Electricity: electrical systems and devices – Control circuits for electromagnetic devices – Systems for magnetizing – demagnetizing – or controlling the...
Reexamination Certificate
1999-07-30
2001-07-03
Sherry, Michael (Department: 2836)
Electricity: electrical systems and devices
Control circuits for electromagnetic devices
Systems for magnetizing, demagnetizing, or controlling the...
C361S084000, C361S091500, C361S187000, C361S194000, C361S195000, C361S196000, C361S210000
Reexamination Certificate
active
06256185
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to electrical control modules and specifically to electrical control circuits for use with solenoids.
BACKGROUND OF THE INVENTION
A solenoid is a common electrical device used to convert electrical energy into mechanical energy. Solenoids are well known in the art and are often utilized as a means of moving a component a predetermined distance at a predetermined time. In its most basic form, a solenoid is an electromechanical device that converts electrical energy into linear or rotary motion. Electrical voltage passes through a coil of insulated copper wire producing a magnetic field, which moves a ferromagnetic plunger located within the core of the coil. Steel parts surround the coil to contain the flux path for maximum pull, push or rotational force. A solenoid can be used to open a valve, activate a switch, apply a brake or a number of other activities where mechanical movement is required and only an electrical energy source is available or practical.
A typical solenoid comprises a steel frame or shell that surrounds the coil of wire and directs the flux path. The coil assembly, when energized with an electrical voltage, creates the magnetic lines of force. A plunger, located within the coil assembly, reacts to the magnetic pull and moves to the center of the coil against a stop or pole piece. The pole piece provides a stop for plunger movement. However, it is often required in a solenoid application that the plunger be retained or held against the pole piece. In order to retain the plunger against the pole piece, a sufficient amount of electrical voltage must be continuously applied to the coil assembly.
To accomplish the plunger hold function, prior art solenoids have included two (2) coil assemblies. A first voltage is applied to the first coil assembly thereby causing the solenoid to perform its work, i.e. the movement of the plunger from its initial position to the pole piece. A second voltage is then applied to the second coil to retain the plunger in its position against the pole piece. The first coil is typically comprised of a heavier gage wire to provide greater ampere turns whereas the second coil is comprised of a lighter gage wire with fewer ampere turns. The first voltage is typically a relatively high voltage and the second voltage is a lower voltage. Solenoids having two coil assemblies have drawbacks including increased expense, increased size, increased weight, and the necessity for entire replacement when one coil burns out (even though the other coil is intact).
Other prior art devices utilize a single coil assembly solenoid, but also provide a control module that applies a high voltage to the coil assembly to perform the work and a lower voltage to the solenoid to perform the hold function. Typically, these dedicated controllers are neither robust nor equipped with versatile connection means to allow use with a broad range of solenoid coils. These prior art devices all exhibit various limitations that the present invention overcomes including a narrow operation voltage range and susceptibility to damage if connected to the power source with improper polarity.
The present invention provides further enhancements in that it allows for direct and continuous connection of the primary power source to the module's power input terminal and also for fixed and continuous connection of the solenoid coil(s) to the module. Control of the application of electrical energy to the solenoid coil(s) can be accomplished by applying a +8 volt to +30 volt (ground reference) low current (less than 10 milliamps) signal to the auxiliary input terminal of the module. This feature allows solenoid systems to be wired without the need for high current switches or relays to control the primary current to the solenoid which in many cases on engine applications exceeds 50 amps.
Other prior art devices utilize an electronic control module that provides a timed application of high energy to the heavier gage winding of a dual winding or dual coil solenoid; however the heavier winding coil becomes inactive after the initial “pull-in” period. Thereafter, the solenoid operates using only the lighter gage coil resulting in low efficiency. In such a system incorrect connections of the control module to the solenoid coils may result in damage to the solenoid and or the control module.
While pulse width modulation has been utilized in the past to control the movement of a solenoid, a pulse width modulation circuit having the structure and benefits, as set forth below, is believed to be novel. The inventor is not aware of any prior art that teaches the unique combination of components and resulting benefits.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a solenoid control module that can supply a solenoid with a first voltage to perform mechanical work and a second voltage to perform a mechanical hold function without prematurely burning out the solenoid coil assembly. It is a further object to provide a control module that can be used with both single and double coil assembly solenoids. It is a further object to provide a control module that will not damage or destroy the solenoid if the solenoid is improperly connected to the control module output. It is a further object to provide a control module that will not be damaged or destroyed if connected to the power source with improper polarity. It is a yet further object to provide a solenoid module that is well suited for applications in the internal combustion engine industry. For example, diesel engines often require solenoid to operate fuel on/off levers. Many engine applications require remote or automatic operation of throttle levers. These solenoids must be able to perform a specified amount of work during the retraction or extension of the solenoid plunger and then hold the plunger in a predetermined position for an extended period of time.
These and other objects are achieved by the present invention wherein an electrical control module supplies two different voltages to a single coil or double coil solenoid.
In one embodiment, the invention may be described as an electric circuit for controlling a solenoid including a first voltage control means for providing a first electrical voltage to the solenoid for a predetermined time period; the first voltage control means being connected to the solenoid; a second voltage control means for providing a second electrical voltage to the solenoid; the second voltage control means also being connected to the solenoid; and the second voltage being a pulse width modulated voltage. The second means may include a free wheeling diode for maintaining a continuous current through the solenoid during pulse width modulation with reduced power dissipation and improved magnetic drive to the solenoid. In a preferred embodiment, the free wheeling diode is a Schottky diode. A transient voltage suppressing means may be provided for protecting the circuit from an over voltage condition. In another preferred embodiment, the transient voltage suppressing means is a transient absorption zener diode.
The circuit includes a first, a second and a third output connections, said first and second output connections being adaptable for connection to a single coil solenoid and said first, second and third connections being adaptable for connection to a double coil solenoid. Resistor means and capacitor means are provided to determine the predetermined time period of the first voltage control means.
The circuit preferably includes reverse polarity protection means associated with said first and second voltage control means for opening said circuit in the event that the polarity of said circuit is reversed. A fuse may also be provided, the fuse being sized to open when a reverse polarity condition is detected. In addition, low voltage protection means may be provided for disabling the first and second voltage control means when an inadequate input voltage is supplied to said circuit. The input voltage is preferably in the rang
Ryan Kromholz & Manion S.C.
Sherry Michael
Trombetta, LLC
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