Geometrical instruments – Miscellaneous – Light direction
Reexamination Certificate
1999-03-01
2001-10-09
Gutierrez, Diego (Department: 2859)
Geometrical instruments
Miscellaneous
Light direction
C033S0010DD
Reexamination Certificate
active
06298565
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to angular sensors and more particularly relates to angular sensors used to detect steering wheel position, especially a steering angle sensor used for yaw angle control in an automotive vehicle.
2. Description of Related Art
In control systems for yaw angle control of an automobile, it is important that a value describing the angle position of the front wheels is in-put. However, for practical reasons it has become usual not to directly measure the steering angle of the wheels but rather the angle of rotation of the steering wheel which is closely associated with the angle position of the front wheels. To accomplish this, there are sensors which work with a so-called code disk operatively coupled with the steering wheel. Such a device has been described in the applicant's patent application 185 32 903.1. To effect a finer adjustment of the desired angle position of the wheels and to reduce the energy effort needed for steering, however, a transmission is inserted between the steering wheel and the vehicle wheels so that a plurality of revolutions of the steering wheel is necessary for adjusting the vehicle wheels by a larger angle.
Since the above-mentioned code disk is coupled with the steering wheel, it is possible to indicate the absolute angle position of the steering wheel, yet not how many revolutions of the steering wheel have already taken place, starting from a neutral position of the vehicle wheels.
One solution is to measure the difference in the speeds of rotation of the front wheels of a vehicle during driving. This allows for a rough determination of the angle position of the front wheels so that it is possible to determine the number of revolutions already performed by the steering wheel, starting from a normal position. In this manner, permanently adding the steering wheel revolutions in one direction or in the other direction, it is possible to follow the number of the momentarily available steering wheel revolutions and to thus provide corresponding information. This is, however, impossible for modern steering angle sensors with electric or electronic evaluation such as in the case of the above-described code disk since, during parking, the electric power of these vehicles is turned off while it must nevertheless be possible to pivot the wheels in the turned-off condition. When turning on the electric power again, in this case, the relevant value of revolution would actually differ from the value stored at the time when the electric power supply was turned off. Additionally, the determination of the number of revolutions becomes quite inaccurate during extremely slow speeds due to different speeds of rotation of the front wheels.
SUMMARY OF THE INVENTION
It is an object of this invention to provide, in such a steering angle sensor, the possibility of precisely stating the momentary number of revolutions of the steering wheel even when the steering wheel has been moved, with the supply voltage turned off, and thus a number of revolutions is relevant upon the start of the vehicle which differs from the value at the time of turning-off the supply voltage.
Thus, this invention utilizes an additional counter which provides information describing the actual number of revolutions of the steering wheel. It is possible to provide this information electronically since it will only be needed when the electric power supply of the vehicle is turned on because yaw angle determination is for the purpose of eliminating any danger of skidding. Mechanical coupling between the code disk and the counter ensures that the latter will preparatorily be adjusted to the correct value even if the electric power supply is turned off. Even when the supply voltage is turned off, the counter will follow the change of the steering angle of the wheels, yet will provide information only when the electric power supply has been turned on again.
While it is necessary to couple the code disk mechanically with the counter in order to realize this invention, a further object of this invention uses a gear reduction similar to that in a clockwork to ensure that the counter will index by one step to the next position in case of a full revolution of the code disk. However, it is also possible to use a step-by-step switch as mechanical gearing which will index by one step to the next position when the code disk has covered a full revolution. In such an arrangement, the code disk may move both a rotating and an axially displacing actuator.
When an electric signal is used as an output signal characteristic of the revolutions, the present invention may employ a rotary switch that emits electric signals, the rotary switch being driven by a mechanical gearing formed by a step-by-step switch.
Additionally, in order to electrically evaluate the momentarily available number of steering wheel revolutions with respect to the total momentarily available number of revolutions, a voltage is applied to one contact out of a sufficient plurality of contacts describing the maximum number of revolutions. A voltage applied to a certain contact will therefore render a unique value with regard to the momentarily available number of revolutions.
A design is disclosed wherein each number of steering wheel revolutions deviating from the zero position is assigned a contact of its own. By supplying electric power to a particular contact it is thus possible to provide electric information on the number of momentarily available revolutions of the steering wheel. The direction of rotation of the steering wheel determines whether to add the following numbers of revolutions to the computed value or whether to subtract it therefrom. If the steering wheel has performed three clockwise revolutions, starting from a zero position, revolution number
3
will have been reached. If, subsequently, a counterclockwise revolution is performed with the steering wheel, a revolution is subtracted, resulting in a setting of revolution number
2
. The analogous procedure occurs with a counterclockwise revolution of the steering wheel, proceeding from the zero position.
A design of the rotary switch is disclosed wherein a voltage applied to the contact ring, designed as a slip ring, is applied to one of the circularly arranged contact pieces which rotates with the number of revolutions. Regarding the evaluation of the electric signals describing the number of revolutions it is also possible to connect each contact piece with another resistor and to connect these resistors parallel to each other. If the internal resistance of the current source is big enough or if, instead of the individual resistors, each time a voltage divider is used, it will be possible to evaluate the voltage applied each time to the resistors as representing a value of revolutions. For a step-by-step counter, the code disk is connected with at least one trigger cam indexing a ratchet wheel by a corresponding number of teeth of the ratchet wheel to the next position.
In another feature of this invention, the ratchet wheel will not be turned until it is driven by one or two trigger cams on the code disk. In this case, the ratchet wheel is prevented from revolving by two ratchet teeth which intersect with the outside periphery of the code disk. The ratchet wheel is locked since the teeth cannot be moved on due to their big depth and since, otherwise, they would abut against the periphery of the code disk. Between the two driving teeth, each time, there is lying a driving tooth of lower depth which ends above the covering surface of the code disk. The code disk can thus rotate below this ratchet tooth. A first trigger cam on the code disk carries the flat ratchet tooth along. The trigger cam is followed by a recess on the code disk so that the neighboring deep ratchet tooth can be turned as well. The following flat ratchet tooth is carried along by a second trigger cam. As the deep ratchet tooth is turned outwards, the subsequent flat ratchet tooth is advanced across the contour of the code disk. Thereupo
Hohler Christian
Neckel Klaus
Traub Harald
Weber Petra
Gonzalez Madeline
Gutierrez Diego
ITT Manufacturing Enterprises Inc.
Rader & Fishman & Grauer, PLLC
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