Electricity: motive power systems – Battery-fed motor systems
Reexamination Certificate
2000-02-28
2001-10-30
Nappi, Robert E. (Department: 2837)
Electricity: motive power systems
Battery-fed motor systems
C318S599000
Reexamination Certificate
active
06310449
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a device including a motor whose speed is controlled by the energization and deenergization thereof in a pulsating manner.
Such a device of the type defined in the opening sentence is commercially available and frequently used in practice, and it is consequently known. For such a device reference can be made, for example, to the patent document EP 0 222 042 A1, FIG. 3.
The known device includes two separate switching means, of which a first switching means serves for connecting and disconnecting the coil arrangement of the motor in a pulsating fashion for the purpose of controlling the speed of the motor, and of which a second switching means serves to produce turn-off voltage transients across the coil arrangement. The known device further includes a control pulse generator for each of the two switching means. Two such switching means and two such control pulse generators are comparatively expensive and further have the problem that an undesired interaction may occur between the processes caused by the switching means, which may lead to invalidation of the results of these processes.
SUMMARY OF THE INVENTION
It is an object of the invention to improve a device of the type defined in the opening sentence and to provide an improved device having a simple construction, which precludes an invalidation of results by the switching means, as can occur in the prior art device.
The characteristic features provided in accordance with the invention result in a substantially simplified device in which an interaction between switching means is avoided and, consequently, no interactions between the processes caused by the switching means can occur, as a result of which the results of such processes cannot be invalidated.
The single switching means may be constituted, for example, by a bipolar transistor, but when such a bipolar transistor is used care must be taken that the available d.c. supply voltage is at least a factor of ten (10), but preferably an even greater factor, higher than the saturation voltage of the bipolar transistor used, because otherwise a comparatively large portion of the energy provided by the d.c. supply voltage is transformed into heat. It has proved to be particularly advantageous if a device in accordance with the invention uses a field effect transistor as the single switching means because the construction of the single switching means as a field-effect transistor (FET) makes it possible to achieve an energy saving and simple voltage supply to its control electrode. Moreover, by an appropriate dimensioning of the voltage boosting means the FET can be given a low turn-on resistance when the motor is connected to the d.c. supply voltage, which is of particular importance for the connection of a variable-speed motor to a d.c. supply voltage.
A device in accordance with the invention can be operated with a d.c. supply voltage which is only slightly higher than the direct voltage required for controlling the control electrode of the single switching means. A variant of the device having the characteristic features defined in claim
3
has proved to be particularly advantageous because a reliable starting of the motor is then even guaranteed if the value of the d.c. supply voltage available during operation is smaller than the minimum value of the control voltage required for the control electrode of the single switching means.
The starting means may take the form of, for example, a wiper contact or a bipolar transistor. However, it has proved to be advantageous when the starting means is a clamping circuit coupled to the control electrode of the single switching means. This measure guarantees a particularly reliable starting of the motor, starting being highly independent of aging as compared with a wiper contact.
For a highly reliable starting of the motor of the device in accordance with the invention the provision of a timing means coupled to the starting means has proved to be very advantageous. The coupling of a timing means to the starting means, constructed as a clamping circuit, enables a well controlled and efficient use of the clamping circuit.
The abovementioned as well as further aspects of the invention will become apparent from the two examples of embodiments described hereinafter and will be elucidated with reference to these examples.
REFERENCES:
patent: 4458183 (1984-07-01), Neilson
patent: 5268987 (1993-12-01), Sakoh
patent: 5602448 (1997-02-01), Yaguchi
patent: 5703447 (1997-12-01), Higuchi
patent: 5811948 (1998-09-01), Sato et al.
patent: 6060859 (2000-05-01), Jonokuchi
patent: 19754574 (1999-06-01), None
patent: 0222042A1 (1987-05-01), None
patent: 0637874A1 (1995-02-01), None
patent: 57097385-A (1982-06-01), None
Bartlett Ernestine C.
Franzblau Bernard
Martin Edgardo San
Nappi Robert E.
U.S. Philips Corporation
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