Charging plug, charging cable and charging method for an electric vehicle

This application claims priority under 35 USC 119 to German Patent Appl. No. 10 2014 111 334.9 filed on Aug. 8, 2014, the entire disclosure of which is incorporated herein by reference.

1. Field of the Invention.

The invention relates to a charging plug for an electric vehicle, a charging cable having such a plug, and a method for charging an electric vehicle.

2. Description of the Related Art.

Vehicles with a battery that can be charged by a public power supply system are known in the field of electromobility. A large number of power supply systems, charging plugs and charging cables are in use worldwide for this purpose and satisfy an extremely wide variety of quality standards and are subject to ageing influences. An extremely wide variety of demands also are made on the use of this infrastructure.

U.S. Pat. Nos. 6,905,362, 8,729,856 and 8,573,994 have proposed equipping charging plugs with temperature sensors to be able to reduce or disconnect the charging current as required to avoid overloading the infrastructure components during charging.

U.S. Pat. No. 8,573,994 and DE 20 2008 009 929 U1 disclose attempts to use a Hall sensor to check the correct fitting of the charging plug in the coupling or bushing. DE 20 2008 009 929 U1 discloses a charging plug apparatus for motor vehicles having an electric drive comprising a plug part, a socket part and a Hall sensor which, when the charging plug apparatus is connected, delivers a different voltage than when the plug apparatus is not connected.

The invention relates to a method and apparatus for detecting the temperature profile directly between the charging bushing or coupling and the charging plug during the charging process. Imminent overheating of the plug connection in the event of improper use of the charging cable can therefore be identified in good time and avoided by disconnecting the charging plug or reducing the current.

The apparatus may comprise a printed circuit board that faces the charging bushing. Temperature sensors and a Hall sensor carried by the printed circuit board can be provided for checking the plug connection. Therefore, the electrical supply system connection required for charging can be checked for fundamental compatibility of the two plug parts even before the actual charging process. A variety of elements, for example NTC elements, PTC elements or thermistors are suitable as temperature sensors.

Thermally conductive contact areas may be provided on the printed circuit board and may be connected directly to the contact pins for coupling the temperature sensors to the contact pins. Therefore, the printed circuit board simultaneously functions as a mounting platform, connection, wiring and contact point for the temperature and Hall sensors. In addition, further components can be mounted on the printed circuit board for connecting the charging plug in a protected manner.

The charging plug may be connected by electrical signal lines to a so-called in-cable control box (in-cable control and protective device). The in-cable control box can use the common signal lines to activate both the Hall sensor and the temperature sensors.

A further temperature sensor may be set away from the contact pins for detecting an environment-related temperature influence on the charging plug. The proposed geometric arrangement may be on a protective conductor contact part of the charging plug. The contact part may be connected electrically to one of the contact pins and allows, in combination with the sensors that are on the power contact pins, measurement and evaluation of the temperature from the inoperative state and environmental influences, such as sun, or ambient temperature in comparison to the temperature profile to be carried out during a charging process.

A prespecified electrical resistance of at least one of the signal lines for encoding a thermal behavior of the charging plug allows an extremely wide variety of plug and housing variants to be used. In each case different thermal behavior of the variants and corresponding characteristic curves can be stored in the charging electronics and assigned to allow power reduction processes or disconnection processes derived therefrom to be initiated.

One exemplary embodiment of the invention is illustrated in the drawings and will be described in detail in the text that follows.

FIG. 1 shows a charging plug provided on a charging cable according to the invention, with a plan view of the printed circuit board of the charging plug.

FIG. 2 is a longitudinal section through the charging plug of FIG. 1 in conjunction with a corresponding coupling or supply system plug socket.

FIG. 3 is a longitudinal section that corresponds to FIG. 2 , highlighting the temperature sensors of the charging plug.

FIG. 4 is a simplified circuit diagram of the charging plug of FIG. 3 together with the charging cable and also the in-cable control box of the charging cable.

FIG. 5 shows an optimum characteristic curve of the negative temperature coefficient or NTC resistors which form the basis of the temperature sensors.

FIG. 1 is a front view of a charging plug 10 according to the invention. The charging plug 10 has contact pins L 1 , N, PE for establishing a plug connection to the corresponding coupling 12 and also has temperature sensors NTC 1 , NTC 2 , NTC 3 that are coupled thermally to the contact pins L 1 , N, PE. The temperature sensors NTC 1 , NTC 2 , NTC 3 are used by an in-cable control box ICCPD, not illustrated in FIG. 1 , during the charging process to detect the temperature profile between the charging plug 10 and the coupling, not illustrated in FIG. 1 , of said charging plug.

The printed circuit board LP faces the viewer of FIG. 1 and functions as a mounting platform for the temperature sensors NTC 1 , NTC 2 , NTC 3 and at the same time carries a Hall sensor 14 for checking the plug connection between the charging plug 10 and the coupling. Thermally conductive contact areas 16 of the printed circuit board LP fully enclose the contact pins L 1 , N, PE and, by virtue of their direct connection to the contact pins L 1 , N, PE, ensure that the contact pins are coupled thermally to the temperature sensors NTC 1 , NTC 2 , NTC 3 .

Further components (not illustrated) can be mounted on the printed circuit board LP to realize connection of the plug connector 10 in a protected manner.

The longitudinal section of FIG. 2 illustrates a relative arrangement of the Hall sensor 14 of the charging plug 10 in relation to a corresponding magnet 24 beneath the mating surface of the coupling 12 or supply system plug socket when the contact pins L 1 , N, PE of the charging plug 10 engage in corresponding contact openings in the coupling 12 . FIG. 2 also shows the alternative position of the temperature sensor NTC 1 that is set away from the contact pins L 1 , N, PE in the housing interior of the charging plug 10 and can be arranged on a protective conductor contact part 22 , which is connected to the corresponding contact pin PE.

In contrast, FIG. 3 highlights, using the example of temperature sensor NTC 3 , the specific design of the temperature sensors NTC 1 , NTC 2 , NTC 3 that, as negative temperature coefficient resistors or NTC resistors, comprise a so-called NTC pill 26 together with corresponding contact lugs 28 that are packed into a thermally conductive and electrically insulating housing made of glass, ceramic or similar material and are connected in an interlocking manner to the associated contact pin L 1 , N, PE by means of the housing. This together with FIG. 5 produces a particularly suitable characteristic curve 30 that shows the specific resistance R of each temperature sensor NTC 1 , NTC 2 , NTC 3 as a function of the temperature T at the corresponding contact pin L 1 , N, PE.

The interaction between the charging plug 10 of FIG. 3 and the charging cable 36 (illustrated schematically) that encloses the charging plug, and the in-cable control box ICCPD of the charging cable is shown in FIG. 4 . To this end, the in-cable control box ICCPD, which controls the charging process, is connected to the charging plug 10 by a six-pole signal ring 34 using suitable electrical signal lines 18 that also activate the Hall sensor 14 and the temperature sensors NTC 1 , NTC 2 , NTC 3 . Two of said signal lines 18 have prespecified electrical resistances R 1 , R 2 for encoding the thermal behavior of the charging plug 10 , the values of the electrical resistances being correlated with the memory of a microcontroller 32 of the in-cable control box ICCPD and this therefore permitting conclusions to be drawn about the thermal behavior of the charging plug 10 .