Abstract:
A charging apparatus ( 22 ) for a motor vehicle ( 10 ) has a plurality of plug connection members ( 12, 14, 16 ) to connect the charging apparatus ( 22 ) to at least one external electrical energy source ( 18, 20 ), a plurality of temperature measuring elements ( 26, 28, 30 ) are associated respectively with the plug connection members ( 12, 14, 16 ) to detect a temperature of the plug connection members ( 12, 14, 16 ), and an evaluation unit ( 32 ) electrically connected to the temperature measuring elements ( 26, 28, 30 ) to evaluate the detected temperature of the temperature measuring elements ( 26, 28, 30 ). The temperature measuring elements ( 26, 28, 30 ) are connected to the evaluation unit ( 32 ) by a common first connecting line ( 42 ), and connectable electrically to the control unit ( 32 ) individually by a second connecting line ( 36, 38, 40 ) in each case.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority under 35 USC 119 to German Patent Appl. No. 10 2015 112 349.5 filed on Jul. 29, 2015, the entire disclosure of which is incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a charging apparatus for a motor vehicle, comprising a plurality of plug connection members to connect the charging apparatus to at least one external electrical energy source, a plurality of temperature measuring elements that are associated respectively with the plug connection members to detect a temperature of the plug connection members, and an evaluation unit that is connected electrically to the temperature measuring elements to evaluate the detected temperature of the temperature measuring elements. 
         [0004]    The invention further relates to a motor vehicle comprising an electrical machine for providing drive power, an electrical energy store for storing electrical energy for the electrical drive machine, and a charging apparatus for charging the electrical energy store. 
         [0005]    Finally, the invention relates to a method for detecting a temperature of a plurality of plug connection members of a charging apparatus of a motor vehicle. 
         [0006]    2. Related Art 
         [0007]    Electrically driven motor vehicles usually have charging sockets to connect the motor vehicle to external charging stations and to charge an internal electrical energy store. During a charging process, large quantities of electrical energy usually are transmitted via the charging sockets, and therefore the charging sockets can heat up during a charging process. To protect the charging sockets against excessive temperatures and temperature-related damage, the charging sockets usually have temperature sensors that detect the temperature of the charging sockets and accordingly transmit the temperature to a central control unit for controlling the charging process. The control unit may, if necessary, abort the charging process if the temperature of the charging sockets exceeds a threshold value. A charging apparatus with temperature-monitored charging sockets is known from CN 103138316 A for example. 
         [0008]    One disadvantage of this is that each individual temperature sensor is separately electrically connected to an operational amplifier by means of two electrical lines, and therefore the outlay on cabling for the temperature sensors in the motor vehicle is high. 
         [0009]    An object of the invention is to provide a charging apparatus for a motor vehicle, and in particular a charging apparatus with temperature measuring elements that can be connected electrically to an evaluation unit with a low level of technical outlay. 
       SUMMARY 
       [0010]    The invention relates to a charging apparatus with temperature measuring elements connected to an evaluation unit by a common first connecting line. Additionally, the temperature measuring elements are connected electrically or can be connected electrically to the control unit individually by a second connecting line in each case. The charging apparatus may be used for charging the electrical energy store of motor vehicle. The method of the invention may include are individually sequentially electrically connecting the temperature measuring elements to the evaluation unit for separately detecting the respective temperature of the plug connectors. 
         [0011]    The outlay on cabling is reduced considerably by connecting the temperature measuring elements to the evaluation unit by a common first connecting line because the temperature measuring elements have only an individual electrical line for making electrical contact. Furthermore, the second electrical contact connects the temperature measuring elements to the evaluation unit by the common electrical connection line. 
         [0012]    The individually electrically connection of the temperature measuring elements sequentially to the evaluation unit in accordance with the method of the invention enables an individual evaluation unit to evaluate the measurement signals from plural temperature measuring elements, thereby further reducing the technical outlay. 
         [0013]    Each of the two connecting lines can be connected to the evaluation unit by a controllable switch. As a result, the temperature measuring elements can be connected individually to the evaluation unit, and therefore an individual evaluation unit in the form of, for example, an operational amplifier can be used for all temperature measuring elements, and therefore the technical outlay is reduced further. 
         [0014]    The controllable switches may be connected to a control unit to open and close the controllable switches and accordingly to connect the temperature measuring elements selectively to the evaluation unit. As a result, an offset current on the common first connecting line can be avoided, and therefore precise measurement of the temperature is possible. 
         [0015]    The control unit may be designed to connect a temperature measuring element to the evaluation unit. The temperature measuring element may be associated with a plug connection member that is connected to an external energy source. As a result, the temperature of the respectively used plug connection member can be detected, and an excess temperature by the plug connection member during charging can be avoided. 
         [0016]    The temperature measuring elements can be connected to an electrical connection of the evaluation unit by one of the controllable switches in each case. As a result, an individual evaluation unit can be used for evaluating the temperature of various temperature measuring elements, and therefore the technical outlay is reduced further. 
         [0017]    The evaluation unit may be designed to calculate an electrical charging power that is transmittedvia the plug connection member based on the detected temperature of the plug connection member used. As a result, the electrical charging power can be limited and damage to the electrical components can be avoided. 
         [0018]    The temperature measuring elements may be in the form of temperature measuring resistors. As a result, the temperature of the plug connection members can be detected precisely with a low level of technical outlay. 
         [0019]    The evaluation unit may be an operational amplifier. As a result, the detected temperature signal from the temperature measuring elements can be evaluated precisely. 
         [0020]    The plug connection members may be charging sockets of the motor vehicle. Thus, reliable and simple connection of the charging apparatus to an external electrical energy source, such as a charging station for example. 
         [0021]    Overall, the charging apparatus enables the outlay on cabling for the temperature measuring elements to be reduced considerably due to the common first connecting line and the individual second connecting line because the temperature measuring elements each have only one individual feed line and are connected or can be connected to the evaluation unit by a common return line. 
         [0022]    The features mentioned above and those still to be described below can be used in the respectively specified combination and also in other combinations or on their own without departing from the scope of the invention. 
         [0023]    Exemplary embodiments of the invention are illustrated in the drawings and will be explained in greater detail in the following description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]      FIG. 1  is a schematic illustration of a motor vehicle comprising a charging apparatus for charging an electrical energy store. 
           [0025]      FIG. 2  is a schematic illustration of a circuit for electrically connecting various temperature measuring elements to an evaluation unit. 
           [0026]      FIG. 3  shows a further embodiment of the circuit for connecting the temperature measuring elements to an evaluation unit. 
           [0027]      FIG. 4  shows a flowchart of a method for determining a temperature of a used charging socket of a motor vehicle. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]      FIG. 1  shows a schematic plan view of a motor vehicle which is designated  10  in general. The motor vehicle  10  can be in the form of a purely electrically driven vehicle or a motor vehicle with a hybrid drive and has three electrical charging sockets  12 ,  14 ,  16  to connect connect the motor vehicle  10  electrically to one or a plurality of electrical energy sources  18 ,  20  and accordingly to supply electrical energy to electrical loads and/or electrical energy stores. 
         [0029]    The charging sockets  12 ,  14 ,  16  are connected electrically to a charging unit  22 . The charging unit  22  is connected electrically to an electrical energy store  24  of the motor vehicle  10  to charge the electrical energy store  24 . 
         [0030]    The charging unit  22  functions to forward a high electrical voltage from the external electrical energy sources  18 ,  20  to the electrical energy store  24  and, if necessary, to convert the voltage into a charging voltage. 
         [0031]    A respective temperature sensor  26 ,  28 ,  30  is associated with the charging sockets  12 ,  14 ,  16  to detect the temperature of the respective charging socket  12 ,  14 ,  16  to avoid excess temperatures during the transmission of electrical energy by means of the charging sockets  12 ,  14 ,  16 . The temperature sensors  26 ,  28 ,  30  generally are connected electrically to a control unit  32  to evaluate the temperature signals from the temperature sensors  26 ,  28 ,  30  and accordingly to control the charging process. 
         [0032]    The temperature sensors  26 ,  28 ,  30  are connected generally to the control unit  32  by an individual electrical line in each case. Thus, all of the temperature sensors  26 ,  28 ,  30  are connected to the control unit  32  by a common return line, as is explained in greater detail below. Therefore, the technical outlay for electrically connecting the temperature sensors  26 ,  28 ,  30  to the control unit  32  can be reduced. 
         [0033]      FIG. 2  shows a first embodiment of an electrical circuit of the control unit  32  and also of the temperature sensors  26 ,  28 ,  30  that are connected to the control unit  32 . 
         [0034]    The temperature sensors  26 ,  28 ,  30  are temperature measuring resistors in this embodiment. The control unit  32  has three operational amplifiers  34 ,  36 ,  38 . A first electrical connection of the operational amplifiers  34 ,  36 ,  38  is connected to the temperature sensors  26 ,  28 ,  30  by an individual electrical line  36 ,  38 ,  40  in each case. The temperature sensors  26 ,  28 ,  30  are connected to a second electrical connection of the operational amplifiers  34 ,  36 ,  38  by a common electrical line  42 . This electrical contact-connection of the temperature sensors  26 ,  28 ,  30  reduces the technical outlay on cabling for the temperature sensors  26 ,  28 ,  30  since the common electrical line  42  is used as a return line for connecting the temperature sensors  26 ,  28 ,  30  to the operational amplifiers  34 ,  36 ,  38 . 
         [0035]      FIG. 3  shows a further embodiment of a circuit of the control unit  32  and also of the temperature sensors  26 ,  28 ,  30  that are connected to the control unit. 
         [0036]    In this embodiment, the control unit  32  has only one operational amplifier  44 , and it is possible to connect the first input connection of the operational amplifier to the temperature sensors  26 ,  28 ,  30  by the individual electrical lines  36 ,  38 ,  40 . The electrical lines  36 ,  38 ,  40  each have a controllable switch  46 ,  48 ,  50  for individually connecting the temperature sensors  26 ,  28 ,  30  electrically to the first input connection of the operational amplifier  44 . The temperature sensors  26 ,  28 ,  30  are connected to a second input connection of the operational amplifier  44  by the common electrical line  42 . The control unit  32  further has a controller  52  that is connected to the controllable switches  46 ,  48 ,  50  to open and close the controllable switches  46 ,  48 ,  50  sequentially and to connect the temperature sensors  26 ,  28 ,  30  electrically to the operational amplifier  44  individually and in succession. The controller  52  preferably is a microcontroller. 
         [0037]    The individual connection of the temperature sensors  26 ,  28 ,  30  by the controllable switches  46 ,  48 ,  50  enables the temperature measurement values from the temperature sensors  26 ,  28 ,  30  to be read out and evaluated with a time delay by an individual operational amplifier  44 , and therefore the technical outlay on the control unit  32  is reduced. 
         [0038]    Furthermore, the controllable switches  46 ,  48 ,  50  can be used to prevent an offset current on the common electrical line  42 . As a result, the measurement signal from the temperature sensors  26 ,  28 ,  30  can be detected precisely and is not influenced by the offset current. 
         [0039]    Owing to a sequential delayed electrical connection of in each case one temperature sensor  26 ,  28 ,  30  to the operational amplifier  44 , all of the temperature measurement signals can be read out in succession, and therefore the temperature of the charging sockets  12 ,  14 ,  16  can be detected in succession and at regular intervals and reliable temperature measurement of the charging sockets  12 ,  14 ,  16  is possible. If only one of the charging sockets  12 ,  14 ,  16  is connected electrically to an external electrical energy source  18 ,  20  for charging the electrical energy store  24 , in each case only the correspondingly associated temperature sensor  26 ,  28 ,  30  can be connected to the operational amplifier  44 , and therefore only the used charging socket is monitored in this case. 
         [0040]      FIG. 4  schematically shows a schematic flow chart for explaining the process of reading out a measurement value from the temperature sensors  26 ,  28 ,  30 . The method is designated  60  in general. The method begins with step  62 . In step  64 , a self-test by the controllable switches  46 ,  48 ,  50  is first carried out. In step  66 , the control unit  32  checks which of the charging sockets  12 ,  14 ,  16  for charging the electrical energy store  24  is connected. In step  68 , a check is made to determine whether a first charging socket  12  is in operation and, if the first charging socket  12  is in operation, the controllable switch  46  is driven in step  70 , and the measurement value from the temperature sensor  26  is read out in step  72 . 
         [0041]    If the first charging socket  12  is not in operation, a check is made in step  74  to determine whether the second charging socket  14  is in operation and, if the second charging socket  14  is in operation, the controllable switch  48  is driven, that is closed, in step  76 , and the measurement value from the temperature sensor  28  is read out in step  78 . 
         [0042]    If it is determined in step  74  that the second charging socket  14  is not in operation, a check is made in step  80  to determine whether the third charging socket  16  is in operation and, if the third charging socket  16  is in operation, the controllable switch  50  is closed in step  82 , and the temperature measurement value from the temperature sensor  30  is read out in step  84 . If none of the charging sockets  12 ,  14 ,  16  is connected, the method  60  returns to step  66 , as is shown by the feedback  86 . This check can be made at regular intervals, for example once every second. 
         [0043]    The controllable switches  46 ,  48 ,  50  can be closed in a targeted manner by the method to read a specific one of the temperature sensors  26 ,  28 ,  30  and to measure the temperature of the charging socket  12 ,  14 ,  16  that is accordingly in operation.