JP6759779B2 - Electric power steering device - Google Patents

Description

The present invention relates to an electric power steering device.

The electric power steering device disclosed in Patent Document 1 has a steering shaft to which a steering wheel is connected to one end, and a steering column that rotatably supports the steering shaft through the inside. Further, this steering device decelerates the rotation speed of the torque sensor for detecting the steering torque given to the steering wheel by the driver, the electric motor that rotates according to the steering torque, and the electric motor. It has a speed reducer that transmits auxiliary steering torque to the steering shaft, and a housing that forms a part of the steering column. The housing houses the torque sensor and reducer and supports the electric motor.

Further, the steering shaft and the steering column can be contracted so as to absorb the impact when the automobile collides. Specifically, the steering shaft has a lower shaft and an upper shaft that is spline-connected by being fitted so as to be relatively movable with respect to the lower shaft. Further, the steering column has a lower tube (inner jacket) in which the housing is fixed at the lower end, and an upper tube (outer jacket) fitted so as to be relatively movable with respect to the lower tube.

When the driver hits the steering wheel in the event of a vehicle collision, the impact acts from the steering wheel to the upper tube, which is directed toward the front of the vehicle with the steering wheel and upper shaft, and the lower shaft. And relative to the lower tube. As a result, the impact energy associated with the collision can be absorbed.

Here, if the relative displacement amount (E / A stroke amount) of the upper tube with respect to the lower tube can be sufficiently secured, the impact energy can be sufficiently absorbed, but the relative displacement amount can be sufficiently secured due to space restrictions and the like. It is assumed that it cannot be secured. In this case, when the upper tube reaches the lower end of the lower tube, it bottoms out against the housing, and at that time, a bottom thrusting load is generated. When the bottom thrust load becomes large, the absorption of impact energy is hindered.

In Patent Document 2, the housing is provided with an impact energy absorbing portion for reducing the bottom thrust load. Specifically, the impact energy absorbing portion is provided on a rivet for fixing the lower tube to the housing and an upper tube provided so as to be movable relative to the lower tube, and the lower tube is provided at a portion overcoming the rivet. It is composed of a caulked part that has been crimped.

Then, the crimped portion gets over the head of the rivet before the upper tube bottoms out to the housing, thereby mitigating the impact when the upper tube bottoms out to the housing and reducing the bottoming load. ..

JP-A-2007-261425 Japanese Unexamined Patent Publication No. 2013-154762

As described above, Patent Document 2 makes the impact energy absorbing unit absorb the impact energy before the upper tube bottoms out so that the bottom thrust load does not increase.
However, when the impact energy absorbing portion is provided as described above, it is necessary to separately provide a member for cushioning at the portion before the upper tube bottoms out, and in some cases, the E / A stroke amount is increased. You have to sacrifice.

An object of the present invention is to provide an electric power steering device capable of reducing a bottom thrust load without the need to newly provide a member for cushioning.

In order to solve the above problems, the electric power steering device of the present invention decelerates the rotation speed of the electric motor output according to the steering torque applied to the steering shaft by a speed reducer to reduce the auxiliary steering torque to the output side. The steering column into which the steering shaft is inserted is fitted with an upper tube located on the rear side of the vehicle and a lower tube located on the front side of the vehicle while the upper tube is movably fitted in the axial direction. Including, the lower tube is connected to a housing that houses the speed reducer and the torque sensor that detects the steering torque, and the torque sensor is connected between an input shaft and an output shaft connected to the steering shaft. In an electric power steering device in which the steering torque is detected according to the amount of twist of the connected torsion bar and the input shaft is rotatably supported with respect to the housing via the bearing body, the bearing body is , The upper tube is arranged so as to face the front end surface of the vehicle, and when the upper tube moves in the axial direction and collides, it is attached so as to be movable in the axial direction by pressing the upper tube. It is something that is.

According to the above configuration, the impact when the driver hits the steering wheel due to the collision of the automobile acts from the steering wheel to the upper tube, and the upper tube is accompanied by the steering wheel and the upper shaft on the lower front side of the vehicle body. Relative displacement with respect to the lower shaft and lower tube towards. Then, when the upper tube collides with the bearing body, the bearing body moves in the axial direction due to the pressing of the upper tube.

When the bearing body moves with respect to the housing, shock absorption is performed so that the bottom thrust load does not increase.
Further, the steering shaft includes an upper shaft connected to the steering wheel and a lower shaft coaxially connected to the input shaft and spline-connected so as to be movable in the axial direction with respect to the upper shaft. The upper shaft and the lower shaft preferably have interference portions that interfere with each other after the bearing body moves in the axial direction by the upper tube.

According to the above configuration, after the bearing body is moved in the axial direction by the upper tube, the interference portion of the upper shaft and the interference portion of the lower shaft interfere with each other.

According to the present invention, it is not necessary to newly provide a member for cushioning, and the bottom thrust load can be reduced.

FIG. 3 is a cross-sectional view of an electric power steering device according to an embodiment of the present invention. Explanatory drawing which shows the action of one Embodiment.

An electric power steering device (hereinafter referred to as a steering device) according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2.
As shown in FIG. 1, the steering device includes a steering shaft 10 in which a steering wheel (not shown) is fixed to an end portion (right end portion in FIG. 1) on the rear side of the vehicle. The steering shaft 10 is rotatably inserted in the steering column 14 by being pivotally supported by the bearing 12. The front end of the steering shaft 10 (front end: left end in FIG. 1) is connected to an intermediate shaft (not shown) via a universal joint. Therefore, the rotation and steering torque associated with the steering operation are transmitted to a steering mechanism such as a rack and pinion mechanism that changes the steering angle of the steering wheel (not shown). The steering shaft 10 is mounted on the vehicle in a state of being inclined so that the end portion on the front side of the vehicle is located below the end portion on the rear side of the vehicle in the vertical direction.

As shown in FIG. 1, the steering shaft 10 includes a hollow upper shaft 16 to which a steering wheel (not shown) is fixed, and a lower shaft 18 housed in the upper shaft 16.

A spline fitting portion 16a is formed on the inner circumference of the upper shaft 16, and a spline fitting portion 18a is formed on the outer circumference extending from the upper portion (end portion on the rear side of the vehicle) to the central portion of the lower shaft 18. The lower shaft 18 is internally fitted to the upper shaft 16, that is, the spline fitting portions 16a and 18a are spline-fitted, so that the lower shaft 18 has an axis with respect to the upper shaft 16. It is configured so that it can slide relative to each other in the direction and can rotate integrally. A diameter-expanded portion 18b having a diameter larger than that of the upper portion and the intermediate portion is provided at the lower portion of the lower shaft 18. The enlarged diameter portion 18b is arranged so as to face the front end surface (that is, the front end surface) of the upper shaft 16 on the vehicle front side, and can come into contact with the upper shaft 16 when the upper shaft 16 moves to the housing side. The front end surfaces of the upper shaft 16 that come into contact with the enlarged diameter portion 18b and the enlarged diameter portion 18b correspond to interference portions, respectively.

Further, the steering column 14 includes an upper tube 20 that supports the upper shaft 16 via a bearing 12 and accommodates a part thereof, and a lower tube 22 that accommodates a part of the lower shaft 18. The front end portion of the lower tube 22 is integrally connected to the rear member 52 of the housing 50, which will be described later.

The upper tube 20 is fitted inside the lower tube 22 so as to be slidable relative to the lower tube 22 in the axial direction. This relative sliding in the axial direction enables telescopic adjustment, which will be described later. Further, the lower tube 22 is supported by a support mechanism (not shown) with respect to the vehicle body (not shown). Since this support mechanism has a known configuration, detailed description thereof will be omitted.

As shown in FIG. 1, at the front end portion of the lower tube 22, torques arranged around the output shaft 24 and the output shaft 24 of the power assist unit PA that applies an assist force for assisting the steering operation to the steering system. A housing 50 for accommodating the sensor S is provided. The housing 50 has a rear member 52 and a front member 54 that bolts and supports the posterior member 52.

Hereinafter, the torque sensor S will be described.
As shown in FIGS. 1 and 2, the torque sensor S includes an input shaft 26, an output shaft 24, a torsion bar 28, a magnet 30, a resin member 31 for fixing the magnet 30 to the input shaft 26, and a magnetic collecting ring assembly. 32, a magnetic yoke assembly 33 is provided, and is housed in a rear member 52 which is a sensor housing.

The input shaft 26 is rotatably supported by a ball bearing 34 as a bearing body with respect to the rear member 52 of the housing 50. That is, the maximum outer diameter portion 26a of the input shaft 26 is supported by the ball bearing 34 in the radial direction with respect to the rear member 52. In the ball bearing 34, the inner ring is press-fitted and fixed to the maximum outer diameter portion 26a, and the outer ring is press-fitted and fixed to the inner peripheral surface of the rear member 52.

As shown in FIG. 2, the ball bearing 34 and the torque sensor S are arranged so as to be separated by a distance L3. FIG. 2 shows a place where the magnetic yoke assembly 33 and the ball bearing 34 are separated by a distance L3.

As shown in FIG. 1, the ball bearing 34 is arranged so as to face the front end surface of the upper tube 20, and can be brought into contact with the upper tube 20 when it moves in the axial direction, that is, toward the housing 50. It has become. In other words, the ball bearing 34 is arranged on the movement line where the upper tube 20 moves toward the front side of the vehicle.

Further, the ball bearing 34 is attached so as to be movable in the axial direction when the upper tube 20 collides with the upper tube 20 and a load of a predetermined value or more is applied. The predetermined value is the value of the press pressure when the ball bearing 34 is press-fitted and fixed to the maximum outer diameter portion 26a of the rear member 52 and the input shaft 26.

The rear end portion of the input shaft 26 is connected so as to be coaxial with the lower shaft 18, and is further connected to a steering wheel (not shown) arranged on the rear side.
As shown in FIG. 1, the input shaft 26 has a front end inserted into the inner diameter side of the output shaft 24 and is rotatably connected to the output shaft 24. The rear end of the input shaft 26 and the front end of the output shaft 24 are connected to both ends of the torsion bar 28 inserted into the internal space penetrating the center of both.

As shown in FIG. 2, the magnet 30 is mounted on the outer periphery of the input shaft 26 via the resin member 31. The magnetic collecting ring assembly 32 is mounted on the inner circumference of the rear member 52. The magnetic yoke assembly 33 is mounted on the outer circumference of the output shaft 24 and is inserted inside the magnetic collecting ring assembly 32. Further, the magnet 30 is positioned inside the magnetic yoke assembly 33 at a position facing the magnetic collecting ring assembly 32.

The torque sensor S configured as described above detects the steering torque associated with the steering operation according to the amount of twist of the torsion bar 28.
As shown in FIG. 1, the rear end portion of the output shaft 24 is rotatably supported by the rear side member 52 via the bearing 35, and the front end portion is rotatably supported by the front side member 54 via the bearing 36. There is. As shown in FIG. 1, a worm wheel 37 of a speed reducer is integrally rotatably fitted to the output shaft 24. The front end portion of the output shaft 24 is connected to the intermediate shaft (not shown) via the universal joint. The output shaft 24 constitutes the steering shaft 10 together with the upper shaft 16 and the lower shaft 18.

The output shaft 24 is steered by reducing the rotation speed of an electric motor (not shown) supported by the housing 50 by a speed reducer composed of a worm wheel 37 and a worm gear (not shown) and transmitting auxiliary steering torque. It is possible to give an assist force to the system. A power assist unit PA that applies an assist force to the lower part of the steering column 14 is configured by an electric motor, a speed reducer, a torque sensor S, or the like.

As shown in FIG. 1, the steering column 14 (that is, the steering device) is supported by a tilt mechanism (not shown) so as to be tiltable about a tilt central axis O provided in the housing 50.

By rotating the steering shaft 10 and the steering column 14 around the tilt central axis O, the height position of the steering wheel (not shown) can be adjusted (so-called tilt adjustment).

Further, by expanding and contracting the steering shaft 10 and the steering column 14 in the column moving direction (that is, the axial direction), the front-rear position of the steering wheel (not shown) can be adjusted (so-called telescopic adjustment).

(About column shrinkage)
L1 is the distance between the end face of the upper tube 20 on the housing 50 side and the ball bearing 34 (bearing body) in the state before column contraction, and is the column contraction amount (that is, E / A stroke) of the present embodiment. It is supposed to be. L2 is the distance between the end face of the upper shaft 16 on the housing 50 side and the enlarged diameter portion 18b at the end of the lower shaft 18 in the state before the column contraction, and is longer than L1. In this embodiment, L2-L1 ≦ L3.

(Action of Embodiment)
The operation of the steering device configured as described above will be described.
For convenience of explanation, FIG. 1 assumes that the steering wheel (not shown) is the most distant from the housing 50 by telescopic adjustment.

When the vehicle does not collide with an external object as shown in FIG. 1, each of the steering shaft 10 and the steering column 14 is in the most extended state.
At this time, in the steering device, the upper shaft 16 and the upper tube 20 are in the state of being farthest from the housing 50, respectively. That is, the upper tube 20 is separated from the ball bearing 34 by the E / A stroke (L1).

When the vehicle collides with an external object and the driver collides with a steering wheel (not shown) in reaction to the collision, the impact is applied from the steering wheel (not shown) to the upper shaft 16 and the upper tube 20 from the rear upper side of the vehicle. It works.

As a result, the upper tube 20 moves relative to the lower shaft 18 and the lower tube 22 together with the steering wheel (not shown) and the upper shaft 16. Then, as shown by the alternate long and short dash line in FIG. 2, the upper tube 20 collides with the ball bearing 34.

At this time, the shock absorption until the upper tube 20 collides with the ball bearing 34 is performed as follows.
First, the energy due to the impact described above is absorbed by the movement of the upper tube 20 to the ball bearing 34 by the E / A stroke. Further, when the energy due to the above-mentioned impact cannot be completely absorbed by the movement of the E / A stroke, the upper tube 20 further collides with the ball bearing 34, and a load of a predetermined value or more is applied to the ball bearing 34. Up to the distance L3, the ball bearing 34 can move to the torque sensor S side to absorb the above-mentioned impact. Therefore, by moving the ball bearing 34, the energy due to the above-mentioned impact can be absorbed and the bottom thrust load is reduced.

Further, this reduces the impact when the upper shaft 16 after that comes into contact with the enlarged diameter portion 18b of the lower shaft 18.
The present embodiment has the following features.

(1) In the present embodiment, the ball bearing 34 (bearing body) that rotatably supports the input shaft 26 of the torque sensor S on the housing 50 is arranged relative to the upper tube 20, and the upper tube 20 is the axis. When it moves in a direction and collides, it is attached so as to be movable in the axial direction by pressing the upper tube 20. As a result, it is not necessary to newly provide a member for cushioning the moved upper tube, and the bottom thrust load can be reduced.

Further, according to the present embodiment, since the ball bearing 34, which is a bearing body, is provided between the input shaft and the housing, the bearing body can be easily made to function as a sealing member.

Further, the ball bearing 34, which is a bearing body, is press-fitted and fixed to the housing, and the holding load of the bearing body in the housing can be appropriately tuned by appropriately adjusting the press pressure at the time of press-fitting.

(2) In the steering device of the present embodiment, the steering shaft 10 is coaxially connected to the input shaft 26 and the upper shaft 16 connected to the steering wheel (not shown), and is movable in the axial direction with respect to the upper shaft 16. Includes a spline-connected and internally fitted lower shaft. The upper shaft 16 and the lower shaft 18 each have a diameter-expanded portion 18b and a front end surface (interference portion) that interfere with each other after the ball bearing 34 (bearing body) moves in the axial direction by the upper tube 20. As a result, according to the present embodiment, after the ball bearing 34 (bearing body) is moved in the axial direction by the upper tube 20, the front end surface (interference portion) of the upper shaft 16 and the enlarged diameter portion 18b (interference) of the lower shaft 18 Interferes with the part). In the present embodiment, the impact at the time of this interference can be reduced by the action of (1).

The embodiment of the present invention is not limited to the above embodiment, and may be changed as follows.
-In the above embodiment, the ball bearing 34 is used as the bearing body, but the bearing body is not limited to the ball bearing 34. The bearing body may be a needle bearing or a slide bearing.

-In the above embodiment, L2-L1 ≦ L3 is set, but L2-L1> L3 may be set. In this case, the upper tube 20 collides with the ball bearing 34 with the torque sensor S, which may be used.

-In the above embodiment, the rear member 52 and the lower tube 22 are integrally formed, but both may be provided separately and assembled to each other.

10 ... Steering shaft, 12 ... Bearing, 14 ... Steering column,
16 ... upper shaft, 16a ... spline fitting part, 18 ... lower shaft,
18a ... Spline fitting portion, 18b ... Expanded diameter portion (interference portion),
20 ... upper tube, 22 ... lower tube, 24 ... output shaft,
26 ... Input shaft, 28 ... Torsion bar, 30 ... Magnet, 31 ... Resin member,
32 ... Magnetic collector ring assembly, 33 ... Magnetic yoke assembly,
34 ... ball bearing (bearing body), 35 ... bearing, 36 ... bearing,
37 ... worm wheel, 50 ... housing, 52 ... rear member, 54 ... front member,
S ... Torque sensor, PA ... Power assist unit,
L1 ... Column contraction amount (E / A stroke), L2 ... Distance between the upper shaft 16 and the enlarged diameter portion 18b at the end of the lower shaft 18.
L3 ... The distance between the magnetic yoke assembly 33 and the ball bearing 34.

Claims (2)

The rotation speed of the electric motor output according to the steering torque applied to the steering shaft is decelerated by the speed reducer to transmit the auxiliary steering torque to the output side, and the steering column through which the steering shaft is inserted is on the rear side of the vehicle. A torque for detecting the speed reducer and the steering torque, including an upper tube located in the above and a lower tube in which the upper tube is movably fitted in the axial direction and located on the front side of the vehicle. The torque sensor is connected to a housing for accommodating the sensor, and the torque sensor detects the steering torque according to the amount of twist of the torsion bar connected between the input shaft and the output shaft connected to the steering shaft. In an electric power steering device in which the input shaft is rotatably supported with respect to the housing via a bearing body.
The bearing body is arranged so as to face the vehicle front end surface of the upper tube, and can be brought into contact with the upper tube when it moves in the axial direction, and can be brought into contact with the upper tube by pressing the upper tube in the axial direction. An electric power steering device that is movably mounted on the vehicle. The steering shaft
Includes an upper shaft connected to the steering wheel and a lower shaft coaxially connected to the input shaft and spline-connected to the upper shaft so as to be movable in the axial direction.
The electric power steering device according to claim 1, wherein the upper shaft and the lower shaft have interference portions that interfere with each other after the bearing body moves in the axial direction by the upper tube.

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