Electric heating – Inductive heating – With heat exchange
Reexamination Certificate
2001-12-10
2002-12-03
Leung, Philip H. (Department: 3742)
Electric heating
Inductive heating
With heat exchange
C219S632000, C219S670000, C122S026000, C126S247000, C237S01230R
Reexamination Certificate
active
06489598
ABSTRACT:
The present invention relates generally to a heat generator for motor vehicles and primarily to one for reducing emissions from the internal combustion engine of a motor vehicle.
U.S. Pat. No. 4,484,049 discloses a water-cooled heat generator for the passenger compartment of a motor vehicle. The heat generator comprises a shaft driven by the vehicle engine, which shaft is common to the rotor in an electric generator and a rotor in the heat generator itself. Alternating current drawn from the stator winding of the electric generator is rectified and fed as magnetising current to the rotor in the heat generator. The latter also has a laminated stator with armature bars connected between two short-circuit rings, the bars like the short-circuit rings being hollow. The armature bars, in which the rotor of the heat generator generates induction currents as it rotates, are, like the short-circuit rings, cooled by water that circulates through them. The water thus heated is in turn used for heating the vehicle passenger compartment.
The said heat generator is bulky, complicated and also has poor efficiency.
U.S. Pat. No. 5,573,184 discloses a heat generator based on friction heating. This heat generator, too, is bulky owing to a high volume/output ratio, a relatively high-viscosity operating liquid moreover being required.
PCT/SE99/00283 describes a heat generator with a permanently magnetised, disc-shaped rotor, a stator, which is axially separated from the rotor and in which the rotor induces electric currents as it rotates, which generate heat in the stator, and adjoining the stator a cooling duct for a flowing liquid in order to dissipate the heat generated in the stator.
This heat generator is compact and provides very efficient heating of the cooling liquid, which is intended for use in heating the coolant in an internal combustion engine in an initial phase after starting the internal combustion engine.
Because of the highly efficient conversion from mechanical work, which drives the heat generator, to generated heat in the cooling liquid, it may be necessary in many applications to control the generated heat output according to a varying demand. This might obviously be done by corresponding variation of the mechanical power delivery, which drives the heat generator, by adjusting the speed of rotation of the rotor of the heat generator. Such a speed variation is not possible in all applications, however, since other requirements may be crucial for the magnitude of the mechanical power output, for example the power needed to propel a vehicle. In such a case the desired heat output can nevertheless be produced by connecting the heat generator intermittently in such a way that the mean value of the generated heat output corresponds to the desired heat output. This intermittent connection, however, presupposes a connecting arrangement, which requires space and may mean that the heat generator becomes complicated and/or undesirably expensive.
An object of the present invention is to provide a heat generator for motor vehicles, which is compact but still permits easy adjustment of the heat generated.
A heat generator according to the invention has a permanently magnetised, disc-shaped rotor; a stator, which is axially separated from the rotor and in which the rotor induces electric currents as it rotates, which generate heat in the stator; and adjoining the stator a cooling duct for a flowing cooling liquid in order to dissipate the heat generated in the stator. The rotor and the stator are furthermore axially moveable in relation to one another, in order to adjust the distance between them and thereby to adjust the heat generated in the stator or the heat output. This makes use of the fact that an adjustment of the distance between the rotor and the stator affects the magnitude of the currents. that the rotor induces in the stator and hence the magnitude of the heat generated by the said currents. Finally, means are arranged for determining the heat output generated in the stator by acting axially on the rotor in the direction of the stator with a variable force against the action of a repelling force, generated by the currents induced in the stator. The rotor can thereby be set to an axial position in relation to the stator depending on the heat output to be generated in the stator.
The stator preferably comprises two metallic layers, which define a narrow, substantially radial gap, which constitutes a part of the cooling duct designed for radial flow. In this way the distance over which the liquid in the cooling duct is heated is rendered relatively short, which is a pre-requisite for rapid heating utilising a high output.
In addition, the cooling duct suitably comprises two annular spaces, which adjoin the radial gap on that side thereof remote from the rotor and are designed for a circumferential flow of the cooling liquid. This design means that the cooling liquid follows intersecting paths on both sides of one of the two metallic layers, represented by the layer furthest from the rotor. Because of these intersecting flows of cooling liquid, such phenomena as evaporation and film boiling, which might otherwise occur as a result of the rapid heating and lead to cavitation and overheating, can be prevented.
The means for acting axially on the rotor in the direction of the stator, that is to say for adjusting the distance between the rotor and the stator depending, for example, on the desired heating of the flowing liquid, may be designed in many different ways, but they suitably comprise a soft magnetic material, which constitutes part of the stator, so that the magnetic field of the rotor is closed and a magnetic attraction force acts between the permanently magnetised rotor and the stator.
Of the two metallic layers, one nearest the rotor may comprise an electrically conductive, preferably non-magnetic material, and one furthest away from the rotor may comprise the soft magnetic material.
The force generated in the stator, which has a repelling action on the rotor, may be dimensioned so that at a predetermined speed of rotation it moves the rotor away from the stator against the action of the magnetic attraction force between the permanently magnetised rotor and the stator. This is achieved, for example, through the choice of stator magnetic material and through the choice of its volume and distance from the rotor.
The means for acting axially on the rotor may comprise spring means, pneumatic or hydraulic piston and cylinder units and/or electrically operated units. The said means may strengthen and/or weaken the magnetic attraction force or the repelling force in order to permit the achievement of a predetermined output/speed profile.
The means for acting axially on the rotor may furthermore comprise an override means for positively shifting the rotor to a desired output position or locking the rotor in a lower output position, for example when the entire output of the car engine is required for acceleration.
The means acting axially on the rotor may furthermore be controlled by an override signal from control electronics, which control the internal combustion engine, for limiting the heat output generated in the stator by positively shifting the rotor in relation to the stator, and achieving a position with limited output. Such an override signal might be generated by the control electronics in connection with acceleration, for example from stationary or in excess of a predetermined limit, the rotor being shifted to and locked in a lower output position.
By giving the means for applying force to the rotor in the direction of the stator a suitable force/distance profile, the heat output generated in the stator can thus take on a predetermined output/speed profile.
The currents that the rotor induces in the stator increase normally with increasing speed. In order to take account of this increased current, the distance of the rotor from the stator can also be suitably increased as the speed of the rotor increases. This increase may be used, for example, to achieve the desired h
AB Konstuktions-Bakelit
Birch & Stewart Kolasch & Birch, LLP
Leung Philip H.
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