Device for testing a contact force of an electromechanical connection and charging device for an electric vehicle

Abstract

Device for testing a contact force of an electromechanical connection, - with at least one test contact (4, 6), - with at least one force measuring device (8, 10) for measuring axial forces and - with at least one supporting structure (16), - wherein the force measuring device (8, 10) is attached to the support structure (16) and - wherein the test contact (4, 6) is attached to the force measuring device (8, 10).

Description

The present invention relates to a device for checking a contact force of an electromechanical connection and to a charging device for an electric vehicle having such a device.In the field of electromobility, charging plug connectors have the highest requirements with regard to their stability and safety, wherein charging currents of up to 500 A are currently transmitted. This presupposes that, for example, a permanently installed charging plug of a public charging column retains its performance even after many years of use with thousands of charging cycles.Devices for checking a contact force of an electromechanical connection and charging devices for electric vehicles are already known in the prior art.For example, DE 20 2014 100 714 U1 describes a device for testing a contact force of an electromechanical connection, having at least one test contact, having at least one force measuring device for measuring forces, and having at least one supporting structure.DE 20 2004 007 830 U1 also describes a device for testing a contact force of an electromechanical connection, having at least one test contact, having at least one force measuring device for measuring forces.DE 10 2010 044 091 A1 describes a charging device for an electric vehicle comprising an electrical contact pin and / or an electrical contact socket, wherein the charging device has a spreading device for spreading the electrical contact pin and / or a reducing device for at least partially reducing the inner diameter of the electrical contact socket.DE 10 2012 020 592 A1 describes a charging device for charging an electric vehicle at a charging station, having a first charging module on the charging station side and a second charging module on the vehicle side, which charging module have electrical contact elements that can be connected to one another, wherein the charging station has an automatic advancing device, by the actuation of which the electrical contact elements of the charging station can be connected to the electrical contact elements of the electric vehicle.The contact systems of charging plug connections usually consist of one or more contact pairs which are inserted into one another and are resiliently braced against one another on the circumferential side. Thus, a contact pair can be formed, for example, as round pins and slotted bushing, wherein the pin, in the inserted state, is seated in the bushing and spring elements of the bushing bear against an outer lateral surface of the pin. Due to the resilient elastic clamping of the pin within the socket, a contact normal force is formed between the pin and the socket, which makes it possible to conduct electric current via the contact parts. A wear-induced reduction in the contact normal force leads to the transition resistance of the electromechanical plug connection being increased. Falling below a critical normal force should therefore be avoided in order to ensure the electrical function.In general, any defect at the electrical power contacts, whether due to wear, dirt or suspect damage to such a charging plug connector, entails the risk that the contact resistance of the electromechanical plug connector is increased during the charging process. An increase in the transition resistance leads to an increased voltage drop across the load contacts, which results in an increased power loss. The heat generation associated therewith can in extreme cases be so high that the load contacts ignite the surrounding plastic material of the plug connector and / or the cables.In order to monitor a charging process, it is known, for example, to use a disconnection device with temperature sensors which monitor the temperature of the load contacts and end a charging process when a limit temperature is exceeded. A disadvantage for the end customer is that he does not finish the charging process promptly at the relevant charging station and, in addition, the vehicle can be damaged. Furthermore, such a temperature monitoring does not exclude that a defective charging plug, which may be responsible for the temperature exceeding, is used again after cooling in a subsequent charging process until the temperature limit is reached.Against this background, the present invention is based on the technical problem of specifying a device and a charging device for an electric vehicle which do not have the aforementioned disadvantages or at least to a lesser extent, and in particular enable reliable, permanently operationally reliable transmission of charging power to electric vehicles, wherein a defective charging plug can be detected in particular before use thereof.The above-described technical problem is solved by a device according to claim 1 and a loading device according to claim 9.When an electric vehicle is mentioned here, this is a motor vehicle which is driven at least partially or completely electrically and has at least one drive battery or traction battery.According to a first aspect, the invention relates to a device for testing a contact force of an electromechanical connection, having at least one test contact, having at least one force measuring device for measuring axial forces and having at least one supporting structure, wherein the force measuring device is fastened to the supporting structure and wherein the test contact is fastened to the force measuring device.It has been found that by measuring axial forces during the production and / or release of a plug connection along a plug-in direction, the contact normal force of a charging plug connection can be deduced. Thus, the contact normal force results, for example, from an axial pulling force measured when the plug connection is released multiplied by a coefficient of friction of the material pairing of the plug connection. The contact normal force is oriented in particular perpendicular to the measured axial pulling force.The device can be used, for example, to check the mechanical contactability of socket contacts of a charging plug fastened to the charging column between charging processes on a charging column by inserting the checking contact of the device into an associated socket contact of the charging plug and measuring an axial pulling force when the plug connection is released.A drop below a required minimum pulling force indicates the presence of an excessively low contact normal force during a charging process. The charging plug or a socket contact of the charging plug can therefore be checked for its mechanical contacting capability between the charging processes. If a minimum pulling force is undershot, the relevant charging column can be blocked and report a defect in the charging plug.The device can therefore be, in particular, a testing device for testing an axial pulling force when releasing a plug connection. The normal force between the contacts of an electromechanical charging plug connection can be deduced from the axial pulling force.The plug connection, which can be formed between the test contact and a contact of a charging plug, can be a purely mechanical plug connection. Thus, the test contact can be formed from a non- or poorly conducting material or can be coated with a non- or poorly conducting material. The plug connection, which can be formed between the test contact and a contact of a charging plug, can be an electromechanical plug connection. Thus, the test contact can be formed from a conductive material or coated with a conductive material. Regardless of whether the test contact is conductive or non-conductive, the device serves to test the mechanical contacting capability of a contact to be tested, in particular its capability of forming a minimum contact normal force to a corresponding contact partner of a contact pairing of a plug-in charging connection.According to a further embodiment of the invention, the test contact is a test pin which is configured for insertion into a sleeve-shaped load contact of an electric vehicle charging plug. Accordingly, the test pin can be shaped in the manner of a load contact pin which, on a charging socket of a motor vehicle, forms the counterpart to the sleeve-shaped or socket-shaped load contact of the electric vehicle charging plug.It can be provided that the test pin has the same or a smaller diameter than the standard diameter of a load contact pin of an electric vehicle assigned to the sleeve-shaped load contact to be tested. Alternatively or additionally, the test pin can have a friction-reducing coating at least in sections. Thus, the wear of a load contact to be tested can be reduced by the test processes.The test pin can have a diameter which corresponds to the standard diameter of a load contact pin of an electric vehicle assigned to the sleeve-shaped load contact to be tested. Such a test stick may be coated or uncoated.The test contact can be a sleeve or socket which is provided for testing the mechanical contacting capability of a contact pin. Such a sleeve-shaped or socket-shaped test contact can have a larger receiving diameter than the standard receiving diameter of a load contact sleeve associated with the pin-shaped load contact to be tested, in order to reduce the wear caused by the test processes. Alternatively or additionally, the sleeve- or socket-shaped test contact can have a friction-reducing coating at least in sections. Thus, the wear of a load contact to be tested can be reduced by the test processes.According to a further embodiment of the device, the support structure has at least one linear unit for moving the test contact between at least one first position and at least one second position. The device can therefore be configured to execute a plug-in and release movement of the test contact relative to a contact of a charging plug to be tested. Thus, the linear unit can be configured in particular to execute a lifting movement between the first position and the second position.The linear unit can have an electromechanical drive, with a spindle, a reciprocating piston, a chain, a belt or the like.It can be provided that the force measuring device is fastened to a support plate of the support structure, a drive of the linear unit is mounted on a base plate of the support structure, and a linear guide is formed between the support plate and the base plate. In this way, a reliable and repeatably precise linear movement of the test contact can be achieved.The force measuring device can be fastened to the supporting structure by means of an elastic compensating element, such as a plastic buffer or the like, in order to compensate alignment errors or the like during the production of a plug connection to a contact to be tested and to avoid mechanical stresses resulting from alignment errors.Alternatively or additionally, it can be provided that the test contact is fastened to the force measuring device in a form-fitting and releasable manner by means of a holder. Thus, the test contact can have, for example, a collar arranged on the end side and running around a circle, which is inserted into a holder formed as a slotted pocket. Alternatively or additionally, the test contact can be screwed, pinned or clamped to the force measuring device and / or the holder.Alternatively, it can be provided that the force measuring device is not fastened indirectly to the support plate or the support structure with the aid of an elastic compensating element, but without a compensating element. Likewise, according to alternative embodiments, the test contact can be fastened directly to the force-measuring device not indirectly via a holder, but rather directly, without the provision of the holder.A further embodiment of the device is characterized in that at least two test contacts are provided, wherein each test contact is assigned a force measuring device. Thus, the device can have a plurality of test contacts, wherein, depending on the contact layout to be tested, a corresponding test contact is provided for each contact of a charging plug. In particular, test contacts for testing each load contact and each data or control contact of a charging plug can be provided.Alternatively, the apparatus can have exactly two test contacts, wherein each of the two test contacts is assigned a force measuring device. In particular, the two test contacts can be configured to test load contacts of a charging plug which, in charging operation, transmit the electrical charging power to an electric vehicle to be charged.In particular, the test contacts can have parallel longitudinal axes spaced apart from one another, wherein the distance of the longitudinal axes corresponds to the standardized distance of the load contacts of a charging plug according to one of the standards SAEJ1772, IEC62196-2, GB / T20234.2-2015, IEC 62196-3, GB / T20234.3-2015.According to a further embodiment of the device, it is provided that the force measuring devices of the at least two test contacts or of the exactly two test contacts are fastened to the support plate. Thus, the force measuring devices can be displaceable together with the associated test contacts.A test contact may have sensors, such as a temperature sensor, a current sensor, a voltage sensor or a humidity sensor, in order to acquire further measured values.According to a second aspect, the invention relates to a charging device for charging an electric vehicle, having a housing, having a charging cable, having a charging plug which is arranged on the end side of the charging cable and which has at least one contact, having a receptacle formed on the housing for holding the charging plug, having a device according to the invention for testing a contact force of an electromechanical connection, wherein the device according to the invention is assigned to the receptacle, wherein the test contact is mechanically connectable to the contact of the charging plug, and wherein the force measuring device is configured to measure a pulling force when releasing a mechanical connection formed between the test contact and the contact of the charging plug, and / or a plugging force when establishing a mechanical connection formed between the test contact and the contact of the charging plug.The device according to the invention is used as part of the charging device according to the invention in the present case to check the mechanical contact-making ability of the contact of the charging plug between charging processes at the charging column by connecting the test contact of the device according to the invention to the contact of the charging plug and, for example, measuring an axial pulling force when the plug connection is disconnected.Falling short of, for example, a required minimum pulling force indicates the presence of an excessively low contact normal force during a charging process. The charging plug or a socket contact of the charging plug can therefore be checked for its mechanical contacting capability between the charging processes. If a minimum pulling force is undershot, the relevant charging column can be blocked and report and / or indicate a defect in the charging plug.The establishment and detachment of the plug connection between the test contact and the contact of the charging plug and the measurement and evaluation of the axial forces measured by the force measuring device can be automated.It can be provided that the test contact and the contact of the charging plug are arranged coaxially or flush, as viewed along a plug axis.The device according to the invention can therefore be, in particular, a testing device integrated into a charging device for testing an axial pulling force when a plug connection is released. The normal force between the contacts of an electromechanical charging plug connection can be deduced from the measured axial pulling force.A further embodiment of the charging device is characterized in that the charging device has a locking device with at least one locking element, such as a bolt or the like, wherein the locking device is configured to lock the charging plug electromechanically in the receptacle, as long as a predetermined minimum force is undershot during the checking of the contact force between the checking contact and the contact of the charging plug. The charging plug cannot be removed from the receptacle in the locked state, so that a defective charging plug can be detected before it is used and can be blocked for further use.It can be provided that the charging plug is automatically locked immediately after the insertion into the receptacle and the locking is released only after a positive test result by the device for testing the contact force.It can be provided that the measurement results of the test device are stored and transmitted to a central database in order to document the long-term wear behavior of the contacts of a charging plug. For this purpose, the charging device can have a data interface for transmitting measurement data.It can be provided that, if the charging plug is held in the receptacle, in particular locked, the test contact is movable from a first position, in which the test contact is at a distance from the contact of the charging plug, in the direction of the contact of the charging plug into a second position, in order to form a mechanical connection to the contact of the charging plug, and that the test contact is movable from the second position, in which the test contact is mechanically connected to the contact of the charging plug, into the first position. According to alternative embodiments of the invention, it is likewise conceivable for the charging plug to be pulled into the housing in the direction of a fixed test device and to be disengaged again in order to carry out the test process.The charging cable can be a charging cable fixedly installed on the charging device, in particular for DC charging.The invention is described in more detail below with reference to a drawing illustrating exemplary embodiments. They show in each case schematically: FIG. 1 shows an apparatus according to the invention for checking a contact force in a perspective view from above; FIG. 2 shows the device from FIG. 1 in a side view; FIG. 3 shows the device from FIG. 1 in a plan view; FIG. 4 shows test contacts with sleeve-shaped load contacts in a perspective view from above; FIG. 5 shows the test contacts and load contacts from FIG. 4 in a longitudinal section in a first position; FIG. 6 shows the test contacts and load contacts from FIG. 4 in a longitudinal section in a second position; FIG. 7 shows a charging device according to the invention for charging an electric vehicle in a perspective view; FIG. 8 shows an enlarged illustration of the charging plug of the charging device from FIG. 7 ; FIG. 9 shows the device according to the invention from FIG. 1 in a state mounted in the charging device from FIG. 7 ; FIG. 10 shows the arrangement from FIG. 9 in a longitudinal section in a first position; FIG. 11 shows the arrangement from FIG. 9 in a longitudinal section in a second position.FIG. 1 shows a device 2 for testing a contact force of an electromechanical connection. The apparatus 2 has two test contacts 4, 6, each of which is assigned a force measuring device 8, 10 for measuring axial forces along the axes 12, 14.The apparatus 2 has a supporting structure 16, wherein the force measuring device 8 and the force measuring device 10 are each fastened to the supporting structure 16. The test contact 4 is fastened to the force measuring device 8. The test contact 6 is fastened to the force measuring device 10, as can be seen in particular from FIGS. 2 and 3.The support structure 16 has a linear unit 18 for moving the test contact 4 and the test contact 6 from a first position (FIG. 10 ) into a second position (FIG. 11 ).As can be further seen from FIGS. 1, 2 and 3, the force measuring device 8 and the force measuring device 10 are fastened to a support plate 20 of the support structure 16. A drive 22 of the linear unit 16 is mounted on a base plate 24 of the supporting structure 16. A linear guide 26 is formed between the support plate 20 and the base plate 24.The force measuring device 8 is fastened to the support plate 20 by means of an elastic compensating element 28. The force measuring device 10 is fastened to the support plate 20 by means of an elastic compensating element 30.The test contact 4 is fastened to the force-measuring device 8 in a form-fitting and releasable manner by means of a holder 32. The test pin 6 is fastened to the force-measuring device 10 in a form-fitting and releasable manner by means of a holder 34. The holders 32, 34 are each a slotted pocket 32, 34, into which a respective associated test contact 4, 6 is inserted.According to further exemplary embodiments of the invention, it can be provided that the force measuring devices 8, 10 are not fastened indirectly to the support plate 20 with the aid of the elastic compensating elements 28, 30, as shown in the present example, but instead are fastened directly to the support plate 20 or the support structure 16 without the compensating elements 28, 30. Likewise, according to alternative exemplary embodiments, the test pins 4, 6 can be fastened directly to the force measurement devices 8, 10 without the provision of the holders 32, 34.In the present case, the test contacts 4, 6 are test pins 4, 6 which are configured for insertion into sleeve-shaped load contacts 36, 38 of an electric vehicle charging plug 46 (see FIGS. 4-6, 10, 11).The test pins 4, 6 have a smaller diameter than the standard diameter of a load contact pin of an electric vehicle assigned to the sleeve-shaped load contacts 36, 38. Furthermore, the test pins 4, 6 in the present case have a friction-reducing coating in the region of their outer lateral surfaces.FIG. 7 shows a charging device 40 according to the invention. the charging device 40 has a housing 42 and a charging cable 44.The load contacts 36, 38 shown in FIG. 4 form the load contacts 36, 38 of the charging plug 46 (cf. FIGS. 10, 11 ).The housing 42 has a receptacle 48 for holding the charging plug. After the end of a charging process, the charging plug 46 is accordingly inserted into the receptacle 48 and is held there.The charging device 40 has a device 2 according to the invention, which is arranged in the housing interior. The device 2 is assigned to the receptacle 48 so that the test pins 4, 6 of the device 2 are arranged axially aligned with the load contacts 36, 38 of the charging plug 46. The test contacts 4, 6 are therefore movable by means of a linear movement from a first position (FIG. 10 ) into a second position (FIG. 11 in order to form a plug connection to the load contacts 36, 38.The test contacts 4, 6 can accordingly be mechanically connected to the load contacts 36, 38 of the charging plug 46, wherein the force measuring devices 8, 10 of the device 2 are configured to measure a pulling force when releasing the mechanical plug connection formed between the test contacts 4, 6 and the load contacts 36, 38 of the charging plug 46, that is to say in the case where the load contacts 4, 6 are pulled back from the second position (FIG. 11 ) into the first position (FIG. 10 ) with the aid of the linear unit 18.The charging device 40 also has a locking device 50, having a locking element 52, wherein the locking device 50 is configured to lock the charging plug 48 electromechanically in the receptacle 48 if a predetermined minimum force is undershot during the checking of the contact force between the checking contacts 4, 6 and the load contacts 36, 38 of the charging plug 46.Reference numerals denote reference numerals2 Device 4 Test contact 6 Test contact 8 Force measuring device 10 Force measuring device 12 Axis 14 Axis 16 Supporting structure 18 Linear unit 20 Supporting plate 22 Drive 24 Base plate 26 Linear guide 28 Compensating element 30 Compensating element 32 Holder 34 Holder 36 Load contact 38 Load contact 40 Charging device 42 Housing 44 Charging cable 46 Charging plug 48 Receptacle 50 Locking device 52 Locking element

Claims

Device for testing a contact force of an electromechanical connection, - with at least one test contact (4, 6), - with at least one force measuring device (8, 10) for measuring axial forces and - with at least one supporting structure (16), - wherein the force measuring device (8, 10) is fastened to the supporting structure (16) and - wherein the test contact (4, 6) is fastened to the force measuring device (8, 10).Device according to claim 1, characterised in that the test contact (4, 6) is a test pin (4, 6) which is configured for insertion into a sleeve-shaped load contact (36, 38) of an electric vehicle charging plug (46).Device according to claim 2, characterised in that - the test pin (4, 6) has the same or a smaller diameter than the standard diameter of a load contact pin of an electric vehicle assigned to the sleeve-shaped load contact (36, 38) and / or - the test pin (4, 6) has a friction-reducing coating at least in sections.Device according to one of claims 1 to 3, characterised in that the support structure (16) has at least one linear unit (18) for moving the test contact (4, 6) between at least one first position and at least one second position.Device according to claim 4, characterised in that - the force measuring device (8, 10) is fastened to a support plate (20) of the support structure (16), - a drive (22) of the linear unit (18) is mounted on a base plate (24) of the support structure (16), and - a linear guide (26) is formed between the support plate (20) and the base plate (24).Device according to one of Claims 1 to 5, characterized in that - the force-measuring device (8, 10) is fastened to the supporting structure (16) by means of an elastic compensating element (28, 30), such as a plastics buffer or the like, and / or - the test contact (4, 6) is fastened to the force-measuring device (8, 10) in a positively locking and releasable manner by means of a holder (32, 34).Device according to one of Claims 1 to 6, characterized in that - at least two test contacts (4, 6) or exactly two test contacts (4, 6) are provided, - each test contact (4, 6) being assigned a force measuring device (8, 10) in each case.Device according to Claim 5 and Claim 7, characterized in that the force-measuring devices (8, 10) of the at least two test contacts (4, 6) or of the exactly two test contacts (4, 6) are fastened to the supporting plate (20).Charging device for charging an electric vehicle, - having a housing (42), - having a charging cable (44), - having a charging plug (46) which is arranged on the end side on the charging cable (44) and which has at least one contact (36, 38), - having a receptacle (48) formed on the housing (42) for holding the charging plug (46), - having a device (2) for checking a contact force of an electromechanical connection according to one of Claims 1 to 8, - wherein the device is assigned to the receptacle (48), - wherein the checking contact (4, 6) can be mechanically connected to the contact (36, 38) of the charging plug (46), and - wherein the force measuring device is configured to - measure a pulling force when releasing a mechanical connection formed between the checking contact (4, 6) and the contact (36, 38) of the charging plug (46), and / or a plug-in force when establishing a mechanical connection formed between the test contact (4, 6) and the contact (36, 38) of the charging plug (46).Charging device according to Claim 9, characterized in that - the charging device (40) has a locking device (50) having at least one locking element (50), such as a bolt or the like, - wherein the locking device (50) is configured to lock the charging plug (46) electromechanically in the receptacle (48), if a predetermined minimum force is undershot during the checking of the contact force between the checking contact (4, 6) and the contact (36, 38) of the charging plug (46).Charging device according to one of claims 9 or 10, characterised in that - the test contact (4, 6), insofar as the charging plug (46) is held in the receptacle (48), is movable from a first position, in which the test contact (4, 6) is at a distance from the contact (36, 38) of the charging plug (46), in the direction of the contact (36, 38) of the charging plug (46) into a second position, in order to form a mechanical connection to the contact (36, 38) of the charging plug (46), and - the test contact (4, 6) is movable from the second position, in which the test contact (4, 6) is mechanically connected to the contact (36, 38) of the charging plug (46), into the first position.

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