Patent Application
20090250302
The present invention relates to a vehicle circuit design and method for providing a fast turn-off and fast turn-on of an inductive load.
In all wheel drive (AWD) and four wheel drive systems in motorized vehicles, the front and rear axles can be coupled via an electromagnetic clutch which enable all of the vehicle's wheels to rotate in relation to one another. These vehicles can also be equipped with driver assistance systems, such as, stability control, traction control, and anti-lock brake systems (ABS). When a stability event occurs, and the vehicle's stability control, traction control, and/or ABS system is in use, the wheels can be decoupled from each other so that they can rotate and react independent of each other. The effectiveness of the driver assistance systems depends on the time it takes to decouple the vehicle's wheels; front-to-rear and side-to-side. If the vehicle's wheels are not decoupled quickly then activation of the vehicle's driver assistance systems will be delayed.
The response time of the stability control system is dependent on the time it takes to decay the current in a circuit which creates the electromagnetic field. In addition, the torque in an electromagnetic clutch system is dependent on the amount of current flowing through a coil which is used to create the electromagnetic field. The rate at which the electromagnetic field is created is directly proportional to the rate at which the current builds in the system. Likewise, the rate at which the magnetic field collapses in a system is proportional to the rate at which the current decays in the coil. Thus, the rate at which the current decays in a coil is proportional to the resistance in the circuit. The lower the resistance in the circuit the faster the circuit decays, causing the torque of the electromagnetic clutch to decay at a rate that is proportional to the current decay of the clutch coil.
Therefore, it is desirable to develop a circuit design where the current in a coil dissipates quickly in order to quickly decay an electromagnetic field, and the current passing through the coil creates an electromagnetic field quickly.
The present invention relates to a fast turn-off and fast turn-on circuit providing at least one power source, at least one switching device, a coil, and at least a first voltage control device. The at least one switching device is connected to the at least one power source for selectively connecting the at least one power source to portions of the circuit. An electrical current from the at least one power source charges the coil and creates an electromagnetic field when the at least one switching device is in a closed position and connects the at least one power source with the coil. The first voltage control device is connected to the coil, and the first voltage control device limits a voltage in the circuit when the electromagnetic field decays.
Another embodiment of the present invention relates to a method for a fast turn-off and fast turn-on circuit having the steps of first providing a controller interfaced with a plurality of switching devices, where the plurality of switching devices are used for selectively connecting at least one power source with other portions of the circuit. Providing a coil connected to the plurality of switching devices, where the coil produces an electromagnetic field when at least one of the pluralities of switching devices is closed and the coil is connected at least one power source, such that an electrical current passes through the coil. Determining if the electromagnetic field needs to be decayed. Commanding at least one of the plurality of switching devices to open by a controller if it is determined that the electromagnetic field needs to be decayed. Opening at least one of the plurality of switching devices in order for the electrical current to dissipate from the coil and decay the electromagnetic field. Providing at least a first voltage control device connected to the coil, where the first voltage control device is connected to the coil and limits a voltage in the circuit when the electromagnetic field is decaying.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
Referring to
In an embodiment, the first power source 12 can be in series with the coil 16, and a second power source 20 can be in parallel with the coil 16. Typically, both power sources 12, 20 are the same type of power source which have the same voltage, but it is within the scope of the present invention that power source 12 can have a different voltage than power source 20.
Typically, the first switching device 14 is connected to the power source 12, and a second switching device 22 is connected to the second power source 20. Thus, when the switching devices 14, 22 are closed, the power sources 12, 20, respectively, are connected to the coil 16 so that an electrical current can pass through the coil 16. The switching devices 14, 22 can be the same type of switching device, such as but not limited to, a MOSFET transistor or the like. When the switching devices 14, 22 are the same type of device they are capable of opening and closing substantially simultaneously, if desired. However, it should be appreciated that the switching devices 14, 22 can be different types of devices, so long as the switching devices 14, 22 can open and close at substantially the same rate.
In one embodiment, the first voltage control device 18 is a voltage clamping device. By way of explanation and not limitation, the first voltage control device 18 can be a zener diode or the like. Thus, the zener diode or first voltage control device 18 can be tuned to a predetermined voltage in order to control the voltage or a voltage spike in the circuit, such that the first voltage control device 18 will clamp the voltage in the circuit 10 so that the voltage does not exceed a predetermined voltage limit.
In an alternate embodiment, a second voltage control device 24 (shown in phantom) can be connected between the first power supply 12 and the first switching device 14. The second voltage control device 24 can be used for increasing the voltage in the circuit 10, which results in a larger electrical current in the circuit 10, when creating the electromagnetic field by passing current through the coil 16. The second voltage control device 24 can be by way of example but not limitation, a voltage multiplier or the like, where the voltage from the first power supply 12 is multiplied by the second voltage control device 24 in order to create a larger current in the circuit 10. The second voltage control device 24 allows the circuit 10 to be a fast turn-on circuit in order to quickly create the electromagnetic field as current passes through the coil 16 due to the larger current in the circuit 10 as a result of the voltage from the first power supply 12 being multiplied
The circuit 10 can also have a third voltage control device 26 that is in parallel with the coil 16. Typically, the third voltage control device 26 creates a loop with the coil 16 when at least the second power source 20 is connected to the coil 16. Thus, an electrical current is continuously passing through the coil 16 due to the third voltage control device 26 being in parallel with the coil 16 which creates the electromagnetic field. An example of the third voltage control device 26 is, but not limited to, a flyback diode or the like. The third voltage control device 26 can also clamp the voltage of the circuit 10 at a predetermined voltage such that the voltage in the circuit 10 does not exceed a predetermined voltage limit.
A controller 28 can be connected to either or both the first switching device 14 and second switching device 22. The controller 28 is used to command actuation of switching devices 14, 22 in order to open and close the circuit 10, which either allows current to pass through the coil 16 or prevent an electrical current from passing through the coil 16. The controller 28 can be, but is not limited to, an engine control unit, a controller that is interfaced with the engine control unit, or the like. Thus, as described below, the controller commands at least one of the switching devices 14, 22 to open or close based upon operating conditions of a motorized vehicle (not shown).
In an embodiment, predetermined components of the circuit 10 can be included in an interactive torque management control unit generally indicated at 27 (shown in phantom). The interactive torque management control unit 27 can include, by way of example but not limitation, the power sources 12, 20, the switching devices 14, 22, the second voltage control device 24, the control unit 28, or a combination thereof. Additionally, predetermined components of the circuit 10 can be included in an interactive torque management clutch unit generally indicated at 29. The interactive torque management clutch unit 29 can include, by way of example but not limitation, the coil 16, the ground connection 17, the first voltage control device 18, the third voltage control device 26, or a combination thereof. Thus, the interactive torque management control unit 27 and the interactive torque management clutch unit 29 can be interfaced with one another.
In reference to
At decision box 32, the electromagnetic clutch is activated, such that an electrical current is passing from the power supplies 12, 22 through the coil 16. At decision box 34, a situation arises where the electromagnetic clutch needs to be deactivated. An example of the situation where it is desirable to deactivate the electromagnetic clutch is, but not limited to, when a driver assistance system is activated and the motorized vehicle's stability control system, traction control system and/or the vehicle's anti-lock brake system is in use. At this time it is desirable for the wheels of the motorized vehicle to decouple and rotate independently of each other, such that the armature and rotor are no longer rotating with respect to one another.
When the situation arises where the electromagnetic clutch needs to be deactivated, as in decision box 34, the control unit 24 commands at least one of the switching devices 14, 22 to open, at decision box 36. At decision box 38, when at least one of the switching devices 14, 22 are opened, the electrical current no longer passes from the power supply 12, 22 depending upon which switching device 14, 22 was open, to the coil 16.
At decision box 40, when an electrical current no longer passes from one of the power supplies 12, 22 to the coil 16, the polarity of the coil 16 reverses so that the electrical current is attracted to a ground connection 17. When the polarity of the coil 16 changes, the current flowing through the coil 16 begins to flow in the opposite direction so the current no longer passes continuously through the loop with the third voltage control device 28 and is instead attracted and flows to the ground connection 17. At decision box 42, the current dissipates in the coil 16 and the electromagnetic field decays, since there is no longer an electrical current passing from the power supplies 12, 22 to the coil 16. At decision box 44, the first voltage control device 18 limits a voltage spike in the circuit 10 which is caused by the polarity of the coil 16 reversing. Thus, the first voltage control device 18 clamps the voltage of the circuit 10 at a predetermined voltage limit. If the voltage spike and/or the current in the circuit 10 are not controlled it could cause severe damage to the circuit 10 and other components in the motorized vehicle due to the other components not being able to withstand a high voltage and/or high current.
In reference to
At decision box 52, when the situation arises for the electromagnetic clutch to be activated, the control unit 28 commands at least one of the switching devices 14, 22 to close. At decision box 54, an electrical current passes from at least one power source 12, 20 to the coil 16 in order for the electrical current to pass through the coil 16 and create an electromagnetic field. At decision box 56, when the second voltage control device 24 is used, the voltage from the first power supply 12 is multiplied in order to increase the voltage in the circuit 10 which results in an increase of current flowing through the circuit 10 and passing through the coil 16 that creates a stronger electromagnetic field and/or the larger current more quickly creates the electromagnetic field when compared to a circuit that does not include the second voltage control device 24.
At decision box 58, the third voltage control device 26 forms a continuous loop with the coil 16 in order to continuously pass the electrical current through the coil 16 to form the electromagnetic field. The third voltage control device 26 is used when the control unit 28 commands the second switching device 22 to close, which connects the second power source 20 with the coil 16.
With respect to
The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US2006/033272 | 8/25/2006 | WO | 00 | 6/15/2009 |
| Number | Date | Country | |
|---|---|---|---|
| 60711780 | Aug 2005 | US |
