged to surround the outer portion of the second bearing 36 supporting the other end of the worm shaft 32 facing the resilient cover 50 An elastic cap 70 is arranged to be connected to the housing.

Further, the first bearing 34 is coaxial with one of the supporting ends of the worm shaft 32, and is recessed in a position spaced apart from the enlarged portion 32a of the worm shaft 32 and the enlarged portion 32a by a set distance. It is disposed between the fixing ring 45 inserted into the fastener (33a) and the snap ring 80 connected to the fixing groove (4a) formed in the housing 4 to support one side of the elastic cover 50 have.

In addition, the hollow portion of the elastic cap 70 has an elliptical shape in cross-section so that the other end of the worm shaft 32 and the second bearing 36 supporting the flexible shaft can flexibly swing.

In addition, the outer portion of the elastic cap 70 is formed with a receiving port 71 is connected to the compression ring 60 in the concentric position where the second bearing 36 is located inside.

In addition, the receiving port is formed with a plurality of through-holes 70b penetrating to the hollow portion 70a of the elastic cap 70.

In addition, a washer 90 and a urethane damper ring 91 are stacked and arranged between one side of the elastic cover 50 and the snap ring 80.

In addition, 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 of the second bearing ( It is provided with a compression ring 60 bent to preload the other end of the worm shaft 32 rotatably supported by 36, so that the worm shaft 32 and the worm wheel 42 are always in contact with each other have.

Further, 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 compression ring 60. Is provided in the outer portion of the elastic cap 70, the receiving port 71 is connected to the compression ring 60 is formed in the concentric position where the second bearing 36 is located inside, the compression ring 60 Is configured to enable radial pressurization.

5 and 6, the compression ring 60 has an outer accommodation port of the elastic cap 70 surrounding the outer portion of the second bearing 34 supporting the shaft end of the worm shaft 32. It is constructed to be able to flexibly absorb or compensate the axial and radial play of the worm shaft 32 in contact with the inside.

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 resilient cover 50 is positioned to surround the first bearing outer portion for supporting the worm shaft 32, which is a reduction gear, when the reduction gear is worn due to frequent friction, the play is regulated to the maximum force As a result, it is possible to reduce the noise due to irregular contact between the gear teeth.

In addition, due to the addition of the compression ring 60, by applying a preload to the second bearing 36 of the shaft supporting the other shaft of the electric motor output shaft 30, the worm shaft and the worm wheel is always 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 compression ring 60, surrounding the said other support end part. Therefore, the support end of the other end of the worm shaft 32 is spaced apart from the worm wheel 42 is to be blocked at the source.

The first bearing 34 and the damper ring 91 are in contact with one side of the support end side first bearing 34 and the elastic cover 50 of the worm shaft 32. An elastic force is applied and pressurized so that play caused by wear of the housing 4 is always compensated.

Thus, the various kinds of elastic clearance compensation means intervene between the housing 4 together with the first and second bearings 36, thereby simultaneously absorbing or compensating the axial and radial clearances of the worm shaft 32. Will be.

As described above, according to the present invention, the worm shaft clearance absorbing structure of the column type electric power steering device is provided with a clearance compensation device for applying an elastic force to the outside of the bearing supporting the rotation of the worm shaft, thereby absorbing the clearance of the worm shaft due to wear between gear teeth. Thus, it is possible to prevent the vibration and noise of the device in advance, and thus, it is possible to further increase the performance and reliability of the product.

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 (6)

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 the steering force 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, a housing in which the drive electric motor and the reduction gear are built; A column type electric power steering apparatus including an ECU for controlling a driving force of an output shaft of a drive electric motor by calculating signals input from a steering angle sensor, a vehicle speed sensor, and a torque sensor, the amount of which extends on both sides of a worm shaft of the reduction gear. First shaft on the output shaft side of the electric motor of both bearings supporting the support end so as to be rotatable. A resilient cover arranged to surround the outer and end portions of the ring together, and a hollow resilient cap arranged to surround the outer portion of the second bearing supporting the other end of the worm shaft opposite the resilient cover. Column type electric power steering system. The method of claim 1, The first bearing is coaxial with one of the supporting ends of the worm shaft, the fixing ring inserted into the enlarged portion of the worm shaft and a fixture formed concave at a predetermined distance from the enlarged portion, and to support one side of the elastic cover. The column type electric power steering apparatus characterized in that it is arranged between the snap ring is fixed to the fixed groove formed in the housing. The method of claim 1, The hollow portion of the elastic cap is a column-type electric power steering device, characterized in that the cross-sectional shape made of an elliptical shape. The method of claim 1, The outer portion of the elastic cap is a column type electric power steering device characterized in that the receiving port is connected to the compression ring in the concentric position where the second bearing is located inside. The method of claim 4, wherein The receiving port is a column type electric power steering device characterized in that a plurality of through-holes penetrating to the hollow of the elastic cap is formed. The method of claim 2, The column type electric power steering device, characterized in that the damper ring of the washer and the urethane material is laminated between one side of the elastic cover and the snap ring.

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