JP2015229378A - Electric power steering device and vehicle provided with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a rattle noise caused by a gap inside a shaft bearing of a worm gear mechanical unit and backlashes while transmitting torque in a non-contact manner.SOLUTION: In an electric power steering device 9, an output shaft 13a is arranged eccentrically toward a worm wheel 22 side with respect to a worm shaft 21, and a magnetic reduction gear 30 having a pair of disks 31, 32 is provided at a joint part of the output shaft 13a and the worm shaft 21. The magnetic reduction gear 30 is provided with a permanent magnet pair 50 including a first annular magnet row 51 arranged on one disk face and a second annular magnet row 52 arranged on the other disk face. The first annular magnet row 51 and the second annular magnet row 52 are arranged such that different poles are disposed to oppose to each other in the axial direction, when respective plural permanent magnets are at positions where torque is transmitted between mutual disk faces in a non-contact manner, and the numbers of respective plural permanent magnets are set according to a gear reduction ratio.

Description

  The present invention relates to an electric power steering apparatus that transmits a steering assist force (assist torque) to a steering system.

  This type of electric power steering apparatus urges the driving force of the electric motor as a steering assist force to the steering system via the worm gear mechanism. Generally, in the worm gear mechanism portion, a joint portion between a worm shaft integrally formed with a worm and an output shaft of an electric motor is mainly contact-type spline coupling.

  However, depending on the road surface condition during driving and steering of the vehicle, the impact torque from the steered wheels at the time of riding on the shoulder may be applied as a reverse input to the steering system. In this case, if the joint between the output shaft of the electric motor and the worm shaft is splined, the reverse input to the steering system directly reaches the output shaft of the electric motor via the worm gear mechanism. For this reason, even if a high-precision spline is used, there is a risk of generating an abnormal sound (noise) such as a rattle sound.

  Further, when torque is generated by reverse input, excessive torque is generated in the steering assist force transmission system by the motor inertia. Therefore, in order to prevent the transmission system of the steering assist force from being damaged, it is necessary to increase the strength of each part, which causes a problem that the cost of the electric power steering device is increased and the size of the device is increased. Alternatively, in order to prevent an excessive torque from being transmitted to the steering assist force transmission system, there is a problem that a torque limiter mechanism needs to be added separately.

  Therefore, for example, in the technique described in Patent Document 1, torque transmission is performed by a non-contact type magnetic joint in which a joint portion between the output shaft of the electric motor and the worm shaft of the worm gear mechanism portion has permanent magnets with different poles facing each other. It is possible. According to the technique described in Patent Document 1, torque transmission is enabled by the attraction force of permanent magnets that are opposed to each other and are opposed to each other in a non-contact manner, so that the output shaft of the electric motor and the worm shaft of the worm gear mechanism portion The occurrence of abnormal noise (noise) and abnormal wear at the joint between the two can be prevented.

JP 2006-51913 A

  By the way, this type of electric power steering apparatus has a problem that rattle noise is generated even when there is an internal gap (backlash) in a bearing that supports a worm shaft integral with the worm. Conventionally, as a countermeasure against rattle noise caused by the internal clearance (backlash) of the bearing that supports the worm shaft, a four-point contact ball bearing with no internal clearance or a preload damper is used to adjust the axial load and adjust the worm shaft Preload is applied to the bearing. However, such a rattle noise countermeasure increases the cost of the electric power steering apparatus.

  Further, in addition to the internal clearance (backlash) of the bearing, the backlash of the worm gear mechanism also causes rattle noise. In order to prevent the occurrence of rattle noise due to the backlash, for example, when a worm pressing mechanism using a spring is employed, if the joint portion is splined, the gap management becomes important. If the gap is narrow, competition occurs, and if the gap is wide, it causes noise, and a high-precision spline is required. Thus, since it becomes a factor of the further cost increase of an electric power steering apparatus, there exists a problem that gap management is difficult.

  In addition, as a countermeasure against rattle noise caused by backlash of the worm gear mechanism part, a structure that applies preload to the worm shaft by elastic coupling using rubber is adopted. Since this changes, there is a problem that rigidity management and material management are difficult. In addition, when the misalignment between the output shaft of the electric motor and the worm shaft is large, a problem such as abnormal wear of the elastic coupling occurs, so that there is a problem that management of misalignment becomes severe.

  With respect to such a problem, the magnetic coupling described in Patent Document 1 enables torque transmission by non-contact, but when permanent magnets with different poles facing each other are arranged opposite to each other in the radial direction (Example of the same document) 1 (FIG. 2 of the same document)), no preload can be applied to the bearing supporting the worm shaft from the axial direction. Also, the backlash of the worm gear mechanism cannot be adjusted.

  Here, Patent Document 1 does not describe at all about the point of adjusting the axial load and applying the preload to the bearing, but in another example of the magnetic coupling described in the same document, different poles are opposed to each other. The case where the permanent magnets are arranged opposite to each other in the coaxial direction (Example 2 of the same document (FIG. 3 of the document)) is also shown. If permanent magnets facing different poles are arranged opposite to each other in the coaxial direction, a preload can be applied to the bearing from the axial direction.

  However, when preloading is applied to the bearing from the axial direction only by the permanent magnet assembly for torque transmission in which the permanent magnets with different poles facing each other are arranged in the coaxial direction, the backlash of the worm gear mechanism is sufficiently reduced. It cannot be adjusted. Therefore, it is insufficient to prevent the generation of abnormal noise such as rattle noise caused by the bearing internal clearance and backlash of the worm gear mechanism, and for example, a worm pressing mechanism using a spring is used for adjusting the backlash of the worm gear mechanism. The problem of having to adopt it separately is not solved.

  Accordingly, the present invention has been made paying attention to the above-described problems, and transmits torque without contact, and prevents or suppresses rattle noise caused by the bearing internal clearance and backlash of the worm gear mechanism. It is an object of the present invention to provide an electric power steering apparatus and a vehicle including the same.

  In order to solve the above problems, an electric power steering apparatus according to an aspect of the present invention includes an electric motor that generates a steering assist force, and a worm gear mechanism that transmits torque generated on an output shaft of the electric motor to a steering system. And an electric power steering device that transmits the torque generated on the output shaft of the electric motor to the worm shaft of the worm gear mechanism portion in a non-contact manner, wherein the output shaft is relative to the worm shaft. The magnetic reducer includes a pair of disks provided at a joint portion between the output shaft and the worm shaft and facing each other with a gap therebetween. This disk has a first annular magnet array composed of a plurality of permanent magnets arranged in an annular shape on one disk surface and an annular shape arranged on the other disk surface. A plurality of permanent magnet sets, each of the first annular magnet row and the second annular magnet row being arranged between the disk surfaces. Are arranged so that different poles face each other in the axial direction when the torque is transmitted in a non-contact manner, and the number of the plurality of permanent magnets is set to a different number according to the reduction ratio. And

Here, in the electric power steering apparatus according to one aspect of the present invention, it is preferable that the bearing supporting the worm shaft is a deep groove ball bearing.
In order to solve the above problem, a vehicle according to an aspect of the present invention includes the electric power steering device according to an aspect of the present invention.

  According to the electric power steering apparatus according to one aspect of the present invention, the output shaft is arranged eccentrically toward the worm wheel with respect to the worm shaft, and the magnetic reduction gear is provided at a joint portion between the output shaft and the worm shaft. The disk surfaces are provided with a pair of disks facing each other with a gap, and the pair of disks includes a permanent magnet set arranged to face each disk surface. Since the first annular magnet row and the second annular magnet row are arranged so that different poles face each other in the axial direction when the torque is transmitted, the non-contact type magnetic speed reducer is Torque transmission from the output shaft to the worm shaft can be transmitted in a non-contact manner by a pair of disks opposed in the axial direction. The first annular magnet array and the second annular magnet array transmit torque at a predetermined reduction ratio because the number of the plurality of permanent magnets is set to a different number according to the reduction ratio. be able to.

  Therefore, according to the electric power steering device and the vehicle including the electric power steering device according to one aspect of the present invention, the non-contact type magnetic reduction device is used to reduce the predetermined speed between the output shaft of the electric motor and the worm shaft of the worm gear mechanism. Since torque can be transmitted at a ratio, abnormal noise such as rattle noise and abnormal wear at the joint are prevented. In addition, this magnetic speed reducer has a configuration in which a pair of disks face each other with a gap therebetween, so that abnormal wear due to abnormal noise and misalignment of the joint itself does not occur, so dimensional control with high accuracy is possible. Is unnecessary, and a cost reduction effect can be obtained.

  In addition, the joint between the output shaft of the electric motor and the worm shaft of the worm gear mechanism portion transmits torque with a predetermined reduction ratio by a non-contact type magnetic reduction gear opposed in the axial direction. When excessive torque is generated due to reverse input, the magnetic speed reducer functions as a torque limiter, and damage to each part of the transmission system can be prevented. Therefore, it is suitable for reducing the cost of the electric power steering device and for making the device size compact.

  Furthermore, according to the electric power steering apparatus according to one aspect of the present invention, since the axial load is always generated by the non-contact type permanent magnet set opposed in the axial direction, the preload is applied to the bearing supporting the worm shaft. Can be granted. Therefore, according to the electric power steering apparatus and the vehicle including the same according to one aspect of the present invention, it is possible to eliminate the internal clearance (backlash) of the bearing that supports the worm shaft, and thus the internal clearance of the bearing that supports the worm shaft. While preventing or suppressing rattle noise caused by (backlash), a separate incidental device for the countermeasure is unnecessary. In addition, a relatively low-cost deep groove ball bearing can be used as the bearing that supports the worm shaft, and the cost of the electric power steering apparatus can be reduced.

  In the magnetic speed reducer, the attractive force between the permanent magnets facing different poles is inversely proportional to the transmitted torque (the attractive force is maximum when torque is not transmitted, and the attractive force is transmitted when torque is transmitted). Minimize). For this reason, it is possible to efficiently apply a preload to the bearing at the time of low torque transmission in which abnormal noise of the bearing is likely to occur. In addition, when high torque transmission where the need for preload is low, the preload is lower than when low torque is transmitted, which is suitable for improving transmission efficiency.

  According to the electric power steering device according to one aspect of the present invention, the output shaft is arranged eccentrically toward the worm wheel side with respect to the worm shaft, so that the action of the attractive force between the permanent magnets of the magnetic reducer Thus, a moment load can be generated toward the worm wheel with respect to the worm shaft. Thereby, in addition to the internal clearance of the bearing, the preload amount can be adjusted so as to reduce the fluctuation of the operating torque with respect to the backlash of the worm gear mechanism portion, and a separate auxiliary device (for example, a worm pressing mechanism using a spring) is used for the countermeasure. It is unnecessary.

In particular, since a relatively low-cost deep groove ball bearing can be used as the bearing that supports the worm shaft, the cost of the electric power steering device can be reduced, and the device can be downsized. In other words, if the bearing that supports the worm shaft is a deep groove ball bearing, the deep groove ball bearing is capable of relative inclination of the inner and outer rings, so that an axial load is generated on the worm shaft by the permanent magnets facing in the axial direction and the output is This is suitable for giving the worm shaft an inclination corresponding to the moment load due to the shaft being eccentric or inclined on the worm wheel side.
In addition, when a normal contact type speed reducer is used for the joint portion, if the worm shaft is inclined, abnormal noise and abnormal wear due to poor meshing of the speed reducer itself of the joint portion may occur. Since the magnetic speed reducer included in the electric power steering apparatus according to one aspect is a non-contact type, it is excellent in that such abnormal noise and abnormal wear do not occur. Therefore, according to the electric power steering apparatus according to one aspect of the present invention and the vehicle including the same, the internal clearance (backlash) of the bearing that supports the worm shaft and the backlash of the worm gear mechanism unit are suppressed, and rattle noise is generated. It is more suitable for preventing or suppressing.

  As described above, according to the present invention, torque can be transmitted in a non-contact manner, and rattle noise caused by the bearing internal clearance and backlash of the worm gear mechanism can be prevented or suppressed.

It is a schematic block diagram which shows one Embodiment of the steering system in a vehicle (an example of a right-hand drive vehicle) provided with the electric power steering apparatus which has the magnetic reduction gear concerning this invention. FIG. 2 is an explanatory diagram of the first embodiment of the electric power steering device of FIG. 1, in which FIG. 1 (a) shows the electric power steering device from the front side of the vehicle, and the main part thereof is a cross section along the axis of the electric motor. FIG. 2B is an enlarged view of the magnetic speed reducer portion in FIG. It is AA sectional drawing in FIG.2 (b).

Hereinafter, an embodiment of the present invention will be described with reference to the drawings as appropriate.
In FIG. 1, reference numeral 1 denotes a steering mechanism that constitutes a steering system of a vehicle. The steering mechanism 1 includes a steering shaft 3 that is disposed on the right side of the vehicle and is rotatably mounted on a steering column 4. A steering wheel 2 is mounted on the steering column 4 at the rear end of the vehicle.

  The steering shaft 3 is provided with a steering gear mechanism 5 composed of a rack and pinion mechanism having a pinion shaft 5a and a rack shaft 5b at the front end portion of the vehicle. The steering shaft 3 is connected to the rack shaft 5b via the pinion shaft 5a, and both ends of the rack shaft 5b are connected to the steering wheel 7 via the tie rod 6, respectively.

  An electric power steering device 9 is attached to the steering column 4. The electric power steering device 9 has a reduction gear box 10 disposed on the steering column 4. The reduction gear box 10 is made of a material having high thermal conductivity. Examples of the material having high thermal conductivity include aluminum, aluminum alloy, magnesium, and magnesium alloy. The reduction gear box 10 is formed by die-casting any one of these materials having high thermal conductivity. A worm gear mechanism 11 is built in the reduction gear box 10.

  The electric power steering apparatus 9 includes an electric motor 13 and a controller (EPS ECU) 12. The electric motor 13 and the controller 12 are attached to the reduction gear box 10. The electric motor 13 is, for example, a brushless three-phase electric motor. The axial direction of the electric motor 13 is arranged orthogonal to the column axial direction of the steering column 4 and is provided on the left side in the vehicle width direction. The controller 12 is disposed on the right side in the vehicle width direction with respect to the electric motor 13 and is mounted on a controller mounting portion 8 formed in the reduction gear box 10.

  When power is supplied from the battery by turning on an ignition switch (not shown) of the vehicle, the controller 12 executes steering assist control processing by a micro control unit (MCU). Thus, a steering assist current command value is calculated based on detection values of a torque sensor and a vehicle speed sensor (not shown), and current feedback processing is executed based on the steering assist current command value and the motor current detected by the motor current detection unit. To calculate a voltage command value.

  Then, based on the calculated voltage command value, the controller 12 sends a necessary motor driving current to the electric motor 13 to drive the electric motor 13 so as to generate a steering assist force required in the normal rotation or reverse rotation direction. . As a result, a steering assist force corresponding to the steering torque of the steering wheel 2 is generated from the electric motor 13, and this steering assist force is transmitted to the steering shaft 3 via the worm gear mechanism portion 11 in the reduction gear box 10. The steering wheel 2 can be steered with a light steering force.

  Here, as shown in FIG. 2, the electric power steering apparatus 9 uses a magnetic speed reducer 30 at a joint portion between the output shaft 13 a of the electric motor 13 and the worm shaft 21 of the worm gear mechanism portion 11. . This magnetic speed reducer 30 uses the magnetic force of a permanent magnet as torque transmission means, and can transmit assist torque in a non-contact manner.

Specifically, as shown in FIG. 2, a worm wheel 22 is coaxially fixed to the steering shaft 3. A worm 21 a that meshes with the worm wheel 22 is provided integrally with the worm shaft 21. Both ends of the worm shaft 21 are rotatably supported by bearings 41 and 42 at upper positions in the reduction gear box 10. As the bearings 41 and 42, deep groove ball bearings capable of relative inclination of the inner and outer rings are used.
In the bearing 42 on the electric motor 13 side, the outer peripheral surface of the outer ring of the bearing 42 is directly fitted into the inner surface of the reduction gear box 10, and the inner peripheral surface of the inner ring of the bearing 42 is directly fitted into the outer peripheral surface of the driven shaft 21. On the other hand, in the bearing 41 opposite to the electric motor 13, the outer ring outer peripheral surface of the bearing 41 is directly fitted into the inner surface of the reduction gear box 10, but the shaft end outer peripheral surface of the driven shaft 21 is made of resin. The inner ring inner peripheral surface of the bearing 41 is fitted into the outer peripheral surface of the resin bush 44 with a gap fitted. The output shaft 13a of the electric motor 13 is also rotatably supported by a bearing 14 that employs a deep groove ball bearing.

  2B, the axis L1 of the output shaft 13a of the electric motor 13 and the axis L2 of the worm shaft 21 of the worm gear mechanism 11 are parallel to each other but are coaxial. It is not located on the top. In this example, the axis L1 of the output shaft 13a is located closer to the worm wheel 22 with respect to the axis L2 of the worm shaft 21, and is arranged eccentrically by a predetermined eccentric amount E on the worm wheel 21 side.

  The end portion of the output shaft 13a and the one end portion of the worm shaft 21 are opposed to each other with a predetermined distance in the axial direction. The end portion 13b of the output shaft 13a and the end portion 21b of the worm shaft 21 are each formed with a small diameter to form a step portion, and the center portions of the pair of disks 31 and 32 are fixed to the position of the step portion, respectively. ing. Each of the disks 31 and 32 is provided coaxially with the fixed output shaft 13a and worm shaft 21. The pair of disks 31 and 32 is a disk-shaped disk body, and the disk surfaces 31m and 32m are arranged to face each other with a predetermined gap (magnetic gap) therebetween. In this example, as shown in FIG. 3, the disk 31 on the worm shaft 21 side has a larger diameter than the disk 32 on the output shaft 13a side.

Here, the magnetic speed reducer 30 has a non-contact type speed reduction mechanism by having a permanent magnet set 50 arranged oppositely on the outer peripheral sides of the opposing disk surfaces 31m and 32m.
Specifically, the permanent magnet set 50 is arranged in a ring shape on the first disk surface 31m, the first ring magnet array 51 composed of a plurality of permanent magnets 51a and 51b, and on the other disk surface 32m. And a second annular magnet row 52 including a plurality of permanent magnets 52a and 52b.

  In the present embodiment, as shown in FIG. 3, the first annular magnet array 51 includes a plurality of permanent magnets 51a formed in a substantially fan shape concentrically with the disk surface 31m on the worm shaft 21 side with respect to the axis center. (The opposing side is an N pole) and a plurality of permanent magnets 51b (the opposing side is an S pole) are alternately embedded along the circumferential direction and arranged in an annular shape. In this example, a total of 12 permanent magnets 51a and 51b are used.

  On the other hand, as shown in FIG. 2B, the second annular magnet row 52 is provided on the disk surface 32 m on the output shaft 13 a side of the electric motor 13. 3, the second annular magnet row 52 is arranged in an annular shape having a smaller diameter than the first annular magnet row 51, and the permanent magnet of the first annular magnet row 51 is permanent. A plurality of permanent magnets 52a (opposite side is S pole) and a plurality of permanent magnets 52b (opposite side is N pole) are formed in a substantially fan shape so that different poles correspond to the magnets 51a and 51b at predetermined positions. They are alternately embedded along the direction and arranged in an annular shape. In this example, a total of six permanent magnets 52a and 52b are used.

  As a result, the first annular magnet row 51 and the second annular magnet row 52 have different poles when the plurality of permanent magnets are in a non-contact torque transmitting position between the disk surfaces 31m and 32m. Arranged to face each other. That is, in the example of this embodiment, the opposing magnets are set to be located at the same position in plan view at the lower position in FIG. 3 (the position of the peripheral end on the side where the output shaft 13a is eccentric). At this position, an attractive force is generated between the opposing magnets, and torque transmission is performed in a non-contact manner.

  Then, as the torque transmission is sequentially transferred by the adjacent permanent magnets with the rotation, the number of each of the plurality of permanent magnets is set to a different number according to the reduction ratio (in this example, the first ring The number of magnet arrays 51 and the number of second annular magnet arrays 52 are 6), so that the speed is reduced at a predetermined reduction ratio. Further, by transmitting torque at the position of the peripheral end on the side where the output shaft 13a is eccentric, the moment load toward the worm wheel 22 side with respect to the worm shaft 21 due to the action of the attractive force of the magnetic reducer 30. Can be generated. In addition, the white arrow shown in FIG.2 (b) has shown the image of the attractive force by the permanent magnet group 50, and the preload provided to a bearing.

Next, operations and effects of the above-described electric power steering device 9 for a vehicle will be described.
The vehicle described above includes the electric power steering device 9 in the steering system, and the electric power steering device 9 is configured such that the permanent magnet set 50 of the magnetic reducer 30 faces different poles from the other permanent magnets facing each other. The arranged permanent magnets are arranged so as to face each other at a predetermined position in the axial direction, and the number of the plurality of permanent magnets is set to a different number corresponding to the reduction ratio, so that the output of the electric motor 13 The rotational torque of the shaft 13a is transmitted to the worm shaft 21 in a non-contact manner at a predetermined reduction ratio.

That is, when the output shaft 13a of the electric motor 13 rotates, the permanent magnets 52a and 52b of the second annular magnet row 52 embedded in an annular shape on the outer periphery of the small-diameter disk 32 on the output shaft 13a side rotate accordingly. When the permanent magnets 52a and 52b are rotated, different poles are disposed so as to face each other in the axial direction between the disk surfaces 31m and 32m when the torque is transmitted in a non-contact manner (in this example, the output shaft The permanent magnets 51a and 51b of the first annular magnet row 51 embedded in the outer periphery of the disk 31 on the worm shaft 21 side facing the position) are permanent magnets. The rotational force is transmitted in a non-contact manner by the suction force with 52a and 52b.
When the rotational force is transmitted to the permanent magnets 51a and 51b of the first annular magnet row 51, the worm shaft 21 in which the permanent magnets 51a and 51b are embedded also rotates together. At this time, torque transmission is sequentially transferred to the adjacent permanent magnets in the circumferential direction with rotation, and the first annular magnet row 51 and the second annular magnet row 52 are equal to the number of the plurality of permanent magnets. Is set to a different number according to the reduction ratio (in this example, 12 first annular magnet rows 51 and 6 second annular magnet rows 52), a predetermined reduction ratio (in this example, 2 : Decelerate in 1). Therefore, the magnetic speed reducer 30 can transmit the rotational torque of the output shaft 13a of the electric motor 13 to the worm shaft 21 in a non-contact manner at a predetermined reduction ratio.

  And according to this magnetic reduction gear 30, the output shaft 13a of the electric motor 13 and the worm gear mechanism part 11 are transmitted by transmitting the output torque of the electric motor 13 to the worm gear mechanism part 11 using the attractive force of the permanent magnet set 50. The worm shaft 21 can be made non-contact. Therefore, it is possible to prevent the occurrence of rattle noise and abnormal wear at the joint portion between the output shaft 13a of the electric motor 13 and the worm shaft 21 of the worm gear mechanism portion 11.

Further, the torque transmission by the magnetic reducer 30 is a torque transmission system in which the joint portion between the output shaft 13a of the electric motor 13 and the worm shaft 21 of the worm gear mechanism portion 11 is opposed in the axial direction. Due to the relationship between the strength of the magnetic force of the permanent magnets and the facing distance between the permanent magnets, when an excessive torque greater than the transmittable torque is applied, the motor rotates idly without being transmitted.
Therefore, by adjusting the strength of the magnetic force of the permanent magnet set 50 and the facing distance between the permanent magnets 51a and 51b and the permanent magnets 52a and 52b, it functions as a torque limiter when an excessive torque exceeding the set torque is applied. . Therefore, when excessive torque is generated due to reverse input such as when riding on the shoulder of the road, the magnetic speed reducer 30 functions as a torque limiter, and damage to each part of the transmission system can be prevented. Therefore, the cost of the electric power steering device 9 can be reduced, and the size of the device can be made compact.

  Further, according to the magnetic reducer 30, since the permanent magnet set 50 has the permanent magnets opposed to each other with opposite poles in the axial direction, the axial load is always generated. be able to. Therefore, a preload can be easily applied to the bearing 42 of the worm shaft 21 using a deep groove ball bearing. Therefore, the cost of the electric power steering device 9 can be suppressed by using a relatively low-cost deep groove ball bearing for the bearing 42 while preventing or suppressing the generation of rattling noise.

  Further, according to the magnetic reducer 30, the attractive force between the permanent magnets is inversely proportional to the transmitted torque (the attractive force is maximum when torque is not transmitted and the attractive force is minimum when torque is transmitted). For this reason, preload can be applied efficiently during low torque transmission, where abnormal noise is likely to occur in the bearings 41, 42, and preload is higher than during low torque transmission during high torque transmission where the need for preload is low. Since it becomes low, it is suitable for improving transmission efficiency.

  And according to the electric power steering apparatus 9 of this embodiment, since the output shaft 13a is eccentrically arranged on the worm wheel 22 side with respect to the worm shaft 21, by the action of the attractive force of the magnetic reducer 30, A moment load can be generated toward the worm wheel 22 with respect to the worm shaft 21. As a result, in addition to adjusting the internal clearances of the bearings 41 and 42, the amount of preload can be adjusted so as to reduce fluctuations in the operating torque for the backlash of the worm gear mechanism 11 as well, and a separate auxiliary device (for example, using a spring) is used as a countermeasure. Worm pressing mechanism) is not required.

  That is, according to this magnetic reduction gear 30, the attractive force of the permanent magnets that are opposed to each other and that are opposed to each other in a non-contact manner increases in inverse proportion to the distance between the opposed permanent magnets. Therefore, when the backlash is large with respect to the backlash amount of the worm gear mechanism 11, the distance between the opposed permanent magnets is narrowed, so that the preload can be increased. On the other hand, when the backlash is small, the distance between the opposed permanent magnets is widened, so that the preload can be reduced. As a result, an appropriate preload can be applied in proportion to the backlash amount of the worm gear mechanism unit 11, and fluctuations in operating torque of the worm gear mechanism unit 11 can be suppressed. Such an effect can be said to be an excellent effect that cannot be achieved by a worm pressing mechanism using a conventional spring.

  In addition, since the magnetic reducer 30 is configured such that the pair of disks 31 and 32 face each other with a gap between the disk surfaces 31m and 32m, abnormal wear due to abnormal noise and misalignment of the joint itself does not occur. Highly accurate dimensional management is unnecessary, and a cost reduction effect can be obtained. In particular, a relatively low-cost deep groove ball bearing can be used for the bearings 41 and 42 that support the worm shaft 21, the cost of the electric power steering device 9 can be suppressed, and the size of the device can be reduced. it can.

  That is, since the bearings 41 and 42 that support the worm shaft 21 are deep groove ball bearings that allow the relative inclination of the inner and outer rings, an axial load is generated on the worm shaft 21 by the permanent magnet set 50 of the magnetic reducer 30 and the output is output. The inclination of the worm shaft 21 corresponding to the moment load due to the shaft 13a being eccentrically arranged on the worm wheel 22 side is caused to follow by the relative inclination of the inner and outer rings of the bearings 41 and 42, and thus the worm shaft 21 A preload can be applied.

  In addition, when a normal contact type speed reducer is used for the joint portion, if the worm shaft 21 is inclined, abnormal noise or abnormal wear due to a poor meshing of the speed reducer itself of the joint portion may occur. Since the magnetic reducer 30 of the form is a non-contact type, it is excellent in that such abnormal noise and abnormal wear do not occur.

  As described above, according to the electric power steering device 9 included in the above-described vehicle, the assist torque can be decelerated and transmitted by the magnetic reducer 30 in a non-contact manner, and the bearings 41 and 42 of the worm gear mechanism 11 can be transmitted. Rattle noise caused by internal gaps and backlash can be prevented or suppressed. The electric power steering apparatus and the vehicle including the same according to the present invention are not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

For example, in the above-described embodiment, an example in which a brushless three-phase electric motor is applied as the electric motor 13 has been described. However, the present invention is not limited to this, and a brushless multiphase electric motor having four or more phases can also be applied. An electric motor with a brush can also be applied.
For example, in the above-described embodiment, the permanent magnet 51a and the permanent magnet 51b that are adjacent in the circumferential direction are not in direct contact with each other, but are separated from each other. The “magnet” is not limited to the example shown in FIG. 3, and for example, a multi-pole magnetized monolithic permanent magnet can be used. Even in this case, it can be regarded as “a plurality of permanent magnets” composed of the permanent magnets 51 a and 51 b that are adjacent in the circumferential direction.

DESCRIPTION OF SYMBOLS 1 Steering mechanism 2 Steering wheel 3 Steering shaft 4 Steering column 5 Steering gear mechanism 6 Tie rod 7 Steering wheel 9 Electric power steering device 10 Reduction gear box 11 Worm gear mechanism part 12 Controller 13 Electric motor 22 Worm wheel 30 Magnetic reduction gear 41,42 Bearing 44 Bush 50 Permanent magnet set 51 First annular magnet array 52 Second annular magnet array L1 Axis of output shaft L2 Axis of worm shaft E Predetermined amount of eccentricity

Claims (3)

An electric motor that generates a steering assist force, a worm gear mechanism that transmits torque generated on the output shaft of the electric motor to a steering system, and torque generated on the output shaft of the electric motor on the worm shaft of the worm gear mechanism An electric power steering device comprising a magnetic reduction gear that transmits without contact,
The output shaft is arranged eccentric to the worm wheel side with respect to the worm shaft,
The magnetic speed reducer includes a pair of disks that are provided at a joint portion between the output shaft and the worm shaft and face each other with a gap therebetween, and the pair of disks are circular on one disk surface. A permanent magnet set having a first annular magnet array composed of a plurality of permanent magnets arranged in an annular shape and a second annular magnet array composed of a plurality of permanent magnets arranged in an annular shape on the other disk surface;
The first annular magnet row and the second annular magnet row are arranged so that different poles face each other in the axial direction when the plurality of permanent magnets are in a position to transmit torque between the disk surfaces in a non-contact manner. In addition, the number of the plurality of permanent magnets is set to a different number according to the reduction ratio. In claim 1,
An electric power steering device in which a bearing for supporting the worm shaft is a deep groove ball bearing.   A vehicle comprising the electric power steering device according to claim 1.

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