Electricity: motive power systems – Alternating current commutating motors
Reexamination Certificate
1999-09-30
2001-01-09
Ip, Paul (Department: 2837)
Electricity: motive power systems
Alternating current commutating motors
C318S470000, C318S245000, C318S466000, C388S911000, C324S160000, C324S177000
Reexamination Certificate
active
06172473
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a device for determining the rotational number of a dc motor which is used particularly for driving a moving body of an automobile accessory such as a sunroof, a pane of glass in a power window, or an electrically operated seat device.
2. Description of Related Art
A conventional device of the kind is disclosed in the U.S. Pat. No. 5,497,326 granted to Berland et al. In this patent, the device issues a signal indicative of the amount of motor rotation. The signal is in the form of a pulse signal, which is generated in such a manner that a ripple component of a current flowing through the motor is formed into a pulse mode by being passed through a circuit including a low-pass filter and other components.
The frequency range of the ripple component of the current which the low-pass filter can treat is limited, which necessitates the provision of a compensating means to make the signal correct even though the range of the frequency range of the ripple component falls outside the ability of the low-pass filter.
However, providing such a compensating means is very cumbersome.
SUMMARY OF THE INVENTION
It is therefore, a principal object of the present invention to provide a device without the foregoing drawback.
In order to attain the foregoing object, the present invention provides a device for determining the rotational number of an electric dc motor comprising;
a switched capacitance filter for eliminating noise from the motor, a cutoff frequency of the switched capacitance filter being dependent on a clock input thereof;
a pulse shaping circuit for generating a ripple pulse signal indicative of the rotational number of the motor by wave-shaping an output of the switched capacitance filter; and
a pulse generating circuit providing an out put pulse signal so as to establish a condition wherein the frequency of the ripple pulse signal is equalized to the cutoff frequency of the switched capacitance filter.
REFERENCES:
patent: 4514670 (1985-04-01), Fassel et al.
patent: 5017846 (1991-05-01), Young et al.
patent: 5483132 (1996-01-01), Agata et al.
patent: 5497326 (1996-03-01), Berland et al.
patent: 5646497 (1997-07-01), Stickel
patent: 5787134 (1998-07-01), Kovacs
Aoki Koji
Ishikawa Hitoshi
Kanie Hideyuki
Oka Toshimitsu
Aisin Seiki Kabushiki Kaisha
Ip Paul
Leykin Rita
Sughrue Mion Zinn Macpeak & Seas, PLLC
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