Electrical transmission or interconnection systems – Vehicle mounted systems – Automobile
Reexamination Certificate
1999-08-19
2001-12-25
Fleming, Fritz (Department: 2836)
Electrical transmission or interconnection systems
Vehicle mounted systems
Automobile
C307S121000, C307S010700
Reexamination Certificate
active
06333568
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
This application claims the priority of German patent document 19837 585.9, filed Aug. 19, 1999, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a switching arrangement and to a process for disconnecting an electric energy source of a vehicle, in which two switching elements (through which the consuming devices of the vehicle are supplied with electric energy) are mounted near the electric energy source. In the event of a fault, both switching elements are opened by means of an all-pole switch off.
The switching arrangement according to the invention is particularly applicable to vehicles driven by an electric motor, such as electric and hybrid vehicles having an accumulator (traction battery) or a fuel cell as an electric energy source.
A switching arrangement of this generic type is disclosed, for example, in International Patent Document WO 95/01887, which performs an all-pole separation from an accumulator arrangement and from a generator in the event of a fault (that is, a recognized accident), as well as a switch-off during normal operation.
An all-pole switch-off of this type is also disclosed in Japanese Patent Document JP-A-07059202.
Contrary to these prior art arrangements, it is an object of the present invention to limit the expenditures for components, while maintaining safety-related switch-off functions.
This and other objects and advantages are achieved by the switching arrangement according to the invention, in which one of the two switching elements is used as an operating switch for switching off the electric energy source in normal operation. As a result, only one of the two switching elements needs be designed to perform the switch-off in normal operation (that is, to be operated more frequently, without destroying it in the process). It is thus important that the switching operation via this switching element does not require very high expenditures associated with such more frequent operation. The other switching element, however, will be operated only in the event of an accident or an emergency switch-off, which of course occurs less frequently; therefore, it can be accepted in the case of this switching element that the switching operation itself requires higher expenditures, or possibly that wear occurs because of burning of the electrodes or contacts.
U.S. Pat. No. 3,842,228, discloses a switching element in which a plate made of an electrically non-conducting material is pushed between the two contacts of an electric switch in order to separate the electric contacts, one of which is spring biased. The insertion of the plate separates the latter electric contact from the other contact against the force of the spring. In this manner, a spark discharge which occurs during the separation of the switch contacts (particularly at high electric voltages), is cut off. Thus, this construction of the switching element is also characterized as “extinguishing the spark discharge by a guillotine”. The operation of this switching element results in comparatively high expenditures.
One embodiment of the switching arrangement according to the invention incorporates such a switching element, which is suitable for switching large currents (that is, a higher capacity switch), so that it can be used as an emergency cutout switch in the switching arrangement, as explained herein.
For switching large currents, German Patent Document DE 44 15 794 A1 discloses a switching arrangement which is connected in series with the consuming device, as well as a control element for controlling (or automatically controlling) the power consumption of the electric switch. During a switch-off one switch in the switching arrangement is opened only when the load current has been adjusted downward by the control element. Similarly, the latter switch is closed before the current consumption of the consuming device is “driven up” by the control element. As a result, the burden on the switch is relieved in that the currents to be switched thereby are limited.
In such a control element, the design of the operating switch can be correspondingly simple. A contactor can be used whose mechanical loading is limited in the normal operation.
In the above-mentioned embodiment of the switching arrangement according to the invention, the other of the two switching elements forms an emergency cutout switch, in which, during separation of its contacts, an element made of a non-conducting material is pushed between the two contacts. This element can be moved back again so that electric connection of the two contacts can be reestablished. Even though switching by means of this emergency cutout switch requires comparatively high expenditures, it is advantageous (in contrast, for example, to the use of a fusible cutout or a pyrotechnic fuse) that the emergency cutout switch can be reused after a one-time response (that is, an opening), and that it can also trigger when the accumulator arrangement is virtually empty.
This embodiment can safely switch larger currents, which is important particularly in the event of a fault. It will then therefore not be necessary to design both switches for the permanent switching of large currents. A contactor can be provided as the operating switch which, in the event of a fault, is opened, for example, only after the operation of the emergency cutout switch. However, since, on the other hand, the emergency cutout switch is rarely operated, it can be accepted that this switching operation requires slightly higher expenditures.
In another embodiment of the invention, the emergency cutout switch is opened during a switch-off event in normal operation, when the operating current is larger than a first threshold value after a defined first time period t
1
following the initiation of the switch-off operation, or when the operating switch does not open at all.
By opening the emergency cutout switch, the accumulator arrangement can be switched off when the operating switch fails to open, or when the downward control of the load current before the switch-off by the operating switch does not work.
The latter two fault events can be recognized by corresponding current measurements. That is, a first current measurement occurs at time T
1
, and a fault during downward control is recognized if the operating current is then larger than the first threshold value, for example, 20 A. Thereafter, a second current measurement is made after the operating switch has been triggered for the opening, and a fault is recognized if the operating current is larger than 0.
The first threshold value may be in the range of tens of amperes (for example, to 20 A).
In this case, the larger load current is advantageously switched off by the emergency cutout switch after the expiration of the time period t
1
, if the emergency cutout switch is designed to switch off larger currents, and therefore also to switch off the load current existing in this operating condition.
In another embodiment of the invention, in a vehicle driven by an electric motor in normal operation, the accumulator arrangement is switched off by first controlling the driving current of the electric motor downward, and then opening the operating switch when the driving current has been decreased. As a result, the operating currents which must be switched by the operating switch are advantageously minimized, and the operating switch is subjected to a lower mechanical load (i.e., a lower capacity switch). This is particularly advantageous in the case of the comparatively large operating currents of a vehicle driven by an electric motor.
In yet another embodiment of the invention, both the emergency cutout switch and the operating switch are opened if the operating current exceeds a defined second threshold value, or if a sensor system detects an accident during which the air bag was triggered.
Because of its suitability for switching large currents, it is advantageous to switch the emergency cutout switch earlier than the operating switch. It is also
Bitsche Otmar
Streit Robert
Crowell & Moring LLP
Daimler-Chrysler AG
Fleming Fritz
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