Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
1999-05-03
2001-09-18
Le, Que T. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S231180, C356S139000, C341S013000
Reexamination Certificate
active
06291815
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for measuring a rotation angle of a rotary element, and more particularly, to a rotation angle measuring device employing two circular arrays of signaling means arranged coaxially around a center of rotation and three detection means for detecting the signaling means.
2. Description of the Prior Art
As a typical construction of a rotation angle sensor, it is known to prepare a shutter disk adapted to rotate in accordance with a rotation of a rotary element of which a rotation angle is to be measured, the shutter disk having a circular array of slits centered at the rotation axis of the disk, while a light emitter and a light receiver are arranged on opposite sides of the shutter disk to align with the circular array of the slits, so that a series of electrical pulses are obtained according to a rotation of the shutter disk. In such a construction, when two sets of light emitters and light receivers are provided with a relative shifting including a fraction of the pitch of the array of the slits therealong, it is possible to detect the rotation of the shutter disk, with an identification of either of two opposite directions of rotation according to an identification of either of two different relative shiftings in the occurrence of the detection of light by the two light receivers.
When such a photo-electric sensor composed of a light emitter and a light receiver to operate with an array of slits of a shutter disk has been developed to be of some semiconductor constructions including a light emitting diode and a photo transistor, there arose a problem that the measurement of a rotation angle based upon the counting of electric pulses generated in the photo transistor due to irradiation and non irradiation of the photo transistor to the light emitted from the light emitting diode through the slits of the shutter disk is often liable to an error due to electrical noises induced in either or both of the light emitting diode and the photo transistor. If such errors in the counting due to electrical noises are left uncorrected, the errors are accumulated so much that the measurement is rendered useless. In Japanese Patent Laid-open Publication 9-113260, it is described that if such a counting error occurs in a rotation angle sensor for a steering shaft of a vehicle, the error is corrected each time when the steering shaft was turned beyond a predetermined limit angle.
SUMMARY OF THE INVENTION
In the modern art of vehicle behavior control for automatically controlling the running behavior of vehicles to be more stable against spinning, difting out or other instabilities, the rotation angle of the steering shaft is one of the most important parameters to be known at high accuracy. If any such counting error has occurred in the rotation angle sensor of the steering shaft of a vehicle, the error should be detected for a correction as soon as possible before the steering shaft is turned so large as to traverse a relatively large limit angle.
Therefore, it is a primary object of the present invention to provide an improved device for measuring a rotation angle of a rotary element so as to be able to detect an error in the measurement almost immediately upon the occurrence thereof.
It is a further object of the present invention to provide such an improved rotation angle measuring device with an ability of identifying the kinds of errors occurred.
According to the present invention, the above-mentioned primary object is accomplished by a device for measuring a rotation angle of a rotary element, comprising:
first, second and third detection means;
rotary means rotatable about a central axis thereof in accordance with a rotation of the rotary element, the rotary means having first and second circular arrays of signaling means arranged coaxially around the central axis thereof, the first array of signaling means being adapted to be detectable by the first detection means so as to generate a first signal alternating between “on” and “off” each time when the rotary means rotate each five times of a unit angle, the second array of signaling means being adapted to be detectable by the second and third detection means so as to generate second and third signals, respectively, the second and third signals each alternating between either “on” and “off” or “off” and “on” each time when the rotary means rotate alternately two times and three times of the unit angle, the “on” and “off” alternations of the first, second and third signals being shifted from one another by a multiple (including one) of the unit angle;
means for increasing a measurement value of the rotation angle of the rotary element by the unit angle each time when one of the “on” and “off” alternations of the first, second and third signals successively occurs in a first order with regard to the first, second and third signals, while decreasing the measurement value by the unit angle each time when one of the “on” and “off” alternations of the first, second and third signals successively occurs in a second order with regard to the first, second and third signals opposite to the first order, so as to provide the measurement value with a positive
egative sign indicative of a direction of the rotation; and
means for checking each occurrence of the “on” and “off” alternations of the first, second and third signals with respect to at least one of the first and second orders in each set of five consecutive occurrences of the “on” and “off” alternations, so as to detect an error in the order, when occurred.
The device may further comprise means for counting each detection of an error by the checking means, so as to stop the rotation measurement operation of the device when the count reaches a predetermined count number.
The device may further comprise means for dispatching a warning signal when the predetermined number of errors have been counted.
As a preferred embodiment, the device may be constructed such that the rotary means comprise a disk member, the signaling means comprise first and second circular arrays of openings formed therein such that each opening presents a pair of radial edges circumferentially spaced with an angle of a corresponding multiple of the unit angle, and the first, second and third detection means comprise first, second and third sets of light emitting diode and photo transistors, each set of the light emitting diode and the photo transistor being adapted to detect the radial edges of the corresponding array of the openings according to whether or not a light beam emitted from the light emitting diode is received by the photo transistor through a corresponding one of the openings. In such an embodiment, the openings of the first array may be a notch open to a periphery of the disk.
REFERENCES:
patent: 4593269 (1986-06-01), Nakamura et al.
patent: 4827123 (1989-05-01), Gray
patent: 5003171 (1991-03-01), Paley
patent: 5091643 (1992-02-01), Okutani et al.
patent: 42 43 778 A1 (1994-06-01), None
patent: 2 529 665 A1 (1982-07-01), None
patent: 2 045 990 A (1980-11-01), None
patent: 4-278883 (1992-10-01), None
patent: 6-127417 (1994-05-01), None
patent: 9-113260 (1997-05-01), None
Inagaki Shoji
Kondo Takashi
Sugiyama Mizuho
Le Que T.
Luu Thanh X.
Oliff & Berridg,e PLC
Toyota Jidosha & Kabushiki Kaisha
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