The present application claims priority from Japanese Patent Application No. 2006-301135 filed on Nov. 7, 2006, the entire content of which is incorporated herein by reference.
The present invention relates to a tilt-type steering apparatus which can adjust a position of a steering wheel of a vehicle in a heightwise direction.
A tilt-type steering apparatus is one of height adjusting apparatuses for a steering wheel, and is operable to adjust a height of the steering wheel in accordance with a physique and a driving posture of a driver.
Conventionally, various types of structures are employed for the tilt-type steering apparatus (see, e.g., JP 10-007003 A and JP 1-173072 U).
In order to adjust a vertical position of the steering wheel 1, the upper fixing bracket 7 includes a pair of vertical plate portions 8 which are parallel to each other, and vertically elongated slots 9 are formed in the respective vertical plate portions 8. More specifically, each of the slots 9 is formed in an arc shape having its center at a position of the lateral shaft 4, and is formed at respective positions on the vertical plate portions 8 such that the slots 9 align with each other. A lift bracket 10 is fixed to a lower surface of the intermediate portion of the steering column 3, e.g., by welding. The lift bracket 10 is formed by bending a metal plate having a required rigidity, The lift bracket 10 is fixed to the steering column 3 between the pair of vertical plate portions 8. Through holes 11 are formed in the lift bracket 10 so as to be concentric with each other in a lateral direction (a right-and-left direction in
When adjusting the heightwise position of the steering wheel 1 in the above described tilt-type steering apparatus, first, the tilt nut 14 is loosened by operating the tilt lever 15 so that a space between the tilt nut 14 and the head portion 13 is increased. Then, the tilt bolt 12 is moved along the slots 9 of the upper fixing bracket 7 to lift or to lower the rear end portion of the steering column 3 is lifted or lowered, thereby moving the steering wheel 1 to a desired heightwise position. The tilt nut 14 is then tightened by the tilt lever 15 so that the space between the head portion 13 and the tilt nut 14 is narrowed, whereby the upper portion of the steering column 3 can be fixed at the adjusted position.
As described above, the structure disclosed in JP 10-007003 A includes the lower fixing bracket 5 and the swivel bracket 6 which are connected to each other via the lateral shaft 4, thereby allowing the front end portion of the steering column 3 to swivel with respect to the vehicle body. Thus, the swivel support portion at the front end portion of the steering column 3 becomes complex, resulting in an increase in cost.
Although a cost reduction can be achieved in the structure disclosed in JP 1-173072 U, it is disadvantageous in terms of ensuring durability. Namely, the bent portion 22, which is a swiveling center of the steering column 3, is a portion formed by largely bending the metal plate in a perpendicular direction. Therefore, due to such a bending process, a large magnitude of distortion (residual tensional stress) exists inside the bent portion. In particular, in a case in which a thickness of the metal plate (i.e., the lower support bracket 19) is increased in order to ensure sufficient supporting rigidity, the distortion increases. Thus, in the event that the heightwise position of the steering wheel is repetitively adjusted, possibility cannot be denied that damage such as cracking is generated in the bent plate portion 22. Generally, this may not be a big problem because it is usually not often to adjust the heightwise position of the steering wheel. However, commercial vehicles, such as rental cars, company cars and taxies, are driven by different drivers day after day and, therefore, the heightwise position of the steering wheel is frequently adjusted. In such cases, it is considered difficult to improve rigidity by increasing the thickness of the plate and also to enhance durability at the same time in the structure shown in
It is an object of the present invention to provide a tilt-type steering apparatus having a durable structure with low cost.
According to an aspect of the invention, a tilt-type steering apparatus includes a steering column, a swivel support bracket which swivelably supports the steering column, and a fixing bracket which supports an intermediate portion of the steering column such that a heightwise position of the intermediate portion of the steering column with respect to the fixing bracket is adjustable. The swivel support bracket includes a coupling plate portion in which an opening is formed at a central portion thereof, a support plate portion extending in a forward direction, and a bent portion which continuously connects an upper end edge of the coupling plate portion and the support plate portion. The coupling plate portion includes a low-rigidity portion at an intermediate portion in a vertical direction thereof. Bending rigidity of the low-rigidity portion is lower than that of the other portion of the coupling plate portion with respect to a force attempting to relatively displace an upper portion and a lower portion of the coupling plate portion in a front-and-rear direction.
Other aspects and advantages of the invention will be apparent from the following description, the drawings and the claims.
The electric power steering device applies an auxiliary rotational force (an assist force) to a steering shaft 2a from an electric motor 18 via a worm-type reduction gear, thereby reducing a force required to operate a steering wheel (a steering force). When applying the assist force, a force in a clockwise or counterclockwise direction in
The swivel support device 23 includes a swivel support bracket 24 which supports the housing 16 with respect to the vehicle body. The swivel support bracket 24 is formed by bending a metal plate having a required rigidity, e.g., a carbon steel plate, or a stainless steel plate. The swivel support bracket 24 includes a coupling plate portion 25, which extends in a vertical direction, and a support plate portion 26, which is bent in a forward direction substantially at right angle from an upper end edge of the coupling plate portion 25, and a bent portion 27 which continuously connects the coupling plate portion 25 and the support plate portion 26. The support plate portion 26 is fixed to the vehicle body with bolts when assembled into the vehicle. In order to increase bending rigidity of the bent portion 27, a reinforcement bead 28 is formed at a central portion of the bent portion 27, and bent edges 29 are formed on both right and left end edge portions of the bent portion 27. Thus, a bending angle of the bent portion 27 does not change even when the steering column 3 is displaced in its tilting direction.
An opening 30 is formed in a central portion of the coupling plate portion 25. A member (e.g., an output shaft of the power steering device) for transmitting a rotational force of a steering shaft 2, which is rotationally supported within the steering column 3, is inserted through the opening 30. Both right and left lower end portions of the coupling plate portion 25 are fixedly connected to a front surface of the housing 16. According to the exemplary embodiment, three positions on a swivel support plate 17a are fixed to three positions on the front surface of the housing 16 with bolts 31a, 31b. The two lower bolts 31a fix the right and left lower end portions of the coupling plate portion 25 and right and left lower end portions of the swivel support plate 17.
A gap 32 is provided between a portion of a rear side surface of the coupling plate portion 25 (i.e., a portion from an intermediate portion to an upper end portion thereof) and a front side surface of the swivel support plate 17a. In order to provide this gap 32, raised portions 33, which project in the forward direction, are provided at the right and left lower end portions on the front surface of the swivel support plate 17. The coupling plate portion 25 and the swivel support plate 17 are fixedly connected to the housing 16 with the two bolts 31a in a state in which the right and left lower end portions on the rear side surface of the coupling plate portion 25 are brought into abutment with apex portions of the raised portions 33.
The coupling plate portion 25 includes low-rigidity portions 34 at its intermediate portion in a vertical direction (shaded portions in
When adjusting the heightwise position of the steering wheel 1 (see
According to the tilt-type steering apparatus of the exemplary embodiments described above, firstly, the low-rigidity portion 34 is a portion of the swivel support bracket 24, and the steering column 3 can be swiveled (i.e., the tilt angle of the steering column can be adjusted) by bowing the low-rigidity portion 34. Thus, the numbers of components involved and an amount of assembling work can be decreased, whereby the manufacturing cost can be saved.
Further, the low-rigidity portion 34 according to the exemplary embodiments are different from the bent portion 22 shown in
When the electric power steering device is in operation, a reaction force associated with the assist force applied to the steering shaft 2 from the electric motor 18 is applied in a clockwise direction or a counterclockwise direction in
While description has been made in connection with exemplary embodiments of the present invention, it will be obvious to those skilled in the art that various changes and modification may be made therein without departing from the present invention. It is aimed, therefore, to cover in the appended claims all such changes and modifications falling within the true spirit and scope of the present invention.
Number | Date | Country | Kind |
---|---|---|---|
2006-301135 | Nov 2006 | JP | national |