JP2013233879A - Impact-absorbing electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase an impact-absorbing stroke where a steering shaft and a column tube move while being accompanied by each other to absorb impact energy within a range of the whole length along an axial direction of a steering shaft in an electric power steering device, and also to reduce the whole length of the electric power steering device required for securing a certain amount of impact-absorbing stroke in the steering shaft.SOLUTION: An impact-absorbing electric power steering device 1 includes a shaft entering space 60 into which an upper shaft 11 that is moved by an impact can slide, on an inner peripheral side of a torque sensor 51 inside a sensor housing 32.

Description

  The present invention relates to an impact absorbing electric power steering apparatus.

  As described in Patent Document 1, as a shock absorbing electric power steering device, a steering shaft is inserted into a column tube, and a torque sensor for detecting steering torque input to the steering shaft is built in the sensor housing. It has an electric motor that is driven according to the result and outputs steering assist torque. The upper shaft and the lower shaft, which are divided into the upper and lower parts of the steering shaft, are fitted non-rotatably and telescopically, and the upper shaft rotates to the column tube. Some of them are supported freely and the lower shaft is rotatably supported on the sensor housing of the torque sensor.

  In the shock absorbing electric power steering device described in Patent Document 1, when the vehicle collides with a front obstacle and the impact caused by the collision of the vehicle driver with the steering wheel acts on the steering shaft, the upper shaft of the steering shaft. And the column tube are allowed to move in the axial direction. The impact energy can be absorbed during the movement of the upper shaft and the column tube of the steering shaft.

  At this time, the maximum stroke of the column tube relative to the inner periphery of the sensor housing is a distance until the end surface of the column tube comes into contact with the outer peripheral protrusion of the lower shaft. This distance becomes an absorption stroke of impact energy obtained in the process of moving the upper shaft of the steering shaft and the column tube.

Japanese Patent No.3883761

  In the shock absorbing electric power steering device described in Patent Document 1, the distance until the end surface of the column tube comes into contact with the outer peripheral protruding portion of the lower shaft is the shock energy absorbing stroke acting on the steering shaft. At this time, the outer peripheral protrusion of the lower shaft is a bearing provided on the inner periphery of the sensor housing and supported by a bearing provided on the upper end side (steering wheel side) in the axial direction from the torque sensor built in the sensor housing. Yes. Therefore, the end surface of the column tube does not enter the side of the torque sensor built in the sensor housing when moving for absorbing the shock, and the column tube is within the total length along the axial direction of the steering shaft in the electric power steering apparatus. There is a difficulty in increasing the maximum travel stroke of the tube and thus increasing the shock energy absorption stroke.

  The object of the present invention is to increase the shock absorption stroke that the steering shaft and the column tube can move together to absorb the impact energy within the entire length range along the axial direction of the steering shaft in the electric power steering apparatus, and thus The object is to reduce the overall length of the electric power steering apparatus necessary to ensure a certain shock absorbing stroke on the steering shaft.

  According to the first aspect of the present invention, the steering shaft is inserted into the column tube, a torque sensor for detecting the steering torque input to the steering shaft is incorporated in the sensor housing, and the steering assist is driven according to the detection result of the torque sensor. It has an electric motor that outputs torque, and the upper shaft and lower shaft, which are divided into upper and lower steering shafts, are fitted in a relatively non-rotatable and telescopic manner, and the upper shaft is rotatably supported by the column tube. In the shock absorbing electric power steering device in which the upper shaft of the steering shaft and the column tube are movable in the axial direction by an impact acting on the steering shaft, which is rotatably supported by the sensor housing of the torque sensor. Sensor housing In part, the inner peripheral side of the torque sensor, in which as formed by a shaft entry space that permits slip to come upper shaft moved by the impact.

  According to a second aspect of the present invention, the steering shaft is inserted into the column tube, a torque sensor for detecting the steering torque input to the steering shaft is incorporated in the sensor housing, and the steering assist is driven according to the detection result of the torque sensor. It has an electric motor that outputs torque, and the upper shaft and lower shaft, which are divided into upper and lower steering shafts, are fitted in a relatively non-rotatable and telescopic manner, and the upper shaft is rotatably supported by the column tube. In the shock absorbing electric power steering device in which the upper shaft of the steering shaft and the column tube are movable in the axial direction by an impact acting on the steering shaft, which is rotatably supported by the sensor housing of the torque sensor. Sensor housing In part, the axial direction of the side near the torque sensor, in which upper shaft coming moved by impact is set to be provided with a sensor entry space that permits push the torque sensor.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the torque sensor further includes a sensor case inserted into the sensor housing, an excitation coil and a detection coil stored in the sensor case. The change of the magnetic field due to the magnetostrictive effect according to the torque of the magnetostrictive film applied to the surface of the lower shaft is detected.

(Claim 1)
(a) In an impact-absorbing electric power steering apparatus in which the upper shaft and the column tube of the steering shaft are movable in the axial direction by an impact acting on the steering shaft, the torque sensor On the inner circumference side, a shaft entry space was provided that allowed the upper shaft that was moved by the impact to enter. Therefore, when the steering shaft moves for absorbing the shock, the upper shaft of the steering shaft can be brought into the shaft entry space on the inner peripheral side of the torque sensor. Thus, the shock absorbing stroke that can be moved together in order to absorb the impact energy can be increased within the entire length of the electric power steering apparatus along the axial direction of the steering shaft. Therefore, it is possible to reduce the overall length of the electric power steering apparatus necessary for ensuring a constant shock absorbing stroke on the steering shaft.

(Claim 2)
(b) In an impact-absorbing electric power steering device in which the upper shaft and the column tube of the steering shaft are made to move in the axial direction due to an impact acting on the steering shaft, the torque sensor A sensor approach space portion is provided on the side in the axial direction so that the upper shaft that is moved by impact can push the torque sensor. Therefore, the upper shaft of the steering shaft can be moved to the sensor entry space portion where the torque sensor can be pushed in during the movement for absorbing the impact of the steering shaft. Thus, the shock absorbing stroke that can be moved together in order to absorb the impact energy can be increased within the entire length of the electric power steering apparatus along the axial direction of the steering shaft. Therefore, it is possible to reduce the overall length of the electric power steering apparatus necessary for ensuring a constant shock absorbing stroke on the steering shaft.

(Claim 3)
(c) The torque sensor has a sensor case, an excitation coil stored in the sensor case, and a detection coil, and detects changes in the magnetic field due to the magnetostrictive effect according to the torque of the magnetostrictive film applied to the surface of the lower shaft. To become.

FIG. 1 is a cross-sectional view illustrating an impact absorbing electric power steering apparatus according to a first embodiment. FIG. 2 is an enlarged cross-sectional view showing a main part of FIG. FIG. 3 is a cross-sectional view showing an impact absorbing state of the electric power steering apparatus. FIG. 4 is a cross-sectional view showing the shock absorbing electric power steering device of the second embodiment. FIG. 5 is a cross-sectional view showing an impact absorbing state of the electric power steering apparatus.

Example 1 (FIGS. 1 to 3)
The impact absorbing electric power steering apparatus 1 shown in FIGS. 1 to 3 includes a steering shaft 10 to which a steering torque applied to a steering wheel by a driver is input. The steering shaft 10 has an upper shaft 11 and a lower shaft 12 which are divided into upper and lower parts, and a male-female fitting that is relatively non-rotatable and telescopic with their fitting shafts, a female spline shaft 11A and a male spline shaft 12A in this embodiment. Has been. The position of the steering wheel is moved in the axial direction so that the driver obtains an optimal driving posture, and the upper shaft 11 and the lower shaft 12 of the steering shaft 10 are adjusted by the spline shafts 11A and 12A in order to adjust the position. It is a male-female fitting that is relatively unrotatable and telescopic.

  In the present embodiment, the lower shaft 12 is divided into two parts, an upper lower shaft 12U and a lower lower shaft 12D. The lower shaft 12 is configured by coaxially press-fitting and integrating an upper lower shaft 12U formed with a male spline shaft 12A and a lower lower shaft 12D provided with magnetostrictive films 59A and 59B described later.

  The upper shaft 11 of the steering shaft 10 is rotatably supported by a bearing 13 provided on the inner periphery on the upper end side (steering wheel side) of the column tube 20. The bearing 13 is fixed by press-fitting the inner ring and the outer ring into the outer periphery of the upper shaft 11 and the inner periphery of the column tube 20 respectively. A retaining ring 14 is engaged with the upper end side (steering wheel side) of the bearing 13 in the axial direction on the outer periphery of the upper shaft 11 and in the vicinity of the inner ring of the bearing 13. As a result, the upper shaft 11 and the column tube 20 of the steering shaft 10 are integrated in the axial direction via the retaining ring 14 and the bearing 13 due to the impact acting on the steering shaft 10 due to the collision between the driver and the steering wheel, and are accompanied by each other. And move.

  The lower shaft 12 of the steering shaft 10 is rotatably supported by bearings 15 and 16 provided on inner circumferences of a gear housing 31 and a sensor housing 32 of a steering assist unit 30 described later.

  An upper bracket 21 is attached to the outer periphery on the lower end side of the column tube 20. The column tube 20 is supported by a body frame (not shown) by the upper bracket 21. The upper bracket 21 is detached from the vehicle body frame when an impact acting on the steering shaft 10 is applied via the column tube 20.

  The lower end portion of the column tube 20 is provided with a slit (not shown) in a part in the circumferential direction, and is fitted to the outer periphery of the sensor housing 32, and to the outer periphery of the sensor housing 32 by the tightening member 22. Tightened or released. Thus, when the tightening member 22 releases the tightening exerted on the column tube 20, the female spline shaft 11 </ b> A of the upper shaft 11 of the steering shaft 10 that is integrated with the column tube 20 in the axial direction becomes the male of the lower shaft 12. Sliding along the spline shaft 12A, the upper shaft 11 and the lower shaft 12 can be expanded and contracted.

  The electric power steering apparatus 1 includes a gear housing 31 and a sensor housing 32 constituting a steering assist unit 30 by bolting. The steering assist unit 30 is supported on a vehicle body frame (not shown) by a lower bracket 33 attached to the gear housing 31. The gear housing 31 and the sensor housing 32 rotatably support the lower shaft 12 of the steering shaft 10 via the bearings 15 and 16 described above.

  An electric motor 40 is attached to the gear housing 31, and a worm wheel 42 that meshes with a worm gear 41 coupled to a rotation shaft of the electric motor 40 is press-fitted into the lower shaft 12 of the steering shaft 10 and fixed.

  The sensor housing 32 incorporates a torque sensor 51 of the torque detecting means 50. The torque sensor 51 includes a sensor case 52, a bobbin 53 stored in the sensor case 52, an excitation coil 54 and detection coils 55A and 55B wound around the bobbin 53. The torque sensor 51 has a sensor case 52 fitted to the inner periphery of the sensor housing 32 from the connection side with the gear housing 31, and one end of the sensor case 52 is provided on the inner side of the sensor housing 32 on the inner side (the steering wheel side). The other end of the sensor case 52 is engaged with the inner side of the sensor housing 32 on the side where the outer ring of the bearing 16 is loaded. The positioning ring 57 is positioned and held via the end ring 58.

  The torque detecting means 50 is formed by plating magnetostrictive films 59A and 59B having predetermined axial widths on the surface of the lower shaft 12 surrounded by the torque sensor 51 so as to have magnetic anisotropies in opposite directions at two upper and lower positions, respectively. Has been granted. The detection coil 55A corresponds to the magnetostrictive film 59A, and the detection coil 55B is provided corresponding to the magnetostrictive film 59B. When steering torque is applied to the upper shaft 11 and the lower shaft 12 of the steering shaft 10, the steering torque is also applied to the magnetostrictive films 59A and 59B, and a magnetostrictive effect is generated in the magnetostrictive films 59A and 59B according to this torque. Therefore, a high-frequency AC voltage (excitation voltage) is supplied from the voltage supply source to the excitation coil 54, and a change in the magnetic field due to the magnetostriction effect of the magnetostrictive films 59A and 59B according to the steering torque is detected by the detection coils 55A and 55B. Detect as change. The steering torque applied to the steering shaft 10 is detected based on this impedance or induced voltage.

  The electric motor 40 is driven and controlled by a control device (not shown) according to the steering torque detected by the torque sensor 51, and outputs a steering assist torque.

  Therefore, in the electric power steering apparatus 1, the steering torque applied by the driver operating the steering wheel passes through the upper shaft 11 and the lower shaft 12 of the steering shaft 10 and via the rack and pinion type steering apparatus (not shown). It is transmitted to a steered wheel (not shown). Further, the output of the electric motor 40 is transmitted to the lower shaft 12 of the steering shaft 10 via the worm gear 41 and the worm wheel 42, and by appropriately controlling the rotational force and the rotational direction of the electric motor 40, the output suitable for the lower shaft 12 is obtained. Steering assist torque can be applied.

  Further, in the electric power steering apparatus 1, when the vehicle collides with an obstacle in front and then the driver of the vehicle collides with the steering wheel, an impact acts on the upper shaft 11 of the steering shaft 10, and consequently the column tube 20. Subsequently, the upper bracket 21 of the column tube 20 is detached from the vehicle body frame, and the upper shaft 11 of the steering shaft 10 and the column tube 20 move together in the axial direction. The upper shaft 11 of the steering shaft 10 moves around the outer periphery of the lower shaft 12 by sliding the female spline shaft 11A on the male spline shaft 12A of the lower shaft 12, and the column tube 20 extends along the outer periphery of the sensor housing 32. Slide. The upper shaft 11 of the steering shaft 10 moves while squeezing a shock absorbing plate (not shown) during the moving process, so that the impact energy is absorbed.

  However, the electric power steering apparatus 1 has the following configuration in order to increase the shock absorption stroke in which the upper shaft 11 of the steering shaft 10 and the column tube 20 move together to absorb the impact energy. .

  In other words, the electric power steering device 1 has a lower shaft that is fitted on the inner periphery of the sensor housing 32 and is held on the inner periphery side of the sensor case 52 in the torque sensor 51 by the impact of the driver colliding with the steering wheel. A shaft entry space portion 60 that allows the upper shaft 11 that moves around the outer periphery of the twelve to be submerged is provided (FIGS. 1 and 2). The shaft entry space 60 is formed by an annular gap between the inner circumference of the bobbin 53 housed in the sensor case 52 and the outer circumference of the lower shaft 12 to which the magnetostrictive films 59A and 59B are provided.

  In the upper shaft 11, the lower end portion of the female spline shaft 11A constituting the tip of the upper shaft 11 passes the lower end portion of the male spline shaft 12A of the lower shaft 12, and further moves a certain distance. (Fig. 3).

According to the present embodiment, the following operational effects can be obtained.
(a) In the shock absorbing electric power steering apparatus 1 in which the upper shaft 11 and the column tube 20 of the steering shaft 10 are movable in the axial direction by an impact acting on the steering shaft 10, the sensor housing 32 Internally, a shaft entry space portion 60 that allows the upper shaft 11 that is moved by an impact to enter the inner circumference side of the torque sensor 51 is provided. Therefore, the upper shaft 11 of the steering shaft 10 can be brought into the shaft entry space 60 on the inner peripheral side of the torque sensor 51 when the steering shaft 10 moves for absorbing the impact. This increases the shock absorption stroke that the steering shaft 10 and the column tube 20 can move together to absorb the impact energy within the entire length range along the axial direction of the steering shaft 10 in the electric power steering apparatus 1. Can do. Therefore, it is possible to reduce the overall length of the electric power steering apparatus 1 necessary for ensuring a constant shock absorbing stroke on the steering shaft 10.

  (b) The torque sensor 51 includes a sensor case 52, an excitation coil 54 and detection coils 55 </ b> A and 55 </ b> B housed in the sensor case 52, and torques of the magnetostrictive films 59 </ b> A and 59 </ b> B applied to the surface of the lower shaft 12. The change of the magnetic field due to the magnetostrictive effect according to the above is detected.

Example 2 (FIGS. 4 and 5)
The second embodiment differs from the first embodiment in that the sensor case 52 is positioned on the side of the sensor case 52 in the axial direction of the torque sensor 51 that is fitted and held on the inner periphery of the sensor housing 32. The upper shaft 11 that moves around the outer periphery of the lower shaft 12 due to the impact of the driver colliding with the steering wheel is located near the connection side of the retaining ring 57 held by the gear housing 31 with the sensor case 52. A sensor entry space portion 70 that can be pushed in is provided (FIG. 4). The sensor entry space 70 is formed by an axial interval L (FIG. 4) formed between the retaining ring 57 provided on the inner periphery of the sensor housing 32 and the bearing 16.

  In the upper shaft 11, the lower end portion of the female spline shaft 11A constituting the tip of the upper shaft 11 passes the lower end portion of the male spline shaft 12A of the lower shaft 12, and further moves a certain distance. 53), the sensor case 52 is pushed into the sensor entry space 70 (FIG. 5).

  According to the present embodiment, in the shock absorbing electric power steering apparatus 1 in which the upper shaft 11 and the column tube 20 of the steering shaft 10 are movable in the axial direction by an impact acting on the steering shaft 10. Inside the sensor housing 32, a sensor approach space 70 is provided on the side of the torque sensor 51 in the axial direction so that the upper shaft 11 that moves due to an impact can push the torque sensor 51. Therefore, the upper shaft 11 of the steering shaft 10 can be moved to the sensor entry space portion 70 that allows the torque sensor 51 to be pushed in when the steering shaft 10 moves for absorbing an impact. This increases the shock absorption stroke that the steering shaft 10 and the column tube 20 can move together to absorb the impact energy within the entire length range along the axial direction of the steering shaft 10 in the electric power steering apparatus 1. Can do. Therefore, it is possible to reduce the overall length of the electric power steering apparatus 1 necessary for ensuring a constant shock absorbing stroke on the steering shaft 10.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration of the present invention is not limited to this embodiment, and even if there is a design change or the like without departing from the gist of the present invention. It is included in the present invention. For example, the present invention can be applied to an impact absorbing electric power steering apparatus using a torque sensor other than the magnetostrictive torque sensor.

  In the present invention, a steering shaft is inserted into a column tube, a torque sensor for detecting a steering torque input to the steering shaft is incorporated in a sensor housing, and driven according to a detection result of the torque sensor to output a steering assist torque. The upper shaft and lower shaft, which have an electric motor and the steering shaft is divided into upper and lower parts, are fitted in a relatively non-rotatable and telescopic manner, and the upper shaft is rotatably supported by the column tube. An impact absorption type electric power steering device in which an upper shaft of a steering shaft and a column tube are allowed to move in the axial direction by an impact acting on a steering shaft, which is rotatably supported by the housing. And torr The inner peripheral side of the sensor, with a shaft admission space portion which allows penetration of the upper shaft coming moved by the impact. This increases the shock absorption stroke that the steering shaft and the column tube can move together to absorb the impact energy within the entire length of the electric power steering apparatus along the axial direction of the steering shaft, and thus the steering shaft. It is possible to reduce the overall length of the electric power steering apparatus necessary for ensuring a constant shock absorbing stroke.

DESCRIPTION OF SYMBOLS 1 Electric power steering apparatus 10 Steering shaft 11 Upper shaft 12 Lower shaft 20 Column tube 32 Sensor housing 40 Electric motor 51 Torque sensor 52 Sensor case 54 Excitation coil 55A, 55B Detection coil 59A, 59B Magnetostrictive film 60 Shaft approach space part 70 Sensor approach Space

Claims (3)

Insert the steering shaft into the column tube,
A torque sensor that detects steering torque input to the steering shaft is built in the sensor housing,
An electric motor that is driven according to the detection result of the torque sensor and outputs a steering assist torque;
The upper and lower shafts, which are divided into the upper and lower parts of the steering shaft, are fitted in such a way that they cannot be rotated relative to each other and can be expanded and contracted. The upper shaft is supported rotatably on the column tube, and the lower shaft is supported rotatably on the sensor housing of the torque sensor. And
In the shock absorbing electric power steering device in which the upper shaft and the column tube of the steering shaft are made to move in the axial direction by an impact acting on the steering shaft,
An impact-absorbing electric power steering apparatus comprising a shaft entry space portion that allows an upper shaft that moves due to an impact to enter an inner peripheral side of a torque sensor inside a sensor housing. Insert the steering shaft into the column tube,
A torque sensor that detects steering torque input to the steering shaft is built in the sensor housing,
An electric motor that is driven according to the detection result of the torque sensor and outputs a steering assist torque;
The upper and lower shafts, which are divided into the upper and lower parts of the steering shaft, are fitted in such a way that they cannot be rotated relative to each other and can be expanded and contracted. The upper shaft is supported rotatably on the column tube, and the lower shaft is supported rotatably on the sensor housing of the torque sensor. And
In the shock absorbing electric power steering device in which the upper shaft and the column tube of the steering shaft are made to move in the axial direction by an impact acting on the steering shaft,
Shock absorbing electric power characterized in that the sensor shaft has a sensor entry space that allows the torque sensor to be pushed in by the upper shaft that moves due to the impact inside the sensor housing. Steering device.   The torque sensor has a sensor case inserted into the sensor housing, an excitation coil and a detection coil stored in the sensor case, and is based on a magnetostrictive effect according to the torque of the magnetostrictive film applied to the surface of the lower shaft. The shock absorbing electric power steering apparatus according to claim 1 or 2, wherein a change in magnetic field is detected.

Images