JP3919447B2 - Electric power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric power steering apparatus using a motor as a generation source of steering assist force.
[0002]
[Prior art]
Automobile steering is performed by turning a steering wheel arranged inside the passenger compartment to a steering mechanism arranged outside the passenger compartment for steering the steering wheel (generally the front wheels). Done.
[0003]
FIG. 7 is a cross-sectional view showing a configuration of a conventional electric power steering apparatus, and FIG. 8 is a cross-sectional view showing a configuration of a speed reduction mechanism and a motor portion.
As an electric power steering apparatus for an automobile, as shown in FIG. 7, for example, a first steering shaft 101 connected to a steering wheel 100 for steering, and the steering shaft 101 are coaxially connected via a torsion bar 102. A second steering shaft 103 connected to a steering mechanism connected to a wheel (not shown) and torque applied to the first steering shaft 101 by rotating the steering wheel 100 are applied to the torsion bar 102. Torque sensor 104 detected by the generated torsion, steering assisting motor 105 driven based on the detection result of torque sensor 104 (see FIG. 8), worm 106 interlocked with the rotation of motor 105, and worm A worm wheel 107 that meshes with 106, and a pair of support holes 108 that rotatably support the worm 106 and the steering shaft 103. And a housing 110 having 109, the operation of the steering mechanism according to the rotation of the steering wheel 100 is assisted by the rotation of the motor 105, and the labor burden on the driver for steering is reduced. .
[0004]
FIG. 9 is a sectional view showing another configuration of the conventional electric power steering apparatus.
Further, as an electric power steering device, as shown in FIG. 9, a worm wheel having an annular tooth portion 111 made of synthetic resin meshing with the worm 106 and a metal holding body 112 fitted inside the tooth portion 111. It is known that 113 is supported on the steering shaft 103 to reduce noise caused by meshing with the worm 106.
[0005]
The worm 106 constituting the reduction gear mechanism of the electric power steering apparatus is disposed so as to intersect with the axis of the steering shaft 103, and is fitted into the fitting holes 108 and 108 of the housing 110 via a pair of rolling bearings 114 and 114. The second steering shaft 103 that is supported and supports the worm wheel 107 or 113 is supported by the fitting holes 109 and 109 of the housing 110 via a pair of rolling bearings 115 and 115, and the worm 106 and the worm wheel. 107 and 113 are prevented from moving in the radial direction and the axial direction.
[0006]
In the electric power steering apparatus using the worm 106 and the worm wheel 107 or 113 as described above, an appropriate backlash amount is provided at the meshing portion of the worm 106 and the worm wheel 107 or 113 to thereby provide the worm 106 and the worm wheel 107. , 113 are rotated smoothly. When the backlash amount is large, a rattling sound is generated, and the rattling sound leaks into the interior of the automobile. When the backlash amount of the meshing portion is small, the worm 106 and the worm wheels 107 and 113 are connected. It cannot be rotated smoothly.
[0007]
[Problems to be solved by the invention]
However, the conventional electric power steering apparatus configured as described above may cause clogging of the worm 106 and the worm wheels 107 and 113 even when assembled with the backlash amount set appropriately. Improvement measures were requested.
[0008]
As a result of pursuing the cause of this meshing clog, the inventor is a passenger car having a relatively small number of boarding times, and is equipped with a worm wheel 113 having a synthetic resin tooth portion 111 and a metal holding body 112. I found out what was happening in the power steering system. As a result of further pursuit, the holder 112 of the worm 106 and the worm wheel 113 is made of metal, and the annular tooth portion 111 provided on the outer periphery of the holder 112 is made of synthetic resin. It was found that when no load is applied, the tooth portion 111 swells little by little due to moisture in the atmosphere, the backlash amount becomes excessively small, and clogging occurs.
[0009]
The present invention has been made in view of such circumstances, and by providing a moisture intrusion prevention member for preventing moisture from entering the housing area of the driven gear in the housing in which the driven gear is accommodated, It is an object of the present invention to provide an electric power steering device that can satisfactorily suppress swelling of a tooth part, can maintain an appropriate backlash amount of a meshing part, and can eliminate the occurrence of meshing clogging. .
[0010]
In addition, by using a rolling bearing having a sealing ring for preventing moisture from flowing between the inner ring and the outer ring as the moisture intrusion preventing member, and supporting the rotating shaft inside the housing, the inner side of the housing and the rotating shaft can be It is an object of the present invention to provide an electric power steering device that can satisfactorily suppress swelling of a tooth portion due to moisture without being specially processed or increasing the number of parts.
[0011]
Further, by using a sealing ring for contacting the inside of the rotating shaft and the housing as the moisture intrusion preventing member to prevent the flow of moisture, the sealing ring is easily held on one of the rotating shaft and the housing. It is an object of the present invention to provide an electric power steering device that can be used.
[0012]
In addition, by adopting a configuration in which the sealing ring is attached between a rolling bearing that supports the rotating shaft on the housing and a convex portion that protrudes to face one end of the rolling bearing. An object of the present invention is to provide an electric power steering device in which a sealing ring can be easily attached by incorporation.
[0013]
[Means for Solving the Problems]
An electric power steering apparatus according to the present invention includes a drive gear rotated by a steering assist motor, a driven gear having a tooth portion made of synthetic resin meshing with the drive gear, and a housing in which the driven gear is accommodated. , through the housing, the rotation of the driven gear and a rotating shaft for transmitting a steering mechanism, an electric power steering apparatus for steering assistance by the rotation of the motor, inside the rotary shaft and the housing A seal ring for preventing moisture from entering and flowing through the housing area of the driven gear is provided in the housing, a rolling bearing for supporting the rotating shaft on the housing, and an inner side of the housing And a metal plate having an annular flange on the outer peripheral edge thereof, and a metal plate having a convex portion protruding to face the outer ring of the rolling bearing. And an elastic plate having an inner peripheral edge portion, wherein the annular flange portion is attached between the outer ring of the rolling bearing and the convex portion, and the inner peripheral edge portion of the elastic plate is attached to the rolling bearing. It is characterized by being in contact with the inner ring and the rotating shaft .
[0014]
In the present invention, the sealing ring provided in the housing through which the rotating shaft passes is in contact with the inside of the rotating shaft and the housing to prevent moisture intrusion into the accommodation area of the driven gear. Swelling of the tooth portion due to moisture can be satisfactorily suppressed without specially processing the inner side and the rotating shaft or increasing the number of parts. Moreover, by incorporating the rolling bearing inside the housing, the sealing ring can be attached between the rolling bearing and the convex portion, and the assembling work of the sealing ring is easy.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.
Embodiment 1
FIG. 1 is a cross-sectional view showing a configuration of an electric power steering apparatus according to the present invention, and FIG. 2 is an enlarged cross-sectional view showing a configuration of a speed reduction mechanism and a torque sensor portion.
As shown in FIGS. 1 and 2, the electric power steering device is inserted into the first steering shaft 2 having an upper end connected to the steering wheel 1 for steering and having a cylindrical portion 20 at the lower end, and the cylindrical portion 20. The upper end of the torsion bar 3 is coaxially connected to the lower end of the first steering shaft 2 and is twisted by the action of the steering torque applied to the steering wheel 1, and the upper end of the torsion bar 3 is around the cylinder portion 20. Relative rotation of the second steering shaft 4 which is inserted and whose lower end is coaxially connected to the lower end of the torsion bar 3 and the first and second steering shafts 2 and 4 according to the torsion of the torsion bar 3 A torque sensor 5 for detecting a steering torque applied to the steered wheel 1 according to a displacement amount, and a rotor arranged so that a rotation center thereof intersects with an axis of the second steering shaft 4; Drive based on torque detected by 5 A steering assisting motor 6, a reduction gear having a worm 71 serving as a driving gear and a worm wheel 72 serving as a driven gear that decelerates and transmits the rotation to the second steering shaft 4 in conjunction with the rotation of the motor 6. A gear mechanism 7, a cylindrical first housing 8 in which the first steering shaft 2 is accommodated, and a lower end portion of the first housing 8 are fitted and fixed to the cylindrical portion 20, the second steering. A shaft 4, a torque sensor 5, and a second housing 9 made of aluminum in which the reduction gear mechanism 7 is accommodated are provided.
[0022]
The first steering shaft 2 includes a first shaft 2a having an upper end connected to the steering wheel 1, and a second shaft 2c connected to a lower end portion of the first shaft 2a via an impact energy absorber 2b made of synthetic resin. The cylinder portion 20 is connected to the lower end of the second shaft 2c. A keyway 2d is provided in the middle of the first shaft 2a.
[0023]
The second steering shaft 4 penetrates the lower end portion of the second housing 9 and constitutes a rotating shaft that transmits the rotation of the worm wheel 72 to the steering mechanism, and the worm wheel is located in the middle in the axial direction thereof. The first fitting portion 4a to which 72 is fitted, and the second and third fitting portions 4b and 4c are provided on both sides of the first fitting portion 4a via an annular step. Yes.
[0024]
A mounting hole 81 for a key cylinder unit is formed on one side of the first housing 8, and a cylinder (not shown) in which the key cylinder unit is housed is fixed around the mounting hole 81. The
[0025]
The second housing 9 communicates with the inside of the first housing 8, and has a substantially cylindrical first housing portion 9a in which the tubular portion 20 and the torque sensor 5 are housed, and is continuous with the first housing portion 9a. The substantially cylindrical second storage chamber 9b in which the second steering shaft 4 and the worm wheel 72 are accommodated and one side of the second accommodation portion 9b, and the substantially cylindrical shape in which the worm 71 is accommodated. The motor 6 having a third housing portion 9c and having a case communicating with the third housing portion 9c is attached to one end of the third housing portion 9c.
[0026]
A conductor insertion hole 91 through which a conductor connected to the torque sensor 5 is inserted, and a lid 92 that closes the open end to the outside of the conductor insertion hole 91 are provided on one side of the first housing portion 9a. .
[0027]
A first support hole 93 for rotatably supporting the upper end portion of the cylindrical portion 20 via a needle bearing 10 is provided at the upper end portion of the first accommodating portion 9a. In the second accommodating portion 9b, second and third supporting the second steering shaft 4 rotatably via the first and second rolling bearings 11 and 12 on both sides of the accommodating area of the worm wheel 72. Support holes 94 and 95 are provided.
[0028]
FIG. 3 is a cross-sectional view showing the configuration of the reduction gear mechanism and the motor portion.
The third accommodating portion 9c is elongated in the axial direction of the worm 71, and a pair for rotatably supporting the worm 71 via a pair of third rolling bearings 13 and 13 on both sides of the accommodating area of the worm 71. The fourth support holes 96 are provided. A screw hole 97 is provided at one end on the motor side, and a screw ring 14 for adjusting the position of the worm 71 in the axial length direction is screwed into the screw hole 97. A nut 15 is screwed. Moreover, the other end of the 3rd accommodating part 9c is closed.
[0029]
The reduction gear mechanism 7 is arranged so as to intersect with the axis of the second steering shaft 4, and is located between the metal worm 71 having shaft portions 71 a and 71 b at both ends and the second steering shaft 4. And a worm wheel 72 to be fitted and fixed. The shaft portion 71 a is connected to the output shaft 60 of the motor 6 via a shaft joint 73, and the rotation of the output shaft 60 is decelerated by the meshing of the worm 71 and the worm wheel 72, thereby the second steering shaft 4. And transmitted from the second steering shaft 4 to, for example, a rack and pinion type steering mechanism (not shown) via a universal joint.
[0030]
The shaft portions 71a and 71b of the worm 71 are rotatably supported by the fourth support holes 96 and 96 through the third rolling bearings 13 and 13, respectively.
[0031]
The third rolling bearings 13, 13 are provided with a pair of sealing rings 13a in a space between both ends of the inner ring and the outer ring in the axial length direction and the rolling elements, and a lubricating oil such as grease filled in the space. , And the mixing of the lubricating oil for the bearing and the lubricating oil for the gear applied to the meshing portion of the worm 71 and the worm wheel 72 is prevented.
[0032]
Figure 4 is Ri enlarged sectional view showing the structure of a worm wheel portion, shown as a reference example.
The worm wheel 72 includes an annular tooth portion 72a made of a synthetic resin having a plurality of teeth meshing with the worm 71, and a metal holding body 72b fitted inside the tooth portion 72a. A through hole drilled in the center of the body 72b is fitted and fixed to the first fitting portion 4a of the second steering shaft 4. For example, a nylon resin is used for the tooth portion 72a.
[0033]
The second steering shaft 4 to which the worm wheel 72 is fitted and fixed has its second and third fitting portions 4b and 4c sealed in the accommodation area of the worm wheel 72, and moisture enters the accommodation area. The inner rings 11a and 12a of the first and second rolling bearings 11 and 12 that constitute a moisture intrusion preventing member that prevents this are fitted. Then, by fitting the outer rings 11b and 12b of the first and second rolling bearings 11 and 12 into the second and third support holes 94 and 95, the second steering shaft 4 is moved to the second housing portion. 9b is rotatably supported and the accommodation area of the worm wheel 72 is hermetically sealed to prevent moisture from entering the accommodation area.
[0034]
The first rolling bearing 11 includes an inner ring 11a and an outer ring 11b that are loosely fitted via a plurality of rolling elements 11c, and a space 11d between both ends of the inner ring 11a and the outer ring 11b in the axial length direction and the rolling element 11c. And a pair of sealing rings 11e. An annular groove 15f for fitting and fixing the outer peripheral portion of the sealing ring 11e is provided on the inner peripheral surface of both ends of the outer ring 11b, and the inner peripheral portion of the sealing ring 11e is provided on the outer peripheral surface of both ends of the inner ring 15a. An annular groove 11g for loosely fitting and labyrinth sealing is provided.
[0035]
The second rolling bearing 12 includes an inner ring 12a and an outer ring 12b loosely fitted via a plurality of rolling elements 12c, and a space 12d between one end in the axial length direction of the inner ring 12a and the outer ring 12b and the rolling element 12c. And a sealing ring 12e provided on the surface. An annular groove 12f for fitting and fixing the outer peripheral portion of the sealing ring 12e is provided on the inner peripheral surface of one end portion of the outer ring 12b, and the inner peripheral portion of the sealing ring 12e is provided on the outer peripheral surface of one end portion of the inner ring 12a. An annular groove 12g is provided for loose fitting and labyrinth sealing.
[0036]
In the electric power steering apparatus configured as described above, external air enters the first housing 8 from the key cylinder portion attached to one side of the first housing 8, and the intruding air enters the second housing. 9 enters the first housing portion 9a through a gap between the 10 needle bearing portions, and the seal ring 11e is provided between the first housing portion 9a and the second housing portion 9b in which the worm wheel 72 is housed. Therefore, it is possible to satisfactorily prevent moisture contained in the intruding air in the first housing portion 9a from entering the second housing portion 9b. Furthermore, since the lower end opening of the second housing portion 9b through which the second steering shaft 4 passes is sealed by the second rolling bearing 12 having the sealing ring 12e, moisture contained in external air Can be satisfactorily prevented from entering the second housing portion 9b.
[0037]
In this way, the rolling bearings 11 and 12 that support the second steering shaft 4 inside the second housing 9 favorably prevent moisture from entering the housing region of the worm wheel 72. And the swelling of the tooth part 72a by moisture can be suppressed favorably, without processing the 2nd steering shaft 4 specially, or increasing a number of parts. Therefore, an appropriate amount of backlash can be maintained satisfactorily, and the occurrence of clogging can be eliminated.
[0038]
Note that the communication path through which the second storage portion 9b and the third storage portion 9c communicate is a relatively small communication path in which the meshing portion of the worm wheel 72 with the worm 71 is inserted. Lubricating oil such as gear grease is applied between the meshing portion of the wheel 72 and the periphery of the worm 71 so that it is difficult to communicate therewith, so that the air in the third housing portion 9c is in the second housing portion 9b. There is little intrusion amount. Further, since the motor side opening of the third housing portion 9c that houses the worm 71 is closed by the motor 6, the outside air hardly enters the third housing portion 9c, and the third housing portion 9c. Since the motor side opening is sealed by the third rolling bearing 13 having the sealing ring 13a, the outside air is less likely to enter the third accommodating portion 9c.
[0039]
The first embodiment described above is a reference example, and in the first embodiment, the first rolling bearing 11 has a structure having the sealing rings 11e on both ends, but in addition, the sealing ring 11e only on one end. It is good also as a structure which has. Further, the sealing ring 11e may be a labyrinth seal in which the inner peripheral portion or the outer peripheral portion is not in contact, or a contact seal in which the inner peripheral portion or the outer peripheral portion is in contact.
[0040]
Embodiment 2
FIG. 5 is a sectional view showing the configuration of the second embodiment of the electric power steering apparatus, and FIG. 6 is an enlarged sectional view showing the configuration of the worm wheel portion.
[0041]
In the electric power steering apparatus according to the second embodiment, instead of using the first rolling bearing 11 having the sealing ring 11e as a moisture intrusion preventing member, the first fitting portion 4a and the second support hole 94 are used. The first rolling bearing 17 that does not have the sealing ring 11e is used as a bearing that supports the upper end side of the second steering shaft 4 using a sealing ring 16 for preventing moisture from flowing in contact therewith. Is.
[0042]
Sealing ring 16 is provided with a metal plate 16a having an annular flange on the outer periphery, coupled by vulcanization bonding to the metal plate 16a, and an elastic plate 16b of the synthetic rubber or the like having a lip on the inner periphery. In addition, the second accommodating portion 9b is provided with an annular convex portion 18 projecting from one end of the second support hole 94 in the radial direction.
[0043]
In the second embodiment, the annular flange of the sealing ring 16 is fitted and brought into contact with the second support hole 94, the inner peripheral edge is brought into contact with the second fitting portion 4b, and the lip is brought into contact with the first rolling bearing 17. As shown in FIG. 6, the inner peripheral edge of the elastic plate 16b is in contact with the second fitting portion 4b and the inner ring. An annular flange portion on the outer peripheral side of the sealing ring 16 is attached between the outer ring of the first rolling bearing 17 fitted in the second support hole 94 and the convex portion 18.
[0044]
In the second embodiment, it is possible to satisfactorily prevent moisture from entering the housing region of the worm wheel 72 using the fitting portion of the first rolling bearing 17, and the first rolling bearing 17 The sealing ring 16 can be easily attached by fitting into the second support hole 94.
[0045]
In the second embodiment, the sealing ring 16 may be used instead of the second rolling bearing 12 or may be used instead of the first and second rolling bearings 11 and 12. In this case, a bearing for supporting the second steering shaft 4 on the side where the seal ring 16 is arranged Ru can be used rolling bearings not having sealing ring 11e, 12e.
[0047]
Since other configurations and operations are the same as those of the first embodiment, the same components are denoted by the same reference numerals, and detailed description and operations thereof are omitted.
[0048]
The reduction gear mechanism 7 of the embodiment described above is a worm gear provided with a drive gear 71 that is a worm and a driven gear 72 that is a worm wheel, and is also a driven gear that is a hypoid pinion and a driven wheel that is a hypoid wheel. It may be a hypoid gear provided with a gear. Further, the reduction gear mechanism may be a bevel gear.
[0049]
【The invention's effect】
According to the present invention, the seal ring contacts the rotating shaft and the inside of the housing to prevent moisture intrusion into the accommodation area of the driven gear. without or increased, the swelling of the teeth due to moisture can be satisfactorily suppressed, a proper backlash amount can be favorably maintained, it is possible to eliminate the occurrence of meshing clogging. Moreover, by incorporating the rolling bearing inside the housing, the sealing ring can be attached between the rolling bearing and the convex portion, and the assembling work of the sealing ring is easy.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a configuration of an electric power steering apparatus according to the present invention.
FIG. 2 is an enlarged cross-sectional view showing a configuration of a speed reduction mechanism and a torque sensor portion of the electric power steering apparatus according to the present invention.
FIG. 3 is a cross-sectional view showing a configuration of a reduction gear mechanism and a motor portion of the electric power steering apparatus according to the present invention.
FIG. 4 is an enlarged cross-sectional view showing a configuration of a worm wheel portion of the electric power steering apparatus according to the present invention.
FIG. 5 is a cross-sectional view showing a configuration of a second embodiment of the electric power steering apparatus according to the present invention.
FIG. 6 is an enlarged cross-sectional view showing a configuration of a worm wheel portion of a second embodiment of the electric power steering apparatus according to the present invention.
FIG. 7 is a cross-sectional view showing a configuration of a conventional electric power steering apparatus.
FIG. 8 is a cross-sectional view showing a configuration of a speed reduction mechanism and a motor portion of a conventional electric power steering apparatus.
FIG. 9 is a cross-sectional view showing another configuration of a conventional electric power steering apparatus.
[Explanation of symbols]
4 Second steering shaft (rotary shaft)
6 Motor 9 Second housing (housing)
11, 12 1st and 2nd rolling bearing (moisture intrusion prevention member)
11a, 12a Inner ring 11b, 12b Outer ring 11c, 12c Rolling elements 11e, 12e Sealing ring 16 Sealing ring 17 First rolling bearing 18 Convex part 71 Worm 72 Warm wheel 72a Tooth part

Claims (1)

A drive gear rotated by a steering assist motor; a driven gear having a synthetic resin tooth portion meshing with the drive gear; a housing in which the driven gear is housed; A rotating shaft that transmits the rotation of the motor to the steering mechanism, and in the electric power steering device that assists steering by the rotation of the motor , contacts the inner side of the rotating shaft and the housing to the accommodation region of the driven gear. A sealing ring for preventing moisture from entering and circulating is provided in the housing. The sealing ring includes a metal plate having an annular flange on an outer peripheral edge, and an elastic plate coupled to the metal plate and having an inner peripheral edge. Yes and挾着the annular flange portion between the outer ring and the convex portion of the rolling bearing, characterized in that the inner peripheral edge portion of the elastic plate are in contact with the inner ring and the rotary shaft of the rolling bearing Electric power steering device.

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