A device and method for operating automotive battery system relays and related switches. By aligning a magnetic field with a direction of current flow in a contact plate disposed between magnets that are producing the field, a generated lorentz force can be used to promote arc extinguishing during a relay opening sequence, while simultaneously reducing the tendency of the lorentz forces to interfere with the operation of a solenoid or other switch-activating mechanisms. By using a rotary-based mechanism to establish contact between a contact plate and current-carrying terminals, the likelihood of inadvertent opening of the relay is reduced. Such devices and methods may be used in conjunction with hybrid-powered and electric-powered vehicles.
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1. A vehicular propulsion system comprising:
a plurality of batteries;
a motive force; and
a switching assembly configured to permit selective delivery of an electric current from said plurality of batteries to said motive force, said switching assembly comprising:
a solenoid comprising at least a coil and a plunger rotatably responsive to electric current flowing through said coil;
a contact plate;
a plurality of electrically-conductive terminals cooperative with said solenoid and said contact plate such that upon said solenoid being energized, rotational movement of said plunger forces said contact plate into contact with said plurality of terminals to complete an electric circuit therebetween; and
a plurality of arc-extinguishing magnets disposed about a region defined at least in part by said contact between said contact plate and said plurality of terminals such that a field created by said plurality of magnets extends in a direction such that a lorentz force formed by coupling between said field and a current flow between said plurality of terminals during said contact between said contact plate and said plurality of terminals is substantially inhibited or formed along a direction that does not substantially promote premature separation of said contact plate from said plurality of terminals.
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This application claims the benefit of the filing date of U.S. Provisional Application No. 61/432,811, filed Jan. 14, 2011.
This invention relates generally to a device and method to reduce the magnitude of a Lorentz force formed on solenoid-based rotary contact plate, and more particularly to a device and method to reduce such magnitude while maintaining arc-extinguish features when the contact plate is opened or otherwise de-energized.
Solenoids are often used to open and close relays, switches and related electrical circuit contacts. Moreover, solenoids may be of a generally linear configuration or a rotary configuration. In either configuration, a high-voltage contactor employs the solenoid to move a contact plate into selective connection with a pair of stationary current-carrying terminals to complete an electrical circuit between the terminals. The contact is open when the solenoid is de-energized, and closed (or completed) when the solenoid is energized. In the particular configuration associated with a rotary solenoid, the solenoid's plunger or shaft rotates clockwise or counter-clockwise, depending on whether the solenoid is energized or de-energized. The contact-plate that attaches to the plunger will likewise rotate such that in an energized solenoid state, the contact plate will close the circuit between the two terminals, while in a de-energized solenoid state, the contact plate will open the circuit between the two terminals.
The presence of high voltage and current can cause arcing between the contact plate and the terminals at the time immediately after separation. Such arcing is not desirable, especially in high current modes of operation, as the power created by the arc tends to get absorbed by (or otherwise acts upon) nearby components that may not be electrically hardened.
Attempts to reduce or extinguish the arc have included enclosing the contact plate and terminals inside a chamber filled with a dielectric gas that introduces arc-inhibiting features by absorbing some of the energy during the arc formation. Such a configuration also reduces the packaging and provides some level of environment-independent usage. Despite this advantage, such a solution has a disadvantage in device cost and complexity.
In another attempt, supplemental magnet pairs have been placed on opposing sides of the contact plate and terminals to take advantage of the Lorentz force acting upon the terminals or other current-carrying members that are exposed to the magnetic field. The inherent Lorentz force can be used in the instant immediately after the circuit is opened at the contact plate to accelerate arc elimination by taking advantage of the arc's polarity and stretching it over a larger region. Such an approach is generally satisfactory for helping to extinguish the arc. Unfortunately, the Lorentz force produced by the supplemental magnets is also imparted onto the nearby contact plate during normal closed-circuit operation. Because this force (which by virtue of the orientation of the magnets relative to the current flowing through the contact plate is generally in a direction that could promote premature separation of the contact plate from the terminals) can interfere with the operation of the solenoid in general and the contact plate in specific, there remain ways in which solenoid operation may be improved.
Lithium-ion batteries are being used to provide partial (in the case of hybrid system) or total (in the case of all-electric systems) motive power for automotive applications. Significant levels of one or both voltage and current are needed to provide electrical power to a motor that in turn can provide propulsive power to a set of wheels. The high levels of electrical power employed by such battery systems could, if left uncorrected, lead to significant arcing during relay and related switch operation. In systems that employ some form of magnet-based arc-extinguishing feature (such as that discussed above), Lorentz forces induced by the magnetic fields are large enough to interfere with the plates and contacts of conventional relay and related switch assemblies by moving them to a different degree (or at a different time) than that for which they were designed. In particular, a downwardly-directed Lorentz force may overcome the bias established by the induced magnetic force on the solenoid's plunger, which in turn could cause inadvertent opening of the contacts and the formation of the very arcing that the supplemental magnets were included to avoid. This untimely contact plate opening may have deleterious effects on the operation of a battery-powered automotive propulsion system.
According to a first aspect of the invention, a switching assembly is disclosed. In the present context, a switching assembly corresponds to an arrangement of components that together allow for selective opening and closing of an electric circuit. As such, electric current passing through the switching circuit can be used to switch on or off a secondary electric circuit. In one example, such a secondary circuit could be a work-performing circuit configured to deliver electric current from one or more batteries (such as a lithium-ion battery) to an electric motor or other devices that can provide propulsive power for a car, truck or related vehicular or motive application. In particular form, the switching assembly of the present invention may be configured as a relay, switch or related circuit-opening and circuit-closing mechanism. The supplemental magnets used for a relay, switch or related solenoid-based device can be arranged in conjunction with the direction of electric current flow through the terminals and contact plate to reduce the magnitude of the Lorentz force produced by the interaction of the magnetic field and electric current while simultaneously reducing the arcing associated with de-energized contacts. This latter feature, with its reduction in the likelihood of a partially-open contact, promotes more stability in the current path from one terminal to the other. In other words, since the Lorentz force on the contact plate is minimized, the potential for the contact to be inadvertently disconnected from the terminals due to such force is decreased.
The rotary nature of the connection between the solenoid, contact plate and terminals ensures a faster disconnect; this in turn produces a faster elimination of the arcing produced during contact plate and terminal disconnect. Furthermore, the rotary nature of the connection between the solenoid and the contact plate promotes stronger joint potentials and a concomitant increase in device robustness for high-voltage contactors such as those encountered in lithium-ion battery systems. For example, unlike a linear solenoid (where the shaft interacts with the contact plate through a relatively small ball-shaped region, the rotary design may enable a large region of connection that promotes a more durable construction.
As stated above, one advantage of the design is that it prevents the Lorentz force from inadvertently opening the contact between the plate and the terminals during high current pulses. Such prevention is in evidence in situations where the supplemental (i.e., arc-extinguishing or arc-breaking) magnets are placed such that the current and magnetic field are in parallel as shown and described below. In theory, this parallel arrangement of the current flow and the magnetic field equates to complete elimination of the Lorentz force on the contact plate. Importantly, because this force on the contact plate has nothing to do with the arc-breaking effect of the Lorentz force on the area around the connection between the terminals and the contact plate, such arc-breaking force still exists because the current at that location is orthogonal rather than parallel with the magnetic field.
The rotary design according to the present invention may have variations as well. In one variation, the supplemental magnets may, instead of being placed such that the field produced between them is parallel to the flow of electric current through the connected terminals, be placed across the terminals such that the magnetic field is directed in an orthogonal direction to that of the current flowing through the terminals. Under linearly-actuated contact plate configurations (i.e., where the plunger from the solenoid translates under the force of an applied current through the solenoid's coil), such orthogonality between the magnetic field and the current flow through the terminals may promote the Lorentz force problems discussed above, as induced forces could lead to inadvertent opening of the contact between the plate and the terminals during normal operation. Under a variation of the present invention where such orthogonality does exist, a Lorentz force is generated, but nevertheless avoids the contact opening difficulties discussed above because the contact points are oriented in a direction not influenced by the induced force. Under this variation of the design, the supplemental magnet configuration may be left in place in a manner generally similar to that of previous designs, but because of the nature of the rotary contact and the contact plate, the Lorentz force (while not eliminated in the same manner as the design discussed in the previous paragraphs) becomes less likely to interfere with the operation during high current flows while maintaining the arc-extinguishing features of the supplemental magnets during contact opening and closing events.
Optionally, the magnets may be arranged such that a field produced by the plurality of magnets extends in a direction generally parallel to the direction of the electric current such that creation of the Lorentz force onto the contact plate is substantially inhibited. In another option, the field produced by the plurality of magnets extends in a direction generally perpendicular to the direction of the electric current such that the created Lorentz force acts upon the contact plate in the direction that does not substantially promote premature separation of the contact plate from the plurality of terminals. For example, the orientation of the switching assembly may be such that the Lorentz force produced during normal operation current flow through the closed circuit is imparted to the contact plate in a generally downward direction, while the direction of movement of the contact plate defines a generally circular path that is out of the plane of the created Lorentz force; in this way, the Lorentz force brings nothing to bear upon the plate that would either promote or inhibit its movement. In a more particular from, the direction that does not substantially promote premature separation of the contact plate from the plurality of terminals extends substantially along an axis formed by the rotational movement of the plunger.
Each of the above optional configurations has its own advantages. The first embodiment is effective in that by generally aligning the current and field, the generation of the Lorentz force is stunted. Thus, by aligning a magnetic field with a direction of current flow (or opposite of the current flow) in a contact plate disposed between magnets that are producing the field, the tendency of the Lorentz forces to interfere with the operation of a solenoid or other switch-activating mechanisms during normal (i.e., uninterrupted) current flow are precluded, while simultaneously preserving the Lorentz force used to promote arc extinguishing during a relay opening sequence (where the electric current travels in a direction normal to the field as well as the flow of current during routine closed-circuit operation). The second embodiment, even though oriented to leave the Lorentz force in place (by virtue of the generally orthogonal orientation of the current flow and the magnetic field), has more potential to be effectively packaged in a space-saving (i.e., square) configuration. As such, the configuration used will depend on the needs of the automotive or related system into which the particular configuration is placed.
According to another aspect of the invention, a vehicular propulsion system is disclosed. The system includes numerous batteries, a motive force and a switching assembly configured to permit selective delivery of an electric current from the batteries to the motive force. The switching assembly includes a solenoid substantially as described above.
In one optional form, the numerous batteries are lithium-ion batteries. In another preferred form, the motive force is an electric motor that is rotationally coupled to one or more vehicular wheels. A transmission may be used between the electric motor and the one or more wheels as a way to vary an amount of rotational power being delivered to the wheel or wheels by the electric motor. As discussed above, the field produced by the magnets may extend in a direction generally parallel to the direction of the electric current (in one form) or in a direction generally perpendicular to the direction of the electric current (in another form). In the first configuration, the creation of the Lorentz force on the contact plate is substantially non-existent, while in the second it acts upon the contact plate is in the direction that does not substantially promote premature separation of the contact plate from the terminals.
According to another aspect of the invention, a method of operating a switching assembly is disclosed. The method includes disposing a contact plate adjacent electrically-conductive terminals and operating a solenoid. When the solenoid is energized, it forces the contact plate into contact with the terminals to complete an electric circuit Likewise, when the solenoid is de-energized, it permits the contact plate to separate from the plurality of terminals to open (i.e., disable) the electric circuit. The switching assembly also includes numerous arc-extinguishing magnets disposed about a region defined at least in part by the contact points. In this way, it operates substantially as described in the previously-discussed aspects of the invention.
In one optional form, the switching assembly is made as at least a part of an automotive relay. The electric circuit forms a portion of a power circuit that may include numerous electric batteries and wiring configured to convey electric current from the electric batteries to a motive force through the relay. As discussed above, one example of such a motive force is an electric motor that is rotationally coupled to one or more vehicular wheels. In one preferred form, the batteries are lithium-ion batteries. As discussed above, the field produced by the plurality of magnets may be made to extend in a direction generally parallel to the direction of electric current flowing through the electric circuit such that creation of the Lorentz force onto the contact plate is substantially inhibited, or in a direction generally perpendicular to the direction of electric current flowing through the electric circuit. In either configuration, no action of a Lorentz force can promote premature separation of the contact plate from the plurality of terminals. In one form, the solenoid and the contact plate are affixed to one another such that movement of a solenoid component (such as a plunger that moves in response to a field set up in the solenoid's coil) forces the contact plate toward or away from the terminals, depending on whether the solenoid id being energized or de-energized.
The following detailed description of specific embodiments can be best understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:
As discussed above, arcing at the opening contactor portion of a linear switching assembly (such as a relay) can have a deleterious effect on the assembly and adjacent components. Depending on the configuration of the switching assembly, as well as the voltage and current flowing through the circuit, such arcing occurs very promptly, often on the order of a few hundred microseconds Likewise, prior art approaches have included placing magnets adjacent a contactor portion that includes the contact plates and terminals used to establish a high voltage contactor. Referring first to
Referring next to
By the construction of the relay 10 from
{right arrow over (F)}={right arrow over (I)}×{right arrow over (B)},
the resulting Lorentz force is oriented along a direction that is substantially orthogonal to the plane of cooperation between the current {right arrow over (I)} and magnetic field {right arrow over (B)}. This orthogonal interaction between the magnetic field formed by magnets 36 and 38 and the current flow through terminals 32 (shown presently as rightmost terminal 32A and leftmost terminal 32B) produces two different imparted forces, depending on the direction of the current flow {right arrow over (I)}.
Referring next to
As discussed above (and referring with particularity to
While helpful in extinguishing any arcs that may form upon contact opening, the magnets 36 and 38 also generate Lorentz force on the linearly-reciprocating contact plate 34. This is shown in
The present inventors have determined that a configuration where there is linear coupling between the terminals and the contact plate should be avoided. Referring next to
Referring with particularity to
While certain representative embodiments and details have been shown for purposes of illustrating the invention, it will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention, which is defined in the appended claims.
Hsu, Chih-Cheng, Namou, Andrew J.
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