Optical: systems and elements – Mirror – With support
Reexamination Certificate
2000-05-05
2001-11-13
Sikder, Mohammad (Department: 2872)
Optical: systems and elements
Mirror
With support
C359S872000, C359S877000, C359S876000
Reexamination Certificate
active
06315420
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a rear-view mirror apparatus for a road vehicle. The apparatus positions the mirror according to a control signal.
BACKGROUND OF THE INVENTION
In our earlier UK Patent No 2 259 064, we disclosed and claimed apparatus in which the position of a rear-view mirror was controlled according to the angle between the tractor and the trailer so that the driver can always see, using the mirror, along the side of the trailer on the inside of the turn. This was done by sensing the rotation of the trailer relative to the tractor in an articulated road vehicle. Each mirror was provided with a drive means comprising an arcuate gear member driven by a worm gear rotated by an electric motor, a potentiometer serving to provide an electrical signal indicative of the angular position of the mirror.
A problem with constructing such an arrangement is that of eliminating backlash in the gears without making the cost excessive. It is also desirable to be able to allow for impact to deflect the mirror without damaging it, and to permit rapid restoration of the desired alignment of the deflected mirror.
The present invention seeks to overcome these problems.
SUMMARY OF THE INVENTION
According to the invention, there is provided an adjustable rear-view mirror apparatus for a road vehicle, the mirror having drive means for rotating the mirror to an angle determined by a control signal thereto, the drive means comprising an output gear driven by a drive gear rotated by a motor, the motor and the drive gear being mounted in such a manner as to bias the drive gear into engagement with the output gear while allowing separation of the gears when a predetermined loading on the gears is exceeded.
The drive gear, which is suitably a worm gear, is preferably carried by a leaf spring. The mirror apparatus preferably comprises electronic circuit means for receiving the control signal and for controlling operation of the motor to position the mirror, the electronic circuit means being mounted on a resiliently flexible circuit board which also serves as the leaf spring.
The output gear is suitably an arcuate gear member, for example of 180° of arc.
The circuit board is suitably of the commonly-available type manufactured from glass-reinforced resin.
The mirror is suitably mounted on a rigid chassis attachable to the vehicle, the circuit board being fixed to the chassis at one end thereof, and additionally clamped to the chassis at a position intermediate the ends of the board according to the force required between the gears. The position will depend on the nature and thickness of the board, and in particular its resilience or springiness.
The arrangement of this aspect of the invention permits compactness and simplicity of construction, while permitting the mirror to move quickly out of position, for example in the event of an impact, without damage to the mirror or to the drive mechanism.
According to another aspect of the invention, there is provided an automatically-adjustable rear-view mirror apparatus for a road vehicle, the apparatus having drive means for rotating the mirror to an angle determined by a control signal thereto, and control means for receiving the control signal and for controlling operation of the motor to position the mirror, the control means comprising means for signalling the current angular position of the mirror, means for signalling the current velocity of the mirror or the motor, means for comparing the current angular position of the mirror with the desired position determined by the control signal and for determining therefrom the direction and speed required to move the mirror to its desired position, means for comparing the velocity so determined with the current velocity to produce a velocity error value, and means for adjusting the motor speed according to the error value.
The invention also provides a method of adjusting the position of a rear-view mirror for a road vehicle, the mirror having drive means for rotating the mirror to a desired angular position determined by a control signal thereto, the method comprising measuring the current angular position of the mirror and determining from the difference between the measured position and the desired position the direction and speed required to move the mirror to its desired position, determining the current speed of the mirror and adjusting the mirror speed according to the difference between the current speed and the required speed.
The desired speed may be determined by means of stored data in the form of look-up tables, in which speed values are stored against angular error values. The adjustment of speed may also be carried out on the basis of stored look-up table determining the change of power supplied to the motor on the basis of the error from the desired speed. Alternatively, the motor may be supplied with power on a pulse width modulation basis, the relative width of the power pulses being varied according to the error, either on a linear relationship, or by means of look-up table values. The motor can also be controlled to brake the motion of the mirror.
Controlling the speed of rotation of the mirror according to the error from the calculated speed permits the device to use a simple electric motor to drive the mirror instead of the more costly stepper motors and the like, while still permiting accurate positioning with smooth adjustment, rather than rapid abrupt movements which make use of the mirror difficult.
The invention is applicable to the positioning of mirrors controlled by joystick or similar controls, or to automadcally-rotated mirrors for use with articulated road vehicles, for example as described in our Patent No. GB2 259 064.
In yet another aspect of the invention, there is provided a device for providing an electrical signal indicating the relative angle between the tractor and trailer of an articulated road vehicle, the device comprising a roller mounted in or adjacent to the fifth wheel plate on the tractor in such a position as to be rotated by a trailer when coupled to the tractor, the roller driving signalling means providing a signal in response to rotation of the roller.
The signalling means may be a simple switch providing a pulse signal as the roller rotates. The switch may be a mechanical contact, an opto-electronic device, a magnetic device or any other means signalling rotations digitally. Alternatively, the roller may be arranged to drive, for example through suitable gearing, a device such as a potentiometer giving a continuously changing signal as the roller rotates.
The output from the device can be used to provide information about the relative angle of the trailer to the tractor, for example for use in the device according to the other aspects of the invention, where the angle of the rear-view mirror on the tractor can be varied according to the turning of the tractor relative to the trailer to permit the driver in the tractor to continue to be able to see the rear end of the trailer as he or she turns around corners. It will be appreciated that, because the angle given by the device cannot be absolute, as it depends on the orientation of the tractor during coupling to the trailer, it will be necessary to provide some form of calibration for use by the driver before beginning a journey. This may be done, for example, by simply pressing a calibration switch when the boiler appears to the driver to be aligned with the tractor.
The invention also provides a system for providing an electrical signal indicating the relative angle between the tractor and trailer of an articulated road vehicle, the system comprising two or more devices of the invention, spaced apart from each other, and means for processing the signals from all the devices to provide a single signal in which errors due to the effects of unwanted movement between the components of the fifth wheel arm minimised.
REFERENCES:
patent: Re. 29411 (1977-09-01), Newell
patent: 5636184 (1997-06-01), Boyd
Standen Christopher Allan
Standen John Paul
Delbridge Robert F.
Sikder Mohammad
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